· 1509 w. swann avenue suite 225 tampa, florida 33606 (813) 258-8818 ... southwest jetty against...

APENDICE M

1509 West Swann Avenue, Suite 225 Tampa, Florida 33606 Phone (813) 258-8818 v Fax (813) 258-8525

TECHNICAL MEMORANDUM

To: Thomas Cordero

From: Michael Herrman, P.E.

Date: November 18, 2009

Subj: Discovery Bay Marina Circulation and Flushing Modeling

Cordeco Land Services Corp. engaged Moffatt & Nichol to evaluate the circulation and flushing efficiency

of the proposed Discovery Bay Marina for use in preparing the project Environmental Impact Statement

(EIS). M&N developed a MIKE21 HD/AD numerical model to simulate water circulation and to

determine flushing efficiency for the proposed basin configurations. The model included the effects of

local tide fluctuation, groundwater inflow, and flow augmentation using pumps. Subsequent to

completion of the modeling and analysis, the groundwater inflow volume analysis was revised, resulting

in a reduction of groundwater inflow into the marina basin. This technical memorandum outlines the

resulting modification to the flushing analysis to reflect the revised groundwater inflow volume.

The numerical flushing model presented in the EIS included 9,240 m3 of groundwater inflow per day.

This groundwater, when combined with normal daily tidal excursion and 108,000m3/day of mechanical

circulation resulted in a residual concentration of approximately 37% after 96 hours, suggesting “good”

water quality as defined by USEPA and USACE. Further analysis found that the system behaved in a

“linear” fashion whereby the pumping schedule may be modified to pump for shorter daily durations so

long as the full daily volume of 108,000 m3/day is pumped into the marina basin. Addition of the

relatively small freshwater inflow to the mechanical pumping volume results in 117,240m3/day total

inflow into the marina basin.

Reduction of the freshwater inflow to 1,890 m3/day, as described in the update to the hydrogeological

study, may also be evaluated linearly. This reduction is projected to require the pump output to be

increased to approximately 115,500 m3/day to maintain the total inflow volume of 117, 240m3/day. The

pumping system, including the gravity fed intake and sump system as well as the discharge manifolds

Technical Memorandum Discovery Bay Marina Circulation and Flushing Modeling November 18, 2009 Page 2 of 2 and the pumps are sufficiently sized to accommodate this additional flow without modification.

Discharge velocities in the immediate vicinity of the outfalls may also increase proportionally but are

expected to remain below the design velocity threshold and are not expected to impact berthing at the

proposed docks.

1509 W. Swann Avenue Suite 225

Tampa, Florida 33606

(813) 258-8818 Fax (813) 258-8525

July 6, 2009

Thomas Cordero Cordeco Northwest Corp. P.O. Box 610 Aguada, PR 00602

Subject: Discovery Bay Resort and Marina Draft Environmental Impact Study Response to USFWS Comments

Dear Mr. Cordero:

Moffatt & Nichol reviewed the U.S. Fish and Wildlife Service (USFWS) comments dated April 8, 2009 pertaining to the Discovery Bay Resort and Marina Draft Environmental Impact Study and Joint Permit Application. This letter report provides responses to the marine related comments as follows.

1)d) The southern jetty will impact part of the Espinar mangrove. There is very little detail of how hydrology will be maintained to these wetland areas.

The Espinar mangrove will be located behind the Aguada levee structure. Tidal flows will be maintained into the mangrove via a flood control structure. The flood control structure will be constructed to allow the propagation of the full tidal prism into the mangrove during normal tidal flows. During periods of elevated water levels, the flood control structure will be closed to prevent flooding. These periods of elevated water levels occur infrequently and last for 12 to 18 hours at which point normal tidal flows will be restored to the mangrove.

3)e) Appendix M: The marina design is essentially a dead end canal. According to the study, the narrow opening will not allow adequate tidal exchange and the 2.5 mgd outflow of freshwater from the aquifer will generate current and hydraulic head that essentially will keep the salt wedge at bay but does not allow for adequate flushing. While the document outlines the EPA Best Management Practices for marina construction, and the document states that different marina designs would have improved flushing, the final marina design does not change. A mechanical means of providing some form of flushing is proposed. The applicant proposed to mechanically pump seawater into the marina basin at three locations at the rate of 108,000 cubic meters per day to increase flushing efficiency in the marina. We have serious concerns over the reliability of this alternative to work throughout the life of the project. Mechanical pumping of sea water is energy intensive, costly, corrosive, and subject to breakdown. Break down even for a few days could cause a drastic drop in water quality. We recommend that the applicant consider alternative designs that would not require such a massive pumping operation and would rely on more natural processes to maintain water quality.

The marina at the proposed Discovery Bay Resort and Marina will be the access point and primary feature for resort guests and residents including fishermen and boating tourists. The

Discovery Bay Resort and Marina Response to DEIS USFWS Comments July 6, 2009 Page 2 of 3 marketability of the marina with boaters and associated success of the project requires the water quality within the marina to be equal to the adjacent open water. As such, marina water quality is of primary importance to the project design team. The limited ambient tidal range fully propagates into the proposed marina; however this flow volume is insufficient to meet the targeted flushing guidelines. The proposed mechanical marina circulation system is designed to flush the marina within 4 days, resulting in good flushing characteristics as characterized by the USACE (CEM, Section V-5-10-a-2-b).

The proposed circulation system design includes parallel pumping systems. This design allows the system to continue to operate during routine or unscheduled maintenance of one pump. The pumps are located upland in an enclosed building providing protection from waves or storms. A gravity fed sump system draws ocean water to the pumps via inlets located 3 to 4 feet above sea bottom. These inlets are protected by armor stone and navigation warning signs. Sediment entering the inlets will be scoured through the system by the flow velocity. In addition, maintenance will be scheduled semi-annually (twice per year) to inspect and clean the pipes and inlet system.

Alternative marina basin configurations were considered. These alternatives did not meet the project design criteria which include minimizing impacts to existing mangroves, meeting international design guidelines for safe navigation, and sufficient space for 500 wet-slips.

4) Coastal Engineering Analysis and Coastal Erosion

a) Appendix M – This Appendix makes several references to Appendix X which is not included in the CD making it difficult to corroborate the document. The document suggests that the existing jetties at the mouth of the Cano Madre Vieja have reached equilibrium with the adjacent sand beach, with sediments periodically accreting and eroding. The proposed jetties will extend further into the sea to the 4 meter contour and have been designed for a 25 year life span. It is stated that a future equilibrium will occur and it is stated that the maximum retreat will be some 5 meters. A 5 meter shoreline retreat in this area needs to be carefully evaluated by Planning Board and DNER.

Appendix X is a typographical error that should refer to (sub)Appendix A included within Appendix M. The maximum projected shoreline change is localized to the lee of the jetties and is based on the maximum possible uncertainty in the analysis. Actual shoreline change will likely be significantly less and may be mitigated by adding beach fill in the lee of the jetties to pre-fill the expected fillet.

b) The study states that sand will accumulate on the north jetty. After 3-7 years the sand accumulating in the north jetty will eventually start to spill into the marina entrance and result in the need for maintenance dredging. This suggests a fair amount of long shore sand transport. This is contrary to the statements made meetings and in sections of the Joint Permit Application, to the effects that there is little sand transport in the area.

See response to C below.

c) In summary, based on our interpretation of the information on page 4-2 of Appendix M, the construction of the jetties will result in the southern beach experiencing a shoreline

Discovery Bay Resort and Marina Response to DEIS USFWS Comments July 6, 2009 Page 3 of 3 retreat on the order of 5 meters while the north jetty will accumulate sand to the extent that in 3-7 years it will bypass the jetty and begin to infill the marina channel.

The coastline in the vicinity of the Discovery Bay project site is characterized by two existing groin/jetty structures with similar location and orientation to the proposed entrance jetties. The proposed jetties are an extension of the existing structures designed to stabilize the existing southwest jetty against wave penetration, to provide wave reduction and sheltering to boats in the marina entrance channel for navigation safety, and to stabilize the entrance channel to the design water depth. Analysis of historic shoreline change shows periods of accretion along the entire shoreline followed by erosion along the entire shoreline. This, combined with the absence of accretional fillets in the lee of the existing structures suggests cross-shore (on-shore/off-shore) dominated processes with minimal alongshore sediment transport.

The Shoreline Change and Sediment Transport Analysis was conducted in coordination with Dr. Jorge Capella of the University of Puerto Rico. Dr. Capella provided insight into historical shoreline change and provided assistance in data collection. Dr. Capella, as well as Morelock (1978, 1984, 2000) and the Evans Hamilton/GeoSea Consulting (2003 for the USACE), conclude that the shoreline in the project vicinity is relatively stable with the predominant changes occurring due to cross-shore (onshore/offshore) processes during tropical events and negligible net alongshore transport over the long term.

During accretion events along the entire shoreline, consistent with cross-shore dominated processes, sediment will accumulate adjacent to the jetties at a rate consistent with the remainder of the shoreline. During subsequent erosion events along the shoreline, the sediment adjacent to the jetties will erode at rate consistent with the remainder of the shoreline. This is consistent with visual observation of existing processes that report minimal fillet formation adjacent to the existing structures. The shoreline change analysis under proposed conditions indicates that the structure extension will not alter the existing cross-shore dominated coastal dynamics and sediment transport. Changes are limited to short-term equilibration in a limited area in the lee of the structures that may be mitigated by adding beach fill to these areas.

Please feel free to contact me at (813) 258-8818 or by e-mail at [email protected] should you have any additional questions or comments.

Best regards,

MOFFATT & NICHOL

Michael N. Herrman, P.E. Coastal Engineer

mailto:[email protected]



(813) 258-8818 Fax (813) 258-8525

July 6, 2009


Subject: Discovery Bay Resort and Marina Draft Environmental Impact Study Response to USGS Comments

Dear Mr. Cordero:

Moffatt & Nichol reviewed the U.S. Geological Survey (USGS) comments dated May 4 2009 pertaining to the Discovery Bay Resort and Marina Draft Environmental Impact Study. This letter report provides responses to the two comments concerning 1) Coastal Dynamics and 2) Water Quality. The USGS comments contain no specific questions. Therefore, the following responses include paraphrased questions extracted from each comment.

Coastal Dynamics

Question:

The USGS comments question the following topics as paraphrased from the text of the letter:

• Thoroughness of coastal dynamics study

• Extents of studied areas

• Accuracy and impacts of rectification error for aerial photographs

• Conclusions regarding existing coastal stability and sediment transport dynamics

Response:

Introduction


Discovery Bay Resort and Marina Response to DEIS USGS Comments July 6, 2009 Page 2 of 3 The shoreline response due to the proposed structure extension is calibrated based on the historic shoreline response of the existing structures. The shoreline change analysis under proposed conditions indicates that the proposed structure extension will not alter the existing cross-shore dominated coastal dynamics and sediment transport. Changes are limited to short-term equilibration in a limited area in the lee of the structures that may be mitigated by adding beach fill to these areas.

Study Methodology, Extents, and Accuracy

The Shoreline Change and Sediment Transport Analysis was conducted in coordination with Dr. Jorge Capella of the University of Puerto Rico. Dr. Capella provided insight into historical shoreline change and provided assistance in data collection. Dr. Capella, as well as Morelock (1978, 1984, 2000) and the Evans Hamilton/GeoSea Consulting (2003 for the USACE), conclude that the shoreline in the project vicinity is relatively stable with the predominant changes occurring due to cross-shore (onshore/offshore) processes during tropical events and negligible net alongshore transport over the long term.

The project study area was defined based on available historical data. Available data include aerial photographs from 1963 through 2006. The northeastern analysis extent coincides with existing armored shoreline reaches (gabions, rock revetments, seawalls). The western extent of the analysis area corresponds to the shoreline area influenced by the mouth of the Rio Culebrinas. These analysis extents accrete or erode at similar rates during each analysis period, consistent with cross-shore dominated accretion and erosion processes.

The older aerial photographs used in the study were not rectified in space prior to this study. As such, visible structures and landmarks were used to locate the aerials in geographic coordinates. Typically, the shoreline location is verified using historic T-sheets, lidar surveys, or shoreline survey maps; however, these data were not available at the time of the study for this portion of the coast. Using accepted methodology, the accuracy of each aerial rectification is judged to be on the order of 3 meters. Over the entire 43 year study period the maximum error is judged to be on the order of 0.14 meters (0.45 feet) per year. Based on the intermediate shoreline locations and the apparent long term shoreline stability, the actual error is likely to be significantly lower than the maximum.

Conclusions

The existing project shoreline is characterized by two existing jetties. The jetties are in a similar location and orientation as the proposed jetties. Analysis of the average shoreline change rate from 1985 to 2006 following construction of the existing jetties versus the rate from 1963 to 1977 prior to jetty construction shows that the average rates are similar and that jetty construction resulted in no-appreciable long term impacts to the shoreline. The results are consistent with cross-shore dominated coastal processes with minimal net alongshore sediment transport.

The proposed jetties extend farther offshore than the existing structures to provide wave protection to the marina entrance channel and the marina basin and to stabilize the entrance channel. Analysis shows that extension of the existing structures will not alter long-term sediment transport, and the resulting shoreline change rates, in the project vicinity. Localized

Discovery Bay Resort and Marina Response to DEIS USGS Comments July 6, 2009 Page 3 of 3 changes in the lee of the structures during equilibration of the beach following construction may be minimized by adding beach fill to these areas.

Water Quality

Question:

The USGS comments question the following topics as paraphrased from the text of the letter:

• Efficacy of pumping system for flushing

• Potential for inlets to become clogged with sediment.

Response:

The marina at the proposed Discovery Bay Resort and Marina will be the access point and primary feature for resort guests and residents including fishermen and boating tourists. The marketability of the marina with boaters and associated success of the project requires the water quality within the marina to be equal to the adjacent open water. As such, marina water quality is of primary importance to the project design team. The proposed marina circulation system is designed to flush the marina within 4 days, resulting in good flushing characteristics as characterized by the USACE (CEM, Section V-5-10-a-2-b).

The proposed circulation system design includes parallel pumping systems. This design allows the system to continue to operate during routine or unscheduled maintenance of one pump. The pumps are located upland in an enclosed building providing protection from waves or storms. A gravity fed sump system draws ocean water to the pumps via inlets located 3 to 4 feet above sea bottom. These inlets are protected by armor stone and navigation warning signs. Sediment entering the inlets will be scoured through the system by the flow velocity. In addition, maintenance will be scheduled semi-annually (twice per year) to inspect and clean the pipes and inlet system.


Best regards,

MOFFATT & NICHOL





(813) 258-8818 Fax (813) 258-8525

July 6, 2009


Subject: Discovery Bay Resort and Marina Draft Environmental Impact Study Response to DRNA Comments

Dear Mr. Cordero:

Moffatt & Nichol reviewed the Departamento De Recursos Naturales Y Ambientales (DRNA) comments dated June 15, 2009 pertaining to the Discovery Bay Resort and Marina Draft Environmental Impact Study and Joint Permit Application. This letter report provides responses to the marine related comments as follows.

El analisis del impacto de los espolones a las playas arenosas …


The Shoreline Change and Sediment Transport Analysis was conducted in coordination with Dr. Jorge Capella of the University of Puerto Rico. Dr. Capella provided insight into historical shoreline change and provided assistance in data collection. Dr. Capella, as well as Morelock (1978, 1984, 2000) and the Evans Hamilton/GeoSea Consulting (2003 for the USACE), conclude that the shoreline in the project vicinity is relatively stable with the predominant changes occurring due to cross-shore (onshore/offshore) processes during tropical events with negligible net alongshore transport over the long term.

During accretion events along the entire shoreline, consistent with cross-shore dominated processes, sediment will accumulate adjacent to the jetties at a rate consistent with the remainder of the shoreline. During subsequent erosion events along the shoreline, the sediment adjacent to the jetties will erode at rate consistent with the remainder of the shoreline. This is consistent with visual observation of existing processes that report minimal fillet formation adjacent to the existing structures. The shoreline change analysis under proposed conditions indicates that the structure extension will not alter the existing cross-shore dominated

Discovery Bay Resort and Marina Response to DEIS DRNA Comments July 6, 2009 Page 2 of 2 coastal dynamics and sediment transport. Changes are limited to short-term equilibration in a limited area in the lee of the structures that may be mitigated by adding beach fill to these areas.

En el studio de Moffat y Nichols se indica que la marina …

Construction of the Discovery Bay Marina basin will be performed under dry conditions, to the extents possible, using land based excavation and earth moving equipment. An earthen plug will remain in place in the inlet throughout excavation to prevent turbid waters within the excavation area from mixing with open water. Floating turbidity curtains will be installed around the basin entrance during construction as an additional precaution to prevent discharge of turbid water into open water. A self-directed turbidity monitoring plan will be employed during excavation to monitor the adjacent open water for increases in turbidity above background levels. If increases are detected emanating from the site, construction will be halted until the source of turbidity is rectified.

Flow through the Caño Madre Vieja will be maintained separately from the marina basin to maintain existing habitats along the Caño and prevent excess water from entering the excavation area. Excavation of the basin will begin in the areas away from the Caño and the proposed inlet. Excavated material containing excess moisture will be placed within onsite containment areas designed to contain any effluent and facilitate dewatering of the material via evaporation. This material, if found to be geotechnically suitable, will be reused onsite for levee construction and upland fill. Unsuitable material will be trucked offsite for non-structural fill, agriculture, or as cover material in solid waste facilities based on the material characteristics.


Best regards,

MOFFATT & NICHOL



Environmental Impact Statement

ENVIRONMENTAL IMPACT STATEMENT

Coastal Engineering Analysis

Prepared By:

Moffatt & Nichol

1509 West Swann Ave

Suite 225

Tampa, Florida, 22606

Prepared For:

Cordeco Land Services Corp

PO Box 610

Aguada, PR 00602

November 12, 2007

Discovery Bay Resort and Marina Environmental Impact Statement

Page i-2 November 2007

Table of Contents

2 PROJECT DESCRIPTION.............................................................................................. 2-1

2.1 DISCOVERY BAY MARINA DESIGN ........................................................................ 2-1

2.1.1 Marina Entrance....................................................................................................... 2-1

2.1.2 Shoreline Treatments ............................................................................................... 2-4

2.1.3 Marina Layout.......................................................................................................... 2-4

2.1.4 Boat Ramp ............................................................................................................... 2-5

2.1.5 Dock and Pier Configuration ................................................................................... 2-6

2.1.6 Reconfiguration Perimeter ....................................................................................... 2-6

2.1.7 Construction Methodology ...................................................................................... 2-7

2.1.8 Construction Sequence............................................................................................. 2-7

3 EXISTING CONDITIONS.............................................................................................. 3-1

3.1 METEOROLOGIC AND OCEANOGRAPHIC INFORMATION ................................ 3-1

3.1.1 Water Levels and Currents....................................................................................... 3-1

3.1.2 Winds ....................................................................................................................... 3-2

3.1.3 Waves....................................................................................................................... 3-2

3.1.4 Tropical Systems...................................................................................................... 3-3

3.2 COASTAL PROCESS MODELING .............................................................................. 3-5

3.2.1 Wave Modeling........................................................................................................ 3-6

3.2.2 Shoreline Change and Sediment Transport Analysis............................................... 3-9

3.2.3 River Sediment Load Analysis .............................................................................. 3-12

4 WITH-PROJECT CONDITIONS ................................................................................... 4-1

4.1 IMPACTS ON COASTAL PROCESSES....................................................................... 4-1

4.1.1 Longshore Sediment Transport Model .................................................................... 4-1



4.1.2 River Sediment Load Analysis ................................................................................ 4-2

4.1.3 Marina Flushing Analysis ........................................................................................ 4-7



List of Figures

Figure 2-1: Channel Depth Schematic.............................................................................. 2-9

Figure 2-2: Existing Shoreline Structures......................................................................... 2-9

Figure 3-1: Project Location Map (USACE Jacksonville District, 2005) ...................... 3-14

Figure 3-2: Aguadilla-Mayaguez/Discovery Bay Water Level Comparison ................. 3-14

Figure 3-3: Discovery Bay Measured Current................................................................ 3-15

Figure 3-4: Aguadilla Airport Wind Data (1961-1970).................................................. 3-15

Figure 3-5: Aguadilla Wave Rose – Measured and Predicted........................................ 3-16

Figure 3-6: Hurricanes and Tropical Storms Passing within 100 km of Aguadilla, Puerto Rico from 1950 to 2003.................................................. 3-16

Figure 3-7: Historical Shoreline Change Rates Near Caño Madre Vieja ....................... 3-17

Figure 4-1: Transformed and Locally Generated Combined Wave Rose ...................... 4-14

Figure 4-2: Project Vicinity Map.................................................................................... 4-15

Figure 4-3: Sediment Load – Flow Correlation.............................................................. 4-15

Figure 4-4: Property Boundaries and Wetland Areas ..................................................... 4-16

Figure 4-5: Preliminary Basin Configuration ................................................................. 4-17

Figure 4-6: Revised Marina Configuration Bathymetry (left) and Residual Concentration with Groundwater – 96 hours (right).................................... 4-17

Figure 4-7: Revised Marina Configuration Residual Concentration with Distributed Pumping – 96 hours .................................................................. 4-18

Figure 4-8: Marina Pumping System Configuration ...................................................... 4-18



List of Tables

Table 3-1: Tidal Datum Relationship .............................................................................. 3-2

Table 3-2: Hurricanes and Tropical Storms Passing within 100 kilometers of Aguadilla, Puerto Rico from 1950 to 2003.................................................... 3-4

Table 3-3: Storm Surge Elevation ................................................................................... 3-5

Table 3-4: Extreme Wave Statistics for WIS Station L1-8 (19N, 67W)......................... 3-5

Table 3-5: Operational Wave Statistics based on WIS hindcast data for NSW model.............................................................................................................. 3-6

Table 3-6: Extreme Wave Transformation Results ......................................................... 3-8

Table 3-7: Wind Wave Frequency of Occurrence........................................................... 3-9

Table 3-8: Average Historical Shoreline Change Rates Near Caño Madre Vieja............................................................................................................. 3-11


Page 2-1 November 2007

2 PROJECT DESCRIPTION

2.1 DISCOVERY BAY MARINA DESIGN

The Discovery Bay Marina has been designed to provide protected mooring for up to 1000 recreational boats ranging in length from 9.1m (30-feet) to over 55m (180-feet). The marina consists of 500 wet slips and 500 dry slips. The following sections describe the design of the marina including entrance channel design, marina layout, dock and pier configuration, and shoreline treatments.

2.1.1 Marina Entrance

Located on the relatively sheltered western coast of Puerto Rico, the Discovery Bay Marina outlets to the open waters of Aguadilla Bay in an area of coastline exposed periodically to large waves refracted from offshore as well as significant locally generated wind waves. Protective structures will be required at the entrance of the Discovery Bay Marina to provide a quiescent marina entrance channel that allows approaching vessels to reduce speed prior to entering the marina basin while also preventing the large offshore waves from propagating into the marina basin.

Entrance Channel

The Discovery Bay Marina entrance channel has been designed with sufficient width and depth to allow the expected marina traffic to safely and efficiently navigate out of the marina basin during peak access periods through all phases of the tide.

Design Width

The U.S. Army Corps of Engineers, in EM 1110-2-1615 Hydraulic Design of Small Boat Harbors, conservatively recommends that for safe navigation the width of each navigable lane be 200% of the design vessel beam plus an additional 60% of the boat beam for bank clearance on each bank and an additional 80% of the boat beam for passing clearance between adjacent lanes resulting in a total of 600% of the design vessel beam for a two-lane access channel. For the Discovery Bay Marina the resulting design channel width for an 8-meter boat beam, corresponding to a typical 30.5m (100-foot) boat, is approximately 50 meters wide.

Design Depth

The U.S. Army Corps of Engineers EM 1110-2-1615 Hydraulic Design of Small Boat Harbors suggests that channel depths should account for vessel draft and squat, wave conditions, and safety clearances, as shown in Figure 2-1. Additional depth may be considered to account for advanced maintenance dredging. Finally, an extreme low-water level, such as a recurring minus tide, may require increased design depths. Considering these elements, the entrance channel depth has been designed to be 3.35-meters deep relative to MLLW with an additional 0.3m of advanced maintenance dredging for a total elevation of -3.65m MLLW. The channel side slopes have been designed with a 4H:1V slope for slope stability and to minimize maintenance dredging.



Existing Structures

The location of the Discovery Bay Marina entrance coincides with the location of the existing Caño Madre Vieja outlet into Aguadilla Bay. The mouth of the Caño Madre Vieja is approximately 50m wide as defined by two existing shore-normal structures, shown in Figure 2-2. The existing structures consist of an armored earthen jetty to the north of the outlet and a stone jetty to the south.

The crest elevation of the jetty north of the mouth of the Caño Madre Vieja is 4m MSL and extends approximately 100m offshore in a westerly direction bearing 285 degrees, terminating at approximately the 2m offshore depth contour. The crest of the jetty averages approximately 15m wide and is paved, allowing vehicular parking and pedestrian access. The slopes of the jetty are armored with large angular stones of varying size, with the largest stones appearing to be on the order of 1m in diameter, based upon a visual survey, corresponding to a weight of approximately 2 tonnes (1000 kg).

The rock jetty south of the Caño Madre Vieja mouth consists of a stone mound with a crest elevation approximately 1.4m above MSL. The jetty is constructed of angular stone similar in size and appearance to the armor stone used on the jetty structure. The jetty extends in a westerly direction of 312 degrees, terminating approximately 30m offshore in 0.5m deep water.

Sediment periodically accretes and erodes along the beaches adjacent to these jetties. Analysis of long term sedimentation patterns indicates that while the existing structures occasionally impound sediment, the long term shoreline position has been stable since the structures were built and have not negatively impacted the regional littoral system.

Proposed Entrance Structures

To provide protection to the entrance channel and marina basin, as discussed above, the existing jetties will be reshaped and extended, resulting in two stone jetties flanking the entrance channel. The project structures have been designed with a 25-year design life. The design parameters for the structures are based on a probabilistic exceedance of wave heights and water levels occurring during the project’s lifespan. Wave heights and water level parameters associated with a return period of 50-years, which have a 2 percent probability of exceedance annually or 50 percent probability of exceedance over 25 years, were applied in design of the structures.

The 50-year water level was extracted from the FEMA FIS water levels and the 50-year wave conditions at the site were computed using the MIKE21 Near Shore Wave (NSW) model. A deepwater wave, with a height of 12.5m and a corresponding period of 14s, was propagated from offshore to the project location.

Analyses of MIKE21 NSW model results indicate that the design wave will shoal, refract, and break as it approaches the project location. The design wave, corresponding to offshore waves origination from the north, is 3.5m in height with a period of 14s and an approach angle of 330 degrees (N=0 degrees) at the project location.



Structure Configuration

To adequately protect the entrance channel and marina basin from waves approaching predominantly from the NW quadrant, the existing jetty will be reconfigured into a northern jetty extending approximately 100m beyond the existing structure to the 4m depth contour. Similarly, to protect the channel from wave reflection and sediment impoundment from the shoreline to the south, the southern jetty structure will be extended approximately 140m beyond the existing structure.

Structure Orientation

The proposed entrance structures must be capable of providing a navigable entrance to the marina under operational conditions. Wave penetration into the marina entrance was evaluated using the MIKE21 Elliptical Mild-Slope (EMS) Wave module. The MIKE21 EMS wave module may be used to calculate wave fields in smaller coastal areas where diffraction and wave breaking are important, as is the case with marina entrance jetties.

The MIKE21 EMS Wave module was used to evaluate unit waves (unitless wave height of 1) for the range of typical refracted wave periods and directions predicted by wave hindcasting. Additional simulations were performed corresponding to locally generated wind directions for fully developed waves. Analysis of the modeling results indicate that the wave heights of 8 second period waves reduce quickly to less than half of the initial height after propagating 20m to 30m into the marina entrance and to less than 10% of the initial height after propagating 50m, regardless of initial wave direction. Longer period, fourteen second waves penetrate approximately 10% further into the entrance than the 8 second waves. Penetration distance for 14 second waves is also insensitive to initial wave direction.

The entrance channel orientation has been set to 285 degrees west of north, equal to the orientation of the existing jetty structures. This orientation provides protection from the predominantly northwesterly wave direction while providing a slight bend of 18 degrees in the entrance channel, preventing waves from propagating directly into the marina.

Armor Stone Sizing and Structure Geometry

Wave height and period are used to determine the properties of the armor stone and underlayer stone to be used for entrance structure construction and to establish the structure crest elevation. The jetty cross sections have been designed in accordance with the methodologies outlined in the USACE Coastal Engineering Manual (CEM, 2002).

The Hudson formula was used in conjunction with the design wave conditions to size the armor stone. The assumed stone density was 2.64 tonnes/m3. A side slope of 2H:1V was selected for the jetty faces to minimize the required structure footprint while maintaining slope stability under the expected wave conditions.

The resulting median stone size for armor stone on the main trunk of the structure is 4.25 tonnes. The head of the structure requires larger 6.0 tonne stone.



The crests of the structures have been set to an elevation of 3m MSL to ensure that the structure is visible above the wave crests during operational conditions while limiting the required footprint area and material quantities. The crest width of the structures is 3.6m.

2.1.2 Shoreline Treatments

Two types of shoreline treatments were developed and employed as follows: 1) a vertical flood wall to protect the upland development and 2) a natural edge along the undeveloped edge of the marina.

A vertical wall will be installed along the southern, developed edge of the marina to act as part of the levee system floodwall as well as to provide a quick transition to navigable berthing area from the final developed upland elevation. The vertical wall will consist of a steel or concrete sheet pile wall with a concrete cap that will be anchored with a tie rod and deadman system. The sheet pile wall will extend to elevation +2m above MSL where it is backed by a promenade walkway followed by the flood control levees.

Fields, treed areas, and mangroves border the northern, undeveloped edge of the marina. To preserve the flow of water and to create a natural appearance in these areas while providing erosion protection to the earthen slopes, the edge slope will be revetted with armor stone. The predominate erosion mechanisms are waves generated by boat wakes. Analysis of expected boat wake suggests that 2 layers of 0.14 tonne armor stone over two layers of 13.6kg underlayer stone will provide sufficient protection to the 2H:1V slope.

2.1.3 Marina Layout

The Discovery Bay Resort and Marina development program includes a marina basin capable of berthing 500 vessels within the constraints of the basin shape. The shape of the Discovery Bay Marina basin has been influenced by the property boundaries and the proposed flood protection structures. Vessels expected to berth in the marina range from 9.1m (30-feet) to 55m (180-feet) in length. To minimize dredging quantities and improve flushing while maintaining efficient berthing arrangements and fairway navigation, the layout of the 500 slip basin has been sub-divided into groups of vessels by length. The slips for the largest vessels, whose length exceeds 18.3m (60-feet), are located closest to the mouth of the marina basin with additional side-tie dockage capable of berthing vessels up to 55m (180-feet) in length. The water depth required to accommodate the vessels in this area, encompassing 2.55 hectares, is 3.66m below MLLW. Vessels with lengths from 9.1m to 18.3m are located in the 6.94 hectare center region of the basin where water depths are designed at 2.44m below MLLW. The final area of the marina will be limited to vessels having low vertical profiles due to height restrictions to permit navigation under a bridge that crosses the marina. Water depths required for navigation in this 2.63 hectare area are 1.98m below MLLW.

Interior channels were sized with consideration of basin geometry, safe navigation, and the expected level of traffic. An interior access channel extends along the outside edge of the marina. The width of the marina access channel varies from 50m at the marina entrance to 30m in the center area to 15m in the areas furthest from the entrance, as design vessel beams and traffic levels decrease in each area. Maintenance services and the launching of vessels stored in



dry stacks will be provided in the area adjacent to the aforementioned bridge crossing the marina between the center and far areas of the marina. To permit large vessel access to the maintenance and dry storage areas, the marina access channel has been designed for a constant 3.66m depth up to the maintenance and dry storage launch areas. The access channel shallows to 1.98m beyond this area to accommodate the smaller draft of the design vessels for this area. Staging docks are provided in the vicinity of the dry stack.

The marina’s fueling pier has been located near the entrance of the marina, providing easy access for transient vessels as well as resident vessels. The fueling pier has been designed to accommodate a minimum of four vessels re-fueling simultaneously. The wide entrance channel near the fuel pier provides an area for additional boats to queue while waiting to re-fuel.

2.1.4 Boat Ramp

A boat ramp was designed to provide boat launching access in the Discovery Bay Marina. Boat ramp design includes consideration of the number of ramps, the width of the ramp lanes, the slope of the ramps, and upland amenities that will serve the boaters launching and retrieving their vessels. The following sections describe each of these parameters.

Ramp Design

Boat ramp lanes must be sufficiently wide to allow for safe trailer and boat maneuvering, especially when adjacent ramps may be in use. The single lane ramp at the Discovery Bay Boat Ramp has a lane width of 5.5m. A boarding dock is located adjacent to the boat ramp to provide access and staging to boats being launched and retrieved.

The slope of the boat launch ramp should allow boaters to safely back trailers into launching position while efficiently reaching water deep enough to launch the boat. The ramps at the Discovery Bay Boat Ramp have been designed to a 14% slope.

The in-water ramp approach area consists of a basin dredged to elevation 1.7m below MSL with sufficient space to maneuver multiple vessels during queuing.

Ramp Approach Area

The landside ramp approach area must be configured to allow drivers to maneuver their vehicle and trailer into position on the boat ramp. A vehicular-trailer movement study of the ramp approach area was conducted to determine the projected pathways of vehicle and trailer during launching operations (approach, back-up, and pull-away maneuvers at the ramps). The AutoTurn© program, which simulates the wheel movements of selected vehicle type as it progresses through a pre-defined path, was applied for a combination car/truck and boat trailer moving at a constant speed of 9.7 kilometers per hour. The analysis indicates that the incorporation of a partial round-about will allow vehicle-trailer units to “set-up” the orientation of the trailer prior to reaching the hardstand area in front of the ramp. A typical-car trailer requires a 10.7m turning radius. The inside radius of the round-about has been set to this distance.



Boat Launching

The boating launch ramp has been designed with a boarding float to allow boaters to load and unload personnel and property during launch and retrieval operations. The boarding float is 18.3m long to accommodate multiple boats simultaneously. Boats may be positioned on either side of the boarding float. The float is 1.8m wide and is accessible via a 1.5m wide articulating gangway. The deck height of the boarding float has been designed at 0.5m above water level to allow comfortable access to boats in the water.

2.1.5 Dock and Pier Configuration

The Discovery Bay Marina may experience extreme fluctuations in water level during episodic flood events from the Caño Madre Vieja and Rio Culebrinas. To protect the marina infrastructure, the boat docks have been designed as floating platforms capable of rising and falling with the potential flood waters. The docks will be anchored by steel or concrete guide piles extending a sufficient distance above the projected flood level to secure the floating platforms as they rise with the flood water, preventing the docks from floating away. Under typical conditions, the dock platforms will float 0.5m above the still water level with a similar depth extending below the surface to provide buoyancy.

Vessels in the marina during flood events may be subject to high velocity flows. To reduce potential drag forces, the docks have been aligned so as to orient the keel of the vessels parallel to the direction of flow. Where possible, vessels will be oriented with their bow into the flood flow to further reduce drag.

Dock access will be limited to pedestrian traffic and motorized carts and will be controlled by access control gates. To accommodate the expected traffic levels, the main docks have been designed to a width of 3m. This will provide sufficient room for the carts to safely pass other carts and pedestrians and to safely turn around. The finger piers extending perpendicular from the main pier will be 1.5m wide in the areas with boats greater than 9.1m. The finger piers in the area with boats less than 9.1m will be 0.9m wide. Dock access from the promenade area will be via 3m wide ramps that will be sloped to meet Americans with Disabilities Act (ADA) guidelines as required.

Dockside amenities include potable and fire-suppression water supplies and electrical services. Sanitary waste pumpout stations are included at each re-fueling dock. In addition, the three docks nearest the marina entrance (Docks A, B, and C) offer in-slip sanitary pump-outs. These docks (Docks A, B, and C) also have in-slip diesel fueling. All pump-out and fueling activites shall be performed by trained marina staff. Spill prevention and containment plans shall be prepared and implemented by the marina staff.

2.1.6 Reconfiguration Perimeter

A Reconfiguration Perimeter has been established and is shown on the accompanying permit drawings. The Reconfiguration Perimeter encompasses the entire berthing area within the marina. The proposed Reconfiguration Perimeter would allow Discovery Bay Resort & Marina limited flexibility to modify the widths and lengths and make slight changes in the locations of



the docks and piles within the Reconfiguration “envelope” to meet any field conditions encountered during construction, ongoing maintenance, and replacement needs of the floats and/or changes in the needs of Discovery Bay Resort & Marina.

The Reconfiguration Perimeter, however, would not allow Discovery Bay Resort & Marina to extend beyond that area presently being approved, nor to exceed 500 boats slips or the square footage of floats being approved. The net effect would be to encourage safer use, management and future maintenance by allowing for the minor adjusting of the widths, lengths and/or locations of the structures.

2.1.7 Construction Methodology

Construction of the Discovery Bay Marina basin will be performed under dry conditions, to the extents possible, using land based excavation and earth moving equipment. Flow through the Caño Madre Vieja will be confined to mangrove areas or temporarily diverted back into the Rio Culebrinas upstream of the project site. The mouth of the Caño will be plugged to prevent flow into the excavation from the Aguadilla Bay. If found to be geotechnically suitable, the material excavated from the marina basin construction will be reused for levee and upland fill.

The existing entrance structures will be reshaped and extended using land based construction methods. The existing armor stone will be removed as necessary and stockpiled for reuse. Land based equipment will be used to extend the core, underlayer, and sideslope armor of the jetty to the offshore terminus. The structure crest has been designed to be sufficiently wide to accommodate typical land based equipment to facilitate land based construction.

Erosion and sediment control will be maintained with floating turbidity curtains around the entrance jetties during construction and with silt fencing around the marina basin excavation. Water collecting in the marina basin will be routed to a ponding area where sedimentation and clarification of the water will occur prior to discharge.

2.1.8 Construction Sequence

The construction of the Discovery Bay Marina will begin with the installation of erosion and sediment control measures around the perimeter of the area to be disturbed during construction. With erosion and sediment control in place, the site may be cleared of vegetation and existing structures which consist primarily of culverts under unpaved access roads.

Basin excavation will begin following site clearing and structure demolition, and the construction of a settling/collection basin. Hydraulic pumping into the settling/collection basin is required to maintain dry conditions. Excavation of a perimeter trench to finish grade will enable construction of the marina bulkheads and interior shore protection revetments while basin excavation is ongoing. The marina entrance channel will be dredged following the installation of a floating turbidity curtain. Jetty reshaping and extension may then proceed with the armor stone extending to the channel bottom.

Following basin excavation, bulkhead and revetment construction, and jetty reshaping and extension, the marina entrance may be fully connected to Aguadilla Bay, allowing the basin to



flood. The marina dock guide and fender piles will be driven from floating barges followed by floating dock and utility installation.



Figure 2-1: Channel Depth Schematic

Figure 2-2: Existing Shoreline Structures

South Jetty

North Jetty

Cano Madre Vieja



3 EXISTING CONDITIONS

3.1 METEOROLOGIC AND OCEANOGRAPHIC INFORMATION

The parcel of land proposed for the development of the Discovery Bay Resort and Marina is located on the northwest coast of Puerto Rico, bordered by the towns of Aguadilla to the northeast and the Espinar District of Aguada to the southwest, as shown in Figure 3-1. The Aguadilla Bay lies northwest of the site and the Rio Culebrinas and its surrounding floodplain border the parcel on the southeast. The majority of the parcel lies within the Rio Culebrinas floodplain and consists of low-lying fields intermixed with patches of upland forested areas. The Caño Madre Vieja, meanders through the fields and exits to the Aguadilla Bay through a tidally influenced lagoon bordered by black mangroves. An earthen jetty consisting of fill material armored with large stone stabilizes the north side of the Cano Madre Vieja outlet. A small rubble-mound groin stabilizes the southern side of the outlet during daily tidal fluctuations but is readily overtopped during periods of elevated water levels.

Severe rainfall events cause the Rio Culebrinas to periodically overflow its banks, inundating the fields and flooding sections of both Aguadilla and Aguada. Flood control structures, in the form of a levee system as shown in Figure 3-1, have been proposed by the U.S. Army Corps of Engineers to provide protection for the towns of Aguadilla and Aguada during flood events. Cordeco Land Services Corp proposes constructing these flood control structures in conjunction with the Discovery Bay Resort and Marina project.

The impacts of this periodic flooding, in additional to other environmental site conditions, including water levels, currents, bathymetry, winds, waves, tropical systems, and littoral transport, must be taken into consideration. Understanding these issues is important in the development of the project and the evaluation of design parameters.

3.1.1 Water Levels and Currents

Water level fluctuations and currents in Aguadilla Bay are due to astronomical tides and meteorological events. Astronomical tides are the rising and falling of the water that results from the gravitational attraction of the Moon, Sun and other astronomical bodies acting upon the Earth. The following paragraphs describe the astronomical tides and currents at the project site. Meteorological forcing of water levels due to tropical systems is described in Section 3.1.4 below.

Tides

Tides in the project region are semi-diurnal with two high tides and two low tides per day. The tidal datum relationships, referenced to Mean Lower Low Water (MLLW), are listed in Table 3-1. Figure 3-2 shows tide data measured at the site plotted with predicted Aguadilla and Mayaguez water levels from October 2004. The spring tide range at the project site is on the order of 0.34 meters. See Appendix X for additional information regarding the determination of the tidal datum at Discovery Bay.



Table 3-1: Tidal Datum Relationship

Datum Discovery Bay (meters)

Mean Higher High Water (MHHW)

0.342

Mean High Water (MHW) 0.298

Mean Tide Level (MTL) 0.169

Mean Sea Level (MSL) 0.166

Mean Low Water (MLW) 0.040

Mean Lower Low Water (MLLW)

0.000

Currents

Current velocities and directions measured at the project site are shown in Figure 3-3. Peak current velocities are on the order of 0.15 to 0.20 m/s and move in a direction parallel to shore. For additional information regarding the currents at Discovery Bay, see Appendix X.

3.1.2 Winds

Hourly wind data measured at the Aguadilla Airport is available for the period from 1961-1970. The directions and intensities depicted as a wind rose are shown in Figure 3-4. Analysis of the wind statistics shows 72.8% of the winds at Aguadilla Airport are from 67.5 through 112.5 degrees (SE through NE) reflecting the dominance of the Caribbean trade winds. Directions considered significant to conditions at the project site are from 247.5 through 360 degrees (WSW through N) and contributed 3.4% of the wind occurrences. Tropical storms and hurricanes are not reflected in the airport wind record. This is likely due to power outages and gauge damage during the storm event. The highest recorded wind speed for the range of directions approaching the project site is 8m/s with a frequency of occurrence of approximately 0.1% during the recorded period. For additional information regarding winds at Discovery Bay, see Appendix X.

3.1.3 Waves

The U.S. Army Corps of Engineers, through the Wave Information Studies (WIS) program, maintains a database of wave hindcasts generated using wind and wave models. Histograms for hindcast locations west and north of Puerto Rico indicate that the prevailing wave direction is from the east at those locations. The project site, located along the shoreline of Aguadilla Bay, is sheltered from the prevailing Atlantic Ocean waves.



For the identified regional WIS stations, the most frequent wave direction is east-northeast (67.5ºN) with the directional sector north-northwest (337.5ºN) to east (90ºN) (going clockwise) accounting for 99 percent of all occurrences. Due to the sheltering of the project site by the mainland, only offshore waves from the directional wave sector north-northwest (337.5ºN) to northeast (45ºN) are expected to contribute to waves at the project site.

The U.S. Army Corps of Engineers deployed a directional wave buoy in October 2001 in Aguadilla Harbor, approximately 2.2 kilometers north-northeast of the project site. The data recorded is not continuous and the total sampling duration during the 3 years from October 2001 through March 2004 is 414.5 days. The wave rose generated from this data is shown in Figure 3-5. The wave rose indicates that the most frequent wave direction at Aguadilla Harbor is from the northwest. However, this directional wave information is not directly transferable to the Discovery Bay project site. The project site is more exposed to waves approaching from the north and east as they refract around the northwest coast of Puerto Rico. Since refraction of waves approaching the site is relatively minor because of the milder nearshore slope and uniform contours (Figure 3-5), more northerly wave predominance is expected at the site than in the waves approaching Aguadilla Harbor. For additional information regarding waves at Discovery Bay, see Appendix X.

3.1.4 Tropical Systems

Puerto Rico is located in a region of the Caribbean that experiences frequent hurricanes and tropical storm activity. The island lies along a track where storms generally cross into the Atlantic Ocean from the Caribbean Sea or continue on their westward track to the United States or the Gulf of Mexico. Passing storms can cause elevated water levels and wave heights that may lead to extensive damage to coastal structures. Large swells radiating from tropical systems typically result in significant erosion upon making landfall.

According to the Federal Emergency Management Agency (FEMA) Flood Insurance Study (FIS) for Puerto Rico, published in April 2005, while the Rio Culebrinas Basin may be subject to flooding from hurricane-induced tidal surges, riverine flooding caused by rainfall events, including tropical storm and weather front passage, is considered more significant in coastal areas of the basin. This may be attributed to island geometry in conjunction with the typical east-to-west storm track in this region, resulting in hurricane tides on the western coast of Puerto Rico being smaller than elsewhere on the island.

Since 1950, nine hurricanes and tropical storms, shown in Figure 3-6 as provided by NOAA Coastal Services Center (2005), have passed within 100 kilometers of Aguadilla, Puerto Rico. The corresponding peak wind speeds for these storms are given in Table 3-2.



Table 3-2: Hurricanes and Tropical Storms Passing within 100 kilometers of Aguadilla, Puerto Rico from 1950 to 2003

Wind Speed

Year Storm Name m/s mph Category

1950 Baker 18 40 Tropical Storm

1956 Betsy 40 90 Category 1

1963 Edith 34 75 Category 1

1975 Eloise 22 50 Tropical Storm

1979 Frederic 22 50 Tropical Storm

1981 Gert 27 60 Tropical Storm

1996 Hortense 36 80 Category 1

1998 Georges 49 110 Category 2

2000 Debby 34 75 Category 1

Storm Surge

Storm events affect water levels due to the frictional effects of wind blowing over the water causing a “setup” or “setdown” of the surface, known also as storm surge. Atmospheric pressure differentials, often accompanying tropical storm events, also contribute to storm surge.

As the path of hurricanes and tropical storms historically move across Puerto Rico from east to west, storm surges are generally lower on the western side of Puerto Rico in contrast to other parts of the island. Storm surge elevations have been calculated by the Federal Emergency Management Agency (FEMA) using the Sea, Land, and Overland Surge from Hurricanes (SLOSH) model. Table 3-3 shows the storm surge elevations predicted by the SLOSH model results combined with their probability of occurrence in the vicinity of the project area. Stillwater elevations, also given in Table 3-3, include the effects of wave set-up, seasonally high water, and sea level rise in addition to surge elevation tidal effects.



Table 3-3: Storm Surge Elevation

Surge Elevation Stillwater Elevation Location

(Latitude/Longitude) 10-Year

(m MSL)

100-Year

(m MSL)

500-Year

(m MSL)

100-Year

(m MSL)

Cell 63 - Aguadilla Grid

(18.4462° / 67.1590°)

0.2 0.6 0.9 1.5

Cell 68 - Aguada Grid

(18.4171° / 67.1617°)

0.2 0.6 0.9 1.5

Storm Waves

The annual maximum wave height was extracted from the 20-year (1980 to 1999) wave hindcast data at WIS Station L1-8. Analysis of the incident direction of the historical extreme waves suggests that extreme waves originate from directions east of north. The results are shown in Table 3-4.

Table 3-4: Extreme Wave Statistics for WIS Station L1-8 (19N, 67W)

Return Period

(year)

Significant Wave Height

(m)

5 6.5

10 8.1

25 10.5

50 12.5

For additional information regarding tropical systems in the vicinity of Discovery Bay, see Appendix X.

3.2 COASTAL PROCESS MODELING

Coastal processes at Discovery Bay were evaluated using analytical and numerical modeling techniques. Evaluated processes include normal and extreme waves, shoreline change and alongshore sediment transport, and river sediment transport. The following sections describe the analyses of these processes. For additional information regarding the Coastal Process Modeling performed, see Appendix X.



3.2.1 Wave Modeling

Waves at the Discovery Bay Resort and Marina project site are comprised of offshore swells that propagate to the nearshore and locally generated wind-waves. The offshore wave conditions discussed in Section 3.1.3 are transformed to the project site using the Nearshore Spectral Wave (NSW) module of the MIKE21 hydrodynamic model suite. Locally generated wind-waves are evaluated for fully developed conditions using equations set forth in the USACE Coastal Engineering Manual (CEM) (USACE, 2003).

Offshore Wave Transformation

The MIKE 21 NSW model describes the propagation, growth, and decay of waves. The model includes the effects of refraction and shoaling, energy dissipation due to bottom friction and wave breaking, and effects of wave-current interaction. The model determines the significant wave height, mean wave period, and mean wave direction at locations within the model domain.

Normal Conditions

The wave climate was grouped into five wave height, five period and 16 direction combinations resulting in 400 total wave scenarios. Review of the statistical bins shows that 64.0% of wave occurrences are from the east though east-northeast directions, which do not refract sufficiently to reach the project site. Offshore waves that reach the project site are comprised of 29 statistical bins resulting in a cumulative percent occurrence for the studied cases of 34.4% as summarized in Table 3-5. Nearshore wave results have been extracted at a location offshore of the existing jetty.

Table 3-5: Operational Wave Statistics based on WIS hindcast data for NSW model

Offshore Nearshore

Case Wave Height

(m)

Peak Wave Period

(s)

Mean Direction

(degrees N)

Occurrence

(%)

Wave Height

(m)

Mean Wave Period

(s)

Mean Direction

(degrees N)

1 1.5 6 45 1.112 0.05 5.0 354.5 2 1.5 8 337.5 0.126 1.27 6.7 335.7 3 1.5 8 0 0.361 0.68 6.7 342.6 4 1.5 8 22.5 1.274 0.17 6.7 348.5 5 1.5 8 45 5.401 0.10 6.7 349.7 6 1.5 10 337.5 0.264 1.29 8.3 335.2 7 1.5 10 0 0.576 0.61 8.3 339.4 8 1.5 10 22.5 1.572 0.17 8.3 341.9 9 1.5 10 45 3.590 0.11 8.3 343.2

10 1.5 12 337.5 0.134 1.33 10.0 334.7 11 1.5 12 0 0.312 0.59 10.0 338.0



12 1.5 12 22.5 0.892 0.15 10.0 336.6 13 1.5 12 45 2.657 0.11 10.0 337.5 14 1.5 14 22.5 0.164 0.15 11.7 335.6 15 1.5 14 45 0.560 0.10 11.7 335.9 16 2.5 6 45 0.842 0.07 5.0 354.5 17 2.5 8 22.5 0.382 0.29 6.7 348.5 18 2.5 8 45 2.269 0.17 6.7 349.7 19 2.5 10 337.5 0.224 2.16 8.3 335.2 20 2.5 10 0 1.008 1.01 8.3 339.4 21 2.5 10 22.5 2.036 0.29 8.3 341.9 22 2.5 10 45 2.701 0.19 8.3 343.2 23 2.5 12 337.5 0.377 2.21 10.0 334.6 24 2.5 12 0 1.079 0.97 10.0 338.0 25 2.5 12 22.5 1.813 0.26 10.0 336.6 26 2.5 12 45 1.697 0.18 10.0 337.5 27 2.5 14 0 0.165 1.06 11.7 336.9 28 2.5 14 22.5 0.316 0.24 11.7 335.6 29 2.5 14 45 0.541 0.17 11.7 335.9

Total 34.440 <0.75 All All 0.16

The directional spread of the nearshore wave directions at the project site resulting from the wave transformation modeling is superimposed upon the wave rose for Aguadilla Harbor shown in Figure 3-5. These results show that the nearshore wave direction at the project site is more northerly relative to the measured data at Aguadilla Harbor. The offshore waves approaching from the north-northwest through the northeast quadrants are transformed into a much narrower nearshore directional band of 335 to 355 degrees (N = 0 degrees) due to the refraction effects of the landform and nearshore bathymetry. Analysis of nearshore wave heights indicates that waves greater than 1m have less than 3% frequency of occurrence at the project site.

Storm Waves

Storm waves typically govern structural design considerations. Storm wave conditions at the site are evaluated using the MIKE21 NSW model. The 25 and 50 year extreme wave heights, correlated with the relevant storm surge levels described in Section 3.1.1, are extracted from the 20-year (1980 to 1999) wave hindcast data at WIS Station L1-8, described in Section 3.1.3 and are transformed to the project site.

Incident wave direction is critical to the transformed wave height at the project site. The north-south orientation of the project shoreline results in larger nearshore waves originating from westerly directions. However, analysis of the incident direction of the historical extreme waves suggests that extreme waves originate from directions east of north. The incident wave directions for the extreme wave cases were taken to be 0 degrees (N), 22.5 degrees (ENE), and



45 degrees (NE), producing a set of 6 storm wave scenarios to be transformed to the nearshore region using the NSW wave model.

Table 3-6 shows the results of the storm wave transformation modeling extracted near the 4m contour offshore of the project site, representing the expected terminus of the proposed entrance structures. Wave transformation model results indicate that waves from the north result in the largest waves at the project site. The 25-year storm is capable of producing 3.4m waves while the 50-year storm may produce waves on the order of 3.5m.

Table 3-6: Extreme Wave Transformation Results

Offshore Nearshore

Return Period

(Years)

Wave Height

(m)

Wave Period

(s)

Mean Wave Direction

(degrees N)

Wave Height

(m)

Wave Period

(s)

Mean Wave Direction

(degrees N)

25 10.5 14 45.0 0.81 14 327.1

25 10.5 14 22.5 1.41 14 327.4

25 10.5 14 0.0 3.37 14 328.1

50 12.5 14 45.0 0.96 14 327.2

50 12.5 14 22.5 1.67 14 327.6

50 12.5 14 0.0 3.47 14 328.3

Locally Generated Wind Waves

Locally generated seas may result in a wave environment at the project site that exceeds the desired operational conditions. The conditions at the project site may be influenced by locally occurring winds that differ significantly in amplitude and direction from the regional conditions. Frontal passage and air temperature gradients are two of the conditions that may result in local wind fields differing from the regional wind fields captured in the WIS hindcasting data.

The locally generated waves may be evaluated using wind readings taken from the Aguadilla Airport, as describe in Section 3.1.2. Due to the local shoreline orientation, winds originating from 247.5 degrees through 360 degrees (0 degrees = N) are capable of generating waves at the project site. Statistical analysis of the wind records shows 3.4% of the winds at Aguadilla Airport are within this directional range. Table 3-7 shows the frequency of occurrence for winds from 247.5 degrees through 360 degrees from 1961-1970. The highest recorded wind speed for this range of directions is 8m/s with a frequency of occurrence of approximately 0.09% during



the recorded period. Using methodologies outlined in the USACE CEM (USACE, 2003), local wave heights may be estimated assuming that the wave is fully developed (wind blows for a sufficient duration over a long fetch). The fully developed wave height for an 8m/s wind speed is 1.90m with a period of 7.3 seconds. These values are conservative as the fetch required to fully develop a wave under these conditions is over 100km and is not expected at the project site.

Table 3-7: Wind Wave Frequency of Occurrence

Wind Speed

(m/s)

Frequency of Occurrence

(%)

Fully Developed Wave Height

(m)

0-2 0.98% 0.10

2-4 1.89% 0.43

4-6 0.45% 1.02

6-8 0.09% 1.90

3.2.2 Shoreline Change and Sediment Transport Analysis

This section described the existing shoreline change and sediment transport patterns in the project area.

Previous Studies

Jack Morelock of the University of Puerto Rico at Mayagüez has conducted long term studies of shoreline change along the Puerto Rico coast. In his 1978 publication “Shoreline of Puerto Rico” he reviewed the condition of the coast from Aguadilla to Punta Gorda, indicating that at that time continuous beach was present in this area with erosion existing from Río Culebrinas southwest to Punta Gorda. No erosion was present at the project site near Caño Madre Vieja.

Morelock updated his 1978 publication with more recent information in a 2003 field trip guide published online. He noted that from Río Guayabo, Aguada to Aguadilla, including the project site, the shore faces to the northwest in most of the area, leading to a different wave regime and local coastal processes than found for the remainder of the west coast. The coast is exposed to both swell and high amplitude waves that come from the north and northwest and the insular platform is narrower. A net loss of sand was measured at Aguadilla from 1963 to 1987. Low to moderate erosion rates occurred along the beach during this period. No shoreline changes were observed along this reach from 1936 to 1964, except at a station near Río Culebrinas where erosion occurred. Major erosion also occurred from 1964 to 1978. This was caused by both tropical and extratropical storm events. Accretion occurred from 1978 to 1987.

Evans-Hamilton and GeoSea Consulting (2003) performed a Sediment Trend Analysis (STA) under contract to the US Army Corps of Engineers. This analysis was focused on identifying



sediment transport pathways in proximity to the breakwater protecting Aguadilla Harbor, constructed in 1995, which rapidly and unexpectedly filled with sand. The STA project area included the proposed project site. The sediment transport pathways near the proposed project site showed an overall south trend with nearshore reversals to the north. An overall trend of net erosion was suggested by the analysis. In addition, sampling along the beach at Parque de Colón west of the Caño Madre Vieja indicated that the mouth of the Caño is subject to infilling, with the material related to the beach sands to the south. On a conceptual level GeoSea suggests that sediments are transported south in the offshore by deep ocean currents, then move shoreward and northward in a nearshore counterflow. Beach face sediments are also subject to some wave-driven littoral transport from north to south, although GeoSea suggests that this transport is limited to the dominance of wave activity at the beach face rather than the nearshore northward flowing countercurrent.

Shoreline Change Analysis

To evaluate the existing conditions at the site, a shoreline change analysis was conducted using historical aerial photographs. Photographs from 1963, 1977, 1985, 1989, 1995, 2000 and 2006 were scanned and georectified. The wet/dry line in each photo was identified to represent the shoreline. The location of this line can be influenced by a variety of factors including time of year and tidal stage. Seasonal influences affect the wave climate, periodically eroding and rebuilding the beach. In addition, the wet/dry line will be further landward during high tide than during low tide. The exact date and time of these photographs is unknown; therefore tidal and seasonal influences cannot be determined in the analysis. The resolution and quality of some of the photographs obscures or distorts the location of this area of the shoreline. Considering these various influences there is a margin of error of +3 meters on the shoreline location for each photograph. A system of transects at 3 meter intervals was developed and the distance from a baseline to the shoreline was computed for each transect. These distances were then compared for each date to develop an estimate of the historical shoreline change rates for the site. Results are presented in Figure 3-7.

The existing jetties were constructed in the period between the 1977 and 1985 photographs. The area between the two structures is the mouth of the Caño Madre Vieja which is subject to periodic infilling and scouring. The project shoreline was divided into two littoral cells. One cell is the 250 meters of shoreline north of the jetty structures at which point the shoreline curves north and east. The second cell is the 1150 meters of shoreline south of the jetties. This cell is terminated approximately 400 meters north of the Río Culebrinas. In Figure 3-7 the dark purple line represents the period before the structures from 1963 to 1977. For comparison purposes this portion of shoreline was analyzed using the same divisions as the post-structure littoral cells. During this period the shoreline appears to have remained relatively stable or slightly erosive as the analysis shows a loss of -0.14 m/yr in the north cell and -0.21 m/yr in the south cell. This is within the margin of error and may be due to tides or seasonality. The long term shoreline change rates since the construction of the structures, presented in Table 3-8 (shown in red on Figure 3-7), show a relatively stable shoreline with a possible small amount of net erosion as shown in the results depicting a rate of -0.05 m/yr north of the jetties and -0.15 m/yr south of the jetties. These small shoreline change rates are within the margin of error determined for the analysis.



Table 3-8: Average Historical Shoreline Change Rates Near Caño Madre Vieja

1963-1977

1977-1985

1985-1989

1989-1995

1995-2000

2000-2006

Overall 1985-2006

Shoreline Change Rate

Location (m/yr) (m/yr) (m/yr) (m/yr) (m/yr) (m/yr) (m/yr)

Average Appx 250 m North of

Jetties -0.14 0.81 -0.40 0.31 -0.09 -0.13 -0.05

Average Appx 1150 m South of

Jetties

-0.21 0.84 -0.80 0.80 -1.28 0.28 -0.15

During the period from 1963 to 2006, four tropical storms and four hurricanes passed within 100 km of the project site. Storm waves combined with storm surge typically associated with tropical storms and hurricanes, cause accelerated erosion and reshaping of the beach profile with sediments being transported offshore. The periodic erosion and accretion indicated in Table 3-8 is consistent with erosion caused by storm events followed by accretion during normal wave conditions.

The periodic reversals and accumulation on both the north and south sides of the existing structures are also somewhat consistent with the findings of the STA analysis. During periods of wave domination, net transport in the nearshore and beach face would be to the south in this area, and accumulation on the shoreline north of the jetties would be expected. This may explain the shoreline behavior during the 1985-1989 and 1995-2000 time periods. When waves do not dominate, transport may be driven by nearshore northward countercurrents bringing sediments north from the Río Culebrinas towards the jetty, potentially explaining the 1989 to 1995 accumulation on the south side of the jetties. Because the south jetty is low-profile and easily overtopped, some material may also be transported from the south into the Caño Madre Vieja mouth. These sediments as well as sediments brought to the mouth from upland sources by the Caño flows are consistent with the cycle of periodic infilling in the mouth of the Caño Madre Vieja.

The shoreline orientation northwest and southeast of the project site suggest a wave driven littoral drift toward the south while an ambient flow field causes a littoral drift to the north. While the long term shoreline change rates in the area have been slightly erosional from 1985 to 2006, as summarized in Table 3-8, more erosion overall has been observed at the south side of the armored inlet. This suggests that wave conditions are slightly dominant. Severe erosion south of the inlet has not been observed in the long term. However, if wave action dominates, some erosion south of the south jetty would be expected. Conversely, during periods of mild wave activity, nearshore currents would be expected to transport material northward, at least partly replenishing the beaches south of the south jetty.



3.2.3 River Sediment Load Analysis

The project site is located adjacent to the Caño Madre Vieja and Río Culebrinas, as shown in Figure 3-1. With heavy rains and flooding, sediment is washed down from the mountains into the river plains with some overbank flows passing through the project area. An analysis has been undertaken to estimate the sedimentation potential of the Río Culebrinas and Caño Madre Vieja.

For this study, limited hydrodynamic and sediment characteristics data is available for model development and calibration. The potential for sedimentation in the Discovery Bay Marina is characterized based on empirical and analytical methods.

Drainage Area and Flow Characteristics

The US Geological Survey (USGS) currently maintains two gages on the Río Culebrinas. The location closest to the project site is Margarita Dam. The second gage is located at Highway 404 near the town of Moca, approximately 11 km upstream of the Margarita Dam gage. The entire Río Culebrinas watershed has been estimated at approximately 295 square kilometers. The drainage area at the Moca gage is approximately 184 sq km; at the Margarita Dam, the drainage area is 245 sq km.

Flow data were available at the Margarita Dam gage spanning the time period from July 1998 to April 2007. At the Moca site, flow data were available from July 1967 to April 2007. Discrete water quality measurements were also available during a number of time periods. The water quality sampling data were used to develop a correlation between the flow rate and suspended sediment concentration.

It should be noted that the three highest recorded average daily flows during the monitoring period were recorded on September 16, 17 and 18 of 2004 during Tropical Storm Jeanne. Based on FEMA characterization of discharge the flooding was comparable to a 10-Year storm event as measured at the Margarita Dam site. It is important to note the USGS record identifies a high degree of uncertainty in the average daily discharge measurements at both these gage locations.

In order to assess the flows of the Río Culebrinas and Caño Madre Vieja at the project site, drainage areas were delineated extending from the Margarita Dam to the project limits for the Culebrinas and covering the entire drainage area of the Caño Madre Vieja up to open water. Total contributing drainage areas of the Rio Culebrinas and Cano Madre Vieja were delineated to be 114 km2 and 6.2 km2, respectively.

Unit discharge from the Margarita Dam gage was multiplied by the additional drainage area to obtain the additional discharge due to that area, then added to the gauged discharge to develop a time series from July 1998 to September 2003. For the Caño Madre Vieja, the drainage area was multiplied by the unit discharge at the Moca gage. This unit discharge was selected because the gage is located in a mountainous region and significant portions of the Caño drainage area are mountainous. In addition, the unit discharges for the Moca gage were higher, providing a more conservative estimate of the flow in the Caño. The time period was selected to be consistent with the data available at the Margarita Dam, July 1998 to September 2003.



Flow Classification and Sediment Load

Once the time series of flows were established for both the Caño Madre Vieja and the Río Culebrinas, the percent exceedance curves for each were developed, for each class of flow. Flows in the Río Culebrinas would be equal to or less than 10 m3/sec 60 to 70 percent of the time. The average daily discharge in the Cano Madre Vieja is estimated to between 0 and 3 cubic meters per second (cms) for greater than 99.6 percent occurrence. The average daily discharge in the Rio Culebrinas at P.R. 115 is estimated to be less than or equal to 42.5 cms for 96.4 percent of the time.

The Haested Methods program FlowMaster was run for each class of flow at a cross-section of each water body just upstream of the marina location. Cross-sections were developed using a combination of the recent topographic survey and the channel inverts presented in the Federal Emergency Management Agency’s Flood Insurance Study (FIS) for Puerto Rico. The FlowMaster program provides water surface elevations based on the flow and cross-section. The FlowMaster model was calibrated to match flood elevations reported in the FEMA FIS. Results of the FlowMaster analysis are presented in Appendix X

The overbank areas of the Río Culebrinas between the river and the project are at approximately elevation 3.0 m. Flows with 1 to 5 % frequency of occurrence from the Rio Culebrinas may affect the marina. The marina lies along the route of the Caño Madre Vieja; therefore all classes of flows will impact the marina.



Project Site

Figure 3-1: Project Location Map (USACE Jacksonville District, 2005)

Aguadilla and Mayaguez vs. Discovery Bay

Water Level Comparison

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

10/21/040:00

10/22/040:00

10/23/040:00

10/24/040:00

10/25/040:00

10/26/040:00

10/27/040:00

10/28/040:00

10/29/040:00

10/30/040:00

10/31/040:00

Time

Wa

ter

Le

ve

l (m

MS

L)

Aguadilla Predicted Water Level Mayaguez Predicted Water Level Discovery Bay Measured Water Level

Figure 3-2: Aguadilla-Mayaguez/Discovery Bay Water Level Comparison



Measured Current Velocity and Direction

0.00

0.05

0.10

0.15

0.20

0.25

0.30

10/21/20040:00

10/22/20040:00

10/23/20040:00

10/24/20040:00

10/25/20040:00

10/26/20040:00

10/27/20040:00

10/28/20040:00

10/29/20040:00

Time

Cu

rre

nt

Ve

loc

ity

(m

/s)

0

60

120

180

240

300

360

Cu

rren

t D

irec

tio

n (

de

g)

Measured Current Velocity Measured Current Direction

Figure 3-3: Discovery Bay Measured Current

Figure 3-4: Aguadilla Airport Wind Data (1961-1970)



A: COE Wave buoy at Aguadilla BreakwatersB: Cano Jetty

A

B

N

Shore Normal to South BeachShore Normal

to North Beach

DirectionalSpread forWaves ReachingProject Location(8m depth)

DirectionalSpread forWaves reachingAguadilla WaveBuoy (17m depth)

Figure 3-5: Aguadilla Wave Rose – Measured and Predicted

Figure 3-6: Hurricanes and Tropical Storms Passing within 100 km of Aguadilla, Puerto Rico from 1950 to 2003



Shoreline Change Rates

(- erosion/+ accretion)

-30

-25

-20

-15

-10

-5

0

5

10

15

20

1 51 101 151 201 251 301 351 401 451 501

Transect Number

Sh

ore

lin

e C

ha

ng

e (

m/y

r)

1963-1977 1977-1985 1985-1989 1989-1995 1995-2000 2000-2006 Post Structure 1985-2006

North Jetty South Jetty

Figure 3-7: Historical Shoreline Change Rates Near Caño Madre Vieja



4 WITH-PROJECT CONDITIONS

4.1 IMPACTS ON COASTAL PROCESSES

The proposed project includes an inland marina that will require modification to existing coastal structures. The following sections describe the impacts of the proposed construction on coastal sediment transport, marina sedimentation, and marina flushing.

4.1.1 Longshore Sediment Transport Model

Wave-driven longshore sediment transport and the projected shoreline change rate were further assessed by evaluating the wave climate at the site and estimating the potential longshore transport rate under the action of the waves using the LITPACK module of the Mike21 suite of models. The LITPACK module computes the alongshore drift rates and the resulting shoreline change. The presence of coastal structures may be included. The LITPACK module accepts wave input in the form of time series generated from the wave event duration table comprising the percentage occurrence of each wave scenario (wave height-period-direction), which in combination form the annual wave rose.

Data from the US Army Corps of Engineers Wave Information Studies (WIS) hindcast, described in Section 3.1.3 and the transformation of these wave cases to nearshore described in Section 3.2.1, was used. Results of the wave transformation analysis for the 29 cases from wave directions in the 337.5oN to 45oN directional band account for approximately 35 percent of the total annual occurrences. The remainder of the year, offshore conditions at the WIS stations indicated wave directions that would not be expected to result in swell reaching the site. During this time, wave conditions would be dominated by local wind-generated seas, which would be expected to be generally mild. Waves resulting from the local winds were generated assuming fully developed conditions. The locally generated wind-waves were pro-rated based on their frequency of occurrence and were combined with the transformed waves to yield the combined wave rose as shown in Figure 4-1.

The model input also incorporated an ambient current field based on the anecdotal evidence of the existence of a large scale oceanographic gyre just offshore of the project site possibly as a result of the flow through the Mona Passage. The annual average rate of shoreline change was used to calibrate the model and required imposition of an ambient flow field of 0.25m/s to the north.

With-Project Conditions

The proposed marina development at Discovery Bay involves the enlargement of the existing jetty system to provide navigation access to the anticipated boat traffic. The existing north jetty is to be extended by approximately 105m along the existing alignment. The south jetty is to be extended parallel to the north jetty. The longshore sediment transport is presently interrupted by the existing jetties, suggesting that modifications to the structures may result shoreline conditions similar to the existing conditions. Historical sedimentation rates with the existing structures at a similar orientation suggest that the proposed structures will have no long term impacts on the littoral system.



To the northwest of the jetty system, the model predicts insignificant changes to the shoreline as a result of the proposed jetty extension. The model results indicate a short term increase in the net sediment transport rate from 5,500 m3/yr to 6,000m3/yr as the system adjusts to the equilibrium condition.

To the southeast of the jetty system, the extended south jetty increases the wave shadow zone where diffraction-induced counter flow in combination with the ambient flow results in an accretion zone that stretches from the south jetty for a distance of about 90m. Beyond the shadow zone the shoreline is expected to be erosional over approximately 160m in response to the enlarged shadow zone. The maximum predicted shoreline retreat resulting from the adjustment of the equilibrium shoreline position is on the order of 5m, reflecting the deficit in the sediment volume that has accreted immediately against the south jetty. The net sediment transport rate along this stretch of shoreline is predicted to be 6,800 m3/yr.

The size of the north fillet that will be formed by the proposed jetty enlargement is estimated analytically assuming that the nearshore predominant wave approach direction is represented by 340oN. When the planform reaches equilibrium, the shoreline will be oriented such that shore normal is parallel to the predominant wave direction. At equilibrium the fillet will reach its full capacity and the southward directed longshore transport will begin to bypass the tip of the north jetty. The capacity of the full fillet is on the order of 17,000 m3. For a range of annual longshore transport rate of 2,500 to 6,000 m3/year, sediment bypassing of the north jetty will likely occur after 3 - 7 years after which infilling of the marina entrance may take place requiring maintenance dredging.

4.1.2 River Sediment Load Analysis

This section details the assessment of potential sedimentation rates from riverine flooding at the project. The project site is located adjacent to the Caño Madre Vieja and Río Culebrinas, as shown in Figure 4-2. Flood stage flows in both of these water bodies are expected to affect the proposed marina basin. All flow and sediment from the Cano Madre Vieja will be conveyed directly to the basin. A portion of the discharge and sediment load from the Rio Culebrinas will also be directed to the proposed marina during overbank flooding events. With heavy rains and flooding, sediment is washed down from the mountains into the river plains. This sediment is expected to have an impact on the maintenance requirements at the proposed marina. An analysis has been undertaken to estimate the sedimentation potential of the Río Culebrinas and Caño Madre Vieja.

Sedimentation in mobile boundary systems is a complex, three-dimensional phenomena comprised of the following processes: erosion, entrainment, transport, deposition, resuspension and consolidation of particles. Processes are driven by particle characteristics (e.g. size, density, composition, settling velocity) and hydrodynamic forcing (waves and tidal currents). Methods for evaluating the potential sedimentation and effectiveness of sediment management strategies range from simple empirical and analytical methods to fully dynamic three-dimensional coupled hydrodynamic and geomorphologic models. The appropriate method(s) are dependant on the project objectives, site specific conditions (wave or current driven forces), mode of transport (bed or suspended load), sediment characteristics (cohesive/non-cohesive), and available data.



For this study, limited hydrodynamic and sediment characteristics data is available for model development and calibration. The potential for sedimentation in the Discovery Bay Marina is characterized based on empirical and analytical methods. Conceptual mitigation strategies to reduce the potential sedimentation rate within the proposed marina are presented based on site constraints, existing topography, discharge frequency and velocity distribution (as characterized in the FLO-2D model output).


In order to assess the flows of the Río Culebrinas and Caño Madre Vieja at the proposed marina site, drainage areas were delineated extending from the Margarita Dam to the marina for the Culebrinas and covering the entire drainage area of the Caño Madre Vieja up to the marina. Total contributing drainage areas of the Rio Culebrinas and Cano Madre Vieja were delineated to be 114 km2 and 6.2 km2, respectively.



The overbank areas of the Río Culebrinas between the river and the marina are at approximately elevation 3.0 m. This indicates that only the 95-99% and 99-100% classes of flows would impact the marina from the Culebrinas side. The marina lies along the route of the Caño Madre Vieja; therefore all classes of flows would impact the marina.

Potential Sedimentation

Correlations were developed for sediment load and flow which were used to estimate the sediment load for each flow class. Reviewing of the available data suggests two distinct correlations for the sediment concentration and flow data as shown in Figure 4-3. One, with a milder slope, was developed using low flow events from the Moca gage and higher flow events at the Margarita Dam, with the exception of one outlier from Margarita Dam. The other, with a steeper slope (higher sediment concentration for a given flow) was developed using only data from the Moca gage. However, the Margarita Dam outlier appears to lie approximately along the steeper line as shown in Figure 4-3. These two curves show the difference that topography makes in sediment yields of a given watershed. The Moca gage is located just below a mountainous region of the watershed. The higher stream slopes lead to higher velocities which in turn are able to mobilize more sediment. The gage near the dam is located in a wide floodplain where velocities are slower and less apt to mobilize sediment.



The milder sloped line was used for the Culebrinas and the steeper sloped line was used for the Caño Madre Vieja. The steeper slope reflects the increased loading due to the Moca station location in the mountains. Because the Caño Madre Vieja watershed is partly mountainous, this was determined to be more applicable.

It is assumed that all discharge and sediment from the Cano Madre Vieja will be conveyed directly to the Marina. The total potential load from the Cano Madre Vieja is estimated to be from approximately 1,000 to 2,500 tons/year. Only a portion of the discharge and sediment load from the Rio Culebrinas will be directed towards the proposed marina during overbank flooding events. The channel capacity of the Rio Culebrinas is estimated to be 42.5 to 50 cms downstream of Highway 418; discharge in excess of these rates will likely result in flooding elevations great than +3 m MSL. The total potential overbank load from the Rio Culebrinas to the marina basin is estimated to be 10,000 to 40,000 tons/year.

The magnitude and rate of potential sediment deposition within the marina is a function of the grain size characteristics (particle size, settling velocity) as well as hydrodynamics in the receiving basin. During typical discharge events from the Cano Madre Vieja (0-2 cms) with low current velocity, the bed load material from the Cano will settle out, in close proximity to the point of discharge into the marina. Fine material (clay and silt) will continue to travel in suspension within the marina. During flood events from the Culebrinas, the total load will be further distributed in the marina under high velocity; fines will continue to be transported as the flood recedes until the supply of sediment is exhausted. The potential distance which a particle travels is estimated for the range of anticipated currents (as a function of the particle settling velocity and current magnitude). The area of sediment distribution and potential shoaling within the marina will increase during flood events. Where the Cano Madre Vieja discharges into the proposed marina, the total potential shoaling rate is estimated from 0.05 to 0.2 m/ year based on sediment discharge from the Cano. Additional sediment discharge from the Rio Culebrinas during flood events is estimated to result in up to an additional 0.3 m to 0.4 m/year. The predicted accretion is expected to be limited to the area immediately adjacent to the confluence of the flood flow and the marina.

Planning Considerations

Conceptual mitigation strategies to reduce the potential sedimentation rate within the proposed marina are presented based on site constraints, existing topography, discharge frequency and velocity distribution.

Water surface elevations and velocities during flood events are reviewed below. These water surface elevations and velocities provide insight into opportunities to mitigate sedimentation within the marina basin.

Water Surface Elevation and Velocity Distribution

Hydrologic and hydraulic models (HEC-HMS and FLO-2D) were developed and applied by Dr. Rafael Segarra to evaluate the potential water surface elevations and velocity distribution that may result under proposed marina development and floodway improvements for the Rio Culebrinas. The hydrodynamic model, FLO-2D, is a simplified two dimensional finite difference



model which is applied to evaluate peak water surface elevation during low frequency storm events. The peak discharge was estimated from hydrologic investigations to be 713 and 1340 cubic meters per second (cms) for 2-Year and 10-Year frequency storm events respectively (vicinity of the planned marina).

The peak water surface elevation for the 10-year storm is estimated to be approximately +6.6 m MSL west of Highway 2, decreasing to 5.3 m over a distance of 800m. West of 418, the overbank flow is directed due north from the Rio Culebrinas towards the Cano Madre Vieja. Direction of the flow path is a key consideration in potential sedimentation management strategies. The peak water surface elevation at P.R. 115 is estimated to be +5.6 m MSL. The elevation of highway 115 varies within the project vicinity from + 5.7 m MSL at the crossing of Rio Culebrinas to +3.5m MSL at the crossing of the Cano Madre Vieja. The maximum depth of water above P.R. 115 is projected to be approximately 2 m; this occurs at the crossing of the Cano Madre Vieja. During higher frequency flooding events, the general flow path from the Rio Culebrinas towards the Cano Madre Vieja would be similar, however only a portion of the highway will be overtopped. For comparison, during a 2-Year 24-Hour storm, the estimated peak water surface elevation at P.R. 115 is approximately 4.5 m. Additionally, the flow and sediment load may be directed from the main stem of the Rio Culebrinas (west of P.R. 115) into the south end of the marina.

Site Constraints – Topography, Land Ownership, Natural Resources

Figure 4-4 depicts a site map of the project area. The limits of the parcels currently under ownership and jurisdictional wetlands are identified. Spot topographic elevations are also noted. The vegetated area bound by the Rio Culebrinas to the south and Cano Madre Vieja to the north is the predominant flowpath for flooding of the Culebrinas during low frequency events. This property is currently under ownership and is a potential location for a sediment trap for overbank flow from the Culebrinas. The only land currently under ownership which is contiguous with the Cano Madre Vieja is located within the footprint of the proposed marina basin (Figure 4-4). In addition to providing valuable natural resources habitat, the wetland areas serve as a natural sediment sink allowing for deposition of sediment during overbank flooding events.

Sediment Management Strategies

Two general strategies are considered for managing potential sedimentation: (1) reduction of the sediment load in transit to the marina basin (e.g. sediment traps, diversion channels) or (2) design of the marina in anticipation of maintenance dredging in the receiving basin.

Reduction of Sediment Load to the Marina Basin

Sediment may be removed from the flows entering the marina by implementing a sedimentation basin sited in the stream bed or floodplain at a location or locations where it will be effective in settling out material and periodic maintenance of the sediment trap may be easily performed. Several site constraints influence the range of locations which may be considered.

Two existing upland areas will be regraded and planted as wetlands. These wetland areas will act as sediment traps and will capture a portion of the total sediment load. The first area is



located south of P.R. 115 and the second will be located just upstream from the confluence of the Cano Madre Vieja and the marina basin.

Potential sediment loading from the Rio Culebrinas is during flood events as described above. The predominant flow path west of Road 418, is due north from the Rio Culebrinas towards the Cano Madre Vieja. The first sedimentation basin may be constructed within existing property limits, in the floodway west of Road 418. The effectiveness of a sedimentation basin is a function of its physical dimensions, sediment characteristics, mode of transport and the hydraulic forcing which the channel is subject to.

During flood events bed load is transported short distances at high velocities and will be controlled by local hydraulic conditions. Suspended load will be transported at lower velocities; deposition will occur following flood recession or in “dead zones” at location of flow separation. Sedimentation of the coarser fraction of suspended sediment may be encouraged by increasing the cross-sectional area (lower the elevation) within the floodplain. Theoretically, the effectiveness of a sediment trap design may be determined as a function of sediment discharge capacity and shear stress. For deposition to occur over the channel reach, the following criteria must be met: (a) boundary shear stress, τ, must be less than critical shear stress, τc, and (b) sediment transport capacity (Qs) must be less than the incoming sediment load (Qin). For erosion to occur, two conditions need to be realized: (a) τ > τc and (b) Qs>Qin. Total boundary shear stress may be approximated based on the assumption of gradually varied, uniform flow, with shear stress averaged over the total wetted perimeter

Methods for evaluating sediment transport capacity are dependant on the mode of transport, availability of erodible sediment, velocity, tidal range and bed form. The Englund-Hansen formula for bed-material (total) load, derived for sand in channels with gradually varied flow, is used.

Frequency of erosion and deposition within the channel reach may theoretically be determined based for the range of discharge conditions. Critical shear stress may be estimated as a function of particle size with van Rijn’s formula (Van Rijn, 1989). The amount of sediment that will settle in the trap depends on the flow velocity, trap length and original water depth. As depth increases, theoretically the flow velocity decreases, resulting in an increase in deposition within the trap.

Alternative sedimentation basin depths and configurations were considered for reducing the potential sediment load from flood events to the marina. Based on the characterization of hydraulics and sediment transport potential described above, the potential effectiveness for each alternative was evaluated. The most effective concept calls for lowering the floodplain elevation by a depth of 2 m over an area approximately 125 m wide and a length of 200m. This primary area is expected to reduce sediment load in flood waters from the Rio Culebrinas. A second basin located prior to the confluence of the Cano Madre Vieja and the marina basin is expected to reduce sediment load in flow from the Cano Madre Vieja. Increasing the cross-sectional area of the floodplain is estimated to result in settlement of 10 to 30% of the total sediment load under a narrow range of discharge conditions (from approximately 42.5 to 120 cms). Above this discharge rate, increasing the cross-sectional area is not very effective. By lowering the floodplain elevation, it is estimated to result in a reduction in average annual total load to the



marina from the Rio Culebrinas by 2,000 to 4,000 m3/year. The areas are expected to support wetland plantings.

Modifications to the Marina Design

Further consideration is made to marina basin design. The design depth and layout of the marina in the vicinity of the confluence of the basin and the Cano Madre Vieja allows for sedimentation without affecting operations of the marina. Overdredging in this location may minimize the frequency of maintenance dredging of the channel and boat slips.

4.1.3 Marina Flushing Analysis

This section describes the methodology used to assess tidal-driven circulation and constituent flushing within the proposed Discovery Bay Marina basin.

USEPA Marina Design Guidelines

The biological health, water quality and aesthetic appeal of a semi-enclosed marina basin may be evaluated by analyzing the flushing efficiency of the target waterbody. Flushing efficiency, measured as flushing time, is defined as the amount of time required for an average water particle within the basin to travel out of the basin. Flushing time is largely dependent upon the size of the basin and how well water circulates within the basin. The U.S. Environmental Protection Agency (USEPA) has published a list of Best Management Practices (BMP’s) for marina design in the National Management Measures to Control Nonpoint Source Pollution from Marinas and Recreational Boating, (EPA 841-B-01-005, November 2001) [Section 4-1] (extracted from www.epa.gov/owow/nps/marinas.html) to promote good circulation and a well flushed marina basin under normal conditions. The management measures primarily apply to new and expanding marinas and include the following:

§ Ensure that the bottom of the marina and the entrance channels are not deeper than adjacent navigable channels

§ Consider design alternatives in poorly flushed waterbodies to enhance flushing. For example, consider an open design where a semi-enclosed design is not functional or floating wave attenuators in lieu of fixed breakwaters.

§ Design new marinas with as few enclosed water sections or separated basins as possible to promote circulation within the entire basin.

§ Consider the value of entrance channels in promoting flushing when designing or reconfiguring a marina.

§ Establish two openings at the most appropriate locations within the marina to promote flow-through currents.

§ Consider mechanical aerators to improve flushing and water quality where basin and entrance channel configuration cannot provide adequate flushing.

http://www.epa.gov/owow/nps/marinas.html)



The Discovery Bay Marina basin has been designed using the above guidelines and accepted industry standards to encourage good marina basin water quality through flushing.

Marina Flushing Standards

The USEPA and the U.S. Army Corps of Engineers (USACE) cite analyses performed by van de Kreeke and Larsen (1981) and Boozer (1979) to quantify a well flushed marina. These analyses suggest that flushing times of 2-4 days provide sufficient water circulation to maintain healthy dissolved oxygen levels and to prevent the buildup of high pollution concentrations within a marina. Estimation of a basin’s flushing time must take into consideration that each water particle within the basin has a different flushing time depending upon location; particles near the basin entrance may flush nearly instantaneously while remote particles may take days or weeks to flush. Analyses by van de Kreeke (1983) show that the average flushing time in a basin is equal to the amount of time required for the average concentration of an instantaneously injected conservative constituent (tracer particle) to be reduced to 1/e, or 36.8 percent (where e = 2.718), of the initial concentration throughout the basin. By these guidelines, a marina is considered well flushed if the initial concentration of a conservative constituent introduced instantaneously throughout the basin is reduced to an average of 36.8 percent of the initial concentration within 4 days (96 hours). These guidelines are recommended by the USEPA and are considered the industry accepted flushing standard for marinas.

Preliminary Basin Configuration

The initial marina basin configuration was developed using the following criteria: 1) provide flood protection to the Towns of Aguadilla and Aguada, 2) preserve aquatic habitat and mangroves, 3) maximize water exchange, 4) maximize the use of the basin for boats and other water-based recreational craft, and 5) maximize developable land along the southern property line.

The location of the proposed flood control levees, the undulating northern property boundary, and location of the existing mangrove areas placed a constraint on the shape of the basin. The flood control levees bound the project site on the north and south sides.

Water depths within the inner basin will range from 1.83m deep to 2.74m deep relative to Mean Sea Level (MSL), resulting in a total basin volume of approximately 350,000 m3.

Analytical Analysis

An initial analytical flushing time analysis was performed on the preliminary basin configuration to establish whether basin flushing mechanisms were sufficient to flush the basin under normal conditions. In non-riverine, semi-enclosed water basins, tidal exchange is the primary flushing mechanism. Basin flushing efficiency may, therefore, be described in simplistic terms as a relationship between basin volume and tidal exchange volume. This relationship may be extended to flushing time by factoring in the tidal period (12.4 hours for semi-diurnal tides).

Using this methodology and the tidal relationships discussed in Section 3.1.1 to convert the basin volume to low water levels (0 m MSL = 0.208 m MLLW (0.68 feet)), the average flushing time



for the preliminary basin configuration was approximately 77 hours. This analytical method provides a simplified means to determine the exchange characteristics of a semi-enclosed waterbody and typically relates to a single idealized basin, with one basin entrance. This method does not account for reintroduction of previously flushed particles and assumes a perfectly mixed basin. In simplified form, the methodology is little more than a volume replacement calculation.

Because the interaction of the tidal forcing mechanism and basin geometry at Discovery Bay Marina is more complex, a numerical modeling study was undertaken to better define the flushing efficiency and times of the marina basin. Numerical modeling incorporates the effects of inlet and basin geometry on tides and currents and provides a more accurate representation of water mixing within the basin.

Numerical Analysis

The flushing time of the marina basin was analyzed using the MIKE21 suite of hydraulic simulation modules (http://www.dhisoftware.com/mike21). The MIKE21 hydrodynamic module (HD) was used to simulate tides and tidal currents which represent the primary hydrodynamic forces at the project site. Wind and wave induced currents, which would enhance mixing and improve flushing, were excluded from the model setup to present a more conservative flushing estimate. The output of the hydrodynamic model was used with the coupled MIKE21 Advection/Dispersion module (AD) to evaluate the flushing time for the basin.

Neap tides represent the period of lowest tide range and tidal current velocity. Flushing during neap tide conditions is generally less efficient than during average tide conditions; therefore (as a conservative measure), a neap tide is selected as the primary forcing tide for the flushing model. The data collection period, October 21 through 28, 2004, was selected to correspond to a neap tide period.

The period selected for the numerical model, 12:00PM on October 21 through 12:00PM on October 25, 2004, corresponds to the period of time representing typical, neap conditions. Comparison of model results against the measured data indicates that the model is well calibrated, reproducing representative tides and tidal currents at the project location.

The basin’s flushing efficiency was modeled using the AD module of the MIKE21 suite. The AD model was initialized with a conservative (non-decaying) tracer placed throughout the basin at a uniform concentration, while the areas outside of the basin had an initial tracer concentration of zero. The model was then run using the conservative neap tide record over four days to determine the average residual tracer concentration throughout the marina basin at the conclusion of the 96 hour period.

Preliminary Basin Flushing Results

Flushing model results of the preliminary marina basin configuration indicate that basin would not achieve the desired flushing efficiency under neap tidal exchange. The average residual constituent concentration was 80% after 96 hours. This flushing inefficiency is attributed to the high length to width ratio of the basin configuration inhibiting the propagation of non-basin

http://www.dhisoftware.com/mike21)



water throughout the basin and the small tide range at the project site relative to the marina basin depths.

Groundwater Flow

Elevated groundwater flow in the surficial aquifer of the Rio Culebrinas watershed has been observed. Groundwater flow may contribute to the flushing efficiency of a basin by introducing additional flow into the waterbody. The contribution of groundwater to the interior basin and its influence on the exchange of water and flushing times within the basin were evaluated. Groundwater flow was calculated by Hydro-Environmental Associates Inc. (HEA) using the Modular Three-Dimensional Finite Difference Groundwater Flow Model (MODFLOW TM) code, developed by McDonald and Harbaugh of the U.S. Geological Survey.

Groundwater Flow Model Configuration

The MODFLOW river package was used to simulate the Rio Culebrinas. Hydraulic conductivity (permeability) values for the surficial aquifer were based on field data collected at the site by HEA representatives. In-situ hydraulic conductivity values were obtained for the site by conducting single well aquifer recovery tests (slug tests) at six (6) existing monitoring wells located at the subject site. The monitoring wells were spatially located within the area of the proposed marina. These in-situ hydraulic conductivity values were required to estimate groundwater flow volumes anticipated to discharge into the marina area.

Groundwater Flow Model Results

The results of the MODFLOW simulation indicate that the average rate of total groundwater inflow into the proposed marina basin is approximately 9,240 m3 per day while maintaining the water level in the basin at mean sea level. Based upon the model simulations, approximately 22 percent of the groundwater flow is from the vicinity of the Rio Culebrinas, approximately 36 percent of the flow is from the north originating from the Cordillera Jaicoa, approximately 9 percent of the flow is from the south, and the remaining 33 percent is upward flow from the base of the surficial aquifer.

The predicted groundwater inflow rates were distributed into twenty “flow zones”, or segments, describing the marina basin. These inflow rates were then represented in the numerical flushing model as a single point source for each of the 20 segments. Flushing model results reveal that the contribution of groundwater to flushing efficiency is minimal, reducing the residual concentration by 3% at the end of 96 hours from 80% (no groundwater) to 77% (with groundwater). Residual concentrations for the revised marina configuration are shown in Figure 4-6.

Modified Entrance Channel Configurations

To evaluate the influence on flushing efficiency of the entrance channel connecting the basin to Aguadilla Bay, the preliminary basin configuration was modeled with entrance channels of various widths, lengths, and depths. The addition of a second entrance channel to the basin was also investigated.



Channel widths ranging from 32m to 48m were compared to the initial 40m wide channel configuration. Model results indicate that flushing efficiency varies less than 5 percent when widening or narrowing the entrance channel. Entrance channel length was reduced from 120 meters long to 50 meters long. Reduced channel length improved flushing up to 10% relative to the longest channel. However, property boundaries and land use planning preclude relocation of the marina basin closer to the Aguadilla Bay and/or shortening the entrance channel. The entrance channel depths were varied to establish the influence of water depth on flushing efficiency. Deepening of the entrance channel from 2.74m to 3.66m resulted in no change in flushing efficiency.

Improved water basin circulation is often achieved through the addition of a second entrance channel. The location of the second channel a sufficient distance from the main channel is necessary to induce circulation from potential tidal elevation differences between the two entrances. A basin configuration with a second entrance channel was evaluated. Flushing efficiency was improved with the addition of the second channel by 15%. This improvement is insufficient to cause the basin to meet the desired flushing thresholds. Existing land use and property limits, in addition to potential impacts to the shoreline, precluded the addition of a second channel to the Discovery Bay Marina basin.

Results of numerical modeling of modifications to the marina entrance channel suggest that, with land use and property limit considerations, entrance channel configuration modifications do not improve basin flushing efficiency sufficiently to meet the prescribed flushing threshold requirements.

Modified Basin Configurations

Further analyses were performed to determine whether modifications to the basin geometry would influence flushing efficiency at the project location. The investigation of circular basin configurations, generated without regard for property and land use limitations, show that flushing times for a circular basin improve with reduced basin volumes. Additionally, basins with a center of mass closer to Aguadilla Bay flush better than basins with a center of mass further from Aguadilla Bay.

Subsequent model runs were performed for basin configurations generated within the limitations of property limits and existing land use, with the basin center of mass shifted closer to Aguadilla Bay than the preliminary basin configuration. Basin depths and open water configurations were modified for each case investigated. Model results suggest that a 16.6 hectare basin sited close to the marina entrance with shallow 1.7 m channels and 0.8 m open areas (total volume of 267,000m3) and a modified inlet structure that channeled flow into the basin would achieve the desired flushing parameters. However, the water depths and shape of this naturally flushing scenario do not meet the project’s program objectives in terms of the projected number of boat slips and the desired basin and land use.

Mechanical Flow Augmentation

To improve basin flushing efficiency, in addition to that generated by tidal forcing, a mechanical flow augmentation system was considered. Flow augmentation may be achieved through



mechanical means that include aeration systems, current induction systems, and pumping systems. Aeration systems generally consist of bottom-mounted bubblers that improve dissolved oxygen levels while promoting local mixing through agitation caused by the bubbles. Current induction systems generate localized current flow through the frictional effects of the movement of large plates through the water. Pumping systems introduce additional volume to the water basin from a remote source via pumps, creating positive water surface head flowing out of the marina during most tide phases, providing the benefits of both improved dissolved oxygen and flow circulation.

The long, narrow shape of the basin suggests that basin flushing efficiency may be best augmented with a mechanical pumping system. Mechanical pumping was investigated at the project basin through the addition of a point source flow to the numerical flushing model. Preliminary investigation of a circular basin suggests that volumetric flows approaching 1 m3/s will be required to flush a 17 hectare, 470,000 m3 basin.

A revised marina configuration was developed to reflect continued upland master plan development including the incorporation of the proposed marina entrance structures. The revised marina layout was modeled with the addition of a mechanical system to increase flushing efficiency in the marina basin. Analysis of these model results indicate that a continuous volumetric flow rate of 1.25 m3/s over twenty-four hours, introduced at the head of the marina, is necessary to achieve the desired flushing efficiency.

Pump Inflow Configuration

The most efficient location for the pumping inflow, in terms of total volumetric flushing, is at the head of the marina. However, this single source configuration results in localized areas of high residual concentration. Further analyses performed with the flow distributed to multiple locations throughout the marina reduced the highest residual concentrations to within 10% of the desired levels throughout the basin while maintaining the average residual concentration throughout the basin to below 37% after 96 hours, as shown in Figure 4-7.

Additional flushing model runs were conducted to assess the effect of scheduled pumping versus continuous pumping. Scenarios included daytime or nighttime pumping only (12 hrs pumping and 12 hrs no-pumping per day) and pumping during the flooding or ebbing tide phase only (6 hr alternating pumping/non-pumping over entire day). Modeling results indicate that the system behaves in a near linear manner whereby halving the daily total pumping time would require doubling the pumping rate to achieve similar performance. For all scenarios analyzed, the total daily volume of inflow required to achieve the desired rate of flushing was constant at 108,000m3/day, regardless of the pumping schedule.

Discovery Bay Marina Pumping System

The proposed Discovery Bay Marina pumping system is capable of pumping 2.52 m3/s. The capacity of the pump allows the system to meet the required pumping volume of 108,000m3/day in 12 hours, allowing the system to be idle 12 hours per day. The proposed hydraulic pumping system is driven by a diesel/electric engine that circulates hydraulic fluid through the pump to power the impellor. The pumping system draws fresh water from a gravity flow fed sump



connected to Aguadilla Bay via two pipes. The sump inflow pipes extend to the 4m contour and are aligned with the proposed jetty entrance structure. The inflow pipes will be marked with navigation aids and will each have a safety cage to prevent debris from entering the pipeline and to protect swimmers. The pump flow is piped from the sump to three areas throughout the marina, as shown in Figure 4-8, via reinforced concrete pipe. The pipeline will be sized to allow the appropriate volume of water to flow to each area of the marina. Each outlet will have a flow diffuser and one-way valves to reduce exit flow velocities into the marina to below 0.3 m/s and to prevent debris from entering the pipeline. Periodic access vaults along the pipeline route will facilitate maintenance and cleaning.



Figure 4-1: Transformed and Locally Generated Combined Wave Rose



Figure 4-2: Project Vicinity Map

y = 95.304x

R2 = 0.9273

y = 33.497x

R2 = 0.9301

0

500

1000

1500

2000

2500

3000

3500

0 10 20 30 40 50 60 70 80

Flow (cubic meters per second)

Su

sp

en

ded

Se

dim

en

t (m

g/L

)

Combined Series

Rio Culebrinas at Moca

Rio Culebrinas at Margarita Dam

Margarita Dam Outlier

Linear (Rio Culebrinas at Moca)

Linear (Combined Series)

Figure 4-3: Sediment Load – Flow Correlation



Figure 4-4: Property Boundaries and Wetland Areas



Figure 4-5: Preliminary Basin Configuration

Bathymetry (meter)Above -0.5

-1 - -0.5-1.5 - -1

-2 - -1.5-2.5 - -2

-3 - -2.5-3.5 - -3

-4 - -3.5-4.5 - -4

-5 - -4.5Below -5Land

0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6(kilometer)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

1.6

1.7

(kilo

met

er)

Concentration (Unit)Above 0.9

0.8 - 0.90.7 - 0.80.6 - 0.70.5 - 0.60.4 - 0.50.3 - 0.40.2 - 0.30.1 - 0.2

Below 0.1

0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6(kilometer)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

1.6

1.7

(kilo

met

er)

Figure 4-6: Revised Marina Configuration Bathymetry (left) and Residual Concentration with Groundwater – 96 hours (right)




0.8 - 0.90.7 - 0.80.6 - 0.70.5 - 0.60.4 - 0.50.3 - 0.40.2 - 0.30.1 - 0.2

Below 0.1

0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6(kilometer)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

1.6

(kilo

met

er)

Q = 27,000 m3/day

Q = 27,000 m3/day

Q = 54,000 m3/day

Figure 4-7: Revised Marina Configuration Residual Concentration with Distributed Pumping – 96 hours

Figure 4-8: Marina Pumping System Configuration

ENVIRONMENTAL IMPACT STATEMENT

Appendix A:

Coastal Engineering Analysis

Prepared By:

Moffatt & Nichol

1509 West Swann Ave

Suite 225 Tampa, Florida, 33606

Prepared For:

Cordeco Land Services Corp

PO Box 610

Aguada, PR 00602

November 12, 2007


Appendix A-1 November 2007

APPENDIX A: COASTAL ENGINEERING ANALYSIS

Table of Contents

A.1 METEOROLOGIC AND OCEANOGRAPHIC INFORMATION ............................... A-5

A.1.1 Water Levels and Currents...................................................................................... A-5

A.1.2 Winds ...................................................................................................................... A-7

A.1.3 Waves...................................................................................................................... A-8

A.1.4 Tropical Systems..................................................................................................... A-8

A.2 COASTAL PROCESS MODELING ........................................................................... A-16

A.2.1 Wave Modeling..................................................................................................... A-16

A.2.2 Shoreline Change and Sediment Transport Analysis............................................ A-19

A.2.3 River Sediment Load Analysis ............................................................................. A-24

A.2.4 Marina Flushing Analysis ..................................................................................... A-31

A.3 DISCOVERY BAY MARINA DESIGN ..................................................................... A-61

A.3.1 Marina Entrance.................................................................................................... A-61

A.3.2 Shoreline Treatments ............................................................................................ A-65

A.3.3 Marina Layout....................................................................................................... A-65

A.3.4 Boat Ramp ............................................................................................................ A-66

A.3.5 Dock and Pier Configuration ................................................................................ A-67

A.3.6 Reconfiguration Perimeter .................................................................................... A-68

A.3.7 Construction Methodology ................................................................................... A-68

A.3.8 Construction Sequence.......................................................................................... A-69

A.4 REFERENCES ............................................................................................................. A-75



List of Figures

Figure A.1-1: Project Location Map (USACE Jacksonville District, 2005) ..................... A-12

Figure A.1-2: Aguadilla-Mayaguez/Discovery Bay Water Level Comparison ................ A-12

Figure A.1-3: Discovery Bay Measured Current............................................................... A-13

Figure A.1-4: Aguadilla Airport Wind Data (1961-1970)................................................. A-13

Figure A.1-5: Wave Information Study (WIS) Station Histogram, Puerto Rico............... A-14

Figure A.1-6: Aguadilla Wave Rose ................................................................................. A-14

Figure A.1-7: Hurricanes and Tropical Storms Passing within 100 km of Aguadilla, Puerto Rico from 1950 to 2003................................................. A-15

Figure A.1-8: FEMA SLOSH Model Water Level Prediction Cells................................. A-15

Figure A.2-1: NSW Wave Model Nested Domain Grids .................................................. A-40

Figure A.2-2: NSW Nearshore Model Results vs. Measured Aguadilla Data .................. A-41

Figure A.2-3: Project Vicinity Map................................................................................... A-42

Figure A.2-4: Net Sediment Transport Pathways (GeoSea and Evans-Hamilton, 2003) ........................................................................................................... A-43

Figure A.2-5: Historical Shoreline Change Rates Near Caño Madre Vieja ...................... A-44

Figure A.2-6: Transformed and Locally Generated Combined Wave Rose ..................... A-45

Figure A.2-7: Historical Flows at the Río Culebrinas ....................................................... A-46

Figure A.2-8: Cano Madre Vieja Flow Classification....................................................... A-46

Figure A.2-9: Río Culebrinas Flow Classification ............................................................ A-47

Figure A.2-10: Sediment Load – Flow Correlation............................................................. A-47

Figure A.2-11: Total Sediment Load – Discharge Histogram for Cano Madre Vieja............................................................................................................ A-48

Figure A.2-12: Total Sediment Load – Discharge Histogram for Rio Culebrinas.............. A-48

Figure A.2-13: Input Hydrographs for 2-year and 10-year Frequency Storm Events......... A-49



Figure A.2-14: Peak Water Surface Elevation and Velocity Distribution for 10-Year Storm.................................................................................................. A-50

Figure A.2-15: Sediment Reduction Concept Consideration Areas (Existing Wetlands Shown) ........................................................................................ A-51

Figure A.2-16: Preliminary Basin Configuration ................................................................ A-52

Figure A.2-17: Model Domain and Bathymetry with Basin Alternative 1 ......................... A-53

Figure A.2-18: Measured Water Level ................................................................................ A-54

Figure A.2-19: Water Level Calibration.............................................................................. A-55

Figure A.2-20: Preliminary Marina Configuration Bathymetry (left) and Residual Concentration – 96 hours (right)................................................................. A-56

Figure A.2-21: Revised Marina Configuration Bathymetry (left) and Residual Concentration with Groundwater – 96 hours (right)................................... A-56

Figure A.2-22: Naturally Flushing Marina Configuration Bathymetry (left) and Residual Concentration – 96 hours (right).................................................. A-57

Figure A.2-23: Idealized Marina Configuration Bathymetry (left) and Residual Concentration with Pumping – 96 hours (right) ......................................... A-57

Figure A.2-24: Revised Marina Configuration Residual Concentration with Single Discharge Pumping – 96 hours ................................................................... A-58

Figure A.2-25: Revised Marina Configuration Residual Concentration with Distributed Pumping – 96 hours ................................................................. A-59

Figure A.2-26: Marina Pumping System Configuration ..................................................... A-60

Figure A.3-1: Channel Depth Schematic........................................................................... A-70

Figure A.3-2: Existing Shoreline Structures...................................................................... A-71

Figure A.3-3: Marina Basin Alternative 1......................................................................... A-72

Figure A.3-4: Marina Basin Alternative 2......................................................................... A-73

Figure A.3-5: Preferred Marina Basin Configuration........................................................ A-74



List of Tables

Table A.1-1: Tidal Datum Relationship ............................................................................. A-6

Table A.1-2: Wind Frequency of Occurrence at Discovery Bay ....................................... A-7

Table A.1-3: Hurricanes and Tropical Storms Passing within 100 kilometers of Aguadilla, Puerto Rico from 1950 to 2003................................................... A-9

Table A.1-4: Storm Surge Elevation ................................................................................ A-10

Table A.1-5: Extreme Offshore Wave Statistics for WIS Station L1-8 (19N, 67W) ........................................................................................................... A-11

Table A.2-1: Operational Wave Statistics based on WIS hindcast data for NSW model........................................................................................................... A-17

Table A.2-2: Extreme Wave Transformation Results ...................................................... A-18

Table A.2-3: Wind Wave Frequency of Occurrence........................................................ A-19

Table A.2-4: Average Historical Shoreline Change Rates Near Caño Madre Vieja............................................................................................................ A-22

Table A.2-5: Flow Classes, Water Surface Elevations and Sediment Load .................... A-26



A.1 METEOROLOGIC AND OCEANOGRAPHIC INFORMATION

The parcel of land proposed for the development of the Discovery Bay Resort and Marina is located on the northwest coast of Puerto Rico, bordered by the towns of Aguadilla to the northeast and the Espinar District of Aguada to the southwest, as shown in Figure A.1-1. The Aguadilla Bay lies northwest of the site and the Rio Culebrinas and its surrounding floodplain border the parcel on the southeast. The majority of the parcel lies within the Rio Culebrinas floodplain and consists of low-lying fields intermixed with patches of upland forested areas. The Caño Madre Vieja meanders through the western half of the fields and exits to the Aguadilla Bay through a tidally influenced lagoon bordered by black mangroves. A jetty consisting of fill material armored with large stone, stabilizes the north side of the lagoon outlet. A small rubble-mound groin stabilizes the southern side of the lagoon outlet during daily tidal fluctuations but is readily overtopped during periods of elevated water levels.

Severe rainfall events cause the Rio Culebrinas to periodically overflow its banks, inundating the fields and flooding sections of both Aguadilla and Aguada. Flood control structures, in the form of a levee system as shown in Figure A.1-1, have been proposed by the U.S. Army Corps of Engineers to provide protection for the towns of Aguadilla and Aguada during flood events. Cordeco Land Services Corp proposes constructing these flood control structures in conjunction with the Discovery Bay Resort and Marina project.

The impacts of this periodic flooding, in addition to other environmental site conditions, including water levels, currents, bathymetry, winds, waves, tropical systems, and littoral transport, must be taken into consideration. Understanding these issues is important in the development of the project and the evaluation of design parameters.

A.1.1 Water Levels and Currents

Water level fluctuations and currents in Aguadilla Bay are due to astronomical tides and meteorological events. Astronomical tides are the rising and falling of the water that results from the gravitational attraction of the Moon, Sun and other astronomical bodies acting upon the Earth. The following paragraphs describe the astronomical tides and currents at the project site. Meteorological forcing of water levels due to tropical systems is described in Section A.1.4 below.

Tides

The National Oceanic and Atmospheric Administration, National Ocean Service Division (NOAA/NOS) collects water level data for stations throughout the United States and the U.S. Territories including Puerto Rico. The NOAA/NOS tide station closest to the project location is located to the north at Crash Boat Beach in Aguadilla with the next closest station near Mayaguez, approximately 24 km due south (over 36 km along the shoreline).

Analysis of the historical water level data at the two stations shows similar tide ranges. Tides in this region are semi-diurnal with two high tides and two low tides per day. The tidal datum relationships, referenced to Mean Lower Low Water (MLLW), are listed in Table A.1-1.



Table A.1-1: Tidal Datum Relationship

Datum Aguadilla (meters)

Mayagüez (meters)

Discovery Bay (meters)

Mean Higher High Water (MHHW) 0.427 0.427 0.342

Mean High Water (MHW) 0.355 0.372 0.298

Mean Tide Level (MTL) 0.194 0.211 0.169

Mean Sea Level (MSL) 0.193 0.208 0.166

Mean Low Water (MLW) 0.037 0.050 0.040

Mean Lower Low Water (MLLW) 0.000 0.000 0.000

A tide and current gauge was deployed offshore of the existing jetty at the project site near the 9 meter depth contour. Water levels and currents were measured for a seven day period corresponding to a neap tide condition. Neap tides represent the period of lowest tide range and tidal current velocity. Figure A.1-2 shows the measured data plotted with the predicted Aguadilla and Mayaguez water levels from October 2004. Comparison of the data measured at the project site with predicted tide data shows that the tidal phase at Aguadilla and Mayaguez are similar to the tidal phase at the project site and that tidal amplitudes at Aguadilla and Mayaguez are 15 to 20 % higher than at the project site. Therefore, the predicted tides at the two stations may be considered representative of the tides at the project site following a 15 to 20% reduction in tidal amplitude with the resulting tidal datum relationships shown in Table A.1-1. The resulting spring tide range is on the order of 0.34 meters at Discovery Bay.

Currents

Current velocities and directions at the deployed tide gauge were measured 3.6 meters above the sea bottom, a depth judged to be representative of depth-averaged currents. The measured current data is shown in Figure A.1-3.

Peak current velocities are on the order of 0.15 to 0.20 m/s and move in a direction parallel to shore. Analysis of the tide and current data suggests that a weather front passed through the region in the latter part of the collection period as evidenced by a general rise in the tide levels and current velocities.



A.1.2 Winds

Hourly wind data measured at the Aguadilla Airport is available for the period from 1961-1970. Table A.1-2 shows the frequency of occurrence for the cardinal wind directions. The directions and intensities depicted as a wind rose are shown in Figure A.1-4.

Table A.1-2: Wind Frequency of Occurrence at Discovery Bay


Direction 0-2

(m/s) 2-4

(m/s) 4-6

(m/s) 6-8

(m/s) 8-10 (m/s)

10-12 (m/s)

12-14 (m/s)

All

22.5 0.5% 1.7% 0.6% 0.1% 0.0% - - 2.9%

45 0.5% 2.5% 2.8% 1.6% 0.3% 0.0% 0.0% 7.7%

67.5 0.6% 2.8% 5.8% 6.4% 2.5% 0.5% 0.0% 18.7%

90 3.7% 10.5% 10.9% 8.1% 2.8% 0.7% 0.0% 36.6%

112.5 4.7% 8.9% 2.8% 0.8% 0.2% 0.0% 0.0% 17.5%

135 3.5% 3.3% 0.4% 0.1% 0.0% 0.0% - 7.3%

157.5 1.4% 0.9% 0.1% 0.0% 0.0% - - 2.5%

180 1.0% 0.6% 0.1% 0.0% 0.0% - - 1.7%

202.5 0.3% 0.4% 0.2% 0.0% 0.0% 0.0% - 0.8%

225 0.1% 0.3% 0.1% 0.1% 0.0% 0.0% - 0.7%

247.5 0.1% 0.1% 0.1% 0.1% 0.0% - - 0.3%

270 0.1% 0.2% 0.1% 0.0% 0.0% - - 0.5%

292.5 0.1% 0.2% 0.1% 0.0% - - - 0.4%

315 0.2% 0.4% 0.1% 0.0% - - - 0.6%

337.5 0.2% 0.4% 0.1% 0.0% - - - 0.6%

360.0 0.3% 0.6% 0.1% 0.0% - - - 1.0%

All 17.3% 33.8% 24.5% 17.4% 5.8% 1.3% 0.1% 100.0%



Analysis of the wind statistics shows 72.8% of the winds at Aguadilla Airport are from 67.5 through 112.5 degrees (SE through NE) reflecting the dominance of the Caribbean trade winds. Directions considered significant to conditions at the project site are from 247.5 through 360 degrees (WSW through N) and contributed 3.4% of the wind occurrences. Tropical storms and hurricanes are not reflected in the airport wind record. This is likely due to power outages and gauge damage during the storm event. The highest recorded wind speed for the range of directions approaching the project site is 8m/s with a frequency of occurrence of approximately 0.1% during the recorded period.

A.1.3 Waves

The U.S. Army Corps of Engineers, through the Wave Information Studies (WIS) program, maintains a database of wave hindcasts generated using wind and wave models. Histograms for hindcast locations west and north of Puerto Rico, shown in Figure A.1-5, indicate that the prevailing wave direction is from the east at those locations. The project site, located along the shoreline of Aguadilla Bay, is sheltered from the prevailing Atlantic Ocean waves.

For the identified regional WIS stations, the most frequent wave direction is east-northeast (67.5ºN) with the directional sector north-northwest (337.5ºN) to east (90ºN) (going clockwise) accounting for 99 percent of all occurrences. Due to the sheltering of the project site by the mainland, only offshore waves from the directional wave sector north-northwest (337.5ºN) to northeast (45ºN) are expected to contribute to waves at the project site.

The U.S. Army Corps of Engineers deployed a directional wave buoy in October 2001 in Aguadilla Harbor, approximately 2.2 kilometers north-northeast of the project site. The data recorded is not continuous and the total sampling duration during the 3 years from October 2001 through March 2004 is 414.5 days. The wave rose generated from this data is shown in Figure A.1-6. The wave rose indicates that the most frequent wave direction at Aguadilla Harbor is from the northwest. However, this directional wave information is not directly transferable to the Discovery Bay project site. The project site is more exposed to waves approaching from the north and east as they refract around the northwest coast of Puerto Rico. Since refraction of waves approaching the site is relatively minor because of the milder nearshore slope and uniform contours (Figure A.1-6), more northerly wave predominance is expected at the site than in the waves approaching Aguadilla Harbor.

A.1.4 Tropical Systems

Puerto Rico is located in a region of the Caribbean that experiences frequent hurricanes and tropical storm activity. The island lies along a track where storms generally cross into the Atlantic Ocean from the Caribbean Sea or continue on their westward track to the United States or the Gulf of Mexico. Passing storms can cause elevated water levels and wave heights that may lead to extensive damage to coastal structures. Large swells radiating from tropical systems typically result in significant erosion upon making landfall.

According to the Federal Emergency Management Agency (FEMA) Flood Insurance Study (FIS) for Puerto Rico, published in April 2005, while the Rio Culebrinas Basin may be subject to flooding from hurricane-induced tidal surges, riverine flooding caused by rainfall events,



including tropical storm and weather front passage, is considered more significant in coastal areas of the basin. This may be attributed to island geometry in conjunction with the typical east-to-west storm track in this region, resulting in hurricane tides on the western coast of Puerto Rico being smaller than elsewhere on the island.

Since 1950, nine hurricanes and tropical storms, shown in Figure A.1-7 as provided by NOAA Coastal Services Center (2005), have passed within 100 kilometers of Aguadilla, Puerto Rico. The corresponding peak wind speeds for these storms are given in Table A.1-3.

Table A.1-3: Hurricanes and Tropical Storms Passing within 100 kilometers of Aguadilla, Puerto Rico from 1950 to 2003

Wind Speed

Year Storm Name m/s mph Category

1950 Baker 18 40 Tropical Storm

1956 Betsy 40 90 Category 1

1963 Edith 34 75 Category 1

1975 Eloise 22 50 Tropical Storm

1979 Frederic 22 50 Tropical Storm

1981 Gert 27 60 Tropical Storm

1996 Hortense 36 80 Category 1

1998 Georges 49 110 Category 2

2000 Debby 34 75 Category 1

Storm Surge

Storm events affect water levels due to the frictional effects of wind blowing over the water causing a “setup” or “setdown” of the surface, known also as storm surge. Atmospheric pressure differentials, often accompanying tropical storm events, also contribute to storm surge.



As the path of hurricanes and tropical storms historically move across Puerto Rico from east to west, storm surges are generally lower on the western side of Puerto Rico in contrast to other parts of the island. Storm surge elevations have been calculated by the Federal Emergency Management Agency (FEMA) using the Sea, Land, and Overland Surge from Hurricanes (SLOSH) model. Ninety-nine years of historical climatology records for tropical storms and hurricanes in the vicinity of Puerto Rico were analyzed using the joint probability method to determine cumulative probability distribution functions for central pressure depression, radius to maximum winds, forward speed, and heading. Synthetic storms were generated based on the probabilities of these parameters, which were applied to the SLOSH model. Table A.1-4 shows the storm surge elevations predicted by the SLOSH model results combined with their probability of occurrence in the vicinity of the project area, at the grid locations shown in Figure A.1-8. Stillwater elevations, also given in Table A.1-4, include the effects of wave set-up, seasonally high water, and sea level rise in addition to surge elevation tidal effects.

Table A.1-4: Storm Surge Elevation

Surge Elevation Stillwater Elevation Location

(Latitude/Longitude) 10-Year

(m MSL)

100-Year

(m MSL)

500-Year

(m MSL)

100-Year

(m MSL)

Cell 63 - Aguadilla Grid

(18.4462° / 67.1590°) 0.2 0.6 0.9 1.5

Cell 68 - Aguada Grid

(18.4171° / 67.1617°) 0.2 0.6 0.9 1.5

Storm Waves

The annual maximum wave height was extracted from the 20-year (1980 to 1999) wave hindcast data at WIS Station L1-8. An extreme value analysis was performed using the Weibull distribution. Analysis of the incident direction of the historical extreme waves suggests that extreme waves originate from directions east of north. The results are shown in Table A.1-5.



Table A.1-5: Extreme Offshore Wave Statistics for WIS Station L1-8 (19N, 67W)

Return Period

(year)

Significant Wave Height

(m)

5 6.5

10 8.1

25 10.5

50 12.5



Project Site

Figure A.1-1: Project Location Map (USACE Jacksonville District, 2005)

Aguadilla and Mayaguez vs. Discovery Bay

Water Level Comparison

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

10/21/040:00

10/22/040:00

10/23/040:00

10/24/040:00

10/25/040:00

10/26/040:00

10/27/040:00

10/28/040:00

10/29/040:00

10/30/040:00

10/31/040:00

Time

Wa

ter

Le

ve

l (m

MS

L)

Aguadilla Predicted Water Level Mayaguez Predicted Water Level Discovery Bay Measured Water Level

Figure A.1-2: Aguadilla-Mayaguez/Discovery Bay Water Level Comparison



Measured Current Velocity and Direction

0.00

0.05

0.10

0.15

0.20

0.25

0.30

10/21/20040:00

10/22/20040:00

10/23/20040:00

10/24/20040:00

10/25/20040:00

10/26/20040:00

10/27/20040:00

10/28/20040:00

10/29/20040:00

Time

Cu

rre

nt

Ve

loc

ity

(m

/s)

0

60

120

180

240

300

360

Cu

rren

t D

irec

tio

n (

de

g)

Measured Current Velocity Measured Current Direction

Figure A.1-3: Discovery Bay Measured Current

Figure A.1-4: Aguadilla Airport Wind Data (1961-1970)



Project Location

Atlantic Ocean

North

Puerto Rico

Figure A.1-5: Wave Information Study (WIS) Station Histogram, Puerto Rico

A

B

A: COE Wave Buoy atAguadilla BreakwatersB: Existing Jetty

Hourly data:a) 11/10/01 15:00 – 3/23/02 17:00 (minor gaps)b) 4/30/03 17:00 – 3/4/04 15:00

Figure A.1-6: Aguadilla Wave Rose



Figure A.1-7: Hurricanes and Tropical Storms Passing within 100 km of Aguadilla, Puerto Rico from 1950 to 2003

Figure A.1-8: FEMA SLOSH Model Water Level Prediction Cells

Project Location



A.2 COASTAL PROCESS MODELING

Coastal processes at Discovery Bay and the effects of the proposed project were evaluated using analytical and numerical modeling techniques. Processes evaluated include normal and extreme waves, shoreline change and longshore sediment transport, river sediment transport, and water circulation. The following sections describe the analyses of these processes.

A.2.1 Wave Modeling

Waves at the Discovery Bay Resort and Marina project site are comprised of offshore swells that propagate to the nearshore and locally generated wind-waves. The offshore wave conditions discussed in Section A.1.3 are transformed to the project site using the Nearshore Spectral Wave (NSW) module of the MIKE21 hydrodynamic model suite. Locally generated wind-waves are evaluated for fully developed conditions using equations set forth in the USACE Coastal Engineering Manual (CEM) (USACE, 2003).

Offshore Wave Transformation

The MIKE 21 NSW model describes the propagation, growth, and decay of waves. The model includes the effects of refraction and shoaling, energy dissipation due to bottom friction and wave breaking, and effects of wave-current interaction. The model determines the significant wave height, mean wave period, and mean wave direction at locations within the model domain.

The numerical wave model utilizes bathymetry based on the NOAA nautical charts for Puerto Rico augmented with hydrographic surveys performed by the University of Puerto Rico. A nested model domain comprised of three model grid sizes was created to model the offshore area and to achieve a fine spatial resolution for the project site. The grid resolutions for each domain, as shown in Figure A.2-1, are: 1) regional domain - 20m by 80 m, 2) medium domain - 4m by 16m, and 3) local domain - 1m by 4m.

Normal Conditions

The offshore wave hindcast discussed in Section A.1.3 was used as the offshore boundary condition in the nearshore wave model to determine the expected normal (non-storm) wave climate for the Discovery Bay vicinity. The entire set of offshore wave conditions developed for WIS station L1-8 (Figure A.1-5) were divided into five wave height classifications (<0.75m, 0.75m < 1.5m, 1.5m < 2.5m, 2.5m < 3.5m, and 3.5m < 4.5m) for five wave periods (6s, 8s, 10s, 12s, and 14s). These wave height and period combinations were grouped by wave direction into 22.5 degree bins resulting in 400 total statistical bins. Analysis of the occurrences within a sector bounded by the north-northwest to easterly quadrants shows that these combinations encompass 98.9% of all offshore wave occurrences reflecting the predominance of the easterly sectors versus the moderate westerly component of the offshore wave climate. Further review of the statistical bins shows that 64.0% of wave occurrences are either from the east though east-northeast directions, which do not refract sufficiently to reach the project site, or are waves greater than 2.5m, which are considered beyond typical operational conditions for a marina (discussed below). The resulting 29 statistical bins were established by setting a minimum frequency of occurrence of 0.1%, resulting in a cumulative percent occurrence for the studied



cases of 34.4%. The wave transformation modeling results are summarized in Table A.2-1. Nearshore wave results have been extracted in a location offshore of the existing jetty.

Table A.2-1: Operational Wave Statistics based on WIS hindcast data for NSW model

Offshore Nearshore

Case Wave Height

(m)

Peak Wave Period

(s)

Mean Direction

(degrees N)

Occurrence

(%)

Wave Height

(m)

Mean Wave Period

(s)

Mean Direction

(degrees N)

1 1.5 6 45 1.112 0.05 5.0 354.5 2 1.5 8 337.5 0.126 1.27 6.7 335.7 3 1.5 8 0 0.361 0.68 6.7 342.6 4 1.5 8 22.5 1.274 0.17 6.7 348.5 5 1.5 8 45 5.401 0.10 6.7 349.7 6 1.5 10 337.5 0.264 1.29 8.3 335.2 7 1.5 10 0 0.576 0.61 8.3 339.4 8 1.5 10 22.5 1.572 0.17 8.3 341.9 9 1.5 10 45 3.590 0.11 8.3 343.2

10 1.5 12 337.5 0.134 1.33 10.0 334.7 11 1.5 12 0 0.312 0.59 10.0 338.0 12 1.5 12 22.5 0.892 0.15 10.0 336.6 13 1.5 12 45 2.657 0.11 10.0 337.5 14 1.5 14 22.5 0.164 0.15 11.7 335.6 15 1.5 14 45 0.560 0.10 11.7 335.9 16 2.5 6 45 0.842 0.07 5.0 354.5 17 2.5 8 22.5 0.382 0.29 6.7 348.5 18 2.5 8 45 2.269 0.17 6.7 349.7 19 2.5 10 337.5 0.224 2.16 8.3 335.2 20 2.5 10 0 1.008 1.01 8.3 339.4 21 2.5 10 22.5 2.036 0.29 8.3 341.9 22 2.5 10 45 2.701 0.19 8.3 343.2 23 2.5 12 337.5 0.377 2.21 10.0 334.6 24 2.5 12 0 1.079 0.97 10.0 338.0 25 2.5 12 22.5 1.813 0.26 10.0 336.6 26 2.5 12 45 1.697 0.18 10.0 337.5 27 2.5 14 0 0.165 1.06 11.7 336.9 28 2.5 14 22.5 0.316 0.24 11.7 335.6 29 2.5 14 45 0.541 0.17 11.7 335.9

Total 34.440 <0.75 All All 0.16

All model runs for operational conditions were conducted with the water surface at Mean Sea Level (MSL). Both wave-current interaction and the effect of wave breaking on the mean wave period were excluded from the model computations; the effect of bottom dissipation on the mean wave period was included. The directional spread of the nearshore wave directions at the project



site resulting from the wave transformation modeling is superimposed upon the wave rose for Aguadilla Harbor shown in Figure A.2-2. These results show that the nearshore wave direction at the project site is more northerly relative to the measured data at Aguadilla Harbor. The offshore waves approaching from the north-northwest through the northeast quadrants are transformed into a much narrower nearshore directional band of 335 to 355 degrees (N = 0 degrees) due to the refraction effects of the landform and nearshore bathymetry. Analysis of nearshore wave heights indicates that waves greater than 1m have less than 3% frequency of occurrence at the project site.

Storm Waves

Storm waves typically govern structural design considerations. Storm wave conditions at the site are evaluated using the MIKE21 NSW model. The 25 and 50 year extreme wave heights, correlated with the relevant storm surge levels described in Section A.1.1, are extracted from the 20-year (1980 to 1999) wave hindcast data at WIS Station L1-8, described in Section A.1.3 and are transformed to the project site.

Incident wave direction is critical to the transformed wave height at the project site. The north-south orientation of the project shoreline results in larger nearshore waves originating from westerly directions. However, analysis of the incident direction of the historical extreme waves suggests that extreme waves originate from directions east of north. Therefore, the incident wave directions for the extreme wave cases were taken to be 0 degrees (N), 22.5 degrees (ENE), and 45 degrees (NE), producing a set of 6 storm wave scenarios to be transformed to the nearshore region using the NSW wave model. Table A.2-2 shows the results of the storm wave transformation modeling extracted near the 4m contour offshore of the project site, representing the expected terminus of the proposed entrance structures.

Table A.2-2: Extreme Wave Transformation Results

Offshore Nearshore

Return Period

(Years)

Wave Height

(m)

Wave Period

(s)

Mean Wave Direction

(degrees N)

Wave Height

(m)

Wave Period

(s)

Mean Wave Direction

(degrees N)

25 10.5 14 45.0 0.81 14 327.1

25 10.5 14 22.5 1.41 14 327.4

25 10.5 14 0.0 3.37 14 328.1

50 12.5 14 45.0 0.96 14 327.2

50 12.5 14 22.5 1.67 14 327.6

50 12.5 14 0.0 3.47 14 328.3



Wave transformation model results indicate that waves from the north result in the largest waves at the project site. The 25-year storm is capable of producing 3.4m waves while the 50-year storm may produce waves on the order of 3.5m.

Locally Generated Wind Waves

Locally generated seas may result in a wave environment at the project site that exceeds the desired operational conditions. The conditions at the project site may be influenced by locally occurring winds that differ significantly in amplitude and direction from the regional conditions. Frontal passage and air temperature gradients are two of the conditions that may result in local wind fields differing from the regional wind fields captured in the WIS hindcasting data.

The locally generated waves may be evaluated using wind readings taken from the Aguadilla Airport, as described in Section A.1.2. Due to the local shoreline orientation, winds originating from 247.5 degrees through 360 degrees (0 degrees = N) are capable of generating waves at the project site. Statistical analysis of the wind records shows 3.4% of the winds at Aguadilla Airport are within this directional range. Table A.2-3 shows the frequency of occurrence for winds from 247.5 degrees through 360 degrees from 1961-1970. The highest recorded wind speed for this range of directions is 8m/s with a frequency of occurrence of approximately 0.09% during the recorded period. Using methodologies outlined in the USACE CEM (USACE, 2003), local wave heights may be estimated assuming that the wave is fully developed (wind blows for a sufficient duration over a long fetch). The fully developed wave height for an 8m/s wind speed is 1.90m with a period of 7.3 seconds. These values are conservative as the fetch required to fully develop a wave under these conditions is over 100km and is not expected at the project site.

Table A.2-3: Wind Wave Frequency of Occurrence

Wind Speed

(m/s)


(%)

Fully Developed Wave Height

(m)

0-2 0.98% 0.10

2-4 1.89% 0.43

4-6 0.45% 1.02

6-8 0.09% 1.90

A.2.2 Shoreline Change and Sediment Transport Analysis

This section describes the existing shoreline change and sediment transport patterns in the project area and the potential response to construction of coastal structures at the project site. The project area with the proposed coastal structures and proposed marina basin configuration is shown in Figure A.2-3.



Previous Studies

Jack Morelock of the University of Puerto Rico at Mayagüez has conducted long term studies of shoreline change along the Puerto Rico coast. In his 1978 publication “Shoreline of Puerto Rico” he reviewed the condition of the coast from Aguadilla to Punta Gorda, indicating that at that time continuous beach was present in this area with erosion existing from Río Culebrinas southwest to Punta Gorda. No erosion was present at the project site near Caño Madre Vieja. Beach sediments were approximately equal parts carbonate shell material, quartz and feldspar, and igneous rock fragments.

Morelock updated his 1978 publication with more recent information in a 2003 field trip guide published online. He noted that from Río Guayabo, Aguada to Aguadilla, including the project site, the shore faces to the northwest in most of the area, leading to a different wave regime and local coastal processes than found for the remainder of the west coast. The coast is exposed to both swell and high amplitude waves that come from the north and northwest and the insular platform is narrower. A net loss of sand was measured at Aguadilla from 1963 to 1987. Low to moderate erosion rates occurred along the beach during this period. No shoreline changes were observed along this reach from 1936 to 1964, except at a station near Río Culebrinas where erosion occurred. Major erosion also occurred from 1964 to 1978. This was caused by both tropical and extratropical storm events. Accretion occurred from 1978 to 1987.

Evans-Hamilton and GeoSea Consulting (2003) performed a Sediment Trend Analysis (STA) under contract to the U.S. Army Corps of Engineers. This analysis was focused on identifying sediment transport pathways in proximity to the breakwater protecting Aguadilla Harbor, constructed in 1995, which rapidly and unexpectedly filled with sand. The STA project area included the proposed project site. Sediment samples were taken on a grid throughout an area extending from approximately 2 km north of the Aguadilla Harbor to approximately 0.5 km south of the mouth of the Caño Madre Vieja and 0.5 to 1 km offshore. The STA theory uses changes in the grain-size distributions of the bottom sediments to determine the sediment transport regime. The results of the analysis are presented in Figure A.2-4. The sediment transport pathways near the proposed project site showed an overall south trend with nearshore reversals to the north. An overall trend of net erosion was suggested by the analysis. In addition, sampling along the beach at Parque de Colón west of the Caño Madre Vieja indicated that the mouth of the Caño is subject to infilling, with the material related to the beach sands to the south (represented by the Total Deposition I arrows). On a conceptual level GeoSea suggests that sediments are transported south in the offshore by deep ocean currents, then move shoreward and northward in a nearshore counterflow. Beach face sediments are also subject to some wave-driven littoral transport from north to south, although GeoSea suggests that this transport is limited to the dominance of wave activity at the beach face rather than the nearshore northward flowing countercurrent.

Shoreline Change Analysis

To evaluate the existing conditions at the site, a shoreline change analysis was conducted using historical aerial photographs. Photographs from 1963, 1977, 1985, 1989, 1995, 2000 and 2006 were scanned and georectified. The wet/dry line in each photo was identified to represent the shoreline. The location of this line can be influenced by a variety of factors including time of



year and tidal stage. Seasonal influences affect the wave climate, periodically eroding and rebuilding the beach. In addition, the wet/dry line will be further landward during high tide than during low tide. The exact date and time of these photographs is unknown; therefore tidal and seasonal influences cannot be determined in the analysis. The resolution and quality of some of the photographs obscures or distorts the location of this area of the shoreline. Considering these various influences there is a margin of error of +3 meters on the shoreline location for each photograph. A system of transects at 3 meter intervals was developed and the distance from a baseline to the shoreline was computed for each transect. These distances were then compared for each date to develop an estimate of the historical shoreline change rates for the site. Results are presented in Figure A.2-5.

The existing jetties define the littoral cells along the shoreline for this analysis. The project shoreline was divided into two littoral cell: 1) the 250 meters of shoreline north of the jetty structures at which point the shoreline curves north and east and 2) the 1150 meters of shoreline south of the jetties. The southern cell is terminated approximately 400 meters north of the Río Culebrinas. In Figure A.2-5 the dark purple line represents the period prior to jetty construction from 1963 to 1977. For comparison purposes this portion of shoreline was analyzed using the same divisions as the post-structure littoral cells. During this period the shoreline appears to have remained relatively stable or possibly slightly erosive as the analysis shows a loss of -0.14 m/yr in the north cell and -0.21 m/yr in the south cell which is well within the margin of error. The jetties were constructed in the late 1970’s which is represented by the 1977 and 1985 photographs. The area between the two structures is the mouth of the Caño Madre Vieja which is subject to periodic infilling and scouring. The green line in Figure A.2-5 shows the shoreline change rate between 1977 and 1985. During this time period the shoreline in the project vicinity accreted an average of 0.81 m/yr north of the jetties and 0.84 m/yr south of the jetties (Table A.2-4). The accretion north of the jetties may be due to wave-induced impoundment updrift of the structure. From 1985 to 1989 (light blue line), the area north of the jetties eroded at a rate of -0.40 m/yr, while the area south of the jetties eroded at -0.80 m/yr. Following that time period, there appears to have been a net reversal in sediment transport direction from 1989 to 1995. During the 1989 to 1995 time span (light purple line), the area north of the jetties accreted at a rate of 0.31 m/yr and the shoreline south of the jetties accreted at 0.80 m/yr. From 1995 to 2000 (yellow line), the area north of the jetties lost material at a rate of -0.09 m/yr and the shoreline south of the jetties lost material at -1.28 m/yr. The most recent period from 2000 to 2006 (dark blue line) appeared to have erosion north of the jetties at a rate of -0.13 m/yr and accretion south of the jetties at 0.28 m/yr. As a result of these fluctuations, the long term shoreline change rates since the construction of the structures, presented in Table A.2-4 (shown in red on Figure A.2-5), show a stable shoreline with a small rate of net of -0.05 m/yr north of the jetties and -0.15 m/yr south of the jetties. Note, however that the shoreline change rates determined from the analysis are less than the margin of error of the study.



Table A.2-4: Average Historical Shoreline Change Rates Near Caño Madre Vieja

1963-1977

1977-1985

1985-1989

1989-1995

1995-2000

2000-2006

Overall 1985-2006

Shoreline Change Rate

Location (m/yr) (m/yr) (m/yr) (m/yr) (m/yr) (m/yr) (m/yr)

Average Appx 250 m North of

Jetties -0.14 0.81 -0.40 0.31 -0.09 -0.13 -0.05

Average Appx 1150 m South of

Jetties

-0.21 0.84 -0.80 0.80 -1.28 0.28 -0.15

During the period from 1963 to 2006, four tropical storms and four hurricanes passed within 100 km of the project site. Storm waves combined with storm surge typically associated with tropical storms and hurricanes, cause accelerated erosion and reshaping of the beach profile with sediments being transported offshore. The periodic erosion and accretion indicated in Table A.2-4 is consistent with erosion caused by storm events followed by accretion during normal wave conditions.

The periodic reversals and accumulation on both the north and south sides of the existing structures are also somewhat consistent with the findings of the STA analysis. During periods of wave domination, net transport in the nearshore and beach face would be to the south in this area, and accumulation on the shoreline north of the jetties would be expected. This may explain the shoreline behavior during the 1985-1989 and 1995-2000 time periods. When waves do not dominate, transport may be driven by nearshore northward countercurrents bringing sediments north from the Río Culebrinas towards the jetty, potentially explaining the 1989 to 1995 accumulation on the south side of the jetties. Because the south jetty is low-profile and easily overtopped, some material may also be transported from the south into the Caño Madre Vieja mouth. These sediments as well as sediments brought to the mouth from upland sources by the Caño flows are consistent with the cycle of periodic infilling in the mouth of the Caño Madre Vieja.

The shoreline orientation northwest and southeast of the project site suggest a wave driven littoral drift toward the south while an ambient flow field causes a littoral drift to the north. While the long term shoreline change rates in the area have been slightly erosional from 1985 to 2006, as summarized in Table A.2-4, more erosion overall has been observed at the south side of the armored inlet. This suggests that wave conditions are slightly dominant. Severe erosion south of the inlet has not been observed in the long term. However, if wave action dominates, some erosion south of the south jetty would be expected. Conversely, during periods of mild wave activity, nearshore currents would be expected to transport material northward, at least partly replenishing the beaches south of the south jetty.



Longshore Sediment Transport Model

Wave-driven longshore sediment transport and the projected shoreline change rate were further assessed by evaluating the wave climate at the site and estimating the potential longshore transport rate under the action of the waves using the LITPACK module of the Mike21 suite of models. The LITPACK module computes the alongshore drift rates and the resulting shoreline change. The presence of coastal structures may be included. The LITPACK module accepts wave input in the form of time series generated from the wave event duration table comprising the percentage occurrence of each wave scenario (wave height-period-direction), which in combination form the annual wave rose.

Data from the U.S. Army Corps of Engineers Wave Information Studies (WIS) hindcast, described in Section A.1.3 and the transformation of these wave cases to nearshore described in Section A.2.1, was used. Results of the wave transformation analysis for the 29 cases from wave directions in the 337.5oN to 45oN directional band account for approximately 35 percent of the total annual occurrences. The remainder of the year, offshore conditions at the WIS stations indicated wave directions that would not be expected to result in swell reaching the site. During this time, wave conditions would be dominated by local wind-generated seas, which would be expected to be generally mild. Waves resulting from the local winds were generated assuming fully developed conditions. The locally generated wind-waves were pro-rated based on their frequency of occurrence and were combined with the transformed waves to yield the combined wave rose as shown in Figure A.2-6.

The model input also incorporated an ambient current field based on the anecdotal evidence of the existence of a large scale oceanographic gyre just offshore of the project site possibly as a result of the flow through the Mona Passage. The annual average rate of shoreline change was used to calibrate the model and required imposition of an ambient flow field of 0.25m/s to the north.

With-Project Conditions

The proposed marina development at Discovery Bay involves the enlargement of the existing jetty system to provide navigation access to the anticipated boat traffic. The existing north jetty is to be extended by approximately 100m along the existing alignment. The south jetty is to be extended parallel to the north jetty. The longshore sediment transport is presently interrupted by the existing jetty system, suggesting that modifications to the structures may result shoreline conditions similar to the existing conditions.

To the northwest of the jetty system, the model predicts insignificant changes to the shoreline as a result of the proposed jetty extension. The model results indicate a short term increase in the net sediment transport rate from 5,500 m3/yr to 6,000m3/yr as the system adjusts to the equilibrium condition.

To the southeast of the jetty system, the extended south jetty increases the wave shadow zone where diffraction-induced counter flow, in combination with the ambient flow, results in an accretion zone that stretches from the south jetty for a distance of about 90m. Beyond the shadow zone the shoreline is expected to be erosional over approximately 160m in response to



the enlarged shadow zone. The erosion distance varies along the shoreline from 0m to a maximum predicted shoreline retreat on the order of 5m resulting from the adjustment of the equilibrium shoreline position. This reflects the deficit in the sediment volume caused by the accretion immediately against the south jetty and is expected to take 5 to 10 years to equilibrate. The net sediment transport rate along this stretch of shoreline is predicted to be on the order of 6,800 m3/yr. The magnitude of the shoreline response may be reduced by pre-filling the fillets adjacent to the jetties with compatible beach sand.

The size of the north fillet that will be formed by the proposed jetty enlargement is estimated analytically assuming that the nearshore predominant wave approach direction is represented by 340oN. When the planform reaches equilibrium, the shoreline will be oriented such that shore normal is parallel to the predominant wave direction. At equilibrium the fillet will reach its full capacity and the southward directed longshore transport will begin to bypass the tip of the north jetty. The capacity of the full fillet is on the order of 17,000 m3. For a range of annual longshore transport rate of 2,500 to 6,000 m3/year, sediment bypassing of the north jetty will likely occur after 3 - 7 years after which infilling of the marina entrance may take place requiring maintenance dredging.

A.2.3 River Sediment Load Analysis

This section details the assessment of potential sedimentation rates from riverine flooding at the project. The project site is located adjacent to the Caño Madre Vieja and Río Culebrinas, as shown in Figure A.2-3. Flood stage flows in both of these water bodies are expected to affect the proposed marina basin. All flow and sediment from the Cano Madre Vieja will be conveyed directly to the basin. A portion of the discharge and sediment load from the Rio Culebrinas will also be directed to the proposed marina during overbank flooding events. With heavy rains and flooding, sediment is washed down from the mountains into the river plains. This sediment is expected to have an impact on the maintenance requirements at the proposed marina. An analysis has been undertaken to estimate the sedimentation potential of the Río Culebrinas and Caño Madre Vieja.

Sedimentation in mobile boundary systems is a complex, three-dimensional phenomena comprised of the following processes: erosion, entrainment, transport, deposition, resuspension and consolidation of particles. Processes are driven by particle characteristics (e.g. size, density, composition, settling velocity) and hydrodynamic forcing (waves and tidal currents). Methods for evaluating the potential sedimentation and effectiveness of sediment management strategies range from simple empirical and analytical methods to fully dynamic three-dimensional coupled hydrodynamic and geomorphologic models. The appropriate method(s) are dependant on the project objectives, site specific conditions (wave or current driven forces), mode of transport (bed or suspended load), sediment characteristics (cohesive/non-cohesive), and available data.

For this study, limited hydrodynamic and sediment characteristics data is available for model development and calibration. The potential for sedimentation in the Discovery Bay Marina is characterized based on empirical and analytical methods. Conceptual mitigation strategies to reduce the potential sedimentation rate within the proposed marina are presented based on site constraints, existing topography, discharge frequency and velocity distribution (as characterized in the flood stage FLO-2D model output).




The US Geological Survey (USGS) currently maintains two gages on the Río Culebrinas. The location closest to the project site is Margarita Dam (see Figure A.2-3). The second gage is located at Highway 404 near the town of Moca, approximately 11 km upstream of the Margarita Dam gage. The entire Río Culebrinas watershed has been estimated at approximately 295 square kilometers. The drainage area at the Moca gage is approximately 184 sq km; at the Margarita Dam, the drainage area is 245 sq km.

Flow data were available at the Margarita Dam gage spanning the time period from July 1998 to April 2007. At the Moca site, flow data were available from July 1967 to April 2007. Flows were reported in cubic feet per second and converted to cubic meters per second. The historical flow data are presented in Figure A.2-7. Discrete water quality measurements were also available during a number of time periods, indicated in Figure A.2-7. The water quality measurements included suspended sediment concentration in milligrams per liter and contemporaneous flow data. The water quality sampling data were used to develop a correlation between the flow rate and suspended sediment concentration.

It should be noted that the three highest recorded average daily flows during the monitoring period were recorded on September 16, 17 and 18 of 2004 during Tropical Storm Jeanne. Based on FEMA characterization of discharge the flooding was comparable to a 10-Year storm event as measured at the Margarita Dam site. It is important to note the USGS record identifies a high degree of uncertainty in the average daily discharge measurements at both these gage locations.

In order to assess the flows of the Río Culebrinas and Caño Madre Vieja at the proposed marina site, drainage areas were delineated extending from the Margarita Dam to the marina for the Culebrinas and covering the entire drainage area of the Caño Madre Vieja up to the marina. Total contributing drainage areas of the Rio Culebrinas and Cano Madre Vieja were delineated to be 114 km2 and 6.2 km2, respectively.



Once the time series of flows were established for both the Caño Madre Vieja and the Río Culebrinas, the percent exceedance curves for each were developed, for each class of flow. Figure A.2-8 and Figure A.2-9 illustrate the projected flow rate frequency curves. Flows in the Río Culebrinas would be equal to or less than 10 m3/sec 60 to 70 percent of the time. The average daily discharge in the Cano Madre Vieja is estimated to between 0 and 3 cubic meters per second (cms) for greater than 99.6 percent occurrence. The average daily discharge in the



Rio Culebrinas at P.R. 115 is estimated to be less than or equal to 42.5 cms for 96.4 percent of the time.

The Haested Methods program FlowMaster was run for each class of flow at a cross-section of each water body just upstream of the marina location. Cross-sections were developed using a combination of the recent topographic survey and the channel inverts presented in the Federal Emergency Management Agency’s Flood Insurance Study (FIS) for Puerto Rico. The FlowMaster program implements Manning’s equation and provides water surface elevations based on the flow and cross-section. The FlowMaster model was calibrated to match flood elevations reported in the FEMA FIS. Results of the FlowMaster analysis are presented in Table A.2-5.

Table A.2-5: Flow Classes, Water Surface Elevations and Sediment Load

Río Culebrinas Caño Madre Vieja

Flow Class

(% of typical year's peak flow) Flow

(m3/sec)

Water Surface

Elevation

(m)

Sediment Load

(mg/L)

Flow

(m3/sec)

Water Surface

Elevation

(m)

Sediment Load

(mg/L)

0-10% 1.21 0.69 40 0.04 1.59 4

10-20% 2.04 0.80 68 0.06 1.62 6

20-30% 3.04 0.92 102 0.08 1.64 8

30-40% 4.19 1.00 140 0.11 1.67 10

40-50% 5.51 1.10 185 0.14 1.69 13

50-60% 7.38 1.30 247 0.18 1.72 17

60-70% 10.04 1.40 336 0.24 1.76 23

70-80% 14.38 1.60 482 0.33 1.81 31

80-85% 18.76 1.80 628 0.44 1.86 42

85-90% 23.64 2.00 792 0.58 1.91 56

90-95% 31.45 2.50 1053 1.03 2.08 98

95-99% 45.20 3.76 1514 2.33 2.53 222

99-100% 113.12 4.00 3789 16.23 3.45 1546



The overbank areas of the Río Culebrinas between the river and the marina are at approximately elevation 3.0 m. This indicates that only the 95-99% and 99-100% classes of flows would impact the marina from the Culebrinas side. The marina lies along the route of the Caño Madre Vieja; therefore all classes of flows would impact the marina.

Potential Sedimentation

Correlations were developed for sediment load and flow which were used to estimate the sediment load for each flow class. Reviewing of the available data suggests two distinct correlations for the sediment concentration and flow data as shown in Figure A.2-10. One, with a milder slope, was developed using low flow events from the Moca gage and higher flow events at the Margarita Dam, with the exception of one outlier from Margarita Dam. The other, with a steeper slope (higher sediment concentration for a given flow) was developed using only data from the Moca gage. However, the Margarita Dam outlier appears to lie approximately along the steeper line as shown in Figure A.2-10. These two curves show the difference that topography makes in sediment yields of a given watershed. The Moca gage is located just below a mountainous region of the watershed. The higher stream slopes lead to higher velocities which in turn are able to mobilize more sediment. The gage near the dam is located in a wide floodplain where velocities are slower and less apt to mobilize sediment.

The milder sloped line was used for the Culebrinas and the steeper sloped line was used for the Caño Madre Vieja. The steeper slope reflects the increased loading due to the Moca station location in the mountains. Because the Caño Madre Vieja watershed is partly mountainous, this was determined to be more applicable.

Potential rates of sedimentation in the marina are developed using the methodology outlined in Chapter 9 of Herbich’s “Handbook of Dredging Engineering – Second Edition (2000)”. Sediment loading and the cross-sectional data at the Río and Caño confluence with the marina were used along with sediment fall velocity to estimate the amount of sedimentation caused by each class of flow. To estimate the sediment fall velocity, it was assumed that the particles carried to the marina consisted of primarily silty sand.

Figure A.2-11 and Figure A.2-12 illustrate the total potential load estimated based on limited Total Suspended Sediment (TSS) data available for each river. Total load is comprised of bed material load and wash load. No local field data was available to provide a characterization of the particle size distribution or mode of transport (suspended vs. along the bed). Several assumptions are made to estimate the total potential annual sediment load to the marina; this represents the “baseline conditions”, if no sediment strategies are implemented.

Discharge and sediment from the Cano Madre Vieja will be conveyed directly to the Marina. The total potential load from the Cano Madre Vieja is estimated to be from approximately 1,000 to 2,500 tons/year. Only a portion of the discharge and sediment load from the Rio Culebrinas will be directed towards the proposed marina during overbank flooding events. The channel capacity of the Rio Culebrinas is estimated to be 42.5 to 50 cms downstream of Highway 418; discharge in excess of these rates will likely result in flooding elevations great than +3 m MSL. The total potential overbank load from the Rio Culebrinas to the marina basin is estimated to be 10,000 to 40,000 tons/year.



The magnitude and rate of potential sediment deposition within the marina is a function of the grain size characteristics (particle size, settling velocity) as well as hydrodynamics in the receiving basin. During typical discharge events from the Cano Madre Vieja (0-2 cms) with low current velocity, the bed load material from the Cano will settle out, in close proximity to the point of discharge into the marina. Fine material (clay and silt) will continue to travel in suspension within the marina. During flood events from the Culebrinas, the total load will be further distributed in the marina under high velocity; fines will continue to be transported as the flood recedes until the supply of sediment is exhausted. The potential distance which a particle travels is estimated for the range of anticipated currents (as a function of the particle settling velocity and current magnitude). The area of sediment distribution and potential shoaling within the marina will increase during flood events. For example under a uni-directional current of 0.05 m/s a fine sand particle discharged into the marina (depth of 3.8 m) will travel a potential distance of approximately 15m. Under a current of 0.5 m/s a medium sand particle discharged into the marina will travel approximately 50m before settling to the bottom. Where the Cano Madre Vieja discharges into the proposed marina, the total potential shoaling rate is estimated from 0.05 to 0.2 m/ year based on sediment discharge from the Cano. Additional sediment discharge from the Rio Culebrinas during flood events is estimated to result in up to an additional 0.3 m to 0.4 m/year. The predicted accretion is expected to be limited to the area immediately adjacent to the confluence of the flood flow and the marina.

Planning Considerations

Water surface elevations and velocities during flood events are reviewed below. These water surface elevations and velocities provide insight into opportunities to mitigate sedimentation within the marina basin.

Water Surface Elevation and Velocity Distribution

Hydrologic and hydraulic models (HEC-HMS and FLO-2D) were developed and applied by Dr. Rafael Segarra to evaluate the potential water surface elevations and velocity distribution that may result under proposed marina development and floodway improvements for the Rio Culebrinas. The hydrodynamic model, FLO-2D, is a simplified two dimensional finite difference model which is applied to evaluate peak water surface elevation during low frequency storm events. The model has a coarse grid spacing (60m) which is appropriate for regional floodplain mapping. Variations in topography within the elements are obscured within the model. Although the model is not an appropriate design tool for evaluating site specific sedimentation management strategies, results provide a general indication of depth and velocity distribution for flood events. Figure A.2-13 illustrates discharge hydrographs for 2-Year and 10-Year frequency storm events for the Rio Culebrinas. The peak discharge was estimated from hydrologic investigations to be 713 and 1340 cubic meters per second (cms) for 2-Year and 10-Year frequency storm events respectively (vicinity of the planned marina).

Figure A.2-14 depicts the peak water surface elevation and velocity distribution based on the FLO-2D model application for 10-year 24-hour recurrence interval storm. The peak water surface elevation is estimated to be approximately +6.6 m MSL west of Highway 2, decreasing to 5.3 m over a distance of 800m. West of 418, the overbank flow is directed due north from the



Rio Culebrinas towards the Cano Madre Vieja. Direction of the flow path is a key consideration in potential sedimentation management strategies.

During the 10-year event, the peak water surface elevation at P.R. 115 is estimated to be +5.6 m MSL. The elevation of highway 115 varies within the project vicinity from + 5.7 m MSL at the crossing of Rio Culebrinas to +3.5m MSL at the crossing of the Cano Madre Vieja (Figure 8). The maximum depth of water above P.R. 115 is projected to be approximately 2 m; this occurs at the crossing of the Cano Madre Vieja. During higher frequency flooding events, the general flow path from the Rio Culebrinas towards the Cano Madre Vieja would be similar, however only a portion of the highway will be overtopped. For comparison, during a 2-Year 24-Hour storm, the estimated peak water surface elevation at P.R. 115 is approximately 4.5 m MSL. Additionally, the flow and sediment load may be directed from the main stem of the Rio Culebrinas (west of P.R. 115) into the south end of the marina.

Site Constraints – Topography, Land Ownership, Natural Resources

Figure A.2-15 depicts a site map of the project area. The limits of the parcels currently under ownership and existing jurisdictional wetlands are identified. Spot topographic elevations are also noted. The vegetated area bound by the Rio Culebrinas to the south and Cano Madre Vieja to the north is the predominant flowpath for flooding of the Culebrinas during low frequency events. This property is currently under ownership and is a potential location for a sediment trap for overbank flow from the Culebrinas. Additional area adjacent to the marina may be used to capture sediments from the Cano Madre Vieja. The sediments traps may be in the form of wetland areas. In addition to providing valuable natural resources habitat, the wetland areas serve as a natural sediment sink allowing for deposition of sediment during overbank flooding events.

Sediment Management Strategies

Two general strategies are considered for managing potential sedimentation: (1) reduction of the sediment load in transit to the marina basin (e.g. sediment traps, diversion channels) or (2) design of the marina in anticipation of maintenance dredging in the receiving basin.

Reduction of Sediment Load to the Marina Basin

Sediment may be removed from the flows entering the marina by implementing a sedimentation basin sited in the stream bed or floodplain at a location or locations where it will be effective in settling out material and periodic maintenance of the sediment trap may be easily performed. Several site constraints influence the range of locations which may be considered.

Two existing upland areas will be regraded and planted as wetlands. These wetland areas will act as sediment traps and will capture a portion of the total sediment load. The first area is located south of P.R. 115 and the second will be located just upstream from the confluence of the Cano Madre Vieja and the marina basin.

Potential sediment loading from the Rio Culebrinas is during flood events as described above. The predominant flow path west of Road 418, is due north from the Rio Culebrinas towards the



Cano Madre Vieja. The first sedimentation basin may be constructed within existing property limits, in the floodway west of Road 418. The effectiveness of a sedimentation basin is a function of its physical dimensions, sediment characteristics, mode of transport and the hydraulic forcing which the channel is subject to.

During flood events bed load is transported short distances at high velocities and will be controlled by local hydraulic conditions. Suspended load will be transported at lower velocities; deposition will occur following flood recession or in “dead zones” at location of flow separation. Sedimentation of the coarser fraction of suspended sediment may be encouraged by increasing the cross-sectional area (lower the elevation) within the floodplain. Theoretically, the effectiveness of a sediment trap design may be determined as a function of sediment discharge capacity and shear stress. For deposition to occur over the channel reach, the following criteria must be met: (a) boundary shear stress, τ, must be less than critical shear stress, τc, and (b) sediment transport capacity (Qs) must be less than the incoming sediment load (Qin). For erosion to occur, two conditions need to be realized: (a) τ > τc and (b) Qs>Qin. Total boundary shear stress may be approximated based on the assumption of gradually varied, uniform flow, with shear stress averaged over the total wetted perimeter using the following equation.

τ = γRS

τ = average boundary shear stress

γ = unit weight of sediment

R = hydraulic radius

S = slope of the energy grade line

Methods for evaluating sediment transport capacity are dependant on the mode of transport, availability of erodible sediment, velocity, tidal range and bed form. The Englund-Hansen formula for bed-material (total) load, derived for sand in channels with gradually varied flow, is used. The Englund-Hansen formula relates sediment concentration to the U-S product (rate of energy expended per unit weight of water) and the R-S product (shear stress) as identified in the following equation.

( )[ ]

−−

−=

dsRS

gdsUS

ssCs )1(11

05.0 5.0

Cs = sediment concentration (parts per million (ppm))

s = specific gravity

U = current velocity

S = slope of energy grade line

R = hydraulic radius

d = diameter of sediment



Frequency of erosion and deposition within the channel reach may theoretically be determined based for the range of discharge conditions. Critical shear stress may be estimated as a function of particle size with van Rijn’s formula (Van Rijn, 1989). The amount of sediment that will settle in the trap depends on the flow velocity, trap length and original water depth. As depth increases, theoretically the flow velocity decreases, resulting in an increase in deposition within the trap. The trapping efficiency may be estimated by the following:

UHL s /ωαβ =

α = a coefficient adjusted for non uniform distribution of sediment

L = trap length

ωs = settling velocity

U = discharge velocity

H = depth

Alternative sedimentation basin depths and configurations were considered for reducing the potential sediment load from flood events to the marina. Based on the characterization of hydraulics and sediment transport potential described above, the potential effectiveness for each alternative was evaluated. The most effective concept calls for lowering the floodplain elevation by a depth of 2 m over an area approximately 125 m wide and a length of 200m. This primary area is expected to reduce sediment load in flood waters from the Rio Culebrinas. A second basin located prior to the confluence of the Cano Madre Vieja and the marina basin is expected to reduce sediment load in flow from the Cano Madre Vieja. Increasing the cross-sectional area of the floodplain is estimated to result in settlement of 10 to 30% of the total sediment load under a narrow range of discharge conditions (from approximately 42.5 to 120 cms). Above this discharge rate, increasing the cross-sectional area is not very effective. By lowering the floodplain elevation, it is estimated to result in a reduction in average annual total load to the marina from the Rio Culebrinas by 2,000 to 4,000 m3/year. The areas are expected to support wetland plantings.

Modifications to the Marina Design

Further consideration is made to marina basin design. The design depth and layout of the marina in the vicinity of the confluence of the basin and the Cano Madre Vieja allows for sedimentation without affecting operations of the marina. Overdredging in this location may minimize the frequency of maintenance dredging of the channel and boat slips.

A.2.4 Marina Flushing Analysis

This section describes the methodology used to assess tidal-driven circulation and constituent flushing within the proposed Discovery Bay Marina basin.



USEPA Marina Design Guidelines

The biological health, water quality and aesthetic appeal of a semi-enclosed marina basin may be evaluated by analyzing the flushing efficiency of the target waterbody. Flushing efficiency, measured as flushing time, is defined as the amount of time required for an average water particle within the basin to travel out of the basin. Flushing time is largely dependent upon the size of the basin and how well water circulates within the basin. The U.S. Environmental Protection Agency (USEPA) has published a list of Best Management Practices (BMP’s) for marina design in the National Management Measures to Control Nonpoint Source Pollution from Marinas and Recreational Boating, (EPA 841-B-01-005, November 2001) [Section 4-1] (extracted from www.epa.gov/owow/nps/marinas.html) to promote good circulation and a well flushed marina basin under normal conditions. The management measures primarily apply to new and expanding marinas and include the following:

§ Ensure that the bottom of the marina and the entrance channels are not deeper than adjacent navigable channels

§ Consider design alternatives in poorly flushed waterbodies to enhance flushing. For example, consider an open design where a semi-enclosed design is not functional or floating wave attenuators in lieu of fixed breakwaters.

§ Design new marinas with as few enclosed water sections or separated basins as possible to promote circulation within the entire basin.

§ Consider the value of entrance channels in promoting flushing when designing or reconfiguring a marina.

§ Establish two openings at the most appropriate locations within the marina to promote flow-through currents.

§ Consider mechanical aerators to improve flushing and water quality where basin and entrance channel configuration cannot provide adequate flushing.

The Discovery Bay Marina basin has been designed using the above guidelines and accepted industry standards to encourage good marina basin water quality through flushing.

Marina Flushing Standards

The USEPA and the U.S. Army Corps of Engineers (USACE) cite analyses performed by van de Kreeke and Larsen (1981) and Boozer (1979) to quantify a well flushed marina. These analyses suggest that flushing times of 2-4 days provide sufficient water circulation to maintain healthy dissolved oxygen levels and to prevent the buildup of high pollution concentrations within a marina. Estimation of a basin’s flushing time must take into consideration that each water particle within the basin has a different flushing time depending upon location; particles near the basin entrance may flush nearly instantaneously while remote particles may take days or weeks to flush. Analyses by van de Kreeke (1983) show that the average flushing time in a basin is equal to the amount of time required for the average concentration of an instantaneously injected

http://www.epa.gov/owow/nps/marinas.html)



conservative constituent (tracer particle) to be reduced to 1/e, or 36.8 percent (where e = 2.718), of the initial concentration throughout the basin. By these guidelines, a marina is considered well flushed if the initial concentration of a conservative constituent introduced instantaneously throughout the basin is reduced to an average of 36.8 percent of the initial concentration within 4 days (96 hours). These guidelines are recommended by the USEPA and are considered the industry accepted flushing standard for marinas.

Preliminary Basin Configuration

The initial marina basin configuration, shown in

Figure A.2-16, was developed using the following criteria: 1) provide flood protection to the Towns of Aguadilla and Aguada, 2) preserve aquatic habitat and mangroves, 3) maximize water exchange, 4) maximize the use of the basin for boats and other water-based recreational craft, and 5) maximize developable land along the southern property line.

The location of the proposed flood control levees, the horizontally undulating northern property boundary, and location of the existing mangrove areas placed a constraint on the shape of the basin. The flood control levees bound the project site on the north and south sides. The upland development portion of the project will lie between Espinar in Aguada and the south levee system. The proposed northern levee system will start near P.R. Road 115 and end near



Discovery Park, following an east-west alignment that parallels the city limits of the Town of Aguadilla.

The proposed interior basin will be excavated from the land between the two levee systems. The undulating northern property boundary and the existing mangrove areas near the northwestern edge of the property constrained the shape and orientation of the basin shoreline in this area. The resulting inner basin is elongated along an east-west axis, extending from shoreline to P.R. 115 and encompassing approximately 15.1 hectares. Water depths within the inner basin will range from 1.83m deep to 2.74m deep relative to Mean Sea Level (MSL), resulting in a total basin volume of approximately 350,000 m3.

The existing Cano Madre Vieja discharges into Aguadilla Bay through an existing channel passing between two existing jetties. The channel will be widened to create a 50-meter wide by 120-meters long channel to connect the proposed basin with Aguadilla Bay. The geometry of the channel was developed to provide boating access between the inner basin and the bay and to improve the flushing efficiency of the basin.

Analytical Analysis

An initial analytical flushing time analysis was performed on the preliminary basin configuration to establish whether basin flushing mechanisms were sufficient to flush the basin under normal conditions. In non-riverine, semi-enclosed water basins, tidal exchange is the primary flushing mechanism. Basin flushing efficiency may, therefore, be described in simplistic terms as a relationship between basin volume and tidal exchange volume. This relationship may be extended to flushing time by factoring in the tidal period (12.4 hours for semi-diurnal tides). Flushing times for a semi-enclosed basin influenced by tides may be estimated analytically using the following formula:

tide

L

flush tv

vVt 2

+=

where VL is the volume of the basin at low water

ν is the mean tidal volume

ttide is the tidal period

Using this methodology and the tidal relationships discussed in Section A.1.1 to convert the basin volume to low water levels (0 m MSL = 0.208 m MLLW), the average flushing time for the preliminary basin configuration was approximately 77 hours. This analytical method provides a simplified means to determine the exchange characteristics of a semi-enclosed waterbody and typically relates to a single idealized basin, with one basin entrance. This method does not account for reintroduction of previously flushed particles and assumes a perfectly mixed basin. In simplified form, the methodology is little more than a volume replacement calculation.



Because the interaction of the tidal forcing mechanism and basin geometry at Discovery Bay Marina is more complex, a numerical modeling study was undertaken to better define the flushing efficiency and times of the marina basin. Numerical modeling incorporates the effects of inlet and basin geometry on tides and currents and provides a more accurate representation of water mixing within the basin.

Numerical Analysis

The flushing time of the proposed marina basin was analyzed using the MIKE21 suite of hydraulic simulation modules (http://www.dhisoftware.com/mike21). The MIKE21 hydrodynamic module (HD) was used to simulate tides and tidal currents which represent the primary hydrodynamic forces at the project site. Wind and wave induced currents, which would enhance mixing and improve flushing, were excluded from the model setup to present a more conservative flushing estimate. The output of the hydrodynamic model was used with the coupled MIKE21 Advection/Dispersion module (AD) to evaluate the flushing time for the basin.

The HD model was developed using a nested grid, consisting of outer regional and inner local model domains. Nested grids allow more efficient model execution over the smaller local domain while using boundary conditions located farther from the project site generated within the regional model domain. The regional model encompasses an area measuring 3.5 km by 3.0 km with a grid size of 8m per side. Hydrodynamic and advection dispersion model result data are transferred from the regional model to the local model boundaries. The local model domain extends over an area 2.0 km by 2.2 km with a grid size of 8m per side. The project location is centered within the local model domain to allow sufficient distance for transient boundary condition flows to stabilize. The bathymetry for the model domains includes digitized contours from nautical charts supplemented with data from a nearshore bathymetric survey performed on November 18 and 23, 2000 by the University of Puerto Rico. The model domains with bathymetry are shown in Figure A.2-17.

Calibration of a numerical model is the means by which a model is adjusted to accurately reproduce the physical processes occurring in nature. Verification of model calibration is achieved by comparing model results to measured data. Typically, modeled tide elevations and current velocities are compared to measured tides elevations and current velocities. A tide and current gauge was deployed offshore of the proposed project location at the 9 meter contour, as shown in Figure A.2-17. Current velocities and directions were measured 3.6 meters above the sea bottom, a depth assumed to be representative of depth averaged currents. This measured data was used in calibration.

Neap tides represent the period of lowest tide range and tidal current velocity. Flushing during neap tide conditions is generally less efficient than during average tide conditions; therefore (as a conservative measure), a neap tide is selected as the primary forcing tide for the flushing model. The data collection period, October 21 through 28, 2004, was selected to correspond to a neap tide period. The measured tide and current data is shown in Figure A.2-18.

Analysis of the tide and current data indicates that a weather front passed through the region in the latter part of the collection period as evidenced by a general rise in the tide levels and current velocities. The period selected for the numerical model, 12:00PM on October 21 through

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12:00PM on October 25, 2004, corresponds to the period of time representing typical, neap conditions. The open-water boundaries for the regional model were specified by transferring the measured data from the gauge to the model boundaries via phase shifts using long wave approximations for tidal wave propagation. Local model boundary conditions consist of transferred boundaries from the regional model outputs.

Comparison of model results against the measured data indicates that the model is well calibrated, reproducing representative tides and tidal currents at the project location. Modeled tidal amplitude and phase, shown in Figure A.2-19, correlate well with measured values. Modeled current directions, also shown in Figure A.2-19, are also consistent with measured directions. Peak current velocities in the model are of the same amplitude as measured peak current velocities. Differences in current velocity phasing may be attributed to the depth averaged nature of the numerical model when compared to the discrete current measurement as well as the non-tidal elements represented in the measured data and are considered to be within accepted tolerances.

The basin’s flushing efficiency was modeled using the AD module of the MIKE21 suite. The AD model was initialized with a conservative (non-decaying) tracer placed throughout the basin at a uniform concentration, while the areas outside of the basin had an initial tracer concentration of zero. The model was then run using the conservative neap tide record over four days to determine the average residual tracer concentration throughout the marina basin at the conclusion of the 96 hour period.

Preliminary Basin Flushing Results

Flushing model results of the preliminary marina basin configuration indicate that while the basin would flush naturally over the long term, it is not expected to achieve the desired flushing efficiency under neap tidal exchange. The average residual constituent concentration was 80% after 96 hours, as shown in Figure A.2-20. This flushing inefficiency is attributed to the high length to width ratio of the basin configuration inhibiting the propagation of non-basin water throughout the basin and the small tide range at the project site relative to the marina basin depths.

Groundwater Flow

Elevated groundwater flow in the surficial aquifer of the Rio Culebrinas watershed has been observed. Groundwater flow may contribute to the flushing efficiency of a basin by introducing additional flow into the waterbody. The contribution of groundwater to the interior basin and its influence on the exchange of water and flushing times within the basin were evaluated. Groundwater flow was calculated by Hydro-Environmental Associates Inc. (HEA) using the Modular Three-Dimensional Finite Difference Groundwater Flow Model (MODFLOW TM) code, developed by McDonald and Harbaugh of the U.S. Geological Survey.

Groundwater Flow Model Configuration

A series of constant head cells, at an assumed elevation of mean sea level, were used to represent the proposed marina basin during average tidal conditions. To provide a conservative estimate



of the groundwater influence into the proposed marina basin, the model was conducted using steady-state conditions, without the influence of precipitation or evapotranspiration. The model was set up as a three layer hydrogeologic system, with the upper two layers representing the surficial aquifer, and the third layer representing the underlying Aymamon Limestone aquifer. The surficial aquifer was divided into two layers to simulate the effects of the proposed marina basin.

Each model layer was discretized into 10,000 cells, 30.5m by 30.5m in size (100 rows by 100 columns). Constant head boundaries were used to define the Atlantic Ocean and the Cordillera Jaicoa outcroppings. The model elevation of the constant head boundary representing the Atlantic Ocean was assumed to be at MSL. The constant head boundary cells representing the face of the Cordillera Jaicoa to the north of the Rio Culebrinas was estimated to be at an elevation of 4.6m above MSL, based upon a review of the Aguadilla USGS 7.5-minute quadrangle map. For modeling purposes, the constant head boundaries representing the face of Cordillera Jaicoa south of the Rio Culebrinas were varied linearly from a maximum of 4.6m to zero meters MSL, based upon the general topography of the area.

The MODFLOW river package was used to simulate the Rio Culebrinas. Based upon review of the Aguadilla USGS 7.5-minute quadrangle map, the upstream extent of the Rio Culebrinas was located at the intersection of State Road 115 with an estimated elevation of 2.7m above MSL. The downstream river elevation was assumed to be at MSL.

The top of the surficial aquifer, for the purposes of this model simulation, was conservatively assumed to be flat at an assumed model elevation of 1.2m above MSL. The base of the surficial aquifer was assumed to be at -30.5m MSL. Hydraulic conductivity (permeability) values for the surficial aquifer were based on field data collected at the site by HEA representatives. In-situ hydraulic conductivity values were obtained for the site by conducting single well aquifer recovery tests (slug tests) at six (6) existing monitoring wells located at the subject site. The monitoring wells were spatially located within the area of the proposed marina. These in-situ hydraulic conductivity values were required to estimate groundwater flow volumes anticipated to discharge into the marina area.

Groundwater Flow Model Results

The results of the MODFLOW simulation indicate that the average rate of total groundwater inflow into the proposed marina basin is approximately 9,240 m3 per day while maintaining the water level in the basin at mean sea level. Based upon the model simulations, approximately 22 percent of the groundwater flow is from the vicinity of the Rio Culebrinas, approximately 36 percent of the flow is from the north originating from the Cordillera Jaicoa, approximately 9 percent of the flow is from the south, and the remaining 33 percent is upward flow from the base of the surficial aquifer.

The predicted groundwater inflow rates were distributed into twenty “flow zones”, or segments, describing the marina basin. These inflow rates were then represented in the numerical flushing model as a single point source for each of the 20 segments. Flushing model results reveal that the contribution of groundwater to flushing efficiency is minimal, reducing the residual concentration by 3% at the end of 96 hours from 80% (no groundwater) to 77% (with



groundwater). Residual concentrations for the revised marina configuration are shown in Figure A.2-21.

Modified Entrance Channel Configurations

To evaluate the influence on flushing efficiency of the entrance channel connecting the basin to Aguadilla Bay, the preliminary basin configuration was modeled with entrance channels of various widths, lengths, and depths. The addition of a second entrance channel to the basin was also investigated.

Channel widths ranging from 32m to 50m were compared to the initial 40m wide channel configuration. Model results indicate that flushing efficiency varies less than 5 percent when widening or narrowing the entrance channel. Entrance channel length was reduced from 120 meters long to 50 meters long. Reduced channel length improved flushing up to 10% relative to the longest channel. However, property boundaries and land use planning preclude relocation of the marina basin closer to the Aguadilla Bay and/or shortening the entrance channel. The entrance channel depths were varied to establish the influence of water depth on flushing efficiency. Deepening of the entrance channel from 2.74m to 3.66m resulted in no change in flushing efficiency.

Improved water basin circulation is often achieved through the addition of a second entrance channel. The location of the second channel a sufficient distance from the main channel is necessary to induce circulation from potential tidal elevation differences between the two entrances. A basin configuration with a second entrance channel was evaluated. Flushing efficiency was improved with the addition of the second channel by 15%. This improvement is insufficient to cause the basin to meet the desired flushing thresholds. Existing land use and property limits, in addition to potential impacts to the shoreline, precluded the addition of a second channel to the Discovery Bay Marina basin.

Results of numerical modeling of modifications to the marina entrance channel suggest that, with land use and property limit considerations, entrance channel configuration modifications do not improve basin flushing efficiency sufficiently to meet the desired flushing threshold requirements.

Modified Basin Configurations

Further analyses were performed to determine whether modifications to the basin geometry would influence flushing efficiency at the project location. The investigation of circular basin configurations, generated without regard for property and land use limitations, show that flushing times for a circular basin improve with reduced basin volumes. Additionally, basins with a center of mass closer to Aguadilla Bay flush better than basins with a center of mass further from Aguadilla Bay.

Subsequent model runs were performed for basin configurations generated within the limitations of property limits and existing land use, with the basin center of mass shifted closer to Aguadilla Bay than the preliminary basin configuration. Basin depths and open water configurations were modified for each case investigated. Model results suggest that a 16.6 hectare basin, shown in



Figure A.2-22, sited close to the marina entrance with shallow 1.7 m channels and 0.8 m open areas (total volume of 267,000m3) and a modified inlet structure that channeled flow into the basin would achieve the desired flushing parameters. However, the water depths and shape of this naturally flushing scenario do not meet the project’s program objectives in terms of the projected number of boat slips and the desired basin and land use.

Mechanical Flow Augmentation

To improve basin flushing to the desired efficiency, in addition to circulation generated by tidal forcing, a mechanical flow augmentation system was considered. Flow augmentation may be achieved through mechanical means that include aeration systems, current induction systems, and pumping systems. Aeration systems generally consist of bottom-mounted bubblers that improve dissolved oxygen levels while promoting local mixing through agitation caused by the bubbles. Current induction systems generate localized current flow through the frictional effects of the movement of large plates through the water. Pumping systems introduce additional volume to the water basin from a remote source via pumps, creating positive water surface head flowing out of the marina during most tide phases, providing the benefits of both improved dissolved oxygen and flow circulation.

The long, narrow shape of the basin suggests that basin flushing efficiency may be best augmented with a mechanical pumping system. Mechanical pumping was investigated at the project basin through the addition of a point source flow to the numerical flushing model. Preliminary investigation of a circular basin suggests that volumetric flows approaching 1 m3/s will be required to flush a 17 hectare, 470,000 m3 basin. Residual concentrations in the circular marina, augmented with pumping, are shown in Figure A.2-23.

A revised marina configuration was developed to reflect continued upland master plan development including the incorporation of the proposed marina entrance structures. The revised marina layout was modeled with the addition of a mechanical system to increase flushing efficiency in the marina basin. Analysis of these model results indicate that a continuous volumetric flow rate of 1.25 m3/s over twenty-four hours, introduced at the head of the marina, is necessary to achieve the desired flushing efficiency.

Pump Inflow Configuration

The most efficient location for the pumping inflow, in terms of total volumetric flushing, is at the head of the marina, as shown in Figure A.2-24. However, this single source configuration results in localized areas of high residual concentration. Further analyses performed with the flow distributed to multiple locations throughout the marina reduced the highest residual concentrations to within 10% of the desired levels throughout the basin while maintaining the average residual concentration throughout the basin to below 37% after 96 hours, as shown in Figure A.2-25.

Additional flushing model runs were conducted to assess the effect of scheduled pumping versus continuous pumping. Scenarios included daytime or nighttime pumping only (12 hrs pumping and 12 hrs no-pumping per day) and pumping during the flooding or ebbing tide phase only (6 hr alternating pumping/non-pumping over entire day). Modeling results indicate that the system



behaves in a near linear manner whereby halving the daily total pumping time would require doubling the pumping rate to achieve similar performance. For all scenarios analyzed, the total daily volume of inflow required to achieve the desired rate of flushing was constant at 108,000m3/day, regardless of the pumping schedule.

Discovery Bay Marina Pumping System

The proposed Discovery Bay Marina pumping system is capable of pumping 2.52 m3/s. The capacity of the pump allows the system to meet the pumping volume of 108,000m3/day in 12 hours, allowing the system to be idle 12 hours per day. The proposed hydraulic pumping system is driven by a diesel/electric engine that circulates hydraulic fluid through the pump to power the impellor. The pumping system draws fresh water from a gravity flow fed sump connected to Aguadilla Bay via two pipes. The sump inflow pipes extend to the 4m offshore contour and are aligned with the proposed jetty entrance structure. The inflow pipes will be marked with navigation aids and will each have a safety cage to prevent debris from entering the pipeline and to protect swimmers. The pump flow is piped from the sump to three areas throughout the marina, as shown in Figure A.2-26, via reinforced concrete pipe. The pipeline will be sized to allow the appropriate volume of water to flow to each area of the marina. Each outlet will have a flow diffuser and one-way valves to reduce exit flow velocities into the marina to below 0.3 m/s and to prevent debris from entering the pipeline. Periodic access vaults along the pipeline route will facilitate maintenance and cleaning.



20m x 80m 4m x 16m

1m x 4m

Figure A.2-1: NSW Wave Model Nested Domain Grids



A: COE Wave buoy at Aguadilla BreakwatersB: Cano Jetty

A

B

N

Shore Normal to South BeachShore Normal

to North Beach

DirectionalSpread forWaves ReachingProject Location(8m depth)

DirectionalSpread forWaves reachingAguadilla WaveBuoy (17m depth)

Figure A.2-2: NSW Nearshore Model Results vs. Measured Aguadilla Data



Figure A.2-3: Project Vicinity Map



0.5 0 0.5 1 Kilometers

N

Trend LinesDynamic EquilibriumMixed CaseNet AccretionNet ErosionTotal Deposition I

Figure A.2-4: Net Sediment Transport Pathways (GeoSea and Evans-Hamilton, 2003)

Caño Madre Vieja

Proposed Project Site



Shoreline Change Rates

(- erosion/+ accretion)

-30

-25

-20

-15

-10

-5

0

5

10

15

20

1 51 101 151 201 251 301 351 401 451 501

Transect Number

Sh

ore

lin

e C

ha

ng

e (

m/y

r)

1963-1977 1977-1985 1985-1989 1989-1995 1995-2000 2000-2006 Post Structure 1985-2006

North Jetty South Jetty

Figure A.2-5: Historical Shoreline Change Rates Near Caño Madre Vieja



Figure A.2-6: Transformed and Locally Generated Combined Wave Rose



0

100

200

300

400

500

600

5/8/1967 10/28/1972 4/20/1978 10/11/1983 4/2/1989 9/23/1994 3/15/2000 9/5/2005

Date

Da

ily M

ean

Str

ea

mfl

ow

(c

ub

ic m

ete

rs p

er

sec

on

d)

MocaMargarita DamFlows When Margarita WQ Samples TakenFlows When Moca WQ Samples Taken

Figure A.2-7: Historical Flows at the Río Culebrinas

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 1 2 3 4 5 6 7 8 9 10Flow (cms)

Pe

rce

nt

Gre

ate

r T

ha

n

Cano Madre Vieja

Figure A.2-8: Cano Madre Vieja Flow Classification



0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 50 100 150 200 250Flow (cms)

Perc

en

t G

rea

ter

Th

an

Rio Culebrinas at Marina

Figure A.2-9: Río Culebrinas Flow Classification

y = 95.304x

R2 = 0.9273

y = 33.497x

R2 = 0.9301

0

500

1000

1500

2000

2500

3000

3500

0 10 20 30 40 50 60 70 80

Flow (cubic meters per second)

Su

sp

en

ded

Se

dim

en

t (m

g/L

)

Combined Series

Rio Culebrinas at Moca

Rio Culebrinas at Margarita Dam

Margarita Dam Outlier

Linear (Rio Culebrinas at Moca)

Linear (Combined Series)

Figure A.2-10: Sediment Load – Flow Correlation



Figure A.2-11: Total Sediment Load – Discharge Histogram for Cano Madre Vieja

Figure A.2-12: Total Sediment Load – Discharge Histogram for Rio Culebrinas



Figure A.2-13: Input Hydrographs for 2-year and 10-year Frequency Storm Events



Figure A.2-14: Peak Water Surface Elevation and Velocity Distribution for 10-Year Storm



Figure A.2-15: Sediment Reduction Concept Consideration Areas (Existing Wetlands Shown)



Figure A.2-16: Preliminary Basin Configuration



Local Model Domain

Regional Model Domain

Tide and Current

Gauge Location

Local Model Domain

Regional Model Domain

Tide and Current

Gauge Location

Figure A.2-17: Model Domain and Bathymetry with Basin Alternative 1



Measured Water Level

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

10/21/20040:00

10/22/20040:00

10/23/20040:00

10/24/20040:00

10/25/20040:00

10/26/20040:00

10/27/20040:00

10/28/20040:00

10/29/20040:00

Time

Wa

ter

Le

vel

(m M

SL

)

Measured Current Velocity

0.00

0.05

0.10

0.15

0.20

0.25

0.30

10/21/20040:00

10/22/20040:00

10/23/20040:00

10/24/20040:00

10/25/20040:00

10/26/20040:00

10/27/20040:00

10/28/20040:00

10/29/20040:00

Time

Cu

rre

nt

Velo

cit

y (

m/s

)

Measured Current Direction

0

60

120

180

240

300

360

10/21/20040:00

10/22/20040:00

10/23/20040:00

10/24/20040:00

10/25/20040:00

10/26/20040:00

10/27/20040:00

10/28/20040:00

10/29/20040:00

Time

Cu

rren

t D

irec

tio

n (

deg

rees)

Figure A.2-18: Measured Water Level



Water Level Calibration

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

10/21/2004 0:00 10/22/2004 0:00 10/23/2004 0:00 10/24/2004 0:00 10/25/2004 0:00 10/26/2004 0:00 10/27/2004 0:00

Time

Wa

ter

Lev

el (m

MS

L)

Measured Water Level Modeled Water Level

Current Velocity Calibration

0.00

0.05

0.10

0.15

0.20

0.25

0.30

10/21/2004 0:00 10/22/2004 0:00 10/23/2004 0:00 10/24/2004 0:00 10/25/2004 0:00 10/26/2004 0:00 10/27/2004 0:00

Time

Cu

rren

t V

elo

cit

y (

m/s

)

Measured Current Velocity Modeled Current Velocity

Current Direction Calibration

0

60

120

180

240

300

360

10/21/2004 0:00 10/22/2004 0:00 10/23/2004 0:00 10/24/2004 0:00 10/25/2004 0:00 10/26/2004 0:00 10/27/2004 0:00

Time

Cu

rre

nt

Dir

ec

tio

n (

de

gre

es

)

Measured Current Direction Modeled Current Direction

Figure A.2-19: Water Level Calibration




0.8 - 0.90.7 - 0.80.6 - 0.70.5 - 0.60.4 - 0.50.3 - 0.40.2 - 0.30.1 - 0.2

Below 0.1

0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6(kilometer)

0.0

0.1

0.2

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0.4

0.5

0.6

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0.8

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1.0

1.1

1.2

1.3

1.4

1.5

1.6

1.7

(kilo

met

er)


-1 - -0.5-1.5 - -1

-2 - -1.5-2.5 - -2

-3 - -2.5-3.5 - -3

-4 - -3.5-4.5 - -4


0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6(kilometer)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

1.6

1.7(k

ilom

eter

)

Figure A.2-20: Preliminary Marina Configuration Bathymetry (left) and Residual Concentration – 96 hours (right)


-1 - -0.5-1.5 - -1

-2 - -1.5-2.5 - -2

-3 - -2.5-3.5 - -3

-4 - -3.5-4.5 - -4


0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6(kilometer)

0.0

0.1

0.2

0.3

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1.0

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1.2

1.3

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1.6

1.7

(kilo

met

er)


0.8 - 0.90.7 - 0.80.6 - 0.70.5 - 0.60.4 - 0.50.3 - 0.40.2 - 0.30.1 - 0.2

Below 0.1

0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6(kilometer)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

1.6

1.7

(kilo

met

er)

Figure A.2-21: Revised Marina Configuration Bathymetry (left) and Residual Concentration with Groundwater – 96 hours (right)




0.8 - 0.90.7 - 0.80.6 - 0.70.5 - 0.60.4 - 0.50.3 - 0.40.2 - 0.30.1 - 0.2

Below 0.1

0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6(kilometer)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

1.6

1.7

(kilo

met

er)


-1 - -0.5-1.5 - -1

-2 - -1.5-2.5 - -2

-3 - -2.5-3.5 - -3

-4 - -3.5-4.5 - -4


0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6(kilometer)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

1.6

1.7(k

ilom

eter

)

Figure A.2-22: Naturally Flushing Marina Configuration Bathymetry (left) and Residual Concentration – 96 hours (right)


0.8 - 0.90.7 - 0.80.6 - 0.70.5 - 0.60.4 - 0.50.3 - 0.40.2 - 0.30.1 - 0.2

Below 0.1

0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6(kilometer)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

1.6

1.7

(kilo

met

er)


-1 - -0.5-1.5 - -1

-2 - -1.5-2.5 - -2

-3 - -2.5-3.5 - -3

-4 - -3.5-4.5 - -4


0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6(kilometer)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

1.6

1.7

(kilo

met

er)

Figure A.2-23: Idealized Marina Configuration Bathymetry (left) and Residual Concentration with Pumping – 96 hours (right)




0.8 - 0.90.7 - 0.80.6 - 0.70.5 - 0.60.4 - 0.50.3 - 0.40.2 - 0.30.1 - 0.2

Below 0.1

0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6(kilometer)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

1.6

(kilo

met

er)

Q = 108,000 m3/day

Figure A.2-24: Revised Marina Configuration Residual Concentration with Single Discharge Pumping – 96 hours




0.8 - 0.90.7 - 0.80.6 - 0.70.5 - 0.60.4 - 0.50.3 - 0.40.2 - 0.30.1 - 0.2

Below 0.1

0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6(kilometer)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

1.6

(kilo

met

er)

Q = 27,000 m3/day

Q = 27,000 m3/day

Q = 54,000 m3/day

Figure A.2-25: Revised Marina Configuration Residual Concentration with Distributed Pumping – 96 hours



Figure A.2-26: Marina Pumping System Configuration



A.3 DISCOVERY BAY MARINA DESIGN

The Discovery Bay Marina has been designed to provide protected wet slip mooring for up to 500 recreational boats ranging in length from 9.1m (30-feet) to over 55 m (180-feet) and dry stack capacity for up to 500 boats less than 9.1m in length. The following sections describe the design of the marina including entrance channel design, marina layout, dock and pier configuration, and shoreline treatments.

A.3.1 Marina Entrance

Located on the relatively sheltered western coast of Puerto Rico, the Discovery Bay Marina outlets to the open waters of Aguadilla Bay in an area of coastline exposed periodically to large waves refracted from offshore as well as significant locally generated wind waves. Protective structures are required at the entrance of the Discovery Bay Marina to provide a quiescent marina entrance channel, allowing approaching vessels to reduce speed prior to entering the marina basin while also preventing the large offshore waves from propagating into the marina basin. In addition, because the access channel passes through the littoral zone of the adjacent beaches, the entrance structures will provide protection from episodic longshore sediment transport, discussed in Section A.2.2, which may cause accretion in the entrance channel.

Entrance Channel Design

The Discovery Bay Marina entrance channel has been designed with sufficient width and depth to allow the expected marina traffic to safely and efficiently navigate out of the marina basin during peak access periods through all phases of the tide.

Design Width

The U.S. Army Corps of Engineers, in EM 1110-2-1615 Hydraulic Design of Small Boat Harbors, conservatively recommends that for safe navigation the width of each navigable lane be 200% of the design vessel beam plus an additional 60% of the boat beam for bank clearance on each bank and an additional 80% of the boat beam for passing clearance between adjacent lanes resulting in a total of 600% (60% + 200% + 80% + 200% + 60%) of the design vessel beam for a two-lane access channel. For the Discovery Bay Marina the resulting design channel width for an 8-meter boat beam, corresponding to a typical 30.5m (100-foot) boat, is approximately 50 meters wide.

Design Depth

The U.S. Army Corps of Engineers EM 1110-2-1615 Hydraulic Design of Small Boat Harbors suggests that channel depths should account for vessel draft and squat, wave conditions, and safety clearances, as shown in Figure A.3-1. Additional depth may be considered to account for advanced maintenance dredging. Finally, an extreme low-water level, such as a recurring minus tide, may require increased design depths. The following paragraphs describe these factors.



Vessel Draft

Vessel draft varies significantly by boat style, length, and manufacturer. An analysis of current market trends indicates that a design draft of 2.45-meters (8.0-feet) will accommodate the class of recreational vessels targeted to use the facility.

Squat

Squat for small recreation craft moving at reasonable speed in entrance channels is generally taken to be 0.3m. Squat at low speed in interior channels, moorage areas, and turning basins is about 0.15m.

Wave Conditions

A combination of wind waves and boat wakes may generate waves in the marina on the order of 0.3m. Therefore, additional depth equal to half of this wave height, or 0.15m corresponding to the depth of the wave trough, is suggested.

Safety Clearances

The U.S. Army Corps of Engineers and American Society of Civil Engineers recommend a minimum clearance of 0.6m for channels with soft bottoms, such as sand or silt and 0.9m for channels with rocky bottoms. A 0.6m safety clearance is selected for the Discovery Bay Marina.

Extreme Low Water Level

Predicted low tides at Mayaguez (tides predicted using only astronomical forces) range as high as +0.3m MLLW to as low as -0.15m MLLW. The magnitude of the occasional minus tide is small and may be neglected.

Considering the above elements, the entrance channel depth has been designed to be 3.35-meters deep relative to MLLW with an additional 0.3m of advanced maintenance dredging for a total elevation of -3.65m MLLW. The channel side slopes have been designed with a 4H:1V slope for slope stability and to minimize maintenance dredging.

Existing Structures

The location of the Discovery Bay Marina entrance coincides with the location of the existing Caño Madre Vieja outlet into Aguadilla Bay. The mouth of the Caño Madre Vieja is approximately 50m wide as defined by two existing shore-normal structures, shown in Figure A.3-2. The existing structures consist of an armored jetty to the north of the outlet and a stone jetty to the south.

The crest elevation of the jetty north of the mouth of the Caño Madre Vieja is 4m MSL and extends approximately 100m offshore in a westerly direction bearing 285 degrees, terminating at approximately the 2m offshore depth contour. The crest of the jetty averages approximately 15m wide and is paved, allowing vehicular parking and pedestrian access. The slopes of the jetty are



armored with large angular stones of varying size, with the largest stones appearing to be on the order of 1m in diameter, based upon a visual survey, corresponding to a weight of approximately 2 tonnes (1000 kg).

The rock jetty south of the Caño Madre Vieja mouth consists of a stone mound with a crest elevation approximately 1.4m above MSL. The jetty is constructed of angular stone similar in size and appearance to the armor stone used on the jetty structure. The jetty extends in a westerly direction of 312 degrees, terminating approximately 30m offshore in 0.5m deep water.

As discussed in Section A.2.2, sediment periodically accretes and erodes along the beaches adjacent to the Caño Madre Vieja following the construction of the structures. Analysis of sedimentation rates indicates that while the existing structures occasionally impound sediment, the long term shoreline position has been stable since the structures were built and have not negatively impacted the regional littoral system.

Proposed Entrance Structures

To provide protection to the entrance channel and marina basin, as discussed above, the existing jetty system will be reshaped and extended, resulting in two stone jetties flanking the entrance channel. The project structures have been designed with a 25-year design life. The design parameters for the structures are based on a probabilistic exceedance of wave heights and water levels occurring during the project’s lifespan. Wave heights and water level parameters associated with a return period of 50-years, which have a 2 percent probability of exceedance annually or 50 percent probability of exceedance over 25 years, were applied in design of the structures.

The 50-year water level was extracted from the FEMA FIS water levels discussed in Section A.1.4 and the 50-year wave conditions at the site were computed using the MIKE21 Near Shore Wave (NSW) model as discussed in Section A.2.1. A deepwater wave, with a height of 12.5m and a corresponding period of 14s from the WIS hindcast record, was propagated from offshore to the project location. From the discussion in Section A.2.1, North was selected as the worst case origination direction.

Analyses of MIKE21 NSW model results indicate that the design wave will shoal, refract, and break as it approaches the project location. The design wave, corresponding to offshore waves origination from the north, is 3.5m in height with a period of 14s and an approach angle of 330 degrees (N=0 degrees) at the project location.

Structure Configuration

To adequately protect the entrance channel and marina basin from waves approaching predominantly from the NW quadrant, the existing jetty will be reconfigured into a northern jetty extending approximately 100m beyond the existing structure to the 4m depth contour. Similarly, to protect the channel from wave reflection and sediment impoundment from the shoreline to the south, the southern jetty structure will be extended approximately 140m beyond the existing structure. To maintain the 50m design channel width, the southern structure will require two segments connected by an 18 degree bend. The first segment is aligned with the existing



structure, extending approximately 50m beyond the structure head. The jetty then bends to the west to maintain a 50m distance from the northern structure and extends approximately 70m further offshore to the 2m depth contour.

Structure Orientation

The proposed entrance structures must be capable of providing a navigable entrance to the marina under operational conditions. Wave penetration into the marina entrance was evaluated using the MIKE21 Elliptical Mild-Slope (EMS) Wave module. The MIKE21 EMS wave module may be used to calculate wave fields in smaller coastal areas where diffraction and wave breaking are important, as is the case with marina entrance jetties.

The MIKE21 EMS Wave module was used to evaluate unit waves (unitless wave height of 1) for wave periods of 8 and 14 seconds originating from 335 and 315 degrees which correspond to the range of typical refracted wave periods and directions predicted by wave hindcasting as described in Section A.2.1. Additional simulations were performed for 8 second waves from 292.5 and 280 degrees corresponding to locally generated wind directions for fully developed waves. Analysis of the modeling results indicate that the heights of 8 second period waves reduce quickly to less than half of the initial height after propagating 20m to 30m into the marina entrance and to less than 10% of the initial height after propagating 50m, regardless of initial wave direction. Longer period, fourteen second waves penetrate approximately 10% further into the entrance than the 8 second waves. Penetration distance for 14 second waves is also insensitive to initial wave direction.

The entrance channel orientation has been set to 285 degrees west of north, equal to the orientation of the existing and proposed jetty structures. This orientation provides protection from the predominantly northwesterly wave direction while providing a slight bend of 18 degrees in the entrance channel, preventing waves from propagating directly into the marina. Historical sedimentation rates with the existing structures at a similar orientation suggest that the proposed structures will have no long term impacts on the littoral system.

Armor Stone Sizing and Structure Geometry

Wave height and period are used to determine the properties of the armor stone and underlayer stone to be used for entrance structure construction and to establish the structure crest elevation. The jetty cross sections are designed in accordance with the methodologies outlined in the USACE Coastal Engineering Manual (CEM, 2002).

The Hudson formula is used in conjunction with the design wave conditions to size the armor stone. A side slope of 2H:1V was selected for the jetty faces to minimize the required structure footprint while maintaining slope stability under the expected wave conditions. Locally available rock will be used to construct the entrance jetties. The armor stone size for the main trunk and structure head are expected to be on the order of 3.0 to 6.0 tonnes.

The crests of the structures have been set to an elevation of 3m MSL to ensure that the structure is visible above the wave crests during operational conditions while limiting the required



footprint area and material quantities. The crest width of the structures is on the order of 3.6m, corresponding to a minimum of three (3) armor stone diameters.

A.3.2 Shoreline Treatments

Two types of shoreline treatments were developed and employed as follows: 1) a vertical flood wall to protect the upland development and 2) a natural edge along the undeveloped edge of the marina.

A vertical wall will be installed along the southern, developed edge of the marina to act as part of the levee system floodwall as well as to provide a quick transition to navigable berthing area from the final developed upland elevation. The vertical wall will consist of a steel or concrete sheet pile wall with a concrete cap that will be anchored with a tie rod and deadman system. The sheet pile wall will extend to elevation +2m above MSL where it is backed by a promenade walkway followed by the flood control levees.

The northeast perimeter of the basin generally follows the alignment of the Cano Madre Vieja. A 5 meter buffer is maintained between the Cano Madre Vieja and construction of the marina perimeter. To maintain a natural appearance in these areas while providing erosion protection to the earthen slopes, the marina edge slope will be revetted with armor stone. The predominate erosion mechanisms are waves generated by boat wakes. Analysis of expected boat wake suggests that 2 layers of 0.14 tonne (300lb) armor stone over two layers of 13.6kg (30lb) underlayer stone will provide sufficient protection to the 2H:1V slope.

A.3.3 Marina Layout

The Discovery Bay Resort and Marina development program includes a marina basin capable of berthing 500 vessels within the constraints of the basin shape. Multiple basin configurations were developed to evaluate the basin shape and area required to meet the project programming goals. Two alternative configurations are shown in Figure A.3-3 and Figure A.3-4. These alternatives, while spatially efficient and located close to the coast, cause impacts to existing mangroves and adjacent properties. The preferred marina configuration is shown in Figure A.3-5. The shape of the preferred Discovery Bay Marina basin configuration reflects the influence of the property boundaries and the proposed flood protection structures. The following paragraphs describe the configuration of the marina elements within the basin perimeter.

Vessels expected to berth in the marina range from 9.1m (30 feet) to 55m (180 feet) in length. To minimize dredging quantities and improve flushing while maintaining efficient berthing arrangements and fairway navigation, the layout of the 500 slip basin was sub-divided into groups of vessels by length. The slips for the largest vessels, whose length exceeds 18.3m (60 feet), are located closest to the mouth of the marina basin with additional side-tie dockage capable of berthing vessels up to 55m (180 feet) in length. The water depth required to accommodate the vessels in this area, encompassing 2.55 hectares, is 3.66m below MLLW. Vessels with lengths from 9.1m to 18.3m are located in the 6.94 hectare center region of the basin where water depths are designed at 2.44m below MLLW. The area of the marina furthest from the entrance will be limited to vessels having low vertical profiles due to height restrictions



to permit navigation under a bridge that crosses the marina. Water depths required for navigation in this 2.63 hectare area are 1.98m below MLLW.

Interior channels are sized with consideration of basin geometry, safe navigation, and the expected level of traffic. An interior access channel extends along the outside edge of the marina. The width of the marina access channel varies from 50m at the marina entrance to 30m in the center area to 15m in the areas furthest from the entrance, as design vessel beams and traffic levels decrease in each area. Maintenance services and the launching of vessels stored in dry stacks will be provided in the area adjacent to the aforementioned bridge crossing the marina between the center and far areas of the marina. To permit large vessel access to the maintenance and dry storage areas, the marina access channel has been designed for a constant 3.66m depth up to the maintenance and dry storage launch areas. The access channel shallows to 1.98m beyond this area to accommodate the smaller draft of the design vessels for this area. Staging docks are provided in the vicinity of the dry stack.

Fueling piers are located near the entrance of the marina and on the staging piers for the dry stack, providing easy access for transient vessels as well as resident vessels. The fueling piers are designed to accommodate a minimum of eight vessels re-fueling simultaneously. The wide channels near the fuel piers provide areas for additional boats to queue while waiting to re-fuel.

A.3.4 Boat Ramp

A boat ramp is located at the Discovery Bay Marina to launch trailered boats. Boat ramp design includes consideration of the number of ramps, the width of the ramp lanes, the slope of the ramps, and upland amenities that will serve the boaters launching and retrieving their vessels. The following sections describe each of these parameters.

Ramp Design

Marina industry standards suggest that boats being launched and/or retrieved will occupy a ramp position for 10 to 15 minutes. Therefore, 4 to 6 launches or retrievals can occur on a single ramp lane each hour if peak efficiency is achieved. At these rates, the maximum number of cycles during a 12-hour period (typical day) is approximately 48 to 72 for a single ramp lane.

Boat ramp lanes must be sufficiently wide to allow for safe trailer and boat maneuvering, especially when adjacent ramps may be in use. Multilane ramps require less width per lane for maneuverability than single lane ramps. Boating industry standards recommend 4.6m wide lanes on launching ramps of two or more lanes and 4.9m to 6.1m wide lanes on single lane launching ramps. The single lane ramp at the Discovery Bay Boat Ramp has a lane width of 5.5m. A boarding dock is located adjacent to the boat ramp to provide access and staging to boats being launched and retrieved.

The slope of the boat launch ramp should allow boaters to safely back trailers into launching position while efficiently reaching water deep enough to launch the boat. Boating industry standards recommend slopes ranging from a minimum of 12% to a maximum of 16% with a recommended slope of 14%. The ramps at the Discovery Bay Boat Ramp have been designed to a 14% slope.



The in-water ramp approach area consists of a basin dredged to elevation 1.7m deep NAVD 88 (elevation -1.5m MLLW) with sufficient space to maneuver multiple vessels during queuing.

Ramp Approach Area

The landside ramp approach area must be configured to allow drivers to maneuver their vehicle and trailer into position on the boat ramp. A vehicular-trailer movement study of the ramp approach area was conducted to determine the projected pathways of vehicle and trailer during launching operations (approach, back-up, and pull-away maneuvers at the ramps). The AutoTurn© program, which simulates the wheel movements of selected vehicle type as it progresses through a pre-defined path, was applied for a combination car/truck and boat trailer moving at a constant speed of 9.7 kilometers per hour. The analysis indicates that the incorporation of a partial round-about will allow vehicle-trailer units to “set-up” the orientation of the trailer prior to reaching the hardstand area in front of the ramp. A typical-car trailer requires a 10.7m turning radius. The inside radius of the round-about has been set to this distance.

Boat Launching

The boating launch ramp has been designed with a boarding float to allow boaters to load and unload personnel and property during launch and retrieval operations. The boarding float is 18.3m long to accommodate multiple boats simultaneously. Boats may be positioned on either side of the boarding float. The float is 1.8m wide and is accessible via a 1.5m wide articulating gangway. The deck height of the boarding float has been designed at 0.5m above water level to allow comfortable access to boats in the water.

A.3.5 Dock and Pier Configuration

The Discovery Bay Marina may experience extreme fluctuations in water level during episodic flood events from the Caño Madre Vieja and Rio Culebrinas. To protect the marina infrastructure, the boat docks have been designed as floating platforms capable of rising and falling with the potential flood waters. The docks will be anchored by steel or concrete guide piles extending a sufficient distance above the projected flood level to secure the floating platforms as they rise with the flood water, preventing the docks from floating away. Under typical conditions, the dock platforms will float 0.5m above the still water level with a similar depth extending below the surface to provide buoyancy.

Vessels in the marina during flood events may be subject to high velocity flows. To reduce potential drag forces, the docks have been aligned so as to orient the keel of the vessels parallel to the direction of flow. Where possible, vessels will be oriented with their bow into the flood flow to further reduce drag.

Dock access will be limited to pedestrian traffic and motorized carts and will be controlled by access control gates. To accommodate the expected traffic levels, the main docks have been designed to a width of 3m. This will provide sufficient room for the carts to safely pass other carts and pedestrians and to safely turn around. The finger piers extending perpendicular from the main pier will be 1.5m wide in the areas with boats greater than 9.1m (30 feet). The finger



piers in the area with boats less than 9.1m (30-feet) will be 0.9m wide. Dock access from the promenade area will be via 3m wide ramps that will be sloped to meet Americans with Disabilities Act (ADA) guidelines.

Dockside amenities include potable and fire-suppression water supplies and electrical services. Sanitary waste pumpout stations are included at each re-fueling dock. In addition, the three docks nearest the marina entrance (Docks A, B, and C) offer in-slip sanitary pump-outs. These docks (Docks A, B, and C) also have in-slip diesel fueling. All pump-out and fueling activities shall be performed by trained marina staff. Spill prevention and containment plans shall be prepared and implemented by the marina staff.

A.3.6 Reconfiguration Perimeter

A Reconfiguration Perimeter has been established and is shown on the accompanying permit drawings. The Reconfiguration Perimeter encompasses the entire berthing area within the marina. The proposed Reconfiguration Perimeter would allow Discovery Bay Resort & Marina limited flexibility to modify the widths and lengths and make slight changes in the locations of the docks and piles within the Reconfiguration “envelope” to meet any field conditions encountered during construction, ongoing maintenance, and replacement needs of the floats and/or changes in the needs of Discovery Bay Resort & Marina.

The Reconfiguration Perimeter, however, would not allow Discovery Bay Resort & Marina to extend beyond that area presently being approved, nor to exceed 500 boats slips or the square footage of floats being approved. The net effect would be to encourage safer use, management and future maintenance by allowing for the minor adjusting of the widths, lengths and/or locations of the structures. Without the Reconfiguration Perimeter, Discovery Bay Resort & Marina would have to undertake lengthy annual regulatory reviews to obtain permission to undertake even the most minor changes. The Army Corps of Engineers has endorsed this concept not only in individual permits that are issued but also in their Nationwide Permits.

A.3.7 Construction Methodology

Construction of the Discovery Bay Marina basin will be performed under dry conditions, to the extents possible, using land based excavation and earth moving equipment. Flow through the Caño Madre Vieja will be maintained separate from the marina basin. If found to be geotechnically suitable, the material excavated from the marina basin construction will be reused for levee and upland fill.

The existing entrance structures will be reshaped and extended using land based construction methods. The existing armor stone will be removed as necessary and stockpiled for reuse. Land based equipment will be used to extend the core, underlayer, and sideslope armor of the jetty to the offshore terminus. The structure crest has been designed to be sufficiently wide to accommodate typical land based equipment to facilitate land based construction.

Erosion and sediment control will be maintained with floating turbidity curtains around the entrance jetties during construction and with silt fencing around the marina basin excavation.



Water collecting in the marina basin will be routed to a ponding area where sedimentation and clarification of the water will occur prior to discharge.

A.3.8 Construction Sequence

The construction of the Discovery Bay Marina will begin with the installation of erosion and sediment control measures around the perimeter of the area to be disturbed during construction. With erosion and sediment control in place, the site may be cleared of vegetation and existing structures which consist primarily of culverts under unpaved access roads.

Basin excavation will begin following site clearing and structure demolition, and the construction of a settling/collection basin. Hydraulic pumping into the settling/collection basin is required to maintain dry conditions. Excavation of a perimeter trench to finish grade will enable construction of the marina bulkheads and interior shore protection revetments while basin excavation is ongoing.

The marina entrance channel will be dredged following the installation of a floating turbidity curtain. Jetty reshaping and extension may then proceed with the armor stone extending to the channel bottom.

Following basin excavation, bulkhead and revetment construction, and jetty reshaping and extension, the marina entrance may be fully connected to Aguadilla Bay, allowing the basin to flood. The marina dock guide and fender piles will be driven from floating barges followed by floating dock and utility installation.



Figure A.3-1: Channel Depth Schematic



Figure A.3-2: Existing Shoreline Structures

North Jetty

South Jetty

Cano Madre Vieja



Figure A.3-3: Marina Basin Alternative 1



Figure A.3-4: Marina Basin Alternative 2



Figure A.3-5: Preferred Marina Basin Configuration



A.4 REFERENCES

Aguadilla Breakwater Wave Buoy Data: ERDC Field Analysis Branch web-site: (http://sandbar.wes.army.mil/public_html/pmab2web/htdocs/puertorico/puertorico.html)

Bathymetry Data: NOAA GEODAS web-site: (http://www.ngdc.noaa.gov/mgg/geodas/geodas.html)

Dean, R.G., and R.A. Dalrymple (2002), Coastal Processes With Engineering Application, Cambridge University Press, Campbridge, 475 pp.

Galvin, C. J. (1979) Relation between immersed weight and volume rates of longshore transport, CERC TP 79-1, US Army Waterways Experiment Station, Vicksburg, MS.

Kendall, M.S., M.E. Monaco, K.R. Buja, J.D. Christensen, C.R. Kruer, and M. Finkbeiner, R.A. Warner (2001), On-line Reference, “Methods Used to Map the Benthic Habitats of Puerto Rico and the U.S. Virgin Islands,” Internet Web site: http://biogeo.nos.noaa.gov/projects/mapping/caribbean/startup.htm. Also available on U.S. National Oceanic and Atmospheric Administration. National Ocean Service, National Centers for Coastal Ocean Science Biogeography Program. 2001. (CD-ROM). Benthic Habitats of Puerto Rico and the U.S. Virgin Islands, Silver Spring, MD, National Oceanic and Atmospheric Administration.

McLaren, P., and S. Hill (2003), “A Sediment Trend Analysis (STA®) at Aguadilla, Puerto Rico,” GeoSea Report to the United States Army Corps of Engineers, Jacksonville District.

Mercado, Aurelio. Coastal Flooding Impact Report (100-Year Return Period Event). Report to Cordeco Land Services Corp. March, 2002.

Morelock, J. (1978) Shoreline of Puerto Rico. <http://geology.uprm.edu/Morelock/GEOLOCN_/clnpr.htm>

Morelock, J. (1984), “Coastal Erosion in Puerto Rico,” Shore and Beach, Vol. 52, No. 1, pp. 18-27.

Morelock, J. (2003) Coastal study sites west coast Puerto Rico, Field Trip Guide. <http://geology.uprm.edu/Morelock/GEOLOCN_/clnsite.htm>

Morelock, J. and M. Barreto. (2003), “An Update on Coastal Erosion in Puerto Rico,” Shore and Beach, Vol. 71, No. 1, pp. 7-11.

NOAA Coastal Services Center, Historical Hurricane Tracking Tool, Electronic Reference. Retrieved February 25, 2005, Internet Web Site: http://hurricane.csc.noaa.gov/hurricanes

NOAA-CO-OPS. September 2005. <http://www.co-ops.nos.noaa.gov/>.

http://sandbar.wes.army.mil/public_html/pmab2web/htdocs/puertorico/puertorico.html

http://www.ngdc.noaa.gov/mgg/geodas/geodas.html

http://biogeo.nos.noaa.gov/projects/mapping/caribbean/startup.htm

http://geology.uprm.edu/Morelock/GEOLOCN_/clnpr.htm>

http://geology.uprm.edu/Morelock/GEOLOCN_/clnsite.htm>

http://hurricane.csc.noaa.gov/hurricanes

http://www.co-ops.nos.noaa.gov/



NOAA-NOS-NWC June, 2005. <http://www.nhc.noaa.gov/>.

NOAA-NWS Forecast Center. June 2005. http://www.srh.noaa.gov/tlh/climate/)

Segarra, Dr. Rafael, P.E. Hydrologic-Hydraulic Study for the Relocation of a Flood Control Levee at Rio Culebrinas Barrio Espinar Aguadilla, Puerto Rico. October, 2001.

USACE. Hydraulic Design of Small Boat Harbors. EM 1110-2-1615. Department of the Army. Washington D.C. September 1984.

USACE. (2003). Coastal Engineering Manual.

WIS Data: Wave Information Studies web-site (http://frf.usace.army.mil/wis/)

http://www.nhc.noaa.gov/

http://www.srh.noaa.gov/tlh/climate/

http://frf.usace.army.mil/wis/

PUERTO RICO

DISCOVERY BAY RESORT AND MARINA

VICINITY MAP LOCATION PLAN

PERMIT SUBMITTAL

NOT TO BE USED FOR CONSTRUCTION

12 NOV 2007

PROJECT SITE

PROJECT LOCATION

AGUADA, PUERTO RICO 00602P.O. BOX 610

CORDECO LAND SERVICES CORP.

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· 1509 w. swann avenue suite 225 tampa, florida 33606 (813) 258-8818 ... southwest jetty against...

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