technical memorandum alternatives analysis –d final

Technical Memorandum

Mt. View Sanitary District 1Peyton Slough Hydraulic Relief Project September 15, 2014

C:\pwworking\sac\d0602225\Alt Analysis_PDR_DRAFT FINAL_9-15-2014.docx

ALTERNATIVES ANALYSIS – DRAFT FINAL

Mt. View Sanitary District, Peyton Slough Hydraulic Relief Project September 15, 2014

Reviewed by: Dennis Huff, P.E., Dolly Chen, P.E. Prepared by: Kevin Calderwood, P.E.

1. Introduction

BackgroundMt. View Sanitary District (District) is an independent district, formed in 1923, that provides wastewater collection, treatment, and disposal services for the central portion of the City of Martinez and adjacent unincorporated areas to the northeast. The District serves an estimated population of 18,253 residents in a service area of approximately 4.7 square miles.

Mt. View Sanitary District was the first wastewater agency on the West Coast to construct and reclaim a wetland (Moorhen Marsh) using wastewater effluent as the primary water source. As wastewater flows to the treatment plant and effluent flows from the plant increased, the acreage of the wetlands grew from 21 to 86 acres. Additional acreage was acquired as a result of joint management agreements with other agencies for a total of 151 acres of wetlands. The District now has primary management responsibility for the original effluent dominated Moorhen Marsh and the tidally influenced McNabney Marsh (formerly Shell Marsh) which is located adjacent to I-680 and Waterfront Road in Martinez, CA.

The Moorhen/McNabney marsh system is shown in Figure 1 below.

The management of McNabney Marsh is advised by the Peyton Slough Wetlands Advisory Committee (PSWAC). The Committee is co-chaired by Mt. View Sanitary District and the California Department of Fish and Wildlife and is comprised of adjacent land owners, interested regulatory agencies, and various interested organizations and individuals.




Figure 1. Moorhen/McNabney Marsh System

Peyton Slough crosses Waterfront Road and the Union Pacific Railroad (UPRR) connecting McNabney Marsh to the Suisun Bay to the north. In 2009, the District, Rhodia, Inc., and the Contra Costa Mosquito Vector Control District, with the support of the PSWAC, completed improvements to tide gates on Peyton Slough, allowing tidal action into McNabney Marsh for the first time in nearly a century. However, an existing box culvert under the UPRR appears to be too small and shallow to allow full tidal flow into McNabney Marsh. Figure 2 shows the existing culvert, seen from Waterfront Road, which is located ½ mile south of the Peyton Slough tide gates. Previous studies have identified UPRR’s box culvert as a critical impediment to the restoration of tidal flows to McNabney Marsh. However, these studies offered differing views on the feasibility of restoring the marsh.




Figure 2. Existing UPRR Culvert on Peyton Slough

UPRR planned to replace the box culvert as mitigation for impacts elsewhere, but later elected to pursue another mitigation project due to the political challenges associated with the slough and tide gates at the time. Since then, the District has taken control of the project. To date, the project focus been on replacement of the box culvert with a conventional trapezoidal channel and a rail bridge. Other alternatives have not been thoroughly evaluated or discussed with UPRR.

In early 2014, Tesoro Corp. completed construction of a new pipe bridge to support and protect their oil pipeline running along the southern side of the UPRR tracks. This pipeline can be seen in the foreground of Figure 2, and the new pipe bridge is shown in Figure 3.




Figure 3. Tesoro Pipeline Bridge

PurposeThe objective of the Peyton Slough Hydraulic Relief Project (Project) is to restore tidal action and brackish water conditions to the McNabney Marsh by removing the hydraulic restriction limiting tidal flows into and out of the marsh.

The existing UPRR culvert has been identified as a possible hydraulic bottleneck limiting tidal action in McNabney Marsh. The existing box shaped structure appears to be both too narrow and too shallow to provide optimal water exchange between the marsh and Suisun Bay/Carquinez Strait. During operation of the Peyton Slough Tide Gates, which began in 2009 and have continued intermittently since, the high tides provide tremendous energy to drive flow through the tide gates, up Peyton Slough, and through the restriction into McNabney Marsh. However, during low tides, there is much less hydraulic energy available to push flows back through the restriction out of the marsh. More water enters than can exit, resulting in a “pumping up” of the marsh. This pumping up phenomenon has the effect of creating high water levels within McNabney Marsh, threatening flooding of waterfowl nesting habitat and adjacent infrastructure including Waterfront Road, existing petroleum pipelines, Arthur Road, and existing local storm-drainage channels. The lack of proper drainage also increases the residence time of the water and the natural tendency of the marsh to develop areas of nearly stagnant water, impacting the water quality and habitat values within the marsh. In 2012, the marsh experienced an unprecedented algal bloom, which appeared to be exacerbated by the lack of water exchange between the Marsh and the Strait.

Replacement of the UPRR culvert may serve to help accomplish the Project objective. If, however, constraints elsewhere in the marsh were to prevent adequate tidal exchange,




replacement of the culvert may not be warranted. A detailed hydraulic evaluation of the marsh as well as a thorough identification and evaluation feasible alternatives are needed to select the best alternative for improving tidal action in McNabney Marsh.

2. Work Completed to Date

Topographic Surveying A topographic survey of the area around the UPRR culvert was conducted in September, 2013. The survey extended along Peyton Slough for approximately 500 feet from the UPRR culvert to the north and south, and along the UPRR/Waterfront Road corridor for approximately 500 feet to the east and west. Mapping was provided with a 1-foot contour interval, on the NAVD 88 Vertical Datum, and on the California Coordinate System of 1983, Zone 3 horizontal control system.

Additional surveying was conducted in November, 2013 to investigate an apparent high spot in the Peyton Slough channel north of the UPRR crossing (discussed below) and to confirm the dimensions of the existing culvert. The culvert was initially thought to be shallower than indicated by the first topographic survey. The subsequent survey also showed that the UPRR culvert does not appear to be a concrete bottom—rather it appears to be a 10-foot wide “bridge” structure resting on wide concrete footings at either side. Figure 4 shows a typical section through the existing culvert. Note that the sizes of the footings and the thicknesses of the culvert walls and ceiling are shown schematically—actual dimensions are unknown.

Figure 4. UPRR Culvert Section

The subsequent survey work showed that the bottom of the existing channel north of the UPRR culvert is higher than the rest of the slough bottom. In this section, the slough bottom is between 0.6 and 1.0 feet higher than the slough bottom within the UPRR culvert. The effects of this




condition are discussed in the Hydraulic Modeling section below. A third round of surveying was completed in July 2014 to determine the channel geometry north of previous surveys to the Peyton Slough Tide Gates, and to allow the hydraulic model to be extended to the tide gates. This survey did not find additional high spots other than the one near the UPRR culvert. While the slough channel geometry varies throughout the reach, in general it consists of a trapezoidal channel with a bottom width of approximately 15 to 18 feet, sides sloping between 2:1 and 3:1, and a top width of 32 to 35 feet. A typical slough section is shown in Figure 5.

Figure 5. Typical Peyton Slough Section

The topographic mapping is included in Appendix A.

Hydraulic Modeling A detailed hydraulic evaluation of Peyton Slough was undertaken to identify the best likely alternative for restoring the marsh. The initial assessment focused on determining the degree to which a larger UPRR opening would improve tidal exchanges between Peyton Slough north (downstream) of the structure and McNabney Marsh south (upstream) of the structure. The performance of design alternatives was compared with the performance of the existing structure for typical differences in the water surface.

A HEC-RAS hydraulic model of Peyton Slough in the vicinity of the UPRR was developed from the detailed topographic data. The model extended approximately 750 feet north and 510 feet south of Waterfront Road Bridge. Typical roughness and entrance loss values were used. The base model included the existing UPRR crossing. Copies of the base model were modified to evaluate alternatives for the existing structure. A Technical Memorandum was prepared describing the modeling efforts and detailing the results. This TM is included in Appendix B.

Hydraulic modeling results for each alternative are discussed in Section 4 below, however one significant result should be noted. The high spot in the Peyton Slough bottom discovered north of the UPRR bridge was included in the model, and scenarios were run with and without the high spot (without to evaluate the results of dredging the slough to eliminate the obstruction). The modeling showed that removal of the high spot would have a significant effect on flows into and out of the marsh, particularly at low tidal stages. The additional surveying conducted in July 2014 and subsequent modeling confirmed these results.




3. Project Alternatives Three alternatives were developed for the replacement of the UPRR culvert: 1) replacing the culvert with a new railroad bridge and full-width trapezoidal channel, 2) twin reinforced concrete box culverts installed by traditional open-cut excavation methods, and 3) twin reinforced concrete circular culverts installed by trenchless methods (i.e., bore-and-jack). The project alternatives are described in greater detail below.

Alternative 1 – New UPRR Bridge The first alternative is the construction of a standard UPRR railroad bridge with a trapezoidal slough channel. This is the alternative originally planned by UPRR but abandoned due to political challenges associated with the tide gate construction. The bridge would be approximately 40 feet long by 30 feet wide (to accommodate the twin UPRR track at this location). The trapezoidal channel below would have side slopes at 1 ½:1, and a bottom elevation to match the adjacent slough. The proposed bridge is shown in Figure 6.

Figure 6. UPRR Standard Rail Bridge

Alternative 2 - Twin Rectangular Box Culverts The second alternative is the replacement of the existing culvert with two pre-cast reinforced concrete box culverts. The culverts would be installed by conventional, open-cut construction methods. For the purposes of this evaluation, the culverts were sized at six feet square. Final wall thickness and structural details for the culverts would be determined during final design, if this alternative is carried forward. The proposed culverts are shown in Figure 7.




Figure 7. Twin Rectangular Box Culverts

Alternative 3 - Twin Circular Culverts The third alternative is the replacement of the existing culvert with two 84-inch diameter circular reinforced concrete culverts, installed by trenchless methods, as shown in Figure 8. Note that for modeling purposes, the existing channel was assumed to be abandoned or plugged, with flow through the new culverts only. For trenchless crossings of this diameter and length, typical construction methods include bore-and-jack and pipe ramming. Bore and jack crossings require strong backstops for the jacking frame to push against. This backstop is usually constructed along the back wall of a jacking shaft. Because the culverts must be placed at a very shallow excavation, construction of a backstop is somewhat problematic. Also, the risk of overexcavation and settlement above the casing is greater with bore and jack crossings. Settlement beneath the railroad tracks is unacceptable. For these reasons, pipe ramming is a more appropriate trenchless method for this installation.

In pipe ramming, a steel casing is driven through the existing soils with a pneumatic ram. A jacking shaft/backstop is not required. Because the soil within the casing is not removed until after the casing has been installed, the risk of settlement is much lower. Pipe ramming is commonly used for casing installation beneath railroads, and UPRR is familiar with the technology. Figure 9 shows a typical pipe ramming setup.




Figure 8. Twin Circular Culverts

Figure 9. Pipe Ramming

4. Alternatives Evaluation

Hydraulic Performance In general, the hydraulic modeling indicates that none of the alternatives provides substantial improvement in tidal flows into or out of McNabney Marsh. For flows from McNabney Marsh, no scenario modeled improves efficiency through the culvert by more than about five percent. Results for flows into McNabney Marsh are similar. This would indicate that the existing UPRR culvert is not a significant impediment to flows, particularly at low stages. This is most likely due to the short length of the culvert and the low velocities associated with low tidal stages.

Figures 10 and 11 show the modeling results for flows into and out of McNabney Marsh. In each figure the orange line represents existing conditions, the dark blue line the dredged channel with no improvements to the UPRR culvert, and the other lines the various modeled alternatives. These figures show that a relatively large improvement can be made by dredging the channel




upstream of the UPRR crossing, but replacing the culvert only provides marginal additional benefit.

Looking at Figures 10 and 11 at a given stage, the flows are much larger for the dredged existing channel than for the existing channel without dredging, while the additional benefit of improving the UPRR culvert is much less. Also, it can be seen that the improvement are very similar for all of the modeled alternatives. The differences in hydraulic performance of the alternatives do not appear to be a significant factor in selecting a preferred alternative.

Figure 10. Flows from McNabney Marsh

2

2.5

3

3.5

4

4.5

0 10 20 30 40 50 60 70 80 90 100

Stage,feet,N

AVD8

8,inMcN

abne

yMarsh

Flow (cfs)

Stages in McNabney Marsh for Alternatives with Dredged Channeland Low Stages in North Peyton Slough

Existing UPRR Bridge Two 6' Box Culverts

Two 84 RCP Culverts No Structure Existing w/o dredging




Figure 11. Flows into McNabney Marsh

Impacts to UPRR Because of the limited space between Waterfront Road and the UPRR tracks and the presence of multiple petroleum pipelines in this area, working on the south side of the railroad does not appear feasible. The only access to the available areas along the north side of the railroad is from the tracks themselves. Therefore, it is likely that any alternative would require that materials and equipment be brought in via the railroad. Furthermore both Alternatives 1 and 2 would be constructed with traditional open-cut methods and would require removal and replacement of UPRR tracks. While the construction of Alternative 2 would be of a shorter duration than Alternative 1, it is likely that impacts on UPRR operations for either of these alternatives would be large. Alternative 3 can be installed with trenchless methods, minimizing impacts to UPRR operations. This alternative is clearly superior with regards to this criterion.

Impacts to Waterfront Road All alternatives can be constructed without requiring the closure of Waterfront Road. Because construction staging will need to be north of the railroad, and materials and equipment would need to be brought in via the railroad, impacts to Waterfront Road would likely be minimal (and similar) for all alternatives.

2

2.5

3

3.5

4

4.5

0 10 20 30 40 50 60 70 80 90 100

Stage,feet,N

AVD8

8,inNorth

Peyton

Slou

gh

Flow (cfs)

Stage in North Peyton Slough for Alternatives with Dredged Channeland Low Stage at McNabney Marsh






Layout/Construction Area Needs As described above, layout space for construction of all alternatives would need to be located north of the UPRR railroad. Layout/construction area for Alternative 1 would be greater than for either Alternative 2 or 3, due to the greater excavation required for the trapezoidal channel and the complexity of constructing a new railroad bridge. Alternatives 2 and 3 would require less room, and layout/construction area needs for those alternatives would be similar.

For each alternative, a gravel construction mat would be required to provide a stable, level, dry surface on which to work. For Alternative 1, the required mat is estimated to be 250 feet long by 30 feet wide, and would be constructed along the north side of the rail line. Temporary culvert piping installed beneath the gravel mat could be used to allow Peyton Slough flows to reach McNabney Marsh. For Alternatives 2 and 3, the required mat is estimated to be 150 feet long by 30 feet wide, with similar accommodation for Peyton Slough flows. In all cases, removal of the gravel mat and restoration of the wetlands would be needed upon completion of construction.

Layout/construction area requirements are shown on figures included in Appendix C.

Because Alternatives 2 and 3 require less layout space than Alternative 1, they are ranked higher in this category.

Potential Environmental Impacts As part of this Alternatives Analysis, HDR performed a preliminary environmental screening analysis of the proposed alternatives to identify the major potential environmental constraints (endangered species, habitat types, and permitting requirements) for the proposed alternatives.

Habitat types in the project area include wetlands/waters of U.S. (Peyton Slough) and marshlands. The dominant vegetation in the project area consists of California bulrush (Scirpus californicus),narrow-leaved cattail (Typha angustifolia) and three-square (Scirpus americanus). This vegetation forms a band immediately adjacent to the top of the banks of the Slough. Other subdominant species that occur along the Slough include common reed (Phragmites australis),Baltic rush (Juncus balticus), and tall flatsedge (Cyperus eragrostis). Wetland vegetation that extends east and west of the Slough in the project area includes the following dominant species: saltgrass (Distichlis spicata), fat hen (Atriplex triangularis), Baltic rush, pickleweed (Salicorniavirginica), and alkali heath (Frankenia salina). These habitat types and vegetation communities provide suitable resting, foraging, roosting, and breeding habitat for several terrestrial and aquatic animal species. Special Status Species with the potential to be affected by the proposed alternatives are listed in Table 1, along with their listing status under federal and state law.




Table 1. Potentially Affected Special Status Species

Species name

Listing Status

Federal Endangered Species Act

(ESA)

State Endangered Species Act (CESA)

California Native Plant Society

(CNPS)

InvertebratesSpeyeria callippe callippe callippe silverspot butterfly E None NA

Fish Hyposmesus transpacificus delta smelt T T NA

Critical habitat for delta smelt T None NA Oncorhynchus mykiss steelhead - Central Valley, California ESU

T None NA

Critical habitat for Central Valley steelhead T None NA

Oncorhynchus tshawystscha Sacramento River winter-run Chinook salmon

E E NA

Critical habitat for Sacramento River winter-run Chinook salmon E None NA

Oncorhynchus tshawystscha Central Valley spring-run Chinook salmon

T T NA

Critical habitat for Central Valley spring-run Chinook salmon T None NA

Oncorhynchus tshawystscha Central Valley fall/late fall-run Chinook salmon

Ca SC NA

Critical habitat for Central Valley fall/late fall-run Chinook salmon Ca None NA

Pogonicthys macrolepidotus Sacramento splittail

T SC NA

BirdsFalco peregrinus anatum American peregrine falcon

DMNBMC F Pr. NA

Haliaeetus leucocephalus bald eagle PD E

F Pr. NA

Rallus longirostris obsoletus California clapper rail E E

F Pr. NA

Sterna antillarum (=albifrons)browni California least tern

EMNBMC

EF Pr. NA

MammalsReithrodontomys raviventris salt marsh harvest mouse

E EF Pr.

NA

PlantsCordylanthus mollis spp. mollis soft bird’s-beak

E Rare S1.1

1B




Notes:E – Endangered T – Threatened PE – Proposed for listing as Endangered PT – Proposed for listing as Threatened Ca – Candidate for listing SC – Species of Concern MNBMC – Migratory Nongame Birds of Management Concern D – Delisted PD – Proposed for Delisting Pr – CDFW Protected F Pr – CDFW Fully Protected California Native Plant Society S1.1 – Very Threatened and less than 6 environmental occurrences (EOs) OR less than 1,000 individuals OR less than 2,000 acres 1B – Rare or Endangered in California and elsewhere

The proposed alternatives would each result in potentially significant environmental impacts given the sensitive habitat types and species that occur or are likely to occur in the project area. The level of impacts to habitat types and species in the project area would be generally the same amongst the proposed alternatives and would only vary by the acreage of affect to individual habitat types and the species that utilize those habitat types. Thus, preparation of an Environmental Impact Report under the California Environmental Quality Act (CEQA) would be the appropriate level of environmental documentation for the project. In addition, each of the proposed alternatives would require approvals and permits in compliance with the following federal and state laws and regulations. Additional local approvals and permits (City and County ordinances and standards) may also be required for the proposed alternatives.

Clean Water Act, Section 404 Compliance (for fill of wetlands and waters of the U.S. administered through the U.S. Army Corps of Engineers [USACE])

Federal Endangered Species Act, Section 7 Compliance (administered through the USACE 404 permitting process and issued by the U.S. Fish and Wildlife Service [USFWS] and the National Marine Fisheries Services [NMFS])

National Historic Preservation Act, Section 106 Compliance (administered through the USACE 404 permitting process and issued by the State Historic Preservation Officer [SHPO])

Clean Water Act, Section 402 Compliance (National Pollutant Discharge Elimination System (NPDES) Program administered through the Regional Water Quality Control Board [RWQCB])

Clean Water Act, Section 401 (Water Quality Certification administered through RWQCB)

California Endangered Species Act, California Fish and Game Code (CDFG Code) 2081 Compliance (administered through the California Department of Fish and Wildlife [CDFW])

CDFG Code Section 1602 (Streambed Alteration Agreement administered through CDFW)




Bay Conservation and Development Commission (BCDC) Permit

Bay Area Air Quality Management District (BAAQMD), Authority to Construct Permit

Easement or Right-of-Way Needs Because all permanent improvements would be located within the UPRR right-of-way, no permanent easement or property needs should be required. All alternatives will require an encroachment permit from UPRR.

All alternatives will require temporary construction easements within marshlands on both sides of the railroad, with the majority of the space required on the north side. Because the work needed for a new bridge is much more extensive and complicated than for box culverts or circular culverts, the temporary construction easement needs for Alternative 1 are greater than those for Alternative 2 or 3.

Temporary construction easement requirements are shown on the figures in Appendix C.

Cost Planning-level cost estimates have been prepared for all three alternatives. The detailed estimates can be found in Appendix D; costs are summarized in Table 2 below. These costs include allowances for engineering design and construction management, but do not include easement acquisition.

Table 2. Estimated Alternative Costs

Alternative Description Estimated Construction Cost

1 New UPRR Bridge $2,510,400

2 Reinforced Box Culverts $1,165,100

3 Trenchless Circular Culverts $1,727,100

Risk Construction of all alternatives should be relatively straightforward, with no “cutting-edge” or high-risk methods required. Alternatives 1 and 2 will require closure of the rail line and removal of track. This railroad alignment is a busy line, used for both freight and Amtrak’s Capital Corridor passenger trains. Unexpected construction delays that affect rail operations are a risk for each of these alternatives, though the risk is greater for Alternative 1 due to the more complicated nature of bridge construction and longer construction schedule.




Alternative 3 would use trenchless methods, so the risk of unexpected impacts to rail operations is much lower than with the other two alternatives. Trenchless construction always carries higher risk than conventional open-cut construction, as unexpected obstacles can stop a trenchless installation and are more difficult to resolve without excavation. Because of the short lengths of the crossings, this risk is considered low, and can be mitigated with an appropriate geotechnical investigation during the design phase.

5. Recommendations

Alternative Ranking A matrix for evaluating alternatives has been developed and is presented in Table 3 below. In this matrix, raw scores from one to five (one being least favorable, five being most) have been assigned to each criterion discussed in Section 4 for each alternative. Furthermore, a weight factor has been assigned to each criterion to account for that criterion’s importance to the alternative selection. Weight factors are also from one to five (one being least heavily weighted, five being most). Scores for each criterion are the product of the raw score and the weight factor. Scores for each alternative are totaled, and the alternative with the highest total is the most favored alternative.

Table 3. Ranking Matrix

CRITERIA WEIGHTFACTOR

ALTERNATIVES

1 - RAIL BRIDGE 2 - TWIN BOX CULVERTS

3 - TWIN CIRCULAR CULVERTS

(TRENCHLESS) Raw

Score Weighted

Score Raw

Score Weighted

Score Raw

Score Weighted

Score

Hydraulic Performance 4 3 12 3 12 3 12

Impacts to UPRR 4 1 4 2 8 4 16

Impacts to Waterfront Rd 2 2 4 2 4 2 4

Layout/Construction Area Needs 2 2 4 4 8 4 8

Potential Environmental Impacts 4 2 8 3 12 3 12

Easement or right-of-way needs 3 2 6 4 12 4 12

Cost 4 2 8 5 20 3 12

Risk 3 2 6 3 9 4 12

Total: 52 85 88




Preferred Alternative As can be seen on Table 3, Alternative 3 is the highest ranked alternative. Its low cost (compared to a new rail bridge) and low impacts to UPRR operations make it the preferred alternative among those evaluated.

It is important to note, however, based on the hydraulic analysis (see Appendix B), none of the alternatives alone are expected to substantially improve flows beneath the UPRR railroad, and none can be expected to significantly improve tidal action in the McNabney Marsh. Because improved tidal action and restoration of brackish conditions to McNabney Marsh are the stated objectives of the Project, none of the alternatives evaluated can be recommended for meeting those goals.

The hydraulic analysis indicates that dredging the Peyton Slough channel to eliminate the high spot in the channel bottom north of the UPRR crossing would be a much more effective measure for meeting the Project goals. The additional topographic mapping conducted in July 2014 and the subsequent hydraulic modeling have served to confirm this conclusion. It is recommended that this be explored further.

6. Next Steps A detailed evaluation of the issues associated with dredging the Peyton Slough channel is beyond the scope of this report, however such an evaluation appears to be warranted, given the potential benefits. A more thorough evaluation should include:

Investigation and evaluation of the costs, permitting requirements, potential environmental impacts, etc., of a slough improvement project.

Development of a Preliminary Design Report (PDR) for a slough improvement project summarizing the results of the evaluation and identifying a proposed project scope, design criteria, etc.

This evaluation and PDR could then be followed by detailed design of channel improvements.

APPENDICES

Appendix A

Topographic Mapping

Appendix B

Hydraulic Analysis Technical Memorandum


Mt. View Sanitary District 1 Peyton Slough Hydraulic Relief Project August 28, 2014 \\Sac-filsrv2\imagery\Projects\028_217143_MtView_SD_TO1_Peyton_Slough\Hydraulics\MVSD_Peyton Slough_Hydraulic Modeling TM_DRAFT 8.docx

HYDRAULIC MODELING – D R A F T Mt. View Sanitary District Peyton Slough Hydraulic Relief Project August 29, 2014

Project Background

Exhibit 1



Hydraulic Assessment

Findings



Exhibit 2

Table 1. Key Elevations

Location, Significance Elevation, feet, NAVD88

Bay MHHW (Martinez Gage) 5.82 Bay MLLW (Martinez Gage) 1.42 Minimum stage from the 2012 MVSD stage observations 2 Target stage for Rhodia marsh 3.62-3.92 Target stage for McNabney Marsh 3.2 Lowest elevation in Waterfront Road, highest allowable stage 4.1 Representative invert of existing UPRR crossing 0.62

Exhibit 3 Table 2



Table 2. Datums for MSVD Sondes

Gage Calculated Elevation of Tip (Bottom), ft NAVD88

Concurrent Observed Stage and Gage Pressure

Peyton Rhodia 2.08 2.18 Peyton McNabney 1.61 1.57 East Channel -0.02 n/a



Exhibit 6

Exhibit 7



Flows from McNabney Marsh Table 2

Table 2



Table 3. Stages in McNabney Marsh for Benchmark Flows, ft NAVD88

Alternative

Stage in Northern Peyton Slough

feet, NAVD88

Flow in cfs

10 20 30 40 50 60 70 80 90 100

Existing 2.0* 2.23 2.55 2.81 3.03 3.22 3.4 3.56 3.71 3.86 4.00

4.0 4.01 4.03 4.06 4.1 4.15 4.21 4.28 4.36 4.44 4.52

UPRR 2.0* 2.22 2.53 2.78 2.98 3.16 3.33 3.47 3.61 3.74 3.87

4.0 4.01 4.02 4.05 4.08 4.13 4.18 4.23 4.29 4.36 4.42

Two 6' W Box Culverts

2.0* 2.23 2.53 2.78 2.99 3.17 3.33 3.48 3.62 3.76 3.88

4.0 4.01 4.02 4.05 4.09 4.13 4.18 4.24 4.3 4.37 4.44

Two 84" RCP Culverts

2.0* 2.23 2.53 2.78 2.99 3.17 3.34 3.48 3.62 3.76 3.89

4.0 4.01 4.02 4.05 4.09 4.13 4.18 4.24 4.3 4.37 4.44

No Structure 2.0* 2.23 2.53 2.78 2.99 3.18 3.34 3.48 3.62 3.76 3.89

4.0 4.01 4.02 4.05 4.08 4.13 4.18 4.23 4.29 4.36 4.42

Table 3



Table 4. Stages in McNabney Marsh with Dredged Peyton Slough for Benchmark Flows, ft NAVD88

Alternative

Stage in Northern Peyton Slough

feet, NAVD88

Flow in cfs

10 20 30 40 50 60 70 80 90 100

Existing 2.0* 2.06 2.22 2.42 2.63 2.84 3.03 3.17 3.38 3.57 3.75

4.0 4.01 4.02 4.05 4.09 4.13 4.19 4.25 4.31 4.39 4.46

UPRR 2.0* 2.05 2.19 2.36 2.55 2.74 2.92 3.04 3.23 3.41 3.58

4.0 4 4.02 4.04 4.07 4.11 4.15 4.2 4.25 4.31 4.37


2.0* 2.05 2.19 2.37 2.56 2.75 2.93 3.06 3.25 3.44 3.61

4.0 4 4.02 4.04 4.07 4.11 4.15 4.21 4.26 4.32 4.39


2.0* 2.05 2.19 2.37 2.56 2.75 2.94 3.06 3.26 3.44 3.61

4.0 4 4.02 4.04 4.07 4.11 4.16 4.21 4.26 4.32 4.39

No Structure 2.0* 2.05 2.19 2.37 2.56 2.75 2.93 3.05 3.25 3.43 3.59

4.0 4 4.02 4.04 4.07 4.1 4.15 4.19 4.25 4.3 4.36

Figure 1 Table 3



Flows Into McNabney Marsh Tables 4 5 Figure 2

2

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0 10 20 30 40 50 60 70 80 90 100Stag

e, fe

et, N

AVD8

8, in

McN

abne

y M

arsh

Flow (cfs)

Figure 1 - Stages in McNabney Marsh for Alternatives with Dredged Channel and Low Stages in North Peyton Slough





Table 5. Stages in North Peyton Slough for Benchmark Flows, ft NAVD88

Alternative

Stage in McNabney

Marsh feet, NAVD88

Flow in cfs

10 20 30 40 50 60 70 80 90 100

Existing 2.0* 2.23 2.53 2.78 3 3.2 3.39 3.59 3.77 3.95 4.12

4.0 4.01 4.03 4.07 4.12 4.18 4.25 4.32 4.41 4.49 4.59

UPRR 2.0* 2.22 2.51 2.76 2.97 3.15 3.33 3.5 3.66 3.81 3.96

4.0 4.01 4.02 4.05 4.08 4.13 4.18 4.24 4.3 4.37 4.43


2.0* 2.23 2.52 2.76 2.98 3.16 3.33 3.51 3.67 3.82 3.97

4.0 4.01 4.02 4.05 4.09 4.13 4.18 4.24 4.3 4.37 4.44


2.0* 2.22 2.51 2.75 2.96 3.15 3.32 3.49 3.65 3.81 3.95

4.0 4.01 4.02 4.05 4.08 4.13 4.18 4.24 4.3 4.37 4.44

No Structure 2.0* 2.22 2.51 2.75 2.96 3.14 3.31 3.48 3.64 3.8 3.95

4.0 4.01 4.02 4.05 4.08 4.13 4.18 4.23 4.29 4.36 4.43



Table 6. Stages in North Peyton Slough with Dredging for Benchmark Flows, ft NAVD88

Alternative Stage in McNabney Marsh feet, NAVD88

Flow in cfs

10 20 30 40 50 60 70 80 90 100

Existing 2.0* 2.07 2.23 2.45 2.67 2.89 3.1 3.33 3.53 3.73 3.9

4.0 4.01 4.02 4.05 4.09 4.13 4.19 4.25 4.31 4.39 4.46

UPRR 2.0* 2.05 2.19 2.38 2.57 2.77 2.96 3.18 3.38 3.56 3.73

4.0 4.00 4.02 4.04 4.07 4.1 4.15 4.2 4.25 4.31 4.37

Two 6' Box Culverts

2.0* 2.05 2.19 2.38 2.58 2.77 2.97 3.19 3.39 3.57 3.75

4.0 4.00 4.02 4.04 4.07 4.11 4.15 4.2 4.26 4.32 4.38


2.0* 2.05 2.19 2.38 2.57 2.77 2.96 3.22 3.42 3.61 3.78

4.0 4.00 4.02 4.04 4.07 4.11 4.16 4.21 4.27 4.33 4.4

No Structure 2.0* 2.06 2.2 2.39 2.6 2.8 3.00 3.18 3.38 3.56 3.73

4.0 4.00 4.02 4.04 4.07 4.1 4.15 4.2 4.25 4.31 4.37



Sedimentation and Erosion

2

2.5

3

3.5

4

4.5

0 10 20 30 40 50 60 70 80 90 100

Stag

e, fe

et, N

AVD8

8, in

Nor

th P

eyto

n Sl

ough

Flow (cfs)

Figure 2 - Stage in North Peyton Slough for Alternatives with Dredged Channel and Low Stage at McNabney Marsh





1

Conclusions and Recommendations


Exhibit 1 – Study Area

!

!

!

McNabney Marsh

North Marsh

South Marsh

Tide Gates

Shallow Reach

§̈¦680

§̈¦680

Marina Vista AveWaterfront Rd

SP Railroad

SP R

ailro

ad

PeytonSlough

Source: Esri, DigitalGlobe, GeoEye, i-cubed, Earthstar Geographics, CNES/AirbusDS, USDA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GISUser Community

National Geographic, Esri,DeLorme, HERE, UNEP-WCMC, USGS, NASA, ESA,

0 1,000Feet

F:\P

roje

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028_

2171

43_M

tVie

w_S

D_T

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Pey

ton_

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ugh\

Hyd

raul

ics\

MX

D\R

epor

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_8/2

7/20

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chav

ez

RailroadInterstate HwyHighwayMajor RoadStream

! GageCross Section

Service Layer Source: Esri, DigitalGlobe, GeoEye, i-cubed, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP,swisstopo, and the GIS User Community

National Geographic, Esri, DeLorme, HERE, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, increment P Corp.Gauges; HDR. Map information was compiled from the best available sources. No warranty is made for its accuracy or completeness.

Projection is NAD_1983_StatePlane_California_III_FIPS_0403_Feet

Exhibit 1

Study Area Study Area

1 inch = 1,000 feet


Exhibit 2 - Peyton Slough 2012 Stages


Exhibit 3 – McNabney Marsh Tide Gages


Exhibit 4 – Peyton Slough Stages (December 2010-May 2011)


-1

0

1

2

3

4

5

6

7

8

9

11/18/10 12/8/10 12/28/10 1/17/11 2/6/11 2/26/11 3/18/11 4/7/11 4/27/11 5/17/11 6/6/11

Stag

e , f

eet,

NAV

D88

Exhibit 4- Peyton Slough Stages - December 2010-May 2011

Martinez Peyton Slough at Tide Gates 1001695-Peyton Rhodia 1001696-Peyton McNabney 1006344-East Channel


Exhibit 5 – MVSD Sonde Stages (March- April 2014)


0

1

2

3

4

5

6

7

3/17/14 3/22/14 3/27/14 4/1/14 4/6/14 4/11/14 4/16/14 4/21/14

Stag

e, ft

, NAV

D88

Exhibit 5 -MVSD Sonde Stages-March-April 2014

Martinez 1001695 Peyton Rhodia 1001696 Peyton McNabney 1006344 East Channel


Exhibit 6 – MVSD Sonde Stages (March 2014)


2

2.2

2.4

2.6

2.8

3

3.2

3.4

3.6

3.8

3/18/14 12:00 AM 3/19/14 12:00 AM 3/20/14 12:00 AM 3/21/14 12:00 AM 3/22/14 12:00 AM 3/23/14 12:00 AM

Stag

e, ft

, NAV

D88

Exhibit 6 - MVSD Sonde Stages-March 17-21, 2014

1001695 Peyton Rhodia 1001696 Peyton McNabney 1006344 East Channel


Exhibit 7 – Sample HEC-RAS Profile

0 500 1000 1500 2000 2500 3000-4

-2

0

2

4

6

8

10

12Peyton Slough Plan: Existing Flow Series 4ft 8/27/2014

Main Channel Distance (ft)

Ele

vatio

n, fe

et N

AV

D88

(ft)

Legend

EG 100 cfs

WS 100 cfs

Ground

Appendix C

Construction Layout and Easement Needs

Appendix D

Preliminary Opinion of Probable Construction Costs

technical memorandum alternatives analysis –d final

Documents