feasibility study blackwells mills dam removal nj … · 2019-07-12 · feasibility study...

FEASIBILITY STUDY BLACKWELLS MILLS DAM REMOVAL

NJ DAM NO. 25‐203 MILLSTONE RIVER

HILLSBOROUGH AND FRANKLIN TOWNSHIPS, SOMERSET COUNTY, NEW JERSEY

PREPARED FOR:

STONY BROOK‐MILLSTONE WATERSHED ASSOCIATION

31 TITUS MILL ROAD PENNINGTON, NJ 08534

PREPARED BY:

PRINCETON HYDRO, LLC 1108 OLD YORK ROAD, SUITE 1

P.O. BOX 720 RINGOES, NEW JERSEY 08551

(P) 908.237.5660 • (F) 908.237.5666 email •[email protected]

FUNDED BY: FEBRUARY 2011 PRINCETON HYDRO PROJECT NO. 0390.004



FEBRUARY 2011

Princeton Hydro Project No. 0390.004

TABLE OF CONTENTS

1.0 Introduction........................................................................................................................ 1 2.0 Project Goals ...................................................................................................................... 1 3.0 History of Blackwells Mills Dam and Blackwells Mills, NJ .................................................. 2 4.0 Blackwells Mills Dam Construction and Condition............................................................. 3 5.0 Dam Ownership .................................................................................................................. 3 6.0 Impounded Sediment and Hydraulic Backwater................................................................ 4 7.0 Surrounding Geology.......................................................................................................... 9 8.0 Vegetation Survey ............................................................................................................ 10 9.0 Alternatives Evaluated ..................................................................................................... 11 10.0 Conceptual Approach to Full or Partial Dam Removal ..................................................... 11

10.1 Full Dam Removal ............................................................................................................. 12 10.2 Partial Dam Removal......................................................................................................... 12

11.0 Preliminary Hydrologic and Hydraulic Analysis ................................................................ 13 11.1 Storm Flows....................................................................................................................... 14 11.2 Geometry Data .................................................................................................................. 14 11.3 Roughness Coefficient ‘n’.................................................................................................. 15 11.4 Contraction and Expansion Coefficients ........................................................................... 15 11.5 HEC‐RAS Model ................................................................................................................. 15 11.6 Results ............................................................................................................................... 15

12.0 Anticipated Regulatory Permitting and Approvals........................................................... 16 12.1 NJDEP Dam Safety Construction Permit ........................................................................... 16 12.2 NJDEP Land Use Regulation Program (Bureau of Freshwater Wetlands) ......................... 17 12.3 NJDEP Division of Fish and Wildlife................................................................................... 18 12.4 State and Federal Historic Preservation Acts Review ....................................................... 18 12.5 Soil Conservation District .................................................................................................. 18 12.6 Local Approvals ................................................................................................................. 19

13.0 Cost Estimates for Construction ............................................................................................ 20 13.1 Full Removal ..................................................................................................................... 20 13.2 Partial Removal ............................................................................................................... 21 13.3 Engineering Design, Permitting and Construction Administration .................................. 21

14.0 Schedule ................................................................................................................................ 22 15.0 Conclusions and Recommendations ..................................................................................... 22 16.0 Next Steps.............................................................................................................................. 23

TABLE OF FIGURES

Figure 1. Date information from bridge p.2 Figure 2. Historic Blackwells Canal house p.2 Figure 3. Mill Race Spillway p.3 Figure 4. Dam Spillway looking upstream p.3 Figure 5. Spillway and toe facing east p.3 Figure 6. Locations of soil samples analyzed for contamination p.5



FEBRUARY 2011

Princeton Hydro Project No. 0390.004

TABLE OF TABLES

Table 1. Grain size analysis results for Millstone River sediment samples. p.6 Table 2. Chemical analysis results for Millstone River sediment samples. p.8 Table 3. Flow Rate and Frequency p.14 Table 4. Hydraulic Properties Summary p.16 Table 5. Preliminary Cost Estimate for Full Dam Removal p.20 Table 6. Preliminary Cost Estimate for Partial Dam Removal p.21

Appendices:

Appendix A – Project Information Maps Appendix B – Summary of Laboratory Analytical Results Appendix C – Vegetation Survey Appendix D – Base Maps Appendix E – Hydrologic and Hydraulic Information Appendix F – References

Princeton Hydro Project No. 390.004 1

1.0 Introduction

Princeton Hydro, LLC (Princeton Hydro) was contracted by the Stony Brook‐Millstone Watershed Association (SBMWA) to complete a feasibility study for the potential removal of the Blackwells Mills Dam located on the Millstone River, a major tributary to the Raritan River (please refer to the USGS Location map and Aerial map in Appendix A). The study was funded, in part, by the American Rivers (AR) ‐ National Oceanic and Atmospheric Administration (NOAA) Community‐Based Restoration Program. The Blackwells Mills Dam is a low head dam less than five feet in height. It is an old run‐of‐the‐river mill dam that no longer serves its intended economic purpose, quite typical of the types of dams commonly being removed all across the East Coast. The dam is the second known impediment to diadromous fish passage on the Millstone River upstream of the confluence with the Raritan River. The Weston Causeway Dam is the only known impoundment downstream of the Blackwells Mills Dam on the Millstone River. As a run of the river structure, the Blackwells Mills Dam has no ability to attenuate flows. The dam is approximately five feet high with a concrete weir spillway that varies between two and three feet in height. Under low or no flow conditions, the impoundment extends approximately 3.5 miles upstream, however, under any measurable flows, there is little to no impoundment as the dam is fully submerged. This feasibility study is the result of the effort by the SBMWA, AR, NOAA and a number of other project supporters, including:

• New Jersey Department of Environmental Protection (NJDEP), Bureau of Dam Safety and Flood Control;

• The Geraldine R. Dodge Foundation; • Conservation Resources Inc.; and • Patricia Kallesser of the Delaware and Raritan (D&R) Canal State Park, representing the

dam owner.

Removal of dams, which allows for restoration of diadromous fish passage, (a primary element of the function of NOAA under their Open Rivers Initiative), is required to address the restoration of the riparian corridor functions. These functions include natural flooding processes, sediment transport, and self‐sustaining fringe and floodplain wetlands. No other alternative to fish passage, such as fish ladders, rock ramps or nature‐like fishways, addresses all of the target riparian functions, and therefore, was not considered within this feasibility study. 2.0 Project Goals

SBMWA initiated this study after consulting the current dam owner, the NJDEP, and confirming its interest in investigating removal options. The owner is interested in removing the structure to reduce the potential public safety hazard, and to remove the corresponding regulatory requirements as promulgated by the New Jersey Dam Safety Regulations. While the dam is not in immediate danger of failure, the dam contains a number of structural deficiencies that require repair. Additionally, NJDEP has preliminarily classified it as a Significant Hazard Structure (Class II) – the failure of which may cause significant damage to property. Therefore, to reduce their liability for loss of life from the dam’s presence and liability for property damage in the event of its failure, the dam owner is interested in the possibility of removal or partial removal.

Likewise, the SBMWA is striving to restore the Millstone River to a free‐flowing state, maximize fish passage and provide ecological uplift within the watercourse. With these goals in mind, the


Figure 2. Historic Blackwells Mills Canal H

SBMWA has formed a natural partnership with AR and NOAA, a nonprofit‐government collaboration that focuses funding on removal efforts. Other alternatives, which may be viable, such as a fishway or fish ladder, would not be eligible for additional financial support under the AR‐NOAA program. In conducting the feasibility study for the removal of the Blackwells Mills Dam, three distinct design alternatives were evaluated, including the "no action" alternative, partial dam removal, and full removal of the dam. Various impacts resulting from implementation of each approach were evaluated including a preliminary hydrologic and hydraulic analysis, vegetation survey, and a comprehensive sediment analysis. 3.0 History of Blackwells Mills Dam and Blackwells Mills, NJ

Limited information is available on the Blackwells Mills Dam, so the full history of the dam is unknown. File reviews were completed with the D&R Canal State Park and NJDEP Bureau of Dam Safety & Flood Control and no existing information on the dam was available. Based on information from the Blackwells Mills Canal House Association and other local sources, it is assumed that the dam serviced the mill and was originally constructed with the mill in 1746 as described below. A placard was found on the current dam abutment dated 1915.

Blackwells Mills was situated on the west bank of the Millstone River about two miles south of Millstone Borough. A mill was first built there in 1746 by Peter Schenk. Through his daughter, the mill passed to the Mercer family, and later sold to Blackwell, who built a house on the land. According to a plaque on the bridge, the mill burned down in 1910. The D&R Canal along the river from Millstone to Blackwells Mills was a major force in the commercial development of the entire State of New Jersey. It was built to complete connections in the Intracoastal Waterway from New York State to Florida. The Blackwells Mills Canal House, located at Blackwells Mills Causeway and Canal Road in Franklin Township, was built around 1835 to house the swing bridge tender. The bridge tender would open the swing bridge when canal boats came through, then close it to allow traffic to cross over the canal. In 1932, the canal closed and the swing bridges were dismantled. Subsequently, ownership of the house and the canal were transferred to the State of New Jersey. The house continued to be occupied for more than 40 years. In 1971 a group of local canal supporters formed the Blackwells Mills Canal House Association. The State owns the house, but the Association together with the Meadows Foundation maintains the house as a community center, museum, and library. The adjacent Delaware and Raritan Canal is a state and national historic site and a New Jersey State Park.

Figure 1. Date information from Bridge


4.0 Blackwells Mills Dam Construction and Condition

The Blackwells Mills Dam is approximately three (3) feet in height and approximately 90 feet in length. The majority of the dam appears to be comprised of cast‐in‐place concrete. There was no visual evidence of the dam’s foundation construction, or the original superstructure of previous spillways. The embankments are vegetated earth with cast‐in‐place concrete abutments. The NJDEP identifies the dam as a Significant Hazard Structure (Class II). During low flow conditions, the linear impoundment is approximately 3.5 miles long in aerial extent. Immediately upstream of the dam is a bridge crossing for Blackwells Mill Causeway. The bridge spans Hillsborough and Franklin Townships. Upstream of the Blackwells Mills Causeway on river right, a portion of a remnant concrete spillway for the mill race still exists. This ancillary structure is approximately 18.9 feet long and is approximately 1.5 feet high.

Princeton Hydro engineers completed an informal visual inspection of the dam for compliance and to ascertain its current condition. Representatives of the NJDEP Bureau of Dam Safety and Flood Control were contacted to determine the dam’s original construction and condition, however, no historical construction information was available. The downstream face of the spillway appears to be in good condition. The upstream face is not visible as there is some sediment accumulation immediately behind the dam itself. An extensive hydraulic roller forms during routine flows.

An existing USGS gauge is located by the Blackwells Mills Causeway bridge and is listed as USGS Gauge No. 01402000 Millstone River at Blackwells Mills, NJ. The gauge has been collecting continuous data on the river since August 1921. Currently, the gauge collects temperature, river stage, and flow measurements. Since the gauge is located immediately upstream of the dam, it will require recalibration should the dam be removed. 5.0 Dam Ownership

The State of New Jersey through the Delaware and Raritan Canal State Park is the sole owner of the Blackwells Mills Dam. According to the tax records, the dam is located within Lot 7A of Block 206 in Hillsborough Township and within Lot 2 of Block 60 in Franklin Township. According to

Figure 5. Spillway and Toe Facing East. Figure 4. Dam Spillway Looking

Upstream

Figure 3. Mill Race Spillway


tax records the NJDEP is the listed owner of both properties as shown on the figure included in Appendix A of this study. 6.0 Impounded Sediment and Hydraulic Backwater Princeton Hydro staff investigated Blackwells Mills Dam and upstream reaches on the Millstone River on Thursday, March 4, 2010 following heavy precipitation and the recession of flood level flows. The USGS gauge (No. 01402000) recorded a discharge of 1400 cubic feet per second (CFS) at 8:30 AM, having dropped from the recent peak flow several hours earlier at 1430 CFS. The flows observed during this site visit exceeded 679 CFS, the mean of daily mean discharge for March 4th, 2010 based on 87 years of record as reported by USGS. In comparison with other recent flows preceding this site visit, February 25th recorded a larger peak flow of 3270 CFS; a recent low flow was recorded on February 15th of 227 CFS. Flows observed by Princeton Hydro staff were near bankfull levels with signs of recent overbank flows and flooding throughout the floodplain corridor between Millstone River Road and the Delaware and Raritan Canal State Park Trail. Evidence included ponded water, fine sediment and large woody debris deposited in the floodplain in addition to road signage warning of a recent road closure due to flooding. Large woody debris accumulations are indicative of the magnitude of flooding that occurs in this active corridor. Blackwells Mills Dam is a low‐head concrete dam with abutments approximately 5‐feet in height and a concrete weir spillway 2 – 3 feet in height. A deeper scour pool is located at the toe of the spillway though was difficult to discern or measure due to high flow conditions. Flows during this site investigation completely submerged the dam, allowing for the Princeton Hydro jon‐boat to motor up and over without difficulty. Existing NJDEP flood hazard area delineation maps indicate the impoundment of the dam may extend over 3.5 miles upstream of the dam to the Griggstown Causeway. Princeton Hydro investigated the majority of the impoundment and this theoretical upstream extent. However, during this site investigation, little or no impoundment effect was observed upstream of the dam. Despite the low gradient of the Millstone River at the dam and in the upstream reaches, the low‐head dam is only able to impound water during low flows. At higher flows, the dam is fully submerged and velocities are too high to allow for sediments to accumulate. Sediment Distribution and Volume Sediment samples were taken downstream of the dam, upstream of the dam within the impoundment and upstream of the impoundment (Figure 6). Multiple locations were sampled before sediment of sufficient grain size (i.e. fine sand, silt, and clay) was extracted and retained; many areas downstream and upstream of the dam were coarse and compacted. A composite sediment sample was taken from each of the three locations using a steel core sampler.


Figure 6. Locations of soil samples analyzed for contaminants. DS = Downstream of dam; US = Upstream of dam.

Grain Size Samples for geotechnical analysis were placed into sealed 2‐gallon plastic bags and transported to Princeton Hydro’s in‐house AASHTO‐certified geotechnical laboratory in Sicklerville, New Jersey. To characterize the physical attributes of the sediment, Princeton Hydro completed several index tests including grain size with hydrometer (ASTM D422), moisture content (ASTM D2216/2974). Sediments from all three locations were predominantly fine grained (Table 1). Grain size distribution is included in Appendix B.


Table 1. Grain size analysis results for Millstone River sediment samples.

USDA Classification Sample ID Sample Location

% Coarse % Fine Description DS‐0 Downstream of Dam 16 84 Gravelly Silt Loam US‐1 Impoundment 12 88 Silty Clay Loam US‐2 Upstream of Impoundment 44 56 Clay Loam

Chemical Analysis Of concern during a dam removal is the potential impact of a contaminated sediment release that could cause acute or chronic impacts on downstream biota. . To assess the possible impacts of a release, sediment samples were collected within the impoundment, upstream of the impoundment, and downstream of the impoundment to assess sediment contamination levels. By reviewing the system’s overall contamination, any detected contaminants can be evaluated in context and determine if a sediment release would cause or exacerbate any negative environmental conditions. To evaluate potential impacts, Princeton Hydro reviewed both the United States Environmental Protection Agency (USEPA) Consensus‐based Sediment Quality Guidelines and the NJDEP Ecological Sediment Screening Criteria (Table 2). The consensus based criteria were determined through various known sediment criteria and essentially the probable effects concentration (PEC) was agreed upon as the most reasonable to determine possible impacts. The NJDEP criteria used were the lowest concentrations in which possible negative effects may occur; these criteria are very conservative, but were evaluated to understand the context to which the sediment may be viewed by NJDEP. In addition, in the event that sediment must be removed from the impoundment due to excessive volumes and/or potential ecological concerns, the NJDEP Site Remediation Standards were compared to the sediment analysis results. These results are used to assess whether the sediment could be placed in upland areas as unrestricted (i.e. no concern for impacts to humans) or if disposal at a regulated facility will be required. In order to analyze sediments for contamination, composite samples were placed in sterile bottles supplied by the laboratory, maintained at a temperature of 4°C within in an insulated cooler, and transported to Integrated Analytical Laboratories, LLC in Randolph, New Jersey. Samples were collected using an acetate corer or Ponar (clam shell) sampler depending on water depth and sediment cohesiveness. Sampling equipment was cleaned of gross particles and chemically decontaminated between sediment sampling locations (non‐phosphate detergent, nitric acid, methanol, and distilled water) so as not to cross contaminate samples. The samples were placed in pre‐decontaminated bottles supplied by the laboratory and maintained at a temperature of 4°C within an insulated cooler. Additionally, samples for grain‐size analysis were placed into one (1) gallon sealable plastic bags and transported to Princeton Hydro’s AASHTO‐certified geotechnical laboratory in Sicklerville, New Jersey.


The samples were analyzed for a broad suite of pollutant parameters including volatile organic compounds (VOC), base neutral/acid extractable compounds (BNA or semi‐volatile organic compounds; SVOC), polychlorinated biphenyls (PCB), pesticides, metals, total cyanide, and chromium (hexavalent/trivalent). Analytical results were compared against Soil Remediation Standards (SRS) utilized by the NJDEP (NJAC 7:26D) which established the minimum residential direct contact and non‐residential direct contact soil remediation standards. Laboratory results, included in Appendix B, revealed that all constituents of concern with a corresponding standard were well below the NJDEP Residential and Non‐residential Direct Contact Soil Remediation Standards (Table 2). Therefore, preliminarily if any sediment is removed, disposal may be considered “unrestricted”, or could be deposited in any area outside of regulated wetlands, floodplains or their corresponding buffers. All sediment analysis results were well below the USEPA’s Consensus‐based Sediment Quality Guidelines, however, several of the constituents were at or above the NJDEP lowest effects levels. Regardless, as a review of Table 2 above indicates, the constituents found above the NJDEP eco‐screening levels were either found upstream or downstream of the impounded area, or the contaminants were indicative of the entire river system. Therefore, any sediment release would not negatively impact downstream resources and exacerbate existing conditions. Based on a review of all major classes of analyzed contaminants including volatile organic compounds, semivolatile base neutral acids, PCBs, pesticides, metals and total cyanide, Princeton Hydro concludes that there is no cause for further investigation regarding sediment impacts. It was additionally noted that similar sediment concentrations were detected within the samples upstream, within and downstream of the subject impoundment of Blackwells Mills Dam.


Table 2. Chemical analysis results for Millstone River sediment samples.

NJDEP

RESIDENTIAL NON‐RESIDENTIAL

Consensus Based SQG4.

NJDEP Eco Screen

DIRECT CONTACT SOIL REMEDIATION STD REMEDIATION STD

PEC1 LEL2. 3.

DS‐0 US‐1 US‐2

(mg/kg) – criteria effective 06/2008 (mg/kg) (mg/kg) (mg/kg)

Volatiles Acetone 70000 NA 0.042 0.00715 0.022 Carbon disulfide 7800 110000 0.014 0.00213 ND Methylene chloride 34 97 0.159 0.00817 0.00637 0.00294

Semivolatiles – BNA Anthracene 17,000 30,000 0.845 0.22 ND ND 0.020 Benzo[a]anthracene 0.6 2 1.05 0.320 0.026 0.038 0.098 Benzo[a]pyrene 0.2 0.2 1.45 0.37 0.023 0.028 0.095 Benzo[b]fluoranthene 0.6 2 10.4 0.030 0.038 0.122 Benzo[g,h,i]perylene 38,0000 30,000 0.170 0.105 ND ND Benzo[k]fluoranthene 6 23 0.240 0.031 0.036 0.119 Chrysene 62 230 1.29 0.34 0.030 0.045 0.150 Dibenz[a,h]anthracene 0.2 0.2 0.135 0.060 0.060 ND ND Fluoranthene 2,300 24,000 2.23 0.75 0.045 0.086 0.220 Indeno[1,2,3‐cd]pyrene 0.6 2 0.200 0.074 ND ND Phenanthrene NA 300,000 1.17 0.204 ND 0.038 0.090 Pyrene 1,700 18,000 1.52 0.490 0.045 0.064 0.200

Metals Aluminum 78,000 NA 25,500 37,900 43500 36,100 Arsenic 19 19 33 9.98 8.10 5.44 10.2 Barium 16,000 59,000 174 215 182 Beryllium 16 140 1.86 1.77 1.77 Cadmium 78 78 4.98 0.990 ND ND 0.359 Chromium (NA) (NA) 111 43.4 51.2 45.9 55.5 Cobalt 1,600 590 50 24.4 20.0 19.9 Copper 3100 45,000 100 31.6 28.9 29.4 41.6 Lead 400 800 128 35.8 35.2 22.3 46.9 Manganese 11,000 5,900 630 407 722 534 Mercury 23 65 1.06 0.20 0.029 0.064 0.226 Nickel 1,600 23,000 48.6 22.7 46.8 38.5 36.8 Selenium 390 5,700 5.28 5.48 6.13 Silver 390 5,700 0.5 ND ND 0.475 Thallium 5 79 0.300 0.315 0.275 Vanadium 78 1,100 58.9 57.5 59.5 Zinc 23,000 110,000 459 121 138 116 172

ND = Analyzed for but Not Detected at the MDL 1. Probable Effects Concentration 2. Lowest Effects Levels 3. Concentration of criteria the higher of the two where multiple parameters listed. 4. Ingersall, Christopher G, MacDonald, Donald D, et.al. 2000. 5. Sediment criteria highlighted in grey (e.g. 121) indicate at least one of the samples had exceedances of the criteria. All sediment results in bold indicate an exceedance of a criteria to the left.


Impounded Sediment Management As was observed during the field investigation for impounded sediment, it was determined that the Blackwells Mills Dam does not impound a significant quantity of sediment. In fact, top of substrate elevation measurements revealed an insignificant difference between upstream and downstream sediment deposition. There are a number of factors that would corroborate the lack of sediment impounded behind the Blackwells Mills Dam. As will be discussed, these include the existence of upstream impoundments, an entrenched channel that would promote scour during equivalent “bankfull” events, and the low profile of the dam compared with the entrenchment depth of the stream. The Millstone River drains approximately 258 square miles to the Blackwells Mills Dam. While this area is quite large, the entire river system is relatively low gradient (less than 0.5% slope). The river’s upper reaches are located within the Coastal Plain physiographic province in Mercer, Middlesex and Monmouth Counties, while the lower reaches, northwest of US Route 1 are predominantly within the Piedmont physiographic province. The Coastal Plain areas of the watershed are underlain by predominantly sands, silts and clays with low‐gradient meandering streams, while the areas within the Piedmont are underlain by shales, argillites, diabase of the Passaic Formation and are also characterized as predominantly low gradient streams. Weathered parent rock of the Passaic formation tends to be comprised of fine grained materials (silt) easily transported downstream during high flows within the entrenched channels of the reaches of the Millstone below Carnegie Lake Dam. Carnegie Lake dam itself acts as a sink for transported sediment from the upper reaches of the Millstone River and thus no bed load of coarser materials is transported to the lower reaches of the Millstone. Therefore, the predominant sediment supply for the subject reach of the Blackwells Mills Dam is from fine bedrock materials, with some source of bed load consisting of coarser gravels, if the stream beds are founded in bedrock. What was evident from our visual observations in the field was that the Millstone River channel is entrenched below the “bankfull” or bank forming storm events; this maintains higher energies in the channel and thus suspended sediments. As the subject dam is only a few feet in height and well below the height of bank within the river channel, it does not provide a significant impediment to sediment transport, nor does it provide the backwater needed to reduce velocities which would allow for suspended sediment to “drop out”. Based on our field observations and measurements and sediment analysis results, it is our professional opinion that aside from minor quantities of sediment located immediately behind the Blackwells Mills Dam, no sediment management is necessary for this reach of the river, and in fact, sediment transport will not be significantly affected by the breach or removal of this dam. 7.0 Surrounding Geology

At the Blackwells Mills Dam, the Millstone River valley is underlain by bedrock formations dominated by siltstone and shale. The area of the dam and impoundment is underlain by JTrp – Passaic Formation siltstone and shale (see Bedrock Geology map included in Appendix A). Surficial geology datalayers from NJDEP show the river within a band as much as 20 feet thick of alluvium including sand, gravel, silt, minor clay and peat (see Surficial Geology map included in Appendix A). Immediately to the west of the dam, the surficial geology changes to


Wisconsonian glaciofluvial deposits consisting of sand‐pebble to cobble‐gravel as much as 50 feet thick. 8.0 Vegetation Survey A vegetation survey was completed for the Blackwells Mills Dam, located on the Millstone River. The survey was completed both upstream and downstream of the impoundment with the downstream portion of the survey serving as the reference reach for the project. All areas are dominated by non‐native species (Appendix C); short and long‐term management planning will be necessary to control these species. Upstream of the Dam ‐ River Left This area predominantly consisted of floodplain wetland with a monoculture of reed canary grass. Emergent wetland was observed as well, consisting of sweet flag, nodding smartweed, soft rush, yellow flag iris, fox sedge and jewelweed. A forest fringe was present proximate to the Millstone river, dominated by silver maple, mugwort and box elder. Adjacent to Millstone River Road an upland fringe dominated by multiflora rose was present. Upstream of the Dam ‐ River Right This area predominantly consisted of a park‐like setting associated with the Delaware and Raritan Canal that was dominated by maintained lawn. A forest fringe was observed immediately proximate to the Millstone River dominated by box elder, mugwort, jewelweed and poison ivy. Moving upstream and away from the dam the maintained lawn setting transitions into a forested wetland that abuts the existing D&R Canal trail. This portion of the floodplain was dominated by jewelweed, poison ivy, multiflora rose, Japanese honeysuckle, skunk cabbage, Japanese stiltgrass and silver maple. Downstream – River Left This portion of the Millstone River floodplain includes Millstone River Road. The vegetative survey was terminated at the road due to the presence of private residential property on the opposite side of the road. Forested wetland was the predominant habitat type with narrow upland bands proximate to the road and abutting the Blackwells Mills Causeway bridge that spans the Millstone River. The dominant vegetation within the forested wetland was jewelweed, gray’s sedge, multiflora rose, pin oak, red maple and silver maple. The upland portions were dominated by Japanese honeysuckle, mugwort, Japanese stiltgrass and lady’s thumb. Downstream – River Right This portion of the Millstone River floodplain was dominated by forested wetland. Narrow upland islands were observed and an emergent wetland complex abutted the existing D&R Canal trail. The forested wetland was dominated by jewelweed, wood‐reedgrass, reed canary grass, halberd‐leaved tearthumb, creeping jenny, slender woodland sedge, gray’s sedge, box elder, green ash and silver maple. The emergent wetland was dominated by broadleaf


arrowhead, sweet flag and fox sedge. The upland portions were dominated by multiflora rose, poison ivy, Japanese honeysuckle and Japanese stiltgrass. A full wetland delineation has not yet been completed for the project area. A detailed wetland delineation will be completed and the results of this delineation will be utilized during final design. 9.0 Alternatives Evaluated Three options exist for the Blackwells Mills Dam. These include full dam removal, partial dam removal, and the “no action” alternative. Full Dam Removal entails excavating the entire width of the dam and allowing the channel to return to a free‐flowing condition. In contrast, Partial Dam Removal entails cutting out and removing a portion of the dam on a side or in the middle of the channel so that no water is impounded. In this case, the river would be directed through the dam breach. The “no action” alternative includes no change to the existing dam structure or impoundment. Of the three alternatives evaluated, only two address the liability, safety and ecological concerns posed by the dam. Each alternative was evaluated based on impacts to wetlands, threatened and endangered species habitat, soil erosion and stream scour potential, sedimentation, riparian corridor impacts, human health and safety impacts, and long‐term maintenance by the dam owner. The “no action” alternative does not address any of these concerns. In fact, the “no action” alternative is the only alternative that will result in required long‐term maintenance responsibilities for the dam owner. If the dam is not removed or partially removed, it will still be regulated and long‐term maintenance and inspections will be required in accordance with the NJDEP Dam Safety Standards. Additionally, leaving the dam in‐place will result in no improvement to the existing riparian habitat or stream corridor. Existing fisheries within the Millstone River would not be expanded and the potential to enhance and increase support to various water dependent threatened and endangered species would not be realized. Retaining the dam will not change any erosion patterns in the river since it provides no storage and does not contain any significant amount of sediment. Existing wetlands in and around the existing dam would remain as they are today, driven by the existence of the manmade dam structure. Furthermore, retaining the dam poses a threat to public safety as it is currently accessible to the public from the park. These types of dams and the currents they create result in a potential drowning hazard. The hydraulic condition created at the downstream toe can create “boils,” which are situations where water from below the surface moves back towards the dam in a circular motion. These boils can trap swimmers particularly because the dams themselves often appear non‐threatening from the surface. Both partial and full dam removal are described in greater detail in Section 10 below, however, since the “no action” alternative does not result in any change from existing conditions, it is not described in as much detail. If the dam is not removed, fish passage will still be inhibited and there will be no change to the wetlands, riparian habitat, or river geometry. 10.0 Conceptual Approach to Full or Partial Dam Removal

Long‐term monitoring for either approach described below can be completed using the monumented cross‐sections set in the field by B&B Hi‐Tech as part of the overall survey effort.


These cross‐sections are shown on a map included in Appendix D for reference. Monitoring completed can document changes in vegetation, channel geometry and water depths post dam removal.

10.1 Full Dam Removal

To completely remove the dam, an excavator would be utilized to break up the entire concrete dam and spillway into slabs that are hauled off site for disposal. Any separated river stone that is part of the existing dam shall be left on site to be used to stabilize and naturalize the channel. Removal of the dam will provide fish passage and allow the river to recreate a natural channel through the former structure. In addition, due to the low slope of the bed in the impoundment, engineered grade control structures designed to insure aquatic organism passage are not necessary. If necessary, banks on the outside bends or adjacent to roads (i.e. Millstone River Road) or structures could be stabilized with accepted bioengineering practices that employ rock, vegetation and geotextiles. Sediment bars on the impoundment margins could be replanted with native trees, shrubs, and seed mix to stabilize newly exposed sediment and to inhibit the establishment of nonnative invasive species. These areas would provide important riparian habitat as well as storage of flood volumes and dissipation of overbank velocities. At the toe of the existing embankments on both sides of the current dam, Princeton Hydro proposes installing boulders to enhance long‐term stability and protect the banks from excessive velocities and debris during high flows. Deleterious impacts (e.g. construction related impacts to the riparian zone or reduction in fringe wetland communities existing only as a result of the artificial impoundment) associated with full removal on the surrounding aquatic and wetland habitats are expected to be minimal. As previously stated, the primary goal of dam removal is to restore fish habitat and restore the natural flow the river system. It is anticipated that benefits will be realized to the surrounding wetland communities and aquatic biota as well, such as decreased temperature in the water in the former dam impoundment. Initially, there may be a reduction in wetland communities as a result of the removal of the artificial impoundment, however, it is anticipated that over the long‐term, the wetland communities will recover and flourish in the more natural river system that is re‐established. This will allow for in‐stream health to increase and increase opportunity for aquatic biota as well. The potential for re‐introduction of fish and other aquatic species that have been impeded due to the presence of the dam will also exist. As shown on the Critical Species Habitat maps included in Appendix A of this study, there is habitat for bald eagles and other threatened and endangered species; however, deleterious impacts to these species and their habitats are expected to be minimal and temporary; these impacts would be related mainly to the construction work necessary to remove the structure only. Removal of the dam will fully restore diadromous fish passage, which should increase the presence of water dependent species such as the bald eagles as fish are their primary food source.

10.2 Partial Dam Removal

Partial removal of the dam would require specialized concrete cutting tools, such as a diamond wire saw, to cut the spillway and remove a portion of the dam. The use of such a saw would create a “cleaner” and neat edge of spillway to remain. Leaving portions of the dam in place would not be practical for the Blackwells Mills Dam. The dam itself is the same width as the existing channel downstream. As previously stated, the dam provides little to no impoundment


and a partial removal is not anticipated to provide any benefits to the system other than deregulating the dam itself. Any remaining remnants of the structure would be designed to remain secure, but since the dam itself spans only the existing channel, leaving a portion of the structure in place will result in greater potential for long‐term riverbed scour and sediment deposition. In addition, there will be a pinch point created where the channel is artificially narrowed, which may impact the long‐term stability of the channel both upstream and downstream of the dam. As described above, impacts associated with partial removal on the surrounding aquatic and wetland habitats are expected to be minimal. As previously stated, the primary goal of dam removal is to restore fish habitat and restore the natural flow the river system. Unlike the full removal, this option does not restore the full natural flow of the river system. As the dam spans the entire channel, only removing a section of the dam will not restore the entire channel width. Therefore, the velocities during low flow events will be accelerated through the narrow opening resulting in potential for increased bed and bank scour in the vicinity of the dam. It is anticipated that partial removal will result in only minimal improvements to existing wetlands and aquatic biota would be minimal. Minor improvements in the riparian corridors and wetlands might result from the partial removal of the dam since it will eliminate the artificial impoundment and restore riparian habitat, thus benefitting water dependent waterfowl and other wildlife dependent on fish and aquatic organisms in the river. Removing the impoundment and restoring the natural river function, will allow the restoration of fish passage for fish species otherwise barricaded by the dam itself. With a partial removal, there exists the potential that the remaining structure could become debris during a flood at a later date, which may have a greater impact on the existing aquatic and wetland habitats than the full removal alternative described above. Deleterious impacts to aquatic biota may result as the debris could create a “dam” and impound water, thus increasing the temperature of the water behind the dam. Debris jams could also increase localized flooding and increase bank erosion and channel stability long‐term. 11.0 Preliminary Hydrologic and Hydraulic Analysis

In accordance with NJAC 7:20, Dam Safety Standards, a partial or complete removal must neither negatively affect the downstream reaches of a stream, nor increase the water surface elevations of the 10‐, 50‐ and 100‐year flood events. To determine the potential effect on the stream and the associated floodplain, the United States Army Corps of Engineers (USACE) Hydrologic Engineering Centers’ River Analysis System (HEC‐RAS), Version 4.1, model was employed. In order to perform the HEC‐RAS analysis, various existing data were compiled to represent the condition of the stream. This section of the Millstone River was previously studied by NJDEP for a State adopted floodplain delineation, dated February 1973, using HEC‐2 software. The HEC‐2 data used for this project, however, was obtained from updates completed by United States Department of Agriculture (USDA) Natural Resource Conservation Service (NRCS) and the USACE for the Millstone Rover Watershed PL‐566 Flood Damage Reduction Project most recently updated in July 2002. The HEC‐2 model was updated subsequent to 2002 for the completion of the inundation analysis for the Carnegie Lake Dam. The hydrologic data, geometric data, roughness coefficients, and other parameters were utilized from the original model and not adjusted in this river reach. This HEC‐2 State Study was utilized for this preliminary analysis as


this study represents the best readily available data for this reach and because it is of more than sufficient detail. As the primary goal of this analysis is to inform the feasibility of partial or complete removal, the study should be considered preliminary, and as such, would need to be updated with more detailed input to inform any future proposed design and permitting. The modeled reach extends downstream of the dam for a total length of approximately 2,500 feet and upstream of the dam for a total length of more than one mile.

11.1 Storm Flows

The 2‐, 10‐year, 50‐year, and 100‐year peak flow rates in Millstone River at the Blackwells Mills Dam were collected from the existing USGS gauge located at the Blackwells Mills Bridge (USGS Gauge No. 01402000). Additionally, the Flood Hazard Area Design Flood was also analyzed. Normal depth was used for downstream boundary conditions. The flow rates at the Blackwells Mills Dam utilized for this study are listed in Table 3 below.

Table 3. Flow Rate and Frequency

Frequency Flow Rate (CFS)

Mean Annual 379

2‐year 5,890

10‐year 12,200

50‐year 20,200

100‐year 24,300

NJFHA 22,950

11.2 Geometry Data

The geometry data utilized for the existing conditions (before removal) scenario was adopted from the previously completed HEC‐2 study files as described above. River Stations described herein indicate the distance (in feet) along the Millstone from the station to the confluence of the Millstone and Raritan Rivers. The geometric data are attached in Appendix E, which include cross sections and profiles of the channel.

For the proposed conditions (post‐full removal scenario) the geometry of the Millstone River was revised just downstream of the concrete dam to approximately 90 feet upstream. The remainder of the geometry of the stream is not changed. Specifically, the geometry of both cross‐section (side slope, bottom width, depth) and profile (slope) were adjusted to mimic existing conditions beyond the influence of the dam. It should be noted that for this feasibility study, the proposed conditions reflect the full removal (bank to bank) of the dam. This was considered a conservative approach with regard to changes in WSEL and velocities. During any future proposed design, this model would be updated to include more accurate input as it becomes available during the design process. Attached in Appendix E are comparisons between existing and proposed conditions geometry.


11.3 Roughness Coefficient ‘n’

All roughness coefficients (Manning’s ‘n’ values) were adopted from the previously completed HEC‐2 study and were not changed under the existing conditions model. The ‘n’ values before dam removal are shown in the Geometry Data attached in Appendix E. Channel coefficients were set to 0.042 for both existing and proposed conditions, as both existing and proposed conditions are estimated to be relatively straight, with sandy substrate and no deep pools. Again, during proposed design, these assumptions should be verified, and modified as necessary to reflect actual design conditions. Overbank ‘n’ values were set to 0.07 within this reach to reflect the marshy floodplain conditions, for both existing and proposed scenarios.

11.4 Contraction and Expansion Coefficients

Contraction or expansion of flow due to changes in cross sectional area results in energy loss. Contraction coefficients in the study varied from 0.1 to 0.3, with the highest values occurring at the dam. Expansion coefficients varied from 0.3 to 0.5, with the higher values occurring at the dam and the Blackwells Mills Causeway bridge upstream of the dam.

11.5 HEC‐RAS Model

Using the HEC‐RAS model, a one‐dimensional, steady peak flow, combined subcritical and supercritical (mixed flow) analysis was performed. For all events normal depth using a slope of 0.0002 ft/ft was used for the upstream boundary conditions. For the downstream boundary conditions known WSEL for the Delaware River backwater influence was used. The energy, standard step modeling procedure was utilized to determine the water surface profile.

11.6 Results

The HEC‐RAS program was utilized to analyze existing conditions and the post removal scenario. The water surface profiles post dam removal using HEC‐RAS were compared with the existing conditions results for the same flow rate. The results, attached in Appendix E, illustrate that the water surface profiles pre‐dam removal and the water surface profiles post dam removal satisfy the requirements of NJAC 7:20 of no negative impact on downstream reach and no increase in water surface elevations of the 10‐, 50‐, or 100‐year flood events. Table 4 summarizes results for existing and proposed conditions for selected cross‐sections below, at and above the dam. Froude # is a unitless metric of turbulence, whereby values below 1.0 indicate slow and deep flow (subcritical), values above 1.0 indicate shallow and fast flow (supercritical) and values near 1.0 indicate transitional flows (critical). Downstream of the dam (River Station 149553), minimal changes occur in water depth, average velocity, and Froude # post‐dam removal.


Table 4. Hydraulic Properties Summary

Water Elevation Channel Velocity

(ft) (ft/s) Froude # River Station

& Location Profile

Existing Proposed Existing Proposed Existing Proposed

10‐yr 41.45 41.42 4.99 4.86 0.25 0.23 50‐yr 44.59 44.55 6.13 6.04 0.27 0.26

149656 Upstream of

Dam 100‐yr 45.89 45.84 6.66 6.58 0.28 0.27

10‐yr 41.47 41.45 4.21 4.09 0.21 0.19 50‐yr 44.63 44.59 5.15 5.06 0.23 0.21

149570 Top of Spillway 100‐yr 45.94 45.90 5.58 5.51 0.24 0.23

10‐yr 41.38 41.39 4.51 4.37 0.22 0.21 50‐yr 44.50 44.51 5.55 5.41 0.25 0.23

149553 Downstream

of Dam 100‐yr 45.79 45.81 6.03 5.89 0.26 0.25

As is shown in the Table 4 above, there are some slight changes in water surface elevation and velocity within the channel post dam removal; however, none of these changes are significant. Since the dam is completely submerged during normal and flood flows, there are no significant benefits resulting from the removal relating to flood control. It is anticipated that the removal of the dam will not increase downstream flooding since the dam does not provide any measurable flood control. The removal of the dam will eliminate localized bed and bank scour downstream as the dam itself will no longer exist and the “roller” created during low flows over the dam will be eliminated. Based on the results of the preliminary hydrologic and hydraulic analysis, it is our professional opinion that the partial or complete removal of Blackwells Mills Dam would neither negatively affect the downstream reaches, nor increase the water surface elevations of the 10‐, 50‐ and 100‐year flood events. 12.0 Anticipated Regulatory Permitting and Approvals The approvals for the removal of dams in general can be a complicated process. In addition to complying with the NJ Safe Dam Act, a dam’s location within a riparian corridor and their age will require approval from several other State and possibly Federal agencies. The following paragraphs will discuss the various anticipated approvals that will be necessary and their affect on the timing and physical impacts of the dam removal project:

12.1 NJDEP Dam Safety Construction Permit

In New Jersey, stream obstructions or structures that have the ability to raise the water levels over the existing stream or land surface greater than five (5) feet are regulated under the New Jersey Safe Dam Act. The Dam Safety Regulations (NJAC 7:20) provide guidance on the means and methods for obtaining approvals and the physical requirements for dam construction, which includes partial and complete removal. Under the current version of the regulation, to obtain


an approval to remove a dam an applicant must demonstrate that the modification will reduce the regulatory height of the dam, mitigate an increase in downstream flooding, and prepare a sediment stabilization and control plan to minimize to the maximum extent practicable, the discharge of impounded sediment downstream. As we understand, the NJ Dam Safety Section is in the process of finalizing guidance to stabilize the exposed bed of reservoirs, lakes and ponds. As part of the process of a dam removal, public notice must be provided in a local newspaper, and to all property owners that abut the impoundment but do not own the dam. The public will have 30 days to petition the NJDEP and comment on the project. Within 30 days of an additional public notice of a hearing, the NJDEP Commissioner will hear a case for maintaining the dam. Usually, the Commissioner’s decision is based on the protection of public safety and the willingness of the opposition to provide monetary assistance for the restoration of the dam. If the opposition will not provide monetary assistance, the decision will be made to approve the removal. To issue a construction permit to remove the dam, the owner or applicant must submit engineering plans and specifications. The permit is always conditioned on receiving all other required approvals.

12.2 NJDEP Land Use Regulation Program (Bureau of Freshwater Wetlands)

As this removal would involve work within a stream and its associated fringe wetlands, an application for approval under the Freshwater Wetlands Protection Act Rules, NJAC 7:7A must be submitted to the NJDEP’s Division of Land Use Regulation (DLUR). The Rules have general permits that allow similar activities throughout the State be conducted as long as specific conditions are met. For repair, partial removal or complete removal of a dam, NJAC 7:7A provides a permit identified as a Freshwater Wetlands Statewide General Permit No. 18, Dam Repairs (GP‐18). The conditions of this permit allow for the permanent disturbance of no more than one (1) acre of Freshwater Wetlands. The review of an application includes a determination of whether or not there are negative impacts to State or Federal threatened or endangered species, and impacts to structures or features of historic significance. As will be discussed below, it is expected that due to the age of the structure and that Federal funding may be used to finance the project, there will be a review by the State Historic Preservation Office (SHPO). The issuance of the GP‐18 will be predicated on satisfying SHPO. Hunter Research, Inc. has been retained by SBMWA to complete Phase 1 Cultural Resource Survey of the dam to support the review of the project by SHPO. An alternative to a GP‐18, if the project is funded in any part by a Federal grant for the purpose of habitat restoration, would be a General Permit No. 16, Wetland Enhancement (GP‐16). The benefit of the GP‐16 is that there is no limit on wetlands impacts, as it is assumed that such impacts would be positive; i.e. restoration or enhancement. An application for a GP‐18 or GP‐16, as in all Freshwater Wetlands permits, will require public notice to all property owners within 200 feet of the project area or property area (depending on whether project is small compared to the property boundary) and notification to the municipality and county where the project resides. A copy of the permit application must be submitted to the municipality’s clerk to allow review by the public.


12.3 NJDEP Division of Fish and Wildlife

The Division of Fish and Wildlife will have a dual role in a review of a dam removal application. First and foremost, they would provide comment during the Dam Safety Permit and Freshwater Wetlands application process. Secondly, any water lowering of an impoundment must apply for a Division of Fish and Wildlife Water Lowering Permit, a Scientific Collectors Permit and a Stocking Permit. The Water Lowering Permit will address the requirements to protect game fish during dewatering. The Scientific Collectors Permit may be required to catch the fish within an impoundment, however, it is expected that all fish within the impoundment are riverine species what will not require relocation. The Stocking Permit will be required if the game fish within the impoundments are to be relocated to another impoundment. During the LURP general permit review, the Division of Fish and Wildlife will review the impacts to the fishery within the reservoirs, as well as to the downstream water resources (i.e. trout production and maintenance waters). In addition, the Division will comment and make recommendations on the restoration of the resulting exposed lake beds and stabilized stream. While general gamefish may not be an issue, an additional timing restriction may be imposed as follows:

• Water bodies that support general game fish

May 1 to June 30 Other restrictions could apply area restrictions for water bodies that support pickerel and walleye, however, the Millstone River in this reach is not known, nor is a viable habitat for these fish species.

12.4 State and Federal Historic Preservation Acts Review

Any structure that is determined to be greater than 50 years in age may be subject to review under both the NJ Register of Historic Places Act and the National Historic Preservation Act Section 106. A Phase 1 Cultural Resource Survey is being conducted independent of this feasibility report. Although a full or partial removal would most likely not be opposed by SHPO, mitigation may be required. Mitigation may be in the form of preserving artifacts of the site, such as leaving key elements in place, however, the exact form of mitigation will be established with SHPO during the permitting phase of this project.

12.5 Soil Conservation District

Under the purview of the Soil Erosion and Sediment Control Act of 1975 (NJSA 4:24‐39 et. seq NJAC 2:90‐1.1 et seq), a project that disturbs greater than 5,000 square feet of land area must apply to the County Soil Conservation District (SCD) for a Soil Erosion and Sediment Control (E&S) Plan approval. Since the impoundment is approximately 2,300 feet long and nearly 100 feet wide, the area of land to be disturbed is likely over 5,000 square feet. As Blackwells Mills is located entirely within Somerset County, the Somerset‐Union Soil Conservation District will take jurisdiction for this review. It is also noted that any project that proposes to disturb greater


than one (1) acre of land will also be required to submit an application for a Request for Authorization (RFA) under the NJ Pollution Discharge Elimination System (NJPDES) for approval to discharge construction related runoff. As part of the approval process a Stormwater Pollution Prevention Plan (SPPP) must be prepared that describes the controls for mitigating sediment laden runoff from a construction site. The E&S Plans must be prepared in accordance with the SCD specifications. An E&S Plan and Notes are usually prepared and provided as the last sheets in a set of engineering plans. Aside from the SPPP the RFA is simply required to provide the NJDEP with data of construction projects to satisfy the Federal Clean Water Act’s inventory requirements for construction related stormwater runoff. The SPPP plan will describe the methods of mitigating sediment laden stormwater runoff, emergency measures in the event of a discharge of sediment slugs and overall maintenance procedures similar to those required and listed in the E&S Plan and Notes sheets.

12.6 Local Approvals

While the Blackwells Mills Dam impoundment does not contain a large sediment volume, it is worth noting that both Hillsborough and Franklin Township require soil disturbance approvals that may apply if sediments are to be removed from the dam site. In Hillsborough Township, the following applies, “Any soil transported into and within the Township of Hillsborough will require a certification from an approved laboratory stating that the soil is not contaminated and is suitable, clean material meeting the standards of the New Jersey Department of Environmental Protection.” In Franklin Township, both a Soil Importation Permit and a Soil Exportation Permit would be required depending on whether material is brought in or removed. The fee for these permits is anticipated to be less than $1,000 for each Township.


13.0 Cost Estimates for Construction

13.1 Full Removal

Table 5. Preliminary Cost Estimate for Full Dam Removal.

Activity Unit Cost/Unit Number Cost

Mobilization/Demobilization LS $ 15,000.00 1 $15,000.00

Concrete Demolition & Removal CY $ 150.00 300 $45,000.00

Transport of Concrete to Recycling Facility

Tons $ 10.00 450 $4,500.00

Disposal of Concrete Tons $ 15.00 450 $6,750.00

Management of Trapped Sediments (Excavation/Placement of Unconsolidated Sediments)

CY $ 20.00 500 $10,000.00

Bank Stabilization LF $ 100.00 200 $20,000.00

Soil Erosion and Sediment Control LS $ 5,000.00 1 $5,000.00

Miscellaneous Items LS $ 11,500.00 1 $10,000.00

TOTAL $116,00.00


13.2 Partial Removal

Table 6. Preliminary Cost Estimate for Partial Dam Removal.

Activity Unit Cost/Unit Number Cost

Mobilization LS $ 15,000.00 1 $ 15,000.00

Concrete Cutting Day $ 20,000.00 1 $ 20,000.00

Concrete Demolition & Removal CY $ 150.00 150 $ 22,500.00

Transport of Concrete to Recycling Facility

Tons $ 10.00 225 $ 2,250.00

Disposal of Concrete Tons $ 15.00 225 $ 3,375.00

Management of Trapped Sediments (Excavation/Placement of Unconsolidated Sediments)

CY $ 20.00 250 $ 5,000.00

Soil Erosion and Sediment Control LS $ 10,000.00 1 $10,000.00

Miscellaneous Items LS $ 15,000.00 1 $ 15,000.00

TOTAL $ 88,125.00

13.3 Engineering Design, Permitting and Construction Administration

To complete the engineering designs and permit applications, it is estimated that the following soft costs would be incurred for the complete and partial removal options.

• Engineering and Permitting $ 35,000.00 • Permit Application Fees $ 3,500.00 • Construction Administration $ 18,000.00 • As‐built Surveys $ 5,000.00

These costs do not reflect the effort required to complete stream enhancement designs or permitting necessary upstream of the dam removal area.


14.0 Schedule

The most time consuming aspect of the project will be related to permit reviews. Specifically, permit application reviews by NJDEP Dam Safety and NJDEP Land Use Regulation Program are anticipated to require approximately six (6) to eight (8) months. If final design and permitting were authorized to start in June 2011, then it is expected that all permits and approvals would be in hand by February 2012. Construction of the removal could be completed by summer 2012.

Activity Expected Time

Preliminary Design 2 months

Final Design 3 months

Permitting 8 months

Construction 1 month 15.0 Conclusions and Recommendations Princeton Hydro was contracted to assess the feasibility of a full dam removal, partial dam removal, and the “no action” alternative. The three alternatives were evaluated to determine which would adequately restore the riparian functions of the Millstone River within the reach of the Blackwells Mills Dam and its associated impoundment and protect/enhance human health and safety. Based on the desktop study, field work, and data analysis, we offer the following conclusions regarding the removal or partial removal of the Blackwells Mills Dam:

• Since the Blackwells Mills dam creates a hydraulic jump immediately downstream of the

spillway, there exists an ongoing safety concern for potential drownings. Similar low‐head dams in the state and region have resulted in deaths and injuries in recent years.

• Based on our preliminary modeling of the pre‐ and post‐removal comparisons of the

Blackwells Mills Dam, it was determined that, in accordance with NJDEP Dam Safety regulations, that the 10‐, 50‐, and 100‐year flood recurrence, 24‐hour duration events will not increase flooding downstream.

• As a major tributary to the Raritan River, the Millstone River, based on studies

conducted by the US Fish and Wildlife Service has the potential for diadromous fish migration, including blueback herring (Alosa aestivalis), alewife (Alosa pseudoharengus), and American Eel (Anguilla rostrata). There is also the potential for American shad (Alosa sapidissima) and hickory shad (Alosa mediocris), and coupled with the removal of the Weston Causeway Dam may have significant potential for spawning of these larger herring species.

• The removal of this dam is critical in the reestablishment of migratory fish passage on

the Millstone River, a primary goal of NOAA, the agency charged with the restoration, protection and maintenance of the United State’s commercial fisheries. Diadromous


fish such as Shad and river herring are considered important commercial and recreational fish species.

• The full removal or partial removal of the Blackwells Mills Dam will be vital in restoring

the ecological functions and values of a true riparian system. Other fish passage techniques such as fish ladders, nature‐like fishways, and rock ramps will not reestablish the natural function of the impounded section, and may in fact be detrimental to bottom feeding riverine species that would require a coarser substrate than that if fines trapped behind dams.

• Based on the survey completed by Princeton Hydro, the impoundment of the Blackwells

Mills Dam contains very limited accumulated sediment. It is our professional opinion that the simple removal of the dam structure and its associated fills (soil and rock on the upstream face), will not discharge a measurable quantity of sediment downstream that would negatively impact the resource of the Millstone River. While there will be temporary migration of sediment and stream bed materials downstream, this impact will be temporary and full recovery of the corridor downstream of the removal would be expected within several months of removal, while the impoundment would recover from its nearly 265 years of impacts within 2‐3 years of removal via the colonization of vegetation. It is noted that such vegetative colonization should be monitored and managed to preclude the establishment of non‐native and aggressive invasive plants.

In conclusion, both the “no action” and partial dam removal options were eliminated. The “no action” approach was eliminated as it does not meet the overall objective of the project to provide migratory fish passage along the Millstone River, does not eliminate existing threats to public safety, and does not eliminate the need for long‐term maintenance and upkeep of the dam by the State. The partial dam removal was eliminated as it does not provide for complete restoration of the river ecosystem functions and could cause localized stream scour in the vicinity of the structure as the dam remnants would create a "pinch point" along the existing river. Despite FEMA Flood Insurance Rate Mapping to the contrary, our field and desktop investigation concluded that the Blackwells Mills Dam only impounds water during low flows. At higher flows, the dam is fully submerged and velocities are too high to allow for sediment to accumulate. 16.0 Next Steps This feasibility study has compiled the initial data and provided conclusions and recommendations for the restoration of the Millstone River within the footprint of the existing dam and the near vicinity. The following sequence of effort is recommended to achieve the goals of the project partners in the removal of the Blackwells Mills Dam.

• Initiate a pre‐application meeting with the NJDEP to assess additional concerns by the agencies involved in the removal of the dam. The following areas of NJDEP must be invited to a pre‐application meeting:

o Bureau of Dam Safety and Flood Control o Land Use Regulation Program, Bureau of Freshwater Wetlands o NJDEP Division of Fish and Wildlife


o NJDEP State Historic Preservation Office

In addition to these areas within NJDEP, it is also recommended that the following project partners or other interested NGO and governmental agencies be included in the pre‐application meeting:

o Delaware and Raritan Canal State Park o Delaware and Raritan Canal Stakeholders (including NJWSA, SHPO, etc.) o USDA, Natural Resource Conservation Service o American Rivers o National Oceanic and Atmospheric Association

• As we understand, SBMWA has retained Hunter Research, Inc. to complete a Phase I

Cultural Resources Study for the dam.

• Set up baseline monitoring data and monumenting to allow the project partners and regulatory agencies to develop long term data on river response to dam removal. It is recommended that the monitoring protocols of the “Stream Barrier Removal Monitoring Guide”, prepared by the Gulf of Maine Council on the Marine Environment, dated December 2007 be used to establish monitoring goals and objectives. This document can be found at http://www.gulfofmaine.org/streambarrierremoval/.

• Following input from NJDEP, other local, State and Federal agencies and NGOs, the

design can be completed and submitted with associated permit applications for approval.

Princeton Hydro, LLC Project No. 0390.004

APPENDICES


APPENDIX A

PROJECT INFORMATION MAPS

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USGS LOCATION MAPBLACKWELLS MILLS DAM REMOVALFEASIBILITY STUDYSTONY BROOK MILLSTONE WATERSHED ASSOCIATIONHILLSBOROUGH & FRANKLIN TOWNSHIPSSOMERSET COUNTY, NEW JERSEY

NOTES:

1. USGS Topographic Digital Raster Graphic obtained from TerrainNavigator Pro Edition 2.0, Monmouth Junction, NJ Quadrangle.

Map Projection: State Plane New Jersey (feet) NAD83

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AERIALBLACKWELLS MILLS DAM REMOVALFEASIBILITY STUDYSTONY BROOK MILLSTONE WATERSHED ASSOCIATIONHILLSBOROUGH & FRANKLIN TOWNSHIPSSOMERSET COUNTY, NEW JERSEY

NOTES:1. 2007 orthoimagery obtained from NJGIN Information Warehouse website. AccessedDecember 2008; https://njgin.state.nj.us/NJ_NJGINExplorer/IW.jsp?DLayer=NJ%202007%20Orthophotography2. Streams and dams obtained from NJDEP GIS website. Accessed December 10, 2009 and2001, respectively; http://www.state.nj.us/dep/gis/


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TAX MAPBLACKWELLS MILLS DAM REMOVALFEASIBILITY STUDYSTONY BROOK MILLSTONE WATERSHED ASSOCIATIONHILLSBOROUGH & FRANKLIN TOWNSHIPSSOMERSET COUNTY, NEW JERSEY

NOTES:1. Tax parcels obtained from NJ Geographic Information Network (NJGIN) website, SomersetCounty. Accessed June 21, 2010, https://njgin.state.nj.us/NJ_NJGINExplorer/index.jsp2. 2007 orthoimagery obtained from NJGIN Information Warehouse website. AccessedDecember 2008; https://njgin.state.nj.us/NJ_NJGINExplorer/IW.jsp?DLayer=NJ%202007%20Orthophotography



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BEDROCK GEOLOGYBLACKWELLS MILLS DAM REMOVALFEASIBILITY STUDYSTONY BROOK MILLSTONE WATERSHED ASSOCIATIONHILLSBOROUGH & FRANKLIN TOWNSHIPSSOMERSET COUNTY, NEW JERSEY

NOTES:1. 2007 orthoimagery obtained from NJGIN Information Warehouse website. AccessedDecember 2008; https://njgin.state.nj.us/NJ_NJGINExplorer/IW.jsp?DLayer=NJ%202007%20Orthophotography2. Bedrock geology obtained from NJDEP Geological Survey website. Accessed January 5,2009; http://www.state.nj.us/dep/njgs/geodata/index.htm#geology



LegendJTrpPassaic Formation-Siltstone and Shale

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Dam

SURFICIAL GEOLOGYBLACKWELLS MILLS DAM REMOVALFEASIBILITY STUDYSTONY BROOK MILLSTONE WATERSHED ASSOCIATIONHILLSBOROUGH & FRANKLIN TOWNSHIPSSOMERSET COUNTY, NEW JERSEY

NOTES:1. 2007 orthoimagery obtained from NJGIN Information Warehouse website. AccessedDecember 2008; https://njgin.state.nj.us/NJ_NJGINExplorer/IW.jsp?DLayer=NJ%202007%20Orthophotography2. Surficial geology obtained from NJDEP Geological Survey website. Accessed January 5,2009; http://www.state.nj.us/dep/njgs/geodata/index.htm#geology



LegendQwf, LATE WISCONSINAN GLACIOFLUVIAL DEPOSITSSand and pebble-to-cobble gravel, minor silt;yellowish brown to reddish brown. As much as 50 feet thick.Qal, ALLUVIUMSand, gravel, silt, minor clay and peat;reddish brown, yellowish brown, brown, gray. As much as 20 feet thick.

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Blackwells MillsDam

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LANDSCAPE PROJECTCRITICAL HABITATSBLACKWELLS MILLS DAM REMOVALFEASIBILITY STUDYSTONY BROOK MILLSTONE WATERSHED ASSOCIATIONHILLSBOROUGH & FRANKLIN TOWNSHIPSSOMERSET COUNTY, NEW JERSEY

NOTES:1. 2007 orthoimagery obtained from NJGIN Information Warehouse website. AccessedDecember 2008; https://njgin.state.nj.us/NJ_NJGINExplorer/IW.jsp?DLayer=NJ%202007%20Orthophotography2. Landscape Project 2.1 obtained from NJDEP GIS website. Accessed December 18, 2008;http://www.state.nj.us/dep/gis/



LegendGrassland

Suitable Habitat (1)Emergent Wetlands

Priority Concern Species Observed (2)Great Blue Heron

Forested WetlandsState Threatened Species Observed (3)Cooper's HawkGreat Blue Heron

ForestState Threatened Species Observed (3)Cooper's HawkGreat Blue Heron

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LANDSCAPE PROJECTCRITICAL SPECIES HABITATBLACKWELLS MILLS DAM REMOVALFEASIBILITY STUDYSTONY BROOK MILLSTONE WATERSHED ASSOCIATIONHILLSBOROUGH & FRANKLIN TOWNSHIPSSOMERSET COUNTY, NEW JERSEY

NOTES:1. 2007 orthoimagery obtained from NJGIN Information Warehouse website. AccessedDecember 2008; https://njgin.state.nj.us/NJ_NJGINExplorer/IW.jsp?DLayer=NJ%202007%20Orthophotography2. Bald eagle foraging habitat (Landscape Project 2.1) obtained from NJDEP GIS website.Accessed December 18, 2008; http://www.state.nj.us/dep/gis/



LegendBald Eagle Foraging Habitat

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APPENDIX B

SUMMARY OF LABORATORY ANALYTICAL RESULTS

Project: 390.004 T:, Stony Brook Millstone WA, Blackwells Mills Feasibility Location:

Sample Depth% Moist. % Org. % Fines Plasticity USDA USDA Sand USCS USCS USDA

(D2216/2974) (D2974) (C117) (D4318) % Coarse % Fine % Coarse % Medium %Fine % Fines % Fineness Description

US-2, I Bulk 47 4.2 56 NP 44 56.0 3 0 38 56 NT Clay Loam

US-1, II Bulk 76 9.1 86 NP 12 88.0 3 1 9 86 NT Silty Clay Loam

DS-0, III Bulk 47 7.1 67 NP 16 84.0 2 1 12 67 NT Gravelly Silt Loam

'file:///Q:/0390/Projects/0390004/Laboratory/0390.004.Labresults.ods'#$ASTM C 422 Results_2

Hillsborough Township, NJ

0.0010.0100.1001.00010.000100.000

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1002 in 1.5 in 1.0 in 0.75 in0.375 in 4 6 8 10 12 16 18 20 30 35 40 50 60 80 100 140 200 2 5 15 30 60 120 250 480 1440 Pan

GRAIN SIZE DISTRIBUTION

ASTM D422

US-2, I US-1, II Sieve Number DS-0, III

GRAIN SIZE (mm)

PERCENT PASSING

INTEGRATED ANALYTICAL LABORATORIES, LLC.

SUMMARY REPORTClient: Princeton Hydro, LLCProject: BLACKWELLS MILLS DAMLab Case No.: E10-02034

Downstream of Dam Impoundment Upstream of ImpoundmenClient ID: NJDEP NJDEP DS-0 US-1 US-2

Sample Depth: RESIDENTIAL NON-RESIDENTIALLab ID: DIRECT CONTACT SOIL DIRECT CONTACT SOIL 02034-001 02034-002 02034-003

Date Sampled: REMEDIATION STD REMEDIATION STD 03/04/2010 03/04/2010 03/04/2010Matrix: (mg/kg) - 06/2008 (mg/kg) - 06/2008 Sediment Sediment Sediment

Volatiles (ppm) Conc Q RL Conc Q RL Conc Q RLDichlorodifluoromethane 490 230000 ND 0.00166 ND 0.0015 ND 0.00093Chloromethane 4 12 ND 0.00166 ND 0.0015 ND 0.00093Vinyl chloride 0.7 2 ND 0.00166 ND 0.0015 ND 0.00093Bromomethane 25 59 ND 0.00166 ND 0.0015 ND 0.00093Chloroethane 220 1100 ND 0.00166 ND 0.0015 ND 0.00093Trichlorofluoromethane 23000 340000 ND 0.00166 ND 0.0015 ND 0.00093Acrolein 0.5 1 ND 0.033 ND 0.030 ND 0.0191,1-Dichloroethene 11 150 ND 0.00166 ND 0.0015 ND 0.00093Acetone 70000 NA 0.042 0.00332 0.00715 0.003 0.022 0.00186Carbon disulfide 7800 110000 0.014 0.00166 0.00213 0.0015 ND 0.00093Methylene chloride 34 97 0.00817 C 0.00332 0.00637 C 0.003 0.00294 C 0.00186Acrylonitrile 0.9 3 ND 0.033 ND 0.030 ND 0.019tert-Butyl alcohol (TBA) 1400 11000 ND 0.00664 ND 0.006 ND 0.00372trans-1,2-Dichloroethene 300 720 ND 0.00166 ND 0.0015 ND 0.00093Methyl tert-butyl ether (MTBE) 110 320 ND 0.00166 ND 0.0015 ND 0.000931,1-Dichloroethane 8 24 ND 0.00166 ND 0.0015 ND 0.00093cis-1,2-Dichloroethene 230 560 ND 0.00166 ND 0.0015 ND 0.000932-Butanone (MEK) 3100 44000 ND 0.00166 ND 0.0015 ND 0.00093Chloroform 0.6 2 ND 0.00166 ND 0.0015 ND 0.000931,1,1-Trichloroethane 290 4200 ND 0.00166 ND 0.0015 ND 0.00093Carbon tetrachloride 0.6 2 ND 0.00166 ND 0.0015 ND 0.000931,2-Dichloroethane (EDC) 0.9 3 ND 0.00166 ND 0.0015 ND 0.00093Benzene 2 5 ND 0.00166 ND 0.0015 ND 0.00093Trichloroethene 7 20 ND 0.00166 ND 0.0015 ND 0.000931,2-Dichloropropane 2 5 ND 0.00166 ND 0.0015 ND 0.00093Bromodichloromethane 1 3 ND 0.00166 ND 0.0015 ND 0.00093cis-1,3-Dichloropropene 2 7 ND 0.00166 ND 0.0015 ND 0.00093Toluene 6300 91000 ND 0.00166 ND 0.0015 ND 0.00093trans-1,3-Dichloropropene 2 7 ND 0.00166 ND 0.0015 ND 0.000931,1,2-Trichloroethane 2 6 ND 0.00166 ND 0.0015 ND 0.00093Tetrachloroethene 2 5 ND 0.00166 ND 0.0015 ND 0.00093Dibromochloromethane 3 8 ND 0.00166 ND 0.0015 ND 0.000931,2-Dibromoethane (EDB) 0.008 0.04 ND 0.00166 ND 0.0015 ND 0.00093Chlorobenzene 510 7400 ND 0.00166 ND 0.0015 ND 0.00093Ethylbenzene 7800 110000 ND 0.00166 ND 0.0015 ND 0.00093Total Xylenes 12000 170000 ND 0.00332 ND 0.003 ND 0.00186Styrene 90 260 ND 0.00166 ND 0.0015 ND 0.00093Bromoform 81 280 ND 0.00166 ND 0.0015 ND 0.000931,1,2,2-Tetrachloroethane 1 3 ND 0.00166 ND 0.0015 ND 0.000931,3-Dichlorobenzene 5300 59000 ND 0.00166 ND 0.0015 ND 0.000931,4-Dichlorobenzene 5 13 ND 0.00166 ND 0.0015 ND 0.000931,2-Dichlorobenzene 5300 59000 ND 0.00166 ND 0.0015 ND 0.000931,2-Dibromo-3-chloropropane 0.08 0.2 ND 0.00166 ND 0.0015 ND 0.000931,2,4-Trichlorobenzene 73 820 ND 0.00166 ND 0.0015 ND 0.00093Hexachlorobutadiene 6 25 ND 0.00166 ND 0.0015 ND 0.00093Naphthalene 6 17 ND 0.00166 ND 0.0015 ND 0.00093Methyl acetate 78000 NA ND 0.00166 ND 0.0015 ND 0.00093TOTAL VO's: NA NA 0.064 C 0.016 C 0.024 CTOTAL TIC's: NA NA ND ND NDTOTAL VO's & TIC's: NA NA 0.064 C 0.016 C 0.024 C


Semivolatiles - BNA (ppm)N-Nitrosodimethylamine 0.7 0.7 ND 0.055 ND 0.050 ND 0.049Benzaldehyde 6100 68000 ND 0.055 ND 0.050 ND 0.049Phenol 18000 210000 ND 0.055 ND 0.050 ND 0.049Bis(2-chloroethyl) ether 0.4 2 ND 0.055 ND 0.050 ND 0.0492-Chlorophenol 310 2000 ND 0.055 ND 0.050 ND 0.0491,3-Dichlorobenzene 5300 59000 ND 0.055 ND 0.050 ND 0.0491,4-Dichlorobenzene 5 13 ND 0.055 ND 0.050 ND 0.0491,2-Dichlorobenzene (NA) (NA) ND 0.055 ND 0.050 ND 0.0492-Methylphenol 310 3400 ND 0.055 ND 0.050 ND 0.049Bis(2-chloroisopropyl) ether (NA) (NA) ND 0.055 ND 0.050 ND 0.0494-Methylphenol 31 340 ND 0.055 ND 0.050 ND 0.049N-Nitrosodi-n-propylamine 0.2 0.3 ND 0.055 ND 0.050 ND 0.049Acetophenone 2 5 ND 0.055 ND 0.050 ND 0.049Hexachloroethane 35 140 ND 0.055 ND 0.050 ND 0.049Nitrobenzene 31 340 ND 0.055 ND 0.050 ND 0.049Isophorone 510 2000 ND 0.055 ND 0.050 ND 0.0492,4-Dimethylphenol 1200 14000 ND 0.055 ND 0.050 ND 0.0492,4-Dichlorophenol 180 2100 ND 0.055 ND 0.050 ND 0.0491,2,4-Trichlorobenzene 73 820 ND 0.055 ND 0.050 ND 0.049Naphthalene 6 17 ND 0.055 ND 0.050 ND 0.049Hexachlorobutadiene 6 25 ND 0.055 ND 0.050 ND 0.049Caprolactam 31000 340000 ND 0.055 ND 0.050 ND 0.0492-Methylnaphthalene 230 2400 ND 0.055 ND 0.050 ND 0.049Hexachlorocyclopentadiene 45 110 ND 0.055 ND 0.050 ND 0.0492,4,6-Trichlorophenol 19 74 ND 0.055 ND 0.050 ND 0.0492,4,5-Trichlorophenol 6100 68000 ND 0.055 ND 0.050 ND 0.0491,1'-Biphenyl (NA) (NA) ND 0.055 ND 0.050 ND 0.0492-Nitroaniline 39 23000 ND 0.055 ND 0.050 ND 0.0492,6-Dinitrotoluene 0.7 3 ND 0.055 ND 0.050 ND 0.049Acenaphthylene NA 300000 ND 0.055 ND 0.050 ND 0.049Acenaphthene 3400 37000 ND 0.055 ND 0.050 ND 0.0492,4-Dinitrophenol 120 1400 ND 0.055 ND 0.050 ND 0.0492,4-Dinitrotoluene 0.7 3 ND 0.055 ND 0.050 ND 0.049Diethyl phthalate 49000 550000 ND 0.055 ND 0.050 ND 0.049Fluorene 2300 24000 ND 0.055 ND 0.050 ND 0.0494,6-Dinitro-2-methylphenol 6 68 ND 0.055 ND 0.050 ND 0.049N-Nitrosodiphenylamine 99 390 ND 0.055 ND 0.050 ND 0.0491,2-Diphenylhydrazine 0.7 2 ND 0.055 ND 0.050 ND 0.049Hexachlorobenzene 0.3 1 ND 0.055 ND 0.050 ND 0.049Atrazine 210 2400 ND 0.055 ND 0.050 ND 0.049Pentachlorophenol 3 10 ND 0.055 ND 0.050 ND 0.049Phenanthrene NA 300000 ND 0.055 0.038 J 0.050 0.090 0.049Anthracene 17000 30000 ND 0.055 ND 0.050 0.020 J 0.049Carbazole 24 96 ND 0.055 ND 0.050 ND 0.049Di-n-butyl phthalate 6100 68000 ND 0.055 ND 0.050 ND 0.049Fluoranthene 2300 24000 0.045 J 0.055 0.086 0.050 0.220 0.049Benzidine 0.7 0.7 ND 0.055 ND 0.050 ND 0.049Pyrene 1700 18000 0.045 J 0.055 0.064 0.050 0.200 0.049Butyl benzyl phthalate 1200 14000 ND 0.055 ND 0.050 ND 0.0493,3'-Dichlorobenzidine 1 4 ND 0.055 ND 0.050 ND 0.049Benzo[a]anthracene 0.6 2 0.026 J 0.055 0.038 J 0.050 0.098 0.049Chrysene 62 230 0.030 J 0.055 0.045 J 0.050 0.150 0.049Bis(2-ethylhexyl) phthalate 35 140 ND 0.055 ND 0.050 ND 0.049Di-n-octyl phthalate 2400 27000 ND 0.055 ND 0.050 ND 0.049Benzo[b]fluoranthene 0.6 2 0.030 J 0.055 0.038 J 0.050 0.122 0.049Benzo[k]fluoranthene 6 23 0.031 J 0.055 0.036 J 0.050 0.119 0.049Benzo[a]pyrene 0.2 0.2 0.023 J 0.055 0.028 J 0.050 0.095 0.049Indeno[1,2,3-cd]pyrene 0.6 2 0.074 0.055 ND 0.050 ND 0.049Dibenz[a,h]anthracene 0.2 0.2 0.060 0.055 ND 0.050 ND 0.049Benzo[g,h,i]perylene 380000 30000 0.105 0.055 ND 0.050 ND 0.049TOTAL BNA'S: NA NA 0.469 J 0.373 J 1.11 JTOTAL TIC's: NA NA 1.38 2.48 1.76TOTAL BNA'S & TIC's: NA NA 1.85 J 2.85 J 2.87 J


PCB's (ppm)Aroclor-1016 0.2 1 ND 0.060 ND 0.052 ND 0.051Aroclor-1221 0.2 1 ND 0.060 ND 0.052 ND 0.051Aroclor-1232 0.2 1 ND 0.060 ND 0.052 ND 0.051Aroclor-1242 0.2 1 ND 0.060 ND 0.052 ND 0.051Aroclor-1248 0.2 1 ND 0.060 ND 0.052 ND 0.051Aroclor-1254 0.2 1 ND 0.060 ND 0.052 ND 0.051Aroclor-1260 0.2 1 ND 0.060 ND 0.052 ND 0.051Pesticides (ppm)alpha-BHC 0.1 0.5 ND 0.012 ND 0.010 ND 0.010beta-BHC 0.4 2 ND 0.012 ND 0.010 ND 0.010gamma-BHC 0.4 2 ND 0.012 ND 0.010 ND 0.010Heptachlor 0.1 0.7 ND 0.012 ND 0.010 ND 0.010Aldrin 0.04 0.2 ND 0.012 ND 0.010 ND 0.010Heptachlor epoxide 0.07 0.3 ND 0.012 ND 0.010 ND 0.010Endosulfan I 470 6800 ND 0.012 ND 0.010 ND 0.0104,4'-DDE 2 9 ND 0.012 ND 0.010 ND 0.010Dieldrin 0.04 0.2 ND 0.012 ND 0.010 ND 0.010Endrin 23 340 ND 0.012 ND 0.010 ND 0.010Endosulfan II 470 6800 ND 0.012 ND 0.010 ND 0.0104,4'-DDD 3 13 ND 0.012 ND 0.010 ND 0.010Endosulfan sulfate 470 6800 ND 0.012 ND 0.010 ND 0.0104,4'-DDT 2 8 ND 0.012 ND 0.010 ND 0.010Methoxychlor 390 5700 ND 0.012 ND 0.010 ND 0.010Chlordane (alpha and gamma) 0.2 1 ND 0.150 ND 0.131 ND 0.127Toxaphene 0.6 3 ND 0.150 ND 0.131 ND 0.127Metals (ppm)Aluminum 78000 NA 37900 171 43500 151 36100 156Antimony 31 450 ND 1.71 ND 1.51 ND 1.56Arsenic 19 19 8.10 0.854 5.44 0.756 10.2 0.779Barium 16000 59000 174 17.1 215 15.1 182 15.6Beryllium 16 140 1.86 0.427 1.77 0.378 1.77 0.390Cadmium 78 78 ND 0.427 ND 0.378 0.359 J 0.390Chromium (NA) (NA) 51.2 3.42 45.9 3.02 55.5 3.12Cobalt 1600 590 24.4 3.42 20.0 3.02 19.9 3.12Copper 3100 45000 28.9 3.42 29.4 3.02 41.6 3.12Lead 400 800 35.2 0.854 22.3 0.756 46.9 0.779Manganese 11000 5900 407 1.71 722 1.51 534 1.56Mercury 23 65 0.029 0.024 0.064 0.021 0.226 0.021Nickel 1600 23000 46.8 1.71 38.5 1.51 36.8 1.56Selenium 390 5700 5.28 3.42 5.48 3.02 6.13 3.12Silver 390 5700 ND 0.854 ND 0.756 0.475 J 0.779Thallium 5 79 0.300 J 0.427 0.315 J 0.378 0.275 J 0.390Vanadium 78 1100 58.9 3.42 57.5 3.02 59.5 3.12Zinc 23000 110000 138 3.42 116 3.02 172 3.12General AnalyticalHexavalent Chromium 240 20 ND 1.66 ND 1.51 ND 1.49Cyanide, Total 1600 23000 ND 1.66 ND 1.50 ND 1.49Trivalent (III) Chromium 120000 NA 51.2 3.42 45.9 3.02 55.5 3.12

~ = Sample not analyzed forND = Analyzed for but Not Detected at the MDL J = The concentration was detected at a value below the RL and above the MDLC = Common Laboratory and/or Bottle Contaminant.All qualifiers on individual Volatiles & Semivolatiles are carried down through summation.


APPENDIX C

VEGETATION SURVEY

BLACKWELLS MILLS VEGETATION SURVEYDOWNSTREAM OF DAM

SAMPLING POINTS RR‐1 RR‐1b RR‐1c RR‐1d RL‐1 RR‐2 RR‐2b RR‐2c RR‐2d RL‐2 RL‐2b RR‐3 RR‐3b RR‐3c RR‐3d RL‐3 RL‐3b RL‐3c

COMMON NAME LATIN NAME NATIVE(Y/N)Japanese honeysuckle Lonicera japonica N x xMugwort Artemisia vulgaris N xSlender yellow wood sorrel Oxalis dillenii Y xSilver maple Acer saccharinum Y x x x x x xMultiflora rose Rosa multiflora N x x x x x x xJapanese stiltgrass Microstegium vimineum N x x x x x x x xJewelweed Impatiens capensis Y x x x x x xPin oak Quercus palustris Y x xRed maple Acer rubrum Y x xLady's thumb Polygonum persicaria N x xGray's sedge Carex grayi Y x x xHalberdleaf tearthumb Polygonum arifolium Y x x xCreeping jenny Lysimachia nummularia N x x x xGreen ash Fraxinus pennsylvanica Y x x x xBox elder Acer negundo Y x x x x x xWood‐reedgrass Cinna arundinacea Y xSlender wood sedge Carex digitalis Y x x x xEastern poison ivy Toxicodendron radicans Y x x xCommon dodder Cuscuta gronovii Y xReed canary grass Phalaris arundinaceae N xBroadleaf arrowhead Sagittaria latifolia Y x xSweet flag Acorus calumus N xFox sedge Carex vulpinoidea Y x

rr: river right looking downstreamrl: river left looking downstream

BLACKWELLS MILLS VEGETATION SURVEYUPSTREAM OF DAM

SAMPLING POINTS RR‐1 RR‐1b RR‐1c RL‐1 RL‐1b RL‐1c RR‐2 RR‐2b RR‐2c RL‐2 RL‐2b RL‐2c RL‐2d

SPECIES LATIN NAME NATIVE(Y/N)Wood‐reedgrass Cinna arundinacea Y x xJapanese stiltgrass Microstegium vimineum N x xJapanese honeysuckle Lonicera japonica N xMultiflora rose Rosa multiflora N x x x x xSilver maple Acer saccharinum Y x x x x xReed canary grass Phalaris arundinaceae N x x x x xMugwort Artemisia vulgaris N x xBox elder Acer negundo Y x xSweet flag Acorus calumus N xNodding smartweed Polygonum lapathifolium Y xSoft rush Juncus effusus Y xPale yellow iris Iris pseudacorus N xFox sedge Carex vulpinoidea Y x xJewelweed Impatiens capensis Y x x x x x x xPoison ivy Toxicodendron radicans Y x x x x xViolet species Viola sp. xCommon ragweed Ambrosia artemisiifolia N xSkunk cabbage Symplocarpus foetidus Y xSlender wood sedge Carex digitalis Y

rr: river right looking downstreamrl: river left looking downstream


APPENDIX D

BASE MAPS


APPENDIX E

HYDROLOGIC AND HYDRAULIC INFORMATION

StreamStats Data-Collection Station Report

USGS Station Number 01402000 Station Name MILLSTONE RIVER AT BLACKWELLS MILLS NJ Click here to link to available data on NWIS-Web for this site. Descriptive Information

Station Type Gaging Station, continuous record Regulated? True Period of Record 1920-2007 Remarks Latitude (degrees NAD83)

40.475

Longitude (degrees NAD83)

-74.57584

Hydrologic unit code 02030105 Local Basin - County 035-Somerset MCD - Directions to station

Physical Characteristics

Characteristic Name Value Units Citation Number

Contributing_Drainage_Area 258.000 square miles 31 Drainage_Area 260.155206265 square miles 82 Main_Channel_Length 40.7858922292206 miles 82 Mean_Basin_Elevation 161.000 feet 31 Percent_Forest 22.4625563947 percent 82 Percent_Storage 20.6757808581 percent 82 Soil_Infiltration 3.9000 inches 31 Stream_Slope_10_and_85_Method 3.8000 feet per mi 31

Page 1 of 6StreamStats Data-Collection Station Report

1/10/2011http://streamstats.usgs.gov/gagepages/HTML/01402000.htm

Streamflow Statistics

Statistic Name Value Units Citation Number

Peak-Flow Statistics 10_Year_Peak_Flood 12200 cubic feet per second 82 100_Year_Peak_Flood 24300 cubic feet per second 82 2_Year_Peak_Flood 5890 cubic feet per second 82 200_Year_Peak_Flood 24200.0 cubic feet per second 31 25_Year_Peak_Flood 16500 cubic feet per second 82 5_Year_Peak_Flood 9390 cubic feet per second 82 50_Year_Peak_Flood 20200 cubic feet per second 82 500_Year_Peak_Flood 36200 cubic feet per second 82 Log_Mean_of_Annual_Peaks 3.7730 Log base 10 31 Log_Skew_of_Annual_Peaks 0.3010 Log base 10 31 Log_STD_of_Annual_Peaks 0.2080 Log base 10 31 Mean_Annual_Flood 3930.00 cubic feet per second 31 Regression_10_Year_Peak_Flood 11900 cubic feet per second 82 Regression_100_Year_Peak_Flood 19900 cubic feet per second 82 Regression_2_Year_Peak_Flood 6510 cubic feet per second 82 Regression_25_Year_Peak_Flood 14700 cubic feet per second 82 Regression_5_Year_Peak_Flood 9700 cubic feet per second 82 Regression_50_Year_Peak_Flood 17200 cubic feet per second 82 Regression_500_Year_Peak_Flood 25400 cubic feet per second 82 Systematic_peak_years 87 years 82 Weighted_10_Year_Peak_Flood 12200 cubic feet per second 82 Weighted_100_Year_Peak_Flood 24100 cubic feet per second 82 Weighted_2_Year_Peak_Flood 5900 cubic feet per second 82 Weighted_25_Year_Peak_Flood 16400 cubic feet per second 82 Weighted_5_Year_Peak_Flood 9400 cubic feet per second 82 Weighted_50_Year_Peak_Flood 20000 cubic feet per second 82 Weighted_500_Year_Peak_Flood 35500 cubic feet per second 82 WRC_Mean 3.7855 Log base 10 82 WRC_Skew 0.402 Log base 10 82 WRC_STD 0.2294 Log base 10 82 Flood-Volume Statistics 1_Day_10_Year_Maximum 8783.7 cubic feet per second 81 1_Day_100_Year_Maximum 15649.9 cubic feet per second 81



1_Day_2_Year_Maximum 4732.2 cubic feet per second 81 1_Day_20_Year_Maximum 10655.8 cubic feet per second 81 1_Day_25_Year_Maximum 11289.8 cubic feet per second 81 1_Day_5_Year_Maximum 7026.2 cubic feet per second 81 1_Day_50_Year_Maximum 13373.2 cubic feet per second 81 15_Day_10_Year_Maximum 2105.1 cubic feet per second 81 15_Day_100_Year_Maximum 2981.8 cubic feet per second 81 15_Day_2_Year_Maximum 1377.0 cubic feet per second 81 15_Day_20_Year_Maximum 2375.5 cubic feet per second 81 15_Day_25_Year_Maximum 2460.7 cubic feet per second 81 15_Day_5_Year_Maximum 1819.1 cubic feet per second 81 15_Day_50_Year_Maximum 2722.4 cubic feet per second 81 3_Day_10_Year_Maximum 5735.5 cubic feet per second 81 3_Day_100_Year_Maximum 9737.6 cubic feet per second 81 3_Day_2_Year_Maximum 3256.2 cubic feet per second 81 3_Day_20_Year_Maximum 6846.1 cubic feet per second 81 3_Day_25_Year_Maximum 7218.5 cubic feet per second 81 3_Day_5_Year_Maximum 4675.0 cubic feet per second 81 3_Day_50_Year_Maximum 8430.5 cubic feet per second 81 30_Day_10_Year_Maximum 1489.94 cubic feet per second 31 30_Day_100_Year_Maximum 1708.7 cubic feet per second 81 30_Day_2_Year_Maximum 1030.28 cubic feet per second 31 30_Day_20_Year_Maximum 1333.4 cubic feet per second 81 30_Day_25_Year_Maximum 1680.3 cubic feet per second 81 30_Day_5_Year_Maximum 1321.6 cubic feet per second 81 30_Day_50_Year_Maximum 1808.7 cubic feet per second 81 7_Day_10_Year_Maximum 3317.8 cubic feet per second 81 7_Day_100_Year_Maximum 5028.1 cubic feet per second 81 7_Day_2_Year_Maximum 2077.5 cubic feet per second 81 7_Day_20_Year_Maximum 3820.3 cubic feet per second 81 7_Day_25_Year_Maximum 3983.4 cubic feet per second 81 7_Day_5_Year_Maximum 2810.8 cubic feet per second 81 7_Day_50_Year_Maximum 4497.7 cubic feet per second 81 Low-Flow Statistics 1_Day_10_Year_Low_Flow 12.48 cubic feet per second 81 1_Day_2_Year_Low_Flow 34.31 cubic feet per second 81 1_Day_20_Year_Low_Flow 8.91 cubic feet per second 81 14_Day_10_Year_Low_Flow 19.38 cubic feet per second 81 14_Day_2_Year_Low_Flow 48.95 cubic feet per second 81 14_Day_20_Year_Low_Flow 14.13 cubic feet per second 81 3_Day_10_Year_Low_Flow 14.89 cubic feet per second 81



3_Day_2_Year_Low_Flow 37.19 cubic feet per second 81 3_Day_20_Year_Low_Flow 11.05 cubic feet per second 81 30_Day_10_Year_Low_Flow 24.67 cubic feet per second 81 30_Day_2_Year_Low_Flow 61.06 cubic feet per second 81 30_Day_20_Year_Low_Flow 18.10 cubic feet per second 81 30_Day_5_Year_Low_Flow 34.80 cubic feet per second 81 7_Day_10_Year_Low_Flow 16.99 cubic feet per second 81 7_Day_2_Year_Low_Flow 42.37 cubic feet per second 81 7_Day_20_Year_Low_Flow 12.51 cubic feet per second 81 7_Day_5_Year_Low_Flow 23.93 cubic feet per second 81 90_Day_10_Year_Low_Flow 46.09 cubic feet per second 81 90_Day_2_Year_Low_Flow 96.38 cubic feet per second 81 90_Day_20_Year_Low_Flow 37.64 cubic feet per second 81 Low_flow_years 54 years 81 Flow-Duration Statistics 1_Percent_Duration 3050 cubic feet per second 41 10_Percent_Duration 816 cubic feet per second 81 20_Percent_Duration 471.5 cubic feet per second 41 25_Percent_Duration 398 cubic feet per second 81 30_Percent_Duration 335 cubic feet per second 41 40_Percent_Duration 255 cubic feet per second 41 5_Percent_Duration 1380 cubic feet per second 41 50_Percent_Duration 200 cubic feet per second 81 60_Percent_Duration 152.5 cubic feet per second 41 70_Percent_Duration 117 cubic feet per second 81 75_Percent_Duration 101 cubic feet per second 81 80_Percent_Duration 86 cubic feet per second 41 90_Percent_Duration 58 cubic feet per second 81 95_Percent_Duration 42 cubic feet per second 81 99_Percent_Duration 21 cubic feet per second 41 Annual Flow Statistics Daily_flow_years 69.000 years 31 Harmonic_Mean_Streamflow 124 cubic feet per second 81 Mean_Annual_Flow 379 cubic feet per second 81 Stand_Dev_of_Mean_Annual_Flow 115.000 cubic feet per second 31 Monthly Flow Statistics April_Mean_Flow 538.000 cubic feet per second 31 April_STD 289.000 cubic feet per second 31 August_Mean_Flow 218.000 cubic feet per second 31 August_STD 231.000 cubic feet per second 31 December_Mean_Flow 449.000 cubic feet per second 31



December_STD 290.000 cubic feet per second 31 February_Mean_Flow 582.000 cubic feet per second 31 February_STD 242.000 cubic feet per second 31 January_Mean_Flow 496.000 cubic feet per second 31 January_STD 310.000 cubic feet per second 31 July_Mean_Flow 248.000 cubic feet per second 31 July_STD 301.000 cubic feet per second 31 June_Mean_Flow 236.000 cubic feet per second 31 June_STD 201.000 cubic feet per second 31 March_Mean_Flow 672.000 cubic feet per second 31 March_STD 264.000 cubic feet per second 31 May_Mean_Flow 366.000 cubic feet per second 31 May_STD 228.000 cubic feet per second 31 November_Mean_Flow 338.000 cubic feet per second 31 November_STD 248.000 cubic feet per second 31 October_Mean_Flow 189.000 cubic feet per second 31 October_STD 169.000 cubic feet per second 31 September_Mean_Flow 224.000 cubic feet per second 31 September_STD 261.000 cubic feet per second 31 Seasonal Flow Statistics Winter_7_Day_10_Year_Low_Flow 51 cubic feet per second 81 General Flow Statistics Average_daily_streamflow 381.897 cubic feet per second 41 Maximum_daily_flow 22000 cubic feet per second 41 Minimum_daily_flow 5 cubic feet per second 41 Std_Dev_of_daily_flows 636.624 cubic feet per second 41 Base Flow Statistics Average_BFI_value 0.394 dimensionless 42 Number_of_years_to_compute_BFI 82 years 42 Std_dev_of_annual_BFI_values 0.061 dimensionless 42 Precipitation Statistics 24_Hour_2_Year_Precipitation 3.4000 inches 31 Mean_Annual_Precipitation 43.000 inches 31 Temperature Statistics Mean_Min_January_Temperature 24.000 degrees F 31

Citations

Citation Number

Citation Name and URL



31 Imported from Basin Characteristics file 41 Wolock, D.M., 2003, Flow characteristics at U.S. Geological Survey

streamgages in the conterminous United States: U.S. Geological Survey Open-File Report 03-146, digital data set, available on World Wide Web at URL http://water.usgs.gov/lookup/getspatial?qsitesdd

42 Wolock, D.M., 2003, Base-flow index grid for the conterminous United States: U.S. Geological Survey Open-File Report 03-263, digital data set, available on World Wide Web at URL http://water.usgs.gov/lookup/getspatial?bfi48grd

81 Watson, K.M., Reiser, R.G., Nieswand, S.P., and Schopp, R.D., 2005, Streamflow characteristics and trends in New Jersey, water years 1897-2003, U.S. Geological Survey Scientific Investigations Report 2005-5105, 131 p.

82 Watson, K.M.,and Schopp, R.D., 2009, Methodology for estimation of flood magnitude and frequency for New Jersey streams, U.S. Geological Survey Scientific Investigations Report 2009-5167, 51 p.



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NewMillstoneData Plan: 1) Removal 1/11/2011 2) Existing 1/11/2011

Main Channel Distance (ft)

Ele

vatio

n (ft

)

Legend

WS 100-Year - Removal

WS 100-Year - Existing

WS NJFHA - Removal

WS NJFHA - Existing






WS 2-Year - Removal

WS Mean Annual - Removal

WS Mean Annual - Existing

Ground

Ground

Millstone Main

HEC-RAS River: Millstone Reach: MainReach River Sta Profile Plan Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl

(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) Main 158156 2-Year Existing 5890.00 27.00 39.53 39.57 0.000153 2.05 5732.00 1041.23 0.11Main 158156 2-Year Removal 5890.00 27.00 39.52 39.56 0.000154 2.05 5722.44 1041.13 0.11Main 158156 10-Year Existing 12200.00 27.00 43.09 43.13 0.000155 2.48 9719.58 1178.37 0.12Main 158156 10-Year Removal 12200.00 27.00 43.07 43.12 0.000156 2.49 9697.52 1178.31 0.12Main 158156 50-Year Existing 20200.00 27.00 46.37 46.43 0.000151 2.81 13604.09 1188.84 0.12Main 158156 50-Year Removal 20200.00 27.00 46.34 46.40 0.000152 2.82 13568.64 1188.76 0.12Main 158156 100-Year Existing 24300.00 27.00 47.78 47.83 0.000152 2.97 15272.42 1192.62 0.12Main 158156 100-Year Removal 24300.00 27.00 47.74 47.80 0.000153 2.98 15230.71 1192.51 0.12Main 158156 NJFHA Existing 22950.00 27.00 47.33 47.39 0.000151 2.92 14742.56 1191.38 0.12Main 158156 NJFHA Removal 22950.00 27.00 47.29 47.35 0.000153 2.93 14698.01 1191.28 0.12Main 158156 Mean Annual Existing 379.00 27.00 31.78 31.79 0.000130 1.06 356.94 75.71 0.09Main 158156 Mean Annual Removal 379.00 27.00 31.59 31.60 0.000148 1.11 342.45 75.63 0.09

Main 157947 2-Year Existing 5890.00 27.00 39.51 39.54 0.000110 1.92 6234.26 1070.40 0.10Main 157947 2-Year Removal 5890.00 27.00 39.50 39.53 0.000110 1.92 6224.32 1070.16 0.10Main 157947 10-Year Existing 12200.00 27.00 43.06 43.11 0.000123 2.41 10369.03 1227.17 0.11Main 157947 10-Year Removal 12200.00 27.00 43.05 43.09 0.000123 2.42 10345.83 1227.12 0.11Main 157947 50-Year Existing 20200.00 27.00 46.35 46.40 0.000124 2.76 14410.00 1235.20 0.11Main 157947 50-Year Removal 20200.00 27.00 46.32 46.37 0.000125 2.77 14372.88 1235.13 0.11Main 157947 100-Year Existing 24300.00 27.00 47.75 47.80 0.000127 2.92 16143.09 1239.25 0.11Main 157947 100-Year Removal 24300.00 27.00 47.71 47.77 0.000128 2.93 16099.46 1239.16 0.11Main 157947 NJFHA Existing 22950.00 27.00 47.30 47.36 0.000126 2.87 15592.67 1237.89 0.11Main 157947 NJFHA Removal 22950.00 27.00 47.27 47.32 0.000127 2.88 15546.05 1237.78 0.11Main 157947 Mean Annual Existing 379.00 27.00 31.77 31.77 0.000054 0.72 543.17 115.72 0.06Main 157947 Mean Annual Removal 379.00 27.00 31.57 31.58 0.000062 0.75 520.81 115.57 0.06





Main 156854 2-Year Existing 5890.00 25.00 39.37 39.40 0.000099 1.89 6461.83 1051.83 0.09Main 156854 2-Year Removal 5890.00 25.00 39.36 39.39 0.000099 1.89 6451.33 1051.79 0.09Main 156854 10-Year Existing 12200.00 25.00 42.93 42.96 0.000114 2.40 10463.98 1170.57 0.10Main 156854 10-Year Removal 12200.00 25.00 42.91 42.94 0.000115 2.40 10440.68 1170.38 0.10Main 156854 50-Year Existing 20200.00 25.00 46.21 46.26 0.000122 2.80 14350.59 1203.34 0.11Main 156854 50-Year Removal 20200.00 25.00 46.18 46.23 0.000123 2.81 14313.12 1202.33 0.11Main 156854 100-Year Existing 24300.00 25.00 47.60 47.66 0.000131 3.04 16089.26 1270.20 0.12Main 156854 100-Year Removal 24300.00 25.00 47.57 47.63 0.000132 3.05 16042.91 1270.14 0.12

HEC-RAS River: Millstone Reach: Main (Continued)Reach River Sta Profile Plan Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl

(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) Main 156854 NJFHA Existing 22950.00 25.00 47.16 47.22 0.000131 2.99 15525.53 1269.49 0.12Main 156854 NJFHA Removal 22950.00 25.00 47.12 47.18 0.000132 3.00 15475.92 1269.43 0.12Main 156854 Mean Annual Existing 379.00 25.00 31.59 31.59 0.000036 0.68 556.30 95.13 0.05Main 156854 Mean Annual Removal 379.00 25.00 31.37 31.37 0.000041 0.71 535.45 94.77 0.05







Main 155707 2-Year Existing 5890.00 26.00 39.23 39.26 0.000141 1.93 5977.27 1096.73 0.10Main 155707 2-Year Removal 5890.00 26.00 39.22 39.25 0.000142 1.93 5965.51 1096.63 0.10Main 155707 10-Year Existing 12200.00 26.00 42.77 42.81 0.000144 2.35 10088.57 1222.36 0.11


(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) Main 155707 10-Year Removal 12200.00 26.00 42.75 42.79 0.000145 2.36 10062.85 1222.33 0.11Main 155707 50-Year Existing 20200.00 26.00 46.06 46.11 0.000140 2.67 14112.90 1228.30 0.11Main 155707 50-Year Removal 20200.00 26.00 46.03 46.07 0.000141 2.67 14072.98 1228.25 0.11Main 155707 100-Year Existing 24300.00 26.00 47.46 47.51 0.000141 2.82 15830.89 1230.69 0.11Main 155707 100-Year Removal 24300.00 26.00 47.42 47.47 0.000142 2.83 15784.31 1230.63 0.11Main 155707 NJFHA Existing 22950.00 26.00 47.01 47.06 0.000140 2.77 15285.36 1229.97 0.11Main 155707 NJFHA Removal 22950.00 26.00 46.97 47.02 0.000142 2.78 15235.43 1229.90 0.11Main 155707 Mean Annual Existing 379.00 26.00 31.49 31.51 0.000160 1.06 366.61 120.55 0.09Main 155707 Mean Annual Removal 379.00 26.00 31.26 31.28 0.000162 1.13 341.01 100.03 0.09






Main 154804 2-Year Existing 5890.00 26.00 39.07 39.10 0.000118 1.99 6038.45 956.11 0.10Main 154804 2-Year Removal 5890.00 26.00 39.06 39.09 0.000118 2.00 6027.31 956.03 0.10Main 154804 10-Year Existing 12200.00 26.00 42.61 42.66 0.000141 2.58 9703.33 1106.64 0.11Main 154804 10-Year Removal 12200.00 26.00 42.59 42.64 0.000142 2.59 9678.43 1106.57 0.11Main 154804 50-Year Existing 20200.00 26.00 45.90 45.96 0.000146 2.97 13357.24 1115.23 0.12Main 154804 50-Year Removal 20200.00 26.00 45.87 45.93 0.000147 2.98 13319.41 1115.17 0.12Main 154804 100-Year Existing 24300.00 26.00 47.30 47.36 0.000150 3.15 14915.19 1117.53 0.12Main 154804 100-Year Removal 24300.00 26.00 47.26 47.32 0.000151 3.16 14871.22 1117.47 0.12Main 154804 NJFHA Existing 22950.00 26.00 46.86 46.92 0.000148 3.09 14420.70 1116.80 0.12Main 154804 NJFHA Removal 22950.00 26.00 46.81 46.87 0.000150 3.10 14373.50 1116.73 0.12Main 154804 Mean Annual Existing 379.00 26.00 31.25 31.26 0.000068 0.84 459.21 90.73 0.07


(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) Main 154804 Mean Annual Removal 379.00 26.00 30.99 31.00 0.000079 0.89 435.82 87.70 0.07







Main 153634 2-Year Existing 5890.00 26.00 38.87 38.91 0.000149 2.26 5228.52 857.13 0.11Main 153634 2-Year Removal 5890.00 26.00 38.86 38.90 0.000150 2.26 5217.46 857.06 0.11Main 153634 10-Year Existing 12200.00 26.00 42.38 42.44 0.000186 2.97 8395.83 1005.89 0.13Main 153634 10-Year Removal 12200.00 26.00 42.35 42.42 0.000188 2.98 8371.24 1005.83 0.13Main 153634 50-Year Existing 20200.00 26.00 45.65 45.73 0.000189 3.39 11702.91 1013.65 0.14Main 153634 50-Year Removal 20200.00 26.00 45.62 45.69 0.000191 3.40 11666.08 1013.56 0.14


(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) Main 153634 100-Year Existing 24300.00 26.00 47.04 47.13 0.000193 3.59 13115.79 1016.95 0.14Main 153634 100-Year Removal 24300.00 26.00 47.00 47.09 0.000195 3.60 13073.17 1016.84 0.14Main 153634 NJFHA Existing 22950.00 26.00 46.60 46.69 0.000192 3.53 12667.32 1015.90 0.14Main 153634 NJFHA Removal 22950.00 26.00 46.56 46.64 0.000194 3.54 12621.53 1015.79 0.14Main 153634 Mean Annual Existing 379.00 26.00 30.91 30.92 0.000059 0.76 544.58 112.11 0.06Main 153634 Mean Annual Removal 379.00 26.00 30.58 30.59 0.000073 0.81 507.93 111.95 0.07







Main 152623 2-Year Existing 5890.00 26.00 38.67 38.70 0.000155 2.22 5659.12 996.99 0.11


(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) Main 152623 2-Year Removal 5890.00 26.00 38.65 38.69 0.000156 2.23 5644.82 996.86 0.12Main 152623 10-Year Existing 12200.00 26.00 42.16 42.21 0.000174 2.80 9311.18 1139.83 0.13Main 152623 10-Year Removal 12200.00 26.00 42.13 42.18 0.000176 2.81 9280.99 1138.96 0.13Main 152623 50-Year Existing 20200.00 26.00 45.44 45.50 0.000169 3.14 13120.69 1163.22 0.13Main 152623 50-Year Removal 20200.00 26.00 45.41 45.46 0.000171 3.16 13075.81 1163.22 0.13Main 152623 100-Year Existing 24300.00 26.00 46.84 46.90 0.000169 3.31 14740.31 1163.22 0.13Main 152623 100-Year Removal 24300.00 26.00 46.79 46.86 0.000171 3.32 14688.88 1163.22 0.13Main 152623 NJFHA Existing 22950.00 26.00 46.40 46.46 0.000169 3.25 14227.11 1163.22 0.13Main 152623 NJFHA Removal 22950.00 26.00 46.35 46.41 0.000171 3.27 14171.68 1163.22 0.13Main 152623 Mean Annual Existing 379.00 26.00 30.71 30.72 0.000114 1.02 418.06 91.13 0.08Main 152623 Mean Annual Removal 379.00 26.00 30.32 30.34 0.000151 1.11 383.26 90.76 0.10






Main 151078 2-Year Existing 5890.00 25.00 38.47 38.49 0.000144 1.75 7081.69 1458.33 0.10Main 151078 2-Year Removal 5890.00 25.00 38.46 38.47 0.000145 1.76 7058.12 1458.07 0.10Main 151078 10-Year Existing 12200.00 25.00 42.00 42.02 0.000110 1.92 12598.18 1726.83 0.10Main 151078 10-Year Removal 12200.00 25.00 41.97 41.99 0.000112 1.92 12549.02 1724.73 0.10Main 151078 50-Year Existing 20200.00 25.00 45.30 45.33 0.000099 2.12 18501.96 1786.60 0.09Main 151078 50-Year Removal 20200.00 25.00 45.26 45.29 0.000100 2.13 18430.00 1786.60 0.09Main 151078 100-Year Existing 24300.00 25.00 46.70 46.73 0.000096 2.21 20996.24 1786.60 0.09Main 151078 100-Year Removal 24300.00 25.00 46.65 46.68 0.000097 2.22 20914.22 1786.60 0.09Main 151078 NJFHA Existing 22950.00 25.00 46.26 46.28 0.000097 2.18 20206.34 1786.60 0.09


(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) Main 151078 NJFHA Removal 22950.00 25.00 46.21 46.23 0.000098 2.19 20117.77 1786.60 0.09Main 151078 Mean Annual Existing 379.00 25.00 30.29 30.37 0.000662 2.24 169.48 37.54 0.19Main 151078 Mean Annual Removal 379.00 25.00 29.76 29.86 0.000902 2.52 150.42 35.18 0.21







Main 150239 2-Year Existing 5890.00 24.97 38.36 38.40 0.000167 2.25 5329.08 977.21 0.12Main 150239 2-Year Removal 5890.00 24.97 38.34 38.39 0.000169 2.25 5312.33 976.76 0.12Main 150239 10-Year Existing 12200.00 24.97 41.89 41.94 0.000166 2.69 8910.97 1026.59 0.12Main 150239 10-Year Removal 12200.00 24.97 41.86 41.91 0.000168 2.70 8880.63 1026.59 0.12


(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) Main 150239 50-Year Existing 20200.00 24.97 45.19 45.25 0.000169 3.11 12294.47 1026.59 0.13Main 150239 50-Year Removal 20200.00 24.97 45.15 45.21 0.000171 3.12 12251.97 1026.59 0.13Main 150239 100-Year Existing 24300.00 24.97 46.58 46.65 0.000173 3.31 13720.33 1026.59 0.13Main 150239 100-Year Removal 24300.00 24.97 46.53 46.60 0.000175 3.32 13671.95 1026.59 0.13Main 150239 NJFHA Existing 22950.00 24.97 46.14 46.21 0.000172 3.24 13268.99 1026.59 0.13Main 150239 NJFHA Removal 22950.00 24.97 46.09 46.16 0.000174 3.25 13216.73 1026.59 0.13Main 150239 Mean Annual Existing 379.00 24.97 29.84 29.86 0.000223 1.20 317.02 91.77 0.11Main 150239 Mean Annual Removal 379.00 24.97 28.94 28.98 0.000554 1.60 236.58 87.80 0.17





Main 149740 2-Year Existing 5890.00 24.38 38.22 29.91 38.24 0.000085 1.67 7092.55 1320.15 0.09Main 149740 2-Year Removal 5890.00 24.38 38.20 29.91 38.22 0.000086 1.67 7070.07 1319.55 0.09Main 149740 10-Year Existing 12200.00 24.38 41.71 33.98 41.74 0.000091 2.05 11870.74 1559.67 0.09Main 149740 10-Year Removal 12200.00 24.38 41.68 33.98 41.71 0.000092 2.06 11825.68 1558.23 0.09Main 149740 50-Year Existing 20200.00 24.38 44.97 35.21 45.00 0.000091 2.32 17636.54 1691.21 0.10Main 149740 50-Year Removal 20200.00 24.38 44.92 35.21 44.96 0.000092 2.33 17562.92 1689.03 0.10Main 149740 100-Year Existing 24300.00 24.38 46.34 35.63 46.37 0.000093 2.47 20011.91 1780.63 0.10Main 149740 100-Year Removal 24300.00 24.38 46.29 35.63 46.33 0.000094 2.48 19923.76 1777.38 0.10Main 149740 NJFHA Existing 22950.00 24.38 45.90 35.50 45.94 0.000092 2.42 19247.26 1752.19 0.10Main 149740 NJFHA Removal 22950.00 24.38 45.85 35.50 45.89 0.000094 2.44 19153.56 1748.67 0.10Main 149740 Mean Annual Existing 379.00 24.38 29.78 25.62 29.79 0.000075 0.77 493.18 121.71 0.07Main 149740 Mean Annual Removal 379.00 24.38 28.80 25.62 28.81 0.000170 1.01 376.76 115.53 0.10

Main 149720 Bridge

Main 149700 2-Year Existing 5890.00 24.89 38.21 30.44 38.23 0.000091 1.68 7010.87 1319.77 0.09Main 149700 2-Year Removal 5890.00 24.89 38.19 30.44 38.21 0.000092 1.69 6988.28 1319.17 0.09Main 149700 10-Year Existing 12200.00 24.89 41.70 34.22 41.73 0.000095 2.06 11786.29 1559.14 0.09Main 149700 10-Year Removal 12200.00 24.89 41.67 34.22 41.70 0.000096 2.07 11741.05 1557.69 0.09Main 149700 50-Year Existing 20200.00 24.89 44.96 35.28 44.99 0.000093 2.33 17551.27 1690.69 0.10Main 149700 50-Year Removal 20200.00 24.89 44.91 35.28 44.95 0.000094 2.34 17477.46 1688.51 0.10Main 149700 100-Year Existing 24300.00 24.89 46.33 35.70 46.36 0.000095 2.47 19925.36 1779.94 0.10Main 149700 100-Year Removal 24300.00 24.89 46.28 35.70 46.31 0.000096 2.48 19837.02 1776.67 0.10Main 149700 NJFHA Existing 22950.00 24.89 45.89 35.57 45.93 0.000094 2.43 19161.14 1751.50 0.10Main 149700 NJFHA Removal 22950.00 24.89 45.84 35.57 45.88 0.000096 2.44 19067.22 1747.97 0.10


(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) Main 149700 Mean Annual Existing 379.00 24.89 29.77 26.19 29.78 0.000113 0.88 428.96 118.20 0.08Main 149700 Mean Annual Removal 379.00 24.89 28.78 26.19 28.80 0.000287 1.20 315.50 110.50 0.13


Main 149616 2-Year Existing 5890.00 26.97 38.06 32.52 38.17 0.000487 3.23 2805.68 473.15 0.19Main 149616 2-Year Removal 5890.00 23.97 38.06 38.16 0.000353 3.03 2990.80 473.12 0.16Main 149616 10-Year Existing 12200.00 26.97 41.47 35.40 41.64 0.000543 4.21 4457.82 485.36 0.21Main 149616 10-Year Removal 12200.00 23.97 41.45 41.62 0.000446 4.09 4633.49 485.36 0.19Main 149616 50-Year Existing 20200.00 26.97 44.63 36.81 44.88 0.000602 5.15 5991.66 485.36 0.23Main 149616 50-Year Removal 20200.00 23.97 44.59 44.84 0.000523 5.06 6159.74 485.36 0.21Main 149616 100-Year Existing 24300.00 26.97 45.94 37.38 46.24 0.000636 5.58 6630.25 485.36 0.24Main 149616 100-Year Removal 24300.00 23.97 45.90 46.19 0.000561 5.51 6794.96 485.36 0.23Main 149616 NJFHA Existing 22950.00 26.97 45.53 37.14 45.81 0.000625 5.44 6428.72 485.36 0.23Main 149616 NJFHA Removal 22950.00 23.97 45.48 45.76 0.000549 5.37 6591.44 485.36 0.22Main 149616 Mean Annual Existing 379.00 26.97 29.69 28.06 29.74 0.000741 1.70 226.18 98.26 0.20Main 149616 Mean Annual Removal 379.00 23.97 28.75 28.77 0.000212 1.18 320.76 93.59 0.11

Main 149570 Inl Struct





Main 149213 2-Year Existing 5890.00 24.97 37.88 38.01 0.000334 3.28 3041.76 550.92 0.17Main 149213 2-Year Removal 5890.00 24.97 37.88 38.01 0.000334 3.28 3041.76 550.92 0.17Main 149213 10-Year Existing 12200.00 24.97 41.23 41.41 0.000406 4.29 4900.83 555.40 0.20


(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) Main 149213 10-Year Removal 12200.00 24.97 41.23 41.41 0.000406 4.29 4900.81 555.40 0.20Main 149213 50-Year Existing 20200.00 24.97 44.34 44.59 0.000464 5.21 6626.94 555.40 0.22Main 149213 50-Year Removal 20200.00 24.97 44.34 44.59 0.000464 5.21 6626.94 555.40 0.22Main 149213 100-Year Existing 24300.00 24.97 45.63 45.92 0.000495 5.64 7343.39 555.40 0.23Main 149213 100-Year Removal 24300.00 24.97 45.63 45.92 0.000495 5.64 7343.40 555.40 0.23Main 149213 NJFHA Existing 22950.00 24.97 45.22 45.49 0.000486 5.50 7113.81 555.40 0.22Main 149213 NJFHA Removal 22950.00 24.97 45.22 45.49 0.000486 5.50 7113.81 555.40 0.22Main 149213 Mean Annual Existing 379.00 24.97 28.44 28.48 0.000859 1.70 226.27 112.85 0.21Main 149213 Mean Annual Removal 379.00 24.97 28.44 28.48 0.000859 1.70 226.27 112.85 0.21






Main 148322 2-Year Existing 5890.00 24.00 37.75 37.81 0.000197 2.47 4237.42 664.61 0.13Main 148322 2-Year Removal 5890.00 24.00 37.75 37.81 0.000197 2.47 4237.42 664.61 0.13Main 148322 10-Year Existing 12200.00 24.00 41.06 41.15 0.000254 3.31 6452.23 678.79 0.15Main 148322 10-Year Removal 12200.00 24.00 41.06 41.15 0.000254 3.31 6452.19 678.79 0.15Main 148322 50-Year Existing 20200.00 24.00 44.13 44.27 0.000297 4.06 8539.58 678.79 0.17Main 148322 50-Year Removal 20200.00 24.00 44.13 44.27 0.000297 4.06 8539.58 678.79 0.17Main 148322 100-Year Existing 24300.00 24.00 45.41 45.56 0.000320 4.40 9404.39 678.79 0.18Main 148322 100-Year Removal 24300.00 24.00 45.41 45.56 0.000320 4.40 9404.40 678.79 0.18Main 148322 NJFHA Existing 22950.00 24.00 45.00 45.15 0.000313 4.29 9127.16 678.79 0.17Main 148322 NJFHA Removal 22950.00 24.00 45.00 45.15 0.000313 4.29 9127.16 678.79 0.17Main 148322 Mean Annual Existing 379.00 24.00 28.17 28.20 0.000201 1.19 317.38 82.35 0.11


(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) Main 148322 Mean Annual Removal 379.00 24.00 28.17 28.20 0.000201 1.19 317.38 82.35 0.11





Main 147086 2-Year Existing 5890.00 24.00 37.50 29.43 37.56 0.000200 2.49 4946.88 1070.97 0.13Main 147086 2-Year Removal 5890.00 24.00 37.50 29.43 37.56 0.000200 2.49 4946.88 1070.97 0.13Main 147086 10-Year Existing 12200.00 24.00 40.78 34.17 40.84 0.000200 2.94 8617.32 1163.02 0.13Main 147086 10-Year Removal 12200.00 24.00 40.78 34.17 40.84 0.000200 2.94 8617.32 1163.02 0.13Main 147086 50-Year Existing 20200.00 24.00 43.83 35.98 43.91 0.000200 3.34 12469.63 1282.69 0.14Main 147086 50-Year Removal 20200.00 24.00 43.83 35.98 43.91 0.000200 3.34 12469.63 1282.69 0.14Main 147086 100-Year Existing 24300.00 24.00 45.10 36.43 45.18 0.000200 3.49 14095.15 1282.69 0.14Main 147086 100-Year Removal 24300.00 24.00 45.10 36.43 45.18 0.000200 3.49 14095.15 1282.69 0.14Main 147086 NJFHA Existing 22950.00 24.00 44.69 36.29 44.77 0.000200 3.44 13573.73 1282.69 0.14Main 147086 NJFHA Removal 22950.00 24.00 44.69 36.29 44.77 0.000200 3.44 13573.73 1282.69 0.14Main 147086 Mean Annual Existing 379.00 24.00 27.90 24.87 27.92 0.000200 1.21 328.57 85.34 0.11Main 147086 Mean Annual Removal 379.00 24.00 27.90 24.87 27.92 0.000200 1.21 328.57 85.34 0.11


APPENDIX F

REFERENCES

References Hillsborough Township, www.hillsborough‐nj.org/Cit‐E‐Access/webpage.cfm?TID=45&TPID=6331. Delaware and Raritan Canal State Park, www.dandrcanal.com/friends_bwm.html. The Meadows Foundation. www.themeadowsfoundation.org/blackwell‐mills.html. N.J.A.C. 7:20, Dam Safety Standards, last amended June 16, 2008. N.J.A.C. 7:26D, Soil Remediation Standards, last amended November 4, 2009. United States Army Corps of Engineers. Hydrologic Engineering Centers River Analysis System (HEC‐RAS),

Version 4.1, January 2010.

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