Cobbett's Pond Watershed Based Plan

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

Cobbett’s Pond Watershed Restoration Plan

Final Draft: July 6, 2010

Prepared For:

Cobbett’s Pond Improvement Association

20 Turtle Rock Road Windham, NH 03087

Prepared By:

289 Great Road, Suite 105 Acton, MA 01720 www.geosyntec.com Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

Table of Contents

1. INTRODUCTION ...... 3 2. LITERATURE AND DATA REVIEW ...... 6 2.1 Summary of Existing Water Quality Reports ...... 6 2.2 Review of Windham Ordinances and Regulations...... 10 3. 2009 MONITORING DATA ...... 14 3.1 Water Quality Monitoring ...... 14 3.2 Trophic Status Assessment ...... 22 3.3 Aquatic Vegetation Survey ...... 26 3.4 Algae Sampling...... 31 3.5 Flow Monitoring ...... 32 4. WATERSHED ASSESSMENT ...... 34 4.1 Storm Drainage Mapping ...... 34 4.2 Watershed Soils ...... 34 4.3 Watershed Imperviousness ...... 36 4.4 Septic System Investigation...... 39 5. COBBETT’S POND PHOSPHORUS BUDGET ...... 40 5.1 Land-Use Based Pollutant Modeling ...... 40 5.2 Phosphorus Loading From Septic Systems ...... 44 5.3 Internal Phosphorus Loading ...... 44 5.4 Atmospheric Deposition ...... 46 5.5 Estimated Annual Phosphorus Loading Budget...... 46 5.6 Vollenweider Equation Results ...... 47 5.7 Recommended Phosphorus Reduction Goal ...... 50 6. OPTIONS FOR REDUCING PHOSPHORUS LOADING TO COBBETT’S POND ...... 52 6.1 Storm Water Management...... 52 6.2 Potential Community Septic Systems Locations ...... 77 6.3 Phosphorus Loading From Watershed Land Uses...... 80 7. SUMMARY OF TECHNICAL AND FINANCIAL SUPPORT ...... 82 7.1 Technical Support ...... 82 7.2 Financial Support ...... 82 8. PUBLIC INFORMATION AND EDUCATION ...... 84 9. SCHEDULE AND INTERIM MILESTONES...... 85 10. EVALUATION CRITERIA AND MONITORING ...... 87 11. REFERENCES ...... 88

1 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

FIGURES Figure 1: Cobbett’s Pond Watershed - USGS Topographic Map Figure 2: Cobbett’s Pond Subwatersheds Map Figure 3: Historic Total Phosphorus Concentrations in the Epilimnion of Cobbett’s Pond Figure 4: Water Quality Monitoring Locations Map Figure 5: 2009 Dissolved Oxygen Profiles, North and South Deep Spot Figure 6: 2009 Temperature Profiles, North and South Deep Spot Figure 7: 2009 Epilimnion Total Phosphorus Concentrations, North and South Deep Spot Figure 8: 2009 Hypolimnion Total Phosphorus Concentrations, North and South Deep Spot Figure 9: Carlson Trophic State Index Figure 10: Aquatic Vegetation Map, July 27, 2009 Figure 11: Fossa Road Subwatershed Hydrograph, July 31, 2009 Figure 12: Turtle Rock Road Subwatershed Hydrograph, July 31, 2009 Figure 13: USDA-NRCS Soil Survey Map Figure 14: Impervious Cover Model, Center for Watershed Protection Figure 15: Impervious Surface Map – Cobbett’s Pond Watershed Figure 16: Impervious Cover of Cobbett’s Pond Subwatersheds Figure 17: Estimated Internal Phosphorus Loading, Cobbett’s Pond North and South Basins Figure 18: External Sources of Phosphorus to Cobbett’s Pond Figure 19: External Sources of Phosphorus to Cobbett’s Pond North and South Basins Figure 20: Vollenweider Plot for Cobbett’s Pond Figure 21: Schematic of Typical Bioretention Cell Figure 22: Potential Community Septic System Locations Map Figure 23: Implementation Schedule and Interim Milestones

TABLES Table 1: Aquatic Vegetation Tally Sheet, July 27, 2009 Table 2: Algae Sampling Results, May – October 2009 Table 3: Phosphorus Export Coefficients by NH-GRANIT Land Use Category Table 4: Subwatershed Land Cover Areas Table 5: Subwatershed Phosphorus Loading Summary Table 6: Cobbett’s Pond Vollenweider Model Parameters Table 7: Vollenweider Model Parameters, North and South Basins Table 8: Potential Community Septic Systems Table 9: Summary of Proposed Actions to Reduce Phosphorus Loading

APPENDICES Appendix A: Water Quality and Flow Monitoring Data Appendix B: Cobbett’s Pond Stormwater Infrastructure Maps Appendix C: Septic System Inventory Maps Appendix D: Stormwater BMP Load Reduction and Cost Estimate Data

2 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

1. INTRODUCTION Geosyntec Consultants, Inc. (Geosyntec) was contracted by the Cobbett’s Pond Improvement Association (CPIA) to develop a Watershed Restoration Plan (WRP) for Cobbett’s Pond in Windham, NH. Financial support for this project was provided by a grant from the New Hampshire Department of Environmental Services (NHDES) with funding from the U.S. Environmental Protection Agency under Section 319 of the Clean Water Act.

Cobbett’s Pond (302 acres) has experienced declines in water quality in recent years, as indicated by increasing in-lake phosphorus concentrations and increasing occurrences of nuisance blue-green algae blooms. Cobbett’s Pond has been included on the Draft 2010 List of New Hampshire Threatened or Impaired Waters for “aquatic life” impairments related to low levels of dissolved oxygen and elevated levels of chlorophyll-a and total phosphorus. The lake was also listed as impaired for “primary contact recreation” due to recent blooms of cyanobacteria that have the potential to produce toxins.

In freshwater lakes, phosphorus is usually the most important nutrient determining the growth of algae and aquatic plants. Because phosphorus is typically relatively less abundant than nitrogen, it is considered the “limiting nutrient” for biological productivity. As such, increases in phosphorus levels tend to be strongly correlated with decreased water clarity, increased algal abundance and other indicators of declining water quality. The primary purposes of this WRP are: a. to identify and quantify specific sources of phosphorus contributing to the lake’s water quality impairments; and b. to develop a management plan to reduce phosphorus loading to the lake to a targeted level that would significantly improve in-lake conditions.

To achieve the goals listed above, this WRP includes the following nine elements, in conformance with the U.S. Environmental Protection Agency’s guidance for watershed based plans: 1. Identify Pollutant Sources (Sections 2, 3 and 4) 2. Pollutant Load Reduction Estimates (Section 5) 3. Describe Nonpoint Source Pollution Management Measures (Section 6) 4. Estimate Technical and Financial Assistance (Section 7) 5. Public Information and Education (Section 8) 6. Implementation Schedule (Section 9) 7. Interim Milestones (Section 9) 8. Evaluation Criteria (Section 10) 9. Monitoring (Section 10)

3 N

0 600 1,200 2,400 3,600 Legend Feet Cobbett's Pond Watershed USGS TOPOGRAPHIC MAP OF COBBETT'S POND WATERSHED Cobbett's Pond Windham, NH

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USGS Topographic Map data layer provided NH Granit Statewide GIS Clearinghouse Acton, MA 2-JUL-2010 1 

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SW 8 Town Beach Area SW 9 Fossa Rd. Area ð   N Legend 0 600 1,200 2,400 3,600 Feet Cobbett's Pond Watershed COBBETT'S POND Subwatershed Boundary SUBWATERSHEDS Stream Cobbett's Pond Windham, NH Highway Major Road FIG Water Body Acton, MA 2-JUL-2010 2 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

2. LITERATURE AND DATA REVIEW 2.1 Summary of Existing Water Quality Reports

This section provides a summary of the findings from several previous reports and data sources that address water quality conditions in Cobbett’s Pond. The report summaries are presented below in chronological order. NHDES Water Supply and Pollution Control Division – Biology Bureau Cobbett’s Pond Lake Trophic Data, 1986-1987 Summary of Comments: • NHDES classified Cobbett’s Pond as mesotrophic in 1986. In 1976, the pond was classified as oligotrophic. The change in trophic status was due to increased plant growth (sparse to abundant), and less hypolimnetic (pond bottom) dissolved oxygen. The report noted that the change in hypolimnetic oxygen was probably due primarily to a greater sampling depth and not an actual decline in water quality. At both ST1 and ST2, dissolved oxygen levels declined abruptly at depths greater than 9 meters. • The whole water phytoplankton was 60% greens and 25% cryptomonads at ST1, with 65% greens and 20% diatoms at ST2. Tiny green flagellates were dominant (50%) at both stations. • Plant growth in Cobbett’s Pond was sparse in 1976. Plant surveys in 1985 and 1986 confirmed that the pond was ringed with abundant growth of Potamogeton perfoliatus, a species that was not observed during the 1976 survey. Other common plants included Elodea nuttallii, Eriocaulon septangulare, and Potamogeton Robbinsii. No non-native, invasive species were observed.

NHDES Water Division – Watershed Management Bureau Cobbett’s Pond Lake Trophic Data, 2003-2004 Summary of Comments: • NHDES classified Cobbett’s Pond as oligotrophic in 1976, mesotrophic in 1986, and eutrophic in 2003. There was an explosive growth Potamogeton perfoliatus in 1985 and the non-native Myriophyllum heterophyllum (Variable Milfoil) was first observed in 1995. Other trophic parameters have worsened over the years. • VLAP data since 1988 show a worsening trend for chlorophyll-a, Secchi disk transparency and hypolimnetic phosphorus at both stations ST1 and ST2. Elevated phosphorus and total Kjeldahl nitrogen in the hypolimnion suggest internal nutrient loading. • Elevated sodium, chloride and conductivity values indicate salt runoff from watershed roads, including the adjacent Interstate 93. • Diatoms were very abundant during winter sampling. • Numerous ducks, geese and seagulls were observed on the lake. • Residents report that fishing is excellent and that an eagle visited the lake throughout the summer of 2003.

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

• Potamogeton perfoliatus was abundant around the entire shoreline. Growth of ten other species was observed to be sparse, including and the non-native Variable milfoil. Variable milfoil was treated with the herbicide Diquat in 1996, 1998, 202 and 2003 to help control its spread.

NHDES Volunteer Lake Assessment Program (VLAP) 2006 Biennial Report; 2010 Interim Report Summary of Observations and Recommendations for Cobbett’s Pond from 2006 and 2010 Reports: • Chlorophyll-a is an indicator of algal abundance. September 2006 chlorophyll-a concentrations at both deep hole stations were below the state median but exceeded the median for similar lakes. The 2009 chlorophyll-a mean was greater than both the state and similar lake medians. Chlorophyll-a concentrations have increased significantly (worsened) during the VLAP sampling period of 1988 to 2009. • In September 2006, Secchi disk transparency was greater than the state median but below the median. The 2009 mean transparency was slightly less than the state median and less than the similar lake median. The historical data indicates that the transparency has decreased (worsened) since monitoring began in 1988. • In 2006, phosphorus concentrations at both deep spots were slightly greater than the state median and greater than the median for similar lakes. The 2009 mean epilimnetic phosphorus concentration was greater than the state and similar lake medians. The monitoring data suggest that internal phosphorus loading is occurring in the pond. In 2006, elevated phosphorus concentrations were also noted for Connie’s Brook and Castleton Brook. • In 2006, the dominant phytoplankton species at the deep spot locations were Dinobryon, Rhizosolenia, Synedra and Ceratium. A small amount of the cyanobacteria Anabaena and Oscillatoria were observed in 2006. A cyanobacteria bloom occurred in the pond during August 2009. A beach advisory was issued on 8/12/2009 and a lake warning was issued on 8/14/2009 notifying the public of the presence of potentially toxic cyanobacteria. The cyanobacteria were identified as Anabaena and Microcystis, both which have the potential to produce toxins. More detailed information on the 2009 algae sampling conducted by Geosyntec is provided in Section 3.4 of this report. • The pond’s pH ranged from approximately 7.4 in the epilimnion to 6.8 in the hypolimnion. The acid neutralizing capacity of the pond was well above the state median, indicating that the lake is not vulnerable to impacts from acid input. • Conductivity in the pond and its tributaries continues to be much greater than the state median, indicating the influence of pollutants such as failed or poorly functioning septic systems, agricultural runoff, and road runoff containing road salt. • Hypolimnetic oxygen concentrations were below 1 mg/L at both deep spots during the September sampling events, consistent with many previous sampling results. When oxygen levels are depleted to this extent, phosphorus that is normally bound in the sediment may be released into the water column.

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

2.1.1 Discussion of Phosphorus Concentration Data for Cobbett’s Pond Eutrophication is the gradual process of nutrient enrichment in aquatic ecosystems such as lakes. Eutrophication occurs naturally as lakes become more biologically productive over geological time, but this process may be accelerated by human activities that occur in the watershed. Nutrients that contribute to eutrophication can come from many natural and anthropogenic sources, such as fertilizers applied to residential lawns and agricultural fields; septic systems; deposition of nitrogen from the atmosphere; erosion of soil containing nutrients; and sewage treatment plant discharges. Land development not only increases the sources of nutrients, but also decreases opportunities for natural attenuation (e.g. uptake by vegetation) of such nutrients before they can reach a water body.

Nutrients such as phosphorus and nitrogen can stimulate abundant growth of algae and rooted plants in water bodies. Over time, this enhanced plant growth leads to reduced dissolved oxygen in the water, as dead plant material decomposes and consumes oxygen. Phosphorus is typically the “limiting nutrient” for freshwater lakes, which means that plant productivity is most often controlled by the supply of this nutrient. As such, increases in phosphorus load in a lake watershed are closely correlated with increases in plant productivity and accelerated eutrophication.

Figure 3 on the following page illustrates the historic trend for phosphorus concentrations in the epilimnion (surface water layer) of Cobbett’s Pond. This data, collected between 1988 and 2009 through the NH-VLAP program, indicated a progressive increase in phosphorus concentrations over the 21 year period, with concentrations at both the North Deep Spot and South Deep Spot exceeding the median for New Hampshire lakes.

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

Figure 3. Historic Total Phosphorus Concentrations, Cobbett’s Pond Epilimnion (Figure from NH-VLAP 2009 Interim Report for Cobbett’s Pond)

Station 1: Monthly and Historical Total Phosphorus Data

Total Phosphorus Concentration (µg/L) (µg/L) Concentration Phosphorus Total

Station 2: Monthly and Historical Total Phosphorus Data

Total Phosphorus Concentration (µg/L) (µg/L) Concentration Phosphorus Total

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

2.2 Review of Windham Ordinances and Regulations

Geosyntec reviewed the Town of Windham ordinances and regulations to identify (1) potential conflicts to the long-term goal of reducing stormwater pollutant loading to Cobbett’s Pond, and (2) areas where existing ordinances and regulations may require modification and where revisions could be adopted to promote stormwater improvements such as Low Impact Development (LID) stormwater management practices.

As described below, the new Cobbett’s Pond Watershed Protection Ordinance is by far the most significant local regulation related to land use, development and water quality protection for the Cobbett’s Pond watershed. By establishing a new Watershed Protection Overlay District (WPOD), this ordinance creates a set of standards for the watershed that are more stringent than those which exist under Windham’s Zoning Ordinance, Land Use Regulations, Site Plan Regulations and Subdivision Control Regulations.

Cobbett’s Pond Watershed Protection Ordinance (CPWPO) The CPWPO was passed by Town Meeting vote in March 2009. This ordinance represents a significant new regulatory tool for the protection and improvement of the Pond’s water quality and has received considerable attention throughout New Hampshire and neighboring states as a model ordinance for lake protection. The CPWPO established a watershed protection overlay district (WPOD) that provides additional review requirements and performance standards for development projects and land use practices within the Cobbett’s Pond watershed. A summary of some of the major elements of the CPWPO regulations is a follows: • The CPWPO is generally supportive of LID stormwater management practices. Although LID is defined in the definitions section (Section 1.4.s), LID is not specifically mentioned at any other point in the regulations. However, in Section 1.6.c(2) (Review Requirements for Development in the Watershed Protection Overlay District), the ordinance requires that “Best Management Practices (BMPs) are in place and are sufficient to remove or neutralize those pollutants that present a potential impact to the water body.” The definition of BMP in the ordinance references several NHDES publications which include a listing and description of LID practices, including bioretention, infiltration trenches, grassed swales, and the extensive use of vegetation to filter runoff prior to discharge to a waterbody. • Specified activities and land uses are prohibited within the WPOD, including storage, use and disposal of hazardous materials; • Land development proposals must include a hydrologic study documenting that the proposed project will provide “the same or a greater degree of water quality protection as existed on the sites(s)” at the time of application; • Grading and removal of vegetation at development sites must be minimized and lawn area is limited to 10% of all dry land; • Septic system pumping and inspection must occur at least every three years or more frequently if recommended by a licensed septic service provider; • A 100-foot buffer zone shall be maintained along the edge of any tributary to Cobbett’s Pond and all wetlands bordering those tributaries;

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

• Specified activities and materials are prohibited within the 100-foot buffer zone and within 25 feet of the buffer zone, including septic tanks/drain fields, trash containers, and the storage of hazardous materials, road salt, lawn fertilizers and other specified materials; • Site construction standards prohibit impervious driveways within 75 feet of surface waters or wetlands, and limit the impervious surface area of any lot to 30%; and • Application of fertilizers (including manure) and pesticides is prohibited within 200 feet of surface waters or wetlands.

Other Town Regulations Geosyntec reviewed the Town of Windham Zoning Ordinance, Land Use Regulations, Site Plan Regulations, Subdivision Control Regulations and Water Supply Regulations. In general, Geosyntec found that these regulations neither specifically promote or present any significant barriers to the implementation of LID stormwater practices. As described above, the new CPWPO has created additional protective standards that are more stringent than these town-wide regulations. Several sections within the town regulations that could be modified for greater compatibility with LID stormwater practices are as follows: • Town of Windham Zoning Ordinance and Land Use Regulations: ¾ Section 611 provides specific provisions for Open Space Residential Development, and encourages flexibility in design “to promote the development of balanced communities in harmony with natural land features.” A similar set of provisions could be included in these regulations to actively promote LID practices in new developments and allow similar flexibility in design standards where appropriate. LID ordinances are discussed below in Section 5.4.1. ¾ Section 704.2 (Design of Off-Street Parking and Loading Spaces) states in 704.2.5 that parking and loading spaces “shall be paved to the specifications prepared by the Planning Board with the advice of the Town Engineer”, except in the case of parking spaces for dwellings. These specifications should be updated to allow for design flexibility and encourage the use of permeable pavement products (e.g. interlocking concrete pavers, porous asphalt, open cell pavers). ¾ Section 704.2.11 (Curbing) states that “where landscaped areas abut parking areas and/or driveways, the landscaped areas shall be protected from vehicular encroachment by curbs and berms”. LID practices that can be incorporated into parking areas (e.g. bioretention) typically require “open drainage”, which allows the free flow of stormwater runoff from paved areas into a downgradient treatment area. The requirement for curbs and berms should be revised to allow for design flexibility for parking areas incorporating LID practices, such as specifically allowing curb cuts, gaps in curbing, or alternate barriers to protect landscaping (e.g. timber fencing, bollards, etc.). • Town of Windham Subdivision Control Regulations: ¾ Section 602.18 (Curbs) states that granite curbing shall be used on all major and collector streets and that bituminous concrete cape cod berm shall be used on all secondary streets. As discussed above for parking areas, this section should be

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

revised to allow for design flexibility to promote LID practices to treat road runoff. • Town of Windham Site Plan Regulations: ¾ Section 1205 (Landscaping) includes specific provisions related to the function, aesthetics and siting of landscaping features on a development site. Given the integral nature of vegetation in many LID storm water practices (e.g. bioretention, rain gardens, vegetated water quality swales, vegetated buffers, etc.), this section should be revised to include a section specific to LID practices.

2.2.1 Review of Low Impact Development Regulatory Tools Stormwater regulatory controls for residential, commercial and industrial development are changing. In the past, stormwater ordinances, subdivision regulations, and municipal development regulations focused on drainage and flood control to safely convey stormwater during storm events. Surface water protections at the federal and state levels are changing the stormwater paradigm to also require water quality treatment and stormwater volume reduction through the use of LID techniques. LID approaches recognize that land development alters the natural hydrologic cycle by increasing stormwater volumes, runoff velocity and pollutant loads, and by disrupting the natural cycle of infiltration and evapotranspiration. These adverse impacts can be controlled and minimized through the application of LID practices, which includes careful site planning and the use of both structural and nonstructural Best Management Practices (BMPs). LID techniques include: site planning, erosion and sediment controls during construction, minimizing impervious cover, maintaining existing vegetation, and use of practices such as bioretention, raingardens, porous surfaces, dry wells, and other structural controls to maintain or restore the natural site hydrology.

Land use is primarily regulated at the municipal local level through zoning, ordinances and bylaws. Every state has developed enabling legislation to allow local cities and towns to adopt regulations to control land use and manage stormwater. As the federal government and state environmental agencies continue to encourage LID, more communities are implementing LID regulatory controls. The New Hampshire Stormwater Manual was recently revised in December 2008 to provide technical guidance to municipalities on LID stormwater control techniques and to provide guidance on developing local regulatory control mechanisms. This manual is available at: (http://des.nh.gov/organization/divisions/water/stormwater/manual.htm).

The Regional Environmental Planning Program (REPP) has recently developed guidance for model ordinances and regulations including innovative land use techniques, for municipalities to use to develop their own local ordinances. The Innovative Land Use Planning Techniques: A Handbook for Sustainable Development contains chapters on multi-density zoning, environmental characteristics zoning and site level design. This Handbook specifically includes a model ordinance for stormwater management that is consistent with New Hampshire stormwater and water quality regulations. It is available at: http://des.nh.gov/organization/divisions/water/wmb/repp/innovative_land_use.htm.

References to information on LID regulatory controls that have been implemented in New England communities is provided below: • City of Nashua, NH. The City’s Land Use Code was modified recently to allow alternative stormwater management techniques.

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

• New London, NH – New London’s recently revised subdivision regulations specify the use of LID landscaping in new projects. Appendix A of the regulation presents a detailed section on LID Design Criteria. www.nl-nh.com/vertical/Sites/%7B26F9F697-D5BE-4423-95D7- E1EECBB7F549%7D/uploads/%7BFC33F5D8-5973-4395-9D45-8FA7EE164427%7D.PDF • New Durham, NH – In March 2010, New Durham revised their Town Zoning Ordinance to require the use of LID controls for all new parking areas. www.newdurhamnh.us/Pages/NewDurhamNH_Planning/regs/zoning2010.pdf • Connecticut. http://clear.uconn.edu/tools/lid_reg/index.htm. Listing of municipal LID regulations in CT. • Massachusetts. http://www.mass.gov/envir/smart_growth_toolkit/pages/SG-bylaws-lid.html The Smart Growth Tool kit provides model LID bylaws and examples of LID practices. Approximately 30 communities in Massachusetts have passed LID regulations. • Low Impact Development Center. www.lowimpactdevelopment.org The LID Center provides information to individuals and organizations on proper site design and LID techniques.

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

3. 2009 MONITORING DATA

3.1 Water Quality Monitoring

3.1.1 Water Quality Monitoring Methodology Geosyntec conducted a water quality monitoring program at the following locations (Figure 4): • Two (2) in-lake deep spot locations near the approximate 50-foot depth contour (NHDES- VLAP Station 1 and Station 2); • Castleton Brook inlet; • Connies Brook inlet; • Dinsmore Brook inlet; • Fossa Road inlet; • Turtle Rock Inlet; and • Bella Vista Inlet.

At each monitoring site on each monitoring date, Geosyntec sampled for the following parameters: • Dissolved oxygen (in-situ); • Temperature (in-situ); • Specific conductance (in-situ); • pH (in-situ); • Turbidity (in-situ); • Total phosphorus (lab); • Chlorophyll-a (lab, samples at in-lake epilimnion stations only); and • Secchi disk transparency.

In-situ measurements were taken with a YSI multi-parameter sampler (or comparable unit). Grab samples taken for laboratory analysis were obtained with a Kemmerer sampler and sent to the NHDES laboratory. Grab samples and in-situ analyses were taken just below the water surface at all tributary and storm water outfall sampling locations. At the two in-lake deep spot locations, (1) in-situ measurements were taken throughout the water column at 0.5-meter intervals and (2) grab samples for lab analyses were taken at three locations in the water column (epilimnion, metalimnion and hypolimnion).

Geosyntec conducted a six month water quality sampling program from May 2009 to October 2009. In addition, Geosyntec collected sets of samples during three storm events at the tributary and stormwater discharge sites listed above.

3.1.2 Water Quality Monitoring Results The following paragraphs discuss selected results of the water quality monitoring program. A full record of the results is attached in Appendix A.

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VU111 kj Dinsmore Brook Inlet

 111  ð UV jk North Deep Spot kj Castleton Brook Inlet

kj ð     Connies Brook Inlet        ð Bella Vista Inlet jk ð      93     ¦¨§   ð     ð       ð ð     ð                ð  ð ð ð     ð                               ð  ð            ð 93     ¦¨§          Turtle Rock Inlet kj  ð  ð ð        ð      ð  jk        ð South Deep Spot

ð    

   Fossa Road Inlet jk   ð

ð

ð ð

ð N 

Legend 0 400 800 1,600 2,400 Feet kj Sampling Locations Stream WATER QUALITY SAMPLING LOCATIONS Cobbett's Pond Pond Cobbett's Pond Windham, NH Wetland Highway Major Road FIG Minor Road Acton, MA 2-JUL-2010 4 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

Temperature/Dissolved Oxygen profiles are important measurements that aid in an understanding of a lake’s stratification. A lake will typically be well mixed in the winter and then will separate into three layers throughout the summer. An upper layer (epilimnion) will contain warm water with high levels of dissolved oxygen caused by its contact with the atmosphere and wind/wave mixing. The middle layer (metalimnion) is a transition zone between the warm upper layer and the cooler, denser lower layer. The deepest layer (hypolimnion) typically exhibits low temperature and low DO concentrations, as biological decomposition of organic sediments depletes the available oxygen.

DO levels have an important impact on fish and other aquatic biota within a lake. Low dissolved oxygen concentrations can impair the health and spawning of fish and other organisms. Anoxic (oxygen depleted) conditions in the hypolimnion are also associated with the release of phosphorus from lake sediments back into the water column, fueling summer algae and plant growth.

Figure 5. 2009 Dissolved Oxygen profiles for the North and South Deep Spot sampling locations.

Figure 6. 2009 temperature profiles at North and South Deep Spot sampling locations.

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

As shown in Figures 5 and 6, Cobbett’s Pond undergoes a typical summer thermal stratification. As the summer progresses, DO within the hypolimnion becomes progressively depleted due to decomposition of organic material in the sediment. By October, cooler temperatures eliminate the density barrier that exists during summer stratification, allowing DO to once again mix into the hypolimnion. A distinct increase in DO concentrations was observed in the metalimnion during the late spring/early summer months of 2009, possibly caused by abundant phytoplankton settling and collecting above the denser waters of the hypolimnion and releasing oxygen through photosynthesis.

Total phosphorus (TP) is a measure of all organic and inorganic phosphorus forms present in the water. In freshwater lakes, phosphorus is usually the most important nutrient determining the growth of algae and aquatic plants. Because phosphorus is typically relatively less abundant than nitrogen, it is considered the “limiting nutrient” for biological productivity. The NHDES considers epilimnion TP concentrations greater than 20 ug/L to be an indicator of eutrophic (nutrient-rich) conditions. The median TP concentration for New Hampshire lakes similar to Cobbett’s Pond is 12 ug/l.

An average in-lake concentration was estimated by proportionally weighting observed 2009 total phosphorus concentrations by the volume of water within the layer which they were sampled. For example, epilimnetic concentrations received a higher weight in the averaging process because the epilimnion represents a higher proportion of the overall lake volume. The following equation describes the weighing calculation:

∑ 0.27 0.05 0.008 0.49 0.15 0.04 , , , , , , 6

where m represents one of the six sampling events, N signifies the North Basin, S signifies the south basin, and E, M, and H signify the epilimnion, metalimnion, and hypolimnion, respectively.

Based on the above equation and Geosyntec’s 2009 sampling data, the estimated average in-lake TP concentration for Cobbett’s Pond was 15.5 ug/l, 29% above the state median of 12 ug/l. This 2009 observed mean TP concentration is roughly equal to the modeled concentration of 15.6 ug/l predicted by the Vollenweider equation in Section 5.6. The lowest concentrations measured were 0.009 mg/l, occurring within the epilimnion and metalimnion on several dates. The highest concentration measured was 130 ug/l, measured at the North Deep Spot hypolimnion on September 17, 2009. According to the NHDES trophic classification system, an average TP concentration of 15. ug/l places Cobbett’s in the middle of the “Average” category for this water quality parameter. A complete analysis of Cobbett’s Pond’s trophic classification based on the NHDES system and the Carlson Trophic Status Index is presented in Section 3.2 of this report.

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

As shown below in Figure 7, TP concentrations in the South Deep Spot epilimnion (surface waters, 0- 5m) were at or above the state median on all six sampling dates. The North Deep Spot epilimnion was at or above the state median on four dates and below the median on two dates.

(ug/L)

10 Phosphorus

Total North Deep Spot: Epilimnion (0‐5m) South Deep Spot: Epilimnion (0‐5m) NH Median Eurtophication Benchmark (NHDES) 0 09 09 09 09 09 09 09 ‐ ‐ ‐ ‐ ‐ ‐ ‐ Jul Jun Oct Sep Aug

Nov May Date

Figure 7. Epilimnion total phosphorus concentrations at the deep spot sampling locations.

Elevated TP concentrations at the North Deep Spot hypolimnion indicate that anoxic (oxygen depleted) conditions are causing phosphorus normally bound to lake sediments to be released into the water where it can fuel algae growth. This process is known as internal phosphorus loading. Figure 8 shows a dramatic pulse of phosphorus being released at the North Deep Spot hypolimnion as the summer progresses. Although similar anoxic conditions existed at the South Deep Spot during August and September 2009, hypolimnetic phosphorus concentrations were elevated rather modestly in comparison to the North Deep Spot.

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

150 8

North Deep Spot: 6 Hypolimnion TP 100 South Deep Spot:

(ug/L) 5 (mg/L) Hypolimnion TP

4 North Deep Spot: Oxygen Hypolimnion DO Phosphorus 3 50 South Deep Spot: Total Dissolved Hypolimnion DO 2

0 0 09 09 09 09 09 09 09 ‐ ‐ ‐ ‐ ‐ ‐ ‐ Jul Jun Oct Sep Aug Nov May Date

Figure 8. Hypolimnion total phosphorus and dissolved oxygen at the deep spot sampling locations.

TP measurements at the tributary monitoring locations ranged from 10 ug/L to 61 ug/L during the dry weather sampling events, and 16 ug/L to 75 ug/L during the wet weather sampling events. The Bella Vista Road tributary had the highest average dry weather concentration of 35 ug/L, and the Castleton Brook inlet had the highest one-time dry weather phosphorus concentration of 61 ug/L. The Fossa Road inlet had the highest average wet weather concentration of 59 ug/L, and Connie’s Brook inlet had the highest one-time wet weather phosphorus concentration of 75 ug/L.

Chlorophyll-a measurements provide an indirect measure of algal biomass and, as discussed in Section 3.2, can be used as a metric to estimate a lake’s trophic status. Chlorophyll-a is a green pigment used by plants, phytoplankton and cyanobacteria to convert sunlight into the chemical energy needed to convert carbon dioxide into carbohydrates. The median summer chlorophyll-a concentration for New Hampshire’s lakes and ponds is 4.58 mg/m3 and the mean is 7.16 mg/m3. The NHDES categorizes chlorophyll-a results as follows:

The 2009 chlorophyll-a results for the North Deep Spot ranged from a high of 7.77 mg/m3 in late July to a low of 2.78 mg/m3 in late October. The South Deep Spot results ranged from a high of 7.60 mg/m3 in late May to a low of 3.27 mg/m3 in late October. The mean chlorophyll-a concentration for the summer months (June-September) was 5.47 mg/m3, with a mean of 5.87 mg/m3 at the North Deep Spot and 5.07 mg/m3 at the South Deep Spot. The slightly higher measurements

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

for the North Deep Spot are consistent with the slightly lower measurements for Secchi disk clarity at this location.

According to the Carlson Trophic Index (TSI), the summer chlorophyll-a results would classify Cobbett’s Pond within the range for mesotrophic lakes, indicating moderately clear water and an increasing probability for hypolimnetic anoxia during the summer. The formula for calculating TSI from chlorophyll-a concentrations is:

TSI = (9.81) (In Chlorophyll-a) + 30.6

Based on an average 2009 summer chlorophyll-a concentration of 5.47 mg/m3, the formula above results in a TSI of 47.27. The TSI range for mesotrophic lakes is 40-50.

The Secchi disk is a weighted black and white disk that is lowered into the water by a calibrated chain until it is no longer visible. This method provides a measure of water clarity (light penetration), which is primarily a function of algal productivity, water color, and turbidity caused by suspended particulate matter. Water clarity influences the growth of rooted aquatic plants by determining the depth to which sunlight can penetrate to the lake sediments.

Secchi disk depths ranged from 4.5 ft (during the May sampling event at the north deep spot) to 12.5 ft (during the June sampling event at the north deep spot). The Cobbett’s Pond mean summer Secchi disk clarity for the two deep spot sampling locations was 11 ft (3.35 m), which is considered to be “good” water clarity according to the NHDES trophic classification system.

pH is a measure of acidity based on the presence of hydrogen ions. A pH of 7.0 is neutral. Values below 7.0 indicate acidic waters and values above 7.0 indicate basic waters. Lower pH values found at depth are due to biological decomposition that leads to anoxic (oxygen-depleted) conditions and other chemical reactions that reduce pH. Most fish cannot tolerate a pH below 4 or above 11, and their growth and health is affected by long-term exposure to a pH less than 6.0 and over 9.5.

pH values within Cobbett’s Pond ranged from 6.1 to 7.7 during the 2009 monitoring, with the lower pH values found in the hypolimnion. The epilimnion (upper layer) pH values for the deep spots ranged from 6.9 to 7.7. The median pH value for the epilimnion in New Hampshire’s lakes and ponds is 6.6. The tributaries exhibited a pH range of 6.8 to 7.8 during dry weather sampling events, and 5.3 to 7.9 during wet weather sampling events.

Specific conductance measures the ability of water to conduct electricity by measuring the presence of ions in solution. Chloride is typically the predominant ion found in surface waters, including man-

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

made sources of chloride ions such as wastewater and road salt. The primary natural sources of chloride ions in surface waters include the weathering of soils and rocks, and wet and dry precipitation. Regional variations in watershed geology can result in a wide range of “normal” conductance levels from lake to lake. However, abnormally high conductance levels can be an indicator of pollutants sources such as road salting, wastewater discharges, and runoff from developed areas. The median conductance value for New Hampshire’s lakes and ponds is 0.04 mS/cm.

Conductivity measurements within Cobbett’s Pond ranged from 0.19 mS/cm to 0.49 mS/cm. Conductivity measurements at the tributary monitoring locations ranged from 0.29 mS/cm to 1.00 mS/cm during the dry weather sampling events, and 0.01 mS/cm to 0.46 mS/cm during wet weather sampling events.

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

3.2 Trophic Status Assessment

Surface water bodies are typically categorized according to trophic state as follows: • Oligotrophic: Low biological productivity. Oligotrophic lakes are very low in nutrients and algae, and typically have high water clarity and a nutrient-poor inorganic substrate. Oligotrophic water bodies are capable of producing and supporting relatively small populations of living organisms (plants, fish, and wildlife). If the water body is stratified, hypolimnetic oxygen is usually abundant. • Mesotrophic: Moderate biological productivity and moderate water clarity. A mesotrophic water body is capable of producing and supporting moderate populations of living organisms (plant, fish, and wildlife). Mesotrophic water bodies may begin to exhibit periodic algae blooms and other symptoms of increased nutrient enrichment and biological productivity. • Eutrophic: High biologically productivity due to relatively high rates of nutrient input and nutrient-rich organic sediments. Eutrophic lakes typically exhibit periods of oxygen deficiency and reduced water clarity. Nuisance levels of macrophytes and algae may result in recreational impairments. • Hypereutrophic: Dense growth of algae throughout the summer. Dense macrophyte beds, but extent of growth is light-limited due to dense algae and associated low water clarity. Summer fish kills are possible.

Geosyntec calculated the trophic status for Cobbett’s Pond using both the Carlson Trophic Status Index and the New Hampshire DES trophic classification system. As described below, both methods resulted in mesotrophic classification for Cobbett’s Pond.

3.2.1 Carlson Trophic Status Index The Carlson Trophic State Index (TSI) is one of the most commonly used means of characterizing a lake's trophic state. As illustrated in the Figure 3, the TSI assigns values based upon logarithmic scales which describe the relationship between three parameters (total phosphorus, chlorophyll-a, and Secchi disk clarity) and the lake's overall biological productivity. TSI scores below 40 are considered oligotrophic, scores between 40 and 50 are mesotrophic, scores between 50 and 70 are eutrophic, and scores from 70 to 100 are hypereutrophic.

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

Figure 9. Carlson Trophic State Index (Figure from 1988 Lake and Reservoir Restoration Guidance Manual. USEPA. EPA 440/5-88-002.)

The TSI for Cobbett’s Pond was calculated based on Geosyntec’s 2009 data as follows:

Transparency: Cobbett’s Pond summer 2009 mean Secchi Disk = 3.35m; TSI = 60 - 14.41In Secchi Disk (m) TSI = 42.6 (Mesotrophic)

Chlorophylll-a: Cobbett’s Pond summer 2009 mean chlorophyll-a = 5.47ug/l; TSI = (9.81) (In Chlorophyll-a) + 30.6 TSI = 47.3 (Mesotrophic)

Total Phosphorus: Cobbett’s Pond 2009 mean in-lake TP =15 ug/L; TSI = (14.42) (In TP ug/L) + 4.15 TSI = 43.2 (Mesotrophic)

Geosyntec collected data on a monthly basis from May through October 2009. Where a “summer mean” is referenced above (for chlorophyll-a and Secchi disk), it refers to the mean of the data collected on 4 sampling events which occurred during the summer (June 25, July 27, August 20 and September 17). The mean includes data collected at both the North Deep Spot and South Deep Spot. The DO ranking was based on August/September conditions when oxygen depletion was at its maximum. As shown in the calculations above, Cobbett’s Pond has a TSI in the mesotrophic range for each of the three parameters.

3.2.2 NHDES Trophic Classification System Geosyntec calculated Cobbett Pond’s trophic status based on the NHDES trophic classification system and Geosyntec’s 2009 data. The NHDES classification system assigns points based on summer dissolved oxygen levels, Secchi disk transparency, aquatic plant abundance and chlorophyll-a. The point total for all parameters is used to determine trophic class, as indicated below:

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

1. Summer Bottom Dissolved Oxygen Points a. D.O. >4mg/L 0 b. D.O. = 1 to 4 mg/L & hypolimnion volume <10% lake volume 1 c. D.O. = 1 to 4 mg/L & hypolimnion volume >10% lake volume 2 d. D.O. <1mg/L in <1/3 hypo. volume & hypo. volume <10% lake volume 3 e. D.O. <1mg/L in >1/3 hypo. volume & hypo. volume <10% lake volume 4 f. D.O. <1mg/L in <1/3 hypo. volume & hypo. volume >10% lake volume 5 g. D.O. <1mg/L in >1/3 hypo. volume & hypo. volume >10% lake volume 6 2. Summer Secchi Disk Transparency: a. > 7m 0 b. > 5m – 7m 1 c. > 3m – 5m 2 d. >2m – 3m 3 e. >1m – 2m 4 f. >0.5 – 1m 5 g. <0.5m 6 3. Aquatic Vascular Plant Abundance: a. Sparse 0 b. Scattered 1 c. Scattered/Common 2 d. Common 3 e. Common/Abundant 4 f. Abundant 5 g. Very Abundant 6 3 4. Summer Epilimnetic Chlorophyll-a (mg/m ): a. <4 0 b. 4 - <8 1 c. 8 - <12 2 d. 12 - <18 3 e. 18 - <24 4 f. 24 - <32 5 g. >32 6

NH Trophic Stratified Classification Lakes Oligotrophic 0-6 Mesotrophic 7-12 Eutrophic 13-24

The NHDES Trophic Classification system results for Cobbett’s Pond were as follows:

1. Summer Bottom Dissolved Oxygen (DO): DO <1mg/L in >1/3 hypolimnion volume and hypolimnion volume <10% lake volume = 4 points

2. Summer Secchi Disk Transparency (Cobbett’s Pond summer mean = 3.35m): > 3m – 5m = 2 points

3. Aquatic Vascular Plant Abundance: Scattered/Common = 2 points

4. Summer Epilimnetic Chlorophyll-a (Cobbett’s Pond summer mean= 5.74 mg/m3): 4 mg/m3 -<8 mg/m3 = 1point Total Score = 9 points Trophic Classification: Mesotrophic

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

The Secchi disk, chlorophyll-a and total phosphorus data used for the NHDES trophic classification was the same as used for the Carlson TSI. The plant abundance ranking is based on the Geosyntec survey conducted on July 27, 2009. As discussed in Section 3.3, Cobbett’s Pond was characterized by sparse to moderate plant growth over the vast majority of its littoral zone. Approximately half (46%) of the sampling stations had trace (0-5% density) to sparse (6-25% density) growth, while approximately half (48%) had moderate growth (26-50% density). Based on these results, Geosyntec assigned the “scattered/common” ranking of 2.

Overall, the NHDES trophic classification system is consistent with the Carlson TSI for Cobbett’s Pond, with both placing the pond within the mesotrophic range.

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

3.3 Aquatic Vegetation Survey

3.3.1 Aquatic Vegetation Survey Methodology On July 27, 2009, Geosyntec conducted a macrophyte survey of Cobbett’s Pond. Plant species were identified at 46 sampling locations (Figure 10) by visual inspection and by using an aquatic vegetation grappling hook to sample submerged vegetation. At each station, the plant growth density, biomass and dominant plant(s) were recorded. As categorized in Table 1, plant density is an estimate of aerial coverage when looking down to the lake bottom from the water surface. Biomass estimates the amount of plant matter within the water column. For example, a sampling station with dense growth of low-growing plants may have a high density estimate but a relatively low plant biomass estimate. A station with dense growth of a long, ropey plant like Variable Milfoil, with stems reaching the water surface, would have both high plant density and high biomass estimates.

3.3.2 Aquatic Vegetation Survey Results General Notes: • Cobbett’s Pond was characterized by sparse to moderate plant growth over the vast majority of its littoral zone (area of rooted plant growth). Approximately half (46%) of the sampling stations had trace (0-5% density) to sparse (6-25% density) growth, while approximately half (48%) had moderate growth (26-50% density). Only 3 stations (7%) had dense or very dense plant growth. • 28 species of macrophytes were documented in Cobbett’s Pond during the 2009 survey. A list of the species observed is provided in Table 1, which organizes the species according to growth habit (submersed, floating-leaf and emergent). A tally sheet listing the results from each of the 50 sampling stations is provided in Table 2, including information on vegetation density, plant biomass, and dominant plants at each station. • The 2009 species richness index for Cobbett’s Pond was 5.2. The species richness index is the average number of species observed at the vegetation sampling stations. Over half (53%) of the species were observed at 3 stations or fewer out of the 46 sampling stations and 6 species were observed at only one sampling station.

Invasive/Non-native Species:

• Variable Milfoil (Myriophyllum heterophyllum) was the only invasive, Variable milfoil non-native plant observed in Cobbett’s Pond. This plant was found growing in very small quantities at only two sampling stations. One of these stations (station #36) was located just north of the midpoint along the pond’s eastern shorline. The second station (station #16) was located in the southern portion of the western shoreline.

Native Species: Only seven plant species were observed at 25% or more of the 46 sampling stations. These seven native species, which comprised the majority of the plant assemblage in Cobbett’s Pond, are described below. Robbin’s Pondweed

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

• Robbin’s Pondweed (Potamogeton robbinsii) was the most abundant and dominant species in the Pond. This submerged plant was observed at 74% of the sampling stations (23 stations) and was a dominant plant at 15 stations. Robbin’s Pondweed is also known as Fernleaf Pondweed for the fern-like appaearence of its leaves. This plant was observed as part of a relatively low-growing undercanopy in many areas around Cobbett’s Pond.

• Bladderwort species, including Little Floating Bladderwort (Utricularia Little Floating radiata) and Common Bladderwort (Utricularia vulgaris) and were Bladderwort found throughout the Pond (37 stations, 80%), most often in small quantities. Little Floating Bladderwort was the most common of these species, although the bladderwort species were reported collectively because of the difficulty in confirming species identification at several sites due to specimens lacking key identifying features. When in flower, Little Floating Bladderwort is easily recognized by its yellow flower that is supported above the water by oblong leaves that act as pontoons. Bladderworts are carnivorous plants that trap and digest zooplankton (microscopic animals) in clusters of “bladders” for Musk Grass which they are named. • Musk Grass (Chara vulgaris) and Rough Stonewort (Chara aspera) are actually structured forms of algae rather than true vascular aquatic plants. Musk Grass was found at just over half of the sampling stations and was a dominant plant at 11 stations, second only to Robbin’s Pondweed in dominance among all species in the 2009 vegetation survey. Musk Grass is easily identified by its brittle stems that have a musky, skunk-like odor when crushed. Rough Waterweed Stonewort, found at 12 sampling stations, is similar in structure to Musk Grass but smaller. • Waterweed (Elodea canadensis) was observed throughout the Pond (28 stations, 61%). This plant was generally found in relatively low quantities, although it was a dominant plant at 4 stations. Waterweed is a submergent plant that can grow in diverse conditions, sometimes to nuisance levels. The most notable growth of Waterweed during the 2009 vegetation survey was a dense, monotypic stand observed to the south of station #1 in the northeast corner of the Pond. Wild celery • Water Celery (Vallisneria americana) was found growing at 26 stations (57%) distributed around the Pond, but was not a dominant plant at any stations. This submergent plant has flat tape-like leaves, and both the leaves and underground tubers of the plant provide food for a variety of aquatic animals. • Bushy Pondweed (Najas flexilis) is a slender, submerged plant that has a branched stem with narrow leaves that are oppositely arranged. This plant was found at 21 stations (47%) and was a dominant plant at 4 stations. Bushy Pondweed

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

Table 1: Cobbett’s Pond Aquatic Plant Species List (July 27, 2009)

Type Scientific Name Common Name

Chara aspera Rough Stonewort Chara vulgaris Musk Grass Elatine minima Small Waterwort Elodea canadensis Waterweed Heteranthera dubia Water Star-grass Isoetes sp. Quillwort Myriophyllum heterophyllum Variable Milfoil

Submersed Najas flexilis Bushy Pondweed Species Potamogeton bicupulatus Snailseed Pondweed Potamogeton gramineus Variable Pondweed Potamogeton perfoliatus Clasping Pondweed Potamogeton pulcher Heartleaf Pondweed Potamogeton pusillus Small Pondweed Potamogeton robbinsii Robbin's Pondweed Utricularia spp. Bladderwort spp. Vallisneria americana Water Celery Lemna minor Lesser Duckweed

Floating Leaf Nuphar variegatum Yellow Water Lily Species Nymphaea odorata White Water Lily Potamogeton natans Floating Leaf Pondweed Alisma plantago-aquatica Water Plantain Eleocharis robbinsii Robbin’s Spike Rush Eriocaulon sp. Pipewort

Emergent Juncus canadensis Canada Rush Species Pontederia cordata Pickerelweed Scheuchzeria palustris Rannoch Rush Sparganium sp. Bur-Reed Typha latifolia Broad-leaf Cattail

Table 1: Aquatic Vegetation Survey Tally Sheet

Location: Cobbetts Pond, Windham NH Date: 7/27/09 Surveyed by: Hartzel ● species present at monitoring station ● species dominant at monitoring station

Monitoring Locations inant inant

Plant Species ations ations present

dom 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 # st # st

BlBlaaddedderrwworortt (U(Uttricriculariaularia sppp .)) 3737 22 ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● ●● Robbin's Pondweed (Potamogeton robbinsii) 34 15 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● Waterweed (Elodea Canadensis) 28 4 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● Water Celery (Vallisneria americana) 26 0 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● Musk Grass (Chara vulgaris) 24 11 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● Bushy Pondweed (Najas flexilis) 21 4 ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● Rough Stonewort (Chara aspera) 12 0 ● ● ● ● ● ● ● ● ● ● ● ● Pipewort (Eriocaulon septangulare) 6 0 ● ● ● ● ● ● Heartleaf Pondweed (Potamogeton pulcher) 5 1 ● ● ● ● ● Floating Leaf Pondweed (Potamogeton natans) 5 0 ● ● ● ● ● Robbin's Spike Rush (Eleocharis robbinsii) 5 0 ● ● ● ● ● Lesser Duckweed (Lemna minor) 4 0 ● ● ● ● Clasping Pondweed (Potamogeton perfoliatus) 4 0 ● ● ● ● Small Pondweed (Potamogeton pusillis) 3 0 ● ● ● Rannoch Rush (Scheuchzeria palustris) 3 0 ● ● ● Cattail (Typha latifolia) 2 0 ● ● Variable Pondweed (Potamogeton gramineus) 2 0 ● ● Small Waterwort (Elatine minima) 2 0 ● ● Variable Milfoil (Myriophyllum heterophyllum )* 2 0 ● ● Pickerelweed (Pontederia cordata) 2 0 ● ● Water Star-grass (Heteranthera dubia) 2 0 ● ● Yellow Lily (Nuphar spp.) 2 0 ● ● White Lily (Nymphaea odorata ) 1 1 ● Snailseed Pondweed (Potamogeton bicupulatus) 1 0 ● Quillwort (Isoetes sp.) 1 0 ● Water Plantain (Alisma plantago-aquatica) 1 0 ● Canada Rush (Juncus canadensis) 1 0 ● Bur-reed (Sparganium sp.) 1 0 ● Plant Density Rating 2 1* 1 1 2 1* 1 1 1* 1* 1* 1 1 1 2 1 1* 2 1 2 2 2 2 2 2 1 2 2 2 2 2 2 1 1 1 3 2 2 3 4 2 1 2 2 2 0 Plant Biomass Rating 2 1* 1 1 1 1* 1 1 1* 1* 1* 1 1 1 1 1 1* 1 1 1 1 2 1 1 1 1 1 1 1 2 2 1 1 1 1 2 2 2 2 3 1 1 1 1 1 0 # of species present 13 3 5 5 5 3 5 6 6 1 2 4 1 7 5 7 4 8 6 5 4 5 6 6 5 2 7 5 6 4 5 6 5 4 5 7 4 7 8 6 6 6 7 5 5 0

Key to Density and Biomass Ratings * Non-native, invasive species Density Biomass 0 Absent: 0% Macrophytes absent Trace plant growth, macrophytes 1* Trace: 0-5% density virtually absent Scattered plant growth; or primarily at 1 Sparse: 5-25% density lake bottom Plants generally protruding into less 2 Moderate: 26-50% density than half of water column Substantial growth through majority of 3 Dense: 51-75% density water column Abundant growth throughout water 4 Very Dense: 76-100% density column to surface 2 3 45 1 4 46 44 43 5 42 6

8 40 38 39 37

9 36 35

10 11 12

16 15

17 32

31 30 18

29 19

20 28

27 21 Legend 25 26 Vegetation Survey Stations Vegetation Density 22 24 23 Sparse: 0-25% Moderate: 26-50% Dense: 51-75% Very Dense: 76-100%

Notes -Base data from NH GRANIT. -2005 Imagery from NH GRANIT.

450 0 450 900 1,350 Feet

Cobbetts Pond Vegetation Density July 27, 2009 Windham, NH

Figure W0131-Cobbetts_Pond\Projects\lake_veg.mxd W0131-Cobbetts_Pond\Projects\lake_veg.mxd

Acton, Massachusetts 22-Dec-2009 Q:\GISProjects\B Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

3.4 Algae Sampling

3.4.1 Algae Sampling Methodology On the six sampling dates listed below in Table 10, Geosyntec collected samples from the two deep-spot sampling locations (North Deep Spot and South Deep Spot) for analysis of relative algal abundance to the genus level. The algae samples were analyzed at the NHDES Limnological Laboratory at no cost to the project.

Geosyntec collected the algae samples using an 80-micron phytoplankton net. The plankton net was towed vertically from mid-thermocline to the surface. The samples were stored in a 250 ml glass bottle and preserved with 1-2 drops of Lugol’s solution.

The original scope of work for this project included three rounds of algae sampling scheduled for June, August and October 2009. However, in response to concerns related to nuisance cyanobacteria blooms that have occurred at Cobbett’s Pond, Geosyntec conducted sampling during each of the six monthly in-lake sampling events to provide more robust data on seasonal phytoplankton population trends.

3.4.2 Algae Sampling Results The results of the 2009 algae sampling results are presented below.

Table 2. Algae Sampling Results, May-October 2009

% Dominance 5/21/2009 6/25/2009 7/27/2009 8/20/2009 9/17/2009 10/23/2009 Division Genus ND SD ND SD ND SD ND SD ND SD ND SD Chrysophyta Dinobryon 40 46 39 40 42 18 60 82 Bacillariophyta Rhizosolenia 7 58 52 Bacillariophyta Synedra 34 32 27 18 10 7 9 Bacillariophyta Tabellaria 13 9 24 28 37 20 21 27 15 Cyanobacteria Oscillatoria 9 4 Pyrrophyta Ceratium 45 30 30 40 Cyanobacteria Anabaena 12 4 Bacillariophyta Asterionella 13

Notes:

1. ND and SD refer to the North Deep Spot and South Deep Spot sampling locations, respectively.

The 2009 algae sampling results indicate that Cobbett’s Pond was heavily dominated by golden- brown algae (Chrysophyta) and diatoms (Bacillariophyta) during the May, June and July sampling events. Diatoms and golden-brown algae are common in New Hampshire’s less productive lakes and ponds. A mix of dinoflagellates (Pyrrophyta), diatoms and golden-browns were dominant during the August and September sampling event, with golden browns and diatoms dominating in October.

Also notable was the relative abundance of cyanobacteria (Ocillatoria and Anabaena) during the July (9% at North Deep Spot), August (12% at North Deep Spot) and October (4% at South Deep

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

Spot) sampling events. Following Geosyntec’s August sampling, Cobbett’s Pond experienced a cyanobacteria bloom. Based on additional sampling conducted by NHDES in response to a reported algae bloom, a beach advisory was issued by NHDES on 8/12/2009 and a lake warning was issued on 8/14/2009 due to the presence of the potentially toxic cyanobacteria Anabaena and Microcystis. Both Anabaena and Microcystis have the potential to produce toxins that are harmful to humans and wildlife if ingested. It is important to note that the presence of potentially toxin-producing cyanobacteria is common in Anabaena sp. fresh water bodies and that it is relatively uncommon for these cyanobacteria to produce toxins in levels that are considered a threat to human health. As a conservative standard, the NHDES recommends that a water contact advisory be issued when an algae bloom is comprised of over 50% cyanobacteria species or when the total cell count of a sample exceeds 70,000 cells/ml. These advisory guidelines are not based on the presence of toxins in the water, but reflect that such conditions have the potential to develop and change rapidly during a cyanobacteria bloom. The beach advisory was removed on 8/18/2009 and the lake warning was removed on 8/27/2009.

3.5 Flow Monitoring

3.5.1 Flow Monitoring Methodology Geosyntec conducted continuous flow monitoring at the following locations: • Castleton Brook inlet; • Dinsmore Brook inlet; • Connies Brook inlet; • Fossa Road inlet; • Turtle Rock inlet; • Bella Vista inlet.

Flows were monitored by installing Solinst automated water level recorders at available control points (i.e. culverts). In cases where no control points were available (Dinsmore Brook inlet and Bella Vista inlet), a temporary plywood weir was installed. Water level measurements from locations with culverts were converted to flows (cubic feet per second, cfs) using standard culvert equations available from the Federal Highway Administration (FHA, 2005). Water level measurements for locations with plywood weirs were converted to flows using the formula for a V- notch weir:

8 2 tan 15 2 where Q is the discharge, Cd is a coefficient (~0.58), g is acceleration due to gravity (32.2 ft/s2), Θ is the angle of the v-notch (in this case, 90o), and H is the distance between the water elevation and the weir invert.

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

In addition to the flow measurement, Geosyntec installed a tipping-bucket rain gage in a vacant lot along Armstrong Road to collect continuous precipitation data. Data from the flow and precipitation monitoring equipment was collected during monthly water quality sampling.

3.5.2 Flow Monitoring Results Hydrographs (graphs of stream discharge over time) were produced to depict flow measurements at the 6 monitoring locations. The shapes of the hydrographs are useful in characterizing the behavior of stormwater and pollutant transport within a subwatershed. For instance, hydrographs that rise and fall gradually indicate that stormwater is moving slowly to the discharge point, most likely over vegetated surfaces. Slow moving stormwater has less erosive power and is more effectively filtered while moving over or through vegetated surfaces. A sharply rising hydrograph indicates stormwater flowing quickly from impervious surfaces such as roads and rooftops. Quickly moving stormwater can cause erosion of channels, degradation of stormwater infrastructure, and can cause more sediment to be delivered to the pond.

Figures 11 and 12 below show two hydrographs from a storm event on 7/31/09. The contributing subwatersheds are approximately the same size and slope, but have differing land use characteristics. The Fossa Road subwatershed (Figure __) has the highest percentage of impervious surfaces in the entire watershed, and quickly conveys stormwater to the measuring point via roads and roadside ditches. The Turtle Rock Road watershed (Figure ___) drains through a natural stream in a mostly forested area, resulting in a more gradually sloping hydrograph.

The full results of the flow monitoring are presented in Appendix B.

Fossa Road

2.0 1.5 1.0 0.5 0.0 Discharge (cfs) 10:00 12:00 14:00 16:00 18:00 20:00 22:00 Time (hrs)

Figure 11. Fossa Road Subwatershed Hydrograph, 7/31/2009

Turtle Rock Road

2.0 1.5 1.0 0.5 0.0 Discharge (cfs) 10:00 12:00 14:00 16:00 18:00 20:00 22:00 Time (hrs)

Figure 12. Turtle Rock Road Subwatershed Hydrograph, 7/31/2009

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

4. WATERSHED ASSESSMENT 4.1 Storm Drainage Mapping Geosyntec conducted a field investigation to identify and map all accessible storm drains and other surface water flow paths discharging to Cobbett’s Pond (e.g. intermittent streams). Based on the field data collected, Geosyntec has created a series of maps which depict infrastructure locations (e.g. catch basins, culverts, pipe outfalls, etc.), pipe diameter, pipe type, etc. These drainage infrastructure maps are provided in Appendix C and will be provided to the CPIA and the Town of Windham in digital format to allow for future updating as structures are retrofit and new structures are installed.

Example section of the storm drainage map for Cobbett’s Pond Road area at the southern tip of the lake, showing catch basins, drainage pipe connections and surface water flow paths.

4.2 Watershed Soils The soils found within the vast majority of the Barrett Pond Watershed are well suited for bioretention cells, raingardens and other stormwater management techniques promoting infiltration. As shown on Figure 13 (USDA-NRCS Soil Survey Map), most of the watershed has soils that are classified as either “well drained” or “moderately well drained”. This indicates that the native soils have a good capacity to infiltrate stormwater and that infiltrating stormwater practices can be expected to perform well without presenting unusual design challenges or cost implications in most areas.

¦¨§93

¦¨§93 111UV VU111 UV111

Canobie Lake

Cobbetts Pond

¦¨§93

Legend 0 600 1,200 2,400 3,600 Feet Cobbett's Pond Watershed NRCS Drainage Class Water Body Excessively SOIL DRAINAGE CLASSES MAP Highway Somewhat excessively Major Road Well Cobbett's Pond Moderately well Windham, NH Somewhat poorly Poorly Very poorly FIG Not rated Multiple classes Acton, MA 31-MAR-10 13 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

4.3 Watershed Imperviousness Geosyntec mapped the impervious surfaces in the Cobbett Pond watershed based on an analysis of satellite imagery. Figure 15 shows that the impervious surfaces are estimated to comprise approximately 12.4% of the Cobbett’s watershed. As shown below, the Impervious Cover Model developed by the Center for Watershed Protection predicts that at 10% impervious cover, streams begin to transition from the “sensitive” to “impacted” category with regard to stream quality indicators. As such, the Cobbett’s Pond watershed appears to be at a critical juncture with regard to planning for future watershed development and related efforts to protect and restore the water quality of the Pond and its tributaries. Geosyntec also assessed imperviousness at the subwatershed level as shown on Figure 16. Imperviousness of the subwatersheds ranged from a low of 8.0% (Subwatershed 6, Ministerial Road Area) to a high of 18.3% (Subwatershed 9, Fossa Road Area).

Figure 14. Impervious Cover Model, Center for Watershed Protection.

The Impervious Cover Model (Center for Watershed Protection)

Cobbett’s Pond Watershed Imperviousness = 12.4%

  

      ð                ð ð

 93  ¦¨§   ð           ð 

93 ð 111  ¦¨§ UV  111



 VU





  ð 111   UV ð



ð



     ð             ð  ð   ð        ð      ð        ð ð     ð    ð ð  ð           ð  ð                                             ð    ð           ð                     ð   ð              ð   ð ð ð

ð   ð     ð                     ð  93   ¦¨§ 

    ð ð ð      ð    ð               ð         ð N

0 600 1,200 2,400 3,600 Legend Feet

Cobbett's Pond Watershed IMPERVIOUS SURFACES WITHIN COBBETT'S POND WATERSHED Impervious Surface Cobbett's Pond Windham, NH

FIG

Acton, MA 31-MAR-10 15 SW-1 (Castleton Brook Area)

SW-3 (Dinsmore Brook Area)

ð

 



 ð      

    SW-5 (Connie's Brook Area) 111

ð VU 111  UV  SW-4 

  (Water's Edge Rd. Area) 













ð

SW-2   ð  ðð (North Shore Area)                SW-6 93  ¦¨§  (Ministerial Rd. Area)   ð UV111 ð             ð  ð      ð ð        ð 

   SW-14    

ð   (Armstrong Rd. Area)

  Cobbetts Pond     



  SW-7  SW-13 (Cobbett's Pond Rd.  (Bella Vis ta Rd. Area) Area)

SW-12 (Horseshoe Rd. Area)

Canobie Lak  ð  ð   ð      SW-11  ð      93    (Turtle Rock Rd. N. Area)  ¨§  ¦     ð ð

SW-10 (Turtle Rock Rd. S. Area)

SW-9 ð   (Fossa Rd. Area)  SW-8  (Town Beach Area) N

SUBWATERSHED % IMP 0 500 1,000 2,000 3,000 Legend 6 Ministerial Rd. Area 8.0 Feet Watershed Boundary 12 Horseshoe Rd. Area 11.1 1 Castleton Brook Area 12.0 Subwatershed Boundary 2 North Shore Area 12.1 COBBETT'S POND SUBWATERSHEDS Impervious Surface 11 Turtle Rock Rd. N. Area 12.5 IMPERVIOUS COVER Percent Impervious 14 Armstrong Rd. Area 12.5 13 Bella Vista Rd. Area 12.7 Cobbett's Pond 4 Water s Edge Rd. Area 13.0 Windham, NH 10 < >15 5 Connie s Brook Area 13.2 10-12.5 12.5-15 7 Cobbett's Pond Rd. Area 14.8 10 Turtle Rock Rd. S. Area 14.9 FIG 8 Town Beach Area 15.0 3 Dinsmore Brook Area 17.0 16 9 Fossa Rd. Area 18.3 Acton, MA 31-MAR-10 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

4.4 Septic System Investigation

Geosyntec conducted research on septic systems located around the perimeter of Cobbett’s Pond to refine the data used to develop the Pond’s phosphorus budget as presented in Section 4. Geosyntec collected all information available from the Windham Board of Health (BOH) on the location, age, capacity and type of septic system on properties bordering the lake perimeter. Once this data was collected, Geosyntec and the CPIA distributed a septic system information survey via email and hard copy mail to residences for which no BOH data was available. Upon compilation of all BOH data and survey responses, Geosyntec prepared a series of maps that present septic system available information for each parcel. These maps are provided as Appendix D.

Example section of the septic system map for the Ministerial Road/Gaumont Road area.

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

5. COBBETT’S POND PHOSPHORUS BUDGET 5.1 Land-Use Based Pollutant Modeling

Geosyntec conducted land-use based modeling to estimate annual phosphorus export from fourteen subwatersheds depicted on Figure 2. Land use data available at the New Hampshire GIS data clearinghouse (GRANIT) was used to represent the current Watershed’s land-use condition. The land use data was primarily derived using the 1998 United States Geological Survey (USGS) 1:12,000-scale, black & white, Digital Orthophoto Quadrangles. Land-use pollutant export coefficients (represented in lbs/acre-yr) were derived from New Hampshire GIS data (GRANIT) information.

Table 3. Phosphorus Export Coefficients by NH GRANIT Land Use Category

Phosphorus Land Use Export Land Use Category Code Coefficient (lbs/ac-yr)

11 Residential Development 0.446

12 Industrial/Commercial Development 0.446

14 Paved Roads 0.446

17 Recreational 0.535

20 Agricultural 0.535

40 Forest 0.178

70 Open Land 0.446

Land use based exports are an average measure of pollutant export and are typically reported for specific land use categories. These data were used in a land-use based pollutant model to predict annual phosphorus loading from the Watershed. The area of each land cover type is shown below in Table 4. A table summarizing the results of the land-use loading model is provided in Table 5.

Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

Table 4. Subwatershed Land Cover Areas (all values in acres)

Paved Open Subwatershed Residential Commercial Recreation Agriculture Forest Total Road Land

1: Castleton Brook Area 40.5 20.71 16.88 5.4 0.0 227.8 62.7 374.0

2: North Shore Area 2.5 0.0 0.1 0.0 0.0 0.0 0.0 2.6

3: Dinsmore Brook Area 2.6 7.6 1.8 0.0 0.0 22.6 4.3 38.9

4: Water’s Edge Rd. Area 26.5 0.1 3.0 0.0 0.0 25.2 1.9 56.7

5: Connie’s Brook Area 16.7 17.7 4.6 0.0 0.0 100.3 9.3 148.6

6: Ministerial Rd. Area 79.6 0.0 7.0 0.0 0.0 49.1 0.0 135.7

7: Cobbett’s Pond Rd. Area 12.6 0.0 1.6 0.0 0.0 8.0 0.0 22.1

8: Town Beach Area 34.8 0.0 2.3 0.0 0.0 19.0 0.0 56.1

9: Fossa Rd. Area 21.6 0.0 1.8 0.0 0.0 5.4 0.0 28.8

10: Turtle Rock Rd. (South) 44.5 0.0 4.0 0.0 0.0 45.9 4.1 98.6

11: Turtle Rock Rd. (North) 14.4 0.0 1.3 0.0 0.0 29.0 0.2 44.9

12: Horseshoe Rd. Area 84.5 0.0 8.4 0.0 24.3 48.9 0.0 166.0

13: Bella Vista Rd. Area 17.4 0.0 3.2 0.0 33.1 17.0 0.0 70.7

14: Armstrong Rd. Area 16.7 2.7 2.8 0.0 6.1 38.8 4.6 71.6

Table 5. Subwatershed Pollutant Loading Summary

Estimated Annual % of Total Area Watershed Subwatershed Phosphorus Load (lb/yr) (acres) Phosphorus Load Total Per acre 1: Castleton Brook Area 374.0 106.3 0.28 25.7 2: North Shore Area 2.6 1.1 0.42 0.3 3: Dinsmore Brook Area 38.9 10.6 0.27 2.6 4: Water’s Edge Rd. Area 56.7 17.6 0.31 4.3 5: Connie’s Brook Area 148.6 35.3 0.24 8.5 6: Ministerial Rd. Area 135.7 47.4 0.35 11.4 7: Cobbett’s Pond Rd. Area 22.1 7.7 0.35 1.9 8: Town Beach Area 56.1 19.8 0.35 4.8 9: Fossa Rd. Area 28.8 11.5 0.40 2.8 10: Turtle Rock Rd. (South) 98.6 31.7 0.32 7.6 11: Turtle Rock Rd. (North) 44.9 12.3 0.27 3.0 12: Horseshoe Rd. Area 166.0 60.8 0.37 14.7 13: Bella Vista Rd. Area 70.7 30.0 0.42 7.3 14: Armstrong Rd. Area 71.6 21.6 0.30 5.2 Cobbett’s Pond Watershed (total) 1315.3 416.0 0.32 100%

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The land-use based phosphorus loading model provides a tool for estimating and comparing (1) total annual phosphorus loads (in pounds per year) and (2) annual pollutant load rates normalized to the watershed area (in pounds per acre per year) for each subwatershed. Land-use pollutant loading model estimates provide a useful comparative measure of the relative impact that each subwatershed has on lake water quality, and therefore can help in the prioritization of sites for watershed improvements. A brief summary of the land-use pollutant loading model results for each subwatershed is provided below:

Subwatershed 1 (Castleton Brook Area): Covering 374 acres to the northwest of the Pond, this is the largest subwatershed. This area is dominated by forested land (60.9%), open land (16.8%, including the Interstate 93 interchange), and residential land (10.8%). The estimated phosphorus load from this subwatershed is 0.28 lb P/ac/year, which accounts for 25.7% of the Pond’s total predicted phosphorus load. Although this subwatershed contributes by far the largest phosphorus load to Cobbett’s Pond, its loading rate is among the lowest of all subwatersheds.

Subwatershed 2 (North Shore Area): Subwatershed 2 is the smallest subwatershed (2.6 acres) and is located along the Pond’s northern. Land use in this subwatershed is almost entirely residential (94.9%). As a result, this small subwatershed has the highest estimated phosphorus loading rate (0.42 lb P/ac/year), although this accounts for only 0.3% of the total predicted watershed load.

Subwatershed 3 (Dinsmore Brook Area): Subwatershed 3 includes 38.3 acres to the north of the Pond which drain to Dinsmore Brook. This subwatershed is primarily comprised of forest (58.1%) and commercial development (19.6%). The phosphorus loading rate from Subwatershed 3 is 0.27 lb P/ac/year, accounting for 2.6% of the total predicted phosphorus load.

Subwatershed 4 (Water’s Edge Rd. Area): Subwatershed 4 covers 56.7 acres and drains the area between Dinsmore Brook (Subwatershed 3) and Connie’s Brook (Subwatershed 5). Land cover is dominated by residential development along the shoreline (46.7%) and forest to the north of Route 111A (44.4%). The phosphorus loading rate from Subwatershed 4 is 0.31 lb P/ac/year and accounts for 4.3% of the total predicted phosphorus load.

Subwatershed 5 (Connie’s Brook Area): Subwatershed 5 includes 148.6 acres draining to Connie’s Brook. This subwatershed is predominantly forested (67.5%), with some commercial and residential development (12% each). The phosphorus loading rate of Subwatershed 5 is 0.24 lb P/ac/year, accounting for 8.5% of the Pond’s total predicted phosphorus load.

Subwatershed 6 (Ministerial Rd. Area): This subwatershed includes a significant portion of the northwest shore of the Pond. It covers 135.7 acres between the Connie’s Brook inlet and the Pond outlet. The subwatershed is dominated by residential development (58.7%) and forest (36.2%). The phosphorus loading rate of Subwatershed 6 is 0.35 lb P/ac/year, accounting for 11.4% of the Pond’s total predicted phosphorus load.

Subwatershed 7 (Cobbett’s Pond Rd. Area): Subwatershed 7 covers 22.1 acres between the Cobbett’s Pond outlet and the Town Beach. The subwatershed is dominated by residential development (56.7%) along Cobbett’s Pond Road and Horne Road. The phosphorus loading rate of Subwatershed 7 is 0.35 lb P/ac/year, accounting for 1.9% of the Pond’s total predicted phosphorus load.

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Subwatershed 8 (Town Beach Area): This subwatershed is located along the southwestern portion of the Cobbett’s Pond watershed. It covers 56.1 acres and is dominated by residential development (62.0%) and forest (33.9%). The subwatershed drains through a wetland area north of Range Road onward to a culverted outlet at the Town Beach. The phosphorus loading rate of Subwatershed 8 is 0.35 lb P/ac/year, accounting for 4.8% of the Pond’s total predicted phosphorus load.

Subwatershed 9 (Fossa Rd. Area): This subwatershed is located at the southern end of Cobbett’s Pond, to the east of the Town Beach. The subwatershed is 28.8 acres and is 74.9% residential development. The watershed drains to the Fossa Road inlet. The phosphorus loading rate of Subwatershed 9 is 0.40 lb P/ac/year, accounting for 2.8% of the Pond’s total predicted phosphorus load.

Subwatershed 10 (Turtle Rock Rd. South Area): This subwatershed is located along a long portion of the southern shore of Cobbett’s Pond. It includes 98.6 acres between the Fossa Road inlet and a stream inlet running under Farmer Road. The subwatershed is dominated by residential development (45.2%) and forest (46.6%). The phosphorus loading rate of Subwatershed 10 is 0.32 lb P/ac/year, accounting for 7.6% of the Pond’s total predicted phosphorus load.

Subwatershed 11 (Turtle Rock Rd. North Area): This subwatershed covers a 44.9 acre area around the northern portion of Turtle Rock Road. It drains to a stream that runs along Turtle Rock Road and under Farmer Road. The watershed is dominated by forest (64.6%) and residential development (32.0%). The phosphorus loading rate of Subwatershed 11 is 0.27 lb P/ac/year, accounting for 3.0% of the Pond’s total predicted phosphorus load.

Subwatershed 12 (Horseshoe Rd. Area): This subwatershed covers a 166.0 acre area in the vicinity of Horseshoe Road and Sawtelle Road. The subwatershed is dominated by residential development (54.4%), with a mixture of forest (32.0%) and agriculture (7.9%). The phosphorus loading rate of Subwatershed 12 is 0.37 lb P/ac/year, accounting for 14.7% of the Pond’s total predicted phosphorus load.

Subwatershed 13 (Bella Vista Rd. Area): Subwatershed 13 drains portions of Griffin Park, Range Road, and the Bella Vista Road area (including a new residential development between Armstrong Road and Bella Vista Road). Drainage is collected in a stream that runs along Bella Vista Road to a wetland area and onward to the Pond. The subwatershed is covered by a mixture of forest (24.1%), residential development (21.9%), recreational area (18.3%), and agriculture (31.2%). The phosphorus loading rate of Subwatershed 13 is 0.42 lb P/ac/year, accounting for 7.3% of the Pond’s total predicted phosphorus load.

Subwatershed 14 (Armstrong Rd. Area): This watershed covers 71.6 acres between the Bella Vista Road stream inlet and the Castleton Brook inlet. A stream running under Armstrong Road is a significant path of drainage in the subwatershed. The subwatershed is dominated by forest (54.1%), with a mixture of residential (31.8%), open space (6.3%), and commercial development (3.8%). The phosphorus loading rate of Subwatershed 14 is 0.30 lb P/ac/year, accounting for 5.2% of the Pond’s total predicted phosphorus load.

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5.2 Phosphorus Loading From Septic Systems

Geosyntec conducted an assessment to estimate phosphorus loads from on-site sanitary systems located around the perimeter of Cobbett’s Pond. On-site sanitary systems considered in the analysis included septic tanks with leaching fields, septic tanks with chambers, cesspools, holding tanks, chemical toilets, etc. As described in Section 4.4, Geosyntec developed a septic system inventory using information obtained through the Windham Board of Health records and a septic system questionnaire given to waterfront homeowners. This investigation included 293 parcels surrounding the Pond, of which 263 were occupied with a home. 231 of the homes either had a confirmed septic system on site or were assumed to have a septic system on site (when no information was available from Board of Health records or surveys). Homes that were serviced by holding tanks were assumed to contribute no phosphorus load to the pond.

As estimated by Derek Monson of the CPIA, 172 homes are occupied year-round and 91 are occupied seasonally. For this study, seasonal occupancy was assumed to be 3 months per year, resulting in an average occupancy of 9 months per year for all 263 homes.

The estimated phosphorus load to the Lake from on-site sanitary systems was 138 lbs P/yr, as calculated using the following equation:

M=(ES)(# Capita Years)(1-SR)

Where: M is the predicted phosphorus loading; ES is the phosphorus export coefficient of 1.1 lbs P/capita-year; # Capita Years is the product of the number of parcels with septic systems (231 parcels) multiplied by the average number of residents per parcel (2.9 residents/parcel for Windham, NH) and the average occupancy (9 of 12 months or 0.75); SR is the soil retention coefficient (0.75). ES was determined based on literature published by the US Geological Survey and the University of Delaware extension program.

The estimated total phosphorus load from septic systems (138 lb/year) represents 22% of the total annual estimated phosphorus load to the Lake.

5.3 Internal Phosphorus Loading

Internal recycling of phosphorus can be a significant source of overall phosphorus load to a pond. Lake sediments contain phosphorus that is bound to the sediment particles. During periods of anoxia (oxygen depletion), phosphorus can be released into the water from the sediment in soluble form, making it biologically available to fuel increased algal productivity.

As shown in Figure 8 (page 19), the north and south basins exhibited strikingly different patterns of internal phosphorus loading during the summer of 2009. Phosphorus concentrations at the North Deep Spot hypolimnion became dramatically elevated during the period of late summer anoxia, indicating the presence of phosphorus-rich sediments in that basin and a relatively high rate of

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phosphorus release. By comparison, the increase in hypolimnetic P levels at the South Deep Spot was relatively modest.

Geosyntec estimated phosphorus release rates for the two basins by assuming that the hypolimnion did not exchange significant amounts of phosphorus with the epilimnion during summer stratification. The difference in hypolimnion phosphorus concentration between the beginning of the sampling season (May 21, 2009) and the time of the highest observed hypolimnion concentrations (September 17, 2009) was multiplied by a control volume (4 m3, i.e. a 4 m deep hypolimnion over a 1 m2 section of sediment) to obtain an estimated phosphorus release rate in g/m2/yr. The estimated release rate was 0.44 g/m2/yr for the north basin and 0.06 g/m2/yr for the southern basin. Because shallower sediments were assumed to have lower release rates than the deepest sediments, the P release rates were varied linearly with depth, from a maximum value at deep spot locations to 0 g/m2/yr for sediments near the surface.

For this study, Geosyntec only measured dissolved oxygen at two deep spot locations within the lake. As such, the extent to which the pond’s sediments are exposed to anoxia could not be accurately defined. Geosyntec calculated an internal load for scenarios where differing areas of sediment contribute to the internal phosphorus release. Figure 17 below shows the internal load in each basin for varying depths below which sediment P is released. As a low estimate, assuming that sediments at depths greater than 40 feet release phosphorus under anoxic conditions, approximately 24 lbs P/yr could be released. At the other extreme, assuming that all sediments at depths greater than 10 feet release phosphorus under anoxic conditions, approximately 120 lbs P/yr could be released. The actual annual internal load is most likely somewhere between these two estimates, possibly in the range of 60 to 80 lbs P/yr. A more refined estimate could be determined through additional future sampling and monitoring, including mapping the spatial extent and duration of anoxia during the stratified months.

Estimated Internal P Load (lbs/yr) 0 50 100 (ft) 10 Occurs 20 Release 30 which

Below 40 North Basin

Depth South Basin 50

Figure 17. Estimated Internal Phosphorus Load from the Cobbett’s Pond North and South Basins

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5.4 Atmospheric Deposition

Atmospheric deposition of phosphorus is an estimate of the load of phosphorus delivered through wet or “dryfall” precipitation depositing phosphorus-containing particles directly on the lake surface. The annual atmospheric deposition load was calculated assuming a deposition rate of 0.185 lb P/ac/yr, for a total atmospheric load of 56 lb P/yr.

5.5 Estimated Annual Phosphorus Loading Budget

To estimate the annual external phosphorus loading budget for Cobbett’s Pond, Geosyntec has combined the phosphorus load from septic systems and atmospheric sources with the watershed loading estimates derived from the land use pollutant loading model presented in Section 3.1 of this report.

The estimated annual external phosphorus budget of 630 lb/year is summarized below and presented in Figure 18. The estimated loads from this phosphorus budget are used in the Vollenwieder equation which predicts in-lake phosphorus concentrations in Section ____. • The phosphorus load resulting from runoff from the varying land uses in the 14 subwatersheds of Cobbett’s Pond accounts for 65% (406 lb) of the annual external phosphorus load to the lake. • Phosphorus entering the lake through tributary baseflow accounts for approximately 5% (30 lb) of the total phosphorus load to the lake. • Phosphorus loading from septic systems is estimated to account for 22% of the annual external phosphorus load. Geosyntec has estimated an annual load from septic systems of 138 lb P/year. • Atmospheric deposition, including wet and dry deposition, is estimated to account for 9% of the annual external phosphorus load (56 lb P/year).

Baseflow P Load (lbs/yr), 30, 5% Septic System Load (lbs/yr), 138, 22%

Land Use P Load (lbs/yr), Aerial P 406, 64% Load (lbs/yr), 56., 9%

Figure 18. External Sources of Phosphorus to Cobbett’s Pond.

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5.6 Vollenweider Equation Results

The Vollenweider model is commonly used to predict in-lake phosphorus concentrations as a function of annual phosphorus loading, mean lake depth and hydraulic residence time. The Vollenweider model is based on a five-year study of about 200 waterbodies in Europe, North America, Japan and Australia.

The Vollenweider Equation is provided below, with calculations for Cobbett’s Pond based on the phosphorus loading estimate discussed above, including phosphorus from stormwater runoff, septic systems, baseflow loading, and aerial deposition. For this calculation, Geosyntec estimates annual phosphorus loading to Cobbett’s Pond to be 630 lb P/yr.

Vollenweider Equation:

where: P = mean in-lake phosphorus concentration (mg/L);

Lp = annual phosphorus load/lake area, (grams/m2/year);

τw = hydraulic residence time (yr);

qs = hydraulic overflow rate=mean depth /hydraulic residence time (m/yr)= z/ τw;

z = average depth (m)

Hydraulic residence time reflects the results of a water budget that Geosyntec calculated for Cobbeett’s Pond Watershed.

/ where: Q = annual discharge passing through the pond (m3/yr); 3 V = pond volume (m )

Annual discharge, Q, was taken from previous NHDES Lake Trophic Data reports. Volume, V, was estimated based on bathymetry maps of Cobbett’s Pond. Table 9 below summarizes the parameters used in the Vollenweider calculation.

The Vollenweider equation contains an implicit assumption that particulate phosphorus becomes sequestered in lake sediment via settling to the pond bottom. The formula makes the assumption that settling velocity can be approximated as:

Typical measured values of settling velocity range from 5 to 20 m/yr (Chapra 1975). For Cobbett’s Pond (qs=2.35 m/yr, τw=2.12 yr),

2.35 2.12 3.42 /

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or 3.42 m/yr (lower than the typical range). Using a low settling velocity value could lead to an erroneously high modeled in-lake P concentration. To provide a better representation of conditions specific to Cobbett’s Pond, a settling velocity coefficient was included in the equation as described below.

Brett & Benjamin (2008) state, “…both the particulate phosphorus fraction and the particulate settling velocity distribution vary greatly during the course of the year in most lakes and especially between lakes, and… as a result, v is likely to have different values in different lakes, and during different seasons in a single lake, thereby reducing the predictive value of the equation.” They statistically analyzed several variations of the Vollenweider model, including the version above and another version that assumed

They found that the addition of a settling velocity coefficient as in the above formula yielded a better statistical fit to existing data for over 300 lakes. A similar approach has been used below to calibrate the Vollenweider equation to match the observed average in-lake P concentration (15 µg/L) for Cobbett’s Pond.

Table 6: Vollenweider model parameters VOLLENWEIDER MODEL PARAMETERS W Total P Loading Rate 286 kg/yr V Volume 6,145,750 m3 z Average Depth 5.1 m Q Annual Discharge 2,883,200 m3/yr As Lake Area 1,222,150 m2 L Areal Loading Rate 234 mg/m2

qs Hydraulic Overflow Rate (m/yr) 2.35 m/yr

τw Hydraulic Residence Time (yr) 2.12 yr k Settling Velocity Coefficient 3.7

In-lake P concentration = 15.6 µg/L ..√.

Based on the estimated annual phosphorus load of 630 lb/yr, the Vollenweider equation predicts an in-lake phosphorus concentration of 15.6 µg/L.

Because of the particular bathymetry of Cobbett’s Pond and the differences in water quality between the North and South basins, Geosyntec also modeled the pond as a two-basin system. The annual discharge for the north basin was estimated as approximately 70% of the annual discharge of the whole pond, based on 70% of the watershed draining to that basin. Annual discharge for the South Basin was assumed to be equal to that of the entire pond, given that the North Basin discharges to it. Phosphorus loads were divided according to the basin to which they

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contributed. For example, if a home was on the shore of the South Basin, its septic load was allocated to the South Basin. The South Basin also receives an additional annual load of phosphorus from water flowing from the North Basin. This additional phosphorus load was calculated by multiplying the annual discharge from the North Basin by the average epilimnetic phosphorus concentration. The phosphorus loads for each basin are shown in Figure 19, and the Vollenweider Model Parameters for each basin are summarized in Table 7.

North Basin: Phosphorus Load South Basin: Phosphorus Load

Baseflow P Load from Septic Load North Basin System (lbs/yr), 20, (lbs/yr), 60, Load 5% 20% (lbs/yr), 63, Baseflow P Land Use P 16% Load Load (lbs/yr), 10, (lbs/yr), 126, 3% 42%

Aerial P Load (lbs/yr), 21, 6% Septic System Land Use P Load Load (lbs/yr), 72, (lbs/yr), 280, 24% 73% Aerial P Load (lbs/yr), 35, 11% Figure 19. External phosphorus sources to the North and South Basin.

Table 7: Basin-specific Vollenweider model parameters VOLLENWEIDER MODEL PARAMETERS (NORTH AND SOUTH BASINS) NORTH BASIN SOUTH BASIN 174 kg/yr 137 kg/yr W Total P Loading Rate 2,073,450 m3 4,072,290 m3 V Volume 4.5 m 5.4 m z Average Depth 2,075,900 m3/yr 2,883,200 m3/yr Q Annual Discharge 465,390 m2 765,760 m2 As Lake Area 374 mg/m2 179 mg/m2 L Areal Loading Rate 4.46 m/yr 3.76 m/yr qs Hydraulic Overflow Rate (m/yr) 0.99 yr 1.41 yr τw Hydraulic Residence Time (yr) 4.5 1.7 k Settling Velocity Coefficient

When the loads and model parameters for the basins are separated, there are noticeable differences in each basin’s phosphorus cycling behavior. Settling velocity coefficients were adjusted in order to calibrate the Vollenweider equation to achieve a phosphorus concentration of 15.6 ug/L in each basin. The North Basin had a coefficient of 4.5, which led to an estimated settling velocity of:

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· 4.46· 4.5 √0.99 20 / which is at the high end of the typical range of settling velocities provided in Chapra (1975). Given that settling velocity represents physical removal of particulate-bound phosphorus from the water column, and that 73% of the North Basin’s Phosphorus load is from stormwater runoff, which is likely to contain particulate phosphorus, it is likely that the removal rate through settling in the North Basin is actually in the upper range of typical values. On the other hand, the South Basin’s phosphorus load is comprised of sources that are likely contain mostly dissolved phosphorus, such as the septic system load and the load of phosphorus flowing in from the North Basin. As such, the South Basin has been estimated to have a significantly lower settling velocity coefficient of 1.6 and an estimated settling velocity of:

· 3.76· 1.7 √1.41 7.6 /

Understanding the difference in phosphorus settling in these two basins also helps to explain the differences in observed hypolimnetic phosphorus concentrations discussed in Section 3.1.2. The particulate sources of phosphorus to the north basin and its high phosphorus settling rate indicate that this basin has a high potential for significant phosphorus accumulation in sediments and therefore a high potential for release of sediment-bound phosphorus during periods of hypolimnetic anoxia. As discussed above, the peak 2009 summer hypolimnetic phosphorus concentrations indicate a strong pulse of phosphorus released from the sediment in the North Basin. In the South Basin, less phosphorus is removed from the system via settling, and the relatively lower phosphorus concentrations in the South Basin hypolimnion support the model results.

5.7 Recommended Phosphorus Reduction Goal To improve water quality conditions in Cobbett’s Pond and reduce the occurrence of nuisance algal blooms, Geosyntec recommends targeting an in-pond total phosphorus concentration reduction of 3.6 µg/L, which would reduce the current predicted concentration from 15.6 µg/L to 12 µg/L. This phosphorus concentration reduction would improve Cobbett’s Pond to the median phosphorus concentration for similar New Hampshire lakes. This reduction is expected to improve in-lake conditions with regard to water quality indicators such as water clarity and algal abundance.

As shown in Figure 8, the Vollenweider equation predicts that the lake’s phosphorus load must be reduced by 145 lb P/yr in order to achieve the recommended target in-lake phosphorus concentration of 12 µg/L. The recommended P load reduction represents approximately 20% of the estimated annual phosphorus load for the pond. Section 5 provides a discussion of how the recommended phosphorus load reduction may be achieved.

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630 lb, 15.6 ug/L

15 485 lb, 12 ug/L

145 lbs

5 In-Lake P Concentration (ug/L)

0 0 200 400 600 800

P Load (lbs/yr)

Figure 20. Vollenweider Plot for Cobbett’s Pond

Based on the modeled annual phosphorus load estimate of 630 lb P/yr, the Vollenweider equation predicts that an annual load reduction of 145 lb P/yr would be required to achieve a target in- pond P concentration of 12 ug/L. Each reduction of 40 lb in annual P load is predicted to lower the in-pond P concentration by 1 ug/L.

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6. OPTIONS FOR REDUCING PHOSPHORUS LOADING TO COBBETT’S POND This section presents a discussion of potential measures that could be implemented in the Cobbett’s Pond watershed to reduce phosphorus loading. This section provides a discussion of potential phosphorus reduction measures that relate to storm water management, septic systems, and watershed land uses. Table 9 (pg. 81) provides an overview and prioritization of all proposed measures that are presented in this Section.

6.1 Storm Water Management

6.1.1 Field Watershed Investigation Robert Hartzel (Senior Water Resources Scientist, Certified Lake Manager) and Daniel Bourdeau, P.E. (Water Resource Engineer) of Geosyntec conducted a field watershed investigation on May 19-20, 2009 to identify potential storm water improvement sites and other opportunities to reduce phosphorus loading to Cobbett’s Pond. Mr. Hartzel and Mr. Bourdeau are both Certified Professionals in Sediment and Erosion Control (CPESC). A CPESC is a recognized specialist in soil erosion and sediment control, with certification by the Soil and Water Conservation Society and the International Erosion Control Association.

The following pages provide descriptions of the sites identified during the field investigation and recommended improvements. It is important to note that the sites discussed in this section are not intended to be a comprehensive listing of all possible stormwater improvements in the Cobbett’s Pond watershed. Rather, these sites are representative examples of potential stormwater improvements and retrofits that could be implemented at numerous sites throughout the watershed.

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SITE 1: Castleton Center Parking Area Site Summary: The asphalt parking lot of the Castleton Banquet and Conference Center drains primarily to a catch basin located at its southern end (photo 1-1), which discharges via a culvert to Castleton Brook. Proposed Improvement: Several areas within the parking lot could be retrofit as bioretention areas to promote infiltration and reduce discharge of pollutants to Cobbett’s Pond via surface water runoff. A schematic of a typical bioretention cell is provided as Figure 21. Proposed improvement areas include: Photo 1-1 • Two grassed islands shown in photos 1-2 and 1- 3. Renderings of bioretention cells in these areas are provided on the following page. • The area in the immediate vicinity of the catch basin (photo 1-1) could also be retrofit as a bioretention cell with an overflow pipe to prevent flooding in the parking lot.

Estimated Cost: $27,900 - $34,100

Estimated Pollutant Load Reduction: 0.39 - 0.43 lbs P/yr

Photo 1-2

Photo 1-3

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SITE 1: Castleton Center Parking Area (continued)

Renderings of proposed bioretention cells areas shown in photos 1-2 and 1-3 on the preceding page. The blue arrows indicate curb cut areas allowing storm water runoff to flow into the bioretention cell.

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Figure 21. Cross-section of a typical bioretention cell with a riser pipe and outlet connection.

BIORETENTION CELLS are shallow landscaped depressions that incorporate plantings and an engineered soil mixture with a high infiltration rate. Bioretention cells are used to (1) control storm water runoff volume by providing storage capacity, (2) reduce peak discharge by increasing the travel time of storm water through a watershed, and (3) remove pollutants through physical, chemical and biological processes that occur in the plants and soil media. Storm water that drains into a bioretention cell ponds temporarily and infiltrates the engineered soil mixture. Bioretention cells are typically designed to provide an infiltration rate approximately equal to the peak discharge rate for the 10-year, 24-hour storm event. Infiltration rates are enhanced during by uptake from vegetation within the cell. Installed costs for engineering, materials and construction of a typical bioretention cell generally range from $3,000 up to $30,000 (for a large retrofit cell requiring significant earthwork). Pre- fabricated “planter box” bioretention cells (e.g., Filterra™) can treat storm water runoff from an area up to 0.25-acres and cost approximately $7,000 each (installed cost). RAIN GARDENS are small-scale bioretention cells, constructed as shallow vegetated depressions designed to capture and infiltrate storm water runoff. Rain gardens are often appropriate for residential properties, to treat runoff from roofs driveways and lawns. The total installed cost of a typical rain garden is approximately $1,500 to $3,000, depending on garden size, soil conditions, type of plantings used, and other site conditions.

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SITE 2: 6-8 Armstrong Road

Site Summary: Erosion is occurring at a culvert that conveys runoff to the west under Armstrong Road (photo 2-1). Areas upgradient of the culvert (photo 2-2) to the north and south are also eroding and require stabilization.

Proposed Improvement: • Stabilize culvert inlet with geotextile and rip- rap; • Install water quality swale for approximately 30 feet to the north and south of the culvert.

Estimated Cost: $2,200 - $2,700

Estimated Pollutant Load Reduction: 0.34 - 0.38 lbs P/yr Photo 2-1

Photo 2-2

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SITE 3: Sawtelle Road

Site Summary: Two catch basins on Sawtelle Road appear to be in disrepair. These catch basins were observed surcharging to the road during dry weather at the time of Geosyntec’s site visit (photos 3-1 and 3-2).

Proposed Improvement: • Retrofit existing catch basins with new deep sump catch basins; • A stone wall exists on the side of the road opposite from the catch basins, allowing insufficient space for a swale between the wall Photo 3-1 and road. Pending review of property ownership and related easements, it may be possible to divert flows from the proposed deep sump catch basins to a vegetated water quality swale in the field on beyond the stone wall (photo 3-3).

Estimated Cost: $10,300 - $12,600 Estimated Pollutant Load Reduction: 0.18 – 0.22 lbs P/yr

Photo 3-2

Photo 3-3

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SITE 4: Griffin Park

Site Summary: Stormwater runoff from the Griffin Park parking lot flows via an existing grassed swale (photos 4-1 and 4-2) to a catch basin (photo 4-3) at the eastern edge of Range Road (Rt. 111A), just beyond the northwestern corner of the park.

Proposed Improvements: A broad grassy area exists adjacent to the swale at its northernmost segment (photo 4-2). This area could easily be converted to a large bioretention area, promoting on-site infiltration and reducing the volume of stormwater discharging off-site to the Photo 4-1 storm drainage system at Rt. 111A. Proposed improvements include: • Install 2,500 square foot bioretention cell; • Install outlet structure; and • Connect outlet structure to Rt. 111A catch basin • A schematic overview of the proposed improvement locations is provided on the following page.

Estimated Cost: $34,500 - $42,200

Estimated Pollutant Load Reduction: Photo 4-2 0.85 – 1.04 lbs P/yr

Photo 4-3

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SITE 4: Griffin Park (continued) Schematic of proposed Griffin Park bioretention cell area.

Connect to Rt. 111A catch basin

Bioretention cell

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SITE 5a: Farmer Road Site Summary: Farmer Road intersects Horseshoe Road at two locations. Storm water in this area is collected by catch basins (photos 5-1 and 5-3) and grassed swales (photo 5-2). Geosyntec observed significant sediment accumulation around the catch basins at both Farmer Road/Horseshoe Road intersections Proposed Improvement: • Retrofit catch basins to bioretention cells with underdrains; • Improve existing swale by re-grading to provide wider bottom width and install gravel subbase to promote infiltration and provide storage. Photo 5-1

Estimated Cost: $22,000 - $26,900

Estimated Pollutant Load Reduction: 0.21 – 0.25 lbs P/yr

Photo 5-2

Photo 5-3

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SITE 5a: Farmer Road (continued) Rendering of bioretention cell (bottom photo) with riser pipe and adjacent grass filter strip proposed for the area shown in photo 5-3 (top photo).

Existing catch basin

Riser pipe

Bioretention cell

Grass filter strip

61 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

SITE 5b: Farmer Road /Horseshoe Road Site Summary: The catch basin shown in photo 5-4 is located on the northern side of Horseshoe Road, near the southern intersection with Farmer Road. Proposed Improvement: Install an approximate 60-foot long by 6-foot wide (360 s.f.) bioretention cell upgradient of the catch basin on the northern side of Horseshoe Road.

Estimated Cost: $4,600 – $5,700 Estimated Pollutant Load Reduction: 0.14 – 0.17 lbs P/yr

Photo 5-4

62 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

SITE 6: 20-24 Turtle Rock Road Site Summary: Soil erosion is occurring along the road edge and a drainage culvert near 20-24 Turtle Rock Road. This culvert drains directly to Cobbett’s Pond via a 12- inch culvert pipe that discharges at 20 Turtle Rock Road. Proposed Improvement: • Install two vegetated water quality swales, extending 50 feet to the north and south of the culvert. • Install riprap stabilization at the inlet of the culvert.

Estimated Cost: $3,300 - $4,000 Photo 6-1 Estimated Pollutant Load Reduction: 0.05 – 0.06 lbs P/yr

Photo 6-2

63 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

SITE 7: 34 Turtle Rock Road Site Summary: An existing catch basin (photo 7-1) is located within a grassed portion of the property at 34 Turtle Rock Road, close to where the driveway intersects the road. Proposed Improvement: Install raingarden (approximately 100 square feet) with riser pipe in area surrounding the catch basin.

Estimated Cost: $1,200 - $1,400 Estimated Pollutant Load Reduction: 0.01 – 0.02 lbs P/yr

Existing catch basin

Photo 7-1

64 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

SITE 8: 74 Turtle Rock Road Site Summary: A catch basin is located within an unpaved parking/storage area in the vicinity of 74 Turtle Rock Road (photo 8-2). This catch basin discharges directly to Cobbett’s Pond via a 12-inch culvert pipe. A small adjacent section of Turtle Rock Road is also unpaved (photo 8-1). Proposed Improvement: • Pave the adjacent, approximately 2,300 square foot unpaved section of Turtle Rock Road with standard asphalt.

Estimated Cost: $10,800 - $13,200 Estimated Pollutant Load Reduction: 0.09 – 0.10 lbs P/yr

Photo 8-1

Catch basin

Photo 8-2

65 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

SITE 9: Summer Street Area

Site Summary: A portion of the fields located to the north and east of Sawtelle Road drain to a drainage ditch located between the fields and the southern end of Summer Street. Fill has been placed in the ditch (photo 9-1), blocking the normal flow path within the ditch and directing erosive storm water flows across the adjacent property and along Summer Street. Several major storms in March 2009 resulted in severe erosion in these areas (photo 9-2). Flooding and severe sediment accumulation also occurred at several downgradient culvert locations at Summer Photo 9-1 Street/Spring Street and Spring Road (photo 9-3).

Proposed Improvements: • Restore drainage ditch. Remove fill blocking flow and construct stabilized vegetated swale with sufficient capacity to convey flows from the drainage area in a non-erosive manner; • Re-grade and stabilize the eroding lawn, driveway and sections of Summer Street. Re- surface Summer Street with a specification hardpack to minimize future surface erosion and migration of fine-grained particles. Photo 9-2 • Retrofit culverts to improve flow capacity and stability at Summer Street/Spring Street and Spring Road.

Estimated Cost: $10,000 – $12,200

Estimated Pollutant Load Reduction: 0.36 – 0.45 lbs P/yr

Photo 9-3

66 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

SITE 9: Summer Street Area (continued)

Aerial view of proposed improvement areas.

Cobbett’s Pond

Retrofit culverts to improve flow capacity and stability.

Retrofit culverts to improve flow capacity and stability (photo 9-3).

Re-grade and stabilize eroding lawn, driveway and sections of Summer Street (photo 9-2).

Restore drainage ditch; Remove fill blocking flow (photo 9-1).

67 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

SITE 10: 60-62 Horseshoe Road

Site Summary: Road drainage in the area of 60-62 Horseshoe Road is conveyed via a grassed swale and culvert as shown in photos 10-1 and 10-2.

Proposed Improvement: • Convert the grassed swale on both sides of the driveway at 62 Horseshoe Road into a linear bioretention cell. • Daylight (remove) an approximate 25-foot section of 15-inch corrugated plastic pipe culvert at 60 Horseshoe Road and convert this area to a linear bioretention cell that is contiguous with the two areas described above.

Estimated Cost: $9,700 - $11,800 Photo 10-1

Estimated Pollutant Load Reduction: 0.31 – 0.38 lbs P/yr

Photo 10-2

68 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

SITE 11: 58 Horseshoe Road Site Summary: A short paved flume directs stormwater from the area near 58 Horseshoe Road into a catch basin (photo 11-1). This catch basin ties into a 15-inch drainage pipe across the street that discharges to an intermittent channel at 35 Horseshoe Road, enters a 24-inch culvert and ultimately discharges to Cobbett’s Pond at 34 Horseshoe Road. Proposed Improvement: The area in the immediate vicinity of the catch basin could be retrofit with a bioretention cell (approximately 400 square feet) with an overflow pipe to prevent flooding.

Estimated Cost: $5,100 - $6,300 Estimated Pollutant Load Reduction: 0.48 - 0.58 lbs P/yr

Existing catch basin

Photo 11-1

69 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

SITE 12: Woodland Ridge Area (Rt. 111) Site Summary: Road runoff has caused significant erosion on NH- DOT property just east of the Woodland Ridge development on the north side of Rt.111. Rilling and unstabilized soils were observed in a channel (photo12-2) that conveys storm water to a concrete culvert pipe. Geosyntec observed evidence of previous unsuccessful efforts to stabilize this area, including the coir fiber wattles observed in the channel (photo 12-3). Proposed Improvements: • Install curb and gutter along Rt. 111 approximately 500 linear feet; Photo 12-1 • Install two catch basins with double grates on either side of Rt. 111; • Install BaySeparator (or similar BMP) with associated storage manhole at proposed catch basins; • Install a bioretention cell (approximately 500 square feet); and • Construct energy dissipation structure, level spreader and rip-rap stabilized channel along the north side of Rt. 111; and • Construct vegetated swale along the south side of Rt. 111. Photo 12-2 Estimated Cost: $38,600 - $47,200 Estimated Pollutant Load Reduction: 1.68 – 2.05 lbs P/yr

Photo 12-3

70 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

SITE 13: 35 Cobbett’s Pond Road

Site Summary: Two catch basins in Cobbett’s Pond Road drain to a rock-lined flume that has become filled with sediment. The catch basins discharge via a culvert that is perched approximately two feet above the rock-lined flume.

Proposed Improvement: • Retrofit the outlet pipe to discharge at grade to a stone infiltration strip with a level spreader oriented parallel to the retaining wall (approximately 4-foot wide by 20-foot long).

• Immediately downgradient of the infiltration strip Photo 13-1 and level spreader, construct a 4-foot wide by 20-foot long raingarden planted with native shrubs on 3-foot centers. The size of the raingarden could be larger, pending discussions with the property owner.

Estimated Cost: $1,700 - $2,100

Estimated Pollutant Load Reduction:

0.19 – 0.23 lbs P/yr

Photo 13-2

71 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

SITE 14: Windham Town Beach Site Summary: A stormwater outfall at the Windham Town Beach receives flow from a wetland area to the south and adjacent portions of Cobbett’s Pond Road. Road runoff from the north (photo 14-1) flows into a 12- inch concrete pipe via a grassed area located on the eastern side of the road (photo 14-2). Proposed Improvement: • Retrofit the grassed area shown in photo 15-2 to incorporate an approximate 400 square foot bioretention cell.

Estimated Cost: $5,100 - $6,300 Estimated Pollutant Load Reduction:

0.11 – 0.13 lbs P/yr Photo 14-1

Photo 14-2

72 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

SITE 15: Fossa Road / Range Road (Rt. 111A) Site Summary: Just south of the intersection of Range Road and Fossa Road, an intermittent stream channel (photos 15-1 and 15-2) has become unstable and eroded due to high volume and velocity flows during large storm events. Significant sediment deposition has occurred at the outfall of this stream, which is located at 5 Lakeshore Road. The drainage for this stream includes a portion of Range Road to the east of Fossa Road (photo 15-3).

Proposed Improvement: • Just east of the intersection of Range Road and Photo 15-1 Fossa Road, construct an approximately 90-foot long, 6-foot wide stone-lined swale to collect road runoff. • Convey runoff from the swale described above to an 18” culvert under Fossa Road and discharge west of the road to a stone apron. Construct a cement headwall for the culvert inlet and outlet. • At the outlet of the existing channel to the north of Range Road, install an approximately 65-foot long, 6-foot wide stone-lined swale, which discharges via a stone level spreader. • From the swale/level spreader described above, re-construct the upgradient portion of the channel Photo 15-2 (approximately 160 linear feet) into a series of three stilling basins with level spreaders. • Re-grade and stabilize the final 100 linear feet of eroded channel (downstream reach to existing culvert headwall, photo 15-2) with stone, geotextile, and plantings.

Estimated Cost: $37,500 - $45,900

Estimated Pollutant Load Reduction: 6.08 – 7.43 lbs P/yr

Photo 15-3

73 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

SITE 15: Fossa Road / Range Road (continued)

Aerial view of Site 15 and proposed improvement areas.

Stabilize eroded channel

FFFooossssssaaa RRRddd... Stone apron 18” culvert with inlet Stone‐lined swale Series of 3 stilling basins and outlet headwalls with level spreaders

Stone‐lined swale/ level spreader

RRRttt... 111111111AAA

74 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

SITE 16: Hawley Road

Site Summary: The northern edge of Hawley Road is eroding and rilled from the intersection with Baker Road to the intersection with Range Road (photos 16-1 and 16- 2). At the intersection with Range Road, runoff from this area drains to a culvert with a concrete block headwall that is in disrepair and requires stabilization (photo 16-3).

Proposed Improvement: • Stabilize the road edge with approximately 175 linear feet of grassed water quality swale, 4- feet wide. Photo 16-1 • In conjunction with the water quality swales, install raingardens where adequate space exists to capture and infiltrate runoff from residential parcels (estimate 5 raingardens at 100 square feet each).

Estimated Cost: $12,200 - $14,900

Estimated Pollutant Load Reduction: 0.60 – 0.74 lbs P/yr

Photo 16-2

Photo 16-3

75 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

6.1.2 Estimated Storm Water BMP Pollutant Load Reduction Phosphorus load reductions were estimated for each of the proposed improvements described above in Section 6.1.1. The phosphorus load reductions were estimated using published pollutant reduction rates for BMPs as follows:

The predicted phosphorus load entering each BMP was estimated based on the land cover in the drainage area contributing flows through the BMP. Each BMP drainage area was delineated based on United States Geological Survey (USGS) topography maps and Geosyntec’s field investigations of the watershed and storm drainage structures.

Next, land use categories from existing land use data were assigned to the drainage area. An annual pollutant load was estimated for each catchment using the Simple Method described in the New Hampshire Stormwater Manual. This pre-BMP annual phosphorus load represents the amount of phosphorus expected to enter the Pond if the BMP was not in-place.

Next, published BMP phosphorus reduction values were used to estimate the total amount of phosphorus which is expected to be removed (provided that the BMP is properly installed and maintained). Reduction values were obtained from the New Hampshire Stormwater Manual when available. BMP reduction values not provided by the New Hampshire Stormwater Manual were obtained from the Massachusetts Stormwater Handbook. The post-BMP pollutant load represents the pollutant load predicted to enter the Lake if the BMP was installed. Table 9 provides a summary of the phosphorus load reductions estimated for each proposed BMP site. Appendix E includes the Simple Method calculations, phosphorus load reduction calculations and costing assumptions used for each site.

The BMPs proposed for Sites 1-16 are estimated to reduce the annual phosphorus load to Cobbett’s Pond by 13.4 lb/year. This load reduction represents about 9% of the targeted phosphorus load reduction (145 lb/year) for Cobbett’s Pond as discussed in Section 4.4. However, as previously stated, Sites 1-16 are not intended to be a comprehensive listing of recommended stormwater improvements in the Cobbett’s Pond watershed. Rather, these sites are representative examples of potential stormwater improvements and retrofits that could be implemented at numerous sites throughout the watershed. Significantly greater phosphorus load reductions could be attained from a watershed-wide effort to improve stormwater management through LID practices (e.g. raingardens on residential lots) and improvements to existing storm water drainage features. As such, we estimate that a realistic range of potential phosphorus load reduction from a watershed-wide effort to install storm water BMPs is between 13.4 and 65 lb/year.

76 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

6.2 Potential Community Septic Systems Locations

Geosyntec conducted a preliminary review to identify potential areas for community septic systems (Table 8). The review was based on (1) the density of existing homes in close proximity to the Lake and (2) data on soil types and soil drainage classes in the areas surrounding the Lake. Nine potential sites for community septic systems serving 249 homes are shown in Figure 22. As shown in Figure 13, the majority of the soils surrounding the Lake have been classified by the USDA-NRCS as well-drained soils, which tend to be suitable for siting wastewater treatment facilities.

Geosyntec identified the nine areas listed below as potential sites for community septic systems. For each of the nine clusters of homes, the maximum piping distance from a home to a centrally located community septic system would be approximately 0.25 miles.

Table 8: Potential Community Septic Systems

# of Estimated P Area Location Shoreline Reduction Homes (lbs/yr)

Southern tip of the lake (from intersection of Cobbett’s 1 23 3.0 – 7.2 Pond Road /Horne Road to 8 Cheryl Road)

Horne Road/Fish Road area (from 2 Horne Road to 40 2 20 2.6 – 6.3 Fish Road)

3 Ash Street/ Gaumont Road / Viau Road area 35 4.6 – 11.0

1st Street / North Shore Road area (from 20 1st Street to 4 27 3.5– 8.5 14 Gardner Road) Rocky Ridge Road area (from southern end of Bell 5 20 2.6 – 6.3 Road to southern end of Water’s Edge Road) Northeast Shore area (from 35 Armstrong Road to 27 6 26 3.4 – 8.2 Walkeys Road)

7 Grove Street / Sawyer Road / Sawtelle Road area 32 4.2 – 10.1

Farmer Road / Horseshoe Road area (from 1 Farmer 8 30 3.9 – 9.4 Road to 24 Horseshoe Road) Turtle Rock Road area (18 Turtle Rock Road to 9 36 4.7 – 11.3 southern end of Turtle Rock Road)

Total: 32.7 – 78.4

The installed cost for a community septic system can vary widely depending on site specific conditions such as soils, slopes, piping distances, etc. In general, the cost of a community system per household will decrease significantly as the number of homes sharing the system increases. For general costing purposes, a cluster mound system servicing 25 homes will cost about $400,000 to install ($16,000 per house). This cost includes $150,000 to install the system and $250,000 to install piping connections, assuming an average of 100 feet of small diameter pipe per home at $10 per linear foot. Annual maintenance costs for this type of system are estimated at $5,000 ($200 annually per home).

The potential phosphorus load reductions that may be achieved by installing community septic systems can vary widely depending on variables including: the proximity and condition existing on-site septic systems; the location of the proposed community septic systems (e.g.

77 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

distance from the lake); and treatment technology of the systems. For the 249 homes located within the nine potential community septic system locations, a conservative estimated phosphorus removal efficiency range of 25%-60% would result in an estimated total phosphorus load reduction of 32.7 to 78.4 lbs P/year. This reduction would represent 23% to 54% of the targeted annual phosphorus load reduction discussed in Section 4.4.

6.2.1 Septic System Maintenance - Cobbett’s Pond Watershed Protection Ordinance (CPWPO) As discussed in Section 2.2, the recently (March 2009) enacted CPWPO requires septic system pumping and inspection at least every three years. Pumping and inspection is required more frequently if recommended by a licensed septic service provider. This maintenance requirement will very likely result in a more frequent maintenance and improved function for septic systems around the Cobbett’s Pond, particularly for systems that are found to found to be substandard and required to have more frequent pumping/inspection. The inspection program may also result in the identification of failing systems that will be required to be replaced. Although the CPWPO maintenance program will very likely reduce the phosphorus load from septic systems, the amount the reduction is difficult to estimate. If the maintenance program results in a 10%-15% net decrease in septic system phosphorus load, this would equal an annual load reduction of 13.8 to 20.7 lbs P/year.

78 VU111

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0 300 600 1,200 1,800 Legend Feet Water Body PROPOSED COMMUNITY Highway SEPTIC SYSTEM REGIONS Cobbett's Pond Major Road Windham, NH

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Acton, MA 31-MAR-10 22 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

6.3 Phosphorus Loading From Watershed Land Uses

Landscaping/Lawn Fertilizers Landscaping fertilizers can be a significant source of phosphorus from areas of residential development and other areas where grass lawns are maintained (e.g. office parks, schools, sports fields, etc.). The CPIA and/or the Town of Windham could develop a program to reduce pollution from fertilizer applications within the watershed. Such efforts are consistent with and would complement the CPWPO ban of fertilizer use within 200 feet of surface waters and wetlands. This program could be modeled after similar efforts that have been implemented successfully in other communities and include the following: • As an incentive to promote the use of phosphorus-free fertilizers, the CPIA could offer this type of fertilizer to homeowners at a reduced price. Fertilizer retailers (e.g. local hardware stores, etc.) could be selected to provide reduced-priced fertilizer for homeowners living in the watershed. The retailers would be subsidized by for the balance of the fertilizer cost. Homeowners using the fertilizer would be provided signage (optional) to post in their yard, which would educate neighbors about the phosphorus-free fertilizer and its role in protecting water quality. A follow up survey is recommended to evaluate the performance of the program. Printed public outreach materials (e.g., brochure, flyer) are also recommended to ensure that watershed residents are informed of the program, including a discussion of the benefits of and options for “no-fertilizer” landscaping. • Develop landscaping fertilizer bylaws or ordinances to reduce the use of phosphorus- based fertilizer. There have been numerous successful local ordinances regulating the use of phosphorus fertilizer on lawns. Examples include statewide programs in Maine and Minnesota, and county programs in Dane County (WI), Muskegon County (MI), and Ottawa County MI). A report on the effectiveness of the Minnesota law is available at: www.mda.state.mn.us/phoslaw.

The phosphorus load reductions that can be achieved by a fertilizer reduction program are expected to vary widely depending on how the program is structured and implemented. For purposes of developing a load reduction estimate for this report, we have assumed that the program would be targeted to the 400 residential homes located in closest proximity to Cobbett’s Pond, and that 25% these homes (100 homes) fertilize a 2,000 square foot lawn area twice per growing season using 10-10-10 (N-P-K) formula fertilizer at a typical application rate of 3.5 lbs per 1000 square feet. If 25% to 50% of the homes using fertilizer are convinced to switch to phosphorus-free fertilizer, the amount of phosphorus applied to lawns within the Cobbett’s Pond watershed would be reduced by approximately 117 to 233 lbs. per year. If 10% of the applied fertilizer phosphorus washes into the lake via storm water runoff, then the estimated annual phosphorus load reduction would range from 11.7 to 23.3 lbs. P/year.

Costs for a one-year fertilizer reduction program as described above are anticipated to be in the range of $8,000 to $10,000. These costs include printed outreach materials (brochure, signage, homeowner survey), and costs associated with providing a rebate or subsidy for purchase of phosphorus–free fertilizer. Assuming that 100 homes participated and purchased four bags of fertilizer, and assuming a rebate of $15 per bag, the total cost of the rebate would be $6,000.

80 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

Table 9: Summary of Proposed Actions to Reduce Phosphorus Loading

Estimated P Cost per lb. of BMP Load Site Proposed Actions Estimated Cost 1 P Reduced Priority Type Reduced (x $1,000) (lb/yr)

Site 1: Castleton $27,900 – • Install bioretention cells in 2 parking lot islands and one area adjacent to a catch 0.4 – 0.5 55.8 – 85.3 MEDIUM Center Parking Area basin. $34,100

Site 2: • Stabilize culvert inlet with geotextile and rip-rap; $2,200 - $2,700 0.3 - .0.4 5.5 – 9.0 MEDIUM 6-8 Armstrong Rd. • Install water quality swale for 30 feet to the north and south of the culvert.

• Retrofit 2 existing catch basins with new deep sump catch basins; Site 3: $10,300 - $12,600 0.2 51.5 – 63.0 HIGH Sawtelle Rd. • Pending review of property ownership/easements, potentially divert flows from the deep sump catch basins to a vegetated water quality swale in the adjacent field.

• Install 2,500 square foot bioretention cell; Site 4: $34,500 - $42,200 0.9 – 1.0 34.5 – 46.9 HIGH Griffin Park • Install outlet structure; • Connect outlet structure to Rt. 111A catch basin • Retrofit catch basins to bioretention cells with underdrains; Site 5a: $22,000 - $26,900 0.2 – 0.3 73.3 – 134.5 LOW Farmer Rd. • Improve existing swale by re-grading to provide wider base and install gravel subbase to promote infiltration and provide storage.

Site 5b: Farmer Rd. • Install an approximate 50-foot long by 6-foot wide bioretention cell upgradient of the $4,600 - $5,700 0.1 – 0,2 23.0 – 57.0 LOW /Horseshoe Rd. catch basin on the northern side of Horseshoe Rd.

• Install 2 vegetated water quality swales, extending 50 ft. north and south of the Site 6: culvert. $3,300 - $4,000 0.06 55.0 – 66.7 LOW 20-24 Turtle Rock Rd. • Install riprap stabilization at the inlet of the culvert. Site 7: $1,200 - $1,400 0.02 60.0 – 70.0 LOW 34 Turtle Rock Rd. • Install 100 s.f. raingarden with riser pipe in area surrounding the catch basin. Site 8: $10,800 - $13,200 0.1 108.0 – 132.0 LOW 74 Turtle Rock Rd. • Pave the 2,300 s.f. unpaved section of Turtle Rock Rd. with standard asphalt.

• Restore drainage ditch. Remove fill blocking flow and construct vegetated swale with capacity to convey flows from the drainage area in a non-erosive manner; Site 9: • Re-grade/stabilize the eroding lawn, driveway and sections of Summer Street. Re- $10,000 - $12,200 0.4 – 0.5 20.0 – 30.5 HIGH Summer St. Area surface Summer Street with a specification hardpack to minimize future erosion; • Retrofit culverts to improve flow capacity/stability at Summer St., Spring St. and Spring Rd. Stormwater BMPs • Convert the grassed swale on both sides of the driveway at 62 Horseshoe Road Site 10: into a linear bioretention cell. $9,700 - $11,800 0.3 - .0.4 24.3 – 39.3 LOW 60-62 Horseshoe Rd. • Daylight 25-ft section of 15-inch culvert at 60 Horseshoe Rd. and convert this area to a linear bioretention cell that is contiguous with the two areas described above. Site 11: $5,100 - $6,300 0.5 – 0.6 8.5 – 12.6 MEDIUM 58 Horseshoe Rd. • Retrofit area adjacent to catch basin with 400 s.f. bioretention cell, overflow pipe

• Install curb and gutter along Rt. 111 (approx. 500 linear feet); • Install 2 catch basins with double grates and a BaySeparator (or similar) with Site 12: storage manhole on both sides of Rt. 111; $38,600 - $47,200 1.7 – 2.1 18.4 – 27.8 HIGH Woodland Ridge Area • Install 500 s.f. bioretention cell on north side of Rt. 111; • Energy dissipation, level spreader and rip-rap channel on north side of Rt. 111; • Construct vegetated swale on south side of Rt. 111. • Retrofit outlet pipe to discharge at grade to a stone infiltration strip with a level Site 13: spreader oriented parallel to the retaining wall (approximately 4-ft wide by 20-ft long); $1,700 - $2,100 0.2 8.5 – 10.5 HIGH 35 Cobbett’s Pond Rd. • Downgradient of the level spreader, construct a 4-ft wide by 20-ft long raingarden planted with native shrubs on 3-foot centers.

Site 14: • Retrofit the grassed area shown in photo 15-2 to incorporate an approximate 400 $5,100 - $6,300 0.1 51.0 – 63.0 MEDIUM Windham Town Beach square foot bioretention cell.

• East of Range Rd./Fossa Rd. intersection, construct 90-ft by 6-ft. stone-lined swale to collect road runoff; • Convey runoff from swale to 18” culvert under Fossa Rd. and discharge west of the road to a stone apron. Construct a cement headwall for the culvert inlet and outlet; Site 15: $37,500 - $45,900 6.1 – 7.4 5.1 – 7.5 HIGH Fossa Rd. /Range Rd. • At the outlet of the channel to north of Range Rd., install 65-ft by 6-ft stone-lined swale, which discharges via a stone level spreader; • Convert upgradient 160 ft. of the channel into 3 stilling basins with level spreaders; • Re-grade and stabilize the final 100 linear feet of eroded channel (to existing culvert headwall) with stone, geotextile, and plantings.

Site 16: • Stabilize the road edge with approx. 175 lf of grassed water quality swale, 4-ft wide; $12,200 -$14,900 0.6 – 0.7 17.4 – 24.8 HIGH Hawley Rd. • Install raingardens on residential parcels (estimate 5 raingardens at 100 s.f. each).

Area 1: Southern tip of the lake (intersection of Community septic system (23 homes). $368,000 3.0 – 7.2 MEDIUM Cobbett’s Pond Rd. /Horne Road to 8 Cheryl Rd.)

Area 2: Horne Road/Fish Road area (from 2 Community septic system (20 homes). $320,000 2.6 – 6.3 MEDIUM Horne Road to 40 Fish Road)

Area 3: Ash Street/ Gaumont Road / Viau Road Community septic system (35 homes). $560,000 4.6 – 11.0 MEDIUM

Area 4: 1st Street / North Shore Road area (from st Community septic system (27 homes). $432,000 3.5– 8.5 MEDIUM 20 1 Street to 14 Gardner Road)

Area 5: Rocky Ridge Road area (southern end of Community septic system (20 homes). $320,000 2.6 – 6.3 50.8 – 122.0 MEDIUM Septic Bell Road to southern end of Water’s Edge Road) Systems Area 6: Northeast Shore area (from 35 Armstrong Community septic system (26 homes). $416,000 3.4 – 8.2 MEDIUM Road to 27 Walkeys Road)

Area 7: Grove Street / Sawyer Road / Sawtelle Community septic system (32 homes). $512,000 4.2 – 10.1 MEDIUM Road area Area 8: Farmer Road / Horseshoe Road area Community septic system (30 homes). $480,000 3.9 – 9.4 MEDIUM (from 1 Farmer Road to 24 Horseshoe Road) Area 9: Turtle Rock Road area (18 Turtle Rock Community septic system (36 homes). $576,000 4.7 – 11.3 MEDIUM Road to southern end of Turtle Rock Road)

Cobbett’s Pond Watershed CPWPO Septic System Maintenance Program NA 13.8 – 20.7 NA HIGH

Fertilizer $8-10K Cobbett’s Pond Watershed Fertilizer reduction program. 11.7 – 23.3 0.3 – 0.8 HIGH Reduction (1 year)

$4,228,700 (low) 70.2 (low) $30.9 (low) TOTALS: $4,283,500 (high) 136.7 (high) $61.0 (high)

1. Estimated ranges in cost are approximate and represent installed cost where applicable.

81 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

7. SUMMARY OF TECHNICAL AND FINANCIAL SUPPORT 7.1 Technical Support

Most of the phosphorus loading reduction measures described in Section 4.0 will require a moderate to high level of technical support. The required types of technical support include site topographic surveys, preparation of existing conditions base plans, and preparation of definitive site drawings by an Engineer that would be used for permitting, contractor bidding and construction. Stormwater improvement sites requiring low level of technical support would generally be appropriate for design-build construction using field manuals. A listing of the stormwater improvement sites according to estimated level of required technical support is as follows:

Level of Technical Support Required for Stormwater BMP Sites Low Moderate High Site 2: 6-8 Armstrong Rd. Site 4: Griffin Park Site 1: Castleton Parking Area Site 3: Sawtelle Rd. Site 5a: Farmer Road Site 9: Summer Street Area Site 6: 20-24 Turtle Rock Rd. Site 5b: Farmer Rd. /Horseshoe Rd. Site 12: Woodland Ridge Area Site 8: 74 Turtle Rock Rd. Site 10: 60-62 Horseshoe Rd. Site 15: Fossa Rd./Range Road Site 16: Hawley Rd. Site 11: 58 Horseshoe Rd. Site 13: 35 Cobbett’s Pond Road Site 14: Windham Town Beach

In addition to the technical support described above, construction of some of the projects described in Section 6 may require a Minimum Impact Wetlands Application to the NH DES Wetlands Bureau. Wetlands were not delineated as part of this project. As such, technical support from a New Hampshire certified wetland scientist would be required on sites where wetlands are present for wetland delineation and permitting support.

Improvements related to on-site wastewater management and the proposed community septic systems discussed in Section 6.2 will require a high degree of technical support from a wastewater engineering firm. Such support is expected to include a feasibility study with detailed investigations and recommendations on siting options and costing for the proposed community systems. Detailed engineering plans for the systems would then be required.

Other types of technical support that may be required for the required for the measures discussed in Section 6 include graphic design and printing support for public outreach and educational materials, septic system inspection services, and legal assistance for development of regulatory language for future municipal bylaws.

7.2 Financial Support

Site improvements and management recommendations described in Section 6 will require funding to install and complete. Likely sources of funding include, but are not limited to, CPIA dues and Cobbett’s Pond Watershed District funding, Section 319 grant funds and NHDES Small Outreach and Education Grants. Alternative funding may be in the form of donated labor from the Town of Windham Highway Department, CPIA volunteers and local contractors. Brief descriptions of potential grant funding sources are provided below:

82 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

Section 319 Grant Funding: Funds for NH DES Watershed Assistance and Restoration Grants are appropriated through the U.S. Environmental Protection Agency under Section 319 of the Clean Water Act (CWA). Two thirds of the annual funds are available for restoration projects that address impaired waters and implement watershed based plans designed to achieve water quality standards. A project eligible for funds must plan or implement measures that prevent, control, or abate no-point source (NPS) pollution. These projects should: (1) restore or maintain the chemical, physical, and biological integrity of New Hampshire's waters; (2) be directed at encouraging, requiring, or achieving implementation of BMPs to address water quality impacts from land-use; (3) be feasible, practical and cost effective; and (4) provide an informational, educational, and/or technical transfer component. The project must include an appropriate method for verifying project success with respect to the project performance targets, with an emphasis on demonstrated environmental improvement.

Nonprofit organizations registered with the N.H. Secretary of State and governmental subdivisions including municipalities, regional planning commissions, non-profit organizations, county conservation districts, state agencies, watershed associations, and water suppliers are eligible to receive these grants. More information on the NH DES Watershed Assistance and Restoration Grants can be found at: http://www.des.state.nh.us/wmb/was/grants.htm.

Small Outreach and Education Grant: The NHDES provides funding to promote educational and outreach components of water quality improvement projects. This program provides small grants of $200 to $2,000 for outreach and education projects relating to NPS issues that target appropriate audiences with diverse NPS water quality related messages. These small grants are available year round on an ongoing basis, which allows applicants to move forward with outreach and education projects without having to wait for annual application deadlines. The NH DES Watershed Assistance Section administers the grant program using $20,000 each year from the U.S. EPA under Section 319 of the CWA. More information on the Small Outreach and Education Grant can be found at: http://www.des.state.nh.us/wmb/was/grants.htm.

83 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

8. PUBLIC INFORMATION AND EDUCATION Public information and education will be used to enhance public understanding of the phosphorus loading reduction projects. Public awareness encourages the use of storm water improvements and other measures throughout a watershed. Public information and education about the BMPs implemented in the watershed are provided via a project website (listed below) and informational brochure. State grants are available, as described above, to assist with future public information and education efforts. • Project Website: A project web site is available to provide the public with access to all project-related documents and reports. The website is a convenient method for reviewing and commenting on this watershed management plan and other project deliverables. The project website can be accessed at: http://projects.geosyntec.com/BW0131

• Brochure: In cooperation with the CPIA, Geosyntec developed an educational brochure specific to the Cobbett’s Pond watershed and potential improvements and practices to reduce phosphorus loading to the lake. A copy of the brochure developed through this project is available from the CPIA.

• Field Guide to the Aquatic Plants of Cobbetts’s Pond: Geosyntec developed a field guide to the aquatic plants in Cobbett’s Pond based on the results of the July 2009 aquatic vegetation survey conducted as part of this project. The field guide can be downloaded at: www.cobbettspond.org.

• Public Education Workshops: Geosyntec developed a series of four public education presentations and workshops to present the findings of this watershed management plan to the CPIA members, the Town of Windham and other watershed stakeholders. In addition to project-specific presentations presentations, Geosyntec also provided a workshop on “Lakeshore Landscaping”. This workshop provided information on the siting, design and installation of LID landscaping techniques for residential properties. LID techniques presented included raingardens/bioretention, porous pavements, vegetated buffers, and other techniques focused on promoting infiltration and the use of native vegetation to reduce phosphorus loading in lake watersheds. Slides of the presentations and workshops can be viewed at the project website referenced above.

84 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

9. SCHEDULE AND INTERIM MILESTONES The improvements recommended for Cobbett’s Pond and its watershed are ranked in order of priority as described in Section 5 of this report. A proposed schedule and associated interim milestones for these improvements are provided below.

85 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

Figure 23. Cobbett’s Pond Watershed Restoration Plan - Implementation Schedule and Interim Milestones

TASKS 2010 2011 2012 2013 Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Complete Draft and final Watershed-Based Plan ●

Updates to Project Website

Distribute Educational Brochures and other ● Educational Materials Select Priority Sites for Final BMP Design Prepare Priority BMP Site Final Designs /Permitting M Construct Priority BMP Sites 1 Prepare grant applications for final design/construction of additional BMP sites Obtain grant funds for final design/construction of ● ● additional BMP sites

Prepare additional BMP Site Final Designs /Permitting

Construct additional BMPs

CPWPO Septic System Maintenance Program (including documentation)

Fertilizer Reduction Program

Conduct VLAP Monitoring to evaluate P concentration and algae trends

10. EVALUATION CRITERIA AND MONITORING As discussed in Section 4, this watershed management plan recommends targeting an in-lake total phosphorus (TP) concentration for Cobbett’s Pond of 12 µg/L. To achieve this TP concentration, the Vollenweider equation in Section 5 predicts that the annual phosphorus load to the lake must be reduced by an estimated 145 lb/year. Section 6 of this report describes management measures that may be implemented to achieve this targeted phosphorus load reduction. Geosyntec recommends the following monitoring and evaluation criteria to determine the effectiveness of these proposed measures in reducing in- lake phosphorus concentrations and improving the water quality of Cobbett’s Pond. • Phosphorus Monitoring: The CPIA should continue monitoring in-lake phosphorus concentrations through the NH-VLAP program. In-lake phosphorus measurements will provide the most direct means of evaluating the effects of measures which have been implemented specifically to reduce phosphorus loading. As discussed in Section 4.4, the in-lake phosphorus concentrations predicted by the Vollenweider equation are based on an assumption that the lake is uniformly mixed. As such, the results of epilimnetic phosphorus monitoring during the summer (when the lake is stratified) are likely to understate the phosphorus levels that would be measured if the lake was uniformly mixed. However, regular monitoring of phosphorus levels from a profile (samples from the epilimnion, metalimnion and hypolimnion) at the North Deep Spot and South Deep spot monitoring locations will provide useful data on phosphorus concentration trends in response to implementation of the measures recommended in Section 6. • Algae Monitoring: In recent years, an increase in the reported incidence of nuisance blue-green blooms has been one of the most notable and visible symptoms of nutrient enrichment and declining water quality in Cobbett’s Pond. Continued monitoring of the abundance and composition of the lake’s algal community will provide a useful metric for understanding water quality trends in response to implementation of the measures recommended in Section 6. • Public Outreach, Education and Land Use Activities: In addition to the monitoring efforts described above, the effectiveness of recommended measures related to public outreach and land use activities can be evaluated with several simple metrics, including: ¾ Quantify the number of public education brochures that are distributed to watershed residents; ¾ Quantify the number of homes involved annually in the CPWPO septic system maintenance program, including the number of septic system inspections and pump-outs conducted, the number of septic system required to perform more frequent inspections, etc. ¾ Quantify the number of homes involved in the proposed fertilizer reduction program, including information on specific program elements such as the quantity of no-phosphorus fertilizer applied within the watershed. ¾ Quantify other watershed improvements initiated by homeowners as a result of outreach and education efforts, such as installation of residential raingardens and other LID practices.

87 Cobbett’s Pond Watershed Restoration Plan FINAL DRAFT: July 6, 2010

11. REFERENCES

Chapra, S. C. 1997. Surface Water Quality Modeling. WCB McGraw-Hill, Boston, MA.

Brett, M. T., Benjamin M. M. 2008. A review and reassessment of lake phosphorus retention and the nutrient loading concept. Freshwater Biology 53:194–211.

Burack, T. S., M. J. Walls, H. Stewart. 2008. New Hampshire Stormwater Manual, Volume 1: Stormwater and Antidegradation. New Hampshire Department of Environmental Services.

Caraco, D. and T. Brown. 2001. Crafting an Accurate Phosphorus Budget for Your Lake. Urban Lake Management, Watershed Protection Techniques 3(4): 782-790.

Carlson, R. 1977. A Trophic State Index for Lakes. Limnol. and Oceanogr. 22:261-369 Mifflin Co., NY.

Cohen, A. J., A. D. Randall. Mean annual runoff, precipitation, and evapotranspiration in the glaciated northeastern United States, 1951-80. USGS Open-File Report 96-395. Map.

Federal Highway Administration. 2005. Hydraulic Design of Highway Culverts.

Larsen, D. P., Mercier, K. W. 1976. “Limnology of Shagawa Lake, Minnesote, Prior to Reduction of Phosphorus Loading.” Hydrobiologia 50(2): 177-189.

Steuer, J., W. Selbig, N. Hornewer and J. Prey. 1997. Sources of contamination in an urban basin in Marquette, Michigan and an analysis of concentrations, loads, and data quality. USGS Water Resources Investigations Report 97-4242. Wisconsin DNR and EPA.

Vollenweider, R.A. 1975. Input-output models with special references to the phosphorus loading concept in limnology. Schweiz. Z. Hydrol. 37:53-62.

Appendix A: Water Quality and Flow Monitoring Data 289 Great Road Suite 105 Acton, MA 01720 978-263-9588 www.geosyntec.com

To: Mr. Derek Monson, CPIA From: Robert Hartzel, Geosyntec Consultants Date: 8/3/2009 Re: June 2009 Cobbett’s Pond Monitoring Results

Geosyntec Consultants is conducting on-going water quantity and quality monitoring as part of a Watershed Restoration Plan for Cobbett’s Pond in Windham, NH. Water quality data is being collected monthly at selected in-pond and tributary locations, along with three additional collections at tributary locations during precipitation events. Water quantity is being measured at tributary locations and a rain gage is deployed in the watershed to record precipitation amounts.

The following tasks pertaining to water quality and flow monitoring were completed during the month of June:

Retrieval of Flow/Precipitation Data (6/18/2009): Water level data were collected at all of the tributary locations except for Dinsmore Brook. Precipitation and weather data were collected from the rain gage and pressure/temperature sensor on the NH state owned property along Armstrong Road. This period of data covers 5/27/2009 to 6/18/2009.

Installation of Flow Monitoring Equipment (6/20/2009): A plywood V-notch weir and water level logger were installed along Dinsmore Brook between Rt. 111A and Heron Cove Road.

Monthly Dry-weather Water Quality Sampling (6/25/2009): A dry weather sampling event was conducted at the deep spot and tributary locations. We are considering this event to be “dry weather,” although it should be noted that 0.55 inches of precipitation fell over the previous three days (0.3 inches of which fell the previous day).

Figure 1 and Table 1 below show the monitoring locations and their identification codes. Figure 2 shows the results of water quantity monitoring at the tributary locations, along with a plot of precipitation intensity. Figure 3 presents the results of in-situ water quality profiles at the in-lake deep spot monitoring locations, and Tables 3 and 4 provide further water quality monitoring results. A brief description of the various parameters measured in this study is provided at the end of this document.

Figure 1. Sampling Location map with NHVLAP IDs.

Table 1. Sampling Locations and corresponding NHVLAP Station IDs.

Sampling Location VLAP STATION ID South Deep Spot COBWINSD North Deep Spot COBWINND Fossa Road Inlet COBWINFR Turtle Rock Road Inlet COBWINMS Bella Vista Road Inlet COBWINBV Castleton Brook Inlet COBWINI Dinsmore Brook Inlet COBWINB Connies Brook Inlet COBWINCB

______8/18/2009 2

Fossa Road Flow Temperature

1.0 18 0.8 16 0.6 14

0.4 12 (oC) (cfs)

Discharge 0.2 10 Temperature 0.0 8 5/27 6/3 6/10 6/17

Turtle Rock Flow Temperature

2 18

1.5 16 14 1

12 (oC) 0.5

(cfs) 10 Temperature Discharge 0 8 5/27 6/3 6/10 6/17

Bella Vista Flow Temperature

1.6 20

1.2 18 16 0.8 (oC)

(cfs) 14

Discharge 0.4 12 Temperature Temperature 0 10 5/27 6/3 6/10 6/17

Castleton Brook Flow Temperature

35 18

30 16 re

arge 25 14 atu

20 12 (oC) (cfs)

Disch 15 10 Temper 10 8 5/27 6/3 6/10 6/17

Connie's Brook Flow Temperature

4 18

3 16 14 2

12 (oC) (cfs) 1 Discharge 10 Temperature Temperature 0 8 5/27 6/3 6/10 6/17

Precipitation Gage (Armstrong Road) Rainfall

2.5 2.0 1.5 1.0 0.5

Rainfall (in/hr) 0.0 5/27 6/3 6/10 6/17

Figure 2. Discharge and Temperature monitoring for Cobbett’s Pond Tributaries (5/27/2009-6/18/2009)

______8/18/2009 3

North Deep Spot North Deep Spot

Dissolved Oxygen Temperature pH Conductivity

Temperature (oC) Conductivity (mS/cm) 01 02 03 0 0.3 0.35 0.4 0.45 0.5 0 0 0 0 2 2 2 2 4 4 4 4 6 6 6 6 8 8 8 8 Depth (m) (m) Depth Depth (m) 10 10 10 10 12 12 12 12 14 14 14 14 0 5 10 15 6.4 6.8 7.2 7.6 DO (mg/L) pH

(North Deep Spot Secchi Disk Transparency = 12.5’)

South Deep Spot South Deep Spot

Dissolved Oxygen Temperature pH Conductivity Conductivity (mS/cm) Temperature (oC) 0.3 0.35 0.4 0.45 0.5 01 02 03 0 0 0 0 0 2 2 2 2 4 4 4 4 6 6 6 6 8 8 8 8

Depth (m) 10 10 Depth (m) 10 10 12 12 12 12 14 14 14 14 0 5 10 15 6.4 6.8 7.2 7.6 8 DO (mg/L) pH

(South Deep Spot Secchi Disk Transparency = 13.0’)

Figure 3. Deep Spot location water quality profiles (6/25/2009)

______8/18/2009 4

Table 2. Dry Weather Tributary in-situ water quality results (6/25/2009). Temperature Conductivity DO pH Turbidity Site (oC) (mS/cm) (mg/L) (NTU) COBWINFR 14.3 0.623 9.6 7.1 0.1 COBWINMS 15.5 0.403 9.5 7.4 2.3 COBWINBV 16.1 0.669 9.2 7.3 1.5 COBWINI 15.2 0.711 8.1 7.0 1.3 COBWINDB 14.1 1.007 9.0 7.0 3.7 COBWINCB 15.7 0.417 9.3 7.3 ND

Table 3. Dry Weather Total Phosphorus / Chlorophyll-a sampling results (6/25/2009). Depth TP Chl-a Site (m) (mg/L) (ug/L) COBWINSD 13 0.012 - COBWINSD 7 0.015 - COBWINSD 0 0.015 - COBWINSD COMP - 4.3 COBWINND 13 0.015 - COBWINND 7 0.024 - COBWINND 0 0.009 - COBWINND COMP - 5.2 COBWINCB 0 0.014 - COBWINDB 0 0.013 - COBWINI 0 0.015 - COBWINI DUP 0.013 - COBWINBV 0 0.043 - COBWINMS 0 0.012 - COBWINFR 0 0.021 - COBWINND BLANK ND ND

______8/18/2009 5 289 Great Road Suite 105 Acton, MA 01720 978-263-9588 www.geosyntec.com

To: Mr. Derek Monson, CPIA From: Robert Hartzel, Geosyntec Consultants Date: 8/18/2009 Re: July 2009 Cobbett’s Pond Monitoring Results

The following tasks pertaining to water quality and flow monitoring were completed during the month of July:

Retrieval of Discharge/Precipitation Data (7/27/2009): Water level data were collected at all of the tributary locations except for Connie’s Brook (a water level probe was not collecting data properly). Precipitation and weather data were collected from the rain gage and pressure/temperature sensor on the NH state owned property along Armstrong Road. This period of data covers 6/18/2009 to 7/27/2009.

Monthly Dry-weather Water Quality Sampling (7/27/2009): A dry weather sampling event was conducted at the deep spot and tributary locations.

Figure 1. Sampling Location map with NHVLAP IDs.

Table 1. Sampling Locations and corresponding NHVLAP Station IDs.

______8/18/2009 2

Fossa Road Flow Temperature

2.0 22

1.5 20 18 1.0

16 (oC) (cfs)

Discharge 0.5 14 Temperature 0.0 12 6/18 6/25 7/2 7/9 7/16 7/23

Turtle Rock Flow Temperature

2 20

1.5 18

1 16 (oC) (oC) 0.5 14 (cfs) Temperature Discharge 0 12 6/18 6/25 7/2 7/9 7/16 7/23

Bella Vista Flow Temperature

2.4 22 2 20 1.6 18 1.2 16 (oC) (cfs) 0.8 14 Discharge

0.4 12 Temperature 0 10 6/18 6/25 7/2 7/9 7/16 7/23

Castleton Brook Flow Temperature

50 20

40 18

30 16 (oC) (cfs) 20 14 Discharge Temperature 10 12 6/18 6/25 7/2 7/9 7/16 7/23

Dinsmore Brook Flow Temperature

1 20 0.8 18 0.6 16

0.4 (oC) (cfs)

Discharge 0.2 14 Temperature 0 12 6/18 6/25 7/2 7/9 7/16 7/23

Precipitation Gage (Armstrong Road) Rainfall

4.0

3.0

2.0

1.0

Rainfall (in/hr) 0.0 6/18 6/25 7/2 7/9 7/16 7/23

Figure 2. Discharge and Temperature monitoring for Cobbett’s Pond Tributaries (6/18/2009-7/27/2009)

______8/18/2009 3

North Deep Spot North Deep Spot

Dissolved Oxygen Temperature pH Conductivity

Temperature (oC) Conductivity (mS/cm) 0 102 03 0 0.2 0.25 0.3 0.35 0 0 0 0 2 2 2 2 4 4 4 4 6 6 6 6 8 8 8 8 Depth (m) Depth (m) (m) Depth 10 10 10 10 12 12 12 12 14 14 14 14 0 51 01 5 6.4 6.8 7.2 7.6 DO (mg/L) pH

(North Deep Spot Secchi Disk Transparency = 9.5’)

South Deep Spot South Deep Spot

Dissolved Oxygen Temperature pH Conductivity Conductivity (mS/cm) Temperature (oC) 0.2 0.25 0.3 0 102 03 0 0 0 0 0 2 2 2 2 4 4 4 4 6 6 6 6 8 8 8 8

Depth (m) 10 10

Depth (m) 10 10 12 12 12 12 14 14 14 14 0 51 01 5 6.4 6.8 7.2 7.6 8 DO (mg/L) pH

(South Deep Spot Secchi Disk Transparency = 9.5’)

Figure 3. Deep Spot location water quality profiles (7/27/2009)

______8/18/2009 4

Table 2. Dry Weather Tributary in-situ water quality results (7/27/2009). Temperature Conductivity DO pH Turbidity Site (oC) (mS/cm) (mg/L) (NTU) COBWINFR 19.2 0.400 9.2 7.2 ND COBWINMS 20.2 0.369 8.9 7.3 ND COBWINBV 19.9 0.372 8.6 6.8 ND COBWINI 18.7 0.476 7.0 6.8 ND COBWINDB 17.5 0.577 8.1 6.9 3.7 COBWINCB 19.7 0.354 8.8 7.2 ND

Table 3. Dry Weather Total Phosphorus sampling results (7/27/2009). Depth TP Site (m) (mg/L) COBWINSD 13 0.021 COBWINSD 7 0.022 COBWINSD 0 0.012 COBWINND 13 0.034 COBWINND 7 0.013 COBWINND 0 0.009 COBWINFR 0 0.016 COBWINMS 0 0.015 COBWINBV 0 0.053 COBWINBV DUP 0.055 COBWINI 0 0.027 COBWINDB 0 0.049 COBWINCB 0 0.025 COBWINND BLANK 0.012

______8/18/2009 5 289 Great Road Suite 105 Acton, MA 01720 978-263-9588 www.geosyntec.com

To: Mr. Derek Monson, CPIA From: Robert Hartzel, Geosyntec Consultants Date: 12/21/2009 Re: August 2009 Cobbett’s Pond Monitoring Results

The following tasks pertaining to water quality and flow monitoring were completed during the month of August:

Retrieval of Discharge/Precipitation Data (8/20/2009): Water level data were collected at all of the tributary locations. Precipitation and weather data were collected from the rain gage and pressure/temperature sensor on the NH state owned property along Armstrong Road. This period of data covers 7/27/2009 to 8/20/2009.

Monthly Dry-weather Water Quality Sampling (8/20/2009): A dry weather sampling event was conducted at the deep spot and tributary locations.

Figure 1 and Table 1 below show the monitoring locations and their identification codes. Figure 2 shows the results of water quantity monitoring at the tributary locations, along with a plot of precipitation intensity. Figure 3 presents the results of in-situ water quality profiles at the in-lake deep spot monitoring locations, and Tables 2 and 3 provide further water quality monitoring results. A brief description of the various parameters measured in this study is provided at the end of this document.

Figure 1. Sampling Location map with NHVLAP IDs.

Table 1. Sampling Locations and corresponding NHVLAP Station IDs.

______12/21/2009 2

Figure 2. Discharge and Temperature monitoring for Cobbett’s Pond Tributaries (7/27/2009-8/20/2009)

______12/21/2009 3

North Deep Spot North Deep Spot

Dissolved Oxygen Temperature pH Conductivity Temperature (oC) Conductivity (mS/cm) 0 10 20 30 0.2 0.3 0.4 0.5 0.6 0 0 0 0 2 2 2 2 4 4 4 4 6 6 6 6 8 8 8 8 Depth (m) 10 10 Depth (m) 10 10 12 12 12 12 14 14 14 14 0 5 10 15 6.4 6.8 7.2 7.6 DO (mg/L) pH

(North Deep Spot Secchi Disk Transparency = 10.0’)

South Deep Spot South Deep Spot

Dissolved Oxygen Temperature pH Conductivity Conductivity (mS/cm) Temperature (oC) 0.2 0.3 0.4 0.5 0 10 20 30 0 0 0 0 2 2 2 2 4 4 4 4 6 6 6 6 8 8 8 8 Depth (m)

Depth (m) 10 10 10 10 12 12 12 12 14 14 14 14 0 5 10 15 6 6.4 6.8 7.2 7.6 8 DO (mg/L) pH

(South Deep Spot Secchi Disk Transparency = 10.5’)

Figure 3. Deep Spot location water quality profiles (8/20/2009)

______12/21/2009 4

Table 2. Dry Weather Tributary in-situ water quality results (8/20/2009). Temperature Conduct i vty i DO pH Turbidity Site (oC) (mS/cm) (mg/L) (NTU) COBWINFR 17.3 0.707 8.8 7.1 ND COBWINMS 21.2 0.555 8.8 7.5 ND COBWINBV* * * * * COBWINI 16.8 0.907 6.9 6.9 ND COBWINDB 18.7 0.847 7.4 7.1 ND COBWINCB 20.7 0.735 9.9 7.4 ND *At the time of sampling, stream COBWINBV was dry.

Table 3. Dry Weather Total Phosphorus and Chlorophyll-a sampling results (8/20/2009). Dept h TP Chlor-a Site (m) (mg/L) (ug/L) COBWINSD COMPOSITE 5.67 COBWINSD 13.00 0.03 - COBWINSD 7.00 0.02 - COBWINSD 0.00 0.02 - COBWINND COMPOSITE 6.14 COBWINND 13.00 0.11 - COBWINND 7.00 0.02 - COBWINND 0.00 0.02 - COBWINCB 0.00 0.06 - COBWINDB 0.00 0.05 - COBWINDB DUP 0.06 - COBWINI 0.00 0.06 - COBWINBV 0.00 - - COBWINMS 0.00 0.03 - COBWINFR 0.00 0.02 - COBWINND BLANK ND -

______12/21/2009 5 289 Great Road Suite 105 Acton, MA 01720 978-263-9588 www.geosyntec.com

To: Mr. Derek Monson, CPIA From: Robert Hartzel, Geosyntec Consultants Date: 12/21/2009 Re: September 2009 Cobbett’s Pond Monitoring Results

The following tasks pertaining to water quality and flow monitoring were completed during the month of September:

Wet-weather Sampling Event (8/29/2009): Tributary sampling was performed during a precipitation event. Water quality parameters were measured and total phosphorus samples were collected.

Retrieval of Discharge/Precipitation Data (9/17/2009): Water level data were collected at all of the tributary locations except for Fossa Road Inlet (the water level probe was not collecting data properly). Precipitation and weather data were collected from the rain gage and pressure/temperature sensor on the NH state owned property along Armstrong Road. This period of data covers 8/20/2009 to 9/17/2009.

Monthly Dry-weather Water Quality Sampling (9/17/2009): A dry weather sampling event was conducted at the deep spot and tributary locations.

Figure 1 and Table 1 below show the monitoring locations and their identification codes. Figure 2 shows the results of water quantity monitoring at the tributary locations, along with a plot of precipitation intensity. Figure 3 presents the results of in-situ water quality profiles at the in-lake deep spot monitoring locations. Table 2 presents the results of the wet-weather sampling, and Tables 3 and 4 provide further water quality monitoring results. A brief description of the various parameters measured in this study is provided at the end of this document.

Figure 1. Sampling Location map with NHVLAP IDs.

Table 1. Sampling Locations and corresponding NHVLAP Station IDs.

______12/21/2009 2

Figure 2. Discharge and Temperature monitoring for Cobbett’s Pond Tributaries (8/20/2009-9/17/2009)

______12/21/2009 3

North Deep Spot North Deep Spot

Dissolved Oxygen Temperature pH Conductivity Temperature (oC) Conductivity (mS/cm) 0 102 03 0 0.2 0.22 0.24 0.26 0.28 0 0 0 0 2 2 2 2 4 4 4 4 6 6 6 6 8 8 8 8 Depth (m) 10 10 (m) Depth 10 10 12 12 12 12 14 14 14 14 05 1 06.4 6.8 7.2 7.6 DO (mg/L) pH

(North Deep Spot Secchi Disk Transparency = 11.0’)

South Deep Spot South Deep Spot

Dissolved Oxygen Temperature pH Conductivity Conductivity (mS/cm) Temperature (oC) 0.1 0.2 0.3 0 10 20 30 0 0 0 0 2 2 2 2 4 4 4 4 6 6 6 6 8 8 8 8 Depth (m) (m) Depth

Depth (m) (m) Depth 10 10 10 10 12 12 12 12 14 14 14 14 0 51 06.4 6.8 7.2 7.6 8 DO (mg/L) pH

(South Deep Spot Secchi Disk Transparency = 11.5’)

Figure 3. Deep Spot location water quality profiles (9/17/2009)

______12/21/2009 4

Table 2. Wet Weather Tributary in-situ water quality and Total Phosphorus results (8/29/2009).

Temperature Conduct i vty i DO pH Turbidity Total Phosphorus Site (oC) (mS/cm) (mg/L) (NTU) (mg/L) COBWINFR 15.9 0.097 9.0 7.9 3.9 0.054 COBWINMS 15.8 0.183 9.7 7.6 8.7 0.052 COBWINBV 16.5 0.202 8.0 7.3 2.7 0.058 COBWINI 16.0 0.240 8.3 7.2 30 0.051 COBWINDB 15.7 0.307 8.2 7.0 11.3 0.069 COBWINCB 15.2 0.404 9.4 7.2 11.5 0.075

Table 3. Dry Weather Tributary in-situ water quality results (9/17/2009). Temperature Conduct i vty i DO pH Turbidity Site (oC) (mS/cm) (mg/L) (NTU) COBWINFR* * * * * COBWINMS* * * * * COBWINBV* * * * * COBWINI 12.33 0.603 5.84 6.84 5.9 COBWINDB 12.72 0.579 10.25 7.4 28.2 COBWINCB* * * * * *At the time of sampling, streams COBWINFR, COBWINMS, COBWINBV, AND COBWINCB were dry.

Table 4. Dry Weather Total Phosphorus and Chlorophyll-a sampling results (9/17/2009). TP Chlor-a Site Depth (mg/L) (ug/L) COBWINSD COMPOSITE - 3.73 COBWINSD 13 0.029 - COBWINSD 7 0.018 - COBWINSD 0 0.015 - COBWINND COMPOSITE - 4.36 COBWINND 13 0.130 - COBWINND 7 0.023 - COBWINND 0 0.014 - COBWINDB 0 0.016 - COBWINI 0 0.019 - COBWINCB 0 - - COBWINDB DUP - - COBWINBV 0 - - COBWINMS 0 - - COBWINFR 0 - - COBWINND BLANK - -

______12/21/2009 5 289 Great Road Suite 105 Acton, MA 01720 978-263-9588 www.geosyntec.com

To: Mr. Derek Monson, CPIA From: Robert Hartzel, Geosyntec Consultants Date: 12/21/2009 Re: October 2009 Cobbett’s Pond Monitoring Results

The following tasks pertaining to water quality and flow monitoring were completed during the month of October:

Monthly Dry-weather Water Quality Sampling (10/23/2009): A dry weather sampling event was conducted at the deep spot and tributary locations.

Wet--weather Water Quality Sampling (10/24/2009): A wet weather sampling event was conducted at the tributary locations. In-situ water quality parameters were measured and total phosphorus samples were collected.

Retrieval of Discharge/Precipitation Data (10/24/2009): Water level data were collected at all of the tributary locations. Due to memory limitations, the water quantity data since the last collection date on 9/17/09 is only partial. Precipitation data were collected from local weather stations (the gage at Armstrong Road lost power during this time period). This period of data covers 10/13/2009 to 10/24/2009.

Figure 1 and Table 1 below show the monitoring locations and their identification codes. Figure 2 shows the results of water quantity monitoring at the tributary locations, along with a plot of precipitation intensity. Figure 3 presents the results of in-situ water quality profiles at the in-lake deep spot monitoring locations. Table 2 presents the results of the wet-weather sampling, and Tables 3 and 4 provide further water quality monitoring results. A brief description of the various parameters measured in this study is provided at the end of this document.

Figure 1. Sampling Location map with NHVLAP IDs.

Table 1. Sampling Locations and corresponding NHVLAP Station IDs.

______12/21/2009 2

Figure 2. Discharge and Temperature monitoring for Cobbett’s Pond Tributaries (10/13/2009-10/24/2009)

______12/21/2009 3

North Deep Spot North Deep Spot

Dissolved Oxygen Temperature pH Conductivity Temperature (oC) Conductivity (mS/cm) 0 5 10 15 0.1 0.2 0.3 0 0 0 0 2 2 2 2 4 4 4 4 6 6 6 6 8 8 8 8 Depth (m) 10 10 Depth (m) 10 10 12 12 12 12 14 14 14 14 0 5 10 15 6.4 6.8 7.2 7.6 DO (mg/L) pH

(North Deep Spot Secchi Disk Transparency = 8.0’)

South Deep Spot South Deep Spot

Dissolved Oxygen Temperature pH Conductivity Conductivity (mS/cm) Temperature (oC) 0.1 0.2 0.3 0 5 10 15 0 0 0 0 2 2 2 2 4 4 4 4 6 6 6 6 8 8 8 8 Depth (m)

Depth (m) 10 10 10 10 12 12 12 12 14 14 14 14 0 5 10 15 6.4 6.8 7.2 7.6 DO (mg/L) pH

(South Deep Spot Secchi Disk Transparency = 7.0’)

Figure 3. Deep Spot location water quality profiles (8/20/2009)

______12/21/2009 4

Table 2. Wet Weather Tributary in-situ water quality and Total Phosphorus results (10/24/2009). Temperature Conduct i vty i DO pH Turbidity Total Phosphorus Site (oC) (mS/cm) (mg/L) (NTU) (mg/L) COBWINFR 9.8 0.132 9.9 6.6 7 0.071 COBWINMS 8.6 0.325 11.5 7.0 3 0.025 COBWINBV 9.3 0.310 10.7 7.0 68 0.058 COBWINI 8.8 0.298 10.5 7.8 4.7 0.020 COBWINDB 9.3 0.460 9.6 7.2 1.6 0.021 COBWINCB 8.2 0.315 11.1 7.3 1.7 0.016

Table 2. Dry Weather Tributary in-situ water quality results (10/23/2009). Temperature Conduct i vty i DO pH Turbidity Site (oC) (mS/cm) (mg/L) (NTU) COBWINFR 11.6 0.319 8.7 6.9 1.3 COBWINMS 8.1 0.341 11.2 7.2 5.8 COBWINBV 9.4 0.291 9.6 7.2 0.1 COBWINI 9.9 0.482 8.3 6.9 1.9 COBWINDB 9.5 0.560 9.9 7.0 3.3 COBWINCB 8.2 0.480 11.0 7.3 0.1

Table 3. Dry Weather Total Phosphorus and Chlorophyll-a sampling results (10/23/2009). TP Chlor-a Site Depth Date Event (mg/L) (ug/L) COBWINND COMPOSITE 10/30/2009 Dry - 2.78 COBWINND 13 10/23/2009 Dry 0.02 - COBWINND 7 10/23/2009 Dry 0.015 - COBWINND 0 10/23/2009 Dry 0.012 - COBWINND BLANK 10/23/2009 Dry - - COBWINSD COMPOSITE 10/30/2009 Dry - 3.27 COBWINSD 13 10/23/2009 Dry 0.023 - COBWINSD 7 10/23/2009 Dry 0.009 - COBWINSD 0 10/23/2009 Dry 0.031 - COBWINBV DUP 10/23/2009 Dry 0.012 - COBWINBV 0 10/23/2009 Dry 0.0093 - COBWINCB 0 10/23/2009 Dry 0.0099 - COBWINDB 0 10/23/2009 Dry 0.031 - COBWINFR 0 10/23/2009 Dry 0.057 - COBWINI 0 10/23/2009 Dry 0.014 - COBWINMS 0 10/23/2009 Dry 0.024 -

______12/21/2009 5

Appendix B: Stormwater Infrastructure Maps 1 93

111 2 3 4 111

111

28 6 8 10

7 9 11

13 15

0 750 1,500 3,000 12 COBBETT'S POND 93 Feet 14 16

COBBETT'S POND 18 STORMWATER 17 INFRASTRUCTURE

20 19 93 INDEX

21 7-A-417 5 12 7-A-29 7-A-409 68 7-A-30 7-A-412 66 2

10 7-A-416

12-A-700 6 7- Legend

7-A-415 A-31 15" 59 6 7-A-60 7-A-413 8 70 Catch Basin 7 7-A-605 4 6 603 7-A-32 Culvert/Inlet/Outlet 4 7-A-414 8" 12" 7-A- 5 72 7-A-33 Drainage Swale

7-A-34 7-A-604 7-A-601 74

15" 2 7-A-35 7-A-37 76 Stream 78 3 -A-602 82 7 Drainage Pipe

7-A-500 84 15" Pond 7-A-600 1 12-A-607 12" Wetland 12-A-606

-957- A-5 18" 81 Watershed Boundary

95   12-A-601   ð Pavement 12- 91 A-600 89 93

12-A-602 Assessor's Parcels (approx.)

12-A-500A 0 125 250 500 11- C-700 Feet

COBBETT'S POND 93 STORMWATER 93 INFRASTRUCTURE

11-C-500

3 11-C-300 MAP ID: 01

87 11-C-100

83 11-C-500 11-C-100 3 87

11-C-300

11-C-350 Legend

11-C-800 83 Catch Basin 11-C-125 Culvert/Inlet/Outlet 55 Drainage Swale 3 87 11-C-100 Stream 11-C-702

Drainage Pipe 77 79 Pond 75 11-C-170 11-C-155

11-C-180 Wetland 71 11-C-190 F 86 2 Watershed Boundary 86 17-J-80 17-J-90 12" RCP

11-C-701 17-J-90C 61 11-C-425 12" RCP 82 Pavement 1/3 17-J-126 1 17-J-96 4 80 3 88 17-J-90A Assessor's Parcels (approx.) 17-J-85

17-J-98 17-J-1 17-J-125 8" HDPE 17-J-176 12" 5 17-J-90 4/6 RCP 5 24" RCP 7 3 12 1 0 1 17-J-113 7-J-107 8 17-J-124 1 111 17-J-175 17-J-1 17-J-120 8 4 -119 10 17-J-121 16 18 6 23 17-J 5 14 0 125 250 500 17-J-103 9 17-J-141 17-J-104 2 17-J-117 Feet 111 6 11 6 17-J-150 4 21 13 2 19 15 23/25 17 4 18 17-J-149 17-J-131 16 8 17-J-132 8 14 17-J-133 12 COBBETT'S POND 9/12 10 1 10 -7 J-6 STORMWATER 17-J-148 1 16-D-200 17 1 3 7- 17-J-310 -J-1 11 5 J INFRASTRUCTURE 60 17-J-145 - 1 16-D-1 4 3 9 7 13 8 12 7 17- J-137 17 14 15 MAP ID: 02 19 COBBETT'S POND 11 14 16-D-6 23 21 17-J-300 13 16 16-D-5

17-J-143A

16 1 6 16-D-12 - 23/28 16- D-7 D - 8 20 17 12-A-500A

11-C-100 12-A-500 83 21 12-A-560 Legend

11-C-12 119

11-C-6 Catch Basin 1 107 12-K-1 5 Culvert/Inlet/Outlet 3 11-C-1 11-C-5 Drainage Swale

-13 3 11-C-2 91 11-C Stream

Drainage Pipe

12-A 17-G-2 24" RCP 117 -537 94 Pond 12-A-550

-J- 115 Wetland 1786 80 121 98 12-A-53 Watershed Boundary 17-G-1 88 17-J-85 5 17-J-70 Pavement 111

90 Assessor's Parcels (approx.)

92B

17-J-50 0 130 260 520 Feet

92 17-G-6

17-J-1 102 93 56 COBBETT'S POND STORMWATER

COBBETT'S POND 60 H

-- INFRASTRUCTURE

1 1

17-M-1735 33 17-M-16

 1 7-H-20 17-M-15 64 MAP ID: 03 31 17-J-2

19 21 ðð 17-M-23 17 37 17-M-24 13 8 17- 6 M-26 29 17-I-2 17-G-20 17-M- 17-M-1327 82 15 4 27 17-M-12 17-M-3011 2 1 23 25 21 12-A-500

12-A-510 12-A-501 9 5 Legend Catch Basin

12-A-520 Culvert/Inlet/Outlet

12-A-560 11 7 Drainage Swale 119 2-A-515 1

111 Stream

Drainage Pipe 42 12-A-503 12-A-525 12-A-537 48 Pond 44 508 117 18-L-450 -A- Wetland 12-A-536 12 43 121 12-A-530 Watershed Boundary

34 50 12-A-535 123 24" RCP Pavement

12-A-5 15" RCP 12-A-532 Assessor's Parcels (approx.) 125

18-L-400 111 49 111 0 130 260 520 Feet ððð  54 17-H-1

ð 57

17-H-2 18-L-302 56 59 COBBETT'S POND

61 STORMWATER

18-L-300 INFRASTRUCTURE 17-H-10

60 63 18-L-310 83

7-2017 ð MAP ID: 04 -H

64 18-L-201 67

ðð 16-D-6 13 16 16-D-7 14

16-D-8 60 16-D-200 17 20 19 16-D-9 16-D-400 16-D-12 23/28 21 16-D-11 Legend Catch Basin 25

16-D-14 Culvert/Inlet/Outlet

16-D-1527 16-F-1030 16-D-200 16-D-16 Drainage Swale

60 29 16-P-191A 16-D-17 Stream

31 29 35 Drainage Pipe

16-D-18 27 16-R-600 16-P-560 43 45 47 24 23 41 40 Pond 16-P-191 31 24 16-P-190 39 38

16-P-192B 22 20 20 43 36 Wetland 34 16 18 25 18 41 21 30 32 Watershed Boundary 16-P-200 17 16 39 16-P-19411 37 22 29 11 13 16-P-199 14 35 28 16-P-193 12 33 Pavement 10 26 39 9 24 17-L-130 15 16-R-183B29 6 31 22 7 16-R-183 25 Assessor's Parcels (approx.) 16-P-1002 5 4 20 9 18 23 16-R-18 37 16-P-500 16-R- 27 16-P-197 1 3 13 2 18 310 4 2A/13 16-R-185 19 21 16 35 7 16-P-1004 15 COBBETT'S POND 16-R-185B 17 33 70 16-R-490 16-Q-300 47 0 16 11 14 0 130 260 520 5 8 31 16-P-3 30 16-R-780 Feet 16-P-353 6-P-46 9 7 1 14 16-Q-185D 17 59 16-R-186B 9 10 -L-86A 29 17-L-100 16-P-580 1 5 7 11 7-L-90 17 22 8 -L-8 6 27 10 5 6 16-Q-205A 13 6 3 5 20 1 8 3 16-Q-1864 17 7-L-9018 2 9 15 -L-859 4 1 7-L- B COBBETT'S POND 6 16-Q-205 1 17- 87 1 16-Q-207 7-L- 61 1 L-88 STORMWATER 1 -P-203B 2 17 84 17-L-8 8 4 16 16 3 11 7 6-P-470 5 9 14 INFRASTRUCTURE 1 2 1 6 48 26 19 16-Q-208 17-L-823 12 17-L- E- 2 4

CMP ð 50 " 18 " 46 16 16-E-25 89A -E- 16- 24 8 16-Q-213 16 16-Q-209 17-L-81 1

16- 16-Q-211B 4 Q- 16-Q-211A 22 17-l-80 16-E-11 16-E-20 214 24 22 MAP ID: 05 36 16-E 1 14 16-Q-210 6-Q-214A - 42 -22 6 10 17 l-81B 18 20 33 17-L-79 12" RCP 16-Q-211 26 16- 21 E-2850 17-L-78A 16-E-30 28 17 48 39 -L-214 16-E-33 30 17-L-78 16-E-13 16-E-21 32 13 16-E-12 25 46 15 16-E-31 17-L-77 34 17-L-215 16-E-51 44 9 17-L-76 35 5 14 16-D-7 20 16-D-8 16

16-D-10 16-D-10 17

16-D-9 19

20 21

Legend Catch Basin COBBETT'S POND Culvert/Inlet/Outlet Drainage Swale

17-I-112B Stream

32 Drainage Pipe 34 Pond

17-I-110 Wetland

29 Watershed Boundary 31 17-I-111 Pavement

Assessor's Parcels (approx.)

17-C-96A 11 9 17-C-104 17-C-103 17-I-20 33 550 17-C-103A 17-C-97 37 7 0 50 100 200 300 7 Feet 17-C-103B 35 17-C-200

5 17-I-500 17-C-94A 19

17-C-94 39 17-C-21 41 17-C-22 COBBETT'S POND

6" PVC "HDPE8" 3 10 17-C-10043 STORMWATER

17-C-105 17-C-105C 13 17-C-93 6 31 17-C-20 INFRASTRUCTURE 8 17-C-16

17-C-105A 17-C-111 17-C-23 17-C-101D 21 17-C-13 17-C-19 8" CPP 17-C-9928 30 4 11 17-C-9229 45 9 19

17-L-120 17-C-101 MAP ID: 06 17-C-101C 39 27 17-C-24 17 CPP 18" 2X

17-C-17 1 17-C-105B 47 26 2

17-C-25 17-L-130 17-C-106 7 12 37 5 25 3 17-C-106B 17-C-12 17-C-102A 17-C-102C 30 19/23 10 17-L-100 1 17-C-101B 6 17-C-18 17-C-6 71-L-91B35 17-C-5 8 17-C-26 2 4 33 17-L-140 23 3 1 17-L-120 30 10117 -101C1 17-C-14 21 39 17-C-92 -C- 7-C 45 17-C-19 17-C-24 17 17-C-17 27 47 9 19 26 1 2 17-C-25 12 17-L-130 17-C-106 7 37 3 5 17-C-106B 25 17-C-12 17-C-102C

17-C-102A

- 1 10 1 7-C 71-L-91B 17-C-18 8 17-C-6 1 4 0 COBBETT'S POND 17 1B - 33 35 C 6 17-L-91A 23 2 - 3 5 18" CPP 1 30 17-L-100 17-C-107 17-C-4

17-L-90A Legend 3 1 2 7- 24 -C- 7-C-107A 31 17 1 C-7 Catch Basin 17-C-27 4 21 17-C-107B 18/22 Culvert/Inlet/Outlet 17-L-910 29 Drainage Swale 17-L-86A 6

17-L-90 17-C-8 17-C-8 -C-1 CMP6" 11 17-L-110 19 20 Stream 20 17-L-86 17  ð 17 -C-110 22 27  Drainage Pipe 108 17-L-90B 17 Pond 17-L-85 17-L-86B - 18 I 9 - 400 Wetland 17-L-87 17 16 -L 19/23 -140 17-L-84 14 17-L-88 Watershed Boundary 7 17-L-87A

17-L-89 8 Pavement 12 5 17-L-83 6 17-L-89B Assessor's Parcels (approx.)

3 17-L-82 17-L-89A 4 20

0 50 100 200 300 17-L-81 17-L-89D 2 Feet

17-L-89C 1  ð

 24 17-l-80

22 17-l-81B 17-L-880 18 COBBETT'S POND 12" RCP 11 17-L-79 17-L-1 STORMWATER 26 21 17-L-81C INFRASTRUCTURE 12" RCP  17-L-78A 28  ð  ð 17-L-88D  MAP ID: 07 17-L-78 19 30

17-L-214 39 17-L-78L2 32 17-L-77 8 17-L-150 24" RCP 15" RCP 17-L-215  34 17-L-76 35 15" RCP 28/13

24" CMP  ð17-L-213 17-L-30A 36 17 4 2 - 25 27 11 17-M-27 M-12 3 1 0" 7 C - 17-M-30 M M 1 P - 11 37 17-J-2

23 21 17-M-31

19 17-M-32 COBBETT'S POND

17- M-5 1 17 7- Legend 17-M-36 15 M 17-M-40 -33 1 7 - Catch Basin 15 17 M 17-M-41 -3 7/13 5 19 17-I-2 Culvert/Inlet/Outlet

11 12" CPP Drainage Swale

17-M-42 17-M-39 10 17-M-3 1 7- 24 8 Stream I- 6 17-M 3-7 13 114 17- 17-M-38 17-I-112B 17 -I M 32 - -43

113 17-M-37A Drainage Pipe 9 17-M-47 7-M-2 34 29 4 11 1 17-I-115 3 17-I-112A 17-M-46 Pond

28 7-M-48 30 1 1 Wetland 17-I-111 2 17-I-110 17-I-116A -7 I- 113A 9 17-M-1 20 Watershed Boundary 31 29 17-L-111C 27 17-I-1 1 7- I-36 17-I-111B 23 Pavement 22 2 21 0

10 Assessor's Parcels (approx.) 17-I-111D 17-I-111D 18" CPP

8 17-I-35 17-I-550 20 18" CPP 0 50 100 200 300 Feet     24" RCP  7 1  7- ð I- 49

2 X 24" CPP

15" CPP 6 17-I-3 COBBETT'S POND 17-I-500 17-I-30 4 24" RC STORMWATER 13 P 19 17-C-16 INFRASTRUCTURE

15" CPP 17 -I 17-C-13 -200

19 17 21 -I-2 2 X 15" CMP 17-C-17 01 23 MAP ID: 08 17 2X 18" CPP 17-C-108A

25 12 17-C-108 17 15" CPP -C-12 17-C-109 18" RCP 10 14 17-I-501 1 17-C-11 17-I-300 8 98 3 3 17-C-14 17-C-13 23 17-I-3 17-I-500 4 17 19 21 25 19 17-I-49  ð 12 17-C-108  17-C-12 17-I-200

7 8" RCP 15" CPP 1 14 17-C-109 10 8

1 17-I-501

-C-11 17-I-201 3 17 18" CPP

17-C-107 -10 3 17-C Legend 17-C-7 Catch Basin 4 17-C-9 5 Culvert/Inlet/Outlet

Drainage Swale 17-C-8 6 Stream

Drainage Pipe 17-I-200 17- 92/94 I-300 98 Pond Wetland

Watershed Boundary

"CMP6"

22-R-1700 Pavement 95 Assessor's Parcels (approx.)

17-I-400 ð

22-R-1600 1/3

 ð 0 50 100 200 300 108 22-R-1500 Feet 

15" CMP 5/7

 ð 97 22-R-1100  ð COBBETT'S POND

15" CMP STORMWATER 2/4 INFRASTRUCTURE

22-R-1200 17-I-350 104

6/8

22-R-1300 22-R-1300 MAP ID: 09 11 17-L-1

10/12 101 22-R-1000 22-R-1400

8 37 17-J-2 17-G-6 102

Legend 17-G-20 Catch Basin

17-I-2 Culvert/Inlet/Outlet

82 Drainage Swale

Stream

Drainage Pipe

Pond Wetland

17-G-26 Watershed Boundary

Pavement

17-I-36 Assessor's Parcels (approx.) 84/86/88

0 50 100 200 300 Feet

17-I-35

8 6 17-I-3 17-I-30 COBBETT'S POND 93 4 STORMWATER

15" CPP INFRASTRUCTURE

17-G-45

ð 17-I-49 MAP ID: 10

7  ð

 17-I-200 15" CPP

18" RCP

89 17-I-3 90  ð 17-I-49 4 17-G-45  7 15" CPP 18" RCP 17-I-200

ð

Legend Catch Basin ð Culvert/Inlet/Outlet 17-I-201  Drainage Swale 89

17-G-41 Stream ð 92/94 17-I-200 Drainage Pipe

Pond

91 Wetland 22-R-1800 22-R-1800 Watershed Boundary

93 Pavement

15" CMP 98 95 22-R-1700 Assessor's Parcels (approx.)

17-I-300

22-R-1600 1/3 0 50 100 200 300 Feet

15" CMP

22-R-1500 5/7 93 ð  ð 97 22-R-1100  COBBETT'S POND STORMWATER 2/4 15" CMP INFRASTRUCTURE

22-R-1200

6/8

22-R-1300 22-R-1300 MAP ID: 11

10/12 22-R-1000 101

22-R-1400 16-E-33 42 16-E-12 16-E-21 16-E-31 13 16-E-13 25 46 16-E-51 15 44 9 16-E-32   ð 42 16-C- 16-C 16-E-50 16 1 -13 5 38 6 5 - - 1 C- 30 C 4 -1 1 2 16-E-60 40 6 1 ð - 6 1 C - 6 - 28 C- - 1 3 1 C- 10/12 6 0 22 - 1 11 6 16-M-1 C - 6 16-C-1 -2 C -V-8 8 26 - Legend -B-2 15 4 21 16 36 16-B-1 1 14 6 4 16-C-22 24 -C 3 25 Catch Basin 21-V-4 16-B-11 16-B-3 20 -1 21 16-C-17 6 32 21 Culvert/Inlet/Outlet -V-2 18 16-C-21 16-C-18 23 6 5 16-B-4 16 30 16-C-19 -F- 21-V-246 16-B-10 16 16-C-20 15 17 6 Drainage Swale 13 11 16-B-6 28 13 16- 19 7 19 F- 9 5 Stream 17 16-F-26 21 21-V-230 21-V-228A 21-V-227 20 16-F-2 16-F-3 21-V-228 -1 1 6-F 22 4 21-V-231 15 12 Drainage Pipe 8 14 24 13 36 40 16/18 34 10 32 38 Pond 28 30 21-V-237A Wetland 21-V-237 26 Watershed Boundary 24 21-V-249C 21-V-248 22 Pavement 20 21-V-250D 21-V-250 18 Assessor's Parcels (approx.) 16 14 12 6 8 10 COBBETT'S POND 21-V-257 4

21-W-40 2A/2B 0 125 250 500

21- Feet W-3

21-W-16 19 COBBETT'S POND STORMWATER 6 20 21-X-5 -261 30 INFRASTRUCTURE -Z 21 21-Z-26018 34 36 2 16 1-K-4338 40 21 0A -Z-2 -K-41 21 63 42 21-Z-262 14 21- MAP ID: 12 21-X-1 K 2 -40 10 1-K-39 21 44   ð 21-K-38 48 46

  21-Z-264 21-K-37 21-K-37A 7 -X-12 21-Z-264 25 21 6 21- 21-K-37C21-K-38A K-36 21-K-37B 23 54 21-K-3552 50 21-X-11 27 17-L-77 17-L-88D 17-L-1 24" RCP 8 32  ð 17-L-76 34 19 50

24" CMP 15" RCP 17-L-214  17-L-30A 39  17-L-215

 ð 17-L-75A 35 36  28/13  ð 17-L-213

 ð 15" RCP 17-L-75 15" RCP 38 Legend 18" RCP  15" RCP 17-L-212 Catch Basin 40 17-L-74 26 Culvert/Inlet/Outlet

42 17-L-73 15" RCP Drainage Swale 37/24 17-L-211 17-L-208 Stream 15" RCP 17-L-72 17-L-71 44 11 Drainage Pipe   ð Pond  ð 39  Wetland 17-L-210 9 35 48 17-L-68A Watershed Boundary

33 17-L-41 Pavement

12" RCP 41 17-L-209 Assessor's Parcels (approx.) COBBETT'S POND 50 17-L-40 17-L-68 15" RCP

43 17-L-206 0 50 100 200 300 52 17-L-39 Feet

17-L-67 45 29

15" RCP COBBETT'S POND 17-L-38 17-L-68 54 STORMWATER 17-L-65 INFRASTRUCTURE 27 17-L-65A 12" RCP 14

17-L-66 56 17-L-63

25 17-L-37

18" CPP MAP ID: 13 17-L-62A 12 23

17-L-62 10 17-L-64 21 17-L-42 17-L-61 130

17-L-36 17-L-61 58 17-L-63 54 25 1 7 - L 56 -

17-L-62A 18" CPP 37 1 23 7- L- 68 17 - L-66 12 17-L-64

17-L-62 10 21

17-L-61

Legend 17-L-60 58 COBBETT'S POND 19 17-L-36 Catch Basin Culvert/Inlet/Outlet 17 17-L-59 17-L-61 17-L-42 15 17-L-58 Drainage Swale 60 17-L-57 130 15" CPP 13 Stream

11 17-L-56 17-L-60 Drainage Pipe 9 17-L-55 17-L-54 15" RCP 7 Pond 15" CPP

5 17-L-53 Wetland  3 17-L-52  ð Watershed Boundary

17-L-51 1 Pavement

17-L-50 17-L-53A 18 2 Assessor's Parcels (approx.) 21-K-49 4 17-L-46 21-K-48B 21-K-48A -L-451 24 22 7 26 21-K-48 20 132 28 21-K-47A 12" CMP

21-K-47 21-K-68 30 13 15" CPP 0 50 100 200 300 32 21-K-46 Feet

21-K-45 RCP 24

34 21-H-74 36 21-K-44 12"CPP 21-K-60 5 21-K-80   ð 21-K-43 6" CPP COBBETT'S POND 38 17 21-K-69 15   STORMWATER 40 21-K-70B INFRASTRUCTURE 134 21-K-41 0 11 21-K-7 21- 19 K-4 2A 21 -K-71 21-K MAP ID: 14 2 1 - 25 -K-42 138 7 21 2 136

21-K-38A

ð

21-K-102 21-K-70A 139 146 140 22-R-200

25A 19 17-L-88D  15" RCP 17-I-400 39  ð 108

15" RCP 17-L-1

17-L-150

17-L-213 28/13 11 101 22-R-1000

15" RCP 8 Legend

15" RCP Catch Basin 17-L-212 26 Culvert/Inlet/Outlet

15" RCP ð Drainage Swale

11 17-L-208 Stream 6 17-L-17 Drainage Pipe

39 Pond 9 17-L-207 Wetland 17-L-210 4 17-L-16 Watershed Boundary

7 17-L-204 Pavement

41 15" RCP 17-L-209 Assessor's Parcels (approx.) 17-L-15 5

17-L-203 112 111

22-R-900 17-L-206

17-L-39 43 0 50 100 200 300 52 3 17-L-202 Feet 45  ð

17-L-205  1

L-23

15" RCP 47 17- 15" RCP COBBETT'S POND 17-L-38 17-L-201  ð STORMWATER 54  17-L-20 INFRASTRUCTURE 118

49 17-L-200

56 17-L-37 15" RCP 115 22-R-803 MAP ID: 15 17-L-68 51 -22

17-L

58 ð 17-L-36 17-L- 120 7-L-21 1 22-R-802 1 66 60 5" CPP -L-35 119 123/1 17 17-L-64 22-R-801 17-L-34 123/1 22-R-830 12 62 3 5 54 17-L-200 118 17-L-37 22-R-803 56 115 22-R-900 17-L-68 49 17-L-22 111 51

17-L-66

15" CPP 22-R-802 22-R-801

120 17-L-21 119 58 17-L-36

17-L-64

12 ð

60  ð 17-L-35 123/1 Legend

 9 Catch Basin 3 22-R-830 82 -R- 22 17-L-33 Culvert/Inlet/Outlet 62 124 5 17-L-34 Drainage Swale

Stream 17-L-32 126 Drainage Pipe

22-R-800 Pond 125/2 17-L-31 Wetland 130 17-L-42 128 ð 22-R-501 Watershed Boundary 127 Pavement

22-R-804 4 Assessor's Parcels (approx.)

22-R-502 17-L-45

17-L-46 129

4 0 50 100 200 300 132 Feet

22-R-515

22-R-503 7 22-R-500

  ð  ð 131 12" RCP ð 5    COBBETT'S POND

21-K-70B STORMWATER 12" RCP 22-R-504 134 INFRASTRUCTURE 133

12" RCP

18" RCP

ð MAP ID: 16 18" RCP 136 22-R-505 2 139 22-R-200 6 22-R-506

7 22-R-312 21-Z-264

21-X-12 7 6

21-Z-264

23 21-X-11

4 21-Z-266 Legend 21-Z-266A Catch Basin Culvert/Inlet/Outlet

2 21-Z-267 Drainage Swale 

 ð Stream

Drainage Pipe 30 21-Y-277

3 2 Pond 21-Y-278

ððð 25 Wetland 21-Z-268 21-Z-268 5 21-Y-279 21-Y-276 4 Watershed Boundary 21-Y-276A  

1 Pavement

21-Y-275 3 21-Y-275A 21-Z-269 Assessor's Parcels (approx.) 6 5 27 21-Y-279B 21-Y-276B COBBETT'S POND 32 21-C-157 21-Z-270

29 0 50 100 200 300 21-Y-279C7 21-C-274B 34 31 Feet

36 33 21-C-154 35

21-Z-273 COBBETT'S POND 38 15" CPP

21-C-155 9 39 STORMWATER

21-C-279D INFRASTRUCTURE

40 21-C-153

166 MAP ID: 17 21-H-16

12" CMP 8

42A 21-C-151 21 21-H-15 21-H-15A 2 1 - C 42 21-H-14 - 21-C-152 2 7 17 1 21-H-13 19

21-H-55

21-H-12 15 7 46 11 12 21-K-43 21-K-41 36 34 19 40 42 21-K-40 38

44 21-K-39 21-K-42 21

21-K-38

46 12" CPP

48 21-K-37 25 21-K-38A 50 21-K-37A Legend

21-K-36 12" HDPE 25A 21-K-37C 52 Catch Basin 21-K-37B Culvert/Inlet/Outlet 21-K-35 25B 54 21-K-36A Drainage Swale

12" HDPE 27

21-K-34 Stream 56 Drainage Pipe

Pond 21-K-33 12" HDPE COBBETT'S POND 58 21-K-32 Wetland 60 29

62 21-K-31 Watershed Boundary

21-K-35A 64 21-K-30 Pavement 21-K-29 66 Assessor's Parcels (approx.) 21-K-102

21-K-27 146 68

70 21-K-26A

0 50 100 200 300 21-K-25 72 Feet

21-K-24 74 35 12" CPP 21-K-28 21-K-26 37 COBBETT'S POND 21-K-20 STORMWATER 78 INFRASTRUCTURE

21-K-23 21-K-100 21-K-19 150 80 76 MAP ID: 18 21-K-99 152

160 158 21-K-18 21-K-22

21-K-17 162 21-K-150 21-K-16 164 166 21-H- 8

12" CMP

1 6

9 21 2 1 21-C-279D - H 21-H-15 2 - 1 1 - 5 42A H 21-C-151 - 19 1 2 4 1 A - ð H - 15 21-H-12 13 21-C-152 COBBETT'S POND 10" PVC

42 21-H-11 7 17 12" CMP 11 21-H-10B

21-H-14A Legend

21-C-271 12 16 21-H-19 Catch Basin 14 21-H-21 21-H-13 Culvert/Inlet/Outlet 9 21-H-11C 20 7 21-H-10 21-H-8 18 12 -C-150 12 Drainage Swale 5 2 1 -H

46 2 -7 174 45 1 21-H-11A Stream

- 21-H-20 H 3 10 2 - 21-H-1A 6 -1 24" CPP 12" RCP H 21-H-24 - 12" CPP Drainage Pipe 1 5 9 21-H-10A 9 24" CMP 4" HDPE 21-H-25 Pond 47 21-H-7A 21-H-1 6 51 176 Wetland 21-H-4

21-H-2 4" HDPE 4 Watershed Boundary

21-C-124 178 21-H-26 Pavement 53 21-H-26A 21-H-3 194 -21180 H-35 Assessor's Parcels (approx.) 18" CMP 182 18" CMP

18" RCP

21-G-1 183 21-G-21 21-C- 181 12" RCP 0 50 100 200 300 196 1 23 21-G-18 Feet

21-G-24 191 21-G-23A 185 21-G-29 12" RCP 21-G-20 187 2

ð

21-G-25 18" R 12" RCP 21-G-2 C P COBBETT'S POND 2 193 189 1 - 2 C- STORMWATER 122 198 21-G-19 21-G-26 4 INFRASTRUCTURE 195 21-G-230A

21-G-28 21-G-15 21-C-121 4 197 6 21-G-3 21-G-16A

ð 21-

21-G-230 G MAP ID: 19 - 12" RCP 2 199 9 200 2 21-G-4 1 - 21-G-52 G 5 12" RCP 18" - 8 21-G-14 201 3 R 0 C 7 P 21-G-12 2 1 21-G-11 -G-31 21-G-51 4 203 4 21-C-85 11 21-G-10 21-G-32 205 8 2 21-G-13 202 207 21-G-33 3 76 21-K-22 150

158 152 21-K-99 COBBETT'S POND

21-K-150 2 21-K-17 1- K-18 160 162  ð 2 H-12 1- 1- 15" HDPE K-16 164  6 21 8 21 -H-15 Legend

21-H-14 21-K-15 Catch Basin 166 Culvert/Inlet/Outlet

19 21-F-42 Drainage Swale 2 7 1 -H-15A 163

21-H-14A Stream

21-H-19

21-H-21 ð 167 Drainage Pipe 21 20 5 2 -16C -F-41 18 21-H Pond 16 21-H-15B Wetland 170 21-H-40 3 21-H-17 Pavement

21-H-20 Watershed Boundary

21-H-25 174 21-F-57 21-F-40 4 Assessor's Parcels (approx.) 176 171



 ð 6" CMP 0 50 100 200 300 21-F-34 Feet 2 1-F-3 175 179 2

21-F 21-G-1 181 -35 ðð 21-F-58 COBBETT'S POND

"CMP6" 6 STORMWATER 173 21-F-31 INFRASTRUCTURE  1 21 2 -F-33

ðð 2 21-G-2 177

 MAP ID: 20 4

21-F-30

21-G-15 3 6 4 21-G-3 21-F-36

21-G-14

21-G-4 8 7 21-G-15 196 21-G-28 21-G-26 21-G-3 2 21-G-230A 6 1-G- 21-G-230 21-C-122 12" RCP 199 198 2 195 9 197 21-G-16A 4 2 1 - G-30 12" RCP 21-G-14 200 18 RCP 201 8 " 7 21-G-4

21-C-121 5 21-G-52 21- 21-G-12

G- 203 3 21-G 1 11 4 ðð -11 2 21-G-13 ð 2 21-G-10 1-G-3 12" RCP 21-G-51 202  8 8 21-G-5 205 2 4 Legend 21-G-33 ð 207 Catch Basin

21-G-34 21-G-6 Culvert/Inlet/Outlet 1 21-G-7 209 10 3 21-G-53 Drainage Swale 21-G-9 3 5 21-G-8 Stream

21-G-50 211 Drainage Pipe 15" RCP 6 21-G-45 2 Pond Wetland 21-G-54  ð 4 21-G-46

8 15" RCP Watershed Boundary 15" RCP 

Pavement

Assessor's Parcels (approx.)

21-G-47 1

21 -G -48 201 3 10 21-G- 0 50 100 200 300 Feet 

 ð

COBBETT'S POND 12 21-G-200 STORMWATER INFRASTRUCTURE

6 21-G-208 8 21-G-210

21-G-212

21-G-202 MAP ID: 21 14 4

2 21-G-206

Appendix C: Septic System Inventory Maps

COBBETT’S POND WATERSHED RESTORATION PLAN

SEPTIC SYSTEM INVENTORY

Prepared for: Cobbett’s Pond Improvement Association P.O. Box 192 Windham, NH 03087

Prepared by:

289 Great Road, Suite 105 Acton, MA 01720

February 25, 2010

UV111  ðð 11  ð 111  UV 12 10

13 

 ð 9 14 8

 ð   ð 

15  ð  

 16  ð   ð 6  ð ðð

 ð 

  ð COBBETT'S POND  ð  18 17 5

 

  ð 4  ð  ð    ð  19  

 ð

ðð 20 3

 ð Legend

  Assessor's Parcels (approx.) 2   ð

ðð Unimproved Lot ððð

  ðð No records available at town hall 1 System type not available from town records

ðð Holding Tank   ð  Septic System 

ð MAP INDEX (40

21-H-7 Vol.=2000 gal

42A Inst. Date: 2000 ( Bdrms.=3

 

21-C-151 21-H-55 21-H-6

ððð Vol.=2000 gal Inst. Date: 1999 21-C-152 Bdrms.=3 (42 Vol.=2000 gal Inst. Date: 1998 Bdrms.=2 21-H-5 21-H-60 Vol.=1000 gal Inst. Date: 1998 Bdrms.=3

21-C-152 (9

21-H-8 (7

(5 21-H-7 21-C-150 (46 45 3 ( (21-H-6

21-H-1A 21-H-5

(1   ð (6 (47 (51

21-H-4

21-H-2 (4

21-H-1 21-H-1 21-H-3 Vol.=1000 gal (53 Vol.=1500 gal Inst. Date: 1984 Inst. Date: 2008 21-H-35 Bdrms.=6 Bdrms.=5 21-H-3 (182

(194

21-C-124

187

(21-G-23A 21-G-24

(191 21-G-29 (189 21-G-25 (193

21-G-26 (195 (5 197 21-G-28 196  ( ( G-52  ð 21-G-230 0 50 100 200 300 21-G-29 21- (201 (199 Feet 1 21-H-14 Vol.=1000 gal Inst. Date: 2001 Bdrms.=4 21-H-16 Vol.=1000 gal Inst. Date: 1973 Bdrms.=3 21-H-13 Vol.=1000 gal Inst. Date: 2001 21-K-17 Bdrms.=4 162 21-H-15A ( Vol.=1500 gal Inst. Date: 2004 21-H-12 Bdrms.=3 21-K-16 Vol.=1500 gal (164 Inst. Date: 2003 Bdrms.=2

21-H-16

21-K-15 21-H-11 21-H-15A Vol.=1000 gal (166 Inst. Date: 1985 21-H-14 Bdrms.=3 (21 21-H-15 (8

21-H-13

(19 21-H-10B Vol.=500 gal (17 (15 21-H-12 Inst. Date: 1955 21-H-11 (7

21-H-10B 170 (12 ( (11 21-H-14A 21-H-13 21-H-19 21-H-21

(20

9 21-H-11C ( (14 18 2 16 ( ( ( 21-H-16C

7 21-H-8 5 ( (12 ( 21-H-15B

21-H-10 21-H-13 21-H-7 21-H-11A 21-H-40 (10 Vol.=1000 gal (5 Inst. Date: 2001 (3 21-H-17

21-H-24 Bdrms.=4

9 (9 21-H-10A ( 21-H-25 174 21-H-20( 21-H-7A 176 (6 (

21-H-4

ð

4  21-H-10 ( 178  ( Vol.=1000 gal ðð

ð 21-H-26A Inst. Date: 1982 177 (21-F-3 21-H- Bdrms.=4 180 ( 21-H-26 182 21-F-32 ( 35  (179 3 0 50 100 200 300 (181 21-G-1  (183 Feet 2 21-K-35 (52 21-K-34 21-K-35 21-K-33 Vol.=1500 gal Vol.=1250 gal Vol.=2000 gal Inst. Date: 1997 Inst. Date: 2002 Inst. Date: 1997 Bdrms.=3 Bdrms.=3 (54

Bdrms.=3 21-K-34

21-K-32 (56

Vol.=3000 gal 21-K-33 Bdrms.=2

21-K-31 21-K-32 Vol.=1000 gal (58 Inst. Date: 1981 29 Bdrms.=3 21-K-31 ( (60 21-K-30 21-K-30 Vol.=1000 gal (62 Inst. Date: 1988 21-K-29 Bdrms.=5 (64

66 21-K-29 21-K-27 ( Vol.=1000 gal (29 Inst. Date: 2004 68

( 21-K-35A Bdrms.=2

21-K-27 (70 21-K-26A Vol.=1000 gal (146 21-K-20 Inst. Date: 2007 21-K-25 Vol.=1000 gal Bdrms.=3 (72 21-K-28 Inst. Date: 1988 Bdrms.=3 21-K-24 (37 (74 (35 21-K-26 21-K-19 Vol.=1000 gal 21-K-20 Inst. Date: 1982 Bdrms.=3 (78

21-K-19 21-K-23

(80 (76

21-K-17 Vol.=1500 gal 21-K-18 Inst. Date: 1997 Bdrms.=4

(158 (160 21-K-17 21-K-16 Vol.=2000 gal Inst. Date: 1992 (162 Bdrms.=6

21-K-16 21-K-22

21-K-150 0 (164 50 100 200 300 (166 Feet 3 21-K-49 Vol.=1000 gal Inst. Date: 1999 Bdrms.=3 21-K-47A Vol.=1000 gal 21-K-48A Inst. Date: 1980 Vol.=1000 gal Bdrms.=3 Inst. Date: 2000 Bdrms.=2 21-K-47 Vol.=1000 gal Inst. Date: 1997 21-K-48B Bdrms.=2 Vol.=1000 gal Inst. Date: 2005 Bdrms.=2 21-K-46 Vol.=1500 gal Inst. Date: 1991 21-K-48 Bdrms.=2 Vol.=1250 gal Inst. Date: 1997 21-K-45 Bdrms.=3 Vol.=1500 gal Inst. Date: 1986 (1 Bdrms.=3 21-K-43 Vol.=1000 gal 21-K-48B (18 21-K-44 21-K-49 Inst. Date: 2002 17-L-50 21-K-48A Bdrms.=2 Vol.=1500 gal 21-K-48 Inst. Date: 1980 Bdrms.=3 21-K-41 (20 Vol.=1500 gal (22 Inst. Date: 2006 (24 Bdrms.=2 (26

(28 21-K-40 Vol.=3000 gal (30 21-K-47A 21-K-44 Inst. Date: 1980 32 21-K-47 ( 21-K-46 Bdrms.=2 21-K-43 15 (34 ( 21-K-39 21-K-41 (36 21-K-69 Vol.=1000 gal 21-K-45 (17 38 Inst. Date: 1979 ( Bdrms.=4 21-K-40 (40

21-K-37 21-K-42A Vol.=1000 gal (42 (19 Inst. Date: 1987 21-K-39 21-K-38 Bdrms.=3 Inst. Date: 2002 44 Bdrms.=4 21-K-38 ( 21-K-37A Vol.=1000 gal Inst. Date: 1989 (46 (21 Bdrms.=4 21-K-37 21-K-42 21-K-37A (25 21-K-38A (48

(50 21-K-102 146 21-K-36 21-K-25A ( 52 ( (0 50 100 200 37C300 25B 4 (54 ( Feet 17-L-41

(48 17-L-40 17-L-65 17-L-67 (50 17-L-68 Vol.=1000 gal Vol.=1000 gal Inst. Date: 1994 Inst. Date: 1988 (31 17-L-68 Bdrms.=1 Bdrms.=3

17-L-67 17-L-61 Vol.=1000 gal (29 Inst. Date: 1984 Bdrms.=1 17-L-66

17-L-65 17-L-57 17-L-60 Vol.=1500 gal Vol.=3000 gal 27 ( 17-L-65A Inst. Date: 2002 Inst. Date: 2008 (14 Bdrms.=3

17-L-59 17-L-56 17-L-63 Vol.=2000 gal Vol.=3000 gal (25 17-L-64 Inst. Date: 2000 Inst. Date: 2008 (12 Bdrms.=2 Bdrms.=1  17-L-62A (23 17-L-58 17-L-55 Vol.=1250 gal ðð Vol.=2000 gal Inst. Date: 1998 Inst. Date: 2001 Bdrms.=3 Bdrms.=3 17-L-62 (10 17-L-54 (21 Vol.=1250 gal Inst. Date: 2000

Bdrms.=3 17-L-61 17-L-61 17-L-60 17-L-53 17-L-59 Vol.=1250 gal (19 Inst. Date: 2000 17-L-58 Bdrms.=3 17-L-61 17-L-57 17 ( Vol.=1000 gal 17-L-52 17-L-60 Inst. Date: 1984 Inst. Date: 2006 17-L-56 (15 Bdrms.=1 Bdrms.=4 17-L-55 13 17-L-54 (

17-L-53 (11 (9 17-L-60 17-L-52 Vol.=3000 gal (7 Inst. Date: 2008 (5 17-L-51 (3 17-L-51 (2 17-L-53A (1 Vol.=1250/1500 gal Inst. Date: 1997 17-L-50 Bdrms.=3 (18 21- K-49 0 50 100 200 300 (20 Feet 5 3 (2 ( (4 17-L-89C 17-L-81 17-L-81 Vol.=3000 gal Inst. Date: 1987 (1 Bdrms.=4

(24 17-l-80

17-L-79 (22 17-l-81B Vol.=3000 gal 17-L-79 Inst. Date: 1973 Bdrms.=4 (26 (21

17-L-81C 17-L-78A 17-L-78A Vol.=1000 gal (19 Inst. Date: 2001 (28 Bdrms.=4 39 ( 17-L-214 (30 17-L-78 17-L-78 Vol.=1000 gal Inst. Date: 2006 17-L-78L2 Bdrms.=4 (32 17-L-77

34 ( 17-L-76

17-L-76 17-L-30A Vol.=1000 gal 17-L-215 Inst. Date: 2002 (35 Bdrms.=2 (36 17-L-75A

17-L-75A Vol.=1500 gal

Inst. Date: 1995  ð 17-L-75 Bdrms.=2 (38

 17-L-75 Vol.=1000 gal (40 17-L-74 Inst. Date: 1989 Bdrms.=6 (42 17-L-73 37/24 17-L-73 ( Vol.=2500 gal Inst. Date: 1990 17-L-72 Bdrms.=2 (44



17-L-71  ð Vol.=3000 gal Inst. Date: 1990 Bdrms.=3 17-L-68A (35 17-L-68A 17-L-71 48 ( 17-L-41 Vol.=1000 gal Inst. Date: 1981 (33 Bdrms.=3

0 50 100 200 300 17-L-68 (31 6 Feet (50 (39

17-L-130

(37

17-L-91A 17-L-90 Vol.=1250 gal Vol.=1000 gal Inst. Date: 2000 Inst. Date: 1988 Bdrms.=3 71-L-91B Bdrms.=3 (35 17-L-90A 17-L-86 Vol.=1250 gal 17-L-91A Vol.=1250 gal (33 Inst. Date: 1993 17-L-90A Inst. Date: 1999 Bdrms.=3 Bdrms.=3 (31 30 ( 17-L-100

17-L-86A 17-L-90 17-L-910 (29  ð

(11 17-L-110  17-L-86 (22 (27

(20

17-L-140 17-L-90B 17-L-85 17-L-86B 17-L-86A (18 19/23 (9 ( Vol.=1000 gal 17-L-84 17-L-87 Inst. Date: 1992 (16 Bdrms.=3 17-L-88 (14 (7 (8

17-L-89 17-L-87A 17-L-84 (12 17-L-89B Vol.=1150 gal (6 Inst. Date: 1991 (5 17-L-83 Bdrms.=2 (3 17-L-82 17-L-89A 17-L 17 (4 0 50 100 200 300 (1 -81 -L-81 Feet (1 7( 2 17 L 81 17-C-97 Vol.=1000 gal Inst. Date: 2006 Bdrms.=3

17-C-94A Vol.=750 gal Inst. Date: 1955 Bdrms.=2 17-C-19 17-C-104 Vol.=1000 gal Inst. Date: 1987 Inst. Date: 1990 Bdrms.=2 17-C-96A Bdrms.=3 Vol.=750 gal 17-C-105 Inst. Date: 1960 Inst. Date: 1985 Bdrms.=3 17-C-105A Bdrms.=3 Inst. Date: 1981 Bdrms.=3 17-C-103A Vol.=5000 gal Inst. Date: 2007

17-C-96A Bdrms.=2

17-C-21 (9 11 ( 17-C-104 Vol.=1000 gal 17-C-103 Inst. Date: 1968 (33 (7 (37 17-C-97 17-C-103A

17-C-200 (35 17-C-103B (7 17-C-94 17-C-94A (5 Inst. Date: 1991 (39 Bdrms.=2 17-C-21 17-C-94 (41 17-C-22

17-C-93 17-C-19 11 (10 (17-C-105C Bdrms.=4 3 6 17-C-100(43 ( ( (8 17-C-92 (31 17-C-93 17-C-20 Vol.=3000 gal 17-C-105 Inst. Date: 1981 (29 17-C-111 17-C-23 17-C-101D Bdrms.=2 17-C-105A 17-C-99 (30 4 17-C-92 (28 ( (9

17-L-120 17-C-101 (45 39 17-C-101C ( (27 17-C-24 (1 17-C-105B 26 (47 ( (2

17-C-106 17-C-25 (7

17-L-130 (25 17-C-113 (3 17-C-102C (5 37 17-C-106B

( 17-C-102A (30 19/23 (1 17-C-101B 17-L-100 ( 17-C-18 17-C-5 (4 17-C-26 (6 (23 (2 0 50 10017-L-140 200 300 -C-4 17 8 Feet (24 (2 17-M-42 17-I-112A Vol.=1250 gal (15 17-M-40 Inst. Date: 1982 Inst. Date: 2001 Bdrms.=3 Bdrms.=2 17-M-41 17-I-112B (7/13 Inst. Date: 1972 17-I-114 Bdrms.=3 Inst. Date: 1991 (11 Bdrms.=2

17-M-42

17-I-112B 17-M-43 17-I-113 (24 9 (29 ( 17-I-112 (32

3 (34 (30 17-I-115 ( 17-I-112A 17-M-46 (28 17-I-113A 17-I-116A 17-I-110 (7 (29 (20 (31 17-L-111C (27 17-I-111 17-I-120 23 22 17-I-111B ( (

(21 17-I-111D 17-I-111D

17-I-201

17-I-550 17-I-200

17-C-105C (20 Vol.=1250 gal 17-I-550 Inst. Date: 2008 Vol.=3500 gal Bdrms.=2 Inst. Date: 1981 17-I-500 Bdrms.=2

17-C-16 Inst. Date: 1963 17-I-500 (13 Bdrms.=3 Vol.=1000 gal (19 Inst. Date: 1999 Bdrms.=3 11 (17-C-105C

17-C-16

17-C-13

(19 (21 (23 17-C-19 (17 17-C-108A 9 17-C-17 (25 ( 17-C-114

12 17-C-108 (7 ( 17-I-501 17-C-12 14 17-C-109 (10 7-C-11 ( 17-C-106B 0 50 100 200 3001 17-C-6 1 (8 (Feet 9 17-M-17 Vol.=1500 gal 17-J-1 Inst. Date: 2002 (92 17-M-23 Bdrms.=2 Vol.=1600 gal Inst. Date: 2008 17-M-15 17-M-17 Bdrms.=3 Vol.=1500 gal Inst. Date: 2003 (35 17-M-24 Vol.=3000 gal Inst. Date: 1986 17-M-20 17-M-16 33 Bdrms.=2 Vol.=2500 gal ( Inst. Date: 1984 17-M-26 Bdrms.=3 Inst. Date: 1984 17-M-15 Bdrms.=2 17-M-20 (31

(19 17-M-22

17-M-27 17-J-2 17-M-22A Vol.=3000 gal (21 (37 Inst. Date: 1981 17-M-19 Bdrms.=3 17-M-23 17-M-24 (17 (8 17-M-31 Vol.=1000 gal 17-M-26 (6 17-M-21 Inst. Date: 2002 (15 (29

17-M-14 (13 4 17-M-32 ( 17-M-13 Inst. Date: 1986 17-M-25 (27 Bdrms.=3 (11 17-M-12 2 (25 17-M-27 (

17-M-5 17-M-30 17-M-11 Vol.=750 gal Inst. Date: 1970 (1 (23 17-M-31 Bdrms.=2

17-M-33 (21 Vol.=1000 gal 17-M-32  Inst. Date: 1981 (19 Bdrms.=4

17-M-5  ð

17-M-36 17-M-40 17-M-33 (17 17-M-35 (15 17 (15 ( (19 17-M-36 Vol.=1000 gal Inst. Date: 2002

17-M-3 Bdrms.=2 7/13 17-M-39 (10 ( (8 (13 6 17-M-37 ( 17-M-38 17-M-40

3 Vol.=1000 gal (17-M-46 17-M-37A Inst. Date: 1975 17-M-47 (4 (11 17-M-2 Bdrms.=3 17-I-36 (10 I-2 9 0 50 48 100 17-M-1( 200 300 (2 17-M- 17- (7 Feet 10 (79

111 UV 17-J-85 (2 Inst. Date: 1988 17-J-90F 86 ( Bdrms.=8 17-J-90C (86

(82 17-J-80

1/3 17-J-96 ( 17-J-126 (4 17-J-90D (3 80 ( 17-J-90B 88 17-J-98 ( 17-J-90A

17-J-85 17-J-125 (5 17-J-101 17-J-90 (4/6 (5

(1 8 17-J-121 (3 (8 17-J-105 ( 17-J-120 (12 17-J-107 17-J-106

17-J-113 (10

17-J-115 17-J-90A 17-J-100 (5 17-J-109 Vol.=750 gal 17-J-119 (18 17-J-100A Inst. Date: 2008 (16 Bdrms.=2

17-J-103 (14 9 17-J-104 ( 17-J-90 17-J-117 (11 (6 17-J-110 Vol.=1000 gal 17-J-118 17-J-112 17-J-111 Inst. Date: 2007 (13 4 Bdrms.=3

( 17-J-116 (15 23/25 (21 (19 17-J-100 ( 17-J-100A (17 Vol.=1000 gal 17-J-129 17-J-128 18 Vol.=3000 gal (16 ( 17-J-114 Inst. Date: 1995 Inst. Date: 2007 Bdrms.=2 Bdrms.=4 14 ( 17-J-110 Bdrms.=1 17-J-103 Vol.=2500 gal (12 Inst. Date: 1985 17-J-111 Bdrms.=3 17-J-129 Vol.=3000 gal Vol.=1000 gal Inst. Date: 1990 17-J-104 Bdrms.=3 Bdrms.=2 Inst. Date: 1991 Bdrms.=1 17-J-112 Vol.=1000/2500 gal Inst. Date: 1990 Bdrms.=3

17-J-116 Vol.=1500 gal Inst. Date: 1981 Bdrms.=2

0 50 100 200 300 Feet 11 17-J-175 (4 (6 17-J-123 (60 16-D-200

17-J-118

17-J-122 (6 17-J-150 17-J-131 (4 Bdrms.=3 (2 (2 17-J-132 (4 (8 17-J-149 Vol.=500 gal (14 17-J-131

12 17-J-130 Bdrms.=2 17-J-134 (

9/12 17-J-133 ( 16-D-1 17-J-141 17-J-132 (10 17-J-135 (10 (8 (6 17-J-148 17-J-138 (11

17-J-147

17-J-310 17-J-136 9 (Vol.=1000 gal (7 17-J-133 Inst. Date: 1986 (13 Vol.=1000 gal 17-J-145 Inst. Date: 1979 Bdrms.=3 (12 17-J-137 17-J-135 Vol.=10000 gal 15 (17 ( Inst. Date: 1981

17-J-146 Bdrms.=8 (14

17-J-142 17-J-144 17-J-136 17-J-300 Vol.=10000 gal 19 Vol.=1500 gal ( Inst. Date: 1981 23 Inst. Date: 2004 ( 17-J-143 Bdrms.=8 (11 17-J-142A Bdrms.=4 17-J-137 (21 17-J-138 Vol.=1600 gal Vol.=10000 gal 16 ( 17-J-143A Inst. Date: 1995 Inst. Date: 1981 Bdrms.=3 Bdrms.=8

17-J-300 17-J-143 Vol.=1500 gal Inst. Date: 2008 17-J-310 Bdrms.=3

17-J-143A Vol.=1250 gal Inst. Date: 2005 Bdrms.=3

0 50 100 200 300 Feet 12 16-D-1 Vol.=1000 gal Inst. Date: 1987 Bdrms.=3 (9/12

16-D-200

16-D-6

(60 16-D-1

16-D-6 Vol.=1500 gal (9 (14 Inst. Date: 2008 17-J-310 Bdrms.=3 (13 16-D-10 Inst. Date: 1989 Bdrms.=2 16-D-5

16-D-7

16-D-5 16-D-8 Vol.=1500 gal Inst. Date: 2009 (16 Bdrms.=3

16-D-10 (17

(20 16-D-9 16-D-7 Vol.=1500 gal (19 Inst. Date: 1992 Bdrms.=3

16-D-8 (21 Vol.=1500 gal Inst. Date: 1998 Bdrms.=3 16-D-11

16-D-12 16-D-9 23/28 16-D-11 Vol.=2500 gal ( Vol.=2000 gal Inst. Date: 1982 Inst. Date: 1988 Bdrms.=2 (25 Bdrms.=2

0 50 100 200 300 Feet 13 16-D-12 (23/28 (25

16-D-14

16-D-15 (27 16-D-16 (29 16-D-200

(60 16-D-17 Vol.=1000 gal 16-D-17 Inst. Date: 1986 (31

16-P-191A Bdrms.=2

16-D-18 Vol.=1000 gal Inst. Date: 1988 (29 35 Bdrms.=3 (

16-D-18

16-P-188 16-Q-169 (41 (43 16-P-1 16-R-740 16-Q-169(40 Vol.=3000 gal (31 16-P-560 16-R-600 16-R-840 Inst. Date: 1977 16-P-189 (47 16-Q-169A (24 (45 (38 16-R-177D Bdrms.=2 16-P-189A(39 16-Q-169B

16-R-174D 16-P-800 16-R-845 16-P-801 (22 43 16-Q-169A ( (34 16-Q-170 16-R-177C 20 16-R-174C Vol.=3000 gal ( (32 36 16-Q-171 ( Inst. Date: 1977 (18 16-R-174B Bdrms.=2 (25 16-R-177B (41 16-Q-172 16-R-177 (30 16 39 16-Q-169B (21 ( ( 16-Q-173 16-R-187C 16-R-750 Vol.=1500 gal (37 16-R-187A (14 (28 Inst. Date: 2003 16-R-180 (35 16-Q-174 (12 Bdrms.=2 (33 16-Q-176 (26 (10 16-Q-173 16-Q-171 16-R-187 16-Q-178 Inst. Date: 1973 Vol.=1250 gal (24 16-Q-179 Bdrms.=2 Inst. Date: 2007 29 (22 ( 16-R-182(31 Bdrms.=2

16-R-183B 27 16-R-181 ( (20 16-Q-174 16-Q-176 Bdrms.=2 25 16-R-183 ( 16-Q-300A Bdrms.=1

(18 16-R-184 16-Q-179 16-Q-178 Bdrms.=1 (23 Vol.=2500 gal Inst. Date: 1982 Bdrms.=2 (21 (16

16-Q-300

0 50(5 16-Q-205A 100 200 300 (14 14 (Feet9 (21 (18 (16 16-Q-300

(14 (10

16-Q-205A Vol.=1500 gal 16-Q-206A Inst. Date: 2000 Inst. Date: 2005 (5 Bdrms.=4 Bdrms.=2

(13 16-Q-206 16-Q-206A Vol.=1500 gal 16-Q-205 Inst. Date: 2004 Vol.=2000 gal 16-Q-206 Bdrms.=2 (9 Inst. Date: 1995 16-Q-205A Bdrms.=4 (15 16-Q-207 Inst. Date: 1984 (17 16-Q-207 Bdrms.=3

16-Q-205 11 16-Q-207A(

16-Q-208 Inst. Date: 1978 (19 16-Q-208 Bdrms.=2 (8

16-Q-213

(16 16-Q-211B 16-Q-209 (14

16-Q-211A (22

10 ( 16-Q-210

(18 (20

16-Q-211

16-Q-210 16-Q-211 Vol.=2500 gal Vol.=1500 gal Inst. Date: 2004 Inst. Date: 1986 Bdrms.=4 Bdrms.=3

0 50 100 200 300 Feet 15 (6 (2 61 16-R-186C 16-Q-186D ( 16-Q-186A (4 (1 (1 16-R-186F 4 (2 5 16-Q-205A ( 1  ( ( 16-R-450 (3 16-P-203B  ð (50 16-Q-186E (2 (48 (2 16-E-25 16-E-26

(46 16-E-24 16-Q-213 16-Q-214 Vol.=1500 gal (8 Inst. Date: 1999 16-Q-213 Bdrms.=4 16-Q-214 Vol.=2000 gal 4 16-Q-214A ( Inst. Date: 2007 Bdrms.=2 (10 16-E-22 (42 16-Q-212 (33 (6 (14

16-E-28 16-Q-212 16-Q-214A Inst. Date: 1998 (50 Bdrms.=3 16-E-30 Vol.=2000 gal Inst. Date: 2007 Bdrms.=1

16-E-33 16-E-28 48 ( Vol.=1100 gal 16-E-21 (46 Bdrms.=2 16-E-21 Vol.=1500 gal Inst. Date: 1998 16-E-30 (25 16-E-31 Vol.=1000 gal Inst. Date: 1998 Bdrms.=2 (44

16-E-13 16-E-33 16-E-32 Vol.=1000 gal (15 Inst. Date: 1987 (42 Bdrms.=2 ðð 16-E-31

16-C-12 16-C-13 Vol.=1000 gal Inst. Date: 1973 (40 Bdrms.=2

(38 16-E-32 Vol.=1000 gal Inst. Date: 1980

16-C-11 Bdrms.=3

16-C-10 (36 16-C-12 Vol.=1000 gal Inst. Date: 1988 Bdrms.=4

0 50 100 200 300 16 (30 Feet 16-F-8 16-C-21 (24 (25 16-C-10 (32 16-F-7 18 16-C-16 (30 ( 16-F-6 16-C-17 (23 16-C-18 (21 16-C-19 (19 (28 16-F-6 Vol.=1000 gal (17 16-F-5 Inst. Date: 1982 Bdrms.=3 (26

16-F-3 16-F-4 16-F-2 16-F-5 (24 Vol.=1000 gal 16-F-1 Inst. Date: 2005 (22 Bdrms.=1 (20 16/18 ( 16-F-4 Vol.=1500 gal Inst. Date: 2003 Bdrms.=2 16-F-3 16-F-1 Vol.=1000/1500 gal Bdrms.=2 Inst. Date: 2003 Bdrms.=2

16-F-2 Vol.=1250 gal Inst. Date: 1997 Bdrms.=3

0 50 100 200 300 Feet 17 (4 (6 (20 16-C-22 (4 21-V-4 (14 16-B-3 (3 16-B-11 16-C-21 21-V-2 (18 (6 (16 16-B-4

(5 16-B-10 17 (16-C-19 21-V-246 (13 16-B-5 16-C-20 (15 21-V-233A (11 16-B-6 (19 (7 16-B-9 (13 16-B-8 9 21-V-233 ( (17 (21 21-V-234

21-V-227

21-V-228A

21-V 16/18 21-V-230 21-V-227A

-232 16-F-1 21-V- ( 10 (15 ( 21-V-228 (8 21-V-231 229 (13 (12 (14 (40 (36 34

( 21-V-230C 21-V-230D 21-V-230D (38 (32 21-V-230H (28 21-V-230A 21-V-229 21-V-230E Vol.=3000 gal 21-V-227 (30 Inst. Date: 1982 Vol.=1500 gal 21-V-237A Bdrms.=2 Inst. Date: 2005 Bdrms.=2

21-V-237 21-V-237 21-V-228A (26 Vol.=1500 gal Vol.=1000 gal Inst. Date: 1998 Inst. Date: 1982 Bdrms.=3 Bdrms.=2 21-V-249C (24

21-V-248 (22

(20 21-V-250D 21-V-250 21-V-250 Vol.=1500 gal (18 Inst. Date: 2004 Bdrms.=3 12 21-V-253 21-V-254 ( (16 (14 21-V-251

10 21-V-255 21-V-256 ( (6 (8 21-V-252

21-W-40 21-V-257 (4 Vol.=1350 gal Inst. Date: 1956 Bdrms.=7

21-W-40 (2A/2B

21-W-3

0 50 100 200 300 20 21-Z-260 18 Feet (19 ( 21-W-3 21-Z-261 Vol.=2000 gal 21-W-16 Inst. Date: 1998 (19 Bdrms.=3 21-Z-260

(20 21-X-5 (6 21-Z-262 Vol.=1000 gal (18 Inst. Date: 1995 Bdrms.=3 21-Z-261

(16 21-Z-263 Vol.=1000 gal Inst. Date: 1990 (14 21-Z-262 Bdrms.=3

21-Z-263 21-X-10A 21-Z-263A Vol.=1000 gal (10 Inst. Date: 2005 Bdrms.=2 21-Z-263A

21-Z-264 Vol.=2500 gal

21-Z-264 Inst. Date: 1992 (7 Bdrms.=2 21-Z-264 Vol.=2500 gal

21-X-12 21-Z-264 Inst. Date: 1992 Bdrms.=2 (6

(23

21-X-11 (4 21-Z-266 Vol.=1000 gal

21-Z-266A21-Z-266 Inst. Date: 1986 Bdrms.=4

 ð

  (2 21-Z-267  0 50 100 200 300 19 (30 (25 Feet 21-Z-264

21-Z-264 21-X-12 7 ( (6

(23 21-X-11

(4 21-Z-266

21-Z-266A

(2 21-Z-267

(30 21-Y-277

(3 21-Y-278 (25

ððð 21-Z-268 21-Z-268 2 21-Y-276 21-Y-279 ( (5 (4 21-Y-276A   21-Z-269 (1 Vol.=2500 gal

(3 21-Y-275 Inst. Date: 2007 21-Z-269 Bdrms.=2 21-Y-275A

5 ( 21-Y-276B (27 (6 21-Y-279B

21-Z-270 (32 21-C-157 (29 Vol.=2000 gal 21-Z-270 Inst. Date: 1988 (7 21-Z-271 Bdrms.=2 21-Y-279C 21-C-274B 34 ( (31 21-Z-271 (33 21-C-154 Vol.=2000 gal (36 21-Z-272 Inst. Date: 1991 (35 Bdrms.=2 (9 21-C-279D 21-Z-273 (38 21-C-155 (39 21-Z-273 Vol.=2000 gal Inst. Date: 1983 Bdrms.=2 (40 21-C-153 21-H-50 (42A 21-C-151 0 50 100 (42200 300 21-C-152 Feet 20

Appendix D: Stormwater BMP Load Reduction and Cost Estimate Data

TABLE D-1 Geosyntec Consultants, Inc. SIMPLE METHOD CALCULATIONS

Yearly Precipitation 42.6 inches Fraction Contributing to Runoff 0.85

L E W L A R I H A U C I T G I T R L E H N U T E / M C S D I D E N I M R A R E S C P O G E O O E R C R A F R O

Runoff Coefficient ( C ) 0.3 0.7 0.85 0.1 0.1 0.15 0.2

Event Mean Concentration (mg/L) 0.18 0.22 0.23 0.5 0.05 0.79 0.05

Site Total BMP Number Site Name Catchment Area (sf) BMP Catchment Area by Land Use (sf) 1 Castleton Center Parking Area 22871 0 22871 0 0 0 0 0 2 6-8 Armstrong Road 71905 25000 0 21900 0 25005 0 0 3 Sawtelle Road 47129 0 0 13140 0 33989 0 0 4 Griffin Park 52661 0 0 19500 0 0 33161 0 5a Farmer Road 18116 0 0 3575 0 14541 0 0 5b Farmer Road / Horseshoe Road 13637 10062 0 3575 0 0 0 0 6 20-24 Turtle Rock Road 4233 0 0 4233 0 0 0 0 7 34 Turtle Rock Road 2200 2200 0 0 0 0 0 8 74 Turtle Rock Road 3684 0 0 3684 0 0 0 0 9 Summer Street Area ------10 60-62 Horseshoe Road 41908 38208 0 3700 0 0 0 0 11 58 Horseshoe Road 65248 59548 0 5700 0 0 0 0 12 Woodland Ridge Area (Rt. 111) 63164 0 53714 9450 0 0 0 0 13 35 Cobbett's Pond Road 19734 15234 0 4500 0 0 0 0 14 Windham Town Beach 9654 0 0 4827 0 0 0 4827 15 Fossa Road / Range Road (Rt. 111A) 1266037 814637 0 82600 0 368800 0 0 16 Hawley Road 51175 38175 0 13000 0 0 0 0

Site Number Site Name Runoff Volume (cf) 1 Castleton Center Parking Area 0 48309 0 0 0 0 0 2 6-8 Armstrong Road 22631 0 56171 0 7545 0 0 3 Sawtelle Road 0 0 33702 0 10256 0 0 4 Griffin Park 0 0 50015 0 0 15009 0 5a Farmer Road 0 0 9169 0 4388 0 0 5b Farmer Road / Horseshoe Road 9109 0 9169 0 0 0 0 6 20-24 Turtle Rock Road 0 0 10857 0 0 0 0 7 34 Turtle Rock Road 1992 0 0 0 0 0 0 8 74 Turtle Rock Road 0 0 9449 0 0 0 0 9 Summer Street Area ------10 60-62 Horseshoe Road 34588 0 9490 0 0 0 0 11 58 Horseshoe Road 53906 0 14620 0 0 0 0 12 Woodland Ridge Area (Rt. 111) 0 113457 24238 0 0 0 0 13 35 Cobbett's Pond Road 13791 0 11542 0 0 0 0 14 Windham Town Beach 0 0 12381 0 0 0 2913 15 Fossa Road / Range Road (Rt. 111A) 737450 0 211859 0 111285 0 0 16 Hawley Road 34558 0 33343 0 0 0 0

BMP Catchment Site P Export Number Site Name Phosphorus Export to BMP (lb/yr) (lb/yr) 1 Castleton Center Parking Area 0.000 0.663 0.000 0.000 0.000 0.000 0.000 0.663 2 6-8 Armstrong Road 0.254 0.000 0.806 0.000 0.024 0.000 0.000 1.084 3 Sawtelle Road 0.000 0.000 0.484 0.000 0.032 0.000 0.000 0.516 4 Griffin Park 0.000 0.000 0.718 0.000 0.000 0.740 0.000 1.458 5a Farmer Road 0.000 0.000 0.132 0.000 0.014 0.000 0.000 0.145 5b Farmer Road / Horseshoe Road 0.102 0.000 0.132 0.000 0.000 0.000 0.000 0.234 6 20-24 Turtle Rock Road 0.000 0.000 0.156 0.000 0.000 0.000 0.000 0.156 7 34 Turtle Rock Road 0.022 0.000 0.000 0.000 0.000 0.000 0.000 0.022 8 74 Turtle Rock Road 0.000 0.000 0.136 0.000 0.000 0.000 0.000 0.136 9 Summer Street Area1 ------0.450 10 60-62 Horseshoe Road 0.388 0.000 0.136 0.000 0.000 0.000 0.000 0.525 11 58 Horseshoe Road 0.605 0.000 0.210 0.000 0.000 0.000 0.000 0.815 12 Woodland Ridge Area (Rt. 111) 0.000 1.557 0.348 0.000 0.000 0.000 0.000 1.905 13 35 Cobbett's Pond Road 0.155 0.000 0.166 0.000 0.000 0.000 0.000 0.320 14 Windham Town Beach 0.000 0.000 0.178 0.000 0.000 0.000 0.009 0.187 15 Fossa Road / Range Road (Rt. 111A) 8.282 0.000 3.040 0.000 0.347 0.000 0.000 11.669 16 Hawley Road 0.388 0.000 0.478 0.000 0.000 0.000 0.000 0.867 TOTAL: 21.2 1. P Load calculated using STEPL gully tool.

7/6/2010 - 14.73 Range (lbs/yr) P Load Reduction 12.05 GEOSYNTEC CONSULTANTS, INC. Cost Range 13.39 P Load (lbs/yr) Reduction Total: P Load Reduction % 5 4 Cost $11,060 0.90 0.41 $10,000 - $12,200 0.36 - 0.45 Total BMP

NT NT

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S U

S C

C I

E E

8 S

(

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O 3

5 E 0

S 3

A T

D T

G NH ( E

0 3

L L

F F

A I

L 5 E

H M

R R

/ A

E N

O I

A C X E

N N

L L I F

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f A

L t

W i

d D

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R R

S Y A B

B B R U C

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O T S 1760 0 0 8175 0 0 0 0 $41,722 - 6.75 $37,500 - $45,900 6.08 - 7.43

TABLE D-2 1

T T

N A T S

N N

N I A R

BMP COST AND LOAD REDUCTION ESTIMATES

N N

R - P I R

E E

0 0 0 0 100 0 0 0 6 24 40 2 40 24 6 0 0 0 T 100 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $13,520 0.77 0.67 $12,200 - $14,900 0.60 - 0.74 E

L T

U O

N N

2 I

S 0

E E D

1 E

E T A W

1 ______QTY.______

N N

T 0 0 380 0 0 0 0 0 15 0 0 100 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $3,614 $1,300 0.35 0.65 0.05 0.015 $3,300 $1,200 - - $4,000 $1,400 0.05 0.01 - - 0.06 0.02 0 400 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 80 2300 80 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $11,440 0 0 0.38 0 0 0.20 $11,960 0 $10,300 - - $12,600 0 0.18 - $1,872 0.09 0.22 0.65 $10,800 - $13,200 0.21 0.08 - $1,700 0.10 - $2,100 0.19 - 0.23 0 0 0 0 0 0 0 208 0 0 0 208 0 0 0 0 0 270 0 0 0 0 0 0 0 0 0 0 0 0 0 $2,457 0.35 0.38 $2,200 - $2,700 0.34 - 0.42 sf sf ea ea sf sf sf sf lf ea sf cy cy cy ea E

O I 360 0 0 500 0 100 0 2 0 0 100 0 0 0 0 0 0 0 500 0 1 0 0 0 0 0 0 0 0 $5,148 0.65 0 $42,900 0.15 0.98 $4,600 - 1.87 $5,700 $38,600 0.14 - - $47,200 0.17 1.68 - 2.05 750 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $10,725 0.65 0.34 $9,700 - $11,800 0.31 - 0.38 400 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $5,720 0.65 0.53 $5,100 - $6,300 0.48 - 0.58 500 700 400 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $5,720 0.65 0.12 $5,100 - $6,300 0.11 - 0.13 B 0.65 0.35 0.05 0 0 0.65 0 0 0 0.8 0.45 - - - 1200 800 0 0 0 0 0 0 0 0 0 0 0 0 0 $24,440 0.77 0.23 $22,000 - $26,900 0.21 - 0.25 2170 0 0 0 0 0 0 0 0 0 0 0 0 0 0 $31,031 0.65 0.43 $27,900 - $34,100 0.39 - 0.47 2500 0 0 1 0 0 0 0 0 0 0 0 0 0 0 $38,350 0.65 0.95 $34,500 - $42,200 0.85 - 1.04 6 Removal % Unit Cost/Unit $11 $7 $3,000 $2,000 $8 $10 $4 $8 $20 $10,000 $2 $6 $3 $40 $3,000 0.45 BMP Catchment P Export (lbs/yr) - BMP 4233 2200 0.16 0.02 3684 0.14 9654 0.19 36232 13637 0.30 0.23 71905 1.08 41908 19734 0.52 0.32 47129 0.52 22871 0.66 65248 0.82 52661 1.46 51175 0.87 Area (sf) Catchment 4 Griffin Park 6 7 20-24 Turtle Rock Road 34 Turtle Rock Road 3 Sawtelle Road 1 2 Castleton Center Parking Area 6-8 Armstrong Road 8 9 74 Turtle Rock Road Summer Street Area 12 Woodland Ridge Area (Rt. 111) 63164 1.91 5a Farmer Road (site 1) 5b Farmer Road / Horseshoe 11 58 Horseshoe Road 10 60-62 Horseshoe Road 13 35 Cobbett's Pond Road 15 16 Fossa Rd. / Range (Rt. 111A) Hawley Road 1266037 15.00 14 Windham Town Beach Site Site Name Site 1. Unit costs from Charles River Watershed Association " 2. Unit costs based on past Geosyntec projects and contractor estimates 3. Cost Estimate from Stormtech product documents 4. Cost includes additional 30% to reflect mobilization, erosion and sediment controls, contingency, etc. 5. Cost estimate from RS Means catalog Handbook when not available 6. Percent reductions taken from Volume 1 Appendix E of NH Stormwater Manual when available, 2 Massachusetts