This project was funded by: Massachusetts Executive Office of Environmental Affairs South Coastal Watershed Action Plan Chapter Six Plymouth Watersheds Prepared by: 110 Winslow Cemetery Rd. Marshfield, MA 02050 (781) 837-0982 CHAPTER SIX: PLYMOUTH WATERSHEDS Part I. Plymouth Watersheds Assessment 6-2 1.0 Watershed Characteristics 6-2 2.0 Water Quality Impairments 6-4 3.0 Aquatic Habitat Impairments 6-11 4.0 Water Withdrawal Impairments 6-15 Part II. Plymouth Watersheds Five Year Action Plan 6-19 List of Tables Table 6-1. Plymouth South Coastal Watershed Characteristics 6-2 Table 6-2. Stormwater Impacts on Plymouth South Coastal Ponds 6-6 Table 6-3. Percent of Impervious Surface for each Plymouth South Coastal Watershed 6-16 Table 6-4. List of Plymouth Public Drinking Supply and Irrigation Wells located in South Coastal 6-23 Table 6-5. Plymouth South Coastal Waterbodies listed by Watershed 6-24 List of Figures Figure 6-1 Eel River Nitrogen Monitoring Sites 6-8 Figure 6-2 Ellisville Harbor Tidal Marsh 6-13 Figure 6-3 Plymouth Carver Aquifer 6-15 Figure 6-4 Plymouth Wannos Well Contributing Zone 6-17 List of Maps Map 6-1 Plymouth Water Resources Map 6-27 Map 6-2 Plymouth Watersheds Assessment Map 6-28 Map 6-3 Plymouth Watersheds Impervious Surface Vulnerability Map 6-29 Map 6-4 Plymouth Watersheds Action Map 6-30 Plymouth Watersheds in South Coastal Basin Introduction The public process involved in creating this document included two steps,1) an assessment of the Plymouth watersheds and 2) the development of a Five Year Action Plan. The assessment involved extensive literature review and interviews with stakeholders. Based on this process, information and a list of recommended actions were presented to the public at a public forum for additional input and priority ranking. The recommended actions generated as part of the assessment are listed at the end of the discussion of each goal. Based on the input and votes of those who attended the public forum, some of these recommendations were included in the Five Year Action Plan at the end of this chapter. Thus, this chapter consists of two parts; The Assessment and the Five Year Action. Please refer to Appendix A for a detailed description of the public process. PART I. WATERSHED ASSESSMENT 1.0 Watershed Characteristics Table 6-1 Plymouth South Coastal Watershed Characteristics Land Area 63 Square Miles Primary Municipality Plymouth Protected Open Space 3,915 Acres (9.8%) Limited Open Space 2,621 acres (6.5%) NHESP Priority Habitat for Rare Species 8,820 acres (20.4%) Top three land uses 56% Forest; 20% Residential; 6.8% Water/Wetlands # of NPDES Permits-4 # of Dams-39 Most Impaired Waterbodies Plymouth Harbor, Billington Sea Pond, Ellisville Harbor, Russells Mill Pond 1.1 History: For most of its existence, Plymouth was an isolated seacoast community whose economic fortunes were closely linked to the sea and shipping. In the 19th century primary industries included Plymouth Cordage, shipbuilding, and fishing. Towards the end of the century as these industries declined, agriculture, particularly cranberry bogs emerged as a significant source of employment. The 1960’s brought the completion of Route 3, the building of the Nuclear Power Plant and the construction of the North Triangle and Camelot Industrial Parks. During the 1980’s Plymouth was one of the fastest growing communities in Massachusetts with a growth rate of 26% (Open Space Plan 2003). 1.2 Water Resources: Plymouth’s 12 Watersheds include 343 inland ponds (including 32 globally rare coastal plain ponds), 5 anadromous fish runs, and 21 miles of coastline. Please refer to Table 6-1 for waterbodies listed by Watershed.) Please refer to Plymouth Coastal Water Resources Map (Figure 6-5). The five anadromous fish runs are Town Brook, Eel River, Herring River (Bournedale run), Agawam River (spawning at Halfway Pond) and Bartlett Pond. Estuaries include South Coastal Watershed Action Plan 6-2 9/12/2006 Watershed Action Alliance Plymouth Harbor, Plymouth Bay, and Ellisville Harbor all SA waterbodies with excellent habitat for fish, other aquatic life and suitable for primary and secondary recreation (Map 6-1). The most significant river system is the Eel River with a watershed of 15.4 square miles (9,856 acres). The watershed contains several coastal plain ponds that are fed primarily by the groundwater flowing through the aquifer. The Eel River Watersheds’ Coastal Plain Ponds are shallow ponds which were created by glaciers and form a unique wildlife habitat that supports many of Plymouth’s globally rare wildlife species. Over 30% of the Eel River watershed has been designated as BioMap Core Habitat under the Commonwealth’s Natural Heritage and Endangered Species Program (Open Space Plan, 2003). There are two main branches of the river which join below Hayden and Howland Ponds. The northern branch flows southeast from the Town’s new Eel River Headwaters Preserve, and the southern branch, also known as Shingle Brook, flows northeast out of the Pinehills Development. The Plymouth Carver Aquifer, the second largest in Massachusetts and designated as a sole source aquifer (requiring and EIS for federal projects), covers nearly 200 square miles, including all or part of six communities, and stores as estimated 500 billion gallons of fresh water (Plymouth’s Open Space Plan 2003). The boundaries of the groundwater contributing areas within the Plymouth Carver Aquifer are not coincident with the surface watershed boundaries mapped by EOEA. The groundwater contributing areas in the Plymouth Carver Aquifer are more significant then the surface watershed delineation because Plymouth’s surface water bodies — its rivers, streams and ponds— are largely fed by this groundwater aquifer rather than by run-off from rain. The direction and flow of groundwater through the aquifer is radially outward from the high point of the groundwater in the West Plymouth and is controlled by proximity to rivers and coastal discharge boundaries, as well as geologic heterogeneity, rather than the hills and valleys at the surface. The area of groundwater within a watershed system is the area that feeds the rivers, streams and ponds within that watershed. Therefore, watershed boundaries based on surface topography are very different from watershed boundaries defined by groundwater. Watersheds in Plymouth need to be delineated by the zone contributing groundwater to the surface waterbodies. The identification of accurate groundwater contributing zones is key to evaluating how the impact of both permitted groundwater discharges and water withdrawals will affect the surface water bodies in each of Plymouth’s watershed systems. (Neal Price, email correspondence, 2006). This has been done for one watershed, the Eel River Watershed, and the area of groundwater contribution to the watershed differs by over 2000 acres from the surface watershed area (Mettie Whipple, Eel River Watershed Association). Plymouth maintains a thriving commercial fishing fleet that includes more than 65 lobster boats and 25 draggers that operate in the harbor. Providing a harbor that includes a high standard of water quality is central to preserving and enhancing a vital and vibrant local economy (Tri-town Application to EPA for No Discharge Zone, 2005). 1.3 Priority Land and Aquatic Habitats: Plymouth is unique in the region for the amount of open space, although on-going transportation improvements will erode this buffer. The area is rich with unique environments offering globally rare Pine Barrens and has the second highest incidence of rare species occurrence in the state with over 100 records in the Natural Heritage and Endangered Species Program database. Areas of critical ecological significance include the Great South Pond Complex for globally rare species including the triangle floater, blue-spotted salamander, comet South Coastal Watershed Action Plan 6-3 9/12/2006 Watershed Action Alliance darner, spotted turtle, new england bluet, red-belly turtle, and eastern pondmussel. A range of fish can be found throughout the watershed including largemouth bass, small mouth bass, pickerel, alewife, white perch, yellow perch, blueback herring, rainbow smelt, and brook brown and rainbow trout (Open Space Plan, 2003). The Ellisville Harbor Area of Critical Environmental Concern (ACEC) comprises 600 acres of widely diverse habitats and vegetation including a sheltered harbor, sandy beaches, salt marsh, steep bluffs, kettle holes (Center Hill and Black Ponds), a small sphagnum bog and scenic rural upland sites with woodland and meadow. The Herring River ACEC, comprises 4450 acres, contains eleven lakes and ponds (the largest Great Herring Pond), numerous freshwater wetlands, productive cranberry bogs, over 250 acres of protected space and the most important anadromous fish run along the coast. (Open Space Report, 2003) 1.4 Hydrogeology: Deposits of fine to course sand and gravel with occasional, limited lenses of silts and clay predominantly underlie Plymouth Watersheds. The subsurface soils consist of the Carver-Gloucester and Carver-Peat soils as classified by the U.S. Department of Agriculture Soil Conservation Service (USDA 1969). The soil tends to be deep and dry with rapid permeability. The surficial geology in the watershed consists of unconsolidated stratified glacial materials deposited during the last retreat of glacial ice about 15,000 years ago. The lower portion of these stratified materials is saturated with water fed by direct infiltration of precipitation. Ground water table elevations range from sea level to 125 feet about sea level, with the saturated thickness of the aquifer greater than 160 feet in many areas (Eel River TAC). 2. 0 Water Quality Impairments 2.1 Stormwater Nutrients: A primary threat to all waterbodies in Plymouth is the impact of pollution carried by stormwater which originates from rain that travels over the ground surface until it either enters a water body directly (surface run-off) or infiltrates into the groundwater and enters a water body from there (baseflow).