5. NATURAL AND HISTORIC RESOURCES Summary of Existing Natural and Historic Resources in Westborough Strengths Concerns • Woodlands cover more than 41% (more than 5,600 • More than half of the Town’s remaining woodlands acres) of the Town. are unprotected from potential future development. • Over 1,900 acres of wetlands exist in the Town. • Continued growth will result in the loss of farmland, • The Town has several productive groundwater forest, and other open space. aquifers that meet the water needs of the local • Although the water quality of the Assabet River has population. improved greatly over the past decades, the river • Westborough has several attractive water bodies still suffers from excessive nutrient loading. including the Assabet and Sudbury Rivers, Lake • New development threatens water resources and Chauncy, Hocomonco Pond, and the Westborough other natural resources as a result of increased non- Reservoir. point source water pollution, habitat fragmentation, • The Town has over 400 historic buildings, sites erosion, and other impacts. and properties including a National Register • New development may alter the historic character of Historic District downtown. some sections of the Town. • The Cedar Swamp Archaeological District is the • As real estate values increase, there will be more second largest archaeological district in the state. pressure to develop marginal lands and to tear down and replace historic structures. Westborough’s natural and cultural resources provide an important counterbalance to the Town’s developed areas. Undeveloped farms, forests, and wetlands provide clean water, clean air, wildlife habitat, and scenic views. Historic buildings, sites, and landscapes provide a glimpse into the Town’s agrarian and industrial past and help define the Town’s character. This section describes Westborough’s many natural and historic resources. Major sources for natural resource information in this section include the Town’s 1996 Open Space and Recreation Plan, the Phase I Comprehensive Wastewater Management Plan (CWMP), the state’s Natural Heritage and Endangered Species Program, and geographic data from the Town and from MassGIS. Historic information is based on documents from the Massachusetts Historical Commission and Westborough Historical Commission, as well as interviews with representatives from these groups. 5.1 Existing Water Resources The Town of Westborough includes land in three watersheds. The eastern half of the Town is within the Sudbury River Watershed, and forms the headwaters of the Sudbury River. The western half of the Town comprises the headwaters of the Assabet River Watershed. A small portion of the southwest corner of the Town is in the Blackstone River Watershed. As a community at the headwaters of two major river systems, Westborough plays an important role in regulating the water quality and streamflow in these systems. 5.1.1 Streams and Ponds The Assabet River begins in the western section of the Town, near the Shrewsbury border, and flows north and east along the Northborough border. Eventually, the Assabet River joins the Sudbury River in Westborough Master Plan Page 51 Inventory and Analysis the Town of Concord, where it flows north to empty into the Merrimack River and finally the Atlantic Ocean. According to the Organization for the Assabet River, the river suffers from elevated nutrient levels and low dissolved oxygen readings, which impair the river’s habitat values. These conditions are generally the most severe in the upper sections of the river, where there has been little dilution of effluent from the Westborough Wastewater Treatment Plant (WWTP). Both nitrogen and phosphorous are pollutants of concern, but phosphorous is especially problematic. The ongoing Comprehensive Wastewater Management Plan (CWMP) process (see Section 7.6.2) is intended to help address pollution problems emanating from the WWTP. The Sudbury River begins in Cedar Swamp and flows east toward Hopkinton and Ashland. The river has had problems with water quality and low stream flow downstream from Westborough, and the entire river is subject to a fish advisory because of mercury contamination. According to MassGIS, water covers about 630 acres, or 4.6% of the total area of Westborough. Most of this area consists of the Town’s five ponds: Lake Chauncy, Hocomonco Pond, Cedar Swamp Pond, Westborough Reservoir (Sandra Pond), and the SuAsCo Reservoir (Mill Pond). The SuAsCo Reservoir was constructed in the 1970s as a flood control project. The Westborough Reservoir is part of the Town’s public water supply. 5.1.2 Wetlands and Floodplains According to the CWMP, Westborough has a total of about 1,900 acres of wetlands, of which about 685 acres (36%) are unforested wetlands and the remaining 1,215 acres are forested wetlands (see Figure 5- 1). There are also slightly more than 2,300 acres of flood plains in the Town, which generally correspond to the wetland areas. The three major wetland areas in the Town include Cedar Swamp, Crane Swamp, and Assabet Swamp. Cedar Swamp, located just east of downtown, is the largest of these resources and is designated as an Area of Critical Environmental Concern. The Sudbury River originates in Cedar Swamp. Crane Swamp, located northeast of Lake Chauncy and extending into Northborough, drains into the Sudbury River via the Wachusett Aqueduct. Assabet Swamp extends from the discharge point of the SuAsCo Reservoir north toward the Northborough border. 5.1.3 Groundwater Resources Groundwater resources in Westborough serve two important functions: providing base flow1 for the streams and rivers in the Town (including the Sudbury and the Assabet) and providing potable water for the Town’s residences and businesses. Figure 5-1 shows major groundwater resources in the Town, including high-yield aquifers, medium-yield aquifers, and public water supply wells. Westborough’s Aquifer and Watershed Protection District, also shown on Figure 5-1, is divided three zones—Zone I, Zone II, and Zone III—based on a 1995 hydrologic study. Zone I is the protective 400-foot radius around public groundwater wells, and, by state law, must remain in public control and essentially undeveloped. Zone II is the primary groundwater recharge area for the public wells, and includes areas that contribute ________________________________ 1 Base flow is that portion of stream flow that is provided by groundwater infiltration (as opposed to surface runoff). During dry periods, base flow can supply most or all of a stream’s water, so base flow is critical to maintaining water levels during dry months. If base flow is reduced because of excessive groundwater pumping or reduced infiltration, low flow problems can result. Westborough Master Plan Page 52 Inventory and Analysis water to the public wells under the most severe pumping conditions. The Zone III area is the contributing watershed that drains into the Zone II area. See Section 7.7 for additional discussion of the Town’s water supply system. 5.2 Water Quality Analysis As discussed above, water quality is a concern in both the Sudbury and Assabet Rivers. In addition, although groundwater quality is now generally good throughout most of the Town, Westborough must be vigilant in protecting this resource in order to safeguard its public water supply. As a result of national and state environmental laws implemented in the 1970s and 1980s, most of the point sources of pollution (i.e., pollution emanating from a pipe or a single identifiable point) have been identified and addressed. Nevertheless, the Westborough Wastewater Treatment Plant remains a significant point source of pollution. In addition, the potential exists for contamination from the Bay State Abrasives site in the town center and other contaminated sites to enter the groundwater. According to the Town, creosote pollution at the Hocomonco Pond Superfund site has been remediated, although groundwater cleanup efforts continue. In the long term, however, “nonpoint source pollution,” or polluted runoff, is probably the main threat to water quality in Westborough. Nonpoint source pollution derives from many small, individual sources, including roads, farms, lawns and gardens, septic systems, parking lots, and other developed land uses. Nonpoint source pollution can adversely affect lakes, streams, and aquifers. Specific nonpoint source pollutants that are of concern in Westborough include the following: • Sediment: Sedimentation occurs when particles of silt, soil and sand are washed from exposed areas at construction sites, gravel operations, farms, landscaped areas, roads, and other altered areas. Sedimentation tends to increases the turbidity of lakes and streams, thus reducing its habitat and recreational value. In addition, sedimentation clogs wetlands and riparian zones, and reduces their flood storage capacity. • Phosphorous and Nitrogen: Phosphorus and nitrogen are major constituents of wastewater effluent (human wastes, detergents, etc.) as well as chemical fertilizers. Because phosphorous and nitrogen are both critical plant nutrients, increasing the amount of these chemicals in the environment can cause algae blooms, reduced levels of dissolved oxygen, and changes in aquatic and terrestrial species composition. This is what is now occurring in the upper Assabet River because of discharge from the Westborough Wastewater Treatment Plant. Nitrate (a form of nitrogen commonly found in groundwater that can contaminate drinking water supplies) is also a suspected carcinogen. • Metals: Various