Spofford Lake Watershed Management Project
Spofford Lake is the largest lake in the region at 736 acres with a maximum depth of 68 feet. It abuts a number of roads including NH Route 9A and NH Route 63. There are approximately 574 parcels of land that are completely within its watershed. It is of regional significance for recreational opportunities as well as the tourism and economic benefits to the Town. This regional asset has experienced challenges in maintaining the high standards of a healthy lake due to increased development within the watershed, increased activity/usage, environmental threats, and stormwater management. Water testing has indicated that the lake is experiencing a decline in water quality. Two primary contributors are low concentrations of dissolved oxygen and the contribution of non-point pollution. Several steps have been taken over recent years to begin to reverse these trends and improve the water quality of the lake.
Development of a Watershed Management Plan:
The Spofford Lake Watershed Management Plan (WMP) was completed in November 2018 and was funded in part by the NH Department of Environmental Services (NHDES) under Section 604 (b) of the Clean Water Act. This was a coordinated effort led by SWRPC that included the Town of Chesterfield, Spofford Lake Association, community volunteers, and project partners including NHDES and NH Department of Transportation (NHDOT). FB Environmental and Horsley Witten were consultants hired to provide technical assistance to the project. On September 9, 2017, a large group effort was coordinated to conduct three types of surveys within the Spofford Lake watershed. These surveys provided essential data to identify specific areas and issues that may be contributing to the changes that have been occurring in the lake. The surveys included a shoreline survey, a field survey, and a water quality survey. The surveys identified 16 watershed sites and 194 high/medium priority shoreline properties that have some impact on the water quality. Based on the information collected in the surveys and other data sources, the WMP set a goal to reduce pollutant loading to Spofford Lake by 19 kg/yr (12 kg/yr from existing development and 7 kg/yr from anticipated new development in the next 10 years) to improve in-lake median total phosphorus concentration by 5%.
Watershed Implementation Plan Phase I:
The project was completed on December 31, 2021, and was funded in part by the NHDES under Section 319 of the Clean Water Act. The project evaluated and implemented stormwater controls on private and municipal land, including 4 of the 16 watershed survey sites and 6 of the 194 high/medium priority shoreline survey sites that were identified in the WMP. Two of the watershed survey sites were town beaches; Wares Grove Beach and North Shore Beach, which were previously assessed and remediated by the Town prior to the official start of this project; however, pollutant load reduction estimates were still determined for these beach sites as part of this project. Technical consultants assessed each site with landowner permission and developed conceptual designs that included a list of materials, estimated costs, and resources for implementing the recommended stormwater controls. Landowners used the designs to install the stormwater controls on their properties and were reimbursed for material costs as part of the grant. Technical consultants prepared Site Reports and Pollutants Controlled Reports for each project site to document the implementation process and pollutant reduction estimates. By targeting stormwater runoff, the project reduced the amount of nonpoint source pollution in the form of sediment, nutrient, and heavy metal loading to the lake. The final project outcome reduced nutrient loading to the lake by 9.2 lbs/yr of phosphorus.
Watershed Implementation Plan Phase II:
The project is currently underway and will be completed by December 31, 2023. Funded in part by the NHDES under Section 319 of the Clean Water Act, the project will implement stormwater controls in locations identified in the Spofford Lake WMP. The majority of the effort will be spent on the public boat launch and parking lot area. Additionally, three of the high/medium priority shoreline survey sites will also be selected for stormwater management remediation. Treating the four sites will reduce phosphorus loading to the lake by an estimated 4.1 kg/yr, meeting 22% of the 19 kg/yr reduction target set in the WMP. A public outreach effort is also planned to increase awareness of water quality protection actions executed by watershed residents. This project will be a coordinated effort led by SWRPC and will include project partners from NHDES, NHDOT, the Town of Chesterfield, Spofford Lake Association, landowners, and volunteers.