Development of Farm Pond Management Plan Report November 2015 Prepared for: Board of Selectmen and Farm Pond Advisory Committee Town of Sherborn, Massachusetts 19 Washington Street. Sherborn, MA 01770 Prepared by Fay, Spofford and Thorndike 400 Crown Colony Drive Quincy, MA 02169 Table of Contents Overview of Report ....................................................................................................... 1 1.0 Watershed Mapping and Assessment ................................................................ 2 1.1 Watershed Description and Mapping ................................................................... 2 1.1.1 Historical Land Use ...................................................................................... 2 1.1.2 Current Land Use ......................................................................................... 6 1.2 Watershed Soils ................................................................................................... 6 1.3 Review of historical data and reports ................................................................. 10 1.4 Preliminary Hydrologic Budget ......................................................................... 10 2.0 Field Activities................................................................................................... 13 2.1 Bathymetric Map Confirmation ......................................................................... 13 2.2 Water Quality Monitoring - 2014....................................................................... 13 2.2.1 Water Column Physiochemical Characteristics ........................................... 16 2.2.2 General Water Quality Characteristics ........................................................ 18 2.2.3 Nutrients .................................................................................................... 20 2.2.4 Biological Parameters................................................................................. 22 2.2.5 Trophic State Index (TSI) assessment ......................................................... 23 2.3 Aquatic Vegetation Survey ................................................................................ 24 2.3.1 Methods ..................................................................................................... 24 2.3.2 Results ....................................................................................................... 25 2.4 Groundwater Seepage Survey ............................................................................ 26 3.0 Hydrologic and Pollutant Loading Models ...................................................... 28 3.1 Refinement of Hydrologic Model ...................................................................... 28 3.2 Estimate of stormwater inputs............................................................................ 28 3.3 Pollutant Loading Model ................................................................................... 28 4.0 Review of Pond and Watershed Management Options ................................... 35 4.1 Review of Pond Management Options ............................................................... 35 4.1.1 Elements of a Rapid Response Plan ............................................................ 36 4.1.2 Waterfowl control ....................................................................................... 37 4.1.3 Pond Stewardship ....................................................................................... 38 4.1.4 Designation of Farm Pond as an Outstanding Resource Water .................... 38 4.2 Watershed Management Options ....................................................................... 39 4.2.1 Land use conversion ................................................................................... 39 4.2.2 Zoning and land use planning ..................................................................... 40 4.2.3 Waste water management ........................................................................... 40 4.2.4 Behavioral modifications ............................................................................ 41 4.3 Recommendations ............................................................................................. 41 5.0 References ......................................................................................................... 43 Farm Pond Management Plan – November 2015 i Table of Figures Figure 1. Farm Pond watershed map showing current land use ....................................... 4 Figure 2. National Resources Conservation Survey soils of Farm Pond Watershed ......... 8 Figure 3. Farm Pond Bathymetric Map ......................................................................... 14 Figure 4. Farm Pond Field Activities Map .................................................................... 15 Figure 5. Farm Pond Temperature and DO Depth Profiles: Summer 2014. ................... 17 Figure 6. Farm Pond Watershed Limit. ......................................................................... 30 Table of Tables Table 1. Morphometric Characteristics of Farm Pond and its Watershed. ........................ 5 Table 2. Farm Pond Secchi Disk Transparency: 1998-2008. ......................................... 18 Table 3. Farm Pond Water Quality Characteristics – May and August 2014. ................. 19 Table 4. Farm Pond TSI Calculations: 2005 & 2014. .................................................... 24 Table 5. Farm Pond Groundwater Meter Seepage Rates. ............................................... 27 Table 6. Summary of LLRM Calculated Nutrient Loads to Farm Pond. ........................ 32 Table 7. Predicted In-Pond TP Concentrations. ............................................................. 33 Table 8. Predicted Chl-a and Secchi Disk Transparency Depths. ................................... 34 List of Appendices General Aquatic Glossary A. Historical Reports and Prior Information B. Town of Sherborn Information C. Hydrologic calculations D. Field Survey Notes E. Water Quality Data F. Aquatic Vegetation Survey G. Nutrient Loading Model H. Pond Management Options I. Watershed Management Options J. BMP Operation & Maintenance Plan K. Letter from Mass. Division of Fisheries and Wildlife Farm Pond Management Plan – November 2015 ii Overview of Report The Farm Pond Management Report ("Management Report") summarizes recent diagnostic field work, watershed evaluation and analysis, review of pond management options, and recommended actions for conserving and protecting the recreational, ecological, and aesthetic features of the Pond. The authors, Fay, Spofford, and Thorndike (FST) of Quincy, MA (formerly doing business as Norfolk Ram Group) assisted by Dr. David Mitchell, CLM, were selected by the Town of Sherborn (the "Town") and the Farm Pond Advisory Committee (FPAC) as the technical consultant for this project in February 2014. This report provides the results from the field work conducted in spring-summer 2014, analytical results and the findings and recommendations based on these analyses. The report describes the tasks and activities contained in the final scope of work negotiated by the Town with FST. These tasks are organized into four chapters including: · Chapter 1 - Watershed Assessment: watershed base map, soil conditions, historical and current land use and review of existing water quality data and reports, and preliminary hydrologic model. · Chapter 2 - Field Work: water quality sampling, bathymetric confirmation, aquatic vegetation mapping, seepage measurements, and shoreline inspection. · Chapter 3 - Hydrologic and Pollutant Loading models: hydrologic budget, nutrient budget, stormwater contributions, and other sources. · Chapter 4 – Pond and Watershed Management Options: Evaluation of pond and watershed management and preservation options, solutions matrix with permit requirements and final recommendations. Additional information including field notes, laboratory analytical reports, water chemistry data, vegetation survey datasheets, etc. are provided in a series of Appendices. A glossary of aquatic terms is included at the end of this report to provide definitions of specialized limnological terms and expressions which may be unfamiliar to the lay public. Farm Pond Management Plan – November 2015 1 1.0 Watershed Mapping and Assessment Farm Pond (the “Pond”) is a natural waterbody situated within the Town of Sherborn in Middlesex County. The Pond is a kettle pond1 produced by the deposition and subsequent melting of glacial ice remnant produced by retreating glaciers during the last Ice Age. The surface area of the Pond is estimated at 126.3 acres and it drains a watershed area of approximately 409 acres2 within the larger Charles River basin (MADEP 2013). It has only one minor tributary and a relatively undeveloped watershed. There is an isolated shallow cove or embayment located on the eastern shoreline of the Pond, behind a constructed earth-covered rock berm, which apparently acts as an unregulated outlet. Farm Pond is listed as a Great Pond by the State of Massachusetts (MA EOEEA 2014). Table 1 provides a summary of the morphometric parameters associated with Farm Pond. The maximum depth is 58 ft with an average depth of just below 20 ft. It has a low shoreline development index (DL) indicative of its circular shape. Of particular note is the very low watershed to pond area ratio of approximately 3.2 to 1. This low ratio suggests a relatively limited influence of watershed land type on pond water quality.