EVALUATION OF HINCKLEYS POND, HARWICH, MASSACHUSETTS BY WATER RESOURCE SERVICES, INC. AND CDM SMITH JULY 2012 Contents Executive Summary ....................................................................................................................................... 1 Introduction .................................................................................................................................................. 5 Study Approach and Methods ...................................................................................................................... 5 Lake Features ................................................................................................................................................ 8 Physical Attributes and History ................................................................................................................. 8 Water Chemistry ..................................................................................................................................... 12 Sediment Assessment ............................................................................................................................. 17 Phytoplankton ......................................................................................................................................... 19 Zooplankton ............................................................................................................................................ 19 Rooted Plants .......................................................................................................................................... 23 Fish .......................................................................................................................................................... 23 Watershed Features and Loads .................................................................................................................. 23 Watershed Size and Boundary ................................................................................................................ 23 Land Uses ................................................................................................................................................ 24 Surface Water Drainage Issues ............................................................................................................... 29 On-Site Wastewater Disposal Assessment ............................................................................................. 33 Cranberry Bog Assessment ..................................................................................................................... 35 Hydrologic Loading...................................................................................................................................... 42 Water Inputs and Outputs ...................................................................................................................... 42 Nutrient Loading ......................................................................................................................................... 45 Nutrient Inputs and Outputs ................................................................................................................... 45 Lake Loading Response Model ................................................................................................................ 47 Model Inputs ....................................................................................................................................... 47 Model Calculations .............................................................................................................................. 47 Model Predictions ............................................................................................................................... 48 Management Goals ..................................................................................................................................... 50 Current Uses ........................................................................................................................................... 50 Use Impairment ...................................................................................................................................... 50 Rehabilitation Objectives ........................................................................................................................ 50 Possible Loading Targets ......................................................................................................................... 51 Management Options ................................................................................................................................. 51 Additional Information for Artificial Circulation ..................................................................................... 67 Additional Information for Nutrient Inactivation ................................................................................... 72 Prediction of Conditions Achievable Through Management .................................................................. 79 Management Conclusions and Recommendations .................................................................................... 83 Funding Options .......................................................................................................................................... 88 References .................................................................................................................................................. 90 Tables Table 1. Bathymetric features of Hinckleys Pond. ...................................................................................... 11 Table 2. Water quality data for Hinckleys Pond collected by the PALS program, 2005 – 2010. ................ 13 Table 3. Average values for water quality features of Hinckleys Pond, 2005-2010. .................................. 17 Table 4. Sediment quality data from the December 2009 sampling. ......................................................... 18 Table 5. Sediment quality data from the September 2011 sampling. ........................................................ 18 Table 6. Phytoplankton data for Hinckley Pond. ........................................................................................ 20 Table 7. Summary of phytoplankton data for Hinckleys Pond. .................................................................. 21 Table 8. Zooplankton of Hinckleys Pond. .................................................................................................... 22 Table 9. Estimation of nutrient inputs from Title 5 wastewater disposal systems to Hinckleys Pond. ...... 34 Table 10. Results from bog discharge testing at Jenkins and Thatcher Bogs, October 2011. .................... 38 Table 11. Hinckleys Pond water level. ........................................................................................................ 40 Table 12. Estimation of loading to Hinckleys Pond from cranberry bogs. .................................................. 41 Table 13. Water and nutrient loads to Hinckleys Pond. ............................................................................. 44 Table 14. Export coefficients applied in LLRM for Hinckleys Pond. ............................................................ 47 Table 15. LLRM load summary for Hinckleys Pond. .................................................................................... 48 Table 16. LLRM predictions for current conditions with actual data for comparison. ............................... 49 Table 17. Algae management options review ............................................................................................. 52 Table 18. Estimation of phosphorus inactivation dose and cost for Hinckleys Pond. ................................ 74 Table 19. Calculation of the longevity of phosphorus inactivation on phosphorus load to Hinckleys Pond. .................................................................................................................................................................... 76 Table 20. Summary of LLRM output of predicted Hinckleys Pond water quality for various management scenarios. ............................................................................................................. 80 Table 21. Cost comparison of possible internal load reduction approaches. ............................................. 86 Figures Figure 1. Location and general area features of Hinckleys Pond.................................................................. 6 Figure 2. Outlet of Hinckleys Pond in 2011. ................................................................................................ 10 Figure 3. Bathymetric map of Hinckleys Pond. ........................................................................................... 10 Figure 4. Defined edge of muck accumulations that completely cover the bottom of Hinckleys Pond. ... 11 Figure 5. Selected water quality of Hinckleys Pond, 2005 – 2010, expressed for three depth ranges. ..... 15 Figure 6. Graphic summary of algal biomass in Hinckleys Pond. ................................................................ 21 Figure 7. Surface watershed of Hinckleys Pond. ......................................................................................... 25 Figure 8. Groundwater contours in the Hinckleys Pond area. ...................................................................