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I Coastal Nitrogen Loading Project Final Report April, 2002 prepared by Cape Cod Commission Water Resources Office Nauset Marsh/ Town Cove 1 I . I I I Coastal Nitrogen Loading Report I Project 99-03/604 FINAL REPORT I Centerville River/East Bay, Nauset Harbor/Town Cove, Popponesset Bay, and Herring River, Harwich I Prepared by: Cape Cod Commission I Eduard M. Eichner, Water Scientist/Project Manager Thomas C. Cambareri, Water Resources Program Manager Ben Smith, GIS Analyst Van Morrill, Project Assistant I Gary Prahm, GIS Program Manager I Margo Fenn, Executive Director Prepared for: I MASSACHUSETTS DEPARTMENT OF ENVIRONMENTAL PROTECTION BUREAU OF RESOURCE PROTECTION I AND U.S. ENVIRONMENTAL PROTECTION AGENCY I REGION I MASSACHUSETTS EXECUTIVE OFFICE OF ENVIRONMENTALAFFAIRS I Robert Durand, Secretary DEPARTMENTOF ENVIRONMENTALPROTECTION Lauren Liss, Commissioner BUREAU OF RESOURCE PROTECTION I Cynthia Giles, Assistant Commisaiorier DIVISION OF MUNICIPAL SERVICES I Michael Rotondi, Director June, 2002 This project has been financed partially with Federal Funds from the Environmental I Protection Agency {EPA) to the Department of Environmental Protection {DEP) under a S604b Competitive Grant. The contents of this report do not necessarily reflect the views and policies of EPA or of DEP, nor does mention of trade names or commercial I products constitute endorsement or recommendation for use. I I I I Table of Contents I Final Report Coastal Nitrogen Loading Project I June2002 Page I I. INTRODUCTION .................................................................................................................... 1 II. GENERAL EVALUATION PROCESS ............................................................................... 2 I A. NITROGEN LOADING LIMITS AND FLUSHING STUDIES .............••......................•..................... 3 i. Flushing Study Characteristics ................................................................... ; ........................... 3 ii. Nitrogen Loading Limits ....................................................................................................... 4 I iii. Current Regulatory Setting ................................................................................................... 5 B. WATERSHED DELINEATION ..................•.•...................................................•........................... 8 C. LAND USE AND NITROGEN LoADJNG ANALYSIS ..•................................•....•..•.•...........•........•. 9 I D. DEVELOPMENT AND IMPLEMENTATION OF MANAGEMENT STRATEGIES .....•........................ 12 III. CENTERVILLE RIVER/EAST BAY SYSTEM ............................................................. 14 I A. FLUSHING STUDY, CRITICAL LoADS, AND EXISTING AND BUILDOUTNJTROGEN LOADS .... 14 B. POTENTIAL MANAGEMENT STRA TEGJES ....................................................•......................... 19 i. Scudder Bay, Scudder Bay/Bumps River, Centerville River - East/Centerville River, and Scudder I Bay/Bumps River/Centerville River/Centerville River-East/Centerville River-West subwatersheds 19 ii. Phinneys Bay ...................................................................................................................... 21 iii. Whole Centerville River/East Bay system ............................................................................ 22 I C. NEXT STEPS/DISCUSSION/RECOMMENDATIONS ................................................................... 23 IV. NAUSET HARBOR/fOWN COVE SYSTEM ................................................................ 25 I A. FLUSHING STUDY, CRITICAL LOADS, AND EXISTING AND BUILDOUT NITROGEN LOADS ..... 25 B. POTENTIAL MANAGEMENT STRATEGIES FOR SALT POND ............................................•....... 30 C. NEXT STEPS/DISCUSSION/RECOMMENDATIONS ................................................................... 31 I V. HERRING RIVER, HARWICH ......................................................................................... 34 A. INITIAL WATER QUALITY EVALUATION ............................................................................... 34 B. NITROGEN LoADING ANALYSIS ........................................................................................... 38 I C. NEXT STEPS/DISCUSSION/RECOMMENDATIONS ................................................................... 39 VI. POPPO NESSET BAY ......................................................................................................... 41 I A. COORDINATION AMONG MANY PROJECTS ........................................................................... 41 B. PRELIMINARY NITROGEN LOADING ANALYSIS .................................................................... 43 C. NEXT STEPS/DISCUSSIONIRECOMMENDA TIONS ................................................................... 46 I VII. CONCLUSIONS ................................................................................................................ 47 I VIII. REFERENCES ................................................................................................................. 49 I I I I List of Figures I Final Report Coastal Nitrogen Loading Project I June 2002 ~e Figure I. Four Step Approach to Nitrogen Management of Coastal Waters 2 Figure 2. Local vs. System Residence Time 4 I Figure 3. Centerville River/East Bay System Watersheds 15 Figure 4. Existing Nitrogen Loading (Centerville River/East Bay System) 17 Figure 5. Buildout Nitrogen Loading (Centerville River/East Bay System) 18 I Figure 6. Nauset Harbor/Town Cove System Watersheds 26 Figure 7. Existing and Buildout Nitrogen Loading (Nauset Harbor/Town Cove System) 28 I Figure 8. Nitrogen Loading within the Salt Pond Watershed 30 Figure 9. Nitrogen Fluxes (kg/yr) in Town Cove (Teal, et al., 1983) 32 Figure 10. Herring River System Watersheds 35 Figure 11. Herring River Monitoring Locations 36 Figure 12. Popponesset Bay Subwatersheds 42 I List of Tables Final Report I Coastal Nitrogen Loading Project June2002 I Page Table I. 1991 Buzzards Bay Project Recommended Nitrogen Loading Limits 6 Table 2. Current BBP Recommended Coastal Embayment Nitrogen Loading Limits 7 Table 3. Technical Bulletin 91-001 Nitrogen Loading Factors II I Table 4. Residence Times and Volumes in the Centerville River/East Bay Embayment System 14 Table 5. Critical and Watershed Nitrogen Loads in the Centerville River/East Bay Embayment 16 System I Table 6. Selected Potential Nitrogen Management Options Reviewed (Scudder Bay watershed) 20 Table 7. Selected Nitrogen Management Options Reviewed (Bumps River/Scudder Bay combined 20 watershed) Table 8. Selected Nitrogen Management Options Reviewed (Centerville R East/Centerville River) 21 I Table 9. Selected Nitrogen Management Options Reviewed (Centerville River/Scudder 21 Bay/Bumps River/Centerville River East/Centerville River West) Table 10. Selected Nitrogen Management Options Reviewed (Phinneys Bay) 22 I Table 11. Selected Nitrogen Management Options Reviewed (Whole Centerville River/East Bay 23 System) Table 12. Residence Times and Volumes in the Nauset Harbor/Town Cove Embayment System 25 Table 13. Critical and Watershed Nitrogen Loads in the Nauset Harbor/Town Cove Embayment 29 I System Table 14. Selected Potential Nitrogen Management Options Reviewed (Salt Pond watershed) 31 Table 15. .Measured and Project Strearnflow Measurements in Herring River System, Harwich 37 I Table 16. Watershed Nitrogen Loads in the Herring River System (Harwich, MA) 38 Table 17. Preliminary Nitrogen Loads in the Popponesset Bay Watershed 45 I I I I Executive Summary I Most coastal embayments on Cape Cod are degraded by impacts from existing development within their watersheds. Future development will further strain these ecosystems. Creating solutions to restore and protect these ecosystems requires a better understanding of how each individual embayment functions. Analyses need I to be completed to answer questions like: I) how big is the watershed?, 2) what are the nutrient loads coming from the watershed?, and 3) can the tides flush out the nitrogen quicker than it is coming in? Answers to these questions and others will help to provide the basis for developing options to restore or preserve coastal I ecosystems. This report documents nitrogen loading assessments completed by the Cape Cod Commission for the I Centerville River/East Bay coastal system in Barnstable, the Town Cove/Nauset Marsh system in Orleans and Eastham, the Herring River system in Harwich, and the Popponesset Bay system in Mashpee and Barnstable. These assessments are part of an overall effort by the Cape Cod Commission, the state Department of I Environmental Protection, and a number of other agencies and organizations to develop basic information for all of the coastal systems surrounding Cape Cod. Similar previous assessments are currently being used in town comprehensive wastewater assessments and citizen board discussions about appropriate development. I These efforts can also be used as first steps in the process of developing water quality protection standards under the state and federal Total Maximum Daily Load (TMDL) provisions of the Clean Water Act. The Massachusetts Estuaries Project (MEP), which is being led by DEP and UMASS-Dartrnouth School of Marine I Science and Technology (SMAST), will take the next step forward by combining watershed information similar to analyses presented in this report with embayment-specific water quality and ecosystem information I through the use of embayment-specific models. The assessment of the four systems