12/20/2012 SEWER COMMISSION Minutes

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Table 4. Threshold Comparison Results for Mashpee Sewer Commission Scenarios: Waquoit Bay Comparison of TN concentrations for present conditions,threshold loading,and three modeled buildout loading scenarios for the Waquoit Bay system. MEP threshold concentrations for Waquoit Bay are 0.380 mg/L TN for eelgrass(primary),and between 0.400 and 0.500 mg/L TN for infauna(secondary). TMDLs were established for Quashnet River,Hamblin Pond,Little River,Jehu Pond,and Great River in 2007,but the official EPA approval letter does not contain TN concentrations. The thresholds listed below are from the MEP reports for Eastern Waquoit Bay and the overall system. The MEP thresholds for Quashnet River,Hamblin Pond,Little River,Jehu Pond,and Great River did not change in the evaluation of the entire system. Habitat Present TMDL/MEPScenario Option IA Scenario Option 1B Scenario Option 1C TMDL section threshold Threshold mg/L mg/L mg/L mg/L m East Wa uoit-TMDL established Jehu Pond-WB 1 eelgrass 0.630 0.446 0.521 0.529 0.529 Great/Little River-WB3 eelgrass 0.427 0.38 0.374 0.377 0.377 Hamblin Pond-WB4 eelgrass 0.521 0.38 0.415 0.421 0.421 Quashnet River-WB7,WB8 infauna 0.704 0.52 0.502 0.504 0.509 Rest of Wa uoit-MEP Report read for review Upper Wa uoit Bay-WB12 eelgrass 0.400 0.38 0.360 0.361 0.361 Mid Childs River CR2 eelgrass 0.651 0.38 0.688 0.687 0.687 Upper Eel River-ERl infauna 0.669 _0.5 0.680 0.679 0.679 Notes: 1) shaded cells indicate Scenarios that meet TMDL/MEP thresholds for eelgrass or infauna. 2) MEP Thresholds for rest of Waquoit are from: Howes B., S.Kelley,E.Eichner,R. Samimy,J. S.Ramsey,D. Schlezinger,P.Detjens (2011). Massachusetts Estuaries Project Linked Watershed-Embayment Approach to Determine Critical Nitrogen Loading Thresholds for the Waquoit Bay and Eel Pond Embayment System,Towns of Falmouth and Mashpee,MA,Massachusetts Department of Environmental Protection.Boston,MA.