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MEMORANDUM <br /> October 3,2011 <br /> To Town of Mashpee Sewer Commission <br /> Project Watershed Nitrogen Management Plan <br /> From J.Jefferson Gregg,P.E. Tel.No. 774-470-1640 <br /> Subject DRAFT Scenarios Description JbbNa, 8612001 <br /> The Town of Mashpee(Town)is undertaking a Watershed Nitrogen Management Plan(WNMP)to address <br /> nitrogen enrichment issues in the Town's estuaries. One management approach is to collect wastewater, <br /> treat it to a very high level,and then recharge the treated effluent back to the ground.The purpose of this <br /> memorandum is to summarize the two latest approaches being developed for the Town that will be provided <br /> to Massachusetts Estuaries Project(MEP)for evaluation and modeling.That modeling effort is to identify <br /> whether the approach presented will achieve the TMDLs under a future condition. The memorandum <br /> describes the development and outline of these approaches that can then be crafted into alternatives for the <br /> Town to consider as part of the WNMP. <br /> Background <br /> In the Spring of 2008, as part of the WNMP,a Draft Alternatives Scenario Analysis and Site Evaluation <br /> Report was issued,and a"Draft Nitrex'm Technology Scenario Plan"was also prepared in order to evaluate <br /> 5 different scenarios for addressing future nitrogen loadings on the project Planning Area. <br /> These reports,with some update made to the Nitre)Jm approach,were then run through the MEP Modeling <br /> Approach to evaluate their ability to meet the TMDLs established for Popponesset Bay and Waquiot Bay <br /> East,The results were issued in two memorandums dated November 13,2009 and February 9,2010.The <br /> results were compared to embayment thresholds and those Total Nitrogen(TN)thresholds associated with <br /> eelgrass and infauna. <br /> Following the release of those findings, the Sewer Commission then met to discuss possible discharge <br /> locations including those identified previously,such as Site 4(the Transfer Station)and Site 7(part of the <br /> New Seabury Golf Course),and now locations such as several parcels north of John's Pond(identified for <br /> presentation purposes as the Backroads Parcels), expansion of use at Willowbend Golf Course, and <br /> possible expansion of use at the New Seabury Golf Course. <br /> As a result of these MEP Scenario findings,the Sewer Commission has asked GFID to move forward with <br /> two new Scenarios to be modeled.The initial step of establishing these two new scenarios was based on a <br /> Sewer Commission map which re-divided the project planning area into several sections identifying <br /> preliminary collection and treatment locations within the project planning area.These groupings were similar <br /> to those established in the Draft Alternatives Scenario Analysis Report (called out as "sewersheds"); <br /> however, they were often larger and not necessarily based on potential collection system layouts. This <br /> preliminary plan (dated 12-13-10— see attached untitled Figure) shows each of these areas and their <br /> proposed discharge location.This preliminary plan included a portion of Falmouth and Barnstable within the <br /> GHD Inc.1545 yannough Road Hyannis MA 02601 USA <br /> T 1 774 470 1630 F 1 774 470 1631 E hyarnaflOgi-rd.corn W-ghd.coru <br />