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4 <br /> r <br /> and changes to watershed boundaries in response to changing stresses, could be built into the <br /> analysis. <br /> Regarding Popponesset Bay watershed, 113 watershed was direct discharge to the estuary, 113 <br /> discharged to streams and 113 discharged to ponds before traveling to the estuary, providing <br /> complexity to the surface water. Mr. Walter explained the map depicting purple as recharge <br /> areas to estuaries, green as recharge areas to the streams and blue as recharge areas to the ponds. <br /> Mapping the areas and creating model cells would then produce a means.to identify the nitrogen. <br /> loads. Mr. Walter offered a hypothetical situation whereby Mashpee was fully sewered, <br /> maintaining the sane discharge rates at the wastewater treatment facilities, and it was noted that <br /> water levels and gradients would not change greatly. However, partial sewer'ng and water <br /> disposal would create lamer point sources and mounding. fir. Walter explained that the model <br /> would allow a 3-D distribution of mass in the aquifer over a 30 year period. Mr. Walter <br /> summarized that severing would not change the groundwater gradients as much as.the disposal <br /> location. <br /> Chairman Fudala inquired whether a movie could be developed and lam-. Walter indicated that it <br /> became complicated in 3-D. There was discussion about the location of Maishpee Commons and <br /> its relation to the nitrogen plume in the range of -7, and the location of other plumes and high <br /> density areas in Mashpee. Mr. Lyons recommended that,for future reference, Rt. 28, Rt. 151 <br /> and Rt. 130 be added t images. Mr. Lyons also recommended that the two maps be in the same <br /> scale. <br /> Mr. Walter stated that the nitrogen being considered was waste derved nitrogen. Chairman <br /> Fudala inquired whether,existing conditions were from the 2001 MEP and Mr. waiter confirmed <br /> that it was. fir. Walter described the modeling as a cookbook to show its capabilities, noting <br /> that never data could be incorporated into the modeling. The Chair inquired why Sandwich had <br /> such a significant load deep in the aquifer. Mr. Walter stated that there was mre vertical flow in <br /> the area of the watershed divide sending the load deeper into the aquifer. Mr. Walter explained <br /> the cross section of the ponds and layering of the image. <br /> Mr. Walter also discussed the source term run for 100 years and the changing of the load over <br /> many years. The image showed that in 7 years, o°/o of the load in the estuary would be reached <br /> and 0% of the load in 30 years. The image represented timeframe loads for current conditions <br /> to the different major receptor types: estuary, stream and pond. Mr. Walter explained the <br /> differences among the loads of each receptor type.. �&. 'falter also explained the percentage of <br /> the total load and hove-it represented the percentage of the instantaneous load. Mr. Walter <br /> discussed the complexity of the ponds and noted that ponds experienced increased reduction. <br /> Mr. Gregg referenced the NIEP reports and their estimated breakouts,from lamer watersheds and <br /> sub-watersheds, with attenuation assigned to fresh water bodies. Mr. Lombardo believed that the <br /> freshwater attenuation factors were derived from literature estimates. <br /> Mr. Walter discussed the scenarios,the first of which represented full sewering where all return <br /> flow would be removed from the Mashpee planing area while maintaining current wastewater <br /> treatment facilities. After 30 years of transport,the load flushes well except where It lingers <br /> down gradient of the ponds and down gradient of the existing wastewater treatment facilities. <br /> Travel tunes show that 0%would occur in&7'years, indicating that the system should respond <br /> 2 <br />