09/30/1996 BOARD OF SELECTMEN Minutes

Home Browse Search

Town Harbor;naster to inhibit flaw into the river, Dredging of the existing shoal area, which is covered by as little as six inches of watt: at loTN tide, was models d with a minimum low tide depth of 3 ft. Dredged spoils we.'e aseumed to be deposited offsite. Scenario 2: Dredging modeled in Scenario I way exttnded approximately 1,000 ft up 1vlashpee River in the farm of a 30 ft wide channel with A minimum loin tide depth of 3 ft. Dredged material for this scenario was assumed deposited on the tidal flats in Mashpee River adjacent to the dredged channel (sideCastil1g)- Scenario 3: Dredging modeled in Scenario 2 wag extended up Mashpee River to Orsini Bench, approximately one-half mile upstream front the mouth of Mashpee River_ Dredged spoils were assumed tc. be deposited offsitt, exccpt for th` sidecasting described in Scenario 2. Scenario 4: :yiashpee River dredging in Sc}ena:io 3 was extended upstream approximately one And one-halt miles to Conaway`s Cave. A6 in Scenario 3, dredged ma+erial was asaa.red deposited o:isite, exc:pt for tl,e sidecastiz�g desc:ibcd in Scenario 2. Scenario 3: Dredging the shoal from the :notitll of Nlaihpee River into Pop ponessct Bay as well as channel dredg"Ing up the Mas;pee River as described in Scenario 2, combined with mainterance dredging at the mouth of Polap��f:eseck Bay as proposed by BSC, 1996. Scenario 6: lrhia 9cena:-io included all dredging in Sctnario 5 plus dredging of a channel connecting the Popponesoot Bay IrI9t with Maahpec River. Results Scenarios 1-4 were compared to existing; conditions based on a residence time calculation. Residence. time defines the time required for an average parcel of water to migrate out of the Estuary to Nantucket ti:nesld.are indicative` af2l�ghib awater lcRtur Of quality, wa#cr quality. Typically, loin reside since rapid flttshing o: an embayrnent reduces the concentration of nutrthe and pollutants in the water. Individual residence times were cc.1puted fi?r the ci�tirE popponesset Bay Estuary, Ockway Bay, Shoestring Day, and hlasllpee River, and arc presented .n Table I for exfsting conditions a8 well as dredging scunnarios. Table 1 rlso inciudes the tidal prism into Mashpee River and the: modeled volume of dredged material for each scenario. Tidal prism is defined ay the volume of water entering Mashpee River over an a%,erage tidal cycle.