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2 E�avi��nme�atal Analy.ris <br /> c)Suhstantially alter the existv2g dtarnage pattern of the site ot area,it�cluding through the <br /> aJteratiori of the coutse ofa stream or river,in a mar�er whrch would result it�substarr�tral <br /> etasion or slltatran ar�- or off-site? <br /> The stormwater collected at the replacement pump starion and wet we.12 would dischatge through an <br /> existing 24-inch line. The new pump station would have a wet-we�l structure capable of collecting up <br /> to 2,900 cubic feet of stormwater. T'he new pump station would be capable af discharging up to <br /> 32.40 cfs,the p�edicted flow from the 100-year sto�m,which would decrease the potential for <br /> flooding in tl�e area. <br /> The discharge rate from the pump starion woula increase from 13.37 cfs to 32.40 cfs. The new <br /> starion would interconnect to the exisring 24-inch pipeline to the creek. During peak storms, the <br /> flow througlz the e�sting pipeline would�ncrease from appxoximately 4.3 Fps to 14.3 fps. The <br /> increase in discharge into the creek would occur dtiring storm events when runoff was greater than <br /> the discharge from the current pump station. During these events, the water level ir�the cteek would <br /> be higher thaa normal. The increased flow of 10.3 fps woul.d slightly exceed the 10.0 fps design <br /> criteria for the existing 24-inch pipe,but would not result in substantial exosion or siltation of the <br /> cxeek bed. (Less than 5ignificant Irnpact) <br /> d)Substanttally alter the ea�istrng dtatnage pattern of the site at atea, �ircludrilg through the <br /> alteratfon of the course ofa stream or rivex, ot substarlually increase the rate ot amount af <br /> surface rurlaffr� a manner which would result rrl flooditlg otr- or off-site? <br /> See the discussion in item c a�ove concerning the praposed changes to the existing drainage pattern <br /> in the site area. The upgxaded pump station wauld red�ce the potentia.l for flooding in the Bair <br /> Island drainage area,and the increased cjischarge to Redwood Creek during peak storm events would <br /> be an insignificant increase in channeled downstream flows to the Bap. (Less than Significarit <br /> Impact) <br /> e) Cfeate or contribute rurlofl`'water whiclr worrld exceed the capacity ofexisting or planried <br /> starmwater drairlage systems or provide substantial additrorlal sources ofpolluted tunoffl <br /> The proposed joint-use path and sidewalks would add appro�mately 9,000 square feet{0.20 acres) of <br /> new impervious surfaces to tl�e e�sring area. Stormwater along the jaint-use path would be collected <br /> and discharge thraugh a new 24-inch pipe. The new impervious surfaces would not substanrially <br /> alter the e�sring drainage pattems of the project area gi�-en the small footprint and relatively fla� <br /> nature of the project. The new pump starion and wet well would be undergraund, and the emergency <br /> generator housing would be sma.11er than the existing pump station. The additional impervio�s <br /> surface represents O.OQ4 percent of the e�sring total watershed area of Red�vood Cxeek <br /> The pump stauon replacement project would not alter surface drainage patterns in the 22.28-acre <br /> collecrion area along Bair Island Road,which incZudes 4.94 acres of Peninsu].a Park development that <br /> drain into the station. Under the proposed project,the City wou�d install approximately 351inear feet <br /> ?�-�f, US 101 Pedestrian Uraderc�o.r.carag rand B�ir <br /> I.rlarad Kaad Starm Drain Pump Statiosa Project <br />