1205 CRAFTSMAN WAY PORT INFRASTRUCTURE 2016-01-01 MF Import

DRAINAGE NARRATIVE This addendum details the revisions to the stormwatcr systcm for thc North Marina Redevelopment Infrastructure Phase I project. Bid Package 13 necessitates revisions to the Infrastructure Phase 1 design approved by the City. The construction will procced in several separate construction contracts over a period of rime. The first construction contract,designated Bid Package 13, is to construct 13�' Street from West Marine View Drive to 2"d Avenue. The rest of Infrastructurc Phasc 1 will be built in Inter construction phase(s). "Co function separately,this addendum details drainage design revisions for the Bid Package l3 area. "1'Uc Bid Package 13 area includes Drainage Basin 2 and poriions of Basins 1 and 3 from the original design. To providc water quality treatment to the area without installing trcatmcnt facilities in the Basin 1 and Basin 3 azeas,Basin 2 is enlazged to cover the entire Bid Package 13 area. Drainage basins from the original dcsign are prescnted in Pigure ]. Pigure 2 shows thc cnlargcd Basin 2. Surface runoff from the enlazged drainage basin�vill continue to be collcctcd into the pipe system by catch basins. 'Chc collected runoff will be treated by a water quality f'�cility before discharging to the river and mazina basins as previously designed. The portion of the drainage system in the Craftsman district was constructcd with the Craflsman District devclopmcnt. A pipe system to convey storm runoff from this area lias bccn installed through the CraRsman District and will be connected to the water treatment facililies to be installed in Bid Packt+ge 13. As previously designed, stormwuter runo(Twill first be pretreated by an Aqua-Swirl'"� system. Water quality tlows will thcn bc divertcd to a StormFiltcr system for primary water quulity trc�tmcnt. 1'hc high flows are bypassed downstream of the StormFilter system as previously designed. The criteria for determining watcr quality flow�ratcs for ' the Aqua-Swirl"' and StonnFiltcr�systcros havc not cha�iged. The Aqua-Swirl tutd StorniFiltcr�systems in Basin 2 have been increased in size to accommodate the additionnl flow. The calculations for resi•r.ing iltese treatmcnt systems arc attached. As prcviously dcsigncd,the stormwnter pipe system is si��d to wnvey the 25-year storm event. The Rational Method was used lo determine preliminary pipc sizing. Backwater analysis was performcd to conlirm water surface levels comply with city requirements. The pipe sizing calculations are attached. Rcvisions to Uraiungc Basins 1 and 3 are not included in this addendum. These basins will be addressed in future phases. '1'wo copies of thc originnl drainage report for Infrastructure Phase 1 are enclosed. sah�2lcp\OT004�oc nmr inGa ph I -ca\I3th st&2nd ave bid packageWminage narmtive.docUnadldcy Early Roadway and Utilities Ltid Package 13 A�� Stormwater Site Plan Addendum ' �' '