1001 N BROADWAY EVCC PARKING 2018-01-01 MF Import

ID COUGHLiNPORILRLUNDEEN � c�) I I c�5 -� � 3` May 20, 201 I Surface Waterlteviewer City oi Everett 3200 Cedar Scree� Evere[t, WA 98201 RE Everett Communrty College Rite-Aid Parking Lot Storm Woter Design Dear Revicwer: The Surface Watcr design for revisions to the old Rite Aid building east the main Evere[c Communiq College Campui has been designed in acmrdance with the 2010 City of Everea Stormwater Managemenc Manual (SMM) and discussions with Jane Zimmerman and others in the city. The project will remove the old Ilite Aid smre and replace it with paved parking including planters and rain gardens. The project will remove about �2.000-sf of building and surrounding pavements. The project will install plancers and rain gardens into the existing all impervious area, resulting in a reduction o( about 5,700-SF of the impervious area on the site. Water from this area is collected by a local s[orm syscem that then drains [o the City's combined sewer-storm system. Water collected oH the new parL�ing lot will be directed to one of two systems: new rain gardens (6 and 2-half areas) at each end of the parking stalls will co�lect warer trom about 800-sf upslope of each of them. The rest of the lot is col�ected in catch basins and routed to exis[ing storm systems in the area. The rain gardens are sized to collect infiltrate and detain wa[er from these upslope areas. They have been dcsigned per BMP12.�0 in Volume III, Chapter 12 of the City's SMM. Approximately 220•SF of bottom area in each rain garden i I,S�OSF touil) has been provided to provide Ilow attenuation for the water mllecred oH the adjoining pavement. Each garden will have an under drain [o route un-infil[rated water m ehe storm system. Soil, plantings and mulch per the Ciry's design standards will complete the rein gardens. During construction appropriate measures will be uken to control exposed soils and sediment on sire. Smrm inlet protection. barriers and surface treatments will be used where appropriate ro compl� with City of Everett regulations for mnstruction srorm water and sediment mntrol. Sinccrely. Coughlin Porter Lundeen, Inc. � � ' '1i+ fl �'� ��(.., : . Kennech A. Wiersema P.E. Civil Enginccr ,.,, .., . � . ...... . ,,;,�. .,:�;�.,.