1901 MERRILL CREEK PKY 2018-01-01 MF Import

r . . � . _ _ Project Descrlptlon: � The site is located on the northwest quadrant of the intersection of Metrill Creek Parkway and Hardeson Road,between Narbeck Creek and Mecrill Ring Creek in Everett Washington,as shown � on the Site I.ocation Map,Figure 1. The site is borderv,.d by Metrill Cre�lc Parkway to tiie south,and dense forest to the north, west, and east. The site is 14.4 acros of which 8.1 acres is planned for development with the remaining 63 acres to remain undeveloped. Proposed improvements include � the wnstruction of an 218 unit apartrnent complex with associated parking, landscaping, and utilities. ISite Dninage Features: I Topography of the site consists of a relatively flat bench sloping at appnoximately 3%to the north, (ocated on the upland westem portion of the site. From this bench,the site slopes down to the east towardMerrillRingCreekatanaverageslopeinclinationof40%orgreater. Sitevegetationconsists I primarily of older second growth conifer, deciduous trees and thick underbrush. Soils in the area are classified as a Alderwood type soiL Aldenvood soils consist ofgravely loam which is dense and oem�eates very slowly. According to a soils report written by Geo Engineers November 12, 1997 this site can be a potentiai landslide hazard azea, although proper grading will help with slope I. stability. 1 Existingstormwatertravelonsiteconsistsofacombinationofsheetflowoverland,andchannelflow in naturally occuRing streams and ravines. Local precipitation falling on the site flows west and east to two separate drainage basins,the Narbeck Creek Basin and Me�riil Ring Creek Basin. Drainage � enters the site through Mecrill Ring Creek which enters the site from the south and continues north through the entire length of t'��property. � Flow Control and Water Quality Facilities: � Flow control and water quality design criteria for the site are in accordance with the City of Everett Storm Water Management Manual (Chapter 3) dated January 1997. This project is required to provide stream bank erosion controt and runoff treatment due to the creation of more than 5,000 � square feet of impervious and paved surfaces(table 1-1.1). The City of Everett Storm Water Management Manual requires that detention be provided to limit � peak flows from the developed site during the 2-yeat,24-hour stomt to 50%of the existing condition 2-year,24-hour peak storm runof�'rate and to maintain the existing condition peak flow rates for the 10-year and 100-year,24 hour design stom►events with appropriate corrxtion factors. Run-off is � estimated using the Santa Barbara Urban Hydrograph method. Water quality is proposed to be achieved by the construction of a wetpond with a pertnanent pool � volume equal ro the volume of runoff from the 6 month,24 hour design stocm,using developed site conditions. The wetpond is to be composed of two cells, the open watet cell and the wetland ` treatrnent cell. A maximum of 85%of the pem�anent pool volume may be associated with the open. � water cell which is located in a vault. A minimum of 15%of the pertnanent pool volume must be '.