1800 41ST ST 2023-06-23 - Laserfiche WebLink

I PRESERVATION OF NATURAL DRAINAGE SYSTEMS AND OUTFALLS I The project site and surrounding vicinity was substantially developed long ago, so the historic flowpath has been estimated from GIS contour information available from Snohomish County. This contour information was depicted on the Study Area Map included in Appendix 1A of this report. Based on the I regional contour information, it appears that the historic runoff flowpath extended north from the site. The flowpath appears to turn to the northeast approximately 14-mile from the site, and is presumed to have continue northeasterly toward the Snohomish River. Development of the surrounding area appears to have cut-off this historic discharge route, and the regional surface runoff is currently collected and Iconveyed through the City of Everett's public storm drainage system. The project is proposing stormwater detention and treatment facilities to manage runoff from a pavement area equivalent to the new proposed pavement. This detained and treated storm runoff will be I discharged to the City of Everett's public storm drainage system in the 41st Avenue right-of-way. This stormwater network extends easterly along the south side of 41st Street, and ultimately discharges to the Snohomish River. This is expected to maintain the current downstream flowpath,through manmade conveyance elements all the way to the Snohomish River. I I I I I I 1 I I 1800 41st Street—Parking Expansion Drainage Report I