715 RIVERSIDE RD 2016-01-01 MF Import

, Pacific Topsoils Riverside site-Stortn Orainage Report GFKConsulting Ir�,. 2 INTRODUCTION The subject site is currently used as a processing area for clean wocd debris. This drainage investigation and design has been undertaken to pe►mit this activity with the City and the States NPDES program. The site is comprised of approximately 8 acres and is located at the north east comer of the City of Everett along the Snohomish River in the Riverside industrial park. Prior to its current use the site was used by Weyerhaeuser for wood treahnent and equipment maintenance. As a result, this site has been remediated to contain hazardous materials; a portion of the site has an asphalt cap, and a portion is capped with only a soil layer and is currently covere:d with grasses. The scope of the contamination and subsequent remediation adds constrai;�ts to the use, grading and drainage features considered. The Pacific Topsoils processing operation is conducted on the paved area, the meadow area is used for storage of non hazardous materials only. The two surface treatments create two sub basins within the site. Runoff from the paved area is collected within perimeter ditches along the south and east edges and is conveyed to the south east comer where it is then discharged directly into the Snohomish River. Rainfall falling onto the meadow area is observed to infiRrate into the ground as originally designed. As a result ttiis design will only cansider runoff f�om the paved area only, and since the Snohomish River is listed as a receiving water body, only a water quality feature will be engineered. Per the Snohomish County Soils Survey, the soils in this area are Urban land. Refer to the Soils Map in the Appendix. 3 OFFSITE RUNOFF North boundarv The project is bounded to the north by another industrial site that is generally at a lower elevation than the subject site. No runoff expected to enter the site from the north. West boundarv The land west of the site is railroad yard and pasture- it is flat and runoff appears to infiftrate into the ground like the pasture areas onsite. No runoff is expected to enter the site from the west. South and east boundarvs The project is bounded to the south and east by the Snohomish River. No runoff is expected to enter the site from the south or east. sno,zo,o a i I `� J C:\Project data\Project files\PTopsoits Rlverside site\ReportslRiverside4.doc -�/p� .