10013 4TH AVE W 2025-07-28 - Laserfiche WebLink

SECTION II: SITE ASSESSMENT Based on the site reconnaissance and the available topography we have the following info: • Topography: The topography of the site shows a 2 to 4-ft fall to the east. Refer to the grading plan for more details. • Drainage: The majority of the site drains to the east and sheetflows into the neighboring property to follow its natural drainage course and eventually ends up in an unnamed creek which leads to North Creek. No existing problems were found and it appears that our proposal will not aggravate any downstream issues. • Soils: Per SCC survey of Snohomish County, the project site contains Alderwood Urban Land Complex 2 to 8 percent. Refer to the attached soil map later in this report. • Ground Cover: The entire site exists as grass with some thick bushes on the north boundary. • Critical areas: There are no critical areas located within the site. • The property access is from 4th Ave West. The site is located in the commercial area with residential homes located to the north, and south; with commercial property to the west and east. SECTION III: ON-SITE STORMWATER MANAGEMENT A Bioretention Cell is proposed to meet MR#5 to infiltrate the maximum extent feasible. The bioretention cell will generally follow the guidelines of BMP 12.40, however, the sizing and the detail have been modified to allow for more bioretention soil. It has been sized using WWHM. The soils are Alderwood soils with a long term infiltration rate assumed to be 1 inch per hour. It is designed to accommodate mainly the roof area. See the developed basin map later in this report. The parking lot will drain to the east to a 18"wide x24" deep drainage ditch filled with drain rock. The overflow from the bioretention cell along with the parking lot drainage will flow to the east and enter into the existing storm drain system located on the neighboring property to the east to follow its natural drainage path.