1415 BROADWAY CM HEATING 2023-09-25

SECTION VIII: PERMANENT STORMWATER CONTROL PLAN A. OFF-SITE ANALYSIS A site reconnaissance was performed by Brian Kalab of Insight engineering on March 23, 2021 to verify the downstream flow paths and observe any drainage problems downstream of the site. The sky was partly cloudy with a temperature of 52 degrees. The site is currently developed with a home, a commercial building, and parking lot. The site contains one drainage basin that slopes to the slightly to the west. There are no critical areas located within the site. Per NRCS survey of Snohomish County, the project site contains Alderwood soils that have a hydrologic classification of Type"C". No visible on-site drainage problems were observed at the time of field investigations. Upstream Analysis Based on the site reconnaissance and the topographic survey of the site,the off-site area entering the site is very minimal. Refer to the Downstream Analysis Map attached in the next page for more details. Downstream Analysis The site contains one drainage basins that slopes slightly to west. The runoff from the site enters an existing catch basin located in the center of the site and joins the existing combined storm and sanitary sewer system along alley in between Broadway and Mcdougall Ave. The flow continues south for about 1,250 ft before joining the storm and sanitary sewer system along 17th St. It flows east for about 700 ft before turning south again and joining with the storm and sanitary sewer system along the alley between Rainier Ave and Virginia Ave. This is where the drainage analysis was completed. There did not appear to be any restrictions or erosion problems within 1 mile of the site. In the mitigated state the runoff from the site will be connected to the existing storm and sanitary sewer system to the east of the site. The flow is minimal and therefore the downstream channel should not experience any problems in the future. Insight Engineering Co. -Stormwater Site Plan 3/25/2021 -23-