3310 MCDOUGALL AVE 2019-09-06 - Laserfiche WebLink

1. PROJECT OVERVIEW This document is intended to provide engineering information necessary to support the preliminary building permit application to the City of Everett for the proposed warehouse building proposed on lots 24-29. The site is located at 3310 McDougall-Ave, Everett, WA 98201; refer to Figure 1 for a vicinity map. The total project area is approximately 0.41 acres. The existing site contains a building and paved or gravel parking area. The slope of the site is flat and averages less than 5 percent down to the east. The proposed building will be located along the east property line with parking along the south and west sides of the new building. The new driveway will take access from the existing roadway to the east (McDougall Ave). Frontage improvements will be made along McDougall Ave consisting of a sidewalk and parking stalls, which will replace the existing parking areas. This project proposes to construct more than 5,000 sf of new plus replaced impervious surfaces, however since the majority of the site is already covered in impervious surfaces, this project only proposes to construct approximately 212 sf of new impervious surfaces. Therefore, minimum requirements 1-6 apply to all the new impervious surfaces for this project along with all the disturbed pervious surfaces. This proposal does not meet any of the land-use criteria that require specific source control for the final use and a SWPPP has been prepared to address the runoff from the site during construction. Refer to Sections 4 and 5 for a detailed discussion. Figures 2 & 3 are provided to show the existing and developed basins and runoff conditions for the project site. The runoff in the existing conditions will spread over the pervious and impervious surfaces on-site and drain toward the eastern property line. The runoff is then collected within the conveyance system in the McDougall Ave R/W. In the developed conditions, all of.the runoff from the new roof and parking/driveway surfaces will be collected by the proposed parking lot stormwater collection system and directly connected to the combined storm/sewer system. The site stormwater improvements were designed to meet the COE 2010 Stormwater Management Manual along with the modifications to the standards contained in the interim Public Works Policy#2-11. The general soil conditions for this project site as mapped by the USDA Web-Soil Survey were found to be Alderwood-Urban land complex type soils. The downstream system for this project is comprised of underground pipes and catch basins. Due to the size of this project Minimum requirements 1-6 apply to the proposed drainage design as noted above. Included on the following page is a copy of the MR flow chart out of the COE Drainage Manual showing how the applicable minimum requirements were determined. McDougall Warehouse 17-0212 April 2017 Page 3