2425 39TH ST ROYELL MANUFACTURING INC 2019-12-09

1. PROJECT OVERVIEW This document is intended to provide engineering information necessary to support the construction plan submittal to the City of Everett for the proposed access improvements onto this site from 39th St. The site is located at 2425 39th St., Everett, WA 98201; refer to Figure 1 for a vicinity map. The area of the parcel for this project is approximately 20,403 sf, but please note that additional adjacent parcels are used by this applicant/tenant. The proposed access will connect to the paved portion of 39th St along the south side of this parcel and extend the pavement east and then turn north onto this parcel near the southeast corner of the site. As noted, much of the work will be within the RM/ for this project. This project proposes to construct less than 5,000 sf of new plus replaced impervious surfaces. Therefore, minimum requirements 1-5 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 site. The runoff from the gravel and pervious surfaces in the existing conditions will flow to the east and spread over the pervious, moderate sloped vegetated areas at the east end of the R/W and into the BNSF R/R property. In the developed conditions, the runoff from the new pavement will be allowed to drain east and disperse in the same location. The general soil conditions for these properties were found to be Alderwood gravelly sandy loam. The drainage design has been laid out per the COE 2017 Stormwater Management Manual and the 2014 DOE Stormwater Manual. The downstream system for this project is comprised of sheet flow over vegetated surfaces and then collection by the BNSF ditch system along the west side of the existing tracks. Permission to walk the tracks and visit the downstream flow path was not obtained from the railroad so no further information in the field could be obtained. However, previous work on this property was done by this office and permission at that time was obtained. The downstream system visited in the past had substantial capacity and well maintained so no impacts to that system are expected as a result of this project. Due to the size of this project only Minimum requirements 1-5 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. Royell Manufacturing 15-0714 July 2017 Page 3