3003 W CASINO RD BOEING PARKING LOTS - E 6 2025-07-25

I I Drainage Report Boeing Everett-E-6 Parking Lot Expansion July 16, 2013 I are deeper and will run under the expanded parking lot to the west and north. Access to the existing site is from a two-way driveway near the SW corner of the existing parking lot. TABLE 1 summarizes the existing site conditions and land cover. The drainage basin is the project limits I as no offsite flow enters the site's drainage system from either offsite or from the existing asphalt parking lot. I 1.2 Developed Site Conditions The developed site conditions, shown in the project plans submitted under separate cover, will include an additional 51,141 SF of asphalt surrounding the existing asphalt parking lot on three I sides. The north expansion area consists of 16,888 SF, the west expansion consists of 18,886 SF, and the south expansion adds 15,367 SF of new asphalt pavement. Drainage for the developed site will be collected by new Type 1 and Type 2 catch basins connected to the existing drainage I system serving the existing parking lot. New pavement surfaces will be graded to prevent surface flows into the existing parking lot and the proposed catch basins will include downturned 90- degree elbows for spill control and oil/water separation. A landscape strip will remain along the I west side of the proposed parking lot separating the lot from the one-way road to the west. TABLE 1 summarizes the developed site conditions and land cover. 1.3 Site Area and Size of Improvements I The project site is a 2.6 acre area located in the southeast corner of Boeing Everett's north campus, adjacent to Highway 526 and Seaway Blvd. The drainage basin for the project I improvements is the improved area itself as no offsite flow enters the site from any direction. There is an existing electrical substation to the north of the existing site, with electrical transmission lines running overhead near the east edge of the existing site. The site area and size of improvements are shown in the project plans and summarized in TABLE 1. See APPENDIX ID for the Site Plan of the project. I I I I I I 20130715_Drainage Report_Boeing Everett_Gate E-6 Parking Lot.doc Page 2