3003 W CASINO RD BLDG 45-12 2016-10-20

STATIC TEST FACILITY PRELIMINARY STORM DRAINAGE REPORT EVERETT,WASHINGTON SECTION 2: CONDITIONS AND REQUIREMENTS SUMMARY As a condition of approval by Paine Field and the City of Everett, the project must address the minimum requirements within the DOE Manual.The minimum requirements, and how the project proposal addresses each, are listed below. Minimum Requirement#1: Preparation of Stormwater Site Plans: Civil Plans under separate cover and a Storm Drainage Report herein have been prepared for the subject project. Minimum Requirement#2: Construction Stormwater Pollution Prevention: A separate CSWPPP will be prepared and submitted prior to final approval of the drainage plan. Minimum Requirement #3: Source Control Pollution: The completed project does not propose source control for the 115,000sf building, because the roof material will have a protective coating to prevent leaching of zinc. The roof will not have typical HVAC/mechanical system that typically generate pollution. It is assumed that majority of the pollution generating surface is located outside of the building footprint. This area will collect pollution mostly from vehicles. The number of vehicle trips that will use this area is negligible. Review of the HNTB Storm water calculations for the Flightline Expansion—Phase 2,dated April 18,2008 says that"the existing south flightline oil/water separator is able to handle this additional load as verified by Boeing". The report can be found in Section 6 of this report. Minimum Requirement #4: Preservation of Natural Drainage Systems and Outfalls: Discharge from the site will be to the existing existing storm drain system(s) located at the southwest and northwest of the site,as it currently does. These discharges are within the same threshold discharge area(TDA) and converge within a 1/4 mile downstream. Minimum Requirement#5: On-Site Stormwater Mana eg ment: The Boeing Company understands that the on-site stormwater management/LID BMPS are an important part of stormwater management, however, any facility using infiltration would be ineffective considering the poor soils (see the Appendix for the Geotech Report for the Flightline Expansion Phase 2, Stalls 208, 209,210 and 211). The site will utilize the existing detention pond(Alpha Pond)to the northwest, augmented by on-site water quality treatment facility explained in detail in Section 4. Minimum Requirement #6: Runoff Treatment: Paine Field Airport (Snohomish County) has required that runoff from the site comply with Basic Water Quality Treatment standards as specified in the 2012 DOE Manual. In the Stormwater Calculations for the Flightline Expansion Phase (Stalls 206, 207 and 215) and Phase 2 (Stalls 208-211), dated April 18, 2008, analyzed the existing stormwater wetlands at the south end of Alpha Pond and determined that the existing stormwater wetlands can provide Basic Water Quality for the project. Minimum Requirement#7: Flow Control: Flow control is not proposed for this project because the existing Alpha Pond provides flow control for the overall contributing system. Minimum Requirement #8: Wetlands Protection: There are no wetlands on the project site, however, there is a mapped Corps Jurisdictional Ditch #NWS-2013-240 located at the northeast corner of the site. Additionally, there are two mapped wetlands, as well as Boeing Lake, on the north side of 94'St.SW.north of the project. No work is planned within the wetlands and a TESC plan and a SWPPP will be created showing the proposed BMP's to protect Boeing Lake during construction activities. The project proposes to fill the existing jurisdictional ditch. The project also proposes to replace the loss of the jurisdictional ditches water quality treatment with a Stormfilter. This will treat the runoff from a portion of 29'Ave. W and 94'St. SW. CEI Project#141001 Pg.3