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

A few weeks ago, there was a pre-application meeting for two yards and parking areas that The Boeing Company is proposing to expand. One is the Rail Yard Receival area on the west side of the factory and the other is lot E6 on the east side. I was on vacation that week, but I think that you, Dave Tyler and several other city staff may have attended the meeting. John Turner and Russell Larmay attended for Boeing. As I was filling out an environmental checklist for the project, I realized that the area was planned as yards and parking in the 1991 master plan (see attachment#1) and thus would likely be considered "vested" under the City's Planning Directive Interpretation (POI) 09-002 dated 7-29-09 which addressed stormwater standards. ' To validate the 1991 Master Plan drawing, we checked the data in the 1991 Draft EIS, Technical Appendix, Volume I, Section C which analyzed the impacts to the Powder Mill Gulch Basin. Much of the analysis drew on the 1988 Comprehensive Storm Drainage Plan (CSDP). The ' expansion of lot E6 would straddle areas 56 and 75 from the CSDP (see attachment#2). From reviewing these documents we concluded that the areas 56 and 70 had been planned for approximately 22.8 and 10.9 acres of impervious area respectively for a total of 33.7 impervious ' acres (see attachment#3). We took a snap shot from Google Earth to review how the area was actually built out (see attachment ' #4). The total area is 36.9 acres. The calculations for the Powder Mill Gulch Detention Pond assumed 33.7 acres impervious and 3.2 acres pervious. After measuring, we found that instead of 3.2 pervious acres, we actually have more than 6.71 pervious acres. This would leave a balance of 3.51 acres of yards/parking to be built (see attachment#5). Note, despite the balance, we are only proposing to build approximately 1.0 acre. Even though we feel that this area would likely be considered "vested", instead of using an ' impervious surface, we are proposing to obtain a geo-tech study and, assuming the study concludes the soil is suitable, use this area to test a system of pervious concrete. Since this is a pilot project, we would like to add catch basins and tie the area into the existing drainage system in the event that the ' pervious concrete does not work as well as planned. Please let us know if you concur with our analysis and approach. We'd be happy to meet again if you would like to discuss this issue further. ' Sincerely, Peite.Mr-Gwi.r e' ' Pete McGuire The Boeing Company Land Use and Civic Affairs Phone:425-238-3768 Fax(425)266-8105 2