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I <br /> TERRA ASSOCIATES, Inc. <br /> Consultants in Geotechnical Engineering, Geology <br /> and <br /> Environmental Earth Sciences <br /> I <br /> I <br /> February 9, 2006 <br /> Project No.T-5738 <br /> Mr.Richard Burrell <br /> Barclays North,Inc. <br /> 10515—20th Street SE,Suite 100 <br /> Everett,Washington 98205 <br /> Subject: Stormwater Outfall Review <br /> C32-1 Interair Commerce Center <br /> ' 36th Avenue West <br /> Everett,Washington <br /> Dear Mr.Burrell: <br /> As requested by Mr. Steve Pesce of Pacland, we reviewed details of the proposed stormwater outfall systems for <br /> the subject project shown on Sheets D-1.5 and D-1.6 of the project plans prepared by Pacland, dated February 9, <br /> 2005. The information provided to us indicates that three outfalls will serve the project. Two of the outfalls will <br /> ' discharge to existing natural drainage corridors located near the northern margin of the site. A third outfall will <br /> discharge to a relatively flat drainage swale that parallels the eastern side of the Boeing railroad spur west of the <br /> site. <br /> The plans show the outfall systems will discharge via surface dispersion through 12-inch diameter perforated <br /> ' HDPE pipe. The outfalls located near the northern margin of the site will disperse through two 25-foot long <br /> perforated pipe sections. The western outfall is shown as having one 25-foot length of perforated pipe. <br /> Stormwater will be conveyed to each dispersion system through a continuous 8-inch diameter HDPE tightline <br /> pipe. The 100 year maximum release rate and 100-year undetained flow rate to each outfall is as follows: <br /> ' Western Outfall: 1.6 cubic feet per second(cfs)/3.8 cfs <br /> Northwestern Outfall: 2.25 cfs/7.7 cfs <br /> ' Northeastern Outfall: 2.34 cfs/7.1 cfs <br /> 1 <br /> 12525 Willows Road, Suite 101, Kirkland, Washington 98034 <br /> Phone (d2r,1 R21-7777 • Fax (49c1 R91-4334 <br />