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FEB-17-93 WED 16�07 P. 02/02 ,. <br /> MEMO Kramer, Chin & Ma o, Inc. <br /> nate: z/17/93 <br /> To: Bddi O.Tietze and Associates, Don Abbott <br /> From: RB Aldrich <br /> ' Proj. Number. 23405-01 <br /> a Steve Wagner, Jane Zimmerman, Gordon Wichter, Dorothy <br /> VanDevanter <br /> This memo is in response to a letter and plan set recelved by Ar. Harry Gibbons on February <br /> 16, 1993, regarding review commenb for a project on. Silver Lake, Abbott 42-unit Project, <br /> designed by Erich O. Tfetze and Assaiates, The original i.�emo was dated February 8, 1993, <br /> and included apecific comments about the proposed biofiltration systems�and the erosion <br /> control ptan. <br /> Essentially, all the comments and suggestion contained in the origlnal February 8, 1993 <br /> have been satisfactorily addrzssed except for some dLscussien �egarding the actual design of <br /> the ewale system oa the site. The calculations and rationale' for design of the swale system <br /> are accurate and true to a point, although experience has shown that actual rain events <br /> rarely behave as predicted, and that rainfall events tend to have durations 5ignifiCantly <br /> greater than the ideal 24 hour period. This is due prlmarily to the inability of the <br /> methodology used to truly predict continuous events. In any case, the awale system, as <br /> ' designed, wUl probably be wetter during much of the year than anricipated. As a result, <br /> plants that can withstand molst wnditions must � Pk'1 n�t an �ve etationAmix that�would <br /> memo sent to Dr. Gibbor+s, Nir• Abbott is wi111n8 to p Y $ <br /> allow proper furctioning of the ay6tem as t► btofitter. Even though there may be some <br /> reservations about the timing, velocities, and duration of flows in the swale, we <br /> � i recommend a vegetation mlx �hat will thrive under moist conditions• <br /> ' We recommend the following mix of vegetallon in the various biofiltration components: <br /> Swale y t� <br /> Pacific sedge (Carez ubnupta) <br /> Spike-rush (Eleocharis cpp•) <br /> Rush (Juncus spp.) <br /> Small fruited bulixush (Scirpus microcarpus) <br /> Pond Bo om <br /> $pike-rush (Eleocharis spp•) <br /> Rush Uu���us spp.) <br /> Sedge (Carex sppJ;(Planted along pond edges) <br /> KCM • 1917 First Avenue <br /> . Seaitie WA 98101-1027 � (206) 443-5300 • <br /> Fax: (2081 443-537 2 <br /> I <br />