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'e . . <br /> � �°h "1 <br /> i <br /> _ _ <br /> �� <br /> May 15, 1994 � <br /> Mr. Gordon Witcher TRIAD ASSOCIATES <br /> Everett Public Works Department <br /> 3200 Cedar Street P�aicct Managemeni <br /> Everett, WA 98201 C����Enpinee�ing <br /> ' ' Lana Surveying <br /> Re: Intrawest - Seaw:►y ���d u����a����9 <br /> "Formal" S�OCIIIWA�CM DCICOf1011 CAICUTA�I0115 Lantlscapc Archilectorc <br /> S�te Design <br /> Dear Gordon; <br /> We're fast tracking to a Grading Permit submittal on Friday, May 20th. I hope we can meet that <br /> deadline, but it will be a monumental challenge. Provided for your (or Dan's) use, is the "final" <br /> site development conditions, so that you can determine, through the use ofyour SWMA�I model, <br /> the required detention volumes for the two areas of our site. <br /> As we discussed before, we'll be attempting to direct the roof drainage into the open water <br /> feature of the enhanced wetland area. The parkinb lot and associated landscaping will be directed <br /> into a water qualiry / detention pond. Therefore, we will need calculations for two facilities, <br /> including volumes and allowable release rates. Ifyou want ro employ multiple orifices, please let <br /> me know the varied release rates and associated volumes. <br /> Existine Conditions <br /> Area = 17.IG Acres <br /> Ground Cover (prior to the recent activities) ivas second gro�vth forest with light to medium <br /> underbrusli. <br /> Soils were defined as Alderwood Sandy Loam in the Soils Survey, but it's a mess out there now. <br /> I would assrm�e a ftydrologic Group '°C" soil for this analysis. <br /> Based upon the historic ground c�ver and the apparent soils conditions, I would assign a CN <br /> value of 81 to the existing conditions. <br /> The time of concentration (assuming forested conditions) is approximately T� = 45.97 Minutes. <br /> Roof Ton Area <br /> Area = 5.23 Acres <br /> A CN value of 98 is obviously appropriate for this area. <br /> The time of concentration is approximately T� = G.93 Minutcs. <br /> 1'arkine & Landscaneci Are� <br /> Area = 14.02 Acres <br /> 9.11 Acres of Pavement at CN = 98 <br /> 4.91 Acres of Landscaping at CN= 8G <br /> The time of concentration is approximately T� = 7.92 Minutes. <br /> . � � � .. . . .. . .. � _.. . ,. , � . neono . � .. rou r,ca � . . n.,. . <br />