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LSA No. 3140 <br /> A summary of the basic design imf rm tion: <br /> s. Total property area: . . . . . . . . . . . . . . . . . . .9.65 acres <br /> b. Net Development area: . . . . . . . . . . . . . . . . . . . . . . . . .6.1 acres <br /> c. Offsite tributary area: . e . . . . . . . . . . . . . . . . . . . . .0.00 acres 5 <br /> 1� <br /> d• Alderwood logic.Type. (see.attached.map)• • . . . • . . . . • . . • . C C���� <br /> �-�I�' � , <br /> e. Total precipitation (from SCS isopluvial s . � �,t�,d ' h ni <br /> 25-year 24-hour storm. . . . . . . . . . . . . . . . . . . . .2.50 inche dI <br /> 2-year 24-hour storm. . . . . . . . . . . . . . . . . . . . . .1.40 inc s C'� �r" <br /> f. The hydrographic shape of the design storm s assuaed v���,r��5 <br /> to be an SCS Type lA storm. ` �j <br /> g. SCS curve numbers used were as shown for Western ' <br /> Washington in the King County Surface Water Design <br /> Manual. <br /> E. CALCULATIONS <br /> Calculations follow below, including input and output for the <br /> analysis of boch the existing and developed conditions. <br /> Detailed information about the cflmputer program commands and <br /> input parameters can be provided on request. Hpdrograph 1 in <br /> the hydrograph summary portion of the calculations is the 2- <br /> yr release from the pond. Hydrograph 2 is the 25-yr release <br /> from the pond. <br /> The results of this evaluation indicate the developed site <br /> releases an estimated C.06 cfs to the west durinq the 2-year <br /> storm, and 0.53 cfs durinq the 25-pear storm. The pr�- <br /> development flows are 0.11 cfs and 0.58 cfs respectively. <br /> This conforms reasonably well to the criteria established by <br /> the Department of Fisheries. <br /> The volumes required for this peaformance are 19,000 cubic <br /> feet of storage during the 2-yr storm, and 22,700 cubic feet <br /> during the 25-yr storm. A design satisfying these <br /> requirements is shown on the drainage plan. <br /> The pond has been designed to comply with the City of Everett <br /> wetpond criteria. The Criteria include <br /> 5�5 n <br /> a. a pon vblume equal to the vo�lume of the 6-month 24- <br /> hour storm, ��„�( �/„cy,c�n <br /> b. a dead storage volume 50 percent of the ��age- <br /> volume. <br /> c. a treatment zone volume 30 percent of the total, �v h�+h d.<ael � ��✓`t - I <br /> d. a maximum average depth of 1:�� feet in the treatment <br /> zone, I . `33 <br /> e, a grit removal system, � <br /> f. a 3:1 length-to-width ratio, and ' <br /> g. a two-cell architecture, with a solid baffle, and <br /> n�e: ���:,�,.��. Page 4 <br />