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�� <br /> Preliminary Drainane Report <br /> Introduction: <br /> This report has been prepared to provide the basis for the <br /> drainage desiqn on a forty unit apartment complex. The com- <br /> plex is loc�ted in the vicinity of State f'oute 526 near <br /> Casino Road in [verett, Washington. <br /> Desictn Criteria: <br /> The following was used to deter�nine the design for the drain- <br /> a�e system. = p!;� Maximum <br /> Outfall Dischar9e line <br /> Desi9n Storm Frequency = 10 Years <br /> Duration (Time of Concentration) = 10 Minutes <br /> Runoff Coefficients <br /> Paved R Roof Areas = Q•9� <br /> Landscaped = 0.25 <br /> The method of determininq the detention basin requirements <br /> was the Yrjanzinen & Warren Method. <br /> All drainage is based on that collected on site. <br /> Forty-Unit Site: <br /> This site has a total of 1 .44 acres and is approximately 76.5% <br /> paved or roof area. The proposed system would have 2 above <br /> ground detention areas. One on the north end and one on the <br /> south. There would be 6 catch basins in the system. <br /> An outlet structure would provide the necessary qrease trap <br /> separator and outlet control discharge of 2'-i'. <br /> The detention capacity would be from 1230 ft2 - 1530 ft3. <br /> Calculations: <br /> The attached calculations provide the basis for the drainage <br /> layout. A site plan shoNiing preliminary layout is also <br /> attached. <br />