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1 <br />1 <br />1 <br />1 <br />1 <br />u <br />1 <br />1 <br />1 <br />1 <br />1 <br />i� <br />1 <br />1 <br />I <br />1 <br />1 <br />. Discharge area below the outlet must be uniform with a slope flatter than 5H:1 V. <br />Outlet to be constructed level in a stable, undisturbed soil profile (not on fill). <br />. The runoff shall not re -concentrate after release unless intercepted by another <br />downstream measure. <br />. The grade of the channel for the last 20 feet of the dike or interceptor entering the <br />level spreader shall be less than or equal to 1 percent. The grade of the level <br />spreader shall be 0 percent to ensure uniform spreading of storm runoff. <br />. A 6-inch high gravel berm placed across the level lip shall consist of washed <br />crushed rock, 2- to 4-inch or 3/4-inch to 1 %-inch size. <br />. The spreader length shall be determined by estimating the peak flow expected <br />from the 10-year, 24-hour design storm. The length of the spreader shall be a min- <br />imum of 15 feet for 0.1 cfs and shall increase by 10 feet for each 0.1 cfs thereafter <br />to a maximum of 0.5 cfs per spreader. Use multiple spreaders for higher flows. <br />. The width of the spreader should be at least 6 feet. <br />. The depth of the spreader as measured from the lip should be at least 6 inches and <br />it should be uniform across the entire length. <br />Level spreaders shall be setback from the property line unless there is an ease- <br />ment for flow. <br />. Level spreaders, when installed every so often in grassy swales, keep the flows <br />from concentrating. Materials that can be used include sand bags, lumber, logs, <br />concrete, and pipe. To function properly, the material needs to be installed level <br />and on contour. BMP C206: Level Spreader (p.348) and Figure II-4.2.6 Detail of <br />Level Spreader (p.351) provide a cross-section and a detail of a level spreader. A <br />capped perforated pipe could also be used as a spreader. <br />Maintenance Standards <br />The spreader should be inspected after every runoff event to ensure that it is functioning <br />correctl y. <br />. The contractor should avoid the placement of any material on the structure and <br />should prevent construction traffic from crossing over the structure. <br />. If the spreader is damaged by construction traffic, it shall be immediately repaired. <br />2014 Stormwater Management Manual for Westem Washington <br />1 <br />Volume II - Chapter 4 - Page 349 <br />