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CITY OF EVERETT STORMWATER MANAGEMENT MANUAL <br />clayey soils (USDA Classification Type "C" and "D" soils), long grades, and high precipitation <br />areas. When PAM is applied first to bare soil and then covered with straw, a reapplication may <br />not be necessary for several months. <br />3. Loss of sediment and PAM may be a basis for penalties per Revised Code of Washington (RCW) <br />90.48.080. <br />3.2.14 BMP C130: Surface Roughening <br />Purpose <br />Surface roughening aids in the establishment of vegetative cover, reduces runoff velocity, increases <br />infiltration, and provides for sediment trapping through the provision of a rough soil surface. Horizontal <br />depressions are created by operating a tiller or other suitable equipment on the contour or by leaving <br />slopes in a roughened condition by not fine grading them. <br />Conditions for Use <br />1. All slopes steeper than 3:1 and greater than 5 vertical feet require surface roughening <br />2. Areas with grades steeper than 3:1 should be roughened to a depth of 2 to 4 inches prior to <br />seeding <br />3. Areas that will not be stabilized immediately may be roughened to reduce runoff velocity until <br />seeding takes place <br />4. Slopes with a stable rock face do not require roughening <br />5. Slopes where mowing is planned should not be excessively roughened. <br />Design and Installation Specifications <br />There are different methods for achieving a roughened soil surface on a slope, and the selection of an <br />appropriate method depends upon the type of slope. Roughening methods include stair -step grading, <br />grooving, contour furrows, and tracking. See Figure 3.2 for tracking and contour furrows. Factors to be <br />considered in choosing a method are slope steepness, mowing requirements, and whether the slope is <br />formed by cutting or filling. <br />1. Disturbed areas that will not require mowing may be stair -step graded, grooved, or left rough <br />after filling. <br />2. Stair -step grading is particularly appropriate in soils containing large amounts of soft rock. Each <br />"step" catches material that sloughs from above, and provides a level site where vegetation can <br />become established. Stairs should be wide enough to work with standard earth moving <br />equipment. Stair steps must be on contour or gullies will form on the slope. <br />3. Areas that will be mowed (these areas should have slopes less steep than 3:1) may have small <br />furrows left by disking, harrowing, raking, or seed -planting machinery operated on the contour. <br />4. Graded areas with slopes greater than 3:1 but less than 2:1 should be roughened before seeding. <br />This can be accomplished in a variety of ways, including "track walking," or driving a crawler <br />tractor up and down the slope, leaving a pattern of cleat imprints parallel to slope contours. <br />5. Tracking is done by operating equipment up and down the slope to leave horizontal depressions <br />in the soil. <br />Maintenance Standards <br />1. Areas that are graded in this manner should be seeded as quickly as possible. <br />Volume 11— Construction Stormwater Pollution Prevention <br />3-25 <br />