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CITY OF EVERETT STORMWATER MANAGEMENT MANUAL <br />3.2.6 BMP C107: Construction Road/Parking Area Stabilization <br />Purpose <br />Stabilizing subdivision roads, parking areas and other onsite vehicle transportation routes immediately <br />after grading reduces erosion caused by construction traffic or runoff. <br />Conditions of Use <br />• Roads or parking areas shall be stabilized wherever they are constructed, whether permanent or <br />temporary, for use by construction traffic. <br />• Fencing (see BMP C 103) shall be installed, if necessary, to limit the access of vehicles to only <br />those roads and parking areas that are stabilized. <br />Design and Installation Specifications <br />1. On areas that will receive asphalt as part of the project, install the first lift as soon as possible. <br />2. A 6-inch depth of 2- to 4-inch crushed rock, gravel base, or crushed surfacing base course shall <br />be applied immediately after grading or utility installation. A 4-inch course of asphalt treated <br />base may also be used, or the road/parking area may be paved. It may also be possible to use <br />cement or calcium chloride for soil stabilization. If cement or cement kiln dust is used for road <br />base stabilization, pH monitoring and BMPs are necessary to evaluate and minimize the effects <br />on sormwater. If the area will not be used for permanent roads, parking areas, or structures, a <br />6-inch depth of hog fuel may also be used, but this is likely to require more maintenance. <br />Whenever possible, construction roads and parking areas shall be placed on a firm, compacted <br />subgrade. <br />3. Temporary road gradients shall not exceed 15 percent. Roadways shall be carefully graded to <br />drain. Drainage ditches shall be provided on each side of the roadway in the case of a crowned <br />section, or on one side in the case of a super -elevated section. Drainage ditches shall be directed <br />to a sediment control BMP. <br />4. Rather than relying on ditches, it may also be possible to grade the road so that runoff sheet -flows <br />into a heavily vegetated area with a well -developed topsoil. Landscaped areas are not adequate. <br />If this area has at least 50 feet of vegetation, then it is generally preferable to use the vegetation to <br />treat runoff, rather than a sediment pond or trap. The 50 feet shall not include wetlands. If runoff <br />is allowed to sheetflow through adjacent vegetated areas, it is vital to design the roadways and <br />parking areas so that no concentrated runoff is created. <br />5. Storm drain inlets shall be protected to prevent sediment -laden water entering the Sormwater <br />drainage system (see BMP C220). <br />Maintenance Standards <br />1. Inspect stabilized areas regularly, especially after large storm events <br />2. Crushed rock, gravel base, hog fuel, etc. shall be added as required to maintain a stable driving <br />surface and to stabilize any areas that have eroded <br />3. Following construction, these areas shall be restored to preconstruction condition or better to <br />prevent future erosion. <br />Volume ll — Construction Stormwater Pollution Prevention <br />3-8 <br />