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I <br /> BMP C106: Wheel Wash <br /> Purpose Wheel washes reduce the amount of sediment transported onto paved <br /> roads by motor vehicles. <br /> Conditions of Use When a stabilized construction entrance(see BMP C105)is not preventing <br /> sediment from being tracked onto pavement. <br /> • Wheel washing is generally an effective BMP when installed with <br /> careful attention to topography. For example, a wheel wash can be <br /> detrimental if installed at the top of a slope abutting a right-of-way <br /> where the water from the dripping truck can run unimpeded into the <br /> 1 street. <br /> • Pressure washing combined with an adequately sized and surfaced pad <br /> with direct drainage to a large 10-foot x 10-foot sump can be very <br /> effective. <br /> Design and Suggested details are shown in Figure 4.3. The Local Permitting <br /> Installation Authority may allow other designs. A minimum of 6 inches of asphalt <br /> Specifications treated base(ATE) over crushed base material or 8 inches over a good <br /> subgrade is recommended to pave the wheel wash. <br /> Use a low clearance truck to test the wheel wash before paving. Either a <br /> belly dump or lowboy will work well to test clearance. <br /> Keep the water level from 12 to 14 inches deep to avoid damage to truck <br /> hubs and filling the truck tongues with water. <br /> Midpoint spray nozzles are only needed in extremely muddy conditions. <br /> Wheel wash systems should be designed with a small grade change, 6 to <br /> 12 <br /> side inches fora - wd, oasll sediment lw o e l <br /> 1 ofpond to h 10elpfoot-preventide re-suspenionpont ow of sedimentdieto. f Ao drainpipetth withow <br /> a 2-to 3-foot riser should be installed on the low side of the pond to allow <br /> for easy cleaning and refilling. Polymers may be used to promote <br /> coagulation and flocculation in a closed-loop system. Polyacrylamide <br /> (PAM)added to the wheel wash water at a rate of 0.25 - 0.5 pounds per <br /> 1,000 gallons of water increases effectiveness and reduces cleanup time. <br /> If PAM is already being used for dust or erosion control and is being <br /> applied by a water truck,the same truck can be used to change the wash <br /> water. <br /> Maintenance The wheel wash should start out the day with fresh water. <br /> Standards The wash water should be changed a minimum of once per day. On <br /> I large earthwork jobs where more than 10-20 trucks per hour are <br /> expected,the wash water will need to be changed more often. <br /> Wheel wash or tire bath wastewater shall be discharged to a separate on- <br /> site treatment system, such as closed-loop recirculation or land <br /> application,or to the sanitary sewer with proper local sewer district <br /> approval. <br /> 4-10 Volume II—Construction Stormwater Pollution Prevention February 2005 <br />