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1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <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 12-inches for <br />a 10-foot-wide pond, to allow sediment to flow to the low side of pond to help prevent re - <br />suspension of sediment. A drainpipe with a 2- to 3-foot riser should be installed on the <br />low side of the pond to allow for easy cleaning and refilling. Polymers may be used to <br />promote coagulation and flocculation in a closed -loop system. Polyacrylamide (PAM) <br />added to the wheel wash water at a rate of 0.25 - 0.5 pounds per 1,000 gallons of water <br />increases effectiveness and reduces cleanup time. If PAM is already being used for dust <br />or erosion control and is being applied by a water truck, the same truck can be used to <br />change the wash water. <br />Maintenance Standards <br />The wheel wash should start out the day with fresh water. <br />The wash water should be changed a minimum of once per day. On large earthwork <br />jobs where more than 10-20 trucks per hour are expected, the wash water will need to <br />be changed more often. <br />2014 Stormwater Management Manual for Westem Washington <br />Volume 11 - Chapter 4 - Page 275 <br />