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Use a low clearance truck to test the wheel wash before paving. Either a belly dump or lowboy will <br />work well to test clearance. <br />Keep the water level from 12 to 14 inches deep to avoid damage to truck hubs and filling the truck <br />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 12-inches for a 10-foot- <br />wide pond, to allow sediment to flow to the low side of pond to help prevent re -suspension of sed- <br />iment. A drainpipe with a 2- to 3-foot riser should be installed on the low side of the pond to allow for <br />easy cleaning and refilling. Polymers may be used to promote coagulation and flocculation in a <br />dosed -loop system. Polyacrylamide (PAM) added to the wheel wash water at a rate of 0.25 - 0.5 <br />pounds per 1,000 gallons of water increases effectiveness and reduces cleanup time. If PAM is <br />already being used for dust or erosion control and is being applied by a water truck, the same truck <br />can be used to change the wash water. <br />Maintenance Standards <br />The wheel wash should start out each day with fresh water. <br />The wheel wash water should be changed a minimum of once per day. On large earthwork jobs <br />where more than 10-20 trucks per hour are expected, the wheel wash water will need to be changed <br />more often. <br />Approved as Functionally Equivalent <br />Ecology has approved products as able to meet the requirements of this BMP. The products did not <br />pass through the Technology Assessment Protocol — Ecology (TAPE) process. Local jurisdictions <br />may choose not to accept these products, or may require additional testing prior to consideration for <br />local use. Products that Ecology has approved as functionally equivalent are available for review on <br />Ecology's website at: <br />https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per- <br />mittee-quidance-resources/Emerging-stormwater-treatment-technologies <br />2019 Stormwater Management Manual for Western Washington <br />Volume /I - Chapter 3 - Page 281 <br />