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CITY OP EVERETT STORMWATER MANAGEMENT MANUAL <br /> 'I 3.2.5 BMP C106: Wheel Wash <br /> Purpose <br /> Whcel washes reducc thc amount of sedimcnt transporied onto pavcd roads by motor vehicle:;. <br /> Conditlons of Use <br /> When a stabilized constcuction entrance(see BMP C 105)is not preventing sediment from being tracked <br /> onto pavemcnt. <br /> Wtteel washing is gcoecally an effective BMP when installed with careful attentian to topography. Far <br /> example,a wheel wash can be deuimental if installed at the top of a slope abuttiog a rig6t-of-way where <br /> the water(rom the dripping wck can run unimpeded into thc strect. <br /> Pressure weshing com6ined with an adcquatcly sizcd and surfaced pad with direct drainage to a large 10 x <br /> 10-foot sump cen be very effective. <br /> Design and Installafion Specifieafions <br /> 1. Applicable details are shown in Figure 3.1. A minimum oC b inr.hes of asphalt heated base over <br /> crushed base matcrial or 8 inchcs over a go�d subgrade is recommended to pave thc wheel wash. <br /> 2. Use a low clearance huck to test the wheel wash before paving. Either a belly dump or lowboy <br /> will work well to test clearancc. <br /> 3. Keep thc water level from 12 to 14 inches deep to avoid damage to W ck hubs and filting thc <br /> wck rongues with water. <br /> � 4. Midpoint spray nozzles are only needed in extremely muddy wnditions. <br /> � 5. Wheel wash systems should be designed with a small grade change,6 to 12 inches for a 10•Poot- <br /> wide pond,eo allow sediment to flow to the low side of pond to help prc��cnt re-suspension of <br /> sediment. A drainpipe with a 2-to 3doot riser should bc installed on thc low side of the pond to <br /> allow for eesy cleaning and refilling. Polymers may be used to promote coagulation and <br /> flocculation in a closed-loop system. <br /> Maintenance Sfandards <br /> 1. The wheel wash should stett ou[the day with fresh watcr. <br /> 2. The washwater should be changed a minimum of once per day. On lazge carthwork jobs whcrc <br /> more than l0 to 20 wcks per hour aze expected,the washw�ater will need to be changed more <br /> often. <br /> 3. Wheel wash or tirc bath wastewatcr shall be controlled by pumping back on sitc ta an approved <br /> infilhation faciliry,or othcnvise must be prevented from discharging into systcros fibutary to <br /> stete surfece warers. Options include discharge to thc sanitary scwer,or dischargc to an approvcd <br /> offsite trcatment system. For discharges to We sanitary sc�cer,pennits must bc obtained from thc <br /> City's Industrial Pretreatment Program at(425) 257-8874. <br /> Volume II—Construcfion Stormwater Potlution Prevention <br /> 3-6 <br />