7800 EVERGREEN WAY HYUNDAI O&M Manual 2025-04-28

. In a building constructed specifically for washing of vehicles and equipment, which drains to a sanitary sewer. Conduct outside washing operations in a designated wash area with the following features: . In a paved area, construct a spill containment pad to prevent the run-on of stormwater from adjacent areas. Slope the spill containment area to collect washwater in a containment pad drain system with perimeter drains,trench drains or catchment drains. Size the containment pad to extend out a minimum of four feet on all sides of the washed vehicles and/or equip- ment. . Convey the washwater to a sump(like a grit separator)and then to a sanitary sewer(if allowed by the local Sewer Authority), or other appropriate wastewater treatment or recycle system. The containment sump must have a positive control outlet valve for spill control with live containment volume, and oil/water separation. Size the minimum live storage volume to contain the maximum expected daily washwater flow plus the sludge storage volume below the outlet pipe. Shut the outlet valve during the washing cycle to collect the washwater in the sump.The valve should remain shut for at least two hours following the washing operation to allow the oil and solids to separate before discharge to a sanitary sewer. . Use a two way valve for discharges from the containment pad.This valve should be normally switched to direct water to treatment, but may be switched to the drainage system after that pad is clean to handle stormwater runoff. The stormwater can then drain into the con- veyance/discharge system outside of the wash pad (essentially bypassing the sanitary sewer or recycle system). Post signs to inform people of the operation and purpose of the valve. Clean the concrete pad thoroughly until there is no foam or visible sheen in the washwater prior to closing the inlet valve and allowing uncontaminated stormwater to overflow and drain off the pad. Note that the purpose of the valve is to convey only washwater and contaminated stormwater to a treatment system. . Collect the washwater from building structures and convey it to appropriate treatment such as a sanitary sewer system if it contains oils, soaps, or detergents. If the washwater does not con- tain oils, soaps, or detergents(in this case only a low pressure, clean, cold water rinse is allowed)then it could drain to soils that have sufficient natural attenuation capacity for dust and sediment. . Sweep surfaces prior to cleaning/washing to remove excess sediment and other pollutants. . If roof equipment or hood vents are cleaned, ensure that no washwater or process water is dis- charged to the roof drains or drainage systems. . Label all mobile cleaning equipment as follows: "Properly dispose of all wastewater. Do not discharge to an inlet/catch basin, ditch, stream, or on the ground." Recommended Additional BMPs: . Mark the wash area at gas stations, multifamily residences and any other business where non-employees wash vehicles. 2019 Stormwater Management Manual for Western Washington Volume IV-Chapter 2-Page 506