In response to changes in EPA industrial stormwater regulations that removed exemptions for small school districts, the McKinleyville Union School District took a proactive approach to treating washwater and stormwater runoff from its bus maintenance facility and achieved compliance with state stormwater regulations through installation of an underground filtration system.

Each of the district's seven 82-passenger school buses is manually washed once a week at the maintenance facility. A hose with spray nozzle is used to wash and rinse, and long-handled brushes and a mild, environmentally-friendly soap are used to remove dirt or grime. The average flow rate over one wash cycle is about 10 gallons per 20 minutes, or 20 gal/hr, when two buses are washed. Prior to the filtration system, washwater was collected in a low spot adjacent to the outside wash area and then directed to a swale and into the nearby creek.

While the district was already using source controls at the facility, the bus washing activity had the potential to introduce wear metals, antifreeze, tire particulate, cleaning solvents, lubricants, grease, oil, fuel, and debris into the storm drain system.

In order to address these pollutants and assure compliance, the district's engineering firm recommended the CatchBasin StormFilter™, a qualified Best Available Practice manufactured by Stormwater Management Inc., Portland, Ore., for treatment of washwater and stormwater runoff before discharge to the creek.

"We had always been careful about things like oil spills and lubricant drips around the garage, with our equipment maintenance manager taking great pride in running a clean and tidy operation. To continue setting a good example for our children, we want to also use Best Available Practices, and we feel it's not a bad thing to have the state checking on that," noted Nancy Howatt, assistant superintendent for the McKinleyville Union School District.

Based on flow rate and testing data, Stormwater Management recommended the steel CatchBasin StormFilter with one 7.5 gpm filtration cartridge containing the company's patented CSF" leaf media.

During washdown operations, polluted runoff enters the steel unit through a traffic-bearing grate and flows into a setting chamber, where heavier solids drop to a sump. The runoff then flows under a baffle to a cartridge chamber, where lighter solids and soluble pollutants such as heavy metals are removed by media filtration.

A shutoff valve on the storm drain bypass line directs treated water into the sewer sump from where it is pumped to the district's sanitary sewer system.

During normal operations, the bypass line to the storm drain is opened, and the flow goes directly into the storm drain system, which empties into the swale. A cover is also placed over the storm drain inlet to minimize rainwater inflow into the sewer system.

Installation of the system took one day, using labor from the school system and a paving company. The project was supervised by the director of maintenance and operations. "It was pretty much a basic task for our people, who were already familiar with plumbing and drainage," Howatt added.

Phone: (800) 548-4667
Fax: (800) 561-1271
E-mail: industrial@stormwaterinc.com
Web: www.industrystormwater.com
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