Have you ever wondered where storm water runoff from elevated highways and bridges goes? These structures typically have drain inlets that are connected to pipes that convey the storm water, along with trash and other pollutants, to the ground, or storm system below. As part of the Action Plan for Retrofitting Structural BMPs DOT-HWYS recently installed downspout filters under the H-1 viaduct at the Pearl City Baseyard. These downspout filters capture trash and sediment and also contain an oil boom that reduces oil and grease from roadway storm water runoff. This is one of many storm water system retrofit projects that DOT-HWYS has recently completed in an ongoing effort to reduce storm water pollution.

Drain pipes under elevated freeway connecting to storm drain inlets.

Newly installed downspout filter under the H-1 freeway in Pearl City.

Trash and other debris captured by downspout filter.