Storm Water Best Management Practice Improvements at Maintenance Baseyards on Oahu

The Storm Water Best Management Practice (BMP) Improvements at Maintenance Baseyards on Oahu project is part of the State of Hawaii Department of Transportation, Highways Division’s (DOT-HWYS) ongoing efforts to reduce pollution from storm water runoff. DOT-HWYS operates five maintenance baseyards on the island of Oahu. Storm water from these baseyards and other paved areas typically drain through a network of pipes (the Municipal Separate Storm Sewer System, or “MS4”) to outfall locations in stream channels, or drain directly to the ocean. Unfortunately, this storm water runoff often contains trash, oils and greases, and unnaturally high nutrients that can have negative impacts on streams and the ocean.

As part of the Action Plan for Retrofitting Structural BMPs and the Trash Reduction Plan, DOT-HWYS is making improvements and constructing storm water treatment and monitoring systems at several of their maintenance baseyards. Storm water BMP improvements are currently under construction at DOT-HWYS Windward Baseyard Facility in Kaneohe. General improvements include repairing and repaving old, damaged asphalt and rerouting storm water drainage to reduce the risk of contact with pollution sources and to allow for more accurate storm water quality monitoring. Storm water treatment improvements include the construction of a vegetated swale, installation of storm drain inlet filter baskets, and the installation of two automated storm water sampling stations to monitor the quality of storm water leaving the baseyard. This project is being managed by DOT-HWYS Lower Halawa Field Office and is anticipated to be completed by May 2019.  Be sure to look for an update and photos of the completed project in a future newsletter!