Hawaii Department of Transportation's Approach in Meeting TMDL: A Comprehensive Implementation Strategy

Among the many impaired waterbodies on the Island of Oahu that have been listed in the 303(d) of Clean Water Act, three waterbodies, Kawa Stream, Ala Wai Canal, and Waimanalo Stream have EPA approved Total Maximum Daily Loads (TMDL) established by Hawaii Department of Health (HDOH). Load allocations were developed for all three waterbodies as part of the process. Two watersheds, Kawa and Ala Wai Canal, have waste load allocations (WLA) assigned to several NPDES MS4 permit holders including the Hawaii Department of Transportation, Highways Division (HDOT-Hwys). HDOT-Hwys has developed a comprehensive strategy that includes the implementation and monitoring plan for the three watersheds. The TMDL/WLA Implementation Plan identifies specific activities where the reduction of total nitrogen and total phosphorus discharges in each watershed are necessary to comply with the WLAs. The monitoring plan specifies the water quality monitoring and tracking activity necessary to demonstrate efforts to comply with the urban source WLAs assigned to HDOT-Hwys and the effectiveness of the BMPs and the WLA implementation.