Category 4b Demonstration for Petroleum Hydrocarbon Impaired Waters in the Kenai River, Alaska

Abstract

Section 303(d) of the Clean Water Act (CWA) and the US Environm ental Protection Agency’s (USEPA’s) supporting regulations in 40 CFR Part 130.7 require states to develop lists of waterbodies impaired by a pollutant and needing a Total Maximum Daily Load (TMDL) (i.e., the Section 303(d) list) and to prepare a TMDL for each waterbody/pollutant combination. USEPA’s regulations also recognize that other pollution control requirements may obviate the need for a TMDL. These alternatives to TMDLs are commonly referred to as Category 4b waters as described in USEPA’s Integrated Reporting Guidance for Sections 303(d), 305(b), and 314 of the CWA. One of the most visible waterways in Category 4b is the Kenai River. The Kenai River is known worldwide for its prized King Salmon. The initial 20 miles of the lower river attracts over 700 boats per day during the peak fishing season. Water quality data for the Kenai River showed elevated petroleum hydrocarbon levels during the month of July in the lower portion of the river. A water quality assessment conducted by the Alaska Department of Environmental Conservation (ADEC) in 2003 confirmed the source of the petroleum hydrocarbon pollution was from motorboats and subsequent studies identified older, 2-stroke motors as the primary source. The waterbody was subsequently listed as impaired on ADEC’s Section 303(d) list (Category 5). As a result of the 2003 study, ADEC began meeting with Kenai River stakeholders to strategize and develop a waterbody recovery plan and take the necessary actions. By 2007, the Kenaitze Indian Tribe using USEPA Targeted Watershed Initiative Grant monies initiated a buy-back program for older, more polluting, carbureted 2-stroke motors. In 2008, Alaska adopted regulations requiring all outboard engines used in the Kenai River Special Management Area and the personal use fishery to be cleaner motors - either 4-stroke or direct fuel injection 2-stroke motors. For the 2008 reporting cycle, the ADEC assigned petroleum hydrocarbon impaired waters of the Kenai River to Category 4b. Based on water quality modeling results for the river, ADEC expects the implementation strategy will result in attainment of the petroleum hydrocarbon water quality standard by 2010. This paper presents ADEC’s demonstration for assigning these waters to Category 4b according to USEPA’s Category 4b guidance, lessons learned in developing the restoration strategy, and potential challenges for maintaining these waters in Category 4b for future 303(d) reporting cycles.