The Onondaga Lake Tributary Assessment Project is a comprehensive water quality evaluation of Onondaga Lake tributaries to assess the impairment of all Onondaga Lake tributaries. OEI’s assessment was intended to inform New York State’s listing of “impaired waterways” under Section 303(d) of the Clean Water Act (CWA). To this end, OEI compiled, reviewed, and interpreted a large volume environmental studies, existing raw data, and newly acquired field data according to standard procedures developed by USEPA and the New York State Department of Environmental Conservation NYSDEC. The Onondaga Nation, a natural resource trustee, strongly supported the review.

Our approach was consistent with the USEPA mandate that each state is “required to consider all existing and readily available data and information to identify waterbodies on their section 303(d) lists.” OEI’s review included conventional water quality parameters (e.g. turbidity, temperature, oxygen, nutrients, etc.), bioassessments (macroinvertebrate and fish community indices, and habitat scores), and chemical contamination in surface water, sediment, fish, and macroinvertebrates. Data were compared against NYSDEC water quality standards, and USEPA criteria, where applicable; otherwise, criteria developed at other reputable agencies were utilized.

OEI worked cooperatively with USEPA Region 2, NYSDEC, the Onondaga Nation and its representatives, and local scientists and academics to produce a summary of 303(d) listing recommendations, supported by 700 pages of detailed data reviews and analyses. The report was organized by waterbody to maximize utility for regulatory decision-making. As a result of OEI’s evaluation, NYSDEC revised the 2008 303(d) list to incorporate waterbodies and parameters not previously listed, and to drop listings no longer applicable. On-going research aims to fill major data gaps identified during the initial comprehensive review with new field studies. In addition, OEI is conducting follow-up analyses of existing data, results of which will be submitted to NYSDEC and USEPA for consideration prior to release of the next 303(d) list.