A METHODOLOGY FOR PATHOGEN TMDL DEVELOPMENT FOR WATER BODIES CLOSED TO SHELLFISH HARVESTING

The U.S. EPA Region 2 is sponsoring this technical work in order to assist the New York State Department of Environmental Conservation (NYSDEC) in exploring methodologies for developing and implementing water quality control strategies. The goal is to design a flexible yet technically sound TMDL development methodology for waterbodies listed in New York State's (NYS) Clean Water Act Section 303(d) list as closed for shellfish harvesting, and build the state's program development capabilities by providing NYSDEC with an expertise to submit TMDLs of this nature. The study objectives include:identification of water quality target(s) for pathogens based on the designated use of shellfish harvestingassessment of point and non-point sources of pollution that contribute pathogen load to the waterbodyestablishment of linkage between water quality target(s) and sources, thereby, the baseline scenario of pollution loading from point and non-point sources, anddevelopment of load allocations and implementation plans to achieve water quality target(s).HydroQual, Inc., as subcontractor to Battelle Memorial Institute, has been working with EPA Region 2 and NYSDEC in the development of this methodology. The NYS has suggested two waterbodies from the 303(d) list, namely, Oyster Bay Harbor and Flanders Bay in Long Island (New York) for pilot application.As guidance documents, two technical memorandums were submitted to EPA, and were finalized based on the comments received from NYSDEC and EPA. The first one provides detailed information on over 150 public domain and commercial models that were identified and evaluated for their suitability for pathogen TMDL development. The second memorandum provides guidance for various elements of TMDL development including data analysis, modeling frameworks, critical conditions and TMDL allocation procedures suitable for waterbodies with shellfish harvesting based on the following considerations:Background pollutant contributionsTypes and sources of point and non-point sources of pollutionSoil characteristics and current and projected landusesSeasonal variationsCurrent TMDL requirementsWater quality target(s) and margin of safetyWeather (precipitation and wind) conditions selected for TMDL developmentData availability, accuracy and its reliabilityModel's predictive capabilitiesEase of transferabilityMethods for allocation of loadings and their soundness, andPotential controls to achieve allocated loadings for the point and non-point pollution sources.The TMDL development methodology, described in this paper, will be used for all the waterbodies in NYS closed to shellfish harvesting. Technical support documents are being prepared, detailing the pilot application of this methodology to the two waterbodies and developing additional guidance for addressing the remaining listed waterbodies. These documents will include an explanation of the data used, all assumptions and itemized TMDL calculations describing individual waste load allocations (WLA), load allocations (LA), seasonal variations, margin of safety (MOS) and future load allocations for pathogens and pollutant source combinations affecting the waterbodies under investigation.