Water Quality Restoration Planning in Rhode Island
Total Maximum Daily Load (TMDL) Program
Rhode Island's water quality restoration planning efforts are centered on the federally mandated requirement that states develop Total Maximum Daily Load (TMDL) plans for waters not meeting one or more water quality criteria. Consistent with federal Clean Water Act requirements, the Rhode Island Department of Environmental Management's Office of Water Resources identifies those waters not meeting water quality standards based upon the most recent assessment of water quality conditions completed as part of the state's new Integrated Water Quality Monitoring and Assessment Report. The resulting 303(d) List of Impaired Waters identifies these waterbody impairments (waterbody segment and water quality parameter specific) and prioritizes them for TMDL development.
TMDL plans identify water quality goals, necessary pollutant reductions to achieve these goals, the sources of pollution believed responsible for the pollution problems, and the necessary pollution control actions to achieve the required reductions and support the waterbody's designated uses. These water quality restoration plans are in essence a prescription for the waterbody's return to a safe and healthy aquatic ecosystem. The elements of a TMDL plan are described below.
As mentioned, TMDL plans are detailed water quality restoration plans that address waterbody specific water quality problems, for example, bacteria problems in Narrow River. A TMDL determines the water quality goal for the waterbody and how much of a particular pollutant (concentration or load) that the waterbody can assimilate while still supporting its designated uses. Using the Narrow River example, the TMDL's water quality goal was set as the fecal coliform standard, protective of shellfish harvesting (plus an additional 10% reduction to establish an explicit Margin of Safety). Because the fecal coliform standard for shellfish harvesting is more stringent than that for swimming, the TMDL's water quality goal is also protective of the swimming use. Necessary pollutant reductions are determined by first evaluating the current condition(s), and then calculating the reductions needed to meet the target condition(s). Wherever possible, DEM utilizes existing available data in determining current conditions; for example, ambient concentrations of the parameter(s) of concern and/or loads currently discharged into the waterbody. Using the Narrow River example, current conditions were determined by evaluating water quality and pollution source data collected by DEM and Narrow River Preservation Association volunteers. In this case, the necessary pollutant reductions were expressed in % reduction in fecal coliform concentrations needed to meet the TMDL's established water quality goal.
A significant focus of DEM's TMDL development efforts is the identification of the pollution sources contributing to the water quality impairment. DEM staff conduct shoreline and watershed surveys, collect water quality samples, and work with municipal officials, watershed organizations and volunteer water quality monitors to identify and ideally, rank the significance of potential sources. Through this process, DEM examines the presence and relevance of point sources such as industrial and wastewater treatment facility discharges and regulated storm water discharges, and nonpoint sources such as nuisance populations of wildlife and/or waterfowl, septic systems and unchannelized runoff from urban and agricultural areas. The TMDL plan allocates the allowable pollutant load amongst the identified sources in the watershed.
Once a TMDL is completed including public review and comment on the draft plan, the document is submitted to US EPA for its final review and approval. Completing the TMDL plan is just the first step in restoring water quality. Typically, a variety of activities involving numerous government agencies, organizations, and even private citizens must be implemented in order to achieve the ultimate goal of restoring water quality and the public's full use and enjoyment of the resource.
TMDL Background Information
Draft and Approved TMDL Documents
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Draft TMDLs Open for Public Comment
Scott Pond (3/31/14)
Documents Related to
Ten Mile River 2007 Final Data Report
Ten Mile River Water Quality Presentation
Pawcatuck River TMDL Meeting Presentation
Determination Nitrogen Thresholds & Nitrogen Load Reductions Green Hill & Ninigret Ponds
Addendum - Nitrogen Thresholds & Nitrogen Load Reductions Green Hill & Ninigret Ponds, October 2006
Green Hill Pond Bacteria Source Tracking Report
Greenwich Bay Fish Kill Report
Scope of Work - Stormwater Attenuation and Source Reduction
RI DOT Stormwater Management Improvement Study
Mount Hope Bay Kickemuit River Wet Weather Sampling 2006 Final Data Report