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Total Maximum Daily Loads (TMDLs)

TMDL’s are individual limits to control contaminant loadings to impaired waterbodies (for control of nutrients) from both point and non-point sources. In 1972, Congress set forth a step-by-step statutory scheme for establishing pollution limits and spelled out three requirements: (1) Pollution limits were to be expressed as "total maximum daily loads" (2) Pollution limits were required to be established at a level necessary to implement the applicable water quality standards and (3) Pollution limits were to incorporate a "margin of safety" that "takes into account" uncertainties in the calculation of the pollution limits.

Both the federal Clean Water Act and the 1997 Watershed Agreement require the EPA to develop TMDLs for waterbodies in which the water quality standards are not being met by technology-based limitations. Phosphorus, a nutrient that is limited in pristine environments, but abundant in human sewage, fertilizers, run-off and soaps, affects plant growth in reservoirs. Excess phosphorus triggers algae blooms in reservoirs that create conditions that interfere with drinking water disinfection. Several of the watershed reservoirs are not meeting drinking water standards for phosphorus. In 1999, New York State released its proposed Phase II phosphorus TMDLs for the New York City reservoirs. NYPIRG and many environmental allies believed that those proposed TMDLs, which lowered phosphorus levels to 15 micrograms per liter only in the four Catskill/Delaware source reservoirs, were inadequate to protect the drinking water supply. The state’s failure to propose more stringent levels in the Croton system was based, in part, on future filtration of the system.

NYPIRG argued, in public hearings and through public comment, that the proposed TMDLs for the Croton system contravened the Clean Water Act and would induce eutrophication (nitrate and phosphate pollution of the waters) and sprawl. After extensive public hearings, New York State agreed to reduce TMDL levels in three Croton reservoirs. The lower TMDL levels in the New Croton, Croton Falls, and Cross River reservoirs will help restrict sprawl in the Croton system because upstream waterbodies will have to reduce phosphorus loads so that the three downstream reservoirs do not exceed the TMDLs. Currently, NYPIRG is meeting with environmental allies and New York State representatives to help establish a meaningful implementation and enforcement program for the new TMDLs.