Total Maximum Daily Loads (TMDLs)
The Total Maximum Daily Loads (TMDL) program is a water quality based approach designed to maintain designated uses for waterbodies throughout each state. A TMDL is a calculation of the maximum amount of a pollutant that a water body can receive and still achieve water quality standards. The TMDL identifies the reductions needed to meet water quality standards. It then allocates these reductions among point and non-point sources in the watershed. The Total Maximum Daily Loads (TMDL) rule was initiated in section 303 (d) of the 1972 Clean Water Act. Section 303 (d) requires states to identify waters not meeting water quality standards; set priorities for TMDL development; and develop a TMDL for each pollutant for each listed water. A single water body may require multiple TMDLs to be developed. Currently, many states are in the process of implementing the federal TMDL program, which they submit to the federal EPA. The EPA approves or disapproves the state’s submissions, if disapproved; the EPA will act in lieu of the state.
Pollutants typically discharged from aggregate operations consist of total suspended solids, total dissolved solids, pH, oil and grease. Most aggregate facilities have National Pollutant Elimination System (NPDES) permits with allowable discharge limits for the various pollutants listed above. However, an aggregate operation may not use its NPDES permit on a regular basis. Instead, many operations proactively institute no-discharge or recycled waste water systems at their locations.
The Total Maximum Daily Load (TMDL) rule has the potential to adversely affect aggregate mining operations, in at least two ways: (1) Aggregate facilities that have proactively instituted no-discharge or recycled waste water systems may find their allowable permitted discharge limits allocated to other industrial sources that actively discharge into the same receiving stream as the aggregate operation. (2) Aggregate operations that were one of the first industrial sources located along the receiving stream and are actively discharging, may find their permitted discharge limits divided among newer sources locating along the same stream in the future.
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