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Total Maximum Daily Loads (TMDLs) and Waste Load Allocations (WLAs) Final Report, February 1994

Section 303(d) of the Clean Water Act requires states to identify waters that do not or are not expected to meet applicable water quality standards with technology-based controls alone. Once these waters are identified, states are to develop total maximum daily loads (TMDLs) at a level necessary to achieve the applicable water quality standards. The Truckee River at Lockwood is listed on Nevada's 303(d) List for total nitrogen, total phosphorus and total dissolved solids. NDEP has chosen to use the chemical specific approach for the establishing TMDLs.

Section 303(d) of the Clean Water Act requires states implement water quality-based controls where technology based limits and implemented Best Management Practices (BMPs) are not sufficient to achieve water quality standards. A TMDL is a tool for implementing State water quality standards and is based on the relationship between pollutant sources and in-stream water quality conditions. TMDLs integrate the management of both point and nonpoint sources of pollution to a waterbody. The TMDL establishes the allowable loadings or other quantifiable parameters for a waterbody and thereby provides the basis for establishing water quality-based controls. These controls should provide the pollution reduction necessary for a waterbody to meet water quality standards.

A TMDL quantifies pollutant sources and allocates allowable loads to the contributing point and nonpoint sources so that the water quality standards are attained. The greatest amount of loading that a water can receive without violating water quality standards is the loading capacity. The waste load allocation (WLA) is the portion of a receiving water's loading capacity that is allocated to existing or future point sources of pollution. EPA regulations (40 CFR 130.2(g)) provide that load allocations for nonpoint sources and/or natural background "are best estimates of the loading which may range from reasonably accurate estimates to gross allotments...."

This document first describes the methodology used for determining a TMDL for both conservative and nonconservative parameters. Then water quality attainment programs other than waste load allocations in the Truckee Meadows Water Reclamation Facility (formerly known as the Reno/Sparks Wastewater Treatment Facility) NPDES permit are discussed. Finally, TMDLs/WLAs for TDS, TN and TP are discussed including a discussion of the proposed NPDES permit and attainability.

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