Publication Summary

The Spokane River regularly violates water quality standards for zinc. Standards for lead and cadmium are also exceeded frequently, especially at higher flows. A procedure for determining Waste Load Allocations (WLAs) for all NPDES point source discharges to the Spokane River was developed based on meeting aquatic life criteria in the effluent. Permit limits for NPDES dischargers will be developed in the future for each individual discharger under Ecology′s current schedule for permit cycles. Effluent limits for cadmium, lead, and zinc will be determined by comparing existing concentrations of metals in effluent, where adequate data exist, with the water quality criteria associated with the effluent hardness. Whichever results in the lower permit limits will be chosen.

The Spokane River regularly violates water quality standards for zinc. Standards for lead and cadmium are also exceeded frequently, especially at higher flows. A procedure for determining Waste Load Allocations (WLAs) for all NPDES point source discharges to the Spokane River was developed based on meeting aquatic life criteria in the effluent. Permit limits for NPDES dischargers will be developed in the future for each individual discharger under Ecology′s current schedule for permit cycles. Effluent limits for cadmium, lead, and zinc will be determined by comparing existing concentrations of metals in effluent, where adequate data exist, with the water quality criteria associated with the effluent hardness. Whichever results in the lower permit limits will be chosen.

This method should not result in any unreasonable compliance issues and minimizes the addition of metals to a system that is already exceeding the criteria. It is also an alternative to developing very stringent water quality-based effluent limits that are severely restricted due to excessive upstream and out-of-state metal sources. This approach is consistent with the intent of the anti-degradation policy of the federal Clean Water Act and the policy enunciated in the Washington State Water Pollution Control Act (RCW 90.48) requiring "… all known available and reasonable methods by industries and others to prevent and control the pollution of the waters of the state …(AKART)".

Waste Load Allocations are established as a maximum discharge concentration (micrograms per liter) rather than a discharge loading (pounds per day). The federal Clean Water Act allows for the use of allocations in mass per time or other appropriate measure. In this case, a concentration measure is appropriate, because the relationship between the effluent-based criterion and receiving water quality holds for all effluent and river flow rates.

The Spokane River at the state line is the upstream boundary for the present Total Maximum Daily Load (TMDL) in Washington. The proposed TMDL and analysis to address point source discharges and other sources of metals in the Spokane River requires that the Spokane River will meet Washington state′s water quality standards, at a point where the river enters Washington State, within a reasonable period of time. The ultimate success and appropriateness of this TMDL/WLA depends solely on whether the Idaho Department of Environmental Quality or EPA develops and implements an adequate TMDL/WLA and management plan that will result in meeting Washington′s water quality standards at the upstream end of the Spokane River.