Publication Summary

This memorandum presents a revised analysis of waste load allocations (WLAs) for ammonia for the discharge to the White River by the city of Enumclaw during November-April using dynamic modeling techniques. The use of continuous simulation models was proposed by the city of Enumclaw in their June 1995 Appellant Settlement Plan for NPDES Permit Number WA-002057-5. The revisions in this memo supplement analyses presented in a previous memo (Pelletier, 1995). The revisions were made to incorporate comments by Bill Fox (Cosmopolitan Engineering Group).

This memorandum presents a revised analysis of waste load allocations (WLAs) for ammonia for the discharge to the White River by the city of Enumclaw during November-April using dynamic modeling techniques. The use of continuous simulation models was proposed by the city of Enumclaw in their June 1995 Appellant Settlement Plan for NPDES Permit Number WA-002057-5. The revisions in this memo supplement analyses presented in a previous memo (Pelletier, 1995). The revisions were made to incorporate comments by Bill Fox (Cosmopolitan Engineering Group).

The continuous simulation predicts a time series of allowable effluent concentrations of ammonia based on actual combinations of river flow and effluent flow during the November-April permit period between 1987 and 1995. The proposed WLAs and permit limits based on continuous simulations are predicted to protect the magnitude, duration, and frequency requirements of the water quality standard for un-ionized ammonia in the White River. The limits proposed in the draft NPDES permit are more restrictive than the continuous simulation results, and also are predicted to protect the water quality standard. The results of continuous simulation may be used for the NPDES permit. The limits proposed in Appellant Settlement Plan based on steady-state analysis by Bill Fox were not predicted to meet the water quality standard.