Publication Summary

The Upper Chehalis River Basin Total Maximum Daily Load (TMDL) for oxygen demanding substances was developed by the Washington State Department of Ecology (Ecology) and approved by the U.S. Environmental Protection Agency (EPA) on October 21, 1996. The report provided here revises the October 1996 version. It includes revisions agreed to in a settlement of legal action initiated by the city of Centralia, the city of Chehalis, and WestFarm Foods (formerly Darigold Inc.). The current version was approved by the US EPA in February 2000.

The Upper Chehalis River Basin Total Maximum Daily Load (TMDL) for oxygen demanding substances was developed by the Washington State Department of Ecology (Ecology) and approved by the U.S. Environmental Protection Agency (EPA) on October 21, 1996. The report provided here revises the October 1996 version. It includes revisions agreed to in a settlement of legal action initiated by the city of Centralia, the city of Chehalis, and WestFarm Foods (formerly Darigold Inc.). The current version was approved by the US EPA in February 2000.

The TMDL approved by EPA restricted the discharge of biochemical oxygen demanding (BOD) material to the Upper Chehalis River (WRIA 23) from May 1 to October 31 each year. In the case of Chehalis and WestFarm Foods (formerly Darigold Inc.), the existing TMDL reduced the wasteload allocation for the Centralia Reach (that portion of the river between the Highway 6 bridge and the Skookumchuck River) during the May 1 to October 31 period to zero pounds BOD and ammonia. It provided for alternatives allowing Centralia with up to 54.33 labs of ammonia and 533.1 lbs. of CBOD loading at its discharge below the Mellon Street bridge at the lower end of the Centralia Reach.

There is no change to the original approved TMDL regarding possible future alternatives. As stated in the approved TMDL "…many other possible alternatives exist, but are beyond the scope of analysis in this report. As economic and technological feasibility are explored, other alternative TMDL strategies can be analyzed with the Chehalis River model." The approved TMDL provides further that "The exact TMDL values depend on the relative loading levels of ammonia and CBOD, and on the location of loading sources. Therefore, modified values for the TMDL may arise as future scenarios are evaluated."

The revised TMDL represented by this submittal modifies the seasonal restrictions on the discharge of BOD and ammonia, to restrictions based on river flows. When river flow drops below specific thresholds identified in this revised TMDL, the wasteload allocations for Chehalis and WestFarm Foods (formerly Darigold Inc.) remain exactly the same as in the TMDL previously approved by EPA -- zero. When river flows are above those low-flow thresholds, Chehalis and WestFarm Foods are allowed to discharge to the river between the Highway 6 bridge and its confluence with the Skookumchuck River at levels that protect water quality standards for dissolved oxygen.