Publication Summary

The White River, a tributary of the Puyallup River in western Washington State, exhibits high pH values, in exceedence of the state criterion of 8.5 standard units. The high pH is caused by periphytic algae growth, which in turn is related to excessive nutrient concentrations. An assimilative capacity study was undertaken to determine the maximum amount of inorganic nitrogen and orthophosphate that could be discharged to the river, and still maintain pH below 8.5.

The White River, a tributary of the Puyallup River in western Washington State, exhibits high pH values, in exceedence of the state criterion of 8.5 standard units. The high pH is caused by periphytic algae growth, which in turn is related to excessive nutrient concentrations. An assimilative capacity study was undertaken to determine the maximum amount of inorganic nitrogen and orthophosphate that could be discharged to the river, and still maintain pH below 8.5.

The largest contributor of pollutant loading for both nitrogen and phosphorus is from the Enumclaw wastewater treatment plant. The Buckley wastewater treatment plant also contributes a significant amount of phosphorus, and nonpoint sources contribute a significant amount of nitrogen.

Based on an upstream/downstream nutrient-vs.-pH comparison, there does not appear to be significant nutrient loading capacity for the White River downstream of river mile 25. However, there is uncertainty in the assimilative capacity estimate.

Recommendations are made for an adaptive management approach for reducing phosphorus loadings to the White River, starting with reductions of at least 50 percent. If follow-up monitoring determines that pH continues to exceed standards, additional reductions will be required.

The Department of Ecology will be working with the cities of Enumclaw and Buckley, Rainier School, the Muckleshoot and Puyallup Tribes, EPA, and other stakeholders to identify alternative adaptive management strategies for reducing nutrient inputs to the lower White River. The preferred alternative will include specific wasteload allocations for the existing point sources and load allocations for the nonpoint sources in the study area, to be included in the final TMDL for the lower White River.

The public comment period for this draft document has closed.