Publication Summary

A Class II Inspection was conducted at the city of Sequim Wastewater Treatment Plant (WTP) on August 6-8, 1990. The effluent flume was properly configured but comparison of Ecology instantaneous flow measurements to WTP influent flowmeter records could not confirm its accuracy. The WTP effluent V-notch weir needed recalibration. The WTP was performing well during the inspection; the effluent was within all NPDES permit limits.

A Class II Inspection was conducted at the city of Sequim Wastewater Treatment Plant (WTP) on August 6-8, 1990. The effluent flume was properly configured but comparison of Ecology instantaneous flow measurements to WTP influent flowmeter records could not confirm its accuracy. The WTP effluent V-notch weir needed recalibration. The WTP was performing well during the inspection; the effluent was within all NPDES permit limits.

The WTP may be approaching 85 percent of design capacity for BOD5 and TSS mass loadings; loadings should be recalculated after the weir is recalibrated. No acute toxicity was indicated in the WTP effluent by rainbow trout or Ceriodaphnia dubia. No chronic toxicity was indicated by the Ceriodaphnia dubia, but some chronic toxicity was indicated by the echinoderm sperm fertilization bioassay. Further calculations to determine if sludge stabilization is adequate are suggested. Priority pollutants were at low concentrations in the digested sludge. The automati, lead, zinc, polynuclear aromatic hydrocarbons (PAH), and dibenzofuran which were identified as problem chemicals in the waterway during the Commencement Bay Nearshore/Tideflats (CBNT) Remedial Investigation (Tetra Tech, 1985).

The spatial distribution of contaminants in this study indicates that the major sources of problem chemicals to Sitcum Waterway are Terminal 7, in the vicinity of Berth B, and the North Corner Drain. The highest concentrations of problem metals (arsenic, copper, lead, and zinc) and organics (PAHs, and dibenzofuran) associated with SPM were measured at these two locations. This finding agrees with previous investigations in the waterway. In addition, concentrations (averaged over the study period) of zinc, and high molecular weight PAHs (HPAH) near the North Corner Drain, low molecular weight PAHs (LPAH) and dibenzofuran along Terminal 7, Berth B exceeded cleanup objectives for the CBNT and/or Ecology's Sediment Management Standards. These sediments could therefore be expected to adversely affect marine benthic communities.

In most instances, little difference is evident between present (SPM) and historical (bottom sediment) concentrations of problem metals and organics in Sitcum Waterway. Noteworthy exceptions are lead and zinc levels at Terminal 7, Berth B, which appear to be decreasing over time. Decreases in lead and zinc concentrations near Terminal 7 are probably the result of source control actions taken by Ecology, which resulted in the cessation of black ore (i.e., lead c chlorine addition system was not functioning properly during the inspection. WTP and Ecology lab results from sample splits for permit parameter analysis compared well.