Publication Summary

The Palermo Wellfield subdrain system and treatment lagoon were monitored in October 2003 and May 2004. The subdrain lowered groundwater three feet or more below ground surface for the north and central homes, but not at the two southern homes. Sediment has accumulated in subdrain cleanout CO-4. Sediment deposition or scouring does not appear to be occurring in the rest of the subdrain or lagoon. PCE (25 ppb) and TCE (23 ppb) concentrations continue to be highest in water samples from the south and central portion of the subdrain. PCE and TCE concentrations from where the lagoon effluent discharges to the Deschutes River were below the remediation goals of 0.8 ug/L (PCE) and 2.7 ug/L (TCE).

In the late 1980s, groundwater contaminated with trichloroethene (TCE) and tetrachloroethene (PCE) migrated from an upland commercial area to the city of Tumwater′s Palermo Wellfield in the Deschutes River valley. The contaminated groundwater also surfaced at the base of Palermo bluff and ponded as surface water in the yards and crawlspaces of area homes. In 2000 a subdrain system was constructed to reduce the human health risk from the contaminated water by lowering the groundwater table.

Monitoring of the subdrain system was conducted by the Washington State Department of Ecology′s Environmental Assessment Program in October 2003 and May 2004. The goal of the monitoring is to collect water level and PCE/TCE data to determine if the subdrain system is operating within the remediation goals set for the project.

Groundwater levels measured in piezometers were three to five feet below the ground surface near the north and central homes, which meets the remediation goals. As in the past, groundwater levels were less than three feet near the two southern homes. Total depth measurements in the subdrain system and treatment lagoon indicate that sediment deposition or scouring is not occurring, with the exception of cleanout CO-4 which has had some sediment accumulation.

PCE and TCE concentrations continue to be highest from water samples collected from the south and central portion of the trunk drain, with average concentrations of 25 ppb for PCE and 23 ppb for TCE. PCE and TCE concentrations from the lagoon effluent continue to be higher than during the validation period monitoring. TCE concentrations in May were twice as high as concentrations reported the previous year. PCE and TCE concentrations at station 364, where the treated water discharges to the Deschutes River, were below the remediation goals of 0.8 ug/L for PCE and 2.7 ug/L for TCE.

Link to EIM data for User Study ID PALERMO