Publication Summary

Monitoring of the Palermo Wellfield subdrain system and treatment lagoon occurred in December 2002 and May 2003. The water table was lowered three feet or more below ground for the north and central homes below the bluff, but not at the two southern homes. Some sediment has accumulated in subdrain cleanout CO-4. Sediment deposition or scouring is not occurring in the rest of the subdrain or lagoon. PCE (23 ppb) and TCE (24 ppb) concentrations are highest in water samples from the south and central portion of the subdrain. Lagoon effluent PCE and TCE concentrations were higher than during previous monitoring. For better comparison to remediation goals, a sample station will be reestablished where lagoon effluent discharges to the Deschutes River.

See Related Publication below for the addendum to this report.

The Palermo Wellfield in Tumwater, Washington was found to be contaminated with trichloroethene (TCE) in the late 1980s. Groundwater contaminated with TCE and tetrachloroethene (PCE) migrated from an upland commercial area to the Deschutes River valley where the Palermo Wellfield is located. The contaminated groundwater was also found to surface at the base of the Palermo bluff and pond as surface water in the yards and crawlspaces in area homes. In 2000, a subdrain system was constructed to lower the groundwater table.

Monitoring of the subdrain system was conducted by the Department of Ecology in December 2002 and May 2003. Groundwater levels measured in piezometers near the base of the bluff were three to five feet below the ground surface near the north and central homes, and 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 the central station within the trunk drain, cleanout CO-4, which has had some sediment accumulation.

PCE and TCE concentrations continue to be highest in water samples collected from the south and central portion of the trunk drain, with average concentrations of 23 ppb for PCE and 24 ppb for TCE. PCE and TCE concentrations from the lagoon effluent were higher than during previous monitoring, February 2001 through April 2002. During the current monitoring, concentrations exceeded the remediation goals set for PCE and TCE for surface water that discharges to the Deschutes River. During previous monitoring, concentrations were typically below the remediation goals at the lagoon outfall.

For future monitoring, a sample station should be reestablished where surface water from the lagoon watercourse discharges to the Deschutes River. This is approximately 2,000 feet downstream from the lagoon. A station at this location would allow a better comparison of contaminant concentrations to the remediation goals.

Link to EIM data for User Study ID PALERMO