PT01 Risk Management
Exhibit Hall
8:00 AM - Tuesday
(PT05) Risk Remediation of Chlorinated Volatile Organic Compounds in Groundwater.
Brunelle, H1, Lawrence, K1, Esler, C1, Feild, J1, Peterson, M1, Panwhar, S1, Powell, T2, 1 AMEC Earth & Environmental, Inc., Portland, OR, USA2 Formerly of Current Environmental Solutions, Richland, WA, USA
ABSTRACT- Volatile organic compounds (VOCs), such as trichloroethene (TCE), cis-1,2-dichloroethene (DCE), and vinyl chloride (VC), had been detected at concentrations in groundwater 30 feet below ground surface (550 milligrams per liter [mg/L], 370 mg/L , and 27 mg/L, respectively) at a former medical laboratory facility in Portland, Oregon. A prolific potential drinking water aquifer underlies the Site between 60 and 235 feet (18 and 72 m) below ground surface. Therefore, there was concern that potable water for the City of Portland could be impacted. A source area Feasibility Study concluded that electrical resistive heating (ERH) with soil vapor extraction (SVE) would be a suitable Interim Remedial Action Measure. ERH was used to treat 60-ft (46.3-m) wide, 240-ft (74-m) long, 60-ft (18.5-m) deep volume of soil and groundwater. The ERH/SVE system, operated for thirteen months, and reduced total VOC concentrations to below 1 mg/L. Following ERH treatment, a biosparging system was designed and operated for approximately eight months to reduce residual VOC concentrations to below 50 micrograms per liter. During the operation of the biosparging system, a deterministic human health risk assessment (HHRA) was conducted. The HHRA, based on present and future likely VOC distributions, assessed whether theoretical use of groundwater as a potable source posed an unacceptable risk to human health. The HHRA demonstrated acceptable risk levels for TCE, DCE and all other detected constituents except VC. However, the risk-based cleanup goal for VC in groundwater is lower than the commonly achieved detection limit. Human health risks were demonstrated to be acceptable as the result of a capture zone analysis that demonstrated that hypothetical pumping wells in the Site vicinity would not be impacted by Site-related VC. Groundwater will continue to be monitored to document the further reduction in dissolved-phase VOCs and to support risk-based closure.
Key words: electrical resistive heating, chlorinated volatile organic compounds, human health risk assessment , groundwater