Pipe-coating businesses, run by the Hall Process Company and Northwest Pipe and Casing Company, operated on the southern part of the 53 acre property from 1956 to 1985. During the pipe-coating operations, contaminants were released at the Site into the soil and groundwater. These contaminants included volatile organic compounds (VOCs), polynuclear aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs).
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Remedial Action (RA) at the Site, which was divided into an Operable Unit (OU) for soil and an OU for groundwater, was performed between August 1, 2001 and September 8, 2004. The RA consisted of soil excavation and treatment of 32,010 tons of contaminated soil and installation of a two foot cap of clean soil on a portion of the Site, installation of a groundwater treatment system consisting of groundwater circulating wells (GCWs) and monitoring wells, and institutional controls to prohibit the use of groundwater at the Site.
In 2006, the Five Year Review (FYR) of the Site concluded that the groundwater remedy was not functioning as designed. As a follow up to the FYR, EPA Region 10 requested that the EPA Headquarters Remedial System Evaluation (RSE) contractor conduct an analysis of the remedy. The findings established that the groundwater treatment system should be shut down and additional site characterization of the main plume be completed to help determine the southern boundary of the plume. A site wide groundwater monitoring event was conducted in November 2007. During this event a non-aqueous phase liquid (NAPL) was discovered in monitoring well MW-207 located within the Plume 1 source area (Parametrix, 2007). Analysis indicated the sample contained PAHs and VOCs with some PCBs and metals; and that the composition of the dense non-aqueous phase liquid (DNAPL) fraction was similar to that of coal tar which was used at the Site (Parametrix, 2008). (See Table 1.)
Based on the RSE recommendations and the discovery of DNAPL in MW-207, in the fall of 2008, a Supplemental Focused Field Investigation (SFFI) was completed. The SFFI identified three DNAPL bodies, a main body and two smaller bodies within the Plume 1 Source Area. These DNAPL bodies are presumably composed of coal tars. See Figures 2 and 3 and Tables 2, 3 and 4.
Analytical results for soils collected within the DNAPL bodies indicate relatively high concentrations of chlorinated volatile organic compounds (CVOCs), naphthalene, and BTEX (benzene, toluene, ethylbenzene, xylene). In general, CVOCs and BTEX concentrations in subsurface soil are limited in extent both laterally and vertically within the DNAPL bodies. However, naphthalene concentrations in subsurface soil are more pervasive throughout the DNAPL bodies, with detectable concentrations up to 65 feet below ground surface (bgs).
In February 2009, the Region held a conference call with Headquarters and the RSE contractor to discuss the findings, especially considering their previous recommendations and how the discovery of the DNAPL bodies, referred to as coal tar bodies, would affect the groundwater remedy. The RSE contractor indicated that no further effective action could be taken on the groundwater remedy until the coal tar bodies, determined to be sources of soil contamination, were removed or otherwise treated.
In May 2009, the EPA Region 10 Remedial Program requested assistance from the Removal Program in removing the major source of soil contamination remaining at the Site so that a new groundwater remedy could be implemented.
On June 18, 2009, a Removal Assessment site visit was conducted by EPA On Scene Coordinator (OSC) Kathy Parker, EPA Remedial Program Manager (RPM) Mark Ader, Oregon Department of Environmental Quality (ODEQ) Project Manager Debbie Bailey and contractors from Environmental Quality Management, Ecology and Environment, and Parametrix. All participants concluded that further site work is necessary to remove remaining soil contamination before the Remedial Action groundwater remedy is expected to be effective.
The Removal Action Memo was signed on July 28, 2009 and site activities began on August 12, 2009. Work conducted through the fall of 2009 is described in detail in individual POLREPS on this website.
Site work was halted in November 2009 due to the onset of significant precipitation. Rainfall increased the saturation levels of site soils, and therefore increased the weight of excavated material. This additional weight significantly increased transportation and disposal costs. In order to better manage these costs, site work was halted until June 2010.
Proposed Action Description:
DNAPL Source Areas
EPA will excavate an estimated 10,000 tons of contaminated subsurface soil from two DNAPL source areas. The final depth and width of excavations will be determined by visual observation and laboratory analyses using the contaminant cleanup concentrations specified in the ROD. The excavated soil will be segregated on-site by hazard class and disposal method and shipped off-site for disposal at approved hazardous waste and municipal waste facilities, as appropriate. A soil modifier will be placed in the excavations to enhance biological degradation of residual contaminants. The excavations will be backfilled with clean soil and the top two feet of fill material will be replaced to achieve the ROD barrier specifications. Groundwater intrusion into the excavations will be pumped to an on-site water treatment system. Any collected groundwater, surface water, or leachate will be cleaned, analyzed and disposed in an appropriate manner. Disturbed areas will be graded to facilitate surface water drainage and will be revegetated as needed with appropriate plant materials.
Best-Management Practices (BMPs):
Temporary Best Management Practices (BMPs) will be employed throughout construction for control of erosion, fugitive dust, and storm water management, and to minimize and to avoid adverse impacts on wildlife and their habitats. Dust and particulate concentrations at the Site will be monitored with particulate monitors and the results used to modify work practices if particulate levels exceed the on-Site action level of 10 ppm and Site boundary action level of 3 ppm.