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| Title | Montesano Groundwater Investigation of Leaking Underground Storage Tanks: September 2008 and April 2009 | |||
| Month-Year Published | November 2009 | |||
| Online Availability |
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| Short Description |
Groundwater samples for BTEX, TPH-G, and VOCs were collected in September 2008 and April 2009 from 25 monitoring wells in downtown Montesano. Analytical data show the surficial aquifer is contaminated with petroleum products, primarily from three source areas: Whitney′s Inc./Key Bank (Sterling), Tony′s Short Stop/Grays Harbor Grange, and Brumfield-Twidwell. Petroleum contamination from Whitney′s Inc. and Tony′s Short Stop has possibly co-mingled to form a large plume across downtown Montesano. Low concentrations of chlorinated compounds have also been detected in some wells at Key Bank (Sterling) and Grays Harbor Grange, which may indicate the presence of VOC-contaminated plumes in these parts of the study area. (Also see abstract below) | |||
| Publication Number | 09-03-056 | |||
| Author(s) | Marti, P. | |||
| Print Availability | ||||
| Number of pages | 42 + app (73 total) | |||
| Keywords | chlorinated, Grays Harbor , groundwater, leaking underground storage tanks, Model Toxic Control Act, petroleum, river, toxic, water, wells | |||
| Subject Waterbodies |
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| Related Publications | Title | Relationship | ||
| Quality Assurance Project Plan: Montesano Groundwater Investigation of Leaking Underground Storage Tank Sites. | supporting publication | |||
| Montesano Groundwater Investigation of Leaking Underground Storage Tanks, October 2004 and March 2005 | part of a series | |||
| Montesano Groundwater Investigation of Leaking Underground Storage Tanks, October 2005 and March 2006 | part of a series | |||
| Montesano Groundwater Investigation of Leaking Underground Storage Tanks, October 2006 and March 2007 | part of a series | |||
| Montesano Groundwater Investigation of Leaking Underground Storage Tanks, October 2007 and April 2008 | part of a series | |||
| Abstract | Long Description |
The surficial aquifer beneath downtown Montesano, Washington is contaminated with petroleum products. The contamination is largely the result of releases from three identified source areas:
To characterize the lateral extent of contamination, the Washington State Department of Ecology (Ecology) collected groundwater samples from 25 monitoring wells during September 2008 and 24 wells in April 2009. Samples were analyzed for benzene, toluene, ethylbenzene, and xylene (BTEX), total petroleum hydrocarbons as gasoline (TPH-G), and volatile organic compounds (VOCs). The highest concentrations of gasoline-range petroleum hydrocarbons were detected in monitoring wells at or near the three source areas. BTEX and TPH-G concentrations were higher than allowable Model Toxic Control Act (MTCA) cleanup levels for groundwater. Benzene and TPH-G reached concentrations of 9,000 ug/L and 240,000 ug/L, respectively. Free-phase petroleum product observed in wells at the source areas continue to serve as a source of dissolved-phase contamination. Chlorinated solvents were also detected in wells within the study area. Most VOC concentrations are near the reporting limits and are below MTCA cleanup levels for groundwater. Tetrachloroethene is consistently present in wells KBMW-1, GSMW-1, and GSMW-2. The presence of chlorinated compounds in the Key Bank and Grange wells suggests the possible presence of a VOC-contaminated plume in these parts of the study area. Ecology also collected water samples from the city′s storm drain and abandoned sanitary sewer to determine if these underground utilities were providing another contaminant migration pathway. Petroleum-related contaminants were detected. This is of concern since the storm drain empties into the Chehalis River system. Because of the high concentrations of groundwater contamination and the potential for contaminants to continue to migrate from the source areas, additional investigations are being conducted to better define the nature and extent of the contamination. Some remediation has already been completed at Tony′s Short Stop and Brumfield-Twidwell. Work on these projects is continuing. |
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This page last updated August 17, 2011
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