Groundwater Pump and Treat, Air Sparging, and Soil Vapor Extraction at the Cascade Corporation Site, Troutdale Gravel Aquifer, East Multnomah County Groundwater Contamination Site, OU 2, Gresham, Oregon

Site Name:

East Multnomah County Groundwater Contamination Site


Gresham, Oregon

Period of

June 1991 to present


Full scale

Groundwater pump and treat (P&T), air sparging, and soil vapor extraction (SVE)
- Remedy included multiple technologies for the site
- Air sparging was performed in 2 test wells in the same source area as the Total Fluid Extraction (TFE) wells
- An air sparging pilot test was performed using two air sparge wells to determine if sparging would enhance volatilization of VOCs from groundwater, enhance SVE mass removal rates, and enhance the oxygen levels in groundwater
- SVE was performed using 8 SVE wells and the 13 DPE wells
- SVE was shut down from March to October 1999, followed by seasonal SVE shutdown, and permanently ceased operation in December 2001
- Groundwater was extracted from 5 recovery wells and 13 DPE wells; LNAPLs were extracted using TFE in one source area
- Groundwater extraction rates for individual on-site wells in 1998 ranged from 0.01 to 5 gpm; in September and October 1998, total groundwater extraction rates were estimated to range from 8 to 11 gpm
- An off-site control trench was used to intercept the plume and to protect surface water and an underlying aquifer
- Source area groundwater extraction continued through 2002, at which time pulse pump operation began to cyclically desorb contaminants from the soil matrix during off-cycles and extract contaminants during on-cycles

Cleanup Authority:

Remedial Project Manager
Alan Goodman
U.S. Environmental Protection Agency
Region 10
Telephone: (503) 326-3685

Project Manager
Bruce Gilles
2020 SW Fourth Avenue
Suite 400
Portland, OR 97201
Telephone: (503) 229-5263

Site Contractor
Sarah Prowell
Prowell Environmental, Inc.
2216 SW Sunset Blvd.
Portland, OR 97239
Telephone: (503) 452-0972

Tetrachloroethene (PCE), Trichloroethene (TCE), Cis-1,2-dichloroethene (DCE), Halogenated-Volatiles.
- Volatile organic compounds (VOCs) detected in soil at concentrations as high as 0.09 mg/kg (PCE), 5.5 mg/kg (TCE), and 10 mg/kg (1,2-DCE).
- VOCs in groundwater detected at concentrations as high as 920 µg/L (PCE), 11,000 µg/L (TCE), 13,000 µg/L (1,2-DCE), and 106 µg/L (vinyl chloride).
- Chromium detected in groundwater at concentrations as high as 172 µg/L
- Site noted to also have light non-aqueous phase liquids (LNAPLs)

Waste Source:
Suspected releases from site operations, including overflow from an underground storage tank (UST), spills, and on-site land disposal

Type/Quantity of Media Treated:
Soil and groundwater
- TGA consists of gravel with sand, silt, and clay, and is approximately 50 ft thick on-site. Upper TGA materials consist primarily of unconsolidated silty, sandy gravel with cobbles and boulders. The lower TGA is typically an indurated sandstone.
- Depth to groundwater - 10 -12 ft bgs

Purpose/Significance of Application:
Use of multiple technologies to treat chlorinated solvents in soil and groundwater at the site

Regulatory Requirements/Cleanup Goals:
Groundwater (µg/L): PCE - 5, TCE - 5, cis-1,2-DCE - 70, vinyl chloride - 2, and chromium (VI) - 100

Soil (mg/kg): PCE - 0.3, TCE - 0.4, cis-1,2-DCE - 4.0, vinyl chloride - 0.008 mg/kg, chromium (VI) - 1,5000 (total waste analysis), 0.86 mg/L (TCLP)

As of 2003, a total of 958 pounds of VOCs were removed over the 13 year period, consisting of 561 pounds removed from groundwater, 377 pounds removed from soil, and 20 pounds removed as LNAPL. In addition, the TCE plume in the TGA groundwater was significantly reduced.

While the concentrations of the contaminants were reduced, they remained above cleanup levels as of 2003.

Cost Factors:
- Total cost for treatment (without disposal of residues) was approximately $406,000.
- Total cost for groundwater extraction (without disposal of residues) was approximately $2,000,000.
- For the 958 pounds of VOC removed by the system during this time, the unit cost amounts to $2,540 per pound of VOC removed.

The East Multnomah County (EMC) Groundwater Contamination site covers three square miles in Multnomah County, east of Portland, Oregon, and includes multiple facilities. The Cascade site (OU 2), located within the EMC site consists of those portions of Cascade Corporation's property containing soil or groundwater contamination at levels requiring remedial action. Soil and groundwater at the Cascade site are contaminated with chlorinated solvents, primarily PCE, TCE and cis-1,2-DCE, as well as LNAPL. The Record of Decision (ROD), signed for OU 2 in December 1996, specified the use of multiple technologies, including SVE with destruction of VOCs using catalytic oxidation or equivalent; continued operation of on- and off-site IRAMs (using P&T); expansion of the off-site groundwater extraction trench; extraction of LNAPL by co-pumping LNAPL and groundwater; additional on-site groundwater extraction using existing and new wells; and air sparging using approximately 25 on-site wells.

Performance data available through 2003 showed that a total of 958 pounds of VOCs have been removed over a 13 year operating period, consisting of 561 pounds removed from groundwater, 377 pounds removed from soil, and 20 pounds removed as LNAPL. While contaminant concentrations and plume sizes have decreased, concentrations remain above cleanup levels. Operation of the control trench and groundwater extraction are continuing. A pilot test of bioaugmentation is planned for the source area. In addition, 850 poplar trees were planted in 2000 for future use in treating VOCs in groundwater north of the control trench.