Pump and Treat
- Currently, groundwater is extracted using 9 wells in the upper aquifer and one well in the deep aquifer
- Pumping rates ranged from 4-11.5 gpm for the upper aquifer and 1.5-15.8 gpm for the deep aquifer
- Extracted groundwater was treated with a reduction and precipitation system until November 1994; since that time, extracted groundwater has been discharged to a POTW without on-site treatment
- ROD Date: 9/12/86
|EPA Point of Contact:|
Al Goodman, RPM
U.S. EPA Region 10
811 Southwest Sixth Ave.
Portland, OR 97204
|State Point of Contact:|
Utilities Division Manager
Public Works Dept.
City of Corvallis
P.O. Box 1083
Corvallis, OR 97339-1083
Heavy Metals (Chromium)
- Testing in 1983-1984 showed concentrations of chromium up to 3,619 mg/L in the shallow aquifer and up to 30 mg/L in the deep aquifer
Discharge to unlined disposal pit
Type/Quantity of Media Treated:
- 62 million gallons treated as of March 1997
- Groundwater is found at 0-10 ft bgs
- Extraction wells are located in two aquifers, with flow from the upper to lower aquifer and lower to upper at times during the year
- Hydraulic conductivity ranges from 0.5 to 60 ft/day
Purpose/Significance of Application:
Extracted groundwater was treated on-site at the beginning of this application; however, because concentrations dropped over time, on-site treatment was discontinued
Regulatory Requirements/Cleanup Goals:
- Cleanup goals require a concentration for chromium of 10 mg/L in the upper aquifer and 0.10 mg/L in the deep aquifer.
- The system is also required to hydraulically contain the contaminant plume.
- Chromium concentrations in both aquifers have been reduced. In the upper aquifer, average chromium concentrations have been reduced from 1,923 mg/L in August 1988 to 18 mg/L in March 1997. In the deep aquifer, average chromium concentrations have been reduced from 1.4 mg/L in August 1991 to 0.11 mg/L in March 1997. Cleanup goals for chromium have been met in 11 or 23 wells in the upper aquifer and six of seven wells in the deep aquifer.
- Approximately 31,363 pounds of chromium have been removed from the upper aquifer and 96 pounds from the deep aquifer, for a total of 31,459 pounds as of March 1997.
- Actual costs for pump and treat were $4,637,160 ($3,329,840 in capital and $1,307,320 in O&M), which correspond to $75 per 1,000 gallons of groundwater extracted and $140 per pound of contaminant removed.
- Annual operating costs dropped by an order of magnitude when use of the treatment system was discontinued in 1992.
United Chrome products is a former industrial hard chrome plating facility that manufactured and repaired hard chrome plated parts from 1956 until early 1985. In 1956, a disposal pit for liquid waste was dug in the area west of the former on-site building, and chromium-laden wastewater was discharged to the pit from 1956 to 1982. In June 1983, EPA conducted a field investigation at the site, discovering chromium contamination in on-site surface water and soils. The site was placed on the NPL in September 1984 and a ROD was signed in September 1986.
Groundwater contamination was addressed in two phases. Phase 1 was directed at remediation of the upper aquifer and began in August 1988. Phase 2 was directed at remediation of the deep aquifer and began in September 1991. Currently, groundwater is extracted using nine wells in the upper aquifer and one well in the deep aquifer. Until November 1994, extracted groundwater was treated on site; since that time, extracted groundwater has been discharged to a POTW without on-site treatment. Chromium concentrations in both aquifers have been reduced, but have not yet met cleanup goals. Future operations of the groundwater extraction systems will be determined following a 1998 investigation of the remaining soil in the area of the former plating tanks and the disposal pit.