Technology:
Hydraulic Fracturing
- Fractures were created by pushing a 2-inch steel casing and PVC drive point into the subsurface; dislodging the drive point an additional 1-4 inches, cutting a horizontal notch into the soil, pressurizing the notch with injected fluid, and propagating the fracture
- Remediation technologies were evaluated in four test cells with hydraulic fractures: Cell A - steam injection; Cell B - hot air injection; Cell C - iron metal permeable reactive barrier; and Cell D - potassium permanganate oxidation
- Cells A and B (hot fluid injection) were operated with 60 days in Fall 1996 and 45 days in Summer 1997; Cells C and D (reactive barriers) were operated passively during a two-year period
- Each treatment cell had dimensions of 45 ft length, 45 ft width, and 16 ft depth
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Cleanup Authority:
Not provided
Technical Contacts:
Robert L. Siegrist
Colorado School of Mines
Phone: (303) 273-3490
William W. Slack
FRx, Inc.
Phone: (513) 469-6040 | Management Contacts:
Tom Houk
Bechtel Jacobs Company LLC
Phone: (740) 897-6502
Jim Wright
DOE SRS/SCFA
Phone: (803) 725-5608 |
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Contaminants:
Chlorinated Solvents
- Trichloroethene (TCE) and related halocarbons at concentrations as high as 100 mg/kg |
Waste Source:
Disposal of waste oils and degreasing solvents |
Type/Quantity of Media Treated:
Soil and Groundwater
- Silty clay soils; depth to groundwater was 11.5 ft bgs, with soil water content near saturation almost to ground surface
- Soil pH 4-5; Eh 200 mV |
Purpose/Significance of Application:
Field demonstration of hydraulic fracturing with four types of remediation technologies |
Regulatory Requirements/Cleanup Goals:
Evaluate the effectiveness of hydraulic fracturing with four remediation technologies
- No specific cleanup goals were identified |
Results:
Four to five fractures were created in each cell (total of more than 25 fractures) at depths from 4-18 ft bgs and at spacings as little as 2-3 ft
- For Cell B, hot air injection increased the rate of contaminants removed by volatilization, with off-gas containing more than 800 ppmv of TCE and up to 17% methane; in Cell A, a highly heterogeneous distribution of contaminant mass and low levels of contaminants precluded a thorough evaluation of process efficiency
- For Cell C, the iron proppant remained active (30-40% initial degradation of TCE) for up to 27 months after placement, but with little effect to surrounding soil
- For Cell D, the permanganate was more active (>99% degradation of TCE within 2 hours) and created zones of reactive soil that continued to grow away from the fracture over a 27 month period |
Cost Factors:
The actual costs for the demonstration were $1,258,700, including $715,900 (Phase 1 operation), $76,400 (Phase 2 operation), $157,100 (Pre-demonstration site characterization), and $102,300 (project management)
- Costs for sand-propped fractures generally range from $850 to $1,500 per fracture; costs at this site were higher due to working within a radiation zone and higher costs for reactive agents |
Description:
The Portsmouth Gaseous Diffusion Plant (PORTS) is located approximately 80 miles south of Columbus, in south-central Ohio. The industrialized portion of PORTS is 1,000 acres of a 3,714 acre DOE reservation. PORTS was constructed between 1952 and 1956 and has operated since 1955 enriching uranium for electrical power generation. The X-231A unit is located in the southeastern portion of the PORTS site and consists of an old waste oil biodegradation site. The unit, with an area of 950 ft by 225 ft, was reportedly used for the treatment and disposal of waste oils and degreasing solvents.
A field demonstration of hydraulic fracturing was conducted in the southeastern portion of the X-231A unit from 1996 to 1998. The demonstration involved construction of four test cells, with each cell testing hydraulic fracturing in conjunction with a different remediation technology - steam injection, hot air injection, iron PRB, and potassium permanganate. Four to five fractures were created in each cell (total of more than 25 fractures) at depths from 4-18 ft bgs and at spacings as little as 2-3 ft. The passive remediation technologies appeared to be more effective than those using fluid injection (steam or hot air). Of the two passive technologies, permanganate appeared to be more effective than iron. |
