Hydraulic and Pneumatic Fracturing at the U.S. Department of Energy's Portsmouth Gaseous Diffusion Plant, Ohio; Department of Defense; and Commercial Sites

Site Name:

Portsmouth Gaseous Diffusion Plant

Location:

Piketon, Ohio (for PGDP)

Period of
Operation:

July 1991 - August 1996 (multiple demos during this time period)

Cleanup
Type:

Field demonstration

Technical
Information:

Pneumatic:
- J. Liskowitz/T. Keffer, ARS, (908) 739-6444
- John Schuring, NJIT, (201) 596-5849

Hydraulic:
- L. Murdoch, Univ. of Cinc., (513) 556-2519
- W. Slack, FRX, (513) 556-2526
- R. Siegrist, ORNL, Col. Sch. of Mines, (303) 273-3490

Technology:
Hydraulic and Pneumatic Fracturing

- Hydraulic fracturing equipment includes lance, notch tool, slurry mixer, and pump
- Gel-laden proppant is pumped into notch under 60 psig to create a fracture
- Pneumatic fracturing equipment includes high-pressure air source, pressure regulator, and receiver tank with inline flow meter and pressure gauge
- Air is injected at 72.5-290 psi for <30 seconds using a proprietary nozzle
- Design considerations include formation permeability, type, and structure; sand proppant; state of stress; site conditions; and depth
- Fracturing used in conjunction with other in situ technologies such as SVE, bioremediation, and pump and treat

Cleanup Authority:
Information not provided

SIC Code:
9711 (National Security)
Others - information not provided
Point of Contact:
Skip Chamberlain, DOE, (301) 903-7248
James Wright, DOE, (803) 725-5608

Contaminants:
Demonstrations conducted at sites contaminated with Volatile Organic Contaminants (VOCs) (including Trichloroethene (TCE)), Dense Nonaqueous Phase Liquids (DNAPLs), and at uncontaminated sites

Waste Source:
Tinker - Underground Storage Tank
Others - Information not provided

Type/Quantity of Media Treated:
Soil and Ground Water

- Generally applicable in low permeability formations
- At PGDP, was used at uncontaminated site underlain by low permeability clays and silts to a depth of approximately 15-22 ft

Purpose/Significance of Application:
Demonstrations of technology used to increase hydraulic conductivity, contaminant mass recovery, and radius of influence (for example, in a SVE application)

Regulatory Requirements/Cleanup Goals:
- No special permits were required for use in the demonstrations
- Some states may be concerned about injection of fluids and other materials that may alter the pH of the subsurface

Results:
- Hydraulic fracturing demonstrations showed mass recovery increased from 2.8-50 times, and radius of influence from 25-30 times
- Pneumatic fracturing at Tinker Air Force Base increased product thickness in recovery well from 1.5 to 20.2 ft
- Pneumatic fracturing at PGDP doubled hydraulic conductivity, and increased radius of influence by 33% after one day of pumping

Cost Factors:
Capital and annual costs not provided for demonstrations
Hydraulic fracturing projected to cost $5,400 for one-time costs, and $5,700 for daily costs (corresponding to $950-1,425 per fracture, for 4-6 fractures)
Pneumatic fracturing projected to be similar to those for hydraulic fracturing ($400-1,425 per fracture)
Pneumatic fracturing at a SITE demonstration estimated at $140/lb of TCE removed; other estimates predict pneumatic fracturing cost of $8-17/yd3 soil treated

Description:
Hydraulic and pneumatic fracturing are technologies that can enhance access to the subsurface for remediation of contaminants above and below the water table. Enhanced access is provided by creating new or enlarging existing fractures in the subsurface. These fractures enhance the performance of in situ remediation technologies such as SVE, bioremediation, and pump and treat by increasing the soil permeability; increasing the effective radius of recovery or injection wells; increasing potential contact area with contaminated soils; and intersecting natural features. Fracturing can also be used to improve delivery of materials to the subsurface (e.g., nutrients).

A number of demonstrations of hydraulic and pneumatic fracturing have been conducted to show technology applicability and performance in a variety of settings. Hydraulic fracturing demonstrations have showed mass recovery increases from 2.8-50 times, and radius of influence increases from 25-30 times. Pneumatic fracturing demonstrations have been conducted at Tinker Air Force Base and PGDP, with results provided in terms of increased product thickness in recovery wells and increases in hydraulic conductivity and radius of influence. Hydraulic fracturing is commercially available from several companies, while pneumatic fracturing has been patented by the New Jersey Institute of Technology (NJIT). The NJIT has licensed pneumatic fracturing to Accutech Remedial Services (ARS). While hydraulic fracturing produces larger apertures and can be performed at greater depths than pneumatic fracturing, the addition of water in hydraulic fracturing may create a larger volume of contaminated media possibly requiring remediation. Prior to proposing fracturing, sites should be analyzed for permeability. Sites with extensively fractured strata will have permeabilities that are high enough that fracturing may not be required.