&EPA
                                   United States
                                   Environmental Protection
                                   Agency
                EPA/540/MR-93/509
                April 1993
                                  SUPERFUND INNOVATIVE
                                  TECHNOLOGY EVALUATION
                                   Demonstration  Bulletin
                            Pneumatic Fracturing Extraction f™) and
                                     Hot Gas Injection, Phase I
                                   Accutech Remedial Systems, Inc.
Technology Description:  The Pneumatic Fracturing
Extraction<™> (PFE)<™> process developed by Accutech Remedial
Systems, Inc.  makes it possible to use vapor extraction to re-
move volatile organics at increased rates from a broader range of
vadose zones. The low permeability of silts, clays, shales, etc.
would otherwise make such formations unsuitable for cost-effec-
tive vapor extraction and require more costly approaches. Pneu-
matic fracturing provides an innovative means of increasing the
permeability of a formation and thus extending the radius  of
influence so that contaminants can be effectively extracted.

In the PFE process, fracture wells are drilled in the contaminated
vadose zone and left open bore (uncased)  for most of  their
depth. A packer system is used to isolate small (2 ft) intervals so
that short bursts (~20 sec) of compressed air (less than 500 psig)
can be injected into the interval to fracture the formation. The
process is repeated for each interval. The fracturing extends and
enlarges existing fissures and/or introduces new fractures, prima-
rily  in the horizontal direction. When fracturing has been com-
pleted, the formation is then subjected to vapor extraction, either
by applying a vacuum to all wells or by extracting from selected
wells while others are capped or used for passive air inlet or
forced air injection.

The developer also has proposed that catalytic oxidation can be
cost-effectively used for aboveground treatment of the extracted
VOCs, particularly when contaminant concentrations are above
~50 to 100 ppmv. Catalysts suitable for oxidation of chlorocarbons
such as trichloroethene now are commercially available. In addi-
tion; Accutech has suggested injecting the waste heat from cata-
lytic oxidation either directly or indirectly (using a heat exchanger)
into the formation to further enhance volatilization and removal of
VOCs.                                               .

Figure 1 presents a schematic of a total system as it might be
used for remediation. The segments investigated  in this SITE
demonstration are shown with solid lines; the catalytic oxidation
system is shown with dashed lines.

Waste Applicability:  The Pneumatic  Fracturing Extraction
process should be particularly beneficial for the in situ removal of
VOCs from formations with low permeability such as shales and
 Water    o_~_;,,
Knockout   S^
                                                       Carbon
                                                     Adsorption
                                                       System'
     Compressed Air
         Supply
         i n
              Vacuum
              Blower
                               Air to
                              Exhaust
                              Water
                            to Disposal
                               Pressure
                                Blower
        100°0 F
                Fracture/Extraction
                      Well
              Injection Well
 Figure 1.  PFE system and operating modes.
                                                                                      Printed on Recycled Paper

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other rock formations. According to the developer, the process
also improves the vapor extraction  rate for clays and even for
sands, albeit to a lesser degree. The PFE process also  may
provHs increased access to pockets of VOCs  that otherwise
might not be reached by conventional vapor extraction.

Site characteristics can be important in determining whether a site
is suitable for PFE. Natural anomalies and man-made structures
in the formation, such as faults, pipelines, existing wells, founda-
tions, etc. all may influence the pattern achieved by fracturing,
even to the extent of causing unexpected eruption to the surface.
Free water in the vadose zone, such as perched water,  may
Interfere with fracturing and with subsequent vapor extraction, or,
at least, may change the  nature of the fracturing that does occur.

The process has been demonstrated for the removal of chlori-
nated VOCs, specifically trichtoroethene,  but should be equally
suitable for other volatile hydrocarbons such as benzene, toluene,
ethyl benzene and xylenes.

Demonstration Results: The Accutech Pneumatic Fracturing
Extraction process was demonstrated over a four-week period in
August/September 1992 at an industrial site in north central  New
Jersey. A plan was devised to evaluate PFE in terms of air flow
rate, TOE mass removal  rate, and radius of influence for extrac-
tion. Site characteristics and the extent of contamination  limited
the demonstration to the comparison of results from short term (1
to 4 hr) vacuum extraction experiments before and after fracturing
of the formation. To evaluate hot gas injection, hot air (~200°F)
generated by compression heating was injected  into one well in
the formation while extracting from  one or more other wells.
Catalytic oxidation was not investigated in this Phase I demon-
stration.

Based on the results from the SITE demonstration, the following
conclusions were reached concerning the technology's effective-
ness and cost.

  •  The  Accutech Pneumatic  Fracturing  Extraction process in-
    creased the extracted air ffow rate by >600% relative to that
    achievable  in this formation prior to fracturing.
  • While TCE concentration in the extracted air remained approxi-
    mately constant (~50 ppmv), the increased air flow rate re-
    sulted in TCE mass removal rates after fracturing that were an
    average of at least 675% higher over the 4-hr tests.
  • Significantly increased extractedairf tow rates (700%to 1,400%)
    were observed in wells 10 ft from the fracturing well. Even in
    wells 20 ft away, increases in air flow rates of 200% to 1,100%
    were observed. Coupled with well pressure data and tiltmeter
    data for surface heave, these results suggest an effective
    extraction radius of at least 20 ft.
  • Based  on capital and operating cost data provided by  the
    developer and several very optimistic assumptions, a cost of
    $140/lb of TCE removed was estimated for a remediation of the
    demonstration site or a comparable site.
  • Even higher increases in airflow rates and TCE mass removal
    rates were observed when one or more of the monitoring wells
    were opened to allow passive air inlet. Under these conditions,
    air flow rates increased an average of 19,000% and TCE mass
    removal rates increased 2,300%.
  • The results of the hot gas injection experiments were inconclu-
    sive. While  some increase in the soil gas temperature in  the
    formation was observed, it is unclear whetherthis was accom-
    panied by improvements in TCE mass removal.

A Technology Evaluation Report and  an Applications Analysis
Report describing the complete demonstration will be available in
the Summer of 1993.
For Further Information:

EPA Project Manager
Uwe Frank
Releases Control Branch
U.S. Environmental Protection Agency
2890 Woodbridge Avenue
Edison, NJ 08837-3679
(908)321-6626
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