f/EPA
                            United States
                            Environmental Protection
                            Agency
             EPA/540/M5-89/003
             April 1989
                             SUPERFUND INNOVATIVE
                             TECHNOLOGY EVALUATION
                           Demonstration  Bulletin
                                 In-Situ Vacuum Extraction
                                           Terra Vac, Inc.
 TECHNOLOGY  DESCRIPTION:  This  in-situ
 vacuum extraction technology  is a process  for the
 removal and  venting  of volatile organic compounds
 (VOCs) from the vadose or unsaturated zone of soils.
 Often, these  compounds can be removed from the
 vadose  zone  before  they  have a  chance  to
 contaminate groundwater.  In using this technology,
 subsurface organic contaminants are "vacuumed up"
 via a well, vapor/liquid separated, and then exposed
 to activated carbon before the  "vapor" is allowed to
 be released into the atmosphere.

 The technology  uses readily  available  components
 such as extraction and monitoring well(s), manifold
 piping,  vapor/liquid separator,  vacuum pump,  and
 emission control equipment, such as activated carbon
 canisters. Once a contaminated area  is completely
 defined, an  extraction  well (or wells) is installed
 (depending upon the  extent of contamination) and  is
 connected by piping to a vapor/liquid separator device
 (Figure 1). A vacuum  pump draws the subsurface
 contaminants through the well, separator device, and
 an activated  carbon canister before discharge of the
 air streams is allowed to the atmosphere. Subsurface
 vacuum and  soil  vapor concentration are monitored
 via vadose zone monitoring wells.

 The technology  does not require  highly  trained
 operators or  soil excavation, and it also is not depth
 limited. The technology works  best when it is applied
 towards the  remediation   at  sites  which are
 contaminated by liquids having high vapor pressures.
  However, the process is  limited in  applicability;
  diffusion  rates  through  dense  soils  (such  as
  compacted clays) are much lower than through sandy
  soils, and if activated carbon is  used, then  spent
  carbon must be processed. In  addition, depending on
  the soil type  and the depth to groundwater, the radius
  of influence of a single extraction well can range from
tens to hundreds  of  feet.  Typical contaminant
recovery rates  also  range between 20  and  2500
pounds per day and are a function of volatility of the
organic compound recovered. Therefore, the  more
volatile the organic compound, the faster the process
works.  The developer also states that the process is
more  cost effective  where  contaminated soils  are
predominantly  above  the  water table,  although
systems  have  been  designed for  vapor  and
groundwater recovery.

WASTE  APPLICABILITY:  This  technology  is
applicable  to organic compounds  that  are highly
volatile at  ambient temperatures in  soils  and
groundwater.
s

/
                                     Primary
                                     Activatrrl
                                     Carbon
                                     Canisters
  Figure 1.  Process  diagram  for in-situ  vacuum
          extraction.

-------
vvEPA
                            United States
                            Environmental Protection
                            Agency
             EPA/540/M5-89/003
             April 1989
                             SUPERFUND INNOVATIVE
                             TECHNOLOGY EVALUATION
                           Demonstration  Bulletin
                                 In-Situ Vacuum Extraction
                                           Terra Vac, Inc.
 TECHNOLOGY  DESCRIPTION:  This  in-situ
 vacuum  extraction technology  is a process  for the
 removal  and  venting  of volatile organic compounds
 (VOCs) from the vadose or unsaturated zone of soils.
 Often, these  compounds can be removed from the
 vadose  zone  before  they  have a  chance  to
 contaminate groundwater. In using this technology,
 subsurface organic contaminants are "vacuumed up"
 via a well, vapor/liquid separated, and then exposed
 to activated carbon before the "vapor" is allowed to
 be released into the atmosphere.

 The technology  uses readily  available  components
 such as extraction and monitoring well(s), manifold
 piping,  vapor/liquid separator, vacuum pump,  and
 emission control equipment, such as activated carbon
 canisters. Once a contaminated area  is completely
 defined, an  extraction  well (or wells) is installed
 (depending upon the  extent  of contamination) and  is
 connected by piping to a vapor/liquid separator device
 (Figure  1). A vacuum  pump draws the subsurface
 contaminants through the well, separator device, and
 an activated  carbon canister before discharge of the
 air streams is allowed to the atmosphere. Subsurface
 vacuum and soil vapor concentration are monitored
 via vadose zone monitoring wells.

 The technology  does not require  highly  trained
 operators or soil excavation, and it also is not depth
  limited.  The technology works  best when it is applied
 towards the  remediation  at  sites  which are
  contaminated by liquids having high vapor pressures.
  However, the process  is  limited in  applicability;
  diffusion  rates  through dense  soils  (such  as
  compacted clays) are much  lower than through sandy
  soils, and if activated carbon is  used, then  spent
  carbon  must be processed.  In addition, depending on
  the soil type and the depth to groundwater, the radius
  of influence of a single extraction well can range from
tens to hundreds  of  feet.  Typical  contaminant
recovery rates  also range between  20 and  2500
pounds per day and are a function of volatility of the
organic compound recovered. Therefore, the  more
volatile the organic compound, the faster the process
works.  The developer also states that the process is
more  cost effective where contaminated soils are
predominantly  above  the water  table,  although
systems  have  been  designed  for  vapor  and
groundwater recovery.

WASTE  APPLICABILITY:  This  technology  is
applicable  to organic compounds that  are highly
volatile at  ambient  temperatures  in  soils  and
groundwater.
s

/
                                     Primary
                                     Activatrd
                                     Carbon
                                     Canisters
  Figure 1.  Process  diagram  for  in-situ  vacuum
          extraction.

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