EPA/600/S-09/030
ŁEPA
www.epa.gov/ord
science   in   ACTION
                                                           DRINKING  WATER RESEARCH
                                                           PROGRAM
    USE OF SOIL-GAS, GAS FLUX, AND GROUND-WATER MONITORING TO
    EVALUATE POTENTIAL LEAKAGE TO UNDERGROUND SOURCES OF
    DRINKING WATER, THE ATMOSPHERE, AND BUILDINGS DURING
    GEOLOGICAL SEQUESTRATION OF CARBON DIOXIDE
    Issue:
    Geological sequestration (GS) is
    recognized as the injection and
    subsequent long-term trapping of
    gaseous, liquid, or supercritical
    carbon dioxide (CO2) in
    subsurface media - primarily
    saline formations, depleted or
    nearly depleted oil and gas
    reservoirs, and coal seams.
    Carbon capture, transport, and
    storage via GS from stationary
    sources of CC>2 such as refineries,
    and coal-fired electric, ethanol,
    cement, and fertilizer plants could
    allow continued use of fossil fuels
    in a manner that greatly reduces
    CC>2 emissions until alternative
    energy sources are deployed on  a
    large scale in the  coming decades.

    It is widely acknowledged that
    leakage through transmissive
    faults (and associated fractures)
    and well penetrations
    (operational, non-operational, and
             abandoned wells) are the most
             likely potential pathway for CC>2
             release from a storage formation
             at a properly selected site for GS.
             Leakage through transmissive
             faults and well penetrations could
             result in intrusion of CC>2 or brine
             into underground sources of
             drinking water (USDWs), release
             of CC>2 to the vadose zone and the
             atmosphere, and intrusion of CC>2
             into buildings. Release of CC>2 or
             brine into a USDW could be
             accompanied by measurable
             alteration in pH, major ions, and
             mobilization of hazardous
             inorganics. Release of CC>2 into
             the vadose zone could be
             accompanied by compositional
             changes in soil gas and flux to the
             atmosphere. Release of CO2 into
             buildings  could result in increased
             CC>2 and potential reduction in
             oxygen in indoor air.
Scientific Objective:
The U.S. Environmental
Protection Agency's (EPA) Water
Research Program in the Office
of Research and Development is
conducting research to better
detect and quantify leakage into
USDWs, the vadose zone, the
atmosphere, and buildings.
Research in this initiative is
focused in three topical areas:
 .  Evaluation of Leakage
   through Well Penetrations
   Soil-gas, gas flux, and
   ground-water monitoring will
   be conducted at an enhanced
   oil recovery site and/or a site
   where CC>2 will be injected
   into a saline aquifer to assess
   the potential for leakage from
   well penetrations, especially
   abandoned wells.
   Measurements will be
   conducted near and away

                continued on back
    U.S. Environmental Protection Agency
    Office of Research and Development

-------
&EPA
www.epa.gov/ord
                         DRINKING  WATER  RESEARCH  PROGRAM
         continued from from
         from well penetrations to
         detect "spot anomalies" prior
         to and during injection of
         CO2. This concept is similar
         to the use of soil-gas surveys
         to locate gas release from
         faults and fractures in
         volcanic or geothermal areas
         where magna degassing or
         thermo-metamorphic
         alteration of carbonates
         produces large volumes of
         CC>2 and the use of soil-gas
         surveys for mineral or
         petroleum/natural gas
         exploration.
         Gas Intrusion
         Intrusion of sub-surface gases
         into buildings will be
         evaluated at a housing
         division near Wichita, Kansas
         where depletion of oxygen
         and buildup of CC>2 has been
         documented in indoor air after
         a heavy infiltration event.
         This study will  serve as a
         natural analogue to evaluate
         potential CC>2 intrusion into
         buildings due to GS. During
         commercial application of
         GS, it will be necessary to
         have a protocol to discern the
         cause of elevated levels of
         CC>2 to avoid an unnecessary
    shut down of a GS system and
    potential public overreaction.
 .  Soil-Gas Method
    Development
    Despite the long-term use of
    soil-gas sampling to support
    resource exploration and
    hazardous waste
    investigations, quality
    assurance and control
    measures are poorly
    documented or lacking.
    Research on leak, purge, and
    gas permeability testing, will
    be conducted to support
    application of GS.

The National Risk Management
Research Laboratory (NRMRL)
has a long history of conducting
research on subsurface gas flow
(DiGiulio and Varadhan, 2001),
gas and vapor intrusion (DiGiulio
et al., 2006a), and soil-gas
sampling (DiGiulio et al. 2006b).

Application and Impact:
The outcomes of this research,
conducted through the Drinking
Water Research program, will be
used to develop cost-effective
protocols for monitoring GS
systems.  Decreased cost will lead
to increased implementation and
protection of public health and
the environment.
REFERENCES:

DiGiulio, D.C., C. Paul, R. Cody, R. Willey, S.
Clifford, P. Kahn, R. Mosley, A. Lee, and K.
Christensen. 2006a. Assessment of vapor intrusion
in homes near the Raymark Superfund Site using
basement and sub-slab air samples. EPA/600/R-
05/147, U.S. Environmental Protection Agency,
Office of Research and Development, National
Risk Management Research Laboratory.

DiGiulio, D.C., C. Paul, B. Scroggins, R. Cody, R.
Willey, S. Clifford, R. Mosley, A. Lee, K.
Christensen, and R. Costa. 2006b. Comparison of
Geoprobe PRT, AMS GVP soil-gas sampling
systems with dedicated vapor probes in sandy soils
at the Raymark Superfund Site. EPA/600/R-06/11,
U.S. Environmental Protection Agency, Office of
Research and Development, National Risk
Management Research Laboratory.

DiGiulio, D.C. and R. Varadhan. 2001.
Development of recommendations and methods to
support assessment of soil venting performance
and closure, EPA/600/R-01/070, U.S.
Environmental Protection Agency, Office of
Research and Development, National Risk
Management Research Laboratory.


CONTACTS:
Dominic C. Digiulio, Ph.D., EPA's Office of
Research and Development, U.S. Environmental
Protection Agency, 580-436-8605,
digiulio.dominic(g!epa. gov

Richard T. Wilkin, Ph.D., EPA's Office of
Research and Development, U.S. Environmental
Protection Agency, 580-436-8874,
wilkin.rick(g!epa. gov

Robert W. Puls, Ph.D., EPA's Office of Research
and Development, U.S. Environmental Protection
Agency, 580-436-8543, puls.roberttgiepa.gov

Audrey D. Levine, Ph.D., EPA's National Program
Director, Drinking Water Research Program
202-564-1070, levine.audrey(g),epa.gov
      U.S. Environmental Protection Agency
      Office of Research and Development

-------