continued on back 

EPA/600/S-09/030 

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 CO2 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 

CO2 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 CO2 

release from a storage formation 

at a properly selected site for GS. 

Leakage through transmissive 

faults and well penetrations could 

result in intrusion of CO2 or brine 

into underground sources of 

drinking water (USDWs), release 

of CO2 to the vadose zone and the 

atmosphere, and intrusion of CO2 

into buildings. Release of CO2 or 

brine into a USDW could be 

accompanied by measurable 

alteration in pH, major ions, and 

mobilization of hazardous 

inorganics. Release of CO2 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 

CO2 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 CO2 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 
 

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 

CO2 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 CO2 has been 

documented in indoor air after 

a heavy infiltration event. 

This study will serve as a 

natural analogue to evaluate 

potential CO2 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 

CO2 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/R05/147, 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@epa.gov 

Richard T. Wilkin, Ph.D., EPA’s Office of 

Research and Development, U.S. Environmental 

Protection Agency, 580-436-8874, 

wilkin.rick@epa.gov 

Robert W. Puls, Ph.D., EPA’s Office of Research 

and Development, U.S. Environmental Protection 

Agency, 580-436-8543, puls.robert@epa.gov 

Audrey D. Levine, Ph.D., EPA’s National Program 

Director, Drinking Water Research Program 

202-564-1070, levine.audrey@epa.gov