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  Home Publications GSI Environmental Papers 2010-Start SERDP and ESTCP-Funded Research Projects
GSI is leading or supporting the following projects:

Determining Source Attenuation History to Support Closure by Natural Attenuation (ER-1032)
Principal Investigator: Charles Newell - GSI Environmental, Inc.
One of the key constraints on the ability to select remedies for closing sites affected by chlorinated solvents is the typically short time interval for which monitoring data is available to assess trends. This project seeks to reduce the uncertainty associated with assessing long-term concentration trends for use in remedy selection at sites with chlorinated solvent contamination in soil and groundwater. A long-term source history could provide support for natural attenuation in particular.

Enhanced Attenuation of Unsaturated Chlorinated Solvent Source Zones Using Direct Hydrogen Delivery (ER-1027)
Principal Investigator: Charles Newell - GSI Environmental, Inc.
At many contaminated DoD sites, unsaturated chlorinated volatile organic compound (CVOC) source zones located above the water table are producing and sustaining groundwater plumes. Current treatment options for the recovered vapors are both complicated and expensive. The objective of this project is to demonstrate that hydrogen-based treatment can serve as a new remediation technology for the unsaturated zone, either as the initial remediation technology applied at a site or as a polishing technology, and that it will allow site managers to shut down expensive, low-performance soil vapor extraction (SVE) systems.

Basic Research Addressing Contaminants in Low Permeability Zones (ER-1740)
Principal Investigator: Tom Sale – Colorado State University
The objectives of this project are to improve understanding of contaminant storage-release in low permeability zones, demonstrate novel site characterization approaches, advance a set of validated predictive tools, and develop a foundation for selecting remedies. Technical guidance will be developed for parties who are characterizing sites and selecting remedies at sites where contaminants are present in low permeability zones.

Subsurface Thermal Energy Storage for Improved Heating and Air Conditioning Efficiency (SI-1013)
Principal Investigator: Ronald Falta - Clemson University
Although the benefits of using natural and waste heat as alternative energy sources are known, it is difficult to take full advantage of those sources because of their intermittency and seasonality. The objectives of this project are to (1) develop a field application of subsurface thermal energy storage (STES) for exploiting natural or waste sources of heat and cold and (2) couple the STES system with a ground-source heat pump to improve heating and cooling efficiency. With this technology, the heat (or cold) is harvested from the ground using a ground-loop heat pump with two separate ground loops, thus enabling higher efficiencies to be achieved. This method of heating and cooling is more efficient than conventional HVAC systems as well as current geothermal heat pump systems.

Integrated Stable Isotope - Reactive Transport Model Approach For Assessment Of Chlorinated Solvent Degradation (ER-1029)

Objective:

The objective of this project is to improve the capabilities for quantitative assessment of chlorinated solvent mass destruction from natural attenuation processes, using a combined compound-specific stable isotope analysis (CSIA) and numerical reactive transport modeling approach. Existing evidence indicates that CSIA can provide data to support and quantify mass destruction of chlorinated solvents in the subsurface. However, interpretation of results is difficult due to variability in field data and complex flow and transport conditions in situ. In this project, CSIA will be integrated with reactive transport modeling to allow quantitative interpretation of isotope effect in a complex hydrogeological system. This approach will improve site conceptual model development by identifying prevalent degradation pathways, inputs from DNAPL dissolution, and nondegradative sinks such as sorption or volatilization; demonstrate and facilitate more accurate assessment of degradation of the parent contaminant; and allow quantitative assessment of the net degradation/accumulation of the dechlorination intermediates.

Technology Description:

An existing multistep 1-D 13C/12C isotope fractionation model only very recently extended to chlorine (37Cl/35Cl) for anaerobic reductive dechlorination will be further extended to 3-D and to accommodate aerobic degradation processes. The models will be initially calibrated with data from a microcosm study of the reductive dechlorination of tetrachloroethene (PCE). That test will validate the model's simulation of isotope effects in the parent PCE and the degradation intermediates. The main model demonstration will be performed using data from a contaminated field site. Using historical site data obtained from several chlorinated ethene-contaminated plumes within the Department of Defense (DoD), a candidate site will be selected for sampling a plume with active anaerobic reductive dechlorination and aerobic attenuation sections. Following site selection, a detailed field sampling effort will be completed to collect groundwater samples for CSIA on chlorinated ethenes for 13C/12C and 37Cl/35Cl (optionally 2H/1H). Isotope ratios for the additional elements will provide evidence of mechanistic differences in transformation pathways when going from the controlled settings of a microcosm test to a field setting. Finally, the 3-D model will be validated based on results of the CSIA from the demonstration site.

Expected Benefits:

A guidance document and a training course will be developed for site managers to help them understand when CSIA should be applied to sites to support monitored natural attenuation (MNA) remedies and how to utilize the 3-D linked geochemistry and transport model to interpret sampling results. The model and guidance will support demonstration of mass destruction, which potentially could be used to reduce monitoring effort, discontinue active remedies, and facilitate property redevelopment. (Anticipated Project Completion - 2013)

Principal Investigator:

Dr. Paul Philp
University of Oklahoma
100 E. Boyd Street
SEC 710
Norman, OK 73019
Telephone: (405) 325-4469
Fax: (405) 325-3140
E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Use of Compound-Specific Stable Isotope Analysis to Distinguish Between Vapor Intrusion and Indoor Sources of VOCs (ER-1025)

Objective:

The U.S. Environmental Protection Agency is increasingly relying on indoor air testing as a primary tool for evaluating vapor intrusion. However, when testing indoor air, distinguishing between vapor intrusion and indoor sources of volatile organic compounds (VOC) is a significant challenge, greatly increasing the cost and complexity of investigations. The objective of this project is to validate the application of compound-specific stable isotope analysis (CSIA) as a tool to distinguish between vapor intrusion and indoor sources of VOCs. Specific objectives are to:
  • Validate the use of active sorbent samplers for the collection of vapor-phase samples for carbon, chlorine, and hydrogen CSIA of VOCs such as tetrachloroethene (PCE), trichloroethene (TCE), and benzene that commonly drive vapor intrusion investigations
  • Develop a protocol for application of CSIA for vapor intrusion investigations
    • Characterize the stable isotope signatures for common indoor VOCs
    • Characterize the stable isotope signatures of subsurface sources of VOCs and the variability in these signatures in close proximity to potentially affected buildings
    • Develop a protocol for application of CSIA to distinguish between vapor intrusion and indoor sources of VOCs
  • Demonstrate CSIA for vapor intrusion investigations by applying the protocol at four buildings (from two different Department of Defense facilities) potentially affected by vapor intrusion.
Technology Description:

CSIA is a proven laboratory analytical method to measure the ratio of stable isotopes (e.g., 13C/12C; 37Cl/35Cl; D/H) in individual chemicals present in environmental samples. Differences in the isotopic ratios between environmental samples can be used to distinguish between different sources of environmental contaminants and understand biodegradation and other transformation processes occurring in the environment. CSIA has been validated and accepted as an effective tool for distinguishing between different sources of VOCs in groundwater. This project will validate the use of CSIA to distinguish between vapor intrusion and indoor sources of VOCs, a novel application of this technology.

Expected Benefits:

When indoor air testing is conducted, VOCs are commonly detected at concentrations above the applicable indoor air screening criteria. Such results often require extensive follow-up testing programs to definitively identify the source of the detected VOCs (i.e., vapor intrusion versus indoor sources). At Hill Air Force Base, for example, more than 25% of the TCE detections above action levels in indoor air have subsequently been attributed to indoor sources of VOCs rather than vapor intrusion. For PCE and 1,2-dichloroethane (1,2-DCA), indoor sources have resulted in even higher percentages of action level exceedances. However, identification of the indoor VOC source has typically required multiple rounds of sampling and analysis, and in many cases an indoor source is identified only after a vapor intrusion mitigation system has been installed and has failed to improve indoor air quality. Validation of CSIA as a method to distinguish between vapor intrusion and indoor sources of VOCs will significantly reduce the effort and cost of testing indoor air at vapor intrusion sites. The development of a validated procedure for use of CSIA to distinguish between vapor intrusion and indoor sources of VOCs could reduce vapor intrusion investigation costs 25% to 50% by significantly reducing the need for follow-up investigation at buildings with exceedances of indoor air screening levels attributable to indoor sources of VOCs. (Anticipated Project Completion - 2013)

Principal Investigator:

Dr. Thomas McHugh
GSI Environmental, Inc.
2211 Norfolk Street
Suite 1000
Houston, TX 77098-4044
Telephone: (713) 522-6300
Fax: (713) 522-8010
E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it
 
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