The objective of this Statement of Need (SON) was to develop more quantitative assessments of contaminant plumes in groundwater. The overall goals were to improve our ability to identify transition points from active to more passive remedial measures, and to better assess the impacts of interim remedial measures. Specific objectives of this SON included:
- Development of improved tools and techniques to identify trace and discrete contaminant sources for persistent source areas so that they can be effectively captured within conceptual site models (CSMs).
- Development of tools, methods, and approaches to extract useful rate constants for naturally occurring long-term biotic and abiotic transformation processes. These tools should provide some estimate of the uncertainty in the estimated rate constants, to allow for a sensitivity analysis of their contribution in the overall CSM.
- Development of tools and techniques to quantify the processes governing the slow release of contaminants from low permeability zones (LPZs), so that they can be appropriately accounted for in CSMs.
- Development of approaches, methods, and models that will quantify the maximum concentration of a contaminant that can be allowed in groundwater leaving a contaminated source zone. Preferably, such approaches, methods, and models will be appropriate for in situ remedial technologies that can be evaluated with traditional monitoring wells.
- Improved approaches, methods, and models to determine when it is appropriate to stop pumping groundwater or to transition from active treatment of a source or plume to a more passive treatment strategy. The methods should include evaluations of the uncertainty associated with temporal and spatial variations in groundwater flow direction, velocity, and variations in contaminant concentrations.
- Improved understanding of interim remedial measures, in particular to determine whether interim measures will ensure adequate protection of human health and the environment during subsequent natural attenuation.
To provide strategic guidance for future research and demonstrations on management of contaminated groundwater, SERDP and ESTCP conducted a workshop in July 2018 in Seattle, WA. Proposers were strongly encouraged to view the Workshop Report summarizing the research, demonstration, and technology transfer needs prior to submitting their proposal.
Proposals should have addressed one or more of the objectives listed above. Research and development activities at laboratory-, bench-, and field-scale will be considered, but work does not necessarily have to culminate in a field-scale effort. Technologies and approaches should be applicable to a variety of hydrogeologic settings. Proposals should have focused on the common chlorinated solvents found in groundwater (tetrachloroethene, trichloroethene, and their daughter products) and energetic compounds such as RDX were of most interest.
Funded projects will appear below as project overviews are posted to the website.
Research in this area should lead to improved conceptual site models, thereby providing better and more cost-effective protection of human health and the environment. Further, improving our ability to quantitatively assess relevant groundwater process may allow greater use of passive site management resulting in substantial cost savings while remaining protective of human health and the environment.
In July 2018, SERDP and ESTCP held a Workshop addressing management of chlorinated solvents in groundwater. Approximately 60 personnel representing DoD remedial program managers (RPMs), federal and state regulators, engineers, researchers, industry representatives, and consultants attended. Workshop participants identified several research needs that, if addressed, would improve the DoD’s ability to safely and cost-effectively manage chlorinated solvent-contaminated groundwater sites. A more detailed description of identified research needs can be found in the report from the workshop. Proposers are strongly encouraged to review the Workshop Report for additional detail.
Existing CSMs often fail to account for the range of possible mechanisms and processes that sustain and control the persistence of dilute chlorinated solvent plumes. This failure is typically due to several factors, including the inability to verify that all suspected degradation processes are occurring, the inability to sufficiently quantify the significance of the process, and/or the lack of appropriate modeling tools to incorporate these processes into fate and transport models. Examples of mechanisms and processes that are often neglected or poorly characterized and quantified in CSMs include (but are not limited to):
- Persistent low-intensity source areas. Often, source areas persist even after the bulk of the contaminant mass has been removed, and after the contaminant flux has been substantially reduced.
- Naturally occurring long-term biotic and abiotic transformation processes. Even very slow dechlorination processes can have a substantial impact on plume attenuation when considering timescales of decades. However, it is difficult to incorporate these processes in CSMs because of a lack of reliable kinetic data and an inadequate understanding of when these mechanisms and their relative degradation rates are and are not likely to be appropriate for inclusion in a CSM.
- Interactions with low permeability materials. Quantifying the processes that occur within LPZs, and characterizing the interactions between LPZs and hydraulically conductive zones, remains difficult. Proper descriptions of contaminant release and uptake into such zones can require more characterization data than is usually available, and in fact it is often impractical to collect sufficient data with current tools.
Overall, there is an absence of tools and techniques to validate the contribution of these processes on plume persistence. A quantitative assessment of these processes would also allow for better assessment of the maximum concentration of a contaminant that can be allowed in groundwater leaving a source of contamination such that the concentration of the contaminant will not exceed groundwater cleanup levels, and consequently, when it is appropriate to stop pumping groundwater or to transition from active treatment of a source or plume to a more passive treatment strategy.
SERDP and ESTCP have funded several projects in an effort to understand processes that impact contaminants in groundwater. Proposers should be familiar with these past projects, which can be found at https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration. Proposed efforts should be complementary and not duplicative of previously funded projects.
The cost and time to meet the requirements of this SON are at the discretion of the proposer. Two options are available:
Standard Proposals: These proposals describe a complete research effort. The proposer should incorporate the appropriate time, schedule, and cost requirements to accomplish the scope of work proposed. SERDP projects normally run from two to five years in length and vary considerably in cost consistent with the scope of the effort.
Limited Scope Proposals: Proposers with innovative approaches to the SON that entail high technical risk or have minimal supporting data may submit a Limited Scope Proposal for funding up to $200,000 and approximately one year in duration. Such proposals may be eligible for followon funding if they result in a successful initial project. The objective of these proposals should be to acquire the data necessary to demonstrate proof-of-concept or reduction of risk that will lead to development of a future Standard Proposal. Proposers should submit Limited Scope Proposals in accordance with the SERDP Core Solicitation instructions and deadlines.