The objective of this Statement of Need (SON) is to develop an improved understanding of transformation processes and rates for polyfluoroalkyl substances (aka “precursors”) in the subsurface at sites impacted by aqueous film-forming foam (AFFF), specifically to support quantitative assessments of perfluoroalkyl acid (PFAA) mass flux both in the unsaturated and saturated zones. Specific research areas of interest include:

• Identification of microbiological and/or abiotic processes and pathways capable of either transforming or degrading AFFF-relevant precursors.

• Evaluation of relevant environmental factors that affect transformation rates such as subsurface geochemistry, soil chemical/physical properties, or nutrient availability.

• Development of methodologies and/or molecular biological tools (MBTs) to assess or predict the extent and rate of in situ transformation under ambient field conditions.

Proposals may address one or more of the objectives listed above. Research and development activities at laboratory-, bench-, and field-scale will be considered. Work does not necessarily have to culminate in a field-scale effort.

Quantifying the extent and rate of in situ precursor transformation will directly improve site conceptual models and ultimately management and treatment design at AFFF-impacted sites. Likewise, knowledge of the ubiquity with which transformation processes occur, rates of transformation, how those rates potentially change over time, and the relevant terminal will also lead to more accurate site conceptual models and the specific information needed for modeling and design tools.

Per- and polyfluoroalkyl substances (PFAS) are present in AFFF used to extinguish hydrocarbon fires. Different AFFF formulations have been used over time, but all contain a complex mixture of PFAS (all relevant AFFF formulations are applicable to this SON).

Field studies have confirmed the occurrence and predominance of precursors within soil and groundwater at AFFF-impacted sites and have demonstrated the environmental relevance of transformation processes within the subsurface. These studies have shown that many precursors can be partially biodegraded to ultimately form PFAAs under aerobic conditions. Partial biodegradation of precursors has also been observed under anaerobic conditions albeit at much slower rates. Abiotic processes can also contribute to the bulk transformation rate as well. Thus, precursor transformation can potentially sustain PFAA concentrations within source zones at AFFF-impacted sites. However, while much progress has been made in recent years regarding 1) the ability to quantify these precursors; 2) relevant abiotic and biotic transformation processes; and 3) models to assess the mass flux of PFAAs, to date there are no applied tools or models available that incorporate bulk precursor transformation rates into quantitative assessments of PFAA mass flux either in the unsaturated and saturated zones. Quantitative estimates of bulk in situ precursor transformation rates as they relate to PFAA mass flux have proven critical to site management and currently represents a significant data gap.

The cost and time to meet the requirements of this SON are at the discretion of the proposer. The two options are as follows:

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. It is expected that most proposals will fall into this category.

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 $250,000 and approximately one year in duration. Such proposals may be eligible for follow-on 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.