Advancing PFAS Modeling in Support of Holistic Watershed Management

Harry Zhang; Meghna Babbar-Sebens; Ebrahim Ahmadisharaf; Rene Camacho-Rincon; Sanaz Imen

The research on various aspects of PFAS across different water matrices has been active and evolving. Due to the complex nature of PFAS including its persistence across the entire water cycle, it has been challenging for watershed models to explicitly simulate PFAS fate and transport processes to better support holistic watershed management. ASCE Manual of Practice 150, titled “Total Maximum Daily Load Development and Implementation: Models, Methods, and Resources,” identified PFAS modeling as one of the knowledge gaps for watershed and water quality modeling. Therefore, the objectives of this presentation are to summarize the advances in PFAS modeling in the context of holistic watershed management and make recommendations for future research.

One of the feasible strategies to advance the modeling of PFAS is to build from modeling experience gained from polychlorinated biphenyls (PCBs) and consider expanding its applicability in simulating PFAS, since PCBs have emerged as one of the few constituents that could resemble certain aspects of PFAS. In addition, several successful PFAS modeling applications in different watersheds from peer-reviewed publications (e.g., SWAT, WASP, Delft3D, MODFLOW, and HYDRUS) and the model’s pros and cons will be presented. Through this exploratory effort, it is determined that it would be technically practical to customize existing advanced models to approximate PFAS fate and transport processes, depending on the level of accuracy needed and availability of related data. Further research on mechanistic approaches based on more in-depth understanding of PFAS-soil-water-plant interactions are needed to better support holistic watershed management.
 

From Baseline to Milestones: Advancing GI Performance and TMDL Compliance in San Mateo County

John Riverson; Steve Carter; Chris Carandang; Benjamin Bowes

The 2025 Reasonable Assurance Analysis (RAA[BB1.1]) Update for San Mateo County evaluates the performance and cost-effectiveness of Green Infrastructure (GI) implementation to reduce stormwater pollutant loads of polychlorinated biphenyls (PCBs) and mercury to San Francisco Bay. This presentation discusses the application, findings, and use of the RAA as a key component of an adaptive management framework that supports compliance with the Municipal Regional Stormwater Permit (MRP) and Total Maximum Daily Load (TMDL) allocations. Building on prior analyses, this update integrates revised watershed conditions, updated GI configurations, and an extended 10-year hydrologic record to assess pollutant reduction potential under varying climate conditions. The RAA study simulates hydraulic and pollutant removal processes and applies iterative cost-benefit optimization to identify cost-effective GI portfolios based on a linked Loading Simulation Program in C++ (LSPC) baseline model and the System for Urban Stormwater Analysis and Integration (SUSTAIN) GI performance model. Results indicate that achieving the original PCB reduction target of 17.6% requires approximately 348 acre-feet of GI capacity, with adaptive milestones set for 2027 and 2032 to align with the MRP 3.0 and 4.0 milestones. Sensitivity testing of critical storm conditions confirmed negligible differences in optimization outcomes between the 95th percentile and maximum 5-day storm, supporting selection of the latter for resilience under extreme events. The analysis demonstrates that updated GI configurations can enhance pollutant reduction potential while maintaining cost-effectiveness and provides jurisdiction-specific metrics for tracking impervious area retrofits, stormwater volumes managed, and pollutant load reductions. The findings establish a countywide GI implementation trajectory through 2080 and emphasize adaptive management to refine strategies as new data and project opportunities emerge, offering a robust technical foundation for long-term stormwater planning.

Watershed Planning to Protect New Jersey's 3rd Largest Reservoir

Kathleen Hale

The Raritan Water Supply Complex, which includes Spruce Run Reservoir (SRR) and Round Valley Reservoir (3rd and 1st largest reservoirs in New Jersey) and the Delaware & Raritan Canal, provides water supply to 1,500,000+ people. SRR has experienced persistent harmful algal blooms (HABs) and the New Jersey Department of Environmental Protection (NJDEP) designated the contributing watershed as non-supporting multiple designated uses, including public water supply. There has been significant watershed planning and implementation in the SRR watershed; but the lack of a comprehensive watershed restoration and protection plan (WRPP) and targeted recommendations made it difficult to mitigate HABs and achieve water quality standards. Outdated TMDLs addressed bacteria but not nutrients. New Jersey Water Supply Authority (NJWSA) developed a WRPP for the watershed to address water quality impairments and conditions that contribute to HABs. NJWSA’s team evaluated nonpoint source loads and recommended strategies to protect source water quality. The WRPP includes recommendations for stormwater basin retrofits, green infrastructure and agricultural conservation practices. NJWSA’s critical areas criteria were used to identify parcels for preservation to protect water resources. An education component will build on existing efforts, and existing monitoring will help evaluate progress. NJWSA will leverage their source water protection fund and Natural Resources Conservation Service and NJDEP funding for implementation. NJWSA’s Agricultural Cost-share Program and River-Friendly programs will support implementation. WRPP strategies will also be incorporated into watershed improvement plans that are required under municipal stormwater permits. This presentation will discuss the WRPP recommendations, the obstacles encountered and NJWSA’s implementation plan.

Acid Mine Drainage Remediation in West Virginia at the Point and Watershed Scales

Nathan DePriest

Treatment of acid mine drainage (AMD) in West Virginia (WV) has primarily followed a point-source approach focused on individual National Pollutant Discharge Elimination System (NPDES) permitted discharges. Challenges to the point-source approach are evident in long-term liability and restoration efficacy due to the prevalence of unregulated AMD discharges. Alternatively, the watershed-scale approach to AMD treatment aims to treat sources of AMD throughout an entire watershed to maximize stream restoration and minimize treatment cost. Watershed-scale restoration can implement a combination of at-source, in-stream, and centralized treatment. Jurisdictional, regulatory, and technical feasibility challenges are associated with the watershed approach, but benefits are evident in financial and restoration outcomes. The watershed approach has been successfully implemented by the West Virginia Department of Environmental Protection (WVDEP) at the T&T AMD Treatment Plant in the Muddy Creek Watershed, Preston County, WV, where better restoration outcomes have been achieved at a lower long-term treatment cost compared to the point-source approach. WVDEP has expressed interest in implementing this approach in other watersheds. Through funding allocated in the Infrastructure Investment and Jobs Act (IIJA) to address impacts of AMD from abandoned mine lands (AML), the West Virginia Water Research Institute (WVWRI) was awarded a research project by WVDEP to identify and prioritize AMD-impacted watersheds in WV for implementation of the watershed-scale approach to AMD remediation. Two years of AMD characterization and remediation design have been completed and highlight the the need for a diverse approach to watershed-scale AMD remediation particular to the hydrologic and jurisdictional conditions within a given watershed.