Significant New BMP Performance Dataset Available for EWMP/WQIP BMP Design, IGP Level 2 Planning, and PCB RAA Modeling
Over the past seven years, over 120 BMP influent/effluent sample pairs have been collected, analyzed, and found to demonstrate positive BMP performance and pollutant removal at the Santa Susana Field Laboratory (SSFL). This is perhaps the most robust BMP performance dataset for a single site anywhere, and augments data from the International Stormwater BMP Database (ISBD) by focusing exclusively on advanced media amendments and design features (like outlet controls), and rarely studied pollutants.
SSFL is a 2800-acre former federal government rocket engine testing and energy research facility located in the Santa Susana Mountains of eastern Ventura County that is currently owned by The Boeing Company and the U.S. Government. Activities at the site are now limited to demolition, remediation, and restoration. Stormwater discharges from the site are regulated through an individual industrial (NPDES) permit that includes California Toxics Rule-based numeric effluent limits for many constituents at multiple outfalls.
Due to severe site constraints at two of the compliance monitoring “outfalls” (i.e., natural drainages located near the property boundary), “end-of-pipe” stormwater controls are not feasible. Therefore a watershed-based, distributed BMP approach has been implemented, applying advanced treatment trains incorporating sedimentation and flow equalization followed by flow-through media filters (or “biofilters” when vegetated). An independent Expert Panel was engaged in 2010, with Regional Board consent, to oversee this stormwater control planning and design work, as well as to provide input on BMP placement and optimization, pollutant source investigation, and other NPDES permit issues.
Although SSFL is in many ways a unique site, the extensive BMP performance monitoring dataset is of great value to many other stormwater NPDES permit holders. For example:
1. Most statewide IGP permittees are expected to shift to a Level 2 Exceedance Response Action status at the end of this reporting year, with more stringent requirements for structural BMPs to address Numeric Action Level (NAL) exceedances. SSFL data can help these dischargers know whether natural treatment BMPs, which are typically cost-effective due to low maintenance and low energy (e.g., pumping) requirements, can consistently meet the permit’s NALs, the necessary design parameters (e.g., media mixtures, contact time, etc.) for achieving these effluent concentrations, and costs to implement.
2. San Diego and Los Angeles region MS4 permittees are currently moving from the watershed planning phase to the implementation phase, now siting and constructing BMPs to meet pollutant load reduction targets. These agencies are subject to strict deadlines and substantial costs to meet regulatory requirements, including several metals TMDLs. In some cases, flow-through BMPs may be necessary where infiltration is not feasible, and SSFL data can help to inform these design decisions and cost projections.
3. San Francisco Bay Area MS4 permittees are subject to PCB TMDL compliance as the primary driver for BMP retrofits. Dioxins, which are physiochemically similar to PCBs, have been extensively sampled at SSFL’s BMPs. SSFL dioxin removal results and BMP design guidance can be used by Bay Area permittees to inform Reasonable Assurance Analysis modeling (i.e., quantitative forecasts of PCB pollutant removal) and BMP cost estimates.
This presentation will summarize BMP performance data (including a comparison with ISBD data), statistical analyses regarding significance of pollutant concentration reduction, volume capture information (or discharge prevention), comparison between bench-scale lab testing and full-scale field testing results (over three to seven years of sampling), cumulative solids loading relative to expected thresholds for media clogging, advanced BMP design and media filter specifications recommendations, construction costs, and maintenance needs.
Brandon Steets is a licensed chemical engineer, a Senior Principal with Geosyntec Consultants, an industrial stormwater Trainer of Record, and a member of the State's Clean Beaches Task Force. He has worked for over 17 years on challenging stormwater projects that include modeling, monitoring, source investigation, BMP planning, treatment BMP design, NPDES permitting, and strategic regulatory services.
Megan Otto is a Senior Water Resources Engineer with Geosyntec Consultants. She has worked for the past 10 years on water-quality compliance and stormwater management planning projects throughout California.