September 25, 2019

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Geosyntec Staff Featured at the 2019 CASQA Annual Conference

Geosyntec will make substantial technical contributions at the California Stormwater Quality Association (CASQA) Annual Conference at the Monterey Conference Center in Monterey, California on October 7-9, 2019.

Geosyntec-led contributions include 10 oral presentations.

The CASQA Annual Conference draws leading members of the stormwater community including local, state, and federal decision makers, stormwater program coordinators, contractors, consultants, engineers, lawyers, scientists, and planners. Over 1,000 attendees and 60 exhibitors are expected for three days of training and discussions on the future of stormwater programs.

CASQA is a professional member association dedicated to the advancement of stormwater quality management through collaboration, education, implementation guidance, regulatory review, and scientific assessment. CASQA has been a leader since 1989 when the field of stormwater management was in its infancy. CASQA's membership is comprised of a diverse range of stormwater quality management organizations and individuals, including cities, counties, special districts, industries, and consulting firms throughout the state. A large part of its mission is to assist California stormwater permittees in developing, implementing, and maintaining effective stormwater quality management programs, and draw upon the collective experiences of its individual members, to share successes and avoid the pitfalls.

Geosyntec Contributions

Oral Presentations

Title: Countywide Attainment of Polychlorinated Biphenyls (PCBs) Load Reductions using Green Infrastructure
Presenters: Amanda Booth, City of San Pablo and Lisa Austin, P.E. (California) Geosyntec
Session: Total Maximum Daily Loads Development and Implementation
Time: 8:30 – 8:55 a.m. on Tuesday, October 8
Contra Costa County's portion of the urban stormwater wasteload allocation in the San Francisco Bay PCBs Total Maximum Daily Load (TMDL) is 0.3 kilograms per year (kg/yr), which represents a 90% reduction from the TMDL's assumed 2003 baseline PCBs load. Provisions C.11 and C.12 of the San Francisco Bay Municipal Regional Stormwater Permit (MRP) require that the Permittees prepare Reasonable Assurance Analyses (RAAs) to, among other objectives, quantitatively demonstrate that PCBs reductions of at least 0.5 kg/yr will be realized within Contra Costa County by 2040 through implementation of green infrastructure (GI) projects.  

Contra Costa County's RAA reassesses the baseline PCBs load and estimates current and projected PCBs load reductions through existing, planned, and projected public and private (i.e., new development and redevelopment) GI projects. Public GI includes both regulated public projects as well as voluntary GI retrofit projects, which were incorporated into GI Plans prepared by the Permittees per MRP Provision C.3.  The preliminary results of the RAA indicate that the Contra Costa County Permittees would collectively need to reduce an additional 56 grams of PCBs through GI to meet the MRP-required load reductions through GI by 2040.

For comparison, the total PCBs loads reduced through public and private GI projects countywide from 2003 – 2020 is approximately 118 g/yr (or about 7 g/yr on average).  A complicating factor in the implementation of GI to achieve PCBs load reductions is that PCBs load (and therefore, potential load reduction) varies greatly depending on land use type, with "Old Industrial" (i.e., pre-1980s industrial) land uses having the greatest PCBs loads in stormwater runoff. 

In this light, the Contra Costa Countywide Clean Water Program (CCCWP) has been investigating more efficient ways to implement GI to achieve the MRP-stipulated load reduction goal. Some Contra Costa County communities without opportunities to reduce PCBs via GI might potentially fund GI projects in communities that do have such opportunities, including the potential for "trading" of PCBs load reduction credit achieved through implementation of GI in more polluted areas. The Permittees would continue to consider how to balance the goals of efficient PCBs load reduction via GI (which has been demonstrated to be highly location-specific, and not obtainable by all Permittees) versus other GI multiple benefits (e.g., urban greening, other urban runoff pollutant removal, flood control, groundwater recharge, habitat enhancement, etc.).

Because resources are limited, there will ultimately be trade-offs between the goals of PCBs load reduction via GI versus the other benefits of GI. In the majority of Contra Costa communities, which have few or no locations where PCBs loads could be efficiently reduced via GI, the pursuit of a potential Countywide Attainment Strategy would require trade-offs, including minimizing the opportunities to build community engagement and local support for GI. A similar trade-off exists within the communities that do have locations where PCBs loads could be efficiently reduced via GI, as the highest-ranked load-reduction locations rarely coincide with locations where other benefits to the community would be maximized.

This presentation will provide background on status of planning for PCBs TMDL compliance using GI and will discuss the compliance approach that Contra Costa Permittees have incorporated in their GI Plans and the Countywide Attainment scenario.

Title: Using Microbial Source Tracking Tools to Support Public Health Decision Making: Evaluating Beach Water Quality Following Emergency Disposal of Post-Fire Debris Flow Sediment
Presenters: Jared Ervin, Ph.D. and Brandon Steets, P.E. (California), Geosyntec
Session: Monitoring, Science, and Data Management
Time: 9:30 - 9:55 a.m. on Tuesday, October 8
Following the Thomas Fire and subsequent Montecito debris flow in January of 2018, emergency actions were taken by the County of Santa Barbara (County) to remove mud and sediments from roads, creeks, and debris basins. A portion of the material removed from roads and creeks was transported to Goleta Beach approximately 13 miles east of Montecito for disposal. Following the completion of disposal, surf zone water quality monitoring of indicator bacteria (Enterococcus, E. coli, and Total Coliform) remained elevated compared to State standards for several months. Due to the unknown presence of human waste in materials and the potential for elevated public health risks due to pathogens associated with human waste in the surf zone following disposal, the County closed the surf zone to water contact recreation throughout this period.

In May 2018, a study was conducted by Geosyntec Consultants to 1) determine if sands and remaining sediments at the beach were causing or contributing to surf zone bacteria exceedances, 2) identify the spatial extent of elevated bacteria levels in the surf zone and beach sands, and 3) determine if human waste was contributing to bacteria exceedances. Sand and surf zone samples were collected at five locations across the beach on four consecutive days. Samples were analyzed for indicator bacteria and a DNA marker specific to human waste (HF183). Combined with results from ongoing AB411 fecal indicator bacteria monitoring by the County, previous DNA marker sampling at the beach by Geosyntec and a local university (establishing pre-disposal conditions), and human DNA marker and pathogen analysis performed by a local university during and immediately following the disposal, these results showed that although indicator bacteria were elevated across the surf zone due to sands and sediments, human waste was not a significant source of contamination and therefore there was not elevated health risk through water contact recreation. Data analysis also showed that surf zone bacteria concentrations were steadily improving over time after the completion of emergency disposal actions.

This information supported the County in its decision to reopen the beach to water contact recreation in July 2018 after surf zone bacteria levels had dropped below State standards in consecutive samples. And when subsequent bacteria monitoring results were intermittently above the State standard, beach warnings were posted rather than a full closure, based on established procedures for beach posting in non-sewage impacted waters. Additional emergency actions for disposal of debris basin sediments in the Montecito area were conducted at Goleta Beach in February of 2019. Sampling and analysis of debris basin materials, beach sands, and surf zone waters were again conducted to confirm that debris basin sediments did not contain human waste contamination and that sediment disposal did not result in an increased illness risk for water contact recreation in the surf zone.

This presentation will highlight the unique use of microbial source tracking analysis to support County beach management decisions during emergency actions. Results and project conclusions will be discussed and the potential use of these tools for other similar applications will be explored. The audience will be invited to participate through a Q&A session on the utility of these tools for other example applications. This presentation is directly related to the conference's theme as it incorporates leading science and technology to assess the health of a recreational water under a unique water quality challenge.

Title: Statewide Drywell Guidance Update: Results and Recommendations Moving Forward
Presenters: Matthew Freese, SWRCB; Adam Questad, P.E., QISP (California) and Brandon Steets, P.E. (California), Geosyntec
Session: Legislation, Policy, Permitting, Legal
Time: 11:00 - 11:25 a.m. on Tuesday, October 8
The State Water Resources Control Board (SWRCB) is working with Geosyntec Consultants to develop statewide guidance for the siting, design, and implementation of drywells. Drywells continue to be an attractive approach to stormwater management and groundwater supply augmentation, especially for space-limited applications. While drywells do represent a cost-effective means for managing stormwater and replenishing water supply, the increased use of drywells and deep injection of stormwater requires careful planning to protect groundwater and surface water resources. During last year's conference, the SWRCB presented on the overall plan for this project and described the priorities and concerns of the technical advisory committee (TAC). The purpose of this presentation will be to provide an update on the project, including summarizing results from a groundwater contamination risk analysis of landuse-specific stormwater runoff parameters and a summary of pretreatment best management practice (BMP) type effectiveness for specific pollutants of concern (POCs).

To identify the studied parameters in stormwater runoff from specific regional landuses that are expected to frequently exceed applicable groundwater quality objectives (GWQOs), stormwater runoff data collected from locations with dominant landuses were downloaded from multiple databases including the Southern California Coastal Water Research Project (SCCWRP) stormwater landuse database, the Stormwater Multiple Application and Reporting and Tracking System (SMARTS), and other City and County landuse-based stormwater datasets. The distribution of results from these databases were compared to applicable drinking water Maximum Contaminant Levels [MCLs] (representing the typical GWQOs for municipally designated groundwater basins) and the landuse-pollutant combinations presenting the highest potential risk to groundwater contamination were identified. These higher risk landuse-pollutant combinations will be presented as they may be used to tailor drywell siting and design guidance to specific landuses in the future. In addition, BMP influent and effluent data from the International Stormwater BMP Database, a publicly available database of over 700 BMP studies and performance analysis results, has been summarized to demonstrate the specific BMP pretreatment types capable of reducing POC concentrations to below applicable MCLs. This information will be presented as it may be used in the future to guide the selection of pretreatment BMPs to target high groundwater contamination risk POCs. The results of these analyses and previous literature reviews including studies on emerging contaminants that may pose a greater risk to contamination compared to typically studied and understood pollutants, will be used to develop a risk-based framework for future drywell guidance. This presentation will conclude with an overview of how these research results and lessons learned from drywell case studies will be used to develop the future drywell siting and design guidance, anticipated to be complete in early 2020. In addition, the SWRCB will provide an update on how the technical guidance may be used in the future to regulate and/or encourage drywell implementation.

The audience will be invited to participate through a Q&A session to clarify how this guidance may relate to their past, ongoing, or future drywell projects. This presentation is directly related to the conference's theme of "Stormwater… Why We Do What We do: Looking back and Looking forward" as the presentation will address lessons learned from previous drywell implementations and monitoring data collected during previous stormwater studies, which will be used to inform future guidance that promotes drywell implementation as a beneficial tool for stormwater quality and quantity management but is also sufficiently protective of groundwater and surface water resources.

Title: Potential IGP implications from the National Academy of Sciences MSGP Report
Presenters: Michael Stenstrom, UCLA; and Brandon Steets, P.E. (California), Geosyntec
Session: Industrial
Time: 1:30 - 1:55 p.m. on Tuesday, October 8
The National Academies of Sciences, Engineering, and Medicine reviewed the existing Environmental Protection Agency (EPA) Multi-Sector General Permit for Industrial Stormwater Discharges (MSGP) to identify improvements to be considered during the next MSGP revisions planned in 2020 (NAS Report). California's industrial general permit (IGP) was informed by many of the MSGP's components including IGP numeric action levels (NALs) based on the MSGP benchmarks, and therefore the findings of this report may have implications for the future of the IGP. The presenters, including a NAS committee member and NAS Report technical reviewer, will first provide an overview of the NAS recommendations and then focus the remaining time discussing the recommended improvements to benchmark thresholds, which may more directly impact the IGP NALs.

The NAS Report general findings include recommendations on benchmark thresholds, improvements to how control measure effectiveness is measured, monitoring methods and frequency, tiered-based monitoring, and encouraging infiltration and capture and use where feasible. A brief overview of these findings along with potential IGP implications will be discussed at the outset. Following this discussion, the presenters, along with audience participation, will focus on the NAS Report's recommendation that EPA suspend or remove magnesium and iron benchmarks until acute aquatic life criteria are established or benchmarks are developed based on chronic effects from intermittent exposure. Meeting the iron and magnesium NALs has consistently been a challenge for many IGP dischargers due to the low magnesium NAL (originally established based on the highest method detection limit multiplied by 3.18) and the prevalence of iron in background soils and other site materials. A brief overview of IGP discharger stormwater compliance monitoring data will be summarized from the Stormwater Multiple Application and Report Tracking System (SMARTS) to present the distribution of stormwater discharge concentrations compared to the NALs for a variety of industry types based on their standard industrial classification (SIC) code. The discussion will also include other IGP-monitored parameters that are a consistent concern due to non-industrial sources (e.g., Aluminum) or other parameters recommended for evaluation in the NAS Report (selenium, arsenic). Finally, the discussion will conclude with a summary of additional research needs to fill data gaps including an interactive question and answer components with audience members to better understand the state of the science and how these recommendations may lessen or increase future burdens on IGP dischargers.

This presentation will include multiple opportunities for audience engagement and is directly related to the conference's theme of "Stormwater… Why We Do What We do: Looking back and Looking forward" as the presentation provides a review of past regulations and how suggested improvements, if implemented, may impact the future of industrial stormwater regulations in California.

Title: Groundwater-Surface Water Modeling to Support Instream Flow and Algae TMDL Management in the Ventura River Watershed
Presenter: Al Preston, Ph.D., P.E. (California) and Brandon Steets, P.E. (California), Geosyntec
Session: Total Maximum Daily Loads Development and Implementation
Time: 1:30 - 1:55 p.m. on Tuesday, October 8
The Ventura River was identified as one of five priority stream systems for flow management efforts in the 2014 California Water Action Plan (WAP).  Per the WAP, the State Water Resources Control Board (SWRCB) and California Department of Fish and Wildlife (CDFW) are identifying potential actions to enhance and establish instream flow for anadromous fish in these priority streams. Furthermore, in 2012, the Los Angeles Regional Water Quality Control Board (LARWQCB) adopted a Total Maximum Daily Load (TMDL) for algae, eutrophic conditions, and nutrients in the watershed, that developed allocations for stormwater, treated wastewater, agriculture, ranching, and onsite wastewater treatment systems (OWTS).  Many of these nutrient sources enter the groundwater before ultimately re-emerging as surface water in the Ventura River. At the time of the TMDL development a detailed source assessment for discharges of nutrients to surface water via groundwater was not possible. 

These instream flow and water quality management efforts have provided a unique opportunity to cooperatively develop credible, transparent, and scientifically sound models that include groundwater-surface water (GW-SW) interactions and transport of nutrients from the land surface to groundwater and back to surface water.  Geosyntec Consultants is working with the SWRCB and LARWQCB in leading and managing the model development together with major partner Daniel B. Stephens and Associates and leading academic advisors. 

The presentation will summarize the progress in developing the models, including;
• the selection of the USGS Groundwater Surface-Water Flow (GSFLOW) modeling platform,
• linkage to an MT3D-USGS nutrient transport model,
• the data and information required to develop the models and the efforts to obtain such data,
• an overview of hydrologic calibration,
• use of results of a forensic study to identify and prioritize regions within the watershed with high-risk of nutrient sources from OWTS to inform the modeling and the use of the model to potentially refine and improve the interpretation of forensic results,
• challenges posed by the 2017/2018 Thomas Fire,
• benefits of combining modeling efforts for multiple purposes (i.e., instream flow and TMDL efforts),
• use of the models to assess effects of potential future changes (e.g., climate change, population change),
• stakeholder engagement, and
• future efforts to train and transfer the model to SWRCB, CDFW, and LARWQCB staff. 

These tools and concepts are applicable to agencies and regulators who face challenges in implementing TMDLs in watersheds where diffuse nutrient (or other pollutant) sources are transported through groundwater and/or where maintenance of instream flows requires careful management of groundwater.  In particular, the benefit of developing such sophisticated models will be relevant to agencies operating within groundwater basins subject to the Sustainable Groundwater Management Act (SGMA).

Consistent with the conference theme, the presentation will illustrate application of the latest science and modeling techniques to refine TMDL requirements and optimize groundwater basin management to more efficiently and effectively meet the human and ecological needs of watersheds. The authors will engage the audience through a question and answer period. The authors will discuss lessons learned and draw out bigger picture themes to consider for potential future applications to watersheds statewide.

Title: Post Fire Mitigation – Why We Select Which Sites to Mitigate
Presenter: Kathleen Harrison, P.G. (California), Geosyntec
Session: Construction and Post-Fire Response
Time: 1:30 - 1:55 p.m. on Tuesday, October 8
Post-fire mitigation requires rapid response and decision making. With fire storms affecting thousands of acres and funding limitations, professionals working in post-fire mitigation response are often faced with a daunting task of prioritizing sites that warrant protection. And with fires occurring typically immediately prior to the rainy season, making the correct decisions on where to implement mitigation practices becomes even more critical. The purpose of the presentation is to walk through examples of a screening and selection process that has been used in a number of Southern California post-fire mitigation efforts to both identify and eliminate sites that warrant post-fire mitigation practices. 

The objective of post-fire mitigation is to minimize secondary impacts to structures and infrastructure resulting from post-fire conditions. Reduction in vegetative cover and changes to soil structure increases the risk of sediment, debris, and flooding that can further impact communities that are dealing with post-fire cleanup and response. Due to the size of the areas affected in the recent California firestorms, identification of sites that warrant post-fire mitigation measures needs to be conducted quickly to allow for time to develop and implement selected measures prior to storm events.

The presentation will cover tools such as soil and geologic maps, GIS, U.S. Forest Service Burned Area Emergency Response (BAER) Reports, storm water conveyance information, aerial and ground reconnaissance, review of pre-fire storm drain and road maintenance logs, and interviews with municipal staff that can be used to evaluate if a site is susceptible to secondary post-fire impacts. Also, factors such as vendor and subcontractor funding, best management practices (BMP) availability and cost, funding mechanisms, and public perceptions are part of the post-fire mitigation decision making process that is factored into decisions.

Audience participation will be encouraged through presenting examples of previous sites the presenter has assessed and being asked to identify if they think post-fire mitigation measures are warranted.  This will be followed up with a discussion of whether the site received mitigation funding from state or federal funding, and why or why not it was funded.

This presentation is relevant to the conference's theme – "Stormwater…Why We Do What We Do!" as it focuses on the decision-making side of post-fire remediation. Post-fire mitigation is critical to minimize impacts to communities that are dealing with the financial and emotional impacts of a fire. The selection of sites that warrant mitigation measures is critical to protect structures and infrastructure, but due to limited funding and the size of areas being affected, the decisions of what does and does not warrant mitigation can make a significant difference.

Title: The Role of Stormwater in Alleviating a Coastal Water Supply Shortage: The Monterey Peninsula Story
Presenters: Jeff Condit, MRSMP and Kelly Havens, P.E. (California), Geosyntec
Session: Sustainability
Time: 2:30 - 2:55 p.m. on Tuesday, October 8
As populations grow, the climate changes, and water resources are allocated to critical ecological needs, and the water available for municipal uses is diminished. Water supply concerns have been building in the Monterey Peninsula region in recent years due to regulatory limits on the two main sources of municipal water – the Carmel River and the Seaside Groundwater Basin. The State Water Resources Control Board issued a Cease and Desist Order for diversions from the Carmel River in 2009 and the Seaside Groundwater Basin was adjudicated by the Superior Court in 2006. The region is currently developing a recycled water facility but has additional supply needs.

Within this setting, the Monterey Regional Stormwater Management Program (MRSWMP) completed their collaborative regional Stormwater Resource Plan (SWRP) for the Monterey Peninsula, Carmel Bay, and South Monterey Bay planning region. The region includes the political boundaries of six coastal cities and several unincorporated portions of Monterey County and ranges from sea level to 5,000 feet in elevation. The region also includes two groundwater basins, three areas of special biological significance (ASBS), and is adjacent to the Monterey Bay National Marine Sanctuary; as such, maintenance or improvement of water quality and environmental resources is crucial.

As part of the SWRP planning process, MRSWMP explored whether water supply could be supplemented via stormwater capture projects through the locally funded Monterey Peninsula Water Recovery Study (WRS). The WRS evaluated the feasibility of establishing a Peninsula-wide water recovery and reclamation system by identifying and evaluating potential projects to capture sources of wet and dry weather runoff for recovery and use. The study also considered how to store, treat, and transport potential sources of runoff.

A GIS-based approach was used to synthesize public hydrologic, geotechnical, and geophysical data, identifying hundreds of potential water recovery projects, along with thousands of potential stormwater capture (i.e., green infrastructure) projects. Additionally, dozens of already-planned projects from local municipalities and agencies were compiled from responses to a stakeholder project request. Water recovery projects identified as part of the SWRP included lake/reservoir storage, diversions to sanitary sewer to supplement recycled water, direct on-site capture and use, and infiltration to aquifer type projects.

Identified potential water recovery study projects were evaluated for feasibility by examining the estimated annual volume that could be recovered for water supply; the planning level estimate of unit cost; and the ease of implementation (i.e., project financing, permitting, environmental, water rights, and other considerations). Additionally, all projects were prioritized in the region using a quantitative multiple-benefit scoring approach and input received from a Stakeholder Outreach effort and from the project Technical Advisory Committee (TAC). Concept designs (10% designs) were developed for the top seven projects identified, and a 30% design and CEQA Checklist was developed for the highest priority project, the Hartnell Gulch Restoration and Runoff Diversion Project. Project prioritization methods included considerations of hydrology and existing stormwater and water resources infrastructure. The existing natural and infrastructure-based drainage systems require additional connection and integration to provide water supply through stormwater capture projects.

The presentation will focus on how potential water supply augmentation projects were identified and evaluated as part of the Water Recovery Study, and how these stormwater capture projects fit into the broader multi-benefit goals of the region's SWRP. The presentation will engage the audience with specific questions related to identification of alternative water supply sources and multi-benefit stormwater capture projects.

Title: PFAS in Stormwater: What We Know
Presenters: Rula Deeb, Ph.D., BCEEM, PMP; Adam Questad; Brandon Steets, P.E. (California); and John Merrill, Geosyntec
Session: Industrial
Time: 8:30 - 8:55 a.m. on Wednesday, October 9

Per- and polyfluoroalkyl substances (PFAS), including perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), are a class of man-made chemicals not naturally found in the environment. Increasingly, studies are showing their ubiquitous occurrence in the environment as well as their potentially negative effects on human and aquatic health. Due to the strength of their carbon-fluorine bonds, PFAS are highly persistent in the environment and difficult to remediate. This presentation will begin with an overview of PFAS sources, physiochemical properties, environmental fate and transport, exposure pathways and toxicology with a specific focus on how these topics impact stormwater. A brief overview of the occurrence of PFAS in drinking water sources in the U.S. as well as a synthesis of the state of knowledge regarding the characterization and remediation of PFAS-impacted sites will also be discussed.

Next, the results of a recent literature review on emerging contaminants in stormwater will be presented including seven studies with detectable concentrations of PFAS compounds from varying landuses. Some studies showed residential stormwater runoff concentrations below EPA's health advisory level of 70 parts per trillion (ppt), while other studies showed concentrations above this level in stormwater runoff from industrial and commercial sites. These results and other implications on future regulations or downstream impacts from stormwater (e.g., risks/concerns of stormwater infiltration on groundwater quality) will be discussed.

This presentation will conclude with an overview of Geosyntec's ongoing applied research PFAS projects, PFAS and specifically, PFAS in stormwater.  If available, PFAS removal effectiveness of different media blends (used in bioretention or other best management practices [BMPs]) will be presented along with leaching and sorption results for these media combinations. A recently initiated study in collaboration with Texas Tech University and the U.S. Navy National Warfare Center will also be discussed, including an overview of how this project is implementing a novel study plan to determine how structural BMPs are influencing the loading of PFAS and other pollutants of concern in stormwater and the risks of sediment recontamination. The presentation will then conclude with an overview of outstanding questions and additional research needs to fill present data gaps and further our understanding of the fate and transport of PFAS and PFAS-alternative compounds in stormwater and how to cost-effectively treat them.

The audience will be invited to participate through a Q&A session to understand existing and future PFAS concerns. This presentation is directly related to the conference's theme of "Stormwater… Why We Do What We do: Looking back and Looking forward" as the presentation addresses an emerging stormwater topic in its infancy that is gaining increased awareness due to widespread groundwater/drinking water contamination and has the potential to impact future stormwater management planning.

Title: California's First Chemical Human Health Risk Assessment on Stormwater – Results from the Santa Susana Field Laboratory
Presenters: Ruth Custance, Geosyntec; Jeffrey Wokurka, Boeing; Brandon Steets, P.E. (California), Geosyntec; and Michael Stenstrom (UCLA)
Session: Sustainability Track / Scaling Sustainability
Time: 8:30 - 8:55 a.m. on Wednesday, October 9
A quantitative evaluation of human health risks associated with potential surface water discharge contact was conducted for the Santa Susana Field Laboratory (SSFL) (Site), in response to a unique Los Angeles Regional Water Quality Control Board (LARWQCB) order associated with The Boeing Company's (Boeing's) National Pollutant Discharge Elimination System (NPDES) permit for industrial stormwater discharges. The Human Health Risk Assessment (HHRA) evaluated exposure associated with activities that could occur according to beneficial use designations contained in the Los Angeles Water Quality Control Plan (Basin Plan) including non-swimming water contact recreational activities (hiking, rafting and other limited recreational uses that fall under the Basin Plan designation). Direct exposures to surface water – i.e., incidental ingestion and dermal contact – were identified as the most likely potentially complete exposure pathways and were evaluated quantitatively in the risk assessment. In addition, the inhalation pathway and fish consumption (at downstream locations) pathways were evaluated. Over 50 organic and inorganic chemicals were evaluated, and both cancer and non-cancer endpoints considered.

Similar to many areas of California, surface water runoff at SSFL's ephemeral drainages is typically limited to winter months. A challenge in developing the exposure assessment for the HHRA was the intermittent nature of the flow from the majority of the NPDES outfalls at the Site and the limited and uncertain frequency a recreational user may encounter these natural drainages where flow is occurring during the winter months. Flow monitoring data from the outfalls were used to estimate annual discharge frequencies, which were then used to estimate the number of days per year that exposure to surface water exiting each outfall could occur (i.e., exposure frequency). Another challenge was the estimation of surface water concentrations at downstream offsite locations where water is present in sufficient quantity year-round, edible fish are present and there is the potential for fishing and fish consumption.

The results of this risk assessment indicate that potential recreational exposures to constituents in surface water runoff exiting the SSFL are below levels of concern as established by the California Environmental Protection Agency and the United States Environmental Protection Agency. This includes those constituents that have had NPDES permit limit exceedances, including lead and dioxins. The final HHRA was approved by the LARWQCB and the California Office of Environmental Health Hazard Assessment, and the results were presented to the public by the SSFL Stormwater Expert Panel.

This presentation will describe the risk assessment and hydrologic methodologies that were used to develop this first of its kind chemical human health exposure assessment on stormwater. The approaches used in the risk assessment can be applied to other sites where surface water runoff may be present in areas that are used for recreational purposes. The audience will be invited to participate through a Q&A session to understand how this human health exposure assessment may relate to their sites or projects and better understand the research and analyses performed. This presentation addresses the conference theme of "Stormwater… Why We Do What We do: Looking Back and Looking Forward" by presenting the results of the first stormwater human health risk assessment that can be used in the future as a basis to demonstrate whether stormwater discharges pose a human health risk during contact and non-contact recreation near or within recreational receiving waters.

Title: Choose Your Own Exceedance Response Action Adventure: If at First You Don't Succeed, Try Another BMP
Presenter: Julie Walters, CPSWQ, QISP, QSD/P, Geosyntec
Session: Industrial
Time: 3:00 - 3:25 p.m. on Wednesday, October 9
Many stormwater professionals, specifically consultants, can agree that we primarily do what we do for three reasons: (1) to enhance and protect the quality of our waterways, (2) to utilize our critical thinking skills and knowledge of stormwater best management practices (BMPs) to solve complex problems, and (3) because we are genuinely interested in helping our clients achieve their goals with the, oftentimes, limited resources available to them. This presentation will highlight an Exceedance Response Action (ERA) Level 2 success story where client/consultant communication and collaboration, creative thinking, and a willingness to consider that it may take a combination of BMPs to eliminate a Numeric Action Level (NAL) exceedance were essential in forging a path back to Baseline for a southern California dairy product manufacturer. 

As dischargers navigate the world of ERAs, it can be difficult to determine where to start with respect to getting back to Baseline, assuming that is a viable option for the facility. It seems like there are endless possibilities and a multitude of questions are raised; such as, what are the potential sources of the exceedance(s)? how can those sources be eliminated or minimized? and what could addressing the exceedance(s) potentially cost? This case study will explore one approach to answering these questions, and others, for a Level 2 discharger and cover the following main ideas:
1. Critical thinking regarding potential sources;
2. Strategic selection of sampling locations to characterize runoff from suspected source areas;
3. Financial impact analysis/evaluation of alternative courses of action based on an array of potential BMPs;
4. Phased or treatment-train approach to BMP implementation; and
5. Importance of communication, teamwork, and collaboration.

This presentation will be directly applicable to facilities currently in either ERA Level 1 or 2. The presentation will begin by posing the question, "how many of you are dischargers or consult for clients whom have remained in Baseline for all monitored constituents since the effective date of the 2014 IGP?" The expectation is that the number of hands raised will be few to none which will make this presentation applicable to most audience members. The approach is scalable and meant to illustrate that the pathway back to Baseline is not one size fits all and does not always require costly full-capture and treatment. A key takeaway is that it is imperative to evaluate budget constraints and potential alternative BMPs early in the process.

Overall, the implications of this approach are far reaching for other facilities who wish to return to Baseline. This case study showcases an instance where a client who was willing to mix and match BMPs to suit their budget and space limitations was successful at returning to Baseline for a ubiquitous constituent (zinc). Due to strategic BMP selection and placement from a list of many potential alternatives, the site has collected four consecutive QSE samples with zero NAL exceedances for zinc and is expected to return to Baseline for zinc on July 1, 2019.

Downloadable Brochure

Watershed and Stormwater Management

More Information

Learn more about the conference:
Read the Journal or Learn more at: CASQA Conference Agenda.
For consultation regarding stormwater planning or quality, contact Ken Suslio at This email address is being protected from spambots. You need JavaScript enabled to view it..