Assessing human fecal contamination of recreational beach waters is a public health challenge owing to multiple sources and environmental conditions affecting indicator, pathogen, and source marker relationships. Human fecal-associated markers, such as HF183, accurately indicate human waste, but reliance on individual markers risks false negative diagnoses, owing to marker source loading variations and attenuation. Bacterial community analysis is a data-dense approach that could improve the accuracy of human waste detection, but relatedness to actual human health hazards under complex coastal water conditions is unproven. Here, two Malibu and one Pacific Palisades, CA recreational beaches differing in urbanization and sewerage were studied over two years across varying seasonal rainfall, and beach berm, conditions. Fecal indicator bacteria (FIB), HF183, and human norovirus concentrations were quantified and related to bacterial community 16S rRNA gene sequences which were further analyzed for putative human pathogens and sewage proportions. All lower watersheds harbored human fecal sources, and surf zone contamination was enhanced by rainfall runoff with berm breaching, which intensified with urbanization. Notably, for sequenced surf zone waters sampled across all weather conditions (n = 36), sequence-based putative pathogen proportions correlated with qPCR HF183 concentrations (w/ and w/o PMA treatment; p = 0.0) and with human norovirus G1concentrations (p = 0.04) which also correlated with HF183 sequence abundance in bacterial communities (p = 0.02). Although human fecal sources appeared to vary seasonally and a range of physical conditions influenced surf zone fecal contamination, human fecal contamination and associated health hazard were reliably evidenced by bacterial community analysis in this study.

This study focused on understanding the influence of stormwater on sediment recontamination and biota bioaccumulation. Stormwater and sediment sampling was conducted at Paleta Creek San Diego, CA, a mixed-use urban watershed. Stormwater samples were size fractioned into clay, silt, sand, and filtered fractions to better understand the association of PAHs and PCBs with different particle sizes. Settling traps were deployed during storm seasons to capture solid particles deposited by stormwater. Bioaccumulation studies of the receiving water sediments were conducted on bent-nosed clams (Macoma nasuta) both in-situ and ex-situ. The results indicated that the majority of PAHs and PCBs were discharged during the early stages of the storm and were primarily associated with coarser particles (>20 μm). Sediment near the discharge exhibited higher levels of contaminants, consistent with the findings from the settling traps and stormwater discharges. Ex-situ bioaccumulation studies demonstrated that sediment contamination did not correlate with bioaccumulation in Macoma nasuta, whereas porewater accurately reflected bioaccumulation trends. This study highlights the importance of considering stormwater discharge patterns and particle sizes when assessing sediment recontamination but also that the resulting bulk sediment contamination may not reflect bioavailability as measured by organism bioaccumulation. These insights contribute to a better understanding of the impacts of stormwater runoff on sediment and biota in southern California coastal watersheds, aiding in the development of effective management strategies.

SARS-CoV-2 wastewater surveillance (WWS) at wastewater treatment plants (WWTPs) can reveal sewered community COVID-19 prevalence. For unsewered areas using septic tank systems (STSs) or holding tanks, how to conduct WWS remains unexplored. Here, two large STSs serving Zuma Beach (Malibu, CA) were studied. Supernatant and sludge SARS-CoV-2 concentrations from the directly-sampled STSs parameterized a dynamic solid-liquid separation, mass balance-based model for estimating the infection rate of users. Pumped septage before hauling and upon WWTP disposal was also sampled and assessed. Most (96%) STS sludge samples contained SARS-CoV-2 N1 and N2 genes, with concentrations exceeding the supernatant and increasing with depth while correlating with total suspended solids (TSS). The trucked septage contained N1 and N2 genes which decayed (coefficients: 0.09-0.29 h-1) but remained detectable. Over approximately 5 months starting in December 2020, modeled COVID-19 prevalence estimations among users ranged from 8 to 18%, mirroring a larger metropolitan area for the first 2 months. The approaches herein can inform public health intervention and augment conventional WWS in that: (1) user infection rates for communal holding tanks are estimable and (2) pumped and hauled septage can be assayed to infer where disease is spreading in unsewered areas.

Municipal separate storm sewer systems (MS4s) function in urbanized areas to convey flows during both wet weather (i.e., stormwater) and dry weather (i.e., urban runoff as well as subsurface sources of flow) to receiving waters. While urban stormwater is known to contain microbial and chemical pollutants, MS4 dry weather flows, or non-stormwater discharges (NSWDs), are much less studied, although they are also known to contain pollutants, especially when these flows include raw sewage. In addition, some natural NSWDs (e.g., from groundwater infiltrating MS4 pipes) are critical for aquatic habitat protection. Thus, it is important to distinguish NSWD sources to prevent non-natural flows while retaining natural waters (i.e., groundwater). Here, MS4 dry weather flows were assessed by analyzing water samples from MS4 outfalls across multiple watersheds and water provider service areas in south Orange County, CA; potential NSWD sources including sewage, recycled water, potable water, and groundwater were sampled and analyzed for their likely contributions to overall NSWDs. Geochemical and microbiological water quality indicators, as well as bacterial communities, differed across NSWDs, yet water quality within most locations did not vary significantly diurnally or by sampling date. Meanwhile, NSWD source waters had distinctly different bacterial taxa abundances and specific bacterial genera. Shared geochemical and microbial characteristics of certain sources and outfall flows suggested the contributions of sources to outfall flows. The average proportions by sources contributing to MS4 outfalls were further estimated by SourceTracker and FEAST, respectively. The results of this study highlight the use of multiple tools when assessing chemical and microbiological water quality to predict sources of NSWDs contributing to urban MS4 flows during dry weather. This information can be used to support management actions to reduce unnatural and high risk sources of dry weather drainage while preserving natural sources important to environmental health in downstream receiving waters.

Forum papers are thought-provoking opinion pieces or essays founded in fact, sometimes containing speculation, on a civil engineering topic of general interest and relevance to the readership of the journal. The views expressed in this Forum article do not necessarily reflect the views of ASCE or the Editorial Board of the journal.

Dry weather flows to municipal separate storm sewer systems (MS4s) pollute receiving streams. Quantifying sources is necessary to discern non-prohibited (groundwater), versus other, sources. We hypothesized that aquatic bacterial communities could trace MS4 source waters. To test, next generation sequencing of genes encoding 16S rRNA was coupled with bioinformatic analyses to assess source water differences, and for quantifying source proportions to Orange County, CA MS4 outfalls. Geochemical (boron, N species, total dissolved solids or TDS, and methylene blue active substances or MBAS) and microbiological (fecal indicator bacteria, and the human fecal DNA marker HF183) analytes were also measured. By SourceTracker analyses of sequence data, source water proportions in MS4 outfall samples averaged, volumetrically: 66.7% potable water, 16.3% groundwater, 11.4% recycled water, and 0.02% sewage, which correlated to relative abundances of sequences for specific bacterial genera. Estimated source contributions varied between outfalls, yet source proportions appeared stable at each outfall across multiple sampling events, except when recycled water varied diurnally with irrigation. Although sequence-based sewage proportions matched estimates based on E. coli , enterococci, and HF183, other sources were only distinguishable by sequencing. These results support that bacterial community analysis allows for differentiating dry weather flow sources to urban MS4 outfalls.

Although biofilters and bioretention controls have been extensively studied and are encouraged as effective stormwater controls, there is remaining uncertainty concerning their long-term performance and required maintenance. Most full-scale monitoring efforts have been of short duration, with no clogging or breakthrough observed. This paper describes the long-term monitoring results of media-based stormwater controls located at the Santa Susana Field Laboratory (SSFL) in Ventura County, California, an industrial site with historic aerospace and energy research. The 10 stormwater controls examined in this paper were grouped into four types (referred to as culvert modifications, which are media filters installed at drainage road crossings, detention bioswales having large subsurface storage, a large sedimentation pond/biofilter treatment train, and a sedimentation tank/media filter treatment train). Data were available for about 6-9 years of monitoring. This paper examines the trends in performance and usage until major maintenance is required. In almost all cases, the effluent concentrations tracked the influent concentrations, with no significant performance or effluent concentration differences with time. Silt clogging at one facility occurred as predicted based on initial laboratory tests, and the media in that control was replaced on schedule. (C) 2021 American Society of Civil Engineers.

Stormwater biofilters and bioretention controls have been extensively studied and are commonly encouraged as effective stormwater controls. Most of these controls incorporate media to enhance pollutant removal. There is much published research describing laboratory tests on the performance and selection of different media, and many field tests on media treatment of stormwater, but complementary long-term, full-scale field tests compared to prior laboratory tests are not as common. The purpose of this paper is to compare the laboratory evaluations of treatment media targeting a broad range of constituents of concern, to the results of long-term monitoring of full-scale stormwater controls using the selected media. The laboratory evaluations identified which media blend would reduce concentrations of constituents of concern to help meet National Pollutant Discharge Elimination System (NPDES) permit discharge limits and benchmarks, given site specific influent concentrations, when deployed in the field. Besides pollutant reductions, treatment flow rates and maintenance requirements were also of a consideration when selecting the media blend, especially determining the useful life of the media before clogging and/or pollutant breakthrough. Statistical comparison tests of the laboratory results with the full-scale field results resulted in similar effluent quality for most measured constituents (especially for lead and the critical form of dioxin), at all field treatment locations. Therefore, the laboratory observations were confirmed by the long-term, full-scale, stormwater control monitoring activities. The selected media has resulted in reductions in concentrations of the constituents of concern, over long periods of use. (C) 2021 American Society of Civil Engineers.

Microbial source tracking (MST) can identify and locate surf zone fecal indicator bacteria (FIB) sources. However, DNA-based fecal marker results may raise new questions, since FIB and DNA marker sources can differ. Here, during 2 years of summertime (dry season) MST for a Goleta, California recreational beach, surf zone FIB were mainly from gulls, yet low level human-associated DNA-based fecal marker (HF183) was detected in 25 and 14% of surf zone water samples, respectively. Watershed sources were hypothesized because dry weather creek waters had elevated FIB, and runoff-generating rain events mobilized human (and dog) fecal markers and Salmonella spp. into creeks, with human marker HF183 detected in 40 and 50% of creek water samples, dog markers detected in 70 and 50% of samples, and Salmonella spp. in 40 and 33.3% of samples, respectively over 2 years. However, the dry weather estuary outlet was bermed in the first study year; simultaneously, creek fecal markers and pathogens were lower or similar to surf zone results. Although the berm breached in the second year, surf zone fecal markers stayed low. Watershed sediments, intertidal beach sands, and nearshore sediments were devoid of HF183 and dog-associated DNA markers. Based on dye tests and groundwater sampling, beach sanitary sewers were not leaking; groundwater was also devoid of HF183. Offshore sources appeared unlikely, since FIB and fecal markers decreased along a spatial gradient from the surf zone toward nearshore and offshore ocean waters. Further, like other regional beaches, surf zone HF183 corresponded significantly to bather counts, especially in the afternoons when there were more swimmers. However, morning detections of surf zone HF183 when there were few swimmers raised the possibility that the wastewater treatment plant (WWTP) offshore outfall discharged HF183 overnight which transported to the surf zone. These findings support that there may be lowest achievable limits of surf zone HF183 owing to several chronic and permanent, perhaps diurnal, low concentration sources.

Worldwide, fecal indicator bacteria (FIB) evidence coastal water contamination for which sources are unknown. Here, for two FIB-impacted Santa Barbara recreational beaches, hypothesized fecal sources were investigated over three dry seasons (summers) using nearly 2000 field samples of water (ocean, creek, groundwater), sand, sediments, effluent and fecal sources. In years 1 and 2, gull and dog feces were identified as the probable main FIB sources to surf zone waters, yet HF183 human fecal markers were consistently detected. Determining HF183 sources was therefore prioritized, via year 3 sub-studies. In lower watersheds, human and dog wastes were mobilized by small storms into creeks, but no storm drain outfalls or creeks discharged into surf zones. Beach area bathrooms, sewers, and a septic system were not sources: dye tracing discounted hydraulic connections, and shallow groundwater was uncontaminated. Sediments from coastal creeks and downstream scour ponds, near shore marine sediments, and sands from inter-and supratidal zones contained neither HF183 nor pathogens. Two nearby wastewater treatment plant (WWTP) outfalls discharged HF183 into plumes that were either deep or distant with uncertain onshore transport. Regardless, local sources were evidenced, as surf zone HF183 detection rates mostly exceeded those offshore and nearshore (around boat anchorages). The presence of swimmers was associated with surf zone HF183, as swimmer counts (on weekdays, holidays, weekends, and during races) significantly correlated (p<0.05, n = 196) to HF183 detections. Besides comprehensively assessing all possible fecal sources, this study provides new explanations of chronic low-level human markers in recreational beach surf zones, suggesting likely lowest achievable HF183 thresholds.

Recontamination of sediments by stormwater is a major concern when evaluating the potential effectiveness of sediment remediation. Stormwater and sediment sampling were conducted in a mixed-use watershed at Paleta Creek in San Diego, CA to evaluate methods for assessing sediment recontamination by metals. Size-segregated stormwater contaminant loads with simultaneous receiving water and sediment measurements were used to identify dominant sources and contaminants with respect to their impact on sediment recontamination. Most of the stormwater contaminant loads of Cd, Cu, Pb, and Zn were associated with residential and highway sources from the upstream portions of the watershed and As, Ni and Hg were more significantly influenced by the down-stream area of the watershed. Cd was strongly associated with large particles (>63 mu m) and observed to settle in near shore areas with some attenuation due to mixing and dilution. Cu, in contrast, was associated more with the filtered fraction (<0.45 mu m) and clay fraction (0.45-5 mu m), resulting in less near shore sediment recontamination. Depositing sediment and other metals, particularly Cu and Hg, exhibited greater accumulation in settling traps than could be attributed to stormwater loads indicating the importance of other sources or resuspension of bay sediments on surficial sediment concentrations. Pb, Zn, Ni, and As showed influences of both stormwater and other sources. The study showed that measurement of size-segregated stormwater contaminant mass and concentrations combined with simultaneous measurements of deposition in sediment traps could differentiate between recontamination by stormwater and that of other sources. (C) 2020 Elsevier B.V. All rights reserved.

The Santa Susana Field Laboratory (SSFL) occupies about 2,850 acres and is located in Ventura County, California. The site is jointly owned by the Boeing Company and the federal government (the National Aeronautics and Space Administration administers the federal portion of the property). Much of the site was historically used as a rocket engine testing and energy research facility from 1949 to 1998. The site stormwater discharges are permitted by the Los Angeles Regional Water Quality Control Board through an individual industrial NPDES permit that includes numeric effluent limits for a wide range of constituents, including dioxins and metals. A large portion of the site uses distributed source stormwater controls with natural treatment systems utilizing chemically active media. As part of this approach, extensive research was conducted to develop a robust media for use in these controls to meet the discharge objectives. This paper describes the development of the media and its characteristics.

This paper describes the detailed laboratory tests of biofiltration media that are being considered for use in engineered stormwater treatment systems recently proposed for a large field site in the southwestern United States. These stormwater treatment systems were designed to treat 90% of the long-term runoff volume from drainage areas ranging from 5 to 60 acres at the site. The main pollutants of interest for the project include cadmium, copper, lead, and dioxins, and the effluent concentrations had to meet design criteria that are based on numeric effluent limits that are applied to stormwater discharges through the site's NPDES permit. An additional feature of the project is that existing runoff concentrations for the pollutants of interest are generally below levels typically seen in urban and industrial stormwater runoff, therefore the tests needed to simulate site-specific conditions by adjusting raw influent samples to representative levels, where possible. The purpose of this study is to determine optimal biofiltration media combinations and contact times (based on achievement of permit limits in treated effluent), hydraulic properties, and clogging/breakthrough frequency for design purposes and maintenance planning.

This paper describes the detailed laboratory tests of biofiltration media that are being considered for use in engineered stormwater treatment systems proposed for a large field site in the southwestern United States. These stormwater treatment systems were designed to treat 90% of the long-term runoff volume from drainage areas ranging from 5 to 60 acres at the site. The main pollutants of interest for the project include cadmium, copper, lead, and dioxins, and the effluent concentrations had to meet design criteria that are based on numeric effluent limits that are applied to stormwater discharges through the site's NPDES permit. An additional feature of the project is that existing runoff concentrations for the pollutants of interest are generally below levels typically seen in urban and industrial stormwater runoff, therefore the tests needed to simulate site-specific conditions by adjusting raw influent samples to representative levels, where possible. The purpose of this study is to determine optimal biofiltration media combinations and contact times (based on achievement of permit limits in treated effluent), hydraulic properties, and clogging/breakthrough frequency for design purposes and maintenance planning.

This presentation describes the detailed laboratory tests of biofiltration media that is being considered for use in engineered stormwater treatment systems recently proposed for a large field laboratory testing site in the southwestern United States. These stormwater treatment systems were designed to treat 90% of the long-term runoff volume from drainage areas ranging from 5 to 60 acres at the site. The pollutants of interest for the project include cadmium, copper, lead, and dioxins, and the effluent concentrations had to meet design criteria that are based on numeric effluent limits that are applied to stormwater discharges through the site's NPDES permit. An additional feature of the project is that existing runoff concentrations for the pollutants of interest are generally below levels typically seen in urban and industrial stormwater runoff, therefore the tests needed to simulate site-specific conditions by adjusting raw influent samples to representative, where possible. The media tested vary widely in terms of cost, performance, and maintenance requirements. However, because of the large volume of media specified for the proposed designs, unit volume cost savings (during construction) are potentially significant if media volume and types can be optimized. Furthermore, the potential for long-term cost savings is also significant, and therefore this study also considers life-cycle costs (e.g., media replacement frequency) and maintenance problems (e.g., clogging frequency). This optimization activity should result in improved predictions of life-cycle costs, of pollutant removals over the media's lifespan, and of maintenance issues and intervals, and should result in improved design and performance when installed in the field.