Combined Sewer Overflow Outfalls Research Articles

Comparative study of deterministic and probabilistic assessments of microbial risk associated with combined sewer overflows upstream of drinking water intakes

Combined sewer overflows (CSOs) are a source of microbial contamination of drinking water intakes located downstream from their discharge. To safeguard the quality of the source water, it is essential to evaluate the risk levels associated with these municipal structures. This study compares two risk assessment approaches to test their applicability for assessing the risk of CSOs to drinking water intakes in a highly urbanized watershed. The first approach was based on a deterministic equation that combines the characteristics of an overflow structure allowing the risk to be rated as very low, low, medium, high, or very high. The second probabilistic risk assessment approach yielded findings that are probabilistically distributed across the five levels of risk. This approach was developed by constructing a novel Bayesian network to probabilistically link the different factors defining the exposure of water intakes to the hazards of CSOs. The comparison between the results of these two approaches highlighted the importance of simultaneously considering many scenarios for assessing the risk of contamination of source waters. It was possible to use the Bayesian network rather than the deterministic equation, which only supports one scenario at a time. It was also shown that the deterministic approach often overestimated risk levels for CSO outfalls close to the water intake. This occurred because the assessment process emphasized the distance factor between the discharge point and the water intake, while neglecting other crucial characteristics of the overflow, such as duration and frequency. In particular, the deterministic approach tended to underestimate risk for CSOs associated with low overflow frequencies as it did not support scenarios of overflow duration, unlike the probabilistic approach. The validation and sensitivity analysis of the Bayesian model revealed that the population residing in the CSO's drainage basin, along with the frequency and duration of the overflows, exerted the greatest influence on the resulting risk levels. These factors outweighed other variables utilized in the risk assessment, including vulnerability of the drinking water intake, the type of overflow recorder, pipe diameter, and variables defining the exposure of the water intake to the discharge. In the context of implementing action plans, the Bayesian network is estimated as a cost-effective technique as it prioritized overflow structures needing special attention in a highly urbanized watershed, where the same CSOs were deterministically rated as having the same risk level. The results also demonstrated the effectiveness of the Bayesian model in addressing data gaps faced by water managers and stakeholders. The Bayesian model proved capable of assessing risks with uncertainties for CSOs, even with limited input data available. These findings can assist managers in identifying problematic structures by considering various scenarios, unlike the deterministic approach, which left almost half (n = 42) of the study site's overflow structures unassessed due to data limitations.

Chemical prioritization of pharmaceuticals and personal care products in an urban tributary of the Potomac River

Pharmaceuticals and personal care products (PPCPs) are incredibly diverse in terms of chemical structures, physicochemical properties, and modes of action, making their environmental impacts challenging to assess. New chemical prioritization methodologies have emerged that compare contaminant monitoring concentrations to multiple toxicity data sources, including whole organism and high-throughput data, to develop a list of “high priority” chemicals requiring further study. We applied such an approach to assess PPCPs in Hunting Creek, an urban tributary of the Potomac River near Washington, DC, which has experienced extensive human population growth. We estimated potential risks of 99 PPCPs from surface water and sediment collected upstream and downstream of a major wastewater treatment plant (WWTP), nearby combined sewer overflows (CSO), and in the adjacent Potomac River. The greatest potential risks to the aquatic ecosystem occurred near WWTP and CSO outfalls, but risk levels rapidly dropped below thresholds of concern – established by previous chemical prioritization studies – in the Potomac mainstem. These results suggest that urban tributaries, rather than larger rivers, are important to monitor because their lower or intermittent flow may not adequately dilute contaminants of concern. Common psychotropics, such as fluoxetine and venlafaxine, presented the highest potential risks, with toxicity quotients often > 10 in surface water and > 1000 in sediment, indicating the need for further field studies. Several ubiquitous chemicals such as caffeine and carbamazepine also exceeded thresholds of concern throughout our study area and point to specific neurotoxic and endocrine modes of action that warrant further investigation. Since many “high priority” chemicals in our analysis have also triggered concerns in other areas around the world, better coordination is needed among environmental monitoring programs to improve global chemical prioritization efforts.

Characteristics of antibiotic resistance gene distribution in rainfall runoff and combined sewer overflow.

Rainfall runoff and combined sewer overflow (CSO) converge with organic waste, nutrients, and microbes from the ground and wastewater. These pollutants promote the spread and transformation of antibiotic resistance genes (ARGs). In this study, four rainfall runoff and one CSO outfall were chosen, and samples were collected to explore the occurrence and distribution of ARGs. The ARGs were extracted from suspended solids and analyzed using metagenomic sequencing. A total of 888 ARG subtypes, belonging to 17 ARG types, were detected in all samples. Eleven ARG types were shared by all the samples. Multidrug resistance genes had the highest relative abundance. Their total relative abundance reached 1.07 ratio (ARG copy number/16S rRNA gene copy number) and comprised 46.6% of all the ARGs. In all samples, the CSO outfall had the highest total relative abundance (8.25 × 10-1 ratio) of ARGs, with a ratio ranging ND (not detected)-3.78 × 10-1 ratio. Furthermore, the relationship between ARG types and environmental factors was determined using redundancy analysis. The results showed that chemical organic demand (COD) and bacterial abundance were positively correlated with most ARG types, including multidrug, bacitracin, aminoglycoside, β-lactam, tetracycline, and sulfonamide. NH3-N, TN, and TP were positively correlated with rifamycin, fosmidomycin, and vancomycin resistance genes. The relationship among the ARG subtypes was investigated using network analyses. The multidrug resistance gene subtypes had the highest frequency of co-occurrence. This study provides insights into the occurrence and distribution of ARGs under non-point source pollution and may contribute to the control of ARGs.

Culex Mosquitoes at Stormwater Control Measures and Combined Sewer Overflow Outfalls after Heavy Rainfall

Mosquito borne diseases are increasingly problematic as climate change continues to alter patterns of precipitation, flooding, and temperatures that may favor mosquito habitats. Stormwater control measures (SCMs), ecologically sustainable methods of stormwater management, may have varying impacts on Culex mosquitoes, such as in areas with combined sewer overflows (CSOs). We studied spatial and temporal associations of SCMs and Culex mosquito counts surrounding the SCMs, stratifying our examination amongst those that do/do not use pooling and/or vegetation, as well as surrounding CSO outfalls after heavy rainfall (≥95th percentile) during summer 2018. Results indicate Culex mosquito counts after heavy rainfall were not significantly different at SCMs that use vegetation and/or ponding from at those that do not. We also found a 35.5% reduction in the increase of Culex mosquitoes the day of, and 77.0% reduction 7–8 days after, heavy rainfall at CSO outfalls treated with medium SCM density compared to those without SCMs. Our results suggest that SCMs may be associated with a reduction in the increase of Culex mosquitoes at the CSO outfalls after heavy rainfall. More research is needed to study how the impacts of SCMs on mosquito populations may affect human health.

Ribbed mussel in an urban waterway filters bacteria introduced by sewage

The ribbed mussel has been demonstrated to tolerate high levels of urban pollution and inhabits intertidal regions of the New York City estuary. The ability of this bivalve to filter bacteria raises the question of whether it can remove from the water column the fecal bacteria introduced to urban waterways by septic system leakage or sewer overflow. The study here addresses the hypothesis that ribbed mussel filters bacteria introduced by combined sewer overflow (CSO) discharge. Mussels and water were collected from a highly polluted region of the NYC estuary in order to conduct two sets of five trials for filtration of coliform and coccoid fecal indicator bacteria, respectively, Escherichia coli and Enterococcus species. Mussels and water samples were collected in proximity to a major CSO outfall within 1–2 days of a rainfall event to ensure high baseline values of bacterial contamination for filtration trials. For any given Enterococcus or E. coli trial, equal volume water samples were serially distributed across aerated tanks either containing a mussel or not. Comparison of with-mussel versus no-mussel tank water contamination across pooled trials showed significant (P < 0.05) reduction in water exposed to mussel filtration for both, Enterococcus and E. coli trials. For Enterococcus trials, measures of turbidity (suspended particle density) were taken concurrently with measures of bacterial contamination. Regression of contamination against turbidity, with measures standardized across trials, yielded a significant positive association (n = 50, P < 0.0001) across all tank water with a mussel. Thus, contamination reduction was associated with particle removal by mussel filtration.

Can stormwater control measures decrease the vectors of mosquito borne diseases in areas surrounding combined sewer overflows?

Background: Combined sewer systems (CSS) are used by over 750 cities in the United States. They collect storm and sewer water into the same pipes for transport to a wastewater treatment plant. Combined sewer overflows (CSOs) occur during large storm events, when increased volume and flowrate of stormwater runoff cause CSS pipes to exceed capacity. Waterbodies affected by CSOs are organically rich and lack enough oxygen for larger organisms to survive, making them favorable breeding environments for mosquitoes. Stormwater control measures (SCMs), also commonly known as best management practices, utilize retention, infiltration, and/or phytoremediation techniques to decrease the flow rate and volume of stormwater runoff that flows into CSS pipes, thereby decreasing CSOs. Methods: We are researching whether SCM located within a sub-sewershed can decrease the number of mosquitoes surrounding the respective CSO outfall. Mosquitoes caught in our study site, Washington DC, included 850 in the genus Aedes, known to spread Chikungunya, Dengue Fever, West Nile, Yellow Fever, and Zika, and 1,159 in the Genus Culex, known to spread encephalitis and West Nile. Preliminary Results: Based on preliminary results, sub-sewersheds that have a higher density of SCMs have fewer Aedes and Culex mosquitoes at the respective CSO outfalls. SCMs in the sub-sewersheds may have a larger impact on Culex than Aedes mosquitoes, possibly because of a reduction in Culex mosquitoes’ preferred breeding environment, waters containing high amounts of organic matter. Though SCMs may decrease mosquitoes at the CSO outfall, we also studied whether pooling utilized by SCMs contributes to the number of surrounding mosquitoes. Conclusion: Findings from this study may help inform cities of the benefits and drawbacks of using SCMs including decreasing the vectors of mosquito borne diseases in areas with CSOs.

Exploring the structural factors of resilience in urban drainage systems: a large-scale stochastic computational experiment

The focus of infrastructure design and management has turned from a reliability-based approach to a resilience-based one. Resilience is a system's ability to maintain its function and minimize failure consequences when faced with exceptional conditions. This study carries out a large-scale computational experiment to study how resilience is affected by system's structure in a combined sewer system. We build a stochastic generation model, involving a random sampling of facility locations and a graph-based random walk sampling algorithm to generate various layouts of pipelines. The performance of these virtual systems are assessed in the Storm Water Management Model. We apply statistical techniques on these samples to study the relation between resilience and system structure. Results show that the number of combined sewer overflow (CSO) outfalls is a more important factor of resilience compared to the number of wastewater treatment plants (WWTPs). Some locations are found more preferable for WWTP or CSO outfall placement, while adding WWTPs or outfalls at other locations might even lower the system's resilience. Size of the sub-catchments of the CSO outfalls also affects resilience. Although this effect is statistically significant, the extent is not remarkable compared to other factors. We further study the structural features of the cost-effective systems. The highest achievable resilience level increases as the number of CSO outfalls decreases and so does system's cost. This results from the difference in CSO quantity, therefore this dilemma can be cut off by end-of-pipe storage or treatment which specifically tackles CSO. The conclusion of this study provides an insight into the structural factors of combined sewer systems’ resilience and can provide guidance for system's planning.

Modeling the transport of titanium dioxide nanomaterials from combined sewer overflows in an urban river

Combined sewer overflows (CSOs) occur frequently in the United States, discharging an estimated 3.2 billion cubic meters of untreated sewage into receiving waters every year. These discharges contain a variety of contaminants including engineered nanomaterials (ENMs), yet ENMs discharged through CSOs have not been taken into account in ENM fate and transport models. This study fills this knowledge gap by developing a new integrated model that links an urban hydrologic-hydraulic model, using the Storm Water Management Model (SWMM), with a three-dimensional hydrodynamic and water quality model of rivers, using the Environmental Fluid Dynamics Code (EFDC). The modeling framework was applied to predict the concentrations of titanium dioxide (TiO2) ENMs in the Buffalo River in Buffalo, New York, as a result of CSO events. CSOs are shown to have a potential for transient high concentrations of ENMs and thus potentially high localized risk near the CSO outfalls and deposition zones in the river. The present approach provides a promising modeling framework to simulate ENM fate and transport in urban waterways. The model presented in this study can help build a management tool to predict temporally and spatially varying concentrations of ENMs introduced into receiving waters through CSOs.

Contributions of combined sewer overflows and treated effluents to the bacterial load released into a coastal area

The impact of combined sewer overflow (CSO) on the receiving water body is an issue of increasing concern, as it may lead to restrictions in the use and destination of the receiving body, such as bathing or recreational area closures, fish and shellfish consumption restrictions, and contamination of drinking water resources. Recent investigations have mainly referred to the occurrence and loads of suspended solids, organic compounds and, in some cases, micropollutants. Attempts have been made to find correlations between the discharged load and the size and characteristics of the catchment area, climate conditions, rainfall duration and intensity.This study refers to a touristic coastal area in the north-east of Italy, which is characterized by a combined sewer network including 5 CSO outfalls which, in the case of heavy rain events, directly discharge the exceeding water flow rate into channels which, after a short distance, reach the Adriatic Sea. The study analyzed: i) rainfall events during the summer period in 2014 which led to overflow in the different outfalls, ii) the inter- and intra-event variability with regard to E. coli, Enterococci and conductivity, and iii) the hydraulic and pollutant (E. coli and Enterococci) loads discharged by the local wastewater treatment plant and by all the CSO outfalls. Finally, it estimated the contribution of each source to the released hydraulic and pollutant loads into the receiving water body. Moreover, it was also found that the modest water volume discharged by all CSO outfalls (only 8% of the total volume discharged by the area) contains >90% of the microbial load.

Three-dimensional model to capture the fate and transport of combined sewer overflow discharges: A case study in the Chicago Area Waterway System

We used a numerical model to analyze the impact of combined sewer overflows (CSOs) in the hydrodynamics and water quality of the Chicago Area Waterway System (CAWS). We coupled the Environmental Fluid Dynamics Code (EFDC) with the Water Quality Analysis Simulation Program (WASP) to perform three-dimensional simulations of the hydrodynamics and water quality in CAWS. The analysis was performed for two different storms: (i) May 6, 2009 representing a 6-hour duration 4-month return period, and (ii) September 12, 2008 representing a 48-hour duration 100-year return period. Results from the simulations show distinct differences between the two storms. During the May 2009 storm there was only one major CSO pumping event with negligible impact on the water quality of CAWS. During the September 2008 storm there were several CSOs that impacted the hydrodynamics and water quality of CAWS. In particular, CSOs during the September 2008 event induced a reversal flow in CAWS, with a plume of constituents that traveled in the opposite direction as water does under normal conditions. However, the simulation results show that CSOs events in CAWS take place during periods of high rainfall, thus the discharge of CSOs is significantly diluted along the CAWS. As a result, the concentrations of organic matter and inorganic nutrients observed at the downstream boundary in CAWS were significantly lower than those recorded at the CSOs outfalls and are within the limits established in the regulation for regular effluents. These results suggest that even during storms events with significant CSOs into the CAWS there is a significant dilution that reduce the impact in the water quality at the system boundaries.

How does climate change affect combined sewer overflow in a system benefiting from rainwater harvesting systems?

Combined Sewer Overflow (CSO) infrastructure are conventionally designed based on historical climate data. Yet, variability in rainfall intensities and patterns caused by climate change have a significant impact on the performance of an urban drainage system. Although rainwater harvesting (RWH) is a potential solution to manage stormwater in urban areas, its benefits in mitigating the climate change impacts on combined sewer networks have not been assessed yet. Hence, the goal of the present study was set to evaluate the effectiveness of RWH in alleviating the potential impacts of climate change on CSOs. To do so, first, future rainfall was achieved through the Coupled Model Intercomparison Project Phase 5 (CMIP5) based on modified historical record. Then, rainfall-runoff modeling was employed using the U.S. EPA Stormwater management model (SWMM) to study the response of CSO outfalls to future rainfall. The study site was the combined sewer network of the City of Toledo, Ohio. Results showed that under the maximum impact scenario in the near future, climate change might cause up to approximately 12–18% increase in CSOs occurrence, volume and duration in Toledo. However, an RWH plan with the capacity of 0.76m3 (200gal) implemented on half on the buildings throughout the area, appeared to be able to mitigate the potential future impacts, and showed a remarkable controlling performance in the peak flow periods. This plan also met toilet flushing demands. Therefore, RWH can be considered as a feasible solution to mitigate future climate change impacts on CSOs and supply water demands.

Impacts of global change on the concentrations and dilution of combined sewer overflows in a drinking water source

This study presents an analysis of climate change impacts on a large river located in Québec (Canada) used as a drinking water source. Combined sewer overflow (CSO) effluents are the primary source of fecal contamination of the river. An analysis of river flowrates was conducted using historical data and predicted flows from a future climate scenario. A spatio-temporal analysis of water quality trends with regard to fecal contamination was performed and the effects of changing flowrates on the dilution of fecal contaminants were analyzed. Along the river, there was a significant spatial trend for increasing fecal pollution downstream of CSO outfalls. Escherichia coli concentrations (upper 95th percentile) increased linearly from 2002 to 2012 at one drinking water treatment plant intake. Two critical periods in the current climate were identified for the drinking water intakes considering both potential contaminant loads and flowrates: local spring snowmelt that precedes river peak flow and extra-tropical storm events that occur during low flows. Regionally, climate change is expected to increase the intensity of the impacts of hydrological conditions on water quality in the studied basin. Based on climate projections, it is expected that spring snowmelt will occur earlier and extreme spring flowrates will increase and low flows will generally decrease. High and low flows are major factors related to the potential degradation of water quality of the river. However, the observed degradation of water quality over the past 10years suggests that urban development and population growth may have played a greater role than climate. However, climate change impacts will likely be observed over a longer period. Source water protection plans should consider climate change impacts on the dilution of contaminants in addition to local land uses changes in order to maintain or improve water quality.

Climate Change Impact on Combined Sewer Overflows

Combined sewer overflows (CSOs) have major impacts on receiving waters. It is important to investigate the potential impacts of climate change on CSOs. The main objective of this study was to develop projections on the future evolution of CSO frequency and durations in the context of climate change. First, a model was developed based on available CSO data (date of occurrence and durations over the May to October period for the years 2007 to 2009) from 30 CSO outfalls located in southern Quebec. This model estimates the probability of occurrence and the duration of a CSO given the rainfall total depth. Second, two simulated series from a regional climate model were used to estimate the evolution of CSO frequency and durations between 1961-1990 and 2071-2100 periods. Results suggest that the May to October mean CSO number will remain globally unchanged for the 30 CSO outfalls while mean annual CSO duration will slightly increase (+4.2%). On a monthly basis, CSO frequency and duration will decrease in average during July and August, while they will increase in May and October.

Impact of an intense combined sewer overflow event on the microbiological water quality of the Seine River

For a better understanding of the short and mid-term impacts of a combined sewer overflow (CSO) on the microbiological quality of the receiving river, we studied the composition of a CSO discharge and monitored during several hours the changes in the concentration of fecal indicator bacteria (FIB) in the impacted river water mass. The CSO occurred at the Clichy outfall (Paris agglomeration, France) in summer 2008 as a result of the most intense rainfall of the year. In 6h, 578, 705 m3 of sewage and 124 t of suspended matter (SM) were discharged into the Seine River. The CSO contained 1.5 × 106E. coli and 4.0 × 105 intestinal enterococci per 100 mL on average, and 77% of the E. coli were attached to SM. It was estimated that 89% of the CSO discharge was contributed by surface water runoff, and that resuspension of sewer sediment contributed to ∼75% of the SM, 10–70% of the E. coli and 40–80% of the intestinal enterococci. Directly downstream from the CSO outfall, FIB concentrations in the impacted water mass of the Seine River (2.9 × 105E. coli and 7.6 × 104 intestinal enterococci per 100 mL) exceeded by two orders of magnitude the usual dry weather concentrations. After 13–14 h of transit, these concentrations had decreased by 66% for E. coli and 79% for intestinal enterococci. This decline was well accounted for by our estimations of dilution, decay resulting from mortality or loss of culturability and sedimentation of the attached fraction of FIB.

Using Embedded Sensor Networks to Monitor, Control, and Reduce CSO Events: A Pilot Study

Each year in the United States, combined sewer overflow (CSO) events result in the release of 850 billion gallons of untreated wastewater into lakes and rivers, causing drinking water contamination, human illness, animal and fish kills, and eutrophication. This paper examines the ability of an embedded sensor network to reduce the frequency and severity of CSO events by maximizing the existing storage capacity in the combined sewer system (CSS). This novel network system is called combined sewer overflow network (CSONet). CSONet uses data gathered from a distributed network of sensors to provide decentralized, distributed, real-time control of the CSS's storage capacity using automated valves called smart valves. One pilot CSONet was deployed in South Bend, IN, during the summer of 2005. It controlled the storage of storm water runoff in a large retention basin using level data from sensors within the basin and at the CSO outfall, 3.2 miles away. Once there was no longer a threat of a CSO event, CSONet au...

Anthropogenic organic contaminants in the effluent of a combined sewer overflow: impact on Boston Harbor

Effluent from a large combined sewer overflow (CSO) in Boston and receiving waters near the CSO outfall were sampled during dry and wet weather conditions. Surficial sediments were also collected from the vicinity of the CSO and at nearby sites. The samples were analyzed for a variety of organic constituents including organic carbon and nitrogen, linear alkylbenzenes (LABs), coprostanol and polychlorinated biphenyls (PCBs). As judged by the presence of waste-specific markers (LABs, coprostanol), the CSO effluent contains sewage under both dry and wet weather conditions. When rainfall occurs, the concentration of suspended solids and all organic constituents in the particulate phase increase, ultimately approaching those characteristic of untreated sewage. The concentrations of LABs and PCBs in the effluent are strongly correlated, indicating that PCBs in the CSO are derived from sewage inputs. During heavy rainfall, the vast majority (>90%) of the hydrophobic organic substances are associated with suspended particulate matter, whereas during dry weather, a significant fraction resides in the operationally defined ‘dissolved’ phase. Estimates of the mass emission rates of CSO constituents show that >70% of the suspended particles and >90% of the particulate organic carbon, hydrocarbons and trace organics are discharged during wet weather. Particles in the receiving water appear to be strongly influenced by the CSO effluent during wet weather. Concentrations of PCBs in surficial sediments near the CSO are correlated with those of coprostanol and the LABs, indicating that these compounds are derived from similar sources. Based on the observed correlations, approximately 60–80% of the sedimentary PCBs originate from sewage. Comparison of ΣLAB/coprostanol ratios of effluent particles, surficial sediments and sewage sludges suggest that the vast majority of the marker compounds and the PCBs in sediments are not from the CSO, but are derived from one of two sewage treatment plants that discharged sludge into the harbor until 1991. The sludge-derived contaminants were probably carried by tidal currents into Dorchester Bay and deposited in shallow, quiescent embayments where sedimentation is favored. These results illustrate the potential importance of long-range transport of waste-derived contaminants in urban harbors and their rapid accumulation in localized depocenters.

Characterization and aquatic impacts of combined sewer overflows in greater vancouver British Columbia

The Greater Vancouver Regional District has been assessing the environmental concerns and management problems associated with combined sewer overflows (CSOs) as part of their long range liquid waste management plan. There are currently 52 CSO outfalls in the region with some of the major outfalls having 100-150 discharge events/yr concentrated in the winter months. Physical/chemical/microbiological characterization studies of CSO discharge has been investigated at 7 sites. Statistical analysis of these quality data have demonstrated that it can be segregated into three groups based on land use characteristics, namely residential, light industrial, and heavy industrial. These quality characteristics were used along with land use characterization of the 52 collection areas and discharge data to determine the loading of contaminants to the different waterways in the region. The contaminant loading in the region is dominated by the Clark Drive CSO since it contributes 40% of the annual discharge volume to the inner harbor of Burrard Inlet. Contaminant loading calculations from other sources demonstrates that, the sewage treatment plant predominates in the outer harbor, while the CSO and stormwater predominate in the inner and central harbor respectively. At the large Clark Drive outfall, dye tracer and numerical modelling were used to characterize the dispersion plume. Ecological effects of the contaminants were determined using the sediment quality triad. Silver sediment contamination, toxicity bioassays, and benthic invertebrate community structure analysis were useful indicators of the environmental effects of this discharge. Similar studies at the English Bay CSO, which only has 1/90 of the Clark Drive discharge, found sediment contamination levels that exceeded sediment contaminant criteria, but ecological impacts were less severe.

Characterization and aquatic impacts of combined sewer overflows in Greater Vancouver. British Columbia

The Greater Vancouver Regional District has been assessing the environmental concerns and management problems associated with combined sewer overflows (CSOs) as part of their long range liquid waste management plan. There are currently 52 CSO outfalls in the region with some of the major outfalls having 100-150 discharge events/yr concentrated in the winter months. Physical/chemical/microbiological characterization studies of CSO discharge has been investigated at 7 sites. Statistical analysis of these quality data have demonstrated that it can be segregated into three groups based on land use characteristics, namely residential, light industrial, and heavy industrial. These quality characteristics were used along with land use characterization of the 52 collection areas and discharge data to determine the loading of contaminants to the different waterways in the region. The contaminant loading in the region is dominated by the Clark Drive CSO since it contributes 40% of the annual discharge volume to the inner harbor of Burrard Inlet. Contaminant loading calculations from other sources demonstrates that, the sewage treatment plant predominates in the outer harbor, while the CSO and stormwater predominate in the inner and central harbor respectively. At the large Clark Drive outfall, dye tracer and numerical modelling were used to characterize the dispersion plume. Ecological effects of the contaminants were determined using the sediment quality triad. Silver sediment contamination, toxicity bioassays, and benthic invertebrate community structure analysis were useful indicators of the environmental effects of this discharge. Similar studies at the English Bay CSO, which only has 1/90 of the Clark Drive discharge, found sediment contamination levels that exceeded sediment contaminant criteria, but ecological impacts were less severe.

Combined sewer overflows (CSOs) as sources of sediment contamination in the lower Passaic River, New Jersey. II. Polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and polychlorinated biphenyls

Polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) are contaminants ubiquitous to the sediments of industrialized waterways. Non-point sources. such as atmospheric deposition, urban runoff, and combined sewer overflows, are recognized by the U.S. Environmental Protection Agency as important uncontrolled sources of these compounds. The purpose of this study was to investigate the impact of combined sewer overflows (CSOS) on sediments of the Passaic River in New Jersey. In this investigation. we (1) characterize PCB and PCDD/F contamination in sediments impacted by these CSOs, (2) evaluate the spatial distribution of these contaminants, and (3) evaluate the possible sources of PCBs and PCDD/Fs within the respective CSO districts. Ten surficial sediment samples were collected adjacent to each of four CSO outfalls along the lower Passaic River and analyzed for coplanar PCBs and PCDD/Fs. Principal components analysis (PCA) was utilized to assess differences in the distributional patterns of PCB and PCDD/F congeners at each of the four CSO sampling areas. The results indicate that sediments proximate to the CSO outfalls are contaminated with elevated concentrations of these compounds. The spatial distribution and fingerprint patterns of PCBs and PCDD/Fs strongly suggest that the CSOs are a source of contamination in sediments near these outfalls. Evaluation of the industries operating within the CSO districts provides a link between the facilities that discharge wastes to the combined sewer system and PCBs and PCDD/Fs found in the sediments. Until adequate controls are implemented, CSOs will continue to be significant on-going sources of PCB and PCDD/F contamination affecting the water and sediment quality of the Passaic River.

Combined sewer overflows (CSOs) as sources of sediment contamination in the lower Passaic River, New Jersey. I. Priority pollutants and inorganic chemicals

Ten surficial sediment samples were collected adjacent to each of four combined sewer overflow (CSO) outfalls along the lower Passaic River in New Jersey and analyzed for priority pollutant organic and inorganic chemicals. The objectives of this investigation were to (t) characterize chemical contamination in sediments impacted by these CSOs, (2) evaluate the spatial distribution of contaminants. and (3) evaluate the possible sources of contaminants within the respective CSO districts. The results indicate that sediments proximate to the CSO outfalls are contaminated with a range of chemicals including toxic metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), pesticides, and other organic chemicals. The spatial distribution of these contaminants strongly suggest that the CSOs are the primary source of contamination in sediments near these outtalls. While the contribution of residential waste and stormwater may be substantial, evaluation of the industries operating with the CSO districts provides a link between the facilities that discharge wastes to the combined sewer system and chemical contaminants found in the sediments. Until adequate controls are implemented, CSOs will continue to be on-going sources of contamination affecting the water and sediment quality of the Passaic River.