Stormwater Outfalls Research Articles

Seasonal variation in the toxicity of sediment-associated contaminants in Corpus Christi Bay, TX

Seasonal variation in pore water and sediment–water interface (SWI) toxicity at two sites of suspected contamination was investigated using sea urchin embryological development ( Arbacia punctulata) and copepod hatching success ( Schizopera knabeni). Site S1, located inside a marina, was fine-grained and S2, located near a neighboring stormwater outfall, was sandy. Both sites were cored in summer and winter, along with reference sites of equivalent grain sizes. Whereas the muddy contaminated site displayed a slight decrease in sea urchin toxicity from summer to winter, pore water from the sandy contaminated site exhibited an increase in sea urchin toxicity. The sandy sites displayed slight toxicity increase to copepod hatching success in winter, which occurred in the SWI of S2 and in the pore water from the reference site, R2, where it coincided with sedimentation. Cu was the most prevalent metal in the sediment samples. Although Cu concentration increased in the whole sediments and pore waters from summer to winter, its concentration in overlying SWI exposure decreased from summer to winter. Organic compounds exhibited opposite behavior, with smaller variety identified in the winter pore water samples, but more chemicals detected in the SWI samples in winter.

Storm-water jets and plumes in rivers and estuaries

The interaction of storm-water discharges with the flow in rivers and estuaries often involves cross-flowing jets or plumes. This paper reviews the theoretical, experimental, numerical, and field research on this topic. The geometry of the outfall, the jet velocity ratio, and the relative density of the discharging flow have been shown to affect the mixing and dilution of the discharge into the ambient water. Storm-water outfalls are typically circular or rectangular; however, there are numerous open channel outfalls that have trapezoidal or irregular cross sections with large width to depth ratios. The extensive research of pioneers such as N. Rajaratnam on jets and plumes has led to the development of software packages for outfall evaluations. The CORMIX model is an example of one of these packages. The research on which these models are based is discussed, and some guidelines are given for estimating the dilution at outfalls with high width to depth ratios.Key words: storm water, outfalls, jets, plumes, cross flow, modelling.

Considerations for Storm-Water Outfalls off Exposed Coasts

There is a worldwide movement for coastal municipalities in developed countries to replace whole series of storm drains with far fewer storm-water outfalls that discharge well offshore. Such an extended-length pipe, passing into the surf zone along an exposed coastline, is far from easy to plan, support with data, design, install, and operate. This paper is intended to school drainage engineers in these matters.

Increasing Stormwater Outfall Duration, Magnitude, and Volume through Combined Sewer Separation

Combined sewer separation projects designed for water quality benefits will change pipe networks and alter stormwater outfall hydrographs. Separation induced outfall hydrograph changes were explored for the 12.14 ha (0.05 mi2 ) combined sewer overflow (CSO) 050 service and its 29 stormwater catchbasins in Syracuse, N.Y. Topographic and infrastructure analysis together with catchbasin monitoring of stormwater runoff were used to parametrize and validate the Storm Water Management Model for two events in 2003. Sewer separation impacts on outfall hydrographs were then analyzed for 50 historical and 28 design precipitation events, ranging from 15 min to 24 h duration, 2–25 y frequency. Separation of combined sewers increased historic storm median outfall hydrograph duration by 2,044%, peak magnitude by 113%, and volume by 617%, whereas increases in design storm median outfall duration was 879%, peak magnitude was 27%, and volume was 54%. Changes in outfall hydrograph characteristics were explained by system i...

Three-Dimensional Modeling of Fecal Coliform in the Tidal Basin and Washington Channel, Washington, DC

Fecal coliform are widely used as bacterial indicator in the United States and around the world. Fecal coliform impaired water is highly possible to be polluted by pathogenic bacteria. The Tidal Basin and Washington Channel in Washington, DC are on the Total Maximum Daily Load (TMDL) list due to the high fecal coliform level. To support TMDL development, a three-dimensional numerical model of fecal coliform was developed using the EFDC framework. The model calculates the transport of fecal coliform under the influences of flap gate operations and tidal elevation. The original EFDC code was modified to calculate the die-off of fecal coliform under the impact of temperature and solar radiation intensity. The watershed contribution is expressed as storm water inflow and the load carried by the runoff. Model results show that fecal coliform vary strongly in space in both the Tidal Basin and Washington Channel. The storm water only impacts a small area around the storm water outfall in the Tidal Basin and the impacts are negligible in the Washington Channel due to dilution. The water from the Potomac River may affect the fecal coliform level in the area close to the flap gate in the Tidal Basin. The fecal coliform level in the Washington Channel is mainly controlled by the fecal coliform level in the Anacostia River, which is located at the open boundary of the Washington Channel. The potential sediment layer storage of fecal coliform was analyzed and it was found that the sediment layer fecal coliform level could be much higher than the water column fecal coliform level and becomes a secondary source under high bottom shear stress condition. The developed model built solid connection of fecal coliform source and concentration in the water column and has been used to develop TMDL.

Delineation of a chemical and biological signature for stormwater pollution in an urban river

Stormwater is a major source of Escherichia coli in urban waterways. This study assessed the chemical and bacterial contaminant load in stormwater entering an urban river using chemical analyses, E. coli enumeration and antibiotic resistance testing. Inline monitoring of five major stormwater outfalls revealed that E. coli concentrations can range from 100 to >240,000 CFU 100ml(-1) in stormwater; 15% of the samples contained >240,000 CFU 100 ml(-1). E. coli levels increased from <200 CFU 100ml(-1) to between 1,500 and >20,000 CFU 100ml(-1) in the receiving waters following storm events. Metals and nutrients were significantly elevated (p < 0.05) in inline stormwater samples compared with baseflow river water. Chromium, zinc, lead and total phosphorus were co-ordinately elevated in stormwater, but E. coli levels did not correlate to this chemical signature. E. coli isolates from stormwater and river water samples (n = 2,478) were tested for resistance to 10 antibiotics and compared with over 1,800 isolates from human and non-human sources. The antibiotic resistance frequencies of isolates from human sources were considerably higher than those found in non-human sources. Isolates from human sources were resistant to multiple antibiotics; however, no specific multiple resistance pattern was found. One of five stormwater outfalls tested contained E. coli resistant to antibiotics at frequencies that were not significantly different from those of E. coli isolates from wastewater treatment plant influent (p < 0.05). The results from antibiotic resistance testing suggested that the elevated E. coli levels observed after storm events are a mixture of human and non-human sources. The results of this study demonstrate that there is a considerable E. coli load to receiving waters from stormwater and that sanitary sewage inputs may not be limited to recognized sewer overflows.

Chemical tracers as indicator of human fecal coliforms at storm water outfalls

Indicators to distinguish between fecal coliforms of human and animal origin were investigated in water from storm sewer outfalls to a coastal lake during wet and dry weather. The ratio of fecal coliform relative to fecal streptococci count was used as the microbiological indicator. Concentrations of human-activities originated caffeine, anionic surfactant, fluoride, and fluorescence whitening agent (FWA) were used as chemical indicators. The ratio of fecal coliform to fecal streptococci ranged from 0.2 to 3.0, during wet weather making it difficult to interpret the origin of fecal pollution. However, concentrations of caffeine, anionic surfactant, fluoride, and FWA in storm water outflow during wet weather were much higher than those in the lake water during dry weather, indicating the presence of human waste at storm water outfall. Strong correlation between fecal coliform counts and chemical parameter values further indicated the human contribution to the fecal coliform count. In addition, a strong correlation among the chemical parameters suggested that only one of them is needed as chemical tracer to detect the presence of human input.

Bacterial sources, pathways and management strategies for urban runoff

The microbiological quality of diffuse impermeable surface runoff is described in terms of bacterial densities and pathogens observed within urban catchments in North London and Milton Keynes and the use of somatic bacteriophages as faecal indicators are evaluated. The studies show the occurrence of faecal indicator organisms (FIOs) and pathogens to be ubiquitous in stormwater runoff from all types of urban land use surfaces, with the possible exception of major highways. Urban catchments in North London show a progressive downstream increase in FIOs and pathogens consonant with increasing urbanization and incidence of stormwater outfalls and combined sewer overflows (CSOs). Surface water FIOs and pathogens appear to be predominantly of non‐human origin being primarily derived from animal and bird sources, although the effect is over‐ridden in the presence of misconnections and CSO discharges. A combination of infrastructure improvement, end‐of‐pipe detention, source control and more robust local authority regulation is recommended for effective management and remediation of bacteriological urban water quality.

Hydraulic considerations in designing an oil spill control system for a stormwater outfall

Oil spills have been identified to be a serious problem in the Humber Creek subwatershed in Toronto. To capture spilled oil at the storm water outfall, an oil spill control system was designed to perform under different flow conditions. The spill control system consists of an on-line triangular lateral diversion channel (1.7 m by 0.6 m) and an off-line tilted-plate oil–water separator (7 m by 5.4 m by 5.9 m). To investigate the hydraulic behaviour of the spill control system under different flow conditions, a physical model study was conducted at the National Water Research Institute's Hydraulics Laboratory in Burlington, Ontario. The model results confirmed the design conveyance capacity of the lateral diversion channel and indicated that floating objects and settleable solids could be trapped inside the oil–water separator under various flow conditions. A vortex was also observed inside the oil–water separator and was likely caused by the lateral diversion channel. During high flows, the flow through the oil–water separator was controlled by the flow backup from the storm water outfall. Key words: oil spills, lateral channel, oil–water separator, hydraulic models, storm conditions.

Modeling coliforms in storm water plumes

The recreational waters near many large cities in the United States and Canada are severely impaired by pathogens that are present in the storm water runoff. In separated sewers the pathogen sources may be cross-flows between the sanitary and storm water systems. This paper presents the methodology that was used in developing a forecasting model for pathogen indicators for recreational sites in the receiving waters of multiple storm water outfalls. The objective of the model is to give a timelier indicator of beach water quality than conventional beach monitoring, which takes about 2 d for laboratory results. The model used for the study was based on the Princeton Ocean Model. The forecasting system consists of nested hydrodynamic models and a bacteria fate–transport submodel. Calibration and validation is based on 6 years of field studies, laboratory analyses, and experiments. The methodology is illustrated by a case study of the impact of storm water flows on the south shore of Lake Pontchartrain, Louisiana, which has been banned for swimming since 1985. The water quality data included: pathogen indicators (fecal coliform, Enterococci, and E. Coli), water chemistry parameters, turbidity, and nutrients. Key words: modeling, water quality, pathogens, fecal coliform, stormwater runoff.

Flow Variation of Duckbill Valve Jet in Relation to Large Elastic Deformation

Duckbill-shaped elastomer valves are often installed on wastewater effluent diffusers, stormwater outfalls, and industrial flow systems to prevent backflow and sediment/salt water intrusion. Unlike fixed diameter nozzles, the flow from a duckbill valve (DBV) depends both on the driving pressure and the size of the valve opening. A nonlinear large deformation finite element analysis of a prototype DBV is reported herein. The elastomer is modeled as a hyperelastic incompressible solid, and the flow inside the DBV, shaped like a converging nozzle, is treated as energy conserving. The deformed valve is computed iteratively from sequential standard large deformation analysis of the internal flow and pressure loading. The calculations show that the valve opening is lip shaped, and the maximum stress occurs around the two sides of the saddle of the DBV; maximum strains are on the order of 5%. In contrast to the traditional square-root head–discharge dependence, a linear pressure–discharge relation is predicted f...

Urban stream channel hazards

In managing urban stream channels there are pressures to use soft engineering techniques to restore channels wherever possible, to undertake management within a drainage basin context, to produce sustainable solutions and to consider community views. However, specific methods for characterizing the channel network in terms of possible management options have not been developed explicitly for urban areas. A method of characterizing the entire drainage network of urban areas, based upon segmentation of the stream channel network according to the incidence of road crossings and stormwater outfalls, is proposed together with consideration of ways in which the segments can be characterized, including stream channel hazards as a means of providing one basis for urban channel management.

Coastal eutrophication and the Danish national aquatic monitoring and assessment program

Nutrient over-enrichment and cultural eutrophication are significant problems in the Danish marine environment. Symptoms of eutrophication include periods of hypoxia and anoxia in bottom waters, death of benthic-dwelling organisms during anoxia, long-term reductions in the depth distribution of macrophyte communities, changes in the species composition of macrophyte communities, and increases in reports of harmful algal blooms. In 1987 the Action Plan on the Aquatic Environment was adopted to combat nutrient pollution of the aquatic environment with the overall goal of reducing nitrogen loads by 50% and point source phosphorus loads by 80%. The Danish Aquatic Nation-wide Monitoring Program was begun in 1988 in order to describe the status of point sources (industry, sewage treatment plants, stormwater outfalls, scattered dwellings, and fish farms), ground water, springs, agricultural watersheds, streams, lakes, atmospheric deposition, and the marine environment. Another important aspect of the program was to document the effects on the aquatic environment of the measures and investments taken for nutrient reduction as outlined in the Action Plan. The monitoring program should determine if reductions in nutrients are achieved by the measures taken and should help decision makers choose appropriate additional measures to fulfill the objectives. Coordination with international programs and commissions is an important component of the monitoring program to meet internationally agreed upon reductions in nutrient inputs. The future and direction of the Danish National Aquatic Monitoring and Assessment Program will be to a large extent shaped by both the Water Framework Directive and Habitat Directive adopted by the European Union.

On the head-discharge relation of a "duckbill" elastomer check valve

Duckbill-shaped elastomer check valves are often installed on wastewater effluent diffusion systems and stormwater outfalls to prevent baekflow or sea water intrusion. Unlike fixed diameter ports, the jet velocity varies nonlinearly with port discharge flow. A new theory to predict the hydraulic characteristics of a duckbill elastomer check valve (DBV) is presented, and it provides a theoretical basis for the correlation of all DBV hydraulic data. It is shown that a DBV can be considered as a smooth converging nozzle. By modelling the duckbill valve as a two-dimensional rubber membrane, a theory is developed to relate the DBV material properties and flow conditions to the valve deformation. The valve opening area is predicted as a function of the driving pressure head: a linear head-discharge relation is predicted. The predictions are in excellent agreement with ex peri mental data. The derived head-discharge relation can be readily incorporated into a diffuser internal hydraulics code to determine the variation of discharge flow and jet velocity along a multiport diffuser fitted with duckbill check valves.

Distribution of Heavy Metals in Near-Shore Sediments of the Swan River Estuary, Western Australia

Estuarine systems adjacent to urban areas are at risk of contamination by contaminants from anthropogenic sources, such as heavy metals. We anticipated that the sediments of the Swan River estuary, which runs through metropolitan Perth in Western Australia, would show metal contamination related to industrialization and inputs of stormwater. Total Cu, Pb and Cd concentrations, and Cu, Pb, Cr and Zn inoperationally-defined fractions, were determined inseparate sampling exercises in near-shore sediments ofthe upper Swan River estuary.Total metal concentrations in sediments were not high (maximum values of 297 mg kg-1 for Cu, 184 mg kg-1 for Pb and 0.9 mg kg-1 for Cd) when compared with Australian environmental assessmentguidelines for soils. On the basis of linear regressions between sediment metal concentrations andphysicochemical properties of the sediments (pH, organic carbon, particle size distribution), no single parameter could explain the variation in metal concentrations for all metals. Sediment organic carbon content was positively correlated with Cu concentration; Cu concentrations also increased significantly with increasing clay content anddecreasing sand content. Pb concentrations showed a significant increase with increasing sediment pH, and were approximately three-fold higher in sediments adjacent to stormwater drain outfalls than in sediments remote from drains; no such effect was observed for Cu or Cd. No effect of distance downstream was observed. Sequential extraction of sediments showed that most of the metals were in relatively immobile forms, for example bound to Feoxides, or only extractable by aqua regia. The enhanced concentrations of Pb near stormwater outfalls suggest that vehicle-derived Pb may be an important contributor of Pb to the estuary.

Polychlorinated Dibenzo-p-Dioxins and Dibenzofurans in Storm Water Outfalls Adjacent to Urban Areas and Petroleum Refineries in San Francisco Bay, California.

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were analyzed in storm water collected from 15 outfalls in San Francisco Bay, California, considered representative of areas located adjacent to petroleum refineries and mixed urban/commercial/residential land uses. Storm water sampling was conducted hourly over a 12-h period at two outfalls located near the city of Oakland and the suburban community of Benicia, which represent urban and mixed urban/light industrial land uses, respectively. Sampling was conducted hourly to determine temporal changes in the concentrations and distributions of PCDD/Fs during the first major rainstorm event of the 1995/96 winter season. In addition, storm water sampling was conducted in December 1995 and February/April 1996 at six publicly owned treatment work (POTW) outfalls located adjacent to developed, undeveloped, mixed residential/commercial, and industrial lands. Storm water sampling also was conducted at five outfalls located adjacent to petroleum refineries. The sampling results were used to examine changes in PCDD/F loadings to San Francisco Bay at the onset and midway through the winter rainy season and to characterize differences in PCDD/F concentrations, if any, between refinery and nonrefinery areas. The concentrations of tetra- through octa-chlorinated homologues and 2,3,7,8-substituted congeners were assayed in filtered storm water samples according to US EPA Method 1613A. Principal components analysis (PCA) was used as an exploratory technique to examine the similarities and differences in the distributions of PCDD/Fs in storm water from different outfalls. The sampling results showed few significant differences between storm water discharged from outfalls located in mixed urban/commercial/residential areas and outfalls located adjacent to petroleum refineries. The concentrations of 2,3,7,8-TCDD were below the analytical limits of detection in all storm water samples, with the exception of samples collected after the sixth hour of sampling at the Oakland outfall. Fingerprint patterns were generally dominated by the higher chlorinated PCDD/F congeners including OCDD, OCDF, and 1,2,3,4,6,7,8-HpCDD. Total TEQs were generally below US EPA ambient water quality criteria and aquatic ecotoxicology guideline values. The results of this study strongly suggest that discrete sampling of storm water outfalls is insufficient to characterize the concentrations and distributions of persistent hydrophobic contaminants such as PCDD/Fs. In addition to surface water runoff from the city of Oakland, other nonindustrialized urban locations may represent important sources of PCDD/Fs to San Francisco Bay.http://link.springer-ny.com/link/service/journals/00244/bibs/37n3p290.html

Hydraulics of “Duckbill” Elastomer Check Valves

Duckbill-shaped elastomer check valves are sometimes installed on storm-water or sewage outfall ports to prevent backflow or seawater intrusion. Unlike fixed diameter ports, the jet velocity varies nonlinearly with port discharge flow. An analysis of all available experimental data on the head-discharge characteristics of check valves shows that the collective data can be effectively correlated with the parameters of the approach flow in the discharge port. Two dimensionless relations are obtained for the effective percentage jet opening area and the valve head loss. The relations are derived from data for nominal port diameters in the range of 100–305 mm (4–12 in.), and appear to hold generally for elastomer check valves. The head-discharge relations can be used to determine the jet discharge velocity and opening area that are needed as input to numerical plume models for environmental impact assessment and outfall design. The results can also be conveniently incorporated into a diffuser hydraulics code....

ABSTRACTS POSTER PRESENTATIONS

S OF POSTER PRESENTATIONS SOURCES OF SILVER IN THE EAST LOOE RIVER NATURAL OR ANTHROPOGENIC? C.J. Moon and B. Dickie Department of Geology, University of Leicester Both the East and West Looe Rivers have very high concentrations of silver in their lower reaches. Enhancement in silver in the West Looe river is caused by contamination from, and natural enrichment around, the disused lead mines at Herodsfoot. The source in the East Looe river is of comparable intensity but of enigmatic origin. We have traced the silver back to the storm water outfall from Liskeard where sediment values are 25 ppm Ag, 200 ppm Cu and 500 ppm Pb. The poster will present mineralogical data from the outfall to discriminate between a natural vein source and an anthropogenic origin. EXTENSIONAL COLLAPSE IN THE FOOTWALL REGION OF THE LIZARD OPHIOLITE, EASTERN MOUNTS BAY: A METAMORPHIC CORE-COMPLEX ANALOGUE? A.J. Styles, A.C. Alexander, R.K. Shail and R.E. Holdsworth Department of Geological Sciences, University of Durham Camborne School of Mines, University of Exeter Detailed structural field-mapping along the Mounts Bay coastalsection has revealed a group of late-Variscan extensional structures which have, until recently, largely been overlooked by previous workers. Although the extensional style is variable and partitioned, it is likely that they represent broadly coeval deformation which is related to gravity collapse. • Structures verge down the dip of pre-existing regional foliations. • They are dominated by low-angle detachments or shear zones in which the sense of displacement is consistently directed top to the south-east, which show local cross-cutting relationships with ductile features. • The low-angle detachments are associated with a suite of folds and domino faults which do not show overprinting relationships and hence suggest synchronous brittle and quasi-ductile behaviour causing strain hardening. • The late ductile deformation is cut by granite sheets, making it pre-final emplacement in age. • They are cut by moderate to steep post-orogenic normal-faults. • Many stages of quartz and, more rarely, calcite veins are observed, indicating high pore-fluid pressure throughout orogenesis. The features documented along the section form a distinct and continuous group which shows increasingly brittle deformation styles towards the south-east. There are also strong geometric similarities between these structures and soft-sediment slump and slide features, suggesting that in bulk rheological terms, the overthickened crust is acting as a viscous wedge spreading under the influence of gravity. The extensional structures appear to systematically become more brittle away from the Tregonning-Godolphin Granite and towards the Lizard Ophiolite. Kinematic indicators suggest extensional collapse directed away from a ductile region, through a zone of ductile folds, shears and transposing cleavages, and into a region deforming through brittle faulting. The ductile structure in the northwest transposes all earlier structures, but as the extension becomes more brittle to the southeast, earlier compressional features are still preserved. The ductile-brittle transition appears to be analagous to the core, carapace and cover of core complex models. Early brittle extension estimates

Assessment of Benthic Macroinvertebrate and Fish Communities in a Stream Receiving Storm Water Runoff from a Large Airport

ABSTRACT Prior to the opening of Denver International Airport, Stapleton International Airport (SIA) was the major airport in Colorado. Typically, storm water runoff from SIA was collected and directed to a water treatment facility. However, during winter months when deicers were being used, heavy snows or rains periodically taxed the capacity of the storm water collection system and untreated water was diverted directly into Sand Creek. A study was conducted to determine if the benthic macroinvertebrate and fish communities in the creek had been permanently influenced. Samples for chemical and biological analysis were collected at sites upstream and downstream of the airport outfalls. No ethylene or propylene glycol was found in the creek. Benthic macroinvertebrate communities were dominated by pollution-tolerant organisms, with chironomids being the most abundant group. Benthic macroinvertebrate density and diversity downstream of the storm-water outfalls were not significantly different from those at the upstream sites. The most abundant species of fish collected in Sand Creek were creek chub (Semotilus atromaculatus), white sucker (Catostomus commersoni), and fathead minnow (Pimephales promelas). These species dominated the catch at all sites. Fish were most dense downstream of the storm water outfalls; no evidence of stream degradation due to SIA could be found. Sand Creek is an urban stream, historically impacted by chemical and physical perturbations. Fish and benthic macroinvertebrate abundance and diversity in Sand Creek are most likely dictated by available habitat and pre-airport water quality.

The effect of Budapest on the water quality of the Danube

The Danube flowing across Hungary is a moderately polluted river, at least in its middle stretch, where its greatest polluter is Budapest with 2 million inhabitants and a large industrial complex. Serving the river for drinking water supply, as well, it is obvious that the pollution control for the capital is of paramount importance. There is a 20 year planning concept for the improvement of the sewerage, wastewater treatment and storm water outfall. This long term plan, together with its impact on the water quality of the river and the review of the present conditions, are investigated in this paper.