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Final Report: Fate of Pathogens in Storm Water Runoff
EPA Grant Number: R827933C035Subproject: this is subproject number 035 , established and managed by the Center Director under grant R825427
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: Urban Waste Management and Research Center (University New Orleans)
Center Director: McManis, Kenneth
Title: Fate of Pathogens in Storm Water Runoff
Investigators: McCorquodale, J. A. , Englade, A. J.
Institution: University of New Orleans , Tulane University of Louisiana
EPA Project Officer: Krishnan, Bala S.
Project Period: July 1, 2002 through June 30, 2003
RFA: Urban Waste Management & Research Center (1998)
Research Category: Targeted Research
Description:
Objective:The overall objective of this project of the Urban Waste Management and Research Center (UWMRC) was to develop a program for managing safe primary contact use of the lake’s recreational waters at public beaches and shoreline parks. The goal was to permit the opening of certain south shore areas for swimming with the ability to issue intermittent closures when high-risk conditions are expected. An early-warning forecasting model that will estimate the immediate and short-term risk of exceeding pathogen indicator concentration criteria in recreational areas of Lake Pontchartrain based on hydrologic and climatic data was proposed as a means of supplying more timely information on pathogen risks than that available from a monitoring process that takes about 2 days for laboratory results. The proposed model was a three-dimensional hydrodynamic fate and transport model that incorporated the site-specific response to tides and climate and predicted the trajectory of the storm runoff plume as well as the bacteria concentration field. Specific objectives of the project included: (1) collection of field data to determine the current state of water quality in the south shore area of the lake; (2) collection of field data to characterize plumes resulting from pumped stormwater discharges in terms of the plume trajectories, spreading, and dilution and pathogen indicator concentrations; (3) collection of field data within the urban drainage canals to characterize pathogen indicator loading as a result of pumped storm discharges; (4) determination of pathogen indicator kinetics (i.e., die-off in the water column and bottom sediments), including loss because of sedimentation, while incorporating the effects of certain environmental parameters on decay; (5) development of a three-dimensional hydrodynamic and pathogen forecasting model through modification of the Princeton Ocean Model; and (6) development of a Neural Network Model as a tool for use in a beach management program.
Summary/Accomplishments (Outputs/Outcomes):Lakes Maurepas, Borgne, and Pontchartrain in southeastern Louisiana form one of the largest estuaries in the United States. Historically, Lake Pontchartrain has provided recreational opportunities for more than one million residents in the metropolitan area of New Orleans. In the 1980s, the concentrations of fecal coliform (FC) bacteria regularly exceeded state water quality standards for primary contact recreation, and as a result, the Louisiana Department of Health and Hospitals issued an advisory in 1985 to discourage swimming and other primary contact recreation in Lake Pontchartrain.
Urban stormwater runoff from the New Orleans metropolitan area is the most significant anthropogenic factor affecting the water quality on the south shore of Lake Pontchartrain. The average elevation in New Orleans is several feet below sea level, necessitating stormwater runoff to be pumped to the lake. An extensive drainage network consisting of subsurface and open surface canals exists to collect the runoff, which is then discharged to the lake at various points along the shoreline via a system of pump stations and open surface drainage canals. The drainage system, operated and maintained by the Sewerage and Water Board of New Orleans (SWB), has a pumping capacity of more than 31.5 billion gallons per day. The system is designed to handle 1 inch of rain in the first hour and one-half inch per hour thereafter. The urban stormwater contains pathogens, as indicated by FC bacteria, and is the primary suspected source of the bacteria in the near shore waters along the south shore of the lake. It is believed that the effluent is contaminated by cross-flows from the sanitary sewers to the storm drainage system.
Because the runoff has a freshwater density and the lake is typically a brackish water body of greater density, the effluent usually behaves as a surface-buoyant plume. This means that the movement and spreading of the plume water initially is confined to the surface layers of the water column. The difference in buoyancy between the effluent and receiving waters increases the spreading action of the outfall plumes and modifies the mixing and dilution processes. Ideally, as the stormwater runoff is discharged from the drainage canals along the shoreline, it should behave like a jet propelling the discharge out of the nearshore waters and diluting the contaminated runoff by entraining the surrounding lake water to an extent sufficient to avoid pollution. Unfortunately, many of the outfalls along the south shore of the lake have discharge velocities that are insufficient to foster the momentum required to move the effluent away from the nearshore region and to provide adequate momentum mixing. In addition, the presence of ambient alongshore currents often produces narrow outfall plumes that travel along the shoreline resulting in inhibited spreading and dilution.
There is a great deal of concern regarding the discharge of urban stormwater runoff into marine recreational waters and its effect on water quality and the health of swimmers. Bacterial groups such as FC, Escherichia coli, and Enterococci are used as pathogen indicator organisms for evaluating risk to bathers. Complexities in determining water quality in recreational waters include a lack of understanding of the fate and transport of pathogen indicators in stormwater runoff discharges. In addition, laboratory analysis of water samples to measure indicator organisms is a 48-hour process that provides only a 2-day old “snapshot” of water quality conditions. As the indicator bacteria have decay, or die-off, rates that depend on water parameters such as salinity and temperature, and the stormwater runoff discharges have variable travel speeds and migration patterns dependent on the receiving water body, these snapshots rarely are representative of the bacterial environment when the laboratory data are reported. Thus, an early-warning forecasting model that predicts the bacterial water quality is required for decisionmaking regarding the safety of recreational waters.
Lake Pontchartrain, the receiving water body for the stormwater outfall discharges, is a highly dynamic system subject to complex hydrodynamics. There are two natural tidal passes and one manmade tidal pass with diurnal tidal signatures. The lake circulation patterns are dominated by wind shear. The salinity distribution in the lake varies as a result of saltwater inputs from the Gulf of Mexico through the tidal passes and freshwater inputs from diverted Mississippi River floodwaters, runoff from rural and urban watersheds through several river systems, and local streams, as well as seasonal precipitation and evaporation. Thus, the outfall plumes are subject to highly variable migration patterns.
The study of the water quality in the lake with emphasis on the south shore verified the presence of pathogen indicators and correlated the bacterial contamination to the stormwater discharges at four of the five sampling sites. It was found that these discharges typically impact recreational areas adjacent to the outfalls for a maximum period of 3 days. The water quality data also confirm very low dilutions of the effluent from the drainage canals. FC net attenuations (decay and dilution) were in the range of 6 to 10:1 at 30 canal widths from the outfall. The nutrient data, dissolved inorganic nitrogen (DIN), indicated a dilution of less than 4:1 at 30 canal widths from the outfall. A physical model study of thermal buoyant plumes discharged from a rectangular channel (with canal width:depth aspect ratios of 12:1 to 6:1) at 90 degrees to an ambient current confirmed these very low dilutions of approximately 4:1 at 30 canal widths. The study also produced field and laboratory data that were used to develop a forecasting system for assessing the risk level associated with recreational activities in the south shore waters after the occurrence of a stormwater pump event.
A three-dimensional hydrodynamic and mass transport model based on a modification of the Princeton Ocean Model was developed. The model consisted of a whole lake model and a high-resolution near shore model. Both model configurations included density currents due to temperature and salinity whereas the high resolution model had an integrated bacteria fate/transport sub-model. The model computes the pathogen indicator decay as a function of significant environmental factors (i.e., salinity, temperature, light intensity) and loss due to sedimentation. The decay relationships were developed based on laboratory and field data as well as literature relationships (Thomann and Muellen, 1987). The model was calibrated using the field and laboratory data as well as lake data from previous studies on Lake Pontchartrain. The model reasonably predicts FC concentrations as compared to field observations. The 2- to 3-day impact period associated with stormwater discharges was verified by the model as were the highly variable wind-driven plume migration patterns often characterized by shore reattachment as was observed in the field. The model is suitable for forecasting use as part of a recreational use management program for the south shore waters of Lake Pontchartrain in New Orleans.
The shoreline study field data established the frequency and extent of the bacterial contamination associated with such discharges at the five south shore sites. The lowest incidence of unsafe conditions occurs at Old Beach near Bayou St. John. The following “rule of thumb” was confirmed for safe primary contact activity in near-shore recreational waters adjacent to urban drainage canals: “such activities should be avoided for 2 to 3 days following a significant storm event.” The data also indicate that this is a site-specific problem that should be investigated at each area where lifting a swimming advisory is under consideration. The implied relationship between cross-flows and stormwater contamination, suggests that the ongoing efforts to upgrade the sanitary sewer system serving the metropolitan New Orleans area should yield long-term benefits for the south shore water quality, especially in terms of lower FC indicator levels. In terms of the nutrients measured during the shoreline study, DIN was found to be the most significant indicator of stormwater discharges. DIN also is useful in estimating dilution within the stormwater plumes as well as plume migration in this area. DIN was a good calibration variable for the predictive model.
The drifter-tracking, water quality grid-monitoring, and in-canal monitoring data were useful in calibrating and verifying the near-field model. Grid monitoring could be simplified by using a stationary grid positioned with more sampling points with a baseline at the mouth of the canals rather than using a moving grid. Measurement of water quality constituents that behave as tracers, such as DIN, should be part of the grid survey because this provides valuable information on dilution within the plume.
The field study indicated that the sediments were a significant source of bacteria. It is recommended that future modeling efforts should include a sediment transport component and wave model to simulate wave-induced suspension of the lake-bottom sediments.
The development of a 3-D hydrodynamic and mass transport forecasting model that can be used for beach management purposes, as well as to obtain general information on typical plume behavior under varying climatic conditions, was justified. If predictive models are to be useful for forecasting of bacterial contamination in the vicinity of the Inner Harbor Navigational Canal (IHNC), however, studies should be undertaken to identify the source at that site. The near-field model performs well in predicting FC plumes resulting from the stormwater discharges to the south shore area of Lake Pontchartrain. Field observations for FC in stormwater outfall plumes resulting from actual pump events indicate that the model-predicted FC concentrations are reasonable. The response of the plumes to varying wind and tide conditions also agrees well with field observations of migrating plumes. The model verifies the typical 2 to 3-day wet weather effect of stormwater discharges on recreational waters adjacent to the urban drainage canals. Utilization of the near-field model as a forecasting tool for primary contact use advisories at the south shore recreational sites would aid in the revitalization of this natural resource.
A sediment transport component and wave model should be incorporated into the forecasting model to simulate wave-induced suspension of the lake-bottom sediments that appear to be a potentially significant source of pathogens to the water column. For shore water quality modeling, a Supervisory Control and Data Aquisition (SCADA) system similar to that in Jefferson Parish would greatly enhance the forecasting capability of any model that is driven by stormwater runoff.
Supplemental Keywords:human health risk, pathogen indicator, modeling, neural network, hydrodynamics, primary contact recreation, plume tracking, bacteria kinetics,
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Water, TREATMENT/CONTROL, Scientific Discipline, Waste, Ground Water, Water Pollution Control, Wet Weather Flows, Municipal, Ecology and Ecosystems, Urban and Regional Planning, runoff, water quality, wastewater treatment, recreational water quality, water management, monitoring, storm water, sanitary sewer overflows, pathogens, storm drainage, stormwater, urban runoff, stormwater runoff, storm drainage systems, waste management, NPDES, municipal waste
Progress and Final Reports:
Original Abstract
Main Center Abstract and Reports:
R825427 Urban Waste Management and Research Center (University New Orleans)
Subprojects under this Center:
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R825427C001 Comprehensive Evaluation of The Dual Trickling Filter Solids Contact Process
R825427C002 Issues Involving the Vertical Expansion of Landfills
R825427C003 Deep Foundations on Brownfields Sites
R825427C004 Ambient Particulate Concentration Model for Traffic Intersections
R825427C005 Effectiveness of Rehabilitation Approaches for I/I Reduction
R825427C006 Urban Solid Waste Management Videos
R825427C007 UWMRC Community Outreach Multimedia Exhibit
R825427C008 Including New Technology into the Investigation of Inappropriate Pollutant Entries into Storm Drainage Systems - A User's Guide
R825427C009 Investigation of Hydraulic Characteristics and Alternative Model Development of Subsurface Flow Constructed Wetlands
R825427C010 Beneficial Use Of Urban Runoff For Wetland Enhancement
R825427C011 Urban Storm and Waste Water Outfall Modeling
R827933C001 Development of a Model Sediment Control Ordinance for Louisisana
R827933C002 Inappropriate Discharge to Stormwater Drainage (Demonstration Project)
R827933C003 Alternate Liner Evaluation Model
R827933C004 LA DNR - DEQ - Regional Waste Management
R827933C005 Landfill Design Specifications
R827933C006 Geosynthetic Clay Liners as Alternative Barrier Systems
R827933C007 Used Tire Monofill
R827933C008 A Comparison of Upflow Anaerobic Sludge Bed (USAB) and the Anaerobic Biofilm Fluidized Bed Reactor (ABFBR) for the Treatment of Municipal Wastewater
R827933C009 Integrated Environmental Management Plan for Shipbuilding Facilities
R827933C010 Nicaragua
R827933C011 Louisiana Environmental Education and Resource Program
R827933C012 Costa Rica - Costa Rican Initiative
R827933C013 Evaluation of Cr(VI) Exposure Assessment in the Shipbuilding Industry
R827933C014 LaTAP, Louisiana Technical Assistance Program: Pollution Prevention for Small Businesses
R827933C015 Louisiana Environmental Leadership Pollution Prevention Program
R827933C016 Inexpensive Non-Toxic Pigment Substitute for Chromium in Primer for Aluminum Sibstrate
R827933C017 China - Innovative Waste Composting Plan for the City of Benxi, People's Rupublic of China
R827933C018 Institutional Control in Brownfields Redevelopment: A Methodology for Community Participation and Sustainability
R827933C019 Physico-Chemical Assessment for Treatment of Storm Water From Impervious Urban Watersheds Typical of the Gulf Coast
R827933C020 Influence of Cyclic Interfacial Redox Conditions on the Structure and Integrity of Clay Liners for Landfills Subject to Variable High Groundwater Conditions in the Gulf Coast Region
R827933C021 Characterizing Moisture Content Within Landfills
R827933C022 Bioreactor Landfill Moisture Management
R827933C023 Urban Water Issues: A Video Series
R827933C024 Water Quality Modeling in Urban Storm Water Systems
R827933C025 The Development of a Web Based Instruction (WBI) Program for the UWMRC User's Guide (Investigation of Inappropriate Pollutant Entries Into Storm Drainage Systems)
R827933C027 Legal Issues of SSO's: Private Property Sources and Non-NPDES Entities
R827933C028 Brownfields Issues: A Video Series
R827933C029 Facultative Landfill Bioreactors (FLB): A Pilot-Scale Study of Waste Stabilization, Landfill Gas Emissions, Leachate Treatment, and Landfill Geotechnical Properties
R827933C030 Advances in Municipal Wastewater Treatment
R827933C031 Design Criteria for Sanitary Sewer System Rehabilitation
R827933C032 Deep Foundations in Brownfield Areas: Continuing Investigation
R827933C033 Gradation-Based Transport, Kinetics, Coagulation, and Flocculation of Urban Watershed Rainfall-Runoff Particulate Matter
R827933C034 Leaching and Stabilization of Solid-Phase Residuals Separated by Storm Water BMPs Capturing Urban Runoff Impacted by Transportation Activities and Infrastructure
R827933C035 Fate of Pathogens in Storm Water Runoff
R87933C020 Influence of Cyclic Interfacial Redox Conditions on the Structure and Integrity of Clay Liners for Landfills Subject to Variable High Groundwater Conditions in the Gulf Coast Region