Cooperator: City of Madison
Project Chiefs: Robert J. Waschbusch; Steven R. Corsi
Location: Madison
Project Number: 9KP32
Period of Project: January 2002−September 2004
Problem
The City of Madison, Wisconsin contains three lakes with over 20 miles of shoreline. For over 50 years, the Madison Department of Public Health (MDPH) has conducted weekly microbiological testing of the 13 beaches surrounding these lakes. The MDPH has developed beach-closing criteria based on testing results, combined with physical observations of conditions at the beach site. Traditionally the decision to close a beach has been communicated via posting of signs at the beach site as well as press releases. Since 1999, the MDPH has also posted a rating system on their web page to communicate beach conditions.
Although the MDPH has developed beach-closing criteria based on microbial indicators, there is a concern that the criteria may not reflect the actual risk to swimmers since the occurrence of pathogenic microorganisms during periods of high indicator levels has never been determined. The historic records demonstrate that bacterial indicator levels may vary significantly from one beach to another and from location to location within a beach with no apparent explanation for the differences. This variation confounds the beach closing decision-making process. There is a need to gather data to clarify the decision process.
Objective
The objectives of this project were to:
(1) develop a mathematical model that predicts the probability of high E. coli levels based on environmental data that can be monitored and reported in real-time,
(2) evaluate and implement a new sensitive analytical method for detecting E.coli 0157:H7,
(3) develop a model that estimates the risk of pathogen occurrence, and
(4) provide real-time, user-friendly, state-of-the-art water-quality information to the public, including education regarding recreational water-quality issues.
 Approach
Three public swimming beaches were selected for monitoring, one on each of the three lakes representing differing lake morphology and beach user levels. The three beaches selected were:
Vilas Beach: Lake Wingra; high user levels.
Olbrich Beach: Lake Monona; medium user levels.
Spring Harbor Beach: Lake Mendota; low user levels.
During the swimming seasons of 2002 and 2003, the three beaches were continuously monitored for numerous water quality, meteorological and physical parameters. City of Madison beach personnel recorded daily swimmer and waterfowl counts. Madison Department of Public Health personnel collected fixed-interval samples at each beach five days per week for indicator organism and pathogen analysis.
Custom-designed automatic water-quality samplers collected indicator organism and pathogen samples from 12 events at each beach. Events were defined as rainfall-runoff periods, high-turbidity periods, periods of high user counts or high wind/wave periods.
Progress (July 2003–June 2004)
The continuously monitored water quality, meteorological, physical data and indicator organism data were checked, compiled and used to develop probability-based models for real-time assessment of the risk of pathogen and high-level indicator organism occurrence. Although the indicator model significantly improved the prediction of high levels of E. coli the other model did not provide improved predictive ability for pathogen occurrence.
Plans (July 2004–June 2005)
Publication of the final report.
Reports
A final report entitled “Data Collection and Modeling of Enteric Pathogens, Fecal Indicators and Real-Time Environmental Data at Madison, Wisconsin Recreational Beaches for Timely Public Access to Water Quality Information” has been submitted for USGS and USEPA review.
|
