Pathogen TMDL Assessment


Overview

As directed by the NY/NJ Harbor Estuary Program TMDL Oversight Group (OG), the Pathogen Work Group (PWG) has prepared a preliminary assessment of current conditions within the Harbor and how they relate to specific water quality standards. Also, as part of this work, an assessment is prepared to address what it would take to achieve these standards; that is, what are the overall percent reductions that would be required for compliance with these standards.

The assessment of current water quality conditions is performed using recent water quality data collected throughout the Harbor and through application of the calibrated PATH model developed by HydroQual. PATH is also used to assess the percent reduction requirements. Current conditions and the reduction requirements are assessed through categories of water body uses. Therefore, all results are divided into the following categories: recreational, shellfish direct harvest, and shellfish depuration. Additional analysis is also performed for designated beach areas. The following table shows the water use categories and the applicable water quality standards used in this analysis.

Category Pathogen Indicator
Enterococcus Fecal Coliform Total Coliform
Geometric Mean Maximum Geometric Mean 90th Percentile Geometric Mean 90th Percentile
Recreation 35 501 200 400 - -
Direct Harvest - - 14 49 70 330
Depuration - - 88 300 700 3300
Designated Beach 35 104 - - - -

Data Analysis

Data analysis is based on measurements collected in 2003 and 2004. The sources of data include the following agencies: Data analysis results show the 2003, 2004 compliance with the above standards. The sample locations and the number of observations at each location are given.

Model Analysis

Model results are shown for the calibration condition (Water Year 2003) and for a baseline condition using JFK 1988 rainfall condition. It is noted that 2003 represents a "wet" yearly rainfall condition and the baseline condition is representative of an "average" yearly rainfall condition.

For each parameter, a number of statistics are generated. In general, these statistics are as follows: These analysis are performed for the bathing season (May 15 through September 15) for the recreational standards and for the entire year for shellfish standards.

Special Beach Analysis

At the designated beaches, an additional analysis was performed to estimate the percent reduction required to reduce the frequency of enterococcus concentrations exceeding 104. That is, what percent reduction is required to have concentrations less than 104 achieved 90, 95, and 99 percent of the time. These results are in tabular format.

Component Analysis

An additional analysis was performed to give insight to what percent of the concentration of each pathogen indicator at any location is contributed by CSOs. The remainder of the contribution would be from stormwater.

Analysis of Yearly Loadings

The landside model RAINMAN was executed for a thirty one year period (1975-2005) to calculate total loads of pathogen indicator bacteria to the Harbor during bathing season for each year. These results are ranked to assess the relative severity of conditions that were analyzed in both the data and modeling analysis.

Organization of Results

All results, except for the special beach analysis and the analysis of yearly loadings, are displayed on maps of the Harbor. All maps are in JPG format and can be displayed on your screen. The maps may be printed or saved to your computer. The contents of the results are organized as follows.

Viewing Results

In order to view the results of these analysis, simply click-on the desired map from the list.

Note for Internet Explorer Users:After a few seconds, an "expansion button" will appear on the lower right corner of the image. Click-on this button to see the results more clearly. You will need to scroll up or down to see the entire study area. Also, there will be a tool bar in the upper left corner, which will allow the user to either print the image or save the image to a file.