Pennsylvania Water Science Center



CHESTER COUNTY STUDIES

CONTACT FOR MORE INFORMATION

Kirk White
(kewhite@usgs.gov)

 

HISTORICAL TRENDS AND CONCENTRATIONS OF
FECAL COLIFORM BACTERIA IN THE BRANDYWINE BASIN,
CHESTER COUNTY, PENNSYLVANIA

This project was done in cooperation with the Chester County Water Resources Authority and the Chester County Health Department.


FINAL REPORT
USGS Water-Resources Investigation Report 01-4026 


NEED FOR THE PROJECT

Concentrations of fecal coliform bacteria in water samples collected from the Brandywine Creek from March to October at the three U.S. Geological Survey stream-water quality monitoring stations are consistently above 200 organisms per 100 milliliters, which is the bathing-water criteria established by the U.S. Environmental Protection Agency. The Brandywine Creek flows through the heart of Chester County and is widely used for recreation and drinking water. The aesthetic, recreational, and ecological health of the creek are degraded because of the high concentration of fecal coliform bacteria. Bacteria concentrations in stormflow are typically greater than in baseflow and during storm events can reach 50,000 organisms per 100 milliliters and higher.

Graph showing bacteria concentrations 1973-1999


PROJECT OBJECTIVES


DESIGN OF SAMPLING NETWORK

Fecal coliform bacteria were used as the primary indicator of bacterial contamination in this study because they were used in data collection from 1972-97, they are present in water when bacterial pathogens from fecal contamination are present, and they are present in higher concentrations than pathogens and so are easily detected. Fecal coliform bacteria are easy to culture and are typically harmless to humans. Escherichia coli (E. coli) bacteria were used as a secondary indicator of bacterial contamination. E. coli are found in smaller concentrations than fecal coliform bacteria and are more difficult to culture, but are a better indicator of the presence of intestinal pathogens that cause human diseases. E. coli samples were collected along with fecal coliform samples at selected sites.


SAMPLING NETWORK

A network of 40 sites was established in the Brandywine Basin for bacteria sampling. These stations were sampled at baseflow (low flow) in 1998 and both baseflow and storm flow in 1999. All stations were sampled for fecal coliform bacteria, and selected stations were sampled for E. coli bacteria.

Bacteria sampling network map


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