Combined Sewer Overflows and the Multimetric Evaluation of Their Biological Effects http://www.epa.gov/OST/NEW/cso.html
Combined Sewer Overflows and the Multimetric Evaluation of
Their Biological Effects: Case Studies in Ohio and New York
EPA-823-F-96-003
Summary
A new document entitled Combined Sewer Overflows and the Multimetric Evaluation of Their Biological
Effects: Case Studies in Ohio and New York is available from the U.S. Environmental Protection
Agency. This document reports on a project undertaken to measure the biological effects of combined
sewer overflows (CSOs). CSOs are discharges to surface waters of mixtures of untreated domestic
sewage, industrial and commercial wastewaters and stormwater runoff. Concern has grown in recent
years over the possible adverse ecological effects of CSOs.
Effects of CSO Discharges
Aquatic biological communities are exposed to many environmental stressors, which may include point
and nonpoint source pollution and habitat alteration or destruction. How the biological communities
respond to and integrate these impacts are often difficult to interpret. However, biological assessment
methods exist which are designed to evaluate and characterize biological integrity and to identify possible
causes of the biological impacts. One of these is an EPA method known as Rapid Bioassessment
Protocols (RBPs). RBPs include standardized procedures to assess the biological status and habitat
condition of streams, in comparison with minimally impacted steams of the same type. Habitat
assessments are conducted to determine if habitat degradation is a cause of biological impairment, alone
or in combination with water quality problems.
Case Studies
Two case studies were carried out in Ohio and New York, both of which have well-established biological
monitoring and assessment programs and which use methods similar in approach to RBPs. The
availability of historic data allowed comparison of results between studies. The report also explores
whether changes in level of effort, such as smaller sample sizes or a lower level of detail in organism
identification, affect assessment results.
This document is intended to provide information on potential applications of RBPs and biological
assessments. The document is aimed at State and local biologists and managers looking for tools to assess
the biological effects of CSOs and to help prioritize limited resources. Biological assessments have
applications in other watershed protection approaches such as stormwater monitoring, development of
biological criteria, the Total Maximum Daily Load (TMDL) process, and waterbody status reports.
Biological assessments are useful screen tools for identifying and prioritizing unpaired waters. Depending ,
upon how much data are available, biological assessments may provide an indication of causal
relationships between biological impairment and specific environmental stresses, such as habitat
degradation, toxic loading, and organic enrichment. Finally, they may be useful in assessing how effective
pollution control measures are in protecting aquatic life and biological integrity.
Additional Information
. Requests for this document should be sent to the U. S. Environmental Protection Agency, National
Center for Environmental Publications and Information. 11029 Denwook Road, Building 5 -Cincinnati,
05/22/97 09:37:43
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Combined Sewer Overflows and the Multimetric Evaluation of Their Biological Effects
http://www.epa.gov/OST/NEW/cso.htm
Ohio 45242 (513-489-8190), or by e-mail (Waterpubs@epamail.epa.gov). Please refer to the EPA
document number (EPA 823-R-96-002). For more information call Marjorie Coombs at 202-260-9821
(or via the Internet: coombs.marjorie@epamail.epa.gov).
Office of Science and Technology
EPA HOMEPAGE OFFICE Of WATER HOTLINES SEARCH
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