United States
Environmental Protection
Agency
Municipal Environmental Resean
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-81 -113 July 1981
Project Summary
Combined Sewer Overflow
Abatement Program,
Rochester, N.Y.—Volume I.
Abatement Analysis
Frank J. Drehwing, Cornelius B. Murphy, Jr., David J. Carleo, and
Thomas A. Jordan
CSO locations within the Rochester,
New York, Pure Waters District served
as the basis for network modeling
studies. The USEPA Stormwater
Management Model—Version II,
Simplified Stormwater Model, and
receiving water models were used to
evaluate various CSO pollution abate-
ment alternatives.
Nonstructural, minimal structural,
and structurally intensive alternatives
were defined and evaluated by these
models. The nonstructural approach
applied Best Management Practices
(BMP). Structural alternatives in-
volved evaluation of conventional
storage and treatment options. Cost
benefit analyses of all structurally
intensive alternatives were conducted
using optimum treatment process
train configurations developed from
pilot plant evaluations, as reported in
Volume II.*
Preliminary analysis of BMP and
minimal structural alternatives indica-
ted that by addressing the major
sources of pollution and by elimina-
ting throttling constraints within the
existing sewerage system, a substan-
"Combmed Sewer Overflow Abatement Program,
Rochester, N Y Volume II Pilot Plant Evaluations
F J. Drehwing, C B.'Murphy, Jr., S R. Carver, D F
Geisser, and D Bhargava EPA-600/2-79-031b
NTIS Order No PB 80-159 262 (also available from
the Storm and Combined Sewer Branch, MERL
USEPA, Edison, NJ 08837)
tial decrease in the total annual load of
contaminants to the receiving waters
from rainfall-induced CSO can be
achieved for relatively small capital
expenditures. These measures can be
initiated within a short period of time,
thereby immediately reducing pollu-
tion to the receiving waters, while
long term design and construction of
more structurally intensive alterna-
tives are undertaken.
This Project Summary was develop-
ed by EPA's Municipal Environmental
Research Laboratory, Cincinnati, OH,
to announce key findings of the
research project that is fully docu-
mented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
In response to the transient water
quality problems induced by periodic
overflows from the Rochester Pure
Waters District's combined sewer
system, a project was undertaken to
develop an abatement and manage-
ment program necessary to achieve a
cost effective solution to the CSO
induced impairment of the Genesee
River, Irondequoit Bay, and Lake
Ontario.
Other aims of the project were to
demonstrate the usefulness of mathe-
matical models (the Simplified Storm-
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water Model (SSM) developed by
Metcalf & Eddy, Inc., and the USEPA
Stormwater Management Model—
Version II (SWMM)) simulating both the
urban rainfall/runoff process and the
subsequent stormwater flows within a
large combined sewer system; present
the merits of implementing the BMP
program to abate CSO; and evaluate
source and collection system manage-
ment options.
The developed management program
(including the methodology of approach,
urban stormwater mathematical model-
ing, and abatement alternative analysis
that involved both structural and BMP
measures) lead to the formulation of a
master plan for CSO pollution abate-
ment within the Rochester Pure Waters
District.
Problem Definition
All programs adopted by Monroe
County for the Rochester Pure Waters
District are directed at meeting state
and federal water quality standards
established for the Rochester, NY, area.
These programs specifically address the
problem of receiving water quality
degradation due to urban storm runoff
and subsequent CSO. The study area
including the major receiving water
bodies, intercepting sewer network, and
significant overflow relief points are
shown in Figure 1.
Present CSO directly contravenes
established water quality standards for
the Genesee River, imposes heavy
nutrient and chemical loadings on
Irondequoit Bay, and causes bacterial
contamination of the public bathing
beaches along the Rochester Embay-
rrient of Lake Ontario. The latter has
resulted in periodic beach closing days
during the summer months.
Aside from such direct impacts as ob-
jectionable floating material and high
bacteria loadings, the settling of oxygen
demanding materials discharged during
overflow events contribute to contra-
vening stream standards in the lower
reaches of the Genesee River under dry-
weather conditions.
Previous studies of the District's
combined sewer system cited major
deficiencies in the existing sewer
system and identified the effects of CSO
on the area receiving waters.
Project Elements
The project was divided into three
basic elements: a CSO monitoring and
assessment program, a CSO mathe-
matical modeling program, and a pilot
plant demonstration program. The
monitoring and modeling programs are
described in detail in Volume I (summar-
ized here) and the pilot plant studies, in
Volume II.
As part of the overflow monitoring
program, an intensive CSO flow record-
ing and sampling system was imple-
mented to define the frequency,
volume, and pollutant characteristics
associated with the District's CSO dis-
charges. A drainage basin field
investigation was conducted to define
those basin parameters that affect the
urban stormwater runoff process.
These two programs provided the
necessary data sets, including repre-
sentative CSO hydrographsandpolluto-
graphs, drainage basin characteristics,
and sewer system inventory, to facili-
tate model calibration and verification.
Included in the modeling effort was the
refinement and verification of the
previously developed Genesee River
Water Quality Model.
The pilot plant program involved
designing and constructing a pump sta-
tion and pilot treatment facilities to
evaluate the effectiveness of eight unit
processes: high-rate flocculation/sedi-
mentation, swirl degrittmg, swirl
primary separation, high-rate dual-
media filtration, granular activated
carbon adsorption, high-rate disinfec-
tion using chlorine, high-rate disinfec-
tion using chlorine dioxide, and micro-
screening. These results were used to
develop process models and associated
cost effectiveness relationships.
Conclusions
1. A rigorous defining of the existing
system of CSO and stormwater
facilities is fundamental for devel-
oping an abatement program. This
definition includes identifying
major drainage basins, major
trunk and intercepting sewers,
and CSO and stormwater relief
points.
2. Installing and properly maintain-
ing overflow monitoring instru-
mentation are essential for both
receiving water problem defini-
tion and any subsequent sewer
network and water quality model
calibration and verification.
3. Collecting accurate rainfall data
and subsequent statistical
analyses, including defining the
design storm, are essential in
evaluating the response of the
existing system as well as the ef-
fectiveness of various abatement
alternatives.
4. Developing a methodology of
approach and defining applicable
abatement alternatives early in
the program will ensure that the
purpose of the study is not lost and
all data collection activities are
conducted according to the
required analyses.
5. SSM is capable of providing a
preliminary screening of potential
abatement alternatives involving
a balance between storage and
treatment.
6. SWMM can project the urban
storm runoff andquantitieswithin
acceptable confidence limits but is
presently limited in its ability to
simulate overflow quality.
7. Overflow quality can be better t
simulated by applying statistical *
techniques using actual moni-
tored overflow data.
8. The ability to abate CSO pollution
may require implementing
structurally-intensive facilities. In
Rochester, one structural alterna-
tive involves grit removal, in con-
junction with the optimized
operation of the F. E. Van Lare
Treatment Facility.
9. In many situations, significantly
reducing the total annual load of
contaminants discharged to
receiving waters because of CSO
can be reduced through minimal
structural improvements to the
existing sewer system. In
Rochester, minimal structural
abatement alternatives include
removing three throttling con-
straints, modifying or adjusting
overflow weirs and regulators,
and using inflatable dams for
increased in-system storage.
10. Implementing nonstructural
abatement alternatives (BMP)can
reduce the annual load of pollu-
tants discharged by CSO and A
stormwater. Implementing inflow fl
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restriction regulations(e.g., use of
porous pavement) in select areas
and more intensive street clean-
ing and sewer maintenance can
alleviate a portion of CSO induced
water quality degradation.
11. Based on projections using a
simplified mathematical storm-
water model, the nonstructural
and minimal structural abatement
alternatives are expected to
reduce significantly the existing
volume of CSO and the average
annual BODsand TSS loadings to
the Genesee River.
Recommendations
It is recommended that:
1. Network models, such asSWMM,
be relied on, mostly, for determin-
ing runoff and overflow volumes
for selected storm events and less
for estimating the quality of the
runoff. Use statistical analyses of
actual field monitored data to
estimate surface runoff quality.
2. Initial screening, planning, and
designing of storage and
treatment abatement alternatives
be made with a simplified
continuous simulation model to
avoid the prohibitive computer
costs associated with many de-
tailed hydraulic models. Use only
a model that will satisfy the ob-
jectives of a study at the least
possible cost.
3. Hydraulic analysis and design of
sewer systems be conducted with
a detailed network model such as
SWMM.
4. Rainfall characterization be
based, primarily, on the use of
historical precipitation data,
although the design storm ap-
proach may have to be applied in
certain situations. More research
should be conducted on the con-
cept of design storms to establish
design rainfall hyetographs that
could be applied with mathe-
matical network runoff models.
5. Models not be used to predict
runoff/overflow quantities or
qualities without proper field cali-
bration and verification. A rela-
tively detailed field monitoring
program is essential in providing
the background data for proper
model calibration and verification.
6. More statistical analyses be con-
ducted to better establish the
correlation between runoff quality
and parameters such as rainfall
and land use characteristics.
7. Detailed hydraulic analyses be
conducted to better define inter-
ceptor throttling constraints,
regulator/weir modifications, and
control structure locations.
SWMM is capable of providing the
required analyses.
8. BMP be considered when conduc-
ting any CSO abatement program.
In many instances implementing
BMP, possibly in conjunction with
minimal-structural alternatives,
can alleviate many problems
associated with frequent CSO
discharges. Failure to investigate
their effects could severely limit
establishing cost effective abate-
ment solutions.
9. A program be initiated to investi-
gate the effectiveness of in-
creased street sweeping on
reducing the pollutant loadings to
the sewer system. Include
provisions for correlating the
effects of increased street sweep-
ing operations, types of equip-
ment used, street parking use and
restrictions, and program costs for
reducing surface pollutants avail-
able for washoff during storm
events.
10. A master plan for CSO pollution
abatement be developed and
implemented that follows a
sequence of phasing of required
system improvements according
to their projected cost effective-
ness.
11. Scheduled reviews be included in
any CSO abatement program to
periodically evaluate the effec-
tiveness and cost/benefits asso-
ciated with alternative imple-
mentation. This periodic review
will ensure that previously
defined objectives are being met
and, if not, changes to the
program can be made to better
solve the initial problems.
The full report was submitted in ful-
fillment of Grant No. Y-005141 by
O'Brien & Gere Engineers, Inc., under
the partial sponsorship of the U.S.
Environmental Protection Agency.
6 U&QCNEftNMEHtmKnNaOFFICE W1 .T57-OU/7239
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Frank J. Drehwing, Cornelius B. Murphy, Jr., David J. Carleo, and Thomas A.
Jordan are with O'Brien & Gere Engineers, Inc., Syracuse, NY 13201.
Richard Field, Anthony Tafuri, and Lawrence Moriarty (retired) are the EPA
Project Officers (see below).
The EPA Grant Officer is Ralph G. Christensen (see below).
The complete report, entitled "Combined Sewer Overflow Abatement Program,
Rochester. N.Y.: Volume I. Abatement Analysis," (Order No. PB 81'-219 602;
Cost: $15.50, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officers can be contacted at:
Storm and Combined Sewer Section
Municipal Environmental Research Laboratory-Cincinnati
U.S. Environmental Protection Agency
Edison, NJ 08827
The EPA Grant Officer can be contacted at:
Great Lakes National Program Office
USEPA. Region V
Chicago, IL 60604
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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