United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 4-5268
Research and Development
EPA-600/S2-83-053 Sept 1983
Project Summary
Lawrence Avenue Underflow
Sewer System: Monitoring and
Evaluation
Louis Koncza, G. L Miller, and M. R. Quraishi
A bold concept in the design of urban
drainage systems was developed to
help solve combined sewer overflow
problems. A deep tunnel in bed rock61
to 76 m (200 to 250 ft) below the
surface was designed and constructed
for the Lawrence Avenue drainage
basin in Chicago. The tunnel also serves
as a reservoir for capturing small storms
and trapping a significant portion of
the first flush of pollutants from large
storms. The entrapped, combined sew-
age is pumped to the treatment plant at
the end of each storm. Flows and pol-
lutants to the Chicago River and treat-
ment plant from selected outfalls in
the Lawrence Avenue drainage basin
were monitored, and the U.S. Environ-
mental Protection Agency Storm Water
Management Model was calibrated
with the measured data. Performance
of the tunnel system in capturing flows
and pollution was evaluated with the
help of the calibrated model. Ground-
water monitoring was conducted for
preproject and postproject conditions,
and results were analyzed to assess
the influence (if any) of the deep tunnel
system on the underground aquifer.
The results of the study show that
the use of deep rock tunnels in con-
junction with a pumping station is a
very effective means of reducing the
spillage of combined sewer flows and
pollutants to the waterway. Use of
modern tunnel-boring machines has
improved the economics of this design
and installation is also less disruptive
to traffic and to the general public.
This Project Summary was developed
by EPA's Municipal Environmental Re-
search Laboratory. Cincinnati, OH, and
Region V, Chicago, IL, to announce key
findings of the research project that is
fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
Many of our cities are faced with pollu-
tion problems associated with combined
sewer overflows. Reduction or elimination
of these overflows (into the receiving
waters) requires some kind of storage and
treatment facilities, which can be quite
costly, particularly in large cities where
land is scarce. Construction of deep rock
tunnels to serve as main outlets for the
combined sanitary and storm flow offers
an attractive means of minimizing this
problem. The sewer, being below the river
level, provides storage and captures a
large portion of the pollution from com-
bined sewers. Disruption of streets, utili-
ties, sidewalks, etc., and interference with
commercial activity are completely avoided.
The planning, design, and construction of
such a deep tunnel by the City of Chicago
for their Lawrence Avenue drainage basin
was described in an earlier report (Law-
rence Avenue Underflow Sewer System,
Interim Report - Planning and Construc-
tion, EPA-600/2-80-124, U. S. Environ-
mental Protection Agency, Cincinnati, OH
1980). The present report describes the
monitoring of the combined sewer flows
to the Chicago River and the treatment
plant monitoring of the quality of ground-
water in the project vicinity, and evaluation
of the performance of the Lawrence
Avenue Underflow Tunnel System in re-
ducing overflows and pollution to the
waterway.
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Scope of Study
Chicago is located on a low plain adjacent
to Lake Michigan at the mouth of the
Chicago River nearthe Illinois-Indiana bor-
der. The City comprises about 544 km2
(210 miles2) and is part of a combined
sewer system of 971 km2 (375 miles2) in
the Chicago Metropolitan Area. Dry weather
flow from the City is treated at three
sewage treatment plants operated by the
Metropolitan Sanitary District of Greater
Chicago (MSDGC). These plants (the North
Side, West-Southwest, and Calumet) all
discharge their effluents into the Chicago
River System.
Storm and sanitary sewage is handled
by combined sewers feeding interceptor
systems leading to the various treatment
plants. These interceptor systems are gen-
erally designed to carry twice the normal
dry weather flow. During large storms,
runoff in excess of interceptor capacity
flows by gravity or is pumped to the river.
The City of Chicago has an ongoing pro-
gram of building relief sewers, known as
auxiliary outlet sewers, to augment the
discharge capability of the existing drain-
age system. This program was started
more than a century ago.
The Lawrence Avenue Underflow Sewer
System was designed in the late 1 960's
as part of the auxiliary sewer system. The
innovative design uses deep rock tunnels
for temporary storage as well as for con-
veyance of combined sewer flows. As the
first of its kind in the nation, this project
received a demonstration grant by the U.S.
Environmental Protection Agency (USEPA)
(then the Federal Water Pollution Control
Administration).
The objective of the early study was to
assess and demonstrate the effectiveness
of the Lawrence Avenue underflow sewer
system in reducing spillage of combined
flows and pollutants to the north branch of
the Chicago River. The following tasks
were implemented to accomplish this
objective:
• Preproject monitoring of the flows
and pollutants to the river and the
treatment plant from selected out-
falls in the Lawrence Avenue Sewer
System drainage area.
• Calibration of a computer program
(EPA's Storm Water Management
Model) with the data collected.
• Evaluation of the system perform-
ance for a variety of storms using
the calibrated simulation model.
• Implementation of a groundwater
monitoring program and evaluation
of the impact of the Lawrence Avenue
tunnels on the underground aquifer.
• Documentation of the actual operat-
ing and maintenance experience with
the Lawrence Avenue underflow
sewer system.
Findings
Study results show that the use of deep
rock tunnels in conjunction with a pumping
station is an effective means of reducing
the spillage of combined sewer flows and
pollutants to the Chicago River. Modern
tunnel-boring machines make this design
economically competitive with conven-
tional sewers and have the added benefits
of easy construction, no disturbance to
traffic, and minimal inconvenience to the
public. Specific findings include the fol-
lowing:
• The Lawrence Avenue underflow
sewer system reduces the combined
sewer overflow annual volume by84
percent for an average hydrologic
year. The annual mass load reduction
in spillage of BOD and suspended
solids into the waterway is 90 and
94 percent, respectively, compared
with the preproject condition for an
average hydrologic year.
• The Lawrence Avenue system does
not create any noticeable adverse
effect on the quality of groundwater
in the surrounding aquifer, and it
does not cause any pollution hazard
for the Wilson Avenue water tunnel.
• Recently improved technology in the
field of tunneling has improved the
economics of this method and prom-
ises certain advantages over large,
conventional, open-cut sewer con-
struction. The former involved little
interference with traffic, parking, and
commercial activity, minimal incon-
venience to the public, no risk of
accidentally disrupting the numerous
utility lines found in large cities, and
no surface restoration costs.
• Drilled tunnels using rock-boring
machines (moles) are relatively
smooth and need not be lined with
concrete if the rock is structurally
sound and impermeable to exfiltra-
tion of polluted water into the aquifer.
Such tunnels would save on lining
costs and increase the tunnel storage
capacity.
• To convey wet weather flow some
61 to 76 m (200 to 250 ft) from
high-level sewers to the deep tunnel,
an air-entraining dropshaft (Type E-
15) based on hydraulic model test-
ing at the St. Anthony Falls Hydraulic
Laboratory, Minneapolis, MN, was
used for the Lawrence Avenue sys-
tem. In actual operation so far, these
shafts have performed satisfactorily
for the Lawrence Avenue system and
other similar systems in Chicago.
• For larger dropshafts, the sloping
crown of the air collection chamber
requires huge excavations with as-
sociated high costs. The size of the
air chamber may be able to be re-
duced by venting air through a sep-
arate shaft wherever feasible. This
possibility was indicated by tests
carried out later at the St. Anthony
Falls Hydraulic Laboratory in con-
junction with development of drop-
shafts larger than 2.75 m (9 ft) in
diameter for the tunnel and reservoir
plan (TARP) for the MSDGC. In the
TARP design, a separately-vented
dropshaft is desirable for sizes 3.66
m (1 2 ft) or larger in diameter, and
the divider wall in the dropshaft is
thereby eliminated. This type of drop-
shaft (known as Type D-4) has a flat
roof in the air collection chamber that
contractors find desirable for han-
dling equipment. Construction costs
have been considerably less than for
Type E-15 shafts designed for com-
parable flows.
The full report was submitted in ful-
fillment of Grant No. S807116 by the
Department of Public Works of Chicago,
IL, under the sponsorship of the U.S.
Environmental Protection Agency.
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Louis Koncza, G. L Miller, and M. R. Quraishi are with the Department of Public
Works, Chicago, IL 60610.
Clifford Risley, Jr.. and Douglas C. Ammon are the EPA Project Officers (see
below).
The complete report, entitled "Lawrence Avenue Underflow Sewer System:
Monitoring and Evaluation," (Order No. PB 83-229 468; Cost: $ 16.00, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
Douglas C. Ammon can be contacted at:
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati. OH 45268
Clifford Risley, Jr.. can be contacted at:
Region V
U.S. Environmental Protection Agency
Chicago, IL 60604
ftUS GOVERNMENT PRINTING OFFICE 1983-659-017/7200
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