ILLINOIS POLLUTION CONTROL BOARD
July 13, 1988
IN THE MATTER OF:
)
JOINT PETITION OF THE AURORA SANITARY
DISTRICT, THE CITY OF AURORA, AND THE
ILLINOIS ENVIRONMENTAL PROTECTION
)
PCB 85-224
AGENCY FOR EXCEPTION TO THE COMBINED
SEWER OVERFLOW (CSO) REGULATIONS
)
OPINION AND ORDER OF THE BOARD (by RC. Flernal):
This matter comes before the Board on a December 31, 1985
joint petition filed by the Aurora Sanitary District (“ASD”) and
the City of Aurora (“City”) (hereinafter collectively referred to
as “Aurora”) and the Illinois Environmental Protection Agency
(“Agency”) for exception to 35 Ill. Mm. Code 306.305 (a) and (b)
to relieve Aurora from the requirement to construct and operate
certain combined sewer overflow (“CSO”) transport and treatment
facil ities.
Hearing was held at the Aurora City Hall on March 6, 1986.
On June 6, 1986 Petitioners filed a Proposed Order (“Proposed
Order”). On June 20, 1986 the petition was remanded to the
Petitioners by Board Order. On March 27, 1987 Petitioners filed
an Amended Joint Petition (“Amended Pet.”). On July 1, 1988
Petitioners filed a Second Amended Joint Petition (“2nd Amended
Pet.”). No additional hearing has been held.
For the reasons described below, the Board finds that
Petitioners have made the showings requisite for granting the
relief requested. The relief will accordingly be granted,
subject to conditions as stipulated to by Petitioners and
consistent with the Board’s rules and regulations.
CSO REGULATIONS
The Board’s CSO regulations are contained in 35 Ill. Adm.
Code Subtitle C, Chapter I, Part 306. They were amended in R81—
17, 51 PCB 383, March 24, 1983. Sections pertinent to the
instant matter are Sections 306.305 and 306.361(a). Section
306.305 provides as follows:
All combined sewer overflows and treatment plant
bypasses shall be given sufficient treatment to
prevent pollution, or the violation of applicable
water standards unless an exception has been granted
by the Board pursuant to Subpart D.
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Sufficient treatment shall consist of the following:
a) All dry weather flows, and the first flush of
storm flows as determined by the Agency, shall
meet the applicable effluent standards; and
b) Additional flows, as determined by the Agency but
not less than ten times average dry weather flow
for the design year, shall receive a minimum of
primary treatment and disinfection with adequate
retention time; and
c) Flows in excess of those described in subsection
(b) shall be treated, in whole or in part, to the
extent necessary to prevent accumulations of
sludge deposits, floating debris and solids in
accordance with 35 Ill. Adm. Code 302.203, and to
prevent depression of oxygen levels; or
d) Compliance with a treatment program authorized by
the Board in an exception granted pursuant to
Subpart D.
Subpart D allows the discharger to file a petition for an
exception either singly, or jointly with the Agency as Aurora has
done. A joint petition may seek an exception based on minimal
discharge impact as provided in Section 306.361(a):
An exception justification based upon minimal
discharge impact shall include, as a minimum, an
evaluation of receiving stream ratios, known stream
uses, accessibility to stream and side land use
activities (residential, commercial, agricultural,
industrial, recreational), frequency and extent of
overflow events, inspections of unnatural bottom
deposits, odors, unnatural floating material or
color, stream morphology and results of limited
stream chemical analyses.
Pursuant to 306.361(a) Aurora and the Agency assert that
overflows from its combined storm and sanitary sewer system have
minimal impact on the water quality of, and do not restrict the
use of, the Fox River and Indian Creek (the receiving streams).
SUPPORT DOCUMENTS
Petitioners have presented several documents in support of
their petition. Included among these is a two—volume combined
sewer overflow study undertaken by Walter E. Deuchler Associates,
Inc. This document was attached to the Petition and Amended
Petition as Attachment A; it was also admitted as hearing exhibit
9 1—04
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1. Among other matters, the study contains analysis of impact of
the existing CSOs on the Fox River and the reduction of flow and
pollutant loads that can be expected from implementation of
several CSO options.
In response to concerns as expressed by the Board in its
June 20, 1986 Order, Petitioners commissioned and submitted a
study: “An Assessment of Indian Creek Bottom Sediments in the
Vicinity of Combined Sewer Overflow 25 in Aurora, Illinois”,
Illinois State Water Survey Contract Report 412, January 1987.
This report is Appendix G to the Amended Petition of March 27,
1987.
On January 28, 1988 Aurora completed a study, as an
amendment to its Municipal Compliance Plan, which provides an
update on relief sewer projects undertaken as part of the overall
CSO program. This report was submitted to the Board along with
the 2nd Amended Pet as Exhibit I.
BACKGROUND
The ASD provides wastewater treatment for Aurora, North
Aurora, Montgomery, Boulder Hill, and part of Oswego. Its
facility plan area encompasses portions of DuPage, Kane, Kendall,
and Will Counties. The population currently served by the ASD is
approximately 120,000, with a projected population for the year
2003 of 193,000 (R. at 12).
The ASD’S only treatment plant is located west of the Fox
River and south of Montgomery, Illinois. The plant provides
preliminary treatment, primary clarification, biological
oxidation and nitrification, tertiary sand filtration, and
chlorine disinfection. It has a design average flow capacity of
32 mgd, with a design maximum flow capacity of 68 mgd (R. at
12). Discharge is to the Fox River.
The City of Aurora has both combined and separate sanitary
sewer systems, while the remainder of the service area has
separate sanitary and storm sewers. The City’s combined sewers
serve approximately 4,360 acres (6.9 sq. mi.) of the
approximately 50 square miles served by the ASD (R. at 52, 89).
No new combined sewers have been constructed since 1937 pursuant
to a city ordinance (R. at 52).
The system has fourteen CSO overflow points (Amended Pet. at
3). Thirteen are located within the City and one is located at
the ASD plant. All of the discharges are directly to the Fox
River, with the exception of one City point which discharges to
Indian Creek. The overflows occur primarily at diversion
structures which serve to limit wet weather flow to the treatment
plant. Four of the City overflow points are considered major by
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the Petitioners because they collectively receive flow from more
than two thirds of the land areas within the City served by
combined sewers. These four points, plus the ADS treatment plant
overflow, account for 79 of the total overflow volume. The
remaining nine City overflow points are considered minor by the
Petitioners in that they collectively receive flow from less than
1/3 of the acreage served by the combined sewers and account for
only 21 of overflows (Id. at 3—4). The major City overflow
points are numbered 1, 4, 8, and 25; 1, 4, and 8 are located at
the Fox River at Rathbone Avenue, Hazel Avenue, and Benton
Street, respectively; CSO 25 is tributary to Indian Creek.
CONTROL AND IMPACT-REDUCTION OPTIONS
Aurora has investigated options by which it might moot the
need for the relief requested, or, in the alternative, minimize
the impact of its CSOs. Six options were considered, including:
(1) complete elimination of all combined sewers, (2) construction
of facilities necessary to achieve compliance under Section
306.305, and (3) four options
—
identified in the record as
Alternatives A, B, C, and D
—
which provide for progressively
greater reduction in the impact of existing CSOs.
Elimination of all exjsting combined sewers is estimated to
cost at least $160 million (Amended Pet. at 14).
Full compliance with Section 306.305 could be achieved by
providing the necessary treatment to combined sewer discharges.
The required facilities would include large storage basins at
four locations and several relief sewers to assure hydraulic
capacity for all first flush flow. Additionally, three treatment
facilities with a combined capacity of 51 mgd would be required
at the ASD plant to provide treatment for flows up to 10 x
average dry weather flow. The total cost of these facilities is
approximately $99 million (Amended Pet. at 14).
Petitioners contend that neither the complete CSO
elimination option nor the 306.305 compliance option is cost
effective (Amended Pet. at 4), and, moreover, that neither would
materially improve the water quality or enhance any beneficial
uses of the Fox River (R. at 15). Accordingly, Petitioners have
turned to the options which would at least reduce CSO impact.
Petitioners have opted to pursue and present to the Board
Alternative D, which provides the greatest impact reduction among
the four alternatives. Alternative D is designed to assure:
Control option cost figures cited herein are in 1986 dollars.
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1) Complete treatment of peak dry weather flow;
2) Complete treatment of up to 2.5 x average dry
weather flow;
3) Complete treatment of 57 of first flush; and
4) Complete or primary treatment of 65 of flows in
excess of 2.5 x average dry weather flow.
Amended Pet. at 5
Alternative D would conservatively2 also cause a 58.9 reduction
in CSO flows and a reduction in pollutant loads ranging from
50.1 for suspended solids to 77.5 for phosphate (Id. at 6).
At $22.25 million, Alternative D is the most costly of the
four impact—reduction options (Amended Pet. at 13—18). Among the
activities to be undertaken are sewer separations, addition and
replacement of sewer pipes, modification of siphon and weir
structures, re—routing of combined sewer flows, implementation of
inflow/infiltration reduction strategies, and elimination of one
CSO. Aurora has stipulated to carrying out these improvements,
and Petitioners request (Proposed Order at 1—2) that they be
listed in the Board’s Order.
Aurora additionally stipulates to a schedule for completion
of the improvements (Amended Pet., Appen. G, as modified in 2nd
Amended Pet.), and Petitioners request that this schedule also be
incorporated into the Board’s Order. However, the Board notes
that both the internal and final completion dates for all but two
of the many individual projects within the program are now
past. Presumably, therefore, all but two of the projects are now
complete. For this reason the Board will condition the grant of
relief only upon the agreed—upon final dates.
DOCUMENTATION OF MINIMAL IMPACT
Section 306.361(a) requires that Petitioners seeking a CSO
exception on the basis of minimal discharge impact, as is the
case here, make a number of showings. Pursuant thereto,
Petitioners provide the following information and observations:
2 Calculation of CSO impacts under Alternative D was made prior
to certain additional improvements made to the Alternative D
program at the Agency’s suggestion. The precise impact of these
additional improvements has not been determined, and is therefore
not reflected in the Alternative D impact figures (Amended Pet.
at 5, 7).
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Receiving Stream Ratios
The average discharge of the Fox River at Aurora is
approximately 1,810 cubic feet per second (“cfs”). The average
CSO flow rate from all City and ASD overflow points is 3.9 cfs,
or 0.20 of the average river discharge. Petitioners also
contend that pollution loading of the CSOs is small relative to
the load of the Fox River. In support thereof, Petitioners
present the following data:
CSO CONrRIBt7~ION
Total
After
Load
Prior to Alt. D
Alt. D
(tons/yr)
(tons/yr) Percent (Percent)
BDD
26,800
350
1.30
.40
Arrutonia—Nitrogen
530
16
3.02
.79
Nitrate—Nitrogen
3,550
2.1
.06
.02
Phosphate
710
1.9
.27
.06
From these data Petitioners concluded that “it is thus
apparent that the extremely low ratios of CSO flow and pollutant
loads to Fox River flow and pollutant loads assure that the City
and ASD CSOs have no significant impact on Fox River water
quality” (Amended Pet, at 7).
Indian Creek is an intermittent stream with a ten—year,
seven—day low flow of zero (Amended Pet. at 7).
Known Stream Uses
Petitioners report that a 1981 Northeastern Illinois
Planning Commission study listed the following uses for the Fox
River in Kane County:
(i) fishing;
(ii) canoeing;
(iii) other types of pleasure boating;
(iv) picnicking, fishing, hiking, etc., in public parks
along the shore;
(v) agricultural drainage;
(vi) “urban drainage” from commercial and residential land
along the river;
(vii) receiving effluents from several wastewater treatment
plants and overflow diversion structures.
Petitioners additionally point out that the Fox River in the
CSO study area is abutted for the most part by commercial and
residential properties (Amended Pet. at 8). They also note that
“Indian Creek is basically an urban drainage channel” for its
lower 3 to 4 miles, although in its upper reaches it receives
runoff from farmlands (Id.).
9 1—08
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Accessibility to Stream Side Land Use Activities
Regarding accessibility to stream—side land, Petitioners
note:
The combined sewer portion of the ASD service
area consists almost exclusively of residential and
commercial establishments. Agricultural land and
open space account for but a small fraction of
acreage abutting the river in the ASD service area.
Some light manufacturing plants and warehouses abut
the river in the southwest portion of the combined
sewer area. (Appendix A at p. 2—5). Exhibit 4 to
the CSO study details the riparian land use in the
CSO area. Generally, the river is not readily
accessible to the general public, with the exception
of boaters who use two designated “boat access areas”
in the City of Aurora.
Indian Creek is, for the most part, within the
Burlington Northern Railroad right of way and the
activities along the stretch both immediately
upstream and downstream of OVF. No. 25 can be
characterized as industrial.
Amended Pet. at 8—9.
Frequency and Extent of Overflow Events
The CSO study (Ex. 1) estimates that 1,187 overflow events
per year, with a total yearly flow of 914 million gallons,
occurred prior to implementation of Alternative D. Of these, 663
events and 568 million gallons were attributable to the major
overflow points 1, 4, 8, and 25. Full implementation of
Alternative D is expected to reduce yearly overflow events to 658
and total overflow volume to 375 million gallons, reductions of
44.5 and 59.0, respectively (Amended Pet. at 9; see also
footnote 2).
Inspections of Outfalls (Bottom Deposits, Odors, etc.)
Regarding inspections of unnatural bottom deposits,
Petitioners note:
In June, 1983, the Fox River was examined for
sludge deposits, sewer—related odors, sediment in
quiet portions of the river, and sewer—related impact
on vegetation. The purpose of the inspections was to
determine if CSO5 significantly contributed to sludge
deposits or adverse environmental impacts.
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The CSO study details inspection locations,
methods and results. (Appendix A at pp. 3—5 to 3—
11). To summarize, approximately 30 locations in the
river, including points upstream and downstream of
all CSO points, were examined for sediment depth,
color, texture and odor. At the same time depth of
water, the size of the stream—bed area examined, and
the amount and nature of floating debris, if any,
were noted. The inspections revealed that, with the
exception of the shoreline areas, most of the river
bottom is rock or gravel with no sludge deposits.
However, some sludge deposits were noted in low
velocity areas
——
i.e., near shorelines and
downstream of islands. Sewage—related odors were
detectable at a few small and localized areas near
CSO outfalls. Although a relatively large area of
sludge deposits was noted ~pstream of all CSO points,
no comparable deposits were found downstream of the
overflow points. The study concludes that there is
no correlation between the overflow points and sludge
deposits in the Fox River in the Aurora CSO areas.
(Appendix A at p. 3—11).
In addition to inspecting the river, the
contractor reviewed a 1978 NIPC study of sediment
oxygen demand in the Fox River. The study showed
varying sediment oxygen demands at five different
locations in the river. However, no relation between
sediment oxygen demand and CSO5 could be detected.
In fact, of the five sampling points, the highest
sediment oxygen demand was found upstream of all of
the overflow points. (Appendix A at pp. 2—5 to 2—8).
The Agency survey (Appendix D at p. 4) shows
black septic sludge at the site of overflow No. 25.
Further investigations reveal that the most severe
incidence of bottom deposits is limited to 500 or 600
feet downstream of the overflow.
As noted above, sewage—related odors were
detected in localized areas near a few CSO
outfalls. (Appendix A at 3—11). Odors are moderate
to severe near Overflow No. 25, but they can be
detected for some distance downstream (+500 ft.,) and
intermittently throughout Indian Creek.
No unnatural colors were noted in the course of
the river inspection. Floating debris was found in
several locations, but all floating materials noted
were unrelated to sewer overflows
——
the specific
items noted were tree branches, drums, tires,
cardboard boxes and pipes. (Appendix A at pp. 3—6 to
3—10).
9 1—10
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Rags, tissue paper, etc. were observed in brush
and log jams immediately below OVF No. 25 up to a
distance of approximately 200 feet downstream.
Amended Pet. at 9—11
Pursuant to concerns raised at hearing and to the Board’s
Order of June 20, 1986 Petitioners have caused further
investigation of CSO impacts on Indian Creek. In particular, a
study was undertaken by the Illinois State Water Survey and
reached the following conclusions (Amended. Pet., Appendix G at
9—10):
a) Indian Creek below overflow 25 exhibits some
benthic sediment degradation. However, this
degradation is relatively minor and is in line
with that of other streams receiving intermittent
combined sewage overflows or a steady flow of
well—treated effluent.
b) Benthos and phytoplankton productivity is low
both upstream and downstream of the outfall.
C)
The stream supports lush and extensive periphyton
growth. Sediment oxygen demand is contributed by
bottom—dwelling diatoms, iron bacteria
respiration, and ammonia oxidation. The latter
accounts for almost two—thirds of the sediment
oxygen demand in the outfall area, but none of
the sediment oxygen demand at a station above the
outfall.
d) Gross visual and aesthetic pollution due to
discharges from overflow 25 was not evident.
e) A reduction in the frequency and quantity of the
CSO probably would enhance downstream conditions.
Petitioners further note that the sediment oxygen demands of
Indian Creek are comparable to those of the Fox River (Amended
Pet. at 19), and that the impacts of overflow 25 appear to be
localized to the first 600 feet downstream of the outfall (Id.).
Stream Morphology
The condition of the Fox River through Aurora has been
described in a Northeastern Illinois Planning Commission 1981
stream use inventory as “natural” with scarce aquatic vegetation
and “fair to good” aesthetic appeal (Amended Pet. at 11). The
streamside vegetation was noted to be “mature forest/brush”
(Id.). Petitioners further note that the river is locally free
91—11
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of log jams and other accumulations of vegetative debris and that
the river substrate is rock or gravel; some channelization has
occurred in the highly—developed areas (Id. at 11—12).
Indian Creek has a relatively steep gradient and flows in a
series of riffles and pools (Amended Pet. at 12).
Stream Chemical Analyses
Aurora undertook a sampling of CSO water quality and
instream water quality during two storm events in 1981 (See Ex. 1
at 3—1 to 3—4 and Appendix B; Exhibit 10; Exhibit 11). From
these data Petitioners conclude that “there appears to be little
if any correlation between the combined sewer overflows and Fox
River water quality during and after rainfalls” (Amended Pet. at
13). No chemical analyses were conducted on Indian Creek because
the Petitioners “assumed that during the time overflow is active,
the creek would reflect basically degraded conditions” (Id.).
CONCLUS ION
The Board determines that Petitioners have shown pursuant to
35 Ill. Adm. Code 306.361(a) that exception to 35 Ill. Adm. Code
306.305(a), as it relates to first flush of storm flows, and to
35 Ill. Adm. Code 306.305(b) would produce minimal impact on the
receiving stream. Accordingly, the Board will grant the
exception. The Board further will accept the conditions as
agreed to by Petitioners in their June 6, 1986 Proposed Order as
modified in the Amended Petition of March 27, 1987 and Second
Amended Petition of July 1, 1988.
ORDER
Aurora Sanitary District and the City of Aurora are hereby
granted an exception from combined sewer overflow regulations 35
Ill. Adm. Code 306.305 (a) as it relates to first flush storm
flows, and to 35 Ill. Adm. Code 306.305 (b), subject to the
following conditions:
1. The City and District shall implement the following
system improvements:
a. Provide an additional 15” diameter connecting pipe
at overflow No. 1 located at Rathbone Avenue.
b. Modify the existing west siphon chamber at Hurd’s
Island to facilitate maintenance, and provide a
manhole at the bend in the interceptor just north of
the railroad bridge.
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c. Remove siphon over Western United Gas and Electric
Co. discharge tunnels and replace it with a 54”
diameter connecting pipe.
d. Re—route Basins 8 and 33 to the wastewater treatment
plant through the Waubonsie Interceptor.
e. Implement and maintain programmed maintenance on
critical areas comprised of overflows 1, 4 and all
the siphons.
f. Sewer separation upstream of overflow numbers 4, 8,
22 and 25 to reduce runoff into the combined
system. Additionally implement inflow—infiltration
reduction strategies in basins 24, 25, 26, 28, 29,
30 and 36.
g. Eliminate overflow number 6 diverting all flows from
tributary sub—basins into the Hazel Avenue
Interceptor.
h. Raise weirs 6” on overflows 5, 22, and 23 to
eliminate bypassing during small storms.
i. Perform sewer separation in a 60 acre tract
associated with the Transportation center project.
2. Improvements identified in paragraph 1 above shall be
completed by July 31, 1988, with the exception of:
a. 30—inch storm sewer along Plum Street in basins 24
and 25, which shall be completed by November 1,
1988.
b. Removing of storm inlets along Lake Street in Basin
29, which shall be completed by November 1, 1988.
3. The Aurora Sanitary District Treatment facility shall be
operated in accordance with the following provisions:
a. All flows received at the treatment plant must be
screened and metered.
b. All flows up to 74 million gallons per day (“MGD”)
must receive a minimum of primary clarification
prior to and during any occurrence of bypassing.
c. All flows up to 68 MGD must receive full treatment
prior to and during any occurrence of bypassing
ahead of or following primary treatment units.
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4. Aurora Sanitary District and the City of Aurora shall
conduct performance evaluation and reporting of the
improvements specified in this Order in accordance with
the Plan of Study appended to and which is hereby made a
part of this Order.
5. This grant of exception does not preclude the Agency
from exercising its authority to require as a permit
condition a CSO monitoring program sufficient to assess
compliance with this exception and any other Board
regulations and other controls, if needed, for
compliance, including compliance with water quality
standards.
6. This grant of exception is not to be construed as
affecting the enforceability of any provisions of this
exception, other Board regulations, or the Environmental
Protection Act.
IT IS
SO ORDERED.
I, Dorothy M. Gunn, Clerk of the Illinois Pollution Control
Board, hereby certify that the above Opinion and Order was
adopted on the
~
day of
____________________,
1988, by a
vote of
_________.
/7
/L/
(
2~”
Dorothy
~~tL
M~.JGunn,
7
P~
Clerk
Illinois ‘~ol1utionControl Board
91—14
