ILLINOIS POLLUTION CONTROL BOARD
august 4, 1988
IN THE MATTER OF:
)
JOINT PETITION OF THE CITY OF OTTAWA )
PCB 88—52
AND THE ILLINOIS ENVIRONMENTAL
PROTECTION AGENCY FOR EXCEPTION TO
THE COMBINED SEWER OVERFLOW (CSO)
REGULATIONS.
OPINION AND ORDER OF THE BOARD (by R.C. Flemal):
This matter comes before the Board on a joint petition filed
on March 21,
1988L
by the City of Ottawa (“Ottawa”) and the
Illinois Environmental Protection Agency (“Agency”) for exception
to 35 Ill. Adm. Code 306.305 (a) and (b) to relieve Ottawa from
the requirement to construct and operate certain combined sewer
overflow (“CSO”) transport and treatment facilities.
Hearing was held at the Ottawa City Hall on June 9, 1988.
No members of the public were in attendance.
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. 1~dm.
Code Subtitle C, Chapter I, Part 306. They were amended in R81—
17, 51 PCB 383, March 24, 1983. Sections pertinent to the
1 ~ Ill. Adm. Code 306.373 establishes a January 1, 1986
deadline for filing of CSO exception petitions. In a prior
proceeding, PCB 86—165, Ottawa, which had not yet been joined as
co—petitioner by the Agency, sought a variance from this
deadline. By Order of January 22, 1987 (75 PCB 66) the requested
variance was granted until July 1, 1987. Ottawa then moved the
Board to extend the deadline to October 1, 1987, which request
was granted (78 PCB 470). On September 21, 1987 Ottawa once more
moved that the deadline be extended. On October 29, 1987 the
Board established the filing deadline as February 15, 1988. This
notwithstanding, the Board accepted filing of the instant
petition at its March 24, 1988 meeting.
91—131
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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.
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 depr.ession 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 Ottawa 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) Ottawa and the Agency assert that
overflows from its combined storm and sanitary sewer system have
minimal impact on water quality, and do not restrict the use, of
the Fox and Illinois Rivers (the receiving streams).
9 1—132
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SUPPORT DOCUMENTS
Petitioners presubmitted several documents in support of
their petition. Principal among these is Exhibit 5, “C.S.O.S
—
Phase III, Water Quality Evaluation for the City of Ottawa”,
prepared by Robert H. Renwick and Associates, Inc., Ottawa’s
consulting engineers. Exhibit 5 summarizes information gathered
as part of Ottawa’s Municipal Compliance Plan (Exh. 1), Phase I
(Exh. 2) and Phase II (Exh. 3) of Ottawa’s CSO investigations,
and computer modeling of the CSO system (Exh. 4). Exhibit 5 also
presents various water quality evaluations, including results of
field studies, first flush determinations, and evaluation of
assimilative capacities of the receiving streams. Lastly,
Exhibit 5 considers various CSO control strategies.
At hearing Ottawa presented additional exhibits, including
copies of the presubmitted testimony of Ottawa’s Mayor George D.
Small and of its consulting engineers (Exh. 10, 11 and 12), and
responses (Exh. 13) to prehearing questions submitted by the
Board (Board Exh. I). Subsequent to hearing, Joint Petitioners
submitted supplemental information in response to matters raised
during the hearing (Exh. 14, 15, and 16) and a revised proposed
order (Exh. 17).
BACKGROUND
The City of Ottawa, which is the county seat of LaSalle
County, is located at the confluence of the Fox River with the
Illinois River, with the Fox River entering from the north.
Ottawa’s 1980 population was 18,176 and its corporate area
encompasses approximately seven square miles.
The Illinois River divides the city into two major
sections. These are the section north of the Illinois River
(“North ?~rea”), which contains the central business district, and
the section south of the Illinois River (“South Area”). In many
aspects of the Ottawa CSO situation, these two sections operate
as separate systems.
The former course of the Illinois and Michigan Canal also
extends through Ottawa. The water portion of the canal is now
abandoned and used as parkiand (R. at 57). The only waterflow
within the former canal within Ottawa is intermittent flow from a
storm sewer which enters the park near the western edge of Ottawa
(R. at 56).
Ottawa owns and operates a wastewater treatment plant. The
plant is located on the south bank of the Illinois River. It has
an existing capacity of approximately 4.5 MGD. The plant was
originally constructed in 1956 as a primary treatment plant, and
was upgraded to provide secondary treatment in 1969.
91—133
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Ottawa also owns and operates approximately 310,000 feet of
sewers, which includes sanitary, storm, and combined sewers.
Approximately half of the sewers were constructed prior to
1915. Several of the major industries located in Ottawa,
including Libby Owens Ford, U.S. Silica, and Borg—Warner, are not
connected to the city’s sewers (Petition at par. 1). Other major
industries and institutions, including Dr. Pepper Bottling
Company, Snap-On-Tools, Illinois Bell Telephone Company, and
Ottawa Community Hospital, do not contribute wastes to the sewer
system which might create hazardous or toxic conditions at CSOs
(Id.; Exh. 5 at 1—3).
Most of the sewers built prior to 1950 were combined. Since
that time Ottawa has undertaken steps to separate formerly
combined sewers. Nevertheless, at present approximately 50
percent of the sewered area remains on combined sewers (Petition
at par. 4); in general, combined sewers exist in and serve those
areas of Ottawa closest to the Fox and Illinois Rivers. A small
area of the Village of Naplate also contributes sanitary sewer
discharges to the Ottawa system (Exh. 13 at 1; R. at 38).
Under normal flow conditions all sanitary and combined sewer
flow is directed to the waste water treatment plant via a system
of interceptors and force mains. All flows from the North Area
are combined at the Walker Street pump station and pumped across
the Illinois River directly to the treatment plant. Flows from
the South Area are separately delivered to the treatment plant in
two lines (Exh. 5 at 3—7).
Combined sewer flows in excess of 4.5 MGD are diverted at
the treatment plant into three in—series storm water lagoons
(Exh. 7 at 4); no sanitary sewer flow is received by the lagoons
(Cx. 15 at 2). There the excess flows are subject to aeration
and sedimentation. Effluent from the third lagoon is blended
with treatment plant effluent and chlorinated before discharge
into the Illinois River (Id.). Ottawa calculates that the
percentage of storm water bypassed to the storm lagoons for a
design storm of 1.25 in/hr with a one hour duration is between
15 and 25 (Id. at 5).
Excess flow from the combined sewers enters the CSO system
via diversion structures located within manholes (“diversion
manholes” or “DMHs”). There is a total of 21 diversion manholes
in the Ottawa system. For the purpose of its CSO analyses,
Ottawa has divided the city into 10 regions, each of which is
given a number; regions 1—7 are located in the North Area and 8—
10 are located in the South Area (Exh. 5 at 3—5). Each DM11 is
identified by a two number code specifying its city region and
the sequence of the DM11. For the purpose of the CSO control
program, Ottawa has also divided the North Area into sections,
the Northeast Section which contains sewers whose CSOs are
9 1—134
—5—
tributary to the Fox River, and the Northwest Section which
contains sewers whose CSOs are tributary to the Illinois River.
Several factors introduce complexities into analyses of the
Ottawa CSO system. Among these are the substantial age of much
of the combined sewer system, and the attendant uncertainty of
records regarding the nature and location of sewer structures.
Additionally, in the 1930’s the level of the Illinois and Fox
Rivers was permanently raised by construction of the Starved Rock
Dam, which caused submersion of many of the sewer outlets. At
present, four of the CSO outfalls, 009, 014, 018, and 019, are
submerged 100 of the time (Exh. 13 at par. 5; R. at 51).
Although three of these have sluice gates to prevent river backup
into the sewer system (Id.), the submersion inhibits specific
observation of the frequency and magnitude of overflow events at
the actual overflow points.
Additionally, two of the outfalls, 007 and 008, have been
covered over during a construction project (Exh. 13 at par. 6).
Although Ottawa believes that these two still discharge by
percolation through the covering debris (R. at 52), it is
obviously difficult to accurately determine the quantity and
quality of the discharges from these outfalls. Existing, but
inaccessible, hydraulic connections between outfalls adds a
further complication (Exh. 13 at par. 6).
North Area CSOs
There are eleven existing CSO outfalls within Ottawa’s North
Area2, as follows:
Receiving Up—Sewer No. of
ID
Location
Stream
CSOs
DMHs
NORTHEAST SECTION
011 Main St. West
Fox
013, 014,
1
016, 017
013 East Madison
Fox
014,016,107
1
014 S. Guion St.
Fox
none
2
016 C. Superior St
Fox
none
1
017 E. Michigan St. Fox
none
1
018 r’lain St. East
Fox
none
1
2 Early documents in the instant record identify 12 CSOs in the
North Area. One of these, 010, was eliminated during a bridge
construction project in 1984 (Exh. 5 at 2—1).
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NORTHWEST SECTION
006
007
008
009
Riverview Dr.
East Island Ave.
S. Leland St.
S. Buchanon St.
Illinois
Illinois
Illinois
Illinois
none
006
006, 007
none
1
1
1
6
019 S. Chester St.
Illinois
none
Drainage areas directly tributary to individual CSO outfalls
range from 1.5 acres for 008 to 304 acres for 009; populations
range from 36 for 006 to 4,837 for 009 (Exh. 5 at 4—3). However,
because an individual sewer line may have successive diversion
points, it is possible for discharge originating in an up—sewer
area to be diverted into one or more down—sewer CSOs.
Ottawa calculates that the sewer system’s average dry
weather concentrations of BOD5 and suspended solids are 204 mg/i
and 120 mg/l, respectively (Exh. 5 at 4—18).
Ottawa undertook a modeling program, using the U.S.
Environmental Protection Agency’s SWMM3 model, to qu9tify the
magnitude of first flush produced by the design storm
.
An
initial run was made to determine the quantity and quality of
first flush at each of the seventeen diversion manholes. A
separate run was then made to determine the quantity and quality
of the first flush which is actually diverted to the receiving
streams. Results, as found at Exhibit 5, p. 4—39 and 4—40, are:
Volume (cubic feet)
Total Diverted
Diverted
Pollutants (lbs)
BOD
SS
NORTHEAST SECTION
014
1.2 in/hr with a 50 minute duration and
days without a storm event (Cx. 5 at 1—5).
preceded by at least 10
1
CSO
DM11
011
6—2
705
625
4
6
013
6—4
30,750
30,325
1,094
1,068
(014
3—1
3—2
Subtotals)
3,390
6,295
9,685
2,965
5,575
8,540
7
14
~T
28
122
150
016
3—4
305
135
1
1
017
3—5
90,805
82,135
1,011
1,147
018
7—2
740
655
5
9
SECTION TOTALS
133,990 122,415
2,136
2,381
91—136
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NORTHWEST SECTION
006
4—3
565
430
1
8
007
4—2
570
465
2
11
008
4—1
480
375
1
6
009
5—1
490
190
1
5
5—2
2,465
1,595
54
67
5—3
13,370
7,390
12
121
5—4
2,185
2,010
4
40
5—5
800
420
11
32
5—6
156,870 145,330
242
1,774
(009 Subtotals) 176,180 156,935
323
2,040
019
7—3
3,825
2,830
10
25
SECTION TOTALS 181,620 161,035
437
2,089
These data indicate that in the North Area the sewer system
currently captures and diverts to the treatment plant only about
10 of the first flush volume; capture percentage for first flush
BOD and suspended solids is on the same order (Exh. 5 at 4—39, 3—
40). The data also indicate that there is wide variation in both
the quantity and quality of the first flush at the various
diversion manholes and CSO outfalls.
Based on these data Ottawa characterizes three of the
diversion manholes as “major points of interception and overflow”
(Exh. 5 at 3—7). These are DM11 5—6, which contributes to outfall
009, and the diversion manholes which contribute to outfalls 013
and 017, respectively. Each has a first flush volume in excess
of 30,000 cubic feet for the design storm; each also has a
suspended solids load greater than 1,000 pounds. Ottawa further
characterizes the three outfalls, 009, 013, and 017, as appearing
“to have major flow and organic discharges during the design
storm” (Exh. 5 at 1—6; emphasis in original).
Ottawa further used the SWMM3 model to calculate the
quantity and quality of design storm flows beyond the first
flush, and equal in volume to ten—times dry weather flow, for
each the seventeen diversion manholes. The total volume of such
flows is 142,846 cubic feet, and the total BOD and suspended
solids loads are 136 and 743 pounds, respectively (Exh. 5 at 4-
44). The largest volumes and loads are associated with the same
diversion manholes and outfalls which have the largest first
flush volumes and loads.
91—137
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South Area CSOs
Ottawa’s South Area currently has three permitted CSOs:
Receiving Up—Sewer No. of
ID
Location
Stream
CSOs
DMHs
002 Allen Park
Illinois
003, 004
2
003 1st and Prospect Illinois
004
1
004 3rd and Van Buren Illinois
none
1
Outfall 002 has the largest directly contributing area at 171
acres, as well as the largest directly contributing population at
1,737 (Exh. 5 at 4—3). Additionally, because it lies down—sewer
from both 003 and 004, it can receive discharge from the direct—
contribution areas of these outfalls.
Of the South Area diversion manholes, the two contributing
to outfall 002 are characterized by Ottawa as “major points of
interception and overflow” (Exh. 5 at 3—10). However, neither
the diversion manholes nor the outfalls in the South Area were
monitored during the field data collection effort; similarly,
they were not involved in the first flush determinations. Ottawa
explains that:
the South side situation is interrelated to the
proposed Illinois Department of Transportation’s
Route 23 South improvement program. This Plan of
Study also identified a proposed interceptor to be
constructed to convey the Allen Park Overflow No. 002
to the treatment plant. All these factors were
evaluated and the decision by the City was approved
by the Illinois E.P.A. to not monitor or include in
the first flush determination these areas on the
South side of Ottawa. Exh. 5 at 3—11.
Construction of the Route 23 interceptor will cause
elimination of outfall 002 and the conveyance of its former
discharge to the treatment plant (Exh. 5 at Appendix 2).
CONTROL AND IMPACT-REDUCTION PROGRAM
General Alternatives
Ottawa has investigated alternatives by which it might moot
the need for the relief requested, or, in the alternative,
minimize the impact of its CSOs. Five alternatives were
originally considered. The principal elements and costs, as
outlined in Exhibit 5, are:
Alternative 1: construction of facilities necessary
to achieve compliance under Section 306.305, as
9 1—138
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outlined in the Municipal Compliance Plan, Exh. 1;
estimated project cost is $16.5 million with an
annual operation, maintenance, and replacement cost
of $605,000.
Alternative 2: capture of the full first flush at the
five most significant diversion manholes plus phased
sewer separation in the South Area; estimated project
cost is $11.5 million.
Alternative 3: capture of full first flush at the
three most significant diversion manholes plus phased
sewer separation in the South Area; estimated project
cost is $9.8 million
Alternative 4: phased sewer separation in both the
North and South Areas; estimated cost is $9.5
million.
Alternative 5: institution of an operation plan
designed to reduce CSO impacts using existing
collection and transportation facilities with minor
physical changes; estimated project cost is $1.4
million.
Proposed Alternative (Alternative 6)
Upon subsequent discussion with the Agency, Ottawa developed
Alternative 6, which is the alternative here recommended to the
Board by the Joint Proponents. Alternative 6 consists of a five—
part program. It combines the major elements of Alternatives 4
and 5 in that it includes both a sewer separation program and a
program of operations and minor physical modifications.
The principal component of the Alternative 6 plan is
separation of sewers in each of the CSO areas. Separation is
proposed to be undertaken in three phases, with the lineal feet
and sewer to be separated and the completion dates as follows:
Area
Phase I
Phase II
Phase III
Northeast
12,770
7,270
Northwest
5,650
5,650
South
900
6,650
3,380
Completion Date Dec. 1990 Feb. 1993 Sept. 1993
The second part of Alternative 6 consists of an operation
plan which would include, but not be limited to (Exh. 12 at 4):
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1) Regular sewer inspection to monitor the condition
and satisfactory functioning of all parts of the
system;
2) A routine maintenance and cleaning program for
all sewers, catch basins, pump station wet wells,
regulators, and other system appurtenances;
3) Scheduling regular operation of sluice gates on
overflows where rising river stages can create
system flooding with river water;
4) Identifying the hydraulic and storage capacity of
the total sewer system so these features can be
fully utilized during wet weather;
5) Other techniques to ensure the sewage system is
adequately maintained for optimum operation
capability.
Ottawa further asserts that a specific individual on the City
staff will be assigned the responsibility and given the authority
to set up and run this operational plan on a continuing basis.
The third part of the Alternative 6 consists of a program of
physical changes directed to the flood prone and other portions
of the sewer system designed to reduce or eliminate river water
intrusion and other identified major sources of inflow (Exh. 12
at 4—5). Anticipated changes include:
1) Bolt-down and gasketed water tight manhole covers
on all manholes where flooding or surface ponding
can occur;
2) Adjusting overflow weir heights to maximize
sewage diversion to the treatment plant
interceptor and prevent outfall sewer surcharges
backing into the interceptor;
3) Install sluice gates on overflows where rising
river stages can result in river water intrusion;
4) Sewer rehabilitation and replacement to reduce
inflow/infiltration and maintain system
integrity;
5) Inspect and direct all downspouts and yard drains
that can be disconnected from sanitary or
combined sewers and reconnect to surface drainage
or separate storm sewers; and,
91—140
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6) Other procedures and physical changes that will
help retain the available system capacity for
transporting the flows with the most pollutants.
Two final portions of Alternative 6 consist of provisions
for providing the Agency with an annual report of CSO—related
activities and monitoring of the effectiveness of the sewer
modifications projects (Exh. 12 at 5).
The total capital costs of the facilities to be constructed
under Alternative 6 is approximately $5.74 million. This
includes $5.44 million for the sewer separation portions and
$300,000 for the operation, maintenance, and modifications
portions (Exh. 12 at 6).
Alternative 6 Effects
Implementation of Alternative 6 will have a substantial
effect on the impact of Ottawa’s CSOs. Sewer separation alone in
the Northeast Sector will allow for capture of 99.5 of the first
flush (Exh. 5 at 4—56, 4—58; Exh. 13 at par. 11) as opposed to
less than 10 capture at present (Exh. 5 at 4—39, 4—40). First
flush to the Fox River would therefore be effectively
eliminated. Moreover, the two most significant CSO overflows to
the Fox River, 013 and 017, would essentially be eliminated (Exh.
12 at 7).
It is estimated that separation in the Northwest Sector will
cause a reduction in first flush discharged to the Illinois River
from that sector by approximately 20 to 25 over the present
approximately 90 discharge (Exh. 13 at par. 11). Collectively,
the sewer separations in the Northeast and Northwest Sectors
would cause a 54 to 57 reduction in first flush discharges from
the North Side (Id.).
The impact of implementation of Alternative 6 on the South
Area CSOs is less readily quantified because modeling studies
were not conducted for this area. However, the combined program
of Alternative 6, including the separation of over 11,000 lineal
feet of sewers should significantly reduce the number and volume
of CSO discharges reaching the Illinois River from the South Area
(Exh. 12 at 7).
Ottawa does not, at this time, propose to remove any
specific CSO from service. However, Ottawa does propose to
monitor the effectiveness of each of the various steps in
Alternative 6 and to report the results to the Agency (Exh. 12 at
5). Thereafter, removal of CSO outfalls will be undertaken where
feasible (Id..; Exh. 13 at 12).
Part of past problems with CSO discharges has been related
to the fact that 50 manholes which either had no lids or had lids
9 1—141
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with one or more pickholes were subject to flooding during
periods of high river levels. Since 1979 when this circumstance
was quantified, Ottawa has either installed or replaced a
majority of these manhole lids with lids having concealed
pickholes and a sealing gasket (Exh. 2 at par. 8).
Implementation of Alternative 6 will further this effort.
A subsidiary benefit of Alternative 6 is that it would also
alleviate the more critical areas of basement flooding in the
Northwest Sector (Exh. 12 at 7).
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:
Receiving Stream Ratios
Drainage areas of both the Fox and Illinois Rivers are large
at Ottawa, 2,658 and 10,949 square miles, respectively. River
discharges are correspondingly high: seven—day, ten—year low
flows are 250 and 3,200 cubic feet per second, respectively (Exh.
5 at 4—5). Ottawa observes that even under the present CSO
regime, this provides worst—case dilution ratios for the design
storm ranging from 4:1 to 47:1 for the CSO discharges to the Fox
River and 16:1 to 1690:1 for the CSO discharges to the Illinois
River (Exh. 14 at 1). With the significant reduction in CSO
discharges under Alternative 6, the dilution ratios would be
increased from these figures.
Ottawa modeled the impact on the two rivers of the
calculated BOD loadings of the design storm under the seven—day,
ten—year low flow conditions. Some oxygen depletion was noted
below the two large outfalls to the Fox River, 013 and 017, under
the present CSO regime. Ottawa observes:
However, the accumulated depletion of these two
significant sources on the Fox River does not lower
the D.O. concentration below 5.0 mg/I before the
combined flows reach the Illinois River where the
D.O. concentration quickly returns to above 7.0
mg/l. These D.O. values are within the allowable
water quality standards and suggest even these two
significant overflows on the Fox River can be
satisfactorily handled with a quick increase in D.O.
as the flows reach the Illinois River. All the
flows which reach the Illinois River via overflow
No. 009 have such little impact
...
(as to not change
the slope of the Illinois River’s D.O. curve.
Exhibit 5 at 4—45.
91—142
—13—
Implementation of Alternative 6 would eliminate 99.5 of the
first flush volume and 99.8 of the BOD currently discharged to
the Fox River (Exh. 5 at 4—56). Under these conditions, it can
be reasonably assumed that the assimilative capacity of the Fox
will be sufficient to produce a negligible DO impact even under
the worst—case conditions.
Known Stream Uses
The principal water contact activity in the Ottawa area is
water skiing, which is carried out on the Illinois River; the Fox
River is too narrow and shallow for water skiing (Exh. 3 at 9).
Fishing occurs on the Fox and Illinois River both from shore and
boats (Id.). There are no swimming areas or beaches on either
the Fox or Illinois Rivers in the vicinity of Ottawa (R. at 68).
Accessibility to Stream Side Land Use Activities
The Ottawa CSO outfalls are located for the most part in
fully developed residential, commercial, and recreational
areas. However, approximately half of the CSO outfalls are
located along steep rock bluffs and two are located in deep
ravines; access to these is generally limited (Exh. 3 at 9).
Among the CSO outfalls located along low—lying banks, two
are accessible only after a long hike (Exh. 3 at 9). Another,
014, is accessible only across private property which is posted
for no trespassing. Two of the sites, 002 and 018, are generally
accessible to children and shore fisherman (Id.)
Frequency and Extent of Overflow Events
Ottawa contends that due to the complex nature of the Ottawa
sewer system, the minimal impact of the CSOs on the receiving
streams, and the large costs for obtaining the data, that it was
not justified to do a detailed study of the frequency and extent
of overflow events beyond that revealed by the SWMM3 modeling (R.
at 58). The Agency agrees. Joint Petitioners therefore request
that the need to provide this information be waived pursuant to
35 Ill. Adm. Code 306.361(d) (R. at 70). The request is granted.
This notwithstanding, it may be noted that Exhibit 8
contains a computation of the rainfall intensity needed to
trigger an overflow for each of the 21 diversion manholes under
the current CSO regime. These range from 0.04 to 0.52 inches per
hou r.
Ottawa believes that Alternative 6 will significantly reduce
the frequency and extent of overflow events (R. at 61),
commensurate with the projected decreases in the overflow volumes
for the North Side CSOs and the decrease in the amount of
91—143
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combined sewers in both the North and South Areas. Ottawa
further proposes to conduct monitoring of the CSO system as the
various steps of Alternative 6 are completed. Results are to be
reported to the Agency (Exh. 12 at 5).
Inspections of Outfalls (Bottom Deposits, Odors, etc.
A Preliminary Stream Inspection (Exh. 3) was conducted in
February, 1987. This involved a physical inspection of the
Illinois and Fox Rivers and near stream property at each of the
14 existing CSOs to look for any sludge deposits, sewage related
odors, floating debris of sanitary sewer origin, and any other
visible sign of pollution. No evidence of CSO impact was
discovered at ten of the 14 CSO outfalls.
Of the remaining four CSO outfalls, two were discovered to
have a steady dry weather discharge. Ottawa asserts that the dry
weather flow at one of these, 002, was eliminated in April 1987
by raising the height of the diversion weir, as confirmed by
subsequent field inspection (Exh. 13 at par. 8; R. at 54).
Ottawa also asserts that preliminary plans to eliminate dry
weather flow in the second, 016, are being prepared and will be
included in bid letting for a sanitary sewer project in July 1988
(Exh. 11 at 4; R. at 54).
The remaining two, 011 and 017, will be substantially
impacted by sewer separation in the Northeast Section. At both
complete capture of the first flush will occur.
Although inspection of the CSO outfalls was conducted during
the winter, it is contended by Ottawa that an inspection during
warm weather would not have produced significantly different
results. As reasons thereto, Ottawa emphasizes the high scouring
velocities of the Illinois and Fox Rivers, and the fact that
Ottawa has not received any complaints of CSO discharges from the
many warm weather users of the rivers (Exh. 13 at par. 3).
Stream Morphology
All of the CSOs discharge to the main channels of the Fox
and Illinois Rivers, with the exception of outfall 019 which is
located in a slew off the Illinois River. Both rivers are
generally large and straight. Neither river is subject to log
jams or other naturally occuring vegetation debris in the Ottawa
area due to the relatively swift currents in the rivers (Exh. 3
at 8).
In general, the Illinois River in the vicinity of the CSO
outfalls has a bottom consisting of a thin layer (less than 3
inches thick) of silt, sand, and gravel over bedrock. Two
exceptions occur at 018 and 019: the bottom at the former
consists of three to four feet of silt and the latter discharges
91— 144
—15--
into a silty slough. The bottom on the Fox River consists of
silt, sand, and gravel deposits which are generally thicker than
those of the Illinois River (Exh. 3 at 8).
Stream Chemical Analyses
During its field investigation phase, Ottawa collected
sediment samples near each of the CSO outfalls for volatile
suspended solids (“VSS”) analysis. In most cases both upstream
and downstream samples showed VSS concentrations in the range of
0.3 to 15 (Exh. 3 at 9). Two outfalls, 002 and 016, showed an
exception to this pattern, with VSSs as high as 29 and 37.5,
respectively (Id.). Ottawa associates these high concentrations
with the dry weather flow found to occur at both outfalls.
Separation of sewers tributary to 002 and 016 should produce a
significant reduction in the quality and quantity of the
discharges.
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 Joint Petitioners in their Proposed Order as
modified in the Amended Petition of March 27, 1987.
ORDER
The City of Ottawa is hereby granted an exception from 35
Ill. Adm. Code 306.305 (a) as it relates to first flush of storm
flows and from Ill. Adm Cope 306.305(b) for combined sewer
overflows, to the Fox and Illinois Rivers, subject to the
following conditions:
1. The City will prepare an operational plan for and
make modifications to its sewer system, as
specified in the petition, by October 1, 1989.
Thereafter, an annual report detailing
performance of the specified activities will be
submitted to the Agency by January 31st of each
year.
2. The City will construct Phases I, II, and III of
its sewer separation program, as summarized below
and further described in Alternate 6 of the
petition:
9 1—145
—16—
a) Phase I, which consists of a total of
19,320 lineal feet of storm sewer
construction in the Northeast, Northwest,
and South Sectors, shall be completed by
December 1, 1990.
b) Phase II, which consists of a total of
19,570 lineal feet of storm sewer
construction in the Northeast, Northwest,
and South Sectors, shall be completed by
February 1, 1993.
C)
Phase III, which consists of a total of
3,380 lineal feet of storm sewer
construction in the South sector, shall
be completed by September 1, 1993.
3. Upon completion of each phase the City will
conduct flow monitoring for one season to assess
the effectiveness of the separation program and
report the results to the Agency. A plan of
study for each monitoring effort will be agreed
upon by the City and Agency. Where monitoring
indicates that an overflow may be safely removed
from service, the City shall do so according to a
mutually agreeable schedule.
4. The City shall eliminate the illegal sewer
connection near outfall 006 by November 1, 1988.
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.
Section 41 of the Environmental Protection Act, Ill. Rev.
Stat. 1985 ch. 111 1/2 par. 1041, provides for appeal of final
Orders of the Board within 35 days. The Rules of the Supreme
Court of Illinois establish filing requirements.
IT IS SO ORDERED.
Board Member J. Theordore Meyer concurred.
91—146
—17—
I, Dorothy M. Gunn, Clerk of the Illinois Pollution Control
Board, hereby certify that the above qpinion and Order was
adopted on the
~
day of
-~.~--1--
,
1988, by a
vote of 7~’
.
I
~
Dorothy N1.,~unn, Clerk
Illinois P~’llution Control Board
9 1—147
