ILLINOIS POLLUTION C0~TR3L BOARD
January
23,
1986
IN THE MATTER OF:
SITE—SPECIFIC RULEMAKING
)
R85—l5
FOR
THE
SANITARY DISTRICT
OF
DECATUR,
ILLINIOIS
PROPOSED RULE~
FIRST
NDT1C6~
OPINION AND ORDER OF THE BOARD
(by
R.
C.
Flemal):
PROCEDURAL HISTORY
On May 31,
1985,
the Sanitary District
of Decatur
(“District”)
filed
a petition for site—specific rulemaking with
the
Board.
Specifically,
the District requests that
it be
granted exception from 35 IlL
Adm~Code 3O4~120(c), which
presently limits discharges from the District’s sewage treatment
works
to
10 mg/i of
five—day biochemical oxygen demand
(SOD5)
(STORET number 00310)
and 12 mg/i
of suspended solids
(STORET
number 00530).
In place of these limits,
the District proposes
that
its
discharge
be
subject
to
BOD5
not
to
exceed
20
mg/i
and
suspended
solids
not
to
exceed
25
mg/L
Hearing
was held
in this matter September
9,
1985,
at
the
Decatur Public Library~
At hearing the Illinois Environmental
Protection Agency
(“Agency”)
indicated
its support for
the
District’s
request,
and presented
testimony
to that effect.
A
statement favoring the District’s
request was also made by
Richard
3.
Lutovsky, President
of
the Metro Decatur Chamber of
Commerce~ No objections
to the District’s request have been
received
by the Board,
either at hearing or
through filings.
The
Illinois
Department
of
Energy
and
Natural
Resources
made
a
“Negative
Declaration”
of
economic
impact
in
this
matter
on
December
5,
1985,
noting
the
declaration
is
appropriate
based
on
the
statutory
criteria
in
Ill..
Rev~
Stat.,
Ch~ 92 1/2, par~
7404(d)(2).
The Economic Technical Advisory Committee concurred
in this determination
on December
6,
1985.
BACKGROUND
The Sanitary District of Decatur
is located
in Decatur
in
Macon County,
Illinois,
at the address
of
501 Dipper Lane,
Decatur,
Illinois 62522w
The wastewater treatment facility
is
located at mile point
126.4
on the Sangamon River
on the
southwest side of the City of Decatur, Illinois.
The District
provides sewage treatment service
to approximately 136,700
residents
in
the City of Decatur and adjoining areas, and
to
67-563
—2—
industrial customers which contribute 49.5
of the total
flow and
59.3
of the total organic
loading.
The City
of Decatur
is
served primarily by a combined sewer
system; however, more recent
additions and expansions are serviced by separate sanitary and
storm sewer
systems.
The District is presently engaged
in
a large—scale
facilities
improvement program.
Approximately $25 million of
construction was
in progress
at the time of filing of
the
petition.
The entire program, absent the requested relief,
is
estimated to cost approximately $147 million and
is scheduled
for
completion by December
1990.
Planned
facilities include:
bar
screens, grit chambers, circular primary clarifiers,
secondary
fiie—bubble aeration basins, circular secondary clarifiers,
nitrification fine—bubble aeration basins,
circular nitrification
clarifiers, effluent pumps, chlorination facilities,
sludge
return facilities, digested
sludge storage,
sludge land—
application equipment, and tertiary filters.
The District also
plans
to provide treatment of the first flush pollutants
at
five
combined sewer overflow locations
(Petition,
p.
10),
The United States Environmental Protection Agency (“USEPA”)
has reviewed the construction program and has approved and
committed to participating
in funding all major elements
of the
program except the tertiary filters,
The USEPA position is that
tertiary filtration
is not necessary to achieve Illinois’ water
quality standards,
and hence
it has deferred funding on this
matter
(R.
at 135).
Accordingly,
if the filters were to be
emplaced under present circumstances,
the cost would have
to be
borne
in full by the State and the District,
in approximately
equal shares
(R.
at
136),
Granting
of the requested
relief would
in fact allow the
District to exclude the proposed tertiary filters from its
construction program,
as well
as allow alternate design
of the
overall effluent pumping system.
In combination
it
is asserted
that these would
entail
a construction cost reduction of
approximately $9.2 million (Petition at
4;
R.
at
93,
100,
122),
$4.7 million of which would be savings directly to the residents
of
the District and the rest savings to the State
(R,
at
122),
The District would also realize an annual operations savings of
approximately $87,000 (Petition p.
4;
R.
at 93).
The saving
of
these sums constitutes Petitioner’s principal purpose for
requesting the desired
relief
(R.
at 93).
E~VIRO~MENTALIMPACT
Under normal conditions, effluent discharge from the
District’s treatment facilities constitutes
the primary flow in
the Sangamon River
at and below the District’s outfall,
This
condition exists
in part due
to the location of the outfall with
respect to Lake Decatur, which
is located approximately four
miles upstream from the outfall,
During prolonged dry weather
water
is retained
in the lake to maintain pool elevation, with
a
—3--
corresponding loss to downstream flow.
Thus,
the
30—day 10—year
low—flow downstream from the Lake Decatur
darn
is
0 cubic
feet per
second
(cfs)
during
all months except
April,
May,
and June,
when
it
is
75,
95,
and 63
cfs,
respectively
(Ex..
5,
Table
1),
Interest
in quality water
in the Sangamon River below
the
District’s outfall extends beyond
the mandate
of protecting
the
integrity
of
instream uses,
The Sangamon River also offers
the
potential for withdrawal
uses,
including use
as
a raw source for
domestic water,
At present,
the City of Springfield, which
is
located approximately
43 miles downstream,
is considering the use
of the Sangamon River as
an emergency supplementary source of
water
(Petition,
p.
8),
and other similar
withdrawal uses
are
possible.
The District asserts, and
the Agency concurs, that granting
of
the requested relief will
not prevent Petitioner from
complying with present water quality standards
in the Sangamon
River.
In 1982 the Agency,
along with the Illinois Department
of
Conservation and the United States Geological Survey, conducted
an intensive
field study and stream modeling of the Sangamon
River
in the reach between Decatur and Springfield.
Results have
been published
by the Agency
in a three volume report titled
Water Quality Assessment of a Major
Portion
of
Sanganion River
Basin, dated March
31,
1983,
and presented as Joint Agency and
Petitioner’s Exhibit L
A part
of this study addresses the
impact of the District’s outfall on
instrearn dissolved oxygen
(DO).
Specifically considered are six scenarios of varying
carbonaceous 30D5
(CBOD5) and ammonia nitrogen (~IH3—N)‘discharge
concentrations and their
impact on stream DO concentrations under
low flow conditions.
Three
of the scenarios are not germane
to
the instant matter because they consider NH3—~concentrations
substantially in excess
of that anticipated for the new District
facility.
The remaining scenarios consider three levels
of C3OD~
in accompaniment with an NH’~—Ndischarge of 1.5 mg/i,
The
latter
is the intended design level
of NH3—N discharge under
the
proposed
facilities improvement program.
The three CBOD5
concentrations are
10,
15,
and
20
mg/i.
Modeling
of
instrearn DO concentrations at the three specific
CBODç concentrations was accomplished using Qual
II,
a computer—
hasea model developed
by Water Resources Engineers and available
on the USEPA TYMNET system.
Model calibration was accomplished
using two sets of
field data collected during intensive diel
sampling periods
in mid—August and mid—September
of
1982.
In
addition, various
other field studies conducted between June and
November 1982 were relied upon to estimate time—of—travel and
reaeration values.
Sensitivity
analysis, combined with model
calibration, verification,
and recalibration,
suggested
to the
Agency that the model “could
be used with
a very high degree
of
confidence
to predict DO profiles within the study
area,
downstream from the DSD discharge,
for
a wide
range of flow
conditions
(40 to
400
cfs)”
(Joint Exhibit
1,
Vol.
I,
p.
3).
67-565
—4—
Field conditions
at the time
of
the
two
calibration
studies
were
significantly
different.
Several
days
prior
to
and
during
the
August
calibration
period there was
a sustained release of
water
of approximately 100
to 110 cfs over
the Lake Decatur
dam.
Several
days
prior
to
and
during the September sampling
there
was
no release other than leakage
at approximately
2.2
cfs.
Thus,
the September sampling approximates the worst case
condition
regarding
the
ability
of
the
District’s
discharge
to
be
assimilated
by
flows
in
the
Sangamon
River
(IL
at
22).
Model
results
indicate
only
small
differences
in
instream
DO
concentrations
at
the
three
differing levels of CBOD5,
In
particular,
using
the August
1982
calibration
the
maximum
difference
in DO concentrations between a
10 mg/l C8005 discharge
and
a
20 mg/i CBOD~discharge
is 0.2 mg/i, with most differences
being
0,1 mg/I
or
less (Joint Exhibit
1, Vol.
III,
Figure 32);
all absolute values are greater than or equal
to 7.2 mg/i DO.
Using
the September
1982 calibration the maximum difference was
0.7 mg/i with
no absolute values below the District’s outfall
less than 6.3 mg/i DO (Joint Exhibit
1,
Vol.
III,
Figure 33).
On
this basis
the District,
with
the concurrence of
the Agency, has
asserted that no violations of DO water quality standards* would
be occasioned
by limiting the District’s effluent
to
20 mg/l BOD5
(R.
at
40).
The
USEPA
has
contracted
an
outside
review
of
the
Agency’s
modeling effort
(Ex.
5,
Attachment
1),
which
review
is
generally
critical of the modeling.
Notwithstanding this fact,
the USEpA
has drawn conclusions which
support those of the Agency and the
District.
Specifically,
the USEPA concludes that during the
summer** an effluent discharge of 20.0 mg/i CBOD5
and 1.5 mg/i
N9~—Nis adequate
to maintain instream DO criteria
(Ex.
5,
p,IO).
They further
conclude that tertiary filtration, given
the
presence
of
nitrification,
is
not
necessary
to
achieve
a
030D5
of
20
mg/l
(Ex,
5,
p.10),
and
that
therefore
the
“proposed
tertiary
filtration
following
nitrification
is
not
supported
by
the
DO
water
quality
analyses
as
necessary
to
meet
the
DO
and
ammonia
criteria
and
to
result
in
significant
DO
improvement”
(Ex.
5,
p.
11).
It
is noteworthy that
the
assertion
of
no
violation
of
instream standards is based
upon ~H3—M effluent concentrations
not exceeding
1.5 mg/i;
at higher NH3—N discharges modeling
indicates below—standard DO concentrations at both calibrations
*Dissoived Oxygen
(STORET number 00300)
shall not be
less than
6.0 mg/i during at
least
16 hours of
any
24 hour period,
nor
leE
than 5.0 mg/i
at any time
(35 Ill.
.hdrn,
Code 302.206),
**The USEPA is silent
on
the matter
of recommending an exact
C3005 effluent limitation
for
the winter,
noting only that “thj
value should be based
on the expected CBOD5 removal
capability
facilities designed
to achieve
20 mg/l CBOD5 during warm weathe
(Ex.
5,
p.10).
67-566
—5—
for CBOD5
concentrations above
10 mg/i
(Joint Exhibit
1, Vol.
III, Figures
32 and
33).
This
is consistent with ammonia
concentrations exerting
a major control
on
instream DO.
The
Board also notes
that TJSEPA’s conclusion that tertiary filtration
is not necessary for the District to meet water quality standards
is predicated on
the assumption that the District will achieve
a
design effluent limitation of 1,5
rng/l
of
NI13—N
(Ex.
5, p.7).
For its part,
the District asserts,
and the Agency concurs,
that
it will meet the 1.5 mg/i NH3-N discharge condition upon
completion of
its plant improvements
(R.
at
39;
54).
Of
further note
is
that the District does not propose
to
operate
at
a full
20 mg/i BOD5 discharge all
of the
time..
Rather, under normal operating conditions
the BOD5 would be at
some lesser value
(R.
at
109),
This position
is supported by the
conclusion of the IJSEPA that nitrification plants
(as the
District’s
is proposed
to be)
in Illinois
and other States
consistently produce effluents with
a CBOD5
less than 10 mg/i,
and typically within the
range of
4—6
rng/l (~x. 5,
p.10).
In contrast
to exposition of
the environmental impact of the
proposed change
in BOD5,
there
is little
in the record which
focuses
on
the environmental impact of
the accompanying proposed
increase
in suspended solids discharge,
other
than as suspended
solids contribute
to oxygen demand,
The record does support that
increasing the BOD ceiling requires an attendant increase
in the
suspended solids ceiling,
since
it
is the suspended solids which
exert
a significant fraction of the oxygen demand
(R.
at
111).
But with respect to other impacts
the Record only notes
generalities regarding the effects of suspended solids and the
conclusion that
an increase
in loading from the District would
be
small compared
to the
typical background loading
(R.
at
110,
129).
The Board would welcome comments
on
this aspect of
the
proposal during the first notice comment period.
FIRST t~OTICERULE
Both
the District and the Agency assert that there would
be
no violation of water quality standards as
a consequence of
promulgation
of the requested site—specific regulation.
The
Board has
no
reason for disputing the likelihood of this
assertion.
However,
the Board does note that the foundation upon
which the assertion
is based
is that of modeling
of
a proposed
condition,
rather than monitoring
of
an actual
condition.
Models
are,
by their
nature,
subject to inherent uncertainties related
to such matters as
the degree
to which the model
faithfully
portrays complex natural interactions and
the degree to which
simplifying
assumptions are
justified.
The inherent uncertainties
of modeling are not sufficient
grounds for the Board
to reject
the District’s site—specific
request;
in the absence of
an ability to monitor
a future
condition,
the District has had
no recourse other
than
to rely on
the best available forecasting device
(i.e., modeling).
Nevertheless, the Board believes
it necessary to note that
failure of monitoring
results to bear out
the modeling studies,
67-567
—6—
and
attendant
failure
to
meet
water
quality
standards,
would
require the District to take such steps
as would
be necessary to
comply
with
the
appropriate
water
quality
standards
(re:
35
Iii.
Adm. Code 304,105).
The District should further
be
aware
that
these
steps might negate
the District’s ability
to exercise the
full
relief proposed herein.
Alternatively,
the District might
find
it necessary
to consider
some alternate technology
(e.g.,
instream aeration) which would allow water quality standards
to
be met.
The Board has considered whether
the proposed rule should
require
that
the
District
be
responsible
for
monitoring
instream
DO
concentrations.
However,
given
that
the
Agency
currently
operates
ambient
water
quality
monitoring
stations
downstream
from
the
District’s
outfall,
and
that
DO
monitoring
is
a
standard
operational
procedure
at
these stations, the Board refrains at
this
time
from
imposing
this
seemingly
duplicate
effort
on
the
District.
The
Board
does
request
that
the
District
and
the
Agency address
the appropriateness of this course
of action
during the
first notice comment period.
The Board does note
the dependency of instream DO
concentrations on the levels of Decatur’s NH3—N discharge, and
therefore proposes that the requested exception be applicable
only when the modeled level of NH3—N,
namely 1.5 mg/i,
is
actually achieved.
The record does not address whether
this
stricture
is necessary only during warm weather,
or
whether
it
might be relaxed during cold weather.
In the absence of further
information,
no distinction between appropriate warm and cold
weather limitations can
be made by the Board
at this
time..
The
Board will welcome comments on this matter during the first
notice comment period.
The Board also notes
that there
is little distinction made
in the record between CBOD5 and BOD5,
In particular,
all the
modeling
is based
on CBOD5, hut the proposed regulation
is
presented in terms of BOD5 without comment as
to the significance
involved
in how these measures differ.
Since it
is generally
considered that the CBOD5
of
a given effluent will be lower than
the simultaneously measured BOD5
(e.g.,
Ex..
5,
Table
2),
and the
model
results place the apparent necessary ceiling on CBOD5
at 20
mg/i,
a BOD5 limit
of
20 mg/i would appear
to represent
a
conservative request.
Alternatively,
it may be that Decatur does
not need relief
to
a full
20 mg/i
of BOD5.
For purposes
of first
notice the Board
is retaining the District’s proposal for
a 20
mg/l limit expressed as
BODE.
However,
the Board requests that
the District and the Agency address the appropriateness
of this
number during the first notice comment period.
An additional matter
of concern to the Board is the
permanency of
the rule
as offered by the Proponents.
It
is
readily possible
to imagine situations where
a rule fully
justifiable and rational
at
a given point
in time may not
continue
to be so
at
a future date,
In the instant matter, but
by
no means peculiar
to
it,
would
be
a situation where future
dischargers
to the Sangamon River find that their
increment
of
67-568
—7—
discharge induces DO violations
in the River,
but
that the
violations
would not exist
in the absence
of
the exceotion
granted to
the District.
The
record does support the conclusion
that the District’s exception would utilize
a portion
of the
River’s capacity
to assimilate oxygen—demanding wastes
(R.
at
50),
a capacity which would
then not
be
available
to
a future
user.
The
Board questions whether
this circumstance could
lead
to
an
inequitable
and possibly
illogical distribution of the
spoils
(and conversely
the burdens)
of environmental regulation.
Admittedly
the problems
associated with the permanency of
a
rule
can
be challenged by
a counter—proponent who at
a future
date offers
an alternative rule which partially
or
in total
reverses
an existing site—specific
rule.
However,
this places
th.e
burden
on
a party other
than the holder
of the exception.
The Board believes
a more appropriate procedure
is
to require the
holder
of the exceotion
to bear the burden of justification
for
continuing
the exception.
Among other
situations
is
the
oossibility that
.a future
change
in treatment technology,
or,
in the alternative,
a change
in technical
or scientific understanding of
the dynamics of
water
quality,
would reflect negatively
on the exception granted
to
the
District.
The Board cannot
~eterrninethat any such changes
will
occur, but neither can
it definitively say that
they will not,
Given
that the history of environmental management
has witnessed
many such changes,
the prudent posture may be
to limit the
operation
of
an exception
to
a specific
time interval,
after
which
a reconsideration may be undertaken.
Lastly,
as
a general
position,
the 3oard
is
concerned about
the proliferation of site—specific rule oroposals.
While
the
3oari
fully intends
to continue
to
review each
on
its individual
merits,
the Board
is concerned
that the trend will eventually
lead
to an edifice of patchwork site—specific rules,
some of
which will inevitably become obsolete and others which will lose
their
justification with
time.
This situation obligates future
society with
the need
to regularly house clean already cumbersome
regulations.
Accordingly,
the Board believes that there may he
merit
in considering
“sunset” provisions
as
a feature
in site—
specific
rulemakings.
The Board would welcome comment on
the
inclusion of
a sunset provision
in site—specific rules not only
from the participants
in the instant matter,
but from interested
persons
in general.
The Board specifically requests comment
regarding
the effects
of
a sunset provision on federal funding
programs and capital funding costs.
In view
of the above,
the Board proposes,
as
an addition
to
Proponent’s
requested language,
that the rule be limited
to
ten
years
from the date
of completion of
the facility improvements.
In
as much as the District proposes
to complete the second and
final phase
of
its improvements
as
of December
1990
(Petition,
p.12),
the termination date
is set
in the
first notice order
at
December
31,
2000.
Inclusion of this provision in the final
rule
would
not negate the District’s ability
to petition the Board,
prior
to expiration of
the rule,
for
a repromulgation of
a
67-569
—B—
similar
or
identical
rule
justifiable
in
the
context
of
conditions and knowledge
then existent.
A ten year exception
should provide a sufficiently long period
for observation and
study
so that
a well—informed decision on
the continuing merits
can then be made.
ORDER
The Board
hereby adopts
the following rule
for First ~otice
arid
instructs the Clerk
of the Board
to file this rule with
the
Secretary of State:
TITLE
35:
ENVIRONMENTAL PROTECTION
SUBTITLE
C:
WATER POLLUTION
CHAPTER
1:
POLLUTIOt’~CONTROL BOARD
PART
304
SITE—SPECIFIC RULES AND EXCEPTIONS
NOT OF GENERAL APPLIC~BILITY
Section 304.212
Sanitary District of Decatur Discharges
a)
This Section applies only
to effluent discharges
from
the Sanitary District
of Decatur’s Sewage
Treatment
Plant
into
the
Sangatuon
River,
Macon
County,
Illinois
and only during such times
as
ammonia nitrogen
asN
(STORE’T 00610) discharge from
said
plant
is less
than
or equal
to 1.5 milligrams per liter.
b)
The provisions of Section 304.120(c)
shall
not apply to
said discharges,
provided that said discharges shall
not
exceed
29 mg/i of five day bioche~ica1oxygen
demand
(3005)
(STORET number 00310)
and
25 mg/i
of
total suspended solids
(STORET number
00530).
C)
The
provisions
of this section shall
terminate on
December
31,
2000.
IT IS
SO ORDERED,
Joan
Anderson
and
J.
Theodore
Meyer
concurred.
I, Dorothy
M, Gum, Clerk
of the Illinois Pollution Control
Board,
hereby certify that the
above Proposed Rule/~irstNotice
Opinion
and
Order
was
adopted
on
the
~~-~&day
of~~7
1986, by
a vote
of
7—c’
//
/
Dorothy
M.
~unn,
Clerk
Illinois
Pollution
Control
Board
67-570
