United States
Environmental Protection
Agency
Office of Air
Land and Water Use
Washington DC 20460
EPA-600/9-78-019
July 1978
Research and Development
&EPA
Proceedings
Stormwater Management
Model (SWMM)
Users Group Meeting
May 4-5, 1978
Miscellaneous Reports Series
-------
EPA-600/9-78-019
May 1978
PROCEEDINGS
STORMWATER MANAGEMENT MODEL (SWMM)
USERS GROUP MEETING
4-5 MAY 1978
Project Officer
Harry C. Torno
Office of Air, Land, and Water Use
Office of Research and Development
U.S. Environmental Protection Agency
Washington , D.C. 20460
OFFICE OF AIR, LAND, AND WATER USE
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON , D.C. 20460
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CONTENTS
Page
Number
Foreword
Abstract iv
STORMWATER MANAGEMENT DEMONSTRATION STUDY IN ST. THOMAS,
ONTARIO, W. G. Clarke, W. L. Knowles and R. W. Kuzyk 1
APPLICATION OF SWMM-EXTRAN FOR THE ANALYSIS OF EXISTING
URBAN DRAINAGE SYSTEMS, C. W. Eicher 31
CSO FACILITIES PLANNING USING A MACROSCOPIC MODEL, J. A. Lager,
E. J. Finnemore and G. B. Otte 49
STORMWATER MANAGEMENT MODELING AND LAND DEVELOPMENT PROJECTS,
P. E. Wisner 66
APPLICATION OF STORM TO ASSESS THE IMPACT OF AN URBANIZING
AREA, C. Brcic 85
METHODOLOGY FOR CALIBRATING STORMWATER MODELS, T. K. Jewell,
T. J. Nunno and D. D. Adrian 125
A SIMPLIFIED CONTINUOUS RECEIVING WATER QUALITY MODEL, M. A.
Medina, Jr. 174
USE OF THE HYDROLOGICAL ENGINEERING CENTER STORAGE, TREATMENT,
OVERFLOW RUNOFF MODEL - 'STORM' FOR SEWER INFLOW REMOVAL/
TREATMENT COST EFFECTIVE ANALYSES IN THREE SELECTED LOCALITIES,
R. T. Prosser and H. M. Shapiro 209
VERIFICATION AND CALIBRATION OF THE ILLINOIS URBAN DRAINAGE
AREA SIMULATOR (ILLUDAS), F. I. Lorant and C. Doherty 228
List of Attendees 242
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FOREWORD
A major function of the Research and Development programs of the
Environmental Protection Agency is to effectively and expeditiously transfer,
to the user community, technology developed by those programs. A corollary
function is to provide for the continuing exchange of information and ideas
between EPA and users, and between the users themselves. The Stonnwater
Management Model (SWMM) users group, sponsored jointly with Environment
Canada/Ontario Ministry of the Environment, was established to provide such
a forum.
This report, a compendium of papers presented at the last Users Group
meeting, is published in the interest of disseminating to a wide audience
the work of Group members.
T. A. Murphy
Deputy Assistant Administrator
Office of Air, Land and Water Use
111
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ABSTRACT
This report includes nine papers, on various model-rel ated
topics, delivered at the semi-annual Joint U .S .-Canadian Storm-
water Management Model (SWMM) Users Group Meeting, held
4-5 May 1978 in Ottawa, Ontario, Canada.
Topics covered include descriptions of applications of
the SWMM and of STORM (Storage, Treatment Overflow Runoff Model)
in planning, design and infiltration/inflow analysis, a verifi-
cation study of the Illinois Urban Drainage Area Simulator
(ILLUDAS), presentation of a new continuous receiving water
model which can be linked to SWMM and STORM and a paper
describing combined sewer overflow facilities planning using
a macroscopic model.
IV
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DISCLAIMER
This report lias been reviewed by the Office of Air, Land and Water
Use, Office of Research and Development, U.S. Environmental Protection
Agency, and approved for publication. Approval does not signify that the
contents necessarily reflect the views and policies of the U.S. Environ-
mental Protection Agency, nor does mention of trade names or commercial
products constitute endorsement or reconmendation for use.
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STORMWATER MANAGEMENT DEMONSTRATION
STUDY IN ST. THOMAS, ONTARIO
by W. G. Clarke1, w. L. Knowles2, R. W. Kuzyk3
INTRODUCTION
The various research programs in stormwater management
technology conducted by the Urban Drainage Subcommittee
of the Canada/Ontario Agreement on Great Lakes Water
Quality have been on-going for a number of years. As an
outgrowth of the Subcommittee's work, this study was spon-
sored by C.M.H.C. to demonstrate the practical application
of stormwater management and computer modelling to a
representative drainage problem. As a demonstration study,
it was very comprehensive, including the application of
modelling"techniques to flood relief? pollution abatement
and receiving water response. The principal objectives
of the study were:
1) To demonstrate a comprehensive systems approach to
stormwater management applications employing
modelling techniques
2) To evaluate alternatives and determine the optimal
plan for both flood relief and pollution abatement
in the study area
1. W. G. Clarke, B.Sc., P.Eng., Project Engineer, James
F. MacLaren Limited
2. W. L. Knowles, M.A.Sc., P. Eng., Project Director,
James F. MacLaren Limited
3. R. W. Kuzyk, M.Sc., P. Eng., Project Manager, James
F. MacLaren Limited
-------
As a demonstration study, the techniques employed were
to be readily applicable to -other locations. Accordingly/
a considerable portion of the study was devoted to the
development and discussion of new analytical techniques
and adapting existing methods for this purpose. It is this
aspect of the study which will form the basis of this paper.
The Study Area
The City of St. Thomas has a population of 27,000 and is
located on Kettle Creek in Elgin County in southwestern
Ontario (see Figure 1). The total area of 1841 hectares
is 44% residential, 14% industrial, 6.5% commercial and
the remaining 35.5% is open space.
The majority of the storm drainage from the City is conveyed
to Kettle Creek or its tributaries via a system of com-
bined sewers, separated storm sewers and natural channels.
When tributary flows to the treatment plant exceed .37 m /
sec, overflows directly to the Creek begin. This is equiva-
lent to about twice average dry weather flow. The secondary
treatment plant effluent is discharged to Kettle Creek
below the City and currently meets M.O.E. standards.
Approximately 25% of the City area is served by combined
sewers while the remainder of the existing development and
all new development has separated sewers. Much of the
combined sewer system was originally designed as a sanitary
system without capacity for storm drainage. It is there-
fore surcharged and frequently results in extensive basement
flooding. A 1968 report recommended a relief scheme based
on sewer separation and a number of the proposed storm
sewers have been installed.
-------
Receiving Water
Kettle Creek has a watershed area of 44 290 hectares and an
average gradient of 0.144%. From the confluence with Dodd's
Creek where St. Thomas is located, the Creek meanders widely
through a deep flat bottomed valley.
Daily flow records available from the Water Survey of Canada
indicate that extremely low flows may occur in the months
June through October. Figure 2 illustrates the extreme
variation in flow which occurs.
Previous studies of Kettle Creek by the M.O.E. indicated
that the water quality was seriously impaired by waste-
water discharges and a number of large-scale solutions
were proposed including low-flow augmentation, tertiary
treatment or a pipeline to Lake Erie carrying either raw
sewage to a treatment plant or effluent for disposal.
FLOOD RELIEF ANALYSIS
Criteria
The drainage criteria for use in this study can be summarized
in three points:
1. Eliminate basement flooding due to inadequate sewer
capacity
2. Minimize damages resulting from surface flooding of
private property
3. Minimize inconvenience due to street flooding
Stated in this way, basement flooding is not to occur from
insufficient sewer capacity for any storm event while the
-------
degree and frequency of surface flooding becomes a design
variable. The frequency of the design storm, the capacity
of the sewer system, the use of runoff controls, and the
depth of ponding in the street and the corresponding costs
are all evaluated by the analysis of many alternatives based
on the actual local conditions. From this information the
specific criteria for that location are selected.
Detailed Study Area
One drainage area (D-2) within the City of St. Thomas as
defined in a previous (1968) report, was chosen for this
study to develop and screen control measures to relieve
basement flooding. The boundaries of this area embrace
the "Central Business District" and the predominantly
residential areas immediately to the north. The area was
selected for analysis because of frequent street ponding
and extensive basement flooding problems. The results
from this area were extrapolated to the entire City.
Analysis of Alternatives
The range of possible solutions to drainage problems using
stormwater management is very large and complex. For this
reason, a means of screening the many options available was
developed.
In this study, several alternatives were considered which
included combinations of the following control measures:
1. Roof leader disconnection in residential areas
2. Parking lot and roof detention storage in commercial
and industrial areas
3. System surcharge
4. In-system storage
5. Street storage
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Coupled with different design levels and in various
combinations, a very large number of alternatives were
identified as shown in Table 1. Because of the large
number of relief alternatives, the screening of alternatives
on a total system basis using detailed computer models was
not warranted because of cost and time. For the purpose of
screening, two small test areas typical of Area D-2 and
representative in terms of land use and drainage character-
istics were selected to evaluate the cost effectiveness of
different relief alternatives. The first test area was a
2.7 ha residential area while the second was about 2.8 ha
within the Central Business District.
The method employed to evaluate different relief alter-
natives can be described in six stages:
1. Simulate the existing system in D-2 using an his-
torical event and compare the results with measure-
ments or flooding records. The return frequency of
historical flooding events is also determined
2. Simulate the runoff hydrographs for the two test
areas for 2, 5, 10 and 25-year design storms.
3. Determine the control measures required for different
relief alternatives and their corresponding costs for
the two test areas.
4. Pro-rate the control measure requirements and the
costs of relief alternatives to Area D-2.
5. Evaluate the best alternative(s) based on the cost
of the relief systems, effectiveness, impact on
pollution abatement, and subjective parameters using
a matrix scoring technique.
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6. Refine the selected relief alternative(s) by a
detailed simulation of the runoff hydrographs and
peak flows of the relief system for Area D-2
The Stormwater Management Model (SWMM) was applied to the
analysis and design of the relief system. The SWM Runoff
model was used to simulate runoff hydrographs from different
design storms (based on the 'Chicago Method1) and the
EXTRANS hydraulic model (an optional subroutine of SWMM)
was used to route these hydrographs through the sewer
system under both free flow and surcharged conditions.
The storage requirements and pipe sizes for different relief
alternatives were estimated manually by a graphical method
illustrated in Figure 3. Runoff hydrographs were developed
using the SWMM Runoff Block for each combination of test
area and design storm. Required pipe sizes or storage
requirements were then determined assuming constant outflow
rates.
Because of the many alternatives investigated, an accurate
cost estimate for each alternative for Area D-2 was not
warranted. However, the estimated trunk sewer relief
system, based on total separation for a 5-year design storm
was used as a reference cost for other trunk sewer alter-
natives. The reference cost was estimated by simulating
the runoff hydrographs and peak flows for the relief system
for Area D-2 by the SWMM model. The cost for the trunk
sewers for other relief alternatives was pro-rated according
to the relationship between the inflows from the test areas
for each alternative. The costs for the required lateral
pipes and control devices was then added in each case
according to the lateral system control alternative and the
proportion of residential and commercial land use areas in
the area. The cost estimates for selected alternatives are
shown in Figure 4.
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Within, each design level (2-year, 5-year, etc.) the various
alternatives were equally effective in terms of preventing
basement flooding, but each might result in different
degrees of surface flooding. The effectiveness of each
alternative was then determined by the design level and
street flooding aspects. A decision on the best alternative
was made on the basis of cost-effectiveness and the desired
level of protection.
The many subjective parameters included in the evaluation
of alternatives, such as public sensitivity, pollution
abatement and cost factors were considered using a matrix
scoring technique. A total score was then developed for
each alternative for ranking purposes. This was a useful
technique to view each alternative in the light of all
related aspects.
On the basis of this analysis, a relief scheme based on
complete sewer separation and a 5-year design level was
selected.
WATER QUALITY ANALYSIS
General Assumptions
Figure 5 shows the main elements under consideration. In
this study, it was not possible to consider all aspects of
this system to the same degree. The emphasis was placed
on the pollutant loadings to Kettle Creek from the St.
Thomas pollution control plant and the City's storm drain-
age system. The effects of these effluents on the dissolved
oxygen levels in the Creek were considered, to the extent
that the relative significance of different loadings were
identified, and the effectiveness of alternative management
options were estimated.
-------
Dry weather conditions were examined independently of wet
weather conditions. However, the analysis of wet weather
conditions could not proceed unless factors relating to
dry weather conditions were also considered. For both
situations, a number of simplifying assumptions were
required to permit use of the limited available data.
Upstream conditions in periods of low flow had been recorded
and were sufficiently uniform for the actual sources to be
ignored. Therefore, for the dry weather analysis, only the
conditions (i.e. flow and water quality) immediately up-
stream of St. Thomas were considered. Assumptions were
made regarding upstream water quality based on measurements
conducted during predominantly dry weather periods by the
Ministry of the Environment.
For wet weather analysis, it was also assumed that runoff
to the Creek from the more impervious urban area of St.
Thomas would precede and be independent of the runoff from
the rural upstream areas. During the summer period when
critical low flows occur in the Creek, actual runoff from
the rural areas was very limited for most storms. Similarly,
downstream surface runoff flows were not considered signifi-
cant, and were, therefore, also ignored. Schematics of the
wet and dry weather systems considered are shown in Figures
6a and b.
Wet and Dry Weather Loadings
The STORM model was applied to generate pollutant loads from
storm and combined sewered areas of St. Thomas during storm
events. The City was lumped into two catchments representing
the areas served by storm and combined sewers. These two
areas overlap due to partial storm sewer separation for
relief purposes.
Figure 6a illustrates the wet weather loadings on Kettle Creek
-------
that were considered in the study. Average pollutant con-
centrations based on published data were initially used in
the model, but the results of the monitoring program con-
ducted during the study yielded different values that were
subsequently used in the final analysis (see Table 2).
Four parameters were selected for simulation as being repre-
sentative of the various impacts on both the Creek and Lake
Erie. Biochemical oxygen demand (BOD) was considered to
determine the effects on dissolved oxygen (DO) levels in
the Creek. Ammonia nitrogen was converted to equivalent
oxygen demand to obtain an estimate of total oxygen demand
(TOD) which is the sum of BOD^ and the ammonia oxygen demand.
Total phosphorous was selected as an indicator of nutrient
loadings and suspended solids (SS) were included for sediment
loadings.
The treatment plant effluent was assumed to be the only
source of pollutants during dry weather. In this analysis,
"dry weather" days were defined as those days on which the
recorded total precipitation was less than 2.54 mm and the
maximum hourly rainfall was less than 1.27 mm. A schematic
of the dry weather loadings considered in the study is shown
in Figure 6b. To isolate the impact of the loading from
St. Thomas, ideal upstream conditions were assumed. The
treatment plant effluent quality is given in Table 2.
Dissolved oxygen levels of the plant effluent were measured
at 4.1 mg/1.
Receiving Water Response
Dissolved oxygen (DO) was the parameter selected to indicate
the water quality impact in Kettle Creek. This criterion
was selected because previous reports on Kettle Creek water
quality indicated that there might be a DO problem and
because biochemical oxygen demand (BOD) is one of the most
-------
commonly used measures of water quality.
Since complete mixing of the treatment plant discharge with
the incoming upstream flow and subsequent plug flow were
assumed, analysis of the system was carried out using the
well-known Streeter-Phelps equation (see Figure 7).
The Streeter-Phelps equation computes the DO deficit as the
difference between oxygen demand processes and oxygen
renewal processes in a stream. The main processes are
shown schematically in Figure 7. Values of the deoxygena-
tion (K,) and reoxygenation (K ) rate constants used in the
d a
study were taken from a 1976 M.O.E. report.
For the purpose of the computation of dissolved oxygen levels
in dry weather, a constant discharge of 0.18 m /s at the
treatment plant was assumed. The TOD of this effluent was
taken as 28 mg/1 (BOD- of 17.4 mg/1 and ammonia oxygen
o
demand of 10.6 mg/1). In order to isolate the DO deficit
related to the St. Thomas treatment plant discharge from
that attributable to upstream pollutant sources, it was
assumed that upstream of the treatment plant DO was at
saturation levels (C ) .
s
The analysis of stream quality under stormflow conditions
was more complicated than under dry weather conditions due
to the additional unsteady inputs of flow and pollutants
to Kettle Creek. Although discharge of polluted effluents
from combined overflows and storm sewers during a storm are
definitely a dynamic process, a number of assumptions were
made to reduce the system to one suitable for a steady state
analysis by means of the Streeter-Phelps equation. These
are given in Table 3.
The resulting wet weather system is shown schematically in
Figure 6a.
-------
Average wet weather inputs from the combined and storm
sewered areas were determined from the output of the STORM
model. The joint use of STORM and the Streeter-Phelps
equation enabled several years of record to be considered
at a minimal computer cost.
In order to facilitate the analysis of a large number of
storm events, a series of generalized curves were developed.
For given initial conditions, these were used in conjunc-
tion with the simulated pollutant inputs for each event
from STORM to estimate the maximum dissolved oxygen deficit.
Figure 8 presents the deficit curves applicable to events
for which the total stream flow (baseflow + average storm-
flow) results in a velocity of less than or equal to 1.56
m /s. Various other sets of curves corresponding to higher
flow ranges (shorter retention times) were also developed.
For demonstration purposes, the SWMM RECEIV Block was also
used to simulate a selected storm event in the Creek and
to confirm this simplified approach.
The evaluation of receiving water impacts was based on the
MOE minimum criterion of 4 mg/1 for dissolved oxygen levels
in surface waters. The average concentrations of TOD for
each dry day and for each storm runoff event were input to
the Streeter-Phelps DO curves to determine if this criterion
would be violated. The relative importance of wet and dry
weather conditions was then determined on the basis of the
total number of violations incurred for each over the seven
year period analysed. It was found that the wet and dry
weather conditions were equally severe as both resulted in
a large number of violations annually, as shown in Tables
4 and 5.
Evaluation of Alternatives
In evaluating alternatives, the emphasis was placed on pollu-
tant loading to Kettle Creek, rather than on the receiving
11
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water response. Pollution abatement measures were accord-
ingly evaluated for their potential to reduce the BOD load-
ings as an index of both receiving water response and total
loading to the Creek. After screening alternatives using
a scoring matrix, the highest ranking alternatives were
then analysed using the STORM model. Wet weather pollution
abatement alternatives considered were:
1. street sweeping
2. sewer separation
3. in-system storage
4. off-line storage and treatment
Dry weather alternatives were:
1. tertiary treatment
2. pipeline to Lake Erie
3. low flow augmentation
Figure 9 shows the relative effectiveness of various
alternatives based on the STORM model results. Cost esti-
mates were also developed for these alternatives and a
cost effectiveness curve was then prepared (Figure 10).
A similar cost-effectiveness curve for dry-weather
abatement alternatives is shown in Figure 11.
These curves, coupled with subjective matrix scores, were
used for screening pollution abatement alternatives. The
results for water quality alternatives were then combined
with the results of a similar screening process for relief
alternatives to arrive at an integrated management scheme,
as shown in Figure 12.
CONCLUSION
The results of this study indicate the ability of relatively
simplified modelling techniques to account for the system
interactions in urban drainage applications for planning
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purposes. Various methods were developed which enabled a
large number of alternatives to be considered for both flood
control and pollution abatement utilizing a judicious
interfacing of computerized models and manual techniques.
Furthermore, the methods developed are generalized and
applicable to any similar planning application. As a
result of this process, it was possible to obtain a clear
indication of where the limited financial resources of the
City should be invested for maximum benefit.
13
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TABLE 1
RELIEF ALTERNATIVES TESTED
g
M
H
<
W
a
<
i
2
3
4
5
6
7
8
9
10
11
12
13
14
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< <
H H
EH U
2 ft!
W W
Q §
in H a
< w o
§ § °
< n
u
EH £
to w s
« u o
EH 3 U
Res &
Comm.
"
«
"
"
"
"
"
11
11
Res -LU
Existing
11
Redevel-
opment
11
ON TYPICAL TEST AREAS
(N
\ O
.-1 EH
iJ Z CM CO
U ft o n EH
Z « H O EH W
H W EH OS O W ^3
EH EH U iJ K iJ
W < D EH • H W
x u w S a w
W ZCU O\O EnWEH
ZZfaO »Z COUZ Z
HM EnO* s H ^^S 0*—
irf pQ f"j y^ r^j v^ £^ (/j Q5 2] H C/j
HS ZHO «Z IOW cocJ
WO D Q O sO ZEni-5 W>i
3u oi ^ oi MCU H wi w a-"
2-25
XX X
XX X X "
XXX "
X X
X "
XX "
XXX "
XX XX"
XX X "
II
X "
M
X »
J
ft K
K H
W EH
Q
Sw
EH
5 g
g <
S Cu
o w
u w
3 S
U U
Z Z
II II
.H CM
1
2
2
2
2
2
2
2
2
2
1. in Residential areas only
2. in Industrial/Commercial areas only
14
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TABLE 2
ST. THOMAS - MEASURED
AVERAGE EFFLUENT CONCENTRATIONS (mg/1)
(initially assumed values in
brackets)
Combined
Overflows
Separated
Runoff
Secondary
Treated
Effluent
TOTAL
SS
321
(222)
272
(200)
17.4
BOD-
100
(40)
23
(13)
17.4
FREE
AMMONIA
as N
*
1.5
*
0.5
2.3
TOTAL
P
*
1.5
*
0.5
0.9
* From Literature
SS = Suspended Solids
P = Phosphorus as P
BOD5 = 5-day Biochemical Oxygen Demand
15
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TABLE 3
SUMMARY OF ASSUMPTIONS FOR
WET WEATHER DO ANALYSIS
ASSUMPTIONS
1. Basic Streeter-Phelps
Assumptions
2. Upstream BOD =7.3 mg/1
3. Kd = 1. 6 ; Ka=0.8
4. Upstream DO Deficit = 0
5. Travel Time vs Flow rate
from WSC Gauge Station
6. DO less than 4 mg/1 is the
Violation Criterion
10.
Upstream and Downstream
Runoff independent of
St. Thomas Runoff
Base Streamflow on day
of rain is equal to
average flow from
preceeding day
Treatment Plant effluent
= .18 m3/s
Concentrations as per
Table 1
FACTORS ACCOUNTED FOR
Flow travel time to Lake
Erie
NOD
Upstream BOD
- Dissolved Oxygen satura-
tion proportional to
Temperature
Treatment Plant effluent
FACTORS NOT ACCOUNTED FOR
~Benthic BOD
Diurnal Effects
Variable K values
Upstream and Downstream
Runoff
Upstream and Downstream
DO Deficit
16
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TABLE 4
KETTLE CREEK - FREQUENCY OF DO'
1968-1974 DURING DRY
YEAR
1968
1969
1970
1971
1972
1973
1974
TOTAL
AVERAGE
TOTAL i OF
APRIL
0
0
0
0
0
0
0
0
0
MAY
0
0
0
0
0
0
0
0
0
JUNE
2
0
9
16
1
0
0
28
4.0
JULY
5
7
16
26
0
10
2
66
9.4
AUGUST
7
26
30
23
0
12
0
98
14.0
VIOLATIONS
WEATHER*
SEPTEMBER
2
30
27
27
0
26
3
115
16.4
(DAYS)
OCTOBER
0
18
8
29
0
18
0
73
10. 4
NOVEMBER
0
0
0
15
0
0
0
15
2.1
TOTAL
16
81
81
135
1
66
5
395
56. £
DRY DAYS 182
DAYS VIOL./
DRY DAYS
0
% OF ALL
VIOLATIONS 0
167
0
168
17
7.1
182
36
16.7
191
51
24.8
193
60
29.1
173
42
18.5
193
3.8
1449
27
100
*Days with Icr.s than 2.5 mm rainfall and less than 1.2 mm in any hour.
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TABLE 5
WET WEATHER DO DEFICIT
1963-1974
SUMMARY
DISSOLVED OXYGEN DEFICIT VALUES mg/2,
MONTH
April
May
June
July
August
September
October
0-2
0
0
2
0
1
0
0
2-4
4
2
5
0
0
0
1
4-6
1
7
5
0
0
2
1
6-8
3
3
3
0
2
0
3
8+
19
33
31
32
24
27
36
VIOLATIONS
20
35
36
29
24
28
35
EVENTS
27
45
46
32
27
29
41
VIOLATIONS IN MONTH AS
% OF ALL
% OF DAYS VIOLATION
9,5
16,1
17,1
13.4
11.1
13.3
16-1
9.7
16.9
17.4
14.0
11,6
13.5
16.9
00
TOTAL EVENTS 3
12
16
14
202
207
247
1f\
^>.
100
AVERAGE
0.4
1.7
2.3
2.0
28.9
-------
(Q O
0 V
-»^ CD
> 0
en
? A-1 U
SCALE 1=250,000
-------
-j- CD
XS CD
1s
CD , 24-
O
UJ
APRIL
DATA SOURCE: - w.s.c. GAUGE RECORDS
1968 - 1974
MAY
JUNE
JULY
AUG.
SEPT.
OCT.
-------
EXAMPLES: Case 1 - Permissible depth in street of 76 mm resulting in
storage volume A. Using this storage a sewer capacity
of 0.48 m3/sec is required to prevent basement flooding.
Case 2 - Assuming the existing sewer with a capacity of 0.18 m3/sec
is to be relieved by storage alone, and only 76 mm is
permitted on the street (Volume A). An additional volume
of underground storage (Volume B) is required.
0-7-
0-6
0-5
e 0-4
I
0-3
0-2
0-1
COMMERCIAL AREA.
10 YEAR DESIGN STORM.
7Smm STORAGE
IN STREET
CASE 1:
REQUIRED PIPE
(Q=0-48m3/s)
CASE 2:
ADDITIONAL
STORAGE
REQUIRED
/ / ///SS///SSS//////S
EXISTING PIPE
= 0-l8m3/s)
30
40
50 60
TIME - minutes
70
80
Example Of Procedure For
Evaluation Of Relief Alternatives
21
FIGURE 3
-------
40
3-5
3-0
Z
o
V)
o
o
2-0
1-5
ALT I.
ALT4.
ALTS
-ALT 8
O 2
10 IS
DESIGN LEVEL
25 (Y£MS)
ALT.I. TOTAL SEPARATION WITH NO CONTROL MEASURES.
ALT.2. TOTAL SEPARATION WITH ROOF DISCONNECTION
ALT.3. TOTAL SEPARATION WITH RESIDENTIAL ROOF DISCONNECTION AND 75mm STREET STORAGE IN
RESIDENTIAL AND COMMERCIAL AREAS.
ALT4. TOTAL SEPARATION WITH 73mm STREET STORAGE.
ALT. 5 TOTAL SEPARATION WITH ROOF DISCONNECTION AND PARKING LOT STORAGE.
ALT.6. TOTAL SEPARATION. WITH ROOF DISCONNECTION.PARKING LOT STORAGE AND 75mm STREET
STORAGE IN RESIDENTIAL AND COMMERCIAL AREAS.
ALT.7. EXISTING COMBINED SYSTEM WITH 75mm STREET STORAGE AND STORAGE ELEMENTS.
ALT.8. EXISTING COMBINED SYSTEM WITH 150mm AND 75mm STREET STORAGE IN RESIDENTIAL
AND COMMERCIAL AREAS. RESPECTIVELY.
Area D-2 Cost Estimates
For Relief Alternatives
22
FIGURE
-------
S- q
3 |
c ^
E, O
§1
0
o
CD
7?
DRY WEATHER DISCHARGES
POLLUTANTS
FLOWS
Upstream - Industrial and Municipal Discharges
St. Thomas " Treatment Plant Effluent
Downstream - Port Stanley Lagoon Effluent
Upstream - Base Flow + Effluents
St. Thomas - Treatment Plant Effluent
Downstream - Lagoon Effluent
Lower Reach of Kettle Creek
POLLUTANTS
Upstream - Agricultural + Other Rural Sources
St. Thomas - Combined Sewer Overflows
Treatment Plant Bypass
Storm Runoff
Downstream - Agricultural + Other Rural Sources
+ Municipal Runoff
FLOWS
Upstream - Runoff
St. Thomas - Runoff
Downstream - Runoff
WET WEATHER DISCHARGES
-------
Combined sewer overflows
+ treatment plant bypass!
interception rate 2 x DWF
Separated Storm
Drainage
Area - 1308 ha
St. Thomas
Kettle Creek
S 1
llD<;trpflm ha<;pflnw— •
1
| 1
Compl ete
Mixing
Assumed
I
Plu
*\
g flow To
umed y Lake
Erie
Treatment Plant
(Average daily flow
rate on previous day)
Effluent
2 x DWF Max.
CTotal rainfall not less than 2.5 mm OR^ maximum hourly
rate greater than 1.3 mm)
SCHEMATIC OF WET - WEATHER SYSTEM
FIGURE 6A
I St. Thomas I
Kettle Creek
/ /
Uostrpam haseflow —
s
Complete
Mixing
Assumed
Plug flow To
y assumed ) Lake
Erie
*\
Trpatmpnt Plant
(Average daily flow rate)
D.O. = 8.8 mg/1
B.O.D. = 0.0 mg/1
Effluent
D.O. =4.1 mg/1
B.O,D.=17.4 mg/1
SCHEMATIC OF DRY - WEATHER SYSTEM
FIGURE 6B
Schematic Of Loadings From
St. Thomas
24
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* DISSOLVED OXYGEN USED
FOR OXIDIZATION OF
CHEMICALS AND BRAKEDOWN
OF B.O.D.—t
WATER
LEVEL
*DISSOLVED
OXYGEN
IN INFLOW
AIR
*OXYGEN DISSOLVED
FROM AIR AT WATER
SURFACE
^S.7 --
DISSOLVED OXYGEN USED BY
PLANTS IN RESPIRATION
DISSOLVED
OXYGEN
IN OUTFLOW
DISSOLVED OXYGEN REMOVED BY
RESPIRATORY ORGANISMS IN MUD
'DISSOLVED OXYGEN
PRODUCED BY PLANTS
IN PHOTOSYNTHESIS
'-rV-;.-:':-:"•^ v. ,V:; ~ .-,:..:..-.-.• •. ^:-".-:~- y.-
MUD
STREAM SECTION
STREETER-PHELPS EQUATION
D.O. deficit"3
K -KH
a d
where: d = deoxygenation rate constant
K, = re-oxygenation rate constant
d
L = BOD ultimate in inflow to system (mg/1)
a
D, = D.O. deficit in inflow to system (mg/1)
a
N.B. D, = saturation concentration-actual concentration
a
t = travel time (days)
N.B. for simple system distance = velocity x time
* Note: model includes only processes and boundary conditions marked *
in diagram. Parameters are adjusted to account for effects
occurring in the stream and not included in the model.
Oxygen Balance And The
Streeter-Phelps Equation
25
FIGURE 7
-------
.
< 2.
O*
D
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cr>
c:
^3
m
oo
60
SO
E 40
3
li.
a: 30
o
i-
(0
o
O 20
10-
3mg/l
RIVER
RIVER _
TRAVEL TIME
TEMPERATURE
DEFICIT r
DEFICIT = SITIQ/I
DEFICIT . 4mo/l
DEFICIT ^ 3mg/l
-t-
-H
0-5
1-0
2-0
3-0 4-0 5-0
10-0
AVERAGE STORM FLOW / AVERAGE BASE STREAM FLOW BEFORE EVENT, FROM
'STORM* MODEL
-------
TJ m
£- S
= CD
&. a
§o
CD
0
0 0
3. S.
O 0
T3 "^
=±
O
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cr>
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>
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M
J>
M
CD
J>
3«
z
§
<
m
c/i
4k
VI
o>
SUSPENDED SOLIDS REMOVAL EFFICIENCY - %
. n a> -~»
U O Ol <
i j |
1
1 *
1 >
1 S
>
q
1 a-
' " z
J>
<
rn
CO
1
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" ^ w
j> m 0
Saj 2
^ z •»
< »> -4
r"±5
< z
m
] W?
B.O.D. REMOVAL EFFICIENCY - %
- N Ol -4
3 01 O cs
1 1
STREET SWEEPING (1/3 DAYS) BEFORE
'| SEPARATION
1
STREET SWEEPING (1/3 DAYS) + SEPARATION
STREET SWEEPING (1/5 DAYS) BEFORE
| SEPARATION
1
STREET SWEEPING (1/5 DAYS) + SEPARATION
1
STORAGE (CONCRETE TANKS) ^TREATMENT
1
STORAGE (CONCRETE TANKS /EARTH BASINS)
+ TREATMENT
1
SEDIMENTATION + CHLORINATION
1
TOTAL SEPARATION
-------
03
CD
O
CD
3 W
c
3 CD
CD •-*
D
CD
C=
m
i—»•'
o
100
z
z
Ul
ce
d
O 60
o
UJ
eo- -J
40
H
Ul
*
_l
2
20-
* ASSUMES S BYPASSES PER YEAR
**APPROXIMATE COST TO CONVERT THE EXISTING
COMBINED AREA TO SEPARATED SYSTEM, BASED
ON 25% OF THE CITY PRESENTLY SERVED
BY COMBINED SEWERS.
SEPARATION *
STREET SWEEPING (1/3 DAYS)
SEDIMENTATION + CHLORINATION
SEPARATION*
STREET SWEEPING
(1/3 DAYS)
SEPARATION*
STREET SWEEPING (1/3 DAYS)
STORAGE (CONCRETE TANK/EARTH BASIN)
TREATMENT
SEPARATION*
STREET SWEEPING (1/3 DAYS)
STORAGE (CONCRETE TANK)
TREATMENT
-o
A in 19 14 Ifi
~
IA
COST - dollars x I06
-------
? o
CD 9
a?
C CD
>e±. ZJ
*0 0
ZJ 0)
CT O
£1) —*•
CD a
CD
TERTIARY TREATMENT 4-
STREAMFLOW AUGMENTATION
3 4
COST - dollars x I06
-------
> o
^ o
§ £
o) m
9"- =*
< CD
CD o
CO E±
CD
w !3
° CD
0)
CO
o
—1»
03
0
100
TOTAL 5 YEAR
RELIEF SYSTEM
80
o
z
Ld
cr
d
o
03
60
SWEEPING
(ONCE EVERY 3 DAYS)
40
20 •
ST. THOMAS - PORT STANLEY
PIPELINE
8
10
12
CAPITAL COST - dollars x 10
14
e
16
-------
SWMM USERS GROUP MEETING
OTTAWA ONTARIO - 4-5 MAY 1978
APPLICATION OF SWMM - E X T R A N
FOR THE ANALYSIS OF EXISTING URBAN DRAINAGE SYSTEMS
BY
CHRISTIAN W. EICHER, GORE & STORRIE LIMITED
CONSULTING ENGINEERS, TORONTO, ONTARIO
31
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INTRODUCTIO
This paper is a collection of three sample applications of the Extended
Transport Block of the EPA - Storm Water Management Model. The three
examples describe situations in existing systems which cover a diverse
spectrum of problems and solutions.
EXAMPLE NO. 1 Borough of East York - Development of Relief Solutions
for Central Area Sewer System
Development of interim relief solutions for a large combined sewer
system with extensive and frequent basement flooding on the basis
of an ongoing long-term separation programme.
EXAMPLE NO. 2 Borough of Scarborough - Evaluation of Major/Minor Drainage
Performance of a Flood Relief Scheme
for an Existing Residential
Subdivision
Comparative performance analysis of two basement flooding relief
concepts for a relatively new subdivision with separate sewers.
EXAMPLE MO. 3 Borough of Scarborough - Analysis of Impact of Urbanization
on Bendale Creek Drainage Channel
Continuous backwater simulation for a large open drainage channel
and the tributary storm sewer systems to assess the relative impact
of upstream urbanization and the implementation of runoff control
measures (zero-increase-in-runoff concepts).
Apart from the description of the area and the problems that led to the
application of the simulation model, comments are made regarding several
obstacles encountered in the course of the use of the programmes, and suggestions
are given for alternatives as well as further improvements to the Extended
Transport Block.
32
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The usefulness of EXTRAN in the realistic simulation of extremely complex
hydraulic phenomena has been clearly demonstrated in the presented examples,
as well as in other small-scale applications.. The difficulties encountered
are certainly quite often frustrating and over-time consuming.
However, they also reflect the challenge to attach more and more complex
problems as a consequence of having a very powerful engineering tool at
hand. The SWMM Model with the Extended Transport Block definitely ranks among
the best techniques available to the general user at the present time.
33
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BOROUGH OF EAST YORK - Development of Relief Solutions
for Central Area Sewer System
The sewer system in the Central Area of East York is of the combined
type, as in many of the older parts of Metropolitan Toronto. These systems
have been built to generally much lower design standards than are in use
presently. They also suffer from their inherent problematic of having the
sanitary sewage, the stormwater from the roofs and groundwater from the
foundation drains, all connected to one conduit, as well as the connection
from the basement floor drain. Widespread basement flooding has been almost
a fact of life for many homeowners in critical locations. In addition,
redevelopment and more extensive land use have increased the percentage of
impervious area steadily over the years, thereby worsening the surcharge
situation noticeably.
East York's Central Area is among the hardest hit districts in
Toronto in terms of basement flooding. The Municipality has recognized the
need for relief.already years ago, and several studies were commissioned in
order to determine the most suitable methods for relief. It is obvious
that the general name of the game has been separation of the sewer system,
with the existing combined system handling the sanitary flow and the runoff
where roofleader disconnection was not an obvious and logical solution.
With the available outlets rather limited and with street alignments
and the political boundaries not normally in line with watershed limits, the
proposed storm sewer schemes became very long and expensive. This, together
with a number of dry summers, led to slow progress on the implementation of
the proposed separation programmes.
In 1975, Gore & Storrie have been asked by .the Borough to re-assess
the validity of the reports from 1963, after several important segments of the
separation had been completed, with reasonable improvement of the flooding
situation, but also at substantial cost. A further part of the Terms of
Reference was to look into the possibility of interim solutions which would
-------
provide some early benefit from the big trunk tunnels, forming the backbone
of the new storm sewer system. The report confirms the validity of the
general storm sewer scheme and suggests a number of interim solutions. One
of them is the evaluation of selected relief measures arrived at, alleviating
the overload in the existing combined sewer system in strategic locations.
This evaluation is based on a thorough analysis of the extremely complex
sewer system by means of the SWMM Model with the Extended Transport Routine.
It includes an assessment of the improvements obtained with relief overflows
at key locations in the system as well as local reinforcements of bottlenecks.
The Central Area combined sewer system has its outlet north to a
large overflow chamber, located at the Don Valley Parkway. The stormwater overflows
the Don River, and the dry weather flow is intercepted to the Metro Inter-
ceptor system. The overflow chamber represents what used to be the state-of-
the-art and certainly provides little protection for the Don River.
The entire drainage system is far too big for detailed analysis,
and had to be done in several segments. However, for the development of
the boundary conditions, i.e. the water levels in the trunk sewers and the
assessment of the capacity and performance of the overflow with the outlet
sewer to the Don River, the entire system had to be simplified and modelled
in a preliminary phase. Despite the location of the overflow chamber high above
the Don River, the water level in the outfall rises to within a few feet of
the overflow. This is using the simulation of an actually measured storm as
the model input.
The surcharge water levels developed in the simulation of the entire
drainage area have been used subsequently as the basis for the detailed
analysis of different segments of the system. The surcharge levels have been
compared with observations made by the Works Department, as well as some
results from a monitoring study carried out on part of the watershed by
M.M. Dillon Limited.
35
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In the simulations, water in the sewer system was allowed to raise
to street level, from where it v/as routed to other inlets, overflowing to
other drainage watersheds or simply ponding until it would re-enter the
system. This required the addition of surface channels and storage
elements in the model. This was found necessary because otherwise water would
be lost from the system unaccounted, thus reducing the effective load on the
system.
The improvement resulting by a single relief measure or a set of
modifications is clearly shown by the reduced levels of surcharge in the
system. The output from the Extended Transport Routine indicates also how
far-reaching the effects of relief overflows for the trunk system are and
where local storm sewers would still be required. This is generally the
case in the upstream branches of the system where even a free discharge on
a typical 12-inch sewer could not prevent this from surcharging, and local
relief is required.
Significant findings from the study as far as it has been
completed to date are:
1) The locally-looped and interconnected systems in some parts of East
York have markedly better performance than single-ended branches,
because of the possible interaction making use of the dynamic character
of the runoff.
2} The trunk and collector system is in many areas the main cause of the
surcharge problems, more so than the local sewer systems. This is
somewhat contrary to earlier findings based on Rational - Formula
analysis which indicated that the trunk system would have comparably
better capacity. This became clear when the timing of the peaking of the
surcharge levels was analyzed. It v/as also confirmed by information
obtained from house-to-house surveys. The reason for this discrepancy
is most likely the result of the generally simplified procedures used in
the normal application of the Rational Formula, particularly in the
computation of flow at major junctions, which has been found to lead to
the underestimation of the actual load.
36
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3). Relieving the existing combined sewer system at key locations can
significantly improve the protection provided by the existing system
without increasing the number of overflow events to any great extent.
The overflow weirs are designed with crest elevations at the obvert
of the combined sewer and without restriction of the downstream flow.
They act, therefore, only as surcharge relief during a limited number
of storm events per year.
4) The proposed layout of storm separation schemes can be optimized in
many cases such that the most needy areas can be relieved without
immediately implementing the entire scheme. This can provide considerable
improvement in a shorter time than would be possible if the separation
programme had to be based on the ultimate scheme. Some schemes that
provide early relief for the most flooded areas may not appear optimized
for the ultimate system. Their overall effectiveness is substantially
better, however, because they provide for the allocation of funds for
relief projects in other areas of the Borough at an earlier date. It
is obvious, however, that the requirements of the ultimate separation
scheme have to be taken into full account.
The water quality concern: It is quite clear that the proposed
relief by means of additional overflows from the combined sewer system as
an interim measure may raise concern regarding the impact on the quality of
the receiving waters. The Municipality is fully aware of the problem, but
it must be recognized that with the limited funds available for sewer system
improvements, the priority is clearly in the protection of homes against
the hazards and the inconvenience of basement flooding.
The water quality aspect is taken into consideration as far as
possible in the design of the relief structures, as well as in the layout
of the storm sewer outfalls. Overflow weirs are built up to the obvert of
the combined trunk sewer which will, therefore, operate at its maximum
capacity before any overflow occurs. Storm sewer outfalls are designed such
that eventual future storage or treatment facilities can be accommodated
without costly complications such as pumping.
37
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In addition, it must be realized that the surcharge relief over-
flov/s installed at the combined sewer system are strictly meant to be
interim measures. With the gradual development of the entire ultimate
storm sewer scheme, the combined sewers will hopefully cease to surcharge.
This would then also make it possible to improve the existing overflow
structure at the outfall of the combined system in order to provide a
better protection of the receiving stream. The present surcharge of•the
combined system would make any modifications of the simple interceptor
chamber virtually impossible.
38
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BOROUGH OF SCARBOROUGH - Evaluation of Major/Minor Drainage
Performance of a Flood Relief Scheme for
— an Existing Residential Subdivision
Several areas in the Borough of Scarborough have a substantial
record of basement flooding and ponding of water on streets, parks and
parking lots.
One area, known as the Subtrunk "D" Watershed, has a particularly
bad history of problems, starting right from the beginning when the first
subdivisions were developed in the late fifties and early sixties. The area
has separate sewers. The storm sewers have been designed for a five-year
recurrence storm with runoff coefficients of 35 and 45 percent. It would
seem that the lower coefficient was in force when the trunk system was
designed, and the higher value was used for the local sewers. This indicates
already one reason for the flooding problems, caused primarily by overloaded
storm sewers. A secondary reason is the connection of the foundation drains
to the storm sewer which allows the rising water levels in the system to
exert pressure onto basement floors and walls with resulting leakage or
break-up.
The proposed methpd for flood relief for the entire area is based
on a storage scheme, together with the segmentation of the watershed into
isolated sections, with the trunk sewers in each segment capable of handling
the runoff from a major storm. This would at the same time provide for
improved outlet conditions for the local branch sewers. The comparably high
protection proposed for the trunk sewers has been justified by the inability
of the system to sustain even minor surcharges, as well as the fact that
overland flow on the streets along the trunk sewers would result in
intolerable depths of flow and ponding. The subdivision design in the
Subtrunk "D" watershed has not provided for flow routes and outlets for
overland flow, although some parts of the area would allow limited application
of this concept. Basement elevations are as low as only 2 to 3 feet above
the storm sewer obvert in many areas.
39
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The concept of breaking the existing system into a number of
largely independent subsystems has emerged out of the initial runoff
simulations undertaken to assess the magnitude of inadequacy of the existing
conduit system. This has been carried out, using the Runoff and Normal
Transport Blocks of the SWMM Model. Using the re-design option of the
Transport Block, it was possible to obtain a rough estimation of what the
actual runoff and the required conduit sizes would be for different design
storms. Similarly, the system performance has been assessed assuming
different combinations of subsystems, depending on where potential storage
facilities were available to retain the flow from upstream.
A more detailed analysis has been subsequently undertaken for the
upstream section of the watershed, known as the Bridlewood Subdivision.
This analysis served to compare the performance of a system with overland
flow routing for major storm runoff against the concept of providing
increased trunk sewer capacity by means of breaking the system into more
or less independent segments with storage of the upstream flows. The
requirements of modelling both conduit and overland flow, as well as the
full consideration of dynamic backwater conditions have led to the application
of the Extended Transport Block, together with the Runoff Block of the
SWMM Model.
The combined operation of the surface and conduit systems has been
represented in the following manner:
The storm sewer system has been simulated in the usual way such
that it would represent as close as possible the sizes and slopes
of the existing conduits. Some adjustment was necessary in the
location of the manholes in order to have them coincide as far as
possible with the inlets at the low points in the street grade.
The surface system has been represented by a system of trapezoidal
channels with five percent side slope. The trapezoidal profile had
been abstracted from the two roughly triangular channels of the
-------
roadway with the curb and the extension of the flow profile across
the boulevard and sidewalk. The side slope represents the average
shape of the roadway profile and has been determined from contour
plans and field survey.
The connections between the surface channels and the conduit system
has been represented by orifices which were calibrated to represent
average catchbasin capacities or, in some cases, the inlet
restrictions required to prevent the sewer system from surcharging.
The roof areas, with some allowance for driveway catchbasins, have
been simulated to be connected to the conduit system, except where
a proportion of the roofs could be assumed to discharge onto the
ground.
The remaining areas have been assumed to connect to the surface system.
Backyard catchbasins have not been included, although they connect
to the conduit system. Their capacities, however, are small relative
to the street sewer.
Interceptor sewers to storage, as well as the storage facilities
themselves, have been modelled according to the assumptions of the
original concept. Some adjustments have been made in the course
of the analysis to optimize the design in order to compensate for
the lack of detail in the initial analysis.
During this application of the Extended Transport Block as well as
earlier small-scale test applications, it became evident that a number of
modifications were required in the programme to assure that the assumed
major-minor systems would be simulated properly. The following problems have
been encountered and corrected:
Trapezoidal channels with no bottom width cause a divide check in
the calculation of the hydraulic radius if no flow is present.
41
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Surface channels connecting to manholes of the underground system
cause a campening of surcharge and reduction of increase in nodal
depth because of improper computation of available surface areas
in the Model.
The upright orifices assumed by the Model are not ideal for the
simulation of catchbasins and inlet restrictions. Depressed
orifices are not allowed in the present versions of the programme.
Connections to storage facilities must be by orifices. The inlet
conduits are therefore prone to instability because of their
increased sensitivity to surcharging.
Surface channels have a strong tendency to become unstable at
slopes above about two percent, unless very small timesteps are used,
i.e. 5 seconds or less.
With the increasing acceptance of the need to consider both major
and minor drainage in urban developments, the availability of a reliable
accurate runoff model that can handle such systems is important. While the
use of a runoff model may not be essential for new developments where
continuous road grades and overflow easements can be incorporated into the
subdivision design, it is a prerequisite in the analysis of existing systems,
where routing storage, inlet control and partial roofleader disconnection have
to be considered. We have found that several modifications to our programme
were necessary in order to obtain stable operation and to provide a realistic
representation of the drainage system. It would appear desirable to improve the
currently available programme such that dual drainage systems are handled
properly. This is of increasing importance now that several time-sharing
facilities have EXTRAN available to the general user.
42
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BOROUGH OF SCARBOROUGH - Analysis of Impact of Urbanization
on Bendale Creek Drainage Channel
The Bendale Creek is a tributary of the Highland Creek and drains
a major portion of the Borough of Scarborough. The headwater of the
Bendale Creek is in the Town of Markham, with about 540 acres of area north
of Steeles Avenue, the north boundary of Metropolitan Toronto. The entire
watershed will ultimately be urbanized, with the exception of some park-
land. This puts a heavy burden on the Bendale Creek as the main drainage
channel. Host of it has been improved into a formal trapezoidal channel,
but some sections are still in a more or less natural state. Culverts
and bridges date from quite different time periods, as do the design flows
used for their sizing.
Proposals for development in the Town of Markham have initiated
concern with regard to flooding downstream, following widespread flooding of
streets and basements in the Borough of Scarborough in the wake of violent
summer thunderstorms in 1977. Concern was raised in particular for an area
known as the Subtrunk "D" Watershed, which connects to the Bendale Creek
at Highway 401 and Kennedy Road. It was subsequently decided to have Gore
& Storrie Limited investigate the impact on the Bendale Creek resulting from
different development and storm water management assumptions in the upstream
part of the watershed. Special consideration was to be given to the assess-
ment of any adverse effects to the flood-stricken Subtrunk "D" Watershed.
The study had to be on a limited scale only with lumped representation of
the minor tributary watersheds and without detailed surveys of the existing
channel and storm sewer systems.
After some soul-searching it was decided to use the SWMM Model with
the Extended Transport Block Option for this channel analysis. This
decision was based on the following requirements:
1. The channel analysis would have to consider backwater effects
throughout the entire open channel system because of the numerous
flow-controlling culverts and bridges.
43
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2. The storage and routing effect of the many submerged large-size
trunk storm sewers connecting to the creek would have to be
considered in the analysis, requiring a dynamic model.
3. The design of the tributary storm sewer system is based on a 5-year
storm recurrence; the major-storm-events to be analyzed would
obviously require overland flow routing of the excess runoff to
the main drainage channels.
4. The urbanized character of the watershed could best be represented
by means of the Runoff Block of the SWMM Model.
5. Storm Water Management options such as Zero-Increase-in-Runoff
concepts could best be modelled with the Runoff Block.
The first part of the work was to collect data on the major elements
of the drainage system, such as plans of channels, bridges, culverts and
major trunk sewers. A short field survey was carried out to obtain
information on channel roughness, inlet and outlet transitions at culverts
and bridges, as well as a very rough assessment of the overland flow routes
and approximate overland channel profiles. Land-use data was obtained
from aerial photographs and planning data for the future developments.
The input for the Runoff Block of the SWMM Model has been assembled
in the usual manner. The 5600-acre watershed above Ellesmere Road has been
divided into 35 subcatchbasins. Where storm water management techniques
could be assumed, the runoff to the inlet has been controlled by means of
a gutter of fixed capacity instead of a direct connection. The proportions
of controlled to unrestricted flow have been taken from a storm water
management proposal for the Riseborough Development in the Town of Markham,
developed by James F. McLaren Limited, Toronto.
44
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The input to the Extended Transport Block requires some special
considerations. Culverts and bridges cannot be modelled as conduits unless
a very small timestep is used to prevent stability problems with the
relatively short lengths involved. An alternative is the use of orifices.
This requires some adjustment of the orifice coefficient in order to calibrate
the culvert losses to values estimated by manual calculations. A further
factor to be considered is the incorrect handling of weir flow through a
partially-full orifice in case of a backwater condition.
Modelling weir flow over a submerged culvert or bridge has been
attempted, using the weir option of the EXTRAN Module. This has been found
to be unstable unless very small timesteps are used. Large orifices with
modified coefficients have given more satisfactory results. A 30-second
timestep has been used successfully without instability problems after some
initial adjustments.
The findings of the channel analyzing can be summarized as follows:
1. The flows in the Bendale Creek channel are controlled to a major
extent by the culverts and bridges and only to a minor extent by
the channel profiles, except for unimproved sections.
2. The analysis confirmed that the water levels with existing
and future flows have no effect on Subtrunk "D".
3, The submerged trunk storm sewers connecting to the channel experience
substantial alteration of their outlet hydrographs. This stresses
the significance of the water levels in the major drainage channels
for the hydraulic performance of the storm sewer systems.
4. The continuous backwater simulation provides an excellent appreciation
of the dynamics of the flood hydrograph passing through the channel.
5, The evaluation of the impact of storm water management techniques
on approximately 20 percent of the analyzed watershed has shown that
45
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a reduction of the runoff to about 0.5 to 0.6 cfs per acre has an
appreciable effect only for the next two miles along the main
channel. The reduction of the peak flow, four miles downstream, at
Highway 401, was only 10 - 15 percent.
6. When the storm pattern was assumed to move along the drainage channel
at 1.5 miles per hour, the peak flow at Highway 401 increased by
10 percent.
46
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Final Notes
In summary, the following comments-can be made regarding the
application of the Extended Transport Block of the SWMM Model:
1. The availability of this Model option provides the engineer in the
urban drainage field with a very powerful tool to analyze large
and small systems to an extent previously almost impossible because
of their complexity. This applies in particular to relief and
rehabilitation studies in existing systems, where the neglect of
surcharge and the interaction of looped and cross-connected systems
would lead to uneconomical solutions.
2. The complexity and sensitivity of the Extended Transport Module
requires even more understanding and expertise than the application
of runoff simulation models already do. This applies also to the
more recent releases which incorporate testing features to assist
the less experienced user in the determination of a timestep which
should result in a stable programme execution. There still remain
so many obscure reasons for the execution to stop which are difficult
if not impossible to correct without some knowledge of the programme
itself. The cited complexity could ultimately lead to some
programme users developing conversational, interactive versions of
the model, particularly in light of the comparably high cost of
running Extended Transport.
3. The net cost of running EXTRAN on moderate-to-large systems with
approximately 150 conduits and 100 nodes for 30 to 120 minutes of
real time coverage is in the order of $100 to $300 per run. This is
based on the current (1978) rates billed for use of the IBM-CMS-
Time-Sharing System in Toronto, Canada. Since the programme has few
major iteration loops, the cost is largely proportional to the
number of elements and timesteps.
47
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4. With the considerable cost involved it is good practice to run a
drainage system, once it is set up-, for a very small number of
timesteps. This will provide the output of all the system data,
together with remarks generated by the programme regarding revised
elevations, missing links within EXTRAM and from the inlet points
of the RUNOFF Block. This provides an inexpensive means to check
the input data and to eliminate costly runs with crucial errors.
5. The EXT.RAN Block has no continuity check which would allow a
comparison of routed flow volumes with the input hydrograph from the
RUNOFF Block. It is recommended, however, that the user computes a
rough sum of the outfall volumes, taking into account that the
Extended Transport simulation is often not covering the entire
length of the input hydrograph. This comparison is particularly
important if some "exotic" system is to be modelled where it may be
difficult to predict the Model's handling of the data. Instabilities
during the simulation are not always easy to detect in the output
data, and where they occur occasionally, they may not be significantly
for the final results. This can be verified easily with a continuity
check.
48
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CSO FACILITIES PLANNING USING A MACROSCOPIC MODEL
(A CASE STUDY)
by John A. Lager, Vice President, E. John Finnemore, Project Manager, and
George B. Otte, Project Engineer
Metcalf & Eddy, Inc., Palo Alto, CA
Simplified stormwater models can be an effective aid to
facilities planning for combined sewer overflow (CSO) remedial
projects. They are useful in characterizing the sources and
temporal and spatial variations in wet-weather wastewater
flows, identifying responses to alternative routings and
control practices, assisting in the cost-effective sizing of
major system components, and providing useful information for
preliminary design.
In this presentation, an in-progress case study of a macro-
scopic model's adaptation and application in San Francisco's
Wastewater Management Program is described.
MODEL ORIGINS AND INFORMATION SOURCES
Simplified stormwater models have been under development by
several users and investigators since the early 1970's.
Metcalf & Eddy developed its first simplified approach in 1972
in a reconnaissance level study of CSO and stormwater discharges
for the District of Columbia as a necessary companion model
to EPA's SWMM. This approach methodology was extended and
documented for public dissemination in connection with a CSO
study for Rochester, N. Y. in 1976 [1]. Land use related
quality parameters (fixed) were introduced to the model in modi-
fications for the Association of Bay Area Governments' 208
planning study in 1977. This model, MAC (for macroscopic
planning model), is also scheduled for documentation and public
dissemination [2].
-------
Other discussions of the writers' viewpoints with respect to
the utility of simplified models are available in EPA
sponsored short course documents [3], seminar proceedings [4J ,
and state-of-the-art assessments [5].
WHAT THE MODEL DOES
The objective of the model is to create a continuous wet-
weather flow simulation, which is characteristic of the area(s)
and system(s) under evaluation. The present San Francisco
adaptation is identified as SFMAC.
Given a rainfall history, SFMAC computes the quantity and
quality of runoff from differing land use areas, and combines
these with dry-weather flow and other known lateral inflows
into storage. The lateral inflows may be delayed in time, to
represent flow routing. SFMAC next computes pumped with-
drawals from storage, and the resulting storage volume and
overflows, if any. It last computes pollutant removals by
treatment of the pumped withdrawals, and the resulting
quality of the discharged effluent. All computations are
repeated on an hourly basis.
The program prints out the hourly status of all variables,
and summaries for each day, month, water year, and subarea
run. In addition, the hourly withdrawals and/or overflows
may be written on disk files, for future use as input (lateral
inflows read from disk files) to downstream segments.
The fundamental capabilities of SFMAC described above are
depicted in Figure 1. The entire procedure can be repeated
for many different subareas, all within the same run. More
importantly, the basic model may be applied successively from
upstream areas to downstream points, enabling many subareas
and transport/storage/treatment facilities to be linked
together in a manner representative of a citywide system.
-------
yw,
SUBAREA
DRY fEATHER FLO»
FOUR LATERAL INFLOWS
zzzx
MAXIMUM
STORAGE -
CAPACITY
STORAEE
OVERFLOW
POLLUTANT
REMOVALS
PUMPED WITHDRAWAL
EFFLUENT DISCHAR6E
FIGURE 1. SCHEMATIC REPRESENTATION
OF THE SFMAC MODEL CAPABILITIES
51
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Concept
The model has as its foundations (a) the so-called "rational
method", an established tool for the analysis of runoff, and (b)
the basic storage equation: outflow = inflow + A storage. Time
"related rainfall volume {inches per hour or inches per day) is the
primary driving variable of the model. In fact, it is one of
only two input variables which change during each time step,
the other being the diurnal dry-weather base flow variations.
Quantity and Quality Development
Surface runoff quantity and quality are developed by subarea
and land use distributions. Subareas are selected on the
basis of topography, slope-development homogeneity, and
collection system configuration. Gross runoff coefficients
and average quality concentrations are associated with each
land use type and may vary from subarea to subarea.
At the simplified level of analysis, runoff coefficients do
not vary with time into storm or season. However, because of
observed first flush phenomena, a step function was adapted
for quality (BOD and SS) similar to that shown in Figure 2.
Concentrations are highest in the initial storm hour and
decrease with progression into the storm. Mass loadings, on
the other hand, continue to be directly influenced by the
storm hydrograph.
Dry-weather flow diurnal quantity and quality variations are
taken directly from the appropriate treatment plant records.
Routing and Aggregation
Flow routing is accounted for by user selected time offsets,
which are fixed for a single system test configuration.
52
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BOO -
800 -
•DISCRETE VALUES
•ITHIN TIME PERIOD
MEAN VALUES BY TIME PERIOD
10 PERCENTILE
1.0
2.0 3.0 4.0
THE SINCE START OF OVERFLOW, hrc
>5.0
FIGURE 2. CSO QUALITY VS. TIME, SS
53
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Aggregation of runoff from several subareas and appropriate
dry-weather flows is also fixed by the text configuration.
Storage basins are treated as completely mixed each time step
and a treatment quality change associated with basin detention
may be specified. Treatment facilities with negligible
storage are simply represented by specified quality changes,
which could be based on pilot plant performance evaluations.
Withdrawals from storage may also be specified as a step
function in which increased pumping is applied with increases
in flow level in the basin. Two withdrawals from a single
basin may be simulated (e.g., one discharging to the dry-
weather plant and the second to the wet-weather plant).
Displays
The output for each subarea or group of subareas may be
entirely overflow (no treatment), entirely treated effluent
(all runoff processed), or both. Graphical and
numerical display routines have been developed which produce
continuous input hydrographs and pollutographs to any speci-
fied plant in the system, similar displays for overflows,
computations of storage times, and percentages of time the
treatment plants are loaded at or above specified criteria.
REPRESENTATIVE APPLICATION PROCEDURES
As an illustration of model usage in CSO facilities planning,
excerpts from our in-progress San Francisco work are presented.
The intent is to identify, in case study context, selected
application procedures which may assist other municipalities
in developing their own approach concepts.
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Subdivision of Study Area
In San Francisco, the subdivision of the 25,000 acre study area,
Figure 3, proceeded to two levels: major watersheds (7) and
subareas (23) , all of which had definable topographic/system
boundaries. Major watersheds were determined by outfall consol-
idation projects which were in planning, design, and'construction
phases and, to a large extent, constituted givens in the project
work. A principal project objective was to identify and detail
cost-effectiveness evaluations of alternative sizing, routing,
storage-treatment, and discharge schemes to solve existing wet-
weather, CSO, problems. Representative schemes under evaluation
are shown in Figure 4.
Rainfall
Fortunately, San Francisco has had one of the most comprehensive
rainfall reporting and recording networks in the world since
1971, and a base gage which extends the period of record back
over 70 years. Thirty gages in the present system telemeter
rainfall instantaneously to a computer center for observation,
recording, and data analysis.
To take advantage of this information, 4-year 30-gage propor-
tioned records were developed for each of the 23 subareas and
similar weighted 70-year records were made available from the
single long term gage. For reasons of economy and understanding,
a 4-month subset (rainfall 170 percent of normal) was selected
for preliminary alternative analyses using hourly time steps.
55
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LEGEND
*• ' W10R WATERSHED BOUNDARY
•- SUBJkREA BOUNDARY
, BOUNDARY OF SEPARATELY OR
NONSEIERED COMPONENT OF SUBAREA
FIGURE 3. SUBAREAS AND MAJOR WATERSHEDS
56
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Note: Circles represent treatment plants; arrows repre-
sent routings and discharge locations; and shading
represents area tributary to a specific plant.
FIGURE 4. REPRESENTATIVE TOTAL
SYSTEM WET-WEATHER SCHEMES
57
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Subsystems
Simulations were carried out by subsystems (consisting of one
or more watersheds) for various storage-treatment combinations
to pre-optimize each subsystem for any of several specified
"overflow criteria. Results stored on disk included continuous
time, overflow quantity-quality, and treatment or pumped
withdrawal quantity-quality (for the 4-month subset approximately
3,000 hourly values—many obviously zeros—for each parameter
of interest and for each overflow objective). A typical sub-
system is shown in Figure 5.
An example of subsystem optimization using the full 70-year
rainfall record is shown in Figure 6. Here the net effective-
ness, in terms of overflow reduction, is illustrated as a
function of equal capital investments beyond a selected base
level of control. A particular value of this charting is that
not only are the number of overflows apparent, but also the
volumes, months and years in which they occur or do not occur.
Total Composite Systems
The final application step is to assemble the subsystems,
which are now 3 or 4 in number, into a total composite system
(e.g., pumped outflow from one subsystem plus time offset is
new additional inflow to downstream subsystem). Estimates of
capital and operation and maintenance costs are prepared for
each total system and pursued to the environmentally-balanced,
publicly-acceptable, and least (?) cost, apparent best
alternative project.
Of course, optimal solutions on the total system may require
use of the second or third best choice for a particular sub-
system; thus several iterations are to be expected.
58
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FIGURE 5. NORTH SHORE SUBSYSTEM
59
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80
—
Of
* 80
m
o
—i
ui 40-
>
u.
o
u 20-
_j
O
>
0
BASE CONDITION ARBITRARILY ADJUSTED BASE LINE DUE TO
/ SELECTED AT 75» OF /FIRST ADDITIONAL INCREMENTAL
/ DESIGNED LEVEL FOR / INVESTMENT (SEE TEXT)
o^ / PURPOSES OF ILLUSTRATION / CORRESPONDS TO DESIGNED
„
___ _JL
— — z
fT'
1
-I
/ LEVEL OF CONTROL
It
•• n
-i
--o----
.^
y-l-f--'
/
u. a
-ffi-
3
-rif-
-r-i-l
\
CD) OB B
8
80-
60-
-40-
20-
-
ae
TTfl~t~,l
at
i^-rTTt
c
h;
9
O
•t
o
^ (D (O (O (O CD 4D«
O
•»
J
7
*--
» 1 e| ^ | M | f
e
• i «i»
WATER YEAR
FIGURE 6. PROJECTED LONG TERM OVERFLOWS FOR
NORTH SHORE SUBSYSTEM
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CALIBRATION-VERIFICATION
When dealing with simplified models, what can be accomplished
in the area of calibration-verification is obviously limited.
Simplified models do not claim to produce precise results, as
precision is intentionally sacrificed for breadth of coverage,
quick setup, and low cost turnaround. Also, simplified models
are generally resorted to when available data is so sparse
that calibration-verification is more imaginary than real.
In San Francisco, calibration-verification of SFMAC was
accomplished through comparisons of discrete hourly samples of
dry-weather plant influents at the City's 3 existing plants
during six 1977 storm events. Operating rules as to how much
combined flow was pumped or transported from each area to
each plant were defined by the City, but not necessarily
followed by City operations staff, as their response was more
dictated by the individual storm and equipment available.
Representative results for one storm at two plants are shown in
Figure 7. Correlation coefficients after calibration for the
3 plant, 6 storm, several hundred element matrix ranged from
0.6 to 0.9 for flow, 0-4 to 0.7 for BOD concentration, and
0-3 to 0.5 for SS concentration.
UTILIZATION IN PLAN DEVELOPMENT
SFMAC"s adaptation and application in San Francisco's facili-
ties planning process already has yielded many tangible
results, including the following:
• It has provided a common denominator for evaluating
widely differing alternatives;
61
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so si 4-e/Tirne (VST)
SF HfcC, Mode-\ vs Rvchrnond So.nt.e3
Zo-ZT. ,
Fl;
MODEL CALIBRATION EXAMPLE
RESULTS
-------
• It has provided information for preliminary sizing
for all major system components for feasible systems
and target levels of control;
• It has identified significant locations, times, and
volumes of both treated and untreated discharges;
• It has provided detailed potential plant influent
characterization, Figure 8, for synthesizing wet-
weather flows for pilot plant operations;
• It has provided valuable information on travel and
system dewatering times to indicate potential odor
problems;
• It has provided a tool for estimating annual energy
and chemical needs and estimates of sludge production;
• It has served as an important tool in the narrowing
of systemwide alternatives from 40 to 10, and will con-
tinue to be of assistance as alternatives are further
reduced until the final selection of the apparent best
alternative; and finally
• It is providing an effective tool for conveying the
complexities of such system evaluations to the public,
the engineering community, and the decision-makers.
In conclusion, simplified stormwater models, professionally
applied, provide an understanding of wet-weather system opera-
tions and requirements through tools which are highly flexible,
economically applied, and valuable to decision-makers.
63
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• « •» * I
** K M » *
M • * * *
ft M m * •
^ » *
•i HI *
i .
g ""
m
1 -...
*• « >',
M: !:::!: ::• COND TION 3
•;::•::!: :!•: MORE STORAGE,
If ::::;: :>:: SMALLER PLANT
(; :h:h 55::::!::
!: ::::!! : : ; sisi'
: : : :::::: :::i:!:::
•••*•••••• •*•••••••
• •••*••••• *•• ••••!
i::l::-l: ••::::::: : I
MMMUMIM>MHI.,.i< !.,,Jl.l
B r
5 DATE AND TIME, H s
s a
.1
: :
ii
::.
'!•'
i>:
5
1
•
> * i t t i * »
FIGURE 8. TYPICAL COMPUTED INFLOW HYDROGRAPHS
TO WET-WEATHER PLANT
64
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REFERENCES
1. Lager, J.A. , T. Didriksson, and G.B. Otte. Development
and Application of a Simplified Stormwater Management Model.
Office of Research and Development, Environmental Protec-
tion Agency, Cincinnati, Ohio, Report No. EPA-600/2-76-218,
August 1976.
2. Convery, J.J. Letter to R.A.F. Tranter announcing the
award of a research grant to ABAC and Metcalf & Eddy for
"Stormwater Pollution Analysis with MAC Model in Continuing
208 Planning." U.S. Environmental Protection Agency,
Cincinnati, Ohio, April 1978.
3. Applications of Stormwater Management Models - 1975. Manual
for a short course sponsored by the U.S. Environmental
Protection Agency, Storm and Combined Sewer Section, in coop-
eration with the Department of Civil Engineering, Environ-
mental Engineering Program, University of Massachusetts, and
the Division of Continuing Education.
4. Proceedings of Urban Stormwater Management Seminars held at
Atlanta, Georgia, Nov. 4-6, 1975, and at Denver, Colorado,
Dec. 2-4, 1975. Office of Water and Hazardous Materials,
U.S. Environmental Protection Agency, Washington, D.C.
20460, Report No. WPD 03-76-04, January 1976.
5. Lager, J.A., W.G. Smith, W.G. Lynard, R.M. Finn, and
E.J. Finnemore. Urban Stormwater Management and Technology:
Update and User's Guide. Municipal Environmental Research
Laboratory, EPA Office of Research and Development,
Cincinnati, Ohio, Report No. EPA-600/8-77-014, September
1977.
65
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STORMWATER MANAGEMENT MODELLING
AND LAND DEVELOPMENT PROJECTS
PAUL E. WISNER
JAMES F. MACLAREN LIMITED
INTRODUCTION
Several Stormwater Management Studies have recently been
conducted by James F. MacLaren Limited in areas having
potential restrictions to development. Modelling con-
ducted under those circumstances, although requiring more
time than traditional analysis, helped to define drainage
alternatives and trade-offs, which make development of
certain areas acceptable. In addition, it contributed to
better planning and easier approval processes.
Three main types of restrictions related to flood and
runoff control from developments are: development in
floodplains, runoff increases and pollution caused by
runoff. At present, in Canada, most provinces have various
criteria for floodplain control, but only some of the
provinces are in the process of developing criteria for
runoff quantity control. Runoff quality constraints have
been considered only on rare occasions when dealing with
environmentally very sensitive areas. Lately, at the
municipal level, there has been a significant increase in
interest in all three above aspects; a number of progres-
sive municipalities have started to require some form of
runoff control despite the lack of provincial regulations.
More recently, a number of other agencies have also become
involved in stormwater management as, for example, some
conservation authorities such as the Metro Toronto and
Region Conservation Authority. The following typical
examples, which involve modelling related to land develop-
ment, lead to some general considerations regarding the
implementation of Stormwater Management (Table 1).
66
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Zero Runoff Increase
In the absence of specific runoff control regulations,
the requirement of "zero runoff increase" has evolved,
mainly as a consequence of potential downstream
flooding. A typical example is the new 160 acre
residential development in Markham, draining to an
area in Scarborough severely afflicted by basement
and street flooding at present. A traditional drainage
system in the new development would have entailed a
contribution of $1.5 million towards increasing the
capacity of the downstream storm trunk sewers, as well
as delays related to the implementation of relief
sewers in a large area in Scarborough. As against
this, adoption of runoff control for both the minor
and major systems has resulted in maintaining the
1/5 year peak flow at the pre-development level, and
in reduction of overland flow to Scarborough during
major storms. The control system consists of an
underground over-designed pipe, which acts as a storage
unit for the 1/5 year storm runoff, and the use of
parks for dry detention areas, which only operate
during major storms (see Appendix). The analysis
accounted for time lag between the release from the
various storage units and smaller areas without control,
combination of overland and pipe flow, estimation of
surcharges in various parts of the system, etc. This
level of sophistication is, of course, only possible
by using computer programs such as SWMM 6 (WRE). The
project went into the detailed hydraulic design of ease-
ments leading overload flow to detention areas, the
outflow facilities at various elevations from the
detention areas, orifices for flow reduction, etc.
The extra cost of the stormwater management system
consisted mainly in the oversizing of a trunk system,
estimated to cost about $350,000.
67
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A similar project, involving a combination of under-
ground storage and different surface detention
facilities for control up to the 1/100 year flow is
presently being studied for a development in
Newmarket, where other drainage alternatives were
not acceptable to the municipality.
Optimum Use of Existing Storm Sewer Capacity
A frequent problem with new developments is inadequate capa-
city in existing trunk storm sewers. As an example, for a
large development in North-east Edmonton, this constraint
would have required an initial investment of about $15 million
for a new trunk sewer. This large cost was caused by the
distance to the receiving river, and by the need to cross a
ridge separating the development and the river. The exist-
ing trunk sewer, located south of the development, operates
at full capacity for the 1/5 year storm. In addition, there
were major concerns in connection with the effect of new
development on increasing overland flow to the developed
neighbouring areas and, consequently, runoff controls were
considered for storms up to the 1/100 year level. Consider-
able storage (up to 720 acre-feet) is required to reduce the
1/100 year storm flow from 2500 cfs to 50 cfs, a runoff rate
which could be directed into the existing trunk sewer during
a storm. According to our present studies, this storage
could be implemented by means of 19 urban lakes, interconnected
by a system of relatively small pipes and swales. In one of
the alternatives, buffer lakes would be located at the down-
stream end of the system and control gates would regulate
and direct the outflows from these lakes into the existing
trunk sewer only at times when capacity became available. If
the cost of land associated with dedication of 90 acres for
the lakes is neglected, this alternative would cost only about
$4.5 million. The land, however, has to be dedicated in
addition to that considered for parks. However, the lake
system could be implemented over a period of 10-15 years.
The resulting deferment of large initial costs is decisive
for the economics of the whole project.
-------
The performance of the drainage system with lakes over a
period of time was analysed by continuous simulation after
screening Edmonton precipitation records for a period of
over 70 years. It is interesting to note that the critical
situation is a particular sequence of two storms. Other
aspects included in the hydraulic analysis were: effects
of storms with various durations, comparison of summer
storms and snowmelts, analysis of overland flow in the
neighbouring areas, etc. The analysis involved using the
computer programs STORM and HYMO, for hydrologic work, and
the WRE Transport Model, for trunk sewer operation.
RUNOFF QUALITY MANAGEMENT
Water quality constraints from storm runoff appeared in con-
junction with a number of very specific situations. As an
example, the construction of storm outfalls to a large
creek in Edmonton has been delayed because of concerns
expressed by powerful citizen groups. The only other
drainage alternative was connection to a distant trunk sewer.
A James F. MacLaren Limited study, presently under review,
has examined the effect of a storage pond designed to signi-
ficantly reduce first flush effects. The study compared
water quality measurements in the stream with those simulated
for the development with and without storage.
Another example of public concern related to the effects of
urbanization that involves a new development in Ancaster,
Ontario. In this case, the frequency of overflows to down-
stream properties was significantly reduced by initially
diverting the entire drainage system into a detention pond
which, in addition, functions as a sediment trap and then
releasing the outflows into a larger watershed. In both
situations described above, the STORM model and the analysis
of water quality measurements were used to define impacts and
compare alternatives.
69
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Water quality considerations also played a significant role
in planning studies for comparing the effects of various
stormwater management alternatives (storage, street sweeping,
etc.). The first example is a stormwater management demon-
stration study in St. Thomas, Ontario (described in a
separate paper). A similar study, but on a larger scale,
was carried on for the City of Edmonton. The main conclusion
related to stormwater management was that the total pollution
load from the new developments would not have a significant
effect on the water quality in the North Saskatchewan River,
and that other pollution abatement problems related to this-
study have a higher priority.
A watershed assessment, now under review, has been carried
out for a 40 sq. mile watershed tributary to Lake Simcoe,
where various development and stormwater management alter-
natives were assessed from the viewpoint of flood control,
runoff increase and water quality in a receiving stream and
the lake. It was concluded that stormwater management was
required mainly for erosion control and more advanced phases
of development.
The impact of areawide studies of this nature on the land
development industry is very important. There are, at present,
municipalities in the Thames River, Credit River and other
watersheds where development has been frozen by'regulatory
agencies because of lack of assimilative capacity in the
receiving streams. Modelling studies which include urban
runoff effects, alternatives for disposal of sewage, etc.,
may be beneficial for a more scientific land use planning
and consideration of more flexible restrictions in conjunction
with stormwater management.
70
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DIFFUSED VERSUS WATERSHED STORMWATER MANAGEMENT
The example described in the Appendix refers to storrawater
management on a given property. This leads to diffused
stormwater management which may be implemented relatively
easily but may not necessarily optimize the trade-off
between environmental, aesthetic, economic and runoff
control aspects. Formulation of a master plan acceptable
to several land owners with conflicting interests, and
assessment of levies for detention facilities requires
regulatory experience; a good understanding of the scope
and limitations of stormwater management by both the
municipality and the developers is necessary. Attempts in
this direction have been made by Markham for a watershed
with an area of 3.5 square miles which will undergo nearly
complete urbanization. Various alternatives for diffused
and watershed management were assessed from the viewpoint
of flood control, erosion control, environmental impact,
maintenance, economics and acceptability to the developers.
The final alternative involving two wet ponds and a number
of dry detention areas seems to be amenable to the various
parties involved. Modelling of flows with frequencies
between 1/5 years and 1/100 years was carried out using HYMO
and SWMM 6 using a coarse model; routing through the
numerous storages designed for stormwater management or
created by existing culverts was included. Detailed modell-
ing, similar to the one carried out for Riseborough, will be
considered as the various subdevelopments are submitted for
approval.
FINAL REMARKS
The various examples described above indicate a large number
of combinations of physical constraints and simulation pro-
blems involving the whole array of modelling aspects such
as storm selection, selection of models for planning and
design purposes, surcharge effects, combined overland and
71
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pipe flows, calibration of water quality models, etc. In
many situations the use of models has helped the developers
towards a better understanding of the real problems, solving
some of the approval processes and achieving more economical
alternatives. While there is still some confusion regarding
stormwater management alternatives, for example, wet ponds
against dry ponds, or underground detention and cost sharing,
it seems that there are no major problems in understanding
the basic concept and in co-operating with modelling as a
requirement for drainage studies. It seems, therefore, that
there is nothing to prevent the use of a more rigorous
analysis in the planning and design of new developments and
that the experience of progressive municipalities should be
studied.
Figure 1 shows the traditional Rational Method approach.
As indicated in Figure 1, many of the runoff increase
criteria and simplified methods of .computation lead to similar
straightforward design procedures. Elements for site
tailored terms of reference which would give the developer
more flexibility and municipalities better overall alternatives
are outlined in Table 2. Drainage criteria, in this case,
are the result of preliminary planning rather than the input.
72
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TABLE 1
SPECIFIC REQUIREMENTS FOR
RECENT SWM STUDIES
RISEBOROUGH - MARKHAM
(160 ACRES)
NEWMARKET 35-2
(85 ACRES)
NORTH-EAST EDMONTON
(2000 ACRES)
(300 ACRES) SOUTH
EAST EDMONTON
SOMERSET - ANCASTER
UNIONVILLE - MARKHAM
BARRIE ANNEXATION
ZERO RUNOFF INCREASE FOR ALL
STORMS 1/5 TO 1/100 YEAR & HISTORICAL
SAME AS ABOVE
+ FLOOD DAMAGE REDUCTION IN
SMALL EASTERN CREEK
+ CONTROL FOR OTHER PROPERTIES
DRASTIC FLOW REDUCTION
2500 TO 50 CFS IN EXISTING
STORM SEWER
CONTROL OF POLLUTANT LOADING
IN RECEIVING CREEK AND EROSION
CONTROL
PROTECTION OF TROUT PONDS IN
DOWNSTREAM PROPERTIES
PROTECTION OF WATER QUALITY IN
TOOGOOD LAKE AND EROSION IN
BRUCE CREEK
CONTROL OF POLLUTANT LOADING
TO LAKiE SIMCOE
73
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TABLE 2
PRELIMINARY PLANNING
(NO PRESELECTED CRITERIA)
ALTERNATIVES
. DIFFUSE VS, WATERSHED
, 1/5 TO 1/100 YEAR
, ZERO INCREASE, LESS OR MORE
, MAJOR SYSTEM?
CRITERIA
RUNOFF INCREASE
FLOODING
POLLUTION ASPECTS
OTHER SENSITIVE ENVIRONMENTAL
FACTORS (STREAM VALLEY)
CONSTRAINTS AND
PRACTICABILITY
, ECONOMICS
, EXISTING STRUCTURES
, JURISDICTIONS
, STATUS OF PLANNING
, MAINTENANCE
CONFLICTS
, LAND DEDICATION
, VARIOUS OWNERS
, LEVIES
RESULT: CRITERIA AND
TERMS OF REFERENCE
74
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FIGURE 1
(a)
PHYSICAL CHARACTERISTICS
OF AREA UNDER DEVELOPMENT
(A, Bj SOIL)
LAND USE
[IDF CURVE
IPEAK FLOW
PIPE SELECTION
DESIGN
STOf
IS.C.S. PREDEVELOPMENT HYDROGRAPH
|LAND USE
[S.C.S. POSTDEVELOPMENT HYDROGRAPH)
[STORAGE
ON SITE)|
IPIPE SIZEI
SOME REGULATORY TRENDS:
- SIMPLIFICATION OF CRITERIA
- SIMPLIFICATION OF COMPUTATIONS
- SIMPLIFICATION OF REVIEW PROCESS
75
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APPENDIX
SELECTION AND IMPLEMENTATION
OF DRAINAGE DESIGN MODELS IN MARKHAM
D. Mukherjee P. Wisner
D. Keliar S. Vatagoda
Town of Markham James F. MacLaren Limited
INTRODUCTION
In the last few years there has been an increased trend
to replace the Rational Method with more sophisticated
drainage design methods based on computer modelling.
The Canadian Urban Drainage Committee has sponsored a
significant number of model-oriented research projects
and municipalities and land development consultants have
realized that modelling helps reduce the cost of providing
drainage facilities not only by its more precise flows,
but also by allowing a better understanding of how the
drainage system works. Increased pressure for the control
of runoff flow increases and quality has induced the design
of various storage facilities, many of which could not be
sized by the Rational Formula.
While some large municipalities have in-house modelling
expertise, most of them have a user-oriented understanding
of modelling and prefer the use of external consultants. A
new trend is also that of joint ventures in which the
consultant having the responsibility for the overall drainage
plan subcontracts modelling to a specialized group.
As a medium-sized municipality, Markham engineers, after a
period of training by participation at various seminars and
workshops and study of experience in other cities, have
decided to use specialized modelling consulting services. It
76
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was recognized that despite the significant improvements in
the applications of simulation, we are still in a learning
phase in which some of the pitfalls are not avoided and some
of the methods are misused.
While the stormwater management concepts have become quite
popular, there are aspects in both quantity and quality
simulation where extreme care should be exercised in the.
use of models.
Criteria for Model Selection
The channel routing routines of some popular models such as
ILLUDAS or HYMO are very simplistic and cannot simulate, for
example, such conditions as surcharge effects, backwater in
pipes, etc. However, many drainage alternatives'used in
stormwater management require these capabilities for realis-
tic modelling. For example, relief sewer studies in Winnipeg
and Edmonton have indicated that the cut-off relief sewer
may lead to significant savings. This alternative can be
simulated only by models having a sophisticated TRANSPORT
routine such as that in the WRE model developed by Water
Resource Engineers, Inc. and presently available also in
SWMM 6.
Dry or wet ponds may lead to temporary surcharge and backwater
effects in the pipe system which are severely distorted by
some of the "simpler" models (which may be appropriate for
other studies).
The problem becomes even more complex if underground or pipe
storage is considered. Surcharge of trunk sewers may lead to
increased surcharge of laterals and flooding of foundation
tiles. The levels and limits of surcharge have, therefore,
to be determined only by a detailed analysis using a model
which simulates the above aspects realistically.
77
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Another problem in storage analysis which seems to be
ignored in many simplistic simulations, is the effect of
routing on the coincidence or lagging of peak flows from
various tributaries. Modelling in a situation with several
storage units as shown in Figures 1 and 2 should, therefore,
evidence these effects by appropriate routing procedures.
If the analysis is conducted for a major system, channel
routing should consider both street and pipe flow and this
again is possible only by the more complex TRANSPORT routine.
If runoff control is required in connection with flow limita-
tions to pre-development conditions, one should appreciate
the fact that flows from small rural watersheds may be more
approximate than those from urbanized areas with a high
percentage of imperviousness. Comparison between two models
may be useful.
Proper selection of input data may be as important as model
selection. Many studies are still conducted with "design
storms" on the incorrect assumption that the storm frequency
is the same as the flow frequency, while the latter is
strongly influenced by antecedent conditions. In many
storage applications, the critical event may not only be
a storm with a critical duration, but may also be a sequence
j
of storms. Consequently, while design storms are useful in
preliminary studies, real storms have to be considered in
any detailed analysis.
A Case Study
Some of the general principles previously discussed will be
illustrated in the following brief description of the runoff
control analysis carried on for a new development in Markham.
The modelling analysis considered both the pipe or convenience
system and the overland flow or major system. Flow directions
in the major system are indicated in Figure 1.
78
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• Pre-development flows for the 160-acre area were checked
by comparing results with HYMO and SWMM and the results
are given in the following table:
Flows for Pre-Development Conditions (in cfs)
Design Storm SWMM SCS (HYMO)
Frequency Simulation Simulation
1/5 year 50 51
1/10 year 67 79
1/25 year 93 118
• Post-development flows for the 1/5 year frequency for
two-thirds of the area are controlled by means of
underground storage.
• Flows for 1/25 and 1/100 year storms are controlled by
means of two dry detention ponds A and B located in parks
(Figure 2). Street grading, and location of easements
were carried out jointly by the modellers and the con-
sultant working for the developer, Fred Schaeffer and
Associates (in close cooperation with the town engineers).
By close cooperation with the Planning and Parks Depart-
ment, it was possible to locate the surface storage in
parkette and recreational areas. Dry ponds are operated
only for storms with a frequency of less than 1/5 years
and only for a few hours. Under these circumstances,
maintenance problems are minimal. Grading and landscaping
of dry ponds was designed by Daniel Farb, Architect, in
close cooperation with the Parks Department.
A detailed analysis carried out by means of the WRE model has
indicated that surcharge is limited to a small section of
the trunk sewer and will be less than 4 feet for the 1/5 year
storm. Figure 3 illustrates the need to define the lag in
time between flows from the two parts of the watershed.
79
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Pre- and post-development flows are compared in the follow-
ing table. Simulations were carried out not only for
design storms but also for real storms with a frequency
of 1/25 years.
Post-Dev. (no Post-Develop, with
Storm Pre- Stormwater Stormwater Manage-
Recurrence Dev. Management) ment (cfs)
Interval (cfs) (cfs)
2 yr. 32 110 60
5 yr. 50 168 75
10 yr. 67 220 85
25 yr. 93 275 95
Since the downstream watershed is under the jurisdiction
of the Borough of Scarborough, the design and computations
were submitted to this municipality for review at prelim-
inary and final stages. Special modelling aspects were
reviewed independently by Scarborough with the assistance
of a specialized consultant.
It is obvious that by using modellers and landscapers in a
drainage project, the cost of design will be increased as
compared to a traditional method. It was found, however,
that this additional expense is small compared |to the
savings in downstream channelization resulting from flow
reductions. Additional intangible benefits are increased
safety against flooding caused by overland flow and the
well-known environmental advantage of runoff control.
On the other hand, the detailed modelling effort and the
checking of results by various models and independent con-
sultants gave both municipalities the confidence that
future operation of the system was properly predicted.
It may be interesting to note that even if initially there
were some concerns related to the difficulties caused by a
80
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change in computation techniques, cooperation between town
engineers, modellers and consultants working for developers
proved that modelling could be easily implemented and assimi-
lated , even for a project with a higher than usual degree
of complexity.
81
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WEST
RISEBOROUGH
RESIDENTIAL
SUBDIVISION
82
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NORTHERN WATERSHED (94 Ac)
STRUT , PA*K(d»t.ntlon ill.)
S
Overland flow to Catch Ba$ins\ ONLY
STRUT
SOUTHEAST WATERSHED /
HWEST WATERSHED
STEETFSAVENUE
WEST RISEBOROUGH
DEVELOPMENT
SCHEMATIC OF STORM WATER
MANAGEMENT SYSTEM
OPERATION FOR 1/2 YEAR STORM
flow to Scarborough) FIGURE 2
-------
TIME hr
2 3
- 1 H
_e
N,
.s
2H
>-
i—
(X)
2
Uj
*-
Z
4-
100-)
5-YEAR HYETOGRAPH
50-
O
OUTFLOW HYDROGRAPH
FROM NORTHERN
WATERSHED INTO
UNDERGROUND STORAGE
(94 ACRES)
OUTFLOW HYDROGRAPH
FROM UNDERGROUND
v. STORAGE
TIME
3
hr
100-1
50-
100-
OUTFLOW HYDROGRAPH
FROM SOUTHERN
WATERSHED (66 ACRES)
50-
TIME
3
hr
TOTAL OUTFLOW
HYDROGRAPH TO
SCARBOROUGH
TIME
3
hr
FIG. 3 FLOW HYDROGRAPHS OF WEST RISEBOROUGH DEVELOPMENT FOR 1/5 YEAR STORM
-------
APPLICATION OF STORM TO ASSESS
THE IMPACT OF AN URBANIZING AREA
Presented by
C. Brcic, P.Eng.
Gore & Storrie Limited
Ottawa, Ontario
SWMM Users Group Meeting
Ottawa, Ontario May 4-5, 1978
85
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INTRODUCTION
The Rideau River, a major watercourse of Eastern Ontario, has a drainage
area of about 1,580 square miles and passes through the central urban
area of the City of Ottawa, where it drains into the Ottawa River. The
Ontario Ministry of the Environment has recognized the Rideau River as
sensitive with respect to its assimilative capacity and as such has
requested that comprehensive reports be prepared on the effects of
storm water discharge to the River from new developments.
This paper deals with the report on storm water management for the
proposed South Urban Community, which is the largest proposed community
from which all storm water drainage would be to the Rideau River,
either directly or indirectly.
PURPOSE OF STUDY
The proposed development of the South Urban Community and the policy of
the Ministry of the Environment with respect to any discharges to the
Rideau River, required that a detailed analysis be undertaken in order
to determine the quantity and quality aspects of the runoff generated
within this proposed development. The study required detailed analysis
and recommendations for a storm drainage system and method of storm water
management so as to meet quality objectives provided by the Ministry of
the Environment.
STUDY AREA
The study area, as shown on Figure No. 1, straddles the Rideau River
south of the N.C.C. Greenbelt which is a designated area restricting
urban development, surrounding the Ottawa urban area along with the
8fi
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BELLS
CORNERS
TOWNSHIP
OF NEPEAN
SOUTH ^TURBAN :Y
NITY :;•
AREA
TOWNSHIP OF
GLOUCESTER
REGIONAL MUNICIPALITY OF OTTAWA-CARLETON
TOWNSHIP OF NEPEAN TOWNSHIP OF GLOUCESTER
SOUTH URBAN COMMUNITY
REGIONAL SETTING
FIGURE NO. I
SCALE: I "= 3 Miles
SEPTEMBER,1977
GORE a STORRIE LIMITED
CONSULTING ENGINEERS
-------
Ottawa River on the north.
The total area involved in this study encompasses approximately 5,400
acres on both sides of the Rideau River, within the political boundaries
of the Townships of Nepean and Gloucester, on the west and east
respectively.
In addition to the Rideau River, two other water courses drain the study
area and carry runoff to the Rideau, namely the Jock River from the west
and the Mosquito Creek from the east.
The area is predominantly rural including various agricultural uses
extending to the banks of the major water courses. A significant urban
area exists in the northwest sector of the study area, while smaller
rural development is dispersed over the entire area. Thus, the existing
total population is believed to approximate 4,000 people.
PROPOSED DEVELOPMENT
The proposed development is expected to accomodate a population of
approximately 100,000 people when completed. In addition to residential
development, commercial core and industrial development would also be
included. Furthermore, extensive park lands have been proposed, thus
taking advantage of the existing waterways and their natural
surroundings.
A number of different plans for development have been proposed, however,
they differ by small degrees in their layout and extent of the various
projected land uses. Figure Nos. 2 & 3 show typical examples of the
proposed development plans.
In general, the proposed development aims for a distribution so as to
provide for a population of about 65,000 in the Township of Nepean and
approximately 35,000 within the lands situated in the Township of
88
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00
vo
GLOUCESTER TP.
OSGOODE TOWNSHIP
LEGEND:
REGIONAL MUNICIPALITY OF OTTAWA-CAR LETON
TOWNSHIP OF NEPEAN TOWNSHIP OF GLOUCESTER
SOUTH URBAN COMMUNITY
PROPOSED ALTERNATIVE PLAN 2A
FIG. NO. 2
Proposed Residential Development
Proposed Industrial Development
Proposed Core Area
Proposed Pork Lands
SCALE: l"= 5500'
SEPTEMBER 1977
GORE a STORRIE LIMITED
CONSULTING ENGINEERS
-------
vD
o
GLOUCESTER TP
OSGOODE TOWNSHIP
LEGEND:
REGIONAL MUNICIPALITY OF OTTAWA-CAR LETON
TOWNSHIP OF NEPEAN TOWNSHIP OF GLOUCESTER
SOUTH URBAN COMMUNITY
PROPOSED ALTERNATIVE PLAN 2B
FIG. NO. 3
Proposed Residential Development
Proposed Induttrlal Development
Proposed Core Area
Propoeed Park Lands
SCALE: I" 5500'
SEPTEMBER 1977
GORE a STORRIE LIMITED
CONSULTING ENGINEERS
-------
Gloucester. In addition, industrial development is allocated to portions
of the proposed areas in each Township.
RECEIVING WATERS
As mentioned previously, there are three significant watercourses within
the designated study area.
The most significant and largest, the Rideau River, has a drainage area
of about 1,480 square miles at its confluence with the Jock River and
drains the entire study area. The watershed of the Rideau River is shown
on Figure No. 4.
A number of smaller urban communities are situated within the Rideau River
watershed before it enters the urban area of Ottawa, namely the Towns of
Smith Falls, Perth and Kemptville, and in addition, the Village of
Manotick. However, the majority of the watershed is under agricultural
use or undeveloped woodlands.
The base flows during the summer months are in the range of 300 cfs and
can reach above 20,000 cfs during spring runoff.
The Jock River is the largest tributary of the Rideau with a watershed
encompassing about 211 square miles and the two waterways converge
within the present study area. The Town of Richmond and Heart's Desire
are two communities located adjacent to the Jock River. The majority
of the watershed entails agriculture, woodlands, and marshes. Flows
range from 2 cfs to 5,000 cfs.
The Mosquito Creek drains most of the study area on the east side of
the Rideau. This watercourse being relatively small, drains about
9,700 acres of rural land with no measurement of flow quantity available.
91
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10
RIDEAU RIVER WATERSHED
SURFACE WATER RESOURCES
MOSQUITO
CREEK
WATERSHED
SOUTH URBAN COMMUNITY
STUDY AREA
FIGURE NO. 4
REGIONAL MUNICIPALITY OF OTTAWA-CARLETON
TOWNSHIP OF NEPEAN TOWNSHIP OF GLOUCESTER
SOUTH URBAN COMMUNITY
SEPTEMBER 1977
GORE a STORRIE LIMtTED
CONSULTING ENGINEERS
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TABLE NO. 1*
(a) SAMPLING RESULTS - RIDEAU RIVER AT JOCK RIVER CONFLUENCE
Date
January 5, 1976
February 2, 1976
March 3, 1976
April 12, 1976
May 3, 1976
June 1, 1976
July 5, 1976
August 10, 1976
September 7, 1976
October 4, 1976
November 8, 1976
December 6, 1976
Time
(hrs)
10:40
10:50
09:50
13:15
10:00
09:30
09:00
09:30
10:45
10:00
10:00
09.25
Geometric Mean
Maximum
Minimum
Coliform (MF/lOOml)
Total
200
400
384
630
1300
500
400
100
50
200
170
490
294
1300
50
Fecal
10
30
48
1
52
_
-
1
2
8
6
> 10
8
52
1
Enter-
ococci
10
10
60
20
32
8
20
12
6
32
4
2
12
60
2
Dissolved
Oxygen
(mg/1)
12.0
n.o
11.0
12.0
9.0
8.0
10.0
9.0
9.0
9.0
6.0
10.0
9.7
12.0
6.0
5 -Day
BOD
(mg/1 )
3.0
0.4
1.6
-
1.4
1.0
1.8
3.2
1.2
1.2
0.8
0.6
1.5
3.2
0.4
(b) SAMPLING RESULTS - RIDEAU RIVER - 1976
Sampling
Location
Dam at
Kilmarnock
(55 miles)
Downstream of
Bridge at Kars
{24 miles)
Confluence with
Jock River -
Downstream
(15 miles)
Hog's Back Road
Ottawa
(7.1 miles)
St. Patrick St.
Bridge, Ottawa
(1.0 miles)
Geometric Mean
Maximum
Minimum
Geometric Mean
Maximum
Minimum
Geometric Mean
Maximum
Minimum
Geometric Mean
Maximum
Minimum
Geometric Mean
Maximum
Minimum
Coliform (MF/100 mi;
Total
796
35000
10
116
1160
10
294
1300
50
369
14800
50
298
2900
10
Fecal
34
1140
1
5
370
1
8
52
1
7
500
1
16
190
1
Enter-
OCOCC1
8
120
0
5
30
1
12
60
2
4
68
1
11
310
1
Dissolved
Oxygen
(mg/1)
10.3
12.0
8.0
9.4
12.0
8.0
9.7
12.0
6.0
10.2
12.0
8.0
n.o
18.0
6.6
5 -Day
BOD
(mg/1 )
1.4
4.6
0.6
1.1
1.6
0.6
1.5
3.2
0.4
1.0
1.2
0.2
1.1
2.1
0.4
(55 miles) - indicates distance upstream from Ottawa River
93
* Ministry of the Environment, Ontario S.E. Region, 1976 River Basins Water
Quality Data
-------
WATER QUALITY
Present water quality of the Rideau River indicates a B.O.D. value
generally less than 5.0 mg/L and the mean DO to be generally in excess
of 6.0 mg/L. Table No. 1 (a) & (b) following, indicates results of
sampling undertaken by the M.O.E. on the Rideau River at a location
within the area under study as well as at other locations.
The following results are based on limited sampling data but do indicate
the general value of quality parameters in the river water. The various
quality parameters may range well above the cited values during and
following periods of heavy rainfalls.
Some very limited data for the Jock River indicates B.O.D. values
generally below 2.0 mg/L and DO levels in the range of 8.0 to 10.0 mg/L,
with higher B.O.D. values shown to range from 8.0 to 10.0 mg/L during
times of peak runoff.
MINISTRY OF ENVIRONMENT GUIDELINES
Due to the low base flows, the assimilation capacity of the Rideau
River during the summer months is limited, and the Ministry view that
"further development will have to be based on the principle of no
deterioration to the existing quality of local watercourses", the
Ministry has formulated a set of guidelines for quality standards
of storm water discharge to the Rideau River.
The M.O.E. guidelines provide effluent quality objectives and receiving
water quality objectives after mixing. The following water quality
objectives refer to average conditions throughout a "one-year" return
storm event.
94
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Effluent Objectives
B.O.D.
Total Phosphorous
Chlorine
Total Coliform
Fecal Coliform
Fecal Streptococci
S.S.
5 to 6 mg/L
1 mg/L
0.1 mg/L
1000/100 mL
100/100 mL
20/100 mL
maximum removal possible
Receiving Water Criteria
B.O.D.
Chlorine
Total Coliform
Fecal Coliform
Fecal Streptococci
4 mg/L
.02 mg/L
1000/100 mL
100/100 mL
20/100 mL
STORM WATER MANAGEMENT TECHNIQUES
General
The traditional approach to the problem of urban drainage has been to
minimize flooding and inconvenience to the urban community, resulting
in efficient storm water collection and transport systems which provide
a very rapid discharge to the receiving waters. This in turn has
resulted in the following:
a.) rapid washoff and associated increase in contaminants carried
to receiving waters,
b.) increased downstream peak flows possibly compounding erosion
problems,
95
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c.) change in ground cover due to development, with increased
imperviousness affecting the natural course of groundwater
infiltration, with the possible result of lowering ground-
water levels and base flows in natural watercourses.
It is the effect due to increased pollutant loading to the receiving
stream, and in this case the Rideau River, which is of prime concern
in this study.
Runoff Quality Related to Land Use
The rate of pollutant build-up is commonly associated with land use,
as the following table indicates.
TABLE NO. 2
POLLUTANT BUILD-UP RELATED
TO URBAN LAND USE
LAND USE
Residential
Commercial
Industrial
S.S.
B.O-D.
P04
N
(values represent Lbs./Acre per day)
4.8
33.6
9.8
.20
1.52
.44
.0022
.014
.0044
.02
.08
.06
The results in Table No. 2 indicate that the commercial portion of
developed land has the highest rate of build-up, followed by industrial
and then residential land uses. The amount of contaminants actually
washed off depends on the effectiveness of street cleaning practices.
Comparison of results in Table Nos. 2 & 3 show the notable effect of
street sweeping on commercial land use.
96
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TABLE NO. 3
POLLUTANT WASHOFF FROM
URBAN LAND USE
LAND USE
Residential
Commercial
Industrial
S.S.
B.O.D.
P04
N
(values represent Lbs./Acre per day)
4.27
2.58
7.70
.110
.056
.205
.0019
.0011
.0035
.018
.006
.049
The curves in Figure No. 5 show an idealized version of Quality-Quantity
hydrographs during the course of a storm for a typical, medium-sized
city.
Quality Curve
Concentration per Five Days of Accumulation
Total Total Kjcldahl
SolkJs COO BQDi. Phosphates Nitrogen lead Zinc Toll' Fecal
>g/l mg/l mg/l mg/l mg/l tng/l mg/l Cohforms* Colitwrrva
1000 140 70 30 3.0 VB 0 *0 250000 17000-
800 110 56 24 2.4 1.4 0 32 700000 14000 -
600 64 42 16 1.6 1.1 024 160000 10000
400 56 26 1.2 1.2 0.72 0.16 100000 6600 -
200 26 14 0.6 06 0 36 0 06 50000 3400 -
"Approximate Number of Organisms per 100 ml
FIGURE NO. 5
TYPICAL QUALITY-QUANTITY HYDROGRAPH
97
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The previous figure shows, in part, that the mass flow curve coincides
with the peak flow curve, thus indicating the major portion of total
solids to be washed off during the peak of the hydrograph. Conversely,
the latter portion of the hydrograph contributes a relatively small
portion of the mass loadings to the receiving stream.
Storm Water Runoff Controls
a.) Residential Land
Control of storm water on residential lands can be achieved
through:
- minimum grades on residential lots and drainage swales,
- attenuation of peak flows by applying the blue-green
concept and directing runoff from impervious areas
onto green open space areas,
- improving effectiveness of catch basin trap efficiency
through properly maintained sumps or use of filter bags
directly under the grating,
- integrating storm water retention ponds into the storm
drainage system to achieve flow quantity and quality
attenuation.
b.) Commercial, Institutional, Industrial Land
Controls of storm water runoff to some degree on these lands
can be attained through the following:
- retention by way of rooftop storage through the use of
control structures and large flat roof areas,
- parking lot storage of runoff through catch basin inlet
control which can serve to retard flow and can assist
in achieving some quality control if the settled material
is removed on a regular basis,
- integration of storm water retention ponds into the
storm drainage system similar to that applied in
residential areas.
98
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10
0.0
10
20
30
40
SO 60
TIME (Minutes)
70
80
100
no
REGIONAL MUNICIPALITY OF OTTAWA-CARLETON
TOWNSHIP OF NEPEAN TOWNSHIP OF GLOUCESTER
SOUTH URBAN COMMUNITY
RAINFALL INTENSITY DURATION CURVES
FIGURE NO. 6
GORE a STORRIE LIMITED
CONSULTING ENGINEERS
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SYSTEM DESIGN AND ANALYSIS
Current Design Practice
Presently, the municipalities use the Rational Method in the design of
storm sewers. Rainfall intensity is based on a time of concentration
applied to the 5-year rainfall intensity duration curve for the Ottawa
area. Curves for the 2-year, 5-year and 10-year return periods, shown
in Figure No. 6, are the ones used by the municipalities.
A summary of runoff coefficients as applied to the Rational Formula by
the municipalities are tabulated in Table No. 4, following:
TABLE NO. 4
SUMMARY OF RUNOFF COEFFICIENTS
Land Use Runoff Coefficient
Commercial 0.70
Light Industrial 0.60
Multi-Unit & Apartments 0.50 - 0.60
Single Family Residential 0.30 - 0.40
Parks & Playgrounds 0.20
The Rational Method with the above data was used to establish preliminary
sewer sizes for the study area.
Model Simulation
In order to assess the quality of runoff and the relative benefits of
the various storm water management controls, particularly in terms of
100
-------
storage, it was necessary to apply modelling techniques in this analysis.
The models applied and deemed appropriate to this study were the STORM
and SWMM.
Significant Quality Parameters Modelled
Parameters of concern related to storm water runoff from rural and urban
areas are related to the various functions of the receiving waters.
a.) Public Health
Standards used to measure the safety of a water body for primary
recreation uses, such as swimming, relate to levels of total and
fecal col iform and fecal streptococcus. The STORM Model version
used did not simulate coliform bacteria levels. Although newer
versions of the model have this capacity, it is questionable as
to how accurate any prediction of this kind would be, given the
site specific nature and tremendous variations of these parameters,
b.) Stream Eutrophication
Parameters which are the main source of accelerating the aging
process of a water body are Nitrogen and Phosphorous. In light
of the M.O.E. guidelines cited earlier, Phosphorous is regarded
in this study as the more critical with respect to storm water
runoff and therefore has been chosen as a parameter for modelling
purposes.
c.) Fish Life
The quality of fish life which can be supported by a water body
is greatly dependent on the available oxygen levels. As a result,
the Biochemical Oxygen Demand (B.O.D.) contributed by storm
water runoff, is chosen as a parameter for simulation.
101
-------
d.) Suspended Solids
With regard to storm water runoff, the suspended solids content
is significant because most other parameters are associated
with the solids content. Although the M.O.E. guidelines do not
state specific levels for suspended solids in runoff, the
simulation of this parameter is most desirable as it will assist
in determining the other parameters associated with it.
Furthermore, any removal of the solids content from storm water
runoff will similarly affect the associated parameters.
Accuracy of Predications
The accuracy of any predictions provided by the models are directly
dependent on the reliability of the input data. An intensive literature
review was undertaken to arrive at satisfactory pollutant loading rates.
For the most part, research has dealt with urban land uses with a more
limited emphasis on non-urban, undeveloped lands. As it was desirable
to compare the undeveloped and developed state of the study area,
both urban and non-urban loading rates were necessary. The most
significant sources of pollutant loading information, along with the
values suggested by them, are listed in Table No. 5.
At the bottom of Table No. 5 are shown the actual values used as input
for the simulation in this study. These values are similar to Source
No. 1 with some adjustment in order to depict a further breakdown of
land uses in the urban category. While Source No. 1 was regarded as
one of the most comprehensive in this regard, information from the
other sources was used judiciously for some modification.
In order to adequately assess the storm water runoff effects from the
study area in its present relatively undeveloped state, it was
necessary to delineate the various forms of current, predominantly
rural land uses. To this end, the Canadian Department of Agriculture
was helpful in providing a very detailed log of present land uses
102
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TABLE NO. 5
COMPARISON OF POLLUTANT LOADING RATES
Source
1 . EPA-Areawide Assessment
Procedures Manual - Volume I
- 1976 (Pg. 2-66)
2. Journal Water Pollution
Control Federation -
Volume 49, 1977 (Pg. 443)
3. "STORM" Programme Users
Manual - 1974
(Notes 1 & 2)
4. "STORM" Programme Users
Manual - 1976 (Appendix C)
5. EPA - STORM WATER MANAGEMENT
MODEL: Level I - Preliminary
Screening Procedures, 1976
(Pg. 17)
6. EPA - Water Pollution Aspects
of Street Surface Contamin-
ants, 1972 (Pg. 145)
Values used for input in
"STORM" in South Urban Community
Study
Land Use
Urban
Agriculture
Pasture
Forest
Urban
Agriculture
Pasture
Forest
Residential
Commercial
Industrial
Open or Park
Agriculture
Pasture
Forest
Residential
Commercial
Industrial
Agriculture
Pasture
Forest
Residential
Commercial
Industrial
Open or Park
Residential
Commercial
Industrial
Residential
Commercial
Industrial
Open
Agriculture
Pasture
Forest
Loading Rate (Ibs/acre/day)
Suspended
f" *. 1 " J
Sol ids
5.31
3.91
1.05
0.63
4.16
10.27
2.05
0.24
0.24
1.68
0.49
0.05
-
-
-
0.45
-
-
-
-
-
1.33
1.46
1.91
0.033
33.5
10.2
42.4
4.27
2.58
7.70
0.05
3.9
1.05
0.63
BOD.
0.109
0.063
0.027
0.013
0.183
0.044
0.027
0.012
0.011
0.076
0.022
0.002
.02
3.10
0.01
.07
.46
.39
.02
3.10
.01
0.065
0.210
0.080
.0013
0.204
0.056
0.218
.110
.066
.205
.013
.063
.027
.013
P
.0020
.0016
.0008
.0004
.0049
.0026
.0007
.0002
.00003
.00022
.00006
.000006
.022
.112
.000006
.0020
.0127
.0096
.00006
.1118
.000008
.00086
.0016
.00147
.000038
.0217
.0056
.0333
.0020
.0012
.0037
.00024
.00156
.00078
.00039
103
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^v^<^^s3oi^«^p^
LEGEND OF LAND USE
P-PASTURE
H-HAY
A-AGRICULTURAL (IDLE)
S-SOD FARMS, NURSERIES
C-CORN
G- SMALL GRAINS
R-RESIOENTIAL
Z-WOOOEO AREAS
F- SUMMER FALLOW
I - INSTITUTIONAL , CEMETERIES
FIGURE NO. 7
SOUTH URBAN COMMUNITY
CANADA DEPARTMENT OF AGRICULTURE
LOG OF PRESENT LAND USE
104
GORE 8 STORRIE LIMITED
CONSULTING ENGINEERS
-------
within the entire study area. A section of the map providing this
information is shown on Figure No. 7.
The input data depicting pollutant loading rates was applied to the
study area in accordance with the information shown on Figure No. 7.
In this manner, assessment of the study area in its present form was
determined.
In a similar manner, pollutant loading rates for urban land uses, as
shown in Table No. 5, were applied to the study area for the various
proposed development patterns.
Assessment of Development Proposals
It has been mentioned previously that a number of different proposals
for future development of this area have been conceived, while differing
to a minor degree. These differences entail somewhat more extensive
development areas for some and possible alternate location of the
commercial core for others.
In assessing all the development proposals, the STORM Model was used
in order to give relative amounts of washoff from all watersheds within
the study area.
Table No. 6, following, shows the results in terms of pollutant runoff
loading in Ibs/acre annually based on a rainfall record of 17 years.
The total tributary area used for each development proposal as well as
the existing land use was the same so that comparison could readily be
made.
It is noted at the bottom of Table No. 6 that the average washoff for
the existing case is significantly lower than that for the proposed
developments. However, among the 8 differing development plans, there
is no great variation in the results shown in this table, although
105
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TABLE NO. 6
SOUTH URBAN COMMUNITY
RESULTANT POLLUTANT RUNOFF LOADINGS
FOR ALTERNATIVE DEVELOPMENT PLAN PROPOSALS*
(Ibs./acre annually)
WATERSHED
Mosqui tO-F
Mosqul tO-S
Rideau-ES
Rideau-EN
Oarrhavpn-N
Rarrhflven-S
Hearts Desire
Ridp,iu-HWI
Jock-SE
Jock-SC
Jock-SW
Rideau-SWl
RtdDau-SW2
Mud Creek-S
TOTAL AVCRAfiE
Existing
S.S.
BO
220
211
185
169
254
319
41
266
250
224
163
192
198
198
B.O.D
2
4
11
23
13
4
42
2
5
4
4
7
7
4
9
P
.03
.1
.33
.69
.38
.11
1.27
.01
.07
.09
.07
.11
.11
.03
.24
Alternative 1A
S.S.
597
346
218
185
741
382
319
41
437
461
502
504
506
504
410
B.O.D
99
53
13
23
121
53
42
2
66
73
62
82
82
82
62
P
3.4
1.8
.4
.7
4.2
1.8
1.3
.01
2.2
2.5
2.8
2.8
2.8
2.8
2.11
Alternative IB
S.S.
384
378
224
185
749
310
442
41
431
440
494
504
505
503
399
R.O.D
56
62
14
23
123
51
65
2
65
72
81
82
82
82
61
P
1.9
2.2
.4
.7
4.3
1.8
2.2
.01
2.2
2.5
2.8
2.8
2.8
2.8
2.1
Alternative 2A
S.S.
306
359
220
219
713
356
319
366
389
399
267
195
306
198
335
B.0.0
SB
56
24
29
118
46
42
59
53
63
26
26
35
4
46
P
2.0
2.0
.8
.9
4.1
1.6
1.3
2.0
1.8
2.1
.8
.9
1.1
.03
1.53
Alternative 2B
S.S.
375
363
233
185
717
370
319
41
374
388
316
248
332
198
319
1.0.0
56
55
28
23
118
53
42
2
49
60
38
34
41
4
43
f
1.9
1.9
.9
.7
4.1
1.8
1.3
.01
1.6
2.0
1.3
1.1
1.3
.03
1.42
Alternative 3A
S.S.
372
368
384
228
695
332
319
256
365
345
257
261
307
198
335
1.0. D.
53
55
55
31
114
40
42
41
47
51
24
31
35
4
45
P
1.8
1.9
1.8
1.0
3.9
1.3
1.3
1.3
1.5
1.7
.7
1.0
1.1
.03
1.45
Alternative 3D
S.S.
391
346
365
185
700
372
466
63
451
383
249
258
316
198
339
B.0.0
54
50
60
23
115
54
64
2
70
61
22
28
38
4
46
P
1.9
1.7
2.0
.7
4.0
1.9
2.1
.01
2.4
2.1
.7
.9
1.2
.03
1.55
Alternative 4A
S.S.
372
358
375
211
726
428
360
41
485
381
324
285
233
198
341
B.O.D
55
51
62
32
120
64
58
2
79
57
40
34
17
4
48
P
1.9
1.7
2.1
1.1
4.1
2.2
1.9
.01
2.7
1.9
1.3
1.1
.4
.03
1.60
Alternative 4B
S.S.
388
370
446
IBS
724
450
466
54
504
424
324
237
299
198
362
B.O.D
58
55
72
23
119
68
64
2
82
6G
40
33
33
4
51
P
2.0
1.9
2.5
.7
4.1
2.3
2.1
.01
2.8
2.2
1.3
1.1
1.1
.03
1.72
o
CTl
-------
some higher washoff is indicated by Alternatives 1A and IB. These
proposals involve a somewhat greater extent of development within
the study area, while allowing for the same total population.
In view of the fact that none of the discussed proposals have been
adopted, this analysis with the results indicated in Table No. 6, was
considered in making the choice of one development plan proposal for
further analysis. As a result Alternative No. 2B along with a sub.-
option for the location of the central area, has been chosen as being
representative of the proposed development pattern. This plan is used
for the purpose of developing a storm sewer system and associated
storm water management facilities.
APPLICATION OF STORM WATER MANAGEMENT CONTROLS
Street Sweeping
It has been indicated that washoff from urban areas is directly affected
by the effectiveness of street sweeping. Figure No. 8 shows the increase
in pollutant concentration versus time for combined sewers and urban
storm water runoff. These plots imply that an effective street sweeping
program needs to be applied within a time interval more frequent than
20 days. As a result, the following street sweeping time intervals
are recommended as maximums for the proposed development area.
Residential - 2 weeks
Industrial - 2 weeks
Commercial - 2 to 3 days
Storm Hater Retention Ponds
a.) Size and Volume
In this study, the primary purpose of storm water retention ponds
is for quality control. In view of the fact that the M.O.E.
107
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5»0_
400
300
200
too
SUSPENDED SOLIDS
BOO
; ID is
DIIS SINCE USI OVEBFIOI
20
>20
(a) COMBINED SEWER POLLUTANT CONCENTRATION VERSUS
PRECEDING DRY-WEATHER PERIOD. MILWAUKEE. WISCONSIN.
70r
20 -
10 -
1600
- 500
- 400
- 300
• 200
- 100
12 16 20 24 28
STREET SWEEPING INTERVAL, d
32 36 40
(b) STORM WATER POLLUTANT CONCENTRATION VERSUS STREET
SWEEPING INTERVAL. DES MOINES.
FIGURE NO. 8
108
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«
b
1? 3.5
-------
Quality Objectives made reference to a "one year" storm, a
statistical analysis was applied to Ottawa rainfall records to
establish a one year storm. Analysis of arrays including all
events, annual extreme events and a Gumbel Distribution fit to
the extreme values, are shown in the plot on Figure No. 9- As
a result, a rainfall of 1.50 inches was assumed as the one year
storm. The storage required to fully contain the runoff from a
one-year storm in each of the urban watersheds, is shown in
Table No. 7.
TABLE NO. 7
COMPARISON OF STORAGE VOLUME REQUIREMENTS FOR
AND
OPTIMUM SIZE BASED ON RAINFALL RUNOFF
ANALYSIS (STORM)
1-YEAR STORM EVENT
(1.50 INCHES OF RAIN)
Optimum Size Based on Rainfall-Runoff Analysis (STORM)
Watershed
Mosquito-Ind.
Gloucest-Res.
Barrhaven-N
Barrhaven-S
Jock-South
Rideau-SW
Area
(ar.res)
405
1521
1148
815
833
323
Avg. "C"
("STORM")
.49
.40
.46
.46
.39
.37
No. of
Bypasses (Yr.)
3
3
3
3
3
3
Volume
, Ft. 3
480,769
1,442,308
1,282,051
961 ,538
801,282
272,436
Ac. -Ft.
11.0
33.1
29.4
22.1
18.4
6.25
Storage
Acre-Ft.
per Acre
.027
.022
.026
.027
.022
.019
1 Year Storm Event (1.50 inches of rain)
Watershed
Mosquito-lnd.
Gloucest-Res.
Barrhaven-N
Barrhaven-S
Jock-South
Rideau-SW
Area
(acres)
405
1521
1148
815
833
323
Avg. "C"
("STORM")
.49
.40
-46
.46
.39
.37
Runoff
(in.)
.740
.640
.695
.695
.589
.559
Volume
Ft. 3
1,087,910
3,334,821
2,896,228
2,056,120
1,781,011
655,421
Ac. -Ft.
25.0
76.6
66.5
47.2
40.9
15.0
Storage
Acre-Ft.
per Acre
.062
.050
.058
.058
.049
.046
110
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A second method was used to arrive at the size of the storm
water retention facilities. The STORM Model was applied to
analyse the actual rainfall record over an extended period,
with the land use as indicated on proposed development plans
and a pre-set flow through rate based on a desired detention
time. A plot indicating the results of this analysis for the
6 urban watersheds is shown on Figure No.10. Plots in Figure
No.10 indicate an optimum storage size to be where the curves
cease to provide a significant decrease in overflows for
increased storage volume. Therefore, a storage volume
corresponding to about 3 bypasses per year was chosen as the
optimum.
Table No. 7 shows the required storage volumes for each urban
watershed, based on the one year storm volume and on the STORM
Model analysis. Comparison of the data in the table shows a
volume requirement for the one year storm to be more than double
that shown as the optimum by the STORM analysis. Therefore, the
optimum storage volumes based on the latter method were used to
establish the size of the storm water retention ponds.
b.) Location
The location of the various ponding facilities was determined
based on providing a minimal number of outlets and incorporating
the storage facilities into the proposed trunk sewer systems. It was
desirable to have a ponding facility at the downstream end of
each storm s.ewer drainage system, in the case that some form of
treatment such as chemical addition could be readily applied if
the need arose at some time in the future. The locations of all
necessary ponding facilities have been shown on the Storm Drainage
Master Plan in Figure No. 12.
Storage facilities have already been planned or constructed for
portions of the study area located in Nepean Township, north of
the Jock River, and have been shown accordingly. Others have
been indicated in accordance with the analysis just described.
Ill
-------
MOSQUITO - IND
rl YEAR STORAGE
RUNOFF VOLUME
06 0.8 1.0 l!2
STORAGE (« I06 CU.FT.)
GLOUCESTER -RES.
|—I YE
I RUN
YEAR STORAGE
OFF VOLUME
1.3 2.0 2.3 3.0
STORAGE («IOS CU.FT.)
BARRHAVEN - N
I—I Y
I RUI
I YEAR STORAGE
INOFF VOLUME
STORAGE («IO CU.FT.)
(O
r
2
O 30-
• 24 HOUR EMPTYING TIME
12 HOUR EMPTYING TIME
BARRHAVEN - S
APPROXIMATE OPTIMUM
fl YEAR STORAG
RUNOFF VOLUMI
IS 20 25
STORAGE («I06 CU FT.)
JOCK - SOUTH
APPROXIMATE OPTIMUM
r
I YEAR STORAGE
RUNOFF VOLUME
I O 1.3 2.0 2 3
STORAGE (»I06 CU. FT.)
RIDEAU - SW
£ APPROXIMATE OPTIMUM
STORAGE VOLUME , yf-a
a^_^a I RUNG
0.3 04 05 0.6 0.7
I YEAR STORAGE
IFF VOLUME
0.8 0.9
STORAGE («I06 CU.FT.)
REGIONAL MUNICIPALITY OF OTTAWA - CARLETON
TOWNSHIP OF NEPEAN TOWNSHIP OF GLOUCESTER
SOUTH URBAN COMMUNITY
PLOT OF ANNUAL NO. OF OVERFLOWS VERSUS STORAGE CAPACITY
FIGURE NO. 10
GORE 8 STORRIE LIMITED
CONSULTING ENGINEERS
-------
With regard to the watersheds in Gloucester Township, consideration
was given to the apparent erosion problems along the Mosquito
Creek. As a result, outlets to this watercourse were minimal,
with the major portion of the runoff carried as far downstream
as possible.
Alternative locations for the commercial core area have also
been included in the analysis and are also shown on Figure No. 12.
Quality of Runoff
a.) Continuous Simulation
It was desirable to obtain average annual values for quantity
and quality of runoff being generated by the proposed development
area. The STORM Model was used to predict these values based on
recommended storage provided and pre-set flow through rates.
The effectiveness of the retention facilities, based on available
literature and ongoing research projects, has been assumed as
follows, for a retention period of 24 hours:
Suspended Solids Removal - 90%
B.O.D. Removal - 80%
Phosphorous Removal - 60%
In addition, preliminary results of current research indicate a
24-hour retention time to result in an effective die off rate
of coliform bacteria.
Table Nos. 8 & 9 summarize the quality of runoff entering the storm
water retention ponds, the effectiveness of the ponds and the
quality of discharge to the receiving waters. The values in these
tables indicate that the quality of discharge to the receiving
waters closely approaches the previously noted guidelines of the M.O.E.
113
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TABLE NO. 8
TOWNSHIP OF NEPEAN
SUMMARY OF AVERAGE ANNUAL MASHOFF
AND STORAGE TREATMENT EFFECTIVENESS
No Storage
Flow Into Ponds
Flow From Ponds
Flow Bypassed
Total Loading
to Receiving
Water
Watershed
Barrhaven-N
Barrhaven-S
Jock-South
Rideau-SW
Barrhaven-N
Barrhaven-S
Jock-South
Rideau-SW
Barrhaven-N
Barrhaven-S
Jock-South
Rideau-SW
Barrhaven-N
Barrhaven-S
Jock-South
Rideau-SW
Barrhaven-N
Barrhaven-S
Jock-South
Rideau-SW
Volume of ,
Washoff (ftj)
21,086,234
14,910,588
12,790,632
4,760,310
53,547,764
20,377,803
14,910,588
12,730,156
4,760,310
52,778,857
20,377,803
14,910,588
12,731,156
4,760,310
52,778,857
708,431
60,476
768,907
21,086,234
14,910,588
12,790,632
4,760,310
53,547,764
Total Pollutants
In Washoff (Ibs)
SS BOD P
854,107 83,561 4,878
402,539 38,644 2,302
373,766 36,200 2,136
133,883 13,055 758
1,764,295 171,460 10,074
775,887 75,908 4,431
402,539 38,644 2,302
371,999 36,029 2,126
133,883 13,055 758
1,684,308 163,636 9,617
77,589 15,182 1,772
40,254 7,729 921
37,200 7,206 850
13,388 2,611 303
168,431 32,728 3,846
26,974 2,639 154
1,767 171 10
28,741 2,810 164
104,563 17,821 1,926
40,254 7,729 921
38,967 7,377 860
13,388 2,611 303
197,172 35,538 4,010
Concentration of
Pollutant (MG/L)
SS BOD P
649 64 3.7
433 42 2.5
468 45 2.7
451 44 2.6
528 51 3.0
610 60 3.5
433 42 2.5
468 45 2.7
451 44 2.6
511 50 2.9
61 12 1-4
43 8 1.0
47 9 1.1
45 9 1.0
51 10 1.2
610 60 3.5
468 45 2.6
599 59 3.4
79 14 1.5
43 8 1.0
49 9 1.1
45 9 1.0
59 11 1.2
114
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TABLE NO. 9
TOWNSHIP OF GLOUCESTER
SUMMARY OF AVERAGE ANNUAL WASHOFF
AND STORAGE TREATMENT EFFECTIVENESS
No Storage
Flow Into Ponds
Flow From Ponds
Flow Bypassed
Total Loading
To Receiving
Water
Watershed
Mosquito-Ind.
Gloucester-Res.
Mosquito-Ind.
Gloucester-Res.
Mosquito-Ind.
Gloucester-Ind
Mosquito-Ind.
Gloucester-Res.
Mosquito-Ind.
Gloucester-Res.
Volume of ,
Washoff (ft3)
7,953,510
23,244,378
31,197,888
7,894,704
23,023,529
30,918,233
7,894,704
23,023,529
30,918,233
58,805
220,849
279,654
7,953,510
23,244,378
31,197,888
Total Pollutants
In Washoff (Ibs) j
SS BOD P
365,094 35,826 2,094
631,094 61,802 3,599
996,188 97,628 5,693
326,155 32,005 1,871
625,097 61,215 3,565
951,252 93,220 5,436
32,616 6,401 748
62,510 12,243 1,426
95,126 18,644 2,174
2,429 238 14
5,996 587 34
8,425 825 48
35,045 6,639 762
68,506 12,830 1,460
103,551 19,469 2,222
Concentration of
Pollutant (MG/L)
SS BOD P
736 72 4.2
435 43 2.5
512 50 2.9
662 65 3.8
435 43 2.5
493 48 2.8
66 13 1.5
44 9 .99
49 10 1.11
662 65 38
435 43 2.5
483 47 2.8
"71 1 O 1C
/I 10 1 -D
47 9 1.0
53 10 1.1
115
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TABLE NO. 10
COMPARISON OF STORM WATER RUNOFF CHARACTERISTICS
BEFORE AND AFTER URBANIZATION
TOWNSHIP OF NEPEAN
BEFORE URBANIZATION
AFTER URBANIZATION
WATERSHED
Barrhavcn - N
Barrhaven - 5
Jock - South
Rldeau - S.W.
TOTAL
Total Pollutant Washoff (Ibs/yr)
Volume of ,
Washoff (ft ) S.S. BOD P
5.250. UZ
2,544,267
2.630,69?
1,031.791
11,457,477
194,012
207,010
208,250
85.918
695,190
14,924
3,260
3,332
1,615
23.131
436
90
75
23
624
BEfORE PONDING
Total Pollutant Washoff (Ibs/yr)
Volume of ,
Washoff (ftj) S.S. BOD P
21,086.234
14,910.588
12,790,632
4.760,310
53.547,764
854.107
402,539
373,766
133,833
1,764,295
83,561
38.644
36,200
13,055
171,460
4,878
2.302
2,136
758
10,074
Volume ,
Washoff (ftj
21,086,234
14,910,588
12,790,632
4.760,310
53,547,764
AFTER PONDING
S.S. BOD
104.563
40.254
38,967
13.388
197,172
17,821
7.729
7,377
2,611
35.538
P
1,926
921
860
303
4.010
TOWNSHIP OF RLOUCESTER
BEFORE URBANIZATION
AFTER URBANIZATION
WATERSHED
Mosquito - Ind.
Gloucester - Res.
TOTAL
Total Pollutant Washoff (Ibs/yr)
Volume of ,
teshoff (ftj) S.S. BOD P
1,129,031
5,410,805
6.689,836
32,227
327,015
359.242
698
11,408
12,106
17
327
344
Volume of ,
Washoff (ftj)
7,953,510
23,244,378
31,197,888
BEFORE PONDING
Total Pollutant Washoff
S.S. BOD
365.094
631 ,094
996.188
35,826
61 ,802
97.628
(Ibs/yr)
P
2.094
3,599
5,693
Volume of ,
Washoff (ftj)
7,953,510
23,244,378
31,197,888
AFTER PONDING
S.S. BOD
35,045
68,506
103.551
6,639
12,830
19.469
P
762
1.460
2.222
-------
Table No. 10 shows the results of the comparison made on the
various runoff parameters for the study area under conditions
of present land use and after urbanization. This table clearly
shows the increase in the various runoff characteristics due
to urbanization. However, it is also shown that the implementation
of the storm water management practices, particularly the
retention facilities, can reduce significantly the amount of
pollutant washoff.
b.) Instantaneous Simulation
The SWMM Model was used to model a single event with a one year
synthetic storm based on a hyetograph developed by Keifer and Chu.
Characteristics dealing with the watershed and used in the SWMM
simulation are identical to those used with STORM, including the
recommended street sweeping interval. Figure No. 11 shows the
resulting inflow and outflow parameters for 2 urban watersheds,
based on results from the SWMM Model.
DESIGN OF STORM WATER DRAINAGE SYSTEM
Initially trunk storm sewer sizes were designed using the Rational Method
based on a storm with a 5-year return period, as described previously.
The retention pond volume was established based on a limited number
of overflows in an average year and are primarily used for quality
control. However, the ponding facilities will assist in attenuating
peak flows due to added storage being available.
The design of retention ponds, in addition to the total volume requirements,
should include the following:
a.) normal water depth 4 to 6 feet,
117
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-i, '00
RIDEAU - SW
_ —1—
OUTFLOW
•5
I
OUTFUOW
10 12 14
TIME (hr<)
16 IB 20 22 24
O
ffi
009
TIME (hr»)
16 IB 2O 22 24
REGIONAL MUNICIPALITY OF OTTAWA - CARLETON
TOWNSHIP OF NEPEAN TOWNSHIP OF GLOUCESTER
SOUTH URBAN COMMUNITY
RETENTION POND HYDROGRAPHS AND POLLUTOGRAPHS
FIGURE NO. I I
GORE a STORRIE LIMITED
CONSULTING ENGINEERS
-------
b.) provision of emergency overflow or bypass facilities in the
case of a severe storm exceeding the design volume,
c.) minimum pond area of 5 acres for aesthetic and recreational
reasons,
d.) side slopes of banks should be minimum 7 horizontal to 1
vertical for safety and ease of maintenance purposes,
e.) submergence and marking of inlet and outlet pipes for safety
purposes,
f.) minimum detention time of 24 hours for average 1 year storm,
g.) allowance in design for any necessary cleaning operations.
In designing the storm water drainage system, the Transport and Storage
Blocks of the SWMM Model were used to simulate the effect of the
recommended ponding facilities on the trunk sewer sizes. The effect of
the retention facilities on reducing peak flows is shown clearly in
Figure No. 12 , by the reduced pipe sizes downstream of the ponds.
Treatment of Storm Water
The analysis has indicated that chemical treatment will likely not be
required if all recommendations regarding development and storm water
management are followed. However, in the event that chemical treatment
such as a coagulant should be required at some time in the future, the
ponding facilities have been arranged in such a manner so that there is
one at the outlet of each urbanized drainage area. To reduce costs, the
number of these outlets has been kept to a minimum.
119
-------
to
o
PROPOSED TRUNK STORM SEWEF
(106") (SIZE WITHOUT POSOS1
42"
SIZE WITH PONDS
RETENTION PONDS
FIGURE NO. 12
SOUTH URBAN COMMUNITY
SORE 8 STORRIE LIMITED
CONSULTING ENGINEERS
-------
STAGING OF CONSTRUCTION AND ESTIMATED COSTS
Staging
The runoff from construction sites is known to transport a significant
amount of solids to the receiving watercourse. In view of this, it is
recommended that construction of the storm drainage system commence at
the downstream end of each drainage area with the retention facility.
This will provide some form of control for the removal of solids
originating in the active construction areas.
Estimated Costs
Table No. 11 summarizes the storm drainage system costs for the traditional
piped system based on the Rational Method Design and also for the
controlled system including the storm water management controls described
earlier in this study.
The costs shown include the cost of construction of the sewers and ponding
facilities plus an allowance of 15% for engineering and contingencies,
based on 1977 costs.
The system costs, considering the acreage involved in the proposed
development areas, amounts to approximately $8,400 per acre or about
$800 above the cost for the solely piped system. This increased cost,
however, can provide benefits over and above those available through
the traditional storm drainage design.
121
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TABLE NO. 11
ALTERNATIVE SYSTEM DESIGN COST COMPARISON
TOWNSHIP OF NEPEAN
(1156 acres)*
WATERSHED
Jock - S
Rideau - S.W.
Total
SYSTEM
Uncontrolled
Pipe System
Pioe
6,555,000
2,255,000
8,810,000
Controlled System of Pipes and Ponds
Pipe Ponds
5,910,000 1,220,000
2,015,000 595,000
7,925,000 1,815,000
Total
7-130,000
2,610,000
9,740,000
* Area does not include Barrhaven, which system has already been designed
and is to a large extent, constructed.
TOWNSHIP OF GLOUCESTER
(1926
WATERSHED
Mosquito - Ind.
Gloucester - Res.
Total
SYSTEM
Uncontrolled
Pipe System
Pipe
2,225,000
12,490,000
14,715,000
Controlled System of Pi
Pipe Ponds
2,615,000 595,000
9,785,000 3,180,000
12,400,000 3,775,000
aes and Ponds
Total
3,210,000
12,965,000
16,175,000
122
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SUMMARY
The use of modelling techniques has proved to be invaluable in the analysis
carried out in this study. The STORM Model was particularly useful for the
purpose of determining the relative effects on storm water runoff due to
existing land uses and various proposed developments. The SWMM Model enabled
the design of the storm drainage system, based on the use of storage facilities.
Although precise calibration of the Models was not feasible during the course
of this study, such calibration would be desirable for any application of
these models.
With regard to input data and particularly pollutant loading rates, these
have been based on the most recent literature available on the subject.
However, further research of this kind should clarify precisely the climatological
conditions such as annual precipitation, temperature range and thus indicate
the actual time interval represented by annual loading rates. Furthermore,
pollutant loading rates may be based on "build-up" or "washoff" of pollutants,
total or soluble portions, total land area or only impervious portions. These
items should be carefully analysed in the application of loading rates to
the particular models.
123
-------
REFERENCES
1. American Public Works Association, "Water Pollution Aspects of Urban
Runoff", PB 215 532 (1969)
2. Gore & Storrie Limited, "Report on Storm Water Management for the
South Urban Community", (1977)
3. Gore & Storrie Limited, "Report on Storm Water Management for the
Township of Nepean - Men" vale Area", 1977
4. Keifer, C.J. and Chu, H.H., "Synthetic Storm Pattern for Drainage
Design", Proceedings, ASCE August 1957
5. Pitt, R. and Field, R., "Water Quality Effects from Urban Runoff",
Journal of American Waterworks Association, Vol. 69 (Aug. 1977)
6. Urban Land Institute, American Society of Civil Engineers, and
National Association of Home Builders, "Residential-Storm Water
Management - Objectives, Principles & Design Considerations", (1975)
7. U.S. Army Corps of Engineers, Hydraulic Engineering Center, "STORM"
Model Users Manual (1976)
8. U.S. Environmental Protection Agency, "Areawide Assessment Procedures
Manual - Volume I", EPA-600/9-76-014 (1976)
9. U.S. Environmental Protection Agency, "Storm Water Management Model:
Level 1 - Preliminary Screening Procedures", EPA-600/2-76-275 (1976)
10. U.S. Environmental Protection Agency, "Urban Stormwater Management and
Technology - Update and Users' Guide", EPA-600/8-77-014 (1977)
11. U.S. Environmental Protection Agency, "Water Pollution Aspects of
Street Surface Contaminants", EPA-R2-72-081 (1972)
12. Wanielista, M.P., et al, "Nonpoint Source Effects on Water Quality",
Journal Water Pollution Control Federation, 49 (1977)
124
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METHODOLOGY FOR CALIBRATING
STORMWATER MODELS
1 ?
By Thomas K. Jewell , Thomas J. Nunno ,
and Donald Dean Adrian3, M. ASCE
Manuscript submitted for possible publication in Journal of the
Environmental Engineering Division, Proceedings of the American Society
of Civil Engineers.
Instructor, Department of Civil Engineering, University of Massachusetts,
Amherst, 01003
o
Research Assistant, Department of Civil Engineering, University of
Massachusetts, 01003
3
Professor, Department of Civil Engineering, University of Massachusetts,
Amherst, 01003.
125
-------
INTRODUCTION
A primary goal of the Water Pollution Control Act Amendments of 1972
(PL 92-500) is achievement of water quality that allows fishing and swimming
in all our nation's waters by 1983. Section 208 of PL 92-500 requires the
preparation of areawide waste management plans that define the best, mix of
point and nonpoint control strategies to meet this goal. Development of viable
plans is contingent upon knowing the nature of nonpoint pollutants. In urban areas,
nonpoint pollutants are carried by urban stormwater runoff; therefore the charac-
terization of stormwater runoff is of primary importance.
Difficulties involved in gathering storm runoff data and time and monetary
constraints make the complete characterization of urban stormwater runoff from
each catchment nearly impossible. Therefore, increased emphasis is being placed
on the use of computer models for predicting quantity and quality of urban
stormwater runoff. These computer models are cost effective and reasonably accurate
substitutes for extensive field data gathering programs, provided that the models
are calibrated and verified for conditions existent or, the particular catchment
being studied.
Calibration involves minimization of deviation between measured field conditions
and model output by adjusting parameters within the model. Some minimum amount
Point sources of pollution are defined as the pollutant discharges from municipal
sanitary sewer systems and industrial waste discharges. The public or private
agency having jurisdiction over point sources of pollutant discharge must obtain
a National Pollutant Discharge Elimination System Permit (NPDES permit), under
Section 402 of PL 92-500. Nonpoint sources of pollution are all other pollutant
discharge sources including agricultural runoff, storm water runoff and combined
sewer overflows.
126
-------
of field data is required to accomplish a reasonable calibration. Verification
is the process of checking the model calibration using an independent set of data.
Ideally, the verification data set should be as large as the calibration data set.
However, if limited data are available, it is usual practice to use the larger
portion of the data for calibration and the smaller portion of the data for
verification. A poor verification will indicate that more storm events reflecting
a greater range of conditions are needed in the calibration data set, or that the
model is inadequate and should be modified or rejected.
127
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METHODS OF CALIBRATION
Most models for predicting quality of stormwater runoff are coupled with
a quantity simulation model. Calibration of these models has consisted of cali-
bration of the quantity and quality models sequentially, using the output from
the calibrated quantity model as input to the quality model (5) 'Sometimes only
the quantity portion has been calibrated and default or estimated values have been
used for quality parameters (14).
In talking with practitioners of the art of stormwater management modeling,
it has become apparent that there are nearly as many ways to calibrate a quantity-
quality model as there are practitioners. Considering the wide range of approaches
taken, it is surprising that calibration methods are not discussed more frequently
in the literature. Few authors have described how they calibrated a model for
a specific study and fewer still have stated explicity what criteria were used
to determine when an adequate, or "best", fit was achieved. Descriptions of cali-
brations found in the literature follow.
Wanielista (14) used a single rainfall event to calibrate the U. S.
Environmental Protection Agency's Storm Water Management Model (SWMM) for a 28
acre catchment in Orlando, Florida. Impervious area surface storage depth and
resistance factor were adjusted to improve agreement between predicted and measure
hydrographs. Agreement was very good (less than 0.2% error), probably because
the catchment was about 96% impervious and the storm used was a relatively simple
one. The area was discretized into 18 subcatchments and flows were routed through
a system of 27 pipes, which further improved agreement. Very little was done in
the way of quality calibration. Model default values were used for surface pollutant
buildup rates. Predicted and measured mass emission rates were not compared.
128
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The U. S. Army Corps of Engineers Hydrologic Engineering Center's Storage,
Treatment, Overflow and Runoff Model for Metropolitan Masterplanning (STORM)
was calibrated for Atlanta, Georgia, using storm event data gathered from four
small, suburban catchments (5). Fifty-seven grab samples gathered from these four
catchments during 15 storm events were analyzed. Pollutant accumulation rates found
in STORM were adjusted to minimize the predictive error for the total lumped loads
from all four catchments. According to Holbrook, the predictive error for each
pollutant did not exceed 13% of the measured value. No information was given as
to how the predictive error was calculated.
Young (16) suggested that a general method of calibration should involve
adjustment of model parameters to produce dependent variable predictions that
have minimum standard error of estimate with respect to known values of the
dependent variables. Young did not indicate how large a data base would be required
to accomplish a reliable calibration.
Tne User's Manual (6) for the U. S. Environmental Protection Agency Storm
Water Management Model (SWMM) states that once the model is calibrated for one
storm event, little adjustment is needed for others.
129
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OBJECTIVES OF RESEARCH
One of the motivations for1 this research was a belief that the state-of-the-
art of stormwdtc>' management modeling does not allow single storm calibration.
Random storm variations and lack of knowledge concerning basin characteristic
parameters require that several storms be used for calibration and, if possible,
several more storms for verification. Only then can the model be used with
confidence.
The objectives of this research are to show how a stormwater management model
should be calibrated and verified for ar, urban basin using measured quantity
and quality data from several storm events, and how the model can then be used to
predict urban stormwater pollutant loads. Weaknesses of using single storm event
calibration will be pointed out.
130
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RATIONAL APPROACH TOWARD CALIBRATION
In order to generate discussion which will lead to more standardized methods
for calibrating stormwater management models, a new approach toward calibration
has been developed and applied to an urban basin. In developing this approach,
a basic premise was that quantity and quality portions of models should be separated
and calibrated independently. Following calibration, the model could be recombined
and used in its normal manner.
Because each portion of the model is being calibrated separately, it is not
necessary to use the same data set for both. This provides some flexibility as
to what field data are acceptable for calibration purposes. The main concern
is that each data set is representative of the average response of the basin.
The Storm Water Management Model (SWMM) was chosen to illustrate the approach.
SWMM was chosen because of its availability to consultants and planners and because
it is representative of the state-of-the-art in stormwater modeling. Quantity
and quality subroutines of SWMM were separated and calibrated using storm event
data taken from the 1014 acre (410 ha) Maple Brook basin (separate sewers) in Greenfield,
Massachusetts (see Figure 1). Measured rainfall and sewer flow data were used to
calibrate the quantity portion. The measured sewer flow data was used as input
to the quality subroutine and the predicted pollutant mass emission rates were
calibrated against measured mass emission rates. Model parameters were adjusted
to produce mimimum error in total runoff and mass emissions and sums of peak flow
rates across all calibration storms. Standard errors of estimate and normalized
standard errors of estimates were tabulated for each run t indicate relative
accuracy of calibration between runs. Independently calibrated subroutines were
recombined and a preliminary verification accomplished using an independent set
of data. The SWMM Runoff Block was then run in a continuous simulation mode to
131
-------
Figure 1. -- Comparison of Maple Brook Basin with Modeled Basin.
132
-------
MODELED BASIN
86! acres (348ha)/
pervious
MAPLE BROOK BASIN
153 acres (61.9 ha)
impervious
Overland Flow
CO
u>
Slope=
0.054ft/ft
40,000 ft 02,200m)
Not to
Scale
Routing Delay Conduit
S=0.0005ft/ft
L=2000ftBlOm)
n= 0.019
d=12ft. (37m)
asin Area = IOI4acres (4IOha)
Open/Park
Residential
Commercial
Industrial
-------
estimate yearly pollutant loadings from storniwater runoff in Greenfield,
Massachusetts. Pollutants considered were suspended solids, BODjj, total
phosphorus, cadmium, lead, and zinc. Use of SWMM in the continuous simulation
mode is a fairly recent development (12) and allows running SWMM for long periods
of time using one hour time steps and rainfall input from National Oceanic and
Atmospheric Administration (NOAA), Environmental Data Service card image tapes.
Output from continuous SWMM can be input to either the Storage/Treatment or
Receiving Water Blocks for further analysis. Advantages of using continuous SWMM
over the Crops of Engineers' STORM model for planning purposes include a more
sophisticated runoff quantity algorithm, more flexibility with respect to
storage/treatment alternatives, and simulation of receiving water effects.
The sums of peak flowrates described above were found by summing flowrates
at each peak occurring during all storms. Storms with multiple peaks added
multiple values. For example, the six storms used for quantity calibration had
12 peaks.
134
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GREENFIELD STUDY AREA
The Town of Greenfield is located in the northwest central portion of
Massachusetts, at the confluence of the Green, Deer-field, and Connecticut Rivers.
p
Greenfield has a total land area of 21 square miles (54 km ) and a population of
18,500. Land use varies from open, undeveloped land to the concentrated central
business district typical of most New England towns. Light industry is scattered
throughout several portions of the town.
Approximately 80 percent of the urbanized area of Greenfield is drained by
the Maple Brook separate storm sewer system. This sewer system evolved as the
urban area developed. The main trunk sewer was once a streambed. Elements of
the sewer system began appearing when culverts were installed where streets
crossed the brook. These culverts, many of which were constructed before the turn
of the century, were generally of rough stone rubble construction with a Manning
roughness factor of approximately 0.025. Tributary storm drains were laid under
streets perpendicular to the brook as the need arose. Eventually, as development
increased, the brook sections between the cross streets.were enclosed. In many
cases these enclosed sections were made larger and smoother than the older culvert
sections on either end. A schematic of the trunk sewer system is shown in Figure K
For this particular study, the entire Maple Brook basin was considered to
be one subcatchment. Average slope, percent impervious area and gutter length
were computed from data acquired for an earlier system analysis study which divided
the basin into 76 subcatchments. Characteristic width was taken as twice the length
of themain drainage channel through the basin, as was suggested intheSWMM User's
Manual (6). No sewer routing was included in the initial configuration.
135
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QUANTITY CALIBRATION
The objective of both the quantity and quality calibrations was to fit the
model to average catchment conditions. During calibration it was not necessary
to achieve close agreement of measured and predicted data for individual storm
events. The emphasis was on results integrated over the entire calibration data
set. If the assumption of representative data was valid, the calibrated model
would give accurate predictions of average annual runoff and pollutant loadings.
Calibration criteria established were: less than one percent error between
measured and predicted total volume of runoff and less than one percent error
between the sums of measured and predicted peak flow rates. The first criterion
was important because it measured long term volumetric discharge accuracy which was
important in the prediction of receiving waters response. The second criterion
indicated accuracy of short term volume predictions which would be important for
estimating storage/treatment requirements.
To aid in calibration, an auxiliary program was written to compare measured
and predicted flow and pollutant data and to compute representative statistics.
A flow chart of this program is presented as Figure 2. This program could be
used to compare quantity data alone, quality data alone, or both together. Sub-
routine QUAL, used to predict mass emission rates, contained the same logic found
in subroutine QSHED1 of SWMM.
Several statistics for measuring the accuracy of fit between measured and
predicted data were considered. Chow (2) has stated, "the goodness of fit of a
function, fitted to the observed points by any procedure, can be measured and tested
2
approximately by the x parameter." Young (16) has recommended that the standard
error of estimate be used. In a personal communication, Koenig suggested using a
function of the relative error, i.e. (preuicted-rneasured)/measured.
136
-------
Figure 2. -- Flow Chart - SWMM Calibration Program.
137
-------
Inpul from 3WMM |
Quantity Portion J
Calculate Flow
Differences
Calculate Squared
Difference
Print Quantity
Data
Calculate Measured
Mass
Emission Rates
Calculate Predicted
Mass
Emission Rates
(Subroutine Quality)
Calculate Pollutant
Differences
Calculate Squared Differences
Print Quantity
8
Quality Data
138
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Although the standard error of estimate was developed for regression analysis,
it was a frequently used statistic that appeared to have general applicability even
though the model used was not statistical. Thus it was chosen as a representative
statistic to measure the accuracy of fit between the measured and predicted data.
The standard error of estimate had the form
I (p.-m )2
SEE = [-^-^
in which
n = number of predicted and measured data points;
p. = predicted value of ith data point; and
m. = measured value of ith data point.
It expressed the degree of scatter in the measured data (7). A small SEE would
indicate good agreement between the measured and predicted data, and thus an
accurate calibration.
Flow data for calibration were gathered at the outfall of the Maple Brook sewer
using a sharp crested, suppressed weir. Stage was recorded continuously by a
Manning T-1000 transmitter coupled with a Rustrak strip chart recorder. Stage was
converted into flow by a computer program that corrected the standard weir equation
for velocity of approach. A Weathermeasure P501 rain gage was placed approximately
in the center of the basin. Rainfall was recorded in 0.01 inch (0.025 cm) increments
with a Rustrak recorder.
Data from six storm events were utilized for the quantity calibration. Table 1
gives the characteristics of the measured rainfall-runoff data. A wide range of
rainfall intensities and durations were used so the calibration should be
representative of conditions occurring on the catchment. Total rainfall of 3.94
inches (10.0 cm) represented approximately 10 percent of the average annual rainfall
139
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TABLE 1. Measured Rainfall-Runoff Data
Storm
Date
(1)
17 Oct 75
7 May 76
i June 76
7 July 76
11 July 76
3 Oct 76
Verification
Storm
17 Sept 76
Verification
Storm
4 April 77
Total
Rainfall,
in inches (2)
1.71
0.38
0.22
0.34
0.43
0.86
0.36
0.27
Duration,
in minutes (3)
980
70
420
115
260
580
260
300
Vol ume
Duration '
in inches per hour (4)
0.10
0.33
0.03
0.18
0.10
0.09
0.08
0.05
Total
Runoff,
in inches (5)
0.30
0.07
0.02
0.04
0.06
0.06
0.05
0.01
Runoff
Coefficient,
(6)
0.17
0.19
0.10
0.11
0.14
0.07
0.15
0.05
-------
for Greenfield. The average runoff coefficient, weighted by storm event rainfall,
was 0.14.
Initial catchment parameters for input to SWMM were derived from an earlier,
detailed discretization of the Maple Brook basin used for sewer system analysis
(7). Percent impervious area and slope were weighted according to area to
arrive at representative values for the 1014 acre (410 ha) basin. The average
slope remained constant throughout calibration at 0.054 ft/ft. Impervious area
was initially calculated as 23.3 percent. Characteristic width was initially taken
as twice the length of the main drainage channel through the basin, or 40,300 feet
(12,290 m). Default values found in SWMM were used for resistance factors,
depression storage depths and infiltration rates. If necessary, these parameters
could be adjusted during calibration.
Prior to commencing calibration, it was necessary to ascertain model output
sensitivity to changes in input parameters. Four studies have analyzed the
sensitivity of SWMM (4,6,7,10). For each of these studies, all parameters except
one were held constant. Then the parameter being tested was varied through a
range about the accepted mean value. The ratios of parameter values and total
predicted runoff volumes for the first three studies cited were calculated and
are in Table 2. The Procter and Redfern study indicated similar degrees of
sensitivity. Percent impervious area was the most, sensitive parameter.
Sensitivity of the other parameters was somewhat variable depending on the
characteristics of the basin modeled and the range of parameter values used.
With respect to total volume, the output was insensitive to pervious area depression
storage and impervious area Manning's n, and was quite insensitive to characteristic
width. The latter two parameters may, however, have had some effect on hydrograph
141
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TABLE 2. Sensitivity Analysis Results
Parameter
(1)
Percent
Impervious Area
Pervious Area
Minimum
Infiltration Rate
Characteristic
Width
Pervious Area
Manning's n
Impervious Area
Depression Storage
Pervious Area
Depression Storage
Impervious Area
Manning's n
Graham et al .
P-ang^
7:1
1:10
1:79
1:4
1:4
1:4
1:3
Total Volume, ,
2.01:1
1.82:1
2.00:1
1.36:1
1.24:1
1.02:1
1.02:1
Huber et al-
Range(4
-
1:150
-
1:150
1:200
1:50
1:100
Total Volume^
-
1.75:1
-
1.00:1
1.22:1
1.00:1
1.02:1
Jewel 1
Range,,.
vb
4:1
-
2:1
-
1:7
-
1:2,3
Total Volume,-,.
3.58:1
-
1.03:1
-
1.28:1
-
1.02:1
to
-------
shape. Impervious area depression storage may have a significant effect on total
volume of runoff, especially for low rainfall volume storm events. Model output
was sensitive to infiltration rates and pervious area Manning's n for some basins,
however, analysis has shown that pervious areas of the Maple Brook basin did not
contribute a significant amount to runoff. Thus the model output for the Greenfield
basin was insensitive to any changes in pervious area parameters.
From these sensitivity analyses, it was deduced that percent impervious area
would be the primary volume calibration factor. Characteristic width, impervious
area Manning's n, or possibly a routing conduit could be used to change the shapes
of the hydrographs and improve agreement between sums of measured and predicted
peak flows.
No program has been written that will optimize parameter values within a multi-
parameter model such as SWMM, If an optimization model could be written, it would
be complex and expensive to run. Also, the data base available for calibration
would probably not be sufficient to warrant using sophisticated optimization
techniques. Thus model calibration remains a subjective process, aided by
knowledge of model sensitivity and experience gained in previous calibrations.
The accuracy of calibration possible depends on the degree of discretization used.
A detailed discretization of the Maple Brook basin into 76 subcatchments and
routing of the flows through the Transport Block would afford the opportunity
of a more accurate calibration because of the more realistic portrayal of the
basin. The calibrated model using a detailed discretization would yield better
results for individual storm events but would be expensive to run for long periods
of time. For planning purposes (long term simulation) it is much less important
to calibrate for individual storm events so the whole basin can be adequately
portrayed by one subcatchment.
143
-------
Seven calibration runs were made before the criteria stated previously were
met. Table 3 gives the parameters changed and the results for each run. Figure 3
shows the convergence of the volume and sum of peaks criteria and reduction in
standard error of estimate. Figure 1 shows a schematic of the basin as modeled.
The uncalibrated model (run 1) predicted 60 percent more flow than was
measured. Predicted peak flowrates were occurring before measured peak flowrates
and the sum of the predicted peak flowrates was 110 percent high. To improve
total volume agreement, the percent impervious area was reduced by a factor equal
to the Vm/V ratio. This method of adjusting percent impervious area was carried
through subsequent calibration runs. To improve temporal and magnitude agreement
of peak flow rates, characteristic width and impervious area Manning's n were adjusted
during the second and third runs, respectively. It became clear during subsequent
runs that reasonable adjustment of these parameters would not produce agreement
between sums of measured and predicted peak flow rates. Therefore during the fourth
run, a single, 2000 foot (510 m) conduit with a slope of 0.0005 ft/ft was added to
provide routing delay. Size and Manning's n of the conduit were adjusted until the
criterion of +_ one percent between sums of measured and predicted peak flows was
met. The final ratio of predicted and measured volumes (1-000) and the final
ratio of sums of measured and predicted peak flow rates (1.007) were both within
the +_ one percent criteria. Note that the standard error of estimate had a minimum
value after run five then increased slightly through run seven. Although the SEE
is an indicator of accuracy of fit, it is not necessarily minimized by meeting the
calibration criteria set. This is consistent with the objective of calibrating
for long term agreement rather that individual storm event reproduction. Although
both criteria have been met, there is still some time lag between predicted and
measured peaks. If these time lags could be eliminated, it would improve the SEE
144
-------
TABLE 3. Quantity Calibration Data
Run
(Jl
Subcatchment
Parameters ^
•w*
Conduit
Parameters
(O
•r^
1-
•r—
s_
O
Percent * '
Impervious
Area
Characteristic
Width, in feet
Impervious
Area
Manning's n
Diameter,
in feet
Manning's
n
VVP
>VsPp
Standard
Error of
Estimate**
1 (3)
23.3
40300
0.013
-
-
0.626
0.477
21.00
2 w
14.0*
30000*
0.013
-
-
1.044
0.774
13.50
3(5)
14.6*
30000
0.03*
-
-
0.992
0.852
11.43
4 (6)
14.5*
30000
0.03
8.0
0.013
1.023
1.066
8.05
5 (7
14.8*
40000*
0.03
12.0*
0.025*
1.017
1.165
7.56
6(«i
15.1*
40000
0.013*
12.0
0.025
1.007
1.080
7.88
7 (»
15.1
40000
0.013
12.0
0.019*
1.000
1.007
8.40
* **
Indicates parameter has been adjusted from previous run. Units of cubic feet per second.
Note: 1 ft = 0.305 m; 1 cfs = 0.028 m3/m.
-------
25 -i
20 H
b ic
E lb
~v>
LU
«+—
O
O
iS 10
•a
a
•o
c
o
CO
1.2
I.I
1.0
.9
^ 8
W -°
o> .7
(C
5H
.6 -
.5 -
.4
.3
.2
0
T
2
Standard Error of Estimate
4
Run
w
o
•rf
4-1
Cfl
4-1
CO
T3
C
nJ
cfl
•H
M
-------
considerably. To demonstrate, all predicted flow rates were lagged by 5 minutes
and the resulting SEE was 7.87. However, artificially shifting results to achieve
better looking statistics would do nothing for the long terra simulation.
Examination of measured and predicted volume of runoff for individual storms
indicated that single storm calibration could result in signficantly different
total runoff predictions than were generated by the model calibrated across six
storms. For the calibrated model, the overall ratio of measured to predicted
volume was 1.00 while the ratios for individual storms were 1.43, 0.75, 1.20, 0.53,
0.71 and 1.01. The conclusion can be made that the single storm event calibrated
model could predict total volumes of runoff as much as 1.4 times or as little
as 0.5 times the volume predicted by the model calibrated with six storm events.
148
-------
QUALITY CALIBRATION
As described earlier, the calibration program used in this investigation
utilized an adaptation of SWMM subroutine QSHED1, driven by measured flow data,
to simulate pollutant washoff from the watershed. Measured pollutant concentrations
and simulated data were converted to mass emission rates (Ibs/min) for comparison.
The calibration program was structured so that comparisons could be made at time
intervals corresponding to the sampling times of measured data.
Maintenance of the ratio of predicted to measured mass emissions (P/M) at
1.0 was the primary quality calibration criterion. All storms were weighted
equally when predicted mass emissions were adjusted. The normalized standard
error of estimate was utilized for goodness of fit comparisons between different
pollutants.
Samples for quality analysis were collected using a Manning S-4000 automatic
sampler in combination with a Manning T-1000 dipper-transmitter stage recorder.
The sampler intake line was located at approximately middepth, 20 feet (6.1 m)
upstream of a 3.0 foot (.9 m) sharp crested weir. In automatic mode, the sampler
was activated at a preselected stage height and took two 500 ml samples at 15 or
30 minute intervals, until 24 samples had been drawn. Manual mode sample collection
was also utilized, allowing the flexibility of choosing varying time intervals
depending on hydrograph dynamics.
Parameters determined for the quality analysis were suspended solids (SS),
biochemical oxygen demand (BOD5), total phosphorus, and three dissolved metals;
zinc, cadmium, and lead. Biochemical oxygen demand and suspended solids were chosen
because they are common indicators of the impact of urban runoff on receiving
waters. Total phosphorus can also be an important measure of urban runoff pollution,
Analysis of several samples indicated that BOD& was not influenced by toxic materials
for the Maple Brook basin.
149
-------
particularly if the basin drains into a slow moving stream or lake where alyal
blooms or eutrophicatiori may be problems. The choice of dissolved metals to be
monitored was based on a tradeoff between mass loadings in urban runoff and toxicity
to mankind. The importance of a data bass for both heavy metals and nutrients is
pointed out in a recent criticism of the EPA 1976 "Needs Survey" for treatment
of combined and stormwater flows which indicated that a lack of consideration for
these constituents would be an error (15).
Samples for suspended solids, BOD,-, and total phosphorus determinations were
preserved in an ice bath until analyses were performed. Samples for metals
analyses were preserved with 1 part per 100 of 50 percent nitric acid solution.
All analyses were accomplished using approved methods form Standard Methods (13).
The analyses performed were: suspended solids, non-filterable total residue; BOD,-,
five day incubation at 20°C and Winkler titration method for DO determination;
total phosphorus, ascorbic acid spectrophotometric method; zinc, direct flame
spectroscopy (Perkin-Elmer model 303); lead, three replicates through graphite
furnace and model 303 sensing unit (Perkin-Elmer HGA-70 graphite furnace); and
cadmium, same as lead.
Pollutant concentrations were multiplied by measured flow rates to determine
instantaneous mass emission rates for comparison during calibration. Measured
flow rates were also used to drive the SWMM surface pollutant washoff function
(Equation 4). Rainfall data were not necessary for quality calibration. The
quality data for this study was collected from May 1976 to December 1976. During
this period, reliable data was obtained for five storm events; on the dates of
6/1/76, 7/11/76, 9/17/76, 10/20/76, and 11/28/76.
For the initial uncalibrated SWMM simulation run, data was prepared according
to procedures outlined in the SWMM User's Manual, Version II (Huber, et al. 1975).
Surface quality data required included gutter length, street sweeping practices,
150
-------
catchbasin characteristics, and number of dry days antecedent to the storm event.
For purposes of this investigation, the basin was modeled as a single 1014
acre (410 ha) subcatchment. The total gutter length for the basin was found to be
141,700 feet (43,220 m). There were relatively few catchbasins in the Maple Brook
basin, so their effects were not modeled. Street sweeping frequency was approximately
60 days with one pass per cleaning.
SWMM predicts pollutant buildup as a linear function:
P. = DDFACT*QFACT.*ADD (2)
J J
in which
P. = mass of pollutant j on basin at start of storm;
J
DDFACT = dust and dirt accumulation rate for particular land use (lb/day/100 ft
of curb);
QFACT. = fraction of dust and dirt that is pollutant j; and
J
ADO = antecedent dry days (defined in SWMM as number of antecedent days for
which cumulative rainfall is less than 1.0 inch).
Pollutant buildup is corrected for periodic sweeping, when the antecendent dry
period exceeds the street sweeping frequency.
The definition of ADD presented in Equation 3 is consistent with the assumption
made to derive the pollutant washoff decay coefficient of Equation 4. The
assumption was made that 0.5 inches (1.3 cm) would wash off 90 percent of the
pollutants, therefore 1.0 inch (2.5 cm) would wash off 99 percent. Since nearly
all rainfall runs off impervious areas and pollutant washoff is only modeled for
impervious areas, the 1.0 inch (2.5 cm) cumulative rainfall criterion follows.
While initially there was no reason to doubt the ADD definition or the linear.
buildup rate, subsequent calibration efforts indicated that there was some fixed
antecedent period beyond which little additional pollutant accumulation would take
place.
ISi
-------
Default values for DDFACT and QFACT for various land uses are contained in
the model (6). These values were derived from an American Public Works Association
study of Chicago (1). The SWMM user has the option of inputing his own values for
DDFACT and QFACT based on local data.
Default values of DDFACF and QFACT were weighted according to area of the
basin in a particular land use to arrive at initial values for calibration. Area
weighted DDFACT for this basin was 1.39 Ibs of dust and dirt/day/100 ft of curb
(2.06 kg/day/100 m). Area weighted QFACT for BOD5 was 5.29 X 10~3. Suspended
solids QFACT was assumed to be 1.0, as was done in SWMM. QFACTs for total
phosphate were weighted to give an initial estimate for total phosphorus loading.
Since no QFACTs were available for dissolved metals, these were estimated based
on the concentration ranges of the measured data. All initial QFACT*DDFACT values
used are given in Table 4.
Data from five storm events were used to calibrate all pollutants except
suspended solids. Suspended solids data for the storm of 9/17/76 were saved for
preliminary verification, and suspended solids data from the storm of 11/28/76
were not used for calibration because they were believed to be atypical.
The results of the initial simulation run are presented in Table 4. The P/M
ratios for suspended solids and BODj. of 0.259 and 0.125 respectively indicate that
using the uncalibrated model for Greenfield would cause large errors in total mass
emissions. Predicted mass emissions for total phosphorus were two orders of
magnitude lower than measured loadings (P/M ratio = 0.0249); probably because
the SWMM P04 loadings were used as a first estimate of total phosphorus loadings.
Initial run metals emissions cannot be compared because the initial loadings were
not derived from existing model loadings.
152
-------
TABLE 4. Quality Calibration: Initial and First Runs
(1)
Initial
Unca libra ted
Run
First
Calibration
Run
QFACT*DDFACT, in (2)
lb/day/100 ft of Curb
Predicted/Measured
Mass Emissions
Normalized Standard
Error of Estimate
QFACT*DDFACT? in
lb/day/100 ft of Curb
Predicted/Measured
Mass Emissions
Normalized Standard
Error of Estimate
SS
(3)
1.39
0.259
6.42
5.36
1.00
2.80
BOD,
5 (4)
7. 35x1 O"3
0.125
1.57
5.91xlO"2
1.00
1.11
P
(5)
6.95xlO"5
0.0249
2.47
2. 68x1 O"3
1.00
1.47
Cd
(6)
1.39xlO"5
2.305
3.50
6. 03x1 O"6
1.00
3.78
Pb
(7)
3.48xlO"5
0.161
3.10
2.1 6x1 0~4
1.00
2.79
Zn
(8)
4.87xlO"5
0.114
2.05
4.27xlO"4
1.00
1.47
Ul
U)
Note: 1 lb/day/100 ft of curb = 1.485 kg/day/100 m of curb.
-------
After completion of the initial uncalibrated run, the next step was the adjust-
ment of the model parameters to satisfy the total mass emission calibration criteria.
Adjustment of QFACT for each pollutant proved to be the easiest way to make
predicted and measured mass emissions agree. Although this produced some unrealistic
QFACT values (QFACT for suspended solids became greater than 1.00) the only result
of interest was the product of QFACT and DDFACT (Ib of pollutant/day/loo ft of
curb), so QFACT could assume any convenient value.
The method of adjustment used was to divide the old QFACT by P/M to arrive
at a corrected QFACT. In effect, all mass emission rates were increased by the
factor 1/(P/M). When summed across all calibration storms, the adjusted mass
emissions agreed with measured emissions, as is shown in Table 4. This initial
adjustment improved the normalized standard error of estimate of all pollutants
except cadmium. Cadmium may not follow an exponential decay model and other
models should be investigated.
After satisfying the mass emissions criteria, further calibration efforts
focused on achieving a better curve fit. Results are shown in Table 5. To permit
comparison of calibration accuracy between pollutants, the SEE for each pollutant
was divided by the average measured mass emission rate for that pollutant. Thus
the SEE became nondimensional and was called the normalized standard error of
estimate.
The first calibration run seemed to indicate a better fit for BODj-, total
0
phosphorus, lead and zinc than for suspended solids. A review of the development
of the SWMM model revealed that during initial testing it was necessary to add an
availability factor to account for the portion of dust and dirt that is not
normally available for the production of suspended solids. Thus the equation for
prediction of suspended solids washoff ce:1.; as:
154
-------
TABLE 5. Further Attempts at Quality Calibration
First (1)
Calibration Run
(Used for
Continuous SWMMJ
No Availability
Factor
Antecedent Dry
Days Criterion
0.5 inches(l *3cm)
Cumulative
Rainfall
Constant
Pollutant
Loading
ADD=10 days
Mass Loading, in (2)
lb/day/100 ft of Curb
Normalized SEE
Mass Loading
Normalized SEE
Mass Loading
Normalized SEE
Mass Loading
Normalized SEE
SS(3)
5.36
2.80
0.479
3.65
5.36
2.80
4.48
2.86
BOD5 (4)
5.91xlO"2
1.11
5.91xlO~2
1.11
7. 62x1 O"2
0.96
0.111
0.765
P (5)
2.68xlO"3
1.47
2. 68x1 O"3
1.47
3. 36x1 O"3
1.34
5. 30x1 O"3
0.971
Cd (6)
6. 03x1 O"6
3.78
6. 03x1 O"6
3.78
6.81xlO"6
3.86
1.25xlO"5
2.40
Pb (7)
2.16xlO"4
2.79
2.1 6x1 0~4
2.79
2. 68x1 O"4
2.75
5.45xlO"4
2.45
Zn (8)
4.27xlO"4
1.47
4.27xlO"4
1.47
5. 65x1 O"4
1.34
9.61xlO"4
1.10
(Jl
cn
Note: 1 lb/day/100 ft of curb = 1.485 kg/day/100 m of curb.
-------
SSm = MJ0.057 v 1.4 Rm'-') [l-exp(-k Rm At)] (3)
Availability Factor Exponential Decay
m
\
in which
SS = pounds of suspended solids washed off during time step in;
M = pounds of suspended solids on subcatchment at start of time stem m;
R = runoff rate (inches/hour);
k = washoff decay coefficient (inches" ); and
At = simulation time step size (hours).
NOTE: Calculation of washoff for other pollutants is similar but
without availability factor.
The availability factor was a function of runoff rate and was developed using
data from Cincinnati, Ohio (9). Since the availability factor was derived from
site specific data, its generality was questionable. Therefore, it was removed
from the model and suspended solids mass loadings were readjusted to maintain agree-
ment with measured data. The calculated surface mass loading was lower but the
normalized standard error of estimate was higher, indicating that the availability
factor improved suspended solids predictions for the Greenfield data. Generality
of the availability factor is still in question and an indepth study would be
useful.
The next attempt to improve mass emission curve fit involved adjustment of
the washoff decay coefficient (k) in equation,4 from its default value of 4.6.
Changing k changed the shape of the mass emission curve, however, when total pre-
dicted mass emissions were readjusted to agree with measured data, little improve-
ment was made in the standard error of estimate over a wide range of k values
(k = 0.1 to k = 20). Indications were that SWMM was insensitive to changes in
value of k over the range of runoff rates normally encountered. Further research
156
-------
is needed, however, for the present time, it can be concluded that the washoff
decay coefficient is not an efficient calibration variable.
The effects of changing the antecedent dry days definition were also investi-
gated. Changing the criterion for cumulative rainfall from 1.0 inch (2.5 cm) to
0.5 inch (1.3 cm) improved the standard error of estimate for all pollutants except
cadmium by the amounts shown in Table 5. Next, the cumulative rainfall criterion
was completely removed and a constant mass of pollutants was made available at the
start of each, storm. To accomplish this, the ADO for each storm was set equal to
10 days. For constant ADD, standard errors of estimate decreased for all pollutants
except suspended solids. Suspended solids data for the storm of 11/28/76 had
not been included in the initial analysis because of the lo'ng dry period prior
to that storm (34 days). These data were reintroduced into the analysis when a
constant antecedent dry period was used. Results indicated that the pollutant
buildup rate was not linear and that there was a limit to the mass of pollutants
that could accumulate between storms, regardless of the length of dry period.
Sartor and Boyd (11) came to the same conclusions when they examined pollutant
buildup data from six different cities.
The data base for Greenfield was not sufficient to determine the functional
form of the pollutant buildup equation or the maximum pollutant buildup possible.
Therefore, the.published definition of ADD was used and the results of the first
calibration run were used for the calibrated model.
An examination of the individual storms used for quality calibration again
indicated the weakness of single storm event calibration. For example, the BOD5
measured to predicted mass emission ratios for the five storms used for calibration
were 1.31, 1.63, 0.75, 2.67, and 0.52. Thus, if the quality portion of the model
had been calibrated using only one storm, the annual BODK loadings predicted would
w
157
-------
have been anywhere from 0.52 to 2.67 times those predicted by the model as
calibrated over five storm events.
158
-------
VERIFICATION
Data from storms occurring on 1? September 1976 and 23 April 1977 were used
to verify flow and suspended solids predictions. Data from the 23 April 1977
storm was also used to verify BOD5 predictions. Rainfall and runoff characteristics
for these storms are shown at the bottom of Table 1.
Results of the verification were encouraging. The ratio of predicted to
measured total runoff was 0.92 while the same ratio for the sum of peak runoff
rates was 1.06. The ratios for total mass emission of suspended solids and BOD5
were 0.80 and 0.72 respectively.
It would have been better to accomplish the verification using data from four
or five storms of varying magnitude. However, the field data gathering program
in Greenfield has been terminated and further verification data will not be
available.
Data from a third storm was not used for verification because the short
antecedent dry period (.2 days) produced pollutant mass emission predictions that
were much lower than measured mass emissions. The predicted to measured mass
emission ratios for suspended solids and BOD5 were 0.10 and 0.21 respectively.
This provided further evidence that the pollutant accumulation rate was not
linear. A greater mass of pollutant was available on the basin soon after a
storm event than was predicted by the linear accumulation function. A need
exists to investigate improved methods for predicting pollutant accumulation.
159
-------
APPLICATION OF CALIBRATED MODEL
The calibrated model was used to predict annual stormwater pollutant
loadings from the 1014 acre (410 ha) Maple Brook basin. Ten years of hourly rain-
fall record for Amherst, Massachusetts [14 miles (22.5 km) from Greenfield] were
used to drive runoff calculations. No rainfall data tape was available for
Greenfield but a check of annual precipitation indicated that the average rainfall
for both locations was equal.
Annual loadings, average loadings, and standard deviations for the ten
years simulated are given in Table 6. Suspended solids loadings generally followed
annual precipitation, while loadings for the other pollutants showed little vari-
ation with annual rainfall. Lack of variability in BOD-, phosphorus, cadmium, lead,
and zinc indicated that the amount of runoff generated in Greenfield was sufficient
to wash the basin clean each year. The variability of the suspended solids loading
indicated that the converse was probably true for that pollutant. Some of the
suspended solids built up on the basin each year were not washed off and became
part of the basin.
Annual loadings of BOD,- and phosphorus agree quite well with annual loading
estimated from river sampling during an earlier study. DiGiano, et al. (3) sampled
flows during three discrete storm events. In terms of a 365 day year, DiGiano esti-
p
mated BOD^ and phosphorus loadings of 30 and 0.8 Ib/mi /day (5.2 and 0.14 kg/
2 7
km /day), respectively. Continuous simulation predicted a BODr loading of 45 Ib/mi /
o
2 ? 9
day (7.9 kg/km /day) and a total phosphorus loading of 2.0 Ib/mi /day (0.35 kg/km~/
day). Comparison of the annual suspended solids and BODg loadings from the Maple
Brook basin with those coming from the Greenfield secondary sewage treatment plant
indicated that stormwater contributed seven times as much suspended solids and
one-fifth as much BOD5 to the receiving waters as did the sewage treatment plant
effluent.
160
-------
TABLE 6. Yearly Loading Data
Year
(1)
1950
1951
1952
1953
1954
1955
!''!'. 6
1957
1958
1960
ftVG
ss**
Rainfall,
in inches
(2)
42.07
46.12
40.02
49.68
43.59
55.31
40.24
34.07
41.43
47.64
44.02
5.94
Runoff,
in inches
(3)
5.99
6.61
5.70
7.19
6.20
8.23
5.74
4.86
5.90
6.85
6.34
0.93
C*
(4)
0.14
0.14
0.14
0.15
0.14
0.15
0.14
0.14
0.14
0.14
0.14
0.00
SS,
in pounds
(5)
.146 x 107
.161 x 107
.139 x 107
.143 x 107
.130 x 107
.171 x 107
.138 x 107
.856 x 106
.132 x 107
.144 x 107
.139 x 107
.226 x 106
BOD5,
in pounds
(6)
.258 x 105
.278 x 105
.261 x 105
.256 x 105
.257 x 105
.241 x 105
.263 x 105
.249 x 105
.244 x 105
.259 x 105
.257 x 105
.105 x 104
P,
in pounds
(7)
.117 x 104
.126 x 104
.119 x 104
.116 x 104
.117 x 104
.109 x 104
.119 x 104
.113 x 104
.111 x 104
.118 x 104
.117 x 104
.477 x 102
Cd,
in pounds
(8)
2.63
2.83
2.66
2.62
2.62
2.46
2.68
2.54
2.49
2.64
2.62
0.10
Pb,
in pounds
(9)
94.5
102
95.6
93.9
94.1
88.1
96.3
91.1
89.2
94.8
94.0
3.9
Zn,
in pounds
(10)
186
201
189
185
186
174
190
179
176
187
185
8
C = Runoff coefficient
SS = Standard deviation
Note: 1 in = 2.54 cm; 1
Ib = 0.453 kg
-------
From the results shown in Table 6, it appears that two or three years of
continuous simulation would be sufficient to estimate yearly pollutant loadings
for all pollutants with the possible exception of suspended solids. The extra
cost of additional years of simulation is probably not warranted in light of the
consistency of results.
Another useful application of the calibrated model would be to test alter-
native outfall control measures or receiving waters effects. Alternatively,
loading factors could be converted back to individual land uses and the detailed
discretization of the basin could be utilized to test alternative land use distri-
butions and stormwater control measures within the basin. Use of the detailed
discretization would require some further calibration of the quantity portion
of the model but would require no further calibration of the quality portion.
162
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SUMMARY AND CONCLUSIONS
A method has been described for calibrating coupled quantity-quality urban
stormwater management models. By separating the quantity and quality portions
of the model it is possible to calibrate each using only measured data. The
calibrated model will be an accurate and economic tool for predicting alternative
futures.
The simplicity of the calibration procedure used should be emphasized.
Good quantity calibration can be achieved by adjustment of a few basin parameters
and quality calibration involves only the adjustment of pollutant buildup rates
for most cases. An advantage of the method used is that quantity and quality
portions of the model do not have to be calibrated with the same data set.
It is hard to quantitatively compare this calibration method with other pre-
viously used calibration methods because of the lack of discussion of multi-storm
calibrations in the literature and the lack of year long runoff quantity and
quality data sets to check final outputs. If data for other multi-storm calibrations
were available, the normalized standard error of estimate could be utilized to
compare the relative accuracy of methods.
The Storm Water Management Model was designed to be a deterministic model.
Theoretically it could be calibrated using any storm event with similar results (6).
However, the variation between storms of measured to predicted flow volume and
pollutant mass emission ratios (for the calibrated model) indicated that the model
did not precisely portray actual basin conditions. Therefore, different storm
events will result in different calibrations and different predictions. Calibra-
ting for average conditions across several storms will reduce predictive error
and increase confidence in results.
163
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ACKNOWLEDGMENTS
Portions of this study were supported by the following grants: University of
Massachusetts Water Resources Research Center WR-A095 and WR-B059, Massachusetts
Division of Water Pollution Control 76-10-2, and U. S. Environmental Protection
Agency RS03069. Field data were gathered by graduate and undergraduate assistants
Mark Tetreault, David Gaboury, Tom McAloon, Leslie Bruce, Jack Hamm, Bill Yen,
and Ricardo Grinberg-Funes. The authors wish to thank Dr. Francis A. DiGiano
and Professor Bernard B. Berger for their advice throughout this study, officials
of the Town Engineers Office and Department of Public Works of Greenfield for
their willing cooperation, Miss Dorothy Blasko for her typing of the manuscript,
and Dr. Louis Koenig for his advice on statistics.
]64
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APPENDIX I. - REFERENCES
1. American Public Works Association, "Water Pollution Aspects of Urban Runoff,"
tJJP^O-^, Federal Water Pollution Control Administration, U.S. Department
the Interior, Washington, D. C., Jan., 1969.
2. Chow, V. T., ed.s Handbook of Applied Hydrology, McGraw-Hill Book Company,
New York, N.Y., 1964, pp. 8-46 thrj 8-47.
3. DiGiano, F. A., Coler, R. A., Dahiya, R. C., and Berger, B. B., "Characterization
of Urban Runoff - Greenfield, Massachusetts, Phase II," Publication No. 84.
Special Report, Water Resources Research Center, University of Massachusetts,
Amherst, May, 1976.
4. Graham, P. H., Costello. L. S., and Mallon, H. J., "Estimation of Imperviousness
and Specific Curb Length for Forecasting Storrnwater Quality and Quantity,"
Journal of the Water Pollution Control Federation, Vol. 46, No. 4, Apr. 1974,-
pp. 717-725.
5. Holbrook, R. F., Perez, A. I., Turner, B. G., and Miller, H. I., "Stormwater
Studies and Alternatives in Atlanta," Journal of the Environmental Engineering
Divisu>n_, Proceedings of the American Society of Civil Engineers, Vol. 102,
No. EE6~, Dec., 1976", pp. 1263-1277.
6. Huber. W. C., Heaney. J. P., Medina, M. A., Peltz, W. A., Sheikh, H., and
Smith, G. F., "Storm Water Management Model, User's Manual, Version II,"
EPA-670/2-75-017, Environmental Protection Technology Series, U.S. Environmental
Protection Agency, Washington, D.C., 1975.
7. Jewell, T. K., "Application and Testing of the U. S. Environmental Protection
Agency Storm Water Management Model to Greenfield, Massachusetts," special
project report presented to the University of Massachusetts, at Amherst, Ma.,
in 1974, in partial fulfillment of the requirements for the degree of Master of
Science in Environmental Engineering.
8. Lapin, L. L., Statistics for Modern Business Decisions, Harcourt Brace Jovanovich,
Inc., New York, N.Y., 1973, pp. 461-463.
9. Metcalf and Eddy, Inc., University of Florida, and Water Resources Engineers,
Inc., "Storm Water Management Model, Volume I, Final Report," 11024 DOC 07/71.
Water Pollution Control Research Series, U. S. Environmental Protection Agency,
Washington, D. C., July, 1971.
10. Proctor and Redfern Limited and James F. MacLaren Limited, "Storm Water
Management Model Study, Volume I, Final Report," Project No. 73-5-10 Research
Program for the Abatement of Municipal Pollution under the Provisions of the
Canada-Ontario Agreement on Great Lakes Water Quality, Sept., 1976.
165
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11. Sartor. J. 0. and Royd, G. 15.. "Wnlor Pollution Aspects ol Shvei. Surface
Con tarn i nan I-..," I !'A-lw'- /"-OH' , I iwironm. nLa I I'rotei t, ion UvtmoUiiy Serif.,
U. S. Lnvi roninenlal rYol.ecl.ion Agency, Iv.tsh imiton, t>. (.. , Nov., I1)//.
12. Smith, G. F., "Adaptation of the EPA Storm Water Manaqeniont Model for Use in
Preliminary Planning for Control of Urban Storm Runoff," thesis presented to
the University of Florida, at Gainesville, Fla., in 1975, in partial fulfillment
of the requirements for the degree of Master of Engineering.
13. Standard Methods for the Examination of Water and Wastewater, 13th Ed.,
American Public Health Association, Washington, D. C., 1971.
i4. Wanlelista, M. P., "Nonpoint Source Effects," Report No. ESEI-76-b prepared
for Florida State Department of Environmental Regulation, by Florida Technological
University, Environmental Systems Engineering Institute, Orlando, Fla., Jan.,1976.
15. Winklehaus, C., "The 1976 'Needs' Survey for Treatment of Combined and Storm-
water Flows." Journal of the Water Pollution Control Federation, Vol. 49,
No. 1, Jan., 1977, p. 9.
16. Young, G. K. and Tierney, G. F., "Environmental Data Management," Journal of
the Water Resources Planning and Management Division, Proceedings of the American
Society of Civil Engineers. Vol. 102, No. WR2, Nov., 1976, pp. 255-264.
166
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APPENDIX II, - NOTATION
The following symbols are used in this paper:
ADD
DDFACT
k
Mm
m.
QFACT.
Rm
SEE
SSm
At
Subscripts
i
j
m
antecedent dry days;
dust and dirt accumulation rate for particular land use,
in pounds per day per 100 feet of curb;
washoff decay coefficient, in inches ;
mass of suspended solids on subcatchmerit at start of time
step m, in pounds;
measured value of ith data point, in pounds per minute;
number of predicted and measured data points;
mass of pollutant j on basin at start of storm, in pounds,
predicted value of ith data point, in pounds per minute;
fraction of dust and dirt that is pollutant j;
runoff rate during time step m, in inches per hour;
standard error of estimate;
mass of suspended solids washed off during time step m,
in pounds; and
simulation time step, in hours.
data point;
pollutant;
time step.
167
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SUMMARY
Methodology for Calibrating Stormwater Models, by Thomas K. Jewell,
Thomas J. Nunno, and Donald Dean Adrian. (EE). A method for calibrating
coupled quantity-quality stormwater management models is presented. Quantity
and quality subroutines are separated and each is calibrated using measured
data. Model parameters are adjusted based on sensitivity analyses, until
predicted and measured outputs are within stated calibration criteria.
168
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KEY WORDS
Environmental engineering, Hydrology, Modejs., Regional planning, Sewers,
Stormwater management, Storms, Urban p|dnnuKj, Water pollution
ABSTRACT
A method for calibrating coupled quantity-quality stormwater management
models is presented. The U, S. Environmental Protection Agency Storm Water
Management Model is used as an example. Quantity and quality subroutines are
separated and each is calibrated using measured data. Data from six storm
events are used for quantity calibration and data from five storm events are
used for quality calibration. Model parameters are adjusted, based on
sensitivity analyses, until predicted and measured outputs are within
stated calibration criteria. The calibrated subroutines are then recombined
and the coupled model is used to predict annual pollutant loadings. Loading
rates are compared with loading rates predicted using a single storm event
calibrated model.
169
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A SIMPLIFIED CONTINUOUS
RECEIVING WATER QUALITY MODEL
by
Miguel A. Medina Jr.
Department of Civil Engineering
Duke University
Durham, North Carolina 27706
Presented at SWMM
Users Group Meeting
May 4-5, 1978
Ottawa
Ontario, Canada
170
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INTRODUCTION
PROBLEM DEFINITION AND MANAGEMENT TOOLS
In a 1.67 square mile (433 hectare) urban watershed in Durham, North
Carolina, it was found that the dissolved oxygen content of the receiving
watercourse was independent of the degree of municipal waste treatment be-
yond secondary during storm flows (Colston, 1974). Approximately one-half
of the stream miles in the United States are water quality limited and 30
percent of these stream segments are considered polluted to a certain degree
with urban stonnwater runoff (Field, et al.. 1977). The implication is that,
generally, secondary treatment of dry-weather wastewater flows is insuffi-
cient to meet desired receiving water quality standards: therefore, control
of runoff pollution must be considered in areawide wastewater management
plans and abatement programs. The results of a nationwide assessment of
costs and related water quality impacts derived from non-point sources
(Heaney, et al., 1977) were, among others, that:
• wet-weather flows represent at least 50 percent of the
total wastewater flow from urban areas;
• a generalized optimization model, assuming linear costs,
predicted primary type facilities are preferable only up
to a 10 percent level of BOD removal for wet-weather flows,
with a secondary type facility preferable for higher
levels of control; and
• on a national average basis using BOD removal as the effec-
tiveness parameter, approximately 39 percent of the combined
sewer problem and 10 percent of the other wet-weather flows
should be controlled before initiating tertiary treatment
of point sources.
The study also confirmed that gross inadequacies exist in our present data
base and conclusions are highly sensitive to simplifying assumptions neces-
sary for successful simulation of complex physical processes occurring
throughout our watersheds. Nevertheless, mathematical models are needed
to predict variable responses to stochastic hydrologic phenomena.
171
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The 208 planning effort (Section 208, PL 92-500) has established the
need for various levels of urban water management analysis (Field, et al.,
1977) to permit preliminary screening of municipal treatment alternatives.
Four distinct levels of evaluation techniques, ranging from simple to com-
plex procedures which can be integrated with one another, are summarized in
Table 1. The first three levels essentially represent various degrees of
planning detail with models running on hourly time steps for long simulation
periods (years). Mathematical complexity and data requirements are kept at
a minimum. Of course, detailed (single-event) SWMM is typically used with
short time steps (minutes) and short simulation times (hours). Its data
requirements are usually very substantial. The approach guiding the devel-
opment of Level-III Receiving was that the cost-effectiveness of various
treatment alternatives can be determined realistically only by a continuous
analysis of the frequency of violation of water quality standards.
MODEL OVERVIEW
The essence of a rational water quality and quantity management program
is the decision making process. The high cost of pollution control facili-
ties, in terms of both energy utilization and financial burden, obligates
the planning agency to select the optimal strategy for areawide wastewater
management. Such a process must focus on a systematic procedure that identi-
fies and defines: 1) the cause/effect relationships of the physical environ-
ment; 2) the economic realities of control alternatives; and 3) the benefits
to be derived from implementation of these controls. A preliminary analy-
sis that provides an approximation of system responses to proposed treat-
ment measures should aid the selection of the best strategy for restoration
of water bodies to accepted water quality standards. Such an analysis must
never be interpreted as other than a guide to be tempered by professional
judgment. The mathematical models applied need not incorporate all pheno-
mena but rather should be relevant to the problem under consideration. The
problem of specific interest is to assess the separate and combined effects
of the major urban sources of water pollution upon the quality of the re-
ceiving waters. Oxygen concentration is considered the key to the quality
of natural water bodies, although it certainly is not the only water quality
indicator. Thus, the relative impact of these wastewater sources is appraised
172
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Table 1. Levels of Urban Water Management Analysis
(modified after Field, et al., 1977)
Level I: a desktop calculator, statistical analysis procedure, no elec-
tronic digital computer required.
• University of Florida Methodology - permits the user
to estimate the quantity and quality of urban runoff
in the combined, storm and unsewered portions of each
urban area
• Hydroscience, Inc. Methodology - use of a stormwater
simulator and an analytical method based on probability
distribution functions and statistical properties of
rainfall, runoff, treatment and'receiving water impact.
Level II: a simplified continuous simulation model for planning and pre-
liminary^* sizing of facilities, developed by Metcalf & Eddy,
Inc.
Level III: a refined continuous simulation model approach. Continuous
hydrologic simulation models (e.g., STOKM or continuous SWMM)
which generate urban runoff hydrographs and pollutographs are
followed by continuous receiving water impact analyses (Level
III - Receiving model).
• Continuous SWMM - University of Florida
• STOBM - for Corps of Engineers by Water Resources
Engineers, Inc.
• Level III - Receiving - Duke University
Level IV: a sophisticated single event simulation model, EPA SWMM devel-
oped by Metcalf & Eddy, Inc., University of Florida, and
Water Resources Engineers, Inc.
173
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by their effect on the dissolved oxygen concentrations downstream from
the urban area. It is of further interest to distinguish clearly be-
tween the two types of urban stonnwater runoff, separate sewer flow and
combined sewer overflow, and their relative pollutional impacts. In
essence, the mathematical model must be responsive to the land use,
hydrology, and climatology of the drainage area while performing the
following functions:
generate stormwater runoff pollutant loads and dry-weather
sanitary flow pollutant loads;
simulate the pollutant removal efficiency of various treatment
schemes;
simulate the conveyance system, including mixing in com-
bined sewers of wet- and dry-weather pollutants;
mix the various pollutant inflow combinations with pollu-
tants already in the receiving water (from upstream sources);
predict the oxygen balance of the polluted waters downstream
from the waste sources; and
predict the frequency with which wastewater inputs result in
dissolved oxygen levels in the receiving body of water which
exceed a wide range of DO values extending throughout the
possible spectrum (say, 0 to 15 mg/1 intervals of 0.5 mg/1).
Data for the study area are used to simulate the hypothetical response
of the receiving water to the separate and combined effects of BOD waste in-
puts from: 1) upstream sources, 2) dry-weather urban sources, and 3) wet-
weather urban sources. A system schematic is presented in Figure. 1. The
urban community served by a separate sewer system will convey stormwater run-
off and municipal sewage through conduits which are not connected together.
The BOD concentration of the storm sewer runoff is mixed with the dry-weather
flow (DWF) and accumulated sewer solids. An interceptor carries the sanitary
design flow to the municipal sewage treatment plant. The combined sewer
overflow is either given treatment or allowed to discharge directly to the
receiving water. Since complete mixing is assumed, the BOD concentrations
of the combined sewer overflow (Q ) and the flow (DWFCMB) intercepted for
treatment by the DWF facility are identical. Any degree of treatment
desired may be imposed at both the DWF and the wet-weather flow (WWF)
174
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SEPARATE SEWER SOURCE
•"I
URBAN RUNOFF
MUNICIPAL WASTEWATEH
COMBINED SEWER SOURCE
WWF
STORAGE /
TREATMENT
DWF
TREATMENT
35,303-f y OWFCM9, 300.
=
3YPASS
UPSTREAM
SOURCES
Figure 1. Urban Wastewater Inputs to. Receiving Body of Water
175
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treatment plants. The concentration of the combined BOD inputs in the
receiving water is given by:
uu d + BODfl,
Qu + Qd + QW
where BOD = mixed BOD concentration in receiving water, mg/1,
m
BOD = mixed BOD concentration from sources upstream of urban
area, mg/1,
BOD, = BOD concentration of dry-weather flow treatment plant
effluent, mg/1,
BOD = BOD concentration of wet-weather flow treatment facility
effluent, mg/1,
0 = upstream flow, cfs,
Q, » DWF treated effluent, cfs, and
0 = WWF treated effluent, cfs.
The technique for calculation of the quantity and quality of stormwater and
combined sewer overflows is discussed in further detail subsequently. The
BOD concentrations of the DWF and WWF treated effluents are given by:
[BOD . DWFSEP + BOD . DWFCMB](1-R )
BOD = - ± - S - 2_
DWFSEP + DWFCMB
[BOD . Q + BOD . Q ](1-R )
S C C
where BODf = BOD concentration of municipal sewage, mg/1,
BOD = mixed BOD concentration in the combined sewer, mg/1,
BOD = BOD concentration of urban stormwater runoff, mg/1,
S
DWFSEP » DWF contribution from separate sewer area, cfs,
DWFCMB = DWF contribution from combined sewer area, cfs,
176
-------
Qg » urban runoff carried by the separate storm sewer, cf s,
Q = combined sewer flow, cfs,
Rd = fraction removal of BOD achieved by the DWF treatment
facility, and
•
R ~ fraction removal of BOD achieved by the WWF treatment
facility.
The initial conditions of BOD in the river are defined by equation 1, and
the hypothetical impact on the oxygen balance of the receiving stream is
estimated by using simplified mathematical modeling approaches. The total
hours of runoff-producing rainfall throughout the year are separated into
storm events by defining a mininum interevent time. The procedure is dis-
cussed in detail subsequently. For a given storm event, the runoff and pol-
lutant loads are summed and the critical DO deficit is estimated as a func-
tion of several stream parameters: temperature, flow, oxygen concentration,
deoxygenation and reaeration rates, longitudinal dispersion, and BOD con-
centrations. The minimum DO is calculated subsequently and a frequency
analysis is performed. Stream velocity is computed as a function of the dis-
charge and the time and distance to each critical deficit point are obtained
for each event.
The options used for the simulations include:
1. five inflow combinations:
a. river flow + DWF
b. river flow + DWF + separate flow
c. river flow + DWF + combined flow
d. river flow + separate flow + combined flow
e. river flow + separate flow + combined flow + DWF,
2. four DWF treatment rates (variable),
3. three WWF treatment rates (variable), and
4. three fractions of measured upstream flow
may be investigated.
Item 4 is included as a model option to investigate whether the relative im-
pact of urban stormwater runoff is most significant in the upstream portions
of river basins. This effect may be simulated by simply reducing the
177
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upstream flow to any desired fraction of its actual measured value. Thus,
discharge into a dry river bed may be studied.
CALCULATION OF URBAN RUNOFF QUANTITY AND QUALITY
The methods used to generate storm runoff flows and pollutant mass
rates or concentrations depend upon the continuous hydrologic simulation
model selected by the user. Such techniques are well documented for two
models which may be applied to both urban and non-urban watersheds:
1) the Hydrologic Engineering Center's Storage, Treatment, Overflow, Runoff
Model (STORM), and 2) the U. S. Environmental Protection Agency's Storm
Water Management Model (SWMM), continuous version of Runoff Block. The
urban runoff flows and associated pollutant concentrations and mass rates,
derived from storm events over the drainage area of interest, represent
concurrent time series which are read by the program through the standard
card reader devices, or from peripheral storage units (disk/tape/drum).
Since the program has the built-in capability of accessing a user-created
data set, any continuous hydrologic and water quality model may be considered.
The interfacing of Level Ill-Receiving with STORM and continuous SWMM is
discussed in detail in the User's Manual (Medina, 1978). Regardless of
the models used, it should be noted by the user that the urban runoff
quantity and quality time series must represent hourly values.
PROGRAM OPERATION
The relationships among the main program and its Subroutines are
shown in Figure 2. The main program (hereafter referred to as
subroutine MAIN) provides overall control and includes in its entirety
the wet-weather flow model (WWFM). The WWFM is a mathematical abstraction
of the physical system depicted earlier in Figure 1. The WWFM in
subroutine MAIN simulates the conveyance system, including mixing in
combined sewers of wet-weather and dry-weather pollutants during periods
of runoff; the pollutant removal efficiency of various treatment schemes;
mixing of the various pollutant inflow combinations with upstream sources
in the receiving waters to determine initial conditions of BOD, DO, st -eamflow
178
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M
A
1
N
(WWM)
CORREL
MGRAPH
DWFM
PLOT
ROUND
*• CALLING
^, RETURNING
Figure 2, Level III - Receiving Subprograms
179
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and other parameters; and computes the oxygen balance of the polluted
waters downstream from the waste sources. The procedure continues for
each independent storm event as defined by the minimum intervene time
(MIT). After all the wet-weather events have been thusly processed,
frequency analyses are performed on either the resultant DO concentrations
at a specified location downstream, or critical (minimum) DO concentrations
as predicted by the model.
Subroutine CORREL subjects the hydrologic time series (either rainfall
or runoff) to autocorrelation analysis. It automatically defines the MIT
used in the WWFM to separate wet-weather events. This subroutine may be
executed independently of the WWFM, but may be accessed only through
subroutine MAIN. Subroutine MGRAPH, a single and multiple-curve plotting
subprogram, is called by CORREL to display the correlogram of Che time
series. MGRAPH, in turn, calls subroutine ROUND to set the appropriate scale
on the coordinates axes from examination of minimum and maximum values to
be plotted.
Subroutine DWFM performs the same functions as the WWFM, during periods
of no urban runoff. Thus, a model assumption is that no combined sewer
overflows occur. Therefore, there is no "first-flush" effect, and no
storm events over which to average pollutant loads. It may be executed
independently of all other subroutines, except MAIN. Subroutine PLOT is
called by the WWPM (contained in subroutine MAIN) and also by subroutine
DWFM to display frequency histograms of receiving water DO concentrations,
optionally. Likewise, subroutine MGRAPH is called by both models to plot
cumulative, multiple frequency curves of DO concentrations.
COMPUTER SYSTEM CORE REQUIREMENTS
Level Ill-Receiving has been tested with two different Central Processing
Units (CPU) and comparable supporting hardware. The Duke University
Computation Center (DUCC) is connected by a high-speed microwave link to
a dual IBM 370/165 configuration located at the Triangle Universities
Computation Center (TUCC) in the Research Triangle Park. The Northeast
Regional Data Center (NERDC), located at the University of Florida, is
equipped with an AMDAHL 470-V6/II.
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Level Ill-Receiving users have the option of running under either of
the two standard IBM compilers, G or H. IBM's minimum system requirements
for installation of the FORTRAN IV (G) compiler and the FORTRAN IV (H)
compiler are: respectively, 128k bytes and 256K bytes of storage. Further-
more, the user may run Level Ill-Receiving from the actual card version
( program source and data decks) or from a pre-compiled Load Module of the
program stored on disk. All of these options result in varying core storage
capacity requirements for the program. At TUCC, the FORTRAN G compiler is
much faster and is recommended for all debugging runs. However, the FORTRAN
H compiler has an optimization feature which-results in the compiled coding
being "optimized" for faster running in the execution step. Unless the user
actually alters the program, debugging should be unnecessary and most errors
will be due to incorrect formatting or sequencing of input data. Therefore,
the program should be compiled in H and the coding stored on disk for future
production runs. An additional feature is the IBM OS Loader, which replaces
the Link-Edit and Go steps with a single, faster operation. Core storage
capacity and average compilation times are presented in Table 2 for Level Ill-
Receiving under TUCC's IBM 370/165 system. By comparison, the FORTRAN
compiler of the AMDAHL 470-V6/II at NERDC required 110K bytes of core storage
for execution.
Additional computer system requirements include peripheral storage
devices which may consist of disk/tape/drum units depending upon machine
configuration and user-selected input options.
METHODOLOGY
EVENT DEFINITION
The basic approach to define a wet-weather event is to analyze the
runoff time series and establish the minimum number of consecutive dry-
weather hours (DWH) that separates independent storm events. The
independence of these events is not defined in a strictly climatologic
sense, it is in fact statistically derived. The DWH refer to periods
during which no runoff was produced. If STORM is selected to generate the
-------
Table 2, Compilation Times1 and Required
Core Capacity2
Compiler Compile
Time, sec
FORTRAN
G 29.4
FORTRAN
H 60.3
FORTRAN
G with IBM
OS Loader 28.6
Link-Edit Compile Execute
Time, sec Core Core
bytes bytes
10.3 146K 104K
9 . 9 300K 100K
none 14 6K 200K
1
Average values.
2IBM 370/165 system, Triangle Universities Computation Center.
182
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hydrologic time series, depression storage and evaporation rates must
be satisfied before any runoff is predicted but no runoff occurs during
periods of no measurable precipitation. The continuous version of
SWMM allows runoff to decay temporally beyond intervals with zero
•
precipitation input. Therefore, for an identical precipitation time
series, runoff events generated by SWMM will generally be of longer
duration.
The runoff time series is subjected to autocorrelation analysis. For
hydrologic processes, it is practical to estimate the autocorrelation
coefficients by an. open-series approach (Yevjevich, 1972 and Fiering and
Jackson, 1971) :
n-k
rx(k)
1
n-k
fn-k
E x
Li-1
•Q.
I
li-k-KL
x. -
I-fcKL
a
E
i-fcH.
0.5
(4)
where r_(k) » sample estimate of lag-k autocorrelation
coefficient for hydrologic process I,
x » discrete data series (observations) of hydrologic
process I'T for i =» l,2,...,n,
n «• total number of data points or observations,
and
k = number of hourly lags.
The tolerance limits for a normal random time series which is circular and
of lag 1 is given by (Anderson, 1942):
TL
-l±t
(5)
n-1
183
-------
where
t = standardized normal variate corresponding to
probability level 1 - a.
A circular time series is defined as a series where the last value is
followed by the first so that the time series repeats itself. Equation
(5) has been extended for use with an open series, for the general lag
case (Yevjevich, 1972). At a 95 percent probability level, the tolerance
limits are given by:
TL
11"™ i
A plot of the serial correlation coefficients, r(k), against the
number of lags, k, is called a correlogram. The technique of autocorrelation
analysis is essentially a study of the behavior of the correlogram of the
process under investigation (Quimpo, 1968). The model compares the value
of r(k) obtained from equation (1) with TL [r (k) f', computed by equation
(3), for the corresponding number of hourly lags k. The minimum inter-
event time (MIT) which separates independent wet-weather events is defined
as the minimum value of k for which r(k) is not significantly different from
zero at a 95 percent probability level.
EFFECT ON RECEIVING WATERS
A simplified mathematical modeling approach is used in which critical
deficits and resulting minimum DO concentrations are determined for a large
number of waste input combinations, treatment schemes, and receiving water
conditions. The development of a detailed and sophisticated model is not
justified for the problem context: to provide adequate information on the
relative effectiveness of various pollutant control strategies in achieving
selected water quality standards. The basic theory of mathematical modeling
of one-dimensional bodies of water is presented for the spectrum of natural
systems from freshwater streams to tidal rivers and estuaries. The approach
is particularly advantageous for a limited data base on natural system
geometry, hydrodynamic variables, and discrete rather than continuous water
184
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quality measurements.
Assumptions typical of models limited for interim planning are made
(Hydroscience, Inc. 1971):
(1) Temporal steady-state conditions prevail, where all system
parameters and inputs are constant with respect to time, however,
a relatively short time step (1 hour) is used for simulation.
(2) Natural system parameters (such as flow, velocity, hydraulic
depth, deoxygenation and reaeration rates, and longitudinal
dispersion) are spatially constant along the flow axis throughout
each time step.
(3) All waste inflows to the receiving body of water occur at one
point.
(4) The effects of various natural biological processes (algal
photosynthesis and respiration, benthal stabilization) are
incorporated into a background quality which is reflected by
DO deficit (if none, by saturation) upstream from the waste
inflow point. Any benthic buildup is incorporated into the
BOD decay rate.
(5) Waste treatment facilities operate at constant efficiencies,
independent of hydraulic and organic loadings, for the entire
period of simulation.
Oxygen Balance of Polluted Streams and Estuaries
In view of the modeling objectives, pollutant transport processes in
these systems may be adequately approximated by the one-dimensional version
of the classical convective diffusion equation. This partial differential
equation is based on the principle of conservation of mass (continuity)
and is given by:
|£- — [ E|£ - UC ]±IS (7)
3t 3x 9x
185
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where C = concentration of water quality parameter
(pollutant), M/L3,
t - time, T,
DC
-E— = mass flux due to longitudinal dispersion along
the flow axis, the x direction, M/L2T,
UC = mass flux due to advection by the fluid containing
the mass of pollutant, M/L2T,
S = sources or sinks of the substance C, M/L T,
U = flow velocity, L/T, and
2
E = longitudinal dispersion coefficient, L /T.
The equation assumes no diffusion of pollutants through the natural body of
water boundaries (other than what may be included in the source-sink term)
and is best suited to predict concentrations relatively far downstream from
the point of waste injection. Since critical DO deficits usually occur some
distance downstream from the waste source, equation (7) is particularly
well suited for such predictions.
APPLICATION TO STUDY AREA
The City of Des Moines, Iowa is located near the confluence of the
Des Moines River and the Raccoon River. It contains approximately
200,000 people out of the total of 288,000 for the metropolitan area (Davis
and Borchardt, 1974). The mean annual precipitation is 31.27 inches
(795 mm) which is approximately equal to the United States average, and
the average value for the State of Iowa. The urban area covers 49,000
acres (19,830 ha) of land which has gently rolling terrain. Most of the
area, 45,000 acres, is served by separate sewers, while 4,000 acres are
served by combined sewers.
Selection of the study area was based primarily on data availability.
Henningson, Durham & Richardson, Inc., Omaha, Nebraska, conducted an
extensive sampling program of combined sewer overflows, stonnwater discharges,
and surface waters in the Metropolitan Des Moines for the U. S. Environmental
186
-------
Protection Agency (Davis and Borchardt, 1974). The objective was a combined
sewer overflow abatement plan. The sampling program was conducted from
March 1968 to October 1969. Other considerations revolved around the fact
that Des Moines, Iowa is somewhat typical of many urban centers throughout
the country:
(1) it has a medium-sized population;
(2) its domestic and industrial dry weather flows
receive secondary treatment;
(3) its wastewaters are discharged into a non-tidal
receiving stream; and
(4) the urban area receives a mean annual precipitation equal
to the national average.
The verification procedure was preceded by calibration of the urban
runoff BOD_ loading rates for Des Moines, Iowa, as computed by STORM.
The dust and dirt surface loading factors were adjusted to obtain an
annual average BOD_ concentration of 53 mg/1 for urban stormwater runoff.
The above concentration was the average value determined by the field
monitoring program in the separate sewer system. The developed mathemati-
cal model, as discussed in the overview, simulates the mixing of storm-
water runoff and sanitary sewage in the combined sewer system. The
annual average BOD,, concentration of combined sewer overflows was computed
to be 75 mg/1, including the effects of first flush. The average value
measured in the combined sewer system was reported to be 72 mg/1. Model
parameters were adjusted to obtain an adequate fit between calculated
and observed profiles of dissolved oxygen. These curves are shown in
Figure 3, along with other pertinent information, and correspond to a
point 5.6 mi (9.0 km) downstream from the confluence of the Raccoon and
Des Moines Rivers.
The autocorrelation function of hourly runoff events for Des Moines,
Iowa is presented in Figure 4. At a number of hourly lags equal to zero,
the correlation of the discrete open series is unity because this point
represents the linear dependence of the data series on itself. A signifi-
cantly zero correlation (within 95 tolerance limits) between runoff events
first occurs at a lag of approximately 9 hours, defining the minimum
interevent time. The physical interpretation is that periods without
runoff for at least 9 hours separate uncorrelated, and therefore independent,
wet weather events. The hourly urban urban runoff and associated pollutant
187
-------
0.0-1
CD
00
MEASURED FLOW
+ URBAN RUNOFF
0-«
r-o
-20OO
-4OOO
-60OO
-8000
on
— 12,000
M I I I I I I I I I I I I I I II
I
MARCH
SO
100
130 200
DAYS
111• •« • i
260 900
DEC., 1968
|l Illli |HIIHIII|iJIIIII|IIIIIH II11111 jjll (ill
I IO 20 30 40 50
30 40
EVENTS
r-0
-100
— 2OO
-300
I
•O
Figure 3. Application to Des Molnes, Iowa. Measured and computed values of DO
5.6 ml (9.0 km) downstream from confluence of Raccoon and Des Molnes
at
Rivers.
-------
0.8-
-0.2-
MINIMUM INTEREVENT TIME
9 HOURS OF DRY WEATHER
95%T.I_
,f v n
x r^ r
n n
95% T. L.
OJO 10 20 30 40 SO 60 70 80 90 100
LAG k
Figure 4 Autocorrelation Functions of Hourly Urban Runoff
for Des Moines, Iowa, 1968.
189
-------
0.2-
93 % T. t_
\
J\ f\ j
tv / \ /
\A
/VV /V
98% T.L.
-ai-
-O2'
300 310 320 330 340 3SO 360 370 380 390 400
hours
O2<
0.1-
93% T. L.
\j v\j \ r\i\r
\A/\/ \ A/\
93% T. L.
-0.1-
.02-
4OO 410 420 430 440 430 460 470 460 490 30O
LAG K, hours
Figure- 4 (continued) - Autocorrelation Function of Hourly
Urban Runoff for Des Moines, Iowa,
1968.
190
-------
loads within each event (including DWF pollutant loads during DWH periods
less than nine hours duration) are summed, average conditions are determined,
and the model proceeds with the receiving water analysis.
Based on precipitation records obtained from the NOAA Environmental
Data Service (Asheville, North Carolina), the total rainfall that fell
over Des Moines, Iowa, during 1968 was 27.59 inches (701 mm). STOBM
computed a total runoff of 10.28 inches (261 mm) over a water shed area of
49,000 acres (19,600 ha), for an overall urban area runoff coefficient of
0.37. There were 65 days in the year during which rainfall was recorded,
from which 58 wet weather events were defined. The results are presented
in the form of minimum DO frequency curves for the wet weather and dry
weather periods throughout the calendar year.
It is appropriate to examine the model estimates of critical DO
concentration in the Des Moines River, for all waste Inputs, for
conditions assumed to exist in 1968 during periods of urban runoff;
(1) secondary treatment (85 percent BOD removal) of DWF; (2) no storm-
water treatment; (3) full river flow (100 percent of measured flow); and
(4) combined sewer area 8.16 percent of the total urban area. Figure 5
represents the minimum DO frequency curves for these conditions. The
curves indicate clearly that all combinations including s substantial
amount of wet weather flow (WWF) result in a drastic decrease in river
minimum DO concentrations. For example, 42 percent of all the wet
weather events throughout the year produced conditions in the receiving
water that caused minimum DO levels below 4.0 mg/1. Combined sewers
contributed WWF from only 8 percent of the total urban area modeled,
yet the BOD concentration was sufficiently high to inflict an appreciable
reduction in DO levels when compared to DWF sources during periods of
runoff.
Figure 6 displays the minimum DO frequency curves obtained by
varying the percent of the total urban area served by combined sewers.
There is a substantial, but not drastic, decrease in water quality when
the extreme conditions are compared: an area served only by separate
sewers (0 percent combined) versus an area served exclusively by combined
sewers. The curves support the theory that total separation of sewers
is not the answer to the control of urban runoff pollution. The curves
in this figure all represent secondary treatment of DWF, no urban runoff
191
-------
100
PRECIPITATION YEAR OF RECORD « 1968
OWF TREATMENT RATE' 83%(SECONDARY)
WWF TREATMENT RATE ' 0% (NO TREATMENT}
RIVER FUOW'100% (OF MEASURED FLOW)
COMBINED SEWER AREA' 3.16% (OF TOTAL URBAN AREA)
INFLOW COMBINATION
— RIVER FLOW + DWF
RIVER FLOW * OWF + SEPARATE FLOW
— RIVER FLOW •*• DWF*COMBINED FLOW
— RIVER FLOW + SEPARATE FLOW + COMBINED FLOW
RIVER FLOW + DWF 4- SEPARATE FLOW + COMBINED FLOW
INDICATES EVENTS EXCEEDING DESIRED D.O. LEVEL
4.0 6.0 8.0 10.0
DISSOLVED OXYGEN CONCENTRATION, mg/l
Figure 5. Minimum DO Frequency Curves for Existing Conditions
in the Des Moines River.
192
-------
100-
0 90-
0
UJ 80 •
O
0 70-
5
UJ
UJ
w 50-
i
W 40
cr
Ul
X 30
UJ
5 20
1-
UJ
^ 10
5?
T^\
N^~N
xv^ \\
\ \ \\
\ V v.
\ X A
\\v
\v
\N
\
0 2.0
PRECIPITATION YEAR OF RECORD '1968
DWF TREATMENT RATE' 85% (SECONDARY)
WWF TREATMENT RATE ' 0 % (NO TREATMENT)
RIVER FLOW < 100% (OF MEASURED FLOW)
INFLOW COMBINATION'
RIVER FLOW + DWF 4- COMBINED FLOW + SEPARATE FLOW
COMBINED AREA =
s 0% (OF TOTAL URBAN AREA)
\\ ai6% (OF TOTAL URBAN AREA)
x\ 50% (OF TOTAL URBAN AREA)
, \\ |00% (OF TOTAL URBAN AREA)
Y\
x\
*v '• ^\.
x ^ \
V^s~. x\
^^\-\ N\
\ \ v\
\ '''•• ^ \
•. \VN\.
>*wN.[ j*>
ns^T'\
^"^ ^--,
-j 1 | i i i i i i i i '
4.0 6.0 8.0 10.0 12.0 14.0
DISSOLVED OXYGEN CONCENTRATION, mg/l
6.- Minimum DO Frequency Curves for Varied Percent
of Combined Sewer Area.
193
-------
treatment, and full river flow.
The minimum DO frequency curves in Figure 7 compare four treatment
alternatives to reduce water pollution during periods of urban runoff:
1. 95 percent treatment of DWF and no treatment
of urban runoff,
2. 85 percent treatment of DWF and 25 percent
treatment (BOD removal) of WWF,
3. 85 percent treatment of DWF and 75 percent
treatment of WWF, and
4. 85 percent treatment of DWF and no treatment
of urban runoff.
The zero treatment and primary treatment curves are also shown for
comparison, but are not considered acceptable alternatives. It appears
that options 1 and 4 above result in comparable critical DO levels in
the receiving stream. However, options 2 and 3 result in much more
improved critical DO levels. An economic evaluation of these treatment
alternatives, on an annual basis, is presented subsequently.
Dry weather was experienced for approximately 300 days throughout
1968. The model was applied to these periods using a daily time step.
This modification is certainly justified since conditions are more truly
steady-state than during periods of precipitation and subsequent runoff:
for example, waste loadings (DWF treatment plant effluent) and river flow
do not vary as much during the day. For the dry weather simulation period,
upstream river flow was on the average 94 percent of total river flow,
ranging from 82 percent to 99.6 percent. The results are shown in Figure 8.
A remarkable 97 percent of the dry weather days exceed a minimum DO
concentration of 4.0 mg/1. Upgrading DWF treatment becomes meaningful
only if stream DO standards are set higher than 4.0 mg/1. The Des Moines
River carries a relatively high BOD load upstream of the Des Moines
urban area. Thus, even during dry weather periods only, a significant
increase in the DWF treatment rate does not result in a corresponding
increase in the critical DO levels.
To maintain the proper perspective, it is desirable to view the
effects of urban runoff on an annual basis, not just during periods of
wet weather. The frequency curves shown in Figure 7 and Figure 8 are
combined by weighting on the basis of the number of rainfall days and
dry weather days in the year. The composite totals are presented in
194
-------
100 T
O
Q
90 •
C9
"* 70
a
u
UJ
3 so
LU
50
-------
100-
O9O ""
Ci
z
UJ 80-
3
0 70-
s
o
Uj 60-
«? 50~
1
o:40-
LU
Z
^ 30 —
S
> 20-
§
3* 10-
O-
.^^--^^
"• ~ • ~" ". |^-^,7-»
s
1
, \ -^
\ \ \\
N\ V;
T. \ IV
1
1
r
\ \ v-
\\ \
\ \ V
\ \ ^
\ \ V
i
j
i
\ \ '
\\
\\.
SIMULATION PERIOD'
DRY WEATHER DAYS OF 1968
WASTE INPUT*
URBAN DWF + UPSTREAM SOURCES
RIVER FLOW' 100% OF MEASURED FLOW
DWF TREATMENT RATE «
95 % (TERTIARY)
85 % (SECONDARY)
30 % (PRIMARY)
x 0% (NO TREATMENT)
•vx INDICATES EVENTS EXCEEDING
'S\ DESIRED D.O. LEVEL
\\
\\
\\\\
\\v
1
1
\ \ V\
VA^
^"^H^'Xo
^^^^N
4
Y'^X
2.0 4.0 6.0 8.0 10.0 12.0
DISSOLVED OXYGEN CONCENTRATION, mg/l
14.0
%r--Dry Weather Minimum DO Frequency Curves for Varied
DWF Treatment Alternatives.
196
-------
Figure 9. For example, a given stream standard of 4.0 mg/1 is exceeded
90 percent of the time for existing conditions in Des Moines, Iowa,
throughout the year 1968. A significant amount of treatment (75% BOD
removal) of WWF in addition to secondary treatment of DWF results in
critical DO levels such that the same stream standard is exceeded 97
percent of the days in the year. Annual DO duration curves tend to
mask the impact of shock loads of organic pollutants discharged during
periods of urban runoff. A few extended violations of stream DO standards
may cause anaerobic conditions resulting in fish kills and proliferation of
undersirable microorganisms.
MODEL UTILITY FOR AREAWIDE WATER QUALITY MANAGEMENT PLANS
Municipal water pollution control alternatives should be evaluated
in terms of pollutant removal efficiency, receiving water impacts, and
associated costs. The true cost-effectiveness of various treatment
strategies can be determined realistically only by a continuous analysis
of the frequency o^ violation of established water quality standards. Of
course, in the selection of the best control strategy other factors may
become important: 1) recovery of receiving waters from shock loads
generated by urban runoff, 2) local and regional water quality goals
in addition to established standards, 3) public willingness to pay the
additional costs associated with increased control, and 4) dual use of
WWF facilities, as DWF treatment units during periods of no runoff.
The cost figures shown in Table 3 represent the additional
expense incurred in providing storage/treatment beyond that already
available with secondary treatment of DWF and no control of urban runoff
(existing conditions for Des Moines, Iowa). Details of the cost assessment
for typical wet-weather and dry-weather control facilities have been
presented in the nationwide study (Heaney, et al., 1977). The Des Moines
River stretches for 200 mi (322 km) from the City of Des Moines to its
junction with the Mississippi River and is generally wide and swift with
broad flood plain. Bottom material is composed of silt deposits, sand,
gravel and rubble providing numerous habitats for fish and other aquatic life
(State Hygienic Laboratory, 1974). The entire reach is classified by
the Iowa Water Quality Standards such that the absolute minimum DO level
197
-------
SIMULATION PERIOD' 1968
WASTE INPUT • UPSTREAM SOURCES » DWF *
SEPARATE SEWER FLOW » COMBINED SEWER FLOW
RIVER FLOW « 100% OF MEASURED FLOW
COMBINED SEWER AREA = 8.16% OF URBAN AREA
DWF TREATMENT RATE'
95 % (TERTIARY)
85 % (SECONDARY)
- 85 % (SECONDARY)
85 % (SECONDARY)
30 % (PRIMARY)
*\ 0 % (NO TREATMENT)
WWF TREATMENT RATE'
0 % (NO TREATMENT)
75%
25%
0 %(NO TREATMENT)
0%(NO TREATMENT)
0%(NO TREATMENT)
INDICATES EVENTS EXCEEDING DESIRED D.O. LEVEL
2.0 4.0 6.0 8.0 10.0 12.0
DISSOLVED OXYGEN CONCENTRATION, mg/1
Figure 9. ''Annual Minimum DO Frequency Curves.
198
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Table 3. DWF Tertiary Treatment vs. WWF Control
(Heaney, et al.. 1977)
Options
Amortized Annual
Capital Cost
$ (20 yrs, 8%)
Operation and
Maintenance Cost
($/yr)
Total Annual Cost
($/yr)
10
10
1. DWF Complete Tertiary
Treatment, No WWF
Treatment
2. DWF Activated Sludge-
Coagulation-Filtration,
No WWF Treatment
3. WWF 75% BOD Removal,
DWF Secondary Treatment
4. WWF 25% BOD Removal,
DWF Secondary Treatment
2,158,000
4,132,000
6,290,000
1,664,000
9,293,000
816,000
Based on 49,000 acres (19,600 ha) of developed urban area with population approximately
200,000. The total annual cost Includes amortized capital cost (20 yrs, 8%) and
operation and maintenance costs.
-------
must equal 4.0 mg/1, and 5.0 mg/1 during at least 16 hours per day
(State Hygienic Laboratory, 1970). The effects of various control strate-
gies upon the critical (minimum) DO concentrations of the Des Moines River
have been presented. Thus, taking 4.0 mg/1 as the standard or basis for water
quality comparisons, the different control options may be judged by the following
criteria:
1. total annual cost, and
2. violations of the minimum allowable dissolved oxygen level.
Table 4 summarizes control costs versus DO standard violations
for two advanced waste treatment options, two wet-weather control options,
and existing DWF secondary treatment facilities. For comparative purposes,
two additional treatment conditions which are not presently acceptable
by government regulation are present. Detailed process flow charts for
the DWF facilities are included in the nationwide assessment (Heaney, et al.,
1977). Results of the simulation and the economic evaluation reveal that:
1. since both types of tertiary treatment remove essentially
the same amount of BOD-, option 1 is justified over option
2 only when nutrient removal is necessary;
2. option 4 is preferred over any form of advanced waste
treatment;
3. option 3 is attractive because it causes the least amount
of damage to the receiving stream, but it is the most
expensive alternative; and
4. any reduction in the degree of DWF treatment for existing
conditions, option 5, results in a substantial deterioration
to receiving water dissolved oxygen levels and must be
s weighed against the savings incurred.
Furthermore, the issue of shock load prevention seems to favor high
levels of WWF control.
The user should be cautioned that the above results were derived
from application of the model to a specific urban area for a historical
record of storm events occurring during a particular year. However, the
usefulness of the methodology applied should be clear. The success of
its application still relies heavily on the quality of the field data
available. Dissolved oxygen in the receiving water body has been used
as the key indicator of water quality, yet other parameters may have to
be considered depending upon water quality goals. Complex hydrodynamic
200
-------
Table 4. • Cost-Effectiveness of Control Options
% Wet-Weather % Dry Days in Total Incremental Total No. of Days
Events1 Violating Year Violating Annual Cost2 During Year that
Options Standard Standard ($/yr) Standard is Violated3
1.
2.
3.
4.
5.
6.
7.
DWF Complete Tertiary 40 1.5 6,290,000
Treatment, No WWF
Treatment
DWF Activated Sludge 40 1.5 1,664,000
Coagulation- Filtration
Treatment, No WWF
Treatment
DWF Secondary Treatment 3 2.0 9,293,000
WWF 75Z BOD Removal
DWF Secondary Treatment, 30 2.0 816,000
WWF 25% BOD Removal
DWF Secondary Treatment, 42 2.0 0
No WWF Treatment
DWF Primary Treatment1*, 50 3.0 -1,438,000
No WWF Treatment
No DWF Treatment5, 53 7.0 -1,843,000
No WWF Treatment
31
31
8
26
33
42
55
^Defined by a minimum interevent time of 9 DWll.
2In addition to control costs for existing conditions (option 5).
3Based on a minimum allowable DO concentration of 4,0 rog/1.
"•Savings incurred by reducing DWF treatment of trickling filter plant of 35.3 mgd (1.55 cu m/sec).
5Savings by completely eliminating treatment.
-------
conditions will require additional, more detailed modeling efforts.
Engineering judgment must be exercised carefully in the interpretation of
model output and the importance of verification procedures cannot be
overemphasized. The model is a user assistance tool in the preparation of
water quality management plans, not a decision-maker by itself.
CONCLUSIONS
A simplified continuous receiving water quality model has been developed
to permit preliminary planning and screening of areawide urban wastewater
treatment alternatives in terms of frequency of water quality violations.
Model Capabilities
1. Level III-Receiving may be interfaced through peripheral storage
devices with various hourly, continuous urban catchment hydrologic
simulation models.
2. Continuous analysis of receiving water quality allows representation
of the impacts due to the random occurrence and probabilistic nature
of hydrologic phenomena.
3. A large number of wastewater inflow combinations to the receiving
body of water, dry-weather flow and wet-weather flow treatment
rates, and upstream flow conditions may be simulated.
Model Applications
1. Level Ill-Receiving has been developed on a general basis so that
it may be applied to any urban drainage basin by simply changing
the input data to reflect the particular study area and hydrologic
time series. There is virtually no limitation to the size of
catchment modeled.
2. In theory, an unlimited number of storm events may be processed;
however, practical considerations such as computer time and cos-ts
may be limiting to some users.
202
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3. Data requirements are common to engineering analysis on non-point
source problems and complete instructions on data preparation are
provided.
4. Field measurements, quantitative and qualitative, are necessary to
adequately calibrate model parameters and verify predicted values.
Model Limitations
1. The methodology is not applicable to stream and estuarine systems
exhibiting complex hydrodynamic characteristics, or of such
geometry that multi-dimensional analysis is required.
2. Complex water quality conditions, such as eutrophication, non-linear
kinetic interactions, sedimentation and sediment exchange are not
accounted for by the mathematical representation of the physical
system.
203
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REFERENCES
1. Anderson, R. L., "Distribution of the Serial Correlation Coefficients,"
Annals of Mathematical Statistics, Vol. 13, pp. 1-13, 1942.
2. Colston, N. V., "Characterization and Treatment of Urban Land Runoff,"
USEPA Report EPA-670/2-74-096, NTIS-PB 240 987, December 1974.
3. Davis, P. L. and Borchardt, F., "Combined Sewer Overflow Abatement Plan,"
USEPA Report EPA-R-73-170, April, 1974.
£•. Field, R., Tafuri, A. N., and Masters, H. E., "Urban Runoff Pollution
Control Technology Overview," EPA-600/2-77-047, March 1977.
5. Fiering, M. B. and Jackson, B. B., Synthetic Streamflows, Water Resources
Monograph 1, American Geophysical Union, Washington, DC, 1971.
v
6. Heaney, J. P., Huber, W. C., Medina, M. A., Murphy, M. P., Nix, S. J.,
and Hasan, S. M. , "Nationwide Evaluation of Combined Sewer Overflows
and Urban Stormwater Discharges," Volume II: Cost Assessment and Im-
pacts, EPA-600/2-77-064, March 1977.
7. Hydroscience, Inc., "Simplified Mathematical Modeling of Water Quality,"
USEPA, March 1971.
8. Linsley, R. and Crawford, N., "Continuous Simulation Models in Hydro-
logy," Geophysical research Letters, Vol. 1, No. 1, pp. 59-62, 1974.
9. Medina, Miguel A. Jr., "Level Ill-Receiving User's Manual," Department
of Civil Engineering, Duke University, March 1978 (draft).
10. Quimpo, R. G., "Autocorrelation and Spectral Analyses in Hydrology,"
J. Hyd. Div., Proc. ASCE, Vol. 94, No. HY2, pp. 363-373, March 1968.
11. State Hygienic Laboratory, "Des Moines River - Limnology Study," Report
submitted to the Department of Environmental Quality and the Iowa Water
Quality Commission, April 1974.
12. Yevjevich, V., Stochastic Processes in Hydrology, Water Resources
Publications, Fort Collins, Co, 1972.
204
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"USE OF THE HYDROLOGICAL ENGINEERING CENTER
STORAGE, TREATMENT, OVERFLOW, RUNOFF MODEL -
'STORM'
FOR SEWER INFLOW REMOVAL/TREATMENT
COST EFFECTIVE ANALYSES IN
THREE SELECTED LOCALITIES"
Rodney T. Prosser, Project Engineer
Howard M. Shapiro, Director of Engineering
LOZIER Architects Engineers
Rochester, New York
INTRODUCTION TO'INFLOW' & 'INFILTRATION1
Extraneous undesirable flows reaching a sanitary
sewer system are generally classified into two categories,
'Inflow1 and 'Infiltration1. It is generally accepted
that infiltration is caused by leakage from defective pipe
and manholes during high groundwater levels and that
inflow is the product of direct stormwater runoff connections
to the sanitary sewer system. 'Infiltration1 is generally
a relatively constant, seasonally varying flow and 'Inflow' a
rapidly fluctuating, shorter and more intense flow immediately
following rainfall occurrences. When evaluating sanitary
205
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sewer systems the distinction is not generally so clear as
the definitions would suggest and to differentiate the two
extraneous flow causes may be nearly impossible. In fact,
the same defective sewer joint may be a source of both 'Inflow'
from direct runoff during rainy periods and 'Infiltration'
during the Spring if the groundwater level is high and possibly
both at once.
Because 'Inflow' is generally a severe, peaking flow
condition, heavily taxing the capacity of both sewers and
treatment facilities, and because it is very difficult to
estimate what its ramifications might be for various intensity-
duration rainfalls over a period of several years, a reasonable
approach for evaluating its probable impacts and related
system costs had to be found.
In order to compare the costs of removal of inflow
to treatment of inflow a realistic estimate of the amount of
inflow to be expected over a design period must be established.
Inflow characteristics are very similar to stormwater runoff
flow characteristics, except for a decreased quantity (to be
expected) and increased rainfall/inflow lag time. Both these
characteristics can be accomodated by a simple 'stochastic'
model incorporating runoff coefficients of imperviousness and
a method for placing runoff volume into its appropriate time
interval, i.e. the unit hydrograph.
The H.E.C. model 'STORM', was chosen for the analyses.
It is a 'long-term' duration model that simply, but effectively
meets all the necessary requirements. The simplistic nature
206
-------
of the model requires that judicious engineering judgement
be used to set up appropriate system calibration factors
based on actual physical system characteristics. In
most cases, this can be adequately accomplished after flow
monitoring of various selected rainstorms. User's experience
and ability to understand the real mechanics allow meaningful
results to be obtained from a simple model of a highly •
complex situation. More detailed models of a parametric
(more closely approximated) and deterministic nature (function
for each relationship of importance) were not required by the
needs of this study. A close statistical probability and
frequency of various storm related excess flow occurrences
was needed and the capabilities of 'STORM' for meaningful
long term statistical and summary analysis made it ideally
suited for the application. Though its accuracy might be
questionable for close agreement of instanteous rainfall
and related inflow rates in any one storm occurrence, the total
volumes of inflow predicted based on many storms was found
to agree very closely with those measured and generally this
was all that was needed in the cost analyses.
'STORM' provides system analysis as depicted in
Fig. No. I. Rainfall striking impervious areas becomes
runoff after initial abstractions (mostly for depression
storage) have been satisfied. The runoff will become inflow
if tied into the sewer system and must subsequently be
treated or, in the case of a conventional combined system,
possibility overflow the system. The relationship of rainfall
207
-------
/ / '
''/''•' / / /
///// / / / / RAINFALL/SNOWMELT
STORAGE
DRY WEATHER
FLOW
SURFACE
RUNOFF
POLLUTANT
ACCUMULATION
POLLUTANT
V/ASHOFF AND
SOIL EROSION
OVERFLOW
TREATMENT
oo
o
Figure!. MAJOR PROCESSES MODELLED BY STORM
-------
to sewer inflow is governed by initial abstractions, impervious-
ness factors, drainage factors and time of travel defined
by the SCS unit hydrograph; no sewer routing techniques are
employed. All inflow as well as base sanitary flow will first
go to treatment until capacity is exceeded, then subsequently
through storage and to overflow; stored flow is bled through
treatment when allowable. All flow eventually discharges
to the receiving water.
INFLOW INVESTIGATION IN WEBSTER, N.Y.
Inflow problems in a portion of the sewer system
serving the Village of Webster necessitated an in-depth
analysis of the situation prior to design of new facilities.
Proposed improvements included upgrading Village and Town
facilities. Effluent from the Village treatment plant is
to be diverted to combined Town and Village phosphate removal
facilities at the new Town plant. Monitoring of inflow
clearly indicated that the worst problems occurred in the
older Village system, during the summer months of the year.
It was desired to determine the impact of inflow on treatment
facilities at both the Village and Town locations in terms
of frequency and severity of hyraulic overloads and the effect
on treatment facility efficiencies.
The 'STORM1 model was calibrated and verified for the
system. Very close correlation between measured and 'STORM' gener-
ated inflow volume was achieved (Fig. 2). Inflow results (Fig.'s 3 &
4) for the Village and Town plants indicated that even peak
209
-------
FIGURE 2
VILLAGE OF WEBSTER
INFLOW VOLUME VERIFICATION
APRIL 22, 1977
.40
.30
O
I
m
07
.20
.10
" RECORDED EVENT
| (HYDROGRAPH)
T
STORM MODEL
(HYDROGRAPH)
RECORDED RAINFALL
'I'
I
t
I
t
I
t
t
^START RAIN I / x' START FLOW INCREASE *.
>• ./ *^ ./X^ ' '
^ i i «/i£a--n i i i i
j_
1.6
1.4
1.2 z
o
1.0 S
0.6
0.6
0.4
O.Z
m
o
01 23456789
TIME (HOURS) FROM INITIAL FLOW INCREASE
10 II 12
-------
§ AVERAGE
B!
2
Cv
3.0 3.5 4.0
INFLOW RATE + TREATMENT PLANT
DURING STORM EVENTS ONLY
FLOW
4.5
(MGD)
5.0
1.0
INFLOW
PEAK
CM.G.D.)
OZlEB ENGINEERS, INC.
:OCHEST£R,N£W YORK
FIGURE N0.3
IMPACT OF SUMMER INFLOW
VILLAGE OF WEBSTER
PHASE 2
INFLOW/ INFILTRATION STUDY
OCTOBER 1977
211
FILS No. I9827R
-------
FIGURE 4
z
o
en
UJ
o
12.0
AVERAGE INFLOW RATE •*• TREATMENT PLANT FLOW (M.G.D.)
DURING STORM EVENTS ONLY
-A -
5 cc
O Ul
s!S
UJ
L- - ft^
^ O
o p
O
UJ
INFLOW PEAK RATE (M.G.D.)
-B-
IMPACT OF SUMMER INFLOW
TOWN OF WEBSTER
212
-------
inflow could be handled with the hydraulic capacity of the
dry weather facilities. It was then determined from the
small time in which inflow occurred and the fact that the
'fixed' media filters would not be washed out as an activated
sludge process might be during peak conditions that the
overall effect on treatment was negligible. The phosphate
removal facilities were found to be of adequate size, partially
due to the 5 hr. 'lag1 time for effluent from the Village
to reach the Town's facilities, by which time Town inflows
had already been treated and discharged.
The conclusion was that the 0 & M charges for treatment
of inflow would be far less than identification and removal
of the inflow (Tab!el).
TABLE 1
Operation and Maintenance Cost_s_ of Treating Inflow
Village Inflow West Webster Sewer District 3,
Process including Snowmelt Penfield Sewer District 3 Inflow
O&M Over O&M
O&M/yr. Design Period* O&M/yr. Design Period*
Phosphorus
Removal
Disinfection
$1520.00
343.00
$15,283.00
4,462.00
$120.00
27.00
$1203.00
351.00
Totals $1263.00 $19,740.00 $147.00 $1554.00
*Present worth figures based on 20-year period and interest
rate of 7.0%
213
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INTERLAKEN1 INFLOW ANALYSIS
The Village of Interlaken has a small sewer system
and an overloaded treatment plant for which upgrading was
planned. Future treatment facilities would include aerated
lagoon treatment based on a design flow rate of .17 MGD
and a 1.5 peaking factor. The lagoon system requires
detention times of approximately twenty six (26) days to achieve
the removal efficiencies required. This fact brought about the
possibility of use of lagoon freeboard as an 'in-line1 storm
inflow storage technique. Also it was planned to pump from
the lagoon to discharge at a controlled rate, easily allowing
necessary variation of levels in the lagoon that would be more
difficult to achieve with free dis-charge devices.
To analyze the impacts of storm inflow and weigh the
costs of inflow removal against storage/treatment costs required
implementation of 'STORM1 for system statistical analysis for
10 years of rainfall record data. It is important to under-
stand the importance of initial abstraction quantities and
method of obtaining it. In Interlaken, as shown in Fig. 5,
a rainfall comprising two consecutive peaks and their associated
flows were analyzed to show the initial heavier rain produced
less inflow than the subsequent rainfall, since most of it went
to satisfy initial abstraction requirements and none of the
following rain did. Simple comparison provided an initial
abstraction value for the system as well as an imperviousness
factor, later verified for other storms.
The results of the effort were profound. The total
inflow volume over the design period was analyzed as to
214
-------
VILLAGE OF INTERLAKEN N.Y.
FIG.5 EFFECT OF PRECIPITATION ON SEWAGE FLOW
DATS S HQUB
TABLE 2 STATISTICAL STORAGE UTILIZATION
DURING RAINFALL EVENTS
Treatment Plant
Flow Rate (mgd)
Lagoon Freeboard (ft)
Freeboard Storage (mg)
% of Time 50% of Freeboard
Storage Exceeded
Maximum % of Freeboard
Storage Utilized
0.17
1
0.45
20
175
0.17
2
0-90
10
88
0.17
3
1.35
8
60
0.25
1
0.45
6
110
0.25
2
0-90
4
55
0.25
3
1.35
0
37
215
-------
FIGURE 6 VILLAGE OF INTERLAKEN / EXISTING SEWER SYSTEM
NORMALIZED STORAGE UTILIZATION CURVE
TREATMENT RATE = .25 M.G.D. (PEAK RATE)
STORAGE CAPACITY = .90 M.G. (2* FREEBOARD)
100.0 i
80.0 -
UJ
o
CO
o
O
UJ
D:
o
<
x
CO
UJ
60.0 •
ui 40.0
UJ
o
cc
UJ
Q.
20.0 -
10.0
20.0
30.0
40.0
PERCENTAGE OF STORAGE UTILIZED
216
50.0
mpx. for
lOyrs
-------
its treatment costs, including 0 & M charges only. No
extra design capacity or storage was to be needed, a con-
clusion derived from 'STORM1 modeling, including a number
of intense rainstorms, of the proposed facilities. The
'STORM' outputted storage utilization curve, Fig. 6, for the
.25 M.G.D., .90 M.G. storage alternative (Table 2), depicts
the use of freeboard storage, on a percentage basis, during
all rainfall events. This handy, optional output allows the
user to make maximum use of design storage at respective design
flow rates for each alternative.
Cost comparisons of various storage/treatment alterna-
tives then allow design based on the most cost-effective
alternate to achieve the final goal. It is noteworthy that
no increase in design flow capacity was needed for inflow
removal with the storage available when modeling flow rates
based on the peak flow factor, 1.5. The total annual costs
associated with 0 & M for the proposed facilities were as
follows for the .17 MGD design capacity:
POWER $ 7,000
CHEMICALS 3,000
LABOR 12,000
TOTAL $22,000
The average daily inflow was found to be .008 MGD and associated
annual costs therefore .0087.17 x $22,000 = $1,035. The Phase 2
investigation of inflow alone was estimated at $52,700 or $4,975/hr,
Amortized over 20 years at 7% interest.
217
-------
The obvious conclusion was that inflow should be treated.
The client was subsequently saved a needless costly investigation
and rehabilitation program.
CANANDAIGUA, N.Y. INFLOW INVESTIGATION
Canandaigua is an older city of about 15,000
residents. New treatment facilities were being planned to
accept a new county sewer system and relieve existing problems
at the heavily overloaded sewage treatment plant. Preliminary
design plans had been completed without the use of 'STORM1
for inflow investigation and a recommendation for off-line
inflow storage of 3 million gallon capacity had been made,
*
based entirely on the conventional, accepted 'design year'
rainstorm approach and total capture of corresponding inflow.
'STORM' modeling of inflow levels and treatment/storage/overflow
alternatives (Table 3) in conjunction with a stream study of
the receiving waters made it apparent that minor periodic
plant overflows could be accepted if some degree of solids
removal and disinfection were provided. A concurrent investi-
gation of costs of various storage/treatment alternatives to
achieve the same overflow removal rates made it apparent that
storage was a less costly method of capturing inflow for
subsequent treatment than simply increasing plant size without
any storage (Table 4) above the design flow rate required for
sanitary and cost-effective infiltration flows alone.
At this point the system was modeled based on a
combination of storage/treatment alternatives and treatment
218
-------
CANANDAIGUA, N.Y.
TABLE 3 TREATMENT / STORAGE / OVERFLOW ALTERNATIVES
Alternati ve
Treatment
Rate
MGD
6.5
6.5
6.5
6.5
7.0
7.0
7.0
7.0
Storage
MG
0.5
1.0
2.0
3.0
0.5
1.0
2.0
3.0
No. of
Overflow
Events
Overflow
MG
Time of
Overflow
Hr.
74
59
33
26
72
51
30
21
215
171
112
83
166
148
102
71
1103
879
568
411
842
t)TS
429
315
Overflow
Removal
18
35
57
65
37
44
61
73
TABLE 4 TREATMENT / STORAGE / INFLOW REMOVAL COSTS
Alternative
Treatment
Rate
MGD
6.5
6.5
6.5
6.5
7.0
7.0
7.0
7.0
Storage
MG
0.5
1.0
2.0
3.0
0.5
1.0
2.0
3.0
Treatment*
$
500,000
500,000
500,000
500,000
1,000,000
1,000,000
1,000,000
1,000,000
Storaqe
$ '
400,000
600,000
1,000,000
1,300,000
400,000
600,000
1,000,000
1,300,000
Total % Inflow
$ Removal
900,000
1,100,000
1,500,000
1,800,000
1,400,000
1,600,000
2,000,000
2,300,000
18
35
57
65
37
44
61
73
$ x 10°
$/Gal .
Removed
0.050
0.031
0.026
0.027
0.039
0.036
0.033
0.032
* Cost increase from base treatment cost of $12,200,000
for 6 MGD Treatment Plant
219
-------
CANANDAIGUA, N.Y.
TABLE 5 TREATMENT / STORAGE / OVERFLOW ALTERNATIVES
WITH PEAK FLOW CAPACITY ALLOWANCE
Alternati ve
Treatment
Rate
MGD
6.5
6.5
10
10
16.5
16.5
Storage
MG
1
2
1
2
1
2
No. of Over-
flow Events
59
33
25
16
8
4
Overflow
MG
171
112
58
37
18
9
Time of
Overflow
Hr.
879
568
188
125
46
26
% of Ov
Remov
35
57
78
86
93
97
TABLE 6 ALTERNATIVE COSTS / REMOVALS
WITH PEAK FLOW CAPACITY ALLOWANCE
Alternative
Treatment
Rate
MGD
6.5
6.5
10
10
16.5
16.5
Storage
MG
1
2
1
2
1
2
Cost
$
1,100,000
1,500,000
1,100,000
1,500,000
1,100,000
1,500,000
% Overflow
Removed
35
57
78
86
93
97
$ x 106 %
Overflow Removed
0.031
0.026
0.014
0.017
0.012
0.015
220
-------
to
o
UJ
>
o
5
IU
a:
3:
o
rr
UJ
o
o
en
ce
o
o
0.030 i
0.025 -
0.020-
0.0 15 -
0.010-
FIGURE 7
CANANDAIGUA, N.Y.
DOLLARS / % OVERFLOW REMOVED
VS
PLANT FLOW
FOR
6.5 M.G.D.- DESIGN PLANT
_o
0.005-
2.0 M.G. STORAGE
1.3 M.G. STORAGE
!,0 M.G STORAGE
IU
>
P
o
Ul
U-
u.
UJ
H
(/)
o
o
I >
8
10
I 12 13 14 15
PLANT FLOW M.G.O.
16
I
17
18
-------
rates based on the 2.5 hydraulic peaking factor (Table 5).
Overflow removal costs were calculated on the basis of $[%
overflow removed to find the least cost alternative (Table 6).
The results of the modeling indicated a very acceptable
(from stream modeling results), high percentage of removal of
total overflow for the same alternative. This alternative
was then selected for final design purposes. Because of the
infrequency of inflow occurrences and the desire to achieve
equalization of the daily diurnal flow fluctuations and pollutant
concentration variations, it was felt that a modest increase
in storage tank facility capacity was justified to provide
dual purpose, wet weather inflow storage as well as diurnal
variations dampening without sacrificing the former. A simple
mass diagram analysis indicated an additional .3 MG storage
would allow equalization of diurnal flow variation and
maintenance of near constant flow rate through the plant
treatment facilities with subsequent, greatly increased removal
efficiencies in the process which include nitrification and
phosphate removal facilities. A final check was made on the
facilities sizing to insure that 1.3 million gallons storage
with flow variation from 6.5 MGD design rate to 16.5 MGD peak rate
remained cost effective without additional overflow.
The final statistical results indicated that with
the cost-effective facilities (Fig. 7) .6 overflow events/yr.,
amounting to 1.4 MG and an average duration of 4 hrs., might
222
-------
be expected. Only 2.5% time, or less than 1 da./mo., is the
flow rate expected to exceed the design flow rate. Again,
'STORM' allowed design of facilities at a great cost savings
to the client over what other methods would have indicated
was necessary.
SUMMARY & CONCLUSIONS
"STORM1 may be used to model stormwater inflow into
old, existing sanitary sewer systems as easily as for combined
or separate stormwater sewers when the user properly selects
and verifies his critical model calibration factors and basic
assumptions.
The model, in conjunction with costs analyses and/or
receiving stream studies, is a valuable tool at determining
the cost-effective alternative in alleviating the problems
associated with stormwater inflow. ^ Great savings may be
realized over what might be required by standard inflow investi
gation/system rehabilitation and the 'Design Storm1 concept.
223
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VERIFICATION AND CALIBRATION
OF THE ILLINOIS URBAN AREA DRAINAGE SIMULATOR (ILLUDAS)
by F.I. Lorant and C. Doherty
M.M. DILLON LIMITED
CONSULTING ENGINEERS
SWMM USERS GROUP MEETING
OTTAWA, ONTARIO
May 1978
INTRODUCTION
This paper is a result of on-going research carried out by the
staff of M.M. Dillon to calibrate and verify the Illinois
Urban Drainage Area Simulator1 (ILLUDAS).
ILLUDAS is a digital computer model which uses rainfall and
physical basin parameters to predict runoff from paved and
grassed areas.
This study utilizes recorded data collected by M-M. Dillon during
a recent SWMM calibration and verification study which was
initiated by an Urban Drainage Sub-Committee set up under the
Canada/Ontario and Canada/U.S. Agreement on Great Lakes Water
Quality.
DESCRIPTION OF SELECTED URBAN CATCHMENT AREA
The selected urban catchment area is 333 acres in size, and is
located approximately 4 miles to the northeast of downtown
Toronto in the Borough of East York.
1 The Illinois Urban Drainage Area Simulator, by Michael L.
Terstriep and John B. Stall, Illino'y State Water Survey, Urbana,
Bulletin 58. 1974.
2 Storm Water Management Model Verification Study, Borough of
East York, by M.M. Dillon Limited, February 1978.
224
-------
The general surface topography is characterized by a gentle slope.
The land use is predominantly residential (89.1%), the over-
whelming majority of which is comprised of single family
residential units, followed by institutional (5.7%), parks and
open spaces (4.2%) and commercial (1.0%).
The total population within the catchment area was estimated to
be in the region of 14,600.
The total area of impervious elements within the catchment area
was estimated at 187 acres (49% impervious) of which approximately
52% is roads, sidewalks and driveways, 38% is roofs of houses
connected to sewers, 4% is roofs of sheds not connected to
sewers and 6% is miscellaneous.
RECORDED DATA
For the SWMM verification study (Borough of East York), M.M. Dillon
collected and presented data on the following:
. Precipitation
. Runoff quantity and quality
. Air temperature
. Snow cover depth and water equivalent
. Municipal practices
The measurement of precipitation and the quantity of runoff was
used to prepare storm hyetograchs and hydrographs which were used
to calibrate and verify ILLUDAS.
MODELLING
The main object of this study was to simulate the recorded rain-
fall runoff events with ILLUDAS.
The basic method used by ILLUDAS to compute runoff is as follows:
Grassed and paved area supply rates are calculated by
subtracting losses due to depressional storage and
infiltration from the depth of rainfall. Next, a
computation is made of the travel time required for
each increment of runoff to reach the inlet followed by
the derivation of a surface hydrograph. The surface
hydrographs from each sub-basin are accumulated in a
downstream order through the basin and routed through
each section of pipe in order to account for the
temporary storage within each pipe section. The result
225
-------
is a computed outflow hydrograph for each section of
pipe and ultimately a hydrograph at the outfall.
A more detailed explanation may be found in the ILLUDAS Users
Manual, Bulletin No. 58.
DISCRETIZATION OF URBAN TEST AREA
A prerequisite to the preparation of input data is the discretization
of the urban test area, i.e. the division of the area into overland
flow areas and the sewer system into discrete elements for modelling
purposes.
There is no ready rule for discretizing an area but the finer the
discretization the more accurate can the rainfall runoff process
be represented.
The discretization adopted for this study resulted in 33 sub-
catchments ranging in size from 4.3 acres to 25.9 acres. The
sewer system was represented by 33 conduits ranging in size from
18 to 66 inches. This resulted in 70% of the actual sewer system
storage being modelled.
It should be noted that, due to the simplified approach used by
ILLUDAS, several flow dividers which exist within the sewer
system could not be modelled.
QUANTITY CALIBRATION
The ILLUDAS is designated as a "deterministic" model in that,
if all input parameters are accurate, the physics of the processes
are simulated sufficiently well to produce accurate results without
calibration. In practice, however, many of the input parameters
are not or cannot be accurately ascertained, thereby making it
necessary to assume values which may not be representative of
the study area. For this reason, a prerequisite to the verifica-
tion of the ILLUDAS is the calibration process which entails the
adjustment of input parameters until a good fit exists between
the computed and measured hydrographs.
The input parameters that directly affect the quantity and peak
flow rates are length and slope of overland flow, surface
depressional storage, soil group, antecedent moisture conditions,
amount of directly connected paved area and the amount of
supplemental paved area.
226
-------
For this study, the model was first calibrated for the directly
connected paved areas and then the pervious areas. Three
rainfall runoff events were chosen for the calibration procedure.
The storm of July 7, 1976 was chosen to calibrate the directly
connected paved areas and the storms of June 25, 1977 and
June 29, 1977 were chosen to calibrate the pervious areas.
For the initial attempt at the calibration of the directly
connected paved areas, it was decided that all the house roofs,
all the roadways and all the sidewalks, approximately 153 acres,
would be directly connected. This left all the driveways and all
the sheds to be considered as supplemental paved areas approxi-
mately 37 acres. From hydrograph analyses and previous verifi-
cation studies, the depressional storage was set equal to 0.02".
These assumptions resulted in the simulated peak flow being
within 2% of the recorded value and the simulated volume being
within 0.5% of the recorded value. These results, which are
shown in Figure 1, were considered acceptable, therefore no
further calibration was attempted.
The next step entails the calibration of the pervious areas. Four
input parameters affect the amount of runoff from the grassed
areas. These are the supplemental paved areas since they run off
instantaneously on to the grassed areas, the antecedent moisture
condition, the depressional storage and the soil group. For
this study, the supplemental paved area was considered to be the
difference in the measured impervious area and the calibrated
directly connected paved area. The antecedent moisture condition
was determined from rainfall records. The remaining two values,
depressional storage and the soil group were determined by
adjusting these values until a good fit between the recorded and
simulated hydrographs of June 25, 1977 and June 29, 1977 were
achieved. These are shown in Figures 2 and 3 and resulted in a
depressional storage of 0.1" and a soil group C being selected.
VERIFICATION
The verification included the simulation of 19 rainfall-runoff
events. A summary of these events are presented in Tables 1 and 2.
Results typical of these events are shown in Figures 4 to 11.
It should be noted that most of the recorded precipitation events
during this collection period did not have sufficiently high
intensities to overcome the modelled infiltration and depress-
ional storage losses of the pervious areas. This meant that
virtually all runoff originated from the impervious areas. There-
fore it was not possible to verify ILLUDAS for runoff from the
pervious areas.
227
-------
The runoff volumes were simulated fairly accurately with the
average and the standard deviation of the ratio of simulated
to recorded values being 1.001 and 0.134 respectively, and the
average and standard deviation of the ratio of simulated and
recorded peak flow rates being 1.013 and 0.118 respectively.
About 84%, 53% and 26% of the simulated flow volumes were within
20%, 10% and 5% respectively of the record flow volumes. About
89%, 70% and 41% of the simulated peak flow rates were within
20%, 10% and 5% respectively of the recorded peak flow rates.
Since the aforementioned SWMM verification and calibration study
was recently completed on this subcatchment with basically the
same discretization scheme, the following is a comparison made
between the results of these models.
Parameter
Peak Flow
Volume
Number of
Events
31
15
Mean of Sim/Rec
SWMM
1.016
0-970
ILLUDAS
1.026
1.019
Std. Dev.
SWMM
0.116
.078
of Sim/Rec
ILLUDAS
0.111
0.129
SUMMARY AND CONCLUSIONS
Recorded precipitation and urban runoff data has been used to
calibrate and verify the Illinois Urban. Drainage Area Simulator
(ILLUDAS).
Initial results of the ILLUDAS output showed that both the
hydrograph peaks and volumes generated by directly connected
paved areas did not require any calibration. Depression storage
and soil group parameters needed some adjustments for the
calibration of pervious areas. Verification of 37 hydrographs
produced by 19 rainfall-runoff events showed very encouraging
results, indicated by the mean of 1.026 for the simulated and
recorded peak flows and 1.019 for the simulated and recorded
volumes.
Unfortunately, most of the monitored rainfall-runoff events had
rainfall with relatively low intensities. As a result this study
was only able to verify runoff from the pervious areas. However,
the good results obtained do indicate that this relatively
inexpensive computer model can be a fairly accurate tool for
predicting the quantity of runoff from an urban catchment. The
writers are confident that the same encouraging results will be
228
-------
obtained for higher intensity storms after calibrating the
input parameters related to pervious areas.
229
-------
TABLE 1
COMPARISON OF SIMULATED AND
PEAK RUNOFF
Storm Date
Day Mth. Yr.
27 03 76(1)
(11)
31 03 76 1)
11)
111)
IV)
22 04 76
25 04 76(1)
(11)
11 05 76
01 06 76
2.8 06 76
30 06 76(1)
11)
01 07 76
01 07 76
02 07 76(1)
(11)
11 07 76
16 07 76
20 07 76 1)
11),
111)
29 07 76(1)
(ID
31 07 76 1)
n),
111)
IV)
V
VI)
13 08 76
01 09 76(1)
(ID
04 09 76
10 09 76 1)
11)
Number of Peaks
Mean of Simulated
Recorded
Standard Deviation
Si mul ated
Peak Flow
(cfs)
22.3
24.3
15.8
17.0
22.0
25.5
21.0
23.3
17.0
37.0
24.8
21.8
40.1
21.5
37.2
105.5
12.0
24.0
21.3
19.5
26.7
58.0
52.7
38.5
31.5
42.0
19.8
37.5
27.6
23.2
25.8
100.0
58.0
22.5
55.0
87.5
64.0
« 37
Peak Flows
of Simulated
Recorded
Peak Flow
(cfs)
29.3
25.5
14.5
17.0
21.1
25.0
22.5
20.0
17.0
35.8
22.9
19.0
37.0
20.0
30.0
111.0
10.0
22.9
19.0
21.0
24.0
61.3
55.2
41.5
29.5
40.0
20.0
28.5
30.0
23.2
26.6
121.0
64.0
22.5
68.9
104.0
66.7
- 1.013
- 0.118
RECORDED
Ratio of Simulated
to Recorded Peak Flows
0.761
0.953
1.090
1 .000
1.043
1.020
0.933
1.165
1.000
1.034
1.083
1.147
1.084
1.075
1.240
0.950
1.200
1.048
1.121
0.929
1.113
0.946
0.955
0.928
1.068
1.050
0.990
1.316
0.920
1.000
0.970
0.826
0.906
1.000
0.798
0.841
0.960
Recorded
230
-------
TABLE 2
COMPARISON OF SIMULATED AND RECORDED
FLOW VOLUMES
Storm
Day
27
31
22
25
11
01
28
30
01
01
02
11
16
20
31
13
01
04
10
Date
Mth.
03
03
04
04
05
06
06
06
07
07
07
07
07
07
07
08
09
09
09
Yr.
76
76
76
76
76
76
76
76
76
76
76
76
76
76
76
76
76
76
76
Simulated
Flow Volume
(cf)
76,630
213,980
32,670
131,530
71,120
43,630
34,320
180,670
76,600
116,600
81,730
54,670
27,190
279,720
197,610
109,678
104,130
76,630
279,760
Recorded
Flow Volume
(cf)
98,720
236,880
39,800
121,500
80,400
42,250
30,350
163,200
63,200
122,400
64,500
54,600
33,300
300,000
185,300
124,800
99,000
73,800
262,800
Ratio of Simulated
to Recorded Flow
Volumes
0.776
0.903
0.821
1.083
0.885
1.033
1.131
1.107
1.212
0.953
1.267
1.001
0.817
0.932
1.066
0.879
1.052
1.038
1.065
Number of Events
19
Mean of Simulated Flow Volume = 1.001
Recorded
Standard Deviation of Simulation Flow Volume
Recorded
0.134
231
-------
o
18=00
JULY 7,1976
Recorded Runoff
„,. Simulated Runoff
19=00 20=00
TIME (hrs.)
FIGURE 1
Recorded Runoff
Simulated Runoff
05=00 06=00
TIME.(hrs.)
FIGURE 2
232
-------
Recorded Runoff
— •—Simulated Runoff
03:00 04=00 05=00
T»ME(hrs.)
FIGURE J>
06=00
30
.220
I
10
t
y
a u L_T
U U
MARCH 27,1976
Recorded Runoff
Simulated Runoff
15=00 16=00
TIME (hrs.)
FIGURE H
17=00
233
-------
--i£.-3 U U U U U
Recorded Runoff
-.. Simulated Runoff
24=00
OhOO 02=00
TIME (hrs.)
03=00
•~ O.I
If. 013.
30
20
Q
10
FIGURE 5
I5--00
MAY 11,1976
— Recorded Runoff
-.- Simulated Runoff
16=00
17=00
TIME (hrs.)
FIGURE 6
234
-------
rl 0.2r
< c I.UJ
o:~
80
5:
o
40
JULY 1,1976 (p.m.)
-— Recorded Runoff
—.- Simulated Runoff
17=00' 18=00
TIME (hrs.)
FIGURE 7
-0.2
^0.4
f~
_*»
60'
rU"
1
u.
20
JULY 20,1976
-— Recorded Runoff
-.- Simulated Runoff
20=00 21=00 22=00
TIME (hrs.)
FIGURE 3
235
-------
Recorded
Runoff
Simulated
""Runoff
08=00
09=00 10=00
TIME(hrs.)
FIGURE 9
11=00
Recorded Runoff
.-. Simulated Runoff
09=00
10=00 11=00
TIME(hrs-)
FIGURE 10
I2--00
236
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-
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R. Adams,
Multiple Access Computer Group
#3 - 1479 Buffalo Place
Winnipeg, Manitoba
R3T 1L7
Quazi N. A! am
Totten Sims Hubicki Assoc. Ltd.
1A King Street East
Cobourg, Ontario
K9A 1K6
J. C. Anderson
Gore & Storrie Limited
Suite 700
331 Cooper Street
Ottawa, Ontario
K2P OG5
Allan Arbuckle
R. E. Clipsham Limited
16 Mountainview Road South
Hal ton Hills (Georgetown)
Ontario
L7G 4K1
Albert T. Bain
52 Pann Ayr Road
Camp Hill
Pennsylvania
S. G. Barber
Ministry of Housing
6th floor
950 Yonge Street
Toronto, Ontario
M4W 2J4
Jean H. Bastien
City of St. Laurent
777 Laurentien Blvd.
St. Laurent, Quebec
H4M 2M7
Raffi Bedrosyan
Borough of North York
5100 Yonge Street
Willowdale, Ontario
M2N 5N7
C. Bennett
City of Sarnia
City Hall
Sarnia, Ontario
Robert Berwick
Meta Systems
10 Hoiworthy Street
Cambridge, Ma.
02138
I. Bhatia
City of Ottawa
City Hall
111 Sussex Drive
Ottawa, Ontario
KIN 5A1
Ralph A. Bischoff
Beauchemin, Beaton, Lapointe
1134 St. Catherine St. W.
Montreal, Quebec
H3B 1H4
Brian Bodnaruck
Box 86
GRP 327
R. R. #3
Selkirk, Manitoba
R1A 2A8
C. Brcic
Gore & Storrie Limited
Suite 700
331 Cooper Street
Ottawa, Ontario
K2P OG5
David Brier!ey
De Leuw Gather, Canada Limited
133 Wynford Drive
Don Mills, Ontario
M3C 1K1
Eric Brown
Industrial Life-Technical Services Inc.
1202 - 101 Richmond Street West
Toronto, Ontario
M5H IT!
Tas Candaras
Paul Theil Associates Ltd.
700 Balmoral Drive
Bramalea, Ontario
David J. Carleo
O'Brien & Gere Engineers Inc.
1304 Buckley Road
Syracuse, New York
13221
238
-------
Ron Cebryck
City of Edmonton
City Hall
Edmonton, Alberta
Philip G. Clark
O'Brien & Gere Engineers, Inc.
1304 Buckley Road
Syracuse, New York
W. Clarke
James F. MacLaren Limited
320 Adelaide Street South
London, Ontario
N5Z 3L2
E. J. Cole
Township of Nepean
3825 Richmond Road
Ottawa, Ontario
K2H 5C2
Donald G. Cooke
Regional Municipality of Niagara
150 Berryman Avenue
St. Catherines, Ontario
L2R 7E9
G. Couchisne
W. J. Courtis
Walker, Newby & Associates Ltd.
10835 - 120 Street
Edmonton, Alberta
George V. Crawford
Gore & Storrie Limited
1670 Bayview Avenue
Toronto, Ontario
M4G 3C2
Jim Crowley
Ministry of the Environment
Environmental Approvals Branch
135 St. Clair Avenue West
9th floor
Toronto, Ontario
M4V 1P5
A. A. Dagostino
Corporation of the City of Sudbury
P.O. Box 1000
Sudbury, Ontario
P3E 4S5
T. Davis
Regional Municipality of Ottawa-Carleton
222 Queen Street
Ottawa, Ontario
KIP 5Z3
J. C. Dempsey
Department of Physical Environment
City of Ottawa
City Hall
111 Sussex Drive
Ottawa, Ontario
KIN 5A1
C. Doherty
M. M. Dillon Limited
50 Holly Street
Toronto, Ontario
M4S 2E9
R. Dunn
Ministry of the Environment
2378 Holly Lane
Ottawa, Ontario
K1V 7P1
C. W. Eicher
Gore & Storrie Limited
1670 Bayview Avenue
Toronto, Ontario
M4G 3C2
E. John Finnemore
Metcalfe & Eddy Inc.
1029 Corporation Way
Palo Alto
California
94303
Steven D. Freedman
Steams & Wheler
10 Albany Street
Cazenovia
New York
13035
239
-------
G. Hicks
J. R. Gamblin
Albery Puller-its, Dickson & Assoc.
29 Gervais Drive
Don Mills, Ontario
M3C 1Y8
Robert C. Ganley
O'Brien & Gere Engineers Inc.
1304 Buckley Road
Syracuse, New York
13221
R. Gietz
Regional Municipality of Ottawa-Carleton
222 Queen Street
Ottawa, Ontario
KIP 5Z3
Karl Gonnsen
City of Burlington
426 Brant Street
Box 5013
Burlington, Ontario
Martin H. Hawder
R. M. Kostuch Associates Ltd.
1417 C Cyrville Road
Ottawa, Ontario
K1B 3L7
David H. Hay
Environment Canada
Environmental Protection Service
Ottawa, Ontario
K1A 1C8
T. Hearn
City of Guelph
59 Garden Street
Guelph, Ontario
N1E 3P7
Karl Hemmerich
Dorsch Consult Limited
45 Richmond Street West
#1004
Toronto, Ontario
M5H 1Z2
Paris Hindie *
Ecole Polytechnique
University of Montreal
P.O. Box 6079
Succursale A
Montreal, Quebec
H3C 3A7
M. Hulley
St. Lawrence College
Cornwall, Ontario
Izal Hotzer
Polycom Systems
133 Wynford Drive
Don Mills, Ontario
M3C 1K1
L. Jandl
Ministry of Government Services
Downsview Computing Centre
1201 Wilson Avenue
East Building
Downsview, Ontario
M3M 1J8
Thomas K. Jewell
Department of Civil Engineering
University of Massachusetts
Amherst, Massachusette
01003
David Johnson
St. Lawrence College
Cornwall, Ontario
L. Kamp
Environment Canada
Environmental Protection Service
Ontario Region
Bogue Building
River Road
Ottawa, Ontario
W. L. Keay
Regional Municipality of Ottawa-Carleton
222 Queen Street
Ottawa, Ontario
KIP 5Z3
Ian Kennedy
J. L. Richards
864 Lady Ellen Place
Ottawa, Ontario
K1Z 5M2
Shiraz Khimji
Ministry of the Environment
985 Adelaide Street South
London, Ontario
N6E 1V3
1 day registration only
240
-------
Bill Koeutzberger
Enuirex Inc.
5103 W. Beloit Road
Milwaukee, Wisconsin
Dennis F. Lai
Clinton Bogert Associates
2125 Center Avenue
Fort Lee, New Jersey
07024
Gerry Langman
Reid Crowther and Partners Ltd.
200 - 831 Portage Avenue
Winnipeg, Manitoba
R36 ON6
Brian Larkin
Cumming Cockburn & Associates
5385 Yonge Street
Willowdale, Ontario
M2N 5R7
Dr. Guy Led ere
Desjardins & Sauriol & Assoc.
1200 Boulevard St. Martin Quest
Chomedey, Laval, Quebec
H7S 2E4
W. Wayne Lee
Underwood, McLellan (1977) Ltd.
1479 Buffalo Place
Winnipeg, Manitoba
R3T 1L7
Pedro Liang
Corporation of the City of Kingston
Ontario Street
Kingston, Ontario
F. I. Lorant *
M. M. Dillon Limited
50 Holly Street
Toronto, Ontario
M4S 2E9
Jin' Marsalek *
Canada Centre for Inland Waters
867 Lakeshore Road
Burlington, Ontario
L7S 1A1
Barry McBride
James F. MacLaren
1240 Portage Avenue
Winnipeg, Manitoba R3G OT6
Parrel! McGovern
Oliver, Mangione, McCalla & Associates Ltd
1755 Woodward Drive
Ottawa, Ontario
K2C OP9
M. B. McPherson
23 Watson Street
Marblehead, Massachusetts
01945
Dr. Miguel A. Medina Jr. *
Duke University
Durham, North Carolina
P. J. Meehan
Civil Engineering Department
University of Ottawa
Ottawa, Ontario
Constantin Mitici *
Ecole Polytechnique
University of Montreal
P.O. Box 6079
Succursale A
Montreal, Quebec
H3C 3A7
M. Monteith
Ministry of the Environment
2378 Holly Lane
Ottawa, Ontario
K1V 7P1
M. Nyugen Nam
2620 East Blvd. St Joseph
Montreal H1Y 2A4
Quebec, Canada
Van T. V. Nguyen *
Ecole Polytechnique
University of Montreal
P.O. Box 6079
Succursalle A
Montreal, Quebec
H3C 3A7
* 1 day registration only
241
-------
Ronald W. Norton
Administrator
Engineering Services
Corporation of the Township of Nepean
3825 Richmond Road
Ottawa, Ontario
K2H 5C2
Z. Novak
Ontario Ministry of the Environment
Water Resources Branch
135 St. Clair Avenue West
Toronto, Ontario
M4V 1P5
Ron Ohman
McAuto
Box 5992
Berkeley, Montana
63134
T. J. Parent
W. L. Wardrop & Associates
77 Main Street
Winnipeg, Manitoba
R3C 3H1
Mario Parente
Gore & Storrie Limited
Suite 700, 331 Cooper Street
Ottawa, Ontario
K2P OG5
H. Pascoe
City of Ottawa
City Hall
111 Sussex Drive
Ottawa, Ontario
KIN 5A1
A. Peltz
PRIME Computer Inc.
5801 Peachtree-Dunwoody Road
Atlanta, Georgia 30342
L. E. Pond
W. L. Wardrop & Associates
77 Main Street
Winnipeg, Manitoba
R3C 3H1
Rod Prosser
Lozier Engineers
50 ChestnutPlaza
Rochester, New York 14604
A. Puppa
Capital Region
Department of Public Works
19th floor
140 O'Connor Street
East Tower
Ottawa, Ontario
K2P 2H6
Pierre Purenne
Desjardins & Sauroil & Assoc.
1200 Boulevard St. Martin Quest
Chomedey, Laval, Quebec
H7S 2E4
Roger Quesnel
R. M. Kostuch Associates Ltd.
1417 C Cyrville Road
Ottawa, Ontario
K1B 3L7
Richard Race
Enuirex Inc.
5103 W. Beloit Road
Milwaukee, Wisconsin
Division (KMS)
V. A. Radzius
Transport Canada
Surface Structures
Ottawa, Ontario
K1A ON5
Jim Raw!ings
Control Data Canada
130 Albert Street
Ottawa, Ontario
KIP 5G4
Louise Raymond
Bessette, Crevier, Parent, Tanguar & Assoc.
110 Quest Boulevard Cremazie
Suite 1001
Montreal, Quebec
H2L 2G8
C. Riaz
University of Ottawa
Ottawa, Ontario
S. Sarikelle
Dept. of Civil Engineering
University of Akron
Akron, Ohio
44325
242
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P. Sauve"
City of Ottawa
City Hall
111 Sussex Drive
Ottawa, Ontario
KIN 5A1
R. L. Scott
Lawson-Fisher Associates
101 JMS Building
South Bend, Indiana
46601
Dr. U. Shamir
42 Kirk Bradden Road East
Toronto, Ontario
M8V 2E7
Michael Shapiro
Dept. of City and Regional Planning
Harvard University
311 Gund Hall
Cambridge, Massachussets
02138
J. C. Simmonds
City of Ottawa
City Hall
111 Sussex Drive
Ottawa, Ontario
KIN 5A1
Ross Slaughter
Ministry of the Environment
135 St. Clair Avenue West
Toronto, Ontario
M4V 1P5
L. D. Smith
Suite 700 - 331 Cooper Street
Ottawa, Ontario
K2P OG5
Guido S. Sondhe
Indiana State Board of Health
1330 W. Michigan
Indianapolis, Indiana
46206
L. South
Ministry of the Environment
133 Dalton Street
P.O. Box 820
Kingston, Ontario
K7L 4X6
A. Tafuri
U.S. EPA
Edison Waste Quality Res. Lab
Edison, New Jersey
08817
Paul Theil
Paul Theil Associates Ltd.
700 Balmoral Drive
Bramalea, Ontario
H. Torno
Environmental Protection Agency
Office of R & D (RD-682)
Washington, D.C.
20460
Clifford H. Tottle
City of Winnipeg
Water, Waste & Disposal Division
280 William Street
Winnipeg, Manitoba
R3B OR!
J. Trottier
Ray Tugfar
Proctor & Redfern
75 Eglinton Avenue East
Toronto, Ontario
M4P 1H3
Paul S. Turje
Willie, Cunliffe, Tait & Co. Ltd.
827 Fort Street
Victoria, B.C.
V8W 1H6
Mr. A. Underhill
Twiga Consultants Limited
4800 Dufferin Street
Suite 200
Downsview, Ontario
M3H 5S9
David Utmeyer
Black & Veatch
1500 Meadow Lake Parkway
Kansas City, Montana
243
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C. R. Walker
City of Ottawa
City Hall
111 Sussex Drive
Ottawa, Ontario
KIN 5A1
R. Warnock *
University of Ottawa
Ottawa, Ontario
D. Weatherbe
Ministry of the Environment
Water Resources Branch
135 St. Clair Avenue West
Toronto, Ontario
M4V 1P5
R. B. Wigle
James F. Maclaren Limited
435 McNicoll Avenue
Willowdale, Ontario
M2H 2R8
N. Wiggins
University of Ottawa
O'ttawa, Ontario
R. Wilkinson
City of Ottawa
City Hall
111 Sussex Drive
Ottawa, Ontario
KIN 5A1
Paul Wisner
James F. MacLaren Limited
235 McNicoll Avenue
Willowdale, Ontario
M2H 2R8
Hsen Hseng Yen
Envirosphere Co.
19 Rector Street
New York, New York
10006
6. Zukovs
Ministry of the Environment
Wastewater Treatment
Resources Road
Rexdale, Ontario
*1 day registration only
244
* U.S. GOVESMENT PRISTINC OFFICE , 1978 0-720-5U
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