EPA-R2-73-170
APRIL 1974
Environmental Protection Technology Series
Combined Sewer Overflow
Abatement Plan, Des Moines, Iowa
532
ol
Office of Research and Development
t t
U.S. Environmental Protection Agency
Washington, O.C. 20460
• - -• '- ' .- - i -,.•:;•-.•• :,,:- •••--:-;.,-.
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and
Monitoring, Environmental Protection Agency, have
been grouped into five series. These five broad
categories were established to facilitate further
development and application of environmental
technology. Elimination of traditional grouping
was consciously planned to foster technology
transfer and a maximum interface in related
fields. The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
<4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL
PROTECTION TECHNOLOGY series. This series
describes research performed to develop and
demonstrate instrumentation, equipment and
methodology to repair or prevent environmental
degradation from point and non-point sources of
pollution. This work provides the new or improved
technology required for the control and treatment
of pollution sources to meet environmental quality
standards.
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EPA-R2-73-170
April 1974
COMBINED SEWER OVERFLOW ABATEMENT PLAN,
Des Moines, Iowa
by
Peter L. Davis
Frank Borchardt
Contract No. 14-12-402
Project No. 11024FEJ
Project Officer
Ralph G. Christensen
U. S. Environmental Protection Agency
1 North Wacker Drive
Chicago, Illinois 60606
Prepared for
OFFICE OF RESEARCH AND DEVELOPMENT
ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D. C. 20460
For sale by the Superintendent of Documents, U.S.- Government Printing Office, Washington, D.C. 20402- Price $3.20
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EPA REVIEW NOTICE
This report has been reviewed by the Environmental
Protection Agency, and approved for publication.
Approval does not signify that the contents necessarily
reflect the views and policies of the Environmental
Protection Agency, nor does mention of trade names
or commercial products constitute endorsement or re-
commendation for use.
11
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ABSTRACT
Combined sewer overflows, storm water discharges, and surface
waters in the Des Moines, Iowa Metropolitan Area were sampled
for 12 months to determine their pollutional characteristics.
Various systems of separation and collection and treatment of
combined sewer overflow and storm water discharges were de-
signed, estimated and evaluated. Analyses were made of the data
collected and of the various system problems encountered.
The studies indicate 174,500 pounds of BOD are discharged annually
from a 4,000 acre combined sewer drainage area, and 2,668,000
pounds of BOD from 45,000 acres served by separate storm sewers.
Average concentrations of pollutants in storm water were 53 mg/1
BOD, 448 mg/1 SS, 1.78 mg/1 NH3-N, 1.10 mg/1 N03-N, and 1.65 mg/1
Total PO^. Average concentrations of pollutants in combined
sewer overflows were 72 mg/1 BOD, 329 mg/1 SS, 4.79 mg/1 NH3-N,
0.74 mg/1 N03-N, and 8.92 mg/1 Total P04.
Several combined sewer overflow abatement projects are recommended
for implementation.
This report was submitted for completion of Contract Number
14-12-402 between the Environmental Protection Agency and
Henningson, Durham & Richardson, Inc., Omaha, Nebraska 68114.
iii
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CONTENTS
Section
Page
I
II
in
IV
V
VI
VII
VIII
IX
X
XI
XII
XIII
XIV
XV
XVI
Conclusions
Recommendations
Introduction
Project Area
Field Operations and Procedures
Sewage, Overflow and Storm Water Discharge
Data
Rainfall-Runoff Studies
River Data and Analysis
Combined Sewer Separation
Treatment of Combined Sewer Overflows
and Storm Water Discharges
Unusual Problems Encountered
Summary of Cost Estimates
Acknowledgements
References
Glossary
Appendices
-*-*
1
7
11
17
29
47
71
101
119
147
205
213
217
219
221
225
V
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FIGURES
Page
1 Vicinity Map 18
2 Urban Growth Pattern 1970-2020 21
3 Population Trend - Des Moines Urban Area 24
4 Future Land Use 26
5 Water Sports Recreation Within Des Moines 28
6 Typical Wier & Recorder Installations 31
7 Typical Bubbler Installations 32
8 Automatic Sampling Equipment 34
9 Wier Construction 38
10 Discharge Measuring Facilities 39
11 West Side Storm Box 41
12 Flow Monitoring & Rain Gauge Installations 42
13 Sanitary Sewer System & Sample Points 50
14 Storm & Combined Sewer Sampling Points 56
15 Typical Overflow Structures 57
16 Runoff Characteristics Station 0-11 59
17 Runoff Characteristics - Station 0-11 60
18 Runoff Characteristics - Station 0-11 61
19 Runoff Characteristics - Station 0-8 62
VI
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Continued . . .
Page
20 Runoff Characteristics - Station S-3 63
21 Runoff Characteristics - Station S-3 64
22 Runoff Characteristics - Station S-l 65
23 Volumetric Relationship Rainfall-Runoff 66
24 Runoff Volume vs. B.O.D., T.S.S., NO3, 67
& P04
25 Rainfall-Runoff Study Areas 73
26 Modified Thiessen Polygons For Determining 78
Basin Precipitation
27 Computer Print-Out For Rainfall-Runoff 80
Analysis
28 Rainfall-Runoff Relationships/Thompson 83
Avenue Storm Sewer
29 Rainfall-Runoff Relationships/Cummins 84
Parkway Storm Sewer
30 Rainfall-Runoff Relationships/Closes Creek 85
31 Rainfall-Runoff Relationships/20th Street 86
Storm Sewers
32 Relationship of Rainfall & Runoff 88
33 Effect of Rainfall Depth & Intensity On 89
Coefficient of Runoff
34 Rainfall Depth & Coefficient of Runoff 90
35 Rainfall Intensity and Peak Runoff Relationships 92
36 Distribution of Rainfall Intensity With Respect 95
To Time
vii
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Continued . • •
Page
37 Distribution of Rainfall Intensity With 97
Respect To Accumulated Rainfall
38 Location Map River Sampling Points 102
39 Rainfall Intensity-Duration-Frequency Curves 121
40 Sewer Separation Plan-Sheet Index 133
41 Sewer Separation Plan-Sheet 1 135
42 Sewer Separation Plan-Sheet 2 137
43 Sewer Separation Plan-Sheet 3 139
44 Sewer Separation Plan-Sheet 4 141
45 Sewer Separation Plan-Sheet 5 142
46 Sewer Separation Plan-Sheet 6 143
47 Sewer Separation Plan-Sheet 7 144
48 Sewer Separation Plan-Sheet 8 145
49 Rainstorm Volumetric - Design Curves 154
50 Volumetric Analysis Combined Sewage Systems 155
51 Closes Creek System 163
52 Proposed Overflow Pollution Abatement 169
Facilities
53 Birdland Retardation Basin 174
54 Dean Lake Impoundment 177
55 Overflow Interceptors & Lift Station 179
56 Case Lake Treatment Complex 182
Vlll
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Continued . . .
Page
57 Location Plat-Plan B-l & B-2 187
58 Treatment of Storm Water Discharge Study 192
Areas
59 Storm Water Discharge Treatment Layout- 194
Area I
60 Storm Water Discharge Treatment Layout- 197
Area III
61 Storm Water Discharge Treatment Layout- 198
Area IV
62 Normal & Flood Conditions at Outlets 207
63 Flood Conditions In Southeast Des Moines 208
64 Problems Created By Flooding and High 209
Infiltration
65 Interceptor Sewer System - Surcharge Flow 210
Measurements
66 Dry Weather Sanitary Flows 267
67 Dissolved Oxygen-Diurnal Patterns; 272
R-2 and R-5
68 Dissolved Oxygen-Diurnal Patterns; Raccoon 276
River
69 Dissolved Oxygen-Diurnal Patterns; 280
R-10 and R-14
70 Dissolved Oxygen-Diurnal Patterns; 283
R-15 and R-16
71 Station R-2 BOD vs. Flow 293
72 Station R-2 Nitrogen and Phosphate vs. Flow 295
IX
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Continued . • •
Page
73 Station R-9 BOD and DO vs. Flow 297
74 Station R-9 Nitrogen and Phosphate vs. Flow 299
75 Station R-5 BOD and DO vs. Flow 301
76 Station R-5 Nitrogen and Phosphate vs. Flow 303
77 Station R-6 BOD and DO vs. Flow 305
78 Station R-6 Nitrogen and Phosphate vs. Flow 307
79 Bubbler-Type Liquid Level Recorder 311
x
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TABLES
No. Page
1 Mean Monthly Precipitation 19
2 Urban Area Populations 23
3 Combined Sewer Areas Populations 25
4 Summary Description of Monitoring Points 49
5 Summary of Dry Weather Sanitary and 52
Industrial Waste Loads
6 Dry Weather vs. Wet Weather Flows in 53
Combined Sewers
7 Combined Sewage Overflow and Storm Water 55
Discharges
8 Clock-Hour Precipitation Intensity Distribution 94
9 Comparison: Day-Night River Sample Data 104
10 Estimated Annual River Loadings Above 106
Des Moines Metropolitan Area
11 Estimated Annual River Loadings Below Des 107
Moines Metropolitan Area
12 Comparative Data From Project River Sampling 109
13 Present Daily Metro Area Discharges 111
14 Summary of Present Annual Metro Area 112
Discharges
15 Pesticide Concentrations 114
16 Summary of Sanitary Flows 151
17 Summary of Combined Sewage and Overflow 156
Quantities
XI
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No. Page
18 Rainfall Intensities for Intense Storms 157
19 Storm. Water Discharges at Varying Return 19!
Periods
20 Costs, Storm Water Discharge Treatment 199
21 Metro Area Treatment Plans, Annual Cost 200
22 Metro Area BOD Loads for Treatment Plans 202
23 Summary of Project Costs 215
24 Summary of Annual Costs 216
25 Sample Data 241
26 River Station Data 285
XII
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SECTION I
CONCLUSIONS
1. The reduction of combined sewer overflow pollution can be
effected by various combinations of control and treatment facilities.
2. For particular situations, solutions incorporating both sewer
separation and combined overflow treatment have considerable merit.
In this study, two such situations are demonstrated by the Closes
Creek system where separation is most economical and the East 18th
Street System where combined overflow treatment was selected.
3. Of the various schemes investigated for treatment of combined
sewer overflows, the most applicable type of treatment was imppund-
ment. Impoundments designed for storage of storm waters are not
materially affected by the rate of flow, but by the total volume
received. Because of limited available land, impoundments will
usually be heavily loaded and aeration may be required for treatment
and for odor control. A high degree of treatment will be provided,
especially to high-frequency storms. Adequate provision must be
made for the removal of solids.
4. The necessity of having to handle extreme flow ranges materially
increases the cost for mechanical treatment schemes. Primary treat-
ment does not provide the degree of treatment offered by impound-
ments , and secondary biological processes are not generally adaptable
to the intermittent nature and extreme ranges of flow encountered
in storm water treatment.
5. The use of retention or retardation basins with stored waste-
waters returned to the collection system permits combined sewer
flows to be treated by conventional wastewater treatment facilities
during off-peak periods.
6. For the reduction of pollutant discharges to the Des Moines
River, expansion of the existing wastewater treatment facilities
will provide the most effective use of the construction dollar.
Plan B-2, which uses sewer separation in combination with inter-
ception and treatment of overflows, provides the most cost effective
scheme of reducing pollutant discharges from combined sewer overflows,
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7. Components of Plan B-2 can be implemented immediately to re-
duce the overflow of combined wastewaters and to increase the effect-
iveness of existing wastewater treatment facilities.
8. The existence of combined sewers creates operational problems
in the treatment of domestic and industrial wastewaters and permits
discharge of untreated wastewaters during wet weather conditions.
9. For metropolitan areas where the practice of constructing combined
sewers was limited to early periods of growth and make up a relatively
small portion of the total urban area, the organic pollutional impact
from combined sewer overflows will likely be overshadowed by that
from storm water discharges. The case of Des Moines illustrates
this. Drainage from approximately 4, 000 acres receive some quantity
of combined sewer overflow and discharges an estimated 174, 500
pounds of BOD annually. From the remaining 45, 000 acres served by
separate storm sewers, the annually BOD discharge is estimated to be
2, 668,000 pounds.
10. Laboratory analyses of the discharges sampled in Des Moines
showed combined sewer overflows to have slightly higher pollutant
concentrations than storm water discharges, but in the same order of
magnitude. Following is a summary of average pollutant concentra-
tions as determined by the monitoring program.
SUMMARY OF AVERAGE CONCENTRATIONS, IN mg/1
Station B.O.D. T.S.S. NH..-N NOy N T.PO4
Storm Water Discharges
S-l
S-3
0-2
0-11
48
63
44
56
315
578
495
404
1.99
1. 60
1.21
2.30
1. 11
1.47
0.88
0.96
1.25
0.93
2.20
2.23
Average 53 448 1.78 1.10 1.65
Combined Sewer Overflows
O-3
0-6
O-7
0-8
O-8A
69
95
50
68
77
144
592
195
410
303
4.53
9.42
1.84
3.22
4.94
0.26
0.63
1. 15
1. 07
0. 57
11.72
9.88
7. 10
6.96
-
Average 72 329 4.79 0.74 8.92
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11. The total quantity of pollutants discharged, at least for the low and
moderate intensity storms which occurred during the study, is cf.osely
related to the relative volume of flow. This is illustrated by the, data in
Figures 16 to 24 in Section VI of this report. For example, at Station
0-11 the relationship between the volume of runoff and quantity of pollu-
tants discharged during three different storms is as follows:
Date 5-7-69 7-23-69 9-4-69
Rainfall - inches 1.14 0.69 0.22
Runoff -Ac-Ft 23.2 9.30 1.85
-inches 0.238 0.097 0.018
BOD - Ibs/Acre 1.66 0.74 0.27
TSS - Ibs/Acre 18.4 13.4 1.42
Also, as storm intensity and runoff increases, the relative percentage
of sanitary sewage in the combined sewer overflow compared to storm
flow decreases. Conversely, high-frequency, low intensity storms will
produce overflow discharges with a high percentage of sanitary waste-
water.
12. The Des Moines and Raccoon Rivers are heavily used for recreation,
particularly above their confluence at Scott Street. The completion of
the Saylorvill Reservior immediately above the city -will enhance the Des
Moines River as a recreation area. Protection of these waters for re-
creational use should be a consideration in the city's pollution abatement
program.
13. The annual quantity of pollutant material discharged in the effluents
of wastewater treatment facilities is likely to equal or exceed the quantity
of pollutants in combined sewer overflows and urban storm water dis-
charges. Wastewater treatment plant effluents may greatly exceed other
sources if a high degree of treatment is not provided. The Des Moines
plant, which averaged 83.5 percent BOD removal in 1970, was estimated
to discharge 55 percent of the BOD, 91 percent of the nitrates, and 90 per-
cent of the ortho-phosphates discharged from the Metro area during the
year study period, exclusive of overflows or bypassing of wet •weather flows.
14. Treatment plant upset by wet weather flows was not a major factor
at Des Moines. This was due to (1) the ability of the trickling filter process
to adjust to shock hydraulic and biological loads and (2) the hydraulic
capacity limitations which restricted maximum flows to approximately
45 MGD, an increase of only 10 MGD over the average daily load of 35
MGD. Excess flows were stored in the interceptor as much as possible,
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with bypassing of the plant used only to prevent property damage from
basement flooding. Slightly reduced treatment efficiencies resulted
from wet weather flows due to the increased hydraulic load. A high
influx of suspended solids was typical.
15. A typical midwestern river, such as the Des Moines River, re-
ceives and carries enormous quantities of organic materials from rural
areas. In the case studied, incoming river loads, except for phosphates,
are several times the quantity of organic pollutants generated in the
Metro area.
16. The relative magnitude of the river loads compared to those
known to be emanating from the Des Moines urban area indicates a
need for identification of their source and research to develop adequate
methods for control or treatment thereof.
17. Analysis of the stream quality data indicates that the quantity of
organic pollutants and nutrients which would be removed by the com-
plete abatement of overflows is not significant compared to the present
load carried by the rivers. For this reason, the need for an extensive
program of combined sewer overflow abatement is not indicated.
18. High-frequency, low-intensity rainfalls produce a much lower
coefficient of runoff than the values generally acceptable for design of
storm drainage facilities. The results of this study indicate that for
high-frequency storms the coefficient of runoff correlates more closely
with the accumulated depth of precipitation than with the intensity of the
precipitation. Typical values for the 0-11 Station, the 20th Street
Storm Sewer, are as follows:
Accumulated Depth Volumetric Coefficient
of Precipitation, Inches of Runoff, Cy
0.2 0.10
0.4 0. 15
0.6 0. 19
1.0 0.25
2.0 0.33
19. The distribution of precipitation intensities with regard to both
time and the total depth of precipitation can be developed from weather
bureau records and provides the designer a tool for evaluating the
effectiveness of storm water treatment. The procedures used in this
study are described in Section VII.
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20. Circumstances existing in the City of Des Moines during the
course of this investigation offered an excellent opportunity
for a study of this nature. The City straddles a nutrient-rich
river and was found to contribute to the nutrient load as anti-
cipated. Storm water discharges, wastewater treatment plant
effluent, combined sewer overflow during periods of runoff, and
overflow caused by excessive infiltration contributed to the
nutrient load.
21. Analysis of the existing sewerage system to determine the
magnitude of the overflow problem and for the design of corrective
measures was hampered by lack of sufficiently detailed utility
records. This is by no means a problem limited to the study area,
but exists in a large number of cities. Utility records are often
incomplete in older cities and in areas where new development has
occurred without a strong central governmental authority. The
preparation and maintenance of accurate records of utilities
systems should be a prerequisite to any comprehensive planning
program.
22. Planning for the abatement of combined sewer overflows should
begin with an engineering appraisal of the relative magnitude of
the problem and its impact on the receiving stream. Remedial
programs, if required, should be tailored to fit each individual
situation.
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SECTION II
RECOMMENDATIONS
1. The first priority for the metropolitan area water pollution
control program should be provision of continuous adequate treat-
ment of domestic and industrial -wastes as provided by the wastewater
treatment facilities expansion program proposed for Des Moines.
The expanded facility will have capacity to handle infiltration flows
and a substantially greater amount of combined flows. In addition,
it will provide a higher degree of treatment to all flows.
2. An immediate extensive program of sewer separation or com-
bined sewer overflow treatment is not recommended for the City
of Des Moines, based on analysis of river conditions.
3. Two components of the combined sewer overflow pollution abate-
ment Plan B-2 can be implemented immediately to reduce overflows
and provide for more effective treatment of sanitary wastewaters.
a. The Dean Lake Impoundment designed to treat combined
flows from the East 18th Street system will reduce the
storm water flow to the watewater treatment plant,
prevent the dilution of high strength industrial wastes from
that water shed, and relieve flooding problems in the lower
reach of that system.
b. Separation of the scattered combined sewers in the
Closes Creek Watershed will eliminate several
troublesome overflow conditions, reduce the storm-
water load in the West Side Interceptor Sewer, and
prevent bacterial and organic pollutants from this
source from reaching the recreation area above the
Center Street Dam.
4. The City should consider other steps outlined in Plan B-2 to
reduce significant and potentially hazardous overflows.
a. Construction of the reduced Prospect Road Impoundment
would eliminate all overflows from the West Side Inter-
ceptor above Grand Avenue, thus protecting the recrea-
tional area above Center Street.
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c. Frequent overflows of the Ingersoll Run Sewer could be
reduced by constructing facilities to divert high-
frequency overflows to the Southwest Outfall. It is
estimated that approximately one-third of the annual
overflow could be captured by diverting up to 5 MGD
of the overflow to the Southwest Outfall in addition
to that which remains in the Ingersoll Run system.
This would intercept many of the high-frequency over-
flows .
4. Before embarking on programs for separation or treatment of
combined sewer overflows, Des Moines and other cities contending
with the problem of combined sewers should develop and maintain a
detailed master plan for collection and treatment of all waste-
waters. The plan should begin with reproducible documentation
of existing sewer systems. New sewer construction can then be
tailored toward the ultimate goal of the plan. It is recommended
that Des Moines, in .the planning of relief sewer construction,
maintain the domestic and industrial wastewaters from the north
and west areas of the City separate from combined flows to a point
downstream of the central business district, where separate
sanitary flows can be given priority to the treatment facilities.
5. To reduce the volume of extraneous and infiltration water into
the sewer systems, special consideration should be given to pro-
hibiting footing and roof drain connections to sanitary sewers.
Present F.H.A. home construction criteria should be modified to
insure other suitable drainage for footing drains.
6. Where treatment of combined overflow must be considered, the
impoundment method is recommended wherever practical. This method
is the most reliable and flexible, Stormwater flows may be retained
in the impoundment for treatment or returned to the sewer system for
treatment at conventional mechanical plants. Consideration must be
given to loadings, and supplemental oxygen provided if necessary.
Installations in residential or park areas must include landscaping.
The design must include provisions for solids handling.
7. Because of the obvious imbalance noted in this study between
incoming river loads and discharges from the metropolitan area,
it is recommended that a program be initiated to identify all
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sources of the rivers loadings and to develop adequate methods
for control and/or treatment, Such a program should utilize a
basin approach to the problem. To minimize duplication of effort
and provide maximum dissemination of findings, river basin studies
should be coordinated through a single agency.
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SECTION III
INTRODUCTION
PROJECT SCOPE
This project was a multi-phasic study designed to provide engineering
information regarding the volume, character and impact of combined
sewer overflows and urban storm water discharges from a typicallmid-
western metropolitan area. The project includes an engineering evalua-
tion of solutions to the problem, including combined sewer separation
and investigation of facilities for the treatment of both combined sewer
overflows and storm water discharges. In particular, the project en-
compasses the following:
1. Measurement, analysis and evaluation of overflow from
combined sewers and discharges from selected storm
sewers.
2. Analysis and evaluation of the receiving stream.
3. Development of bases of design for transport and treat-
ment of combined sewer overflow waters.
4. Development of preliminary engineering designs and
cost estimates for facilities for the interception, trans-
mission and treatment of combined sewer overflows.
5. Evaluation of existing wastewater treatment facilities
to establish maximum hydraulic and organic treatment
capabilities and to determine their capabilities for
treating stored or retarded combined sewer flows.
6. A detailed combined sewer separation study including
maps and cost estimates for a three square mile area
selected as a typical metropolitan combined sewer
area.
7. Maintenance and operation of a metropolitan rain gauge
network and a detailed rainfall-runoff relationship ana-
lysis for selected drainage areas.
8. Cooperation with local, regional state and federal agen-
cies to obtain available data, to assure compliance with
existing standards and regulations, and to keep them
appraised of the study findings so that recommended im-
provements may be coordinated with their studies and plan-
ning.
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BACKGROUND
The pollution problem attributable to intense, though sporadic, com-
bined sewer overflows and urban storm water discharges is common
to many older cities, including Des Moines. Many of these cities
originated as a river settlement where waterway transportation, not
water pollution, was the prime consideration. Certainly the engineer-
ing problems that would one day have to be solved in order to provide
adequate sewerage and storm drainage facilities were not considered
in the original site selection. Often, the first sewers in the area were
private sewers discharging directly to the adjacent waterway. Some of
these may still be in service. Most, however, have been replaced
with larger conduits and systems by community-minded people who
sought to improve the environment of their community and who had
the foresight to provide reserve capacity to serve the community as
it grew. That these people did not foresee just how much their com-
munity would grow does not detract from their foresight and endeavor.
Unfortunately, these original systems are usually now the built-up
core area of the community, and almost always the most expensive
area for new construction. More recent additions to the original com-
bined system often compound the problem. Sewers which were origin-
ally constructed as separate sewers have since been combined for one
or more of several reasons:
Sanitary sewers, in areas remote from storm sewers,
were tapped to provide "temporary" relief from loca-
lized flooding.
Storm sewers, in areas remote from sanitary sewers,
were tapped for sanitary connections.
Localized overload conditions in either a sanitary or a
storm sewer prompted interconnection for relief.
Unfortunately, the temporary status probably intended for the above con-
nections has long been forgotten. That which is out of sight is too often
also out of mind. Numerous cases have been noted where minor alter-
ing of the route or sizing of new sewers could have separated individual
areas. Now, however, major sewer construction is often required to
do the same job.
Although this study is concerned with combined sewage overflow into the
receiving waters, overflow may also occur within the combined collec-
tion system. Usually such overflow discharges into natural drainageways
or storm sewers and eventually reaches the receiving water. In some
12
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cases the overflow may occur at street inlets. It is possible for these
waters to emerge from one inlet, run overland for some distance^ and
then re-enter the system through another inlet. Where this is the case,
some sanitary significance may be attached to the manner in which the
overflow is transported.
One culprit contributing to sanitary and combined sewer overload and
overflow is the practice of connecting roof and foundation drains to the
sewer. This practice is often prevalent in cities served by combined
systems with the same result - imposition of a sharp hydraulic overload
from roof drains followed by an extended hydraulic overload from founda-
tion drains. During the mid-study period of this project, the study area
received considerable precipitation which resulted in high short-term
and considerable long-term overflow, much of which is believed to have
occurred because of roof and foundation drainage.
Persons involved in water pollution control and regulation recognize
combined sewer overflows and storm water discharges as pollutants of
possible considerable potential. However, the magnitude of the ppten-
tial and its unique behavioral characteristics have not until recently been
investigated to any appreciable depth. Hence this particular study which,
together with similar concurrent studies in other sections of the qountry,
is expected to facilitate a logical, factual assessment of the problem and
feasible solutions.
PROJECT DESCRIPTION
To accomplish, as best possible, the objectives of the project, it was
necessary to establish and maintain a comprehensive system for monitor-
ing and analyzing rainfall, combined sewer overflows, and storm water
discharges. It was also necessary to obtain or develop extensive back-
ground data on the existing metropolitan collection system and treatment
facilities. In addition, river data was obtained from limited sampling by
the contractor and from other agencies. This data was needed in order to
develop an accurate picture of existing river conditions.
The monitoring program involved installation and maintenance of six re-
cording rain gauges and as many as nineteen bubbler-type water level re-
corders. Equipment and installation details are discussed in subsequent
sections. Monitoring locations are shown in Figures 13 and 14. The
rain gauges located within the study area, coupled with two U. S. Weather
Bureau gauges in the area., provided a very good picture of rainfall dis-
tribution. Bubbler-type recorders were designed and assembled for se-
curity and mobility for this particular project. Although semi-permanent
monitoring installations were made for numerous locations, the recorders
13
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wen. located at points of overflow or termini of drainage basins.
However, on several occasions, bubblers were also used to record
flow through wastewater treatment facilities or to determine surcharge
elevations within the collection system.. The surcharged sewer prob-
lem, although not a part of this study, had a profound effect on the con-
duct of the project and is discussed in Section XL
Overflow and runoff sampling was generally done with commercial auto-
matic, timer-actuated, vacuum samplers. Samples were iced during
collection.
Following sample collection and a review of the runoff pattern, a deci-
sion was made whether to analyze individual samples, to prepare com-
posites according to flow rates, or to do both when sufficient sample
was available. This flexibility is one of the positive features of the parti-
cular sampler purchased for this project. Iced samples were then de-
livered to the contract laboratory at Iowa State University for analysis.
Concurrent with the above activities, data and maps were obtained or
prepared for the co.mbined sewer separation study. A. detailed analysis
for combined sewer separation, including estimated costs, is provided
in the form of computer printouts and drawings. Available data on exist-
ing storm sewer systems was often incomplete and required additional
field work to verify existing records. This problem is discussed also in
Section XL
Evaluation of the receiving waterways was accomplished by supplement-
ing the data obtained from the several project samplings with considerably
more extensive data available from the Iowa State Department of Health
and a Corps of Engineers study being conducted by the Engineering Re-
search Institute of Iowa State University (1). Five river samples were
collected as part of this project. These samples were collected above,
in and below the Des Moines Metropolitan area in order to determine sea-
son variations in the quality of the rivers. Twenty-eight hour diurnal
D. O. 's were obtained during four of the samplings. Also, night-time
samples for sanitary analysis were collected in order to show any varia-
tion as a result of sanitary loads. The available river data presents an
interesting, though not unexpected, picture of a receiving stream which
originates and courses through an area of intensive agricultural activity.
One of the key areas for investigation in this study was the feasibility and
economics of treatment of combined sewer overflow as opposed to storm
sewer separation. Various treatment schemes were investigated, in-
cluding lagooning, mechanical treatment, chlorination, and combinations
thereof with and without peak flow retardation. In addition, existing
wastewater treatment facilities were evaluated in order to determine
14
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available capacity for storm water treatment during off peak periods.
The physical problems involved in collecting and transporting storm
water flows are nearly as difficult, if not more difficult, than treating
them. For example, because of prohibitive cost and disruption of exist-
ing utilities, streets and services, it is unlikely that significant addi-
tional hydraulic capacity will be provided through the downtown core
area of Des Moines. Additional capacity could be provided in a conduit
along or in the Des Moines River. This would be expensive, but feasi-
ble.
Treating stormwater, be it combined sewer overflow or separate storm
water discharges, involves numerous considerations, including: (a) de-
termination of a design storm and development of the volumetric re-
quirements (See Section X); (b) projection of land use, population growth
and future overflow and runoff; (c) determination of the capability of
existing wastewater treatment facilities to handle storm waters; and (d)
determination of the degree of treatment required or justified and the
effectiveness of dollars spent for such treatment.
15
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SECTION IV
PROJECT AREA.
GENERAL LOCATION
Located in the heart of the North American land mass, Des Moines is
the largest city in Iowa, the capitol of the State and the county seat of
Polk County. In an urban area of approximately 288, 000, the City of
Des Moines1 1970 population was 200,600. The Study Area lies astride
the Des Moines River in the central part of Iowa, as illustrated in the
"Vicinity Map, " Figure 1. The Raccoon River enters the City from the
west and its confluence with the Des Moines River is within the City
limits.
The Study Area is situated in the upper Mississippi River drainage basin.
In the Des Moines and Raccoon River basins, the land is gently rolling
with broad uplands and the major streams flow in narrow valleys. Des
Moines and its environs cover a multiplicity of topographic features.
Both rivers have relatively wide flood plains in some areas of the City
and narrow or none at all in other areas. In general, drainage is from
northwest to southeast with a high ridge on the left bank of the Raccoon
River separating the two drainage basins so that development to the north
drains to the Des Moines River. These two rivers divide the area into
three sectors; the northwest, the northeast and the south. Major streams
tributary to these include Walnut and Beaver Creeks in the northwest area,
Four Mile and Say lor Creeks in the northeast and Middle Creek and the
North River in the south area. The uplands generally lie above 900 feet
elevation, with the flood plain elevation in the range of 800 feet above sea
level.
Geologically, the entire area is underlain by the Pennsylvania system
which forms the uppermost strata of bedrock. This system, primarily
shales, also includes sandstones, coal and limestone. Overlying the
bedrock are glacial deposits of various clays, sands and gravel. Wind
blown loess, a uniformly fine grain soil, covers the glacial deposits.
It ranges in depth of 5 to 30 feet and is generally visible where the top-
soil has been removed.
Des Moines enjoys a climate which is continental in character, with cold
dry air in the winter and warm moist air during the summer. A marked
seasonal contrast in both temperature and precipitation is characteristic
of the climate. The average annual temperature is 50 degrees, but the
average temperature for the individual months varies from 21 degrees
in January to 76 degrees in July. Extremesvary from an extreme low
of -30 degrees in mid-winter to an extreme high of 110 degrees in mid-
summer. The winter season, lasting about 19 weeks from mid-November
17
-------
JASPER
MA R) N
VICINITY MAP
-------
to late March, has a normal mean temperature of less than 40 degrees.
The summer season, which lasts about 21 weeks from early May to the
beginning of October, has a mean daily temperature of 60 degrees. The
spring growing season and the fall harvest season range between 40 de-
grees to 59 degrees, each lasting about 6 weeks.
Precipitation averages about 31. 5 inches annually, with a minimum of
17. 1 inches in 1956 and a maximum of 56. 8 inches in 1881. The monthly
variation is even more remarkable, from the very dry month of October
1952, with only . 03 inches precipitation to the very wet month of June
1881, with 15. 79 inches of precipitation. Average precipitation for the
winter season is about 6 inches, or approximately 20 percent of the
annual amount. Beginning with the spring growing season, the frequen-
cy and intensity of precipitation increases markedly to a maximum, in
June. The total growing season averages about 25 inches, or approxi-
mately 80 percent of the annual total. The average for the 21 weeks of
summer is about 18 inches. Record mean monthly precipitation is given
in Table 1.
TABLE 1
MEAN MONTHLY PRECIPITATION
January
February
March
April
May
June
1. 14
1. 13
1.92
2.78
4.28
4. 72
July
August
September
October
November
December
3.33
3.54
3.38
2.33
1. 56
1. 16
Annual 31.27
The Raccoon River is the principle source of water for the area. The Des
Moines Water Works supplies all of the developed areas of the City of
Des Moines and wholesales water to the communities of Windsor Heights,
Clave, Urbandale, Pleasant Hill and a number of private residential and
industrial users in the area. The remaining cities and towns in the Study
Area operate their own water supply system, drawing principally from
the Jordan Formation at depths of 2, 500 feet and greater. Shallow wells
in the sand and gravels of the North River are also used for municipal wa-
ter supply.
Local terrain features have lent themselves to cooperation in the planning
and utilization of sewage collection systems and treatment facilities for
many years. Since the original City of Des Moines Sewage Treatment
Plant was placed into service in 1939, it has treated all of the organic
19
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waste from Des Moines and the City of West Des Moines. Tljie Des
Moines system also presently receives waste from the cities'of Clive,
Windsor Heights, and a portion of Urbandale, which are all adjacent
to Des Moines on the west.
STUDY AREA
The basic study area is the urban area of Des Moines and the surround-
ing communities. Field data collected for the study was generally ob-
tained from within the present urban boundaries. In the river sampling
program, monitoring was conducted above Des Moines as well to obtain
basic river quality data. Present and future requirements were based
on conditions within the projected urbanized areas shown on Figure 2.
Specific studies were also conducted in selected areas. While the rain-
fall monitoring network was designed to provide coverage of all the ur-
ban area, rainfall-runoff analysis were limited to five well-defined wa-
tersheds. A detached analysis of combined sewer separation was con-
ducted for an area of approximately 1800 acres in the west-central part
of the City. The areas for such specific studies are described in detail
in subsequent sections.
GROWTH PATTERNS
To evaluate the influence of urban growth on wastewater collection and
treatment requirements, a study of the past, present and future popula-
tion and industrial growth is necessary. Systems designed to carry -
storm and sanitary flow in combined sewers must receive particular at-
tention, since contributions to existing trunk and interceptor sewers are
compounded by growth in upper reaches of the basin. Even where tri-
butary growth areas have separate storm and sanitary systems, the
waste flowing into the combined system carries an increasing pollution-
al load, which will be subject to overflow during wet weather periods.
Growth for the Study A.rea was projected for a 50 year period. A. 20 year
period was considered for wastewater treatment requirements since it
is generally both unsound planning to construct facilities designed beyond
this period and uneconomical to pay interest on an investment which will
not be brought into efficient use within the normal 20 year financing per-
iod. Interim facilities may be designed for shorter periods, but should
be considered in a long range plan. Since the life of a sewer can reason-
ably be expected to be 50 to 75 years, sewer design, whether storm or
sanitary, usually takes into consideration the ultimate development of a
drainage basin insofar as practical. Where extensive drainage basins
are involved, such as in the major rivers and streams, the 50 year
growth pattern is determined and the sewers designed accordingly.
20
-------
EGEND
• — SEWER SERVICE AREA BOUNDARY
URBAN GROWTH PATTERN
I97O - 2O2O
21
FIGURE 2
-------
Figure 2, entitled "Urban Growth Patterns" depicts the anticipated areas
of growth as foreseen by the Central Iowa Regional Planning Commiss-
ion. Population projections for this study considered the entire growth
within the 2020 urban boundary, with the exception of that area south of
the North River basin. The growth Pattern overlays the major sanitary
sewer watershed boundaries so the extent of growth in each basin can be
envisioned. Sewer service areas designated by Roman numerals in Fig-
ure 2 are titled as follows:
I - West Side Interceptor
II - Southwest Outfall
III - East Side Interceptor
IV - East 18th Street Trunk
V - 4-Mile Trunk
VI - Southern Hills Trunk
VII - South Side Trunk
VIII - Bloomfield System
IX - Main Outfall
X - North River Basin
Strong growth to the west is anticipated in the seventies, as well as set-
tlement of the unincorporated areas north of Des Moines including the
corridor running to the City of Ankeny. Between 1980 and 2000 the
growth should swing strongly north and northwest as fingers running
generally along the ridge lines to the existing towns north and west of
Des Moines. The Saylorville Reservoir, now under construction, will
act as a magnet for future growth to continue strongly to the northwest
through 2020. It is of interest to note that, with the exception of the
southerly growth into the North River Basin, nearly all growth is within
and tributary to populated watersheds.
POPULATION PROJECTION
Numerous sources of information were investigated to determine an
appropriate growth estimate for the Des Moines urban area. Past and
present populations were determined from census information. Popula-
tion estimates from recent engineering reports were reviewed and popu-
lation estimates and anticipated growth patterns to the year 2020 were
furnished by the Central Iowa Regional Planning Commission.
Table 2 lists the cities, towns and parts of counties included in the 2020
growth area and gives the populations for each from recent census re-
ports. The estimated future population for the Des Moines urban area.
is also shown graphically in Figure 3. The 1970 population is estimated
to be 287, 850, increasing to 330, 000 by 1980, 385, 000 by 1990, and ;
510, 000 by 2020. This estimate is very close to that prepared by the
firm of Howard, Needles, Tammen and Bergendoff in a planning report
for the Central Iowa Regional Planning Commission. The CIRPC report,
which was done concurrently with this study, put the 1970 urban popula-
tion at 280, 500, with 241, 500 in 1980, 426, 000 in 2000 and 511, 500 in
2020. i
22
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TAB-LE 2
URBAN AREA POPULATIONS
Altoona
A.nkeny
Bondurant
Carlisle
Clive
Des Moin.es
Grimes
Norwalk
Pleasant Hill
Polk City
Ur band ale
Waukee
West Des Moines
Windsor Heights
County Areas (Polk
Dallas, Warren)
Total
1950
763
1,229
328
903
--
177, 965
582
435
--
336
1,777
431
5, 615
1,414
9
26, 831*
218, 679
I960
1,458
2,964
389
1, 317
752
208, 982
697
1,328
397
567
5, 821
687
11,949
4, 715
20,421*
262,444
1965-1966
Special Census
2,424
5,910
500*
1,930
1,735
206, 739
800*
1, 630
1, 006
700*
10,310
480
13, 720
6,409
19, 177*
274, 257
1970
2, 854
9, 151
462
2,246
3, 005
200, 587
834
1, 745
1, 535
715
14,434
1, 577
16,441
6, 303
25, 961*
287,850
*Estimated Populations
23
-------
600
550
500 -
450 -
o
z
O
X
C. 400 -
a.
o
a.
350 -
300 -
250 -
200 -
150
1950
I960
1970
2000
2010
1980 1990
YEAR
POPULATION TREND
DES MOINES URBAN AREA
2020
24
FIGURE
-------
Combined sewers exist only in the older sections of the city, whiclji
are generally developed to near saturation density. For this reason,
only small increases in population are predicted for combined sewer
areas. The areas served by combined sewers are listed in Table 3
with present and estimated future populations. These service areas
can be located on Figure 2.
TABLE 3
COMBINED SEWER AREAS POPULATIONS
Service Estimated Population
Area No. Description 1969-1970 1990 2020
1-1 West Side Intercepter,
Central City 79,000 81,000 84, OJOO
III-l East Side Intercepter,
Central City 16,400 17,500 19,000
IV-2 East 18th Street Trunk 7,000 7,100 7,300
VI South Side Trunk 15, 300 18, OOP 20, OOP
Total 117,700 123, 60P 13P, 3PP
Although some portions of these service areas are not served by cjom-
bined sewers, flow in the trunk collector sewers is combined sewage.
Similarly, it should be noted that all wastewaters, except from th^ Four-
Mile Trunk, is conveyed by the main outfall, a combined sewer.
LAND USE
Future land use is shown in Figure 4. Of particular interest is the in-
dustrial belt in the northeast sector running along Interstate 235 from
the City of Ankeny southward to the southeast bottoms on the left bank
of the Des Moines River. Nearly all of the existing industries which
contribute heavy pollutional loads to the waste treatment facilities are
located in this corridor and fall maihly within the East 18th Street sani-
tary sewer drainage basin (Area IV i- 1 and 2 in Figure 2). This indus-
trial belt is significant with respect to combined sewer problems. The
City of Des Moines should strongly encourage wet process industries
to locate within this corridor.
Commercial and high density residential areas are located to a large
25
-------
LEGEN D
'[ I AGRICULTURAL
IBB RESIDENTIAL LOWS MEDIUM DENSITY
RESIDENTIAL HIGH DENSITY
[COMMERCIAL
INDUSTRIAL
PARKS 8 OPEN SPACES
PUBLIC 8 SEMI -PUBLIC
«M|MtCT
FUTURE LAND
-------
extent near the center of the city on the east and west side of the Des
Moines River, an area served primary by combined sewer systems.
Also of interest is the designation of parks and open spaces along
the Des Moines and Raccoon Rivers. Above the city on the Des Moines
River, the Saylorville Reservoir is currently under construction. Parks
and open spaces are also designated downstream of the city where the
flood pool of the recently completed Red Rock Reservoir reaches to
within the city limits.
DES MOINES AND RACCOON RIVERS: USAGE-POTENTIAL
Both rivers are subjected to extensive usage within the metropolitan
area. The Raccoon River is the primary source of water supply for the
Des Moines Water Works. A recent utilities inventory prepared for the
Central Iowa Regional Planning Commission indicates the existing sup-
ply is adequate for present and immediate future demand. However,
long range demand may require an additional source and the utilities in-
ventory pointed to the Des Moines River, specifically Saylorville Dam,
as the likely source. At present, because of its use as a water supply
and because of its lower flow and shallower depths, the Raccoon River
is not used extensively for water sports recreation.
The Des Moines River does receive extensive water sports and recrea-
tional usage. During open water there is considerable fishing pressure
throughout its course through the City. During the summer, a low head
dam at Center Street maintains sufficient depth in the section upstream
to Euclid Avenue to provide excellent boating opportunity. There are two
private marinas and several public launching areas in this stretch of the
river. Figure 5 illustrates some of the recreational uses.
It is highly improbable that recreational use of the Des Moines River
will decrease, even with the recent completion of Red Rock Dam down-
stream from the city and completion in 1975 of Saylorville Dam imme-
diately upstream. If anything, recreational usage will probably increase,
due partly to the improved quality of the river which should result from
the Saylorville impoundment.
The location of two major impoundments immediately above and below
the metropolitan area, and especially the Saylorville impoundment up-
stream, provides an excellent opportunity for the City of Des Moiraes
to have, within its confines, a water sports and recreation area of sig-
nificant social and economic benefit. The multiple advantages of having
a clean clear river through the heart of the city and metropolitan area
are almost innumerable. Land use planning appears to anticipate this,
since Figure 4 shows parks and open spaces planned for most of the ri-
ver frontage with exception of the downtown area.
27
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FISHING AT SCOTT STREET
BOAT RAMP NEAR STATION O-2
FISHING FROM TOP OF WEST SIDE
STORM BOX
WATER SPORTS RECREATION WITHIN DES MOINES
28
FIGURE 5
-------
SECTION V
FIELD OPERATIONS AND PROCEDURES
GENERAL INFORMATION
This section describes the general concept and execution of the data col-
lection and analyses. To minimize duplication of written material and
cross-referencing, all monitoring and sampling stations are described
in Section VI, with detailed descriptions given in Appendix A. Presen-
tation and discussion of sample and flow data is concentrated in Section
VI.
Field operations were conducted from an office established near the cen-
ter of the project area at East 1st and Locust Streets. This central loca-
tion was very advantageous for dispatching personnel quickly to sample
points during runoff. Office facilities were such that all field equipment
could be easily moved in and out as necessary for service, cleaning and
repair. Two carryall type vehicles were used for transporting tools and
equipment and a station wagon was available for lighter uses.
Field operations were in 8 general areas of endeavor: (1) install and
service monitoring and sampling equipment; (2) conduct scheduled sam-
ple programs such as collection of dry-weather sanitary and river qua-
lity data; (3) spontaneous flow measurement and sampling during runoff
periods; (4) current meter flow measurements to establish flow curves
and hydraulic coefficients; (5) equipment maintenance; (6) preliminary
workup of flow and laboratory data during slack periods between runoffs;
(7) surveying and collection of topographic data; (8) liaison with local
and regional governmental agencies for program coordination and collec-
tion of available related data.
During normal operation, several of the above activities could be con-
ducted simultaneously. During rainfall, however, all effort was direc-
ted toward measurement and sampling of runoff. Following the sample
periods, it was necessary to spend a considerable amount of time on
sample disposition and clean-up of equipment. Routine operation and
servicing of equipment in the field was accomplished by maintaining a
schedule of twice weekly visits to each station. This schedule, once
implemented and ironed out, was satisfactory for continuous operation
of the equipment.
MONITORING AND SAMPLING EQUIPMENT
Water Level Monitoring Equipment
Three types of devices were used to detect overflow and/or record
29
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water levels. They were: (1) stick gauges painted with a. water soluble
paint; (2) drum-type 1 or 7 day float operated recorders; and (3) com-
pressed air 1 or 7 day bubbler type recorders.
Painted stick gauges were used at the outset of the project, while me-
chanical equipment was on order, to gauge frequency of overflow at nu-
merous points. The information obtained was helpful in determining
which overflows should be continuously monitored. The stick! gauges
were simply 1" by 2" boards stapled in place with a ram-set or wedged
into sewer outlets. High water levels could usually be determined quite
accurately by this method, since the water soluable paint would be
washed off to the high water level.
The float operated recorders were Leopold and Stevens Type F Re-
corder, Model 68, with interchangeable gears to enable 24-hour or 7-
day operation. These units were used mainly for temporary setups such
as the dry weather sanitary sampling. The units are light-weight, port-
able and perform very well in temporary installations. Figure 6 shows
installations of the float operated recorders at three sampling stations.
Where turbulent flows are encountered, the float must be protected
with a float tube. Six-inch fibre pipe was found to work quit
-------
5 XI3 INGERSOL RUN
BOX AT D - IA
IN 5 X 6 UNIVERSITY
AVE. BOX AT S -
SURCHARGING PROMPTED PREMATURE REMOVAL. OF RECORDERS
AT SIPHON OUTLET CHANNELS IN D ~ I
TYPICAL WIER a RECORDER INSTALLATIONS
31
FIGURE
-------
STATION O-ll
BUBBLER AMD SAMPLER
INSTALLED AT END OF BOX
SEWER
BUBBLER UNIT
STATION O-6
BUBBLER INSTALLED IN
MANHOLE IN DRIVEWAY
TYPICAL BUBBLER INSTALLATIONS
32
FIGURE 7
-------
3. The unit could be installed at considerable distance
from the actual monitoring point. At several sta-
tions, this distance was 50 to 75 feet. In these and
all cases, the plastic air line was enclosed in alu-
minum electrical conduit for protection against de-
bris and vandals.
4. When secured in place with ram-set bolts and the
cover padlocked, the unit was virtually vandal-
proof.
5. The recording head could be used with either 24-
hour or 7-day charts and required only a simple
screw adjustment to change from one to another.
6. There were no moving parts in the monitored flow
and no significant obstruction in the flow pattern.
Also, the operation was not affected by freezing or
ice cover.
7. The basic principal of operation is widely used in
water and wastewater operations and generally fa-
miliar to operating personnel.
8. The fabricated unit, including assembly, was rela-
tively inexpensive, about $350 each.
The compressed air cylinders were 20 Ib. cylinders furnished and filled
for a fee of $2. 50 per tank by a local supplier of moisture-free air for
skin divers. As noted earlier, a full tank, 2, 000 psi, would last from
1 to 4 weeks. Most stations carried 2 to 3 tanks per month.
Automatic Sampling Equipment
The sampler selected for this project was the Serco Automatic Sampler,
Model NW3-8. This unit is an automatic, timer actuated, vacuum sam-
pler which will collect 24 consecutive individual samples at equal inter-
vals. For this project, 6-hour and 24-hour clocks were used, thus pro-
viding the flexibility of selecting 15 minute or 60 minute sample intervals,
The quarter-hour samples were especially advantageous for flash run-
offs.
Figure 8 shows several photos of the sampler and one series of samples.
The sample bottles hold about 500 ml. Usually 300 to 350 ml. , depend-
ing on suction lift, would be obtained. Where possible, suction lift was
minimized to 5 to 8 feet to obtain the maximum sample. On occasion,
however, samples were successfully collected with lifts of 10 to 11 feet.
33
-------
Xrl
CLEANING SAMPLER
BY BACKFLUSHING
SAMPLER -
WITH SAMPLES
SAMPLER HEAD IN
PLACE AT D - I
COMPLETED
SAMPLE RUN
FROM D - 2
AUTOMATIC SAMPLING EQUIPMENT
34
FIGURE 8
-------
An insulated metal case houses the sampler in the field. The entire unit,
including case, will just pass through a 21-inch manhole opening. For
some sample points, it was necessary to suspend the sampler in a man-
hole in the roadway. This was done by using a belt harness suspended
from a reinforced recessed hanger bar which permitted replacement of
the manhole cover following placement of the sampler. For stations
where the sampler could sit on top of or along side the sewer or stream,
a 55 gallon drum was used to cover the unit and minimize vandalism.
This was especially necessary when charged samplers were left in the
field for extended periods between rainfall. "L"-shaped strap iron was
welded to the base of the drum and slotted to permit padlocking the drum
to short sections of chain secured to the support structure.
The particular sampler used has its advantages and some disadvantages.
Some of the good points are:
1. The sampler, when primed, is self-sufficient and
therefore does not require an external source of
power.
2. Because of "1" above, the sampler can be used in re-
mote locations, such as inside large sewers.
3. The sampler case is well insulated and when pro-
perly iced will adequately cool samples for at
least 24 hours .
4. Collection of individual samples rather than one com-
posite sample gives the engineer the flexibility of ana-
lyzing individual samples, a composite sample, or
both.
5. "4" above also permits visual observation of each
sample.
6. The sampler unit is portable and is light enough that
one man can, if necessary, handle it. Two men make
the job considerably easier, however.
Some of the disadvantages are:
1. Some features of the sarrp ler, in particular the
tripping mechanism and the sampler head, are of
relatively light construction for the type of use re-
quired for this particular project. Repairs were
required on several occasions during the 11 months
of usage.
35
-------
2. The clocks provided are not adequately moistjure-
proof and late in the project were starting to mal-
function.
3. The area beneath the sampler handle bar is ex-
tremely limited. It was very difficult to set or
start a charged sampler without tripping one or
more of the bottles. This problem j.s magnified
in cold weather.
4, The trip arm is rotated by a shaft from the clock
and slippage is prevented by friction from a knurl
headed bolt which must be completely tight or the
trip arm will slip on the shaft. It is sometimes
difficult to determine when the bolt is tight and
several sampling opportunities were missed be-
cause of this problem. A more positive means of
securing the trip arm would be desirable.
5. The sampler head and the 1/4" suction tubes are
subject to clogging by paper, leaves, worms, etc.
One original goal in automatic sampling procedure was ne\fer realized.
That was perfection of a device to actuate the sampling sequence auto- ,
matically at some predetermined depth of flow. A device for that pur-
pose was furnished by the sampler supplier but could not be made to
work within the limitations of the air supply. That device depended on
increasing submergence to release a vacuum which would retract a plun-
ger retaining the trip arm, thus starting the sampling sequence. The
problem was in the vacuum release step. For the flow situations in this
project, submergence was gradual rather than sudden; thus the vacuum
seeped away rather than suddenly retracting the plunger.
Considerable time was spent trying to modify this operation to use pres-
sure from the bubbler unit, rather than vacuum, to lift or retract the
plunger. A double action diaphragm, valve (from the heating system of a
junked automobile), mounted beneath the handle of the sampler and con-
nected to the air control valve shown in Figure 7, was to retract the
plunger at a preset pressure. Although bench tests were successful, the
device did not prove reliable for field operations. Moisture, grime, ants,
etc. soon fouled the needle-type air valve and several mid-night sample
opportunities were missed. For the balance of the project, the samplers
were started manually.
FLOW MEASUREMENT-HYDRAULICS
Hydraulic studies and analyses were an integral, and sometimes unsol-
vable, part of the field operation. Measured flows ranged from 1 MGD
36
-------
dry weather sanitary flow to greater than 200 CFS open channel storm
runoff. Various schemes were used to determine discharge, as de-
scribed hereafter.
Weirs
Weirs were used whenever possible and practical. All dry weather sani-
tary flows were measured by this procedure. Figures 6, 9 and 10 show
weir installations at D-1A, D-2, S-2 and S-3. Basic weir installations
were all of the same general nature. Wooden bulkheads were premea-
sured and cut and then assembled inside the sewer or channel. The
steel weir plate was then bolted to the bulkhead. Joints were caulked
and lapped and burlap was stuffed around the perimeter to minimize leak-
age. In the larger sewers, downstream bracing was necessary to retain
the bulkhead in place. Water level (head) was recorded with either the
float type or bubbler recorders described previously. The following weir
formulae were used to compute discharge:
90° V-Notch Weir Q = 2. 54H 5/2
Rectangular Suppressed Weir Q = 3.33 LH
Rectangular Contracted Weir Q=2.22H3/2 (L-0. 2H)
Where H = Head on weir in feet
L = Length of weir in feet
Q = Flow in CFS
Stage - Discharge Relationship
Stations 0-2 and 0-8 were located in drainageways which carried very
high volumes of water. The only feasible way to determine discharge for
these points was to establish a stage-discharge curve by frequent area-
velocity measurements utilizing a rated current meter. Fortunately,
there were permanent natural or artificial pool controls in the imme-
diate vicinity of both stations. This fortunate circumstance precluded
the need for shifts of the curve to correct for control movement. Fig-
ure 10 shows the stations and controls.
Shifts were not eliminated entirely, however. At Station 0-2 semiper-
manent plus and minus shifts were necessary to compensate for several
changes of the bubbler zero datum.
Hydraulic Gradient Computations
Flows in conduits can be computed from the Manning Formula:
37
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WEIR CONSTRUCTION IN 78
SOUTHWEST OUTFALL. SEWER
AT STAT ION D - 2
WEIR CONSTRUCTION
38
FIGURE 9
-------
STATION! O- 8
SHOWING ROCK
CONTROL FOR
STAGE- DISCHARGE
REL ATIONSH I P
STATION O - 2
SHOWING CONCRETE
SEWER ENCASEMENT
WHICH SERVED AS CONTROL
STATION S - 3
WEIR, BUBBLER AND
SAMPLER SETUP
DISCHARGE MEASURING FACILITIES
39
FIGURE 10
-------
2/3 1/2
Q = 1.486AR S
n
Where Q = discharge in CFS
A = Cross-sectional area in ft.
n = Coefficient of roughness
2
R = Hydraulic radius of flow section in ft. /ft.
S = Slope of the hydraulic gradient in ft. /ft.
Station 0-6 flows were computed by this formula. The input data was
obtained by establishing bubbler stations 0-5 and 0-6 which were on the
same sewer at a known distance apart. The bubblers were referenced
to City datum so that the true water surface elevation could be deter-
mined. Using this data, plus sewer dimensions, invert elevations an4
sludge depth, "A", "R" and "S" could be computed. The coefficient of
roughness "n" was determined by measuring actual flow with the currtent
meter and computing "n. " For this 60-inch brick sewer, "n" was det^r-
mined to be 0. 018. Using the above information, flow tables were pre-
pared for combinations of the three variables - sludge depth, total depth
and hydraulic gradient (slope).
Hydraulic gradient versus flow relationships were also attemped at si-
phon locations D-l and D-5 and for the West Side Storm Box 0-7. The re-
sults were not reliable. Variable indeterminate restrictions in the lines
between the monitoring points, and intermittent backup from downstream
surcharging, introduced too many variables. Figure 11 shows some of
the conditions which adversely affected hydraulic gradient computations
for the West Side Storm Box.
Current Meter Measurements
Current meter flow measurements were used extensively to spot check
flows throughout the sewer system in an attempt to locate the sources
of excessive extraneous flow. The procedure used was to measure depth
of flow, depth of sludge, and average mid-point velocity and from that
data compute the flow. The accuracy of this procedure was checked sev-
eral times by measuring flows at locations upstream from weir installa-
tions. Flows by current meter measurement were usually 5 to 7 percent
higher than those determined by weirs. Figure 12 shows the current me-
ter equipment being used for a sewer flow measurement.
40
-------
MUD
ACCUMULATIO N
AT BIRDS RUN
OUTLET, WEST
SIDE STORM BOX
LEAKS
STORM
ALONG
BOX
RIVER SIDE OF WEST SIDE
DEBRIS IN 6X13
WEST SIDE STORM
BOX BELOW BIRDS
RUN OUTLET
WEST SIDE STORM BOX
41
FIGURE II
-------
MEASURING SEWER
FLOW WITH CURRENT
METER
RIVER SAMPLING AT R - 9
I RAIN GAUGE INSTALLATION AT KSO
(R G. NO. 3 ) WAS UN IQUE
FLOW MONITORING a RAIN GAUGE INSTALLATION
42
FIGURE (2
-------
RAINFALL MONITORING EQUIPMENT
Recording rain gauges were placed at six locations within the study area
to supplement two existing rain gauges maintained by the U. S. Weather
Bureau. Gauges were the weighing-type gauge, with 48-hour chart ro-
tation and 8-day chart drive clocks. Extra chart drums were ordered
after a short period of operation so that charts could be changed in the
office, which proved to be considerably easier than changing in the
field. Except for one gauge located at KSO Radio Broadcasting Com-
pany, temporary platforms were constructed of steel fence posts and
scrap formica-covered plywood bases. At the KSO site, a fenced swim-
ming pool which is no longer in use provided a secure area for the gauge.
The diving board platform served as an excellent base for the rain gauge,
as shown in Figure 12.
All of the sites were fenced areas and no vandalism problems were en-
countered. Arrangements were made with each owner to obtain a key
to the premises or to maintain the gauges when the premises were open.
Gauges were checked and charts changed routinely on a twice per week
basis, generally on Monday and Friday. This provided 1-1/2 to 2 ro-
tations of the chart, but did not interfere with reading the chart. Hourly
precipitation was tabulated for each of the six supplemental gauging sta-
tions in the same format as used by the Weather Bureau. Two items
varied from standard Weather Bureau practice. One was that trace a-
mounts were not recorded as such, but an 0. 01 inch depth in the hour
during which the accumulation reached 0. 01 inch above the previous
reading. Secondly, due to need to correlate rainfall and runoff records,
daylight savings time was used when applicable as opposed to the Wea-
ther Bureau practice of using standard time throughout the year.
SAMPLE COLLECTION AND ANALYSIS
General sampling operations and sample analysis by the various labora-
tories are discussed herein. Dry weather sanitary samples were all 24-
hour composite samples for 2 to 3 days consecutively. Wet weather sani-
tary sampling, combined overflow sampling and storm water discharge
sampling were analyzed as either grab samples or composites of varying
duration. The determination of when to composite samples or when to
analyze grab samples was generally based on the percent of the storm
actually sampled and the desire to obtain peak flow BOD's, DO's or other
constituents. Usually when samples were collected for only a part of
the runoff, grab samples were analyzed for significant points in the flow
curve.
Collection and Preservation
Sanitary sewage, combined overflow and storm water discharge samples
43
-------
were usually collected with the automatic samplers. The major Ex-
ception was the initial dry weather sanitary sampling which was hand
collected prior to receipt of the samplers. River samples were col-
lected by hand, usually from bridges. The small creeks were wa'ded.
Samples for sanitary analysis (BOD, solids, nitrogens and phosphates)
were 1000 to 3000 ml and were iced to retard degradation. Samples
for coliform analysis were collected in sterilized bottles provided by
the laboratory and were taken with the use of a wire basket fabricated
for the particular bottles used. The basket could be suspended from a
bridge with a rope and precluded contamination of the bottle during the
sampling process. Samples for plankton were collected in a one liter
bottle which contained a preservative when received from the labora-
tory. Samples for pesticide were collected in glass quart jars which
had undergone special cleaning procedures in the laboratory.
Dissolved oxygen samples were collected in 300 ml DO bottles with the
use of a DO dunker. The samples were "fixed" or set immediately and
then titrated upon return to the office. Samples for all analyses not dis-
cussed above were collected in gallon jugs with no special handling or
preservation. In all cases samples were delivered to the laboratories
as soon as possible following collection. Figure 12 shows a member of
the field crew collecting a river sample at Station R-9.
Laboratories
All sample analyses, except the temperature, pH and dissolved oxygen
tests done by the field crew, were contracted to three laboratories.
The laboratories and the tests performed by each were as follows:
1. University of Iowa, State Hygienic Laboratory
at Iowa City - Pesticide analyses (DDT, DDE,
Dieldren)
2. City of Des Moines, Department of Public
Health Laboratory - Coliform analysis, total
and fecal
3. Iowa State University, Engineering Research
Institute Laboratory
Abbv. used in this report
Biochemical Oxygen Demand B. O. D.
Chemical Oxygen Demand C. O. D.
44
-------
Abbv. used In this report
Ammonia Nitrogen NHo.N
Nitrite Nitrogen NO?.N
Nitrate Nitrogen NOo.N
Alkalinity
Hardness
Color
Turbidity
Sulfates
Total Phosphate T.PO4
Soluble Phosphate O. PC>4
Total Solids-Volatile and Non-Volatile
Suspended Solids-Volatile and Non-Volatile
Dissolved Solids-Volatile and Non-Volatile
Calcium
Sodium
Chlorides Cl
Chlorine Demand-1 hour
Plankton
Chromium Cr
Cyanide
All analyses were performed in accordance with the procedures outlined
in Standard Methods for the Examination of Water and Wastewater, 12th
Edition,' ' except for the following major exceptions.
1. Use of 1/40 N. Phenylarsine oxide instead of
sodium thiosulfate for DO and BOD titrations.
45
-------
2. Use of glass fibre mats instead of asbestos
mats for suspended solids filtration. This
modification necessitated ignition of the resi-
due at 580" C, instead of 600° C, to preclude
ignition of the mat.
The above modifications were accepted after the laboratory had demon-
strated satisfactory accuracy with their usage. As a matter of interest,
these modifications are also used for the Saylorville Dam Preimpound-
ment Study being conducted by the I. S. U. Engineering Research Insti-
tute, an outside source of data for the analyses in Section 6 of this pro-
ject.
46
-------
SECTION VI
SEWAGE. OVERFLOW AND STORM WATER DISCHARGE DATA
GENERAL
This section describes the results of monitoring and sampling (1) the
dry and wet weather sanitary stations, (2) the combined sewer overflow
stations, and (3) the storm water discharge stations. The characteris-
tics of each monitoring point is described briefly herein, and a detailed
description of each point is contained in Appendix A.
The results of the monitoring and sampling program are tabulated in
Appendix B. This appendix also includes the pounds of the various con-
stituents for those samples where corresponding flow data was avail-
able. A.n interpretation of the results is provided herein, based on ob-
servations in the field as well as laboratory analyses.
TYPES OF SAMPLES
The types of flows which were monitored fall into one of the following
five general categories:
Station Designation
1. Dry Weather Sanitary (combined)
Flow D-
2. Wet Weather Sanitary (combined)
Flow W-
3. Combined Sewer Overflow O-
4. Separate Storm Water Discharges S-
5. Rivers and Creeks R-
The primary purpose of this study was to ascertain and evaluate the
magnitude of the river pollution problem attributable to combined
sewer overflow, hence items "3" and "5" above. Dry and wet weather
sanitary sampling, though questioned at first as being unnecessary,
were left in the program and ultimately proved to be of considerable
value. This data was used to determine domestic and industrial load
impacts for overflow relief sewer design and was especially valuable
in assessing the magnitude of the unusually high infiltration flows
47
-------
measured in the Des Moines sewer system. This data, together with
the separate storm water discharge data, provided compajrative
values for evaluating combined sewer overflow pollutant concentra-
tions.
DRY AND WET WEATHER SANITARY FLOWS
Dry weather flows were sampled at eleven locations as listed below.
A summary description of each point is contained in Table 4. Also,
the points may be located by reference to Figure 13.
The stations sampled and the respective interceptors or drainages
served were as follows:
Station
D-1A*
D-1B*
D-2
D-3*(W-3)
D-4*
D-5*(W-5)
D-6*
D-7
D-8
D-9
* Combined Sewer
Interceptor and Location
West Side Interceptor @ Scott Street
Ingersoll Run Sewer @ 22nd & High
Closes Creek Trunk @ Harding & Pros
pect
Southwest Outfall Sewer (^ Raccoon
River Siphon
East Side Interceptor @ E. 1st &:
Racoon
East 18th St. Interceptor @ Maury St.
South Side Trunk @ Des Moines River
Siphon
Main Outfall @ Wastewater Treatment
Plant
Storm Outlet @ Cornell & Aurora
Fraley Ditch @ E. 30th & Court (storm
sewer outlet)
Four Mile Trunk @ 33rd & E. Granger
48
-------
TABLE 4-
SUMMARY DESCRIPTION OF MONITORING POINTS
STATION
D-l
W-l
W-IA
W-IB(I)
D-l A
D-IB
0-Z
W-2
0-3
W-3
D-4
0-5
W-5
W-5A
0-6
0-7
D-8
0-9
W-9
0-2
0-3
0-4
0-3
O-6
O-7
O-7A
0-78
O-8
0-8A
O-ll
0-14
S-l
S-2
S-J
SEWER SYSTEM
WEST SIDE INTERCEPTOR SEWER
SAME AS D-l
SAME AS D-l
SAME AS 0-1
INGERSOLL RUN SEWER
CLOSES CREEK TRUNK
SOUTHWEST OUTFALL SEWER
SAME AS 0-2
EAST SIDE INTERCEPTOR SEWER
SAME AS 0-3
EAST I8TH STREET INTERCEPTOR
SOUTH SIDE TRUNK SEWER
SAME AS 0-9
SAME AS D-5
DES MOINE5 WWTP
DRAINAGE DITCH
FRALEY DITCH
FOURMILE TRUNK SEWER
SAME AS D-9
CLOSES CREEK DRAINAGE
CLOSES CREEK 8 N.W OUTFALL
WEST SIDE INTERCEPTOR SEWER
WEST SIDE INTERCEPTOR SEWER
SAME AS 0-5
WEST SIDE INTERCEPTOR SYSTEM
SAME AS 0-7
SAME AS 0-7
INGERSOLL RUN SEWER
SAME AS O-8 B D-l A
20TH ST. STORM SEWER
MAIN OUTFALL & WWTP
THOMPSON AVE. STORM SEWER
UNIVERSITY BOX-TUNNEL
CUMMINS PARKWAY STORM SEWER
STATION LOCATION
SCOTT STREET SIPHON OUTLET
SAME AS 0-1
SCOTT STREET SIPHON INLET
WEST 1ST S ELM
22ND a HIGH
ABAND. PUMPSTATION NO PROSPECT
RACOON RIVER SIPHON OUTLET
SAME AS D-2
EAST 1ST a RACOON
SAME AS D-3
EAST I8TH a MAURY
OES MOINES RIVER SIPHON INLET
SAME AS D-5
OES MOINES RIVER SIPHON OUTLE1
DES MOINES WWTP
CORNELL a AURORA
EAST 31 ST a COURT
E GRANGER ABOVE WWTP
SAME AS 0-9
BETWEEN HARDING a PROSPECT
PROSPECT a HICKMAN
2ND a FRANKLIN
2ND a GRAND
451 FEET BELOW 0-5
W.S. STORM BOX » SCOTT ST
W.S. STORM BOX « ELM ST.
W.S. STORM BOX « GRAND AVE.
OVERFLOW OUTLET e I7TH a RAILRO.
SAME AS 0-1 A
20TH ST. B DEAN LAKE
WWTP BYPASS
BIRDLAND PARK LAGOON
W 1ST a UNIVERSITY
63RO a CUMMINS PARKWAY
DRAINAGE AREA ABOVE STATION
EST. 1969
POPU-
LATION
79,000
79,000
79,000
79,000
10, 100
12,300
54,690
54,690
16,400
16,400
17, 300
15,300
15,300
15,300
239.720
luNKNOVW
JAFTER 1
35,600
35,600
12,300
30,300
38.0OO
45,500
46.5OO
79,000
71,800
39,200
14.700
10,100
12,300
239.720
2,300
1,800
1.900
ACRES
8,681
8. 681
6,681
8. 681
927
1,673
15,720
15,720
2.240
2,240
3,024
2,061
2.O6I
2.061
46,167
1 - OMITTEI
NITIAL S«
6.558
6,558
1,673
4,050
4,600
5,600
5,600
8.681
7,900
6.5OO
1.350
927
1,170
46,167
310
193
356
POPU-
LATION
DENSITY
9.1
9.1
9.1
9.1
10.9
7.3
3.5
3.5
7.3
7.3
5.7
7.4
74
7.4
5.2
FROM PF
MPLING.
5.4
5.4
73
7.5
7.9
8.3
8.3
9.1
9.1
9.1
10.9
10.9
10.7
5.2
7.4
9.3
5.3
EST. %
INDUS-
TRIAL
3.0
3.0
3.0
3.0
O.I
0
1.0
1.0
2.4
2.4
6.5
t.l
I.I
I.I
2.2
OGRAM
1.4
1.4
0
0
0
0
0
1
1
1
O.I
O.I
5
2.2
0
0
0
EST. %
COMBINED
SEWERS
18
IB
18
18
81
6
0
0
24
24
5
7
7
7
7
0
0
0
0
6
6
10
25
25
33
33
33
69
81
0
7
0
0
0
FLOW MONITORING
METHOD
OF FLOW
MEASUREMENT
2 WEIRS
NONE
NONE
CURRENT METER
WEIR
WEIR
WEIR
WEIR 12)
WEIR
WEIR (2)
WEIR
WEIR
NONE
NONE
WWTP FLOW METER
WEIR
WEIR
WEIR
WEIR
STAGE DISCHARGE
NONE
NONE
NONE
HYDRAULIC GRADIENT
CURRENT METER ANC
HYDRAULIC GRADIENT
STAGE DISCHARGE
NONE
WEIR
WEIR
WEIR
WEIR
WEIR
MONITORING
EQUIPMENT
FLOAT RECORDER
BUBBLER
BUBBLER
NONE
FLOAT RECORDER
FLOAT RECORDER
FLOAT RECORDER
BUBBLER
FLOAT RECORDER
BUBBLER
FLOAT RECORDER
FLOAT RECOR:EH
BUBBLER
BUBBLER
13)
BUBBLER
FLOAT RECORDER
BUBBLER
BUBBLER
BUBBLER
BUBBLER
STICK GAGE
BUBBLER
BUBBLER
BUBBLER
BUBBLER
BUBBLER
BUBBLER
BUBBLER
BUBBLER
BUBBLER
BUBBLER
FLOAT RECORDER
BUBBLER
SEWER
SIZE
60"
60"
60"
60"
5'X 10'
30"
78"
78"
48"
4B"
66"
36"
36"
24"X45"
78"X84"
DITCH
DITCH
48"
48"
DITCH
36"
60"
60"
60"
60"
60"
60"
5'XI3'
S'XI3'
4'XS1
78"XB4"
5'X 4'
S'X6'
4'X6'
TYPE
REGU-
LATOR
N
N
O.P
N
O.W.
N
N
N
N
N
N
O.W.
O.W.
N
O.W.
N.A.
N A.
N
N
N A.
O.W.
O.W.
O.P
O.W
O.P
O.P
O.R
N.A.
O.W.
N.A.
O.W.
N.A.
N.A.
N.A.
NOTES •
111 STATION WAS USED ONLY FOR FLOW MEASUREMENT
(2) DURING HIGH FLOW WEIR WAS AFFECTED BY DOWNSTREAM SURCHARGE
13) COMPOSITES COLLECTED AND ANALYZED BY WWTP PERSONNEL
STATION CODE i
0- OR*
mcATncr
W- WET WEATHER
0 - OVERFLOW
S - STORM SEWER
TYPE REGULATOR CODE'
N - NONE
O.W.- OVERFLOW WEIR
O.P.- OVERFLOW PIPE
N.A- NOT APPLICABLE
-------
Ln
O
O
c
3J
rn
CAi
L. C O END
(D 0«Y WCATHCH SAMPLE STATION
A PUMP STATION
O MUTE WATER TREATMENT PLANT
SANITARY WATERSHED SOUNOABY
SEVENS
1C IMVTMVCST OWTALL
HI IEASTSMNI MTERCEPTM
ETA
BOTH CTKEET SEWEM
E.N)TN STREET INTERCEP
RMJMIMI.C TNWR
nVTMCBN HUS TMMK
^SANITARY SEWER SYSTEM
V AND
SAMPLE POIMTS
-------
Dry weather flow measurement and sampling was accomplished for
all stations except D-9 during October and November, 1968, but ana-
lytical data is not presented. For reasons unknown, the analytical
data from these initial samplings was extremely erratic and consi-
dered unreliable. Therefore all stations except D-4, D-7 and D-8
were resampled. Station D-7 was determined to be a separate storm
drain and was not resampled because the initial sampling indicated
an absence of sanitary wastes. Station D-4 had considerable quanti-
ties of industrial wastes but was not resampled because in January,
1969, the City began an industrial waste control program which,
when implemented, would materially alter the loadings in these sew-
ers. In lieu of resampling, data from the City's industrial waste
sampling program was used to evaluated present and future indus-
trial waste loads. Station D-8, a storm drain, carried a small a-
mount of industrial wastes. This was removed as a result of the City's
industrial waste control program.
Station D-6 is the wastewater treatment plant. Sampling at this sta-
tion was done by WWTP personnel as part of their routine sampling
program. Unfortunately, the plant fow meter was out of calibration
during the October 1968-Februray 1969 period of dry weather sani-
tary sampling, so comparative total plant loads could not be computed.
For this reason, plant fow and analytical data for A.ugust, September
and October, 1969, were obtained and evaluated.
Table 5 is a summary of the sanitary and industrial loads developed
from a combination of the dry weather sampling and the industrial
waste data obtained from the City.
Because of physical and hydraulic limitations at the wet weather sam-
ple stations, flow measurement could not be obtained. Weirs used for
dry weather sampling were submerged. Attempts to correlate flow
with head loss across river siphons proved extremely erratic, possi-
bly because of constantly changing sediment restrictions in the si-
phons. Also, surcharge from the main outfall caused a constantly
changing hydraulic gradient at all the wet weather stations, some-
times showing a negative gradient which would indicate reverse flow.
Since accurate flow data could not be obtained, wet weather samples
were analyzed either as grab samples or as composite samples based
on estimates of flow made from evaluation of relative surcharge ele-
vations. The analytical data obtained is considered to be useful as a
guide for evaluating the effect of diluting sanitary flows with storm
runoff. A comparison of dry and wet weather data is shown in Table
6. BOD and nutrient concentrations were generally greater in the dry
weather flows, while wet weather flows contained greater concentra-
tions of suspended solids. This is due to the influence of storm runoff
51
-------
which typically contains higher suspended solids and lower BOD's
than dry weather sanitary flows. Wet weather sanitary data was al-
so obtained as part of the overflow monitoring described in subse-
quent paragraphs and in Table 4. Useful data was obtained from:
Station 0-3
Station 0-6
Station 0-8A
West Side Interceptor @ Prospect & Hickman
West Side Interceptor @ Grand Avenue
Ingersoll Run Sewer @ 22nd & High
TABLE 5
SUMMARY OF DRY WEATHER SANITARY
J. AND INDUSTRIAL WASTE LOADS
DRY WEATHER SANITARY SAMPLING
For Stations D-l, D-2, D-3, D-5 and D-9 Combined
Population in Sample Area 200, 900
Average Daily Flow 18.40MGD
Per Capita Flow 91.50GPD
Average Daily BOD 33,229 LBS
Per Capita BOD 0. 165 LBS
Average Daily TSS 32, 747 LBS
Per Capita TSS 0. 163 LBS
WASTEWATER TREATMENT PLANT DATA
August-September-October 1969 (13 Composite Periods)
Average Daily Flow 35.3 MGD
Average Daily BOD 95,800 LBS
Average Dailv TSS 106,000 LBS
FOR 247, 9ZO PRESENT POPULATION
Average Daily Domestic Flow, @ 95 GPCD 23. 6 MGD
Apparent Average Daily Industrial Flow 11.7 MGD
Average Daily Domestic BOD @ 0. 165 Ibs/cap. 40,900 LBS
Apparent Industrial Contribution 54, 900 LBS
Average Daily Domestic TSS @ 0. 163 Ibe/cap. 41,400 LBS
Apparent Industrial Contribution 64,600 LBS
52
-------
TABLE 6
DRY WEATHER VS. WET WEATHER FLOWS IN COMBINED SEWERS
Test
B.O.D.
T.S.S.
V.S.S.
NH3.N
Ui
to NO2.N
NO3.N
T.PO
4
O.PO „
4
D-l
No.
Tests
9
4
4
6
7
6
5
5
Avg.
MG/L
212
228
190
21.30
0. 11
0.98
20. 13
11.49
W-l
No.
Tests
8
8
8
5
5
5
5
5
Avg.
MG/L
63
384
143
7. 20
0. 12
1. 16
12. 79
8. 06
D-3
No.
Tests
10
6
6
5
5
3
5
5
Avg.
MG/L
169
153
117
23.81
0. 12
0. 13
14. 84
9. 08
W-3
No.
Tests
4
4
4
3
3
4
2
4
Avg.
MG/L
128
386
175
22.67
0. 17
0.44
14. 68
6.59
D-5
No.
Tests
5
3
3
3
3
1
3
3
Avg.
MG/L
216
390
250
31. 13
0. 20
0. 16
17. 70
13.21
W-5
No.
Tests
4
3
3
2
2
2
2
2
Avg.
MG/L
138
1079
366
8.48
0. 01
0. 06
16. 20
7. 08
Note: The data for W-5 is for only one runoff period.
The data for W-l and W-3 is for 4 and 3 runoffs respectively.
-------
A summary of the overflow monitoring results is given in Table 7-
As a matter of interest, comparative average BOD for wet weather
sanitary flows are tabulated below for the three stations.
Station 0-3 2 runoff periods, A.vg. BOD = 69 mg/1
Station 0-6 3 runoff periods, Avg. BOD = 72 mg/1
Station 0-8A 4 runoff periods, Avg. BOD = 69 mg/1
COMBINED SEWER OVERFLOWS AND STORM WATER DISCHARGES
Combined sewer overflows were monitored at five locations and storm
water discharges at three locations.
Stations sampled and sewers or drainage areas served were as follows:
Station Sewer or Area
0-2 Closes Creek overflow and drainage area
0-3 West Side Interceptor @ Prospect & Hickman
0-6 West Side Interceptor @ Grand Avenue
0-8 Ingersoll Run overflow @ outlet
0-8A Ingersoll Run sewer @ 22nd & High
S-l Thompson Avenue Storm Sewer
S-3 Cummins Parkway Storm Sewer
0-11 20th Street Storm Sewer (separate sewer)
A summary description of each point is contained in Table 4. Figure
14 shows the location of these points, and a detailed description of each
point is located in Appendix A.
Figure 15 shows typical overflow structures located at Stations 0-5 and
0-6. Both are located on the West Side Interceptor immediately above
Grand Avenue.
54
-------
TABLE 7
COMBINED SEWAGE OVERFLOW & STORM WATER DISCHARGES
Suspended Solids
Station
0_-2_ (12 Storms)
No. Tests
Avg. MG/L
OO (2 Storms)
No. Tests
Avg. MG/L
0-6 (5 Storms)
No. Teats
Avg. MG/L
0-7 (5 Storms)
No. Tests
Avg. MG/L
0-6 (12 Storms)
No. Tests
Avg. MG/L
0-BA (4 Storms)
No. Teats
Avg. MG/L
S_-^(17 Storms)
No. Testa
Avg. MG/L
S-3 (20 Storms)
No. TestB~
Avg. MG/L
0-11 (20 Storms)
No. Teats
Avg. MG/L
B.O.D.
19
44
3
69
10
95
9
50
21
68
7
77
25
48
24
63
35
56
T.S.S.
19
495
3
144
9
592
8
195
20
410
5
303
32
315
24
578
33
404
v.s.s.
19
95
3
77
9
181
8
62
20
142
5
101
30
99
2-1
106
32
110
Nitrogens
NH,.N
J
17
1.21
1
4. 53
7
9.42
8
1.84
18
3.22
5
4.94
9
1.99
11
1.60
29
2.30
NO,.N
£
17
0.03
1
0.08
7
0.14
8
0.01
18
0.03
5
0.03
9
0.15
11
0.03
29
0.04
NO,.N
3
17
0.88
1
0.26
6
0.63
8
I. 15
IB
1.07
5
0.57
9
1.11
11
1.47
29
0.96
Phosphates
T.PO,
T*
14
2. 20
1
11.72
4
9-88
7
7. 10
13
6.96
0
-
7
1.Z5
1
0.93
21
2.23
O.PO.
~
17
1.25
1
8.25
5
9.24
7
3.02
12
5.08
5
6.05
9
0. 18
10
0.43
26
0.57
-------
o
c
3)
m
STORM A COMBINED
SEWER SAMPLING POINTS
-------
LOOKING DOWN AT
3G"OVERFLOW FROM
6O" WEST SIDE
INTERCEPTOR AT
STAT ION O - 5
LOOKING INTO GO
WEST SIDE
INTERCEPTOR FROM
36" OVERFLOW AT
STAT I ON O - 5
BRICK AND MORTAR
OVERFLOW AT
STAT ION O - 6
TYPICAL OVERFLOW STRUCTURES
57
FIGURE 15
-------
Station 0-5 consists of a brick overflow sewer leading directly from
the interceptor; at 0-6 the overflow passes over a brick weir con-
structed in the side of the interceptor sewer. One of the original goals
of this study was to determine the actual quantity of combined sewer
overflows and pollutant material generated from runoffs of various
magnitudes. In retrospect, this goal was idealistic. In many instances
in the system studied, the actual volume of overflow often could not be
determined. Excessive infiltration, almost constant surcharge during
the spring and summer, and limited hydraulic capacity often interfered
with attempts to monitor overflow. When runoff water reaches a sewer
inlet, it may enter there only to emerge at some downstream inlet to
become overland flow. Generally, this condition was predicted for the
design storms and other high intensity storms, but was not considered to
be of great significance for most of the lower intensity storms monitored
during the study. The surcharge conditions and the long period of high ri-
ver stage did, however, interfere to a great extent with monitoring of ma^-
jor combined sewer overflows.
For these reasons, theoretical computations of overflow quantities were
considered more reliable in some cases than the hydraulic measurement
obtained. Measured pollutant concentrations were used in determining
predicted overflow quality. Predictions of area-wide overflow quantities
were based on standardized rainfall curves developed for the1 study area
and the hydraulic capacities of the present sewer system. The results of
these calculations are discussed in Section VIII and X.
Stations 0-2, 0-8, S-l, S-3 and 0-11 each represent the only point of
overflow or storm water discharge from their respective watersheds.
Also, the boundaries of their contributing sewer area could be deter-
mined within an allowable margin of error. For these stations, unit values
of runoff and pollutant quantities were determined. These data are presen-
ted graphically in Figures 16 through 22. The data lends support to the
"first flush" theory. In almost all cases, BOD and TSS concentrations de-
creased with time with little or no relation to the flow pattern. Also,
volumetrically, the BOD and TSS runoff almost always "ran ahead" of
flow. Similarly, chloride concentrations during snowmelt runoff indi-
cate a high initial flush. Serial data on nutrient concentrations was not
adequate to determine if the "first flush" theory relates to these pollu-
tants also, however, logic would suggest that it does.
Figure 23 shows in general the relationship between the volume of rain-
fall and the volume of runoff. In Figure 24, unit pollutant values are plot^
ted for the overflow stations (0-2 and 0-8) and the storm sewer stations
(S-l, S-3 and 0-11). Reference to Table 7 shows the average constituent
concentrations for each of the overflow and storm water stations. Com-
posite and intermittent grab samples were taken throughout runoff per-
iods in order to more closely obtain the true characteristics of the
58
-------
RUNOFF CHARACTERISTICS
CO
1400
1300
I ZOO
1100
1000
900
eoo
700
600
500
400
300
200
100
0
17 18 19 20 21 22 23 24 01 02 03 04 05
70
60
o:
.50
V
.40 t
•z.
UJ
\-
.30 ~
"I
.10
5-7-69
5-8-69
PERTINENT DATA
RUNOFF PERIOD' 1700 HRS 5-7-69
TO 1600 HRS 5-8-69
TOTAL RUNOFF •
23.2 AC. FT.
0.238 INCHES
RAINFALL PERIOD' 1650 HRS 5-7-69
(AT R.G. No.5) TO 2240 HRS 5-7-69
TOTAL RAINFALL = 1.14"
VOLUMETRIC COEFFICIENT OF
RUNOFF = 0.208
ANALYZED RUNOFF'• 22.9 AC. FT.
(99% OF TOTAL)
COMPOSITE PERIODS (2)
(I) 1730 HRS 5-7-69 TO
0030 HRS 5-8-69
COMPOSITE B.O.D. = 31 MG/L
T.S.S. - 381 MG/L
(2) 0130 HRS TO 0830 HRS 5-8-69
COMPOSITE B.O.D. = 22 MG/L
T.S.S. - 97 MG/L
100
90
co eo
_i
i
O 60
sP
C 40
Q 30
q
m 20
10
VOLUMETRIC RELATIONSHIP
B.O.D. VS FLOW
-B.O.D.
0 10 20 30 40 50 60 70 80 90 IOO
RUNOFF % OF TOTAL
RUNOFF CHARACTERISTICS
STATION O- II
2OTH STREET STORM SEWER
59
FIGURE
16
-------
RUNOFF CHARACTERISTICS
1400
1300
1200
1100
1000
W 900
t- 800
700
600
500
400
300
200
100
0
I
70,
60
50
Q
6
OD 40
I
_l
30
20
10
FLOW
B.O.D.
07 08 09 10 II 12 13 14 15 16 17 18
7-23-69 I
70
60
50
40 ,
30
Q:
20
2.8
2.4
o:
i
2.0
16 55
Z
LU
1.2
.4
PERTINENT DATA
RUNOFF PERIOD^ Q700 MRS
TO 1800 MRS 7-23- 69
TOTAL RUNOFF
9.30 AC. FT.
0.097 INCHES
RAINFALL PERIOD' 0630 HRS
(ATR.G. No.5) TO 0745 HRS
TOTAL RAINFALL- 0.69"
VOLUMETRIC COEFFICIENT OF
RUNOFF = 0.141
ANALYZED RUNOFF^ 5.90 AC. FT.
(64% OF TOTAL)
RUNOFF SAMPLES^ 3 GRABS
(I) 0725 HRS- B.O.D. - 37.5 MG/L
T.S.S. - 588 MG/L
(2) 0815 HRS B.O.D. = 35.0 MG/L
T.S.S. - 808 MG/L
(3) 0850 HRS B.O.D. - 23.1 MG/L
T.S.S. - 356 MG/L
100
90
80
70
60
50
40
30
20
10
0
VOLUMETRIC RELATIONSHIP
B.O.D. & T.S.S. VS FLOW
B.O.D.
T.S.S.
10 20 30 40 50 60 70 60 90 100
RUNOFF- % OF TOTAL
RUNOFF CHARACTERISTICS
STATION O - II
2OTH STREET STORM SEWER
60
FIGURE I?
-------
RUNOFF CHARACTERISTICS
co
CO
350
300
25O
20O
ISO
IOO
50
o1-
08 09 10 II 12 13 14 15 16 17
9-4-69
PERTINENT DATA
CO
m
JS
o
b.
O
co
CO
H
-------
RUNOFF CHARACTERISTICS
1300
1200
1100
1000
CO
(O 900
800
I
700
^ 600
500
400
300
200
100
O
I 30
120
110
100
9O
80
70
. 60
50
40
30
20
10
FLOW
17 IB 19 20 21 22 23 24 01 02 03 04
CO
O
60
55
50
45
40
35
30 U-
IL.
25 O
Z
20 a
CC
IS
10
3
0
.60
.50
I
\
Z
.40
CO
.30 UJ
.20
.10
_J
5-7-69
5-6-69
VOLUMETRIC RELATIONSHIP
B.O.D. a TS.S. VS FLOW
v>
at
<
O
10
CO
H
OD
q
m
loop
90
80
70
60
SO
40
30
20
10
0 .
T. S.S:
B.O.D.
ID 20 30 40 50 60 70 80 90
RUNOFF - % OF TOTAL
100
PERTINENT DATA
RUNOFF PERIOD: 1700 MRS. 5-7-69
TO 0400 HRS. 5-8-69
TOTAL RUNOFF . 19.29 AC. FT
0 171 INCHES
RAINFALL PERIOD! 1650 HRS 5-7-69
(ATR.G. No.5) TO 2240 HRS 5-7-69
TOTAL RAINFALL- 1.14"
VOLUMETRIC COEFFICIENT OF
RUNOFF- 0.150
ANALYZED RUNOFF! 18.75 AC. FT.
(97.4 OF TOTAL)
COMPOSITE PERIOD: 1700 HRS -
2300 HRS 5-7-69
COMPOSITE B.O.D. = 44.8 M6/L
T.S.S. = 343 M6/L
RUNOFF CHARACTERISTICS
STATION O - 8
INGERSOLL RUN OVERFLOW AT OUTLE'
62
FIGURE
19
-------
2000
1900
1800
I7OO
1600
I50O
I 1400
° 1300
(D I20°
1100
CO
co 1000
H
90O
I
eoo
— 700
2 600
500
400
3OO
200
IOO
0
RUNOFF CHARACTERISTICS
-i 6.0
18 20 22 24 02 04 06 OS 10 12 14 16 18 20
1-15-69 I 1-16-69
PERTINENT DATA
RUNOFF PERIOD : 1800 MRS 1-15-69
TO 1800 MRS I - 16-69
PRECIPITATION: NONE- SNOWMELT
COMPOSITE PERIOD . SAME AS ABOVE
COMPOSITE B.O.D. - 31 M6/L
T.S.S. = 302 MG/ L
CL- = IOOM6/L
RUNOFF CHARACTERISTICS
STATION S- 3
CUMMINS PARKWAY STORM SEWER
63
FIGURE
20
-------
RUNOFF CHARACTERISTICS
in
OT
1300
I200h
1100
1000
900
I- BOO
1 700
_l
^ 600
0 500
2
400
300
200
100
0
-,.60
450
15 16 17 18 19 20 21 22 23 24
H.IO
JO
VOLUMETRIC RELATIONSHIP
B.O.D. a T.S.S. VS FLOW
O
O
O
CD
100
90
80
70
60
50
40
30
20
10
0
T. S.S:
B.O.D.
10 20 30 40 50 60 70 80 90 100
RUNOFF- %OF TOTAL
PERTINENT DATA
RUNOFF PERIOD' |540 HRS. - 2300 HRS.
6-22-69
TOTAL RUNOFF^ 2.Q8 AC. FT.
0.07 INCHES
RAINFALL PERIODM500 HRS. - 1800 HRS.
TOTAL RAINFALL. 0.42"
(AT R.G. No.5)
VOLUMETRIC COEFFICIENT OF
RUNOFF 0. 167
ANALYZED RUNOFF' 1.92 AC. FT.
(92% OF TOTAL)
RUNOFF SAMPLES^ 5 GRABS
(I) I54O MRS.' B.O.D.. 154 mg/l
T.S.S. - 99 mg/l
(2)1600 HRS.- B.O.D.- 166 mg/l
T.S.S. 1146 mg/l
13)1700 HRS.- B.O.D. 105 mg/l
T.S.S. = 476 mg/l
(4tW3O ttfrS. • ff.O.O. - lit mg/l
T.S.S. 340 mg/l
(5) 1900 HRS. • B.O.D. IN mg/l
RUNOFF CHARACTERISTICS
STATION S - 3
CUMMINS PARKWAY STORM SEWER
64
FIGURE
21
-------
RUNOFF CHARACTERISTICS
to
(ft
650
600
550
500
450
400
I-'
I 350
_| 300
en Z5°
2 200
ISO
100
50
O
110
100
90
9 60
O
-------
6.0
5.0
4.0
3.0
2.0
V)
UJ
0
— 1.0
I
z
o
I-
o
Ul
O.I
O.Z 0.3 0.4
RUNOFF - INCHES
0.9
0.6
L. £ G EN D
A Station 0-2
O " 0-11
© " 0-8
VOLUMETRIC RELATIONSHIP
RAINFALL - RUNOFF
66
FIGURE 23
-------
1.00
.90
.80
.70
.60
.50
.40
.30
.20
.10
STORM RUNOFF
0.50
1.00
1.50
2.00 2.50
B.O.D.
3.00 3.50 4.00
— LBS/ACRE
4.50
5.00
5.50
6.00
.60
.50
.40
.30
.20
.10
0
10
20 25 30 35
S.S. — LBS/ACRE
40
45
50
.60
.50
.40
.30
.20
.10
0
0.025 0.050 O.075 0.100
NITRATE NITROGEN — LBS/ACRE
0.125
.50
.40
.30
.20
.10
0.025 0.050 0.075 0.100
ORTHO- PHOSPHATE — LBS/ACRE
0.125
LEGEND
A Station O-2
G Station 0-8
t. Station S -3
® Station S-1
0 Station O-ll
# Snowmelt Sample
RUNOFF VOLUME
VS.
B.O.D.,T.S.S.,NO3-N, a O
67
FIGURE 24
-------
particular runoff. The points plotted in Figures 16 through 22 are typi
cal of sampling intervals during the runoff.
A cursory review of Table 7 prompts the following observations.
1. Except for Station 0-6, there is little difference
in the average BOD concentrations. Overflow and
runoff flows both run in the 40 to 70 mg/1 rarige.
It is believed that the higher value for Station 0-6
results from the hydraulic limitation of the sewer
above that location, thus limiting diluting storm
waters.
2. A greater range in values was found for suspended
solids concentrations in both overflow and storm
water discharges, but storm water appears to be
generally higher. Volatile content is low (20 to 35
percent) indicating much of the solids are inert ma-
terials such as sand and dirt, probably from streets
and yards.
3. Ammonia nitrogen concentrations were somewhat
higher in overflow samples. This reflects the pre-
sence of raw sewage in these waters. Nitrite and
nitrate concentrations, however, were about the
same for both types of samples.
4. Phosphates were of significantly higher concentra-
tions in the overflow samples, again probably attri-
butable to raw sewage.
STREET DEICERS
Runoff from snow melts were analyzed for chloride and chromium con-
tent to determine the effect of street deicers. The systems for which
data were obtained included S-l, S-3, 0-2, 0-8, 0-11, W-3 and W-5.
The concentration of chlorides varied widely according to type of sys-
tem, the amount of snow melt since application, and the quantity of
flow. Inspection of the data tabulated for these areas in Appendix B
will show the variation in chloride concentrations from various snow
melts. Figures 18 and 19 graphically illustrate the pattern of chloride
concentrations daring snow melts in the S-l and S-3 areas. The quan-
tity of chloride in pounds also increases as the flow begins to increase,
but drops off after the initial flush, thus lending support to the "first
flush" theory. Reference to the data tabulated in Appendix B shows
this pattern. Both composite samples and grab samples were analyzed
to determine chloride quantities.
68
-------
The areas monitored were primarily residential areas with some ma-
jor thoroughfares, but no heavy commercial or business districts
where heavy salting would be expected. On the S-l area, it was de-
termined that approximately 15,000 pounds of chlorides were carried
off in runoffs from January 15 to March 2, 1969, which accounts for
practically all snow melts. This amounted to about 1075 pounds per
mile .of street for the season. Considerable snow, sleet and freezing
rain occurred during the last half of December and the first half of
January, 1969, causing extremely heavy usage of street deicers, but
no significant snow melt occurred until January 15. Although no snow
melt had occurred, it was apparent from the January 15 sampling that
much of the salt applied before that time was no longer on the streets.
Four snow melts from Area S-l had the following quantities of chlor-
ides per street mile:
January 15 & 16, 1969 (0.236 inches runoff) 84.6 Ibs/mile
February 14, 1969 (0.049 inches runoff) 266.3 Ibs/mile
February 5, 1969 (0.038 inches runoff) 79.4 Ibs/mile
February 25, 1969 (0. 149 inches runoff) 36. 8 Ibs/mile
Chloride concentrations of up to 2724 mg/1 were measured at S-3 and
2317 mg/1 at S-l, both of which occurred at quite low flows at the be-
ginning of a snow melt on February 21, 1969. For composite samples
of over 7 hours the chloride concentrations did not exceed 125 mg/1,
however, and ranged to as low as 32 mg/1.
The highest concentration of chlorides found in combined sewers was
in the East Side Interceptor (W-3). The concentration was 817 mg/1
which is considerably less than observed in separate storm sewers.
Inquiries were made to all municipalities in the study area, the State
Highway Commission and the Polk County Engineer regarding the quali-
ty of highway deicers used during the 1968-1969 winter season. Based
on the amount of salt shipped to these agencies, it was estimated that
the Des Moines Metro area had 9270 tons of untreated rock salt, 225
tons of rock salt treated with a rust inhibitor and 295 tons of calcium
chloride applied to streets and highways this season. In terms of the
chloride ion, this amounts to 5380 tons, or 11,660,000 Ibs. With the
exception of an early snowfall on November 10, 1968, the snow removal
season ran from December 17, 1968 to early March 1969. Heaviest
usage occurred during the last half of December and the first half of
January due to the extreme weather conditions.
69
-------
River samples collected by both the Contractor and the State Hygienic
Laboratory included chloride and chromium analysis starting January
1969. These results are tabuled in Appendix C. Chlorides ran signi-
ficantly higher during the winter months than in the summer. During
January and February, chloride concentrations above 40 mg/1 were
common for the stations above Des Moines, the highest being 56 mg/1.
Below Des Moines, the highest concentrations recorded were 86 and 6?
mg/1 at the R-6 station, and 74 mg/1 at R-5. During the spring and
summer months, chlorides fell to below 20 mg/1, but began to climb
into the 20's as the flow dropped off in the fall.
An attempt was made to correlate the chlorides sampled in the river
and storm sewer monitoring programs to that applied in the study area,,
A satisfactory correlation could not be made, however, and this was
omitted rather than make broad speculations. Other studies have in-
dicated that approximately half of the salt applied can be expected in
the discharge. i^)
Because only a small quantity of chromium treated salt was used in
the study area, this material was not included in the previous discus-
sion. Chromium analyses were run on snow melt and river samples,
and are shown in the tables in the appendices. The highesit concentra-
tions were found in the S-3 drainage area, a very small part of which
received treated salt. Concentrations of 1210 and 876 ug/1 were re-
corded from two different snow melt periods. Both of these occurred
during very low flows at the beginning of the snow melt.
70
-------
SECTION VII
RAINFALL-RUNOFF STUDIES
GENERAL
The original primary objective of this part of the study was to deter-
mine the relationship between rainfall and sewage flows in the com-
bined sewer systems. A secondary objective was to develop the re-
lationship of runoff to the amount and intensity of rainfall for various
types of land use within the study area. During execution of the study
it became apparent that the primary objective of relating rainfall to
combined sewer flows could not be met due to a number of unanticipated
conditions in the field. As a result, greater emphasis was placed on
the secondary objective and the development of a procedure for predict-
ing the quantity of pollutants carried to the stream by runoff. A rain
gauging network was established for Des Moines and its environs which
effectively covered the developed watersheds in the study area. Six
rain gauge stations were maintained during the study in addition to the
two existing Weather Bureau stations.
From the rainfall monitoring program, detailed rainfall-runoff rela-
tionships were developed for four selected watersheds. The data ob-
tained from the supplemental monitoring, together with historical data
furnished by the U. S. Weather Bureau, was useful for establishing
rainfall intensity distribution with regard to total depth and duration of
rainfall.
Much of the published data deals with precipitation in the magnitude of
intense storms and is primarily concerned with design of drainage fa-
cilities for peak runoff flows. A. number of attempts have been made
to relate the effect of lesser magnitude storms to combined sewer over-
flow situations (4, 5, 6), but these have generally been based on assumed
runoff relationships. The intense storms monitored during the study
period were not of the magnitude normally considered adequate for de-
sign of storm drainage facilities, and the storm pattern frequently was
not such to produce maximum runoff. They did, however, provide data
for moderate storms from which coefficients of runoff were developed.
From these , evaluation of the annual or seasonal pollution contribu-
tions of combined or separate storm runoff is possible. Where local
conditions dictate treatment of combined or separate urban runoff, in-
formation of this type is desirable for design as well as for evaluating
the degree of treatment that will be provided by a given system or fa-
cility.
The original concept was to provide a rain gauging network which would
cover all developed sanitary and combined sewer watersheds in the Des
71
-------
Moines metropolitan area. Both combined sewer systems and Separate
sanitary systems are known to carry large quantities of extraneous
water during wet weather. It was desired to determine the extent and
source of such flow and the influence of direct rainfall runoff in the
individual systems. This, then, was the initial basis for the flow
monitoring system as well as the rainfall monitoring.
In the actual execution of the monitoring programs, extraneous flows
were found to be of a completely different nature than anticipated.
Very high infiltration overloaded separate sanitary systems and pro-
duced a prolonged surcharge in all major trunk sewers. An extended
period of high river stage further complicated hydraulic measurements,
negating attempts to directly measure runoff through the major river-
front combined systems. As a result, it was concluded that factors
other than direct rainfall runoff were of such magnitude as to
tnake any
attempt to correlate rainfall and sanitary flow very difficult, if not im-
possible. Therefore, rainfall-runoff correlations were limited to sep-
arate storm sewer systems. :
DESCRIPTION OF RAIN GAUGE1 STATIONS
The rain gauge stations are located as shown on Figures 14 and 25 and
are described as follows:
Station No. 1 is located one-half block west of Indianola Avenue on the
north side of Park Avenue. The site is the location of a water! standpipe
operated by the Des Moines Waterworks and was large enough that the
rain gauge could be located so as not to be influenced by the standpipe.
Station No. 2 is located on the premises of the Phillips Petroleum Com-
pany, 4400 Vandalia Road. The site is used for offices, warehouse and
bulk storage of petroleum products and provided ample open sjpace for
locating the rain gauge.
Station No. 3 is located on the premises of the KSO Radio Broadcasting
Company at 3900 N. E. Broadway. A. fenced swimming pool which is no
longer used provided a secure area for the gauge. The diving1 board plat-
form served as an excellent basb for the rain gauge, as was shown in
Figure 12.
Station No. 4 is located in the West Des Moines maintenance yard at
1405 Maple Street. The site is used for equipment storage atjid main-
tenance and adequate space was available to prevent interference with
the rain gauge.
Station No. 5 is located in the vehicle parking compound of ttye Iowa
National Guard Armory at 1915 Prospect Road.
72
-------
00
O
c
•x
m
Raingage Location
RAINFALL - RUNOFF
STUDY AREAS
at
-------
Station No. 6 is located at the UrbandaLe Sanitary District Wastewater
Treatment Plant. The site is immediately north of Interstate 35-80
and one-half mile east of 72nd Street.
Station No. 7 is an existing Weather Bureau gauge located at the Munici
pal Airport. This is a first order station, for which precipitation re-
cords date to 1877. Hourly precipitation records from this station are
published monthly.
Station No. 8 is an existing Weather Bureau Station located at the Fed-
eral Court Building between Walnut and Court on East First Street.
Data from this station is not published, but copies of the gauge charts
were obtained for the storms studied.
All of the sites were fenced areas and no vandalism problems were en-
countered. Arrangements were made with each owner to obtain a key
to the premises or to maintain the gauges when the premises were open.
STUDY AREAS
Four watersheds were selected for making detailed analyses of rain-
fall and runoff. Typical areas were selected to give various topogra-
phic features, land use and degree of development. The watersheds
required relatively well defined boundaries, and could not be inter-
connected with other systems. The basin also required an outlet at a
single point, and needed to be reasonably accessible and not subject
to backwater or complex hydraulic situations.
It was desired to monitor a heavy commercial area in the business dis-
trict, but because of conditions at the outlet, interconnection with other
systems, and the lack of well defined boundaries, it was not possible to
locate a suitable area.
The areas which were selected for detailed study are described below
and are shown on Figure 25.
S-l - Thompson Avenue Storm Sewer
This is a separate storm sewer serving an area of 315 acres. The area
is primarily medium density residential with an estimated population
density of 12 people per acre. The topography is rolling with an eleva-
tion of about 796 feet near the flow monitoring point . The Thompson
Avenue storm sewer is a 5'-3" wide by 3'-10" high concrete box at the
outlet, discharging into the Birdland Park Boat Marina on the east bank
of the Des Moines River. This outlet was submerged during high river
stage, as shown in Figure 62, but several storms were monitored be-
fore and after this period.
74
-------
There are several areas adjacent to and above this system which are
served by combined sewer systems. It could only be assumed that
sufficient inlet capacity existed in the combined sewer areas to pre-
vent overland flows from these areas into the area being monitored.
While it is possible that this was not always the case, it is felt that
the error introduced from this source would be small.
The approximate time of concentration from the most distant point to
the flow monitoring point is 30 minutes. For design, a composite co-
efficient of runoff "C" of approximately 0. 58 would be used for the area
as a whole.
Flow measurement was accomplished by a sharp-edged rectangular
weir without end contractions. Water levels were recorded by the
babbler-type installation described in Section V.
S-3 - Cummins Parkway Storm Sewer
This separate storm sewer system serves a relatively new residential
area of 356 acres. The area is medium density residential with an es-
timated density of 12 people per acre. The topography is rolling with
an elevation of about 838 feet at the flow monitoring point to about 975
feet at the furthest upstream point. The area is approximately 8ZOO
feet in length and 3100 feet in width at the widest point. The time of
concentration from the furthest point to the point of flow monitoring
is estimated to be 40 minutes for a design storm. A composite coeffi-
cient of runoff "C" of approximately 0. 53 would be used for determin-
ing design storm runoff.
The monitoring point was a 6-foot wide by 8-foot high concrete box cul-
vert at Windsor Drive and Cummings Parkway. The drainage from this
system flows in an open ditch from approximately 1700 feet above the
monitoring station to a point near 63rd and Grand where it discharges
to Walnut Creek. Flow measurement was accomplished by a sharp-edged
rectangular weir without end contractions and recorded by the bubbler-
type recorder. The installation is shown in Figure 10.
0-2 - Closes Creek Watershed
This watershed of 1673 acres is drained by numerous storm sewer
systems with 107 acres served by combined sewers. The area is me-
dium density residential with light commercial in neighborhood shop-
ping centers. The population density for the entire area is 7.4 people
per acre, but varies considerably with large areas having a density of
12 people per acre or greater. Topography varies from a relatively
flat plateau at about elevation 970 to very steep, wooded ravines along
75
-------
Closes Creek. The flow monitoring point is just above the Des Moines
River near Harding and Prospect Roads and is at elevation 797. The
distance of flow travel from the monitoring point to the furthest point
is about 20, 000 feet and the width of the area is about 7, 000 feet at the
widest point. The time of concentration from the monitoring point to
the furthest point is estimated to be 70 minutes for a design storm.
The composite coefficient of runoff "C" for the area is estimated to be
0. 57 for the design storm.
Flow measurement was by stage-discharge relationship with an excel-
lent point of permanent control. The control section was a concrete en-
cased sewer crossing the creek and is shown in Figure 10. Sufficient
low flow measurements were made to establish the lower section of the
rating curve and high water measurements were made as often as possi-
ble to provide a basis for projecting the curve. Water levels were re-
corded by a bubbler-type recorder. Only during very high river stage
was the control effected by backwater.
Because of the combined sewer areas, the flow measured at the 0-2
station was adjusted for the storm water flow in the Closes Creek trunk
sewer. Numerous overflows exist in the combined system which bypass
during wet weather. Measured flow was increased on a prorated basis
of the total watershed to the separately served area, but the increase
was limited to the reserve storm water capacity in the main trunk.
0-11 - The 20th Street Storm Sewer
This system serves an area of approximately 1, 166 acres, but is broken
up by several independent separate and combined systems as shown in
Figure 14. The system was originally thought to receive overflows from
the sanitary system, thus the "0" designation. Extensive field investi-
gation failed to locate any overflows and it is now considered a separate
system.
The area is residential with extensive industrial and commercial develop-
ment. The topography of the area is relatively flat, sloping from an ele-
vation of 840 at the furthest upstream point to an elevation of 794 at the
monitoring point with a flow travel distance of 19, 500 feet. The time of
concentration from the furthest point to the monitoring point is estima-
ted to be about 85 minutes for a design storm. The composite coeffi-
cient of runoff "C" for a design storm is estimated to be 0. 53 for the
entire area, but would vary considerably within the area because of large
areas of both dense industrial and commercial development and vacant
land.
The outlet of this system is at the northern-most end of Dean Lake, and
is a 4-foot wide by 6-foot high concrete box sewer at that point. Flow
76
-------
was measured by a sharp-edged rectangular weir without end contrac
tions and the water level was recorded by a bubbler type recorder.
The installation is shown in Figure 7.
RAINFALL-RUNOFF RELATIONSHIPS
Determination of Rainfall
A. method for determining the amount and intensity of rainfall on each
area was developed, adapting the Thiessen Method to analysis by elec
tronic computer. The step by step procedure used in setting up these
analyses is described below.
1. Watershed boundaries for each area were outlined
in 1" = 400' scale topographic maps. City sewer;
plats were checked for storm sewer locations, atad
drainage as well as storm sewer and inlet locations
were field checked.
2. Rain gauges were dispersed over the entire s.tudy
area due to the desire at the outset of the study to
correlate rainfall to wet weather sanitary flows in
all of the major basins in the collection system. |
As a result, the gauges did not fall within the sep-
arate storm drainage basins actually monitored.
Had Thiessen Polygons been drawn on ly around
actual rain gauging stations, the rainfall calculated
for a given basin would generally have been based
on only one of the rain gauge measurements. A.
procedure was developed by the contractor to handle
this condition, which is similar to the procedure
used by Myers (7) for determining average rainfall
on remote mountaiiious areas. Intermediate points,
referred to herein as dummy rainfall stations, were
established on a connecting line between rain gauges.
This permitted interpolation of rainfall to points in
or near the area being monitored. These points, the
dummy rainfall stations, were then used to develop
a system of Thiessen Polygons which would encompass
the basins monitored. This procedure is illustrated
in Figure 26.
This procedure varied from standard practice; there-
fore certain limitations were placed on the data used
for analysis. In order to assure that interpolation
between rain gauges was valid, the rain gauge readings
77
-------
00
cr>
c:
•x
m
DETERMING
THIESSEN POLYGONS
FOR
ASIN PRECIPITATION
-------
used for calculating rainfall on each of the monitored
areas was carefully checked to see that rainfall wajs
occurring relatively uniformly at each station. This
procedure is explained in subsequent paragraphs.
3. The watershed within each polygon was planimetered
to determine the area in acres. Since rainfall at
dummy stations is a function of that recorded at the
gauges, rainfall to the entire watershed was equated
to the rainfall observed at the three gauges nearest
the area.
Procedure for Analysis
The procedure used for developing rainfall and runoff relationships is
as follows:
1. A computer program was developed to process rain-
fall and runoff measurements into 5 minute incre-
ments. Input data consisted of time-depth values
describing each rainfall and head values for the flow
measuring device, each in 5 minute multiples of th$
clock hour. Also, for each watershed the following
constants were input: head correction for flow chart
readings, watershed area in acres, the estimated
minimum time of concentration for runoff, the equa-
tion for determination of discharge rate, and an equa-
tion for determination of the volume of rainfall on
the watershed.
2. A sample of the computer print-out is shown in Figure
27. For each 5 minute increment throughout the storm
and runoff period, the following information is given:
For Runoff - Flow rate (discharge) in cfs.
- Accumulated runoff since the beginning
of the storm, in acre-feet.
- Rate of flow per acre of watershed, in
cfs/acre.
For Rainfall - Average incremental depth of precipi-
tation over entire watershed for 5-
minute increment, in inches.
- Average incremental intensity of pre-
cipitation over entire watershed for
5-minute increment, in inches/hour.
79
-------
AREA S-l (./1 1/64
GAGC CAGE GAGE «f*D
DATf TIWE NO. 3 HO. 5 NO. 6 READING
611*9
61169
1164
1169 .
1169
1169 .
1169 4.
1169 4.
1169 4.
1164 4.
1169 5.
1169 5.
MI69 5.
61169 5.
61169 5.
61169 S.
6116* 5.
61169 5.
61169 S.
61169 S.
61169 S.
61169 5.
61169 6.
61169 6.
61169 6.
61169 6.
6)169 6.
61169 6.
61169 6.
61169 6.
0 .00000 0.
S .00000 0.
0 .00000 0.
S .00000 0.
0 .00000 0.
)5 .00000 0.
0 .00000 0.
5 .00000 0.
0 .05000
S .0*000
0 .04000
S .00333
0 .00333 .
5 .00333
0 .00571
S .00571
0 .00571 .
5 .00571
0 .00571
5 .00571
0 .00571
5 0.00000 .
0 0,00000 .
<, 0.00000 .
0 0.00000 .
S 0.00000
0 0.00000 .
»S 0.00000 .
0 0.00000
)5 0.00000
0000
0000
0000
oooo
0000
0000
0000
0000
5000
0700
0200
0200
0200 0
0200 0
4000 0
4000 0
1000 0
1000 0
1000
0250
0250
02SO
0250
0000
0000
0000
oooo
0000
oooo
oooo o
00)54
00154
00154
00 IS*
00154
00154
00154
00154
0154
0154
0154
01S4
OOOO
oooo
oooo
oooo
oooo
oooo
266T
2667
2667
0125
0)25
0125
Oi25
0125
0125
0125
0125
OOOO
00000
00000
00000
00000
00000
00000
00000
00000
00000
00000
00000
00000
00000
00000
00000
00000
00000
66664
66664
16664
66664
66664
66664
66664
66664
66664
48665
48665
486*5
48665
PAGE )
AREA 5*1 6/11/69
• FLOW ACCUN. FLO* • AVERAGE AVERAGE ACCU*. *"UM' .
• PATE FLO. RATE • DEPTH INTENSITY D£PTH BASlN PRCCIP.
DATE T1M£ • CFS AC-FT CFS/AC • INCHES IN/MS INCHES 4C-FT
1 16
116
116
1 16
1 16
116
1)6
1 16
116
116
1 16
116
116
116
1 6
1 6
1 6
1 61
1 6
116
1 16
116
116
116
1)6
1 16
1 16
1 16
1 16
) 16
1)6
.0 .212
.1 .212
.1 .212
.2 .212
.2 .212
.3 .212
.3 .212
.4 .?12
.4 .212
.50 .212
.55 .21?
.00 .2J2
.0 .212
.1 .212
.1 .212
.2 .2)2
.2 .212
.30 .212
.15 .626
.40 .166
.45 .«08
.50 .537
.55 .344
.00 .273
.05 .167
.10 .172
.15 .236
.20 .454
.25 .702
.30 .9A2
.35 .396
001
003
004
00
00
00
01
Ot
01
01
01
18
19
20
22
23
25
26
31
39
51
69
9?
121
156
199
249
293
332
367
396
001
001
001
001
001 .
001 .
001 .
001 .
001
001
001
001 .
001
001 .
001
001
001
001
002 .
004
006
000
Oil
013 .
016
020
023 .
020
oia
016 .
01 .009
01 .009
01 .009
)01 .009
)01 .009
)01 .009
)01 .009
)01 .009
)01 .009
27 .325
11 .135
11 .135
02 .025
01 .017
01 .017
13 .151
13 .151
04 .050
04 .050
17 .202
IS .177
15 .177
01 .015
01 .015
01 .007
01 .00
01 .00
01 .00
01 .00
01 .00
014 0.000 0.00
001
001
002
003
004
004
005
006
007
034
045
056
OS8
060
061
074
0*6
090
094
111
126
141
42
43
45
45
46
44
47
47
.019
.038
.057
.076
.096
.115
.134
.153
.172
.883
.177
.47Z
.528
.5*4
• 601
.930
.259
.369
.480
.921
.308
.695
.729
.762
.778
.793
.899
.824
.640
.855
.855
PAGE 1
ABEA S-l A/I 1/64
GAGf CAGE GAGE HEAD
61161
1161
1169
1 169
61169
61165
6)169
61169
61169
61169
61169
61169
61169
61169
61169
61169
61169
61169
61169
.40
• 45
.SO
.55
.10
.If
.20
.n
.30
.IS
.40
.AS
.SO
.ss
.00000
.00000
.00000
.00000
.00000
.00000
.00000
.00000
.00000
.00000
.00000
.00000
.00000
.00000
.00000
.00000
.00000
.00000
.00000
.00000
.00000
.00000
.00000
.00000
.00000
.00000
.00000
.0000
.0000
.0000
.0000
.0000
.00000 -.05000
.00000 -.05000
.00000 -.OSOOC
.00000 -.05000
.00000 -.05000
.00000 -.05000
.00000 -.05000
.00000 -.05000
.00000 -.05000
.00000 -.01500
.00000 -.01500
.00000 -.01500
.0 000 -.01500
.0 000 -.01500
.0 000 -.01500
.0 000 -.01500
.0 000 -.01500
PAGE 2
AREA S-l 6/11/64
• PATE FlOtf RATE • DCPTH INTENSITY DCPTH BASIN PRECIP
6116
6116
6116
6116
116
116
1 16
116
116
6116
6116
61 16
6116
6116
6116
6116
6116
6116
6116
6116
61 16
6116
6116
61 16
6.<>0 3.644 .421 .012
6.45 3.029 .442 .010
6. SO 2.453 .459 .006
6.55 1.9)9 .472 .006
7.10 .981 .497 .003
7.15 .779 .502 .002
7.20 .715 .507 .002
7.25 .653 .512 .002
7.30 .S92 .516 .002
7.35 .557 .520 .002
7.40 .523 .523 .002
7.45 . 19 .527 .002
7.50 . 56 .530 .001
7.55 . 24 .533 .001
b.OO . 92 .5)6 .001
0.05 . 62 .531 .001
8.10 .332 .540 .001
9.15 .303 .542 .001
8.?0 .275 .544 .001
H.25 .2(7 ,546 .001
9.30 .259 .549 .001
9.35 .251 .550 .001
9.40 .243 .551 .001
9.45 .235 .553 .001
61169 9. SO .111 .55* .001
.000
.000
.000
.000
.000
.000
.000
.000
.000
• 000
.000
.000
.000
.000
.000
.000
.000
.000
.000
.000
.000
.000
.000
.000
.000
.000
61169 «.00 .212 .557 .001 0.000
.000 .147 3.955
.000 .147 3.955
.000 .147 3.855
.000 .147 I.MS
.000 .14 3.055
.000 .14
.000 .14
.000 .14
.000 .14
.000 .14
.000 .1'.
.000 .14
.000 .14
.000 .14
.000 .14
.000 .14
.000 .14
.000 .14
.000 .14
.000 .14
.000 .14
.000 .14
.000 .14
.000 .14
.000 .14
3.855
3.855
3.855
3.855
3.855
3.855
3.855
3.855
3.855
3.8S5
3.855
3.855
3.855
3.855
3.855
3.855
3.855
3.855
3.855
3.855
3.855
.000 .147 3. «5S
.000 .147 3.855
PAGE 2
AREA s-i is/n/6?
PEAK INTENSITY DETERMINED FROM A 30 MINUTE PERIOD is .134
PEAR BATE OF RUNOFF PEP AC«( IS .023
COEFFICIENT OF RUNOFF FOB PEAK FLOW IS .172
VOLUMETRIC COEFFICIENT Of RUNOFF IS .145
COMPUTER PRINT-OUT
FOR
RAINFALL - RUNOFF ANALYSIS
80
FIGURE 27
-------
- Accumulated depth of precipitation
on watershed since beginning of
storm, in inches.
- Accumulated precipitation on water-
shed, in acre-feet.
Also, the following items are summarized at the end of each computer
run:
- Maximum average rainfall intensity, in
inches/hour, occurring in time of con-
centration given (i.e. , the greatest
value obtained by averaging consecutive
incremental intensities for a period
equal to the time of concentration).
- Peak rate of runoff per acre observed dur-
ing the runoff period, in cfs/acre.
- Coefficient of runoff for peak flow, C,
which is 1. 008 times the peak rate of
runoff per acre divided by the maxi-
mum rainfall intensity for the concen-
tration period.
- Volumetric coefficient of runoff, GVI
which is the acre-feet of accumulated
runoff divided by the acre-feet of accu-
mulated precipitation.
Storms were selected for analysis for each watershed, gen-
erally using the largest magnitude storms for which re-
liable data was available. Also, a few moderate storms
were selected to give a range of values for developing a
curve.
For each storm rainfall and flow data was picked from the
respective chart trace, tabulating time of day and chart
reading for each break point in the trace. Time values
were in multiples of 5 minutes and were recorded from
the beginning of each storm until runoff ceased or re-
turned to near base line flows. The tabulated time-depth
values were then key punched on cards for computer
analysis.
Rainfall and runoff values were first interpolated to 5-
minute increments by the computer, based on the time-
depth values selected from break points on the chart
trace. The analysis was then run to obtain the output
data previously described. To assist in the review of
81
-------
the print-out information, two graphs were plotted by
the computer. An example of these are shown for
each of the four areas studied in Figures 28 to 31.
The upper part of the figure is a plot of rainfall in-
tensity and rate of runoff per acre against time of
day. Since the conversion from inches per hour to
cfs per acre is for practical purposes unity, ijhe
ratio that the runoff per acre is to the rainfalj in-
tensity is the coefficient of runoff "C" in the Rational
formula. The lower part shows accumulated rainfall
and accumulated runoff against time of day. These
show at a glance the pattern of rainfall as compared
to the runoff from the storm.
The computer analysis of each storm was reviewed in
detail to insure reliable results. First, the interpolated
values were reviewed to see that rainfall actually
occurred at the gauges used in the analysis and that it
was reasonably consistent and of approximately the
same magnitude throughout the area. Rainfall for the
three gauges effecting such area were reviewed si-
multaneously from computer print-outs giving1 rain-
fall in 5-minute increments. Scattered showers and
thunderstorms, indicated by very erratic rainfall be-
tween stations, were omitted from further analysis.
The elimination of these localized erratic rainfalls is
not considered to have biased the data since tljiey often
were of a duration less than the time of concentration
to the monitoring point and would not have been used
for analysis anyway.
Where base flows existed, these were deducted for fur-
ther analysis. At the Closes Creek monitoring station,
the flow was also adjusted for estimated storm flow in
the combined sewer. The duration of the storm and the
runoff was noted, as was the total accumulated depth
of precipitation. Values for the volumetric coefficient
of runoff, "Cv" were then manually adjusted to account
for base flows and any other irregular conditions.
Where the coefficient of runoff for peak flow '|C" was
calculated, it was checked to see that the stoijm con-
tinued through the time of the peak flow. The time
of concentration was adjusted as appropriate for each
storm, and new values for the average intensity were
computed. If the storm did not continue through the
82
-------
.300
. L'75
.200
. mo
. 100
.075
.C'SO
RA'NFALL
FLOH. CF'S/RC a RRINFRLL, IN/HR VG TIME
RRER S-l 6-11-69
I
V
^
"• . 250
4 . CCC
3 i'^.0
? IOC
-^ rrjO
? cos
2. 750
2.000
LJ,^0
2.0C2
1.750
i . -30C
750
.•500
JE.O
10
11
12
TIME: OF DRY
RAINFALL
flCCUM. RfllNFRLL a RUNOFF, flC-F-T US TIME
flRER S-l 6-11-69
^^ ituni
RUNOFF
8 Q 10 11 ! 2
TIME OF DRY
RAINFALL- RUNOFF RELATIONSHIPS
THOMPSON AVE. STORM SEWER
83
FIGURE 28
-------
.350
.325
.300
.275
.250
.225
.200
.>75
.150
. 125
.100
.075
.050
.025
.000-
RAINFALL
FLOW, CFS/flC a RRINFRLL,
STRTION S-3 5-05-69
IN/HR US TIME
RUNOFF
6 T B
TIME OF DRY
10
11
12
22.000
'21.000
20.COO
19.000
18.000
17.000
16.000
15.000
14.000
13.000
le.ooo
11.000
10.000
9.000
8.000
7.000
6.000
5.000
4.000
3.000
2.000
1.000
.000
RAINFALL
HCCUM. RRINFRLL a RUNOFF, RC-FT.US TIME
STflTION S-3 5-05-69
RUNOFF
10
11
12
TIME OF DRY
RAINFALL- RUNOFF RELATIONSHIPS
CUMMINS PARKWAY STORM SEWER
84
FIGURE 29
-------
2.300
2.200
2. 100
2.0CO
1.900
i.300
1.700
1.600
1.500
1.400
1.300
1.200
1.100
1.000
.900
.800
.700
.SOD
.500
^00
.300
.200
. 100
.000
rC
FLOW, CFS/RC a RfllNFRLL, IN/HR \}$ TIME
^RAINFALL RRER 3~2 6-11-69 2
L1
--RUNOFF 1
J&F^~J~*z£^__ A Jwi^.
19 20 21 22 23 24
3 9 10 11 12 13
TIME OF DRY
17 13 10
270.COG
260.COO
250.OCC
240.000
230.COC
220.COO
210.CCG
200.CCC
190.000
180.GOO
170.OOC
160.GCC
150.000
140.000
130.000
120,COC
110.CCC
100.0CC
90.030
30.0CC
TO. OOC
60.CCC
50.OOC
40.000
30.OCO
20.CCC
10.OOC
.000
RAINFALL
flCCUM. RfllNFSLL a RUNOFF, flC-FT US TIME
RREfl 0-2 6-11-69 ?.
RUNOFF,
19 20 21 22 23 21 1 2 3 4 5 E '< 3 9 10 11 12 13 14 15 IE 17 IS 19 20 21
TIME OF DRY
RAINFALL- RUNOFF RELATIONSHIPS
CLOSES CREEK
85
FIGURE 30
-------
700
P50
.eco
.530
.500
."•SO
.400
•3'SO
.300
2SC
.23C
. iOC
CLO
/
r
;
_y"
/
^
FLOW, CFS/flC a RPINFRLL- IN/HR ^G TIMF
flRFfl 0-11 5-21-6Q
L, RAINFALL
L
1
1
/"^*"\ «- RUNOFF
7 3 d 10 1 1 12 13 i'* 13 1G 17 10 iu 20 ill 22 23 C i 2 j 4 5 c ? t3 0 10 11 12
TIME". OF rjflv
180. CCG
170 CGC
16CLOOO
150. CDC
KiO.GOC
13C.UOC
120. GOC
110, COC
10C.COC
VO.
PC .
r:o.
'•,0
rc.
ODD
COO
GOG
GOC
GOG
coc
r-in
CCC
.oco
RAINFALL-^
RCCUM. RfllNFSLL a RUNOFF, RC-I-T, US
RRF.fl 0-11 5-2.1-69
RUNOFF
ID a- 1
13
TIME' OF DflV
RAINFALL- RUNOFF RELATIONSHIPS
20TH STREET STORM SEWER
86
FIGURE 31
-------
peak runoff, the value "C" was not computed. Figures
28 and 30 show storms that did not continue through the
peak runoff, whereas Figures 29 and 31 show runoffs
that peaked while the storm was still occurring.
Rainfall-Runoff Relationships
A series of curves were drawn depicting the relationship of rainfall to
runoff as the depth and intensity varies.
One such set of curves is shown in Figure 32, in which the total rain-
fall for the storm is plotted against the total runoff. A separate curve
is plotted for each of the areas to show the variation in runoff charac-
teristics. They have been plotted on a semi-log scale to spread the
points in the lower section of the curve. Plotted to a linear scale, the
curves would straighten considerably. All of the areas follow the same
general curve, the difference being in the degree of runoff. At any
point on the curve, the volumetric coefficient of runoff, HCV", is the
funoff divided by the rainfall.
Rainfall-runoff data is plotted separately for areas 0-2, 0-11 and S-3 in
Figures 33 and 34. These curves show the influence of the total rainfall
depth on the volumetric coefficient of runoff, "Cv"» and provide a com-
parison of the individual areas. Area S-l did not provide enough values
to draw a meaningful curve of this type.
The greatest quantity of data was available for the 20th Street Storm
Sewer 0-11, shown in Figure 33. The total depth of rainfall is plotted
against "Cv" in the upper curve. Although the points are scattered,
the general trend of the curve can be determined. The assumed value
of "Cv" for a 6-inch volumetric storm is also plotted and the curve ex-
tended to that point. The curve is drawn through the grouping of values
toward the right. It is assumed that values plotting substantially to the
left or above the curve were from rainfalls which did not produce opti-
mum runoff due to the storm pattern.
In this figure, "Cv" is also plotted against the average intensity over
the duration of the storm. These values are widely scattered and there-
fore the general ranges of duration are shown. It is of interest to note
that "Cv", or the percentage of runoff, increased with greater dura-
tion. Obviously, the duration is not the influencing factor. For the
types of runoff measured from this watershed, the results indicate that
it is the greater depth of rainfall which occurs over an extended period
that produces a higher percentage volume of runoff, rather than the in-
tensity of the storm. This was verified by inspection of the individual
values plotted. In different terrain with permeable soils or greater ve-
getation, the results may be quite different. Also, the average intensity
87
-------
oo
oo
<0
¥
j
c
STATION S— I
L
STATI ON O - M
STATION O
-2
O.« O.S O.C
RUNOFF FROM STORM — INCHES
O
c
m
OJ
L. E G £T N D
B Station S- I + Station s-3
A Station O-2 ° Station O - //
RELATIONSHIP OF RAINFALL a RUNOFF
-------
CO
ID
O
z
I
z
o
o
UJ
sr
.ft.
u.
o
1-
o.
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o
oo
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i
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13
rc
6.0
S.O
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.07
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.04
DEPTH VS CV,
OURATIOM* TO IO HFIS
6 VOLUMETRIC STORM
/
DUF ATION 2HR
/"" ../
7 /
/
/^ I
/
DURATION ORE/!
H R.
STATION 0
O-AVERAGE
A-DEPTH VS
LESS
TER THAN
-II
INTENSITY VS <
CV
0.90 0.39
CV - VOLUMETRIC COEFFICIENT OF RUNOF-F
EFFECT OF RAINFALL DEPTH a INTENSITY
ON
COEFFICIENT OF RUNOFF
89
FIGURE 33
-------
CO
UJ
x
o
z
o
0.
o
cc
0.
Q.
UJ
o
3.0
2.0
1 .0
.9
8
7
.6
.5
.4
.3
.2
.1
.09
.OB
.07
.06
.OS
.04
.03
.02
-01,
A
A
A
A
s-3y
/
/
NOTE: Me
•
A /
/
/
-
/ /
/ /
A/ Ay
/• 7
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//
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isured values
i
0
...^
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*v
r
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o o
for Station (.
i
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^
A - S-3 ,
0 - 0-2 ,
- // plotted or,
i
D VS. Cy
D VS. Cv
FIGURE 33
1
0 0.10 0.20 0.3O 0.40 0.5O 0.
Cv - VOLUMETRIC COEFFICIENT OF RUNOFF
RAINFALL DEPTH B COEFFICIENT OF RUNOFF
90
FIGURE 34
-------
is a rather arbitrary figure since the observed intensity will most
likely vary greatly during the rainfall period. However, it is obvious
from this, that the average intensity or the duration alone are not
adequate parameters for estimating the total volume of runoff from a
storm, although they may very well be a judgment factor. The depth
of rainfall appears to provide a better basis for estimating the total
quantity of runoff.
Time and resources limited the detail of the analysis described here-
in. In a more rigorous analysis the influence of such factors as infil-
tration into permeable soils, interception by vegetation, and depres-
sion storage should be considered.
Figure 34 shows the depth versus "Cv" curve for the 0-2 and S-3 area.
Fewer values were obtained from these areas, however, the curves
plotted together in Figure 34 closely parallel each other. The 0-2
and 0-11 areas show a greater percentage of funoff from the storms
observed than does the S-3 area. The relative position of the S-3 and
0-2 curves is as expected from the estimated design runoff coefficients,
0. 53 and 0. 57 respectively. For the 0-11 area, where the estimated
design "Cv" factor was 0. 53, the curve was very nearly the same as
the 0-2 curve. While the 0-11 area was relatively flat and contained
some undeveloped areas, open drainage ditches continued to flow in-
to this system for several hours after a storm. This may be ground
water or inter-flow from storm water which had infiltrated the sur-
face. Also, the topographic maps from which the "Cv" factors were
estimated were 6 years old at the time of the study and the rapid de-
velopment for industrial use may have increased the runoff coeffici-
ent.
From the S-3 and 0-11 watersheds, a limited number of values were
obtained for analysis of the peak runoff rate. The "C" versus "I"
values are plotted in Figure 35 and separate curves drawn for each
area. As in the rational method, two basic assumptions were made:
(1) The rate of runoff to the point under consideration is a function of
the average rainfall rate during the time required for water to flow
from the most remote part of the drainage area to that point, said
time of flow being the time of concentration and the duration for the
given intensity, and (2) the peak rate of runoff occurs within the time
of concentration.
The estimated design runoff coefficient for peak flows, "C", is plotted
against the Intensity, "I", for a 10-year frequency storm for Des
Moines. The design "I" values were determined for the time of con-
centration for each area, estimated to be 85 minutes for 0-11 and 40
minutes for S-3. Observed "I" values were for durations selected
for each runoff, but never less than those stated above.
91
-------
3.0
2.0
1.0
.9
.8
.7
.6
.5
.4
or
0 -3
I
UJ
I .2
O
z
H
>- .1
h-
0 9
CO
z .08
^ .07
2 06
.05
.04
.03
.02
.01
- '
O
o
• /
A /
/
/>
/
/
1
DESIGN
DURATI
I = 2.7
C = 0.53
A
o t£
/.
10- YR. FREQU
)N - 40 MIN.
INCHES /HOU
S - 3B
/ V
//
'
A - S- 3 I
o - 0-11 I
i
NCY STORMS
/
y7 /
/ /
.'
/
DESIGN 10-YR
FREQUENCY SI
DURATION =85
.1=1.8 INCHES/
C = 0.53
VS. C
VS C
/
A
I
J
/
ORM
MIN.
HOUR—
0 0.10 0.20 0.30 0.4O Q.5O 0.5
COEFFICIENT OF PEAK RUNOFF-"C"
RAINFALL INTENSITY
AND
PEAK RUNOFF RELATIONSHIP
92
FIGURE 35
-------
Because of the limited number of values and scattering of the points,
the "C" versus "I" curve is a theoretical curve rather than a curve
based entirely on the median of the observed values. The curve used
was a straight line passing through the "design" point and through the
observed values to the right of the grouping. Values falling above and
to the left of this line were assumed to be for storms which did not
produce optimum runoff due to the rainfall pattern, antecedent mois-
ture conditions, or other factors. The curve drawn is therefore con-
sidered to be conservative for the runoffs observed and may be used
as a basis of design for facilities intended to handle lower intensity
storms.
Significance of Results
The data obtained shows the runoff coefficient for peak flow, "C", to be
dependent upon the intensity of the storm. Although the general rela-
tionship of "C" to intensity is shown, it is not adequate to suggest any
modification to the present use of the Rational Formula. In fact, the
principles of the Rational Formula and accepted average "C" values
were used to develop a part of the "C" versus "I" curve shown. The
storms monitored during the study period were not of the magnitude
which would provide data in the range of values meaningful to normal
design practice. A much longer monitoring period would be required,
which would include storms exceeding the 10-year frequency as well as
providing many additional observations.
The data does shed some light on runoff coefficients which could be ex-
pected from lower intensity storms, and is useful in evaluating the
amount of runoff which should be intercepted where collection and treat-
ment of the higher intensity storms is not feasible. Such a case may be
existing sewer systems in heavily built-up business districts where in-
frequent overflow of high intensity storms may be more acceptable than
providing interceptor facilities for storms of the 10-year frequency
r ang e.
If treatment of separate or combined storm runoff is dictated by local
conditions, a basis for estimating the total volume of flow is also needed.
Based on the findings of this study, the total depthof rainfall provides the
best means of estimating the volume of runoff. The accepted runoff co-
efficients for the Rational Formula are assumed to apply to the 6-inch,
24-hour storm used in this study. Storms of this magnitude are very
infrequent, however, and information as to the "Cv" factors applicable
to storms which occur much more frequently is needed.
The curve developed for Des Moines 20th Street Storm, Sewer, Station
0-11, shows that if a "Cv" of 0. 53 is applicable to a 6-inch accumulation
93
-------
in 24 hours, the average annual 24-hour storm of 2. 72 inches would
produce a "Cv" of 0. 25. This type of information is valuable in de-
termining the requirements for treatment of combined or separate
storm runoff, for evaluating the degree of treatment afforded by
existing interceptor and treatment facilities, and for evaluating an-
nual runoff quantities and pollutional loads.
RAINFALL INTENSITY DISTRIBUTION
Included in this part of the study was an analysis of the distribution
of rainfall intensities with regard to (1) the total depth of rainfall,
and (2) the percent of clock hours in which given intensities occur.
Figure 36 shows the relationship of rainfall intensity to the percent
of clock hours in which a given intensity is equaled or exceeded. This
relationship is similar to that developed for Kansas City, Missouri,
by Benjes et. al.' ' Data for the curve shown was developed from
published rainfall records for Des Moines for the 10-year period of
1951 to I960. Rainfall intensities per clock hour were grouped into
ranges of intensities as shown in Table 8. The intensity shown is the
average intensity occurring over one clock hour as recorded and pub-
lished by the Weather Bureau. The percentage of the clock hours in
which the hourly rainfall exceeded the low value for each range was
calculated and plotted as shown in Figure 36.
Table 8
CLOCK-HOUR PRECIPITATION INTENSITY DISTRIBUTION
Intensity
Range
Inches -Hour
0. 01
0. 02-0. 09
0. 10-0. 24
0. 25-0.49
0. 50-0. 99
1. 00-1. 99
Greater than
Avg. No. of
Clock-Hours
Annually
162
241
57
19
8
1. 7*
2.00 0. 13*
% of
Time in
Range
1.85
2.75
0.65
0.21
0. 09
0. 02
0
Intensi-
ty In. /
Hour
0. 01
0. 02
0. 10
0. 25
0. 50
1. 00
2. 00'
% of Time
Intensity
Exceeded
5. 57
3.72
0.97
0.32
0. 11
0.02
0
^Calculated on the basis of return frequency of storms for Des Moines,
as determined from published and unpublished data from the U. S.
Weather Bureau.
94
-------
2.8
CC
3
O
2.4
O
O
SOURCE:
2.0
K
UJ
0.
(O
UJ
£
O I-S
NOTE.
DECENNIAL CENSUS OF U.S. CLIMATE
US. WEATHER BUREAU.
AVERAGE ANNUAL PRECIPITATION FOR
10 YEAR PERIOD- 1951 - I960
DES MOINES, IOWA
MUNICIPAL AIRPORT
INTENSITIES USED FOR THE DEVELOPMENT
OF THIS CURVE ARE NOT ACTUAL INTENSITY,
BUT AVERAGE INTENSITY OCCURRING PER
ONE CLOCK HOUR AS PUBLISHED BY THE
U.S. WEATHER BUREAU.
PERCENT OF CLOCK HOURS WITH RAINFALL INTENSITY EQUAL TO OR GREATER
THAN GIVEN INTENSITY
DISTRIBUTION OF RAINFALL INTENSITY
WITH
RESPECT TO TIME
95
FIGURE 36
-------
The foregoing data is useful in determining the amount of combined
sewer overflow which might be expected annually from a given water.
shed. Given the area of the watershed, the capacity of the combined
sewer, and coefficients of runoff as previously described, the inten-
sity of rainfall that can be contained by the system can be calculated
by the Rational Formula. From this, the percent of time annually
that overflow will occur can be predicted by use of a curve such as
shown in Figure 36. For example, if it were determined that a given
combined sewer would contain the runoff from a rainfall of up to 0. 8
inches per hour intensity before overflowing, overflow would be ex-
pected to Occur 0. 1 percent of the clock hours or approximately 9
hours annually. From this, an estimate of sanitary sewage overflow
is possible.
A. relationship of the same nature.was developed for the total rainfall
depth which occurs at or greater than a given intensity. This relation-
ship is shown in Figure 37. Two sources were used to develop this
curve. Data from one of the supplemental rain gauges for this study
were used to develop the lower intensity values of the curve and intense
storms recorded at the Des Moines Airport Weather Bureau Station
were used for the high intensity ranges.
The rainfall recorded at the gauge located at the West Des Moines City
yards was tabulated for the period from March 1 through October 31,
1969. Theprocedure was similar to that described for the runoff ana-
lysis; i. e; , the time of day and depth were tabulated for all break
points on the chart trace. It was then a relatively simple computer
analysis to determine the intensities between the given points and to
tabulate the depth of precipitation occurring within specified intensity
ranges. The values thus obtained were then plotted as the percentage
of total depth which exceeded the lower limit of each intensity range.
The higher intensity section of the curve was developed from 126 in-
tense storms occuring from 1951 through July 1969. The record con-
tained accumulated depth of rainfall covering time intervals from 5
minutes to 3 hours for each storm. These were first ranked in descend1
ing order of magnitude, listing both the depth and the average intensity-
The depth of precipitation which fell at or above given intensity values
was then accumulated for all of the 126 intense storms. Omitting the
winter months during which no intense storms occurred, the 19 years
accumulation of March through November rainfall was determined.
The accumulated depth occurring at or above each intensity value was
then expressed as a percentage of the 19-year accumulated March to
November rainfall, and plotted against the intensity values. For inten-
sities above 5 inches per hour, this curve transitioned smoothly into
the curve plotted for the lower values.
96
-------
co
UJ
X
O
CO
126 INTENSE STORMS- 1951 - 1969
FOR ALL DURATIONS TO 3 HOURS,
% OF 19 YR, MARCH-NOVEMBER
^ACCUMULATION -o
FWPCA RAINGAGE AT WDM CITY YARDS
[(No.4) FOR MARCH THRU OCTOBER, 1969
20
30
40
50
60
70
80
90
(OO
PERCENT OF ACCUMULATED RAINFALL EQUAL TO OR GREATER THAN
GIVEN INTENSITY
DISTRIBUTION OF RAINFALL INTENSITY
WITH
RESPECT TO ACCUMULATED RAINFALL
97
FIGURE 37
-------
The curve shown in Figure 37 may be used in much the same manner
as that developed for the clock hours exceeding a given intensity. For
example, if a given facility has the capacity to handle the runoff re-
sulting from a rainfall of 1. 0 inch per hour intensity, approximately
22 percent of the average March to November rainfall would be ex-
pected to occur at intensities greater than this. From this the quantity
of overflow can be evaluated.
CONCLUSIONS
The techniques described in this section provide the engineer a means
of relating the quantity of combined or separate storm water runoff to
rainfall events. Rainfall records are available for all metropolitan
areas and are useful for determining local precipitation patterns. In-
tensity-depth distribution information is helpful, although not generally
available. This can be developed, however, and provides a useful tool
for evaluation of the effectiveness of alternate levels of treatment as
well as for the design of facilities for collecting and treating storm
runoff. Runoff coefficients for storms of moderate and low intensity
are also desirable. Due to the lack of more appropriate data, studies
regarding interception ratios for combined sewer systems must often
use assumed or emperical runoff relationships. If storm runoff and
combined sewer overflows are to be treated, appropriate coefficients
of runoff should be developed for the magnitude of the design storm.
Although a treatment facility may be designed hydraulically to contain
or pass a 10 or 25-year frequency storm, the storm which will occur
once, twice or 12 times per year may be the optimum design for satis-
fying the requirement of the receiving waters.
The information developed herein has been used in Section X for deter-
mining the basis of design for stormwater treatment facilities and for
evaluating the effectiveness of the alternate abatement plans.
Because this investigation of rainfall-runoff relationships was only one
part of a very comprehensive study relating to combined sewer over-
flow pollution, procedures were necessary which nornjially would not be
used in a study of this nature. The monitoring program, for instance,
was designed to obtain data from many sewer systems within the Des
Moines area, and rain gauging stations were not located directly within
the watersheds monitored. Also, time and resources limited the a-
mount of effort and detail which could be given to this aspect of the over
all study. Because care was taken in reviewing and using the data ob-
tained, the results obtained herein are believed to be accurate and have
provided a realistic basis for determining design parameters. The pro-
cedures developed herein are sound and may be useful in other areas
98
-------
for evaluating the pollutional effects and the control of combined sewer
overflows and urban storm water discharges.
Rainfall-runoff relationships warrant a separate study in which the
primary objective is to determine these relationships. Most important
is the period of record. Data herein is from one year of monitoring,
in which above-normal precipitation occurred. A much longer period
of record would be desirable to provide additional data ard a broader
base for analysis. This would also provide data on higher intensity
storms than was obtained during this study. It is much more desirable
to have the raingauge stations located within the watersheds being moni-
tored. Runoff monitoring facilities should be more permanent, capable
of accurately measuring high variations in discharge, and be easily
maintained. Also, the influence of such factors as depression storage,
topography, infiltration into pervious soils, and interception by vege-
tation should be considered. These factors vary widely and have signi-
ficant effects on the lower intensity rainfalls which contribute a large
percentage of ubran storm water discharges due to their frequency.
As a result of the experiences obtained from this study, future rainfall-
runoff investigations should be directed toward (1) general studies to de-
termine specific characteristics of specific watersheds or (2) in-depth
studies of long duration in which all influences on the lower to medium
intensity rainfalls can be determined. The procedures developed herein,
however, provide a general approach for determining the magnitude and
frequency of urban storm water discharges.
99
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SECTION VIII
RIVER DATA AND ANALYSIS
GENERAL
To establish existing river quality and to obtain data for evaluation
of the impact of sewage overflow and storm runoff, a network of ri-
ver sampling points were established in the project area. The inset
in Figure 38 shows the location of the sample stations. It will be no-
ted that the stations bracket the metro area in an attempt to be able
to determine and correlate above and below quantitative pollutant
values. The station locations were:
Station R-2 Des Moines River near Saylorville
Station R-3 Des Moines River at Euclid Avenue
Station R-4 Des Moines River at Elm Street
Station R-5 Des Moines River at S. E. 14th Street
Station R-6 Des Moines River at Hwy. 46 Bridge
Station R-7 Raccoon River at 1-35 Bridge
Station R-8 Raccoon River at 63rd Street
Station R-9 Raccoon River at 5th Street
Station R-10 Walnut Creek at 63rd &: Grand
Station R-14 Four Mile Creek at Scott Street
Station R-15 Beaver Creek at Merle Hay Road
Station R-16 Saylor Creek at 12th Street
It would have been ideal to have sarrp led the river stations frequently
and, if possible, concurrently with overflow sampling. Unfortunately
project budget limitations allowed for only five samplings. Within the
limited funds available, the philosophy was to direct primary effort
toward gauging and evaluating overflow and runoff. Additional river
quality data was obtained from two other sampling programs in pro-
gress at the time of this study. They were:
1. Routine river quality monitoring by the Iowa
State Hygienic Laboratory for the State De-
partment of Health.
2. A preimpoundment water quality study for Say-
lorville Dam. This study was sponsored by the
Corps of Engineers and was conducted by the
Iowa State University Engineering Research
Institute.
101
-------
L £ G £ M D
At Iowa State University
Engineering Research Institute
D State Hygienic Laboratory
# This Project
® USGS Streamflow Station
LOCATION MAP
RIVER SAMPLING POINTS
102
FIGURE 38
-------
The State Hygienic Laboratory program began in March 1968. Samples
are generally collected on a monthly basis with more frequent sampling
during critical periods. Sample stations begin at the upper end of the
metro area and extend through the city and into the Red Rock Reservoir
area downstream.
The preimpoundment study was begun in July 1967. Samples were col-
lected weekly at 5 stations from Boone to Saylorville. Beginning in
April 1969, this sampling schedule was expanded to include intermit-
tent sampling in and below Des Moines. The expanded program was
sponsored in part by the research assistance provision of the I. S. U.
laboratory contract for this project*
Figure 38 shows sample station locations for the various programs and
also locations and identification numbers for U. S. Geological Survey
streamflow stations.
Although considerable data is available from the above studies for sam-
ple stations outside the project area, the only data presented herein is
that for stations within the area. Said data is tabulated in Appendix C.
Also presented in Appendix C are figures which show flow, BOD, DO,
nitrogen, phosphates and upstream precipitation for Stations R-2, R-5,
R-6 and R-9, the stations which generally bracket the metro area. In
addition, diurnal DO curves for each station are shown in Appendix C.
SAMPLE SCHEDULING AND PROCEDURE
Five river samplings were accomplished during the project. Four of
them, in February, June, August and October, included £8-hour diur-
nal dissolved oxygen analyses. The April sampling was a high water
sampling during spring runoff.
For sampling, the stations were divided into two runs of about 3 to 3-1/2
hours travel time each. Dissolved oxygen, chemical, bacteriological and
plankton samples were collected on the first run at mid-day and then DO
sampling continued on a 4 hour schedule through 6 additional runs. All
samples except those for DO were delivered to the various laboratories
immediately after the first run. Dissolved oxygen samples were fixed
in the field when collected and then titrated upon return to the project
office. During the August and October samplings, midnight samples were
collected for sanitary analysis (BOD, solids, nitrogens and phosphates)
at selected stations. A comparison of the mid-day and mid-night data
is shown in Table 9.
103
-------
COMPARISON
TABLE 9
DAY - NIGHT RIVER SAMPLE DATA
STATION
AUGUST 20, 1969
R-2 DES MOINES 9 SAYLORVILLE
R-3 DES MOINES 8 EUCLID
R-t DES MOINES 8 ELM
R-5 DES KOINES « SE It
R-6 DES MOINES 8 HHY t6
R-7 RACCOON* 1-35
R-8 RACCOONS 63RO ST.
R-9 RACCOON 9 5TH ST.
ft- 10 WALNUT CREEK
R-l"t FOURMILE CREEK
R-15 BEAVER CREEK
R-16 SAYLOR CREEK
OCTOBER 16, 1969
R-2 DES MOINES « SAYLORVILLE
R-3 DES MOINES 3 EUCLID
R-t DES MOINES 8 ELM
R-5 DES MOINES 8 SE It
R-6 DES MOINES f HWY t6
R-7 RACCOON i 1-35
R-8 RACCOON • 63RD ST.
R-9 RACCOON § 5TH ST.
R-iO WALNUT CREEK
R-l"t FOURMILE CREEK
R-15 BEAVER CREEK
R-16 SAYLOR CREEK
D.O.
DAY
6.90
6.55
6.70
7.20
7. 15
7.80
8.25
7. tO
7.50
8.25
7.70
3.20
12.00
10.70
i 1 . 50
12. i5
1 1 . 30
il.70
12.25
1 1.00
10.50
Jl.25
li.65
5.10
NIGHT
6.90
6.80
7.30
7.35
6.65
7. tO
7.t5
7.55
7.35
7.t5
7.65
t.60
2.55
"3. 15
ii.5o
ii.20
0.35
1.35
i.20
11.50
10.65
10.50
10.80
5.75
B.O.D.
DAY INIGHT
11.9
6.3
5.9
U.t
i 1 . t
7.2
8. 1
3.t
8.7
3.9
t.5
19.9
19.3
13.6
12.6
13.8
12.7
9.0
7.8
7.3
3.6
t.7
5.1
5.7
8.8
8.t
8.9
7.t
8.9
5.6
5.t
5.0
3.5
t. i
2.7
6.1
16.2
1 1.8
9.1
3.6
SUSPENDED SOLIDS
TOTAL
DAY
102
87
iso
130
117
125
98
25t
67
93
175
57
t3
57
36
35
38
to
9
22
83
NIGHT
its
127
168
212
178
195
187
183
170
153
t8
77
51
t9
19
VOLATILE
DAY
18
25
26
17
It
15
8
17
19
20
25
22
21
21
20
32
21
18
7
7
17
NIGHT
36
30
t2
35
t7
28
2t
to
21
2t
15
32
28
26
II
FIXED
DAY
at
62
lot
113
103
110
90
237
ts
73
150
35
22
36
16
3
17
22
2
15
66
NIGHT
112
97
126
177
131
167
163
it3
it9
129
33
t5
23
23
8
NITROGEN
NH3
DAY
0.29
0.36
0.90
0.2t
0. 12
0.20
0. 10
i.35
0.29
1.19
0. 17
0.93
0.36
0.33
0.56
0.75
0.29
O.t7
O.ti
0.28
0.82
0.30
O.t5
NIGHT
0 92
i.50
0.92
i.33
0.29
0.51
o.ts
O.t6
0.65
0.70
o.ts
o.ts
0.39
0.93
0.25
NOz
DAY
0.01
0.01
0.01
0.02
0.01
0.02
0.03
0.01
Oi06
0.02
o.ot
0.27
T
T
T
T
T
0
0
0
0.02
0
o.ot
NIGHT
0.01
0.06
0.02
o.ot
0.02
0.02
0.02
0.05
0.07
0.03
O.It
T
T
T
o.ot
NOs
DAY
0.63
0.72
0.68
1.68
2. It
3.96
3.72
t. 13
0.86
1.08
3.65
i.2t
0.05
0.01
0.10
0.36
0.3E
0.57
O.tt
O.t3
3. 18
2.78
0.35
NIGHT
3.22
1.60
i.8t
2.0t
t.57
2.57
t. it
2.05
i.50
t.9t
l.9t
0.03
0. 19
0.52
O.t9
PHOSPHATE
T. P0«
DAY
0.29
0.26
i.ot
0.75
0.92
O.t2
O.t2
0.63
0.-59
i.t9
0.36
l.3t
0.26
0.29
0.68
o.ts
0.38
0.5t
O.t2
O.t3
0.91
6.tt
0.6t
1.68
NIGHT
0.31
0.27
0.35
0.60
0.26
0.27
0.32
0.29
j.65
0.29
0.86
O.t2
0.33
0.98
1.23
0. P04
DAY
o. is
0.12
i.06
O.t7
0.75
0.07
0.25
0.53
0.39
2. 18
0.23
i.59
o.ot
0.06
o. i i
o.ii
0.5t
0. II
0.08
0.09
0.83
5.55
0.64
O.t9
NIGHT
0.01
o.ot
0.3t
0. it
0.03
0.05
0.07
o. io
i.60
o. io
0.85
o. io
0.08
i.29
i.77
T = TRACE
-------
DISCUSSION OF RIVER DATA
Reference to the figures and diurnal DO curves in Appendix C shows
that the Des Moines River, above the metro area, normally carries
a high BOD load. In fact, the river survives without apparent septi-
city for extensive periods during which BOD concentrations exceed
DO levels. Average values for the periods of available record were
as follows:
R-2 R-9
Des Moines Raccoon
at Saylorville at 5th Street
Available Record June 1967 to March 1968 to
October 1969 October 1969
BOD mg/L 10.33 6.73
DO mg/L 9-95 9.20
NO3 mg/L 2.83 3.88
O.PO4 mg/L 0.44 0.46
Fortunately, the available record covers both dry and wet water years
so a comparison of data was obtained. During the low water year of
1967-68, record minimum discharge was recorded at Station R-2. The
Raccoon River was also very low, though not at record minimum. Re-
presentative average concentrations for the wet and dry periods have
been used to estimate annual BOD, nitrate and phosphate loads incom-
ing to the Des Moines metropolitan area. These estimates are given in
Table 10.
Comparative BOD, nitrate and ortho-phosphate loads for the control
station below the metropolitan area, Station R-6, are shown in Table
11.
The respective drainage areas for the two rivers and unit annual run-
off values are shown in the following summary. The unit values are com-
parable to similar published data.
105
-------
TABLE 10
ESTIMATED ANNUAL RIVER LOADINGS
ABOVE DES MOINES METROPOLITAN A.REA
Low Water Year
Des Moines River
Raccoon River
Total
High Water Year (1969)
Des Moines River 3,
Raccoon River 2±
Total 5,
Average
Des Moines River
(1961-69) 1,
Raccoon River
(1915-69)
Total 2,
Annual
Runoff
(Ac. Ft.)
338, 200
206,800
545, 000
739,600
050, 000
789,600
573, 000
884,000
457, 000
Annual
BOD
(Lbs. )
11, 900, 000
3,649, 000
15, 549,000
63, 900,000
36, 170, 000
100, 070, 000
50, 000,000
15, 225, 000
65, 225, 000
Annual
Nitrate
(Lbs.)
460,000
1,971, 000
2,431, 000
40, 500, 000
19,532,000
60,032, 000
14, 000, 000
8,222, 000
22, 222, 000
Annual
Ortho- Phosphate
(Lbs. )
368, 000
225, 000
593, 000
5, 060, 000
2,232,000
7, 292, 000
2, 000, 000
940, 000
2, 940, 000
-------
TABLE 11
ESTIMATED ANNUAL RIVER LOADINGS
BELOW DES MOINES METROPOLITAN AREA
Annual
Annual Annual Annual Ortho-
Runoff BOD Nitrate Phosphate
(Ac. Ft) (Lbs. ) (Lbs. ) (Lbs. )
High Water
Year-1969 5,847,000 147,000,000 53,200,000 16,600,000
Average
(1940-68) 2,785,000 70,000,000 25,400,000 7,950,000
-------
Des Moines River Raccoon River
Drainage Area 3, 738, 000 Acres 2, 202, 000 Acres
Unit Average Runoff 0.42 Ac.Ft/Acre 0.40 Ac. Ft/Acre
Unit BOD 13.40 Lbs/Acre 6.93Lbs/Acre
Unit N 03 3.75 Lbs/Acre 3.74 Lbs/Acre
Unit O. PO4 0.54 Lbs/Acre 0.42 Lbs/Acre
Additional river data is shown in Table 12, Comparative Data From
Project River Sampling. " These data illustrate the problem often en-
countered in attempting to equate and/or summate consecutive river
station data. For example, the sum of the BOD data for the two up-
stream stations, R-2 and R-7, was on two occasions greater than the
BOD at the downstream station R-6. The same is true for nitrates,
phosphates and plankton. Extensive speculation is not offered as ex-
planation for the apparent discrepancies. Some observations are
made, however, as follows:
The "sometimes" decrease in organic load through the
metro area may be attributable to treatment realized
in the low head impoundments at Scott and Center Streets
on the Des Moines River and just below Fleur Drive on the
Raccoon. To some extent these impoundments may be serv-
ing as intermittent sedimentation and stabilization units.
All BOD data, including that used from the two other
studies, was obtained from unfiltered samples. However,
since the analytical technique was the same for all samples,
the relative magnitude of the data should not be affected.
There has been some speculation thattreated wastewater
effluents may exert an antagonistic or retardant effect on
the BOD exertion rate of the receiving stream. If true,
this may be due to surfactants or to the expected lower
exertion rate of the effluent. In this regard,the decreased
BOD in 4 or 5 measurements between R-5 and R-6 is of in-
terest. Increased loads between the summation of R-4 plus
R-9 versus R-5 are likely due to raw and combined sewage
bypassing the intervening area.
Another, and probably the most practical, possibility for
the discrepancies is the fact that the data is biological and
biochemical in nature and such data does not always pro-
vide predictable comparative summations.
108
-------
COMPARATIVE
TABLE 12
DATA FROM PROJECT RIVER SAMPLING
DATE
RACCOON RIVER
1-35
R-7
63RD ST.
R-8
5TH ST.
R-9
DES MOINES RIVER
SAVLORVILLE
R-2
EUCLID
R-3
ELM ST.
R-4
SE 14TH ST.
R-5
HIY. 46
R-6
T
1-7 t R-2
B. O.D. -LBS/DAY
2/6/89
4/23/69
6/5/69
8/20/69
10/16/69
27,731
96.448
53.684
35. 122
20.034
M. 374
103,787
65.327
39.512
17,363
25, 185
134.189
38.161
16. 585
16, 251
8.247
465. 264
44.969
!•!. 343
61.798
18.555
483. 1«0
64.955
53.562
43,540
22.687
438.423
74. 948
50. 246
40. 339
105. 622
545.468
164. 384
66.88*
80. 333
61.985
466.019
119,119
173. 280
73.929
NO, -LBS/DAY
2/6/69
4/ 23/69
6/9/69
8/20/69
10/ 16/69
16. 337
228.540
52. 326
19.317
1. 462
17.563
192,687
4,851
18, 146
1,269
12.772
228. 540
42.883
20. 146
979
17.016
467.949
260.319
5, 365
160
13.552
535. 949
15. 939
6. 132
224
13.387
557.423
85. 108
5.791
32
27. 174
891.722
17.248
25. 536
582
3A.348
811.667
168.196
32.528
2.096
0. P04- LBS/DAY
2/6/69
4/ 23/69
6/5/69
8/ 20/69
10/16/69
181
12. 287
815
341
245
2,037
7,737
54
1.220
178
174
8,680
3,098
2.583
200
3.134
34.268
3.648
1.533
128
3.519
33. 284
3.647
1.022
192
324
16.016
6.595
9.027
352
60S
23.360
13. 389
7. 144
640
1.26«
42.570
15,2*0
11.400
3,143
35.978
561. 748
98.653
136,465
81.832
33. 393
729.842
312,645
24.682
1.562
3.315
46.555
4.463
1.874
373
PLANKTON- ALGAL UNITS PER ML.
2/ 6/69
6/5/69
8/20/69
10/ 16/69
3.449
22.751
31.425
51,970
2.487
4.013
55,868
27.017
76,330
3,531
33, 799
147, 150
4.465
58.554
3,392
30.837
50,670
118. 267
2. 316
51.037
102. 499
3.448
53.836
48. 155
63. 330
o
sD
-------
DEu MQINES METRO AREA LOAD
Estimated daily and annual metro area loads have been computed from
the runoff and sampling data presented in Sections VI, VII and IX. De-
velopment of the numbers was based on the following criteria:
1. The wastewater treatment plant effluent discharge
during dry weather conditions is based upon average
flows and effluent quality during the study period.
2. Under "wet" dry weather conditions, the wastewater
treatment plant effluent loads is based on the hydrau-
lic capacity of the plant and the average plant effluent
BOD during the "wet" dry weather period in May,
June, and July 1969.
3. The volume of combined sewer overflow is based on
the area, presently served by combined sewers. Run-
off coefficients, average annual rainfall patterns, and
combined sewer overflow quality as determined by this
study served as a basis for these computations.
4. Urban storm water discharges were also computed
from data developed in this study. The depth and fre-
quency of rainfall events were average annual values
obtained from. U. S. Weather Bureau records.
The estimated daily metro area loads for the considered conditions are
tabulated in Table 13. Projecting the data in Table 13, the estimated
average annual loads from the Des Moines area are 11,385,000 Ibs. of
BOD, 703,640 Ibs. of nitrate and 3,092,600 Ibs. of ortho phosphate.
These summations and the conditions on which they are based are shown
in Table 14.
It is recognized that these figures don't match the differences in the
summations of the data in the Tables 10 and 11. Possible explanation
of the BOD discrepancy have already been discussed. Another thought
is to apply unit concentrations to the unaccounted for flow increase be-
tween the summation of R-2 plus R-7 and R-6. The increase is proba-
bly from the intervening creeks. Using the nitrate and phosphate data
for the largest of the creeks, Beaver Creek (R-15), an additional load
of 2, 860,000 Ibs/year of nitrate and 390,000 Ibs/year of phosphate are
obtained. This brings the nitrate value close in line with the annual
river averages. The phosphate data is still unbalanced, however. The
explanation for this is unknown.
110
-------
TA B L E 13
PRESENT DAILY METRO AREA DISCHARGES
WEATHER CONDITION
SOURCE
WWTP EFFLUENT
FLOW, Ac-Ft
BOD, LBS.
K03, LBS.
O.PO^, LBS.
"WET" DRY WEATHER OVERFLOW
FLOW, Ac-Ft
BOD, LBS.
N03, LBS.
O.POij, LBS.
WET WEATHER COMBINED OVERFLOW
FLOW, Ac-Ft
BOD, LBS.
N03, LBS.
O.P04, LBS.
STORM RUNOFF, OVERLAND & STORM SEWER
FLOW, Ac-Ft
BOD, LBS.
N03, LBS.
O.PO^, LBS. .
TOTALS PER WEATHER CONDITION
FLOW, Ac-Ft
BOD, LBS.
N03, LBS.
O.P04, LBS.
DRY
WEATHER
108**
15,800
1,560
6,760
NONE
NONE
NONE
108
15,800
1,560
6,760
"WET" DRY
WEATHER
154**
20,800
2,200
9,600
66
20,700
90
2,440
NONE
NONE
220
41,500
2,290
12,040
6" RAIN
1,011
82,100
12,846
523,000
14,077
646,600
2.72" RAIN
1.50" RAIN
0.75" RAIN
0.375" RAIN
0.175" RAIN*
VALUES ASSUMED CONSTANT DURING ALL WET WEATHER CONDITIONS
VALUES ASSUMED CONSTANT DURING ALL WET WEATHER CONDITIONS
299
40,500
243
6,350
3,580
292,000
6,800
3,900
4,099
374,000
9,333
22,290
100
20,300
136
2,440
1,130
153,000
3,060
1,840
1,450
214,800
5,486
16,320
10
2,710
18
271
495
80,500
1,610
1,010
725
124,710
3,918
13,321
NONE**
169
27,500
550
344
389
69,000
2,840
12,384
NONE **
46
749
ISO
94
264
42,249
2,440
12,134
* BELOW THIS INTENSITY, WHICH REPRESENTS THE 0.10" TO 0.2V~RiNGE, THE AMOOTTTOF RUNOFFT5~HEG11GIBLE
**FLOWS TREATED AT WWTP
-------
TABLE 14
SUMMARY OF PRESENT ANNUAL METRO AREA
DISCHARGES
ts>
CONDITION
WWTP EFFLUENT
DRY WEATHER
"WET" DRY WEATHER
SUBTOTAL
"WET" DRY WEATHER OVERFLOW
WET WEATHER COMBINED SEWER OVERFLOWS
2.72" RAIN
1.50" RAIN
0.75" RAIN
0.375" RAIN
0.175" RAIN
SUBTOTAL
URBAN STORM WATER DISCHARGES
2.72" RAIN
I.5Q" RAIN
0.75" RAIN
0.375" RAIN
0.175" RAIN
SUBTOTAL
TOTAL ANNUAL DISCHARGE
DAYS
257
108
365
108
1
5
12
18
20
56
1
5
12
18
20
56
365
BOD(LBS.)
4,060,600
2,2146,400
6,307,000
2,235,600
40,500
101,500
32,500
0
0
174,500
292,000
765,000
966,000
495,200
149,800
2,668,000
11,385,100
N03 (LBS)
400,900
237,600
638,500
9,700
240
680
220
0
0
1,140
6,800
15,300
19,300
9,900
3,000
54,300
703,640
O.POu(LBS.).
1,737,300
1,036,800
2,774,100
263,500
6,350
12,200
3,2*0
0
0
21,800
3,900
9,200
12,000
6,200
1,900
33,200
3,092,600
-------
PESTICIDE SURVEY
Pesticide samples were collected during each of the river sampling
periods and forwarded to the University of Iowa State Hygienic Lab-
oratory for analysis. The results of these analyses are given in
Table 15.
Inspection of Table 15 shows pesticide levels to be relatively low dur-
ing the June and October survey, indicating that there probably had been
little or no application of pesticides for a few weeks preceding the sampl-
ing. No pesticides were detected in any of the February samples, the
lower limit of detection for chlorinated hydrocarbon insecticides being
0. 01 parts per billion. The August sample showed somewhat high con-
centrations at nearly all stations, and extremely high values were re-
corded for Stations R-6, the Des Moines River at Highway 46 Bridge
(below the city), and for Station 14, Four Mile Creek at Scott Street.
An investigation of pesticide usage in the period before the sampling
revealed that extensive spraying for flies and mosquitoes was done at
the Iowa State Fairgounds in preparation for the fair. Rainfall during
that period had carried the pesticides to Four Mile Creek and subse-
quently the Des Moines River. Thi^ situation confirmed previous State
Hygienic Laboratory experience which showed that the level of pesticide
concentrations in streams was not constant, but varied considerably
and reached its highest levels in small streams adjacent to areas where
the pesticides are used.
EVALUATION: IMPACT OF METROPOLITAN AREA LOAD
Review of the average annual loadings from the Des Moines metro area
during the study period reveals that approximately 75 percent of the an-
nual quantity of BOD, 92 percent of the nitrate and 98 percent of the or-
tho-phosphate was discharged to the river during non-runoff periods.
It should also be noted that about 20 percent of the discharge during the
study period was from combined sewer overflow during non-runoff per-
iods. Non-runoff periods represent about 95 percent of calendar year.
Wet weather combined sewer overflow, which is the primary subject of
concern, represents about 24 percent of the annual BOD load, 10 per-
cent or less of the nitrate and ortho-phosphate loads, and occurs dur-
ing about 5 percent of the calendar year.
As previously discussed, the river sampling program conducted with
this project was limited to five samplings at quarterly intervals. The
data collected was useful for evaluating existing water quality; however,
it was not sufficient to determine what impact, if any, the Des Moines
metro load exerts on the receiving waters. Additional downstream sta-
tions and considerably more sampling would be required to make that
determination.
113
-------
TABLE 15
PESTICIDE CONCENTRATIONS
CONCENTRATION IN PARTS PER BILLION
PESTICIDE
RIVER STATION
R-2
R-3
R-4
R-5
R-6
R-7
R-8
R-9
R-IO
R-14
R-15
R-16
RIVER SAMPLE OF FEBRUARY 6, 1969.
HO PESTICIDES DETECTED IN ANY SAMPLE, STATIONS R-2 TO R-9
RIVER SAMPLE OF JUNE 5, 1969.
DDE
DIELDRIN
-
.004
.039
*
.035
-
.044
-
.036
-
-
.00*
-
.004
RIVER SAMPLE OF AUGUST 20, 1969
DIELDRIN
DDT
DDE
op DDT
op DDE
.006
.005
.009
-
-
.008
-
.008
-
-
.015
.042
.19
.09
.04
.028
.10
.89
.38
.10
.23
.93
14.4
».tl
2.82
.Oil
.003
.020
-
-
.010
.005
.032
'
- -
-
.007
-
. 006
-
.007
N.S.
N.S.
.034
.048
.49
.29
.14
.021
.015
.020
-
-
.20
1.29
17.6
11.2
3.30
.25
.010
.017
-
-
.007
.012
.018
-
-
RIVER SAMPLE OF OCTOBER 16, 1969
DIELDRIN
DDT
POE
DIELDRIN
DDT
DDE
.003
.067
.004
N.S.
.008
.005
.008
.006
.tf*L
.007
.009
.007
.006
.009
.013
.007
N.S.
N.S.
.010
.008
.006
.008
.013
.010
.Oil
.Oil
.007
.009
.014
.008
.013
.Oil
.007
.006
.012
.013
-------
A. conjectural appraisal of the probable impact from the metro area
loads can be developed by comparing the annual metro area load data
to the above and below river data presented herein. It should also be
noted that the metro area loads include both combined sewer overflow
and overland runoff. The comparison is shown in the following:
Parameter
Low Water
Year
High Water
Year
Average Water
Year
BOD, (Ibs)
Incoming
Metro Area
N03 (Ibs)
Incoming
Metro Area
O.P04 (Ibs)
Incoming
Metro Area
15, 549,000
11, 385, 100
2,431, 000
703, 640
593,000
3, 092, 600
100,070,000
11, 385, 100
60,032,000
703, 640
7, 292, 000
3, 092, 600
65,225, 000
11,385, 100
22,222,000
703,640
2,940,000
3, 092, 600
The preceding data indicates that the incoming BOD and NO3 loads to the
metro area range from only slightly greater to over 80 times the load
added in the metro area. The situation reverses for O. PO4 where the
metro area addition exceeds the incoming loads during low and average
water years. But again, for high water years, the incoming phosphate
load is much greater.
Annual loads, although significant in the general picture, do not reflect
the impact from potential "shock" loads during runoff periods. The daily
load data in Table 13, compared to the measured river loads in Table
12, provides a better indication of potential shock effect. Disregarding
the extremes in Table 12, the summated incoming daily load to the me-
tro area is about 36, 000 Ibs of BOD, 25, 000 Ibs of NOs, and 3, 500 Ibs
of O. PO4 . From Table 13, it is obvious that the load from any rainfall
will greatly exceed the average incoming values. Sanitary sewage and
combined sewer overflow alone exceed the incoming BOD by from 150 to
250 percent depending on the rainfall. When overland flow is also con-
sidered the percentages increase to 360 and 1700 percent. Obviously,
an impact evidenced by accelerated degradation would be expected in
the river downstream from the metro area.
The preceding hypothetical situation is not necessarily a correct com-
parison of data. It is unlikely, through not impossible, that a major
rainfall would occur only in the metro area and not also in the contribut-
ing watersheds above and below Des Moines. Therefore, it is likely
that the relative magnitude of the load increase would be much less,
though still significant.
115
-------
The magnitude and continuity of the incoming loads to the metro area
indicate that the Des Moines and Raccoon Rivers are both rich in
organic and inorganic nutrient materials. This is also indicated by
the high algal densities observed in both streams. Considering these
facts, the impact to be anticipated from additional loads, whatever
the source, is questionable and speculative. Obviously, even without
any additional load, neither river will be a clean running stream until
load reduction is accomplished upstream from the Des Moines area.
Because of the current emphasis on nutrients and eutrophication, a
discussion of these matters relative to the study area appears warran-
ted.
The daily and annual loadings incoming to the Des Moines metropolitan
area appear to always be sufficient to maintain an abundant algal growth.
This would be especially true for the two new reservoirs, Red Rock and
Saylorville. Mackenthun (8) states that "a continued high rate of nutrient
supply does not appear to be necessary for continued algal production.
After initial stimulus, the recycling of nutrients within the lake basin is
sufficient to promote algal blooms for at least a number of years. "
Sawyer (9) reports that nuisance algal growths can be expected if the
average concentration of inorganic nitrogen (NH3, NO2, NO3) exceeds
0.3MG/L and the average inorganic phosphorous exceeds 0. 015 MG/L.
These conditions are almost always present in both the Des Moines and
Raccoon Rivers. It seems pertinent therefore to wonder if BOD and
nutrient additions from the Des Moines area are not just dessert at an
already abundant sumptious banquet.
Kuentzel (10) questions the present day public clamor for nitrogen and
phosphorous removal and suggests that carbon dixode (CO2) may be an
easier parameter to control in programs intended to inhibit algal growth.
Algae do, of course, require free CO 2 for growth; and, the most abun-
dant source of free COz is aerobic decomposition. Mr. Kuentzel suggests
that control of bacteria and/or bacterial growth will reduce available
CO2 and inhibit algal growth. This of course reinforces the case for
wastewater treatment and disinfection, especially in areas where up-
stream waters are of high quality.
Ferguson (11) also questions the propriety of forging ahead with elabo-
rate schemes for removal of nitrogen and phosphorous from domestic
wastewaters on the assumption that control of these nutrients will effect
control of algal growth. Referring to the work by Sawyer (9) and sum-
mating known available sources of these nutrients, Mr. Ferguson notes
that "a minimum of about 250 million pounds of phosphorous a year
would still enter surface waters from natural sources even if all phos-
phorous from man-generated sources were excluded. " He adds that
116
-------
the resulting concentration would be more than four times the minimum
concentration needed to induce excessive algal growth.
If the river system above the Des Moines area does in fact carry suf-
ficient nutrients for optimum plankton growth, and this does appear
to be the situation, it will be difficult to justify extensive collection
and treatment of overflow and runoff waters, at the present time.
Evaluation of the annual loads from the Des Moines area reveals
that approximately 92 percent of the nitrate and 98 percent of the ortho-
phosphate^s discharged to the river during non-runoff periods. For
the specific case of Des Moines, about 20 percent of the annual load
during the study period was discharged by overflow during non-runoff
periods. This is not believed to be the typical situation for Des Moines.
Without the severe infiltration which caused "wet" dry weather over-
flow an estimated 108 days during the study period, the percentage of
the annual untreated loads discharged to the river would be considerably
less.
117
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SECTION IX
COMBINED SEWER SEPARATION
SEPARATION STUDY AREA
The study area for combined sewer separation is shown on Figure
40 located at the end of this section. There are 2793 acres in the City
of Des Moines that are now served by combined sewers. Of this total,
1836 acres were selected for detailed analysis for 'combined sewer
separation. This "separation study area" includes all the Downtown
Core Commercial area on the west side of the Des Moines River, the
industrial and warehouse area bordered on the south and east by the
Des Moines and Raccoon Rivers, a large residential area with typical
public facilities interspersed, and core fringe containing commercial
and multi-family areas. Separation of all combined sewers in Des Moines
has been designated Combined Sewer Overflow Abatement Plan "A.. "
DATA UTILIZED FOR STUDY
The data utilized as a basis for study and analysis is as follows:
1. Existing quarter section sewer plats of the separation
study area were furnished by the City of Des Moines.
These plats are at a scale of 1" = 100' and show the
location of existing storm, sanitary and combined sew-
ers. Invert elevations are generally shown at man-
holes except on a large portion of the existing separate
storm sewers and some of the very old combined sewers.
In locations where invert elevations were not shown on
the plats nor in other City records and it was absolutely
necessary for analysis, the invert elevations were mea-
sured by field survey.
2. Existing quarter section topographic maps of the study
area are at a scale of 1" = 100' with 2-foot contour in-
terval. These topographic maps were prepared in 1963
and 1964 and did not include the interstate highway
through the separation study area.
3. Construction plans for the Interstate Highway through
the separation study area were furnished by the Iowa
State Highway Commission. These plans were utilized
to update the topographic maps and the sewer plats in
the study area.
119
-------
4. City of Des Moines microfilm records of sewer con-
struction drawings affecting the separation study area
were utilized to clarify and supplement the sewer plats.
5. Construction drawings of recently constructed storm
and sanitary sewers were furnished by the City of Des Moines.
6. Results of a recent storm sewer inlet survey prepared
by the City of Des Moines showed the number of inlets at
each intersection and were used to check and supplement
the inlets shown on the sewer plats.
DESIGN CRITERIA
Storm Sewers
Rainfall Intensity - Duration - Frequency Curves. The Rainfall Inten-
sity-Duration-Frequency Curves used in this study are those prepared
by the U. S. Weather Bureau in Technical Paper No. 25 (1955) for 5
and 10 year return periods in Des Moines, Iowa (12). See Figure 39.
Time of Concentration. The theoretical time of concentration (dura-
tion) was obtained from a nomograph representing the Hathaway For-
mula:
4.2- 14 o T u
t =2 Ln, where
t = time of concentration in minutes
n = retardation coefficient
L = Length in feet
S = Average slope, ft/ft
The retardance coefficient being as follows:
Paved areas 0.01
Bare packed soil 0. 10
Sparce grass or moderate rough bare
surface 0. 30
Average grass cover 0.40
Dense grass cover 0.80
120
-------
FREQUENCY ANALYSIS BY METHOD OF
EXTREMf VALUES, AFTER 6UUBEL
JO 15 20 50 405060
MINUTES
3 4 66 8 10 12
HOURS
16 24
DURATION
Exctrpt from "RAINFALL INTENSITY-DURATION
FREQUENCY CURVES", Technical Paper No. 25,
U.S. Department of Commerce, Weather Bureau.
RAINFALL INTENSITY - DURATION
FREQUENCY CURVES
DES MOINES, IOWA
I9O3 - 1951
121
FIGURE 39
-------
The minimum time of concentration was limited to 15 minutes,. This
practice is followed by many municipalities to allow reasonable time
for surface retention, surface wetting, lawn storage and gutter stor-
age.
Coefficient of Runoff "C". The following coefficients of runoff "C"
were used for storm sewer design.
Surface "C" Value
Paved areas and building roofs 0. 95
Grassed areas level to 1% slope 0.25
Grassed areas 1% to 3% slope 0.35
Grassed areas 3% to 10% slope 0.40
Grassed areas 10% or more slope 0.45
Unpaved alleys, parking areas & drives 0.80
Runoff Computations. Runoff computations were made by using the
Rational Method:
Q = CIA, where
A = Quantity of flow in cu. ft. /sec.
C - Coefficient of Runoff
I = Rainfall intensity from curves for concentration time (t)
A = Drainage area in acres
Storm Sewer Design Sizing. Storm sewers were sized by using the Man-
ning Formula:
^ 1.486 2/3 1/2
Q = A— R s , where
Q = Capacity in cu. ft. /sec.
n = Coefficient of roughness
R = Hydraulic radius of section in ft. = area of section
wetted perimeter
122
-------
S = Slope of hydraulic gradient in ft. /ft.
A coefficient of roughness "n" of 0. 013 was used for new construction
and 0. 017 was used for old sewers. Velocities were limited as follows:
Sewers of 54" diameter or less 20 ft. /sec.
Sewers of 60" diameter or larger 22 ft. /sec.
A minimum size of 15" diameter was used in sizing all proposed storm
sewers.
Sanitary Sewers
1. The following criteria was used for sanitary sewer
design: An assumed population density of 15 persons
per acre was used as a basis for sizing proposed
sanitary sewer lines.
2. Average daily flow was based on 100 gal. /capita/day.
3. Flow in laterals and sub-main sewers was assumed
to be 400 percent of average daily flow for domestic
sewage plus 150 gal. /capita/day to account for seep-
age and basement drains or a total of 550 gal. /capita/
day.
4. Flow in mains, trunk and outfall sewers was assumed
to be 250 percent of average daily flow for domestic
sewage plus 150 gal. /capita/day to account for seep-
age and basement drains or a total of 400 gal. /capita/
day.
5. Sanitary sewers were sized by using the Manning For-
mula. A coefficient of roughness "n" of 0.013 was used
for new construction. A. minimum velocity for pipes
flowing full of 2. 0 ft. /sec. was used.
6. A minimum sanitary sewer size of 8" diameter was
used.
METHOD OF PROCEDURE
Classification of Existing Sewers
The location of all known existing inlets were plotted on both the topo-
graphic maps and the sewer plats. Using the sewer plats, all sewers
123
-------
carrying combined sewage, only sanitary sewage or only storm water
were designated on work drawing by color codes. All sewers carrying
only storm water and not discharging into a combined sewer were then
eliminated from further study. All sewers carrying only sanitary
sewage were also eliminated from further study except where the
area served contributed to a proposed new sanitary sewer system
or linkage.
The boundaries of areas served by combined sewers or storm sewers
discharging into combined sewers were then outlined on the topographic
maps. The combined sewer systems .were analyzed to determine ttye
most efficient method of separation, either (1) new storm sewer sys-
tems with existing combined sewers used only for sanitary flows or
(2) new storm sewer systems in combination with existing combined
trunk sewers of sufficient size to handle design storm flows with the
sanitary sewage rerouted into new sanitary systems.
Storm Sewers
Using the topographic maps, the drainage areas contributing to all inter-
sections of points of impact within the existing combined sewer area
were outlined. Some 4000 individual drainage areas were involved in the
separation study area. Each area outlined on the topographic maps was
then measured to determine the acres served.
Storm sewer systems were then laid out at a scale of 1" = 400' for all
areas presently served by combined sewers. Existing storm sewers
within those areas were included for analysis together with any large
combined sewers that were of sufficient size and in locations appropriate
for use as storm sewers. The system layout was later revised whqre
the hydraulic analysis indicated that changes were desirable.
Each point of impact, major change of direction, or change of grade was
designated by a number code indicating the system number and the point
number. This numbering system is used on Figures 41 through 48. The
last two digits indicate the point number and the preceding digits indi-
cate the system numbers (2015 indicates system number 20, point num-
ber 15).
The values for runoff factors "C" and time of concentration "t" were
then determined for each impact point. The factor "C" was determined
by detailed analysis of a number of typical areas and the results applied
by using visual comparison for all other similar conditions. The r'e-
sulting factor "C" for each impact point was determined by compositing
the contributing sub-areas as shown in the following example:
124
-------
Point of
Concentration Location
723 17th and Clark
A
Acres
0.71
2. 16
1. 07
1.41
C
0. 60
0. 55
0. 56
0.55
AC
0.43
1. 19
0.60
0.78
5.35
0. 56
3.00
Proposed gradients for storm sewers were then determined by setting
up tables for each proposed system showing the surface elvations at
each point, the distance between points, the proposed inverts, the depth
of cut and the invert elevations of existing sewers crossed. Grades were
determined working upstream from the elevation of discharge through
the system. After analysis, the proposed or existing storm sewer sizes
were included in the table and rechecked for conflicts with other sewers
and for minimum cover. When existing sewer invert elevations were un-
available, they were assumed; except where the location of large exist-
ing sewers was critical the invert elevations were obtained by field
measurement.
Hydraulic analysis was performed by electronic computer. The analysis
was repeated as necessary to obtain a satisfactory design. In the ana-
lysis of existing systems, it was assumed that adequate inlets were in
place. Any existing storm sewer forming a branch of a proposed system
was not considered for reconstruction even though it was found to be of
inadequate size. Existing storm sewers not contributing to combined
sewage flows were not analyzed. Although a separate analysis was made
for 5 and 10 year rainstorm return periods, only the results of the 10
year rainstorm was used for pipe sizing and cost estimating, ^he final
results of the hydraulic analysis for system number 9 is included as an
example.
The storm sewer systems shown in Figures 40 through 48 are those pro-
posed for the purpose of carrying all of the storm water from the areas
now served by combined sewers within the separation study area. These
systems generally fall within, one or more of the following categories.
(1) An independent system with no interconnection with
any existing system discharging into a natural ravine
or a river.
(2) A. branch system, either existing or proposed, dis-
charging into an existing or proposed system.
125
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SAMPLE HYDRAULIC ANALYSIS FOR STORM SEWERS
10 YEAR STORM
RELIEF SEWER NO 9 10 YR STORM OES MOINES IA SEW SEP STY VLH 8 01 69
ro
STAT EXIST EXIST D A
rROM TO
1 2
2 3
3 4
4 5
6 7
7 5
5 8
9 10
10 11
11 8
12 8
8 13
14 13
13 15
15 16
SIZE
TYPE
1 P
1 P
1 P
1 P
1 P
1 P
1 P
1 P
1 P
1 P
1 P
1 P
1 P
1 P
1 P
DRAINAGE AREA
AREA =
FLOW =
44.97
86.38
CAP AREA
CFS AC
0 5.8
0 6.1
0 4.6
0 0.0
0 3.4
0 2.0
0 0.0
0 4.9
0 2.3
0 5.0
0 6.2
0 0.0
0 4.7
0 0.0
0 0.0
TOTALS
CXAP=
CFS/AC=
FLOW AREA
INIT
CFS
13.3
14.4
9.8
0.0
7.6
4.9
0.0
12.0
5.4
13.1
12.1
0.0
11.8
0.0
0.0
0.00
1.92
SUM
AC.
5.8
11.8
16.4
16.4
3.4
5.4
21.8
4.9
7.2
12.2
6.2
40.3
4.7
45.0
45.0
CXAI
C*A OUR ACCUM.
SUM MIN
3.3 18.4
6.8 19.5
9.0 20.2
9.0 21.2
1.9 18.4
3.0 19.3
12.0 21.6
2.8 16.0
4.1 17.2
7.1 18.0
3.3 22.2
22.4 23.3
2.7 15.0
25.1 23.8
25.1 24.1
= 25.09
FLOW
CFS
13.3
26.3
34.2
33.3
7.6
11.7
44.0
12.0
17.0
28.5
12.1
78.6
11.8
86.9
86.4
DUR =
REQD
PIPE
SIZE
24
24
36
36
18
21
36
21
24
27
24
36
24
30
24
24.
CAP
FULL
CFS
16.5
31.0
41.7
48.6
9.7
13.9
49.5
14.3
20.0
31.0
14.8
109.2
12.8
87.7
120.1
09
SLOPE
0/0
.53
1.88
.39
.53
.85
.77
.55
.81
.78
1.00
.43
2.68
.32
4.57
28.20
LTH
FT.
395
480
370
175
315
195
840
330
345
185
185
540
190
310
125
FALL
FT.
2.09
9.02
1.44
.93
2.68
1.50
4.62
2.67
2.69
1.85
.80
14.47
.61
14.17
35.25
VEL
FPS
5.24
9.87
5.89
6.87
5.48
5.78
7.00
5.93
6.36
7.79
4.72
15.45
4.07
17.86
38.24
Note:
(1) Change Pipe Size for Velocity Limit to 30" PTS. 15-16
-------
(3) An existing system downstream of a proposed sewer
extension that is to be enlarged due to its inadequate
size.
(4) A system that is an extension of an existing system
to serve areas conveniently adjacent to that existing
system.
Sanitary Sewers
Where existing combined sewers were to be used for storm water,
separate sanitary systems were designed to remove and reroute sani-
tary sewage from such combined sewers. Gravity sewers were used
wherever possible and lift stations included only where no alternative
was available or practical. Each system was identified by letters,
and various points along the system by numbers; i. e. , point two on
System A was identified as A.02.
The areas contributing to the proposed sanitary systems were outlined
and measured. Proposed gradients were then determined by the same
method as was used for storm sewers. Sanitary flows were analyzed
for each line and lift station. Line sizes and lift station capacities
were then determined.
OTHER METHODS OF SEPARATION CONSIDERED
Ponding or Retardation of Storm Runoff
Retardation of combined sewer overflows and storm runoff for the pur-
pose of reducing pollutant loads and/or storage for return to the com-
bined sewer system is considered in subsequent plans. Retardation for
the purpose of decreasing the size of storm sewers is not considered,
however. The separation study area is an older, heavily developed sec-
tion of the city where land suitable for retardation basins was not avail-
able. Also the terrain in this area is rolling and adequate slope is
available for good drainage.
Construction of Sanitary Sewers Within Large Existing Sewers
This method was considered, however, hydraulic analysis of the pro-
posed and existing storm sewers showed that no significant reserve ca-
pacity was available in these systems. Where it was found necessary
to construct new sanitary sewers, existing storm sewer capacity was
not sufficient to permit inserting a new sanitary sewer within the exist-
ing storm sewer.
127
-------
COST ESTIMATE
Method of Estimating
A unit price schedule was prepared to include all probable items of
cost. Computer data cards were prepared for each run of each sys-
tem to reflect the quantities of all items of construction. All lump
sum items were listed on separate data cards giving the item descrip-
tion and the lump sum cost. Where items occurred that were not listed
in the unit price schedule, the cost of a similar item listed was used
and the additional cost was entered as a lump sum item. As an exam-
ple, where box sewer sections or low head pipe was used due to clear-
ance requirements, the additional cost over a comparable item was
entered as a lump sum item. A contingency factor of 15 percent was
used on all cost estimates to account for conditions not apparent from
the basic data available. The quantities and costs were then computed
and listed by the computer. An example of the detailed cost estimates
is included.
Cost Items Not Included in the Estimate
(1) The cost of plugging existing inlets now connected to
combined sewer systems and the connection of these
inlets to a proposed storm system is not included.
(2) The cost of constructing additional inlets in the upper
reaches of existing storm sewer systems, where the
existing inlets may be inadequate to serve the areas.
This is not a proper cost item for sewage separation
since effective separation is not dependent upon these
additional inlets.
(3) The cost of increasing the existing storm sewers t0
the sizes shown in the hydraulic analysis as required
under the criteria used: This item does not affect
separation since those systems are now separated
at their origin and the existing under-sized sewers
will be connected to the proposed separate storm
sewer systems or discharge independently to natural
ravines.
(4) The cost of ground and utilities surveys, preparation
of final designs and construction supervision.
(5) The cost of right-of-way acquisition.
128
-------
SAMPLE STORM SEWER COST ANALYSIS
SEWAGE SEPARATION STUDY DES MOINES, IA.
COST ESTIMATE STORM SEWER NO. 9 VLH 9-1-69
DESCRIPTION
18 STORM SEWER PIPE IN PLACb
21 STORM SEWER PIPE IN PL*Ct
24 STORM SEWER PIPE IN PLACL
27 STORM SEwEP PIPE IN Pi_ACfc
30 STORM SEWER PIPE IN PLACt
36 STORM SEWER PIPE IN PLACE
EXCAVATION COST OPEN COT UNSHOHLL)
EXCAVATION COST OPEN CUT SHOVEL)
PAVEMENT CUT AND REPLACEMENT
MANHOLE STANDARD DEPTH frF T . OH LESS
MANHOLE EXTRA DEPTH OVEH 6FT
SINGLE INLETS
DOUBLE INLETS
EXISTING INLETS TO BE CONNECTED
WATER MAINS RELOCATED VERTICALLY
WATER MAINS CROSSING ABOVE PIPE
CONCRETE SADDLES FOR SANITARY MAINS
SANITARY MAINS CROSSING AHOVE PIPE
GAS MAINS RELOCATED VERTICALLY
GAS MAINS CROSSING ABOVt PIPE
WATER SERIES RELOCATED VERTICALLY
WATER SERIES CROSSING AaOVt PIPE
SANITARY SERIES RELOCATED VERTICALLY
SANITARY SERIES CROSSING AbOVE PIPE
GAS SERIES RELOCATED VEKTICALLY
GAS SERIES CROSSING ABOVE PIPE
UTILITYPOLES RELOCATED
GRASSED AREAS CUT AND REPLACED
TREES TO BE REMOVED AND REPLACED
HEAOWALL FOR 30 IN PIPE
CONTINGENCY .15
OUANT I TY
.115.00
525.00
1595.00
185.00
435.00
1925.00
1*99.25
9888.31
2284.02
15.00
55.60
22.00
11.00
7.00
3.00
8.00
3.00
2.00
2.00
10.00
1.00
10.00
3.00
6.00
1.00
10.00
3.00
122.53
9.00
UNIT
L.F.
L.F.
L.F.
L.F.
L.F.
L.F.
C.Y.
C.Y.
S.Y.
EA
V.F.
EA
EA
EA
EA
EA
EA
EA
EA
EA
EA
EA
EA
EA
EA
EA
EA
S.Y.
S.Y.
Lb
UNIT COST
5.12
5.98
7.71
9.31
10.64
15.29
2.50
3.00
9.00
300.00
35.00
740.00
1160.00
360.00
100.00
80.00
200.00
150.00
100.00
80.00
50.00
40.00
80.00
80.00
50.00
40.00
150.00
1.00
250.00
AMOUNT
1612.96 !
3142.12
12303.83
1722.35
4628.40
29442.87
3748.12
29664.94
20556.21
4500.00
1946.00
16280.00 j
12760.00 •
2520.00
300.00
64G4f-0
60^.00
300.00
200.00
800.00
50.00
400.00
240.00
480.00
50.00
400.00
450.00
122.53
2250.00
550.00
22899.05
TOTAL 1 75559.38 :
-------
Intangible Cost Items Not Included
Certain intangible cost items are involved with construction of separa-
ted sewer systems in the existing built-up areas, particularly around
the central commercial district. Retail business would be seriously
disrupted during construction, with attendant loss of revenue. De-
touring and maintaining traffic would be a problem and an inconvenience
to motorists would result. Also the noise of construction activities
would create an annoyance to adjacent office buildings. Existing under-
ground utilities would present conflicts, requiring close coordination
with the operating agencies to maintain service.
Cost Summary
The following Tables are a summary of the estimated construction costs
required for separation of storm and sanitary flows in the separation
study area:
System
Proposed Storm Sewer Systems
Acres
Construction Cost
1 (Areas 1, 2, 3, &4) 145. 74
5 194.78
6 6. 12
7 148.31
8 193.02
9 44.97
10 10.13
11 25.72
12 26.72
13 14.55
14 37.94
15 103.42
16 2.86
17 35.82
18 13.03
19 185.80
20 (Existing System with no Additions) 748. 99
21 297.97
22 (Existing System with no Additions) 38. 83
$
23
24
25
154. 06
105. 89
25. 51
26 (Existing System with no Additions) 16. 74
27
17.46
800,686
757,497
13,880
578,153
86, 113
175, 559
36,338
99,195
57,671
53, 448
5,931
256,460
12,703
77,277
16,688
20,077
0
1, 742, 710
0
406, 991
480,112
79,119
0
50, 138
130
-------
System Acres Construction Cost
28 134.73 $ 4,910
29 -- 116,465
30 23.54 46,476
31 43.73 159,376
32 30.82 82,276
33 115.79 596,874
34 94.00 555,052
35 124.73 278,552
36 17.27 65,543
37 13.53 34, 166
Total $ 7,746,436
Proposed Sanitary Sewer Systems
System Construction Cost
A
B
C
D
E
F
G
Total $ 606, 130
$
263, 114
57, 618
22,450
21,415
11,646
225, 969
3,918
Total Construction Costs Storm
and Sanitary Sewer Systems $ 8, 352, 566
Separation Costs Outside of the Detailed Separation Study Area
The cost of separating storm runoff from sanitary flows in those areas
outside of the detailed separation study area was estimated by measur-
ing all known drainage areas contributing to combined sewer systems
and comparing them with similar systems in the separation study area.
The actual areas connected were adjusted to account for storm flows
picked up and carried by these systems enroute to a discharge point.
The areas to be drained were then multiplied by the cost per acre of
a similar situation found in one or more systems within the detailed
separation study area. It was estimated that an additional 100 acres
131
-------
would be found to be connected to the sanitary systems in addition to
those located and measured. An additional 20 percent was added for
overall contingencies. The total cost for separation outside of the
detailed separation study area was found by this method to be
$10, 200, 000. When added to the cost for the detailed separation study
area, the total cost for separation of storm runoff from sanitary flows
for the City of Des Moines would be approximately $18, 550, 000.
132
-------
SEWER SEPARATION PLAN
SHEET INDEX
133
FIGURE 40
-------
1
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hj
::
•J
I
o
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L_jr
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rrf
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i 1
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/ N £
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FIGURE 42
-------
M A T C
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KINSMAN BLVD.
OBSERVATORY
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HARWOOO DR.
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SCALE l"= 800'
138
-------
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SEWER SEPARATION PLAN
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FIGURE 43
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25) AREA 7
PARK ST.
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-------
c- c
SENDER SEPARATION PLAN
SHEET 4
141
FIGURE 44
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SEWER SEPARATION PLAN
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142
FIGURE 45
-------
CRESENT DR.
WOODLAND AVE. — — J£^-P-MV_- p.a: —
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AREA 3
HIGH ST.
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SEWER SEPARATION PLAN
SHEET 6
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FIGURE 46
-------
DAY ST.
FREEWAY
AREA 5
DAY ST.
AREA
FREEWAY
SCALE l"= 200'
SEWER SEPARATION PLAN
SHEET 7
144
FIGURE 47
-------
CENTER ST.
) L
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SCALE I "=200'
SEWER SEPARATION PLAN
SHEET S
145
FIGURE 48
-------
SECTION X
TREATMENT OF COMBINED SEWER OVER-
FLOWS AND STORM WATER DISCHARGES
GENERAL
To establish the requirements of future wastewater collection and treat-
ment systems, a basis for design of such facilities was prepared. Faci-
lities for elimination or collection and treatment of combined sewer
overflows were then designed to be consistent with the envisioned sani-
tary collection and treatment facilities. The various areas or systems
which release combined sewer overflows to the streams are considered
herein according to points of concentration for discharge. Alternate
solutions are first described and evaluated for these individual systems.
Overall schemes for elimination or reduction of combined sewer over-
flow are then developed as a composite of the facilities proposed for in-
dividual systems. The areas which have been investigated include all
known combined sewer areas and are grouped into the following systems:
1. Closes Creek System 6. South Side Trunk System
2. West Side Interceptor 7. Scott Street Lift Station
and Storm Outfall
3. Ingersoll Run System
8. Case Lake Treatment
4. East Side System Complex
5. East 18th Street System
Concepts for Overflow and Stormwater Discharge Abatement
Three basic concepts for abatement of combined sewer overflows and
control of stormwater discharges are considered. The concepts consi-
dered do not provide the same degree of pollution abatement, therefore
the effectiveness of each relative to reducing urban pollution discharges
is discussed. The concepts considered are (1) completely separate all
combined sewers, (2) intercept and treat combined sewer overflows,
and (3) intercept and treat all combined sewer overflows and urban
stormwater discharges.
In all of the concepts, the "wet" dry weather overflow condition is con-
sidered to be eliminated by the construction of additional wastewater
treatment facilities by the City of Des Moines. The expanded plant will
have a maximum hydraulic capacity of 130 MGD and will be capable of
147
-------
treating all combined sewer flows carried to the plant by the existing
outfall sewers (15). It is assumed that the average daily BOD5 dis-
charge from the Des Moines plant will meet the State requirements of
7500 pounds per day to the river. Four plans for combined sewer
overflow abatement have been developed within the concepts described.
They are described as follows:
Plan A is complete separation of all combined sewers. This plan has
been described in detail in Section IX of this report. Further discus-
sion of complete separation will be confined to the evaluation of effect-
iveness at the end of this section.
Plan B-l is to intercept and treat combined sewer overflows. No over-
flow from the combined sewer system would be permitted under this
plan. The plan includes separation of certain areas where interception
and treatment of all combined flows is deemed impractical.
Plan B-2 is to intercept and treat combined sewer overflows as in
Plan B-l, however, greater use will be made of existing systems and
small quantities of overflow will be permitted during high intensity
storms. Only small areas of combined sewers would be separated.
Plan C provides for the treatment of all stormwater discharges in
addition to combined sewer overflow abatement as described in Plan
B-l. Four areas were selected to develop "typical" stormwater treat-
ment facilities. Based on the analysis of these areas, the costs of
treating all urban stormwater discharges will be evaluated.
The improvements proposed for each of the individual systems are
described in detail in subsequent parts of this Section.
FUTURE WASTEWATER COLLECTION SYSTEM
A study was made of urban growth as it pertains to future collection
systems. Certain assumptions were made as to location of future trunk
and relief sewers and the area of service for each system. Reference
to Figures 2 and 13 will assist the reader to envision the improvements
described and the areas served by each system. The assumptions made
are generally in concurrence with the utilities planning report prepared
for the Central Iowa Regional Planning Commission (13). This report
recommends either (1) a future treatment plant site north of Interstate
35-80 on the east side of the Des Moines River, or (2) a future trunk
sewer on the east side of the river which would convey the wastes from
the areas north of the Interstate to an expanded plant below Des Moines.
148
-------
It is assumed that the line on the east side of the river will be con-
structed at some point in the future and will serve the City of A.nkeny,
the Urbandale Sanitary District and other areas developing north of
Des Moines.
The discharge of treated wastes above Des Moines would be to a sec-
tion of river that is already heavily used for recreation and will most
likely increase in usage due to the new Saylorville Reservoir and the
improved river quality therefrom. Two waste treatment facilities pre-
sently discharge to streams which reach the Des Moines River imme-
diately above Des Moines; the Urbandale Sanitary District Plant on
Beaver Creek and the Ankeny-John Deere Plant on Saylor Creek-
Samples were collected from these two streams during the A.ugust and
October river samplings. Both periods showed a dissolved oxygen de-
pletion on Saylor Creek, presumably the result of waste treatment
plant effluent. Development north of Des Moines will undoubtedly be
accelerated by the completion of the Saylorville Reservoir, requiring
the extension of sewer service to this area in the near future.
In the development of a collection system plan, it was assumed that
the existing areas on the west side of the river above the Closes Creek
Basin would be siphoned to the new relief line on the east side. This
would relieve the existing West Side Interceptor, which is already
near capacity due to high infiltration, and would divert a large volume
of separate sanitary flow out of the combined system below Closes
Creek. As subsequently explained, this is consistent with a general
philosophy which Des Moines should adopt regarding extension of their
collection system.
A number of alternatives should be investigated for the proposed East
Side Relief Sewer, such as tunneling from the Birdland Lift Station to
below University A.venue and whether to expand the two existing lift
stations for continued use or abandon them for gravity flow. It appears,
however, that the most feasible route through the business district
would be on the east side, where the relief sewer could be constructed
without connection to the existing combined sewer system. This would
provide a large capacity separate trunk sewer serving the north side,
as the Southwest Outfall does the west side. These separate trunk sew-
ers would then be serving a large percentage of the growth areas and
would connect to the main outfall at a point below the major combined
sewer areas. Reducing the quantity and pollutional strength of com-
bined sewer overflows depends heavily on the general philosophy of
diverting separate sanitary and storm flows from the combined system.
Storm runoff from the separated areas would be maintained separate to
the point of discharge or treatment, as the case may be. Also the col-
lection system can be designed so as to give separate and high strength
149
-------
sanitary wastes priority to conventional mechanical treatment pro-
cesses. By this approach, combined sewer flows would be reduced
in quantity and pollutional load, and may be intercepted and treated
more easily.
The existing Bloomfield system includes the upper reaches of the
Yeader Creek Basin which will expand downstream and eventually
require a trunk sewer outletting somewhere below the Yeader Creek
Lake. It is assumed that such a line would be in existence and tri-
butary to the main outfall by 1990.
The North River Basin is presently served by five separate collection
and treatment systems, therefore present flows for that basin are not
included. This basin will eventually either be served by a single
treatment facility near the mouth of the North River, or the flow will
be transported to a downstream treatment facility serving the entire
metropolitan area. There will undoubtedly be an interim treatment
facility, or facilities, in the Middle Creek and North River Basins.
Future flows estimated for this basin are given for purposes of future
treatment only, since this separate system would not directly affect
overflow problems. Future flows are for the total population of the ba-
sin, and do not consider that this may be served by more than one sys-
tem for an interim period.
BASIS OF DESIGN
Future Sanitary Flows
On the basis of the population studies, the dry weather sanitary wastes
sampling, the measurement of wet-season infiltration, and the indus-
trial waste survey conducted by the City of Des Moines, an estimate
of present and future sanitary flows has been prepared. This data was
used for evaluating the capacity of existing sewers to handle present
and future sanitary flows, and for determining existing sewer's re-
serve capacity for handling combined flow-s. Using pollutant concen-
trations obtained from sampling, estimated flows were also used to
evaluate the load contributed from each drainage basin to overflow stor-
age and treatment facilities.
Table 16 gives the estimated present, 1990 and 2020 sanitary flows,
with contributing populations and the breakdown of domestic, indus-
trial and infiltration flow. Average daily domestic flows were based
on 100 gallons per capita per day which was slightly greater than that
measured during dry weather sampling, but does not include an allow-
ance for infiltration. Present industrial flows account for only the ma-
jor water-using industries surveyed to date by the city. Future
150
-------
TABLE 16
SUMMARY OF SANITARY FLOWS
DESCRI PTION
SYSTEM - AREA NO.
«ST Sire IITERCEPTOli -I-l ©
EAST SIDE INTERCEPTOR -1-2. IU-i, TJI-2(2]
SOUTH KST OUTFALL -U- 1 , H-2
SOUTHER! HILLS TRUNK - H
SCOn STREET SUBTOTAL
SOUTH SIDE TRUNK - HI
EAST IBTH STREET TRUNK -UT-I. H-2
MAIN OUTFALL AREA - IT
BLOOMF 1 ELD SYSTEM - HT1- 1 ©
MAIN OUTFALL • KTP IBIIIIII
FOUR MILE TRUNK - t ©
YEADER CREEK BASIN - HJJ-2 ©
TOTAL TO B*TP
NORTH RIVER BASIN - I ©
PRESENT FLOW - MOD
ESTIMATED
POPULATION
79,000
16,400
54,690
5.080
155.120
15,300
17.300
3,000
13.400
204,120
35,600
-
239. 72D
10.430
DOMESTIC
AVE. DAILY
7.90
1.64
6.47
0.50
15.51
1.53
1.73
0.80
1.34
20.41
3.S6
-
23.97
-
INDUSTRIAL®
AVE. DAILY
0.47
-
-
J-_
0.47
-
2.68
-
-
3. 15
1.70
-
,.,S
-
NFILTRATION
IB.W
2.68
6.47
0.50
30.13
2.30
2.60
0.45
2.01
37.49
5. 32
-
42.81
-
TOTAL
AVE. DAILY,
26.85
4.32
13.94
t.OO
«. ii
3.63
7.01
0.75
3.35
61.05
10.56
-
71.63
-
DESIGN
FLOW
37.46
6.28
20.50
-
62.33
6.73
14.31
-
6.03
86. 18
-
-
93.31
-
PRESENT
SYSTEM
COMBINED
COMBINED
SEPARATE
SEPARATE
COMBINED
COMBINED
COMBINED
SEPARATE ©
COMBINED
COMBINED
SEPARATE
SEPARATE
COMBINED
SEPARATE
NOTES: © PRESENT .«UST<>IAL FLOW DETERMINED FROM CITY OF OES HDIHES URVET
© NORTH SIDE ABOVE CLOSES CPEEX AREA TO EAST SIDE FOR FUTU«
CD YEADER CREEK BASIN INCLUDED ID BLOOMF1ELD SYSTFJf AT PRESENT
© INCLUDES INDUSTRIAL HASTE FUWINfi DKtECTLT TO WWTF
(D FIVE SEPA1ATE SYSTEMS SERVE AREA AT PRESENT
© SEPARATE SANITARY SEM-BS TO HAIR OUTFALL FROM THIS AREA
DESCRI PTION
SYSTEM -^ AREA NO.
KIT lilt IITUHPTBI -I-l ©
EAST till IITEICEPTBB -I-t. TH-I, TH-2(|)
SHTB KIT BITPUl -TJ-I. H-2
,»9Tlt« BIUI IBHI - H
IC8TT IIIftT BITITAL
•in IIBI mil - m
uit un intiT mu -TX-I. rx->
Hlf HTfllL UEI - H.
R9B»ini niTBi - nn-i ©
•in IITIIU • B»rf inrnii
nil mu Tun - 1 ©
Tutu CBKI tun - nn-i ©
TITAI n mp
«9in ii in mil - 1 ©
I99O FLOW- MOD
ESTIMATED
POPULATION
ES.500
as, 500
61,000
18,000
240, 000
18,000
19,000
3,000
5.000
285.000
11,000
11,000
362.000
23.000
DOMESTIC
AVE. DAILY
&.S5
8.55
a. 10
I.BO
24.00
I.M
1.90
0.30
0.50
28.50
6.30
1.40
36.20
2.10
INDUSTRIAL
AVE. DAILY
1.25
0.40
1.30
-
2.95
-
4.56
0.60
-
8. 10
3. It
_
11.15
-
NFILTRATION
16.96
10.13
11.35
l.»
41.04
2.70
2. B5
0.45
0.75
47.79
8.10
A
u.a
2.12'
TOTAL
AVE. DAILY
28.76
19.61
20.75
3.60
87.99
4.50
8.30
I.3S
I.2S
64.39
18.25
3.50
106.14
5.12
DESIGN
FLOW
32. S9
29.48
30.60
-
96.42
7.74
19.57
-
-
I2S.05
-
—
139.09
-
2O2O FLOW- MOD
ESTIMATED
POPULATION
56.500
112,500
[12.000
25,000
306,000
20,000
20,000
3,000
6,000
355,000
95,000
20.000
470,000
40,000
DOMESTIC
AVE. DAILY
5.65
11.25
11.20
2.50
30.60
2.00
2.00
0.80
0.60
35. SO
9.50
2.00
47.00
4.00
NDUSTRIM.
AVE. DAILY
1.40
0.80
2.60
-
4. BO
-
6.70
1.20
-
12.70
4.10
_
17.50
-
NFILTRATION
17. 14
13.87
14.55
2.50
41.06
3.00
3.00
0.15
O.W
S5.ll
II. U
3.00
69.81
4.52
TOTAL
JB/E. DAILY
24.19
2S.92
28.35
5.00
83.48
5.00
11.70
j.95
1.50
103.61
25.70
5.00
134.11
8.52
DESIGN
FLOW
33. M
81.37 '
43.45
-
121.26
6.50
25.25
-
-
I5B. 16
-
—
ITS. 8 1
-
-------
industrial flows include a growth allowance for existing industries
plus an allowance for new industries which may locate in the Des
Moines area. The infiltration allowance used, based on the results
of the wet-season measurements, was generally 150 gallons per
capita per day for existing developed areas and 100 gallons per capi-
ta per day for the growth areas. Existing infiltration allowances
varied from the 150 gallons per capita figure in a very few cases,
based on specific knowledge of the watershed or actual measurement.
The infiltration allowance is expressed in gallons per capita per day
instead of the commonly used design parameter of gpd per mile.
This was due to time limitations on relating measured infiltration to
length of sewer and the fact that footing drains were believed to be
contributing a major portion of the infiltration flow.
Design flows are the maximum instantaneous flow expected and were
determined as follows. For domestic peak flows the formula Q =
q (1 + 14 ) was used, where Q = peak flow rate, q = average
4 H- pO. 5
daily flow, and p = population served in 1, OOO's. This formula de-
scribes curves published in the Water Pollution Control Federation's
Manual of Practice No. 9, "Design and Construction of Sanitary and
Storm Sewers" (14). The ratio of peak to average daily flow deter-
mined by the formula was limited to a maximum of 400 percent and
a minimum of 200 percent for the Des Moines system.
Industrial peak flows were assumed to be 250 percent of average daily
flow in all sewers except the inlet to the treatment plant where 200
percent of average daily flow was used. Infiltration flows were con-
sidered to be at a constant rate.
Peak Combined Flows
Pipe and conduit sizes proposed were determined by the following
criteria:
Storm Flows. Rainfall Intensity-Duration-Frequency Curves for a
10-year return period in Des Moines, Iowa were used. In nearly all
cases the existing combined systems will carry only a portion of a
10-year rainfall, therefore it is assumed that during peak flow periods
only a small portion of the precipitation enters the systems. In some
locations, combined sewage may leave the system and return to the
surface due to lack of capacity in the pipes. This source of pollution
cannot be eliminated without completely rebuilding large portions of
the combined systems. An exact analysis of the combined sewer over-
load could not be made without very exhaustive field surveys and hy-
dralic studies. In most cases the quantity of storm flow at the juncture
152
-------
of the combined systems and the interceptor was based on the estima-
ted pipe capacity upstream minus the average daily sanitary flow.
Sanitary Flows. Existing sanitary drainage basins or subbasins con-
tributing to combined sewer systems are considered for ultimate de-
velopment if the basin will become fully developed within the design
period. Population estimates are based on 1 5 persons per acre for
ultimate development and a reasonable projection for the design period
if ultimate development will not occur. Sanitary flows are based on 100
gallons per capita per day, and peak daily flow in trunk and interceptor
sewers was estimated to be 2. 5 times the average daily flow.
Quantitative Flows. Volumetric storage capacities for ponds and
impoundments are based on the following criteria:
Storm Flows. The design rainstorm selected produces 6 inches; of
precipitation within a period of 24 hours. The rate of precipitation
was assumed to be in direct proportion to the rainfall intensities; for
a 10-year return period. Volumetric design curves are shown in Fig-
ure 49. An illustration of the method used to determine quantity of
storm and sanitary flows is shown in Figure 50.
The average annual maximum precipitation for a 24-hour period was
also evaluated to obtain an estimate of the annual maximum 24-hour
storm. Weather Bureau records of the annual maximum 24-hour pre-
cipitation for the past 18 years were used to obtain an average yalue
of 2. 72 inches in a 24-hour period. The rate of precipitation for the
2. 72-inch rain was assumed to be in direct proportion to the volume-
tric design curve for the 6-inch rain.
Sanitary Flows. That portion of the total combined flow consisting of
sanitary sewage flow was computed on the basis of average daily flows
of 100 gallons per capita per day for the area served.
Quantity of Combined Sewage Overflow
For interception and treatment of combined sewage overflows two al-
ternative plans have been developed. Plan B-l consists of complete
elimination of combined sewage overflows, while Plan B-2 allows a
minor quantity of overflow to enter the river during extreme peak flows.
Where the cost of separating storm and sanitary systems would be mini-
mal, that method was used to reduce the quantity of overflow.
Flows from the known combined sewer areas are listed in summary form
in Table 17. The table contains a breakdown of the storm and sanitary
153
-------
a:
3
o
IE
U
0.
in
A RAINFALL INTENSITY DURATION CURVE
FOR 10 YEAR RETURN - DES MOINES,IOWA
U.S. WEATHER BUREAU BUL. 25
B RAINFALL INTENSITY FOR DESIGN
6 INCH - 24 HOUR DURATION STORM
C RAINFALL INTENSITY FOR (I YEAR RETURN)
2.72 INCH-24 HOUR DURATION STORM
B 10 12 14
TIME IN HOURS
I.CURVE A-PRODUCES TOTAL PRECIPITATION OF 14.07 INCHES IN
24 HOURS
2.CURVE B-PRODUCES TOTAL PRECIPITATION OF 6.00 INCHES IN
24 HOURS. INTENSITIES ARE 0.4264 TIMES CURVE A
INTENSITIES.
3 CURVE C-PRODUCES TOTAL PRECIPITATION OF 2.72 INCHES IN
24 HOURS. INTENSITIES ARE 0.1933 TIMES CURVE A
INTENSITIES.
RAINSTORM VOLUMETRIC
DESIGN CURVES
154
FIGURE 49
-------
A STORM DRAINAGE AREA ACRES
C RUNOFF FACTOR
To TIME OF CONCENTRATION AT POINT CONSIDERED
TP TIME UPSTREAM SYSTEM REACHES CAPACITY
To TIME OVERFLOW BEGINS
AT INCREMENT OF TIME
IM MAXIMUM INTENSITY AT TIME OF CONCENTRATION
Ip INTENSITY AT UPSTREAM SYSTEM CAPACITY
IQ INTENSITY WHEN OVERFLOW BEGINS DUE TO
DOWNSTREAM SYSTEM CAPACITY
Qs RATE OF SANITARY FLOW CFS (AVERAGE DAILY)
Qo RATE OF STORM FLOW CFS
QT RATE OF TOTAL FLOW CFS
Qp RATE OF FLOW TO STORAGE CFS
QO RATE OF OVERFLOW CFS
Vp VOLUME TO STORAGE AC-FT.
Vo VOLUME OF OVERFLOW AC-FT.
DESIGN RAINFALL INTENSITY CURVE
10 12 14 16
T TIME IN HOURS
II 20 22 24
f O RM U LAC
IM FROM CURVE FOR GIVEN TO
Ip = UPSTREAM LINE CAPACITY (CFS)-Qs
CA
Q0 sCIA UPPER LIMIT I«Ip
QT = Qo + Qs
Qp =QT QP MAX.= CAP. DOWNSTREAM LINE
Io - QT- DOWNSTREAM LINE CAPACITY (CFS) Q0 = QT-_DOWNSTR£AM LINE CAPACITY
To =0.25-^P-(TDrO.25)
Vp = (AVE.) QP- AT- 0.08264
Vo =(AVE.) Qo'Ar-0.08264
Tp » 0.25- Y-( TD- 0.25)
TABLE OF COMPUTATIONS
r
MRS
AT
MRS
Qo
CFS
QT
CFS
Qp
CFS
VP
AC-FT.
ACC.Vp
AC-FT
Qo
CFS
Vo
AC-FT
ACC. Vo
AC-FT.
VOLUMETRIC ANALYSIS
COMBINED SEWAGE SYSTEMS
155
FIGURE 50
-------
TABLE 17
SUMMARY OF COMBINED SEWAGE a OVERFLOW QUANTITIES
PLAN B - 1
SYSTEM
8EAVER AVE.
CLOSES CREEK
HICKMAN-CNAIJTAUeUA
FRANKLIN-ARLINGTON
COLLEGE-ARLINGTON
INDIANA 2110 AVE.
FRANKLIN-UNIVERSITY
KEO-GRAND « 1ST » GRAM)
WALNUT 1 1ST
COURT STREET 1 1ST
ELM STREET 1 1ST
INGERSOLL RUN
• 1 ROLAND LIFT TO GRAND
BEIM 81 ROLAND TO 1ST 1 MAPLE
E. DES MOINES AVE. < E, 1ST.
E. GRAND AVE. & E. 1ST
E. LOCUST S EIST
E. WALNUT a E. 1ST
E. COURT ST. 8 E. 1ST
S.E. 8TH ST. • SIPHON
E. I8TH ST. t COURT AVE.
REMAINING DRAINAGE AREA
TOTALS
AD
ACRES
0.00
1493.83
0.00
ii2.ee
ICC. 09
17.70
63. 80
wo.ee
436.38
75.88
98.19
O.OO
288.07
10.56
0.00
ne.es
27.70
VS. 20
118.20
135.87
ISO. 30
45,457.82
148. 1011. 00
OS
CFS.
3.81
3.07
0.07
0.73
O.UI
O.OS
O.UO
i.ee
3.99
0.23
0.33
0.00
3.20
0.23
o.oe
O.K3
o.oe
0.11
0.13
V.OI
1.13
211.93
6"
IP
IN/HR
0.00
0.00
0.00
0.71
0.78
1.145
0.7U
O.OU
O.60
0.614
0.80
0.00
0.18
H.B3
0.00
2.140
2.31
I.9S
0.73
0.18
3.S2
VP
AC. FT
7.6U
13S.OI
O.IK
28.31
N2.3H
14.88
10.77
ion.ee
88.38
23.96
26.26
O.OO
S3. SI
3.«7
0.12
3U.IO
8.02
13.12
ID. 01
27.02
38.82
965.47
24 HOU
VPS
AC. FT
7.BH
7.27
0.114
I.UI
o.ei
0.10
0.78
3.72
7.90
O.K8
o.es
O.OO
e.3H
o.ue
0.12
0.85
0.12
0.22
0.28
7.814
2.2U
19.38
! RAINSTORM
VPD
AC FT
0.00
425 .74
0.00
27.80
141 .53
11.78
18.88
100.87
77.49
23.148
2H.BI
0.00
17. 17
3.01
0.00
33.25
7.80
12.80
13.73
18.08
se.sa
916.11
vo
AC FT
0.00
0.00
0.00
14.27
6.ei
0.27
2.23
26.63
43.88
3.08
2.eo
O.OO
30.80
0.00
0.00
0.00
0.00
0.00
0.00
18.82
0.00
12,034.39
12,178.69
vos
ftXLFI
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
2.72' 24 HO
I MAX
IN/MR
0.00
0.00
0.00
0.814
o.se
0.77
0.77
0.32
0.38
o.se
O.S8
O.OO
0.38
0.87
0.00
0.3S
0.3S
0.311
0.33
0.38
0.88
VP
AC^FT
7.5U
200.27
O.lll
10. 01
22.30
2.38
8.57
61.16
62.44
12. S3
13.10
0.00
314.82
1.83
0.12
18.85
3.70
6.08
0.118
20.714
18.03
515.18
VPS
AC FT
7.5U
7.27
O.lll
l.ll
0.81
0.10
0.78
3.72
7.90
o.ue
O.OS
0.00
0.3)4
O.Ue
0.18
0.88
0.12
0.28
0.26
7.814
2.214
19.31
» RAINSTORM
VPD
AC FT,
0.00
193.00
0.00
11.60
21.148
2.28
7.78
87.113
54.54
12.07
12.145
0.00
28.18
1.37
0.00
18.10
3.S8
6.96
0.23
12.80
10.78
465.84
VO
AC_FT
0.00
0.00
0.00
0.00
0.00
0.00
0.48
0.00
0.00
0.00
0.00
0.00
8.08
0.00
0.00
0.00
0.00
0.00
0.00
14.72
0.00
5,464.28
5,479.17
VOS
AC FT
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
LAN
B - 2
BEAVER AVE.
CLOSES CREEK
HICKMAN-CHAUTAUGUA
FRANKLIN-ARLINGTON
COLLEGE-ARLINGTON
INDIANA-2NO AVE.
FRANKLIN-UNIVERSITY
KEO-efiANO « 1ST t GRAND
WALNUT 1 1ST
COURT ST. 1 1ST
ELM ST. a 1ST
INGERSOLl RUN
81 ROUND LIFT TO GRAND
BELOW Bl ROLAND TO 1ST 1 MAPLE
E. DES MOINES AVE. 8 E.IST
E. GRAND AVE. a E. 1ST
E. LOCUST & E. 1ST
E. WALNUT a E. 1 ST
E. COURT a E.IST.
S.E. 9TH 1 SIPHON
E. I8TH ST. I COURT AVE.
REMAINING DRAINAGE AREA
TOTALS
0.00
100.83
0.00
II2.8B
166.09
17.70
03.80
W43.ee
330.38
75.88
88.18
828.18
288.07
io.se
0.00
110.05
27.70
VS. 20
148.20
135.07
150.30
148,021.03
19, 191. 00
3.81
3.87
0.07
0.73
O.UI
0.05
0.140
i.ee
3.K8
0.23
0.33
2. S3
3.20
0.23
0.06
O.U3
0.00
0.11
0.13
U.OI
1.13
£6.96
0.00
0.28
0.00
0.71
0.78
I.US
0.76
0.61
0.78
0.814
0.80
O.IB
0.18
U.53
0.00
2.UO
2.31
I.8S
0.73
o.ie
3.62
7.5M
23.US
0.114
28.31
»2. 3D
U.88
16.77
iou.ee
85.38
23.88
28.20
72.87
53.61
3.H7
0.12
3U.IO
8.02
13.12
114.01
27.02
38.82
02e.se
7.514
7.27
0.114
I.UI
o.ei
0.10
0.78
3.72
e. si
o.ue
0.86
3.10
6.31
o.ue
0.12
0.88
0.12
0.22
0.28
7.9H
2.214
51.47
0.00
10.18
0.00
27.80
UI.53
U.78
15.88
100.87
76.19
23.U9
21.61
69.67
U7.I7
3.01
0.00
33.25
7.80
12.80
13.73
19.08
38.se
777.11
0.00
11.26
0.00
U.27
5.61
0.27
2.23
25.53
82.08
20.se
27.141
151.61
30.80
0.00
0.00
O.OO
0.00
0.00
0.00
19.52
0.00
I2.U2S.BU
12,832.91
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
e.ee
O.U8
0.05
1.81
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
8.71
0.00
0.38
0.00
0.5U
o.se
0.77
0.77
0.32
0.39
0.58
0.68
o.ue
0.36
0.57
0.00
0.3S
0.35
0.31
0.33
0.38
0.58
7.6U
18.23
O.IU
10. 01
22.30
2.38
8.87
81.18
US.OO
12.83
13.10
en .70
31. aj
1.83
0.12
16.86
3.70
0.08
O.U8
20. 7U
19.03
ses.ce
7.6U
7.27
O.IU
I.UI
0.81
0.10
0.79
3.72
0.91
o.ue
0.86
4.35
6. 31
o.ue
0.12
0.88
0.12
0.22
0.20
7.814
2.2U
52.70
0.00
10.88
0.00
IU.OO
2I.U8
2.28
7.78
57 .U3
U2.78
12.07
I2.US
60.35
28. US
1.37
0.00
16.10
3.58
5.88
6.23
12.80
10.78
332.38
0.00
2.81
0.00
0.00
0.00
0.00
o.ue
0.00
35.02
11.12
11.18
38.ee
8.68
0.00
0.00
0.00
0.00
0.00
0.00
U.72
0.00
o, em .33
5,755. 2U
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
3.0U
0.21
0.29
0.80
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
1.20
DESCRIPTION OF TERMS
AD - COMBINED SEWER STORM DRAINAGE AREA
OS - AVERAGE DAILY FLOK OF SANITARY SEWAGE
IP - MAX. PERCIPITATICN RATE, INCHES PER HR.,
ENTERING SYSTEM
VP - VOLUME ENTERING SYSTEM IN 214 HRS. (TOTAL
SANITARY PLUS STORM FLOWS)
VPS - SANITARY PORTION OF VP
VPD - STORM PORTION OF VP
VO - (TOTAL. RUNOFF + OS) -VP
VOS - VOLUME OF COMBINED SEWAGE OVERFLOW TO
RIVE*
I MAX - MAXIMUM RAINFALL INTENSITY FOR TIME
OF CONCENTRATION
REMAINING DRAINAGE AREA - SEPARATE
SEWERS
-------
flows and the quantity of combined sewer overflow from each area.
Both the 6-inch and 2. 72-inch design rainfalls are listed for the two
Plan B alternatives.
Two rainfall intensity values are given: IP and I Max. IP is the
intensity in inches per hour which will produce a runoff equal to
the capacity of the sewer in question, and is determined by the equa-
tion given in Figure 50. I Max. is the maximum intensity from the
design curve for the time of concentration to the point in quesjtion.
The value given in the table applies to the 2. 72 -inch rainfall only.
Combined sewage overflowing to the river, VOS in the table, is zero
for Plan B-l. In Plan B-2 the combined sewage overflow is 9.71 acre-
feet for the design 6-inch rainfall and 4. 20 acre-feet for the 2. 72-inch
24 -hour rainfall.
Quantity of Storm Water Discharge
Storm water discharge quantities have been developed for all areas hav-
ing separated systems. For Plans A and B, separate storm water is
discharged untreated to the streams; for Plan C, storm water discharge
quantities provide the basis of design for treatment facilities.
rainfalls producing runoff were included in the analyses. The Ra-
tional Formula was used for determining peak flows. Volumetrically,
all holding ponds are designed to contain the 6 -inch rainfall. Coeffi-
cients of runoff were based on rainfall-runoff relationships established
in this study. The rainfall-runoff study, described in Section VII, also
provided data on the intensity of high frequency storms. An analysis
of 126 intense storms occurring from 1951 to July, 1967 produced the
intensity-duration-frequency relationships shown in Table 18.
A detailed basis of design is described for each of the facilities evalua-
ted.
TABLE 18
RAINFA.LL INTENSITIES FOR INTENSE STORMS
Rainfall Intensity in Inches Per Hour
Return Period - Years
Duration
5 min.
10 min.
20 min.
30 min.
1 Hr.
2 Hr.
2
5. 3
4. 1
2.9
2. 3
1.4
0. 83
1
4.6
3. 5
2.4
1.9
1. 2
0. 70
0. 5
3.8
2.9
2. 0
1. 5
0. 91
0. 53
0. 2
2. 7
1.9
1. 3
0. 98
0. 59
0. 33
157
-------
COMBINED SEWER OVERFLOW ABATEMENT SYSTEMS
Individual systems, or areas served by a system of overflow intercep-
tors and treatment facilities, are described herein. The methods con-
sidered for elimination of overflows are discussed, and illustrations,
design criteria, construction costs, and operation and maintenance
costs are given for each alternate.
The "Location Plat, " Figure 57 at back of this discussion, shows the
relationship of each facility to the overall Plan.
Two of the proposed schemes, Plans B-l and B-2, deal with the inter-
ception and treatment of combined sewer overflows.
Plan B-l
In Plan B-l, no overflow from the combined sewer systems would be
permitted. The plan includes separation of certain areas where inter-
ception and treatment are deemed impractical. The improvements pro-
posed for each of the individual systems in Plan B-l are briefly de-
scribed as follows:
(1) The Closes Creek System includes the construction of two
retardation basins for storm runoff containing a small percentage of
combined sewer overflow, separation of two small isolated areas, and
the Prospect Road Impoundment for storage of overflows.
(2) The West Side Interceptor System includes separation of
a small area along Interstate 235 and enlargement of the West Side
Storm Interceptor Box.
(3) The Ingersoll Run System, above the present overflow
structure, will be separated entirely.
(4) The East Side System includes construction of a 48-inch
interceptor sewer to transport combined flows from the northern part
of the basin and modifications and extension of the East Side Storm
Interceptor Box.
(5) The East 18th Street System consists of diverting com-
bined flows to the Dean Impoundment for treatment.
(6) The South Side Trunk System improvements consist of a
lift station for pumping combined sewer overflows into a storm out-
fall for subsequent treatment at the Case Lake Treatment complex.
158
-------
(7) The Scott Street Lift Station and Storm Outfall
transport combined sewer overflows from the central part of the
city to the Case Lake TreatmentComplex.
(8) The Case Lake Treatment Complex, located across the
river from the existing Des Moines Wastewater Treatment Plant,
will provide treatment to all combined sewer overflows not treated
elsewhere in the individual systems.
Plan B-2
In Plan B-2 small quantities of overflow will be permitted during high
intensity storms and greater use will be made of existing facilities
than is proposed for Plan B-l. Only small areas of combined sewers
will be separated. The improvements proposed for each of the indivi-
dual systems in Plan B-2 are briefly described as follows:
(1) The Closes Creek System improvements would consist of
separating all the combined sewers in this basin (approximately 107
acres) plus two additional small areas and construction of the Pros-
pect Road Impoundment to serve the reduced combined sewer over-
flow.
(2) The West Side Interceptor System would include separation
of a small area along Interstate 235 and minor improvements to the
West Side Storm Interceptor Box to permit it to be used as is.
(3) The Ingersoll Run System outlet sewer would be provided
with a diversion structure to divert approximately 60 percent of the
annual overflow to the Southwest Outfall and ultimately to the Case
Lake Treatment Complex.
(4) The East Side System improvements would consist of a
retardation basin which would return overflow to the system and modi-
fication and extension of the East Side Storm Interceptor Box.
(5) The East 18th Street System consists of diverting over-
flows to the Dean Lake Impoundment for treatment as in Plan B-l.
(6) The South Side Trunk System improvements would consist
of an overflow pumping station as in Plan B-l.
(7) The Scott Street Lift Station and Storm Outfall will trans-
port overflows to the Case Lake Treatment Complex as in Plan B-l;
however the size of the facilities will be reduced.
159
-------
(8) The Case Lake Treatment Complex will be constructed
as in Plan B-l; however the size of the facility will be reduced.
The Closes Creek System
This system is located in the northwest sector of the City. The area
involved is that served by the separate and combined systems tribu-
tary to the West Side Interceptor Sewer above Znd and Franklin A,ve-
nues, and consists of approximately 4050 acres. Combined sewers
presently drain 406 acres to this system. The present population of
the area is estimated to be 44, 000. Land use is primarily residential
with light commercial in neighborhood shopping centers.
Closes Creek Retardation Basins. The Closes Creek watershed con-
tains approximately 107 acres served by combined sewers. Overflow
from these sewers discharge to Closes Creek. In Plan B-l two im-
poundments would be used to hold storm runoff containing these over-
flows for a period of time, with subsequent release to the Des Moines
River at a controlled rate. Dams would be constructed on the two
branches of Closes Creek immediately south of Hickman Road at 24th
and 27th Streets. These are shown on the location plat and in Figure
51. The larger of the two impoundments, at 27th and Hickman, will
serve a drainage area of 1104 acres and have an operating volume of
164 acre-feet between elevations 90. 0 and 100. 0. The height of the
embankment is 52 feet and a spillway capacity of 1,400 cfs is provided
to protect the embankment and property downstream. A 42-inch dis-
charge line will permit maximum release of the operating volume
within 24 hours and release of the entire volume with 48 hours. The
smaller of the two impoundments will serve a. drainage area of 283
acres and have an operating volume of 44 acre-feet between eleva-
tions 80. 0 and 86. 0. A spillway capacity of 750 cfs is provided to
protect the embankment and the property downstream. The height of
embankment is 43 feet. A 27-inch discharge line will provide for
maximum release of the operating volume within 24 hours, and re-
lease of the entire volume within 48 hours. Both impoundments would
have intake structures for controlled drawoff at selected levels. The
impoundment areas would be fenced to protect the public.
Each impoundment has capacity in the operating range to store run-
off from approximately a 3-inch rain, or will provide a detention
time of 1 day in the large impoundment and 2 days in the small one
at the low operating level. High runoffs up to the 3-inch rain can be
stored for a period of 5 to 7 days to reduce the pollutional load, then
be discharged to the river at a controlled rate. Rainfall accumulations
of greater than 3 inches which occur during the holding period may
overflow the impoundment, depending upon the duration and intensity.
160
-------
Even so, a 6-inch volumetric, 24-hour rainfall would have a flow-.
through time of approximately 24 hours in the large basin and 36
hours in the small basin. Based on the monitoring of this watershed
at Station 0-2, it was determined that BOD strengths of about 30
mg/1 can be expected from the 3-inch rain and 400 to 600 mg/1 of
total suspended solids. The average of 19 analyses showed suspen-
ded solids to be about 20 percent volatile. Based on studies of
treatment of storm runoff by Evans, et al. (16), BOD and suspended
solids reductions of 35and75 percent, respectively, would be con-
servative for 24-hour detention. The quality of the retardation basin
effluents after 24-hours detention of the 3-inch rain should then be in
the neighborhood of 20 mg/1 of BOD and 100 to 150 mg/1 of suspended
solids. For smaller rainfalls and runoffs that are stored for a period
of several days, the effluent quality would be expected to be propor-
tionately better.
An analysis of oxygen demands in the runoff indicates that the impound-
ments will remain aerobic without the need for mechanical aeration.
No odor problems should be encountered from aerobic basins. Sedi-
ment will accumulate in the basins and will have to be removed eventu-
ally. Due to the depth and size of the impoundments cleaning will be
infrequent and 10-year intervals would be adequate. No lining will be
required to prevent seepage. The sides of the basins would be seeded
to grass to prevent erosion. Mowing and other routine maintenance
will be required to maintain the sites in good condition.
The estimated construction cost for the two retardation basins is
$1, 600, 000, including $730, 000 for land acquisition. Operation and
maintenance includes periodic inspection, site maintenance, periodic
cleaning, and operation of discharge facilities and are estimated to
cost $7, 600 annually.
27th & Payne Separation. This is an area of only 8.85 acres at 27th
Street and Payne Road, as shown on the location plat. It is in the Bea-
ver Avenue System which is essentially a separate system pumped by
the Prospect Road Lift Station. The cost of separation was minimal
for this area since it is adjacent to a natural ravine. The construction
cost is estimated to be $20, 000. This project is included in both Plan
B-l and B-2.
7th & Franklin Separation. This is also a small area, 11.93 acres,
located at 7th Street and Franklin Avenue. A small separate storm
sewer located at this intersection discharges to the 36-inch West Side
Interceptor one-half block east of the intersection. This separate storm
sewer can be discharged to the Des Moines River at minimal cost. The
estimated construction cost is $11,000. The project is included in both
Plan B-l and B-2.
161
-------
14 __ 15
48"
4 »
1
1
'CM
to
CHUTE
PLAN
20.75^ ^-30.00 M
24.75 24.50^3
SECTION
TYPICAL GRIT CHAMBER
SCALE l"- 30'
HICKMAN
STILLING BASIN
32' x 32 -
ROAD
42
SPILLWAY
DAM
INTAKE STRUCTURE
-RETARDATION BASINS-
(PLAN B-l ONLY)
162
-------
N
SCALE I" = 800'
EXISTING
'LIFT STATION
,GATE STRUCTURE
•PROPOSED GRIT CHAMBER
..CLOSES CREEK
JDVERFLOW LINE
DES MOINES
X
AERATION
'PIPING
EXISTING
INTERCEPTOR,
SEWER
XPLAN B-I ONLY>
BLOWER BUILDING::
\\
^PRESSURE LINE-
LIFT STATION-
POND DATA
TOP OF DIKE 27.0
BOTTOM ELEV. 17.0
MAX. WS. 24.0
OPER. LEVEL 20.0
OPER. STORAGE 99 AC. FT. for B-I, 71 AC. FT. for B-2
TOTAL STORAGE 168 AC. FT. for B-I, 121 AC. FT. for B-2
OVERFLOW STRUCTURE
AND DRAIN LINE
-GRIT CHAMBER
PROPOSED
"STORM SEWER
n
FRANKLIN
GATE STRUCTURE-
ARLINGTON AVENUE
OVERFLOW LINE
COLLEGE
GATE STRUCTURE-
-------
Prospect Road Impoundment. A holding pond would be constructed in
the Crocker Woods area north of Prospect Road. The purpose of this
pond is to store all combined sewage flows in excess of the interceptor
capacity from Arlington Street and above, and to reduce flows in the
West Side Interceptor sufficiently to prevent overflows from the inter-
ceptor above Grand Avenue. The areas contributing to the pond are
designated on the Location Plat and the proposed facilities are shown
in Figure 51.
For Plan B-l, combined flows would be picked up and carried by gra-
vity sewers to the lagoon from the following points: On the 30-inch
Closes Creek Sewer near the existing lift station, the Franklin Street
Sewer at Arlington Street, and the College Avenue Sewer at Arlington
Street. Sewers from the latter two points would be combined at Frank-
lin Street enroute to the lagoon.
Grit chambers would be provided in each line before entering the la-
goon. They consist of concrete basins with .a transverse grit-storage
channel as shown in Figure 51. Cleaning of the basins would be on a
routine basis by a mobile crane with a clamshell bucket. The criteria
for the grit chamber design is as follows:
Removal Efficiency 80% of 35 mesh grit.
Grit Storage 20 CF/MG from 6" design storm.
Flow-through-velocity -1.0 fps at maximum flow.
The operating capacity of the pond is 99 acre-feet, which is sufficient
to contain the combined flows resulting from a 6-inch, 24-hour volu-
metric rainstorm. In addition, a minimum water depth of 3 feet would
be maintained to prevent an odor nuisance from solids that may settle
out and to maintain biological growth for treatment if required.
A lift station is provided to return stored sewage to the 36-inch inter-
ceptor sewer during low flow periods when the existing sewer system
can handle it. An overflow and drawoff structure is also provided to
discharge treated effluent to the river in the event excessive flows pro-
hibit pumping the pond contents back to the system. With the modifica-
tions to the downstream system this should be a very infrequent occa-
sion.
Because of the high BOD load to the pond, a diffused air system is pro-
vided to maintain aerobic conditions during storage. A.eration capacity
is designed to satisfy the BOD requirement of the 6-inch design rain,
but would not maintain solids in suspension. Diffusion piping is located
in 3-foot deep, V-cut channels to provide adequate depth at low water
levels and increase efficiency for peak demands.
164
-------
If excessive flows prevent pumping the stored sewage back to the sys-
tem, the contents of the pond would be stored for up to 7 days, then
released at a controlled rate to the stream. The operating storage of
the pond is designed to contain a 6-inch rainfall, whereas the average
annual 24-hour maximum storm is a 2. 7-inch rainfall. Very infre-
quently would a 7-day accumulation of rainfall equal 6 inches. [Even
if a 6-inch rainfall occurred when the pond was full, the pond w!ould
provide almost 2 days detention under aeration.
Criteria for design of the holding pond is as follows:
Store 6" design storm 99 Acre-feet, depth = 4. 0 feet
Total Pond Volume 168 Acre-feet, total depth = 7. 0 feet
BOD: 6" Design Storm- 65 mg/1, l6,8701bs.
2. 72" Annual Max. Storm- 75 mg/1, 11, 600 Ibs.
A.ssume 30% of BOD5 exerted in first 24 hours of storage.
Blowers - 3 Each, firm capacity for 6" Design Storm,
5000 cfm plus standby
Effluent Lift Station - Firm Capacity of 3200 gpm
Pump down Operating Pool in 7 days.
Because this facility is located adjacent to a heavily used recreation
area, the site would be fenced, suitable landscaping would be provided,
and the site must be maintained in an attractive condition.
The estimated construction cost for the Prospect Road Impoundment is
as follows:
(1) Holding pond, complete, including land ac-
quisition ($120,000), aeration system, struc-
tures, fencing ani landscaping $400,000
(2) Line from Closes Creek bypass including
grit removal $ 65, 000
(3) Lines from Arlington and College Ave.
Systems including grit removal $412, 000
(4) Sewage Lift Station and Pressure Line $ 75, OOP
Total Estimated Construction Cost $952, 000
165
-------
The estimated annual operation and maintenance cost including power,
labor, equipment and supplies is $22, 500.
Closes Creek Separation With Impoundment (Plan B-2). The Closes
Creek Watershed contains approximately 107 acres drained by com-
bined sewers, which is everything west of Harding Road that is shown
on the location plat as draining to the Prospect Road Impoundment.
The sanitary drainage area is 1673 acres and the present population
is estimated to be 12, 300.
The alternate presented in Plan B-2 is separation of the 107 acres
served by combined sewers in the Closes Creek watershed. This is
considered because of the large domestic load compared to the com-
bined sewer area. The two retardation basins on Closes Creek would no
longer be needed to treat combined sewer overflows. Separation of this
area also would greatly reduce the flow and BOD to the Prospect Road
Impoundment, thus reducing the volume and aeration requirements.
The areas to be separated include system numbers 9, 10, 11, 12 and
13 in the separation study area (Section IX) and approximately 10 addi-
tional acres outside of this area. The estimated construction cost of
this separation is $511, 000. The Prospect Road Impoundment would
be reduced in operating volume from 99 acre-feet to 71 acre-feet. The
total volume of the reduced pond is 121 acre-feet. The depth remains
the same. The Closes Creek overflow line and grit chamber would not
be required, but the Arlington Avenue overflow line and grit removal
unit would remain the same.
Because of the reduced flow and BOD load to the pond, float-type sur-
face aerators are used in the reduced pond in place of a diffused air
system. These will provide sufficient dissolved oxygen to maintain
aerobic conditions during storage of the 6-inch design storm, but
would not maintain all suspended solids in suspension.
During winter months, the float-type aerators would be removed from
the pond due to freezing and the bypass gates on Arlington Avenue would
be maintained closed to take all storm runoff to the system downstream.
The volume of snow-melt or early spring and late fall storm runoff
would not exceed the downstream capacity of the West Side Interceptor.
The effluent lift station remains as before and the overflow structure
is included to provide the capability of overflowing to the river after
a period of treatment, if required.
Criteria for design of the holding pond is as follows:
166
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Store 6" Design Storm - 71 Acre-feet, Operation, depth = 4. 0 feet
Total Pond Volume - 121 Acre-feet, Total depth = 7. 0 feet
BOD: 6" Design Storm - 55 mg/I, 10,5201bs.
2. 72" Annual Max. Storm - 59 mg/1, 6, 120 Ibs.
Assume 30% of BODs exerted in first 24 hours.
Aeration - 7 aerators for 02 distribution @ 24 Ibs. O^ /hour each
= 4200 Ibs. Oz per day.
Effluent Lift Station - Firm capacity of 3200 gpm, pump down op-
erating pool in 5 days.
The estimated construction cost for this separation and the reduced hold-
ing pond is as follows:'
(1) Holding Pond for 71 Ac-ft. , complete, including
land acquisition ($100,000), aeration system,
structures, fencing and landscaping $295, 000
(2) Line from Arlington Ave. Systems - including
grit removal $412,000
(3) Sewage Lift Station and pressure line $ 75, OOP
Total estimated construction cost $782,000
The estimated annual operation and maintenance cost including power,
labor, equipment and supplies is $17, 000.
West Side Interceptor
The area of concern is that area drained by combined sewers west of
the Des Moines River and north of the Raccoon River which is indica-
ted on the Location Plat as flowing to the Case Lake Treatment Com-
plex. Also included is the area to be separated lying north of the Free-
way along the Des Moines River. The service area, includes the cen-
tral business district west of the river. Land use is heavily commer-
cial with medium and high density residential. The present population
is approximately 25, 000. An additional 25, 000, served by the separate
Northwest Outfall above the Closes Creek Basin, is also tributary to
this system. The area drained by combined sewers is 1028 acres.
167
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Separation of Freeway System (Plans B-l and B-2). This area is lo-
cated between the Freeway and University Avenue and between 2nd
Avenue and 14th Street. It is served by separate sanitary sewers
which are intercepted by a storm drainage system installed during
construction of the Freeway. Flow is west to Keosauqua, and ulti-
mately into a large system known as the Birds Run. The Birds Run
Storm Sewer is an 8-foot diameter, or equivalent section, which
discharges to the West Side Storm Box between Grand and Locust
Streets. By virtue of this separation, combined sewage overflows
to the Birds Run will be eliminated and this storm sewer will be dis-
charged directly to the Des Moines River. This separation project
is included in both Plan B-l and B-2.
Separation would be accomplished by constructing a portion of Sani-
tary System F included in Plan A. The portion to be constructed would
include lines between Manholes F13 to F33 to F12, F12 to F36 to F41.
The estimated construction cost is $136, 000.
Enlargement of West Side Storm Box (Plan B-l). The diversion of
storm flows from the Closes Creek and Arlington Avenue areas will
leave sufficient capacity in the West Side Interceptor to carry all other
combined flows above Grand Avenue. At Grand Avenue a new bypass is
provided which will divert excess storm flows to the West Side Storm.
Box below the Birds Run outlet. The section of the existing storm box
above Birds Run will be abandoned and Birds Run will discharge direct-
ly to the river. For Plan B-l, the existing 6-foot by 13-foot storm box
from this point to the Scott Street Dam would be reconstructed to carry
all excess combined flows from the 60-inch West Side Interceptor.
Figure 55 illustrates layout of the proposed improvements. An aerial
view of the Des Moines River, looking north from the Scott Street Dam
to the Central Business District, Is shown in Figure 52.
The new storm box will be 9 feet by 15 feet and will continue beyond the
Scott Street Dam to the south bank of the river. The line would be a box
section under the river bed and would terminate at a large grit removal
chamber on the west bank of the river between the Chicago Great Wes-
tern R. R. bridge and the Scott Street Dam. In addition to the Grand
Avenue bypass, new connections to the storm box are provided at Wal-
nut, Court, and Elm Streets.
The estimated construction cost of the work under Plan B-l is as follows
(1) Reconstruction of the storm interceptor box $920, 000
(2) Grand Avenue connection to storm box 36, 000
(3) Walnut Street connection to storm box 15, 000
168
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CASE LAKE
IMPOUNDMENT
AREA
DOWNTOWN DES MOINES-
UOCATION OF OVERFLOW INTERCEPTION
AND PUMPING FACILITIES , PLANS B-l & B-2
E. I8TH STREET OVERFLOW IMPOUNDMENT
PROPOSED OVERFLOW POLLUTION
ABATEMENT FACILITIES
169
FIGURE 52
-------
(4) Court Street connection to storm box $ H, 0°°
(5) Elm Street connection to storm box 10. 000
(6) Extension of West Side Storm Box to Grit
Chamber 480.000
Total Estimated Construction Cost $1,472, 000
West Side Storm Box Improvements Without Enlargement (Plan B-Z).
As an alternate to expanding the West Side Storm Box, Plan B-Z calls
for using the storm box at its present capacity and permitting a small
volume of combined sewage to discharge to the river during high in-
tensity storms. As shown in Table 17, overflows would occur at Wal-
nut, Court and Elm Streets. For the 6-inch design storm the total
discharge to the river from these three overflows amounts to 7. 80
acre-feet, and for the 2. 72-inch rain 3. 54 acre-feet is discharged.
The existing box would be extended to the proposed grit chamber as
in Plan B-l and the Birds Run outlet modification would be construc-
ted. Also, the new connections to the storm box would be made.
The estimated construction cost of the work to be accomplished un-
der B-2 is as follows:
(1) Grand Avenue connection to storm box $ 36, 000
(2) Walnut Street connection to storm box 15, 000
(3) Court Street connection to storm box 11, 000
(4) Elm Street connection to storm box 10, 000
(5) Extension of West Side Storm Box to
grit chamber 304, OOP
Total Estimated Construction Cost $376, 000
Ingersoll Run System
Ingersoil Run Separation (Plan B-l). The Ingersoll Run System is a
large combined sewer system west of the central business district
and north of the Raccoon River. It is designated in the Location Plat
as being the area to be separated under Plan B-l.. This combined
sewer system serves an area of 929 acres and has a population of
170
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approximately 10, 000 people. Land use is medium and high denisity
residential and commercial. The Ingersoll Run overflow discharges
to the Raccoon River immediately east of the Fluer Drive Bridge.
A very limited area is available between this outlet and the Raccoon
River, a portion of which is developed as an industrial area. Due to
the limited area available, Plan B-l is to separate this system to
the extent necessary to eliminate combined sewage overflows. This
would be accomplished by construction of Storm Sewer System Nos.
16, 19, 21 and 23, Sanitary Sewer Systems Nos. A, B, C and D,
and a 215 acre portion of Storm Sewer Systems 24, 25 and 27- All
the above systems are shown in the separation study area in Plan A.
Including existing separate storm sewer systems, the area com-
prises 749 acres.
The estimated construction cost for this separation is $3, 790, 000.
Ingersoll Run Diversion (Plan B-2). The existing combined sewer
systems in the Ingersoll Run Watershed would remain as they now
exist under Plan B-2. A. very simple diversion near the outlet of
the Ingersoll Run overflow sewer would divert a portion of the over-
flow to the Southwest Outfall which runs past the outlet. The South-
west Outfall has reserve capacity from this point to the Main Outfall,
based on estimated 2020 flows, to carry an additional 95 cfs. A gate
structure would be provided on the diversion to limit flows to that
amount. This additional flow in the Southwest Outfall would be by-
passed to the overflow collection system at Scott Street for subse-
quent treatment at the Case Lake Treatment Complex.
Based on rainfall-runoff relationships developed in Section VII, the
diversion of 95 cfs from this watershed would intercept rainfalls up
to 0.33 inches per hour intensity. From the studies of rainfall inten-
sities, it is estimated that this intensity would be exceeded by approxi-
mately 43 percent of the average annual March through November rain-
fall and 38 percent of the average annual rainfall. Also, this intensity
is exceeded only 0. 3 percent of the clock hours on an average annual
basis, or approximately 26 hours annually.
The estimated construction cost for the diversion structure is $25, 000.
East Side System
This area lies adjacent to the Des Moines River from Scott Street north
to nearly the City limits. It contains an area of 2, 240 acres, of which
544 are served by combined sewers. The present population is approxi-
mately 16,400. Land use is medium and high density residential and
commercial.
171
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The watershed is served by a 48-inch interceptor along the river
from the Main Outfall at Scott Street to near University Avenue.
A lift station located near Birdland Park discharges to a 36-inch
gravity line on Pennsylvania Avenue which carries the pumped
flow from the no'rth to the 48-inch East Side Interceptor. The com-
bined sewer area above the Birdland Station is 295 acres. Peak
wet weather flows exceed the capacity of the pump station and the
36-inch gravity line. An overflow weir located at the pump station
permits overflowing to the river.
East Side Overflow Sewer (Plan B-l). To eliminate the overflow
at Birdland Station, a 48-inch gravity line from that point to Grand
Avenue is proposed in Plan B-l. Because of a high bluff along the
east bank of the river from Birdland Station to University Avenue,
both tunneling and laying the pipe in encasement in the river were in-
vestigated. Tunneling was chosen because it was considerably cheap-
er than the river route. The tunnel section, approximately 3500 feet,
is 54-inch diameter due to minimum economical tunnel size.
At Grand Avenue, the new 48-inch line is connected to the existing
48-inch East Side Interceptor, as shown in Figure 55. A. new bypass
to the East Side Storm Box is provided for excess storm flow from
the Birdland area as well as for that contributed from the Grand Ave-
nue combined sewer. New overflows are also provided at Walnut and
Court Streets.
The existing East Side Storm Box has the capacity to carry all over-
flow from this system. At the termination of the existing storm box
at the Scott Street Dam, a box section under the river bed will carry
the storm flow to the large grit chamber on the west bank of the river.
The estimated construction cost of the items described above is as
follows:
(1) East Side Overflow Sewer from Birdland
Station to Grand Avenue $ 770, 000
(2) Grand Avenue junction box 15, 000
(3) Walnut Street connection to storm box 52, 000
(4) Court Street connection to storm box 46, 000
(5) Continuation of East Side storm box to
grit chamber 775, OOP
Total Estimated Construction Cost $1, 658, 000
172
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Birdland Park Retardation Basin (Plan B-2). As discussed pre-
viously, a new outfall to serve the growth north of Des Moines should
be located on the east side of the Des Moines River at some time in
the future. If the East Side overflow sewer from Birdland Station is
to be constructed, the City of Des Moines should give consideration
to increasing the size of this line to handle future flows from the north
and making it a part of the northeast outfall system.
With this in mind, a retardation basin in the Birdland Park area was
investigated under Plan B-2 as a means of deferring or eliminating
the need for construction of a separate overflow sewer. This facility,
located in the upper end of the Birdland Park Lake, is shown in Figure
53.
The basin would have an operating capacity of 23. 2 acre-feet. This is
sufficient to store the storm runoff in excess of the Birdland Station
pumping capacity, based on a 6-inch design storm. In addition, a 3-
foot low water depth would be maintained to prevent an odor nuisance
from solids which would settle out.
Flow to and from the basin would be by gravity. High water level in
the basin would be at elevation 21.0, which is 6 inches above the crown
of the 48-inch interceptor sewer, and the operating range would be 4. 0
feet. An overflow structure is provided in the basin at the 21.5 level
to prevent excessive surcharging in the interceptor and possible pro-
perty damage. Inspection of manholes during the study indicated a
surcharge considerably greater than this.
A diversion structure, located at Oxford Street and Guthrie A|venue,
would be of the overflow-weir type with a. flap gate for return of flow
from the basin when the water level in the sewer recedes. The basin
inlet structure would be provided with manually-ope rated, multiple-
level return gates as well as a flap gate on the outlet. This would per-
mit the basin to "float" on the level of the interceptor sewer or be
operated as a holding pond, depending on whether the return gates were
maintained open or closed.
Float-type surface aerators are provided to maintain aerobic condi-
tions in the basin in the event excessive runoff is required to be stored.
Because of the location of this facility in a heavily used park, exten-
sive landscaping and screening would be required.
Criteria for design of the retardation basin is as follows:
Store 6" Design Storm - 23. 2 Acre-feet, 4. 0 feet deep
173
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RELOCATE
..-TING STORM
iEWER
INLET-CONTROL
STRUCTURE
Q
£
£ EXISTING 42"
g EAST SIDE fNTERCEPTOR
\\\
OVERFLOW LINE TO POND
UTHRIE "
my.
^>
£ TOP OF DIKE ELEV. -24.0
° BOTTOM ELEV. - 14.0
I MAX. WATER SURFACE ELEV.-21.0
> OPERATING LEVEL ELEV. 17.0
OPERATING STORAGE -23.2Ac-Ft.
TOTAL STORAGE -39.0Ac-Fl.
B|ROLAND RETARDATION BASIN
174
FIGURE 53
-------
Total Basin Volume - 39. 0 Ac re-feet, 7. 0 feet deep
BOD: 6" Design Storm - 66 mg/1, 4170 Ibs.
2. 72" annual max. storm - 66 mg/1, 1650 Ibs.
Assume 30% of BOD5 exerted 1st day.
Aeration - 3 aerators @ 20 Ibs. O2/hour ea. = 1440 Ibs. /day.
The estimated construction cost for the Birdland Retardation Basin
is $224, 000. Annual operation and maintenance costs, including
power, labor, equipment and supplies are $10,000.
The estimated construction cost for the East Side System as proposed
under Plan B-2 would be as follows:
(1) Birdland Park Retardation Basin $ 224, 000
(2) Grand Avenue Junction Box 15, 000
(3) Walnut Street connection to storm box 52, 000
(4) Court Street connection to storm box 46, 000
(5) Continuation of East Side storm box to
grit chamber 775, OOP
Total Estimated Construction Cost $1, 112, 000
East 18th Street System (Plans B-l and B-2)
This system, including the 20th Street system which is tributary to it,
extends from 18th and Maury to the north City limits and lies adjacent
to the East side Interceptor area.. The area has heavy industrial de-
velopment, as well as extensive commercial and residential areas.
The present population is estimated to be 17,300, and the area includes
approximately 3, 000 acres. Approximately 150 acres, primarily resi-
dential areas, are served by combined sewers. These areas are lo-
cated in the upper end of the East 18th street system as shown in the
Location Plat, Figure 57.
To reduce the quantity of storm water mixing with the high strength in-
dustrial waste and to relieve flooding problems in the east 18th and
Maury areas, excess combined flows will be divered to a lagoon ad-
joining the upper end of Dean Lake. An aerial view of the Dean Lake
175
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impoundment is seen in Figure 52. A diversion structure at East 18th
and Court Avenue would route all combined sewage in excess of 11.5
cfs to the lagoon. The remainder would continue to the plant for treat-
ment. The layout of the lagoon and piping is shown in Figure 54. In-
cluded is a 66-inch pipe from East 18th Street and Court Avenue to
the lagoon and a 66-inch discharge line into the northern section of
Dean Lake. The total capacity of the lagoon would be 54. 60 acre feet
with an operating capacity of 32. 60 acre-feet between normal water
level of 12. 00 and maximum water level of 16. 00. This will be more
than adequate to store the runoff produced by a 6-inch design storm,
which is estimated to be 18. 7 acre-feet. Runoff would be stored for
7 to 10 days, then discharged at a controlled rate to Deans Lake.
A minimum of 3. 0 feet of water would be maintained in the lagoon to
prevent odor nuisances from solids that will settle out. Float-type
surface aerators are provided to maintain aerobic conditions, but are
required only after very heavy rainfalls. They would not be required
during the winter months and would be removed to prevent damage
from freezing.
Criteria for design of the Dean Lake Impoundment are as follows:
Store 6" Design Storm - 32. 6 Ac-Ft. , 4. 0 feet deep
Total Pond Volume - 54. 6 Ac-Ft. , 7. 0 feet deep
BOD: 6" Design Storm - 60 mg/1, 3200 Ibs.
2. 72" Annual Max, Storm - 60 mg/1, 764 Ibs.
Assume 30% of BOD exerted first 24 hours storage.
Aeration - 2 aerators @ 18 Ibs. O2/hour ea. = 864 Ibs/day
The estimated construction cost of the Dean Lake Impoundment and 66-
inch Diversion Line is $371, 000. Estimated operation and maintenance
cost is $4,400 annually.
South Side Trunk (Plans B-l and B-2).
The South Side Trunk drainage basin contains 2, 06 1 acres and has a
population at present of 15,300. Combined sewers serve 142 acres
of this basin, shown on the Location Plat, Figure 57, as the combined
sewer areas south of the Des Moines and Raccoon Rivers. The area is
primarily residential with neighborhood commercial areas.
176
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I
c
23
m
en
EXISTING E. 20TH ST. / /
SANITARY SEWER —- ' '
POND DATA
BOTTOM EL. 9.0O
OPER. LEVEL 12.00
MAX. W.S. 16.00
OPER. STORAGE 32.60 AC. FT.
TOTAL STORAGE 54.60 AC. FT
DEAN AVENUE
DIVERSION STRUCTURE
COURT AVENUE
OVERFLOW a DRAIN
STRUCTURE
VSURFACE.X
EXISTING E. I8TH ST.
INTERCEPTOR
DEAN LAKE IMPOUNDMENT
-------
All separate sanitary and combined flows from this area are tributary
to the existing siphon structure and storm water pumping station at
South East 9th and Jackson Streets. Combined flows from the low .
area adjacent to the Des Moines River are pumped to the siphon
structure, where excess flow discharges to the river.
The existing lift station would remain in service and an additional lift
station would be constructed to handle the overflow from the 9th Street
line. The new lift station would discharge into the storm outfall line
running to the Case Lake Treatment Facility. The estimated construc-
tion cost of the new lift station is $105, 000, and operation and main-
tenance costs are estimated to be $3, 100 annually.
Scott Street Lift Station and Storm Outfall (Plans B-l and B-2)
A large grit chamber would be constructed on the west bank of the Des
Moines River between Scott Street and the Chicago Great Western Rail-
road Bridge. Storm flows from the East and West Side Storm Boxes
would discharge to this chamber. Figures 52, 55 and the Location Plat,
Figure 57, show the location of this chamber as well as the lift station
and storm outfall.
The grit chamber would remove heavy grit and debris and would pro-
tect the lift station from damage. It would not remove fine grit since
this is accomplished at the treatment facility. On the basis of 20 cu-
bic feet of grit per million gallons, 3600 cubic feet of grit storage is
provided. This estimate of the quantity of grit is conservative, but not
unrealistic based upon experience with combined sewers in other loca-
tions (17). Cleaning of the basin would be on a routine basis by a mo-
bile crane with a clamshell bucket.
A large lift station will be constructed just south of East Van Buren
Avenue between SE 1st Street and SE 3rd Street. Under Plan B-l, this
lift station would contain 2 - 100, 000 gpm and 2 - 50, 000 gpm pumps
and would lift a maximum of 650 cfs of combined sewage approximately
47 feet into a surge tank. In Plan B-2, 'the lift station would handle
peak flows of 500 cfs, using 2-80, 000 gpm and 2 - 40, 000 gpm pumps.
The surge tank capacity would be sufficient to contain the peak flow for
a period of 3 minutes. The grit chamber described above, would be
connected to the lift station wet well by two 96-inch tunnels.
A gravity storm outfall would be constructed from the surge tank to a
large lagoon complex in the Case Lake area, located on the south side
of the river opposite the existing treatment plant. This gravity line
would consist of two 96^inch diameter pipes under" Plan B-l and one
108-inch diameter line under Plan B-2. The lines would operate under
178
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o
c
a>
rn
^ ,-
48"EAST SIDE OVERFLOW SE
RELOCATE
OVERFLOW
AT GRAND AVE
CONNECTIONS TO STORM
h- I —
•HI \ \ / XO< •' / ^ *'
k\\K. K -V
OVERFLOW INTERCEPTORS
AND
LIFT STATION
-------
pressure during maximum pumping conditions. At East 9th Street,
this line would pass above the existing gravity line which runs along
East 9th Street and siphons the Des Moines River enroute to the
Main Interceptor. The new storm overflow lift station for the South
Side Trunk area discharges to the storm, outfall at this point.
The estimated construction cost of the facilities is as follows:
Item Plan B-l Plan B-2
(1) Grit removal installation $ 210,000 $ 210,000
(2) Twin 96" tunnels from grit
chamber to lift station 375, 000 375, 000
(3) Lift Station 1,158,000 833,000
(4) Pressure lines, lift sta-
tion to surge tank 34,000 34,000
(5) Surge tank 118,000 118,000
(6) Storm outfall to Case Lake
Treatment Complex
Plan B-l, 2 - 96" lines 2,569,000
Plan B-2, 108" line 2, 167, OOP
Total Estimated Construction Cost $4,464,000 $3,737,000
Estimated annual operation and maintenance costs are $48, 000 for
Plan B-l and $44,000 for Plan B-2.
Case Lake Treatment Complex
This treatment complex is designed to handle combined flow from the
proposed storm water outfall. It is located in the Case Lake area di-
rectly across the river from the present treatment plant. The area
is considered unusable for development by local planning authorities,
partially because of location and partially because a portion of the
area is within the maximum flood pool for Red Rock Reservoir. The
infringement on the flood pool is minor, but has to be considered. The
dikes are designed to withstand the maximum flood elevations. Since
the complex would be handling flow that would otherwise add to the flood
pool, it is possible the infringement can be discounted.
180
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The general philosophy of the treatment complex was to provide a fa-
cility which could handle intermittent large flow from the storm wa-
ter outfall. Storm water flow for the Plan B-l design storm is 280
acre-feet/day, part of which may be received at a peak rate of 650
cfs. For Plan B-2, the design storm water volume to the Case Lake
complex is 350 acre-feet/day, with peak flows of 510 cfs. To treat
the above flows, two treatment schemes were considered. The dif-
ference in the two plans is the method of treating the overflow and
the expected quality of the effluent. The basic plan, shown in Figure
56, includes sedimentation ponds for removal of grit and heavy solids
followed by an aerated stabilization pond. This treatment scheme
would be expected to provide a high degree of treatment. The alter-
nate plan would be grit removal, primary clarification and chlorina-
tion. The effluent would not be as good as for the basic plan and ser-
ious operational problems would be expected due to the intermittent
flows.
The Basic Plan - Lagoon Facilities. The component units of the basic
plan are as follows:
(1) All storm water outfall would be discharged into two non-
mechanical sedimentation ponds providing a minimum detention time
of 15 minutes at 650 cfs peak flow. The ponds would be equipped with
stop log gates at each end to permit alternate draining and cleaning.
Cleaning would be accomplished with a front end loader. Raw BOt)
in the storm flow is expected to be about 60 mg/1. At 280 acre-feet
of flow in Plan B-l, the raw BOD load would be 46, 000 Ibs/day. A
20 percent reduction is expected due to solids removal, leaving a to-
tal of 36, 800 Ibs/day going to the aerated stabilisation pond. In Plan
B-2, the raw BOD load would be 57, 500 Ibs/day and the effluent to
the stabilization pond would contain 46, 200 Ibs/day of BOD.
(2) The effluent from the sedimentation ponds is discharged
into an aerated stabilization pond designed to contain the design flow
from the storm water outfall and hold this for a period of 6 days. If
the pond were full when additional runoff occurred, detention woujld
still be provided. Flow-through time for the runoff from the annual
2. 72-inch rainfall would be 3 to 3. 5 days, depending on the plan, if
the pond were full. Noraml pond operation will be at a depth of 3 feet.
The depth will increase to 7 feet during design storm conditions. A.
variable overflow will be required as will an effluent pump station for
use during periods of high river stage. One of the effluent pumps will
be used for recirculation to the sedimentation ponds to prevent septi-
city and increase mixing in the stabilization pond. Because of the
magnitude of the shock BOD load from the storm water, aeration of
the pond will be required. It is proposed to provide sufficient oxygen
181
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MIN.WATER DEPTH = 3 Ft.
MAX. WATER DEPTH - 7 Ft.'
TOTAL MAX.VOLUME = 525 Ac.-Ft
MAX. STORM OPERATING VOLUME =
280 Ac. Ft.
WATER SURFACE AREA = 75 Acres
B- 2 POND
MIN. WATER DEPTH
MAX. WATER DEPTH
TOTAL MAX. VOLUME
3 Ft-
7 Ft.
630 Ac.F1.
MAX. STORM OPERATING VOLUME"
350 Ac.Ft.
WATER SURFACE AREA i 90 Acres
CASE LAKE TREATMENT
COMPLEX
182
FIGURE 56
-------
on a pound for pound basis to reduce the unit surface BOD load to
50 Ibs/acre. Calculation of the air required considered 30 percent
of the shock load BOD to occur in the first day. Based on the use
of diffused aeration, the air requirement at 5 percent transfer effi-
ciency is 6, 700 cfm for Plan B-l and 8, 700 cfm for Plan B-2. It
is estimated that the effluent BOD will be 20 to 25 mg/1, an effluent
that should be satisfactory for present and anticipated future river
conditions.
(3) An effluent pump station will be required for use during
periods of high river stage. The proposed station will have one
30, 000 gpm pump and two 7, 500 gpm pumps. With this capacity, the
storm water storage can be discharged in 72 hours. One of the 7, 500
gpm pumps would be used for recirculatio.n to the sedimentation ponds.
(4) In addition to construction of treatment units, some land-
scaping and drainage work will be required. An existing drainage
channel will have to be routed around the pond system and through a
levee which will be required for flood protection. (See Figure 56).
The estimated construction cost for the basic plan is:
B-l B-2
(1) Sedimentation ponds $ 120,400 $ 98,000
(2) Aerated stabilization pond,
including discharge line,
Lift Station, recirculation
line and area drainage 1,068,000 1,220,000
(3) Aeration equipment 72,600 87,000
(4) Blower building and
equipment 73, OOP 83, OOP
Total Estimated Construction Cost $1,334,000 $1,488,000
The estimated annual operation and maintenance cost, including power,
labor, equipment and supplies is $24, 000 for Plan B-l and $28, 000 for
Plan B-2.
The Alternate Plan - Mechanical Plant. An alternate mechanical pri-
mary treatment scheme was also investigated. The plant would pro-
vide screening and grit removal, primary sedimentation, chlorina^
tion of the effluent and sludge storage ponds. It soon became apparent
183
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that the plan not only does not provide a comparable degree of treat-
ment, but also was considerably more expensive, $5, 700, 000, as
compared to the Lagoon System. A mechanical plant would provide
serious operational problems due to the high intermittent flows.
This would be particularly true during freezing weather when the
units would have to be drained to prevent freezing. For obvious rea-
sons, the plantwas not considered feasible or satisfactory and so
was not given further attention.
Summary of Construction Costs
Summarized herein are the proposed improvements for each system
described previously as they pertain to the two overall schemes for
elimination or reduction of combined sewer overflows. Cost sum-
maries are listed by system.
Plan B-l
1. Closes Creek System
Closes Creek Retardation Basins $ 1,600,000
27th and Payne Separation 20, 000
7th and Franklin Separation 11, 000
Prospect Road Impoundment 952, 000
2. West Side Interceptor
Separation of Freeway System 136, 000
West Side Storm Box Enlargement 1,472,000
3. Ingersoll Run Separation 3,790,000
4. East Side System, including Overflow Sewer
and East Side Storm Box Improvements 1, 658, 000
5. East 18th Street System 371,000
6. South Side Trunk 105, 000
7. Scott Street Lift Station and Storm Outfall 4,464, 000
8. Case Lake Treatment Complex 1, 334, OOP
Total Estimated Construction Cost-Plan B-l $15, 913, 000
184
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Plan B-2
1. Closes Creek
Closes Creek Separation $ 511,000
27th and Payne Separation 20, 000
7th and Franklin Separation 11, 000
Reduced Prospect Road Impoundment 78,2, 000
2. West Side Interceptor
Separation of Freeway System 136,000
West Side Storm Box as is and reduction
in cost of extension to grit chamber 376, 000
3. Ingersoll Run Diversion 25,000
4. East Side System 1,112,000
5. East 18th Street System 371,000
6. South Side Trunk 105,000
7- Scott Street Lift Station and 108" Storm
Outfall 3,737,000
8. Case Lake Treatment Complex 1,488, OOP
Total Estimated Construction Cost-Plan B-2 $8, 674, 000
185
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186
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- LEGEND
CZZID COMBINED SEWAGE DRAINAGE AREA TO
PROSPECT ROAD IMPOUNDMENT
COMBINED SEWAGE DRAINAGE AREA TO
DEAN LAKE IMPOUNDMENT
COMBINED SEWAGE DRAINAGE AREA TO
CASE LAKE TREATMENT COMPLEX
-i^l DRAINAGE AREA TO BE SEPARATED UNDER PLAN B-l
SS1E3 DRAINAGE AREA TO BE SEPARATED UNDER
PLAN B-l a B-2
(7) SEPARATED UNDER PLAN B-2
(?) TO CASE LAKE TREATMENT COMPLEX UNDER
PLAN B-2 (SEPARATED UNDER PLAN B-l)
LOCATION PLAT
PLAN B-l a B-2
187
FIGURE 57
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STORM WATER POLLUTION ABATEMENT SYSTEMS
All sources of urban pollutant discharges need to be considered. A
major source, whether considered a natural occurrence oif man-made,
is urban storm water discharges. Plan C includes the treatment of all
storm water discharges in the Des Moines Metro Area.
The problems encountered in the collection and treatment of storm wa-
ters are similar to those of handling combined flows. The basic prob-
lem is to handle high volumes of flow at infrequent intervals of time.
The facilities must have the capacity to effectively handle the flows from
a given design storm runoff. It would be impractical to design a mechani-
cal treatment facility to handle the flow rate from a 100-year storm. Such
a facility may never be fully utilized and its cost effectiveness would be
greatly reduced. A second problem is that land in urban areas is often
highly developed. The methods of treatment selected have to be com-
patible with the development in the area or the flow will have to be con-
veyed to a suitable treatment site. Compounding this problem is the fact
that storm water treatment facilities cannot be a centralized unit for an
area such as Des Moines which encompasses approximately 49, 000 acres.
Treatment will be accomplished in smaller, more manageable segments.
A third problem is having the capability financially to support a program
of storm water treatment. Many communities such as De£ Moines are
involved in expansion programs for the treatment of sanitary wastewaters.
It would be an extreme financial burden to increase the city's indebted-
ness and annual costs to the level required for treatment of storm wa-
ters.
Storm Water Discharge Characteristics
The data collected from storm water discharge sampling points is pre-
sented in Section VI, Table 7. The following observations are made fol-
lowing review of the data and comparison of the combined sewer over-
flows and storm water discharges:
(1) Storm water BOD values ranged from 40 to 70 mg/1.
(2) Storm water suspended solids values ranged from 400 to
600 mg/1. The concentrations of suspended solids was generally higher
in the storm waters than in combined sewer overflows.
(3) Ammonia Nitrogen and Phosphate concentrations were lower
in storm waters than in the combined overflows. This reflects the pre-
sence of raw sanitary wastes in the combined sewers.
(4) BOD and suspended solids concentrations are generally
188
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highest in the initial flow of storm waters and combined sewer over-
flows. The concentrations characteristically decrease over the dura-
tion of the flow.
The data accumulated during the Des Moines Study compares favorably
with other studies made of storm water discharges and combined sewer
overflows. The comparative BOD concentrations of storm water and
combined sewer overflow was the only possible exception noticed. Sev-
eral other studies indicate BOD values in combined sewer overflow to
be considerably greater than the concentrations in storm water dis-
charges. In Atlanta, Georgia, BOD concentrations in combined sewer
overflows were 50 percent greater than in storm water discharges (18).
There was little difference in the BOD values as sampled in Des Moines.
The concentration of BOD in these flows varies considerably depending
on the characteristics of the locale, the sewer system, weather condi-
tions and many other variables. For this reason, it is felt that the values
as sampled in Des Moines should be used.
Methods of Storm Water Treatment
The treatment of storm water discharges is confined primarily to phy-
sical treatment methods. Biological systems are difficult to maintain
in an environment where hydraulic flushing occurs at unpredictable in-
tervals and where there are long periods of little or no flow. Some bio-
logical removal of organics can be expected if extended holding periods
can be maintained in lagoon systems. Physical treatment such as short
term detention, settling, and screening will remove high solids concen-
trations and thereby reduce the BOD by removal of settleable or screen-
able organic solids.
The schemes generally considered for treatment are long and short term
detention ponds, grit removal units, settling clarifiers, coarse and fine
screening, dissolved air flotation and chemical disinfection. Each of
these methods has disadvantages. Lagooning requires large areas of
isolated land and poses the problems of intense algae blooms, solids
build up resulting from the lack of solids handling equipment, and the
possibility of anaerobic conditions developing. The mechanical proces-
ses such as screening and conventional clarifiers involve equipment
which will be a high maintenance item. Operational problems will be in-
creased because the equipment will remain idle over two-thirds of each
year. Operations using chemicals must be equipped with chemical feed-
ers and meters large enough to handle very large ranges of flow. A.gain
infrequent use and chemical storage will be a problem. To evaluate the
costs of providing treatment to storm water discharges the following me-
thods were reviewed.
(1) Grit removal units .
189
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(2) Short term retardation basins.
(3) Clarifiers without mechanical solids removal.
(4) Screening, using coarse and fine units.
The volumes to be used for design were developed using the Rational
Method. Runoff coefficients and intensities used were developed from
the rainfall-runoff monitoring in Des Moines. These are shown in Fi-
gures 33, 34 and 35 of this report. Rainfall intensity-duration-fre-
quency curves published by the U. S. Department of Commerce (12)
and data furnished by the Des Moines Weather Bureau was also used;.
Table 19 gives a summary of the peak runoff flow rates and volumes
considered for sizing the treatment units. The design basis for these
systems was determined on the basis of storm intensity and frequency
of return, considering the method of treatment to be evaluated.
Areas of Evaluation
Storm water treatment alternatives have been developed for four dif-
ferent areas within the study area. The areas were selected because
sampling had been done on each and because they demonstrate the dif-
ferent types of areas which would require storm water treatment faci-
lities. The areas are outlined on Figure 58 and described below:
1. Area I includes an area served by the Thompson Avenue Storm
Sewer and additional areas to the northwest. The Thompson Avenue
Storm sewer was sampled at Station S-l. The land area drained is a-
bout 1050 acres. The area is well developed and does not have large
areas available for the use of lagoons or retention ponds.
2. Area II includes the area sampled at Station 0-2 on Closes
Creek. The Closes Creek retardation basins, as described in this
section, are designed to treat the total area runoff and are applicable
to the evaluation in this section. Figure 51 provides a schematic of
the basins. The two basins serve an area of 1387 acres.
3. Area III includes the Cummin's Parkway Storm Sewer service
area sampled at Station S-3 plus an additional area to the southeast.
There are 1370 acres in the area. This area, like Area II, has a drain
age way running through it which could be used for a short term re-
tardation basin. The area is in a residential area with relatively high
property values.
4. Area IV is the area served by the 20th Street Storm Sewer.
The area was sampled at Station 0-11. This system drains toward an
industrial area with some available open land areas. Area IV includes
1170 acres of land.
190
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TABLE 19
STORM WATER DISCHARGES AT VARYING RETURN PERIODS
STORM WATER STUDY AREAS I - El
DESIGN RAINFALL-FREQUENCY, INTENSITY, DEPTH
10 YEAR 1 YEAR
0.5 YEAR
0.2 YEAR
AREA 1, A = 1050 ACRES, TIME OF CONCENTRATION Tc=70MIN.
RAINFALL INTENSITY, 1 ® Tc= 70 MIN
COEFFIEIENT OF PEAK RUNOFF FLOW, C
PEAK FLOW RATE, 0 - CIA
24 HR. RAINFALL ACCUMULATION
VOLUMETRIC COEFFIEIENT OF RUNOFF, Cv
VOLUME OF RUNOFF
2.0 INCHES/HR.
0.50
1050 cfs
4.75 INCHES
0.45
187 ac-ft
I.I INCHES/HR.
0.43
496 cfs
2.72 INCHES
0.33
79 ac-ft
0.9 INCHES/HR.
0.42
398 cfs
2.25 INCHES
0.29
57 ac-ft
0.55 INCHES/HR.
0.36
208 cfs
1 .50 INCHES
0.23
30 ac-ft
AREA II, A = 1387 ACRES, TIME OF CONCENTRATION Tc = 70 MIN.
RAINFALL INTENSITY, 1 @Tc=70MIN.
COEFFICIENT OF PEAK RUNOFF FLOW, C
PEAK FLOW RATE, 0 = CIA
24 HR. RAINFALL ACCUMULATION
VOLUMETRIC COEFFICIENT OF RUNOFF, Cv
VOLUME OF RUNOFF
2.0 INCHES/HR.
0.50
1387 cfs
4.75 INCHES
0.46
253 ac-ft
I.I INCHES/HR.
0.43
656 cfs
2.72 INCHES
0.36
1 13 ac-ft
0.9 INCHES/HR.
0.42
525 cfs
2.25 INCHES
0.33
86 ac-ft
0.55 INCHES/HR.
0.36
275 cfs
1 .50 INCHES
0.27
47 ac-ft
AREA III, A= 1370 ACRES, TIME OF CONCENTRATION, Tc=70MIN.
RAINFALL INTENSITY, 1 @ Tc = 70 MIN.
COEFFICIENT OF PEAK RUNOFF FLOW, C
PEAK FLOW RATE, 0 = CIA
24 HR. RAINFALL ACCUMULATION
VOLUMETRIC COEFFICIENT OF RUNOFF, Cv
VOLUME OF RUNOFF
2.0 INCHES/HR.
0.50
1370 cfs
4.75 INCHES
0.45
244 ac-ft
I.I INCHES/HR.
0.43
649 cfs
2.72 INCHES
0.33
103 ac-ft
0.9 INCHES/HR.
0.42
518 cfs
2.25 INCHES
0.29
75 ac-ft
0.55 INCHES/HR.
0.36
272 cfs
1 .50 INCHES
0.23
39 ac-ft
AREA IV, A = 1170 ACRES, TIME OF CONCENTRATION Tc = 85 MIN.
RAINFALL INTENSITY, 1 @ Tc = 85 MIN.
COEFFICIENT OF PEAK RUNOFF FLOW, C
PEAK FLOW RATE, p = CIA
24 HR. RAINFALL ACCUMULATION
VOLUMETRIC COEFFIEIENT OF RUNOFF, Cv
VOLUME OF RUNOFF
1 .8 INCHES/HR.
0.53
1115 cfs
4.75 INCHES
0.48
222 ac-ft
0.85 INCHES/HR.
0.44
437 cfs
2.72 INCHES
0.38
101 ac-ft
0.72 INCHES/HR.
0.42
354 cfs
2.25 INCHES
0.34
75 ac-ft
0.50 INCHES/HR.
0.38
222 cfs
1 .50 INCHES
0.29
42 ac-ft
-------
I
»
fn
ut
CD
TREATMENT
OF
STORM WATER DISCHARGE
STUOV AREAS
-------
Treatment Schemes and Costs, Areas I, II, III, and IV
The following gives the design basis, the treatment method, system
layouts, and the estimated construction and operating costs for storm
water treatment for the four areas evaluated. Capital and operating
costs are also given on a per acre basis, for ease of comparison.
1. Area I land area = 1050 acres, sampled at station S-l
Design Basis:
0. 5-year return rainfall intensity = 0.9 inches/hour
Peak Flow rate = 400 cfs
Containment of one-year 2. 72 inch storm = 80 ac-ft.
Treatment Method See Figure-59.
Alternate A includes a gravity collection system, grit removal
units, a pump station, an 84-inch pressure sewer to the lagoon, and a
24 acre retention lagoon.
Alternate B includes a gravity collection system grit removal
unit, a pump station, microscreens, and solids handling facilities.
Estimated Construction and Operating Costs
Gravity Collection System Alternate A. and Alternate B
Collection Lines $ 559,400
Non-mechanically cleaned grit chambers 350, 000
450 cfs Pump Station 700, OOP
$1, 609,400
Alternate A: Lagoon
84" Pressure sewer to Lagoon $ 567,000
24 Ac. Lagoon and 96" Outfall 680,000
Collection, Grit Chamber, Pump Station 1,609,400
Fees, Overhead, Contingency 573, 600
Total Construction Cost = $3, 430, 000
Construction Cost per Acre = $3270/Acre
Annual Operations Cost = $9000/Year
Annual Operations Cost/acre = $8. 55/A.cre/Year
193
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STORM WATER DISCHARGE
TREATMENT LAYOUT
AREA I
194
FIGURE 59
-------
Alternate B: Microscreens
Screens and Screening Building $2, 156, 000
96" Outfall 60, 000
Solids Thickeners and Handling 400, 000
Collection, Grit Chamber, Pump Station 1,609,400
Fees, Overhead, Contingency 844, 600
Total Construction Cost $5, 060, 000
Construction Cost per Acre = $4820/A.cre
Annual Operations Cost = $18,000/Year
Annual-Operations Cost/A.cre= $17. 10/A.cre/Year
2. Area II land area = 1387 acres, sampled at station 0-2
Design Basis
Spillway design for 100-year storm
For treatment-containment of 3-inch rainfall
Combined operating storage - 208 ac-ft.
Treatment Method - See Figure 51.
Retention Lagoons using existing drainage ways of Closes Creek,
Estimated Construction and Operating Costs. These estimates
are taken from Section X and are itemized therein.
Total Construction Cost $1, 600, 000
Construction Cost per Acre $1150/Acre
Annual Operations Cost $7600/Year
Annual Operations Cost/acre $5. 50/Acre/Year
3. Area III land area = 1370 acres, sampled at station S-3
Design Basis
Spillway designed for 100-year storm.
0. 5-year return rainfall intensity = 0. 9 inches/hour
Annual Peak flow rate = 518 cfs
Containment of one-year 2. 72-inch storm volume = 103 ac-ft.
195
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Treatment Method. See Figure 60
Retention lagoons using existing drainage ways.
Estimated Construction and Operating Costs
Retention Lagoon $ 866,400
Spillway 255,000
Site Work, Grit Stilling, Bridge 74,600
Overhead and Contingency 254, OOP
Total Construction Cost $1,450, 000
Construction Cost per Acre $1060/Acre
Annual Operations Cost $7000/Year
Annual Operations Cost/Acre $5. 10/A.cre/Year
4. Area IV land area = 1170 acres, sampled at station 0-11
Design Basis
One-year return rainfall intensity = 0.85 inches/hour
Peak flow rate = 440 cfs
One-year 2.72-inch storm volume = 101 A.c-Ft.
Treatment Method. See Figure 61. Grit chambers followed by
non-mechanical rectangular clarifiers. Solids removal will be
done periodically by clamshell or by front end loaders.
Estimated Construction and Operating Costs
Collection piping, site piping $ 644, 500
Land, Site work 200,000
Grit Chambers 326, 000
Clarifiers, dewatering pumps 2, 142, 000
Overhead & Contingency 662, 500
Total Construction Cost $3, 975, 000
Construction Cost per Acre $3390/Acre
Annual Operations Cost $9500/Year
Annual Operations Cost/Acre $8. 10/Acre/Year
The costs of construction and operation are summarized in Table 20
along with the average values of the five evaluations.
196
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TOP BERM EL. 50
H.W.L. EL. 46
BOTTOM EL. 32
a
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SqQoq a QD c
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a
a
D
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0
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Do
a
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oD
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STORM WATER DISCHARGE
TREATMENT LAYOUT
AREA 3IE
197
FIGURE
60
-------
xD
CO
o
c
3J
m
STORM WATER
DISCHARGE TREATMENT LAYOUT
AREA
-------
TABLE 20
Costs, Storm Water Discharge Treatment
Area Treatment Construction Operation Cost/
Evaluated Method Cost/Acre Acre/Year
A.rea I,
Alt. A Pump to Lagoons $3, 270 $ 8. 55
Area I,
Alt. B
Area II
Area III
Area IV
Average
Pump to Microscreens
2 Retardation Basins
Retardation Basin
Non-mechanical clarifiers
__
4,820
1, 150
1, 060
3, 390
$2, 738
17. 10
5. 50
5. 10
8. 10
$ 8.45
Projecting these per acre costs over the entire Des Moines Metro Area,
the estimated costs are $134, 700, 000 for construction, and $415, 700
per year for operation of the storm water treatment facilities.
Evaluation of Plans
Priorities need to be assigned to the abatement of the several types of
discharges from the Des Moines Metro Area. The aim should be to
spend the money so that the most benefit is derived. This is commonly
referred to as cost effectiveness. An effort is made to show the effective-
ness of each Plan and to discuss their benefits. Bear in mind that the al-
ternative plans outlined present different concepts and provide different
degrees of discharge abatement. Briefly, the plans presented are as
follows:
Plan A, complete separation of the combined sewer system;
treatment of only the separate sanitary wastes.
Plan B-l, treatment of all combined overflows, including some
separation of combined sewers.
Plan B-2, treatment of most of the combined overflow, including
a small amount of separation of combined sewers.
Plan C, treatment of all combined overflow and storm water dis-
charges. Each plan includes the improvements and additions for the
199
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wastewater treatment plant as recommended by Vennstra and Kimm
in Part B of the Central Iowa Regional Planning Commission report,
(15).
Cost estimates have been provided earlier in this Section and are sum-
marized in Section XIII. The costs used for this evaluation are the
annual costs to build, finance and operate the facilities of each plan,
including the costs of the wastewater treatment plant improvements
and operation. The annual costs are taken from Table 24 of this re-
port and from the Veenstra and Kimm report. These costs are totaled
and summarized in Table 21.
TABLE 21
Metro Area Treatment Plans, Annual Cost, $/Year
P&I* O&M Total
Proposed WWTP $ 2,615,400 $1,600,000 $ 4,215,400
Facilities
Plan A 4,472,500 1,400,000** 5,872,500
Plan B-l 4,214,500 1,709,600 5,924,100
Plan B-2 3,485,000 1,706,500 5,191,500
Plan C 17,719,100 2,125,300 19,844,400
*Amortized for 20 years at 6% interest
**WWTP O&M costs reduced to $ 1, 400, 000/year
because of decreased operational costs with
separated system.
Table 14 of this report lists the estimated present annual Metro area
discharges. Each plan provides a different degree of treatment of the
discharges. This fact gives some latitude in final decision making as
to how much treatment to provide. From the loads in Table 14 the
parameters least affected by the different Plans are the nitrates and
ortho-phosphates. The schemes developed for the treatment of com-
bined overflow and storm water discharges will not effectively remove
these two constituents. This is true of most physical and biological
treatment schemes. If nutrient treatment were required it would be
most economical to remove phosphates chemically at the wastewater
treatment plant. It is doubtful that even with significant reduction
200
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in these two parameters that the quality of the receiving waters would
change noticeably. As stated previously in the evaluation of the river
data, nuisance algal growths can occur with inorganic nitrogen levels
of 0. 3 m.g/1 and inorganic phosphorous exceeding 0. 05 m.g/1. The
average values sampled at river station R-2 on the Des Moines River
above the city exceeds these concentrations. If an algal problem were
to develop, it could do so without the Metro Area nutrient loads be-
cause of the upstream rural contributions.
The BOD discharged from the Metro Area will vary with the Plan uti-
lized. An estimate of BOD loads discharged by each plan is shown in
Table 22. The Table was calculated using data from Tables 13 and 14
and the following criteria:
1. The average annual discharge of the proposed waste-
water treatment facilities will meet the State dis-
charge requirement of 7500 Ibs/day of BOD.
2. Combined sewer overflow treatment facilities will
discharge an effluent with 25 mg/1 BOD.
3. Storm treatment facilities will provide on the
average, a 50 percent BOD removal efficiency.
From the estimated BOD loads in Table 22 and the respective annual
costs of each plan, justification of an extensive treatment program be-
yond that provided by the proposed new wastewater treatment plant faci-
lities is difficult. Of the four plans, Plan B-2 appears to be the most
favorable considering the results produced for the money spent.
The recreational use of surface waters in Des Moines makes the bac-
terial aspect of combined overflow treatment an important factor. The
disinfection of these flows is accomplished in the treatment systems
proposed by providing long detentiontim.es in the lagoons. The lagoons
are generally sized to contain the volume of flow from a 6-inch storm.
Nearly all of the overflow and storm water volume will be considerably
less than this 6-inch storm.
The cost of providing chlorination of these storm flows would add con-
siderably to the project costs. A 1970 study (19) which included disin-
fection costs, estimated capital costs of overflow treatment at $1000
per acre for conventional contact periods and $900 for a two minute
contact period. These costs did not include land and engineering costs.
201
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TABLE 22
Metro A.rea BOD Loads for Treatment Plans - Lbs/Year
With new
Load Present WWTP Plan A PlanB-1 Plan B -2
Effluent
WWTP 6,259,000 2,737,500 2,737,500 2,737,500 2,737,500
"Wet" dry
overflow 2,235,600
Combined
flow
treated
@ WWTP -- 48,000 -- 48,000 48,000
Untreated
Combined
overflow 174,500 174,500 -- -- 2,500
Treated
Combined
Overflow -- -- -- 62,500 61,500
Untreated
storm
waters 2,668,000 2,668,000 2,899,700 2,668,000 2,668,000
Treated
storm
waters --
Totals 11,385,100 5,628,000 5,637,200 5,516,000 5,517,500
Reduction
from present -- 5,751,100 5,747,900 5,869,100 5,867,600
Plan C
2, 737, 500
--
48, 000
--
62, 500
--
1, 334, 000
4, 182, 000
7,203, 100
-------
If disinfection was required, priority would have to be given to com-
bined overflows. The combined overflow has the higher and potentially
more hazardous bacteria levels. Data collected in Sacramento, Cali-
fornia (20) on urban runoff and overflows showed that the mean com-
bined overflow fecal coliform count was about one thousand times that
of the storm water runoff. Obviously, the source of the combined
overflow coliforms is more likely to be from domestic sewage than
from storm water.
The operation of the overflow and runoff facilities can be an important
factor in the containment of pollutants. Several studies, this one in-
cluded, indicate that the first portion of the combined and storm flows
carry the heaviest pollutional load. This occurs because of the flushing
action during the initial runoff. Consequently, the beginning of a storm
flow is important from the standpoint of retention. If bypass is to occur,
the flow at the end of the storm should be that which is bypassed. Actual
operating procedure would have to be based on sampling and operating
experience. Controlled discharge to the stream during dry weather con-
ditions should be based on effluent sampling. To provide capacity for
subsequent runoffs, discharge should be accomplished as soon as effluent
quality will permit.
The result of the evaluation is that the best return on the dollar would
come from the development of the proposed wastewater treatment faci-
lities. The costs of separation or treatment of overflows and runoff
are quite high relative to the reduction in pollutional load achieved.
The decreased load, beyond the improvement of the wastewater treat-
ment plant, is not significant to the area water quality when compared
to the upstream rural loadings. However, separation or treatment of
combined sewer overflows can be used on a smaller scale to eliminate
specific problems, to protect recreational waters, or to make system
improvements concurrent with other reconstruction programs.
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SECTION XI
UNUSUAL PROBLEMS ENCOUNTEREP
This section describes some of the unusual problems encountered dur-
ing execution of the project. The purpose for including this Section is
two-fold: (1) awareness of the problems may be helpful in the develop-
ment of future studies; and (2) identify items which can and should be
resolved by the entities or agencies involved.
FIELD EQUIPMENT
Generally, once the field equipment had been received and installed,
the performance thereof was satisfactory. The problem was in schedu-
ling the initial selection, procurement, and delivery thereof. Although
there are numerous equipment suppliers in this field, none of the items
available completely satisfied all the specific requirements of this pro-
ject. These particulars are discussed in Section V. Procurement of
equipment took longer than was originally scheduled due to the speciali-
zed nature of many items. It took time to search out pieces of equip-
ment which could be purchased separately and assembled at the project
site or as in the case of the bubbler units, to prepare specifications for
items to be fabricated by contract. Because many of the pieces were
special order items, delivery was often delayed. For the same reason,
items received were not always suitable for the purpose intended, caus-
ing additional delay for modifications or procurement of other equip-
ment. The lesson to be learned is to schedule sufficient time and funds
for equipment procurement and installation when developing project
time and financial schedules.
A problem involving field equipment that must be solved is protection
against vandalism. This was accomplished very successfully in this
project by providing lock-down steel housing for all exposed equipment.
For the bubblers, the housing was incorporated into the design and fab-
rication of the unit. For the float recorders and automatic samplers,
55 gallon steel drums were used. Slotted strap-iron flanges were welded
to the base of the drum to permit the drums to be chained and padlocked
to anchor bolts attached to a base. Although somewhat cumbersome dur-
ing servicing of the units, this provided excellent protection against
vandalism.
EXTENDED FLOODING
The problem which had the most profound effect on project operations
was the extended period and reoccurrence of high river stage, first from
spring runoff and then from upstream rainfall. The time interval extended
205
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fro. - March to mid-August. During this period most of the major over-
flow points were either submerged or at least intermittently affected by
high water. At several points, installation of monitoring and sampling
equipment was physically impossible. Since the period involved is also
the rainy season, the volume of data which might otherwise have been
collected was materially reduced. The only apparent solution for this
problem would be extension of the project through a second, hopefully
dryer, year. Figures 62, 63 and 64 show photos of some of the problems
caused by flooding.
EXCESSIVE INFILTRATION
Excessive infiltration into the metropolitan area sanitary and combined
sewage collection system was a second major problem. During the
rainy period from May until mid-August, excessive infiltration caused
almost continuous overflow at several of the key monitoring points.
This problem was aggravated by the extended high river stage. To
evaluate the magnitude of the infiltration problem, a network of flow
measuring stations was established. Instantaneous flows were deter-
mined from cur rent meter and depth observations. This data was then
compared with the dry weather flows measured earlier in the project.
The measuring station locations and flow data are shown in Figure 65.
It is noted that sewage flows during the "wet" dry weather period reached
2 to 3 times the dry weather flows in some sections, and that the condi-
tion is not limited to any particular section of the city. Because of the
general origin of flows, it is believed that building footing drains are a
primary source of the problem. Sewer infiltration should vary with age
and type of construction, however, high flows were measured in sewers
serving relatively new areas. Although the infiltration flows were ab-
normally high during the study period, these flows have a major impact
on the operation of existing collection and treatment facilities and must
be given consideration in future design.
AVAILABLE RECORDS
The City of Des Moines has a system of sewer quarter-section maps. Be-
cause parts of the combined system are very old, accurate records are
not available. In the past, limited personnel had prevented the staff
from adequately maintaining some of these records. This problem is
recognized by the City and work is being done whenever time is avail-
able to update these records.
The Lack of up-to-date records of storm sewers and inlet locations ne-
cessitated the expenditure of additional time to field check and update
the information on the quarter section maps. Generally this work was
accomplished during non-runoff periods and did not affect collection of
206
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BEFORE FLOOD
DURING FLOOD
RESCUING BUBBLER
AT
WASTE WATER TREATMENT PLANT BYPASS
BEFORE FLOOD
DURING FLOOD
AT STATION S-l
NORMAL a FLOOD CONDITIONS AT OUTLETS
207
FIGURE 62
-------
STATION D-5
SOUTH SIDE TRUNK
SIPHON INUET
FLOOD PREVENTS ACCESS
AND MAINTENANCE WITH
RESULTING SlUTATlON AND
RESTRICTION OF FLOW
THROUGH SIPHONS
SURCHARGE SANITARY SEWERS REQUIRE
RELIEF PUMPING INTO STORM SEWERS
"BLOWN" MANHOLE
CAUSED BY
_ SURCHARGING
FLOOD CONDITIONS IN SOUTHEAST DES MOINES
208
FIGURE 63
-------
BEFORE FLOOD
S TAT ION D - I A
WEST SIDE INTERCEPTOR
SI PHON I N LET
DURING FLOOD
FLOOD WATERS VORTEX
INTO SIPHON CHAMBER
SURCHARGE CAUSES BREAK IN
3O" CLOSES CREEK SEWER
PROBLEMS TREATED BY FLOODING
AND HIGH INFILTRATION
209
FIGURE 64
-------
ts)
i—i
o
o
c
3)
CD
01
INTERCEPTOR
SEWER SYSTEM
SURCHARGE
FLOW MEASUREMENTS
-------
monitoring and sampling data. It did, however, reduce the field en-
gineering time available for management and data analysis. It should
be recognized that the lack of up-to-date records is not an uncommon
problem. Care should be taken in| developing future study programs
to ascertain the completeness of system records.
Another item regarding available records, one which did not affect
this project but which nonetheless deserves comment, is the sources
and availability of river quality data. As noted in Section VIII, river
data was obtained from two outside sources, the State Hygienic Labo-
ratory through the State Department of Health and the Iowa State Uni-
versity Engineering Research Institute. Each of the above have ongoing
sampling programs which to a considerable degree overlap each other.
It is recognized that different levels of data collection is required of
different types of projects. A central source for obtaining this data,
such as the Federal Storet system, should be provided to assist in
disseminating this type of information.
211
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SECTION XII
SUMMARY OF COST ESTIMATES
Estimated project costs for the systems described for Plans A, B-l
and B-2 are shown in Table 23. Project costs are construction costs,
shown in previous sections, plus an allowance for engineering ser-
vices, legal, financial and administrative costs. For Plan A, the
cost of separation is broken down into systems corresponding to those
described in the treatment section.
Annual costs for the the three plans are shown in Table 24. The aver-
age annual principal and interest is based on a 20 year debt retire-
ment at 6 percent interest. Operation and maintenance costs are tabu-
lated and the total average annual costs are given for each system.
The cost of maintaining the collection systems are not included in this
comparison since this should be essentially the same whether separate
or combined systems are used. Nor are the estimated costs for the
wastewater treatment plant improvements included. Operating costs
are the average for the 20 year financing period.
All of the plans described would eliminate or substantially reduce the
overflow pollution load to the river. Average annual costs for Plan
B-l, in which all overflows are contained and treated is approximately
9 percent less than complete separation. Plan B-2, which allows in-
frequent overflows of highly diluted combined wastes and greatly re-
duces the overflow pollutional load, would cost about half of complete
separation.
The Closes Creek System illustrates how treatment of overflows and
separation can be used effectively together in some cases, to minimize
the cost of eliminating combined sewer overflows. For that system as
a whole, the average annual cost of $191, 800 for total separation is
comparable to $289, 100 annually for interception and treatment and
$149, 700 annually where both treatment and separation are proposed.
In the East 18th Street System, diversion and treatment of diluted
combined sewage would eliminate a major problem, i.e. , adding
voluminous quantity to a heavy concentration of industrial waste,
and does so at considerably less than the cost of separating the com-
bined sections of that watershed. In other systems, such as the Free-
way System on the west side, separation was the only practical solu-
tion.
It is apparent that each case must be evaluated on its own merits to
determine whether separation or treatment of combined sewer
213
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overflows is the most feasible means of control. The nature and
use of the receiving waters, public health, aesthetics and public
acceptance, as well as financial considerations, will influence the
selection of overflow control measures.
Plan C, which is essentially Plan B-l with additional treatment
facilities for all storm water discharges, is not included in the
tables. The estimated project cost for storm water treatment alone
is $154, 905, 000 and the estimated operating cost is $415, 700
annually. Adding the costs of Plan B-l, the annual costs of Plan C
would be as follows:
P&I $15,103,700
O&M 525, 300
Total $15,629, 000/year
214
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TABLE 23
SUMMARY OF PROJECT COSTS
Plan A
Plan B-l
Plan B-2
1. Closes Creek System
Retardation Basins
Separation
Prospect Road Impoundment
2. West Side Interceptor
Separation
Storm Box Extension
3. Ingersoll Run System
4. East Side System
5. East 18th Street System
South Side Trunk
6.
7.
Scott St. Lift Station &
Storm Outfall
$ 2,200,000
3,200,000
4,400,000
6,500,000
1,900,000
2,200,000
8. Case Lake Treatment Complex
9. Miscellaneous Separation 900, 000
Total $21,300,000
$ 1,840,000 $
36,000 $ 623,000
1,095,000 899,000
156,000 156,000
1,693,000 432,000
4,400,000 29,000
1,907,000 1,279,000
427,000 427,000
121,000 121,000
5,134,000 4,298,000
1,534,000 1,711,000
$18,343,000 $9,975,000
215
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TABLE 24
SUMMARY OF ANNUAL COSTS
1. Closes Creek System
Retardation Basins
Separation
Prospect Road Impoundment
2. West Side Interceptor
Separation
Storm Box Extension
3. Ingersoll Run System
4. East Side System
5. East 18th St. System
6. South Side Trunk
7. Scott St. Lift Station &
Storm Outfall
8. Case Lake Treatment Complex
9. Miscellaneous Separation
Plan A
Total
191,800
279,000
-
383,6000
566,700
165,700
191, 800
:x
78,500
P&I*
160,400
3, 100
95, 500
13, 600
147, 600
383,600
166, 300
37,200
10, 500
-4-47,600
133,700
-
Plan B-l
O&M*-:= Total
7,600 168,000
3, 100
22,500 118,000
13, 600
147,600
383,600
166,300
4,400 41,600
3, 100 13, 600
48,t)00 — 4957600
24,000 157,700
-
Plan B-2
P&I* O&M** Total
_ _
54,300 - 54,300
78,400 17,000 95,400
13,600 13,600
37,700 - 37,700
2, 500 - 37,700
111,500 10,000 121,500
37,200 4,400 41,600
10, 500 3, 100 13,600
374,700 44-,- 000 —418,700
149,20.0 28,000 177,200
-
$1.857, 100 $1, 599, 100 $ 109, 600 $ 1, 708, 700 $869,600 $106,500 $976,100
* Average Principal & Interest, 20 years @6%
*# Annual Operation & Maintenance
-------
SECTION XIII
ACKNOWLEDGEMENTS
Only through the cooperation and assistance received from the City
of Des Moines was the completion of this project possible. Mr.
Leo Johnson, Director of Public Services, and the entire staff of
the City Public Works Department gave generously and enthusias-
tically of their time and knowledge. Contract analytical services
were provided by the Engineering Research Institute, Iowa State
University under the direction of Dr. E. R. Baumann and by the
State Hygienic Laboratory, University of Iowa under the direction
of Senior Chemist, Lauren G. Johnson.
Numerous other organizations and agencies provided valuable
assistance in the project, including the Central Iowa Regional
Planning Commission, the U. S. Weather Bureau, and the cities of
Urbandale and West Des Moines, to mention but a few.
The support of the project by the Environmental Protection Agency
and the guidance and help provided by Mr. Ralph G. Christensen,
Project Officer, and Mr. W. A. Rosenkranz, Director of the Municipal
Pollution Control Division and his staff; and Mr. Richard Field,
Chief, Storm and Combined Sewer Technology Branch is acknowledged
with appreciation.
217
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SECTION XIV
REFERENCES
(1) Preimpoundment Water Quality Study
Saylorville Reservoir
Des Moines River, Iowa
Engineering Research Institute, Iowa State University.
(2) Standard Methods for the Examination of Water and Wastewater,
12th Edition, 1965.
(3) American Public Works Association;
Water Pollution Aspects of Urban Runoff;
FWPCA Publication WP-20-15; January 1969.
(4) Benjes, H.S.jHaney, P. D. ; Schmidt, O. J. ; and Yarabeck, R.R. ;
Storm Water Overflows From Combined Sewers; Journal,Water
Pollution Control Federation; 33, 12, 1252 (December 1961).
(5) Shifrin, Walter G; and Horner, W.W.; Effectiveness of Interception
of Sewage-Storm Water Mixtures; Journal, Water Pollution Control
Federation; 33, 6, 650 (June, 1961).
(6) Moorehead, George J; Overflows From Combined Sewers in
Washington, B.C.; Journal, Water Pollution Control Federation;
33, 7, 711 (July 1961).
(7) Myers, Victor I> A Method For Determining Average Watershed
Precipitation; Transactions of the American Society of Agricultural
Engineers; 2, 1, 82 (1959).
(8) Symposium on Streamflow Regulation for Water Quality Control;
U. S. Department of Health, Education and Welfare;
Public Health Service; Publication No. 999-WP-30; June 1965;
pp 205-220.
(9) Sawyer, C.N., Basic Concepts of Eutrophication
Journal, Water Pollution Control Federation
38, 5, 737 (May 1966).
(10) Kuentzel, L.E., Bacteria, Carbon Dioxide, and Algal Blooms
Journal, Water Pollution Control Federation
41, 10, 1737 (October 1969).
219
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(11) Ferguson, F.A., A Nonmyopic Approach to the Problem of Excess
Algal Growths; Environmental Science &t Technology; 2:3:188; 1968.
(12) Rainfall Intensity - Duration - Frequency Curves;
Technical Paper No. 25; U. S. Department of Commerce, Weather
Bureau, 1955.
(13) Utilities Inventory, Sanitary Sewer and Water Study;
Central Iowa Regional Planning Commission; 1970.
(14) WPCF Manual of Practice No. 9; Design and Construction of
Sanitary and Storm Sewers; 1966.
(15) Des Moines Metropolitan Sanitary Sewerage System Study;
Central Iowa Regional Planning Commission; 1971.
(16) Evans, F.L. HI; Geldreick, E. E. ; Weibel, S. R. ; and Robeck, G.G.;
Treatment of Urban Stormwater Runoff; Journal, Water Pollution
Control Federation, 40, 5, Part 2, R162 (May 1968).
(17) WPCF Manual of Practice No. 8; Sewage Treatment Plant Design;
1967.
(18) Black, Crow and Eidsness, Inc. ; Storm and Combined Sewer
Pollution Sources and Abatement, Atlanta, Georgia; Water Pollution
Control Research Series 110 24 ELB; January, 1971.
(19) Crane Co., Cochrane Division; Micros training and Disinfection of
Combined Sewer Overflow; Water Pollution Control Research
Series, 11023 EVO; June 1970.
(20) Aerojet-General Corp. , Envirogenics Division; Urban Storm
Runoff and Combined Sewer Overflow Pollution, Sacramento,
California; Water Pollution Control Research Series, 11024
FKM; December, 1971.
220
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SECTION XV
GLOSSARY
Pollution - the act of degrading or reducing the usefulness of a sys-
tem, such as surface waters, by the introduction of physical, chemi-
cal or biological changes and/or additions to that system.
Sanitary Sewage (or Wastewater) - is the water carried wastes which
originate in the sanitary conveniences of a dwelling, business es-
tablishment, factory, or institution.
Storm Water - is the excess water running off from the surface of a
drainage area during and immediately after a period of rainfall.
Infiltration - is the groundwater which gains entrance into the sewers
through joints, improper connections, etc., as differentiated from
surface runoff.
A Sewer - is a pipe or conduit used for the purpose of conveying sew-
age. There are three general classifications of sewers:
ji. A Sanitary Sewer is one designed to carry sanitary
sewage only. In many cases, it will also carry in-
dustrial wastes produced in the area it serves.
b_. A Storm Sewer carries storm runoff and similar
waters not including sanitary sewage.
c_. A Combined Sewer is designed to carry domestic
sewage, industrial wastes, and storm runoff in
a single conduit.
The term Sewerage (or Wastewater Facilities) - is used to designate
a system of sewers and appurtenances for the collection, transporta-
tion, and pumping of sewage and industrial wastes.
Wastewater Treatment Plant - is a comprehensive term encompas-
sing the arrangement of devices and structures for treating sewage
and industrial wastes and sludge.
A Main Sewer - is one to which one or more branch sewers are tribu-
tary.
An Intercepting Sewer - is a sewer which receives dry weather flow
from a number of transverse sewer outlets and frequently additional
221
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predetermined quantities of storm water (if a combined system) and
conducts such waters to a point for treatment or disposal.
An Outfall Sewer - is a sewer which receives the sewage from a col-
lecting system and carries it to a point of final discharge.
Sewage Treatment (or Wastewater Treatment) - refers to any artifi-
cial process to which sewage is subjected in order to remove or alter
its objectionable constituents so as to render the sewage less danger-
ous or offensive.
Sewage Disposal (or Wastewater Disposal)- applies to the act of dis-
posing of sewage by any method. It may be done with or without pre-
vious treatment of the sewage.
Biochemical Oxygen Demand (BOD) - is the quantity of oxygen utilized
in the biochemical oxidation of organic matter in a specified time and
at a specified temperature. It is not related to the oxygen requirements
in chemical combustion, being determined entirely by the availability
of the material as a biological food and by the amount of oxygen utilized
by the microorganisms during oxidation.
Solids - the solid content of a sewage consists of those in the settleable,
suspended, dissolved and total form. The total solids represents the
sum of the suspended and dissolved contents. The total solids and sus-
pended solids are further divided into volatile and nonvolatile for the
purpose of differentiating between the organic and inorganic content.
Settleable solids are those readily amenable to settling irrespective
of their size.
COD - chemical oxygen demand, the measurement of the total quantity
of oxygen required to chemically oxidize all organic compounds, with
a few exceptions, to carbon dioxide and water regardless of the biolo-
gical assimilability of the substances.
Precipitation - includes all forms, such as rain, snow, sleet, etc.
Design Rainstorm - a selected rainstorm of an area, involving the dur-
ation, intensity and recurrence interval of the storm, for use as a de-
sign basis.
Runoff - the flow of waters from precipitation or thaw incidents from
gutters into street inlets or from other connections into storm or com-
bined sewer systems.
Combined Sewer Overflow - the discharge into receiving waters of li-
quid wastes from combined sewers through outlet structures which
222
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regulate the amounts of flows either carried by trunk sewers or dis-
posed of into such receiving water resources.
BOD
DO
COD
TSS
VSS
GCPD
m.g/1
ug/1
ppm
psi
CF/MG
MGD
GPD
WWTP
JCU
ABBREVIATIONS
Biochemical Oxygen Demand, 5-day
Dissolved Oxygen
Chemical Oxygen Demand
Total Suspended Solids
Volatile Suspended Solids
(gal/capita/day) - gallons per capita per day
Milligrams per liter
Micrograms per liter
Parts per million
Pounds per square inch
Cubic feet per million gallons
Million gallons per day
Gallons per day
Wastewater Treatment Plant
Jackson Candle Units
223
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SECTION XVI
APPENDICES
Page
A. Description of Monitoring Points 227
B. Tabulation of Monitoring and Sampling Results 239
Table 25. Sampling Data 241
Figure 66. Dry Weather Sanitary Flows 267
C. River Sampling Data 271
Dissolved Oxygen-Diurnal Patterns
Figure 67- R-2 and R-5 272
Figure 68. Raccoon River 276
Figure 69. R-10 and R-14 280
Figure 70. R-15 and R-16 283
Table 26. River Station Data 285
Figure 71. Station R-2, BOD vs. Flow 293
Figure 72. Station R-2, Nitrogen and 295
Phosphate vs. Flow
Figure 73. Station R-9, BOD and DO vs. Flow 297
Figure 74. Station R-9, Nitrogen and Phosphate 299
vs. Flow
Figure 75. Station R-5, BOD and DO vs. Flow 301
Figure 76. Station R-5, Nitrogen and 303
Phosphate vs. Flow
225
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Continued . . .
Page
Figure 77. Station R-6, BOD and DO. 305
vs. Flow
Figure 78. Station R-6, Nitrogen and 307
Phosphate vs. Flow
D. Design and Assembly of Bubbler - Type Liquid 309
Level Recorder
Figure 79. Bubbler-Type Liquid Level 311
Recorder
226
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APPENDIX A
GENERAL INFORMATION.AND. DESCRIPTION OF SAMPLING STA-
TIONS. MONITORING STATIONS. OVERFLOW POINTS
To avoid repetition in the main body of the report, general informa-
tion and detailed descriptions of the various samplings and monitoring
stations and overflow points are all presented in this Section. For
ease of reference, the individual stations and points are grouped by
drainage area. Contributing areas, populations, and other pertinent
monitoring station information is summarized in Table 4. Sampling
and monitoring point locations are shown in Figures 13 and 14.
WEST SIDE INTERCEPTOR SEWER SYSTEM (Areas I and IA)
Dry Weather Stations: D-l, D-1A, D-1B.
Wet Weather Stations: W-l, W-1A.
Monitored Overflow Stations: O-2, O-3, O-4, O-5, O-6,
O-7, O-8, O-8A.
This system, serving a total of 9, 608 acres and 89, 100 population, is
the largest system from the standpoint of both wastewater flows and
combined sewer overflows. The area is shown in Figure 13 and in-
cludes all the downtown area north and west of the Raccoon and Des
Moines Rivers. About 24 percent of the total area is served by com-
bined sewers. These are located mostly in the downtown area, along
the river front and in the Ingersoll Run (D-1A) area. A few combined
sewers were found in the upper Closes Creek Area, as shown in Figure
14. Practically the entire system, however, suffers from excessive
infiltration - most of which is believed to be from building footing drains.
Following is a description of the individual sampling and monitoring
points.
1. Station D-l
Station D-l was the terminal point of the West Side Interceptor Sewer
and is located at the Scott Street siphon outlet chamber. The siphons
are 30-inch and 42-inch pipe and for part of the route across the river
are encased in the Scott Street Dam. During the October, 1968 dry
weather sampling, samples were taken manually and flows were mea-
sured with a current meter. The measuring section was below the con-
fluence of the two siphon outlet channels. For the January resampling,
weirs were constructed in each of the two siphon channels and float re-
corders were used to record head. Samples were collected with an
227
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automatic sampler. Figure 6 shows the setup and subsequent prob-
lems which occurred at this station.
2. Station D-1A
Station D-1A is located on the Ingersoll Run Sewer System at 22nd
and High Streets. This sewer is tributary to the West Side Intercep-
tor via the Walnut Street Sewer. This particular site was chosen for
monitoring because a major overflow (O-8A) is located immediately
below it. At the sample site, the sewer is a 5' by 13' box section.
Below the overflow, the line is 42-inch diameter, two-ring brick
sewer. The service area is primarily residential housing with some
commercial development along Ingersoll and Grand Avenues. The area
is also quite hilly. Dry weather flows for both sample periods were
measured with a rectangular weir (see Figure"6) and a float recorder.
The station was manually sampled during the first period. During the
second period, an automatic sampler was lowered through a manhole
and was set on a platform similar to the one used for the float recor-
der.
3. Station D-1B
Station D-1B was located on the 30" Closes Creek Trunk Sewer at an
abandoned pump station near the intersection of Harding and Prospect
Roads. This station was sampled only during the first dry weather
schedule. It was not considered significant enough to the overall pro-
gram to re sample this station for quality data alone. Flow data from
the first sampling was used. Because the station was not resampled,
a data sheet was not included in this text.
4. Stations W-l and W-1A
Station W-l is, the same location as D-l. The purpose of this station
was to record water level in attempt to correlate head loss across the
siphon with flow in the siphon... Station W-1A was the upstream station
and was located in the West Side Interceptor siphon inlet chamber. Bub-
bler units were used for water level recording at both stations. Both
stations are subject to frequent extended surcharging, W-l from backup
in the main outfall and W-1A from the excessive infiltration previously
discus sed.
Also, a major overflow is located at W-1A and it was active during
much of the spring and summer. An attempt was made to correlate
water levels at W-l A with measured flows through the overflow,
which sometimes acts as an orifice. The results were erratic, and at
best provided only an approximation of the head-discharge relationship
for this overflow.
228
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5. Station W-1B
Station W-1B was an alternate flow measuring point to Station W-1A
and was located at the first manhole downstream from West 1st and
Elm Streets. Flows were computed from depth and current meter
observations.
6. Station O-2
Station O-2 was located at the apex of the 1700 acre Closes Creek
drainage area. The drainage area is mainly residential, hilly, and
heavily wooded in some sections. Most of the flow measured at this
station was storm sewer discharge and overland runoff. There are
however, about 107 acres around the upper perimeter of the basin
which are combined. Flows at Station O-2 were determined by stage
discharge relationship. Fortunately, the sampling point was at the
site of a permanent control which minimized discharge rating curve
shifts. Sufficient low flow measurements were made to establish the
lower section of the rating curve and then high water measurements
were made as often as possible during runoff periods to provide a
basis for projecting the curve. All sampling was done with the auto-
matic samplers. To facilitate sampling, a special platform was sus-
pended from a foot bridge over the creek. Figure 10 shows the O-2
control.
7. Station O-3
Station O-3 was an overflow point at the upper end of the West Side In-
terceptor Sewer. The station was located on the 30-inch sewer near
Prospect and Hickman Roads at a point below the junction of the Closes
Creek Trunk and the Northwest Outfall. At this point an overflow weir
has been effected by the removal of the upper part of the sewer bar-
rel. The overflow section is enclosed in a concrete box. Overflow
is to a small drainage way leading directly to the river a short dis-
tance to the east. Initially, this overflow was monitored by periodic
inspection of a stick gage. This information indicated that overflow
did occur during periods of significant runoff. Later in the project, a
bubbler unit was installed and samples collected with an automatic
sampler.
8. Station O-4
Station O-4 was an overflow on the West Side Interceptor at the inter-
section of 2nd Avenue and Franklin. The overflow is equipped with a
flood gate to prevent backup of river water into the sewer system.
When operating, the overflow releases surcharge from the West Side
229
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Interceptor and from the Franklin Street Sewer which is tributary
to the interceptor. The actual overflows are weirs in the respective
sewers. Both weirs are relatively high. A stick gage was used to
determine overflow frequency and from this information it was de-
termined that additional monitoring was not warranted.
9_. Station Q-5
Station O-5 is a major overflow on the West Side Interceptor. It
is located within the IPALCO power plant complex at West 1st Street
and Grand Avenue. The main sewer and overflow are shown in Figure
15. From inspection of the overflow and periodic inspection of a stick
gage installed therein, it was determined that this point warranted
continuous monitoring and consequently a bubbler setup wasi construc-
ted. The bubbler recorded incidence of overflow and provided an up-
stream head reading for hydraulic gradient computations to Station
O-6, 451 feet downstream. During high river stage, the overflow was
submerged almost constantly. During normal dry weather operation,
overflow occurs only during peak periods. Because of the relative low
elevation of the overflow and its close proximity to the river, this
point is a prime suspect as the point of access for fish found in the
raw flow at the wastewater treatment plant. It is not however, a
source of river water getting into the sewer system as had been specu-
lated early in the extended high water period. By monitoring the level in the
sewer and cross-checking with river elevations, it was determined
that flow was always in the direction of the river.
10. Station O-6
Station O-6 is also an overflow on the West Side Interceptor in the
area of West 1st and Grand. As noted above, it is 451 feet downstream
from Station O-5 and was a point used for determination of flow by the
hydraulic gradient method. (A table was developed for this section of
sewer to convert head differential and flow depth to discharge. ) The
overflow is a brick wall constructed in a broken out section of the pipe
(see Figure 15). The wall extends to within a foot of the top of the pipe
and monitoring indicated that overflow never occurred at tliiis point.
This was not unexpected considering the major overflow immediately
upstream. All sampling for the O-5/O-6 area was done at Station O-6.
Sampling was done with an automatic sampler which was lowered into
the manhole.
11. Station O-7. (Also O-7A and O-7B)
The O-7 stations were located on the West Side Storm Bo^, a 5 foot by
13 foot concrete conduit located outside the floodwall and along the west
230
-------
bank of the Des Moines River from Scott Street to Grand Avenue.
This box is the recipient of overflows from, several sewers nor-
mally tributary to the West Side Interceptor. The tributary sewers
are in Grand Avenue, Locust Street, Walnut Street, and Elm Street.
In addition, the box receives all storm and combined flow from the
Birds Run Sewer. To accommodate the high peak flows which occur,
mainly as a result of the large Birds Run Sewer, the upper end of the
box is equipped with pressure release flap gates which permit dis-
charge from both ends of the box. The lower end of the box siphons
under the confluence of the Des Moines and Raccoon Rivers and dis-
charges through the face of the Scott Street Dam. This box may
also be used for lowering the pool of the impoundment behind Scott
Street Dam. Wooden sluice gates are provided at the lower end of
the box for this purpose.
Three bubbler stations were located along the length of the box in an
attempt to measure flow by hydraulic gradient. The locations were:
(1) O-7 at the lower end of the box; (2) O-7A about 990 feet above
the end of the box; and O-7B at the upper end of the box. This pro-
cedure did not provide meaningful correlations due to excessive
leakage from the river along most of the length of the box and con-
siderable debris inside the box. Figure 11 illustrates these problems.
Station O-7A was sampled on several occasions to obtain compara-
tive data for highly diluted overflow waters.
12. Station O-8. (Also O-8A)
Station O-8 is the outlet of the Ingersoll Run combined sewer over-
flow at 17th and Railroad Avenue. Flows reaching this point come
from the Ingersoll Run overflow at 22nd and High Streets (Stations
D-1A and O-8A) and from an unknown number of storm sewers in-
tercepted in between. The actual overflow at O-8A is a 21. 5-foot
broad crest weir in the converging section between the 5-foot x
13-foot Ingersoll Run Box and the 42-inch combined sewer down-
stream. Results of early samplings, and the probability that flood-
ing and surcharging at other major overflow points would require
this station to be a major source of information, prompted the es-
tablishment of Station O-8A as a cross-check on the data obtained
from the more dilute flows at Station O-8. Sampling at both stations
was done with an automatic sampler. Water levels were obtained via
bubbler installations. For Station O-8, flows were obtained by stage-
discharge relationship. A rock and debris riffle immediately below
the station served as a satisfactory control for the flow range mea-
sured (see Figure 10).
231
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SOUTHWEST OUTFALL SEWER (Area II)
Dry Weather Station D-2
Wet Weather Station W-2
!_. Station D-2
This system serves the western section of Des Moines and the cities
of West Des Moines, Windsor Heights, Clive and Urbandale. The
contributing area encompasses 15, 720 acres with a population of a-
bout 54,700. The collection systems served are designed as separ-
ate sanitary sewers; however, flow studies made during this project
indicate the systems carry excessive infiltration and/or foundation
and roof drain waters. The contributing area is primarily residen-
tial and light commercial development. Only about 1 percent is in-
dustrial. The terrain is rolling and has extensive foliage.
There are no known overflows in the D-2 system with exception of a
manually operated bypass gate on the outfall at 17th Street. This gate
is to be used only if maintenance is required on the sewer or the si-
phons .
The D-2 sample station was in the Raccoon River siphon outlet struc-
ture near Southwest 7th and Indianola Avenue. Flow was measured
over a 5-foot rectangular weir at the downstream end of the structure.
Samples were collected manually during the October 1968 dry weather
composites. Resampling in January was done with automatic samplers.
Figure 9 shows several photos of the D-2 setup.
2. Station W-2
Station W-2 was the same as Station D-2. For continuous flow moni-
toring, the weir installed for dry weather sampling was left in place
and a bubbler unit installed for water level monitoring. While moni-
toring, it was determined that the station is subject to frequent ex-
tensive surcharging, apparently from the main outfall sewer. Because
of this situation, the original plan to install a bubbler at the siphon in-
let and determine flow from head loss across the siphon was abandoned.
In lieu thereof, sewer flow measurements were made by current meter
at several upstream points during the "wet" dry weather period. These
flows are shown in Figure 65 and led to the previous mentioned conclu-
sion that the system is subjected to excessive infiltration. Whenever
possible, daily "wet" dry weather flows were computed for comparison
with the point flow and dry weather flow measurements. The data obt-
tained confirmed the point flow measurements and the conclusion that
excessive extraneous flows have access to this system.
232
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EAST SIDE INTERCEPTOR SEWER (Area III)
Dry Weather Station D-3
Wet Weather Station W-3
Monitored Overflow Points O-9, O-10
1. Station D-3
This system serves the east side downtown area and a north-south
corridor along the east side of the Des Moines River. The service
area is about 2, 240 acres with an estimated contributing population
of 16,400. About 24 percent of the collection system is combined
sewers and there are two overflows to the Des Moines River, one
at O-9, the Birdland Pump Station, and the other at O-10, the dis-
charge from the East Side Storm Box. Actually, the storm box re-
ceives overflow from the East Grand and East Locust Street sewers
in the downtown area. The Area III terrain is relatively flat except
for a corridor along the river. Except for the east side downtown
area, the sanitary watershed is mainly residential development. In-
dustrial development occupies only 2. 7 percent of the total area.
The D-3 sample station was a manhole at East 1st and Raccoon
Streets. A. 30-inch Cipoletti weir was constructed in the 48-inch
brick sewer and a float recorder used to determine head. Samples
were collected manually during the October, 1968, sampling period
and with an automatic sampler during the February, 1969, re-
s ampling.
2. Station W-3
Station W-3 is at the same location as D-3. The weir used for dry
weather measuring was left in place for use during non-surcharge
conditions. A bubbler unit was used for recording head readings.
The unit was kept in service through the "wet" dry weather period
for recording of surcharge water surface elevations. Because of
its relative elevation, this station was affected less by surcharge
than several of the other wet weather stations. Valuable "wet" dry
weather daily flow data was obtained at this station.
3. Station O-9
This overflow is at the Birdland Pump Station. Stick gate monitoring
indicated that overflow does occur, although apparently only during
significant rainfall. The overflow is gated so can be maintained closed
as long as upstream surcharging does not create a public health haz-
ard or cause property damage. This station was not monitored except
for periodic inspection of the stick gage.
233
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4. Station O-10
The O-10 station was the East Side Storm. Box outlet. This conduit
is identical to Station 0-7, the West Side Storm Box, and is used
for the same purposes, including bypassing of river flow around
the Scott Street Dam. During the course of the project, this box
was never able to be monitored. Flood water prevented monitoring
for much of the rainy period. After recession of the high water, it
was determined that the box was 2/3 to 3/4 filled with sediment,
particularly at the upper end in the vicinity of the Grand and Locust
Street overflows to the box. Also, this box was in use as a river by-
pass around Scott Street Dam for the duration of the study. It is be-
lieved that this box is a major overflow and any remedial program
should include collection of flows therein.
EAST 18TH STREET INTERCEPTOR (Area IVA and IVB)
L. Dry Weather Station D-4
This system serves the east-central area of Des Moines covering
3, OZ4 acres with an estimated contributing population of 17, 300.
Much of the industry in the City is in this area. The sewers in the
collection system are mostly separate sanitary sewers, although a
few combined sewers (5 percent of the area) are known to exist in
the northwestern part of the area. There are no known points of
over-flow in the system. The interceptor discharges into the main
outfall sewer near 18th and Maury Streets.
The D-4 sample station was in a manhole just above the connection
to the main outfall. A 36-inch rectangular weir was constructed in
the 66-inch brick interceptor sewer and a float recorder used to de-
terming head. Samples were collected with an automatic sampler.
This station was only sampled during the initial dry weather sampl-
ing period. This station was not resampled, even though the initial
data is questionable, because it was learned that the industries con-
tributory to the system would soon be improving their inplant waste
treatment systems in accordance with a new industrial waste ordi-
nance and control program. Also, the results of individual indus-
trial waste sampling by the City's staff were made available for our
evaluation.
SOUTH SIDE TRUNK (Area VII)
Dry Weather Station D-5
Wet Weather Stations W-5 and W-5A
Overflow Station O-13
234
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This system serves 2,061 acres with an estimated population of
15, 300 and is located in the south central part of Des Moines.
The area served is an older area of the City and is primarily
residential. About 7 percent of the collection system is combined
sewers.
The system terminates at Southeast 9th and Jackson Streets in a
two-barrel siphon (14 and 20 inch) under the Des Moines River.
Siphon discharge goes into the main outfall at Southeast 9th and
Railroad. The only overflow in the system is at the siphon inlet
structure.
1. Station D-5
The D-5 sample station is in the siphon inlet structure. One of the
siphon channels was blocked off and a weir constructed in the other
channel. A float recorder was used to determine head over the weir.
Sampling was done manually during the November, 1968, dry wea-
ther sampling and with automatic samplers in the February resampl-
ing.
This station has some very severe maintenance problems. Figure
63 shows the station during flood conditions and also one of the siphon
inlet channels filled with sediment. Similar conditions were noted
throughout the study period.
2. Stations W-5 and W-5A
Station W-5 was identical to D-5 except that a bubbler unit was used
instead of a float recorder. Station W-5A was the siphon outlet struc-
ture on the north side of the river. A bubbler ur.it was installed here
in the hope of being able to correlate head loss across the siphon
with incoming wet weather flow. Backup from the main outfall, to
which this line is tributary, affected the head readings during wet
weather and throughout all "wet" dry weather period. This surcharge
caused almost constant overflow just upstream of the siphon during
the wet and "wet" dry weather periods. Flow computations provided
erratic results. No meaningful correlations could be made relative
to the amount of rainfall required to produce overflow at this point.
3. Station O-13
Station O-13 is the overflow point referred to above. This is a major
overflow. As noted above, overflow during spring and summer was
almost continuous, even during relatively dry periods. Because of
the conditions already noted, the volume of overflow could not be
235
-------
determined. Some sampling was done to provide strength data for
comparison with the dry weather sampling.
MAIN OUTFALL AND WWTP (Area IX)
Dry Weather Station D-6
Overflow Station O-14
The Des Moines wastewater treatment plant serves all of the Des
Moines and the surrounding metropolitan area except: (1) Highland;
Hills, a small development south of Army Post Road at the south
edge of the City; (2) Pleasant Hill, a small community east of the
City; and (3) the Urbandale Sanitary District which is a small seg-
ment of the City of Urbandale. The area served by the Des Moines
Plant is about 46, 167 acres and has an estimated contributing popu-
lation of 239, 700.
1. Station D-6
The D-6 sample station was at the bar screen channel at the treat-
ment plant. Samples were collected and analyzed by the treatment
plant chemist. Flow was determined from the raw sewage flow to-
talizer. Unfortunately, the plant was undergoing expansion con-
struction during the dry weather sampling period and was unable to
handle the total raw flow. Therefore, the data obtained for that period
cannot be used for comparison with the in-system dry weather data.
To compensate for this problem, plant operation records for the 3-
months period of August-September-October, 1969, were obtained
and evaluated.
2. Station O-14
Station O-14 was the WWTP raw sewage bypass. Originally it was in-
tended to monitor this point continuously. Two physical problems
prevented accomplishment of that goal and limited actual monitoring
to a short period in March and approximately two months record in
late summer and early fall. Initial delay in monitoring this point
was caused by construction of a flood protection levee and flood
gate at this location. Within a few days after the site became avail-
able for monitoring, the first of several periods of high river stage
occurred. Figure 62 illustrates the flood problem. A. weir and bub-
bler was finally installed after recession of high water. Considering
the data obtained after the bubbler was installed, and recognizing
that bypassing at this point was unlikely during the period of missed
record, it appears that this point was not a major overflow during
the study period. It is likely that upstream overflow, caused by the
surcharged main outfall sewer, minimized occurrence of bypassing
at this location.
236
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CORNELL AND AURORA STORM SEWER OUTLET
l_. Dry Weather Station D-7
This storm sewer was reported to have sanitary connections and
therefore was included in the initial dry weather sampling. The
sample point was at the outlet of the storm sewer in an open ditch
at Cornell and Aurora Avenues. A wooden bulkhead and weir were
constructed in the ditch and a float recorder used to determine head
over the weir. Samples were collected with an automatic sampler.
The station was sampled during the initial dry weather work only,
since observation during setup and sampling and the laboratory data
indicated an absence of sanitary flow.
FRALEY DITCH STORM SEWER OUTLET
!_. Dry Weather Station D-8
This was another storm sewer which was included in the dry wea-
ther sampling program because it was thought to carry sanitary
wastes. The station location was at East 30th and Court Street. A.
90° V-notch weir was installed at the outlet of the storm sewer.
A float recorder was used to determine head and samples were col-
lected with an automatic sampler.
During the November-December dry weather sampling, it was deter-
mined that the station did receive a significant quantity of industrial
waste. Prior to the re-sample period, it was learned that the City
would be including this sewer in its industrial waste control program;
therefore, the station was not re-sampled. Instead, data from the
City's program was obtained. From the City's data it appeared that
the normal flow is free of sanitary wastes but did contain a signifi-
cant quantity of industrial waste. These wastes were subsequently
removed from the system.
THOMPSON AVENUE STORM SEWER
!_. Storm Runoff Station S-l
The station is located at the outlet of the Thompson A.venue Storm
Sewer at the Birdland Park Marina (see Figure 14). The drainage
area served is 310 acres. Most of the area is older residential area
with considerable open park space along the natural waterway. Dis-
charge from this point flows in to the Birdland Park Marina and
thence into the Des Moines River.
237
-------
T'->e station was monitored by constructing a weir and bubbler set-
up at tlie outlet of the box. Except for periods of high river stage
(see Figure 62), satisfactory continuous record was obtained).
This station was a key station in the rainfall-runoff study.
CUMMINS PARKWAY STORM DRAINAGE
_!_. Storm Runoff Station S-3
The Cummins Parkway watershed is located in a rolling hilly area
near the western Des Moines city limits (see Figure 14). The 356
acre area is almost entirely residential and has considerable open
grassy area. Discharge from this station flows into Walnut Creek
near 63rd and Grand.
The station was monitored by constructing a weir and bubbler set-
up at the outlet of a box culvert. The setup is shown in Figure 10.
The station was a key station in the rainfall-runoff study.
20TH STREET STORM SEWER
L. Storm Runoff Station O-ll
The O-ll station was originally expected to be a combined sewer
overflow point, hence the "O" designation. During the study, how-
ever, it was determined that the flow at this point was separate
storm flow. The contributing area to Station O-ll is about 1|170 acres
located in the north-central part of the City and includes considerable
industrial and commercial area. The outlet of the 4' by 5' storm sew-
er is at the upper end of Dean Lake at E. 22nd and Dean Avenue (see
Figure 14). Monitoring was accomplished by installation of a weir
and bubbler unit. Sampling was done with automatic samplers. Fig-
ure 7 shows the monitoring and sampling setup. The 55-gallon drum
is the sampler housing used to prevent vandalism.
238
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APPENDIX B
TABULATION OF MONITORING
AND SAMPLING RESULTS
Wet and Dry Weather Sanitary Flows
Combined Sewer Overflows
Storm Water Discharges
Note:
Caution should be exercised in interpreting the information herein.
Data given for samples collected and analyzed is not necessarily for
a single complete runoff from rainfall or snow melt. Grab samples
are considered point values, although an arbitrary duration may have
been assigned for extension to pounds. Hourly dry weather sanitary
flows are shown graphically in the Figures at the back of this Appen-
dix.
EXPLANATION OF TABLE
The following explanations are given for column headings:
TIME: Given in Military Time System, beginning time for composite
samples.
TYPE: Type designation establishes type of sample and source of
flow. Code established for type of sample is:
C - composite sample
S - single grab sample
Code established for source of flow is:
D - dry weather sanitary flow
W - wet weather sanitary or combined flow
R - overflow or runoff due to rainfall
S - overflow or runoff due to snow melt
239
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DURATION:
FLOW:
MG/L:
LBS:
N.A. :
Time, in hours, for which composite sample was
made up.
Average rate of flow, in cubic feet per second, for
the duration of composite sample, or rate of flow
at the time of grab sample.
Strength of sample in milligrams per liter.
Pounds of pollutants for the duration indicated.
No analysis made.
240
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CD
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2
D
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DES MOINES.JOWA.STOWM waTfc'R POlL'iTION CONTPOL STUDY
STATION 0-1 <•-!) *. SIDE INTFWCIfPTOH AT SCOTT
SUSPENDED SOLIDS
HOD TOTAL VOLATILE
DIM FLOW MG/L MG/L MG/L PEW
ITEM DATE TIME Type HOUR MOD LBS LBS Lbs CENT
1 10/I3/6H 80 CD 24.00 9.0 -N.A.- -N.A.- -N.A.-
2 10/14/68 BO CO ?4.00 10.5 -N.A.- -N.A.- -N.A.-
3 10/15/68 80 CD 24.00 11.0 -N.A.- -N.A.- -N.A.-
4 12/13/68 23 0 SD 1.00 N.A. 278.00 -N.A.- -N.A.-
5 12/13/68 90 SD 1.00 N.A. ?18.00 -N.A.- -N.A.-
6 1/12/69 90 CD 24.00 7.0 194.00 216.00 199.00
11312.1 1259S.O 11603.7
1 1/13/69 90 CD 24.00 7.8 204.00 277.00 260.00
13254.7 17997.8 16893.2
6 1/14/69 90 CD 24.00 8.0 241.00 269.00 234.00
16Q60.2 17926.2 15593.8
9 5/21/69 90 SO 1.00 N.A. 130.00 -N.A.- -N.A.-
10 5/21/69 10 0 CW 2.00 N.A. 69.00 449.00 114.00
11 5/21/69 12 0 CW 4.00 N.A.
12 5/21/69 16 0 C* 7.00 N.A.
13 5/22/69 60 CW 2.00 N.A.
14 6/26/69 11 0 SW 1.00 N.A. 110.00 281.00 149.00
15 6/26/69 1740 Cta 4.00 N.A. 72.00 598.00 12B.OO
16 9/13/69 ?130 C« 2.00 N.A.
17 10/ 2/f>9 711! C» .1.PO N.A.
60
NITROf.l-N
AMMONIA NITRITE
MC>/L l^fi/L
LrtS LBS
F HHCA CONTRACT NO 14-12-402
PHOSPHATES CHLORIDES CHROMIUM
NITRATE TOTAL SOLUABLF
MG/L MG/L MG/L MG/L UG/L
LBS LHS LBS LHS LHS
28.00 595.00 132.00
90.00 256.00 123.00
62.00 113.00 64.00
33.00 409.00 217.00
?
-------
CM
1^
ro
OFS "OINES. luwA.STOW" ^tTE- PdLl.nT I Or, (.JNT-'OL SlufJY
STATION n-1 <*-!> v. S10F I^TH-CFt-TOC « T SCOTT
SUSPENDED SOLIDS
HOD TOT4L VOLATILE
UUP FLOW -»G/L MG/L MC./L Pt'H
ITEM DATE TIME TYPf Him* >
CD
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CD
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DfS HOINES.IOWA.STOWM KATE" POLLUTION CONTHOL STUDY
STATION 0-1A (0-8AI lUbfPSOLL PUN SEWEe AT 22NO AND HIGH
SUSPENOtO SOLIDS
t BOD TOTAL VOLATILE
OUW FLOW "4G/L MG/L MG/L PEH
ITEM DATE TIME TrPE MOUH HGO L8S L8S LBS CENT
1 10/13/68 80 CD 24.00 .9 -N.A.- -N.A.- -N.A.-
2 10/14/6H 80 CO 24.00 1.1 -N.A.- -N.A.- -N.A.-
3 10/15/68 80 CD 24.00 1.3 -N.A.- -N.A.- -N.A.-
•> 12/12/66 23 0 SO 1.00 N.A. 221.00 -N.A.- -N.A.-
5 12/13/6% 90 SD 1.00 N.A. 231.00 -N.A.- -N.A.-
6 1/12/69 90 CD 24.00 1.2 228.00 179.00 168.00
2279.1 1789.3 1679.3
T 1/1Z/69 90 CO 24.00 .9 197.00 235.00 218.00
1476.9 1761.8 1634.3
> » 1X13/6* 90 CO 24.00 .9 178.00 224.00 171.00
1334.5 1679.3 1282.0
• ' t/18/69 10 S« 1.00 N.A.
10 7/18/M 20 SM 1.00 N.A.
11 7/18/69 30 SM 1.00 N.A.
12 7/18/69 50 SH 1.00 N.A.
13 B/ 6/69 1545 CM 3.00 N.A.
14 B/ 7/69 545 Cw 3.00 N.A. 154.00 303.00 101.00
IS 8/21/69 90 CW 2.00 N.A. -N.A.- 394.00 195.00
58.00 90.00 70.00
55.00 666.00 107.00
38.00 -N.A.- -N.A.-
36.00 -N.A.- -N.A.-
44.00 62.00 31.00
NITHOGFN
AMMONIA NITHITE
MO/L Md/L
L«S LHS
FfcPCA CONTRACT NO 14-12-4U2
PHOSPHATES CHLOPIDtS CHROMIUM
NITRATE TOTAL SOLUABLE
MG/L MG/L MG/L MG/L UG/L
LHS LHS LBS LBS LRS
94
93
76
78
16
SO
33
49
-N.A.-
-N.A.-
-N.A.-
33.00
35.80
22.5H
225.7
26*66
199.9
26.11
195.7
-N.A.-
-N.A.-
.75
1.26
«. BO
7.2S
6.55
-N.A.-
-M.A.-
-N.A.-
.35
.61
.10
1.0
.08
.6
0.00
0.0
-N.A.-
-N.A.-
.04
.05
.01
.2?
.05
-N.A.-
-N.A.-
-N.A.-
4.07
6.65
3.04
30.4
0.00
0.0
0.00
0.0
-N.A.-
-N.A.-
.53
1.41
.US
.57
.27
-N.A.-
-N.A.-
- -N.A.-
28.60
29.20
17.25
172.4
21 .05
157.8
18.32
137.3
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
26.00
32.50
9.84
98.4
1 1 .63
87.2
11.50
86.2
-N.A.-
-N.A.-
.47
.81
19.50
3.62
5.84
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.4.-
-N.&.-
-N.A.-
-N.A.-
-N.A.-
-N.4.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-------
OES MOINES.IOOA.STORM HATER POLLUTION CONTROL STUDY
STATION D-2 (*-?) SOUTHWEST OUTFALL SEWEP
tx)
CD
|-
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80D
DUP FLOW MG/L
ITEM DATE TIME TYPE HOUR MGI) LBS
1 10/27/68 80 CO 24.00 u.2 -N.A.-
2 10/28/6B 80 CD 24.00 4.4 -N.A.-
3 10/28/68 80 CD ?4.00 4.0 -M.A.-
-------
DF.S MOlNFS. lOKA.STO^M WATF> POLLUTION CONTROL S
STATION U-3 (*-3> i-AST S1PF IriTF^CFVTO" AT EAST 1ST AND RACCOON
SUSPENDED SOLIDS
HOD TOTAL VOLATILE
FhPCA CONTRACT NO 14-12-402
NITROGFN
PHOSPHATES
AMMONIA NITRITE NITRATE TOTAL SOLUAHLE
CHLORIDES
tv
en
H
CO
|-
m
PO
01
o
o
-T
ITFM
1
2
3
5
7
8
9
10
11
12
14
15
16
17
DATE
10/27/68
10/28/68
10/29/68
12/12/68
12/13/68
?/ P/AQ
C, f Cfaf
2/ 3/69
2/ 4/69
2/ 4/69
2/ 4/69
2/ 4/69
2/ 5/69
2/ 6/69
6/25/69
6/26/69
6/26/69
8/19/69
TIMf
a o
8 0
8 0
23 0
9 n
in n
i U U
10 0
1030
1230
1330
1930
930
10 0
1 1 0
8 0
10 0
11 0
DUR FLO«
TYPF HOUR MGD
CO 24.00 1.3
CD 24.00 1.5
CD 24.00 1.6
SO 1.00 N.A.
SLI 1.00 N.A.
CO 24 00 17
CD 24.00 1.9
CW 2.00 2.4
SW 1.00 2.4
SW 1.00 4.0
SW 1.00 ?.6
SW 1.00 2.3
CD 24 . 00 2.1
Cw 21.00 3.S
CW 2.00 10.3
SW 1.00 7.9
C* 23.00 3.3
MG/L
LBS
1 70.00
1840.9
214.00
2673. 9
-N.A.-
385.00
?06 .00
1 04 .00
1472.7
168.00
2658.9
-N.A.-
-N . A . -
-N.A.-
-N.A.-
-N.A.-
— N . A . —
112.00
2857.2
120.00
858.0
-N. A.-
1 I4.no
3003.2
MG/L
LHS
-N.A.-
-N.A.-
-N.A.-
-N.A.-
1 HH nn
i o o . u u
2662.3
170.00
2690.6
101.00
168.3
162.00
134.9
204.00
283.2
277.00
250.0
94.00
75.0
156. 00
2728.9
174.00
4438.8
491.00
3510.6
-N.A.-
98.00
25H1.7
MG/L
LbS I
-N.A.-
-N.A.-
-N.A.-
-N.A.-
1 C{. n n
2180. 8
153.00
2421.5
101.00
168.3
134.00
111.6
124.00
172.2
130.00
117.3
89.00
71.0
137*00
2396.5
125.00
3188.8
178.00
1272.7
-N.A.-
61.00
1607.0
Pt R
CENT
82
90
100
63
61
47
95
88
72
36
62
KO/L
LBS
20.50
222.0
19.80
247.4
19.10
254.6
29.80
31 .90
39.90
565.0
23.80
376.7
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
15.80
403. 1
-N.A.-
S.49
15. 1
34.19
900.7
MC,/L
LHS
7.68
83.2
.01
.1
«TRACE*
.13
.24
1.3
.04
.6
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
.02
.6
-N.A.-
.14
.4
.02
.6
MG/L
LBS
27.60
298.9
.25
3.1
.18
2.4
1.09
1 .67
On n
. u u
0.0
0.00
0.0
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
.14
3.5
-N.A.-
.8b
2.4
.07
1.8
MG/L
LHS
38.60
418.0
52.70
658.5
44.40
591.8
43.50
33.20
5.14
72.8
4.99
79.0
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
27.40
699.0
-N.A.-
-M.A.-
24.26
639.1
MG/L
LBS
39.20
424.5
24.20
302.4
21.00
279.9
42.20
27.60
2. 79
39.5
2.43
38.5
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
21.10
538.3
-N.A.-
4.20
11.5
18.20
479.5
MG/L
LBS
-N.A.-
-N.A.-
-N.A.-
-N.A.-
— N. A.-
-N.A.-
109.00
181.6
189.00
157.4
817.00
1134.3
595.00
536.9
95.00
75.8
-N.A.-
-N.A.-
-N.A.-
-N.A.-
UG/L
L«S
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.'
-N.A..
-N.A.
-N.A.
-N.4.
-------
DO
m
ro
en
o
o
DES MOlNFS»IO«A.<;TOJ« w
STATION D-3 (v<-3> ^CST SIDE
POLLUTION CONTROL STUDT
CONTRACT NO 14-12-402
AT EAST IsT AND RACCOON
SUSPENDED SOLIDS
NITROGEN
ITEM DATF TIME
18 8/20/69 10 0
19 9/22/69 13 0
20 9/22/69 18 0
31 9/22/69 20 0
300
[)U« FLOW -IG/L
TYPF HOUH MGU LHS
CW i.OO 3.6 148.00
1767.1
Ck 5.00 8.2 147.00
2091.9
CW 2.00 24.1 97.00
1622.8
CD 15.00 2.9 123.00
1857.1
TOTAL
MG/L
LRS
290.00
3462.5
345.00
4909.5
420.00
7026.4
131.00
1977.9
VOLATILE AMMOtMlA
MG/L PER MG/L
LSS CENT LHS
219.00
2614.8
173.00
2461.9
129.00
2156.1
74.00
1117.3
55.29
76 660.1
7.23
50 102.9
-N.A.-
31
5.3d
56 81.2
NITHITE NITRATE
MG/L MG/L
LflS LBb
.12
1.4
.24
3.4
-N.A.-
.44
6.6
.31
3.7
.27
3.8
.34
5.7
.19
2.9
TOTAL
MG/L
L8S
15.27
182.3
14.10
200.6
-N.A.-
12.40
187.2
SOLUABL6
MG/L MG/L
L8S LBS
8.11 -N.A.-
96.8
12.50 -N.A.-
177.9
1.54. -N.A.-
25.8
.87 -N.A.-
13.1
UG/L
L4S
-N.A.
-N.A.
-N.A.
-N.A.
-------
DES WOlNES.IOWA.STORM *ATfR POLLUTION CONTROL STUDY
STATION D-5 (W-51 SOUTH SIDF Tk(jNt<
IN)
^
-J
H
>
CD
|—
m
ro
o
o
SUSPENDED SOLIDS
NITROGEN
FHPCA CONTRACT NO 14-12-402
PHOSPHATES CHLORIDES CHROMIUM
13 a/ 4/69 1830 SW 1.00 N.
14 2/ 5/69 430 Sw I'.OO N
15 6/25/69 11 0 CW 4.00 N
16 6/?6/69 20 SK 1.00 N
17 6/26/69 e 0 C'* 3.00 N
DUK FLOW
HOUR MOO
4.00 1.3
4.00 1.6
4.00 1.2
4.00 1.2
4.00 1.1
1.00 N.A.
1.00 N.A.
1.00 N.A.
1.00 N.A.
1.00 N.A.
1.00 N.A.
1.00 N.A.
1.00 N.A.
1' . 0 0 N.A.
4.00 N.A.
1.00 N.A.
3.00 N.*.
BOD
MG/L
LHS
255.00
?761.4
P06.00
P74S.6
-N.A.-
245.00
2449.0
174.00
1594.4
-N.A.-
-N.A.-
-N.A.-
-N.A.-
• -N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
?01.00
1^0.00
?18.00
TOTAL
HG/L
LBS
-N.A.-
-N.A.-
-N.A.-
1 94 . 0 0
1939.?
137.00
1255.3
303.00
271.00
180.00
105Z.OO
1037.00
849.00
429.00
377.00
165.00
540.00
-N.A.-
966.00
VOLATILE
MG/L PtR
LBS CENT
-N.A.-
-N.A.-
-N.A.-
165.00
1649.3
12S.OO
1145.4
254.00
239.00
137.00
536.00
548.00
456.00
244.00
275.00
163.00
462.00
-N.A.-
434.00
85
91
64
88
76
SI
53
54
57
73
99
86
AMMONIA
Mb/L
LBS
IS. 45
167.3
18.54
247.1
28.10
280.9
47.60
475.8
29.60
271.2
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
lb.20
-N.A.-
14. ?0
NITRITE MTWATE
MG/L MG/L
LHS LBS
.5ft 3.19
6.3 34.5
.0? .70
.3 9.3
.27 2.54
2.7 25.4
.08 0.00
.6 0.0
.20 0.00
1.8 0.0
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
.31 .16
-N.A.- -N.A.-
.01 .06
TOTAL SOLUAHLF
MG/L MG/L MG/L
LRS LHS LBS
-N.A.- -N.A.- -N.A.-
-N.A.- -N.A.- -N.A.-
6.71 3.16 -N.A.-
67.1 31.6
6.50 2.87 -N.A.-
59.6 26.3
-N.A.- -N.A.- 115.00
-N.A.- -N.A.- 139.00
-N.A.- -N.A.- 321.00
-N.A.- -N.A.- 717.00
-N.A.- -N.A.,- 866.00
-N.A.- -N.A.- 762.00
-N.A.- -N.A.- 509.00
39.90 33.60 -N.A.-
-N.A.- -N.A.- -N.A.-
16.50 6.77 -N.A.-
UG/L
LHS
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A,-
-N.A.-
-N.A.-
-N.A.-
-N.4.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
45
-------
oo
00
r
m
rv>
01
o
o
DES MOINES-IOWA,<5TO"M WATtP POLIUTION CONTROL STUDr FWPCA CONTRACT NO 14-12-402
STATION 0-5 (W-S) SOUTH SIDF T^IKJC
SUSPENDED SOLIDS NITROGEN PHOSPHATES CHLORIDES
,800 TOTAL VOLATILE AMMONIA NITRITE NITP-ATE TOTAL SOLUABLE
Dll« FLO« MG/L M&/L MG/L PER MG/L MG/L MG/L MG/L MG/L MG/L OG/L
ITEM DATE TIME TYPE HOUR MGD LBS L8S LbS CENT LRS LHS LHb LBS LHS LBS LHS
18 6/?6/ft9 18 0 SH 1.00 N.A. 123.00 1832.00 516.00 2.75 .02 .07 15.80 7.39 -N.A.- -N.A.-
26
19 6/26/69 19 0 C* 2.00 N.A. 94.00 440.00 148.00 -N.A.- -N.A.- -N.A.- -N.A.- -N.A.- -N.A.- -N.A.-
34
-------
ro
CD
|-
m
r\>
en
o
o
DPS MOINFS.IOH6.STO"M WATff- POLL tTIOiw CONTROL iTUOY
STATION 0-9 fOUH MILF TWUNc StHF-*
SUSPENOEO SOLIDS
FwPCA COMPACT NO 14-12-402
NI T
ITEM
1
2
3
OATfc
ax
2X
2x
2X69
3X69
4X69
TIMt
10
10
10
0
0
0
TYPf
CD
CO
CO
WH
HOLIP
24.00
24.00
24.00
FLOW
Mt,0
2.5
2.6
3.1
HOD
rf&XL
Les
356.00
7413.7
511.00
11067.2
181.00
4674.0
TOTAL
M&XL
LBS
189.00
3935.9
178.00
3855.1
189.00
4880.5
VOLATILE
MGXL PEN
LBS, CENT
162.00
3373.6
162.00
3508.6
161.00
4157.5
86
91
85
AMMONIA
MGXL
LBS
25.75
536.2
26.00
563.1
41.30
1066. b
NITRITt
MGXL
LHS
.03
.6
.1H
3.9
.07
1.8
MTKATE
MGXL
LBS
0.00
0.0
0.00
0.0
0.00
0.0
TOTAL
MGXL
LHS
5.56
115.8
8.43
182.0
5.90
152.4
SOLUAbLE
MGXL
LBS
3.70
77.1
5.22
113.1
3.09
79.8
MGXL
LBS
-N.A.-
-N.A.-
-N.A.-
UGXL
LHS
-N.4.-
-N.A.-
-N.A.-
-------
DFS MOIRES. loWft.sT
STATION u-? CLOStS
"" wait*- POL! M IO.-J
(- ^te K
CONTROL -.TJOY
CONTRACT NO 14-12-402
SUSPENDED SOLIDS
HOO TOTAL VOLATILE
t\)
Cn
O
-t
CD
r
m
Ol
o
o
2
_|
ITEM
1
2
3
4
S
6
7
8
9
10
11
12
13
14
15
16
17
DATE
2/25/69
2/26/h9
3/ 1/69
3/ 1/69
3/ 2/69
4/ 8/69
4/1 5/69
5/17/69
5/19/69
5/2 1/69
5/21/69
5/21/69
5/21/69
5/31/69
5/22/69
7/ 9/69
9/22/69
T1-IF.
13 0
16 0
1430
1430
1330
3330
11 0
030
15 0
930
930
13 0
15 0
20 0
6 0
5 0
1330
TYPf
CS
CS
ss
CS
CS
en
CR
CR
SR
SR
CR
SR
CR
SR
SR
CR
Shi
UHx
HOW
12.00
6.00
1.00
8.00
11.00
8.00
13.00
16.00
1.00
.25
1.00
1.00
2.00
1.00
l.oo
6.00
1 .00
FLOW
CFS
16.1
14.7
3.0
5.4
2.6
2.8
5.8
17.2
23.5
.2
.2
310.0
50.5
N.A.
N.A.
27.2
?4.4
MG/L
LHS
144.00
6249.7
90.00
1 783.2
— N. A .—
39.00
378.5
35.00
334.9
-N.A.-
18.00
381.4
20.00
1336.4
39.00
305.9
1 9.00
.3
16.00
.7
17.00
802.0
-N.A.-
24.00
9.00
36.00
1319. K
?2.00
1?1 . 1
MG/L
L>dS
379.00
1644ft. 8
661.00
17059.3
-N. A.-
716.00
6948.4
336.00
1516.3
863.00
4337.5
310.00
4846.8
681.00
42100.1
446.00
2354.5
1167.00
52.4
-N.A.-
421.00
9551.9
150.00
39.00
970.00
35561 .4
50H.OO
379S.9
MG/L PE«
LHS CENT
94.00
4079.6 25
167.00
3308.8 19
-N.A.-
305.00
1989.4 29
77.00
494.7 33
195.00
981.2 23
83.00
1297.7 27
115.00
7109.4 17
96.00
506.8 22
180.00
8.1 15
-N.A.-
74.00
1679.0 18
62.00
41
17.00
44
117.00
4289.4 12
4V. 00
369.7 10
NI TWUGEN
AMMONI t M T"I Tt
Mb/L
LBS
3.19
138.4
3.07
bO.B
1.41
13.7
1.55
10.0
.91
4.6
• 79
13.4
.55
34.0
.94
5.0
1.18
.1
-N.A.-
.78
17.7
-N.A.-
-N.A.-
.65
23.8
.51
2.*
MG/L
LHS
.02
.7
.01
.2
.01
.1
.01
.1
.01
.1
.00
.0
.03
1.7
.14
.04
.0
-N.A.-
.00
.1
-N.A.-
-N.A.-
.02
•*
.02
.1
M ThATE
MG/L
Lbb
1.14
49. 5
1 .01
20. C
.75
7.3
,5b
3.7
1.51
7.6
.90
14.1
.56
34.6
1.11
5.9
.93
.0
-N.A.-
1.40
31.8
-N.A.-
-N.A.-
1.21
44.4
.H9
4.9
PHOSPHATES CHLORIDES CHROMIUM
TOTAL SOLUAHLE
MG/L
LBS
.27
11.7
.32
6.3
.16
1.6
.08
.5
1.55
7.8
~N • A • —
3.36
307.7
6.41
33.8
5.34
.3
-N.A.-
3.69
83.7
-N.A.-
-N.A.-
2.44
89.5
-N.A.-
MG/L
LHS
.14
6.1
.27
5.3
.04
.4
.03
.3
.97
4.9
1.06
16.6
1.64
101.4
4.80
35.3
4.14
.2
-N.A.-
3.50
56.7
-N.A.-
-N.A.-
.53
19.4
.44
3.4
MG/L
LHS
18.00
3819.2
59.00
1169.0
571 .00
256.5
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
UG/L
LHS
33.00
1.4
50.00
1.0
136.00
.1
54.00
.5
0.00
0.0
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-NiA.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-------
03
r
m
N>
OES "OlNf S«IOWfi«ST<)JM hATtt- POLLUTION CONTROL
STATION U-2 CLOSES OEtK
HOO
Illlx FLO* MG/L
ITFM OATf. TIMf TYPt HOIIK CfS Lhb
18 9/22/69 1430 SB I. 00 2.5
19 9/22/69 1630 CR 5.00 2b.3
20 9/22/69 2130 CR 6.00 3.7
21 10/ 5/69 1615 Ctf 6. 00 3.9
22 10/ 5/69 2215 CR 5.00 13.9
20.00
11.2
33.00
V37.8
205.00
1022.3
20.00
105.1
21.00
327.9
STUDY
SUSPENDED SOLII
TOTAL VOL!
*&/L M&/L
LiS LBS
470.00
264.0
611.00
17362. A
49.00
244.4
154.00
809.5
3RD. 00
5932.7
54.00
30.3
88.00
2500.7
10.00
49.9
60.00
315.4
60.00
936.7
FKfCA CONTOACT NO 14-12-402
PEH
CENT
11
14
20
39
16
AMMONIA
LHS
.46
.3
.82
23.3
1.26
6.3
.56
,2.9
1.87
29.2
UlTtflTE
LHS
.02
.0
.04
1.2
.08
.4
.01
.0
.01
.1
MTfcATE
MO/L
LfaS
.84
.b
1.04
.47
2.3
.36
1.9
.20
3.1
PHOSPHATES CHLORIDES
TOTAL SOLUABLE
«»G/L
LBS
-N.A.-
1.85
52.6
.80
4.0
1.67
8.8
2.92
45.6
MG/L
LHS
.68
.4
1.08
30.7
.80
4.0
.88
4.6
1.26
20.0
MG/L
LHS
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
UG/L
-N.4.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
o
o
-------
tN)
Ul
CO
CD
n
m
ro
01
o
o
DFS KOIMtS. Il)WA,STO-
-------
DF.S WOINF.S-iowA.sToaM WOTEW POLLUTION CONTROL STUDY
STATIOM 0-6 «tST Slt>r INTE^CFPTOP AT b^A.MO AvE.
SUSPENDED SOLIDS
ro
Ul
ITEM
1
2
3
4
5
6
7
8
9
10
11
DATE
5/21/69
5/21/69
5/21/69
5/21/69
5/21/69
5/21/69
5/17/69
8/ 6/69
8/ 7/69
8/21/69
^/22/69
TIME
1015
1130
12 0
1230
1330
16 0
930
1530
530
9 0
1240
TYPF
CR
CR
CR
CR
CR
CR
CR
CR
SR
SR
CR
UUP FLOW
HOUR CFS
1.50 N.A.
.5U N.A.
.50 25.0
.50 N.A.
1.25 N.A.
.50 N.A.
2.00 N.A.
19.00 13.8
1.00 11.6
2.00 12.8
22.00 15.9
HOD
MG/L
LHS
44.00
69.00
29.00
81.4
-N.A.-
34.00
56.00
118.00
76.00
4476.4
215.00
560.3
150.00
862.6
158.00
12415.5
TOTAL
MG/L
LBS
889.00
943.00
1166.00
3274.1
-N.A.-
745.00
237.00
-N.A.-
155.00
9129.6
759.00
1977.8
225.00
1293.9
308.00
24202.4
VOLATILE
MG/L PER
LBS CENT
201.00
179.00
165.00
463.3
-N.A.-
152.00
113.00
-N.A.-
102.00
6007.9
434.00
1130.9
114.00
655.6
167.00
13122.7
23
21
14
20
48
66
57
51
54
CONTRACT NO 14-12-402
NITROGEN PHOSPHATES CHLORIDES CHROMIUM
AMMONIA NITRITE NITRATE TOTAL SOLUABLE
MIJ/L MG/L MG/L MG/L MG/L MG/L UG/L
LHS LBS LbS LBS LBS LBS LflS
3.9« .Ob .hO 9.38 6.53 -N.A.- -N.A.-
-N.A.- -M.A.- -N.A.- -N.A.- -N.A.- -N.A.- -M.A.-
-N.A.- -N.A.- -N.A.- -N.A.- -N.A.- -N.A.- -N.A.-
,bb .02 .76 4.31 2.45 -N.A.- -N.A.-
.SO .08 1.32 5.52 3.05 -N.A.- -N.A.-
-N.A.- -N.A.- -N.A.- -N.A.- -N.A.- -N.A.- -N.A.-
6.88 .04 -N.A.- -N.A.- -N.A.- -N.A.- -N.A.-
13.20 .45 .70 -N.A.- 25*).00 -N.A.- -N.A.-
777.5 26.5 41.2 15196.4
-N.A.- -N.A.- -N.A.- -N.A.- -N.A.- -N.A.- -N.A.-
27.40 .07 .20 -N.A.- 11.40 -N.A.- -N.A.-
157.6 .4 1.2 65.6
13.43 .27 .18 20.30 22.80 -N.A.- -N.A.-
10S5.3 21.2 14.1 1595.2 1791.6
CD
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-------
DCS nOlNt"S« lOhA.ST.jPM
STATION fl-7 *f?T SllJE
f»PCA CONTRACT NO 14-12-402
SUSPENDED SOLIDS
ro
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H
CD
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m
ro
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ITEM DATE
1 2/ 5/69
2 2/ 6/69
3 2/ 6/69
4 IO/ 2/69
S IO/ 2/69
* IO/ 2/69
7 IO/ 5/69
0 IO/ 5/69
9 IO/ 5/69
10 IO/ 5/69
11 ]0/ 5/69
12 IO/ 6/69
13 IO/ 6/69
ni/'' FLO*
TlUf. ITPF riOUH Cf S
17^0 SS 1.00 N.A.
9*«S SS 1.00 N.A.
1*45 SS 1.00 N.A.
430 CM 4.00 N.A.
830 CO 2.00 N.A.
1030 CH 2.00 N.A.
1445 Cft 3.00 N.A.
1745 S* 1.00 N.A.
1845 CO 4.00 N.A.
2245 SR 1.00 N.A.
2345 SR 1.00 N.A.
045 Sft 1.00 N.A.
145 CR 9.00 N.A.
HOI) TOTAL VOLATILE AMMUSiIA MTblTt MTHATE TOTAL SOLUAHLF
MG/L MG/L MG/L PtK HG/L M'i/L MG/L MG/L MG/L MG/L UG/L
LHS LHS LHS CENT L'lb L4S LBS LHS LHS LBS L«S
-«.A.- -N.A.- -N.A.- -N.A.- -N.A.- -N.A.- -N.A.- -N.A.- 71.00 7.00
-N.A.- -N.A.- -N.A.- -N.A.- -N.A.- -N.A.- -N.A.- -N.A.- 57.00 4.00
42. 00 70.00 20.00 1.16 .01 3.89 1.38 1.29 -N.A.- -N.A.-
29
109.00 146.00 46.00 ^.3H .00 .IS 5.37 2.62 -N.A.- -N.A.-
31
51.00 84.00 26.00 ?.18 .01 3.97 2.50 2.06 -N.A.- -N.A.-
31
34.00 76.00 42.00 .32 .01 .10 1.46 .45 -N.A.- -N.A.-
55
41.00 364.00 109.00 -N.A.- -N.A.- -N.A.- -N.A.- -N.A.- -N.A.- -N.A.-
30
53.00 60.00 16.00 3.44 .00 .24 11.10 6.38 -N.A.- -N.A.-
27
28
30.00 170.00 71.00 .82 .01 .16 7.75 1.67 -N.A.- -N.A.-
42
-------
en
CD
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OES MOINES.IOWA.STOSM WATtP POLLUTION
STATION 0-ti INGEHSOLL UUN OVERFLOW AT
DUK FLOW
ITEM OATt TIMF. TYPE MOUP CFS
1 ?/24/69 1555 SS 1.00 .9
2 3/17/69 11 0 CB 8.00 8.5
3 4/14/69 1030 CR 9.00 7.7
4 4/17/69 130 CR 16.00 6.8
5 4/26/69 1915 CR 4.00 37.5
6 4/27/69 2315 CR 12.00 1.2
7 5/ 7/69 17 0 CR 6.00 37.8
8 5/ 7/69 1730 SR .'50 31.2
9 5X 7/69 18 0 SR I.00 12.2
10 5/ 7/69 19 0 SR .75 47.5
11 5/ 7/69 1930 SR .50 46.0
12 5/ 7/69 21 0 SR .75 46.0
13 5/ 7/69 2130 SR .50 46.0
14 5/16/69 2330 CR 6.00 11.0
15 5/21/69 96 CR 2.00 2«.6
16 5/21/69 1130 CR 2.00 173.5
17 5/21/69 1330 CP. ?.00 67.9
CONTwOL
'IUTLET
HOD
HG/L
LRS
31.00
6.3
61.00
931.8
35.00
544.9
32.00
782.1
38.00
1280.4
53.00
171.4
45.00
2292.7
130.00
455.6
-N.A.-
61.00
488.2
33.00
255.8
-N.A.-
96.00
1423.3
53.00
681.0
18.00
1403.1
?6.00
793.?
STUDY
SUSPENDED SOLIDS NITROGEN
TOTAL VOLATILE AMMONIA NITPITE
MG/L MG/L PER Mf,/L MG/L
LRS L8S CENT LBS U«S
627.00
126. fl
229.00
3493.1
286.00
4452.3
150.00
3666.1
311.00
10479.5
91.00
294.4
343.00
17,475.3
1060.00
3714.6
-N.A.-
493.00
394S.4
263.00
2038.3
-N.A.-
645.00
9562.9
560.00
7195.7
-N.A.-
107.00
3264.2
194.00
39.2
89.00
1359.5
114.00
1774.7
68.00
1662.0
218.00
7345.7
26.00
84.1
76.00
3872.1
275.00
963.7
-N.A.-
123.00
984.3
60.00
465.0
-N.A.-
212.00
3143.2
141.00
1811.8
-N.A.-
35.00
1067.7
4.99
31 1.0
11.22
39 171.4
a. 44
40 38.0
£.42
45 59.1
.85
70 28.6
9.03
29 ?9.2
.01
22 .5
-N.A.-
26
2.10
5.8
-N.A.-
25
.66
3.4
-N.A.-
23
.40
2.1
1.83
33 27.1
-N.A.-
25
.13
10.1
~-N.A.-
33
.01
.0
.01
.1
.01
.2
.01
.1
.00
.1
.05
.2
.00
.2
-N.A.-
.01
.0
-N.A.-
.00
.0
-N.A.-
.00
.0
.04
.7
-N.A.-
.01
1.1
-N.A.-
FdPCA CONTRACT NO ln-12-402
PHOSPHATES CHLORIDES CHROMIUN
NITWATE TOTAL SOLUABLF
MG/L MG/L MG/L MG/L UG/L
LBS LHS LBS LBS LHS
.19
.0
0.00
0.0
1.03
16.0
1.21
29.6
.69
23.3
4.42'
14.3
.45
22.9
-N.A.-
.82
2.2
-N.A.-
.70
3.6
-N.A.-
.64
3.3
.60
8.9
-N.A.-
.62
48.3
-N.A.-
-N.A.-
-N.A.-
8.57
133.4
3.77
92.1
1.86
62.7
1.48
4.8
-N.A.-
•-N.A.-
6.41
17.6
-N.A.-
2.99
15.4
-N.A.-
2.10
10.9
7.33
108.7
-N.A.-
-N.A.-
-N.A.-
-N.A.-
.05
.8
4.12
64.1
2.61
63.8
9.31
313.7
8.80
28.5
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
3.91
58.0
-N.A.-
-N.A.-
-N.A.-
150.00 -N.A.-
30.3
-N.A.- -N.A.-
-N.A.- -N.AV--
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-M.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.4.-
-N.A.- -N.A.-
-N.A.- -N.4.-
-N.A.- -N.A.-
-------
ro
DES MOINES.!0«A.STO»M WAT£t< POLLUTION
STATION 0-H 1NGEHSOLL HUN OVERFLOW AT
l)i W FLOW
ITEM DATE TIME TYPE HOUR CFS
18 5/32/69 1530 CR 17.00 2.3
19 8/ 7/
-------
J>
CD
|-
m
DES MOINES.IO..£.STO^M «.ATt^ POLUJTlnN COUT^OL STUDY
STATION 0-hA ]l
-------
M
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H
CD
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01
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Dr S
STJ
ITEM
1
?
3
5
e
7
g
9
10
11
1Z
13
14
15
16
17
MOINES, 10
TJON ?-!
DATt
1/15/69
1/15/69
1/15/69
1/1 6/ti9
1/16/69
1/16/69
1/16/69
1 / 16/69
1/16/69
1/16/69
1/16/69
1/16/69
1/16/69
1/16/69
1/17/69
2/ 4/69
2/ 4/69
rf<..t,Tfl-'Ki • 'AT'-1- POLL*;! 1 JM CONTROL
TrtO*-Pv"-l AVt". KTOUV st»tJ
HOT;
PI!1- F L
-------
flfS *01NFS.TOWA.STO»M WATf* PO| Infirm CONTROL
STATION S-l THOMPSON «VF. STOH" Sk.dF"
FWPCA CONT»ACT NO 1<—12-402
ro
in
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H
CD
m
ro
01
o
o
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H*
I«H
18
19
20
21
?2
23
24
86
*7
SB
30
31
32
33
34
DATE
2/ 4/69
?/ 4/69
2/ 5/69
2/ 5/69
2/ 5/69
2/ 5/69
2/21/69
2/21/69
2/22/69
2/22/69
2««/W
2/24/69
2/24/69
2/24/60
?/?5/69
3/ 1/69
TIME
1615
1715
1115
1315
1515
1615
1440
t6 0
1045
16 5
1050
1515
16 0
?1 0
1440
10 0
14 0
TVPF
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
cs
cs
CS
OIJK
HOUf
1.00
1.00
1.00
j.oo
1.00
1.00
1.00
i.po
1.00
1.00
.50
.50
.50
.50
7.00
12.00
o.OO
SUSk'EUDtO SOLIDS MTXU<»F.N PHOSPHATES CHLORIDES
MOD TOTAL VOLATILE AMMOMA NlTPITt M TPATE TOTAL SOLUABLt
FLOtl *1>/L (46/L MO/L PEW Mf>/L Hii/L MI»/L »0/L Ho/L MO/L
CFS LRb LMS LbS CENT LHb L«S L.MS LHS LHS LBS
1.1 -N.A.- 318.00
7A.6
.2 -H.A.- -N.A.-
1.5 -14. A.- 206.00
69.4
3.1 -14. A.- -N.A.-
?.S -M.A.- -14. A. -
.4 -14. A.'- -N.A.-
.9 -N.A.- 1106.00
223.6
.2 -N.A.- -N.A.-
.8 -N.A.- 450.00
80.9
.2 -N.A.- 33.00
.7
2.5 -N.A.- 649.00
182.2
1.4 -N.A.- 500.00
78.6
.6 -N.A.- -N.A.-
1.5 70.00 471.00
165.1 1111.0
3.3 140.00 522.00
1245.4 4643.6
1.9 '8.00 t>62. 00
97.3 1695.3
-N.A.-
66.00
21.3
-N.A.-
62.00
20.9
-N.A.-
-N.A.-
-N.A.-
254.00
51.4
-N.A.-
122.00
21.9
13.00
.3
175.00
4V. 1
135.00
21.2
-N.A.-
146.00
344.4
177.00
1574.5
159.00
407.2
-N.A.- -N.A.- -N.A.- -N.A.- -N.A.- 1045.00
586.9
27 227.3
-N.A.- -N.A.- -N.A.- '-N.A.- -N.A.- 743.00
33.4
-N.A.- -N.A.- -N.A.- -N.A.- -N.A.- 260.00
30 87. b
-N.A.- -N.A.- -N.A.- -N.A.- -N.A.- 579.00
403.2
-N.A.- -N.A.- -N.A.- -N.A.- -N.A.- 502.00
281.9
-N.A.- -N.A.- -N.A.- -N.A.- -N.A.- 2317.00
208.2
23 194.9
-N.A.- -N.A.- -N.A.- -N.A.- -N.A.- 315.00
14.2
-N.A.- -N.A.- -N.A.- -N.A.- -N.A.- 248.00
27 44.6
1.68 .14 1.11 -N.A.- -N.A.- 137.00
39 .0 .0 .0 3.1
27 .9 .1 .4 66.5
-N.A.- -N.A.- -U.K.- -N.A.- -N.A.- -N.A.-
27
-N.A.- -N.A.- -N.A.- -N.A.- -N.A.- 152.00
10.2
3.66 .24 1 .61 -N.A.- .26 -N.A.-
31 8.6 .6 - 3.8 .6
.61 .16 1.04 .31 .10 51.00
34 5.4 1.4 9.3 2.8 .V 453.7
.38 .11 .80 .10 .02 -N.A.-
24 1.0 .3 2.0 .3 .1
CHWOMIOM
UG/L
37.00
' .0
21.00
.0
-N.A.-
-14. A. -
-14. A. -
-N.A.-
168.00
.0
-0.00
0.0
218.00
.0
-M.A.-
-N.A.-
-N.A.-
148.00
.0
-N.A.-
138.00
41.00
.1
-------
IN)
O
o
r
m
ro
01
8
DFS MOINES. lO/'A « STO^f w k I c i- Rdl.L'IT I .)!
S1ATION 1-1 T«rmPSON AV- . iTfiuM SE«
Oh*-- FLOW
ITEM DATE TIME TY^f HOUR CFS
CONTxOL STUD '
SUSPENDED SOLIDS
HOu TOTAL VOLATILf
FwPCO CONTRACT NO 14-12-402
N]r«0('tN PHOSPHATES CHLOWIUt
AMMONIA NITRITE NITRATE TOTAL SOLUABLE
CHROMIUM
3S 3/
0 SS 1.00 2.4
36 6/25/69 16 0 SP 1.00 .?
37 6/26/69 7 0 SN .50 .3
38 6/26/69 80 S" 1.00 3.8
39 8/20/69 930 CK 4.50 2.2
40 9/ 4/69 845 SR .?-5 3.9
41 9/ 4/69 90 SR .50 ».3
42 9/ 4/69 10 0 SR .50 ?.4
43 9/22/69 1540 SR .50 3.8
44 9/22/69 16 0 CR 1.50 4.2
45 9/22/69 1745 CR .75 9.9
46 10/ 2/69 830 SR 1.00 0.0
47 10/30/69 40 CR B.OO .4
46 10/30/69 10 0 SR 1.00 .4
MO/L
LHS
-N.A.-
131.00
5.9
?3.00
.8
19.00
16.?
38.00
84.5
40.00
8.B
-N.A.-
19.00
S.I
44.00
18.8
30.00
42.5
20.00
33.4
50.00
0.0
35.00
25.2
56.00
5.0
M (J / 1
L'-'S
-N.A.-
156.00
7.0
50.00
1.7
50.00
42.7
138.00
306.9
220.00
48.?
-N.A.-
129.00
34.8
305.00
130.2
294.00
416.1
464.00
773.9
-N.A.-
44.00
31.6
145.00
13.0
Mb/L PER
LHS CENT
-M.A.-
1.4 21
-N.A.-
-N.A.-
45.00
100.1 33
68.00
14.9 31
-N.A.-
40.00
10. 8 31
80.00
34.1 26
75.00
106.1 26
142.00
236.8 31
-N.A.-
32.00
23.0 73
69.00
6.2 48
Mn/L
L«S
-N.A.-
-N.A.-
-N.A.-
-N. A.-
H.36
9.7
-N.A.-
1.94
.9
-N.A.-
-N.A.-
1.07
1.5
-N.A.-
-N.A.-
.79
.6
-N.A.-
Ml,/L Mlj/L MG/L MG/L Mb/L
LBS LBS LBS LBS LRS
-N.A.- -N.A.- -N.A.- -N.A.- 2?6.00
121. H
-N.A.- -N.A.- -N.A.- -N.A.- -N.A.-
-N.n.- -N.A.- -N.A.- -N.A.- -N.A.-
-N.A.- -N.A.- -N.A.- -N.A.- -N.A.-
.OS .97 1.75 .54 -N.A.-
.2 2.? 3.9 1.2
-N.A.- -N.A.- -N.A.- -N.A.- -N.A.-
.04 1.30 .88 .41 -N.A.-
.0 .fa .4 .2
-N.A.- -N.A.- -N.A.- -N.A.- -N.A.-
-N.A.- -N.A.- -N.A.- -N.A.- -N.A.-
.04 .97 1.06 .01 -N.A.-
.1 1.4 1.5 .0
-N.A.- -N.A.- -N.A.- -N.A.- -N.A.-
-N.A.- -N.A.- -N.A.- -N.A.- -N.A.-
.06 .67 -N.A.- .24 -N.A.-
.0 .6 .2
-N.A.- -N.A.- -N.A.- -N.A.- -N.A.-
UG/L
L^s
-N . A . -
-N. A.-
-N.A.-
-N.A.-
-N. A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-------
OES MOINES. IO4A.STO
STATION S-3 CUMMINS
PA>JKHAY STOPM
T>-'i )L
SUSPENDED SOLIDS
HOD TOTAL VOLATILE
K*PCA CONTRACT NO 14-12-402
NITKOOEN PHOSPHATES CHLO»IDtS CHROMIUM
NITHITE NITRATE TOTAL SOLUABLF
IN)
t—i
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CD
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1
ITEM
1
2
3
4
3
6
j
8
9
1 fl
1 U
11
12
13
14
15
1 f.
I O
17
OATE
1/15/69
1/15/69
1/15/69
1/69/69
1/16/69
1/16/69
I/ 16/69
1/16/69
1/16/69
i y i fc/ftQ
I f 1 O/ O^
a/ 4/69
a/ 4/69
a/ 4/69
2/ 5/69
2/ 5/69
2/ 5/69
2/ 5/69
TIMF
18 0
18 0
22 0
2 0
6 0
1045
14 0
17 0
18 0
19 n
IT U
16 0
17 0
18 0
15 0
16 0
17 0
18 0
TYPF
CS
SS
SS
SS
SS
SS
55
SS
SS
cc
Do
SS
SS
SS
SS
SS
gt,
SS
IjlU
HOUW
24.00
4.00
4.00
4.00
4.00
4.00
4.00
1.00
1.00
1.00
1.00
-1.00
-1.00
1.00
1.00
i.oo
1.00
FLU*
CFS
1.8
.3
.4
3.3
1.2
1.4
5.0
.9
.4
B 2
2.3
N.A.
N.A.
?.«
2.0
1.2
.7
MG/L
LHS
31.00
300. H
64.00
17.3
-M.A.-
?4.0(J
71.?
-fJ.A.-
J8.00
47. H
— N • A .- —
-N.A.-
33.00
3.0
-N.A.-
-N.A.-
-N . A . -
-N.A.-
-N.A.-
-N. A . -
-N.A.-
M(j/L
LtlS
302.00
2930.7
450.00
121.3
-N.A.-
454.00
134b.2
-N.A.-
471.00
592.5
— N » A e —
-N.A.-
204.00
18.3
-N.A.-
-N.A.-
-N.A.-
358.00
225.2
-N.A.-
— N . A . —
-N.A.-
Mu/L PtK
LbS CENT
90.00
873.4 30
140.00
37.7 31
-N.A.-
77.00
228.3 17
-N.A.-
104.00
130.8 22
— N • A o —
-N.A.-
66.00
6.1 33
-N.A.-
-N.A.-
-N.A.-
93.00
58.5 26
-N.A.-
-N. A. -
-N.A.-
fti/L M'i/L
LHS LRS
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.ft.- -N.A.-
-N.A.- -N.A.-
-M.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-I^.M.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
MG/L
Lbb
2.17
21.1
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N . A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
MG/L
LHS
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
— N . A •—
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
MG/L
LHS
.12
1.2
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
— N. A .—
-N.A.-
-N.A.-
-N.A.-
-
-N.A.-
-N.A.-
-N.A.-
MG/L
LRS
100.00
970.4
2004.00
540.2
1608.00
1300.4
367.00
108H.2
262.00
282.5
190.00
239.0
34. 00
152.8
34.00
6.9
30.00
2.7
18*00
.8
1731.00
894.4
1734.00
1486.00
1703.00
1071.2
691.00
310.5
f»?ft on
O ' O • U U
182.8
716.00
US XL
LHS
-N.A.-
1210.00
.3
-N.A.-
-N.A.-
200.00
.2
-N.A.-
— N. A.-
-N.A.-
-N.A.-
1 30. 00
.0
199.00
.1
253.00
163.00
-N.A.-
-N.A.-
— N ft *
-N.A.-
112.6
-------
DES MOlMC&t IOHO.ST1SM »STt" POLLUTION OWTKOL STUOT
STATION S-3 CUMMINS P4WI-W4Y STOW-' SE*F."
FrfPLA CONTRACT NO 14-12-402
ro
IN)
H
CD
i-
m
ro
tn
wi
0
O
z
ITEM
18
19
20
21
22
23
_
24
«
27
28
29
30
31
32
33
34
DATE
2/21/69
2/22/69
2/24/69
2/25/69
2/26/69
3/ 1/69
3/ 2/69
3/ 2/69
-- -
3/ 2/69
6/Z2/69
6/22/69
6/22/69
6/22/69
6/22/69
6/26/69
6/26/69
TIME
1625
1130
1510
11 0
1330
IS 0
13 0
14 0
IS 0
A 9 u
16 0
1540
16 0
17 0
18 0
19 0
12 0
1215
TYPE
SS
SS
SS
CS
cs
cs
SS
SS
SS
SS
s*
SR
SR
SR
s«
SP
SS
OMP
HOUf
1.00
1.00
1.00
9.00
7.00
2.00
1.00
1.00
1 .00
1.00
.25
.75
1.00
1*00
1.00
.25
.25
\J" " OC. »
FLO*
CFS
.2
.1
2.0
5.0
3.7
2.2
.3
.9
1.1
.9
.3
3.8
5.8
4.2
9.4
7.5
4.8
If- ~
BOO
HG/L
LRS
-N.A.-
-N.A.-
-N.A.-
153.00
1546.6
125.00
727.3
47.00
46.5
-N.A.-
-N.A.-
-N.A.-
. -X.A.-
154.00
2.6
166.00
106.3
105.00
136.8
111.00
104.7
111.00
234.4
14.00
S.9
-N.A.-
SUSPENDED SOLIDS
TOTlL VOLATILE
MG/L
LHS
531.00
41.8
126.00
2.9
1025.00
460.5
1212.00
12251.9
357.00
2077.1
-N.A.-
-N.A.-
-N.A.-
•N. A»-
-N.A.-
9.00
.2
1 146.00
733.7
476.00
620.2
340.00
320.8
307.00
648.3
14.00
-N.A.-
MG/L PER
LBS CENT
214.00
9.6 23
30.00
.7 23
195.00
87.6 19
182.00
1839.8 15
-N.A.-
-N.A.-
-N.A.-
-U.A.-
•N. A.»
-N.A.-
6.00
.1 67
175.00
112.0 15
60.00
76.2 13
102.00
96.2 30
43.00
90. 6 14
to .00
2.5 — W
-N.A.-
NITKOGFN
AMMONIA NITRITE NITRATE
Mu/L
LBS
-N.A.-
-N.A.-
3.3?
1.5
.86
8.7
2. 6*.
15.5
.69
.7
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
.70
.2
MG/L MG/L
LHS LBS
-N.A.- -N.A.-
-N.A.- -N.A.-
.00 .19
.0 .1
.01 1.02
.1 10.3
.01 .65
.0 3.8
.01 4.49
.0 4.4
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
.01 .2e
.0 .1
PHOSPHATES CHLORIDES
TOTAL SOLUAHLt
MG/L
L9S
-N.A.-
-N.A.-
-N.A.-
.26
2.6
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
.79
.2
MG/L
LBS
-N.A.-
-N.A.-
-N.A.-
.25
2.5
-N.A.-
.05
.0
-N.A.-
-N.A.-
•N. A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
.30
.1
MG/L
,LRS
2724.00
122.4
5H9.00
13.2
-N.A.-
56.00
566.1
34.00
197.8
251.00
248.1
201.00
13.5
179.00
36.2
126.00
31.1
159.00
32.1
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
CHHOMIUM
UG/L
LR«;
876.00
.0
164.00
.0
-N.A.-
345.00
3.5
-N.A.-
167.00
.2
47.00
.0
-N.A.-
139.00
.0
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-------
DCS MOTNES.IOWA.STORM MATER POLLUTION CONTROL STUDY
STATION S-3 CUMMINS PARKWAY STOHM SEWER
BOO
DUK FLOW MG/L
ITEM DATE TIME TYPE HOUR CFS LBS
SUSPENDED SOLIDS
TOTAL VOLATILt
MO/L MG/L PER
LHS LBS CENT
NIIMOGEN
AMMONIA NITRITt
MG/L Mb/L
LBS LBS
FrfPCA CONTRACT NO 14-12-402
PHOSPHATES CHLORIDES CHROMIUM
NITRATE TOTAL SOLUABLE
MbVL MG/L MG/L MG/L UG/L
LBS LBS LBS LBS LHS
CsJ
U>
H
00
f-
m
ro
en
o
o
39
36
„
37
36
39
*0
41
**
43
44
45
46
47
6/26/69
6/26/69
6/26/69
B/ 7/69
8/ 7/69
8/20/69
«/ 4/69
9/ 4/«»
«/ 4/69
»/ 13/69
4/13/69
10/ 2/69
Ifr/ 2/69
-
17 0
1715
1730
730
8 0
10 0
830
845
9 0
2045
21 0
830
845
SR
SR
SR
SR
SR
CR
SR
SR
SR
CR
SR
SR
SR
.25 5.8
.25 47.9
.25 17.1
.50 1.1
.50 .2
4.00 2.7
.25 8.9
.25 0.0
r
.25 0.0
4.00 1.5
.25 10.2
.25 0.0
.25 0.0
-N.A.-
23.00
61.9
22.00
21.1
1 7 on
1 1 . UU
2.1
56.00
1.3
29.00
70.4
27.00
13.5
-N.A.-
53.00
0.0
27.00
36.4
31.00
17.8
56.00
0.0
-N.A.-
3170.00
1032.6
1260.00
3389.5
604.00
580.0
-N.A.-
59.00
143.1
521.00
260.4
-N.A.-
-N.A.-
50.00
67.4
29.00
16.6
-N.A.-
-N.A.-
276.00
89.9
160.00
430.4
82.00
78.7
-N.A.-
12.00
29.1
90.00
45.0
-N.A.-
-N.A.-
17.00
22.9
-N.A.-
-N.A.-
-N.A.-
-N.A.-
9
-N.ft.-
13
.70
14 .7
• 83
.1
-N.A.-
1.94
20 4.7
-N.A.-
17
2.62
0.0
-N.A.-
.78
34 1.1
-N.A.-
-N.A.-
2.47
0.0
-N.A.-
-N.A.-
.02
.0
. 08
.0
-N.A.-
.02
.0
-N.A.-
.06
0.0
-N.A.-
.06
.1
-N.A.-
-N.A.-
.01
0.0
-N.A.- -N.A.-
-N.A.- -N.A.-
.29 1.76
.3 1.7
-N.A.- -N.A.-
.54 .64
1.3 1.6
-N.A.- -N.A.-
.90 1.42
0.0 0.0
-N.A.- -N.A.-
1.02 .45
1.4 .6
-N.A.- -N.A.-
-N.A.- -N.A.-
4.61 1.16
0.0 0.0
-N.A.-
-N.A.-
.66
.6
-N.A.-
.59
1.4
-N.A.-
.89
0.0
-N.A.-
.38
.5
.40
.2
-N.A.-
.69
0.0
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-N.A.- -N.A.-
-------
OES MOINES«IOHA.STO»M *ATE& POLLUTION CONTROL STUDY
STATION 0-11 20TH ST. bTO»M SEwE* AT DEAN LAKt
>
CD
r
m
i»
01
o
o
800
DHU FLOW r*G/L
ITEM DATE TIME TYPE HOUH CFS LBS
1 2/22/69 2330 SS 1.00 .9 -N.A.-
2 2/24/69 1130 SS 1.00 .6 -N.A.-
-3 2/24/69 12 0 CS 24.00 2.6 69.00
967.2
4 2/25/69 12 0 SS I'.OO 3.0 127.00
85.6
5 2/25/69 13 0 SS 1.00 15.0 -N.A.-
f> 2/25/69 14 0 CS 4.00 ?9.4 -N.A.-
7 2/25/69 19 0 SS 1.00 10.0 143.00
321.2
9 2/25/69 20 0 SS 1.00 5.9 -N.A.-
9 g/26/69 21 0 CS 15.00 1.7 129.00
739.0
10 2/27/69 12 0 CS 22.00 5.1 51.00
1285.4
11 2X28/69 1440 SS 1.00 2.2 -N.A.-
12 3/ 1/69 14 0 CS 11.00 4.7 53.00
615.5
13 3/ 1/69 13 0 SS 1.00 3.8 -N.A.-
14 3V 2/69 11 0 CS 12.00 1.7 35.00
160.4
15 3/ 2/69 11 0 SS I.00 .3 -N.A.-
16 3/ 2/69 14 0 SS 1.00 ?.7 -N.A.-
MU-AOA/69__1015 CH 12.00 4.6 37.00
458.4
SUSPENDED SOLIDS
TOTAL VOLATILE
NITKOGF.N
AMMONIA NITWITE
FuPCA CONTRACT NO 14-12-402
PHOSPHATES CHLOHIDES CHROMIUM
NITKATE TOTAL SOLUABLE
MO/L
LBS
162.00
32.8
41.00
5.5
528.00
7401.3
597.00
402.3
-N.A.-
-N.A.-
-N.A.-
167.00
221.3
49.00
280.7
207.00
5217.4
—N • A . —
S29.00
9627.9
-N.A.-
2H7.00
1315.2
-N.A.-
-N.A.-
411.00
5096.5
Mo/L PER
LtiS CENT
57.00
11.5 35
18.00 . -
2.4 44
185.00
2593.2 35
197.00
132.8 33
-N.A.-
-N.A.-
-N.A.-
63.00
83.5 38
35.00
200.5 71
79.00
1991.2 38
-N.A.-
216.00
2508.6 26
-N.A.-
-N.A.-
-N.A.-
-N.A.-
126.00
1562.4 31
MC./L
L>iS
-N.A.-
1.88
.3
3.60
50.5
-N.A.-
.40
1.3
1.80
47.6
.66
1.5
-N.A.-
1.14
6.5
4.57
1 15.2
-N. A.-
.78
9.1
-N.A.-
1.94
8.9
-N.A.-
-N.A.-
.43
5.3
MG/L
LHS
-N.A.-
.20
.0
.03
.4
-N.A.-
.00
.0
.01
.3
.03
.1
-N.A.-
.01
.1
.01
.2
~N» A ,—
.01
.1
-N.A.-
.01
.0
-N.A.-
-N.A.-
.00
' .0
MG/L
LdS
-N.A.-
1.89
.3
.61
B.b
-N.A.-
.31
1.0
,21
7.1
1.06
2.4
-N.A.-
1.21
6.9
1.04
26.2
1.02
11. B
-N.A.-
.66
3.9
-N.A.-
-N.A.-
1.18
14.6
MG/L
LBS
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-«.«.—
-N.A.-
.26
1.5
.29
7.3
.18
2.1
-N.A.-
.09
.4
-N.A.-
-N.A.-
2.32
28.8
Mlj/L
LBS
iN.A.-
-N.A.-
.27
3.8
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
.23
1.3
.28
7.1
.03
.3
-N.A.-
.07
.3
-N.A.-
-N.A.-
.46
5.7
MG/L
LBS
292.00
59.0
139.00
18.7
-N.A.-
114.00
76.8
86.00
289.8
42.00
1109.5
-N.A.-
37.00
49.0
• 42.00
240.6
35.00
882.2
514.00
254.0
-N.A.-
306.00
261.2
-N.A.-
131.00
8.8
111.00
67.3
-N.A.-
UG/L
LHS
139.00
.0
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
137.00
.8
21.00
.5
•M A —
W« ** •
66.00
.8
76.00
.1
47.00
.2
-N.A.-
-N.A.-_
-N.A.-
-------
DFS MO IMPS. IO\
STATION .1-1 1 ?l
to
en
H
CD
r
m
M
m
o
O
z
ITEM
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
OATt
4/17/69
5/ 7/69
5/ 8/69
5/ 7/69
5/ 7/69
5/ 7/69
5/ 7/69
S/ 8/69
5/17/69
5/26/69
7/ 8/69
7/ 9/69
7/ 9/69
7/17/69
7/17/69
7/23/69
7/23/69
n- <-r"
TIME
1845
1730
130
1730
1830
1930
2330
030
3 0
8 0
10 0
2 0
5 0
930
10 0
725
735
'•/» WATt'K POLLUTION CONTROL
. STOP" bf>f« Al UEA.,1 LAKE
TYPt
CR
C(*
CK
SR
SR
SR
SR
SR
CR
CR
CR
CR
CK
SR
CR
SP
SR
HUH
HOUP
23.00
8.00
8.00
1.00
1.00
1.00
1.00
1.00
10.00
5.00
16.00
3.00
5.00
.50
3.00
.50
.SO
FLOW
CF'i
S.5
30.0
6.6
6.2
20.9
31.9
29.4
17.2
14.1
12.0
1.3
6.8
39.0
4S.8
16.5
67.3
67.3
MG/L
LBS
12.00
341.0
11.00
1671.3
22.00
260.9
137.00
190. 8
38.00
178.4
-N.A.-
28.00
184.9
-N. A.-
51.00
1615.4
77.00
1037.8
14.00
65.4
25.00
114.6
28.00
1226.5
12.00
61.7
20.00
222.4
38.00
287.2
STUDf
SUSPENDED SOLIDS
TOTAL VOLATILE
MG/L
L«S
234.00
6649.6
381.00
20541.1
97.00
1150.5
-N.A.-
-N.A.-
640.00
6396.8
-N.A.-
267.00
1031.6
880.00
27873.3
880.00
11861.0
40.00
186.9
358.00
1640.6
658.00
28823.6
202.00
1039.1
135.00
1501.2
508.00
4444.8
MG/L Hl-S
LBS CENT
71.00
2017.6 30
83.00
4474.8 22
28.00
332.1 29
-N.A.-
-N.A.-
224.00
1705.8 27
-N.A.-
76. 00
293.6 28
174.00
5511.3 20
204.00
2749.6 23
15.00
70.1 37
72.00
330.0 20
121.00
5300.4 18
57.00
293.2 28
It). 00
200.2 13
146.00
1103.6 25
NITHOGeN
AMMONIA NITWITF
ML'/L
Lnb
.06
1.7
.32
17.3
.66
7.H
-N.A.-
-N.A.-
-0.00
0.0
-N.A.-
.49
15.5
1.40
18.9
27.78
129.8
.58
2.7
4.74
207.6
.56
2.9
.49
5.".
. 6n
5.1
MG/L
LHS
.15
4.3
.01
. 3
.01
. 1
-N. A.-
-N.A.-
-0.00
0.0
-N.A.-
.03
1.0
.01
.1
.04
.2
.06
.3
.01
.4
.01
.1
.01
.1
08
.6
FKPCA CONTRACT NO 14-12-402
PHOSPHATF.S CMLORIDtS CHROMJu
NITHATF TOTAL SOLUAHLE
MG/L
Ldb
\.d£
34.7
.67
36. 1
1 .HO
21.3
-N. A.-
-N.A.-
-0.00
0.0
-N.A.-
.22
7.0
1.30
17.5
1.96
9.2
1.67
7.7
.68
29.8
.41
Z.I
.52
5.S
11. u
MG/L
LbS
1.37
3H.9
2.08
112.1
1.50
17.8
-N.A.-
-N.A.-
-0.00
0.0
-N.A.-
4.21
133.3
2.61
35.2
.82
3.8
2.63
12.1
2.64
115.6
-N.A.-
.93
10.3
2.66
20.1
MG/L
L8S
1.35
38;4
.60
32.3
1.14
13.5
-N.A.-
-N.A.-
-0.00
0.0
-N.A.-
2.36
74.8
.21
2.8
.20
.9
.52
2.4
.43
18.8
.50
2.6
.73
8.1
.48
3.6
MG/L
Las
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-N.A.-
-0.00
0.0
-N.A.-
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DES MOIRES. lOXft.STOh
STATION 0-1 I 30Tn ST.
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35 7/23/69 1145
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TYPE HOUR CFS LBS
SP .50 40.8 35.00
160.4
SR .50 ?7.2 -N.A.-
SR 1.00 20.9 23.00
108.0
SR .50 3.2 39.00
14.0
SR .50 6.2 -N.A.-
SR .50 H.O 65.00
58.4
SR .50 7.6 -N.A.-
SR .50 6.9 34.00
26.4
SR .5.0 4.6 -N.A.-
SR .50 3.ft 47.00
20.1
CR T.OO 2.0 50.00
157.2
SR .50 2.B 86.00
27.7
CR 2.00 18.8 44.00
371.6
CR 3.00 23.6 38.00
604.4
CR 9.00 4.1 100.00
828.9
SP 1.00 1.1 100.00
24.7
SP 1.00 3." 125.00
106.7
SUSPENDED SOLIDS
TOTAL VOLATILE
MG/L MG/L PER
LHS LBS CENT
NITHUGEN
AMMONIA NITRITE
MGYL MG/L
LHS LHS
F*PCA CONTRACT NO 1<«-12-402
PHOSPHATES CHLOtflDES CHROMIUM
N1TKATE TOTAL SOLUABLE
MG/L MG/L MG/L. MG/L UG/L
LHS LHS LBS LHS L-IS
808.00
3702.8
-N.A.-
356.00
1671.4
196.00
70.4
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280.00
2S1.6
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— N • A . -
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247.00
105.4
95.00
29S.8
569.00
178.9
487.00
4113.4
410.00
6520.6
1053.00
8728.5
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-N.A.-
122.00
559.1
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66.00
309.9
54.00
19.4
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64.00
57.5
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64.00
27.3
41.00
128.9
167.00
52.5
119.00
1005.1
91.00
1447.3
484.00
4012.0
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15
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28
2.42
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23
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1.9
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15.4
1.32
21.0
12.00
99.5
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FIGURE 66 CON'T
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269
FIGURE 66 CONT
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FIGURE 66 CON'T
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APPENDIX D
DESIGN AND ASSEMBLY OF
BUBBLERrTYPE LIQUID LEVEL RECORDER
Bubbler-type liquid level recorders were designed and fabricated by
the Contractor as a part of this project. This was done to provide
a recording device which meetsthe particular requirements of the
monitoring program.
The requirements were as follows:
1. The unit must be capable of recording a wide range of liquid
levels in sanitary, storm, and combined sewers.
2. The unit would be placed in a weather-proof enclosure and
located at street curb, outside in remote locations, and in sewer
manholes.
3. The unit must be portable and self-sufficient. External power
would not be available.
4. The unit must be vandal-proof.
5. The unit should have no moving parts in the monitored flow and
should have no significant obstruction in the flow pattern.
6. The unit should be capable of being installed at some distance
from the monitored point.
7. The unit should not be subject to damage from freezing or ice
cover.
The concept selected was a bubbler-type installation used frequently
for liquid level recording in wastewater treatment facilities and pump-
ing stations. The gas supply would be from high-pressure cylinders
using either dry air or carbon dioxide. A pressure recorder, re-
gulating valves, and gas supply would be enclosed in a water-proof and
vandal-proof case, small enough to be portable. Plastic or other
flexible tubing would be used to convey the gas from the unit to the
point of monitoring.
Figure 79 contains a sketch of the unit with identification of the major
309
-------
components. The unit and typical installations are pictured in
Figure 7 and numerous other figures throughout the text of this
report.
The basic components of the bubbler unit are:
1. Foxboro Model 12 R 12-inch circular case pressure recorder.
The recorder has a two-speed spring wound chart drive for 24-hour
or 7-day operation and simultaneously operating high and low level
recording elements (0 to 30" and 0 to 300" of water) with over-range
protection for the low range element.
2. Foxboro Purge Rotometer, Model D- 105-NX, manually ad-
justable to supply air or CO2 at 0.2 to 2.0 CFH with a metering tube
for visual indication of flow.
3. Foxboro Type 67 supply regulator, with 2" MH outlet pressure
gage. Maximum supply pressure is 250 psi and range of control
pressures (outlet pressure) is 2 to 50 psi.
4. Cornelius CO^ type step-down Regulator, Model 28433-1, with
0 to 2000 psi inlet pressure gage and 0 to 100 psi outlet pressure
gage, for initial pressure reduction from air cylinder.
5. Compressed air cylinders, 20 Ib. size, filled with dry air to
1800 to 2000 psi.
6. Vandal-proof steel case, 10" deep by 24" wide by 36" high.
In the interest of minimizing the time required for assembly and
delivery of the units, the enclosure was fabricated and the unit
assembled by local shops. Metal piping was 1/4" wrought iron pipe.
Mounting of step-down regulator directly to the compressed air
cylinder permitted the use of high pressure plastic tubing connection
to the supply regulator. The case was provided with holes in the
base for securing the unit and an opening in the back for the bubbler
line. Where vandal-proofing was required, the plastic bubbler line
was encased in aluminum electrical conduit.
310
-------
IO"X 24"X36" HIGH, 16 GAGE
( 1/16" ) STEEL CASE , WELDED
WATERTIGHT
!2"X28"xl/4" BASE PLATE
SLOT FOR 1/4"X l" WITH
LOCKING BAR a PADLOCK^
-OUTLET PRESSURE GAGE.O-IOOpsi
HOLE
HANDLE WELDED
ON EACH SIDE
f INLET PRESSURE GAGE , 0 -2000psi
/CORNELIUS CO; TYPE REGULATOR, MODEL 28433-1
-------
SELECTED WATER
RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
A ccession Mo,
w
4. This
Combined Sewer Overflow Abatement Plan, Des Moines, Iowa
7. Authot(s)
Davis, Peter L.
Borchardt, F. A.
9. Organization
Henningson, Durham & Richardson, Inc., Omaha, Nebraska
•Office 'Of Research & Develoflipenit' •,
is. Supplement^ Notes Environmental Protection Agency Report
Number, EPA-R2-73-170, April 1974.
10. Project No.
11024 FEJ
//. Contract/Grant No.
14-12-402
16. Abstract
Combined sewer overflows, storm water discharges, and surface waters in the Des Moines,
Iowa Metropolitan Area were sampled for 12 months to determine their pollutional
characteristics. Various systems of separation and collection and treatment of
combined sewer overflow and storm water discharges were designed, estimated and
evaluated. Analyses were made of the data collected and of the various system
problems encountered.
The studies indicate 174,500 pounds of BOD are discharged annually from a 4,000 acre
combined sewer drainage area, and 2,668,000 pounds of BOD from 45,000 acres served by
separate storm sewers. Average concentrations of pollutants in storm water were
53 mg/1 BOD, 448 mg/1 SS, 1.78 mg/1 NH3-N, 1.10 mg/1 N03-N, and 1.65 mg/1 Total P04.
Average concentrations of pollutants in combined sewer overflows were 72 mg/1 BOD,
329 mg/1 SS, 4.79 mg/1 NH3-N, 0.74 mg/1 N03-N, and 8.92 mg/1 Total PO^.
Several combined sewer overflow abatement projects are recommended for implementation.
17a. Descriptors
*0verflow, *Combined Sewers, *Storm Runoff, *Water Quality, *Waste Treatment,
*Rainfall-Runoff Relationships, Capital Costs, Operating Costs.
17b. Identifiers
*Combiiled Sewer Separation, *Combined Sewer Overflow Abatement, Detention Ponds,
Des Moines, Iowa
17c. COWRR Field & Group
18.
Secure v
$e >rityC!
(Page)
Abstractor
Richard Field
102 (REV JUNE 197))
Send To :
WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON. D. C. 2O24O
S. Environmental Protection Agsncy
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