t:LEAl
WATER POLLUTION CONTROL RESEARCH SERIES
11024FKN11/69
Stream Pollution And Abatement
From Combined Sewer Overflows
BUCYRUS, OHIO
U.S. DEPARTMENT OF THE INTERIOR • FEDERAL WATER QUALITY ADMINISTRATION
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WATER POLLUTION CONTROL RESEARCH SERIES
The Water Pollution Control Research Reports describe the results and
progress in the control and abatement of pollution of our Nation's
waters. T^ey provide a central source of information on +>ie research,
development and demonstration activities of the Federal Water Quality
Administration, Department of the Interior, through in-house research
and grants and contracts with Federal, State, and local agencies,
research institutions, and industrial organizations.
Triplicate tear-out abstract cards are placed inside the back cover to
facilitate information retrieval. Space is provided on the card for
the user's accession number and for additional keywords.
Inquiries pertaining to Water Pollution Control Research Reports should
be directed to the Head, Project Reports System, Room 1103, Planning
and Resources Office, Office of Research and Development, Department
of the Interior, Federal Water Quality Administration, Washington, D.C.
202U2.
Previously issued reports on the Storm and Combined Sewer Pollution
Control Proaram:
WP-20-11 Problems of Combined Sewer Facilities and Overflows -
1967.
¥P-£0-15 Water Pollution Aspects of Urban Runoff.
¥P-20-16 Strainer/Filter Treatment of Combined Sever Overflows.
wP-^O-17 Dissolved Air FloTatron MT*eatment of Commned .^fiwer
Overflows.
WP-'>0-l8 Improved Sealants for Infiltration Control.
WP-20-21 Selected Urban Storm WaLej.- Runoff Abstracts.
WP-20-22 Polymers for Sewer Flow Control.
ORD-lf Combined Sewer Separation Using Pressure Sewers.
DAST-U Crazed Resin Filtration of Combined Sewer Overflows.
DAST-5 Rotary Vibratory Fine Screening of Combined Sewer
Overflows.
DAST-6 Storm Water Problems and Control in Sanitary Sewers,
Oakland and Berkeley, California.
DAST-9 Sewer Infiltration Reduction by Zone Pumping.
DAST-13 Design of a Combined Sewer Fluidic Regulator.
DAST-25 Rapid-Flow Filter for Sewer Overflows.
DAST-29 Control of Pollution by Underwater Storage.
DAST-32 Stream Pollution and Abatement from Combined Sewer
Overflows - Bucyrus, Ohio.
DAST-36 Storm and Combined Sewer Demonstration Projects -
January 1970.
DAST-37 Combined Sewer Overflow Seminar Papers.
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STREAM POLLUTION AND ABATEMENT FROM COMBINED SEWER OVERFLOWS
BUCYRUS, OHIO
A Study of Stream Pollution
From Combined Sewer Overflows and
Feasibility of Alternate Plans for
Pollution Abatement in Bucyrus, Ohio
FEDERAL WATER QUALITY ADMINISTRATION
DEPARTMENT OF THE INTERIOR
by
Burgess and Niple, Limited
Consulting Engineers
2015 West Fifth Avenue
Columbus, Ohio 43212
Contract No. 14-12-401
I 1024 FKN
November, 1969
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price $2.
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FWPCA Review Notice
This report has been reviewed by the Federal
Water Pollution Control Administration and
approved for publication. Approval does not
signify that the contents necessarily reflect
the views and policies of the Federal Water
Pollution Control Administration.
i i
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ABSTRACT
This report contains the results of a detailed engineering investigation
and comprehensive technical study to evaluate the pollutional effects
from combined sewer overflows on the Sandusky River at Bucyrus, Ohio and
to evaluate the benefits, economics and feasibility of alternate plans
for pollution abatement from the combined sewer overflows. The City of
Bucyrus is located near the upper end of the Sandusky River Basin which
is tributary to Lake Erie. Bucyrus has an incorporated area of about
2,340 acres, a population of 13,000, and a combined sewer system with an
average dry weather wastewater flow of 2.2 million gallons per day. A
year long detailed sampling and laboratory analysis program was con-
ducted on the combined sewer overflows in which the overflows were
measured and sampled at 3 locations comprising 64$ of the City's sewered
area and the river flow was measured and sampled above and below
Bucyrus.
The results of the study show that any 20 minute rainfall greater than
0.05 of an Inch will produce an overflow. The combined sewers will over-
flow about 73 times each year discharging an estimated annual volume of
350 million gallons containing 350,000 pounds of BOD and 1,400,000
pounds of suspended solids. The combined sewer overflows had an average
BOD of 120 mg/l, suspended solids of 470 mg/l, total col I forms of
11,000,000 per 100 ml and fecal col I forms of 1,600,000 per 100 ml. The
BOD concentration of the Sandusky River, immediately downstream from
Bucyrus, varied from an average of 6 mg/l during dry weather to a high
of 51 mg/l during overflow discharges. The suspended solids varied from
an average of 49 mg/l during dry weather to a high of 960 mg/l during
overflow discharges. The total coliforms varied from an average of
400,000 per 100 ml during dry weather to a high of 8,800,000 per 100 ml
during overflow discharges.
Various methods of controlling the pollution from combined sewer over-
flows are presented along with their degree of protection, advantages,
disadvantages and estimates of cost. The methods presented include
(I) complete separation, (2) interceptor sewer and lagoon system,
(3) stream flow augmentation, (4) primary treatment, (5) chlorination,
and (6) offstream treatment. It was concluded that the most economical
method of providing a high degree of protection to the Sandusky River is
by collecting the combined sewer overflows with a large interceptor and
using an aerated lagoon system to treat the waste loads from the over-
fIows.
This report was submitted In fulfillment of Contract 14-12-401 between
the Federal Water Pollution Control Administration and Burgess & Niple,
Limited.
ii
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CONTENTS
Section Page
I. Conclusions and Recommendations I
I I. Introduction 7
III. Purpose and Scope 9
IV. Study Area I I
V. Procedures 13
VI. Dry Weather Conditions 17
Collection System 17
Interceptor System 17
Wastewater Treatment Plant 17
Sandusky River 18
VII. Wet Weather Conditions 19
Col lection System 19
Interceptor System I 9
Wastewater Treatment Plant 20
Sandusky River 20
VIII. Meteorological and Hydro logical History 21
Meteorological History 21
Hydrological History 21
IX. Weather Conditions During Study Period 25
Rainfal I Data 25
Sandusky River Flow 25
X. Drainage Characteristics of the Sewer Districts 29
History 29
General Description 29
Detailed Description 30
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Section Pa9e
XI. Hydraulic Analysis of the Sewer and Interceptor
Systems 35
Sewer Systems 35
Interceptor System 36
XII. Analysis of Rainfall and Overflow Data 41
Tabulation of Hydraulic Data 41
Rainfall versus Overflow Graphs 41
Analysis of Rainfall Data 42
XIII. Wastewater Characteristics of Combined Sewer
Overflows and Receiving Stream 47
Dry Weather Samp I Ing 47
Overflow Samples 48
Sandusky River Samples 49
XIV. Aquatic Biology Survey of the Sandusky River 69
XV. Relationship of Rainfall and Runoff 75
Start of Overflow 75
Hydrograph Shape 76
Hydrograph Peak and Volume 77
(I) Rational Formula 78
(2) Hydrograph Method 83
(3) Modified Hydrograph Method 83
XVI. River Response to Rainfall 89
Urban Runoff Hydrograph 89
Upstream Drainage Basin Runoff Hydrograph 89
XVII. Evaluation and Correlation of Waste Load Data 91
Waste Loads versus Overflows 91
Waste Loads versus Rainfall 9'
Effect of Overflows on River Water Quality 92
VI
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Section Page
XVIII. General Design Conditions 95
Design Storms 96
Peak Rate of Overflow 97
Volume of Overflow 98
Design Waste Loads 98
XIX. Alternate Solutions 105
A. Complete Separation of Sanitary
Wastewater and Storm Sewer 105
(I) Advantages of Separate Sewer Systems 105
(2) Disadvantages of Separate Sewer
Systems 105
(3) Cost of Sewer Separation 106
B. Interceptor Sewer and Lagoon System 107
(I) Gravity Interceptor System 107
(2) Interceptor Sewer Using Holding
Tanks 107
(3) Pump Station 108
(4) Aerated Lagoon 108
C. Stream Flow Augmentation 112
D. Primary Treatment of Overflows 113
E. Chlorination of Overflows 114
F. Off-Stream Treatment 114
XX. Procedure for Evaluating Similar Systems in
Other Communities I'7
Analyze Existing Sewer System 118
Select Design Storm and Return Frequencies 118
Determine the Runoff From Design Storms 119
Determine Waste Loads From Design Storms 120
Method of Collection and Treatment 120
XXI. Acknowledgments 123
XXII. References '25
XXIII. Figures 129
VI I
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TABLES
Table Page
I Average Monthly Rainfall at Bucyrus, Ohio 23
2 Percent of Time Indicated Sandusky River Flow at
Bucyrus is Equaled or Exceeded 24
3 Rainfall During Study Period 26
4 Sandusky River Flow During Study Period 27
5 General Drainage Characteristics of Selected
Sewer Districts 32
6 Land Use and Land Cover of Selected Sewer Districts 33
7 Drainage Areas and Classifications 34
8 Maximum Sewer System Capacities and Times of
Concentration 38
9 Maximum Overflow Rates 39
10 Rainfall and Overflow Data - Number 8 Sewer District 43
II Rainfall and Overflow Data - Number 17 Sewer District 44
12 Rainfall and Overflow Data - Number 23 Sewer District 45
13 Data Summary 51
14 Summary of Dry Weather Waste Loads 52
15 Summary of Laboratory Analyses On Overflow Samples 57
16 Summary of Waste Loads for Each Overflow Event 60
17 Summary of Wet and Dry Weather River Analyses 63
18 Summary of Aquatic Biology Survey of the Sandusky
River 70
19 Time to Start of Overflow 75
20 Rainfall to Cause Overflow 76
21 Runoff Coefficients 79
IX
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Table Page
22 Weighted Runoff Coefficients 79
23 Comparison of the Rational Formula to Measured Data 81
24 Overflow Peaks Using Rational Formula for the
Two-year Storm 82
25 Overflow Volume Using Standard Infiltration Curve 84
26 Probability of the Design Storms 99
27 Overflow Peaks and Volume for the Two-year,
One-hour Storm 100
28 Overflow Volumes for the One-year, 24-hour Storm 101
29 Design Storms and Waste Loads 103
30 Summary of Cost Estimates for Alternate Solutions 116
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FIGURES
Figure Page
I Sandusky River Drainage Area 131
2 General Plan of Combined Sewer Districts 132
3 Number 8 Sewer District 133
4 Number 17 Sewer District 134
5 Number 23 Sewer District 135
6 Upstream Sampler and Number 23 Rain Gage 136
7 Number 17 Weir During Overflow and Number 8
Dry Weather Weir 137
8 Numbers 8 and 17 Overflow Weirs 138
9 Number 8 Instrument Shelter and Wastewater
Treatment Plant Overflow Recorder 139
10 Upstream and Downstream Gages 140
II Low Flow Conditions 141
12 Sandusky River Flow at Bucyrus, Ohio 142
13 Comparison of Monthly Discharge and
Monthly RainfalI 143
14 Rainfall Depth - Duration - Frequency Curves 144
15 Intensity - Duration Curves 145
16 Rainfall and Overflow - Number 8 Overflow -
March 24, 1969 146
17 Rainfall and Overflow - Number 17 Overflow -
March 24, 1969 147
18 Rainfall and Overflow - Number 23 Overflow -
March 24, 1969 148
19 Rainfall and Overflow - Number 8 Overflow -
June 13, 1969 149
XI
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Figure
20 Rainfall and Overflow - Number 17 Overflow -
June 13, 1969 150
21 Rainfall and Overflow - Number 23 Overflow -
June 13, 1969 151
22 Intensity - Duration Curves - Rainfall
Corresponding to Measured Overflows 152
23 BOD Concentration versus Time - Number 8 Overflow 153
24 BOD Concentration versus Time - Number 17 Overflow 154
25 BOD Concentration versus Time - Number 23 Overflow 155
26 Suspended Solids Concentration versus Time -
Number 8 Overflow 156
27 Suspended Solids Concentration versus Time -
Number 17 Overflow 157
28 Suspended Solids Concentration versus Time -
Number 23 Overflow 158
29 Total Solids - Number 8 Overflow 159
30 Total Solids - Number 17 Overflow 160
31 Total Solids - Number 23 Overflow 161
32 Nitrate Nitrogen - Number 8 Overflow 162
33 Nitrate Nitrogen - Number 17 Overflow 163
34 Nitrate Nitrogen - Number 23 Overflow 164
35 Ammonia and Organic Nitrogen - Number 8 Overflow 165
36 Ammonia and Organic Nitrogen - Number 17 Overflow 166
37 Ammonia and Organic Nitrogen - Number 23 Overflow 167
38 Total Phosphates - Number 8 Overflow 168
39 Total Phosphates - Number 17 Overflow 169
40 Total Phosphates - Number 23 Overflow 170
XI I
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Figure Page
41 Chlorides - Number 8 Overflow 171
42 Chlorides - Number 17 Overflow 172
43 Chlorides - Number 23 Overflow 173
44 Effect of Settling on BOD and Suspended Solids 174
45 Diurnal Fluctuation in Dissolved Oxygen -
Sandusky River 175
46 Diurnal Effect on Dissolved Oxygen -
Sandusky River 176
47 Dissolved Oxygen Profile of the Sandusky River
During Dry and Wet Weather 177
48 Overflow Peak Time versus Length of Rainfall 178
49 Unit Hydrograph - Number 8 Overflow 179
50 Unit Hydrograph - Number 17 Overflow 180
51 Unit Hydrograph - Number 23 Overflow 181
52 Peak Rainfall versus Peak Overflow Rate -
Number 8 Overflow 182
53 Peak Rainfall versus Peak Overflow Rate -
Number 17 Overflow 183
54 Peak Rainfall versus Peak Overflow Rate -
Number 23 Overflow 184
55 Overflow Hydrograph - 20-Minute Storm -
Number 8 Overflow 185
56 Overflow Hydrograph - 20-Minute Storm -
Number 17 Overflow 186
57 Overflow Hydrograph - 20-Minute Storm -
Number 23 Overflow 187
58 Rainfal I versus BOD 188
59 Rainfall versus Suspended Solids 189
XIII
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Figure
60 Rainfall and Overflow - Two-year, One-hour Storm -
Number 8 Overflow 190
61 Rainfall and Overflow - Two-year, One-hour Storm -
Number 17 Overflow 191
62 Rainfall and Overflow - Two-year, One-hour Storm -
Number 23 Overflow 192
63 Distribution Graph for Urban Runoff -
Downstream Gage 193
64 Separation of Sanitary and Storm Sewer -
Typical Cross Section 194
65 Interceptor and Lagoon System 195
66 Typical Cross Section of Aerated Lagoon 196
67 Flow Augmentation Upground Storage Reservoir 197
XIV
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SECTION I
CONCLUSIONS AND RECOMMENDATIONS
Conclusions
I. Any 20 minute rainfall greater than 0.05 inches will produce an
overflow of wastewater into the Sandusky River at Bucyrus. A rain-
fall of this intensity and duration or greater will occur on the
average of once every 5 days.
2. A typical summer thundershower occurred on June 13, 1969 and pro-
duced I.I Inches of rain, had a duration of 78 minutes and an
average Intensity of 0.84 inches per hour. The runoff from this
storm discharged into the Sandusky River, through the combined
sewer overflows, 5,200,000 gallons of combined sewer wastewater,
1580 pounds of BOD and 23,000 pounds of suspended solids.
3. A storm on August 9, 1969 which produced 0.50 Inches of rain in
about 75 minutes, increased the BOD concentration of the Sandusky
River downstream from Bucyrus from II mg/l (530 pounds per day) at
a river flow of 9 cfs to 51 mg/l (35,500 pounds per day) at a river
flow of 130 cfs.
4. The combined sewers will overflow about 73 times each year dis-
charging an estimated total annual volume of 350 million gallons
or about I million gallons per day.
5 The combined sewer overflows have an average BOD of 120 mg/l, sus-
pended solids of 470 mg/l, total col I forms of 11,000,000 per 100 ml
and fecal coliforms of 1,600,000 per 100 ml.
6. The combined sewer overflows at Bucyrus discharge an estimated
350,000 pounds of BOD and 1,400,000 pounds of suspended solids
annually Into the Sandusky River.
7. The BOD concentration of the Sandusky River, immediately downstream
from Bucyrus, varied from an average of 6 mg/l during dry weather
to a high of 51 mg/l during overflow discharges. The suspended
solids varied from an average of 49 mg/l during dry weather to a
high of 960 mg/l during overflow discharges. The total coliforms
(by membrane filter technique) varied from an average of 400,000
per 100 ml during dry weather to a high of 8,800,000 per 100 ml
during overflow discharges.
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8. The estimated yearly discharge of 15,700 pounds of nitrate nitrogen
(12,200 pounds from overflows and 3,500 pounds from wastewater
plant) from Bucyrus is rather insignificant when compared to the
136,000 pounds and 192,000 pounds found in the river coming from
the upper drainage basin on April 19, 1969 and May 19, 1969,
respectively.
9. The nitrate nitrogen concentration of the Sandusky River, upstream
from Bucyrus, varied from a low of 0.4 mg/l as NO^ to a high of
32 mg/1. The high concentrations occurred during high river flows
in the spring of the year. The estimated nitrate nitrogen dis-
charged from the upstream drainage area is 2,300,000 pounds
annually.
10. The combined sewer overflows discharge about 30,000 pounds of phos-
phates (PO.) into the river annually. The wastewater treatment
plant discharges about 160,000 pounds of P04 each year. An
estimated 110,000 pounds of PO. per year came from the upstream
drainage area.
II. Sludge accumulation in the river from combined sewer overflows at
Bucyrus is estimated to be approximately 47,000 cubic feet per year.
12. The flushing effect of the sewer system during intense rainfalls
causes the majority of the waste load to be discharged during the
peak overflow period as evidenced by the peak concentration of the
various water quality characteristics which tend to coincide with
the peak overflow rate.
13. The effects of the combined sewer overflows on the Sandusky River
in and below the Cfty of Bucyrus are visually apparent. There are
Indications of gross pollution, such as sludge banks, sections of
the river are devoid of oxygen, extensive algae growth, and some
sections of the river are completely devoid of life.
14. The probability of thundershower type storms occurring Is highest
during the summer months. There is a 74^ probability of the 2 year,
I hour thundershower, which has a total rainfall of 1.23 inches,
occurring In June, July and August.
15. The median flow In the Sandusky River at Bucyrus in June, July and
August Is 13 cfs, 6.9 cfs and 4.8 cfs, respectively.
16. The assimilative capacity of the Sandusky River (the ability of the
river for self-purification) is limited to approximately 25 pounds
of BOD per day per cfs at flows less than 10 cfs. Forty percent of
the time the flow In the Sandusky River at Bucyrus Is less than
10 cfs.
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17. The weighted average runoff for a I I storms measured was 19 percent.
For storms with over 1.0 inches of rainfall, the weighted average
runoff through the combined sewers equals 20 percent, 28 percent
and 25 percent for Sewer Districts 8, 17 and 23, respectively.
18. The volume and character of pollutants discharged to surface water-
courses from combined sewer systems in other similar communities
would no doubt be very similar to that found to exist at Bucyrus,
Ohio.
19. The various methods of reducing or controlling pollution from com-
bined sewers considered in this study and the estimated project
cost of each are as follows:
A. Complete separation of the combined sewer system into a sanitary
sewer system and storm sewer system.
I. Construct new sanitary sewers using the existing system
as storm sewer system — $9,300,000.
2. Construct new storm sewer system using existing system as
sanitary sewer system — $8,800,000.
B. Interceptor Sewer and Lagoon System
I. Gravity Interceptor $3,600,000
2. Pump Station 1,000,000
3. Lagoon System 620.000
$5,220,000
C. Stream Flow Augmentation $5,000,000
D. Primary Treatment of Overflows $8,810,000
E. ChiorI nation of Overflows $3,000,000
F. Offstream Treatment
I. Pump Station and
Low Head Dam $1,080,000
2. Lagoon System 620,000
$1,700,000
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20. Sewer separation, at Bucyrus, as a solution to combined sewer over-
flows will only reduce the waste loads discharged to the river by
about 50%.
21. Construction and operation of the "Interceptor and Lagoon System"
or "Off-Stream Treatment" as a demonstration project would be the
most economical method of reducing or controlling pollution of the
Sandusky River at Bucyrus and would provide answers to certain
design, operation and benefit unknowns.
22. Stream flow augmentation as a method of controlling pollution from
combined sewer overflows is not feasible at Bucyrus due to lack of
suitable reservoir sites.
23. Primary treatment of overflows will only reduce the waste loads
discharged into the Sandusky River through the combined sewer over-
flows by 50 to 70 percent.
24. Chlorination of overflows will reduce the bacteria count discharged
into the river by combined sewer overflows but will not reduce
significantly, any of the other pollutional characteristics of the
overflows. Therefore, adequate treatment cannot be provided by
chlorination alone.
Recommendat i ons
I. The "Interceptor Sewer and Lagoon System" for abating pollution
from combined sewer overflows should be adopted for Bucyrus.
The benefits from controlling pollution due to combined sewer over-
flows by the use of an "Interceptor and Lagoon System" are many.
(a) Reduces pollution of the river both within the city of Bucyrus
and downstream.
(b) Stream protection surpasses that to be achieved by combined
sewer separation in that all runoff up to the design storm
will be intercepted and treated.
(c) Increases the value of the stream to the public in the City
and downstream from the City.
(d) Reduces a health hazard within and below the City.
(e) A clean stream provides the possibility through use of land-
scape architecture to beautify the stream, enhance its
esthetic value and make it a real asset to the community.
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2. The lagoon type of treatment should be demonstrated as capable of
providing the degree of treatment required by constructing the
"Off-Stream Treatment" concept as the first phase of the overall
abatement program at Bucyrus, Ohio.
The cost of the interceptor sewer represents a major portion of
the "Interceptor Sewer and Lagoon System" method of abatement from
combined sewer overflows. The "Off-Stream Treatment" method of
protecting the downstream water quality without regard for the
inner-city reach of the river provides a method whereby the initial
project cost can be reduced substantially. The interceptor could
be added for complete protection at a later date, as the final
phase of the project.
The City of Bucyrus is ideally situated in the Sandusky River
watershed to demonstrate and evaluate pollution abatement from
combined sewers on a watershed basis.
(a) There are no large municipalities upstream to contribute
pollutants.
(b) The upstream watershed of approximately 90 square miles is
used for general farming.
(c) The river downstream from Bucyrus is presently used by
several cities as a source of water supply and the river is
destined to become a major source of water supply in the
future.
(d) The benefits of pollution abatement from sanitary waste and
urban storm runoff (combined sewer overflow) to downstream
water uses could be adequately demonstrated.
(e) The reclamation and protection provided a principal river for
all downstream water used would be impressive and could be
used as an example for other watersheds.
(f) Watershed protection rather than pilot or scale concepts is
recommended to more fully evaluate the design storm, hydraulic
variables of storm runoff, large scale operation cost, etc.
The "Off-Stream Treatment" concept which is proposed as the first
phase of the Bucyrus project has many applications where the stream
or river must receive treatment to achieve the desired water quality
standards. A full scale project such as proposed at Bucyrus would
demonstrate the benefits to be derived and design criteria could be
developed which would be valuable for other projects.
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"5. The interceptor system should be constructed as the second and
final phase of abatement when it has been adequately demonstrated
that the lagoon type of treatment is adequate and capable of pro-
viding the water quality protection required.
4. Until such time as effective methods are constructed to control or
eliminate the pollution problem the channels, waterways, or stream
beds into which the overflows are discharged should be protected
from erosion to prohibit the ponding of such overflows in pools
which become septic and cause odors and are very unsightly.
Periodic removal of debris from the stream channel especially in
the urban area should be accomplished at frequent intervals.
5. Municipalities with combined sewer systems should construct
separated systems when extending service to new areas of growth or
replacing existing sewers and new storm sewers constructed should
be discharged to outlets other than existing combined trunk sewers
where and when feasible.
6. Automatic rain gauges, monitoring stations and sampling stations
should be established both upstream and downstream from Bucyrus on
the Sandusky River to provide additional base data for future
evaluation studies on abatement projects undertaken.
7. Install continuous level recorders at the three overflow weirs that
were constructed for this investigation. These recorders will pro-
vide a continuous record of overflow volume.
8. The officials of the City of Bucyrus should be fully informed of
the results of this study and the recommendations contained herein
and that they be given the opportunity to participate in a demon-
stration project for abatement of pollution from their combined
sewer system.
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SECTION I I
INTRODUCTION
To achieve the water quality standards established in Ohio for streams,
rivers and lakes all of the communities with combined storm and sanitary
col lection systems have been placed under orders by the Ohio Water
Pollution Control Board to seek methods of abating pollution from their
combined sewer overflows. Physical separation of the system is of
course one acceptable method.
In a recent study to develop a total water management plan for an area
of 9,144 square miles in northwestern Ohio, preliminary cost estimates
were prepared for the physical separation of combined sewer systems in
48 communities with a total population (1965) of some 812,000 persons.
In some instances the combined system may be converted to a separate
sanitary system and in others to a separate storm system.
The magnitude of the total project for making this conversion is demon-
strated by the $200,000,000 estimated cost to the 48 communities. The
City of Bucyrus, Ohio, which was selected as a site for this study was
one of the 48 communities included in the northwestern Ohio study. The
estimated cost of combined sewer separation in Bucyrus was $5,400,000
or $415 per capita using 1965-66 prices.
The Sandusky River flows through Bucyrus and discharges into Sandusky
Bay and Lake Erie. Future water management plans for the principal
cities in the watershed are based on utilizing the natural flow in the
river and upground storage reservoirs as the major source of water for
the area. The reduction in the pollutants discharged into the river
thus becomes very important if the desired water quality is to be
achieved and maintained for the intended use of the river water.
The need for pollution abatement due to combined sewer overflows is
evident. There is need to determine if there are methods of abating
pollution from combined sewers which would accomplish the task better
than physical separation and at a lesser cost.
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SECTION I I I
PURPOSE AND SCOPE
The study is based on the possibility of interception of all or part of
the combined sewer overflow for treatment prior to release to the stream.
The advantages, disadvantages and economics of abating pollution from
combined sewer overflows by this method will be compared to physical
separation of the combined system.
One of the primary objectives of this study is to determine the relation-
ship of rainfall events to overflow events and the volume of flow in the
Sandusky River. Once this relationship has been established, the design
storm with its resultant overflow rates, volumes and waste characteris-
tics can be selected for the design of the intercepting devices and
treatment fac5 Ii t ies.
Research of historical records of rainfall and flow in the Sandusky River
provided a pattern of rainfall and river flow which could be used to
evaluate data collected during this study period. Available data on
water quality in the Sandusky River was compiled. Rainfall measuring
stations and Sandusky River gaging stations were established to record
rainfall and river flows during the study period.
Weirs for measuring overflows during rainfall were installed at the over-
flow points of three selected sewer districts. Samples were collected
during selected overflow events to determine overflow characteristics
and effects on the stream.
The results of this data collection are presented and discussed in the
following sections of this report. From this data the facilities for
the collection and treatment of combined sewer overflows have been sized
and cost estimates prepared for comparison with physical separation
costs.
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SECTION IV
STUDY AREA
The City of Bucyrus, selected as a typical small midwest community with
a combined sewer system, is located on the Sandusky River near the upper
end of the 1,421 square mile Sandusky River Basin. The river is tribu-
tary to Lake Erie as shown in Figure I. The 90 square mile drainage
area upstream from Bucyrus is level agricultural land. Bucyrus is the
county seat of Crawford County, and has an incorporated area of about
2,340 acres. The City is located on an end moraine and the topography
is generally flat to slightly rolling. The climate Is humid with warm
summers and mildly cold winters. The mean annual temperature is 51 F
and the mean annual precipitation Is 36 inches. The Study Area is shown
in Figures I, 2, 3, 4, and 5.
Bucyrus has a tax valuation of approximately $40,000,000 and a 1968 tax
rate of 33.90 mills per $1,000. The median income in Crawford County is
$9,252 per year per household.
From 1920 through 1950 the population of Bucyrus remained practically
constant between 9,700 and 10,400 persons. The I960 census showed a
population of 12,276 persons and the current estimated population is
13,000 persons.
The City is moderately industrialized. Some of the larger industries are
Timken Roller Bearing Company, Swan Rubber Company, General Electric
Company, Gal ion Iron Works and Manufacturing Company, Ryder Brass
Foundry, Cobey Corporation, Bucyrus Blades, Inc., Crawford Steel Company,
Ohio Locomotive and Crane Company, and Bucyrus Ice Company.
The water supply for the municipal waterworks system is obtained from the
Sandusky River upstream from the City. Water is pumped from the River
and stored in upground storage reservoirs. The water treatment plant is
a lime-soda ash softening plant.
The dry weather wastewater in the combined sewer system is intercepted
at 24 points along the river and conveyed downstream in an interceptor
sewer to the wastewater treatment plant. The plant uses the conven-
tional activated sludge process for treatment of the wastewater. The
plant effluent is discharged into the Sandusky River. Most of the
sewers are at minimum grade due to the flat terrain.
The Sandusky Rfver downstream from Bucyrus is a source of water supply
for the cities of Upper Sandusky, Tiffin, and Fremont. At the present
time there are no significant water development facilities on the River
other than for these public water supplies. However, six (6) multi-
purpose upground reservoirs have been proposed by the Ohio Department
of Natural Resources to provide water development for the area. One of
the purposes of this reservoir system is to provide for a sustained flow
-------
of 3.75 MGD (5.7 c.f.s.) In the Sandusky River during a 20-year fre-
quency drought. This would provide for increased public water supply,
for improved boating and fishing, and in a few places, for swimming in
the Sandusky River. An area near Bucyrus is designated as a site for
one of these reservoirs. The total design capacity of the proposed
Bucyrus reservoir is 2,054 million gallons, 476 million gallons for sus-
tained flow, 1,400 million gallons for public water supply and 178
million gallons for a conservation pool. The total cost of the reser-
voir was estimated to be $2,458,000 in 1966.
The principal pollution problems In the Sandusky River are sediment,
oxygen consuming materials, bacteria, phosphates and nitrates. The
stream drains rich agricultural lands which contribute significant
amounts of sediment and nutrients (phosphates and nitrates). The area
around Bucyrus is intensely cultivated, the main crops being corn,
wheat, and soy beans. Significant oxygen demand and high bacterial
concentration occur below Bucyrus due to discharge of treated and un-
treated sewage. At the present time, all communities discharging
sewage effluents to the Sandusky River provide secondary treatment
facilities.
12
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SECTION V
STUDY PROCEDURES
The procedures followed in accomplishing this study are discussed in the
order in which they were performed.
The overflows from the 24 sewer districts in Bucyrus could not be studied
in detail. Therefore, a preliminary analysis of the districts was made
to determine which districts were representative. The following items
were considered: area, land use, hydraulics of the trunk sewers and the
interceptor, accessibility of the overflow points, and the availability
of channels to accommodate weirs for measurement of overflow volumes and
rates. All overflow points and the wastewater treatment plant were
visited both in wet and dry weather.
Three districts were finally selected — Numbers 8 (179 acres), 17 (452
acres), and 23 (378 acres). (See Figures 2, 3, 4, and 5) These are the
three largest districts in Bucyrus, representing 64% of the total sewered
drainage area. They include different types of waste discharges in
varying proportions.
A detailed analysis was made to determine the drainage characteristics
of Numbers 8, 17, and 23 sewer districts. Except for the times of con-
centration, the characteristics of the remaining districts were esti-
mated by comparing their land use to that of Numbers 8, 17, and 23 sewer
districts. A topographical map and a sewer map were used for the analy-
sis. The maps were substantiated by in-field observations.
A hydraulic analysis of the sewer system was made to determine the flow
capacities of the trunk sewers, the connectors, and the interceptor. A
field survey was made of Numbers 8, 17, and 23 sewer districts and the
interceptor. The sewer map was used for the remaining districts. On
two occasions, once during dry weather and once during wet weather, the
depth of flow in the interceptor was measured at several points and a
hydraulic gradient drawn. The Manning equation, with n = 0.013, was
used to compute the flow in all pipes.
The existing meteorological and hydro logical records for Bucyrus were
obtained and summarized to establish a base line to which the data
measured during the study period could be compared. These records
included rainfall, river flow and quality, and water and wastewater
treatment plant flows and treatment plant efficiencies. These records
were obtained from the U. S. Weather Bureau, the U. S. Geological Survey,
the Ohio Health Department, the Federal Water Pollution Control Adminis-
tration and the City of Bucyrus.
A literature survey was made and a brief summary was compiled of the
technical literature available on combined sewers. Special attention
13
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was given to the technical knowledge and operating experience of exist-
ing facilities similar to units suggested as part of the alternate
solutions.
An industrial waste survey was made to determine the type and volume of
waste to expect during dry weather and overflow sampling. Only the
industries in the three study districts were surveyed. Each industry
was visited and in-plant inspections made when necessary.
Two aquatic biology surveys of the Sandusky River were made to deter-
mine the type of aquatic life present as an indicator of water quality.
The surveys covered the section of the river from ten miles upstream to
thirteen miles downstream from Bucyrus. The surveys were performed by
Rendell Rhoades, Chairman of the Biology Department, Ashland College,
Ashland, Ohio. The first survey was in the fall of 1968 and the second
in the spring of 1969.
A system was established to alert personnel in Columbus, Ohio, of
approaching rain in Bucyrus. By this system, personnel at the U. S.
Weather Bureau at Port Columbus, Columbus, Ohio, upon request, informed
project personnel of the probability, the type, and the time of arrival
of rainfall in Bucyrus, six to twelve hours in advance. This enabled
project personnel to Install the necessary equipment and collect ini-
tial samples from the sewers or the river prior to the arrival of the
rain. Also personnel of the City of Bucyrus notified project personnel
when the rain actually occurred in Bucyrus.
A continuous record of the rainfall on the three sewer districts during
the study period was obtained. Three rain gages were used, one in each
of the three sewer districts. The gages were the weighing type, Bendix
Model 775C Universal Recording Rain andSnowGage. The charts had a 1:1
ratio for rainfall depth and one chart revolution equaled 24 hours.
The charts were changed weekly. See Figure 6 for a picture of the rain
gage in Number 23 sewer district.
Samples and flow measurements were taken of the dry weather wastewater
flow discharged from the three sewer districts, the influent and
effluent of the waste water treatment plant, and the Sandusky River at
the upstream and downstream gages. The purpose of these samples and
flow measurements was to determine the average strength and volume of
the waste at different times of the day and at different times of the
year.
A weir was installed in each trunk sewer. The weirs were a 90 V-notch
weir, a 24 inch rectangular weir, and an 18 inch rectangular weir for
Numbers 8, 17, and 23 sewer districts, respectively. (See Figure 7)
A sample was collected and the flow measured every 15 minutes for the
trunk sewers and hourly for the wastewater treatment plant and river.
The samples were composited proportional to flow on an eight-hour shift
basis. Both samplings were for 24 hour periods.
14
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A rectangular weir was built at each of the three overflow points to
measure overflow during rainfall. (See Figures 7 & 8). The weirs were
constructed of one-inch plywood, which was bolted onto steel angles
imbedded in concrete. The weir plates were 8, 16, and 10 feet long for
Numbers 8, 17, and 23 overflows, respectively.
Water level recorders were mounted in instrument shelters 42 inches
behind the weirs. The recorders were Stevens Type F Recorder, Model 68,
with a 9.6 time scale and a 1:2 gage scale. All recorders were equipped
with automatic starters which would start the clocks at predetermined
water levels. The recorders were reset at least once every week. (See
Figure 8)
The overflows from many storms were sampled during the study period to
determine the quality of the overflow and pollution loads. Only the
overflows from Numbers 8, 17, and 23 sewer districts were sampled. From
July, 1968, through January, 1969, samples were collected manually.
After February I, 1969, Serco Automatic Samplers, Model NW-3, were
installed in the instrument shelters at the overflows. (See Figure 8)
These samplers collected a 300 m.I. sample every five minutes for two
hours during overflow. If the overflow continued longer than two hours,
samples were collected manually at less frequent intervals.
An automatic starter was devised for the samplers that started the clocks
when the water level reached a predetermined height behind the weirs.
The samplers could therefore be left unattended prior to and during an
overflow. The samplers required a vacuum be maintained in the sample
bottles. Because the samplers would lose the vacuum after one or two
days, they had to be installed within 24 hours prior to the overflow.
A continuous record of the flow in the Sandusky River above and below
Bucyrus was obtained for the study period. An existing recording gage
operated by the U. S. Geological Survey located at the first bridge
below the wastewater treatment plant was utilized for downstream flow
measurements. (See Figure 10) Through the cooperation of the U. S.
Geological Survey, project personnel had access to the recorder and
received copies of the charts when removed. A new gaging station was
installed on the River 300 feet upstream from the first overflow point
on the combined sewer system. (See Figure 10) A rating curve for the
gage was plotted using standard gaging techniques. Flow metering equip-
ment was borrowed from the U. S. Geological Survey. The recorders used
at both gaging stations were Stevens Type A35, with 1:6 gage scales.
The time scales for the gages were 4.8 and 2.4 inches per day, for the
upstream and downstream gages, respectively.
The Sandusky River was sampled above and below Bucyrus during the study
period to determine the water quality. The most commonly used sampling
points were the upstream gage, the Au Miller Park ford, and the first
six bridges below the city. All of the dry weather samples and some of
the wet weather samples were collected manually. A separate sample for
15
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dissolved oxygen was collected with a dissolved oxyqen sampler and the
temperature of the water measured.
After February I, 1969, the samples were collected at the upstream and
downstream gages during wet weather by Serco Automatic Samplers. These
samplers were the same type as used for the overflows except they were
set to collect one sample per hour for 24 hours. The samplers were
located on platforms overhanging the water. (See Figure 6) They were
installed and activated shortly before the rain started. Additional
samples were collected for dissolved oxygen.
The Wastewater Treatment Plant bypass overflow measurement was deter-
mined by installing a recorder, float chamber, and instrument shelter
at the bypass manhole. (See Figure 9) This recorder measured the water
level in the chamber in relation to the invert of the overflow pipe. A
rating curve based on the flow characteristics of the overflow pipe was
drawn. The recorder used was a Stevens Type F Recorder, with a 1:1
gage scale and a 1.2 time scale. The chart was changed weekly.
Laboratory analyses were performed on all overflow and river samples
collected for 18 different physical and chemical tests. The parameters
analyzed were (I) biochemical oxygen demand (BOD), (2) chemical oxygen
demand (COD), (3) total solids, (4) suspended solids, (5) total volatile
solids, (6) volatile suspended solids, (7) total phosphates, (8) nitrate
nitrogen, (9) ammonia nitrogen, (10) organic nitrogen, (II) pH, (12)
alkalinity, (13) hardness, (14) chlorides, (15) specific conductance,
(16) total coliforms, (17) fecal coliforms, and (18) fecal streptococci.
All laboratory tests were done in accordance with the "12th edition of
Standard Methods for the Examination of Water and Wastewater".('^
Laboratory analyses of the samples were started immediately upon re-
ceiving the samples. Samples that were not completely analyzed the
first day were preserved by acid and/or refrigeration. When necessary
individual samples collected were composited according to the overflow
pattern. The membrane filter technique was used for the total coliform,
fecal coliform and fecal streptococci tests.
16
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SECTION VI
DRY WEATHER CONDITIONS
Collection System
Since the entire Bucyrus sewer system is combined, the system capacity
is adequate for the normal dry weather wastewater flow. There were no
complaints of dry weather odors or backups during the study. In several
locations the system has been extended beyond the natural drainage
boundaries and the sewers are too shallow to permit gravity drains from
basements.
The major trunk sewers In the older sections of the city are of brick
construction; the remaining sewers are concrete or vitrified clay pipe.
All are laid close to or at minimum grade. Because the larger pipes do
not maintain scouring velocities at low flows, solids accumulate in the
sewers at many locations In the system.
Interceptor System
The Interceptor sewer system consists of control structures in the trunk
sewers which divert the dry weather flow through connector pipes to the
interceptor sewer. The interceptor generally parallels the river through
the city to the wastewater treatment plant. Two types of controls or
diversion structures are used. One is a weir built across the combined
sewer pipe, the other is a depression in the bottom of the pipe. The
size of the connecting pipe regulates the amount of flow diverted.
All of the connector pipes flow by gravity from the bottom of the trunk
sewer to the Interceptor. Most of the connectors are double or triple
the capacity required for the normal dry weather flow. There were no
reports of overflows during dry weather due to insufficient connector
capacity during the study.
The main interceptor is designed to handle four to five times the dry
weather flow. It collects the flow from all 24 sewer districts and dis-
charges It to the wastewater treatment plant wet well and pump station.
The dry weather flows from Numbers 8 and 23 sewer districts were observed
overflowing directly into the river several times during the study period.
There were reports of other sewer districts also overflowing directly
Into the river at various times. In each case the connector pipe was
plugged with a large object or an accumulation of solids. City personnel
reported some connectors require frequent cleaning.
Wastewater Treatment Plant
The Bucyrus wastewater treatment plant was designed as a conventional
activated sludge plant. The raw sewage is pumped from the wet well to
17
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a comminutor then flows by gravity through an aerated grit chamber,
three circular primary settling tanks, three aeration tanks, and two
circular final settling tanks and to the Sandusky River. The sludge is
anaerobically digested and dewatered on sand beds. Plans are being pre-
pared for post-chlorination of the plant effluent in compliance with
orders from the Ohio Water Pollution Control Board.
The daily operational records of the treatment plant for the October,
1968, to September, 1969, study period have been averaged and are sum-
marized below.
BOD - mg/l Suspended Solids - mq/l
Raw Settled Final Raw Settled Final
2.20 119 106 30 128 182 35
Sandusky River
The dry weather water quality condition of the Sandusky River varies
with the season and flow. During the winter and spring months the flow
in the river is high and the river's condition is fair to good. During
the summer and fall months the flow in the river is low and the river's
condition deteriorates.
One half of a mile below the upstream gage the water treatment plant
discharges lime sludge and wash water into the river. During high flow
the sludge is carried downstream with no noticeable affects. During
low flow the sludge settles out on the bottom of the river. (See
Figure II) Neither fish nor aquatic insects can survive under these
conditions. The sludge affects the river for approximately a distance
of one mile, or to the U. S. 30 bridge. Plans are now being prepared
for lagoon ing the lime sludge and wash water which will terminate their
discharge to the River.
The wastewater treatment plant effluent has the greatest affect on the
water quality of the river during dry weather. During the months of
August, September, and October, the flow in the river is too low to
assimilate all of the BOD in the treatment plant effluent. Dissolved
oxygen levels are consistently below 4.0 mg/l for a distance of five
miles downstream from the treatment plant effluent outfall and fre-
quently reach 0 mg/l during the night. Sludge banks are formed on the
river bottom for a distance of three miles downstream.
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SECTION VI I
WET WEATHER CONDITIONS
Col lection System
The Bucyrus sewer system has been extended beyond its original design
capacity. In at least one area the sewers are extended over the natural
drainage divide. Many of the sewers have capacities which are inade-
quate for an average one-year storm. Therefore, there is street ponding
at several locations during the higher intensity rainfalls.
Except for the temporary inconvenience, the street ponding does not
cause any problems. A few corrections and additions to the system would
make it adequate for the present population. However, the surcharged
sewers do cause backups in many homes through the basement drains.
There were several reports of basements flooded with a mixture storm
water and sewage during high intensity storms.
Interceptor System i
The interceptor sewer has the same capacity as the sum of the connector
pipes flowing into it at every point in the system. The total pipe
capacity at the lower end of the system is 19 c.f.s., or four to five
times the average dry weather wastewater flow.
During a storm, however, the interceptor has a capacity only two times
the average dry weather wastewater flow. The capacity is restricted by
the limited rates pumped to the wastewater treatment plant and the resul-
tant overflow level at the bypass manhole, all of which reduced the
hydraulic gradient of the sewer.
Two factors control the diversion capacity of the interceptor during wet
weather. One is the capacity of the connector pipes, and the other is
the water level in the interceptor. From field measurements made during
an overflow, the hydraulic gradient for the flow in the interceptor was
found to be high enough to affect the connector pipe capacities of many
of the sewer districts. The flow in Number 5 connector pipe was
reversed, with the interceptor overflowing through the .sewer district
overflow. Very little overflow occurs at the wastewater treatment plant
in comparison to the volumes overflowing at the 24 individual sewer
districts.
The water level in the interceptor during an overflow has contributed to
one problem. Following the overflow the interceptor remains full for
several days because of the limited rate pumped to the wastewater treat-
ment plant. The low velocities in the trunk sewers, connector pipes and
the interceptor sewer allow the solids to settle out.
19
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The controls and overflows function as designed. The depression type
of control appears to function better than the weir type of control
during wet weather. The weir type control blocks part of the trunk
sewer and in some cases reduces its capacity by one-half. All of the
overflows are part of the original trunk sewer, and most of them are
equipped with flap gates to prevent back flow from the river during
high water.
Wastewater Treatment Plant
During wet weather the sluice gate to the wet well at the wastewater
treatment plant must be closed to limit the amount of flow into the
plant. Experience has shown that when the gate is closed three-fourths
of the way, the flow to the plant will be between 3.0 and 3.5 MGD.
This is the maximum capacity of the plant.
During wet weather the BOD of the waste coming into the plant decreases.
The increase in flow rate decreases the settling time and efficiency
and reduces the suspended solids content in the aeration tanks. The
quality of the effluent remains approximately the same, but the effi-
ciency of treatment decreases.
Sandusky River
All of the overflows discharge directly into the river. The sum of the
overflows give a very distinct hydrograph at the downstream gage. If
the rainfall is a localized thunderstorm, the river returns to its
previous flow. If the rainfall is more generalized, the overflow hydro-
graph wiI I be followed 16 to 40 hours later by the hydrograph of the
runoff from the upstream drainage basin.
The water quality of the river during wet weather varies with the season
and flow. The more flow in the river, the more dilution water is avail-
able for the overflows. Therefore, the condition of the river will be
the poorest following an overflow during the summer and early fall
months.
The overflow wastes have several effects on the river. The most obvious
one is the debris and organic solids which settle in the river in and
below the city. These create odors and unsightly conditions long after
the overflow is past. A second effect is the decrease in quality of the
water moving downstream. BOD's, solids, coliform, etc., are increased.
In turn, dissolved oxygen is decreased. The aquatic life is affected.
Therefore, the usefulness of the water for recreation and water supply
is impaired.
20
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SECTION VIII
METEOROLOGICAL AND HYDROLOGICAL HISTORY
The past meteorological and hydrological records for the Bucyrus area
and the Sandusky River have been reviewed and summarized to provide base
I ine data.
MeteoroIogj ca I Hi story
Daily, monthly and annual rainfall data for Bucyrus were obtained from
the periodical "Climatological Data" published by the Weather Bureau of
the U. S. Department of Commerce. These records date back to 1931. The
average monthly rainfall records since 1931 have been summarized and are
shown in Table I. The average annual rainfall for the Bucyrus area is
35.7 inches.
In addition to summarizing the meteorological records since 1931, the
records for the ten-year period from January 1959 to September 1968 were
studied in more detail and used for comparison with the weather condi-
tions occurring during the study period. The average monthly rainfall
for the study period is shown in Table I and also graphed in Figure 13.
The average annual rainfall for the ten-year period is 32.8 inches.
For the ten-year period studied in detail, July had the highest average
monthly rainfall with 3.88 inches and October the lowest with 1.96
inches. The wettest month during this ten-year period was July, 1966,
when 9.29 inches of rain fell while the driest month was October, 1963,
when only a trace fell.
Detailed study of the ten-year period indicates that on the average there
are 75 days per year when the rainfall is greater than 0.10 inches, 22
days per year when rainfall is greater than 0.50 inches and six days per
year when rainfall is greater than 1.00 inches. Also, July is the
wettest month in terms of amount and intensity of rainfall.
The weather bureau station at Bucyrus reports only daily rainfall totals.
Due to the lack of hourly rainfall data at this station, intensity-
duration information could not be developed. Therefore, the "Rainfall
Frequency Atlas of the United States", Technical Paper No. 40, published
by the U. S. Department of Agriculture, was used to develop rainfall-
duration-frequency relationships for the Bucyrus area. Figure 14,
entitled "Rainfall Depth - Duration - Frequency Curves" and Figure 15,
entitled "Intensity - Duration Curves" were derived from the above men-
tioned source.
Hydrological History
Data on flow rates in the Sandusky River were obtained from the U. S.
Department of Interior Geological Survey publication titled "Surface
21
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Water Records of Ohio" and the Ohio Department of Natural Resources
Printed Bulletin No. 37, 40, and 42. The Geological Survey records
cover the periods August, 1925, to November, 1935; July, 1938 to
December, 1951; and December, 1963, to September, 1966. The Natural
Resources summary is based on gaging records through 1965.
The average flow in the Sandusky River at Bucyrus is 80.2 cfs for the
26 years of records. On a yearly bais, the minimum average flow of 33.8
cfs occurred in 1937 while a maximum average flow of 145 cfs occurred in
1959.
The average daily flows of the Sandusky River at Bucyrus are graphed in
Figure 12 for each month. The contrast between the low daily flows in
July to November and the high daily flows in December to June is evident
from this graph. The months in order of decreasing average daily flow
are: (I) March - 202 cfs, (2) February - 151 cfs, (3) April - 150 cfs,
(4) January - 127 cfs, (5) May - 86 cfs, (6) June - 82.5 cfs, (7)
December - 78 cfs, (8) November - 36.5 cfs, (9) July 26.5 cfs, (10)
August - 18.8 cfs, (II) October - 12.2 cfs, and (12) September - 9.6
cfs.
The maximum daily flow ever observed was 4,600 cfs on December 14, 1927,
and the minimum of 0.6 cfs on September 29, 1941, and September 25, 1946.
The ten-year, seven-day duration low flow average discharge is 0.70 cfs.
Figure 13 compares average daily flows for each month with average rain-
fall for each month. Monthly flow variation is shown to be much greater
than monthly rainfall variation. Maximum rainfall is less than twice
the minimum rainfall, while the ratio of maximum to minimum river flow
is over 20 to I.
Only a little over I percent of the total annual discharge of the
Sandusky River at Bucyrus occurs during the month of September. Five
percent of the total annual discharge occurs during the three month
period - August to October. About 12 percent of the total annual dis-
charge occurs during the five month period - June to November. Over 50
percent of the total annual discharge occurs during the three month
period - February to April. The minimum average monthly discharge, the
minimum average daily discharge and the minimum observed discharge all
occurred in the month of September.
The flow duration probability values for the Sandusky River at Bucyrus
are presented in Table 2, entitled "Percent of Time Indicated Sandusky
River Flow at Bucyrus is Equaled or Exceeded". This table shows that
the median river flow or the flow that is equaled or exceeded 50 per-
cent of the time is 16.8 cfs. The median flow of 16.8 cfs is extremely
lower than the average flow of 80.2 cfs.
22
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TABLE I
AVERAGE MONTHLY RAINFALL AT BUCYRUS, OHIO
Inches of Rai nfalI
1931 - 1968 1959 - 1968
January
February
March
Apri 1
May
June
July
August
September
October
November
December
2.88
2.34
3.15
3.18
3.35
4.50
3.22
3.23
2.73
2.40
2.45
2.24
2.52
2.12
2.34
3.55
3.37
3.09
3.88
2.28
2.52
1.96
3.10
2.11
Average Annual Rainfall
35.67
32.84
23
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TABLE 2
PERCENT OF TIME INDICATED SANDUSKY RIVER FLOW
AT BUCYRUS IS EQUALED OR EXCEEDED
Percent Flow (cfs)
5
10
15
20
25
30
40
50
60
70
75
80
85
90
95
350
170
108
79.0
59.5
45.0
27.0
16.8
10. 1
6.10
4.75
3.80
3.05
2.43
1.80
24
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SECTION IX
WEATHER CONDITIONS DURING STUDY PERIOD
Project personnel made 16 wet weather trips to Bucyrus during the study
period July, 1968, to September, 1969, to collect samples of predicted
overflows. There were 10 days out of the 16 that overflows actually
occurred and were sampled.
Grab samples were collected manually during 5 overflow events that
occurred prior to February 8, 1969. Samples of the remaining 5 overflow
events were collected by automatic samplers and project personnel.
Rainfall Data for Study Period
The total rainfall per month that occurred during the study period is
shown in Table 3. These monthly rainfall totals have been compared to
the past monthly averages and are presented in Table 3 as percentages of
average rainfalI.
The period November, 1968, through January, 1969, was wet, while February
and March, 1969, were dry. April, 1969, marked the start of an unusually
wet four-month period. The rainfall during these four months averaged
162 percent above normal.
Sandusky River Flow During Study Period
A summary of the Sandusky River flow during the study period is presented
in Table 4. This table shows the average, minimum, and maximum river
flow for each month of the study period. Also included in the table is
a comparison of the average flow during the study period with the his-
torical average. December, 1968 and January, April, May, and August,
1969, were extremely wet months ranging from 150 percent to 288 percent
above normal flow.
25
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TABLE 3
RAINFALL DURING STUDY PERIOD
Date
July 1968
August
September
October
November
December
January, 1969
February
March
Apri 1
May
June
July
Inches of
Rainfal 1
3.54
1.97
3.11
0.90
1.45
3.14
3.20
0.94
1.33
5.49
4.91
5.77
6.36
Percentage
Average Rainfal 1
no
61
114
38
159
140
III
40
42
173
147
128
198
26
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TABLE 4
SANDUSKY RIVER FLOW DURING STUDY PERIOD
Date
July, 1968
August
September
October
November
December
January, 1969
February
March
Apri 1
May
June
July
Average
cfs
27
9
9
6
33
146
197
106
62
272
248
50
60
Minimum
cfs
3
3
2
2
2
6
16
24
10
44
19
12
6
Maximum
cfs
330
95
310
36
350
1,800
1,650
700
400
1,850
2,800
275
435
Percent of
Past Average
too
47
90
50
91
187
150
70
66
182
288
62
222
27
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SECTION X
DRAINAGE CHARACTERISTICS OF THE SEWER DISTRICTS
History
The Bucyrus sewer system started as a combined system. Because the city
was built adjacent to the Sandusky River, drainage was not a problem.
The natural drainage system was converted to a combined sewer system
which discharged both storm and sanitary wastes directly into the river.
This led to the development of numerous small sewer districts along each
side of the river, each district with its own separate overflow.
In 1935, the wastewater interceptor sewer was built along the Sandusky
River. Through control structures and diversion pipes, the sanitary
wastewater flow was collected during dry weather and discharged Into the
river at a point west of the city. Later this flow was diverted from the
river to a wastewater treatment plant, thus completing the system. The
system is the same now as in 1935, with the exception of improvements to
the wastewater treatment plant, which were constructed in 1961.
General Description
Bucyrus is located near the drainage divide between the Lake Erie and the
Ohio River Drainage Basins, as shown in Figure I. The change in eleva-
tion from one end of the city to the other is less than 20 feet, except
in the immediate vicinity of the river. The topography resembles a
plateau with the river and its flood plain winding through it. Most of
the building and development is on the plateau area. Most of the sewers
are laid at minimum grade, until they reach the edge of the flood plain.
The existing sewer system is composed of 24 separate sewer districts as
shown in Figure 2. The size of the districts varies from 2.5 to 452
acres. The average size is 65 acres, the median size is 20 acres. All
of the drainage districts border on the river at some point, with the
exception of Number 24. The trunk sewer to district Number 24 was
installed after the interceptor system was constructed and serves the
extreme northwest part of the city.
The sewers in all of the existing sewer districts are extended to the
natural drainage divide or adjacent areas with the exception of Numbers
I, 4, 17, and 24. Additional wastewater or storm water could not be
placed into the systems without pumping. Numbers I, 4, and 17 districts
cover the extreme east side of Bucyrus. Portions of these districts
contain unsewered areas which are occupied by the fairgrounds and farm-
land. The development of this land will require adequate means of
drainage.
29
-------
Detailed Description
A detailed analysis was made of the drainage characteristics of Numbers
8, 17, and 23 sewer districts. This was done to relate the three
drainage districts to each other and to the drainage districts in any
other city. During this analysis the sanitary drainage area, the storm
drainage area, the number and type of waste contributors, the land use,
the land cover, the area slope and the area shape were determined for
each of the three districts. The storm drainage areas and land use
classifications were also determined for the other 21 sewer districts.
This analysis is summarized in Tables 5, 6, and 7.
The three sources of information for this analysis were topographical
maps of Bucyrus and the surrounding area, a sewer map of Bucyrus, and
field observations. The topographical maps were prepared from aerial
photographs and were completed in the fall of 1968. They have a hori-
zontal scale of I" = 200 feet and two-foot contour intervals. All
streets and buildings were shown, as well as other topographical
features. The City of Bucyrus sewer map has a horizontal scale of
I" = 300 feet and shows the locations of sewers and manholes, inverts
of manholes, and the size and grade of the sewers. This map was field
checked where necessary.
The following procedure was used for the detailed analysis. First, the
sewer systems were redrawn onto the topographical maps. The topo-
graphical maps were then taken to the field and a complete survey made
of the three sewer districts. Every street in the sewer districts was
inspected. Each property was labeled as residential, commercial,
industrial, institutional, undeveloped, or railroad. All non-residen-
tial property and residential property with unusual land cover or area
•./ere further classified as to the type of land cover. This was done
by sketching in the boundaries of these various areas and labeling
them. Many manhole covers were lifted to determine the accuracy of the
sewer map. Field checks were made around the boundaries of the drain-
age basins to determine which areas actually drained into their sewer
systems.
Following are the definitions of terms used for land use in this study:
residential - any family dwelling unit - one for each one or two
family unit and one for each family in multi-
family units.
commercial - all places of business excepting those whose major
business is the manufacture of a product to be sold
elsewhere - one for each business occupying a
ground-level storefront.
30
-------
industrial - any place whose major business is the manufacture
of a product to be sold elsewhere - one for each
name regardless of number of separate properties
occupied.
institutional - all schools and churches
undeveloped - without permanent improvements
railroad - track area not owned by private enterprise
The remainder of the detailed analysis of the sewer districts was com-
pleted in the office. First the boundaries of the sanitary and storm
drainage districts were determined. The boundaries were then plani-
metered to determine their areas. The number of each type of property
in each district was counted. The area of each type of land cover and
the total area were then measured.
More than half of the storm drainage area of each sewer district is
normal residential property. This property was not measured directly.
The sums of the areas of the other types of property were subtracted
from the total areas to determine the area occupied by normal residen-
tial property. These residential areas were then divided by the number
of normal residences in each sewer district to determine an average lot
size. Spot checks were then made to determine the average lot land
cover. (See Table 6)
The three sewer districts were classified according to their land use.
All three districts contain residential areas. Number 23 sewer district
is classified as suburban residential because of the low density of
houses per unit of area. Based on these classifications, the remaining
21 sewer districts were also classified. The remaining districts were
compared to Numbers 8, 17, and 23 districts by comparing their land use
on the large scale topographical maps. These classifications and the
drainage areas of all the districts are given in Table 7.
The average slopes of the three drainage districts were determined by
dividing each district into smaller drainage areas. The average slope
of each of these smaller areas was determined by measuring the fall from
the remotest drainage point to the sewer outlet. These values were then
weighted on the basis of their areas and an average slope computed.
(See Table 5)
The final part of the analysis of the sewer districts was the deter-
mination of the shapes of the three study areas. This was done by
approximating the drainage areas with regular polygons. Maximum widths
and lengths were measured. (See Table 5)
31
-------
TABLE 5
GENERAL DRAINAGE CHARACTERISTICS OF SELECTED SEWER DISTRICTS
Sewer Districts
Number of Customers
Residential
Commercial
Industrial
Institutional
Total
Population*
Population
Persons / Acre
Drainage Basin Slope
Weighted Average - % 0-85 0.65 0.25
Drainage Basin Shape
Maximum Length - feet 3,600 8,600 8,000
Maximum Width - feet 5,000 4,500 3,600
Ratio Length to Width O-7 '-9. 2'2
* Based on 3.5 people per residence
No. 8
577
14
4
3
598
2,020
11.7
No. 17
1,228
173
1
15
1,417
4,300
9.1
No. 23
561
23
5
1
590
1 ,960
5.0
32
-------
TABLE 6
LAND USE AND LAND COVER OF SELECTED SEWER DISTRICTS
Land Use - % of Total Area
Residential
Commercial
Industrial
Institutional
Undeveloped
Ra iI road
Streets
Total
Land Cover - % of Total Area
Impervious
Bui Idi ngs
Asphalt & Concrete
Streets
Water
Total
Pervious
Weeds
Lawn
Packed Earth
Gravel
Cornfield
Total
Normal Residential Lot
Lot Area (sq. ft.)
Lot Dimensions (ft.)
House and Garage Area (sq. ft.)
Asphalt & Concrete Area (sq. ft.)
Lawn Area (sq. ft.)
Gravel Area (sq. ft.)
Weeds & Garden Area (sq. ft.)
No. 8
Sewer Districts
No. 17 No. 23
59.6
6.3
7.8
4.6
12.9
0.2
8.6
100.0
14.7
10.5
8.5
0
33.7
20.4
39.8
0.8
0.8
4.5
66.3
8,400
60 x 140
1,400
350
5,000
0
1,650
55.1
1 1.5
7.2
2.3
II. 1
3.8
9.0
100.0
14.1
10.6
9.0
0
33.7
18.5
35.3
0.9
10. 1
1.5
66.3
9,000
60 x 150
1,500
975
5,450
225
850
53.4
4.8
17.6
0.7
15.4
0.2
7.9
100.0
1 1.2
6.4
7.9
0.6
26.1
17.8
49.9
0.3
5.9
0
73.9
16,000
90 x 178
1,900
850
12,300
50
900
33
-------
TABLE 7
DRAINAGE AREAS AND CLASSIFICATIONS
District
No.
I
2
3
4
5
6
7
8
9
10
I I
12
13
14
15
16
17
18
19
20
21
22
23
24
Totals
Sanitary Drainage
Area - Acres
188
475
395
Storm Drainage Area
Sewered Non-Sewered
73.3
2.5
19.4
113 82
32.1
21.0
3.2
179
3.0
7.1
6.2
41 .9
8.8
70.2
10.8
5.0
452 162
5.7
24.5
12.1
7.8
72.4
378
20.7
- Acres
Total
73.3
2.5
19.4
195
32.1
21 .0
3.2
179
3.0
7.1
6.2
41 .9
8.8
70.2
10.8
5.0
614
5.7
24.5
12.1
7.8
72.4
378
20.7
Classification
of Sewered Area*
SD
R
R
R
50$ R,
R
50$ R,
R
R
50$ R,
C
R
75$ R,
R
75$ R,
50$ R,
R
SR
R
SR
SR
SR
SR
SD
50$ C
50$ C
50$ C
25$ C
25$ C
50$
1,570
244
,814
*Symbols:
SD - Semi-developed
SR - Suburban Residential
R - Residential
C - Commercial
-------
SECTION XI
HYDRAULIC ANALYSIS OF THE SEWER
AND INTERCEPTOR SYSTEMS
Sewer Systems
The hydraulic analysis of the sewer systems consisted of two parts: (I)
determining the maximum sewer capacities, and (2) determining the times
of concentration. The Manning equation with n = 0.013 was used to com-
pute the flow and velocity in the pipes.
Because of the steady growth of the city many of the sewers have been
extended beyond the area for which they were originally designed. In
some cases, the systems have been extended beyond the drainage divide.
The result has been street ponding and basement flooding during wet
weather. Number 23 sewer district is an example. In the southern part
of this district, the sewer system has actually been extended beyond the
drainage divide between the Sandusky River and the Little Scioto River.
In this area the combined sewer is only three feet deep. Because of the
flatness of the sewer grades and the small size of the pipes, the City
has limited the number of street inlets which results in ponding rather
than surcharging the sewer system. However, there are frequent reports
of basement flooding in the area.
The maximum capacity of each of the 24 sewer systems was computed. (See
Table 8) The main trunk sewer was the controlling capacity for most of
the sewer systems. However, in a few systems the flow is limited by the
capacity of the sewers discharging into the main trunk sewer. Number 23
sewer district is an example.
The times of concentration for alI 24 sewer districts were determined.
The time of concentration consists of two parts: (I) the time of over-
land flow, and (2) the time of concentration in the sewer. The time of
overland flow depends on the length of travel from the most remote area
in the drainage district to the nearest storm sewer inlet, the type of
ground cover, and the slope of the land. These values were measured
for Numbers 8, 17, and 23 sewer districts. The times of overland flow
for these three districts were computed using the formulas given under
the hydrograph method in the ASCE Sewer Design Manual.2 A maximum of
30 minutes was assumed. Assuming that these values were typical for
the city, they were then applied to the other 21 sewer districts. The
time of overland flow was also determined for the impervious areas.
The time of concentration in the sewer is equal to the travel time from
the most remote inlet in the system to the point where the last inlet
lateral joins the main trunk sewer. These times were computed from the
velocities in the pipes, assuming that the pipes were flowing full.
35
-------
The summary of the values obtained for time of overland flow, time of
concentration in sewer, and total time of concentration Is given in
Table 8. Also given is the total travel time for each district. This
value was determined by adding the time of concentration to the travel
time in the sewer from the last inlet lateral to the overflow.
Interceptor System
The existing interceptor system functions as designed. There were no
reports of overflows during dry weather except when a connector pipe
became plugged. An analysis of the hydraulics of the interceptor was
necessary to determine its capacity and function during wet weather.
During the dry weather sampling on October 9 and 10, 1968, a check was
made on the connector capacity of the three districts studied. The
districts have a connector capacity equal to 0.9 cfs for Number 8 dis-
trict, 4.2 cfs for Number 17 district, and 3.4 cfs for Number 23 district.
These compare with a maximum dry weather flow, measured on March 5,
1969, of 0.5 cfs for Number 8 district, 1.0 cfs for Number 17 district,
and 1.4 cfs for Number 23 district. Therefore, the connector capacities
for these three districts are more than twice the maximum dry weather
fIows.
The existing interceptor pipe is designed to handle a flow of 19 cfs at
the lower end of the system. At each point in the system, the inter-
ceptor pipe capacity is equal to the sum of the connector pipe capac-
ities. The wastewater treatment plant records show that the interceptor
has a maximum daily flow in the spring of 4.5 cfs and an average daily
flow of 3.5 cfs. Therefore, the interceptor has a capacity equal to
four times the maximum hourly flow and five and one-half times the
average daily flow.
An overflow structure is located on the interceptor near the wastewater
treatment plant. During wet weather, flow to the plant is controlled
at about 3 MGD. Flows In the interceptor which exceed 3 MGD are diverted
to the river. The overflow is a 30" corrugated metal pipe with the
invert approximately 5.5 feet above the invert of the interceptor. This
overflow is located near the junction manhole for the northwest trunk
sewer. There are two 24" overflows on the northwest trunk sewer at an
elevation only 0.8 feet above the wastewater treatment plant overflow.
These also act as overflows for the interceptor during wet weather.
The control structures for diverting the dry weather flow consist of
two different types. One type is a simple rectangular weir built across
the trunk sewer pipe, and is usually made of bricks. The connector
pipe to the interceptor is cut into the wall of the trunk sewer pipe.
When the connector pipe is surcharged to the height of the weir, over-
flow to the river will occur.
36
-------
The other type of control structure consists of a depression in the
bottom of the sewer. The connector pipe is cut into the bottom of the
depression, makes a right angle bend, and continues to the interceptor.
When the connector pipe is surcharged to the level of the bottom of the
sewer, overflow will occur. Most of the overflow structures are equipped
with flap gates at the mouth of the overflow to prevent the river from
flowing into the pipe during high river stage. Numbers 8 and 17 over-
flows have the weir type control; Number 23 overflow has two of the
depression type controls.
Both types of control structures have proven successful for diverting
the dry weather flow. However, the weir type control structure is a
restriction in the trunk sewer pipe during high flows during an over-
flow event. Most of the trunk sewers were designed to carry only the
flow from the upstream drainage system. The weir, in many cases, covers
one-half the area of the trunk sewer pipe. The effects of this were
seen during this study. For example, every time the trunk sewer pipe
at Number 17 overflow is flowing full, the cover on the manhole behind
the control structure is blown off. See Table 9 for a comparison of the
capacities of the trunk sewers for Numbers 8, 17, and 23 sewer districts
with the control structure, without the control structure, and the maxi-
mum flows observed from the overflows during the past year.
37
-------
TABLE 8
MAXIMUM SEWER SYSTEM CAPACITIES
AND TIMES OF CONCENTRATION
District
No.
1
2
3
4
5
6
7
8
9
10
1 1
12
13
14
15
16
17
18
19
20
21
22
23
24
Maximum
Sewer
Capacity
cfs
23
4
5
42
25
4
1
105
5
5
61
7
3
29
39
3
140
5
6
5
4
12
65
8
Time of
Overland
Flow
Min.
20
20
20
20
20
20
20
30
20
20
10
20
20
20
20
20
30
20
20
20
20
20
21
Time of
Concentration
in Sewer
Min.
14
1
7
15
9
7
1
24
2
4
4
6
3
16
5
4
34
4
18
6
7
12
39
Time of
Concentration
Min.
34
21
27
35
29
27
21
54
22
24
14
26
23
36
25
24
64
24
38
26
27
32
60
30
Total
Travel
Time
Min.
36
21
33
37
29
27
21
54
22
24
14
26
23
37
25
24
67
24
41
27
28
36
63
For Impervious Areas Only:
8 6
17 4
23 4
24
34
39
30
38
43
30
41
46
38
-------
TABLE 9
MAXIMUM OVERFLOW RATES
Maximum Overflow Rate - cfs
Exi sting
System
50
75
65
Control
Structure
Removed
105
140
65
Measured
by
Weirs
50. 81
71. 02
7. .I3
Sewer
District No.
8
17
23
Measured on July II, 1969, for a 25-year storm.
0
Measured on April 5, 1969, for less than a 1-year storm.
3 Measured on July II, 1969, for a 25-year storm. Also measured
69.3 cfs on May 17, 1969, for less than 1-year storm.
39
-------
SECTION XI I
ANALYSIS OF RAINFALL AND OVERFLOW DATA
Tabulation of Hydraulic Data
The rainfall and overflow data recorded on the charts was transposed
into tabular form for study and analysis. The rain gages recorded the
rainfall as a mass curve with the ordinate as total inches of rainfall
and the abscissa as time. The smallest chart division of time was 20
minutes. The charts were further sub-divided into five or ten-minute
increments for low or moderate intensity rainfalls. For high intensity
rainfalls the charts were read from inflection point to inflection
point. Estimated accuracy of time readings are + 2 minutes, and
accuracy of setting the clocks to the correct time is + 5 minutes. The
vertical total rainfall scale was graduated to the nearest 0.05 of an
inch, and could be read to the nearest .01 of an inch.
Every rainfall that had correspondingly good overflow records was tabu-
lated. This included the clock time, the number of minutes in the time
interval, the accumulated rainfall as recorded on the charts, the rain-
fall during that interval, and the average intensity of the rainfall
during that interval. When no overflow record was obtained, only the
total amount of rainfall was recorded.
The charts from the flow level recorders recorded depth of overflow above
the weir plates versus time. The depth on the vertical scale was gradu-
ated to the nearest 0.02 of a foot, and could be read to the nearest
0.01 of a foot. The time scale was graduated to the nearest 15 minutes,
and could be read to the nearest 2 mintues. When there were rapid
fluctuations in flow, the charts were further sub-divided into five-
minute intervals. The accuracy of setting 0.00 on the recorder chart
to the top of the weir plates was + .01 of a foot. The accuracy of
setting the time on the charts to correspond with the correct time was
+ 2 minutes.
The flow records were also recorded in a tabular form. This included
clock time, minutes in time interval, depth of overflow above weir,
overflow rate per foot of weir, total overflow rate, average rate of
overflow for time interval, overflow volume for time interval, and
accumulated overflow volume for overflow event. Since the flow level
recorders recorded height above weir rather than flow, these had to be
converted to flow by use of tables for rectangular weirs.
Rainfall versus Overflow Graphs
The next step of the data analysis was plotting the rainfall and overflow
data for each overflow event recorded. Both rainfall and runoff were
plotted on the same graph, with rainfall plotted above overflow on the
41
-------
same time scale. The rainfalls were plotted in the form of hyetographs,
the overflows in the form of hydrographs. The time scale remained con-
stant for all graphs and the vertical scale varied according to the peak
rainfall intensity and the peak overflow rate. The rainfall and over-
flow graphs for March 24 and June 13, 1969, are given as examples in
Figures 16 through 21.
Each overflow hydrograph was divided into ten-minute segments. The rate
of flow at the mid-point of each ten-minute interval was read and assumed
to be the average for that interval. These values were summed to deter-
mine the total volume of overflow for the entire overflow event. The
volume was then compared to the volume computed previously in the tabu-
lation of the raw data to check its accuracy. A summary of the rainfall
and overflow data was prepared for each of the three overflows for each
overflow event. (See Tables 10, II, and 12)
Analysis of Rainfall Data
The rainfall data corresponding to the measured overflows were also
plotted as intensity-duration curves (See Figure 22) These rainfalls
represent a variety of different types of storms. May 7 and June 13
were short, intense thunderstorms. April 5 and May 17 were long dura-
tion rainfalls, with short periods of intense rain. The majority of the
storms, such as February 8 and March 24, were of light to medium inten-
sity and lasted between 2 and 12 hours.
None of the storms measured between February 8 and June 13, 1969, sur-
passed a one-year storm over their entire length. Two of the storms did
exceed a one-year storm at some point. May 17 exceeded a one-year storm
during the maximum 12 minutes, and June 13 exceeded a one-year storm dur-
ing the maximum 38 to 80 minutes.
-------
TABLE 10
RAINFALL AND OVERFLOW DATA
NO. 8 SEWER DISTRICT
Date
2/8
3/24
4/5
28
5/7
8
17
6/13
8/9
No.
1
2
3
1
2
3
2,3
1
2
1
2
1
2
1
2
3
1
2
1,2
1
2
1,2
3
Total
Depth
In.
0.25
.14
.17
.10
.47
.30
.77
.03
.14
.16
.04
.09
.12
.27
.40
1.18
.39
.81
1.20
.13
.06
.19
.50
Rainfal 1
Avg.
Intensity
In./hr.
0. 14
.09
. 15
.60
1 .68
.60
.80
.09
.28
.32
.06
.23
.05
.23
.57
.51
1.56
.97
.90
.16
. 10
-
.40
Overf
Dura-
tion
Min.
1 10
90
70
10
17
30
57
20
31
30
40
23
140
70
42
138
15
50
80
55
35
-
75
Total
Vol .
cu.ft.
22,
20,
29,
10,
61,
31,
92,
II,
6,
2,
32,
172,
35,
96,
132,
6,
3,
9,
54,
No
400
300
300
000
300
400
700
No
300
800
300
No
No
No
000
000
200
900
100
400
100
500
000
1 nches
on
Basin
Record
0.034
.031
.045
.015
.094
.048
.141
Record
.017
.Oil
.004
Record
Record
Record
.049
.264
.054
.149
.203
.010
.005
.015
.083
low
Peak
cfs
3
4
7
5
22
1 1
22
4
3
1
19
32
19
27
29
2
1
22
.5
.6
.5
.7
.8
.0
.8
.8
.0
.1
.4
.4
.0
.2
.5
.7
.4
.7
Dura-
tion
Min.
150
180
160
70
105
95
125
1 15
107
65
220
185
325
100
175
200
100
60
140
%
Over-
f low
14
22
26
15
20
16
18
12
7
10
12
22
14
18
17
8
8
8
17
43
-------
TABLE I I
RAINFALL AND OVERFLOW DATA
NO. 17 SEWER DISTRICT
Date
2/8
3/24
4/5
28
5/7
8
17
6/13
8/9
No.
1
2
3
1
2
3
2,3
1
2
1
2
1
2
1
2
3
1
2
1,2
1
2
1,2
3
Total
Depth
In.
0.17
.25
.14
.17
.09
.42
.26
.68
.03
.14
.16
.04
.09
.12
.27
.44
1.16
.37
.83
1.20
-
-
.30
.56
Rainfall
Avg.
Intensity
In./hr.
0.09
.14
.09
.15
.54
.93
.52
.72
.09
.28
.32
.06
.23
.05
.23
.29
.65
2.77
.91
.90
-
-
-
No Record
Overflow
Dura-
tion
Min.
120
1 10
90
70
10
27
30
57
20
31
30
40
23
140
70
92
108
8
55
80
-
-
-
Total
Vol.
cu.ft.
37,000
43,200
48,400
53,800
14,000
142,000
102,000
244,000
0
34,200
18,100
2,900
41,500
12,100
84,000
236,000
655,000
158,000
158,000
0
0
0
148,000
Inches
on
Basin
0.023
.026
.030
.033
.009
.087
.062
.149
0
.021
.Oil
.002
.025
.007
.050
.144
.400
Trace
.096
.096
0
0
0
.090
Peak
cfs
12.1
II. 0
13.5
12.0
14.6
71.0
40.5
71.0
18.9
24.5
2.2
29.2
2.7
28.0
66.5
64.0
63.2
63.2
50.1
Dura-
tion
Min.
105
135
135
145
80
95
100
135
85
60
40
80
102
135
415
265
190
190
110
%
Over-
f low
14
10
21
19
10
20
24
22
0
15
7
5
28
6
19
33
34
0
12
8
0
0
0
16
44
-------
TABLE 12
RAINFALL AND OVERFLOW DATA
NO. 23 SEWER DISTRICT
Date
2/8
3/24
4/5
28
5/7
8
17
6/13
8/9
No.
1
2
3
1
2
3
2,3
1
2
1
2
1
2
1
2
3
1
2
1,2
1
2
1,2
3
Total
Depth
In.
0.24
.26
.16
.15
.10
.27
.17
.44
.04
.12
.20
.05
.11
.1 1
.22
.39
1.06
.18
.72
.90
No
.04
-
.36
Ratnfal 1
Avg.
Intensity
In./hr.
.10
.14
.09
.13
.60
.54
.41
.44
.12
.29
.55
.15
1.32
.05
.22
.59
.62
2.70
.85
.72
Record
.03
-
.31
Overflow
Dura-
tion
MIn.
150
115
110
70
10
30
25
60
20
25
22
20
5
130
60
40
102
4
51
75
80
-
70
Total
Vol.
cu.ft.
35,300
23,100
24,600
30,600
16,800
91,800
62,700
154,500
1,700
24,400
30,000
8,900
34,800
13,300
No
No
534,000
19,000
171,000
190,000
7,700
7,100
14,800
96,200
Inches
on
Basin
0.026
.017
.018
.022
.012
.067
.046
.113
.001
.018
.025
.007
.025
.010
Record
Record
.390
.014
.125
.139
.006
.005
.Oil
.070
Peak
cfs
8.5
5.2
6.0
7.8
8.1
32.3
20.0
32.3
1 .2
10. 1
13.2
4.4
15.1
2.3
69.3
II. 0
59.7
61.2
3.7
1.7
35.3
Dura-
tion
Min.
165
135
140
150
65
140
135
175
45
no
110
75
105
170
265
67
160
177
95
145
170
%
Over-
flow
II
7
M
15
12
25
27
26
3
15
13
14
23
9
37
8
17
15
13
19
45
-------
SECTION XII I
WASTEWATER CHARACTERISTICS OF
COMBINED SEWER OVERFLOWS AND RECEIVING STREAM
The sampling program for the collection of overflow and river samples
began in July, 1968, and continued through August, 1969. From July,
1968, through January, 1969, flows were estimated and samples were taken
manually to determine the concentration range of water quality charac-
teristics. The weirs at the three selected sewer districts were com-
pleted in January, 1969, and after that date the overflows were auto-
matically measured and sampled. Table 13 presents the frequency and
duration of the sampling program and shows when and where samples were
collected and measured. There were five days - February 8, March 24,
May 7, June 13 and August 9 - when overflow events were both measured
and sampled.
The results of the laboratory analyses of all samples collected during
the study period have been summarized into a number of tables and graphs,
each of which will be discussed in this section of the report.
Dry Weather Sampling
Dry weather flow measuring and sampling to provide base data on waste
loads and flow was done on October 9, 1968, and March 4, 1969. The dry
weather sewage flows in sewer districts Numbers 8, 17, and 23 were
measured and sampled at 15-minute intervals for 24 hours. The Sandusky
River, upstream and downstream, was measured and sampled at one-hour
intervals for 24 hours. The wastewater treatment plant influent and
effluent were sampled at one-hour intervals for 24 hours and the flow
measurements taken from the plant records. The samples were composited
into eight-hour shifts which provided three composited samples for each
samp I ing point.
The laboratory results of the dry weather sampling have been summarized
and presented in Table 14. The waste loads from the three sewer dis-
tricts were fairly consistent for both sampling days. The BOD waste
load averaged 110 pounds per day per 100 acres for the three sewer dis-
tricts sampled. This compares very close with the March 4, 1969, total
dry weather BOD at the wastewater treatment plant of 112 pounds per day
per 100 acres of sewered area. The suspended solids waste load averaged
approximately 150 pounds per day per 100 acres.
The October 9, 1968, samples showed an unusually high influent BOD at
the treatment plant. A study of the laboratory results of the total
sampling indicates the unusually high BOD may have been caused by a slug
of industrial waste from a sewer district other than those three sampled.
Also, during the latter part of 1968, which includes September and
October, the wastewater treatment plant was not operating effectively
47
-------
and an unusually high waste load was being discharged into the river, as
indicated by the effluent BOD on the October 9th sampling. However, this
problem was corrected and by January, 1969, the treatment plant was
operating normally.
The total coliforms averaged 44 million per 100 ml for sewer districts
Numbers 8 and 17, and 7 million per 100 ml for sewer district Number 23.
The lower count in sewer district Number 23 is due to a large quantity
of industrial water.
Infiltration of groundwater into the sewerage system can be estimated by
comparing the total flow received at the wastewater treatment plant on
the two dry weather sampling days. The October 9, 1968, sampling
occurred during an extremely dry month and represents conditions of
practically no infiltration. The total flow of 2.05 million gallons
received at the wastewater treatment plant on October 9, 1968, agrees
closely with the water plant output of 2.0 million gallons on the same
day. The March 4, 1969, sampling occurred following spring thawing and
represents saturated ground water conditions. The flow received at the
wastewater treatment plant on March 4 totaled 2.47 million gallons.
The water plant output for this same period was 2.0 million gallons.
Therefore, the infiltration is the difference between the October and
March sampling or approximately 420,000 gallons. This amounts to an
infiltration rate of 270 gallons per day per acre during the times when
the ground water table is high. This infiltration rate is not unreason-
able for a collection system.
Overflow Samples
The laboratory results of the overflow samples from the three selected
sewer districts have been summarized and presented in Table 15. This
table presents the average, minimum, maximum, and median values of the
chemical and bacteriological characteristics of all the individual over-
flow samples collected during this study. Sewer district Number 8 has
an average BOD concentration of 170 mg/l which is considerably higher
than the average BOD concentration of sewer districts Numbers 17 and 23,
each of which have an average BOD of 107 and 108 mg/l respectively.
This difference of BOD concentration is due to the fact that periodic
discharges of slaughter house wastes occur in sewer district Number 8.
It is interesting to note that there is very little difference between
the average BOD concentration of the overflow samples and the average
BOD concentration of the dry weather samples. However, the average
suspended solids concentration of 480 mg/l for the overflow samples is
much higher than the average of 160 mg/l for the dry weather samples.
The average total coliform count for Numbers 8 and 17 overflows was 8.8
million per 100 ml and 16 million per 100 ml, respectively. This is
only 20 percent to 30 percent of the dry weather sample total coliforms.
48
-------
The more significant water quality character!sites of the overflow
samples, which include BOD, suspended solids, total solids, the nitrogen
series, total phosphates and chlorides, have been graphed in comparison
to time after start of overflow and are shown in Figures 23 through 43.
These graphs very clearly show the first flushing effects of the storm
water on the water quality of the overflows. The peak concentrations
of the various water quality characteristics tend to coincide with the
peak overflow rate.
To determine the effects of settling on the overflow samples, two over-
flow samples from Number 17 sewer district were settled and the super-
natant withdrawn at 30-minute intervals for two hours. The supernatant
was analyzed for BOD and suspended solids and the results are shown in
Figure 44. The results indicate that approximately 60 percent to 70
percent of the BOD and suspended solids could be removed with 30 minutes
of sett I ing time.
A summary of the waste loads discharged into the Sandusky River from each
of the five complete overflow events sampled and measured have been
calculated and summarized in Table 16. This table shows that the
August 9, 1969, overflow event discharged into the Sandusky River, from
just three sewer districts, 2,300 pounds of BOD in approximately two
hours. This is more BOD than that received at the wastewater treatment
plant from 24 hours of dry weather flow. Extrapolating the 2,300 pounds
of BOD to include all 24 sewer districts gives a total of 3,500 pounds
of BOD discharged to the river.
Sandusky River Samples
The laboratory analyses of the Sandusky River samples taken upstream and
at various locations downstream, during wet and dry weather, have been
summarized and are presented in Table 17. Dry weather samples represent
conditions of the river without overflow effects and wet weather samples
present the river conditions during times of overflow. Because of the
difficulty in treatment operation at the wastewater treatment plant
during the latter part of 1968, mentioned previously in this report,
only those samples collected after January, 1969 have been used in this
tab Ie.
The major differences in the upstream water quality characteristics dur-
ing dry and wet weather are in the suspended solids, nitrates and
bacteria counts. The average dry weather suspended solids of 32 mg/l
increase to an average 465 mg/l during wet weather. The average dry
weather concentration of nitrates is 7.2 mg/l as NO, and is increased to
an average 21.7 mg/l during wet weather. This increase in nitrates seems
to be due to agriculture runoff. The total coliform count is reduced
from a dry weather average of 59,000 per 100 ml to 3,400 per 100 ml dur-
ing wet weather. This reduction in bacteria is due to the added dilution
water from the upper drainage area.
49
-------
The comparison between the dry and wet weather river samples indicates
that the waste loads from the overflow affect the river quality as far
downstream as the fifth bridge, which is approximately seven miles down-
stream from the wastewater treatment plant. During periods of overflows
the average BOD concentration at the first bridge downstream from the
wastewater treatment plant Is increased from a dry weather average of
6 mg/l to 14 mg/l, the suspended solids increase from 49 mg/l to 192
mg/l, and the total coliforms increase from a dry weather average of
400,000 per 100 mi Hi liters to 4.5 million per 100 mi Hi liters. The
average coliform count at the fifth bridge downstream from the waste-
water treatment plant is increased from an average 4,500 per 100
mi I I iliters to 86,000 per 100 mi IN liters.
The diurnal fluctuation of dissolved oxygen in the Sandusky River is
presented in Figures 45 and 46. Figure 45 shows the dissolved oxygen at
the upstream gage on October 9 and 10, 1968, at the time of the first
dry weather sampling. The dissolved oxygen ranged from 8.2 mg/l to
10.3 mg/l and saturation ranged from 80 percent to 109 percent. The
dissolved oxygen at the first bridge downstream from the wastewater
treatment plant remained at zero (0.0) mg/l for the entire 24 hour
period.
Figure 46 shows the diurnal affect on dissolved oxygen in the Sandusky
River from the upstream gage to the seventh bridge downstream from the
wastewater treatment plant, a total distance of about 12 miles. The
river samples were taken on August 5 and 6, 1969, during dry weather and
river flow of approximately 10 cfs which is considered low flow. This
dissolved oxygen profile shows the normal dissolved oxygen concentration
of the river during low flows.
In addition to the two figures presented above, dissolved oxygen profiles
of the river downstream from the wastewater treatment plant during both
wet and dry weather conditions are shown in Figure 47.
50
-------
TABLE 13
DATA SUMMARY
Date
July 10, 16, 26 - 1968
" 18
September 5
" 12
" 16
" 24
October 2, 9
" 10
November 15
January 16, 17 - 1969
February 8
March 4, 5
" 20, 21
11 24
" 25, 29
Apr! 1 2, 28
ii 5
" 8, 15, 18, 19, 21
May 5, 9, 12, 19, 21
" 7
11 17, 18
June 3, 12, 16, 23, 26
" 13
11 14, 15
July 1, 8, 15, 22, 25, 28, 31
" 3, 5, II, 17, 27
August 1 , 6, 10, 20, 27
" 9
" 16
September 2, 6, 16
" 3, 9, 18
17
Overf lows
Measured
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Overf lows
Samp led
X
X
X
X
X
X
X
X
X
X
River Sewer
Sampled Sampled
X
X
X X
X
X
X X
X X
X X
X
X X
X
X
X
X
X
X
X
X
X
X
X
X
X
51
-------
TABLE 14
SUMMARY OF DRY WEATHER WASTE LOADS
DATE & LOCATION
1.
2.
3.
4.
5.
6.
7.
Upstream
October 9, 1968
March 4, 1969
Sewer District #8
October 9, 1968
March 4, 1969
Sewer District #17
October 9, 1968
March 4, 1969
Sewer District #23
October 9, 1968
March 4, 1969
WWTP-RAW
October 9, 1968
March 4, 1969
WWTP-FINAL
October 9, 1968
March 4, 1969
Downstream - 1st Bridge
October 9, 1968
March 4, 1969
AVERAGE
FLOW
MOD
1.27
24.56
0.13
0.22
0.27
0.50
0.66
0.69
2.05
2.47
2.15
2.59
10.87
29.63
mg/l
2.2
3
192
121
198
118
60
84
232
109
105
24
42
6.0
BOD
Ibs/day
23
f 1 A
614
208
221
445
491
329
482
3960
1969
1882
518
3807
1482
Ibs/day/
100 ac
116
124
98
108
87
128
252
112
52
-------
TABLE 14 (CONTINUED)
SUMMARY OF DRY WEATHER WASTE LOADS
SUSPENDED
SOLIDS
1.
2.
3.
4.
5.
6.
7.
mg/l
12
10
155
109
84
193
62
246
96
143
70
55
13
5
Ibs/day
127
2048
168
199
189
804
344
1417
1638
2941
1255
1 188
1 178
1235
Ibs/day/
100 ac.
94
1 1 1
42
178
91
375
104
187
TOTAL
SOLIDS
mg/l
593
442
768
753
738
862
287
758
847
755
735
822
673
457
TOTAL
VOLAT 1 LE
SOLIDS
mg/l
213
138
252
223
242
273
145
343
333
203
237
257
213
132
SPECIFIC
CONDUCTIVITY
mohos/cm
757
490
1,003
897
1,010
910
573
665
1,117
897
1,063
872
960
538
53
-------
TABLE 14 (CONTINUED)
SUMMARY OF DRY WEATHER WASTE LOADS
1.
2.
3.
4.
5.
6.
7.
_CQD
mg/l
36
63
516
318
781
304
660
537
628
201
327
253
192
46
TOTAL
COL! FORMS
per 100
ml
60,000
23,000
42 x 10^
33 x 10°
61 x IOJ?
42 x 10°
7 x 10*
7 x I06
10 x lo6.
200 x 10
4.2 x I06.
15 x 10°
6.5 x 10?.
1.5 x 10°
FECAL
COL 1 FORMS
per 100
ml
10,000
450
5 x 10*
3.0 x 10°
1.7 x 10*
4.2 x 10°
5.7 x I06
500,000
10 x 10?
8 x 10°
2.0 x I06
6.0 x I06
110,000
FECAL
STREP
00
ml
1,500
1,000
550,000
300,000
I.I x I06
350,000
110,000
18,000
1.5 x I06
360,000
270,000
26,000
320,000
17,000
54
-------
TABLE 14 (CONTINUED)
SUMMARY OF DRY WEATHER WASTE LOADS
1.
2.
3.
4.
5.
6.
7.
NITRATE
NITROGEN
mg/l as N03
0.6
5.1
0.9
1.7
1.0
1.6
0.8
2.6
0.7
0.5
0.6
0.6
0.3
5.1
AMMON 1 A
NITROGEN
mg/l as N
1.2
0.4
55
30
56
35
38
21
48
30
58
24
43
1.8
ORGANIC
NITROGEN
mg/ 1 as N
Trace
2.0
36
33
48
27
14
16
34
21
31
22
17
3.0
mg/l
1.2
3.6
91 .2
62.9
104
62.4
52
37.4
82.5
47
89.1
51
60.4
5.4
TOTAL NITROGEN
AS N
Ibs/day
13
737
98
1 15
234
260
286
215
1410
968
1598
1 102
5475
1334
Ibs/day/
100 ac
55
64
52
57
76
57
90
62
55
-------
TABLE 14 (CONTINUED)
SUMMARY OF DRY WEATHER WASTE LOADS
TOTAL PHOSPHATES
AS P04
1.
2.
3.
4.
5.
6.
7.
mg/l
0.5
0.6
82
13.7
47
19.2
8.7
8.7
31
19
31
19
17
1.6
Ibs/day Ibs/day/
100 ac
5
123
89 50
25 14
106 10
80 4
49 13
50 13
530 34
391 25
556
410
1541
395
CHLORIDES
mg/l as Cl
36
29
122
120
107
113
74
70
169
136
137
133
112
39
TOTAL
ALKALINITY
mg/l as CaCO,
251
159
330
249
300
243
160
155
249
216
227
218
233
170
PH
7.6
7.9
7.3
7.7
7.2
7.9
7.3
8.0
6.8
7.0
7.2
7.3
7.1
7.7
56
-------
TABLE 15
SUMMARY OF LABORATORY ANALYSES
ON OVERFLOW SAMPLES
LOCATION
1 . Overflow No. 8
No. of analyses
Average
Minimum
Maximum
Median
2. Overflow No. 17
No. of analyses
Average
Minimum
Maximum
Median
3. Overflow No. 23
No. of analyses
Average
Minimum
Maximum
Med I an
BOD
mg/l
47
170
II
560
140
54
107
II
265
100
52
108
23
365
78
COD
mq/l
13
372
64
735
394
20
476
120
920
440
21
391
105
795
355
SUSPENDED
SOLIDS
mq/l
42
533
20
2440
360
44
430
90
990
400
32
477
120
1050
385
VOLATILE
SUSPENDED
SOLIDS
mq/l
13
182
70
440
180
24
238
80
570
160
20
228
70
640
200
TOTAL
SOLIDS
mq/l
40
1647
150
3755
1260
33
863
310
I960
780
25
916
370
1965
830
57
-------
TABLE 15 (CONTINUED)
SUMMARY OF LABORATORY ANALYSES
ON OVERFLOW SAMPLES
NITRATE
NITROGEN
mq/l as M03
1. 41
4.54
0.05
13.50
3.30
2. 52
3.79
0.05
21.0
3.10
3. 49
3.89
0.05
21.50
2.40
AMMONIA ORGANIC
NITROGEN NITROGEN
ma/I as N mq/l as N
14
3
0
21
1
21
1
0
2
1
23
2
0
9
1
. 13
. 10
.3
. 10
.08
.10
.2
.1
.7
.10
.0
.8
14
10.3
2. 1
68
5.6
21
8.9
2.8
19.3
6.7
23
7.3
O.I
18.5
5.9
TOTAL
COL 1 FORM
/IOO ml
8.8
0.75
34.0
3.6
16
0.6
49
7.5
6.0
0.2
25
3.6
14
x
x
X
X
12
X
X
X
X
II
X
X
X
X
6
I06
I06
I06
10°
I06
I06
l°«
p\
10°
6
I06
[
10
6
I06
I06
I06
10
58
-------
TABLE 15 (CONTINUED)
SUMMARY OF LABORATORY ANALYSES
ON OVERFLOW SAMPLES
TOTAL
PHOSPHATES
P04
mq/l f
TOTAL
ALKALINITY
mg/l
)H as CaC03
TOTAL
HARDNESS
mg/l as
CaC03
CHLORIDES
mq/l as
"ci
SPECIFIC
CONDUCTANCE
mohoms/cm
31
I I
I
35
8.8
.5
.0
42
6.9
6.5
7.3
7.0
31
127
70
184
I 14
31
183
I 15
290
168
34
203
24
1400
99
42
1721
200
4600
810
2.
42
9.0
2.0
27.2
7.7
47
7.1
6.6
7.4
7. I
35
123
40
280
I 10
35
160
58
290
150
39
120
9
460
I 10
39
502
132
1500
300
3.
41
10.5
2.4
30
7.5
47
7.0
6.6
7.4
7.0
29
123
64
250
100
29
176
105
260
170
31
147
12
660
71
46
825
174
2100
800
59
-------
TABLE 16
SUMMARY OF WASTE LOADS FOR EACH OVERFLOW EVENT
FLOW
1.
2.
3.
4.
5.
OVERFLOW EVENT
DATE & OVERFLOW NO.
February 8, 1969
t 8
#17
#23
TOTAL
March 24, 1969
# 8
#17
#23
TOTAL
May 7, 1969
t 8
#17
#23
TOTAL
June 13, 1969
# 8
#17
#23
TOTAL
August 9, 1969
# 8
#17
#23
Overflow
Period
In
Minutes
120
105
165
150
135
135
107
60
no
200
190
177
140
no
170
Maximum
cfs
3.0
12.0
8.4
4.4
II. 0
5.2
3.0
24.5
13.2
27.8
63.2
61.2
22.7
50.1
35.3
Total
Vo 1 ume
1000 cf
13
37
35
85
22
43
23
88
7
18
30
55
132
158
190
480
54
148
96
TOTAL
398
60
-------
TABLE 16 (CONTINUED)
SUMMARY OF WASTE LOADS FOR EACH OVERFLOW EVENT
1.
2.
3.
4.
5.
Average
mq/l
120
51
86
146
161
104
I 18
172
1 16
41
31
36
177
112
1 12
BOD
Total
Ibs.
98
118
190
406
201
415
149
765
50
194
216
460
331
312
420
1063
600
1040
670
SUSPENDED
SOLIDS
lbs/100/
ac.
55
26
50
112
92
40
28
43
57
185
69
1 1 1
336
230
178
Average
mq/l
570
615
670
675
670
505
430
454
660
375
413
652
_
306
-
Total
Ibs.
464
1416
1480
3360
931
1539
725
3195
184
514
1234
1932
3100
4200
7700
14778
_
2850
-
lbs/100/
ac.
260
313
390
520
340
192
103
114
325
1700
900
2050
_
630
-
2310
61
-------
TABLE 16 (CONTINUED)
SUMMARY OF WASTE LOADS FOR EACH OVERFLOW EVENT
VOLATILE
SUSPENDED
SOLIDS
Average
mq/ 1
1.
_
-
2. 390
289
280
3. 200
291
368
4. 126
96
160
Total
Ibs.
_
-
540
779
404
1733
85
329
689
1103
1023
967
1873
TOTAL
PHOSPHATES
AS P04
Average
mq/l
8.3
6.7
6.5
12.0
11.3
11.8
7.3
12.2
15.1
2.3
2.0
9.7
Total
Ibs.
7
15
14
36
16
30
17
63
3
14
28
45
19
21
113
NITRATE
NITROGEN
AS N03
Average
mq/l
3.0
3.1
2.5
2.0
2.7
2.5
1.4
0.8
0.5
9.1
9.3
16.9
Total
Ibs.
2
7
5
14
3
7
4
14
1
1
|_
3
74
94
198
3863
153
366
62
-------
TABLE 17
SUMMARY OF WET AND DRY WEATHER RIVER ANALYSES
1.
2.
3.
4.
5.
Sandusky River - Upstream
No. of analyses
Average
Minimum
Maximum
Med ian
Sandusky River - Downstream
1st Bridge downstream from
wastewater treatment plant
No. of analyses
Average
Mi nimum
Max i mum
Median
Sandusky River - Downstream
2nd Bridge from WWTP
No. of analyses
Average
Min imum
Max i mum
Median
Sandusky River - Downstream
3rd Bridge from WWTP
No. of analyses
Average
Mi n imum
Maximum
Median
Sandusky River - Downstream
5th Bridge from WWTP
No. of analyses
Average
Mi nimum
Maximum
Median
BOD
mq/l
Dry
Weather
33
4
1
14
3
27
6
2
12
5
9
7
3
22
-
12
4
1
8
4
13
5
2
13
4
1
Wet
Weather
22
5
2
13
4
43
14
4
51
10
8
5
3
8
-
17
6
3
10
6
19
6
2
12
6
SUSPENDED
mq/
Dry
Weather
20
32
5
160
20
14
49
8
190
22
8
44
10
195
22
4
36
27
45
-
5
18
15
25
17
SOLIDS
1
Wet
Weather
13
465
20
1 , 960
240
38
192
5
960
90
8
62
20
135
40
17
36
20
50
40
1 1
90
25
300
50
63
-------
TABLE 17 (CONTINUED)
SUMMARY OF WET AND DRY WEATHER RIVER ANALYSES
TOTAL VOLATILE
SOLIDS
mq/l
Dry
Weather
1. 15
183
2
225
_
Wet
Weather
8
94
35
125
_
TOTAL
SOLIDS
mq/l
Dry
Weather
12
510
400
610
_
Wet
Weather
9
576
405
1,080
-
TOTAL PHOSPHATES
ma/I as P04
Dry
Weather
17
0.8
0.2
3.2
0.6
Wet
Weather
14
0.9
O.I
2.7
0.8
9
128
30
195
130
17
158
30
270
165
9
506
410
710
490
19
746
415
1,335
630
13
1.6
0.2
5.9
1.3
40
3.3
0.8
10.0
2.6
2
168
2
480
3
2,0
6
2.2
2
2.0
15
4.1
1.8
8.0
4.8
14
3.7
2.6
64
-------
TABLE 17 (CONTINUED)
SUMMARY OF WET AND DRY WEATHER RIVER ANALYSES
NITRATE NITROGEN
mq/l as N03
Dry Wet
Weather Weather
AMMONIA
NITROGEN
mq/l as N
Dry Wet
Weather Weather
ORGANIC
NITROGEN
mq/l as N
Dry Wet
Weather Weather
I.
26
7.2
0.4
32.0
3.3
19
21.7
0.5
28.8
14.5
5
0.58
0.13
1.20
9
0.32
0.0
2.60
4
1.51
0.0
6.07
9
1.76
0.0
4.80
20
6.7
0.2
32.0
3.3
41
7.5
0.3
24.8
7.7
5
1.51
I.10
2.12
1.51
2.40
0.60
6.60
1.40
5
2.40
0.80
3.03
3.03
3.79
0.20
14.7
2.80
.0
6
0.9
.0
2
0.8
4
3.7
1.3
5.8
15
1.9
0.5
3.4
1.8
3
6.9
1.4
10.2
14
6.2
0.5
22.2
4.4
I
0.6
2
1.7
65
-------
TABLE 17 (CONTINUED)
SUMMARY OF WET AND DRY WEATHER RIVER ANALYSES
TOTAL COLI FORMS
/IQQ ml
FECAL COL I FORM
Dry
Weather
3
59,000
23,000
95,000
86
0.4 x 10
2,000,
1.5 x 10°
Wet
Weather
4
3,400
1,200
6,300
4.5 x
0.05 x
8.8 x
10
10
FECAL STREP
/100 ml
/ 1 UU
Dry
eather
3
8,000
450
14,000
6
36,000
2,000
110,000
fl I
. - •—•
Wet
Weather
— — H . .
3
900
800
1,000
7
161,000
10,000
320,000
_-- - i —
Dry
Jfeather
3
1,600
1,000
2,400
6
11,000
1,000
24,000
Wet
Weather
• — -•• " — •
3
170
130
200
6
55,000
1,000
157,000
5
15,000
5,600
40,000
I
130,000
4
390
180
500
4
310
70
500
1,400
4
4,500
3,000
5,300
I
86,000
4
380
175
760
3
230
180
300
66
-------
TABLE 17 (CONTINUED)
SUMMARY OF WET AND DRY WEATHER RIVER ANALYSES
TOTAL
COD pH ALKALINITY
mq/l as CaC03
1.
2.
3.
4.
5.
Dry
Weather
12
127
17
422
II
244
24
770
130
2
156
32
280
—
1
48
_
_
•~
_
_
-
_
Wet
Weather
4
65
18
164
14
1 14
28
220
120
4
156
24
430
80
4
112
18
210
—
5
86
24
220
-
Dry Wet
Weather Weather
26
7.9
7. 1
8.9
7.8
24
7.8
7.4
8.5
7.7
6
8.0
7.4
8.4
7.9
5
7.7
7.5
8.2
7.7
5
7.6
7.5
7.7
7.6
14
7.8
7.1
8.5
7.8
37
7.3
7.1
7.8
7.3
6
7.9
7.5
8.2
7.9
14
7.7
7.3
8.2
7.8
10
7.6
7.4
7.8
7.7
Dry
Weather
13
192
152
254
182
9
165
150
180
164
3
183
172
200
2
173
160
186
1
164
-
-
-
Wet
Weather
10
155
98
192
170
19
135
99
166
140
6
166
140
186
6
189
174
240
7
142
86
168
-
67
-------
TABLE 17 (CONTINUED)
SUMMARY OF WET AND DRY WEATHER RIVER ANALYSES
SPECIFIC
CONDUCTIVITY
mohoms/cm
Dry Wet
TOTAL
HARDNESS
as CaCQ5
Dry Wet
Weather Weather
CHLORIDES
mq/l as C_l_
Dry Wet
Weather Weather Weather Weather
10
316
250
372
314
8
283
252
320
290
14
30
13
37
13
31
21
35
18
621
420
770
630
II
524
309
610
550
8
286
260
335
282
17
236
145
305
248
12
38
10
57
38
34
53
23
158
40
14
602
380
750
620
32
504
245
825
520
3
297
288
304
6
285
256
302
3
39
38
40
6
43
39
46
5
674
610
770
6
607
560
620
4.
2
270
240
300
6
293
272
304
3
44
37
50
14
56
37
77
5
651
580
725
14
653
600
742
5.
268
7
271
185
296
5
60
37
69
65
9
47
22
74
43
6
639
563
720
688
9
581
370
740
600
68
-------
SECTION XIV
AQUATIC BIOLOGY SURVEY OF THE SANDUSKY RIVER
A summary of the aquatic biology survey of the Sandusky River is shown
in Table 18.
Sampling stations were established to determine biological productivity
and other pertinent information in the Sandusky River upstream and down-
stream from Bucyrus. Samples were collected in the fall of 1968 and in
the spring and summer of 1969. The study section consisted of 26 miles
of the Sandusky River extending ten miles upstream and thirteen miles
downstream and including three miles of river within the city. The
stream population and stream conditions affecting biological produc-
tivity were observed at ten points.
The results of the aquatic biology survey corroborates the results of
the water quality studies of this report. The river upstream from
Bucyrus has a relatively undisturbed fauna of the types normally found
in unpolluted waters. The river inside the City of Bucyrus shows
indication of gross pollution and has sections completely devoid of life.
The river downstream from Bucyrus, during periods of low flow, is bioti-
cally dead for six to eight miles below the wastewater treatment plant.
69
-------
TABLE 18
Date and Location
10 MIles Upstream
from Bucyrus
March 18, 1969
Upstream Gage
October 26, 1968
March 18, 1969
July 25, 1969
SUMMARY OF AQUATIC BIOLOGY SURVEY
OF THE SANDUSKY RIVER
Life Forms Founc[
Crayfish, snails and clams
Pea clams, snails, leeches
minnows and crayfish
Crayfish, snails, pea clams
and muskrat
Crayfish, snails and minnows
Remarks
No evidence of pollution.
Gravel and rock bottom covered with
algae
Relatively undisturbed stream fauna.
River bottom has been washed clean
by recent floods.
No. 8 Overflow
October 26, 1968
March 18, 1969
Only a few Immature Insect
larvae
No apparent 11fe
Water plant waste lime sludge had
filled most of the niches between
the gravel and stone river bottom.
Blue-green algae scum very apparent,
River very turbid from lime sludge.
01 I siIck on water.
No. 17 Overflow
October 26, 1968
Pea clams, Phepa, leeches,
crayfish, minnows and an
array of immotile aquatic
insects.
Filamentacious algae extremely
abundant.
-------
Date and Location
AuMIMer Park - 2000' Below
No. 17 Overflow
October 26, 1968
November 19, 1968
March 18, 1969
July 25, 1969
Downstream Gage - First
Bridge downstream from
WWTP
October 26, 1968
TABLE 18 (Continued)
Life Forms Found
Pea clams, Phepa, leeches
and crayfish
Pea clams, leeches, snails,
minnows and darters
Pea clams, crayfish and
snal I s
Crayfish, pea clams, leeches
minnows, and various forms
of plankton
SIudge worms
Remarks
This location contains a biotic
abundance including many forms of
algae and other plankton. The
water is very clear.
A tremendous abundance of life
forms. River very clear at this
location.
The biotic abundance found In
October now greatly reduced. The
algae has been swept away and rocks
are clean.
No evidence of pollution. High
flood waters have brought river
back to normaI.
From a biotic standpoint, the river
is dead. The river is black and
the stench is evident before one
sees the stream. Bottom of river
is covered with black sludge
deposits.
November 19, 1968
Sludge worms
A dead river.
-------
K>
Date and Location
Downstream Gage - First
Bridge (Cont'd.)
March 18, 1969
July 9, 1969
July 25, 1969
Fourth Bridge Downstream
5.5 mlles below WWTP
October 26, 1968
March 18, 1969
July 25, 1969
Fifth Bridge Downstream
7.2 miles below WWTP
November 19, 1968
TABLE 18 (Continued)
Life Forms Found
No 11fe forms found
No sample taken
Crayfish and minnows
SIudge worms
No Iife found
Crayfish, leeches, frogs,
minnows and various
plankton
Only immature insect
larvae
Remarks
The river was rather clear and most
of the sludge deposits have been
washed out from the recent high
water.
High river flow and no evidence of
pollution.
Recent high waters have flushed out
sludge deposits and continued high
water has brought life forms.
Biologically, this location seems
more lifeless than the downstream
gage location.
River black and barren.
Flood water has cleaned river bottom
and brought in new life forms.
River was grayish and contained
sludge deposits.
-------
Date and Location
Eighth Bridge Downstream
9.6 mlles below WWTP
November 19, 1968
March 18, 1969
July 25, 1969
Tenth Bridge Downstream
12.9 mi les below WWTP
November 19, 1968
March 18, 1969
TABLE 18 (Continued)
Life Forms Found
Caddis Larvae
Crayfish and all types of
aquatic insects
Crayfish, clams, minnows
and aquatic insects
Minnows, sunfish, crayfish,
caddis and aquatic Insects
Minnows, various types of
fish, crayfish and aquatic
insects
Remarks
Caddis larvae indicate the stream
Is returning to normal. River was
clear and there was no evidence of
sludge deposits.
No evidence of pollution.
River In good condition.
River is fully recovered at this
location.
River is fully recovered at this
location.
-------
SECTION XV
RELATIONSHIP OF RAINFALL AND RUNOFF
The design of interception and treatment or holding facilities for com-
bined sanitary and storm runoff water requires a complete sewer
hydrograph.3 This requires knowing the rainfall-runoff relationship.
Sewer hydrographs were developed first for the three sewer districts
studied in detail, then for all of Bucyrus. Throughout the discussion
the word "overflow" will be used for any water flowing into the river
from the sewer system and "runoff" wi I I be used for any water flowing
into the sewer system. Overflow is assumed to equal runoff for rain-
falls greater than 0.25 inch.
There are three relationships between rainfall and runoff which must be
determined before a complete runoff hydrograph can be defined: one, the
relationship of the start of the runoff hydrograph to the start of the
rainfall; two, the relationship of the shape of the runoff hydrograph to
the duration of the rainfall; and three, the relationship of the peak a
and volume of the runoff hydrograph to intensity and duration of the
rainfall. Whenever possible these relationships will be derived from
the measured data.
Start of Overflow
A table was prepared for each of the three selected overflow points list-
ing all of the overflow events measured. Included in these tables were
the times between the start of the significant rainfall and the start of
the overflow. The period of time varies with the rainfall intensity and
pattern. The following values present in Table 19 are average for rain-
falls of intensities greater than 0.5 inch per hour.
TABLE 19
TIME TO START OF OVERFLOW
Time Between Start of
Sewer Rainfall and Start of Overflow
District No. Minutes
8 10
17 20
23 25
75
-------
The time between the start of the significant rainfall and the start of
the overflow could be called the reaction time of the sewer system. It
is equal to the period of time for a significant amount of runoff to
reach the overflow point.
Before runoff starts, the depression storage must be filled. The runoff
needed to cause overflow is equal to the storage capacity in the system
and either the volume of the interceptor or the capacity of the connector
pipe. An analysis was made of the rainfalls producing little or no over-
flow and having no antecedent rainfall. The following values presented
in Table 20 are the average amounts of rainfall required to cause over-
flow:
TABLE 20
RAINFALL TO CAUSE OVERFLOW
20-Minute RainfalI
Sewer Required to Produce Overflow
District No. Inches
8 .04
17 .06
23 .05
Hydrograph Shape
The unit hydrograph was used to describe the shape of the overflow
hydrographs from each of the three areas. Each unit hydrograph was
derived from the measured overflow data. Only the overflows from short
Intense rainfalls were used. In many cases the rainfall events produced
compound hydrographs. These hydrographs were separated and drawn as
individual hydrographs.
Each overflow hydrograph was divided into ten-minute Intervals. The
average rate of flow in each ten-minute interval was determined and the
total volume of overflow computed. The hydrograph ordinates were then
adjusted to give a total overflow volume equivalent to 1.00 inch of run-
off from the sewer district.
Every overflow hydrograph for each sewer district then had the same
volume, but many different shapes. The shape of the hydrographs is deter-
mined by the length of the rainfall. According to the unit hydrograph
theory, any rainfall less than the length of a unit storm will produce
the same shape hydrograph. If the rainfall continues past this critical
period of time, each additional period of unit storm will produce a unit
76
-------
hydrograph; the sum of these unit hydrographs will produce the hydro-
graph for that rainfall. Each additional unit hydrograph will delay
the peak of the runoff hydrograph by the duration of the unit storm.
Therefore, the period of time from the start of the overflow to the
peak of the overflow will equal the period of significant rainfall for
any rainfall equal to or greater than a unit storm.
A graph was prepared for each overflow, plotting the length of the
significant rainfall in minutes versus the time between the start and
the peak of the overflow in minutes. (See Figure 48 for the summary
of these graphs) For Number 8 overflow, the length of significant
rainfall was equal to the peak time. However, for Number 17 overflow
the peak time is five minutes less than the length of the significant
rainfall, and for Number 23 overflow the peak time was five minutes
greater than the length of the significant rainfall. These variations
in peak time for Numbers 17 and 23 overflows were due to the longer
lengths of time to start overflow (See Table 19) and variations in the
drainage characteristics.
The smallest periods of time between the starts and the peaks of the
overflows measured were five minutes for Number 8 overflow, two minutes
for Number 17 overflow, and ten minutes for Number 23 overflow. (See
Figure 48) The maximum length of significant rainfall producing these
minimum peak times were five minutes for Numbers 8 and 23 overflows,
and seven minutes for Number 17 overflow. Since five minutes was also
the shortest time of significant rainfall measured, the conclusions
are the length of a unit storm is equal to or less than five minutes
for Numbers 8 and 23 overflows, and is equal to seven minutes for
Number 17 overflow.
A unit hydrograph for each overflow was derived from the overflow hydro-
graphs. These unit hydrographs were based on the hydrographs produced
by rainfalls less than or equal to the unit storm for the sewer dis-
trict. The values given in Figure 48 for the times between the start
of an overflow and its peak were used. Twenty minute lengths of rain-
fall were later found to be more convenient to work with than the unit
storm lengths of rainfall. Therefore, the unit hydrographs for 20
minutes of rainfall were summed to equal one hydrograph for each over-
flow. (See Figures 49, 50, and 51) These hydrographs have a volume of
1.00 inch of runoff and will be referred to as "20 minute unit hydro-
graphs" in future discussion.
Hydroqraph Peak and Volume
The two most important elements of a runoff hydrograph are its peak and
volume. The two cannot be separated. Since the shape of the hydrograph
has already been determined, knowing either the peak or the volume of
the hydrograph will completely define it for any rainfall.
77
-------
The two most commonly used methods for determining the peak or the volume
are: (I) the rational formula and (2) the hydrograph method. The appli-
cation of both of these methods to the three sewer districts in Bucyrus
was studied and the results compared to the measured data. Finally a
modification of the hydrograph method was studied and adopted for use in
designing storm water facilities for Bucyrus.
I. Rational Formula
The rational formula is the most commonly used method for designing storm
water facilities. The formula is easy to understand, simple to use, and
coefficients and variables are available from standard references for
either preliminary or detailed design. The most frequent objection to
the rational formula is that only a peak rate of flow can be computed.5
This objection would be overcome if used with the derived unit hydro-
graphs.
In its most commonly used form, the rational formula appears as Q = CIA,
"Where Q is the rate of runoff at a specific point in time, A is the
drainage area tributary to the specific point at the specific time, I is
the average intensity of rainfall over the tributary drainage area for
the specified time, and C is the coefficient of runoff or ratio of rate
of runoff to rate of rainfall applicable to the particular situation."4
The specified time referred to in the definition of I equals the time of
concentration. In other words, the rational formula states that the
rate of runoff is equal to the rate of supply if the length of rainfall
is greater than the time of concentration.
Since this study involves only the wastewater discharged to the river,
only the runoff at the overflow point for each sewer district was deter-
mined. The values for sewered areas given in Table 7 were used for A.
The values of I used were obtained from the intensity duration curves
for Bucyrus, Figure 15, using the times of concentration obtained from
Table 8. Values for C were still required.
The preferred method of obtaining a C value for the three sewer districts
is to use measured rainfall and runoff data. However, this method was
found to be impossible without studying the sewer systems in great detail.
The times of concentration given in Table 8 are 54 minutes, 64 minutes,
and 60 minutes for Numbers 8, 17, and 23 sewer districts, respectively.
These times of concentration exceed the length of any continuous rain-
fall measured during the past year for the three overflows with an
intensity greater than 0.20 inch per hour. Therefore, the only way to
obtain a C value by this method would be to determine by a complete
hydraulic analysis how much of the sewer district area was contributing
at the time the rainfall stopped. An analysis of this type exceeds the
realm of this study. Therefore, values of C for various types of land
cover have been assumed, based on published data, and matched to the
types of land cover for the three sewer districts.2 The C values used
are presented in Tables 21 and 22.
78
-------
TABLE 21
RUNOFF COEFFICIENTS
Impervious C_
Bui I dings (roofs 0.85
Asphalt and Concrete (drives and walks) 0.80
Streets (asphalt and brick) 0.80
Water 1.00
Pervious
Lawns (heavy soil - 2%) 0.15
Weeds (unimproved areas) 0.20
Packed earth (playgrounds) 0.30
Gravel (railroad yard areas) 0.30
Corn Fields 0.20
Using the values for sewered area, given in Table 7, a weighted value
of C for each of the three sewer districts was obtained. (See Table 22)
TABLE 22
WEIGHTED RUNOFF COEFFICIENTS
Sewer District Weighted C
8 0.39
17 0.41
23 0.35
These values compare well with other values of C given for residential
type areas. For example, Linsey gives a C value for flat residential
area, 30 percent impervious, of 0.40.5 This compares to 0.39 and 0.41
for Numbers 8 and 17 sewer districts, each with 33.7 percent impervious
area. Since Number 23 sewer district is only 26.1 percent impervious,
it has a lower C value.
79
-------
The runoff to be expected from a one year frequency storm was computed
using the weighted values of C. (See Table 23) The runoffs from the
total area and just the impervious areas are given. These values are
compared to the measured runoff from the May 17 and June 13 storms.
From Table 23 two things become evident. First, it is possible to get
a higher peak from the impervious areas alone than from the total areas.
The intensity duration curves for high intensity storms drop so rapidly
during the first 20 to 30 minutes that the peak overflow rate from a
smaller area with a shorter time of concentration can be greater than
the peak rate for the entire area.
Second, the computed peak flows for both the impervious areas and the
total areas are more than double the flows measured on May 17 and
June 13, and far exceed the maximum capacity of the sewer system. Since
the peak overflow rates for Numbers 17 and 23 sewer districts were close
to the maximum sewer capacities on May 17 and June 13, a comparison of
these values to the computed values cannot be made. However, the peak
overflow rates for Number 8 overflow on these two dates are 20 cfs less
than the maximum sewer capacity. Therefore, the conclusions are the C
value for Number 8 sewer district is less than one-half the standard
value for this type of area.
A check was made on the maximum sewer capacities of all the sewer dis-
tricts using a two-year storm. (See Table 24) The classifications
given in Table 7 were used to estimate a C value for each of the other
sewer districts based on the weighted C values obtained for Numbers 8,
17, and 23 sewer districts. Nineteen of the twenty-four trunk sewers
have capacities less than the peak runoff from a two-year storm.
The conclusions from the above analysis are that the rational formula is
not an acceptable method of computing the runoff from the sewer districts
in Bucyrus. First, the peak flows for a two-year storm exceed the maxi-
mum sewer capacities of many of the districts. Second, the peak flows
computed with the standard runoff coefficients that do not exceed the
maximum sewer capacities are much greater than the measured values.
Finally, with the rational formula there is no simplified way of deter-
mining how much of the area is contributing for rainfall durations less
than the times of concentration.
80
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TABLE 23
COMPARISON OF THE RATIONAL FORMULA
TO MEASURED DATA
No. 8 Sewer District
Rational Formula
Entire Area
Impervious Only
May 17, 1969
June 13, 1969
Max. Sewer Capacity*
No. 17 Sewer District
Rational Formula
Entire Area
Impervious Only
May 17, 1969
June 13, 1969
Max. Sewer Capacity*
No. 23 Sewer District
Rational Formula
Entire Area
Impervious Only
May 17, 1969
June 13, 1969
Max. Sewer Capacity
Time of
A Concent.
Acres min.
178.9 54
60.4 30
452.5 64
151.5 38
377.8 60
98.5 43
1 C Q
1 Yr. Storm
in/hr. cfs
1.08 0.39 75
1.57 0.82 78
32
30
50
0.95 0.41 176
1.36 0.82 169
67
63
75
1.00 0.35 132
1.26 0.82 102
69
61
65
* With Control Structure
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TABLE 24
OVERFLOW PEAKS USING RATIONAL FORMULA
2 Year Storm for Bucyrus
Sewer
District No.
1
2
3
4
5
6
7
8
9
10
1 1
12
13
14
15
16
17
18
19
20
21
22
23
24
A
Acres
73.3
2.5
19.4
113
32.1
21.0
3.2
178.9
3.0
7.1
6.2
41 .9
8.8
70.2
10.8
5.0
452.5
5.7
24.5
12.1
7.8
72.4
377.8
20.7
Time of
Concent.
min.
34
21
27
35
29
27
21
54
22
24
14
26
23
36
25
24
64
24
38
26
27
32
60
30
1
in/hr.
1.5
2.4
2.1
1.8
2.0
2.1
2.4
1.3
2.3
2.2
2.9
2.1
2.2
1.7
2.1
2.2
1.2
2.2
1.7
2.1
2.0
1.9
1.2
2.0
C
.25
.40
.40
.40
.60
.40
.60
.39
.40
.60
.80
.40
.50
.40
.50
.60
.41
.35
.40
.35
.35
.35
.35
.25
Q
cfs
27.5
2.4
16.3
81.3
38.5
17.6
4.6
90.6
2.8
9.4
14.4
35.2
9.7
47.8
11.3
6.6
222.5
4.4
16.7
8.9
5.5
4.8
158.7
10.4
82
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2. Hydrograph Method
The most widely used hydrograph methods are the Los Angeles Method^ ancl
the Chicago Method.7 Both of these methods are for the design of an
entire sewer system, catch basin by catch basin. The hydrographs for
each sewer lateral are summed and the composit hydrograph peak used for
design.
Since unit hydrographs have been derived for the overflows of the three
districts, a composite hydrograph was not needed. However, the surface
infiltration curves used to determine the volume of runoff from each
small drainage area can be applied to the entire drainage area provided
the area of each type of land cover is known.
The results by using the standard infiltration-capacity curve from the
ASCE design manual for a pervious surface in a standard residential
area was compared with observed data. This curve was plotted in terms
of accumulative mass infiltration capacity and checked against the rain-
fall and runoff data for Number 17 overflow on May 17 and June 13. Mass
diagrams of the rainfall on these two dates were drawn to the same scale
as the filtration curve. (See Table 25 for the comparison of the derived
overflow vo-ume versus measured overflow volume) The three rainfalls of
May 17 were considered as new rainfalls and separate mass curves drawn
for each one.
An analysis of the results in Table 25 indicates that there is a great
?eal of variation in the overflow volumes for the two storms. On
May 17, 30 percent to 60 percent of the rainfall on the impervious areas
ran off. However, the same infiltration curve applied to the rainfall
of June 13 yielded a volume of runoff from the pervious area greater
than the total runoff measured. Both storms were approximately one-year
storms. Comparisons were made for the other two districts and similar
inconsistencies were noted. Therefore, on the basis of this analysis,
the standard residential infiltration curve was not applicable.
3. Modified Hydrograph Method
A relationship between peak overflow rate and rainfall was derived from
the measured data. Three graphs were plotted for each overflow. These
were the maximum 10, 20, and 30 minute rainfall intensities versus the
peak overflow rates which they produced. The intensities of rainfalls
with durations less than the stated times were averaged over the time
period. Compound rainfalls and overflow hydrographs were separated.
A straight line relationship was found between maximum rainfall intensity
for a given duration and peak overflow rate. The least amount of devia-
tion was produced by a rainfall of 20 minute duration. (See Figures 52,
53, and 54) All three graphs distinguish between antecedent rainfall and
no antecedent rainfall conditions. This distinction disappears, however,
at higher intensity rainfalls for Numbers 8 and 17 sewer districts. All
83
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TABLE 25
OVERFLOW VOLUME - NO. 17 OVERFLOW
Using Standard Infiltration Curve
May 17, 1969
1.
2.
•*
Rainfa
Runoff
Inches
Runn-f -f
II, total
, Pervious
depth on
PA r vinu«;
- Inches
Area* -
pervious area
Area - £
1
0.27
0
0
2
0.44
0.14
32
3
1 .16
0.28
24
June 13
1969
1 .20
0.38
32
4. Runoff, Pervious Area -
Inches depth on drainage district 0 0.09 0.19 0.25
5. Overflow, Measured by weir -
Inches depth on drainage district 0.05 0.14 0.40 0.10
6. Runoff, Impervious Area -
Inches depth on drainage district 0.05 0.05 0.21 0
7. Runoff, Impervious Area -
Inches depth on impervious area 0.15 0.15 U.to u
8. Runoff, Impervious Area - %
56 34 54 0
* Standard Infiltration - Capacity Curves for Pervious Surface,
Residential areas (standard curve), Design and Construction of
Sanitary and Storm Sewers, ASCE MOEP No. 37.
84
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three graphs start at or near the origin for antecedent rainfall condi-
tions. For no antecedent rainfall conditions, overflow starts when the
20 minute rainfall exceeds the values given in Table 19. Following are
the mathematical formulas for the relationships shown on the three
graphs:
Maximum Twenty Minute Rainfall versus Peak Overflow Rate
Q = Peak flow, cfs
I = Maximum average 20 minute rainfall intensity, In./Hr.
No. 8 Overflow
I) No Antecedent Rainfall
1^ 0.39, Q = 18 (I - 0.12)
I> 0.39, Same as with Antecedent Rainfall
2) Rainfall within 24 hours
J£ 0.75, Q = \2(l)
I> 0.75, Q = 20 (I - 0.30)
No. 17 Overflow
I) No Antecedent Rainfall
I£ 0.39, Q = I 10 (I - 0.18)
I> 0.39, Same as with Antecedent Rainfall
2) Rainfall within 24 hours
Q = 60 (I - 0.03)
No. 23 Overflow
I) No Antecedent Rainfall
Q = 33 (I - 0.15)
2) Rainfall within 24 hours
Q = 40 (l)
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The maximum ten minute rainfall intensity cannot be used to describe a
20 minute duration rainfall hydrograph. If the unit hydrographs for an
overflow are graphically summed, the resulting hydrograph is the S
curve.5 Assume each unit hydrograph is for a five minute duration unit
storm. Since the rainfall intensity remains constant, the four hydro-
graphs for the 20 minute duration rainfall will have the same maximum
ten minute rainfall intensity as the ten minute duration rainfall with
only two hydrographs. The peaks for the two rainfalls are obviously
di fferent.
The maximum 20 minute intensity can be used to describe a ten minute
rainfall, however. Assuming the two hydrographs from the ten minute
rainfall have the same volume as for the four hydrographs from the 20
minute rainfall, the composite peak for the four hydrographs would be
only a little less than the composite peak for the two hydrographs.
A 30 minute rainfall duration produces more deviation than a 20 minute
rainfall duration because of the nature of the rainfalls measured. Only
one high intensity rainfall lasted longer than 20 minutes and still pro-
duced only one hydrograph peak. The remaining high intensity rainfalls
lasting longer than 20 minutes produced multiple peaks because of the
irregularity of their intensities.
The peak overflow rates shown in Figures Numbers 52, 53, and 54 are
limited by the maximum sewer capacities. With the control structures,
these are equal to 50, 70, and 65 cfs for Numbers 8, 17, and 23 overflows,
respectively. The data plotted for Number 17 overflow in Figure 53
clearly shows the limiting effect of the sewer capacities.
The volumes of overflow were related to rainfall by means of the unit
hydrograph. Since the peaks of the unit hydrographs are directly pro-
portional to their volume, there was also a straight line relationship
between the rainfall and overflow volumes. These relationships were
expressed as the following mathematical formulas:
Twenty M_j_nute Rainfall versus Overflow Volume
0 = Overflow Volume, Depth on sewer district in inches
P = RainfalI, inches
No. 8 Overflow
I) No Antecedent Rainfall
P£: 0.13, 0 = 0.18 (P - 0.04)
P > 0.13, same as with Antecedent Rainfall
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2) Rainfall within 24 hours
P£ 0.25, 0 = 0.12 P
P > 0.25, 0 = 0.20 (P - 0.10)
No. 17 Ove r fIow
I) No Antecedent Rainfall
P^ 0.13, 0 = 0.51 (P - 0.06)
P > 0.13, same as with Antecedent Rainfall
2) Rainfall within 24 hours
0 = 0.28 (P - 0.01)
No. 23 Overflow
I) No Antecedent Rainfall
0 = 0.20 (P - 0.05)
2) Rainfall within 24 hours
0 = 0.25 P
These formulas were used to determine the overflow hydrographs for the
one-year, two-year, and five-year frequency twenty-minute storms. (See
Figures 55, 56, and 57)
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SECTION XVI
RIVER RESPONSE TO RAINFALL
An analysis was made of the discharge records for the Sandusky River
above and below Bucyrus to determine the relationship between rainfall
and runoff for Bucyrus and the upstream drainage basin. The records
used for this analysis covered the time period from February 4, 1969,
to September 24, 1969. The rainfalls were segregated into 24 hour time
intervals. The average rainfall for the entire drainage basin was
obtained by averaging the rainfall from the three rain gages. All hydro-
graphs were separated from the base river flow.
All of the storms passing over Bucyrus move in an Easterly direction.
Since the upstream drainage basin is east of Bucyrus, the storms will
pass over Bucyrus before any rain falls in the upstream drainage basin.
This phenomena produces two distinct runoff hydrographs at the downstream
gage, first the urban runoff hydrograph, and then the upstream drainage
basin runoff hydrograph.
Urban Runoff Hydrograph
The urban runoff hydrograph includes the runoff from: the sewered area
in the combined sewer overflows; the non-sewered drainage areas between
the two stream gages which flows directly to the river; and the area
adjacent to the river for one or two miles above the upstream gage. The
percent of the urban hydrograph from combined sewer overflow varied con-
siderably but was generally about one-half the volume of the urban run-
off hydrograph. The volume of runoff from the area adjacent to the
river above the upstream gage also varies greatly. The peak flow rates
measured at the upstream gage varied from four cfs to 267 cfs for rain-
falls greater than 1,00 inch. This runoff peaks at the upstream gage
1.5 hours after the rainfall has stopped in Bucyrus and becomes part of
the total urban hydrograph.
Figure 63 is the distribution graph for the urban runoff from a unit
storm in Bucyrus. The significant runoff reaches the downstream gage
approximately one hour after the start of the rain. The river peaks two
hours later. In seven hours the river returns to its pre-storm flow.
The maximum hydrograph peak observed during the study period was 332 cfs
on July II. On this date, approximately one-half of this peak was from
the upstream drainage area.
Upstream Drainage Basin Runoff Hydrograph
Following the urban runoff hydrograph the river returns to its pre-storm
flow until the hydrograph from the upstream drainage basin arrives. The
time of arrival depends entirely on the velocity in the river. The lag
89
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time of the peak flow following the end of the rain varies from 40 hours
to 17 hours for river flows of four to 300 cfs at the upstream gage.
For flows greater than 500 cfs the lag time will be approximately 16
hours. The travel time between the upstream and downstream gages also
varies with the velocity. The peak will take an additional 6.5 hours to
travel to the downstream gage at 10 cfs, 1.5 hours at 500 cfs, and one
hour at 2000 cfs.
The hydrograph for the upstream drainage basin is a much flatter hydro-
graph than the urban runoff hydrograph. The minimum time between start
of hydrograph and peak is five hours. The peak of the hydrograph varies
with the season of the year and the length of time since the preceding
rai nfal I .
The relationship between rainfall and runoff for the study period of
February through May was entirely different from the relationship for
June through September. For February through May, there was a straight
line relation between rainfall and peak flow for rainfalls greater than
0.75 inch and peak flows greater than 500 cfs. During this period
normally any rainfall greater than 1.5 inches will produce a peak river
flow greater than 1500 cfs.
Most of the storms measured from June through September were short,
intense thunderstorms. The rainfall intensities for these types of
storms varied greatly between rain gages. The peak flows for the up-
stream drainage basin hydrographs also varied greatly for amounts of
rainfall. For example, a 1.2 inch rainfall produced no peak flow on
June 13 and 500 cfs peak flow on July 20. The minimum peak and maximum
peak flows possible from a 1.5 inch rainfall are 25 cfs and 700 cfs,
respectively.
90
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StiCTION XVI I
EVALUATION AND CORRELATION OF WASTELOAD DATA
Waste Loads versus Overt lows
The strength and amount of waste load discharged from combined sewer
overflows depends on a number of factors, including duration and inten-
sity of rainfall, volume of runoff, number of days between overflow
events, efficiency of street cleaning operation, and design character-
istics of the sewer system. This portion of the report will evaluate
the effect of rainfall, runoff and number of days between overflows on
the strength and amount of waste load discharged to the river.
The relationships between BOD, total solids, suspended solids, chlorides,
phosphates, the nitrogen series, and length of overflow for the three
selected sewer districts have been graphed and are shown in Figures 23
throuqh 43. The E»D and suspended solids concentration generally reach
a peak about 20 minutes after start of overflow and then tend to drop
at a fairly rapid rate for two to three hours and then approach a lower
limit. Samples taken approximately 12 hours after start of overflow
indicate that the BOD and suspended solids concentration will decrease
to about 15 mg/l and 50 mg/I, respectively.
Generally, the longer the period of time between overflows the larger the
waste load for a particular overflow volume. The influence of this
parameter is shown by comparing the BOD waste load of the June 13 and
August 9 overflow events. Table 16 shows that the June 13 overflow
volume was 480,000 cubic feet and the BOD load was 1063 pounds, while
the Auaust 9 event overflow volume was 398,000 cubic feet with a BOD
load of 2310 pounds. The rainfall on June 13 was 1.20 inches with a
peak intensity of 2.77 inches per hour while the rainfall on August 9
was only 0.56 inch with a peak intensity of 2.28 inches per hour. There
was a period of five days of dry weather preceding the June 13 overflow
event and twelve days of dry weather preceding August 9.
Waste Loads versus Rainfall
Figure 58 and Figure 59 show the apparent relationship between the BOD
and suspended solids discharged fron the three combined sewer districts
sampled and total rainfall per storm. These figures have been plotted
using the data from the five complete overflow events sampled during
the study period. These relationships have been developed from five
overflow occurrences and do not consider many other factors that may
influence the waste loads from combined sewer overflows. However, the
graphs definitely indicate a trend.
In addition to the relationship between rainfall and BOD, the number of
days of dry weather preceding overflow has been incorporated into the
91
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rainfall-BOD and rainfall-suspended solids relationships and Is shown on
Figures 58 and 59. The number of days between rainfall appears to have
a greater influence on the BOD than on the suspended solids.
Effect of Overflows on River Water Quality
One of the major objectives of this study is to determine what effect
the combined sewer overflows have upon the water quality of the Sandusky
River. Samples were taken at selected locations upstream, intown, and
downstream during dry and wet weather along with visual observations of
the condition of the river before, during and after overflows. Also, an
aquatic biology survey of the river, which is presented elsewhere in the
report, was made to determine the overflow effects on life forms in the
river.
Table 17 very clearly shows the pollutional effects of the combined
sewer overflows on the quality of the Sandusky River. The BOD concen-
tration at the first bridge downstream (3/4 mile below treatment plant)
is more than doubled by the overflows and the suspended solids have
quadrupled while the total coliform count has increased ten-fold. The
August 9 overflow event increased the BOD concentration at the first
bridge downstream, from II mg/l with a river flow of nine cfs to 51 mg/l
with a flow of 130 cfs. This is a BOD rate increase from 530 pounds per
day before overflow, which is equal to the effluent load from the treat-
ment plant, to 35,500 pounds per day during overflow.
Figure 46 presents a typical dissolved oxygen profile of the river during
times of low flow (10 cfs or less). Normally, due to the wastewater
treatment plant's effluent, the dissolved oxygen of the river below the
wastewater treatment plant is extremely low for about five to seven
miles before the river starts to recover.
Figure 47 compares dissolved oxygen profiles of the river during wet and
dry weather. The graph shows that the combined sewer overflows tend to
lengthen time of recovery for the river.
The assimilation capacity of a river is defined in this report as the BOD
waste load that the river is capable of treating by self-purification
processes and not depress the dissolved oxygen concentration of the river
below 4 mg/l. Laboratory analyses and waste load calculations of
selected river samples have shown that the assimilation capacity of the
Sandusky River at Bucyrus is approximately 25 pounds of BOD per day per
cfs at low flow (less than 10 cfs). This is a population equivalent of
150 per cfs. The calculations and analyses also indicate that the
assimilation capacity of the river increases with flow and temperature.
The quantity of nitrate nitrogen discharged into the river from combined
sewer overflows and the wastewater treatment plant effluent is negligible
compared to the amount of nitrate nitrogen contributed to the river from
rural runoff. The annual nitrate nitrogen load discharged to the river
92
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by overflows is about 12,200 pounds as N03 based on an annual overflow
volume of approximately 365 million gallons and an average NO, concen-
tration of 4.0 mg/l. The wastewater treatment plant contributes about
3,500 pounds per year based on a flow of 2.2 MGD and NO^ of 0.5 mg/l.
This gives a total of 15,700 pounds of N03 per year. In contrast, on
April 19, 1969, approximately 136,000 pounds of nitrate nitrogen (N03>
passed the upstream gage and on May 19, 1969, approximately 192,000
pounds of NO, passed the upstream gage. These large amounts occurred
during times of high river flow in the spring and early summer.
The amount of total phosphates discharged into the river by combined
sewer overflows and the wastewater treatment plant effluent is signific-
ant when compared to the total phosphates contributed by rural runoff.
The wastewater treatment plant effluent discharges into the river about
160,000 pounds of PO. per year while the combined sewer overflows dis-
charge about 30,000 pounds of P04 per year. The phosphates from the
overflows are based on an annual overflow volume of 365 million gallons
and an average PO. concentration of 10.0 mg/l.
On April 19, 1969, approximately 5,600 pounds of P04 passed the upstream
gage and on May 19, 1969, about 34,600 pounds of P04 came off the up-
stream drainage area. Assuming an average PO^ concentration of 0.7 mg/l
and using the average river flow of 80 cfs there is about 110,000 pounds
of PO. passing the upstream gage per year.
Therefore, the wastewater treatment plant effluent discharges about 50
percent of the total phosphates in the river while the combined sewer
overflows contribute about 10 percent of the total phosphates.
93
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SECTION XVI I I
GENERAL DESIGN CONDITIONS
Certain basic design conditions must be established before any alternate
solutions can be evaluated for the combined sewer system. These condi-
tions include the stream water quality which must be protected; the
design storms that result in waste discharges from which the stream must
be protected; the design storms corresponding overflow volume, peak
rates of overflow and the average maximum waste loads.
The stream water quality for the Sandusky River, downstream from Bucyrus
was established by the Ohio Water Pollution Control Board as (I) Minimum
Conditions Applicable to All Waters At All Places and At All Times and
(2) Aquatic Life "A", which have the following criteria:
(I) MINIMUM CONDITIONS APPLICABLE TO
ALL WATERS AT ALL PLACES AND AT ALL TIMES
I. Free from substances attributable to municipal, industrial or other
discharge that will settle to form putrescent or otherwise objec-
tionable sludge deposits;
2. Free from floating debris, oil, scum and other floating materials
attributable to municipal, industrial or other discharges in amounts
sufficient to be unsightly or deleterious;
3. Free from materials attributable to municipal, industrial, or other
discharges producing color, odor or other conditions in such degree
as to create a nuisance;
4. Free from substances attributable to municipal, industrial or other
discharges in concentrations or combinations which are toxic or
harmful to human, animal or aquatic life.
(2) AQUATIC LIFE "A"
The following criteria are for evaluation of conditions for the main-
tenance of a well balanced warm-water fish population at any point in
the stream except for areas immediately adjacent to outfalls. In such
areas cognizance will be given to opportunities for the admixture of
effluents with stream water:
I. Dissolved oxygen: Not less than 5.0 mg/l during at least 16 hours
of any 24-hour period, nor less than 3.0 mg/l at any time;
2. pH: No values below 5.0 nor above 9.0 and daily average (or median)
values preferably between 6.5 and 8.5;
95
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3. Temperature: Uot to exceed 93 F. at any time during the months of
May through November, and not to exceed 73 F. at any time during
the months of December through April;
4. Toxic substances: Not to exceed one-tenth of the 48-hour median
tolerance limit, except that other limiting concentrations may be
used in specific cases when justified on the basis of available
evidence and approved by the appropriate regulatory agency.
Since the Sandusky River through Bucyrus is available for body contact
use and fishing, some consideration should be given to recreational uses
which require, according to the Ohio Water Pollution Control Board the
follow!ng:
WATERS FOR RECREATIONAL USES
The following criterion is for evaluation of conditions at any point in
waters designed to be used for recreational purposes, including such
water-contact activities as swimming and water skiing:
Bacteria: Coliform group not to exceed 1,000 per 100 ml as a
monthly average value (either MPN or MF count); nor exceed this
number in more than 20 percent of the samples examined during any
month; nor exceed 2,400 per 100 ml (MPN or MF count) on any day.
Design Storms
After consideration of the general conditions which prevail during
various rainfall patterns, two design storms were selected — a two-year,
one-hour storm for the peak overflow rate, a one-year, 24-hour storm for
the total volume of overflow. The one-hour storm is the spring, summer
and fall type of thunderstorm, with very high intensities and short
duration. The amount and intensity of rainfall during thunderstorms
varies greatly over the drainage basin. The one-year, 24-hour storm
resembles a more generalized rainfall. The intensities will not vary
greatly during the 24 hours and over the drainage basin. Both types of
storms are most likely to occur during the summer months of June, July,
August, and September. (See Table 26)
Protecting the river from the peak overflows of a two-year, one-hour
frequency rainfall is a logical choice since this rate of flow is the
maximum capacity of most of the trunk sewers of the combined sewer
system. Also very few thunderstorms will last longer than one hour and
any additional rainfall after one hour will not add significant peak
flow.
The probability of the two-year, one-hour storm occurring is the greatest
during the summer months when the flow in the river is the lowest. Dilu-
tion water is usually not available from the upstream drainage basin
during an overflow from this type of storm.
96
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The volume of overflow from the one-year, 24-hour frequency rainfall was
selected, in addition to the peak rate of overflow from the two-year,
one-hour storm, so that the river would be completely protected from
pollution due to combined sewer overflows for a return period of one
year.
Peak Rate of Overflow
The rainfall for a two-year, one-hour storm was read from the intensity
duration curves at twenty minute intervals. (See Figure 15) The
estimated total rainfall equals 1.23 inches. The three 20-minute rain-
falls were arranged to correspond to the storm pattern given In the ASCE
Sewer Design Manual,2 which the peak intensity occurs at three-eighths
of the total storm time. This was approximated by placing the second
highest intensity rainfall in the first twenty minutes of the storm,
with the highest intensity and lowest intensity intervals following.
The peak flows for Numbers 8, 17, and 23 sewer districts were computed,
using the relationships developed in the modified hydrograph method
section. A hydrograph for each overflow was derived for each of the
20-minute rainfalls. No antecedent rainfall conditions were assumed.
Each hydrograph was then lagged behind the start of its corresponding
rain by the amount given in Table 19. The sum of all three hydrographs
for each overflow equaled the hydrograph for the total storm. (See
Figures 60, 61, and 62)
A review of the composite hydrographs in Figure 61 and 62 showed that
the peak overflow rates for Numbers 17 and 23 overflows were limited by
the maximum capacities of their sewer systems. Therefore revised hydro-
graphs were drawn for these two overflows. These hydrographs have the
same runoff volume as the original hydrographs. The peak of the hydro-
graph was assumed delayed until the sewer had sufficient capacity. The
shape of the hydrograph was defined by assuming the hydrograph had the
same recession curve as the original hydrograph, only delayed by the
volume of the peak.
Since Numbers 8, 17, and 23 sewer districts were the only districts for
which unit hydrographs had been determined, the following assumptions
were made for the remaining 21 districts:
I. All hydrographs have the basic shape of a triangle.
2. The hydrograph begins ten minutes after the start of the rainfall.
3. The peak occurs five minutes following the end of the significant
rainfall or 45 minutes after start of rainfall.
4. The hydrograph will end at a time equal to the time of concentra-
tion following the end of the rainfall.
97
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5. The total runoff volumes are equal to the following percentages of
rainfal I:
Semi -developed 2Q%
Suburban-Residential 25%
Residential 30?
Commercial
These assumptions are based on the characteristics of the hydrographs
for Numbers 8, 17, and 23 sewer districts. The runoff percentages are
based on the classification system given in Table 7.
The peak overflow rates and overflow volumes for a two-year, one-hour
storm were computed for the remaining 21 sewer districts using
the above assumptions. (See Table 27) The peak overflow rates of 13
out of the 24 sewer districts were limited by the maximum sewer capac-
ities, and the peak rates of two additional districts were equal to the
maximum sewer capacities. The hydrographs for these districts were
adjusted by assuming the hydrographs had the same recession curves as
the original hydrographs, only delayed by the volumes of the peaks.
Volume of Overflow
For the one-year, 24-hour storm, it was not necessary to plot a hydro-
graph for each twenty minutes of rainfall for Numbers 8, 17, and 23
sewer districts. Instead the following runoff percentages were assigned
the three districts:
Number 8 Sewer District 20%
Number 17 Sewer District 28%
Number 23 Sewer District 25$
These runoff percentages are based on the runoff formulas developed by
the "Modified Hydrograph Method".
The runoff percentages given in assumption five under Peak Rate of Over-
flows were used to compute the runoff from the one-year, 24-hour storm
for the remaining districts. The volumes of runoff obtained for these
districts and Numbers 8, 17, and 23 sewer districts are given in Table
28. A one-year, 24-hour storm has a total rainfall depth of 2.3 inches.
Antecedent rainfall conditions were assumed.
Design Waste Loads
The waste loads discharged from the two design storms, previously pre-
sented, have been calculated for two different conditions, the average
and the maximum.
98
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TABLE 26
PROBABILITY OF THE DESIGN STORMS
2 Year, I Hour Storm
I Year, 24 Hour Storm
Month
January
February
March
Apr! 1
May
June
July
August
September
October
November
December
*Reference:
Probability Order
of Occurring of
%* Magnitude
0
0.5
1
1
2
9
15
13
7
1
0.5
0
50
Rainfal 1
1 1
9
8
6
5
3
1
2
4
7
10
12
Frequency Atlas of
Probabi 1 i ty
of Occurring
%*
5
4
1 1
8
8
1 1
15
12
8
7
6
5
100
the United States,
Order
of
Magnitude
1 1
12
4
7
6
3
1
2
5
8
9
10
Technical Paper No. 40, U. S. Department of
Agriculture, pages 59-61.
99
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TABLE 27
OVERFLOW PEAKS AND VOLUMES
FOR THE
2 YEAR, I HOUR STORM
Overflow Volume
Sewer
District No.
I
2
3
4
5
6
7
8
9
10
II
12
13
14
15
16
17
18
19
20
21
22
23
24
TOTAL
%
Rainfal Is
20
30
30
30
40
30
40
*
30
40
50
30
35
30
35
40
#
25
30
25
25
25
*
20
Depth
Inches
0.25
0.37
0.37
0.37
0.48
0.37
0.48
0.20
0.37
0.48
0.62
0.37
0.43
0.37
0.43
0.48
0.33
0.31
0.37
0.31
0.31
0.31
0.29
0.25
1000
c.f.
65
3
26
151
57
28
6
131
4
13
14
56
14
94
17
9
544
6
33
14
9
81
397
18
Overflow
Peak
cfs
23+
I
5+
42+
21
4+
1 +
49
2
5
5
7+
3+
29+
6
3+
140+
2
6+
5
3
12+
70+
7
1,790
= 13.4 Ml 11 ion Gal Ions
* Overflow volume computed using formulas found on page 86.
+ Peak adjusted to Maximum Sewer Capacity
100
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Sewer
District No.
I
2
3
4
5
6
7
8
9
10
I I
12
13
14
15
16
17
18
19
20
21
22
23
24
TOTAL
TABLE 28
OVERFLOW VOLUMES
FOR THE
YEAR, 24 HOUR STORM
41
10.8
5.0
452.5
5
24
12
.7
.5
.1
.8
7
72.4
377.8
20.7
Overflow Volume
i
Rainfal Is
20
30
30
30
40
30
40
20
30
40
50
30
35
30
35
40
28
25
30
25
25
25
25
20
Depth
Inches
0.46
0.69
0.69
0.69
0.92
0.69
0.92
0.46
0.69
0.92
1.15
0.69
0.80
0.69
0.80
0.92
0.64
0.58
0.69
0.58
0.58
0.58
0.58
0.46
1000
c.f .
122
6
49
282
107
53
II
299
8
24
26
105
26
176
31
17
1,050
12
61
25
16
152
794
35
3,487
= 26 MI I lion Gal Ions
101
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The average waste loads for the design storms have been calculated using
the average BOD and suspended solids concentrations of all of the over-
flow samples analyzed and as summarized in Table 15. The average BOD is
125 mg/l and the average suspended solids is 480 mg/I. These concentra-
tions apply to the first flush out which occurs in approximately two to
three hours after start of overflow. BOD and suspended solids concen-
trations of 20 mg/l and 150 mg/l, respectively, are used as averages for
overflow volumes that occur after three hours duration.
The average BOD and suspended solids waste loads for the two-year, one-
hour design storm, which has an overflow volume of 13.4 million gallons
from all 24 sewer districts, are 14,000 pounds and 53,500 pounds,
respectively. For the one-year, 24-hour design storm, which has an
overflow volume of 26 million gallons from all 24 sewer districts, the
BOD load is 14,000 pounds and the suspended solids load is 62,500 pounds.
The maximum waste loads that could be expected from the two design storms
have been determined from envelope curves that were developed from the
results of the BOD and suspended solids data. These envelope curves,
shown on Figures 23 through 28, indicate the maximum BOD and suspended
solids concentrations versus time after start of overflow that could be
expected. The amount of BOD and suspended solids discharged from each
of the three selected sewer districts is determined by superimposing the
developed envelope curves over the design storm hydrographs and matching
flows with concentrations.
The computed maximum waste loads for the two-year, one-hour design storm
are as follows:
Pounds of
Sewer District Pounds of BOD Suspended Sol ids
No. 8 1,500 10,600
No. 17 6,200 30,000
No. 23 3,700 17,500
The above waste loads give an average BOD of 1,100 pounds per 100 acres
and suspended solids of 5,800 pounds per 100 acres. Expanding this to
include the entire sewered area of Bucyrus gives a design BOD waste load
of 18,000 pounds and a suspended solids load of 90,000 pounds.
The maximum waste loads for the one-year, 24-hour design storm were com-
puted by essentially the same procedure. The maximum BOD expected is
17,100 pounds and the maximum suspended solids expected is 76,000 pounds.
Table 29 presents a summary of the average and maximum waste loads for
the design storms.
102
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TABLE 29
DESIGN STORMS AND WASTE LOADS
Overflow
Total Volume BOD Suspended Solids
Rainfall Million Ibs. Ibs.
Design Storms Inches Gal Ions Average Maximum Average Maximum
2-yr., I hr. 1.23 13.4 14,000 18,000 53,500 90,000
l-yr., 24 hr. 2.3 26 14,000 17,100 68,000 76,000
103
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SECTION XIX
ALTERNATE SOLUTIONS
This section of the report will present various methods of abatement
and/or control of the pollution from combined sewer overflows. The
degree of protection, advantages and disadvantages along with the
estimated costs are presented for each method.
A. Complete Separation of Sanitary Wastewater and Storm Water
Complete separation of sanitary wastewater and storm water has histor-
ically been prime solution for pollution due to combined sewer systems.
However, there are disadvantages as well as advantages of complete
separation as presented below.
(I) Advantages of Separate Sewer Systems
Separation of sanitary wastewater from storm water permits complete
treatment of all sanitary wastewater before being discharged into the
receiving stream. The wastewater treatment plant facilities are required
to process only the dry weather flow. Elimination of storm water from
the treatment plant will enable the plant to operate at a higher
efficiency.
Many of the bacteria and other organisms responsible for intestinal and
other diseases are found in sanitary wastewater. The separate sewer
system delivers the sanitary wastewater to the treatment plant where
these organisms can be controlled.
The separation of the sanitary wastewater from the storm water will elim-
inate basement flooding during times when the combined sewers are inade-
quate to carry the storm runoff.
(2) Disadvantages of Separate Sewer Systems
Many cities such as Washington, D.C., New York, Philadelphia, Detroit,
Milwaukee, Minneapolis and Chicago have found, through engineering studies,
that complete separation is usually not economically feasible. The cost
estimates for separation of the Bucyrus sewer system, presented in this
section of the report, show that the cost is indeed very high.
In addition to the high cost, there are other disadvantages of separation.
Sewer separation only partially reduces the pollutional effects from
combined sewer overflows. Recent studies, including this report, have
shown that storm water runoff from urban areas contains a significant
amount of contaminates harmful to stream water quality. The degree of
pollution of storm water varies from that of very dilute sewage to strong
sewage.
105
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There is also an extreme inconvenience factor to the populace involved
when converting to a separate system. Streets are torn up for years,
utility services are disrupted periodically, traffic rerouted, etc.
The complete separation of the individual house services, roof drainage
lines and basement drain tile is almost impossible.
(3) Cost of Sewer Separation
Separation of combined sewer systems can be accomplished in two ways.
One, the existing combined sewer system can be used as a storm sewer and
a new sanitary sewer system constructed. Two, the existing sewer system
can be used as a sanitary sewer and a new storm sewer system constructed.
Both of these systems have been investigated and cost estimates prepared.
Constructing a new sanitary system involves paralleling the existing
sewer system with sewer pipe sized for sanitary wastewater only. The new
sewer would be a few feet deeper than the existing sewer so that the
house laterals could be connected to the new pipe. A cross section of
the system is shown in Figure 64. This system would include about
208,000 feet of eight inch and ten inch pipe and about 14,000 feet of
trunk sewer. Also, about 3,700 house laterals would have to be dis-
connected from the existing sewer system and re la id to discharge into
the new sanitary sewer. The existing interceptor sewer, paralleling the
Sandusky River, would be used to convey the sanitary wastewater to the
wastewater treatment plant. The existing connector pipes between the
interceptor and the existing sewer system would be plugged so that the
storm water runoff would go directly to the river at the various over-
flows.
The estimated cost for a new sanitary system is $9,300,000.00.
Since the existing combined sewer system is designed to handle a one-in-
two year storm, the construction of a new storm sewer system would con-
sist of paralleling the existing system with approximately the same size
pipe as the existing pipe. The new pipe would be at a more shallow
depth since the existing sewer was constructed deep enough to catch
sanitary wastewater. All of the existing storm inlets would be discon-
nected from the existing sewer and connected to the new storm sewer.
Also, on some of the larger lines there will be house services that
would be cut and these would have to be re I a id to the existing sewer.
A cross section of this method is shown in Figure 64.
The trunk lines of the new storm water system would discharge directly
into the river. The sanitary wastewater would be carried by the exist-
ing sewer system and interceptor to the treatment plant.
The estimated cost for the new storm water system is $8,800,000.00.
106
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B. Interceptor Sewer and Lagoon System
This method of abating pollution from combined sewer overflows proposes
construction of an interceptor sewer to collect the large overflow
volumes, and an aerated lagoon system to treat the waste loads from the
overflows. A pump station is required to pump the overflows to the
lagoon system. (See Figures 65 and 66)
(I) Gravity Interceptor Sewer
The proposed gravity interceptor sewer would parallel the existing inter-
ceptor along the Sandusky River and would terminate near the present
junction manhole with the existing northwest trunk sewer.
The primary concern in the design of the interceptor was determining the
peak capacity the pipe must handle at every point in the system. This
required routing each of the design storms overflow hydrographs down the
interceptor and determining their time base relationship to each other.
A graphical addition of the hydrographs was used to determine which
combination gave the highest peak value at each section of the inter-
ceptor. Each section of pipe was designed for the maximum peak flow.
The following pipe sizes and peak flows were obtained:
Pipe Sizes Peak Flow
Location inches cfs
Below #1 Overflow 36 23
Below #8 Overflow 72 150
Below #17 Overflow 108 348
Below #23 Overflow 120 435
From this analysis it was found that there were 39 minutes of travel
time between Numbers I and 24 overflows. Due to the longer travel times
in Numbers 17 and 23 trunk sewers, which delays the peaks, all three
overflow peaks coincide. Number 8 overflow takes eleven minutes to
travel to Number 17 overflow, and an additional nine minutes to travel
to Number 23 overflow. The peak rate of flow in the interceptor below
Number 23 overflow was equal to 435 cfs, of which 60 percent was from
the three major overflows.
(2) Interceptor Sewer Using Holding Tanks
This is a modification of the proposed gravity interceptor presented
above in item (I) in which the size of the interceptor is reduced by
using holding tanks located at Numbers 8, 17, and 23 overflows. These
tanks were designed to intercept the top one-half of the peak flows and
release them at an even rate. The volumes of the three tanks were com-
107
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puted by determining the volumes in the top one-half of the hydrographs
for the overflows below the preceding tank, and are equal to I.I, 1.9,
and 1.4 million gallons for Numbers 8, 17, and 23 overflows, respec-
tively.
Completely enclosed, concrete tanks were used for the cost estimate.
The tanks are fifteen feet deep, of which the top ten feet is a surge
tank, operating by gravity, and the bottom five feet is pumped.
The interceptor for this method was designed by the same methods used for
the gravity interceptor system. The following pipe sizes and flows were
obta i ned:
Pipe Sizes Peak Flow
Location i nches cfs
Below #1 Overflow 36 23
Below #8 Overflow 60 76
Below #17 Overflow 84 186
Below #23 Overflow 96 235
(3) Pump Station
A 215 MGD (333 cfs) pump station with a 1.0 million gallon wet well is
proposed. The storage volume of the proposed gravity interceptor sewer
is also required during the design storm peak flow of 435 cfs.
The capacity of the pump station for the interceptor sewer using holding
tanks would be 150 MGD with a 0.5 million gallon wet well.
(4) Aerated Lagoon
A system of aerated and non-aerated lagoons is proposed as a method of
treatment for the combined sewer overflow wastewaters. The proposed
facilities could also be utilized as tertiary treatment for the effluent
from the existing city activated sludge treatment plant. The lagoon
system would consist of structures of earthen embankments to form a
retention basin with several sections, as shown in Figures 65 and 66.
This facility would be similar in construction to existing reservoirs
which are used throughout northwest Ohio to store water for municipal
water supply. However, using this type of facility for wastewater
retention and treatment would require consideration of need for changing
water levels, installation of mechanical aerators and removal of accumu-
lated solids. The design requirements to prevent pollution of the stream
are discussed in preceding sections of the report.
108
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The design of the system will provide for biological oxidation of the
combined sewer overflows and would provide for continued biological
oxidation of the effluent from the sewage treatment plant. Three main
design parameters are of importance. These are: detention time, the
biological oxidation rate (designated as the "k" rate of the wastewaters
being treated) and, the air supply. However, the "k" rate essentially
establishes the requirements of both the detention time and the air
supply.
The rate of reaction constant of the degradation of organic matter,
commonly called the "k" rate, varies with the type of organic matter and
the state of oxidation which exists in the wastewater, at the time treat-
ment is begun. The "k" rate for the raw wastewater is greatest and will
decrease with advance stages of treatment. The "k" rate for normal
domestic wastes, as received in a wastewater treatment plant, is usually
about O.I. However, it may vary from half this value to several times
this value. The "k" rate found by Havens & Emerson of combined sewer
overflows was approximately O.I. The "k" rate for activated sludge
effluents, as found by Havens and Emerson, was 0.03l.y In a study of
the effluents from extended aeration plants bv the Ohio Department of
Health, the "k" rates were found to be O.OI3.10 In the Ohio Health
Department study, the flows were found to be about 25 percent of design,
so the detention times were on the order of four days.
The "k" rate also affects the quantity of wastewater that may be dis-
charged into a given stream. A wastewater with a high "k" rate will have
a greater effect on a stream than a wastewater with a lower 'k rate.
Just as a rapid stream will assimilate more wastewater than a slow stream
(with ponding), a given stream will assimilate a higher ultimate BOD load
as the "k" rate becomes less. Assimilation of wastewater of BOD load is
used here to mean that the dissolved oxygen will not be depressed below
a desi red level.
The determination of the possible variations of the "k" rate of combined
sewer overflows or treated overflows is beyond the scope of this study.
Also the variation of "k" rate in partially treated overflow wastewaters
or the possible increase in assimilation capacity of a given stream as
the "k" rate decreases with increased degrees of treatment is beyond the
scope of this study.
From data obtained during this study the range of permissible BOD loading
has been determined. The dissolved oxygen in the Sandusky River below
Bucyrus will be maintained at the desired level of four mg/l if the BOD
wastewater load does not exceed 25 pounds per day per cfs of stream flow.
This Is equivalent to the waste load of a population of 150 persons.
The rainfall-runoff pattern results in an average of about 1.0 MGD of
wastewater, with an average BOD of 125 mg/l and a maximum expected BOD
of 170 mg/l. The BOD load will be treated or controlled by two methods.
One is by settling and biological oxidation. Part of the BOD wi I I be
109
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removed by settling and, In this design, has been assumed to be 50 per-
cent. Biological oxidation of the BOD will follow under aerobic condi-
tions using mechanical aerators.
A "k" rate of 0.10 has been assumed for the first stage treatment or
first five days of detention and a "k" rate of 0.05 for the remaining
15 days of detention. The percent of BOD remaining after a given number
of days will be according to the equation: % = IOO-(l-IO~kt) |QO (when
k = O.I or 0.05 and t = number of days). The degree of treatment of the
wastewater from combined sewer overflows in the lagoon system is esti-
mated to exceed 95 percent after 20 days.
A second method of controlling BOD will be to discharge partially treated
wastewater to the stream. During some periods of rainfall when enough
rainfall has occurred to fill the lagoon, the stream flow will also have
increased. When prolonged rainfall occurs such as a one-year, 24-hour
storm of 2.3 inches, the quantity of urban runoff will be sufficient to
fill the proposed lagoon. However, as a result of such a rainfall the
stream flow will increase due to upstream drainage runoff. Without
tertiary treatment for the wastewater treatment effluent only when the
upstream runoff exceeds 20 cfs can an additional BOD load be discharged
at the rate of 25 pounds per day per cfs. The wastewater collected may
be discharged from the lagoon after partial treatment to increased
stream flow.
If tertiary treatment is provided for the wastewater treatment plant
effluent then either this effluent or the treated combined sewer over-
flow may be discharged to the stream at any flow.
The average runoff from the urban area of Bucyrus is about 1.0 MGD. The
lagoon size must allow for a variation in the peak distribution. A
lagoon designed for an average detention time of 20 days or 20 million
gallons and in addition a volume equal to the two-year, one-hour storm
will provide the required variation. This requires a volume of 33
million gallons. This will protect the stream from any overflows of any
storm less than the two-year, one-hour storm. This protection does not
require any dilution from the upstream drainage area. This volume is
about 27 percent greater than that required for the runoff from a one-
year, 24-hour storm.
A detailed analysis of the past ten-year precipitation records for the
four critical months — July, August, September, and October — show
that the average monthly rainfall plus the rainfall from the two-year,
one-hour storm is greater than the one year maximum monthly rainfall.
The records also show that a total monthly rainfall equal to the average
monthly rainfall plus the rainfall from a one-year, 24-hour storm would
occur only once in eight years. Therefore, a lagoon with a storage
volume of 33 million gallons will protect the stream from the two design
storms and from the one-year maximum monthly rainfall.
110
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The proposed lagoon will provide for greater protection of the stream if
the available dilution water from the upstream drainage area is used.
Storms of longer than 24-hour duration, or when rainfall is such that
the runoff from the urban area is greater than the average of one MGD
plus the two-year, one-hour storm, will produce upstream runoff. One
example of this was a storm on September 16-17, 1969, during which 2.3
inches fell in 19 hours. This resulted in a peak upstream flow of 100
cfs and a total stream volume of 65 million gallons over a three-day
period. In this case about 3,000 pounds of BOD could have been released
to the stream with no detrimental effects. With a BOD concentration of
approximately 75 mg/l or less (having received minimum one-day treat-
ment) at least five million gallons of partially treated overflow could
have been discharged with the higher stream flows. In actual operation,
the BOD may be as low as 50 mg/l which would allow discharging about 7.5
million gallons of partially treated wastes.
A detailed mass diagarm of the past ten years record of stream flow and
rainfall was plotted to determine the required lagoon size using the
assimilation capacity of the upstream dilution water in conjunction with
the treatment capability of the lagoon. The analysis indicated that a
22 million gallon lagoon will protect the stream from pollution by com-
bined sewer overflows if the treatment capacity of the upstream dilu-
tion water is used.
At the present time, there is very little factual information available
verifying assumed treatment efficiencies. Therefore, until it is
demonstrated that the smaller lagoon plus the upstream dilution water
will provide the necessary protection, the larger 33 million gallon
storage volume is recommended.
The lagoon may be located across the river from the existing wastewater
treatment plant. Four cells are proposed, each one 257 feet by 458 feet
from centerline of berm to centerline of berm, and cover an area of 15
acres. The total depth is 22 feet, of which the top four feet is free-
board and the bottom five feet is permanent pool. The earth embankment
has 2 1/2:1 side slope and a ten-feet wide berm. Ten and one-half feet
of the lagoon are below the original ground level.
The lagoon has a total storage capacity of 37.75 million gallons. The
permanent pool would allow approximately three days detention time to
provide tertiary treatment for the existing wastewater treatment plant
effluent. The lagoon dimensions were based on the minimum amount of
earth embankment per volume.
Accumulation of solids in the lagoon are estimated to be about two per-
cent per year. The removal of the accumulated solids will be required
every five to eight years to maintain an overall efficiency of system
of 90 percent.
-------
The cost estimates of the interceptor sewer and lagoon system are as
follows:
Gravity Interceptor, Pump Station and Aerated Lagoon
I. Gravity Interceptor $3,600,000
2. Pump Station 1,000,000
3. Aerated Lagoon 620,000
TOTAL COST $5,220,000
Holding Tanks on System, Gravity Interceptor, Pump Station, and
Aerated Lagoon
I. Holding Tanks $1,500,000
2. Gravity Interceptor 3,000,000
3. Pump Station 800,000
4. Aerated Lagoon 560,000
TOTAL COST $5,860,000
C. Stream Flow Augmentation
Flow augmentation, as used in this report, is a method of controlling
pollution from combined sewer overflows by providing sufficient dilution
water from storage impoundments to maintain a desired concentration of
dissolved oxygen downstream during overflows of wastewater from the com-
bined sewers. This method of control includes an upground storage reser-
voir, a low head dam to capture the flow of water in the river, a pump
station to deliver river water to the reservoir, a discharge channel to
release stored water to river, and a system of rain gages, river flow
indicators and controls to release the required amount of dilution water
into the river. When wastewater overflows occur, sufficient dilution
water must be released from the reservoir so that the combined assimila-
tion capacity of the dilution water and the river flow can maintain a
desired level of dissolved oxygen.
The volume of stored dilution water required at Bucyrus is 4,500 million
gallons. The reservoir would have an average depth of 30 feet, which
includes four feet of freeboard and a two-foot conservation pool. The
area required for the reservoir is about 480 acres. See Figure 67 for
schematic and typical section of flow augmentation facilities. The
volume of stored dilution water was based on an average combined sewer
overflow volume of 380 million gallons per year or approximately 1.0
million gallons per day. The combined sewer overflow has an average BOD
112
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concentration of 125 mg/l which amounts to approximately 1,000 pounds of
BOD per day. The water quality data on the Sandusky River, downstream
from Bucyrus, Indicates that the river's assimilation capacity at low
flows (less than 10 cfs) Is approximate 25 pounds of BOD per day per cfs.
Using this value for the river's waste load assimilation capacity, the
amount of dilution water required, in addition to the probable river
flow, was calculated. The probable river flows were taken from the flow
duration figures presented in Table 2.
The pump station capacity, based on the flow duration curves, is 45 MGD
or 70 cfs.
The preliminary cost estimate for this method of treatment Is
$5,000,000.00.
The effectiveness of this method of treating combined sewer overflows
depends upon the ability of the system to deliver the dilution water at
the time of the overflows. The urban area's response to rainfall is
almost immediate with an average time of 15 minutes from start of rain
to start of overflow. This means that the dilution water must reach the
overflow points immediately after start of rainfall.
The nearest site for a 4,500 million gallon reservoir (about one mile
square) at Bucyrus Is located about five miles upstream, adjacent to the
existing water supply reservoirs. The dilution water from this location
would have an average travel time to the overflow points of approximately
five hours. To deliver the required amount of dilution water to the
overflow, in time to be effective, the dilution water would have to be
released from the reservoir about five hours before start of rainfall.
Obviously trying to determine the start of rainfall five hours before It
occurs Is impractical and, in most cases, impossible. Therefore, flow
augmentation as a method of treating combined sewer overflows is not
feasible at Bucyrus.
D. Primary Treatment of Overflows
This method of controlling stream pollution from combined sewer overflows
proposes providing primary treatment for the overflows. Primary treat-
ment would include a gravity interceptor sewer to collect the overflows,
grit chamber, settling tanks, chlorination facilities, anaerobic digester
and sludge drying beds.
The primary treatment facilities have a design capacity capable of pro-
viding 1.5 hours of detention time for the two-year, one-hour design
storm which discharges 13.4 million gallons of overflow In two hours.
Five parallel settling tanks are proposed to provide for the variation
in overflow volumes received.
I 13
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Each tank Is 70 feet x 250 feet by 20 feet deep. A chlorination contact
tank 70 feet x 100 feet by 10 feet deep would follow each settling tank.
An anaerobic digester is proposed to treat about 1,500 pounds per day of
volatile suspended solids. The proposed sludge drying beds have an area
of approximately 7,500 square feet.
Primary treatment of the overflows could be expected to remove 50 percent
to 70 percent of the BOD and suspended solids waste load from the com-
bined sewer overflows. Chlorination of the overflows would significantly
reduce the bacteria discharge to the stream.
The cost for primary treatment of the overflows is estimated to be
$8,810,000.00.
E. Chlorination of Overflows
Chlorination of overflows is proposed as a method for controlling the
large number of bacteria discharged to the stream by combined sewer over-
flows. The literature survey has indicated that proper chlorination of
the overflows will reduce the peak after-growth of coliforms in the
stream to 10 percent to 30 percent of the coliforms that would develop
if unchlorinated overflows were discharged to the stream.
The proposed chlorination facilities include three chlorine contact tanks
located at Numbers 8, 17, and 23 overflow outlets adjacent to the
Sandusky River, new interceptor sewers that would collect the overflows
from the various overflow points and deliver the overflows to the con-
tact tanks and chlorination facilities capable of providing a chlorine
dosage of up to 40 mg/l. The size of the proposed contact tanks at
Numbers 8, 17, and 23 overflows are 1.6 million gallons, 1.9 million
gallons and 0.7 million gallons, respectively.
The estimated cost for chlorination of the overflows is $3,000,000.00.
F. Off-Stream Treatment
The basic alternate plan of pollution abatement from combined sewer over-
flows as presented and described herein proposes to intercept and treat
the flow from 24 overflow points in Bucyrus thereby eliminating all dis-
charges to the Sandusky River up to the design storms. This .provides
maximum protection to the Sandusky River both "in City" and downstream.
Such protection is the equivalent of collecting and treating the waste
water and the discharge from a storm sewer system in a community with
separate sewer systems.
The cost of such complete abatement plans should not be related to the
cost of physical separation without regard for the pollutional load
created by separate storm sewer discharges.
14
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Pollution abatement from combined sewers may be separated into two
general categories: (I) Inner-City and Downstream Pollution Abatement,
and (2) Downstream Pollution Abatement. The basic approach in this
study has been Inner-City and Downstream Abatement. Should only down-
stream protection be considered at this time as the first phase of an
overall pollution abatement plan, a considerable reduction in cost
would result.
The same or a pumping station similar to that proposed to pump the flow
from the interceptor sewer could be used to divert the flow in the
Sandusky River to the lagoons for treatment during periods of combined
sewer overflow. The same pump capacity as that proposed for the inter-
ceptor sewer without holding tanks (333 cfs) would be capable of
diverting the entire river flow which occurs about 95 percent of the
time. Pumping would only be accomplished during overflow periods and
release from the lagoon would be accomplished during these pumping
periods to satisfy the riparian owners water rights.
This concept of downstream water quality protection would not enhance
the water quality in the river reach within the City, but it would
result in a cost reduction of about $3,500,000 on the basic alternate
plan of pollution abatement and about $7,000,000 on the cost of physical
separation of the sewer systems. At some future date, the interceptor
sewer could be constructed to collect the overflows and convey them to
the pumping station and inner-city protection would be realized.
The reduction in initial cost would appear to justify that the downstream
protection aspect be thoroughly evaluated by a demonstration project.
The demonstration project should include monies for reducing or con-
trolling the channel degradation within the city due to the combined
sewer overflows. Channel projects could include regrading, reshaping or
paving to reduce pools and low velocity areas where solids would other-
wise tend to settle and become septic.
The estimated cost of the pumping station, lagoons and low head dam in
the Sandusky River is $1,700,000.
I 15
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TABLE 30
SUMMARY OF COST ESTIMATES
FOR
ALTERNATE SOLUTIONS
A. Complete Separation of Sanitary Wastewater and Storm Water
(I) New Sanitary System $9,300,000
(2) New Storm Water System $8,800,000
B. Interceptor Sewer and Lagoon System
(I) Gravity Interceptor, Pump Station and Aerated
Lagoon
Gravity Interceptor $3,600,000
Pump Station 1,000,000
Aerated Lagoon 620,000
TOTAL COST $5,220,000
(2) Holding Tanks, Gravity Interceptor, Pump
Station and Aerated Lagoon
Holding Tanks $1,500,000
Gravity Interceptor 3,000,000
Pump Station 800,000
Aerated Lagoon 560,000
TOTAL COST $5,860,000
C. Stream Flow Augmentation $5,000,000
D. Primary Treatment of Overflows $8,810,000
E. Chlorination of Overflows $3,000,000
F. Off-Stream Treatment $1,700,000
116
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SECTION XX
PROCEDURES FOR EVALUATING SIMILAR SYSTEMS IN OTHER COMMUNITIES
The studies and data collection accomplished at Bucyrus and described
herein are typical of the engineering effort necessary to develop
evaluation studies and feasible solutions to pollution abatement from
combined sewers. Each community's needs and methods of abatement are
dependent on growth patterns, topography, capability of existing sewer
system, receiving stream, availability of land, degree of protection
requi red, etc.
Since complete separation of storm and sanitary sewers is presently an
accepted method of correcting overflows from combined sewers, the total
conversion of combined sewers to either storm or sanitary systems if
present storm sewer capacity is inadequate may be the most feasible
solution. Only a detailed analysis of the present combined system with
current design storm conditions and future growth considered will pro-
vide the answer as to whether all or portions of the system should
remain combined.
After the present combined sewer system has been analyzed and decisions
made as to whether all or portions of the combined sewers are to remain
as combined systems the points of combined sewer overflow will have been
determi ned.
The local conditions must be studied and one or more of the following
steps considered and evaluated:
I. Intercept the overflow at each overflow point by a gravity sewer or
pumping station and force main for conveyance to point of treatment,
or
2 Construct holding tanks to level out the peak flow from the combined
sewer and convey same by gravity sewer or pump station and force
main to point of treatment, or
3 Discharge settled effluent from holding tank into receiving stream
if studies have shown that stream can assimilate such waste loads
and comply with minimum water quality standards, or
4. Build treatment facilities designed to protect the minimum water
quality in the stream for all overflow requiring treatment.
The following discussion outlines the procedures, using the results of
the Bucyrus data, that can be used to determine and evaluate the above
mentioned items. The decree to which the Bucyrus data and solutions can
be applied to another community is directly related to the similarity of
that community to Bucyrus.
I 17
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Five basic questions must be answered: one, the peak rate of overflow;
two, the total volume of overflow; three, the total waste load discharged
from the combined sewers; four, what can be discharged into the receiving
water; and five, what is the best method of collecting and treating the
waste that cannot be discharged directly into the receiving water. The
design storms and return frequencies must be selected with consideration
of the five questions.
Analyze Existing Sewer System
The total sewered area must be divided into sewer districts and a detailed
analysis made of each district including the trunk sewers. A detailed
analysts must also be made on the overflow structures and interceptor
sewer.
Often the original design notes or an existing sewer map can be used to
determine the size, grade, and location of the existing combined sewers.
A field check should be made to insure that no additional overflows have
been installed or drainage areas added to the sewer system. Spot checks
should be made in each drainage district to determine the type of land
use. Field work necessary would depend on available information. The
time of concentration must also be determined from the sewer travel time
and time of over-1 and flow.
Select Design Storm and Return Frequencies
The capacity of the existing system must be given consideration in^the
selection of the design storm, since it controls or limits the maximum
overflow rate possible from the sewers. The stream water quality desired
and the tolerance of pollution must also be considered along with the
minimum stream flows which may exist during periods of overflow. In
many communities like Bucyrus, Ohio, there is essentially no stream flow
available a large percentage of the time.
All states have established minimum stream standards for stream water.
The State of Ohio has five classifications for streams which are based
on the water usage. The volume of waste that can be discharged into
the receiving water will depend on how much the stream or lake can
assimilate without deleterious effects or violating the stream^standards.
This amount can be determined by using one of the stream purification
forumulas. However, in most cases in areas similar to northwestern Ohio
a waste load of about 25 pounds of BOD per day per cfs of stream flow at
low flow conditions is the maximum permissible loading.
Protecting a stream or lake against every frequency of rainfall is
uneconomical. There will be a design frequency for which an increase in
the degree of protection cannot be justified. A two-year frequency rain-
fall Is suggested for the design of any overflow collection or inter-
ception system and a one-year frequency rainfall for design of the volume
of any treatment facilities.
118
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The peak, volume, and quality of the combined sewer overflows are
directly related to intensity and duration of the rainfalls. If a
recording rain gage has not been located in the area, the total rain-
fall for various frequencies and durations can be obtained from the
Rainfall Frequency Atlas of the United States, Technical Paper No. 40,
U. S. Department of Agriculture. For the design of an overflow col-
lection or interception system, a rainfall duration equal to or greater
than the maximum time of concentration should be used. A minimum dura-
tion of one hour is suggested.
For treatment facilities with long detention times, such as a lagoon,
the total volume will be directly related to the volume of rainfall
expected during the detention period. One method of obtaining this
volume of rainfall is to take a number of years of rainfall records for
the area, determine the maximum rainfalls for the given detention time,
(20 day period) rank time according to their order of magnitude, assign
frequencies of occurrence, and then select the rainfall corresponding
to the design frequency. A simpler but less accurate method of obtain-
ing this rainfall is to use the total monthly rainfalls. The monthly
rainfall for the design frequency can then be reduced to the detention
time of the treatment facility by determining the maximum rainfall that
fell in the design month and within the detention time.
Determine the Runoff From Design Storms
For any combined sewer system with multiple overflows, a complete sewer
hydrograph is needed for each trunk sewer. Many cities may not be able
to measure their major overflows to determine a unit hydrograph. There-
fore, some assumptions for hydrograph shape must be made.
If a hydrograph method Is already being used successfully for design in
the city, it should also be used to determine the hydrographs at the
combined sewer overflows. If not, either the Chicago Hydrograph Method,
as described in the ASCE Sewer Design Manual, or the Modified Hydrograph
Method, as described in this report, is recommended for .design.
The Chicago Hydrograph Method may be used since the Chicago terrain and
rainfall patterns are representative of a typical midwestern city. A
set of curves is given for the peak rate of runoff per acre drained for
various depression storages and ground slopes. To determine the total
hydrograph shape, mass curves for lateral outflow from uniformly developed
areas must be constructed. This requires a detailed analysis of the
drainage characteristics of the sewer districts and the hydraulics of the
sewer system.
A more simplified method of obtaining a complete runoff hydrograph is the
Modified Hydrograph Method developed in this report. The assumptions and
procedure are found under "General Design Conditions". The time of the
start of overflow and the hydrograph shape were assumed based on the
characteristics of the hydrographs for Number 8, 17, and 23 sewer
I 19
-------
districts. The total volume of runoff for each district was then com-
puted using the runoff percentages and land use classifications developed
earlier. These volumes of runoff were used to determine the peak of the
hydrograph through the assumed hydrograph shape. For most of the sewer
districts in Bucyrus, this peak exceeded the maximum sewer capacities.
A variation of the Modified Hydrograph Method is to use the rational
formula for determining the peak of the runoff and through the assumed
hydrograph shape determine the volume of runoff. This variation might be
more accurate than that used for Bucyrus if coefficients for the rational
formula are well defined for the area and the times of concentration do
not exceed the length of significant rainfall. It should not be used if
the peak rate of runoff exceeds the maximum sewer capacities of many of
the sewer districts.
Determine Waste Loads from Design Storms
The characteristics of the waste from the combined sewer overflows^of any
city similar to Bucyrus will no doubt be similar to that found during
this study. Both the BOD and suspended solids concentration reached a
peak during the first hour of overflow and then decreased. Both reach
a minimum concentration after several hours. For design purposes, an
average BOD concentration of 125 mg/l and an average suspended solids
concentration of 480 mg/l were assumed for the first three hours of
overflow. Overflow after three hours will have an average BOD and sus-
pended solids concentration of about 20 mg/l and 150 mg/l, respectively.
The waste loads discharged during overflows minus the waste load which may
be discharged to the stream, equal the volume of flow and waste load which
must be collected and treated.
Method of Collection and Treatment
At Bucyrus a gravity interceptor was found to be the most economical
method of collecting the combined sewer overflows and carrying the waste
to a common point for treatment. A major pump station is required at
Bucyrus. A detailed analysis should be made of the pipe sizes, grades,
and locations to determine if there are any ways to minimize the cost.
For example, if flow through the treatment facilities can be accomplished
by gravity then the pump station may be eliminated. Another possibility
is splitting the flow into more than one treatment facility and locating
the facilities closer to the overflow points. For Bucyrus, the pump
station capacity was reduced by one-fourth by using storage capacity of
the gravity interceptor and the wet well to store the peak flow.
The capacity of the interceptor must be equal to the peak rate of runoff
from a two-year frequency rainfall minus the rate of runoff that the
river can assimilate. For example, the median flow in the river at
Bucyrus during the summer months is approximately five cfs. The assimila-
tion capacity of the river at this low flow is negligible and the
120
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interceptor was designed to handle all of the peak rate of flow from a
two-year frequency storm. If some of the overflow wastes can be dis-
charged into the stream, a check must be made of the travel times in
the stream between overflow points. If the duration of overflow is
greater than the travel times between overflows, the rates of^overflow
discharged into the stream must be reduced so that their sum is equal
to the assimilation capacity of the stream.
Based on the analysis made for Bucyrus, the aerated lagoon is believed
to be the most economical method of treating combined sewer overflows.
A lagoon can provide the high degree of treatment necessary for the
highly variable flows with a minimum of operation.
The volume of the lagoon must be equal to the volume of runoff from the
one-year frequency 20-day rainfall minus the volume the river can
assimilate. One method of operation is to discharge lagoon effluent^
continuously into the stream at a constant rate the stream can assimi-
late during low flow. The lagoon volume will then equal the volume of
runoff from the one-year frequency, 20-day rainfall minus the volume
discharged into the stream during this 20-day period. The other method
of operation is to discharge into the stream from the lagoon at a rate
determined by the flow in the stream. The total volume discharged during
the 20-day period will then be directly proportional to the flow in the
stream.
121
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SECTION XXI
ACKNOWLEDGMENTS
We wish to acknowledge the assistance and cooperation received from the
City of Bucyrus during the investigation and preparation of this report.
We would especially like to acknowledge the assistance of Bernard C.
Piper, Utilities Director and Gerald E. Staiger, Assistant Utilities
Director.
The aquatic biology survey portion of this report was performed by Mr.
Rendell Rhoades, Chairman of Biology, Ashland College, Ashland, Ohio.
We wish to acknowledge the assistance and cooperation received from Mr.
Harold P. Brooks, Hydrologist, Water Resources Division, Geological
Survey, United States Department of Interior.
We wish to acknowledge the assistance and cooperation received from Mr.
Howard Kenny, United States Weather Bureau, Port Columbus, Columbus, Ohio.
123
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SECTION XXI I
REFERENCES
- Standard Methods for the Examination of Water and Wastewater,
12th Edition. (1965)
2. ASCE - Design and Construction of Sanitary and Storm Sewers, MOEP
No. 37 (I960) pg. 31 - 77.
3. "Basic Information Needs in Urban Hydrology", A Study by the American
Society of Civil Engineers (April 1969) pg. 51 and 52.
4. Fair, G. M., and Geyer, J. C., Elements of Water Supply and Waste -
Water Disposal, John Wiley & Sons, Inc., New York (1958) pg. 54.
5. LInsley, R. K., Kohler, M. A., and Paulhus, J. L., Hydrology for
Engineers, McGraw-Hill Book Company, Inc., New York (1958) pg. 212
and 202.
6. Hicks, W. I., "A Method of Computing Urban Runoff", Proceedings,
ASCE, Vol. 109 (1944) pg. 1217.
7. Tholin, A. L., and Keifer, C. J., "The Hydrology of Urban Runoff",
Journal , Sanitary Division ASCE, Vol. 85, No. SA2, (March 1959)
pg. 47 - 106.
8. Rainfall Frequency Atlas of the United States, Technical Paper No.
40, U. S. Department of Agriculture, Washington, D. C.
9. "Feasibility of a Stabilization - Retention Basin in Lake Erie at
Cleveland, Ohio", A Report Prepared for the Federal Water Pollution
Control Administration under Contract No. 14-12-27 (May 1968)
10. Haggerty, L. T., "Two Methods for the Evaluation of Aerobic Digestion
(Extended Aeration) Waste Treatment Plant Effluents", A Report Pre-
pared for The Ohio Department of Health.
REFERENCES
FROM THE LITERATURE SURVEY
II. Anderson, R. E., "Lake County Adopts Clean Lake Policy", Water and
Sewage Works 115- 9 - 412 (Sept., 1968).
12. Anon., "Characterization, Treatment & Disposal of Urban Stormwater",
Intl. Conf. on Water Pollution Research, Munich, Germany, (Sept.
1966)
125
-------
13. Anon., "Regina Opens Worlds Largest Aerated Municipal Lagoon", Water
and Sewage Works 114- 4 - 80A (Apr., 1967).
14. Anon., Water & Sewage Works I 14 - 12 - 5A (Dec., 1967).
15. Anon., "Depollutlon Study", Water & Sewage Works 115 - 10 - 480
(Oct., 1968).
16. Anon., "Re-using Storm Runoff", Env. Science and Techn 2 - II - 1001,
(Nov., 1968).
17. AWWA, "Problems of Combined Sewer Facilities and Overflows", WPC
Research Series WP-20-II, FWPCA (1967).
18. Benjes, H. H., & others, "Storm - Water Overflows from Combined
Sewers", JWPCF 33 - 12 - (1961)
19. Benzie, W. J., & Courchaine, R. J., "Discharge from Separate Storm
Sewers & Combined Sewers", JWPCF 38 - 3 - 410 (Mar., 1966).
20. Bernardt, H., "Aeration of Wahnbach Reservoir", JAWWA 59 - 8 - 943
(1967).
21. Burm, R. J., and Vaughan, R. D., "Bacteriological Comparison Between
Combined and Separate Sewer Discharges in Southeastern Michigan",
JWPCF 38 - 3 - 400 (Mar., 1966)
22. Burm, R. J., "The Bacteriological Effect of Combined Sewer Overflows
on the Detroit River", JWPCF 39 - 3 - 410 (Mar., 1967).
23. Burm, R. J., and others, "Chemical & Physical Comparison of Combined
and Separate Sewer Discharges", JWPCF 40 - I - 112 (Jan., 1968).
24. Camp, Thomas R., "Chlorination of Mixed Sewage & Storm Water", J. of
the San Engr. Piv. , Proc. of the Am. Soc. of Civil Engrs. 87 - I
(1961 ).
25. Cliassen, Rolf E., "Coliform Aftergrowths in Chlorinated Storm Over-
flows", J. of the San Enqr. Div., Proc. of the ASCE 94 - 371 (1968).
26. Clift, Mortimore A., "Experience with Pressure Sewerage", J. of the
San Enqr. Div., Proc. of the ASCE 9_4 - 849 (1968).
27. Correspondence With City Engineer, City of Regina (Dec. 3, 1968).
28. Dunbar, D. D., & Henry, J. G. F., "Pollution Control Measures for
Stormwaters and Combined Sewor Overflows", JWPCF 38 - 9 (1966).
29. Gifft, H. M., and Symons, George E., "How to Estimate Storm Water
Quantities", Water & Wastes Enqr. 5 - 46 (Mar., 1968).
126
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30. Greeley, Samuel A., & Langdon, Paul E., "Storm Water & Combined
Sewage Overflows", J. of the San Enqr. Div., Proc. of the Am. Soc.
of Civil Engins. 87_ - 57 (1961).
31. Gregory, J. H., and others, "Intercepting Sewers and Storm Stand-by
Tanks at Columbus, Ohio", ASCE Trans. Paper No. 1887 (Oct., 1933).
32. Havens & Emerson, "Master Plan for Pollution Abatement, Cleveland,
Ohio", Vol. I (1968).
33. Jensen, L. D., & Renn, C. E., "Use of Tertiary Treated Sewage as
Industrial Process Water", Water and Sewage Works MJ - 4 ~ I84»
(Apr., 1968).
34 Johnson, C. F., "Equipment, Methods and Results from Washington,
D. C., Combined Sewer Overflow Studies", JWPCF 33 - 7 - 721 (July,
1961).
35. Kalinske, A. A., "Surface Aerators", Water & Sewage Works 115- I -
33 (Jan., 1968).
36. Koelzer, V. A., and Others, "The Chicago I and Deep Tunnel Project",
41st Annual Conf. of WPCF (Sept. 22-7, 1968).
37. Krenki, Peter A., and others, "Impounding and Temperature Effect
on Wastes Assimilation", J. of the San Engr. Div., Proc. ASCE 95_ -
37 (Feb., 1969).
38. Lancashire River Authority, 1st and 2nd Annual Reports for the period
10/15/64 to 3/31/66 and the year ending 3/31/67 152 pp.
39. Laredo, David, & Bryant, E. A., "Silt Removal from Combined Sewers",
Water & Sewage Works 115 - 12 - 561 (Dec., 1968).
40. Lothrap, Thomas L., & Sproul, Otis J., "High-level Inactivation of
Virusis in Wastewater by Chlorination", JWPCF 41 - 4 - 570 (1969).
41. Maneval, D. R., "Western European Waste Water Treatment", Water and
Sewage Works 114 - 6 - 231 (June 1967).
42 McDermott, Gerald N., "Management of Wastewaters from Outside Areas
of Industrial Plants", 41st Annual Conf. of WPCF (Sept. 22-27, 1968).
43. McDonald, D. B., & Schmickle, R. D., "The Effects of Flood Control
Reservoir on Water Quality", Water & Sewage Works IJ4 - II - 411
(Nov., 1967).
44. Patrick, Ruth, "Effect of Suspended Solids, Organic Matter and Toxic
Materials on Aquatic Life in Rivers", Water and Sewage Works 115 -
2-89 (Feb., 1968).
127
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45. Pavia, E. H., & Powell, C. J., "Chlorination & Hypochlorination of
Polluted Storm Water at New Orleans", 41st Annual Conf. of WPCF
(Sept. 22-27, 1968).
46. Quase, H., "Report on Underwater Storage in Washington, D. C.",
Env. Science and Techn. 2 - 8 - 577 (Aug., 1968).
47. Rand Development Corp., "Investigation of the Use of Coal for Treat-
ment of Sewage and Waste Waters", Office of Coal Research Report
No. 12, U. S. Dep't. of Interior (1965).
48. "Results of D. 0. Recorder in River Calder in WhoI ley", Lancashire
River Authority, 1st and 2nd Annual for the Period 10/15/64 to
3/31/66 and the year ending 3/31/67.
49. Riddick, Thomas M., "Forced Circulation of Large Bodies of Water",
J. of the San Engr. Dlv., Proc. of the Am. Soc. of Civil Engrs. 84_ -
1703 (1958).
50. Simpson, George D., "Treatment of Combined Sewer Overflows & Surface
Waters at Cleveland, Ohio", 41st Annual Conf. of WPCF, (Sept. 22-27,
1968.
51. Sullivan, Richard H., "Problem of Combined Sewer Facilities and Over-
flows", JWPCF 41 - 2-113 (1969).
52. Sullivan, Richard H., "Problems of Combined Sewer Facilities and
Overflows", 41st Annual Conference of WPCF (Sept. 22-27, 1968).
53. Thtrumurthi, D., & Nashashlbl, 0. I., "A New Approach for Designing
Waste Stabilization Ponds", Water & Sewage Works, Ref. No. R 208,
(1967).
54. USPHS, "Pollutional Effects of Stormwater and Overflows from Combined
Sewer Systems" USPHS Pub I. No. 1246 (1964).
55. Waller, D. H., "One City's Approach to the Problem of Combined Sewage
Overflows", Water & Sewage Works 114 - 113 (Mar., 1967).
56. Weibel, S. R., and others, "Urban Land Runoff as a Factor In Streams
Pollution", JWPCF 36 - 7 - 914 (July, 1964).
57. Weibel, S. R., & others, "Pesticides & Other Contaminants from Rain-
fall & Runoff as Observed in Ohio", JAWWA 58 - 8 - 1075 (Aug., 1966).
58. WPCF - ASCE, Design & Construction of Sanitary & Storm Sewers, WPCF
Manual of Practice No. 9 (1966).
59. Wright, Darwin, "The Causes and Remedies of Water Pollution from
Surface Drainage of Urban Areas", FWPCA.
128
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SECTION XXIII
FIGURES
-------
LAKE ERIE
•OUTH BASS I.
/
I
V
KCLLEY8 I.
arblthtod
.Cedar Point
Sandusky
STUDY AREA
SCALE IN MILES
10
20
1421
353
980
LEGEND
Drainage areas enclosed by shaded
Drainage areas enclosed by unshaded
lines —— ^— (sq. miles)
Drainage areas above points
90 indicated by arrows - sq. miles
Approximate low-water elevation
in feet above sea level
Figure No. I
SANDUSKY RIVER
Drainage Area
131
-------
132
-------
Average Slope
Population
^—IOO5
Combined Sewer
CONTOUR INTERVAL 5 FEET
SCALE IN FEET
1000
2000
L
J_
PHYSICAL DATA
Sewered Drainage Area 179 Acres
Non-Sewered Drainage Area 0 Acres
Impervious Area 33.7 Acres
Overflow ft Weir Location
0.85 %
2020
Figure No. 3
NO. 8 SEWER DISTRICT
Bucyrus, Ohio
-------
Overflow S Weir Location
PHYSICAL DATA
Severed Drainage Area 452 Acres
Non-Sewered Drainage Area 162 Acres
Impervious Area 33.7 Acres
Average Slope 0.65 %
Population 4300
Figure No. 4
NO. 17 SEWER DISTRICT
Bucyrus , Ohio
CONTOUR INTERVAL 5 FEET
SCALE IN FEET
0 1000 2000
I .... I -. -—I
-------
M^—Sondusky
River
•Overflow a Weir Location
PHYSICAL DATA
Sewered Drainage Area 373 Acres
Non-Sewered Drainage Area 0 Acres
Impervious Area 26.1 Acres
Average Slope 0.25 %
Population I960
CONTOUR INTERVAL 5 FEET
SCALE IN FEET
1000 2000
Figure No. 5
NO. 23 SEWER DISTRICT
Bucyrus, Ohio
-------
NO. 23 RAIN GAGE
UPSTREAM SAMPLER
Rgure No. 6
136
-------
NO. 8 DRY WEATHER WEIR
NO. 17 WEIR DURING OVERFLOW
Figure No. 7
137
-------
NO. 8 OVERFLOW WEIR
NO. 17 OVERFLOW WEIR
Figure No. 8
138
-------
NO. 8 INSTRUMENT SHELTER
WASTE WATER TREATMENT PLANT
OVERFLOW RECORDER
Figure No. 9
139
-------
UPSTREAM GAGE
DOWNSTREAM GAGE
Figure No. 10
-------
RIVER AT NO. 8 , LOW FLOW CONDITIONS
RIVER UPSTREAM FROM NO. 8
LOW FLOW CONDITIONS
Figure No. II
-------
M
M
O
2 J
N
1
\—
[—
—
L—
»••••
mm
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• i
•
• •
•
•
• IBM
—
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.,
40
80
120
160
200
240
280
DAILY DISCHARGE - CFS
• •• AVERAGE FLOW DURING STUDY PERIOD (AUG. 1968 - JULY 1969)
i i AVERAGE FLOW\
MEDIAN FLOW
fPAST RECORDS = (1925-1935,1938-1951,1963-1968)
Figure No. 12
Sandusky River Flow at Bucyrus,0hio
-------
c_\s\x
150
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0
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Figure No. 13
Comparison of Monthly Discharge 8 Monthly Rainfall
Sandusky River at Bucyrus,0hio
143
-------
O
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0
o>
I p
O
i
en
0.2
O.I
10 15 20
MINUTES
30 45 60
4 5 6 78910
HOURS
20 30
-------
20
40 60 80
RAINFALL DURATION - MINUTES
100
Figure No. 15
Intensity - Duration Curves
for Bucyrus , Ohio
-------
:0.8
V
H
1/5
UJ0.4
i
7
S
I
9
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u.
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4 AM
9AM
TIME - HOURS
Figure No. 16
Rainfall and Overflow
No. 8 Overflow - March 24,1969
-------
cr
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16
12
oo
u.
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8 8
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TIME - HOURS
9AM
Figure No. 17
Rainfall and Overflow
No. 17 Overflow - March 24,1969
-------
cr
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0.8
0.4
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7
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8
9
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TIME - HOURS
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Figure No. 18
Rainfall and Overflow
No.23 Overflow - March 24,1969
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Figure No. 19
Rainfall and Overflow
No. 8 Overflow - June 13,1969
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Figure No. 20
Rainfall and Overflow
No. 17 Overflow - June 13,1969
150
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Figure No. 21
Rainfall and Overflow
No.23 Overflow - June 13,1969
151
-------
10
15 20
RAINFALL DURATION - MINUTES
30
Fi gure No. 22
Intensity - Duration Curves
Rainfall Corresponding to Measured Overflows
No. 17 Rain Gauge Feb. 8 - June 13 , 1969
152
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OVERFLOW STARTED AGAIN
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(\) NOV. 15 68
First Flow
©NOV. 15'68
Second Flow
® JAN. 17'69
© FEB. 8 '69
© MAR. 24' 69
First Flow
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Second Flow
© MAY 7 '69
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fi) AUG. 9'69
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ORGANIC NITROGEN
MAR. 24 69
First Flow
3) MAR. 24 69
Second Flow
4) JUN. I3'69
HOURS AFTER START OF OVERFLOW
-------
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ORGANIC NITROGEN
\) FEB. 8 68
MAR. 24'69
First Flow
) MAR. 24'69
Second Flow
?) JUN. I3'69
HOURS AFTER START OF OVERFLOW
-------
Rrv
5 0 0 O O C
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Figure No. 38
Total Phosphates
No. 8 Overflow
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SETTLING TIME - MINUTES
100
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SETTLING TIME - MINUTES
5=00 AM
100 120
6=OOAM
Figure No. 44
Effect of Settling on
BOD 8i Suspended Solids
No. 17 Overflow - Mar. 24 ,1969
-------
DISSOLVED OXYGEN -MG/L
D o ^ S S cr
^m
-
''
^^.
_ , .—
,
--^_
.
D 0 = 0 ® DOWNSTREAM GAUGE DURING 24 HR PERIOD
140
120
z
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=>
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40
20
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M NOON
- —
^
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UPSTREAM GAUGE
DOWNSTREAM GAUGE
468 10 12 246 8
MID- AM
NITE
Figure No. 45
Diurnal Fluctuation In Dissolved Oxygen
Sandusky River - Oct. 9810,1968
175
-------
jcvrus.Ohio Wastewo er
reo
tme
rge
,_• 160
2 120
5s 80
d 40
d 0
Z
69 2-4 P Mr
1969
4-7 A.M.
' •
o
24
12
10
AUGUST 5,1969
2-4 PM
11
E
i
' i
AUGUST 6,1969
4-7 AM
32 I 01 23456789 10
Distance in Miles Above and Below Wastewater Treatment Plant Discharge
Fi gure No. 46
Diurnal Affect on Dissolved Oxygen in the Sandusky River
-------
12
10
8
111
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2101234567
Distance in Miles Above and Below Wastewater Treatment Plant Discharge
IAUG 69 - DRY
LOW FLOW
9 AUG 69 - DRY
LOW FLOW
9 AUG 69
DURING OVERFLOW
20 AUG 69
DRY
17 SEP 69
DURING OVERFLOW
17 SEP 69
AFTER OVERFLOW
18 SEP. 69 - DRY
HIGH FLOW
Figure No. 47
Dissolved Oxygen Profile of the Sandusky River
During Dry and Wet Weather
-------
c-
_
OB
K
i
2
UJ
_
50--
40- -
30- -
20- -
10
—SMALLEST LENGTH OF
RAINFALL MEASURED
H 1 1
10 20 30 40
LENGTH OF SIGNIFICANT RAINFALL - MINUTES
50
Figure No. 48
Overflow Peak Time
vs. Length of Rainfall
No's. 8,17,8 23 Overflows
178
-------
700
600
500
400
O
X
u
O
t/i
LL
U
300
200
20
120
40 60 80 100
TIME - MINUTES
( HYDROGRAPH BASED ON 20 MINUTE RAINFALL )
Figure No. 49
Unit Hydrograph
No. 8 Overflow
179
-------
700
600
50O
400
Ul
o
I
u
z
o
U
300
200
120
140
40 60 80 100
TIME - MINUTES
( HYDROGRAPH BASED ON 20 MINUTE RAINFALL )
160
Figure No. 50
Unit Hydrograph
No. 17 Overflow
180
-------
700
600
500
1
u.
LlJ
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Z
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,-
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u
400
300
200
C
:
20
120
40 60 80 100
TIME - MINUTES
( HYDROGRAPH BASED ON 20 MINUTE RAINFALL )
Figure No. 51
Unit Hydrograph
No. 23 Overflow
140 160
181
-------
o:
x
\
2
i
t
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r:
5
2.8
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/
i
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7
c
/
0
/•
/
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/
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0 NO ANTECEDENT RAINFALL
• RAINFALL WITHIN 24 HOURS
20 30 40 50
PEAK OVERFLOW RATE - CFS
Figure No. 52
Peak Rainfall vs. Peak Overflow Rate
No. 8 Overflow
182
-------
K
T
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Z
i
tfl
llJ
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a
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1
x
2.6
24
2.2
2.0
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1.6
1.4
1.2
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04
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n
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X
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r
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/
/
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/
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0 NO ANTECEDENT RAINFALL
• RAINFALL WITHIN 24 HOURS
20 40 60 80
PEAK OVERFLOW RATE - CFS
100
Figure No. 53
Peak Rainfall vs. Peak Overflow Rate
*:o. 17 Overflow
183
-------
:r
i
en
<
^
X
<
2.0
1.8
1.6
1.4
1.2
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0.8
0.6
0.4
0.2
-
/°
/
i
y/
/'
'/
/
/
/
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/
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f
0 NO ANTECEDENT RAINFALL
• RAINFALL WITHIN 24 HOURS
:
20 40 60 80
PEAK OVERFLOW RATE - CFS
100
Figure No. 54
Peak Rainfall vs. Peak Overflow Rate
No. 23 Overflow
-------
trt
u.
L.
_
3
0 20
40 60 80 100
TIME - MINUTES
140 160
Figure No. 55
Overflow Hydrograph
Twenty Minute Storm
No. 8 Overflow
185
-------
280
240
200
u.
u
3
U.
tt
LLJ
0
40
:
40 60 80 100
TIME - MINUTES
Figure No. 56
Overflow Hydrograph
Twenty Minute Storm
No. 17 Overflow
120
140 160
186
-------
in
U-
u
LU
o
60 80 100
TIME - MINUTES
120 140 160
Figure No. 57
Overflow Hydrograph
Twenty Minute Storm
No. 23 Overflow
187
-------
—
2
50
100
150
200
250
300
BOD - LBS. PER 100 ACRES
-------
g
< 31
Cfl (Q
C
tn ~*
c n
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SUSPENDED SOLIDS - 100 LBS. PER 100 ACRES
-------
2
>-
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m
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80
60
u
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20
2 3
TIME-HOURS
AFTER START OF RAINFALL
Figure No. 60
Rainfall and Overflow
Two Year, One Hour Storm
No. 8 Overflow
190
-------
4
>
H
to
cv
oo
m
200
OVERFLCW
HYDFOGRAPH
! 2 3
TIME - HOURS
AFTER START OF RAINFALL
Figure No. 61
Rainfall and Overflow
Two Year, One Hour Storm
No. 17 Overflow
191
-------
I 4
I
>•
•_
a
-------
(PERCENT BASED ON 30 MINUTE TIME INTERVALS )
Figure No. 63
Distribution Graph for Urban Runoff
Downstream Gauge
193
-------
New Storm Sewer
Relocated Storm Drain
Pavement Replacement
•Trench Excavation
Existing Sewer
Relocated House Lateral
When Cut By New Sewer
NEW STORM SEWER SYSTEM
Existing Sewer
Pavement Replacement
Trench Excavation
Relocated House Service
New Sanitary Sewer
NEW SANITARY SEWER SYSTEM
Figure No. 64
SEPARATION OF SANITARY ft STORM SEWERS
TYPICAL CROSS SECTIONS
-------
Overflows.
•Proposed Grgvity Interceptor Sewer
-Existing Interceptor Sewer
.
<£/
/^
/>
o^
A,'
• New Pump Static
(Overflows Only)
•AERATORS-
a
AERATED
o o o o o
L^ LAGOON
o o o o o
Present Waste Treatment
Plant
SYSTEM
-^
Rgure No. 65
ALTERNATE SOLUTION
INTERCEPTOR ft LAGOON SYSTEM
195
-------
257' X 458' (4 EACH)
10.5
10' BERM
5' PERMANENT POOL
Figure No. 66
TYPICAL CROSS SECTION
OF
AERATED LAGOON
-------
Raw Water Pump Station
And Low Head Dam-
Low Head Dam Creates
Pool For Pumps. Pool Is
Not An Impounding Res-
ervoir For Raw Water.
Upground
Storage
Reservoir
Raw Water Line
Discharge Channel
SCHEMATIC OF FLOW AUGMENTATION FACILITIES
[-Freeboard ^-Water Surface
]* / IT
10'
-I 2" Riprap On 6" Cushion
Conservation
Pool
Stripped Ground
Rock Toe Drain-
SECTION OF EMBANKMENT
Figure No. 67
FLOW AUGMENTATION
UPGROUND STORAGE RESERVOIR
-------
BIBLIOGRAPHIC:
Sewer Overflows. FWPCA PubTTcaTfi
i No. OAST-32 r
eng i neer i ng i nvest i gat i on
i the SandLjsky River at Bucyrus, Ohio and
i the combined sewer ov<
>ws. The City of
2,540 acres, a population of (3,000, and a combined sewer syste
Pleasured and sampled at 3 locations comprising 64% of the City's sewered
area and the river flow was measured and sampled above ana below Bucyrus.
0.05 of an inch will produce an overflow. The combined sewers will over-
flow about 73 times each year discharging an estimated annual volume of
350 million gallons containing 350,000 pounds of BOD and 1,400,000
BOO of 120 mg/l, suspended solids of 470mg/l, total coliforms of
11,000,000 per 100 ml and fecal coliforms of 1,600,000 per 100 ml. The
BOO concentration of the Sandusky River, immediately downstream from
Bucyrus, varied from an average of 6 mg/l during dry weather to a high
of 51 mg/| during overflow discharges. The suspended solids varied from
an average of 49 mg/l during dry weather to a high of 960 mg/l during
400,000 por 100 ml during dry weather to a high of 8,800,000 per 100 ml
during overflow discharges.
BIBLIOGRAPHIC:
burgess 8 Niple, Limited. Stream Pollution and Abatement From Combl_ned_
Sewer Overflows. FWPCA Publication No. DAST-32 November 1969
ABSTRACT:
and comprehensivi
from combined sei
i the results of a detailed engineering investigation
overflows on the Sandusky River at Bucyrus, Ohio and
for pollution abateff-ent from the combined sewer overflows. The City of
is tributary to Lake Erie. Bucyrus has an incorporated area of about
2,340 acres, a population of 13,000, and a combined sewer system with an
average dry weather wastewater flow of 2.2 million gallons per day. A
ducted on the combined sewer overflows in which the overflows were
measured and sampled at 3 locations comprising 64* of the City's sewered
area and the river flow was measured and sampled above and below Bucyrus.
The results of the study show that any 20 minute rainfall greater than
0.05 of an Inch will produce an overflow. The combined sewers will over-
flow about 75 tiroes each year discharging an estimated annual volume of
350 million gallons containing 350,000 pounds of OOC and 1,400,000
pounds of suspended solids. The combined sewer overflows had an average
BOO of 120 mg/l, suspended so I ids of 470 mg/l, total coliforms of
11,000,000 per 100 ml and fecal coliforms of 1,600,000 per 100 ml. The
BOO concentration o< the Sandusky River, immediately downstream from
Liucyrus, varied from an average of 6 mg/l during dry weather to a high
of 51 mg/l during overflow discharges. The suspended solids varied from
an average of 49 mg/l during dry weather to a high of 960 mg/l during
overflow discharges. The total cofiforms varied from an average of
400,000 per 100 mi during dry weather to s high of 8,800,000 per 100 ml
during overflow discharges.
BIBLIOGRAPHIC:
Burgess & Niple. Limited. Strei
Sewer Overflows. FWPCA Pub I lea'
i Pollution and Abatement From Combined
on No. DAST-32 November 1969
ABSTRACT:
This report contains the results of a detailed engineering investigation
and comprehensive Technical study to evaluate the pollutionsi effects
from confined sewer overflows on the Sandusky River at Bucyrus, Ohio and
to evaluate the benefits, economics and feasibility of alterna+e plans
for pollution abatement from the combined sewer overflows. The City of
Bucyrus is located near the upper end of the Sandusky River Basin which
is tributary to Lake Erie. Bucyrus has an incorporated area of about
2,340 acres, a population of 13,000, and a combined sewer system with an
average dry weather wastewater flow of 2.2 million gallons per day. A
year long detailed sampling and laboratory analysis program was con-
ducted on the combined sewer overflows In which the overflows were
measured and sampled at 3 locations comprising 64j of the City's sewered
area and the river flow was measured and sampled above and below Bucyrus.
than
The
The results of the study show that any 20 minute rainfall 91
0.05 of an inch will produce an overflow. The combined sewers will over-
flow about 73 times each year discharging an estimated annual volume of
350 million gallons containing 350,000 pounds of BOD and 1,400,000
pounds of suspended solids. The combined sewer overflows had an average
BOO of 120 mg/l, suspended solids of 470 mg/l, total coliforms of
11,000,000 per 100 ml and fecal coliforms of 1,600,000 per 100 mt.
BOD concentration of the Sandusky River, immediately downstream from
LJucyrus varied from an average of 6 mg/l during dry weather to a high
of e>l mg/l during overflow discharges. The suspended solids varied from
an average of 49 mg/l during dry weather to a high of 960 mg/l during
overflow discharges. The total coliforms varied from an average of
4CO.OOO per 100 ml during dry weather to a high of 8,800,000 per 100 ml
during overflow discharges.
ACCESSION NO.
KEY WORDS:
Combined Sewers
Ora i nage
Hydrographs
Inf iItration
Interceptor Sewer
Overflows
Runo*f
Stream Flow
Urban Runoff
Vtastewater Analysis
ACCESSION NO.
KEY WORDS:
Combined Sewers
Ora i nage
Hydrographs
InfIItration
Interceptor Sewer
Overflows
Runoff
Stream Flow
Urban Runoff
Wastewater Analysis
ACCESSION NO.
KEY WORDS:
Combined Sewers
Ora i nage
Hydrographs
InfiItration
Interceptor Sewer
Overflows
Runoff
Stream Flow
Urban Runoff
Wastewater Analysis
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Various Methods of controlling the pollution from combined i
flows are presented along with their degree of protection, advantages.
disadvantages and estimates of cost. The awttxxJs presented Include
(l» complete separation. (2) interceptor sewer and lagoon system.
(3) stream flow augmentation. (4) primary treatment, (5) ehlorlnatlon,
and (6) offstream treatment. It was concluded that the most economical
Method of providing a high degree of protection to the Sandusky River Is
by collect.ng the combined sewer overflows with a large Interceptor and
using an aerated lagoon system to treat the waste loads from the over-
flows.
This report was submitted In fulfil Intent of Contract 14-12-401 between
tne Federal Water Pollution Control Administration and Burgess & NIple.
United.
Various methods ot controlling the pollution from combined sewer over-
flows are presented along with their degree of protection, advantages.
disadvantages and estieates of cost. The methods presented Include
(I) complete separation. (2) interceptor sewer and lagoon system,
(3) stream flow augmentation, (4) primary treatment, (5) chlorlnatlon,
and <6) offstream treatment. It was concluded thet the most economical
method of providing a high degree of protection to the Sandusky River Is
by collecting the combined sewer overflows with a large Interceptor and
using an aerated lagoon system to treat the waste toads from the over-
flows.
This report was submitted In fulfillment of Contract 14-12-401 between
the Federal Hater Pollution Control Administration and Burgess i NIple.
Limited.
Various methods of controlling the pollution from combined sewer over-
flows are presented along with their degree of protection, advantages,
disadvantages and estimates of cost. The methods presented include
ft) complete separation, 12) Interceptor sewer and lagoon system,
(3) stream flow augmentation, (4) primary treatment, (5) chlorlnatlon,
and (6) offstream treatment. It was concluded thet the most economical
method of providing a high degree of protection to the Sandusky River is
by collecting the combined sewer overflows with a large Interceptor and
using an aerated lagoon system to treat the waste loads from the over-
flows.
Thl* report was submitted in fulfillment of Contract 14-12-401 between
the Federal Mater follutlon Control Administration and Burgess & NIple,
Limited.
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