WATER POLLUTION CONTROL RESEARCH SERIES
11024DMS05/70
Engineering Investigation
of
Sewer Overflow Problem
Roanoke, Virginia
U.S. DEPARTMENT OF THE INTERIOR • FEDERAL xWATER QUALITY ^
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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.
They provide a central source of information on the 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 1108, Planning
and Resources Office, Office of Research and Development, Department of
the Interior, Federal Water Quality Administration, Washington, D.C. 20242,
Previously issued reports on the Storm and Combined Sewer Pollution
Control Program:
WP-20-11 Problems of Combined Sewer Facilities and Overflows -
1967.
WP-20-15 Water Pollution Aspects of Urban Runoff.
WP-20-16 Strainer/Filter Treatment of Combined Sewer Overflows.
WP-20-17 Dissolved Air Flotation Treatment of Combined Sewer
Overflows.
WP-20-18 Improved Sealants for Infiltration Control.
WP-20-21 Selected Urban Storm Water Runoff Abstracts.
WP-20-22 Polymers for Sewer Flow Control.
ORD-4 Combined Sewer Separation Using Pressure Sewers.
DAST-4 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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ENGINEERING INVESTIGATION OF
SEWER OVERFLOW PROBLEM
A Detailed Investigation Into the Cause
and Effect of Sanitary Sewer
Overflows and Recommended
Remedial Measures
for
Roanoke, Virginia
by
Hayes, Seay, Mattern & Mattern
Architects - Engineers
1615 Franklin Road, S.W.
Roanoke, Virginia 24016
for the
FEDERAL WATER QUALITY ADMINISTRATION
DEPARTMENT OF THE INTERIOR
Program No. 11024DMS
Contract No. 14-12-200
May 1970
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FWQA Review Notice
This report has been reviewed by the Federal
Water Quality Administration and approved
for publication. Approval does not signify
that the contents necessarily reflect the views
and policies of the Federal Water Quality
Administration, nor does mention of trade
names or commercial products constitute en-
dorsement or recommendation for use.
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ABSTRACT
Three study areas, representing approximately 2150 acres or 25 per-
cent of the area served by the City of Roanoke, Virginia's separate
sanitary sewerage system, were used in an analysis of stream pol-
lution resulting from rainfall infiltration and sanitary sewer overflows.
Data from rainfall gauges were correlated with historical rainfall data
to establish precipitation frequencies. Flows in the sanitary sewers
and streams were gauged during storm events to measure infiltration
and runoff quantities and to establish their relation to rainfall inten-
sities and durations. Samples were obtained during storm events to
assess the quality of sewer overflows and storm runoff.
A computer program was developed to permit the analysis of the
sewerage system under various rainfall frequencies and durations, to
calculate the overflow quantities discharged to the watercourses and
to assess the sewer overflow problem for the entire urban area.
Rates of infiltration in the sanitary sewers were found to be as high as
24, 000 gallons per inch of pipe diameter per mile per day which pro-
duced overflows from a single storm event equivalent to 14 percent of
the daily untreated sewage.
Various remedial measures were investigated and a program, based
primarily on reducing infiltration by at least 80 percent, was pre-
sented. The cost would be about $61 per capita.
This report was submitted in fulfillment of Contract Number 14-12-200
between the Federal Water Quality Administration and the architectural
and engineering firm of Hayes, Seay, Mattern & Mattern, Roanoke,
Virginia.
111
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CONTENTS
Section Title Page
ABSTRACT iii
LIST OF TABLES viii
LIST OF FIGURES xiii
LIST OF PLATES xvi
1 CONCLUSIONS AND RECOMMENDATIONS .... 1
Conclusions 1
Recommendations 4
2 INTRODUCTION 7
Purpose .................... 8
Scope of Project 8
3 STUDY AREAS 11
Murray Run 13
24th Street 15
Trout Run 16
4 RESULTS OF INVESTIGATION 23
Field Investigation .............. 23
Rainfall Investigation 27
Gauging Streams and Sewers 27
Murray Run Study Area 28
Trout Run Study Area 28
24th Street Study Area 36
Storm Surface Runoff 36
Storm Water Infiltration ......... 45
Water Quality . 49
Water Pollution Control Plant ........ 53
Gauging 53
Overflow Quality 54
v
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CONTENTS
Section Title Page
5 EVALUATION OF RESULTS 57
Field Investigation 57
Streams 60
Dry Weather Conditions 60
Wet Weather Conditions 60
Sanitary Sewers 64
Infiltration 64
Infiltration - Rainfall Relationship .... 68
Computer Program . 69
Overflows in Study Areas ........... 70
Pollution From Overflows 75
Water Pollution Control Plant 80
Overflow 80
Pollutant 91
Overflows from Roanoke Sewerage System . . 91
6 REMEDIAL MEASURES 99
The Problem 99
Alternate Methods 99
Elimination of Infiltration 100
Additional Sewer Capacity ........ 102
increased Treatment Capacity 102
Detention Basins 10Z
Combination of Alternate Methods .... 103
Separation of Supernatant and Overflow . 105
A Program For Controlling Pollution
From Sanitary Sewer Overflows 114
Costs of Remedial Measures 126
Basis of Cost Estimates ......... 126
Cost of Recommended Remedial
Measures 126
Benefits of Remedial Measures 130
7 ACKNOWLEDGEMENTS 131
8 REFERENCES 133
vl
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CONTENTS
Section Title Page
APPENDICES
I FIELD INVESTIGATION 135
Smoke Testing 135
Record of Results . . 136
Costs 136
II HYDROLOGICAL INVESTIGATION 137
Equipment 137
Methodology 137
Problems 139
Costs 139
III GAUGING OF STREAMS AND SEWERS 141
Equipment 141
Methodology 141
Problems 145
Costs 145
IV WATER QUALITY SAMPLING AND TESTING . . 147
Equipment . 147
Methodology 148
Problems 149
V COMPUTER PROGRAM 151
Program Abstract 151
Operating Instructions 152
FORTRAN Source Listing 153
VI RAINFALL INTENSITY AND RATE OF
DISCHARGE FOR THE THREE STUDY
AREAS - FIGURES 34 THROUGH 101 157
vii
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CONTENTS
Section Title Page
VII SAMPLING DATA FOR STREAMS AND
SANITARY SEWERS OF THE THREE
STUDY AREAS AND THE WATER
POLLUTION CONTROL PLANT -
TABLES 51 THROUGH 60 227
VIII SUMMARY REPORT OF LITERATURE
SEARCH 239
Purpose 239
Scope 239
Field Investigation 240
Hydrological Investigation 241
Monitoring and Sampling 242
Analysis 244
Remedial Measures 246
ABSTRACT CARDS
WRSIC ABSTRACT FORM
viii
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TABLES
Number Title Page
1 Tabulation of Points of Entry of
Storm Water Infiltration 24
2 Rainfall Summary 35
3 Storm Surface Runoff 41
4 Storm Water Infiltration in
Sanitary Sewers 47
5 Stream Pollution From Surface Runoff and
Sanitary Sewer Overflows - Trout Run ...... 50
6 Stream Pollution From Surface Runoff -
24th Street 51
7 Stream Pollution From Surface Runoff and
Sanitary Sewer Overflows - Murray Run ..... 52
8 Overflows at the Water Pollution
Control Plant 54
9 Contribution from Typical Overflow From
Water Pollution Control Plant - 22/23
July 1969 Event 55
10 Waste Water Overflow Characteristics -
Water Pollution Control Plant - 22/23
July 1969 Event 56
11 Plant Waste Water Influent Characteristics -
Upstream Manhole Roanoke River Interceptor
22/23 July 1969 Event 56
12 Comparison of Infiltration to Rainfall
in the Three Study Areas 58
13 Study Area Characteristics 59
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TABLES
Number Title Page
14 Daily and Annual Dry Weather Pollutional
Loads in Streams 6l
15 Relative Concentrations of Pollutional
Constituents During Average Wet Weather
and Average Dry Weather Conditions 62
16 Comparison of Concentrations of Pollutional
Constituents from Surface Runoff 63
17 Average Concentration of Pollutional
Constituents in Streams Attributed to
Surface Runoff 64
18 Comparison of Average Pollutants From
Surface Runoff 65
19 Summary of Total Pounds of Pollutants in
Murray Run Stream ................ 66
20 Summary of Total Pounds of Pollutants in
Trout Run Stream . 67
21 Average Yearly Rainfall Data 74
22 Overflow Frequency Data 75
23 Maximum Single Overflows in
Study Areas 75
24 Average Concentrations of Pollutional
Constituents of Sanitary Sewage Overflows
in Study Areas 77
25 Average Concentration of Pollutional
Constituents of Dry Weather Sanitary
Sewage Flow in Study Areas t. . 78
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TABLES
Number Title
26 Computed and Measured BOD From Trout
Run Sewer Overflows 79
27 Pollutional Load From Maximum Single
Annual Overflow Event .............. 79
28 Annual Pollutional Load From Overflows
in Study Areas 80
29 - 33 Calculated Overflows for the Years
1964 Through 1968 84-88
34 Measured Overflows for the Year 1969 89
35 Summary of Calculated Overflows - Water
Pollution Control Plant - 1964 Through 1968 ... 90
36 Classification of Sewer Drainage Areas 93
37 Summary of Overflow Conditions 94
38 Average Annual BOD Contributed to the
Roanoke River by Sanitary Sewage 95
39 BOD Contributed to Roanoke River by
Sanitary Sewage During Maximum Yearly
Rainfall Event 96
40 Sewer Line Replacement Requirements for
Use of a Single Detention Basin - Infiltration
Reduced 80 Percent 104
41 Tabulation of Rainfall Events by Total Rainfall
and Average Intensities Using Five Years of
Climatological Data 109
42 Overflows Based on Five Years of
Climatological Data - Murray Run
Study Area 110
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TABLES
Number Title Page
43 Overflows Based on Five Years of
Climatological Data - Trout Run
Study Area . Ill
44 Overflows Based on Five Years of
Climatological Data - 24th Street
Study Area 112
45 Relationship Between Detention Basin Size,
Rainfall Eventg and Volume of Overflow -
Based on Five Years of Climatological Data ... 113
46 Unit Costs 127
47 Cost Estimate for Remedial Measures in
Each Study Area 128
48 Cost Estimate for Recommended Remedial
Measures for the Entire City of Roanoke ..... 128
49 Operational and Maintenance Costs for
Recommended Remedial Measures for the
Entire City of Roanoke . 129
50 Estimated Costs Per Various Units for
Recommended Remedial Measures 129
51 Stream Sampling Data - Murray Run
Stream 228
52 Stream Sampling Data - Trout Run Stream .... 229
53 Stream Sampling Data - 24th Street Stream ... 230
54 Sanitary Sewer Sampling Data *- Murray Run
Sanitary Sewer • 231
55 Sanitary Sewer Sampling Data - Trout Run
Sanitary Sewer 232
Xii
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TABLES
Number Title Page
56 Sanitary Sewer Sampling Data - 24th Street
Sanitary Sewer ................... 233
57 Sampling Data - Water Pollution Control
Plant Overflow . . . . 234
58 Sampling Data - Roanoke River Interceptor
Above Plant 235
59 Sampling Data - Sanitary Sewer Dry Weather
Flow - 24 Hour Composite • • 236
60 Sampling Data - Stream Dry Weather Flow -
24 Hour Composite 237
xiii
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FIGURES
Number Title Page
1 Open Joint of Pipe in 24th Street
Interceptor 25
2 Roots in Murray Run Interceptor 25
3 Roots in Murray Run Interceptor ...'...... 26
4 Overflow in Trout Run Study Area ........ 26
5 Recording Rain Gauge in Murray Run
Study Area 27
6 Water Level Recorder - Murray Run
Stream . . . . . 37
7 Water Level Recorder - Murray Run
Sanitary Sewer 37
8 Water Level Recorder and Automatic
Sampler - Trout Run Stream ........... 38
9 Water Level Recorder and Automatic
Sampler - Trout Run Sanitary Sewer ....... 38
10 Water Level Recorder - 24th Street
Stream 39
11 Water Level Recorder - 24th Street
Sanitary Sewer 39
12' Sample Hydrograph - Rainfall Intensity
and Rate of Discharge - Murray Run Stream ... 40
13 Relationship of Surface Runoff to Rainfall -
Murray Run Stream 42
14 Relationship of Surface Runoff to Rainfall -
24th Street Stream 43
xiv
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FIGURES
Number Title Page
15 Relationship of Surface Runoff to Rainfall -
Trout Run Stream . 44
16 Sample Hydrograph - Rainfall Intensity and
Rate of Discharge - 24th Street Sanitary
Sewer 46
17 Dry Weather Flow Comparison - 24th Street
Sanitary Sewer 48
18 Water Level Recorder - Water Pollution
Control Plant ................... 53
19 Relationship of Sanitary Sewer Infiltration
Rate to Average Rainfall Intensity 71
20 Relationship of Rainfall Intensity to Rate of
Potential Overflow From Sanitary Sewers .... 73
21 Flow Diagram - Water Pollution Control Plant . . 81
22 Relationship of Overflow to Rainfall - Water
Pollution Control Plant 83
23 Average Annual BOD Contributed to the Roanoke
River by Sanitary Sewage 95
24 BOD Contributed to Roanoke River by Sanitary
Sewage During Maximum Yearly Rainfall
Event 96
25 Rainfall - Overflow Relationship - Murray
Run Study Area 106
26 Rainfall - Overflow Relationship - Trout Run
Study Area 107
27 Rainfall - Overflow Relationship - 24th Street
Study Area 108
XV
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FIGURES
Number Title Page
28 Recording Rain Gauge 138
29 Non-recording Rain Gauge 138
30 Water Level Recorder 142
31 Bristol Pressure Gauge . . . . 142
32 Water Level Recorder Installation in
Sanitary Sewer Manhole 144
33 Serco Automatic Sampler 147
34 - 88 Rainfall Intensity and Rate of Discharge -
Study Areas . 148 - 212
89 - 94 Rainfall and Rate of Overflow - Water
Pollution Control Plant 213 - 218
95 - 100 Stage - Discharge Curves for Streams and
Sanitary Sewers 219 - 224
101 Stage - Discharge Curve - Water Pollution
Control Plant - 54" Diameter 225
XVI
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PLATES
Number Title Page
1 Study Areas - City of Roanoke, Virginia ..... 19
2 Land Use in Study Areas 21
3 Trout Run Study Area 29
4 24th Street Study Area 31
5 Murray Run Study Area 33
6 Detention Basin Site - Murray Run Study Area . . 115
7 Detention Basin Site - Trout Run Study Area ... 117
8 Detention Basin Site - 24th Street Study Area . . 119
9 Detention Basin System Layout for Murray Run
Study Area 121
10 Detention Basin Conceptual Design for Murray
Run Study Area 123
xvii
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SECTION 1
CONCLUSIONS AND RECOMMENDATIONS
CONCLUSIONS
1. It is now well established that overflows from combined sewers
constitute a significant part of the nation's total water pollution problem.
The separation of sanitary and storm sewers has been considered to be
the ultimate solution for the elimination of such overflows. However,
the mere fact that the systems are separated does not necessarily re-
duce the number or pollutional effect of overflows. Separate sanitary
sewers can act as combined sewers due to the excessive infiltration of
surface runoff and produce overflows of untreated sewage.
2. This study was conducted on 25 percent of Roanoke, Virginia's
separate sanitary sewerage system which is probably representative of
most existing separate sanitary sewerage systems installed prior to
1950. The study revealed that overflows from this separate system
amount to one to two percent of the annual average untreated sewage.
Overflows are even more significant on an individual storm basis,
amounting to as much as 14 percent of the daily untreated sewage.
3. Overflows from sanitary sewers are not controlled; therefore,
they occur indiscriminately throughout the watershed causing additional
health and safety problems. Overflowing manholes in streets and
residential property and flooded basements are esthetically objectionable
as well as potential health hazards and should be eliminated.
4. All sanitary sewer overflows are not directly into a stream or
water course. Only 25 percent of the pollution from such overflows
could be actually traced to entering a stream. The remainder either
re-entered the sewer after the storm, ponded, or entered the ground
water table. However, the possibility of some of the pollutants
reaching the stream through undetected leaks or through ground water
cannot be ruled out.
5. The greatest cause of the sewer overflows is excessive infil-
tration. During storms sanitary sewers become,- in effect, storm
sewers due to the numerous entry points for surface runoff. Contrary
to original beliefs, relatively few downspouts and storm drains were
directly connected to the sanitary sewers.
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6. Storm water entry points ranged from perforated manhole covers
to broken pipe sections exposed to surface stream flow. Crushed pipe
resulting from other types of construction operations, broken service
laterals, and service laterals poorly connected to the sewer main were
other major sources of infiltration.
7. No logical relationship could be found between the topographical
characteristics of the drainage area and the rates of infiltration or
number and type of points of infiltration.
8. Flow hydrographs indicated that peaks in the sanitary sewers
occurred simultaneously with, those in the storm sewers. A rainfall
intensity of 0.04 inch in 1 hour was required to cause measurable
infiltration.
9. Throughout the range of storms monitored, the average rate of
infiltration was proportional to the average rainfall intensity, as
shown on Figure 19; thus, the higher the rainfall intensity the higher
the rate of infiltration. Rates of infiltration as high as 24,000 gallons
per inch of pipe diameter per mile per day were recorded, which is
50 to lO'O times the normally specified allowable amount.
10. Total volumes of overflow and infiltration for any particular
rainfall event are a function of storm duration and average rainfall
intensity. Average rainfall intensities greater than 0.4 inch per hour
generally have durations of less than two hours.
11. -Many municipalities rate the capacity of the interceptor sewer as
a multiple of the average dry weather flow. Capacity allowances on
such a basis have no relation to the actual problem other than merely
providing some excess. Rather, capacity allowances for infiltration
in the design of interceptor or trunk sewers should be based on the
total length of upstream sewer.
12. In addition to localized overflows from the sewerage system,
overflows occur at the Water Pollution Control Plant on the average of
10 times per year. This overflow contributes as much as Z7 percent
of the total pounds of untreated BOD as a result of a single storm event.
When added to the overflow from the sanitary sewer, the total over-
flows contribute 43 percent of the daily untreated BOD.
13 . About 77 percent of the total annual overflows occur between May
and October, and constitute about 75 percent of the total overflow
volume. This corresponds to the period of lowest stream flows, and
the peak recreational water use season when water pollution would be
the most critical.
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14. Higher than normal river flows cannot be relied upon for dilution
of the overflows. Localized thunderstorms produce sewer overflows
without significantly affecting the flow of the river.
15. While no in-depth study was made on the pollutional potential of
storm surface runoff, the associated data indicated that its quality was
similar to that of secondary treated effluent. This storm runoff in-
creased the BOD concentrations in the streams three to five times over
that of normal dry weather flow. Considering the volumes of storm
runoff and its quality, the amount of BOD contributed to the Roanoke
River from storm runoff alone could easily be 200 percent of that of the
sewer overflows. Therefore, it appears that pollutional effects of storm
runoff are appreciable and clearly point to the need for better house-
keeping practices in our urban watersheds. A more detailed analysis
may indicate a need for treatment of urban runoff. At any rate our
small urban streams can no longer be given the traditional "backdoor"
approach and treated as conveyors for our refuse.
16. Due to the losses of untreated sewage through overflows, the
effectiveness of pollution control cannot be gauged solely by the
efficiency of a treatment process. The installation of tertiary treatment
facilities to remove additional fractions of pollutants appears un-
warranted when large volumes of the sewage are lost through overflows
and never reach the treatment process. Therefore, the entire "system",
including lines and treatment plant, should be evaluated as a whole.
17. It is concluded that a reduction of pollution from sewer overflows
in Roanoke can best be obtained by a combination of remedial measures.
These measures include more complete sewer separation, replacement
of critical lines to increase capacity, detention of peak flows within the
drainage basin, controlled release based on the system's downstream
capacity, and treatment of all flows at the Water Pollution Control Plant.
The key is the reduction of infiltration by separation or elimination of
storm surface entry points, utilizing the computer to achieve optimum
designs of the system.
18. The possibility of removing all storm water from existing
sanitary sewerage systems, especially older ones, is remote. However,
it is believed that as much as 80 percent could be eliminated through a
program of inspection and repair. The total estimated cost of such a pro-
gram is $61 per capita; far below the cost of complete line replacement.
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19. The use of the computer permits evaluation and optimum selection
of detention basin size and location and pipe capacities under a variety of
trial conditions and storm, events. Unfortunately, a considerable amount
of data is required on the existing sewerage system, much of which must
be determined in the field as it is often not available from office records.
20. The detention basins selected will detain the overflow for treat-
ment during off peak periods from at least 90 percent of the storm events
causing overflows in a five-year period; this corresponds to 90 per-
cent of the overflow volume during the same period.
RECOMMENDATIONS
1. Further sewer separation is essential and it is recommended that
an intensive inspection and repair program be undertaken on a selected
drainage area basis, employing the type of program outlined in this
report.
2. Sewer joint sealing procedures are not new, but there are many
sealing materials which are unproven. It is recommended that the
repair program for the initial drainage basin selected, Murray Run,
be developed as a demonstration project to evaluate the materials,
methods, and effectiveness of the overall program. This demonstration
area will lay the groundwork and supply much needed information for
future improvements to the remainder of the City's sanitary sewer sys-
tem,
3. A significant amount of infiltration originates from storm water
inlet points on private property, through either illegal connections or
breaks. The City's program should provide for a cooperative arrange-
ment between the private owner and the City for these repairs and
separation of storm water. This could be established through uniform
charges for such work or by licensed contractors with established
rates.
4. A sewer leak detection program is of little value if results are
not properly recorded and acted upon. The results of a leak survey
should be promptly evaluated and action taken. Private owners of
property with violations or deficiencies should be promptly notified
and periodic follow ups made to insure corrections have been made.
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5. Pollution from overflows at the pollution control plant can be re-
duced by in-house changes in process piping. It is recommended that
digester supernatant and sludge thickner overflow piping be revised so
that they return to a point other than the overflow manhole; thus, these
extra pollutants are not flushed into the river during storms.
6. It is recommended that more study be directed to the impact of
the pollutional effects of urban storm surface runoff. Such studies
would relate detrimental effects of storm runoff to other known sources
of potential pollution and develop any recommendations for reducing
pollution from this source.
7. Studies involving stream and sewage flow measurements, rain-
fall measurements, and sampling require equipment that often is not
readily available. It is, therefore, recommended that the allowance
for initial start-up time for such studies be a period of three to six
months. Further, such studies are dependent upon weather for the
gathering of data; therefore, the time frame should be flexible to
insure a representative season has been observed.
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SECTION 2
INTRODUCTION
The overflow of untreated sewage from sewers has long been re-
cognized as one of the major contributors to the pollution of water-
courses in this country. In cities with, combined storm and sanitary
sewer systems, the sewers overflow during rainfalls when the com-
bined storm water and sewage flow is greater than the hydraulic capac-
ity of the system. Where the overflows have been large and occurred
frequently, the quality of waters which received the Overflow have
deteriorated badly. In some instances the waters have lost their
recreational value completely.
The recognition of sewage overflow as a major poUutional problem has
prompted extensive investigations and studies aimed at finding economi-
cal methods of solving the problem. Commonly accepted practice is to
separate the combined sewer system so that the storm water and the
sanitary sewage ar-e conveyed in separate lines and theoretically do
not become mixed. Experience with separate systems, however, has
shown that they do not entirely eliminate the sewer overflow problem.
Storm water infiltration in the separate sanitary sewers has become
a formidable problem for many cities. The increase in flow in
sanitary sewers caused by the infiltration of storm water not only
results infrequent sewage overflows in sewer lines but also causes
occasional overloading of the sewage treatment facilities. A study con-
ducted in Johnson County, Kansas and Kansas City, Missouri and pub-
lished in 1965 indicates that during periods of moderate rainfall the
major portions of the flow in the sanitary sewers were from sources
other than water-using plumbing fixtures (1). *
A study of Roanoke, Virginia's separate sanitary sewer system con-
ducted in 1965 revealed that storm water infiltration in the system was
a serious problem (2). The report concluded that overflows from the
sanitary sewers were resulting in unsightly and undesirable pollution
of the watercourses in the City. The study also reported that peak wet
weather flows in the sanitary sewers exceeded the capacity of the Water
Pollution Control Plant, causing raw sewage to be bypassed to the
Roanoke River. The plant is located approximately 10 miles upstream
from Smith Mountain Lake which is used extensively for recreational
purposes.
Numerals in parentheses refer to corresponding items in Section
8 - References.
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PURPOSE
The purpose of this study was to investigate the sanitary sewer overflow
problem in Roanoke, Virginia and to recommend feasible remedial
measures to abate the sewer overflows. In addition, it is intended that
the study establish a basis for the evaluation of the benefits and
economics of alternate methods of controlling water pollution from the
sewage overflows.
SCOPE OF PROJECT
In order to provide the basic data required to completely assess and
evaluate the sanitary sewer overflow problem in Roanoke, it was deemed
necessary to conduct detailed field and hydrological investigations,
gauge flows in streams and sewers, and determine water quality by
sampling and testing. The study was limited to 25 percent of the existing
sanitary sewer system. Three study areas, determined to be generally
representative of other areas within the entire city, were selected as
the models for the detailed investigations.
The study was begun in September 1968 and covered a time span of 15
months, at a budgeted cost of $114,000. The study areas contained
348,000 lineal feet of sewer, 2150 acres of land and 27, 000 people.
The field investigation consisted of smoke testing the sanitary sewers,
manhole cover surveys, and other field observations necessary to deter-
mine the condition of the existing sewers and to locate storm water entry
points. The hydrological investigation included measuring rainfalls
during the study period 6 February 1969 through 5 August 1969. The
gauging consisted of measuring flow in the streams and sewers of the
study areas and gauging of the bypass line at the Water Pollution Control
Plant. The water sampling and testing phase of the study consisted of
sampling the flows in the streams and sewers in the study areas,
sampling the bypass sewage flow at the Water Pollution Control Plant,
and analyzing the samples to determine quantitie s'of various pollutional
constituents . The sampling and water quality analysis reflected both
wet weather and dry weather flows .
Evaluation and analysis of the flow gauging and rainfall data were re-
quired to determine the effect of storm water infiltration on sewage
flowa and to estimate the frequency of overflows in the study areas and
at the Water Pollution Control Plant. The results of the water quality
and testing data served as a basis for assessing the pollutional effect
of the estimated overflows.
8
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The study also includes the investigation of the application of existing
and new technology to the abatement of the overflow problem. From
the assessment of the sewer overflow problem, a program of re-
medial measures is presented together with cost estimates which
permit evaluation of the effort to be applied towards reducing overflows,
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SECTION 3
STUDY AREAS
Roanoke, Virginia lies in the Appalachian Highlands, a system of
mountains, hills and valleys running generally in a northeasterly-
southwesterly direction from New England to Alabama. The City of
Roanoke, as shown on Plate 1, is located in one of a series of valleys
situated just west of the Blue Ridge Mountains. Becaus'e of the Roanoke
Valley's location, runoff from rainfall travels fairly rapidly to the many
streams originating in the higher elevations surrounding the area.
Roanoke!s topographic situation modifies the climatic picture in com-
parison to adjacent areas • Because of its location, with the Allegheny
Mountains to the west and the Blue Ridge Mountains to the east, Roanoke
is afforded some protection from extreme high temperatures in the sum-
mer and extreme low temperatures in the winter. However, the weather
is quite variable, even though the extremes are rare.
Precipitation is fairly well distributed throughout the year with a slight-
ly higher amount during the warmest months. The yearly average is
about 34 inches. Droughts are uncommon as are rainy spells of long
duration.
The Roanoke Valley is drained by the Roanoke River and many small
tributaries. The river begins in the mountain ranges to the west of
Roanoke and flows in a southeasterly direction before depositing its
flow into Albemarle Sound. Most of the City of Roanoke is safe from
flood danger, although a portion of the central business district is
occasionally flooded.
The strata underlying Roanoke is composed primarily of shale, sand-
stone and limestone rocks. Steep slopes occur widely throughout the
valley with about 20 percent of the land area having slopes of 20 per-
cent or greater. Such slopes are not usable for most urban purposes.
Soils are also quite variable in their distribution since they are
strongly conditioned by the bedrock and slope. Water that penetrates
the ground surface percolates through the soil to the impervious layers
of rock below. The water then proceeds along the rock layers until it
comes to a rock outcrop on the surface, or percolates deeper into the
ground through crevices, thus adding to the water table, or generally
flows toward streams and rivers. In predominantly limestone areas
in the valley, the movement of the water underground has eroded sub-
surface channels over a period of time and in some cases large under-
ground rivers and streams have resulted from this movement.
11
-------
The quantity of runoff from a rainfall event is generally related to an
area's land use. The following tabulation shows the land use distribution
within suburban Roanoke and the City of Roanoke.
LAND USE DISTRUIBUTION (3)
Suburban Roanoke
City
Area,
Land Use Classification acres
Residential 14,346
Commercial and
Institutional 2,854
Industrial 1,300
Public 12,628
Transportion 8,458
Total Developed 39,586
Vacant Land 91,802
Total 131,388
Percent
of
Developed
Land
36
7
3
33
21
Percent
of
Area, Developed
acres Land
100
5,483
820
717
1,391
3.051
11,462
5.294
16,756
48
7
6
12
27
100
From the land use table, the areas having medium to high coefficients
of runoff constitute approximately 31 percent of suburban Roanoke's
total developed land area and 40 percent of the City's. Those areas
having medium to low coefficients of runoff constitute about 69 per-
cent of the suburb's total developed land and 60 percent of the City's.
The existing sewerage system was constructed over a period of many
years and in many instances predates the keeping of accurate records.
Up until 1951 the system was comprised of numerous trunk mains
leading from the sewage collection systems and discharging directly into
the Roanoke River, which flows west to east, and Tinker Creek, which
flows north to south. The interceptor system was built in 1951 and con-
veys the wastes to the Water Pollution Control Plant constructed near
the east corporate limits on the Roanoke River.
12
-------
The present system of interceptors and trunk sewers contains approxi-
mately 40 miles of pipeline and serves not only the City of Roanoke,
but also the City of Salem and suburban areas in adjacent Roanoke
County. The system is separated from the storm, sewers except for a
very small area of combined aewers near the business district of
Roanoke. A general layout of the existing interceptor and trunk sewer a
is shown on Plate 1 .
The scope of this study provided that only 25 percent of the City's
sanitary sewer system would be investigated and the results would be
extrapolated to include the entire City sanitary sewer system. Three
separate drainage areas were selected as being representative of the
entire City's system. The areas selected had the following similar
characteristics.
1. A major trunk or interceptor sewer
2. Area drained by a well defined stream
3. A well defined boundary with the sanitary sewered portion
of the area lying completely within the City
The following is a discussion of the characteristics of the study areas
relative to land development, storm surface runoff, storm water infil-
tration into the sanitary sewers and general condition of the interceptor
and collector system.
MURRAY RUN
The Murray Run stream drainage area is an 1818-acre tract of land
lying partly in the City of Roanoke and partly in Roanoke County. The
sewered portion within the City contains 909 acres. Plate 1 shows a
layout of the Murray Run interceptor in relation to the City's entire
interceptor system. There are approximately 95,000 feet of sewer,
ranging in size from 6- to 15-inch, serving about 6000 persons. The
remaining 909 acres in the County are without sewers at present;
however, there are plans to extend lines beyond the City Limits in the
near future.
13
-------
The portion of the stream drainage area in the County is very similar
to its sewered counterpart in the City except it is presently not as
densely developed. Contained within its boundaries at present are a
golf course, a school, medium to high priced single family dwellings
and scattered small commercial establishments. A large shopping
center is scheduled to be completed in the near future.
Land use in the sanitary sewered portion of the Murray Run study area,
as shown on Plate 2, is summarized as follows:
Land Use Area, acres
Residential 635
Commercial 38
Industrial 0
Office and Institutional 32
Open Area 204
Total 909
Residential use, comprising 70 percent of the sewered portion of the
study area, is predominantly single family dwellings ranging in age
from new to 30 years and in value from $20,000 to $80,000. The
houses are generally brick or frame and in good to excellent condition.
With the exception of one large regional shopping center, the com-
mercial land use in the sewered area consists of small business estab-
lishments scattered along the major streets. Commercial use com-
prises approximately 4 percent of the total sewered area.
There are four schools within the sewered area, three elementary and
a large high school. These schools account for the major portion of
office and institutional land use. Three large parks, containing a total
of 204 acres, are the only large open areas.
The top cover of the three parks consists primarily of woods, light
underbrush and grass. The only paved areas in the parks are tennis
courts and some parking areas. A breakdown of top cover characteristics
of the sanitary sewered portion of Murray Run is as follows:
14
-------
Top Cover Area, acres
Roof Area 59
Street and Parking Area 87
Wooded Area 242
Open and Grassed Area 521
Total 909
24TH STREET
The 24th Street stream and sewer drainage areas lie wholly within, the
corporate limits. The 24th Street interceptor and its relation to the
City's entire interceptor system are shown on Plate 1. The study area
contains approximately 93,000 feet of interceptor and collector sewer
ranging in size from 6- to 15-inch.
The area is basically urban, containing a land use mixture of residential,
commercial, industrial, office and institutional and open areas. Its
present population is approximately 10,000 persons. Development of
the 1034-acre area commenced around 1900 and has progressed until
there is presently very little developable land remaining. The overall
density of the present development is approximately 1.1 buildings per
acre.
The land use in the 24th Street study area as shown on Plate 2, is
summarized as follows:
Land Use
Re sidential
Commercial
Industrial
Office and Institutional
Open Area
Total
15
-------
With the exception of one public housing development, which occupies
approximately 3 acres, the residential use is primarily single family
dwellings. The majority of the dwellings are in fair to good condition
and range in value from $10,000 to $30,000. These dwellings, both
brick and frame, were built from about 1910 to the present. A few
older homes in one portion are in poor condition and are of little value.
The commercial development is generally single story, light construction
type.
The industrial land use consists primarily of light manufacturing estab-
lishments. These businesses are concentrated near the railroad in the
southern portion of the study area.
Three schools account for nearly all of the 14 acres of office and
institutional land use. A 124-acre country club and an 87-acre cemetery
constitute a portion of the grassed land.
The top cover characteristics of the 24th Street study area are as
follows:
Top Cover Area, acres
Roof Area 65
Street and Parking Area 112
Wooded Area 0
Open and Grassed Area 857
Total 1034
TROUT RUN
The Trout Run study area is a 997-acre tract of land lying wholly with-
in the boundaries of the City of Roanoke. Plate 1 shows a layout of the
Trout Run interceptor in relation to the City's entire interceptor system.
The 160,000 feet of sewer line ranges in size from 4- to 12-inch and
serves approximately 11,000 persons. The area is completely developed
in a manner typical of the older urban areas throughout the United States.
The streets form a grid pattern with each block containing approximately
3 acres of land. The development is dense, approximately 3 buildings
16
-------
per acre of land, and is a mixture of small industrial buildings, com-
mercial establishments, offices, schools and houses.
The development of the area began around 1900 and has continued to
the present. Many of the older buildings have not been maintained ade-
quately and are in a dilapidated condition.
The land use in the Trout Run study area, as shown on Plate 1, is
summarized as follows:
Land Use Area, acres
Residential 589
Commercial 67
Industrial 260
Office and Institutional 18
Open Area 63
Total 997
With the exception of some industrial land use which is concentrated in
the southern portion of the area along the railroad, the above uses are
found scattered throughout the area.
Residential use, comprising about 59 percent of the total area, is
predominantly single family dwelling units. Approximately half of the
dwellings are old and in very poor condition. These are typically one
and two story frame, closely spaced, ranging in value from $1,000 to
$7,500. The remaining 50 percent of the dwellings are in better
condition and are a mixture of brick and frame, ranging in value from
$6,000 to $15,000.
The commercial land use in the area is varied, ranging from small
neighborhood service stations and grocery stores to large wholesale
distributors. It comprises slightly less than 7 percent of the entire
study area.
17
-------
The 260 acres of land devoted to industrial use constitutes approxi-
mately 26 percent of the total drainage area. Included in the 260 acres
are 122 acres of railroad right-of-way. The remaining 138 acres are
devoted to a variety of light industrial uses such as bakeries, bottling
works and equipment fabrication.
Four schools in the area occupy the major portion of the 18 acres of
office and institutional land in the area. The only large open areas in the
study area are two parks, Eureka and Melrose. The parks, together
with vacant lots scattered throughout the area, account for 63 acres of
open land.
The streets are paved and some have curb and gutter. A breakdown of
top cover characteristics by acreage is as follows:
Top Cover Area, acres
Roof Area 135
Street and Parking Area 160
Wooded Area 0
Open and Grass Area 580
Railroad 122
Total 997
18
-------
WATER PC>UUTION
CONTROt' PtjANT'
^0
Vt^01JT RUN
\STUDY AREA
MURRAY RUN
ST4JDY AREA
24TH STREET
STUDY AREA
LEGEND
I ^ STUDY AREAS
MURRAY RUN STREAM DRAINAGE
ilftlll AREA (NOT SEWERED)
COMBINATION STORM DRAIN & SEWER
TRUNK SEWER OR INTERCEPTOR
— ——— LIMITS OF DRAINAGE AREAS
STUDY AREAS
CITY OF
ROANOKE, VIRGINIA
SCALE IN FEET
1000
PLATE i
3000
-------
Previous Page Blank
IV
TROUT RUN
STUDY AREA
24TH STREET
STUDY AREA
r-.-M
yisSiit^j
MURRAY RUN
STUDY AREA
LEGEND
RESIDENTIAL
INDUSTRIAL OR BUSINESS
PARKS OR RECREATION
SCHOOLS
VACANT OR UNDEVELOPED
LAND USE
IN STUDY AREAS
SCALE IN FEET
1000
PLATE 2
3000
-------
Previous Page Blank
SECTION 4
RESULTS OF INVESTIGATION
FIELD INVESTIGATION
The field investigation, undertaken in each of the three study areas to
assess the condition of the sanitary sewers and to locate sources of
storm water infiltration, consisted of smoke testing the entire sanitary
sewer system, photographic inspection of clogged lines, a manhole
cover survey and various field observations.
The technique of smoke testing was used to locate points for surface
water entry into the sanitary sewers and to locate cross-connections
between storm water drains and the sanitary sewer system. The smoke
testing was conducted by the City of Roanoke under the supervision of
Hayes, Seay, Mattern and Matfcern. The manhole cover survey was
undertaken to locate manholes with perforated covers in low lying areas
which, when flooded, could be expected to act as storm water inlets to
sanitary sewers.
A total of 509 points of entry of storm, water infiltration were located
in the three study areas as a result of the manhole cover survey and
smoke testing. A breakdown of these entry points is given by type and
drainage area in Table 1. The table shows that a major portion of the
entry points are simply leaks in the sanitary sewer system. The vast
majority of the leaks detected were in collector sewers and house
laterals. Nine of the leaks, three in the Murray Run study area and
six in the 24th Street study area, were observed to be exposed to
stream flow during periods of wet weather and some during dry
weather flow. These leaks can be expected to be major contributors of
storm water infiltration. A leak of this type, discovered in the 24th
Street study area, is shown in Figure 1.
The smoke testing revealed only 33 cross-connections between storm
water drains and the sanitary sewers, 27 of which were in the Trout
Run study area. All of these were roof drains connected directly to
sanitary collector sewers. Smoke was observed emitting from 58 curb
inlets which were initially thought to be directly connected to the sani-
tary sewer system. Further investigation, however, revealed that none
of the inlets were directly connected to the sanitary sewers. It was
determined that the smoke reached the inlets by filtering from leaks in
the sanitary sewers into cracks in the nearby storm, sewer, and sub-
sequently into the curb inlets.
23
-------
PhotographicjLnspection of the Murray Run interceptor sewer revealed
that root masses had penetrated the pipe joints and formed large obstruc-
tions in the line as shown in Figures 2 and 3 . The roots severely limit
the capacity of the line to carry flows in excess of normal dry weather
sewage flow. These root conditions were not observed to exist in the
Trout Run and 24th Street interceptor lines. It was found, however,
that peak dry weather flow periodically exceeds the capacity of the
Trout Run interceptor and overflows into the stream, as shown in
Figure 4.
TABLE 1
TABULATION OF POINTS OF ENTRY
OF STORM WATER INFILTRATION
Study Area
Murray Trout 24th
Type of Entry Point Run Run Street
Leaks in Sanitary Sewer Exposed
To Surface Runoff 111 201 63
Leaks in Sanitary Sewer Exposed
To Stream Flow 306
Leaky Manholes 3 00
Roof Drains Connected To
Sanitary Sewer 5 27 1
Manholes with Perforated Covers In
Areas Subject to Ponding 27 45 17
Totals 149 273 87
24
-------
Figure 1. Open Joint of Pipe in
24th Street Interceptor
Figure 2. Roots in Murray
Run Interceptor
25
-------
Figure 3 . Roots in Murray
Run Interceptor
Figure 4. Overflow in Trout
Run Study Area
26
-------
RAINFALL INVESTIGATION
Rainfalls were measured in each of the three study areas during the
study period 6 February 1969 through 5 August 1969 by means of rain
gauges installed at locations shown on Plates 3 through 5. The gauge
shown in Figure 5, installed in the Murray Run study area, was a re-
cording type gauge which provided graphs of accumulated rainfall versus
time. The gauges in the Trout Run and 24th Street areas were the non-
recording type, useful only in recording the total amount of rainfall.
Figure 5. Recording Rain Gauge
in Murray Run Study Area
A tabulation of the characteristics of the major rainfall events is given
in Table 2. A plot of the relationship between rainfall intensity and
time is shown for these storms in Figures 34 through 88 in Appendix VI.
GAUGING STREAMS AND SEWERS
Flows in the streams and the sanitary sewer interceptors were gauged
in each of the three study areas during each major rainfall event and
during dry weather. The gauging techniques employed were selected to
be compatible with the physical characteristics of the streams and
sewers. Water level recorders, where used, were calibrated to record
depth of flow. A limited number of water level recorders precluded
27
-------
the measurements of all streams and sewers during all rainfall events .
Recorders were relocated periodically between study areas and the
Water Pollution Control Plant.
MURRAY RUN STUDY AREA
The gauging technique employed in the Murray Run stream involved
continuous recording of the depth of flow in the stream along a section
where the slope of the stream bed was constant and the flow was uniform.
The depth of flow was monitored by a continuous water level recorder
installed above a stilling basin as shown in Figure 6. The installation
was located in the lower reaches of the study area as shown on Plate 5.
A stage-discharge curve was developed from the Manning Formula using
the measured hydraulic characteristics of the stream. The stage-
discharge curve was then used to estimate stream flow based on depth
measurements. This curve is included in Appendix VI as Figure 95.
The gauging technique used in the Murray Run sanitary sewer inter-
ceptor was basically the same as that used in the stream. Due to the
root masses, the hydraulic characteristics of the sewer when flowing
over 1/2 full could not be determined so that gauged flows could not be
correlated with calculated flows. A weir was installed to permit
overflows to be gauged after the sewer became surcharged. The sewer
was essentially surcharged when the depth of flow reach 0.6 foot. Thus,
the gauge recorded all flows up to this depth and all overflows over
the weir.
TROUT RUN STUDY AREA
The gauging installation used in the Trout Run stream, shown on Figure
8, consisted of a water level recorder which monitored the depth of
flow above a sharp-crested weir. The location of the recorder within
the study area is shown on Plate 3. The stage discharge curve used to
convert the measurements of depth above the weir to stream flows is
included as Figure 96 in Appendix VI.
A water level recorder was installed as shown in Figure 9 to monitor
the depth of flow in the Trout Run interceptor sewer. A stage-discharge
curve based on the Manning Formula and the measured hydraulic char-
acteristics of the sewer were used to convert the depth measurements to
flow estimates. The stage-discharge curve is included as Figure 99
in Appendix VI.
28
-------
^T—FV,, *—~. —T^*"* *^*- ' tff ft—.-.
NON-RECORDING RAIN GAUGE
SEWER LEVEL RECORDER
STREAM LEVEL RECORDER
TRUNK SEWER OR INTERCEPTOR
LIMITS OF STUDY AREA
TROUT RUN
STUDY AREA
SCALE IN FEET
1000
PLATE 3
3000
-------
Previous Page Blank
BW
'/^•TVb-Jr'Ss'L It
^^L^/^Jr^L 7/=s
^/^^4^/Va
iHAlLSDAn
LEGEND
NON-RECORDING RAIN GAUGE
A SEWER LEVEL RECORDER
• STREAM LEVEL RECORDER
—TRUNK SEWER OR INTERCEPTOR
— LIMITS OF STUDY AREA
2HTH STREET
STUDY AREA
SCALE IN FEET
1000
PLATE 4
3000
31
-------
Previous Page Blank
c*7MtMpMS/^-^
v,« C"
r_*-f^-\IQ r u rj«-^^»r r1 \ i*
r% 5
-v - "-°"
nc
|1C^*^C»NjW^oXa v'
Si! .u^lttiSsi^t ,.*5<8#*o»\ \ ^^v*& >SN^-\ ^-w y^
\ ^7 if^«w*o%D\5>r >x;^4?Aw5
I
LEGEND
RECORDING RAIN GAUGE
SEWEft LEVEL RECORDER
STREAM LEVEL RECORDER
— TRUNK SEWER OR INTERCEPTOR
... LIMITS OF STUDY AREA
HURRAY RUN
STUDY AREA
JB»"»
-" \
1000
PLATE 5
3000
-------
Previous Page Blank
TABLE 2
RAINFALL SUMMARY
Murray Run
Rainfall
Eve at
6 Feb
8 Feb
24 Mar
24 Mar
18, 19 May
8, 9 June
9 Jane
14 June
15 June
21 June
1 , 2 July
2 July
12 July
19 July
22, 23 July
3 Aug
5 Aug
Average
Intensity
(in./hr.)
0.053
0.057
0.074
0.087
0.071'
0.000
1.000
0.409
0.126
0.209
0.000
0.000
0.243
0.563
0.391
0.175
0.263
Duration
(hrs.)
4.5
2.8
14.0
4.8
9.8
0.0
0.1
2.3
5.8
2.2
0.0
0.0
0.7
0.8
1.1
2.0
1.9
Total
Rainfall
(inches)
0.24
0.16
1.03
0.42
0.70
0.00
0.10
0.94
0.73
0.46
0.00
0.00
0.17
0.45
0.43
0.35
0.50
Trout Run
Average
Intensity
(in./hr.)
0.053
0.057
0.074
0.088
0.071
0.203
0.413
0.000
0.076
0.628
0.307
0.253
0.514
0.625
*
0.015
0.289
Duration
(hrs.)
4.5
2.8
14.0
4.8
9.8
3.0
0.8
0.0
6,6
3,6
1.3
1.3
0.7
0.8
*
4.5
1.9
Total
Rainfall
(inches)
0.24
0.16
1.03 •
0.42
0.70
0.61
0.33
0.00
0.50
2.26
0.40
0.33
0.36
0.50
0.79
0.70
0.55
24th Street
Average
Intensity
(in./hr.)
0.053
0.057
0.074
0.088
0.071
0.203
0.413
0.000
0.076
0.628
0.231
0.231
0.514
0.625
*
0.015
0.289
Duration
(hrs.)
4.5
2.8
14 ;o
4.8
9-8
3.0
0.8
0.0
6.6
3.6
1.3
1.3
0.7
0.8
*
4.5
1.9
Total
Rainfall
(inches)
0.24
0.16
1.03
0.42
0.70
0.61
0.33
0.00
0.50
2.26
0.30
0.30
0.36
0.50
0.70
0.70
0.55
Woodrum Field
Average
Intensity
(in./hr.)
0.034
0.060
0.064
0.061
0.051
0.200
0.165
0.000
0.071
0.565
0.440
0.140
0.180
0.000
0,100
0.122
0.000
Duration
(hrs.)
7.0
9.0
14.0
7.0
14.0
3.0
2.0
0,0
7,0
4.0
2.0
1.0
2.0
0.0
2.0
6.0
0.0
Total
Rainfall
(inches)
0.24
0.54
0.89
0.43
0.71
0.60
0.33
0.00
0.50
2.26
0.88
0.14
0.36
0.00
0.20
0.73
0.00
*Duration and intensity unknown
Non-recording rain gauges were used in Trout Run and 24th Street study areas,
The Woodrum Field data are from official U. S. Weather Bureau records.
Intensity is computed average for the recorded rainfall period.
-------
E4TH STREET STUDY AREA
The gauging station for the 24th Street stream consisted of a sharp-
crested weir and a water level recorder. The station is shown in
Figure 10, and the stage-discharge curve used to convert the depth re-
cordings to stream flows is given in Figure 97 in Appendix VI.
A water level recorder was installed above a manhole to gauge the
depth of flow in the 24th Street sanitary sewer interceptor. The instal-
lation is shown in Figure 11, and the stage-discharge curve for the
sewer is given in Figure 100 in Appendix VI.
STORM SURFACE RUNOFF
Flows were gauged in one or more of the three streams during 15 sepa-
rate rainfall events. Stream hydrographs were plotted for each re-
corded flow and are included in Figures 34 through 55 in Appendix VI.
A sample hydrograph and rainfall intensity curve for Murray Run is
shown on Figure 12. Surface runoff was calculated from these hydro-
graphs for each rainfall event for which stream flow recordings were
obtained. Table 3 shows storm surface runoff in terms of inches over
the entire drainage area and in terms of gallons per acre. The ratio
of total runoff to total rainfall for all monitored rainfall events are as
follows:
- Murray Run - 0.10
- Trout Run - 0.16
- 24th Street - 0.12
Figures 13, 14 and 15 depict, graphically, the relationship between rain-
fall and surface runoff as measured in the three study areas during the
study period.
36
-------
Figure 6, Water Level Recorder
Murray Run Stream
Figure 7. Water Level Recorder
Murray Run Sanitary Sewer
37
-------
.« I »
Figure 8. Water Level Recorder and Automatic
Sampler - Trout Run Stream
I15|llB|
IJ^PUi ;*» «ww* ^Bi^^^w
^^
' • l(« '-<•"'?*, .,-- , '-w> «> . ,,-"'«'- "i"'^ ''
Figure 9. Water Level Recorder and Automatic
Sampler - Trout Run Sanitary Sewer
38
-------
Figure 10. Water Level Recorder -
24th Street Stream
Figure 11. Water Level Recorder
24th Street Sanitary Sewer
39
-------
FIGURE 12 SAMPLE HYDRQGRAPH
RAINFALL INTENSITY AND RATE OF DISCHARGE
MURRAY RUN STREAM
I i i
19 JULY 1969
30
"O
01
e
2
3
20
LEGEND
- DRY WEATHER FLOW
FLOW DURING RAINFALL
23 SURFACE RUNOFF
4PM
6PM
8PM 10PM
TIME, hrs.
I2N
2AM
40
-------
TABLE 3
STORM SURFACE RUNOFF
Rainfall
Event
6 Feb
8 Feb
24 Mar
24, 25 Mar
18, 19 May
8, 9 June
9 June
15 June
21 June
1 , 2 July
2 July
12 July
19 July
22, 23 July
3 Aug
Rainfall
(inches)
0.24
0.16
1.03
0.42
0.70
0.00
0.10
0.73
0.46
0.00
. 0.00
0.17
0.45
0.43
0.35
Murray Run
Runoff
(inches)
0.020
0.012
0.165
*
%
*
*
*
*
*
*
0.037
*
*
Runoff
(gal./ac.)
533
336
4483
*
*
$
*
*
*
*
*
1007
*
*
Rainfall
(inches)
0.24
0.16
1.03
0.42
0.70
0.61
0.33
0.50
2.26
0.40
0.33
0.36
0.50
0.79
0.70
Trout Run
Runoff
(inches)
0.021
0.026
0.343
0.102
0.067
0.038
0.116
0.374
0.085
0.068
0.039
0.080
0.048
0.104
Runoff
(gal./ac.)
582
712
9303
2758
1836
1043
3159
10,150
2317
1836
1063
2207
1334
2831
Rainfall
(inches)
0.24
0.16
1.03
0.42
0.70
0.61
0.33
0.50
2.26
0.30
0.30
0.36
0.50
0.70
0.70
24th Street
Runoff
(inches)
0.009
0.022
0.189
*
*
*
*
j>
"f
*
*
*
*
*
*
Runoff
(gal./ac.]
242
590
5135
*
*
*
Ki«
*
*
*
*
*
*
*
*Strearn flow not recorded
-------
FIGURE 13 RELATIONSHIP OF SURFACE RUNOFF TO RAINFALL
MURRAY RUN STREAM
10
-------
FIGURE 11* RELATIONSHIP OF SURFACE RUNOFF TO RAINFALL
24t h STREET STREAM
10
u
<0
CO
01
£32
®
0.5
I .0
RAINFALL
1.5
i nchei
2.0
2.5
43
-------
FIGURE 15 RELATIONSHIP OF SURFACE RUNOFF TO RAINFALL
TROUT RUN STREAM
10
09
k.
u
(0
6
a
©
0.5 I 1.5
RAINFALL - inches
©
2.5
44
-------
STORM WATER INFILTRATION
Depths of flow were gauged in one or more sanitary sewer interceptors
during sixteen rainfall events. The results of the gauging were used to
plot sewer hydrographs, such as the one shown on Figure 16. The
hydrographs are Included as Figures 56 through 88 in Appendix VI.
The area of the shaded portion of the hydro graph represents storm
water infiltration. The volume of storm water infiltration in the sewers
was determined using the hydrographs and is summarized in Table 4.
The hydrographs indicate that the Murray Run and Trout Run inter-
ceptors were surcharged during many of the storms. Flows under sur-
charge conditions were not measured; therefore, the amounts of infil-
tration were not measured during these events and volumes are not
listed in Table 4.
Overflows that did occur were generally spread out over the entire in-
terceptor line. Except in a few isolated instances, there were no
intentional overflow pipes installed to discharge the overflow directly to
a stream.
Initially, it was assumed that the dry weather flows in the sanitary
sewer interceptors would remain relatively constant from day to day
and no attempt -was made to continually gauge the sewers during dry
weather. During the course of the study, however, it was found that
there was a significant change in the daily dry weather flow in the
interceptors.
Figure 17 shows dry weather flows in the 24th Street interceptor re-
corded on 15 and 16 July and 29 and 30 April 1969. The flows are com-
parable in the respect that both represent a period beginning 12 noon on
Tuesday and ending 12 noon on Wednesday. The shaded portion of the
graph denotes the amount of variation in dry weather flow during the
selected periods. It was observed that dry weather flow is dependent
upon the rainfall conditions during the period preceding its recording.
This can be illustrated by the fact that 4.8 inches of rainfall were re-
corded during the 30-day period preceding the date of the higher flow
shown by Figure 17, while only 1.4 inches were recorded during a
similar period preceding the date of the lower flow. A plausible ex-
planation for the variation in the dry weather flow seems to be that the
amount of ground water infiltration varies according to the antecedent
rainfalls.
45
-------
FIGURE 16 SAMPLE HYDROGRAPH
RAINFALL INTENSITY AND RATE OF DISCHARGE
24th STREET SANITARY SEWER
2.5
2.0
I .5
T3
CT1
E
.0
0.5
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
m& INFILTRATION
c
2 -
8, 9 JUNE I969
.5
.6
0
9PM
I I PM
AM 3AM
TIME, hrs.
5AM
TAM
46
-------
TABLE 4
STORM WATER INFILTRATION IN SANITARY SEWERS
Rainfall
Event
6 Feb
8 Feb
24 Mar
24, 25 Mar
18, 19 May
8, 9 June
9 June
14 June
15 June
21 June
1 , 2 July
2 July
12 July
19 July
22, 23 July
3 Aug
Murray
Rainfall
(inches)
0.24
0.16
1.03
0.42
0.70
0.00
0.10
0.94
0.73
0.46
0.00
0.00
0, 17
0.45
0.43
0.35
Run Sewer
Infiltration
(gallons)
*
*
*
*
-jr»
T*
0
46,704
*
*
u*
•*T-
0
0
'(•
%
#
*
Trout
Rainfall
(inches)
0.24
0.16
1.03
0.42
0.70
0.61
0.33
0.00
0.50
2.26
0.40
0.33
0.36
0.50
0.79
0.73
Run. Sewer
Infiltration
(gallons)
No Data
No Data
No Data
No Data
62,500
12,510
18,760
0
*
*
*
*
*
*
*
*
24th
Rainfall
(inches)
0.24
0.16
1.03
0.42
0.70
0.61
0.33
0.00
0.50
2.26
0.30
0.30
0.36
0.50
0.70
0.73
Street Sewer
Infiltration
(gallons)
31,200
35,400
256,000
No Data
293,000
126,000
46,700
0
41,700
62,500
182,000
192,000
84,200
No Data
No Data
No Data
*Sewer surcharged
-------
00
1.0
p
FIGURE 17 ,DRY WEATHER FLOW COMPARISON - 21TH STREET SANITARY SEWER
15,16- JULY 1969
29,30, APRIL 1969
.8
.6
2N
I2MT
TiME-hrs.
2N
-------
From the time that this variation was discovered, dry weather flows
were monitored constantly in the interceptor sewers. This provided a
reasonably accurate means of determining the portion of the total flow
during rainfall that could be attributed entirely to storm water infil-
tration. The dry weather flows shown on Figures 56 through 88 in
Appendix VI are flows recorded on days immediately preceding the rain-
fall event so that the shaded areas represent as nearly as possible the
actual amount of storm water infiltration and include no ground water
infiltration.
WATER QUALITY
Stream and sewage samples were taken in each of the three study areas
and analyzed to determine the characteristics of the flow during rain-
fall and during dry weather. The samples were taken as nearly as
possible to the location of the gauging installations, shown on Plates
3 through 5, to facilitate correlation of sampling characteristics and
flow measurements.
Samples were taken systematically during rainfall and identified by a
number, date, time, and place. The samples were obtained both manu-
ally aoid by automatic samplers. Samples were taken during three
rainfalls in the Murray Run and 24th Street study areas and during five
rainfalls in the Trout Run study area. The samples were tested for
BOD, total solids, total volatile solids, suspended solids, suspended
solids volatile, settleable solids and total coliform. The results of the
stream and sewage sampling in the study areas are given in Tables 51
through 56 in Appendix VI.
Twenty four hour composite samples were taken and tested to deter-
mine the dry weather stream and sewage characteristics. These re-
sults are given in Tables 59 and 60 in Appendix VI.
The sampling results were correlated with flow measurements and used
to compute the total pounds of pollutants reaching the streams from sur-
face runoff and from sanitary sewage overflows. This information is
given in Tables 5 through 7. The 24th Street sanitary sewer interceptor
did not surcharge; therefore, it is assumed that the increase in pollutants
in the stream over that normally present during dry weather is en-
tirely the result of surface runoff.
49
-------
(J\
o
TABLE 5
STREAM POLLUTION FROM SURFACE RUNOFF AND SANITARY SEWER OVERFLOWS
TROUT RUN
Date of
Event
6 Feb 1969
8 Feb 1969
24 Mar 1969
22/23 July 1969
3 August 1969
Rainfall
(in.)
0.24
0.16
1.00
0.79
0.70
BOD
(Iba.)
73
83
410
316
280
Total Solids
(Ibs . )
1441
4035
15,284
16,358
15,068
Volatile
Solids
(Iba.)
900
1128
5773
3510
4509
Suspended
Solids
(Ibs.)
620
1027
3296
2103
1836
Volatile
Suspended
Solids (Ibs.)
103
262
1411
472
526
-------
TABLE 6
STREAM POLLUTION FROM SURFACE RUNOFF*
24TH STREET
Rainfall BOD Total Solids
Date (in.) (Ibs.) (Ibs.)
6 Feb
8 Feb
24 Mar
1969 0.24 37 895
1969 0.16 202 3393
1969 1.00 148 8361
Volatile Suspended Volatile
Solids Solids Suspended
(Ibs.) (Ibs.) Solids (Ibs.)
145 235 38
1330 603 285
2502 1250 353
#The interceptor did not surcharge during the sampling period; the results reflect
pollution from storm surface runoff only.
-------
TABLE 7
STREAM POLLUTION FROM SURFACE RUNOFF AND SANITARY SEWER OVERFLOWS
MURRAY RUN
6
8
Date
Feb 1969
Feb 1969
24 Mar 1969
Rainfall
(in.)
0.24
0.16
1.00
BOD
(Ibs . )
200
0
329
Total Solids
aba.)
7982
966
12,552
Volatile
Solids
(Ibs.)
2154
409
3122
Suspended
Solids
(Ibs.)
1644
0
318
Volatile
Suspended
Solids (Ibs.)
722
0
155
-------
WATER POLLUTION CONTROL PLANT
GAUGING
The gauging technique used at the Water Pollution Control Plant was
similar to that employed in the study areas, except the gauging at the
plant was used to monitor the flow in the overflow pipe located in the wet
well intake structure just outside the main building. A more detailed
description of the method of gauging is given in Appendix'III.
Figure 18. Water Level Recorder - Water
Pollution Control Plant
Table 8 summarizes the data from the gauging of the overflow at the
Water Pollution Control Plant.
Reference should be made to Appendix VI, Figures 89 through 94 and
Figure 101, for graphs showing discharge of the overflow versus time
and a stage discharge curve for the plant overflow pipe.
53
-------
TABLE 8
OVERFLOWS AT THE
WATER POLLUTION CONTROL PLANT
Date of
Event
24 Mar 1969
21 Jun 1969
19 Jul 1969
22, 23 Jul 1969
3 Aug 1969
5 Aug 1969
Total
Rainfall
(in.)
1.00
1.25
0.50
0.60
0.50
0.50
Duration
(hrs.)
10.0*
3.5
0.8
1.6
4.5
1.9
Average
Intensity
(in./hr.)
0.10
0.36
0.63
0.37
0.11
0.26
Total
Overflow
(mg)
2.8
2.9
0.6
0.7
.04
.02
^Duration reduced to 10 hours because the event exceeded overflow at
the plant.
OVERFLOW QUALITY
Samples of the plant influent were obtained manually by taking grab
samples in the comminutor room. Automatic samplers were initially
installed but were ineffective because of blockage in the nozzle openings
due to solids, A more detailed description of the sampling technique
is given in Appendix IV.
Table 9 shows the results of sampling during overflow caused by the
rainfall on 23 July 1969. Complete analysis of the sampling is given
in Tables 57 and 58, in Appendix VI.
54
-------
TABLE 9
CONTRIBUTION FROM TYPICAL OVERFLOW FROM
WATER POLLUTION CONTROL PLANT
22/23 JULY 1969 EVENT
Total Suspended
Total Total Volatile Suspended Solids
Rainfall Overflow BOD Solids Solids Solids Volatile
(in.) (nag) (Ibs.) (Ibs.) (Ibs.) (Ibs.) (Ibs.)
0.60
0.7
1192 4892
2672
648
312
Tables 10 and 11 show average waste water characteristics at the plant
overflow and sampling characteristics at an upstream manhole in the
Roanoke River Interceptor during the 22/23 July 1969 event. This data
indicates that the concentrations of pollutants in the overflow at the plant
are about twice that of the incoming sewage just upstream from the
plant. A check of the plant piping arrangement revealed that digester
supernatant and sludge thickner effluent were returned to the overflow
manhole and mixed with incoming raw sewage, thus increasing the
concentration of the mixture. During overflows this more concentrated
mixture is flushed into the Roanoke River.
55
-------
TABLE 10
WASTE WATER OVERFLOW CHARACTERISTICS
WATER POLLUTION CONTROL PLANT
22/23 JULY 1969 EVENT
Total
Over-
flow
Rate BOD
(mgd) (mg./l.)
6.5 239
Total
Solids
(mg./l.)
567
Total Suspended
Volatile Suspended Solids Setteable
Solids Solids Volatile Solids
(mg./l.)
-------
SECTION 5
EVALUATION OF RESULTS
FIELD INVESTIGATION
One of the objectives of this study was to establish a relationship be-
tween the topographic, physical, and socio-economic characteristics of
the study areas and the quantities of storm water infiltration measured
in the sanitary sewer interceptors. This was to be accomplished by
comparing the relative quantities of storm water infiltration in the three
study areas with the differing characteristics of the three areas. The
lack of a suitable method of measuring surcharge flows and overflows in
the sanitary sewer interceptors handicapped efforts to make such a com-
parison. Both the Murray Run and Trout Run interceptors became sur-
charged under very low intensity rainfall conditions, and infiltration was
not measured in these sewers for the vast majority of the rainfall events
during the study period. Only during three rainfall events was it possi-
ble to gauge flows in two or more of the three interceptors. Table 12
gives the amount of storm water infiltration and the ratio of infiltration
to rainfall for these three events. When the infiltration values are com-
pared with the various study area characteristics, given in Table 13, no
logical relationship between infiltration and the study area characteris-
tics is apparent.
Although these results show no logical relationship between study area
characteristics and storm water infiltration, the findings are by no
means conclusive. In fact, it is entirely possible that the method of
measuring storm water infiltration in the Trout Run and Murray Run
sewers was not sufficiently accurate to establish such a relationship.
As explained in Section 4 - Results of Investigation, the total storm
water infiltration in a study area for a particular rainfall was derived
from the shaded portion of the hydrograph of the sewer. An example
hydrograph Ls given in Figure 16. This is an accurate measure of in-
filtration if the sewer does not surcharge and/or overflow upstream
from the gauging installation. When overflow does occur upstream,
however, the amount of infiltration measured at the gauging installation
is less than the actual amount of infiltration.
An upstream overflow is likely to occur when the capacity of the sewer
line immediately upstream from the gauge is significantly less than the
line capacity at the gauge. This condition of a reduced line capacity im-
mediately upstream from the gauge exists in both the Murray Run and
57
-------
TABLE 12
COMPARISON OF INFILTRATION TO RAINFALL
IN THE THREE STUDY AREAS
Murray Run
Rainfall
Event
Infil.
(gal.)
00 18, 19 May *
8
9
, 9 June
June
0
46,700
Rainfall
(in.)
0.70
0
0.10
Infil./
Rainfall Infil .
(gal. /in.) (gal.)
62,500
12,510
467,000 18,760
Trout Run
24th Street
Infil./
Rainfall
(in.)
0.70
0.61
0.33
Rainfall
(gal
89,
20,
57,
./in.)
000
100
000
Infil.
(gal.)
293,000
126,000
46,700
Rainfall
(in.)
0.70
0.61
0.33
Infil./
Rainfall
(gal.
419
206
142
/in.)
,000
,000
,000
*Sewer surcharged
-------
TABLE 13
STUDY AREA CHARACTERISTICS
Drainage
Area
.£> Murray-
Run
Trout
Run
24th
Street
Area
(acres)
909
997
1034
Estimated
Average
Age Of
Buildings
(years)
15
35
25
Length of
Sewer
Line
(ft.)
95,000
60,000
93,000
Length of
Paved
Street
(ft.)
97,000
172,200
104,600
Develop.
Density
(buildings/
acre)
1
3
1
Number Of
Storm
Water Entry
Points
149
273
87
Popu-
lation
6,000
11,000
io.ooo
Estimated
Average
Value Of
Dwellings
$35,000
$ 5,000
$15,000
-------
Trout Run study areas; gauges were located to monitor the entire study
area and to permit monitoring of low-intensity rainfall events. Although
no upstream overflows were actually observed in these areas during the
rainfall events listed in Table 12, unobserved overflows are a distinct
possibility. In the 24th Street interceptor, the gauge is located such
that the line capacity upstream was greater than at the gauge for a dis-
tance of approximately 3500 feet; thus, the possibility of an upstream
overflow is extremely remote. The infiltration values listed in Table
4 and 12 for the 24th Street study area are, therefore, considered to be
a true measure of the total amount of storm water infiltration from the
entire study area.
STREAMS
DRY WEATHER CONDITIONS
The average dry weather flows in the streams in the three study areas
are approximately as follows:
- Murray Run - 4. 0 mgd
- Trout Run -1.0 mgd
- 24th Street -0.7 mgd
The average daily and annual pollutional loads in the streams, computed
from the above flows and the dry weather sampling data in Table 60 in
Appendix VI, are given in Table 14.
WET WEATHER CONDITIONS
The pollutional load in the streams is considerably increased during
rainfalls as a result of surface runoff and sanitary sewer overflows.
Table 15 gives a comparison of the relative concentrations of the pollu-
tional constituents during average wet weather and average dry weather
conditions. The wet weather concentrations are three to six times
greater than dry weather concentrations for all constituents. Since the
wet weather flows are also higher, the total pollutional load is much
greater during rainfall.
In the 24th Street study area, the increase in pollutional load in the
stream can be attributed entirely to surface runoff since there were no
sanitary sewer overflows during the rainfall events sampled. Table 16
60
-------
TABLE 14
DAILY AND ANNUAL DRY WEATHER POLLUTIONAL LOADS
IN STREAMS
Constituents (pounds)
Total
Stream
Murray
Run
Trout
Run
24th
Street
BOD
Daily Annual
(1000)
256 93
25 9
44 16
Total
Daily
8278
2345
1133
Solids
Annual
(1000)
3020
856
414
Volatile
Daily
2837
1227
736
Solids
Annual
(1000)
1036
448
269
Suspended Suspended
Solids Solids
Daily Annual Daily
(1000)
1235 451 401
142 52 67
117 43 41
Volatile
Annual
(1000)
146
25
15
-------
TABLE 15
RELATIVE CONCENTRATIONS OF POLLUTIONAL CONSTITUENTS DURING
AVERAGE WET WEATHER AND AVERAGE DRY WEATHER CONDITIONS
ro
Total
BOD
Stream
Murray
Run
Trout
Run
24th
Street
(mg.
Wet
Wea-
ther
17
18
20
/I.)
Dry
Wea-
ther
8
3
8
Solids
(mg.
Wet
Wea-
ther
623
460
514
/I.)
Dry
Wea-
ther
248
281
194
Total
Volatile
Solids
(mg.
Wet
Wea-
ther
134
139
172
/I.)
Dry
Wea-
ther
85
147
126
Suspended
Solids
(mg./l.)
Wet Dry
Wea- Wea-
ther ther
89 37
93 17
103 20
Suspended
Solids
Volatile
(mg
Wet
Wea-
ther
25
28
34
./I.)
Dry
Wea-
ther
12
8
7
Settleable
Solids
(ml.
Wet
Wea-
ther
2
3
3
/I.)
Dry
Wea-
ther
0
0
0
Flow
(mgd)
Wet
Wea-
ther
7.7
13.8
3.4
Dry
Wea-
ther
4.0
1.0
0.7
-------
gives the concentrations of the pollutional constituents of the surface
runoff in the 24th Street study area in comparison with concentrations
measured in an urban study area in Cincinnati, Ohio,
The Cincinnati study was conducted during the period July 1962 through
July 1964 on a 27-acre drainage area (4). The area was similar to the
24th Street study area in that it contained residential and light commer-
cial development. However, the density of development in the Cincinnati
area was greater than 3 buildings per acre compared with approximately
1 building per acre in the 24th Street study area, partially accounting for
the higher values in Cincinnati.
TABLE 16
COMPARISON OF CONCENTRATIONS OF POLLUTIONAL
CONSTITUENTS FROM SURFACE RUNOFF
BOD (mg./l.)
Total Solids (mg.
/I.)
Total Volatile Solids (mg. /I. )
Suspended Solids
Suspended Solids
(mg./l.)
Volatile (mg. /I. }
24th Street
Study Area
7
230
68
39
13
Cincinnati
Study Area
17
-
-
227
57
Unlike the 24th Street study area, the sanitary sewers surchared in the
Trout Run and Murray Run areas during the rainfall events in which the
streams were sampled. Sanitary sewage overflows were actually ob-
served in the Murray Run area during the 24 March rainfall and in Trout
Run during the 24 March, 22/23 July and 3 August events. No overflows
were observed in either of these two areas during the 6 February and
8 February rainfall events. The sampling data from these two events,
therefore, have been used to determine the characteristics of the sur-
face runoff from these two areas. Table 17 gives the average concen-
trations of the pollutional constituents attributed to surface runoff from
these two rainfalls. It is pointed out, however, that although no sanitary
sewage overflows were observed, the sewer lines did surcharge and
there is a possibility that sanitary sewage reached the stream from an
unobserved overflow or by exfiltration from leaks in the line.
63
-------
TABLE 17
AVERAGE CONCENTRATION OF POLLUTIONAL CONSTITUENTS
IN STREAMS
ATTRIBUTED TO SURFACE RUNOFF
Murray Run Trout Run
Study Area Study Area
BOD (mg. /I.)
Total Solids (mg. /I, )
Total Volatile Solids (mg. /I. )
Suspended Solids (mg. /I. )
Suspended Solids Volatile (mg. /I. )
26
937
212
285
83
15
510
189
153
34
Table 18 gives a comparison of the average pollutants from surface run-
off in terms of pounds per acre per inch of rainfall. The values in
Table 18, determined from sampling data on rainfall events when no
overflows were observed, were used to determine pollution attributed
entirely to surface runoff. The amounts of pollution from surface run-
off thus determined and the amount of normal dry weather flow pollution
were subtracted from the total pollution in the stream to determine the
amount of pollution from the sanitary sewer overflows. Tables 19 and
20 give a breakdown of the pollutional load in the streams during the
rainfall events sampled.
Table 20 shows that the pollutional load was increased considerably in
the Trout Run stream during the 24 March, 22/23 July and 3 August
rainfalls -when the sanitary sewer was observed to have overflowed.
Sewer overflows contributed more BOD to the stream during the 24
March and 3 August rainfalls than was contributed' by surface runoff.
SANITARY SEWERS
INFILTRATION
A primary objective of this study was to determine the frequency and
the magnitude of sanitary sewer overflows in the study areas and to
develop remedial measures aimed at decreasing both the frequency and
the magnitude of such overflows.
64
-------
TABLE 18
COMPARISON OF AVERAGE POLLU-TANTS
FROM SURFACE RUNOFF
Ul
Total Volatile Suspended Solids
Study BOD Total Solids Solids Suspended Solids Volatile
Area (Ibs ./ac./in.) (Ibs ./ac./in.) (Ibs ,/ac./in.) (Ibs ./ac./in.} (Ibs./ac./in.)
Trout
Run
Murray
Run
24th
Street
0
0
0
.39
.46
.25
13
16
8
.7 5.1 4.1
.9 4.0 5.2
.2 2.3 1.4
0.9
1.5
0.5
-------
TABLE 19
SUMMARY OF TOTAL POUNDS OF POLLUTANTS
IN MURRAY RUN STREAM
BOD (Ibs
Rainfall
Event
1969
6 Feb
8 Feb
24 Mar
DWF*
114
53
167
Sur-
face
Run-
off
326
11
538
.) Total Solids (Ibs.)
Sew-
age
Over-
flows DWF*
3650
1722
5860
Sur- Sew-
face age
Run- Over-
off flows
10,273
2046
16,220
Volatile
Volatile Solids (Ibs. 5 Suspended Solids (Iba.) Suspended Solids (Ibs.)
DWF*
1251
590
2009
Sur-
face
Run-
off
2304
480
3359
Sew-
age
Over-
flows DWF*
545
257
874
Sur-
face
Run-
off
3325
429
3014
Sew-
age
Over-
flows DWF*
177
83
284
Sur-
face
Run-
off
1002
91
604
Sew-
age
Over-
flows
-
-
-
*DWF = Dry Weather Flow
-------
TABLE 20
SUMMARY OF TOTAL POUNDS OF POLLUTANTS
IN TROUT RUN STREAM
BOD (Ibs
Rainfall
Event
m I?6?
6 Feb
8 Feb
24 Mar
22/23 July
3 Aug
DWF*
5
4
17
6
10
Sur-
face
Run-
off
73
83
388
307
272
.) Total
Sew-
age
Over-
flows DWF*
879
489
965 1612
227 562
308 912
Solids (Ibs.)
Sur- Sew-
face age
Run- Over-
off flows
1441
4035
13,659 1625
10,767 5559
9571 5497
Volatile Solids (Ibs.)
DWF*
460
256
843
294
477
Sur- Sew-
face age
Run- Over-
off flows
900
1128
5773
3510
3589 920
Volatile
Suspended Solids (lbs.l_ Suspended Solids (Ibs.)
DWF*
52
29
96
33
54
Sur-
face
Run-
off
620
1027
3296
3190
1836
Sew-
age
Over-
flows DWF*
25
14
45
1087 16
26
Sur-
face
Run-
off
103
262
897
472
526
Sew-
age
Over-
flows
_
-
514
_
-
*DWF = Dry Weather Flow
-------
It was not possible to actually gauge the quantity of the overflows be>-
cause of their type and location. Overflows that did occur were gen-
erally spread out over the entire interceptor line. Except in a few
isolated instances there were no intentional overflow pipes installed to
discharge the overflow directly to a stream. When the pipeline capa-
city was exceeded, the excess flow exited by manholes, or small breaks
in lines, backed up into basements, ponded in surface depressions, and
infiltrated into the ground by other ways not visible.
Because of the types of overflows, a synthetic method of estimating
overflow frequencies and magnitudes was developed. From the gauging
data, a relationship was established between rainfall intensity and rate
of infiltration into the sanitary sewers so that for any given rainfall in-
tensity the rate of infiltration of surface water into the sanitary sewers
could be estimated. When the total amount of infiltration for a given
rainfall event was required the duration of the event was applied to the
rainfall intensity. Through use of the derived relationship to estimate
the infiltration, the total flow in the sewer during any given rainfall
event can be estimated by adding the normal dry weather flow to the in-
filtration.
The total flow can then be compared with the capacity of the sewer to
determine the amount of sewage overflow for a given rainfall event or
the amount of flow that exited the system because the capacity was ex-
ceeded. A computer program was developed to expedite the tedious
computations involved in calculating the sewage flows and overflows.
INFILTRATION - RAINFALL RELATIONSHIP
A relationship between rainfall intensity and the infiltration rate of storm
water into the sanitary sewers was derived from data on the 24th Street
study area given in Tables 2 and 4. The infiltration rate for a given
rainfall event was taken to be the total quantity of storm water infiltra-
tion divided by the duration of the rainfall. To make the relationship
applicable to other drainage areas and sub-drainage areas, the assump-
tion was made that total infiltration was proportional to the length of
collector and interceptor sewer lines in the area.. Figure 19 shows
graphically the relationship between rainfall intensity and infiltration
rate in the 24th Street area. The equation of the line of best fit on the
graph, as determined by stepwise multiple regression analysis, is as
f ollows :
R = 1. 984 I - 0. 087 Equation 1
68
-------
R = Rate of surface water infiltration in mgd per
1000 linear feet of sewer line
I = Average rainfall intensity in inches per hour
The derived equation has a standard error of estimate of 0. 017 and a
multiple correlation coefficient of 0. 995. These values indicate that
the derived equation will predict, with a reasonable degree of accuracy,
the amount of storm water infiltration in the 24th Street sewer for a
given rainfall having an intensity in the range covered by the data points
shown on Figure 19. The equation will probably be much less accurate,
however, for higher intensity rainfalls during which sewer lines become
surcharged. Once a sewer line surcharges, it is obvious that little or
no more storm water will infiltrate into the line. This means that the
infiltration rate for that particular line will approach zero. If many
lines surcharge during a rainfall event, the infiltration rate computed
by the equation would be significantly higher than that which actually
occurred. No data were gathered in this study, however, to indicate at
what point the rate of infiltration begins to decrease.
In the three study areas, the collector sewers account for between 88
and 92 percent of the total collector-interceptor system. The collector
sewers are 8- and 10-inch lines and generally have the capacity to carry
from 4 to 10 times the dry weather flow. With this amount of excess
capacity, it would take a very high intensity rainfall to surcharge the
collector lines. For example, it would take a 1-hour rainfall having an
intensity of 1.2 inches per hour to surcharge an 8-inch line on minimum
slope and 2000 feet in length. This intensity is greater than any recorded
during the study period. Therefore, for the purposes of this study, the
equation derived from Figure 19 was used to compute infiltration rates
for all rainfall events in the three study areas.
COMPUTER PROGRAM
A computer program was developed to determine, for any given rainfall
event, the locations and amounts of overflow in the interceptor for a par-
ticular drainage area. Four sets of input data are required for the pro-
gram:
1. The slopes and diameters of the line sections between each
pair of manholes.
2. The length of collectors and interceptors contributing to the
flow in each line section.
69
-------
3. The average dry weather flow from, the entire drainage area.
4. The intensity and the duration of the rainfall event.
From the slopes and diameters, the program computes the capacity of
each line section using the Manning Formula. The program computes
the average dry weather flow in each line section by multiplying the
average dry weather flow, from the entire drainage area, by the ratio
of the section length of collector and interceptor lines to the total length
of collector and interceptor lines. An infiltration rate is computed from
the input rainfall intensity and the rainfall-infiltration relationship de-
veloped from data on the 24th Street study area shown graphically by
Figure 19. The flow due to storm water infiltration in each section of
line is then computed by multiplying the infiltration rate by the length of
collector and interceptor lines contributing to the flow in each particular
line section. Beginning at the upstream end of the area, the flow in the
first line section is computed by adding the infiltration flow to the dry
weather flow. This flow is compared with the capacity of the line to de-
termine if an overflow condition exists at the upstream manhole. If the
flow exceeds the line capacity, the overflow rate is the difference be-
tween the computed flow and computed capacity. The volume of over-
flow at the manhole is computed by multiplying the overflow rate by the
duration of the storm. The program analyzes each succeeding down-
stream line section in the same manner. The printout from the program
gives, for each line section, the line capacity, the dry weather flow, the
total flow in the line, the overflow rate at the upstream manhole and the
volume of overflow at the upstream manhole. The program will also
print out the total pounds of BOD from the overflow if a BOD concentra-
tion is furnished as input to the program. Totals for the entire inter-
ceptor are given at the end of the printout.
The computer program abstract, the source program listing and operat-
ing instructions are included in Appendix V.
OVERFLOWS IN STUDY AREAS
The computer analysis technique was used to determine the relationship
between rainfall intensity and the rate of sanitary sewage overflow for
the total length of interceptor in the three study areas, rate of sanitary
sewage overflow being the rate at which the excess sewage exits the sys-
tem once the line capacity has been exceeded. These relationships are
shown by Figure 20. Two relationships are shown for the Murray Run
area, one based on the capacity of the sewer in its present root-infested
condition and another based on the capacity of the line in a clean condition.
70
-------
FIGURE 19 RELATIONSHIP OF SANITARY SEWER
INFILTRATION RATE TO AVERAGE RAINFALL INTENSITY
o.
o
o
o
,0.2
0.2
0
I
I
1*3,295
37,110 £
0>
30,925
18,555
12,370
CO
id
on
DC
O
I—
-------
Through use of these relationships in conjunction with average yearly
rainfall data for Roanolce, the annual sanitary sewage overflow was es-
timated for the three study areas. The average yearly rainfall data are
based on five years of climatological data from U. S, Weather Bureau
and are shown in Table El. The estimated annual volumes of overflow
caused by storm water infiltration in the three areas are as follows:
- Murray Run - 8 million gallons
- Trout Run - 23 million gallons
- Z4th Street - 4 million gallons
The annual overflow volume estimated for the Murray Run sewer is
based on its present capacity with root infestation.
Table 22 shows the minimum rainfall intensity that will result in over-
flow in each of the study areas. The table also shows the number of
times overflows can be expected to occur in each area annually.
In the 24th Street study area, a rainfall intensity of 0. 11 inch per hour
will create an overflow situation in the sewer. Analysis of rainfall data
from the past five years shows that hourly rainfall intensities greater
than 0. 11 inch per hour occur more frequently during the summer
months than during the winter months. Of the total number of hourly
intensities greater than 0. 11 inch par hour, approximately 75 percent
were recorded during the months of May through October, which is the
period of the year when the dissolved oxygen and stream flows are likely
to be at a minimum.
Because of its restricted capacity, the Murray Run sewer overflows
during very low intensity rainfalls. Figure 20 shows, however, that if
the roots were removed, thereby increasing the line capacity, the over-
flow for a given rainfall intensity would decrease considerably. The
minimum rainfall intensity that causes overflow would increase from
0. 07 inch per hour to 0, 17 inch per hour. As a result, the estimated
number of annual overflows would decrease from 28 to 7 and the esti-
mated annual volume of sewage overflow would decrease from 8 million
gallons to 2 million gallons.
72
-------
FIGURE 20 RELATIONSHIP t)F RAINFALL INTENSITY TO
RATE OF OVERFLOW FROM SANITARY SEWERS
7.0
6.0
5.0
CT
E
oc
CD
3.0
2.0
1 .0
0
O.iO 0.20 0.30 0.^0
RAINFALL INTENSITY - in./hr.
0.50
73
-------
TABLE 21
AVERAGE YEARLY RAINFALL DATA
Average Intensity Of
Rainfall (in. /hr. )
0.50
0.40
0.30
0.20
0.15
0. 10
0.09
0. 08
0.07
0, 06
0.05
0. 04
or greater
- 0.50
- 0.40
- 0.30
- 0.20
- 0.15
- 0. 10
- 0.09
- 0.08
- 0.07
- 0.06
- 0.05
Number of Hours Of
Rainfall Per Year
1.8
1.2
3.0
7.8
29.8
49.2
5.8
23.6
23.2
44.4
46. 0
74.4
Table 22 shows that the Trout Run Sewer surcharges from dry weather
flow alone. In addition, there are an average of 99 rainfalls annually
and each causes some overflow.
Table 23 shows the maximum single overflows expected to occur annu-
ally in each of the three study areas. These maximum single events
account for between 12 and 19 percent of the total annual volume of over-
flow in the study areas.
74
-------
TABLE 22
OVERFLOW FREQUENCY DATA
Minimum Rainfall Intensity
to Cause Overflow Number of
Study Area
Murray Run *
Trout Run **
24th Street
(in. /hr. )
0. 07
0. 00
0. 11
Overflows Per
28
99
15
Year
* Based on present restricted conditions.
** Trout Run sewer surcharges from dry weather flow, thus any
amount of rainfall will result in potential overflow.
TABLE 23
MAXIMUM SINGLE OVERFLOWS IN STUDY AREAS
Study Area
Murray Run
Trout Run
24th Street
Maximum Annual
Overflow
(nig)
1.20
2.69
0.75
Percent of Total
Annual Overflow
Volume
16
12
19
POLLUTION FROM OVERFLOWS
The average pollutional characteristics of the sanitary sewage overflows
in the three study areas are given in Table 24. Comparison of the over-
flow and dry weather concentrations shown in Table 25 reveals that the
concentration of all constituents, except total solids and settleable solids
are greater in the dry weather flow. The reduction in concentration of
the constituents during overflows is obviously caused by dilution from
storm water.
75
-------
Through use of sampling data from the Trout Run stream for 24 March,
23 July and 3 August, when sewage overflows were actually observed,
an attempt was made to correlate computed pollutional loads with mea-
sured pollution loads. The relationships are given in Table 26.
Since it is known that the sewer in the Trout Run area was clogged during
the 24 March storm, the 22/23 July and 3 August storms are taken to be
representative of the relationship between computed and actual overflow
volumes. The average ratio of measured BOD from overflow to com-
puted BOD from overflow is 0. 26. This means that on these dates ap-
proximately 25 percent of the computed overflow, or that amount by
which the line capacity was exceeded, actually reached the stream, the
reason being the types of overflows that existed. Overflows that did
occur were generally spread out over the entire interceptor line. When
the pipe line capacity was exceeded, the excess flow exited by manholes,
small breaks in lines and other ways not visible. Some of the overflow
found its way into nearby streams; however, a larger portion either re-
mained on the surface of the ground near a manhole or was stored under-
ground and either re-entered the sewer or percolated into the ground.
The average concentrations given in Table 24 were used to compute the
maximum annual pollutional load caused by overflow from a single rain-
fall event in each study area. Table 27 shows that maximum single an-
nual overflow in the Trout Run interceptor contributes approximately
1100 pounds of BOD to the stream. This amount of BOD is approximately
equivalent to the amount in the daily untreated sewage from a population
of 5500 persons or about 50 percent of the population in the study area.
The estimated total annual pollution contributed to watercourses from
the overflows in the study areas is given in Table 28. Although the an-
nual amounts of pollutional constituents shown in Table 28 do not appear
to represent any formidable pollutional force, the overflows from the
heavy rainfalls contribute large "shock" loads of pollution. The water-
courses cannot easily recover from this type of pollutional loading.
These shock loads of pollution are not always diluted by increased flow
in the receiving stream, Roanoke River. Many overflows occur due to
thunderstorms that occur only over parts of the watershed and do not
appreciably affect the daily or the mean monthly river flow. This was
illustrated during the 22/23 July and 3 August storm events when the
daily flow in the river was 418 and 308 cfs, respectively, well below the
average of 501 cfs.
76
-------
TABLE 24
AVERAGE CONCENTRATIONS OF POLLUTIONAL
CONSTITUENTS OF SANITARY SEWAGE OVERFLOWS IN STUDY AREAS
Volatile
Total Volatile Suspended Suspended
BOD Solids Solids Solids Solids
Study Area (mg./l.) (mg./l.) (mg./l.) (mg./I.) (mg./l.)
Murray Run &
E4th Street 115 425 ZOO 75 40
Trout Run 199 917 408 149 79
Settleable
Solids
(ml. /I.)
10
13
-------
00
TABLE 25
AVERAGE CONCENTRATIONS OF POLLUTIONAL CONSTITUENTS OF
DRY WEATHER SANITARY SEWAGE FLOW IN STUDY AREAS
Volatile
Total Volatile Suspended Suspended
BOD Solids Solids Solids Solids
StudyArea (mg./l.) (mg./l.) (mg./l.) (mg./l.) (mg./l.)
Murray Run 181 476 241 91 40
24th Street 192 6l6 325 113 53
Trout Run 342 890 473 200 98
Settleable
Solids
(ml. /I.)
9
6
8
-------
TABLE 26
COMPUTED AND MEASURED BOD
FROM TROUT RUN SEWER OVERFLOWS
Rainfall
24 March
22/23 July
3 August
Measured
BOD From
Stream Sampling
(Ibs. )
965
227
308
Computed
BOD
(Ibs. )
860
1060
980
Ratio
Measured/ Computed
1.12
0.21
0.31
TABLE 27
POLLUTIONAL LOAD FROM MAXIMUM SINGLE ANNUAL
OVERFLOW EVENT
Study Area
Murray Run
24th Street
Trout Run
BOD
(1000
Ibs. )
0.3
0.2
1.1
Total
Solids
(1000
Ibs. )
1. 1
0. 7
5. 1
Volatile
Solids
(1000
Ibs. )
0.5
0.3
2.6
Suspended
Solids
(1000
Ibs. )
0.2
0. 1
0.8
Volatile
Suspended
Solids
(1000
Ibs. )
0.1
0. 1
0.5
79
-------
TABLE 28
ANNUAL POLLUTIONAL LOAD FROM OVERFLOWS
IN STUDY AREAS
Study Area
Murray Run
24th Street
Trout Run
BOD
(1000
Ibs.)
1.9
i.O
9.5
Total
Solids
(1000
Ibs.)
6.9
3.5
44.0
Volatile
Solids
(1000
Ibs.)
3.2
1.7
19.6
Suspended
Solids
{1000
Ibs.)
1.2
0.6
7.2
Volatile
Suspended
Solids
(1000
Ibs.)
0.7
0.3
3.8
WATER POLLUTION CONTROL PLANT
OVERFLOW
Roanoke, Virginia's Water Pollution Control Plant is a conventional acti-
vated sludge plant located adjacent to the Roanoke River near the east
city limits as shown by Plate 1. Figure 21 shows a schematic flow lay-
out of the plant facilities. The plant has a design capacity of 22 mgd;
however, a wet weather flow of 30 mgd can be handled before bypassing
is required. The overflow pipe is 54 inches in diameter and is located
in the junction box of the Roanoke River interceptor and Tinker Creek
interceptor. The Tinker Creek interceptor also carries the digester
supernatant and overflow from the sludge thickener to the junction box.
The junction box is located outside the comminutor room adjacent to the
main building. The dry weather flow is never of such magnitude as to
cause the plant to bypass, the average being about 20 mgd. However,
the flow does occasionally reach and exceed 30 mgd with storm water
flow, thus causing the plant to bypass untreated sewage into the Roanoke
River. The overflow conditions always occur during or shortly after
certain types of rainfall events. One objective of this report was to
determine if any plant overflow trends could be found relative to:
1. Frequency of plant overflows .
2. Types of rainfall events that cause overflows.
3. Effect of the overflow from a pollutional standpoint.
80
-------
PRIMARY
CLARIFIERS
ROANOKE RIVER
BYPASS
SAMPLING STATION
AERATION
BASINS "
FINAL
CLARIFIER
RETURN SLUDGE
WASTE ACTIVATED—<
RAW SLUD3E
CHLORINE
CONTACT
CONTROL BLDG
AND PUMPING
STATION
SLUDGE
THICKENER
-SAMPLING
STATION
SLUDGE DRYING
BEDS
.THICKENER
OVERFLOW
-o
m
»
•nS
CD 70
r~ m
i-
HH
o ~n
o z
o
2 CD
—I H-l
O £T3
13 3
m
TO
DIGESTERS
-------
Table 8, in Section 4 - Results of Investigation, shows a summary of
the six overflows occurring at the plant during the study period. Figure
22 is a plot of total overflow versus total rainfall using the data collected
during the six overflow events. The following is an equation of the esti-
mated line of best fit used to describe the relationship in Figure 22.
T = 4. 8 R -2.4 Equation 2
T = Total overflow in million gallons
R = Total rainfall in inches
To completely establish overflow frequency or trends on the basis of six
overflows, all occurring during the same year, is not to be expected.
However, based on Figure 22 it is shown that a linear relationship is
possible between total rainfall and total overflow and, for the purpose of
this report, Equation 2 was used to analyze overflows at the plant. The
following limiting values were used in analyzing the overflow situation
and are exemplified by Figure 22 and Table 8.
1. Minimum total rainfall to cause overflow assumed at 0. 5 inch.
2. Minimum intensity to cause overflow assumed at 0. 10 inch per
hour.
Tables 29 through 33 give summaries of calculated overflows at the
plant for the years 1964 through 1968, with all calculations based on
Equation 2. Table 34 gives measured data for 1969. The rainfall data
are from the Local Climatological Data, furnished by the U. S. Depart-
ment of Commerce. The average annual overflow to be expected at the
plant is 45 mg. Overflow will occur approximately 10 times per year.
82
-------
FIGURE 22 RELATIONSHIP OF OVERFLOW TO RAINFALL
WATER POLLUTION CONTROL PLANT
3.5
3,0
2.5.
01
E
12.0.
oi .5
1,0
0.5
0
fO
_L
J L
0.5 1.0 I .5
TOTAL RAINFALL - in
2.0 2.5
83
-------
TABLE 29
CALCULATED OVERFLOWS
FOR THE YEAR 1964
Date
6 February
29 April
29 May
23 June
12 July
17 July
31 August
29 September
29 September
2 October
24 November
26 December
Total
Rainfall
(inches)
1.32
0.94
0.69
1.02
0.93
0.55
2.61
0.77
0.76
1.28
2.22
0.99
Total
Total
Overflow
(mg)
3.94
2.11
0.91
2.50
2.06
0.24
10.13
1.30
1.25
3.74
8.26
2.35
38.79
84
-------
TABLE 30
CALCULATED OVERFLOWS
FOR THE YEAR 1965
Date
7 February
25 February
7 May
21 May
25,May
4 July
7 July
11 July
19 July
7 October
Total
Rainfall
(inches)
1.46
1.43
0.69
0.67
1.06
1.06
0.65
1.81
0.62
2.17
Total
Total
Overflow
(nig)
4.61
4.46
0.91
0.82
2.69
2.69
0.72
6.29
0.58
8.02
31.79
85
-------
TABLE 31
CALCULATED OVERFLOWS
FOR THE YEAR 1966
Date
13 February
2 May
14 May
10 June
30 July
10 August
1 1 August
14 September
20 September
28 September
19 October
Total
Rainfall
(inches)
1.85
1.45
0.87
0.61
2.72
0.91
1.05
2.74
2.21
0.53
3.39
Total
Total
Overflow
(mg)
6.48
4.56
1.78
0.53
10.66
1.97
2.64
10.75
8.21
0.14
13.87
61.59
86
-------
TABLE 32
CALCULATED OVERFLOWS
FOR THE YEAR 1967
Date
7 March
7 May
31 May
19 June
25 June
15 July
20 July
7 August
24 August
28 September
18 October
3 December
12 December
Total
Rainfall
(inches)
2.55
0.84
1.04
1.41
0.66
0.85
0.94
0.68
2.51
1 .40
0.74
0.93
1.50
Total
Total
Overflow
(mg)
9.84
1.63
2.59
4.37
0.77
1.68
2.11
0.86
9.65
4.32
1.15
2.06
4.80
45.83
87
-------
TABLE 33
CALCULATED OVERFLOWS
FOR THE YEAR 1968
Date
12 March
29 April
27 July
3 August
10 August
11 August
19 October
R oanoke
River Flow*
(cfs)
736
465
309
280
229
407
8210
Total
Rainfall
(inches)
1.32
0.98
1.20
1.42
0.66
0.76
6.83
Total
Total
Overflow
(mg)
3. 94
2.30
3.36
4.42
0.77
1.25
30.38
46.42
* 42-year average is 501 cfs.
88
-------
TABLE 34
MEASURED OVERFLOWS
FOR THE YEAR 1969
Date
24 March
21 June
19 July
22, 23 July
3 August
5 August
* 42-year average
Roanoke
River Flow*
(cfs)
853
319
212
418
308
334
is 501 cfs.
Table 35 shows that about 77 perce
Total
Rainfall
(inches)
1.00
1.25
0.50
0.60
0.50
0.50
Total
snt of the total number
Total
Overflow
(mg)
2.80
2.90
0.60
0. 70
0.04
0. 02
7.06
of overflows
expected annually will occur between May and October. Of the total
annual volume that can be anticipated, 75 percent will occur during the
same period. These same months also correspond to the time of year
when the dissolved oxygen in the Roanoke River is at a minimum for the
year.
89
-------
TABLE 35
SUMMARY OF CALCULATED OVERFLOWS
WATER POLLUTION CONTROL PLANT
1964 THROUGH 1968
Month
January
February
March
April
May
June
July
August
September
October
November
December
Totals
Percent of Total
Number of
Overflows
0
8
4
4
15
8
19
15
11
9
2
5
100
Percent of Total
Volume of
Overflows
0
9
6
2
7
4
14
14
11
25
4
4
100
90
-------
POLLUTANT
To evaluate the effect of the plant digester supernatant and overflow
from the sludge thickener discharging into the junction box of the over-
flow pipe, samples were taken in an upstream manhole along the Roanoke
River Interceptor and at the junction box during an overflow event at the
plant. Figure 21 shows the relative Location of the two sampling points.
Tables 10 and 11, in Section 4 - Results of Investigation, show data which
permit a comparison of sampling characteristics obtained at the two lo-
cations during the 22/23 July 1969 rainfall event. The samples indicate
that the pollutants at the overflow pipe are considerably more concen-
trated than that in the interceptor. The conforms, however, show a
decrease in the junction box as compared to the samples taken in the in-
terceptor. This is apparently due to the chlorine that is added when
overflow occurs. The separation of the digester supernatant and over-
flow from the sludge thickener from the present overflow junction box
would reduce the BOD concentration during overflow conditions, possibly
by 50 percent.
Table 9, in Section 4 - Results of Investigation, shows the pounds of
pollutant'expected from a total rainfall of 0. 6 inch. Using a 0.2 pound
of BOD per capita per day, the 1192 pounds of BOD deposited into the
Roanoke River during the 22/23 July rainfall event is approximately
equivalent to 6000 persons discharging untreated sewage into the river
for a day,
OVERFLOWS FROM ROANOKE SEWERAGE SYSTEM
Pollution of surface waters from the sanitary sewerage system can come
from three possible sources: overflow from interceptors and trunk lines,
overflow at the Water Pollution Control Plant, and treated plant effluent.
An evaluation of overflow from interceptors in the three study areas was
made and provides a basis for analysis of overflow from interceptors
and trunk sewers in the entire system by correlation to the study areas.
This analysis can be us«d, together with additional data, to evaluate the
total pollutional effect to surface waters from all three possible sources
of pollution.
As. described previously, the study areas were selected to be represen-
tative of other areas within the entire City, so as to enable the remain-
ing drainage areas to be classified in accordance with a study area. It
was determined that the drainage areas in the City could be related to a
study area, in regard to pollution of surface waters due to sanitary sewer
overflows, based on the following two criteria:
91
-------
1. Ratio of pipe capacity to dry weather flow (DWF).
2. Proximity of the sanitary sewer to a stream.
In regard to the first criterion, all sewers with capacities less than
two times DWF will have overflows similar to the Trout Run intercep-
tor sewer. All sanitary sewers with capacities greater than two times
DWF will have overflows similar to the 24th Street and Murray Run
interceptors.
As described hereinbefore, approximately 25 percent of the computed
overflow actually reaches an adjacent stream. This is generally true
where a stream parallels an interceptor. If there is no adjacent stream
to an interceptor, the quantity of pollution from overflows reaching any
stream would be minimal. The three study areas all had adjacent
streams. Table 36 shows a breakdown of the City's drainage areas and
their subsequent classification according to capacity in relation to dry
weather flow and proximity to streams. Table 37 shows a summary of
overflow conditions in the study areas and at the Water Pollution Control
Plant.
Table 38 and Figure 23 show average annual BOD deposited in the
Roanoke River due to overflows from interceptors and trunk sewers,
Water Pollution Control Plant overflow and plant effluent.
The volume of sewage from the plant overflow structure of 45 mg was
based on an average of the expected overflows. The pounds of BOD were
arrived at by using a strength of 240 mg. /I. for BOD as indicated in
Table 10, Section 4 - Results of Investigation.
An evaluation of the annual overflow situation does not give a very com-
plete description of the conditions that could prevail. The severity of
the problem can possibly be shown by an evaluation of overflow condi-
tions during a rainfall event. The event chosen was one that occurred
on 23 August 1967. It rained for 17 hours at an intensity of 0. 12 in. /hr.,
giving a total rainfall of 2. 04 inches. This particular type rainfall can
be expected to occur approximately once a year.
Table 39 and Figure 24 show approximate quantities of sewage and BOD
deposited in the Roanoke River during the 23 August 1967 rainfall event
from the Water Pollution Control Plant effluent, the Water Pollution
Control Plant overflow and the sanitary sewer interceptor and trunk
sewer overflows.
92
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TABLE 36
CLASSIFICATION OF SEWER DRAINAGE AREAS
Capacity Under
2 x DWF
With Adjacent
Stream
Trout Run
Lick Run
Grandin Road
Norfolk Ave .
Tinker Creek
Annual
DWF
(mg)
383
296
252
1100
675
Capacity Over
2 x DWF
With Adjacent
Stream.
24th Street
Murray Run
Garden City
Mud Lick
Peters Creek
Annual
DWF
(mg)
278
154
453
325
230
Annual
Areas With DWF
No Stream (mg)
Franklin Road 146
South Roanoke 146
Williamson Road 422
Totals
2706
1440
714
-------
TABLE 37
SUMMARY OF OVERFLOW CONDITIONS
vO
Minimum Rainfall To
Cause Overflow
Area
Pollution
Control Plant
24th Street
Murray Run
Trout Run
Intensity
(in. /hr . )
0.10
0.11
0.07
0.00
Total
(in.)
0.50
0.11
0.07
0.00
Number
Of Annual
Overflows
10
15
28
99
Total
Annual
Overflows
(mg)
45.00
3,97
7.79
22.99
Maximum
Single
Annual
Overflow
{mg)
8.37
0.75
1.20
2.69
Annual
Rainfall
Events
Causing
Overflows
(percent)
10
15
28
100
-------
TABLE 38
AVERAGE ANNUAL BOD CONTRIBUTED TO THE ROANQKE
RIVER BY SANITARY SEWAGE
SOURCE OF BOD
SEWAGE PERCENT POUNDS PERCENT
VOLUME OF TOTAL OF BOD OF TOTAL
POLLUTION CONTROL
PLANT EFFLUENT
POLLUTION CONTROL
PLANT OVERFLOWS
7,300 MG
15 MG
98.1 2,192,000 91.6
0.6
90,000
3.8
79 MG
SANITARY SEWER
OVERFLOWS
TOTALS 7,424 MG
1.0 111,000 1.6
100.0 2,393,000 100.0
FIGURE 23 AVERAGE ANNUAL BOD CONTRIBUTED TO THE
ROANOKE RIVER BY SANITARY SEWAGE
POLLUTION CONTROL
PLANT EFFLUENT
2,192,000 LBS
POLLUTION
CONTROL
PLANT
OVERFLOW
90,000 LBS
SANITARY SEWER
OVERFLOWS I I I,000 LBS
95
-------
TABLE 39
BOD CONTRIBUTED TO ROANOKE RIVER BY SANITARY
SEWAGE DURING MAXIMUM YEARLY RAINFALL EVENT
SOURCE OF BOD
S.EWAGE
VOLUME
PERCENT
OF TOTAL
POUNDS
OF BOD
PERCENT
OF TOTAL
POLLUTION CONTROL
PLANT EFFLUENT
POLLUTION CONTROL
PLANT OVERFLOW
SANITARY SEWER
OVERFLOWS
TOTALS
27.5 MG
7.4 MG
6.2 MG
>H. I MG
66.9
7,570
18.0 14,610
24.3
47.5
15.1 8,790 28.2
00.0 31,170 100.0
FIGURE 2V BOD CONTRIBUTED 'TO ROANOKE RIVER BY
SANITARY SEWAGE DURING MAXIMUM YEARLY RAINFALL EVENT
POLLUTION
CONTROL PLANT
EFFLUENT
7,570 LBS.
POLLUTION CONTROL
PLANT OVERFLOW
14,810 LBS.
SANITARY SEWER
OVERFLOWS
8,790 LBS.
96
-------
The sewage volume of 27.5 mg from the pollution control plant effluent
was the amount measured at the plant during the rainfall event. The
pounds of BOD -were calculated using a sewage strength of 220 mg./l.
and 85 percent removal of BOD by the treatment processes.
A comparison between Tables 38 and 39 assesses the effect of pollution
to the Roanoke River due to overflows from an individual rainfall event
and annual overflows. Plant records reveal that approximately 85 per-
cent removal of BOD can be expected by the plant. "However, the plant
constitutes only one part of the entire sewerage system and to completely
evaluate the effectiveness of pollution abatement the entire system must
be analyzed. In Table 38, 1.6 percent of the annual sewage discharge
never reaches the plant, but overflows to nearby watercourses; 98.4 per
cent of the system's sewage flow reaches the plant and is subjected to
treatment before being discharged to the Roanoke River. However, in
Table 39, 33 percent of the sanitary sewage flow never reaches the
plant during a maximum yearly rainfall event and only 66.9 percent of
the volurae of sewage from the system reaches the plant for treatment.
It is therefore concluded that overflows from individual rainfall events
are significant and can amount to as much as one-third of the total
sanitary sewage flow from the system.
97
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Previous Page Blank
SECTION 6
REMEDIAL MEASURES
THE PROBLEM
The results of the hydrological investigation, gauging of streams and
sewers, and water quality sampling and testing revealed that sewage
overflows occur frequently in portions of Roanoke, Virginia's sanitary
sewer system, resulting in a severely increased pollutional load in
the City's water courses. The overflows occur during periods of rain-
fall and are caused primarily by excessive storm water infiltration
which overloads the sewerage system. Some recurring overflows are
the result of severely reduced line capacities due to tree root infestation,
partial clogging with debris, broken sections of pipe, and other similar
problems which can be corrected by routine maintenance procedures.
The investigations and testing also showed that the sanitary sewage flow
to the Water Pollution Control Plant is increased during rainfall events
and exceeds the capacity of the plant approximately ten times annually.
The flow in excess of the plant capacity is mixed with the digester super-
natant and sludge thickner overflow and is bypassed without treatment
into the Roanoke River, thus increasing the pollutional load in the
river considerably.
The investigation of remedial measures was directed at finding methods
to decrease the frequency and volume of overflows.
ALTERNATE METHODS
The following methods of coping with overflows from the separate
sanitary sewer system were considered:
1. Elimination of infiltration
Z. Additional sewer capacity
3 . Increased treatment capacity
4. Detention basins
5. Combinations of the above
6. Treatment plant modifications
99
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ELIMINATION OF INFILTRATION
The immediately obvious solution to eliminating overflows from sani-
tary sewers is to eliminate their cause which is excessive storm water
infiltration. In view of the tremendous investment the City already
has in its separate sewerage system, the first obvious choice is to
rehabilitate and upgrade it to present recommended standards. There-
fore an investigation was made into the state-of-the-art of existing
sewerage repair technology and methods.
The application of television inspection and in-place grouting to locate
and repair leaks has been widely used with substantial success. Austin,
Texas has embarked on a regular program of inspecting and repairing
40 miles of sewers per year. Television inspection and in-place
grouting with an internal packer are the key features of the program.
A test conducted on 22,000 feet of pipe in Austin showed that repair
of leaks and trouble spots reduced infiltration by 85 percent (5). The
same method was also determined to be of value in reducing infiltration
in Montgomery County, Ohio (6). The use of chemical grout to repair
leaks in the City of Sadbury, Ontario, Canada sewer system was
determined to be 97 percent effective (7). A sewer rehabilitation pro-
gram which included cleaning, inspecting, and sealing some 25 to 28
miles of sewer was undertaken in Fort Myers, Florida. It was esti-
mated that repairs to the sewer system reduced infiltration by 3.0 mgd
at a treatment plant where normal dry weather flow should have been
2.5 mgd but often exceeded 6.0 mgd. Television inspection was used to
locate leaks and chemical grout was used for repair (8). The literature
study indicated that the combined use of television inspection and inter-
nal chemical grouting offers a satisfactory method of repairing sewer
lines, The use of this method of repair offers several advantages:
1. It eliminates the need for excavation and pavement cuts.
2. It reduces the necessity for disturbing other services.
3 . It minimizes the interruption of traffic flow.
4. It can be used successfully in sewers which are in operation.
The method does, however, have certain limitations and does not offer
a "sure-fire" solution to Roanoke's infiltration problem. It has been
found to be uneconomical to repair joints separated by two or more
inches and impractical to repair large breaks and longitudinal cracks
by this method. It also does not offer a solution to the repair of leaky
100
-------
laterals and connections. A review of the results of the smoke testing
in the study areas revealed that a majority of the storm water entry
points were on private property, probably in laterals and connections.
These deficiencies would have to be corrected in the conventional man-
ner of excavating and replacing the damaged sections. However, the
locations of many of these deficiencies would be pinpointed through
smoke testing and television inspection.
Another method of grouting leaks, which is applicable to the repairing
of laterals as well, uses a grouting solution which sets up in cracks and
breaks as a gelatinous material. The section of pipe to be repaired is
plugged and filled with the grouting solution. Hydrostatic pressure is
applied to the solution in the pipe forcing it out cracks and leaks. As
solution is forced out of the pipe it forms a seal. The solution re-
maining in the pipe is pumped out and reused. This method of sewer
line repair was used with apparent success in St. Augustine, Florida
(9). A similar technique was used successfully in Amersham, England
(10). This method of repair is not effective in sections of line that have
large structural faults. Nothing definitive was found in this investigation
regarding the permanency of repairs by use of grouting solutions.
A representative from the Penetryn System Incorporated, a firm ex-
perienced in sewer systems analysis and repair using the above methods,
was consulted on the feasibility of making repairs to reduce infiltration
in Roanoke's sewer system. His review of the results of the smoke
testing and field observations in the three study areas indicated that
Roanoke's problem was similar to that of other systems which had been
successfully rehabilitated. It was his opinion that, through use of a
carefully planned program of systematic investigation and repair, storm
water infiltration in the system could be reduced by 80 percent without
the use of extraordinary measures.
It is concluded that all infiltration cannot be eliminated from the system
by any practical means. However, present sewer repair technology
offers a feasible means of severely reducing infiltration, thereby re-
ducing overflows. Current repair methods could be expected to reduce
infiltration by 80 percent and this assumption has been used in further
developing a remedial program.
101
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ADDITIONAL SEWER CAPACITY
Interceptor and trunk sewers are normally designed for capacities of two
to three times dry weather flow. Capacities sufficient to accommodate
infiltration would be In the range of 8 to 10 times present dry weather
flow, requiring the replacement of 70 to 80 percent of the existing inter-
ceptors. The replaced lines would be the equivalent of combined sewers
which would allow entering storm water to be further polluted by mixing
with sanitary sewage. Therefore, increasing sewer capacities solely
to accommodate excessive infiltration of storm water is obviously not
a satisfactory solution in itself.
INCREASED TREATMENT CAPACITY
Providing additional treatment capacity to treat or partially treat com-
bined sewage is being done in many communities. However, increasing
treatment capacity would only be a partial solution for eliminating
pollution from overflows, as it only eliminates the plant overflows.
Overflows which occur upstream in the sewerage system would be un-
affected unless interceptor capacities were increased substantially to
convey all infiltration to the treatment plant.
The activated sludge treatment process in Roanoke is highly susceptible
to upsets from shock loads with a resultant loss of treatment efficiency.
The high rates of infiltration from storms would produce such shock
loadings, thereby requiring a modification of the treatment process during
overflow events. The addition of tertiary treatment facilities is a
distinct possibility in the future. Tertiary systems now in vogue are
even more susceptible to upsets from shock loads.
DETENTION BASINS
Detention basins, lagoons, and other such methods are now in use in
many localities to delay high peak discharges long enough to allow
a leveling load to the sewers and the treatment plant. The prevailing
use of detention basins is to receive overflows from combined sewers.
Another use of the holding tank is for treatment. The treatment may be
removal of solids which are either removed and disposed of or re-
turned to the sewerage system. The retained flow, after chlorination,
is then allowed to discharge into the stream.
102
-------
Such detention or holding basins are also applicable for eliminating
overflows from separate sewerage systems.
The sewerage system in each of the three study areas was analyzed
with the aid of computer capabilities to determine flows and overflows
in the interceptor sewers for rainfalls of various intensities and
durations. The computations were first made using the existing sewer
line capacities and present infiltration rates. Analysis of the output
showed that overflows occur in both the upper and lower regions of the
three study areas. This precludes using a single basin to store over-
flows without increasing the capacity of portions of the existing inter-
ceptors. To use a single basin under these conditions would require
replacing approximately 67 percent of the 24th Street interceptor, 78
percent of the Trout Run interceptor and 70 percent of the Murray Run
interceptor, in order to contain the flow generated by a rainfall event
with a one year return period.
Preventing overflows at the treatment plant further requires other
holding tanks at the plant or increasing the size of the tanks in the
drainage basins so that the release from the basins does not exceed
the plant capacity.
The extensive increases in interceptor sewer capacity to contain the
excess flows within the system so as to limit the number of detention
basins required for each drainage basin, together with the relative
size of the detention basin, result in a system of major proportions
comparable in size to a combined storm sewer system.
COMBINATION OF ALTERNATE METHODS
No one method offered a complete solution to eliminating overflows from
the sanitary sewerage system; however, each method has merits.
Therefore, remedial measures, incorporating the desirable features of
the various methods discussed could be expected to produce the desired
results.
The obvious key is to eliminate as much storm water as possible from
entering the system, rather than trying to cope with it once it has been
mixed with the sanitary sewage. Present repair technology indicated
as much as 80 percent of this storm water can be eliminated without
resorting to extreme measures. The remaining infiltration is still
103
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sufficient to produce overflows, but the smaller flow rates and volumes
reduce the capacity requirements of interceptor sewers, detention, basins,
and treatment plants. The analysis of the system by computer permits
the optimum design of all of the components.
The systems in the three study areas were analyzed, assuming that infil-
tration could be reduced by 80 percent through repairs to the system,
and the flow and overflow computations for various rainfalls were re-
peated for the three interceptors. The analysis revealed that the re-
duction in infiltration lessened the necessity for line replacement con-
siderably. Table 40 shows that, in order to contain the flow from the
one year rainfall intensity and convey it to a single detention basin, line
replacement requirements are 125 feet in the Murray Run interceptor,
500 feet in Z4th Street interceptor and 6480 feet in the Trout Run inter-
ceptor. To provide enough capacity for the five and ten year intensities,
line replacement requirements are much greater .
TABLE 40
SEWER LINE REPLACEMENT REQUIREMENTS
FOR USE OF A SINGLE DETENTION BASIN
INFILTRATION REDUCED 80 PERCENT
1 Year 5 Year 10 Year
Maximum Maximum Maximum
Study Area Intensity Intensity Intensity
Murray Run
Trout Run
24th Street
125'
6480'
500'
1750'
12,300'
2370'
2345'
12,300'
2370'
Since overflow volume is related to both rainfall intensity and total
rainfall, an investigation of overflows in the study areas from the rain-
fall events recorded for the past five years was undertaken to serve as
a basis for determining volume requirements for detention basins. In
addition, the volume must be sufficient so as to limit the downstream
flow. This allowable downstream flow is the maximum hydraulic capac-
ity of the critical downstream facility, which is the 30 mgd Water
Pollution Control Plant.
104
-------
Relationships were established between overflow volumes from the inter-
ceptors and the total amount of rainfall occurring at a range of inten-
sities between the minimum intensity required to cause overflow and
the maximum annual intensity. These relationships are depicted in
Figures 25 through 27. The relationships were used in conjunction
with the tabulation of rainfalls in the intensity range of 0.15 to 0.75
in./hr., as given in Table 41, to compute the volume of resulting
overflows in the study areas. These overflow volumes are given in
Tables 42 through 44, Table 45 shows the percentage of overflow
events that could be detained completely by detention basins of various
sizes.
Examination of Table 45 reveals that a 150,000 gallon basin in the
Murray Run area would detain 91 percent of the 5 year overflow volume
and reduce the number of overflows by 90 percent. Since very little
increase in these percentages would result from providing larger
basins, the 150,000 gallon basin appears to be the optimum size for
the Murray Run area. From a similar analysis, it appears that a
200,000 gallon basin would be the optimum size for the Trout Run
area and a 100,000 gallon basin would be the optimum size for the 24th
Street area.
Plates 6, 7, 8, 9 and 10 show a suggested location for each detention
basin and a conceptual plan for a typical basin in the Murray Run study
area. The choice of a ground level or underground basin should be
governed by the topographic and socio-economic characteristics of the
area in which it is to be located. A ground level tank would be the less
expensive of the two, but would be aesthetically undesirable in some
areas.
SEPARATION OF SUPERNATANT AND OVERFLOW
The polltitional effect of bypassing sanitary sewage at the Water Pollution
Control Plant can be significantly reduced by separating the digester
supernatant and the overflow from the sludge thickener from the sewage
overflow. This is only a partial solution to the overflow problem, but
its effect could be realized immediately and would abate pollution of the
Roanoke River.
105
-------
t.O
•9
.8
.7
. .6
Dl *
.5.
FIGURE 25 RAINFALL .- OVERFLOW RELATIONSHIP
MURRAY RUN STUDY AREA
.a
.2
. i
o
.90
.80
.70
.60
-.50
-.35
-.30
-.25
-.20
TOTAL RAINFALL-inches
-------
FIGURE 26 RAINFALL - OVERFLOW RELATIONSHIP
TROUT RUN STUDY AREA
1.0
.9
.8
.-7
31
lj-6
E
i-5
.3
.2
. I
0
25
20
I 2 3
TOTAL RAINFALL-inches
107
-------
o
oo
FIGURE 27 RAINFALL - OVERFLOW RELATIONSHIP
2HTH STREET STUDY AREA
3 4
TOTAL RAINFALL-inches
-.25
-------
TABLE 41
TABULATION OF RAINFALL EVENTS
BY TOTAL RAINFALL AND AVERAGE
INTENSITIES USING FIVE YEARS OF
CLIMATOLOGICAL DATA
Total
Rainfall
(in.)
0.
0.
1.
1.
2.
2.
3.
3.
4.
4.
5.
5.
6.
6.
0
5
0
5
0
5
0
5
0
5
0
5
0
5
- 0
- 1
- 1
- 2
- 2
- 3
- 3
- 4
- 4
- 5
- 5
- 6
- 6
- 7
.5
.0
.5
.0
.5
.0
.5
,0
.5
.0
.5
.0
.5
.0
Average Intensities {in./hr.)
.15- .21- .26- .31- .36- .41- .46- .51- .56- .61-
.20* .25 .30 .35 .40 .45 .50 .55 .60 .75
753012
61340111
1 0 2 0 100101
0 0 0 0 00001
2
1 0 1
1
0
0
0
0
0
0
1
*Events with intensities less than 0.15 in./hr. omitted due to 80 percent reduction of infiltration
-------
TABLE 42
OVERFLOWS BASED ON FIVE YEARS
OF CLIMATOLOGICAL DATA
MURRAY RUN STUDY AREA
Rainfall
Interval
(in.)'
0.0 -
0.5 -
0.0 -
0.5 -.
1.0 -
0.5 -
2.0 -
1.0* -
2.5 -
1.0 -
3.0 -
1.0 -
2.5 -
6.5 -
0
1
0
1
1
1
2
1
3
1
3
1
3
7
. 5
.0
. 5
.0
.5
.0
.5
.5
.0
.5
.5
.5
.0
.0
Intensity
Range
(in. /hr .)
.15 -
.21 -
,.26 -
.36 -
.15 -
.41 -
.21 -
.15 -
.26 -
,31 -
.41 -
.46 -
.51 -
.15 -
.26 -
.15 -
.36 -
.15 -
.51 -
.71 -
.26 -
.15 -
.20*
.25
.30
.40
.20
.45
.25
.20
.30
.35
.45
.50
.55
.20
.30
.20
.40
.20
.55
.75
.30
.20
Number
of
Events
7
5
3
1
6
2
1
1
3
4
1
1
1
2
2
1
1
1
1
1
1
1
Overflows (mg)
Individual
Event
.020
.025
.040
.048
.043
.055
.065
.068
.083
.091
.108
.110
.110
.110
.124
.135
.150
.160
.170
.190
.250
.310
Total
.140
.125
.120
.048
.258
.110
.065
.068
.249
.364
.108
.110
.110
.220
.248
.135
.150
.160
.170
.190
.250
.310
#E vents with intensities less than 0.15 in./hr. omitted due to 80
percent reduction of infiltration
110
-------
TABLE 43
OVERFLOWS BASED ON FIVE YEARS
OF CLIMATOLOGICAL DATA
TROUT RUN STUDY AREA
Rainfall
Interval
(in.)
0.0
0.5
0.0
1.0
0.5
2.0
0.5
2.5
1.0
3.0
1.0
2.5
6.5
- 0.5
- 1.0
- 0.5
- 1.5
- 1.0
- 2.5
- 1.0
- 3.0
- 1.5
-3.5
-1.5
- 3.0
- 7.0
Intensity
Range
(in . /hr . )
.15 -
.21 -
.15 -
.26 -
.36 -
.41 -
.15 -
.21 -
.26 -
.31 -
.15 -
.41 -
.46 -
.51 -
.15 -
.26 -
.15 -
.36 -
.51 -
.71 -
.26 -
.15 -
.20*
.25
.20
.30
.40
.45
.20
.25
.30
.35
.20
.45
.50
.55
.20
.30
.20
.40
.55
.75
.30
.20
Number
of
Events
7
5
6
3
1
2
1
1
3
4
2
1
1
1
1
2
1
1
1
1
1
1
Overflows (mg)
Individual
Event
.035
,055
.065
.070
.080
.090
.100
.105
.130
.145
.160
.175
.180
.190
.190
.200
.220
.240
.280
.310
.380
.440
Total
.245
.275
.390
.210
.080
.180
.100
.105
.390
.580
.320
.175
.180
.190
.190
.400
.220
.240
.280
.310
.380
.440
*Events with intensities less than 0.15 in./hr. omitted due to 80
percent reduction of infiltration
111
-------
TABLE 44
OVERFLOWS BASED ON FIVE YEARS
OF CLIMATOLOGICAL DATA
24 TH STREET STUDY AREA
Rainfall
Interval
(in.)
0.0
0.5
1.0
2.0
2.5
3.0
6.5
0.0
0.5
0.0
0.5
1.0
0.5
1.0
2.5
1.0
- 0.5
- 1.0
- 1.5
- 2.5
- 3.0
- 3.5
- 7.0
- 0.5
- 1.0
- 0.5
- 1.0
- 1.5
- 1.0
- 1.5
-3.0
- 1.5
Intensity
Range
(in. /hr .)
.15 -
.15 -
.15 -
.15 -
.15 -
.15 -
.15 -
.21 -
.26 -
.21 -
.36 -
.41 -
.26 -
.31 -
.26 -
.41 -
.46 -
.51 -
.36 -
.26 -
.51 -
.71 -
.20*
.20
.20
.20
.20
.20
.20
.25
.30
.25
.40
.45
.30
.35
.30
.45
.50
.55
.40
.30
.55
.75
Number
of
Events
7
6
1
2
1
1
1
5
3
1
1
2
3
4
2
1
1
1
1
1
1
1
Overflows (rag)
Individual
Event
.000
.000
.000
.000
.000
.000
.000
.010
.020
.020
.039
.040
.042
.060
.065
.080
.090
.100
.110
.130
.150
. 170
Total
.000
.000
.000
.000
.000
.000
.000
.050
.060
.020
.039
.080
.126
.240
.130
.080
.090
.100
.110
.130
.150
.170
#E vents with intensities less than 0.15 in./hr. omitted due to 80
percent reduction of infiltration
112
-------
TABLE 45
RELATIONSHIP BETWEEN DETENTION BASIN SIZE,
RAINFALL EVENTS AND VOLUME OF
OVERFLOW-BASED ON FIVE YEARS OF
CLIMATOLOGICAL DATA
Size of
Basin
(gal.)
Murray Ron
50,000
100,000
150,000
200,000
250,000
Trout Run
50,000
100,000
150,000
200,000
250,000
300,000
24th Street
50,000
100,000
150,000
200,000
Percent Reduction
of Overflow Events
in Five Years
47
70
90
96
98
15
53
70
87
92
9.6
72
91
98
100
Percent of Overflow
Volume Detained
in Five Years
52
79
91
96
98
38
63
79
89
93
96
65
90
99
100
113
-------
A PROGRAM FOR CONTROLLING POLLUTION
FROM SANITARY SEWER OVERFLOWS
Only a limited sampling of the overall problem of sanitary sewer over-
flows was possible in this study. Nevertheless this sampling should
sufficiently indicate the character and magnitude of the problem and
provide guidelines towards solutions not only for Roanoke but also for
other communities faced with similar situations.
A program for a significant reduction of sewer overflows requires a
combination of methods and techniques, as no one method offers a
cure-all. Worthwhile improvements can only be made through a com-
prehensive program of renovation, repair and control measures. Re-
lative priorities should be taken into account in the selection of areas
for restoration so that the worst conditions will be remedied first.
The following outline presents the major features of a restoration pro-
gram.
1 . Once an area has been selected for rehabilitation, the sewerage
system should be visually inspected and smoke tested to locate and
define major storm water entry points and to generally assess the
condition of the system. This method can usually be accomplished
with City forces and is fast and economical. One crew can test up
to 5000 feet per day.
2. The results of such testing should be recorded with both written
descriptions and photographs. Separate listings of deficiencies on pri-
vate property should be made and turned over to the Building Inspector
for any code enforcement. A cooperative program between the City
and the private owner should be developed to simplify and speed cor-
rections on private property.
3. From the results of the smoke testing and inspection program,
obvious deficiencies should be scheduled for repair by the usual
maintenance forces. This would involve cleaning lines of roots and
other obstructions, replacing broken sections, removing storm
water connections, sealing or raising perforated manhole covers in
depressed areas, and correcting other such obvious defects.
4. Smoke testing would also indicate those areas of the system where
more intensive inspections by television are required. The television
inspections will pinpoint defects which require excavating to repair.
While the television inspection is underway, the joint sealing and grout-
ing should be accomplished as necessary. This part of the program
114
-------
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LEGEND
DETENTION BASIN
TRUNK SEWER OR INTERCEPTOR
LIMITS OF STUDY AREA
DETENTION BASIN SITE
MURRAY RUN STUDY AREA
SCALE IN FEET
•4-
•4
^
1000
PLATE 6
3000
Syc
-------
Previous Page Blank
tez^^^^yt^rtz^
LEGEND
•I DETENTION BASIN
TRUNK SEWER OR INTERCEPTOR
— _ LIMITS OF STUDY AREA
DETENTION BASIN SITE
TROUT RUN STUDY AREA
SCALE IN FEET
[»»»»if
4-
1000
PLATE 7
3000
117
-------
Previous Page Blank
LEGEND
DETENTION BASIN
TRUNK SEWER OR INTERCEPTOR
LIMITS OF STUDY AREA
DETENTION BASIN SITE
24TH STREET STUDY AREA
SCALE IN FEET
4-
1000
PLATE 8
3000
119
-------
Previous Page Blank
---- WASENA SCHOQt
/- EX I ST I
/ RUN INTERCEPTO
DETENTION BASIN SYSTEM
LAYOUT FOR MURRAY
RUN STUDY AREA
0 100 200 300
PLATE 9
121
-------
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PLATE 10 DETENTION BASIN CONCEPTUAL DESIGN FOR
MURRAY RUN STUDY AREA
NEW MANHOLE WITH OVERFLOW
WEIR AND FLOW MEASURING
DEVICE
EXISTING
INTERCEPTOR
15" OVERFLOW
LINE
HIGH VELOCITY
FLUSHING SYSTEM
*
Jj
HJ== ?
N ;
B" FORCE MAIN
2-300 GPM PUMPS
PUN VIEW
TOP SLAB REMOVED
HOSE CONNECT!ON
FOR HIGH VELOCITY
FLUSHING SYSTEM
VENT-\
150,000 GALLON
DETENTION BASIN
PUMPING
STATION
EXISTLUG
NTERCEPTOR
SECTIONAL PROFILE
-------
Previous Page Blank
will require either the purchase of television inspection and grouting
equipment for use by City forces or the employment of firms normally
engaged in this work. This is the most expensive and variable part of
the repair program as the exact extent cannot be determined before-
hand.
5. Rainfall and flows in the sewers should be monitored continuously
before, during and at completion of the repair work in order to
evaluate the effectiveness of the repairs. An 80 percent reduction
of infiltration is expected.
6. As all of the infiltration will not have been eliminated by the above
program, the system should be analyzed to determine those line seg-
ments requiring replacement in order to provide adequate hydraulic
capacity. The analysis will also reveal the optimum size and location
of required detention basins to store peak flows.
7. The volume of a detention basin, should be selected to contain the
overflow resulting from at least the maximum storm event with a one
year return frequency. In addition, the detention basin should limit
the outflow from the drainage area so that the hydraulic capacity of the
downstream facilities is not exceeded. In Roanoke's case the limiting
feature is the Water Pollution Control Plant.
8. Sufficient telemetering equipment should be incorporated into the
detention basin facility to permit monitoring during overflow events and
to aid in the overall operation of the system.
9. The reliability of the system will only be as good as the maintenance
program. Routine preventative maintenance will insure that the system
operates properly during the critical storm periods.
10. Once the system has been restored, an effective routine main-
tenance program on a scheduled basis should be established. Con-
nections into the system should be made only by licensed contractors
and in strict compliance with codes. A stepped-up maintenance pro-
gram would alleviate problems in other areas until the comprehensive
sewer repair program can be undertaken.
125
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COSTS OF REMEDIAL MEASURES
BASIS OF COST ESTIMATES
The costs for inspecting, repairing, cleaning, and replacing sewer lines
and providing detention basins are based on the results of detailed in-
vestigations undertaken in the study areas. Application of the required
costs for these measures to the remaining drainage areas in the City
were made according to their similarity to the study areas. The cost
for sewer line replacement is the cost for new sewer line -requirements
in addition to those recommended in "Report on Sanitary Sewerage
Interceptors and Trunk Mains, City of Roanoke, Virginia" (2). The
separation of the combined sewer system in the downtown portion of the
City was recommended in the report (2) and the cost for this measure
was taken from the report and adjusted to reflect current construction
prices.
The estimated unit costs applicable to the remedial measures are given
in Table 46. The costs are considered to be those currently in effect
for this type of work.
Cost estimates were made for implementation of remedial measures in
the three study areas and are presented in Table 47.
COSTS OF RECOMMENDED REMEDIAL MEASURES
The.estimated construction cost of recommended remedial measures
for the entire City of Roanoke is given in Table 48 as $6,149,000.
This cost includes repairs of the sewer system, replacement of sections
of existing sewer lines, television inspection, cleaning, grouting,
separation of combined sewers in a portion of the City and separation
of digester supernatant and sludge thickner flow and sewage overflow
at the Water Pollution Control Plant. The estimated operation and
maintenance cost for 13 underground detention basins and pumping
stations is $22,000 per year as shown in Table 49. Table 50 gives a
breakdown of the remedial measure costs per acre and per capita for
each study area and the entire City,
126
-------
TABLE 46
UNIT COSTS
Item Unit Cost
Repair of Sewers
Repair lateral sewer leak Ea. $ 250.00
Repair collector sewer leak Ea. 500.00
Repair interceptor sewer leak Ea. 500.00
Repair leak detected by smoke
emitting from, catch basin Ea. 1,000.00
Television Inspection, Cleaning and
Grouting of Interceptors and Collectors LF 6.00
Replace Sewer Lines
12- to 24-inch LF 26.00
30- to 36-inch LF 34.00
42- to 48-inch LF 63.00
Detention Basins
Circular underground tank with
pumping station and all appurtenances
100,000 gal. Ea. 115,000.00
150,000 gal. Ea. 128,300.00
200,000 gal. Ea. 146,500.00
Property aquisition per basin LS 10,000.00
127
-------
TABLE 47
COST ESTIMATE FOR REMEDIAL MEASURES
IN EACH STUDY AREA
Replace
Repair of TV Inspect. Detention Portions of
Study Area Sewers and Grout Basin Interceptors Totals
Murray Run $35,500 $210,200 $138,300 $ 3300 $387,300
Trout Run 93,000 309,200 156,500 27,000 585,700
24th Street 27,000 117,200 125,000 13,000 282,200
TABLE 48
COST ESTIMATE FOR RECOMMENDED REMEDIAL
MEASURES FOR THE ENTIRE CITY OF ROANOKE
Item Estimated Cost
Repair of Sewer System $ 715,000
Television Inspection and Grout 2,855,600
Sewer Line Replacement 200,200
Detention Basins 1,835,700
Separation of Combined Sewers 522,500
Separation of Digester Supernatant
from Overflow at Water Pollution
Control Plant 20,000
Total $6,149,000
128
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TABLE 49
OPERATIONAL AND MAINTENANCE COSTS
FOR RECOMMENDED REMEDIAL MEASURES
FOR THE ENTIRE CITY OF ROANOKE
Item Estimated Cost/Year
Clean 13 Basins After Each
Rainfall Event $ 9200
Observations During Rainfall
Events 4600
Maintain Equipment 6200
Electrical Power 2000
Total $22,000
TABLE 50
ESTIMATED COSTS PER VARIOUS UNITS FOR
RECOMMENDED REMEDIAL MEASURES
Area
Murray Run
Study Area
Trout Run
Study Area
Z4th Street
Study Area
Entire City of
Roanoke
Total Project
Cost
$ 387,300
585,700
282,200
6,149,000
Cost Per
Acre
$426
587
273
370
Cost Per
Capita
$65
53
28
61
129
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BENEFITS OF REMEDIAL MEASURES
Overflows presently occur approximately 28 times per year in the Murray
Run study area and 15 times per year in the 24th Street area. The Trout
Run interceptor overflows during nearly every rainfall and occasionally
during dry weather flow. Conditions similar to these are reported in
other areas of the City. Implementation of the remedial measures listed
in Table 48 will eliminate all overflows in Roanoke's sanitary sewerage
system except those from very high intensity rainfalls. The volume of
overflow from higher intensity rainfalls which occur less frequently than
once per year will be reduced. The reduction in frequency of overflows
will provide relief from the offensive and unhealthy conditions created by
the frequent discharges of raw sewage into yards, into basements, onto
streets and sidewalks, and into streams.
The following shows the estimated reductions in overflow volume in the
study areas to be achieved by implementation of the recommended re-
medial measures:
ESTIMATED ANNUAL OVERFLOW VOLUME
Study Area Existing Conditions Improved Conditions
Murray Run 8 mg 0.3 mg
Trout Run 23 mg 0. 6 mg
24th Street 4 mg 0.2mg
For the City as a whole, it is estimated that the present 79 million gal-
lon annual overflow would be reduced to 2.5 million gallons.
It is not within the scope of this study to determine to what extent the
overflow of raw sewage from Roanoke's sewer system and the sewage
bypasses at the pollution control plant contribute to the pollution of
Smith Mountain Lake, which is a 20,000 acre lake four and one half miles
downstream. Neither is it within the scope of the study to determine to
what extent the recommended remedial measures will alleviate the pol-
lutional problem at the lake. It is judged, however, that the implementa-
tion of the remedial measures will enhance the aesthetic and recreational
value of the Roanoke River arm, of the lake.
130
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SECTION 7
ACKNOWLEDGEMENTS
Appreciation is extended to the following persons and their organizations
for their assistance and cooperation during the course of this study:
FEDERAL WATER QUALITY ADMINISTRATION
William A. Rosenkranz - Chief, Storm and Combined Sewer
Pollution Control Branch, Division of
Applied Science and Technology
Henry R. Thacker - Director, Research and Development
Office, Middle Atlantic Region, Project
Officer
PUBLIC AGENCIES
City of Roanoke, Virginia
H. C. Broyles - Director of Public Works
H. S. Zimmerman - Superintendent, Water Pollution Control Plant
Department of City Planning
Roanoke Valley Regional Planning Commission
United States Weather Bureau - Woodrum. Field
Roanoke County Public Service Authority
Virginia State Water Control Board
COMMERCIAL FIRMS
James A. Rogers - Penetryn System, Inc.
Technical Consulting Services, Chemists
131
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SECTION 8
REFERENCES
(1) Weller, L. W. and Nelson, M. K. , "Diversion and Treatment
of Extraneous Flows in Sanitary Sewers", Journal Water Pollution
Control Federation, 37, 343, 1965.
(Z) Report on Sanitary Sewerage Interceptors and Trunk Mains,
City of Roanoke, Virginia, Hayes, Seay, Matter n and Mattern, Roanoke,
Virginia, December 1965.
(3) A Land Use Plan For the Roanoke Valley Region, Roanoke
Department of City Planning, June 1963.
(4) Weibei, S. R., Anderson, R. J., and Woodward, R. L.,
"Urban Land Runoff as a Factor in Stream Pollution", Journal Water
Pollution Control Federation, 36, 914, July 1964.
(5) White, R. H. , "TV Inspection and In-Place Grouting of Sewers",
Water and Wa stes Enginee r ing, September 1968.
(6) Rhodes, Donald E., "Rehabilitation of Sanitary Sewer Lines",
Journal Water Pollution Control Federation, 38, 2, 215, 1966.
(7) Brunton, B. W., "Detection and Sealing of Leaks in Sewers",
Paper presented at Canada Institute of Pollution Control Meeting,
October 1963, Quebec City, Canada.
(8) Nooe, Roger, "Seal Sewer Leaks From the Inside", The
American City, June 1964.
(9) Stepp, Scott G. , "Sealing Process Resolves Infiltration
Problem", Public Works, 1967.
(10) Godbehere, J., "Eliminating Infiltration of Ground Water Into
Sewers", The Surveyor and Municipal and County Engineer, October
1962.
133
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APPENDIX I
FIELD INVESTIGATION
SMOKE TESTING
The nature of this study required as much information as possible con-
cerning the existing condition of the sanitary sewer lines in the three
study areas. To achieve this goal, it was necessary to conduct an
extensive field investigation.
The City of Roanoke had already begun a program of smoke testing
prior to the undertaking of this project. Therefore, the City's smoke
testing crew was assigned the task of smoking the sewers in the study
areas under the supervision of Hayes, Seay, Mattern and Mattern.
Smoke testing was only one of the methods used to establish the con-
dition of the sanitary sewer lines.
The smoke testing crew usually consisted of four men, but varied
at times from three to five. Four men constitute an ideal crew
because of the various functions required during testing.
The equipment used by the City consisted of a Steco Model No. DA-20
blower, powered by a 3-1/2 hp gasoline engine. The blower had a ca-
pacity of 1750 cfm. In conjunction with the blower, smoke bombs as
manufactured by the Superior Signal Company were used. The bombs
produced about 40,000 cubic feet of smoke and burned for about 3 min-
utes. The equipment was transported using a City-owned dump truck,
but a smaller size such as a pick-up truck would suffice.
When the crew arrived at a section of line requiring smoking, the
blower was unloaded and placed alongside an open manhole. The smoke
bomb was attached to the blower by a string using a sliding loop around
the bomb for easy removal. The bomb was lighted and lowered into the
manhole and the blower was started and placed over the manhole
opening.
Once the bomb was lit and the blower in operation, it took only a few
seconds for smoke to appear at various paints. The first place smoke
appeared was from vent pipes on the roofs of homes and businesses. If
any were connected, smoke would soon appear from downspouts and
curb or drop inlets. Smoke also appeared from cracks along walks
and curb and gutter.
135
-------
la an effort to uncover additional smoking violations, sewer lines were
plugged at adjacent manholes upstream, and downstream. However,
no better results were obtained and the time required was about doubled,
so the procedure of plugging the sewer lines was abandoned.
Initially, 3-minute bombs were used. However, 5-mmute bombs gave
better results as they allowed more time to locate and record the test
results.
RECORD OF RESULTS
The results of the investigation were tabulated in a manner describing
the type of infraction in the sewer line that would allow storm-surface-
runoff to enter directly into the sanitary sewer system. Also, the
location of the infraction was noted and the location was recorded on an
area map using symbols to depict the particular type.
COSTS
The following is a breakdown of costs involved in the smoke testing por-
tion of the field investigation:
Equiprnejnt Cost
Steco Model No. DS-20 Blower $220.00
Smoke Bombs, 3-minute $ 12.00 per dozen
It took approximately one smoke bomb per manhole during the testing
program. For 6000 feet of sewer line, there was a manhole about
every 250 feet or 40 manholes in the 6000 feet of line. It would take
about 40 smoke bombs to smoke this section of line. At $12.00 per
dozen this would be approximately $40.00 for smoke bombs.
One crew could test and record the results of about one mile of
collector line per day. The cost of such testing averaged about $300
per mile of sewer.
136
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APPENDIX n
HYDROLOGICAL INVESTIGATION
EQUIPMENT
The geographical location of Roanoke made it necessary to locate
several rain gauges in the valley to obtain a cross-section of all rain-
fall events. The equipment selected was one universal recording rain
gauge and two non-recording gauges. The recording rain gauge,
Figure 28, recorded the rainfall by use of a weighing mechanism which
caused a pen to trace, on a chart, changes in a pre-balanced collection
system. The daily charts used with the gauge could record up to 6
inches of total rainfall. Each non-recording rain gauge, Figure 29,
was a direct reading type as manufactured by Belfort Instrument
Company. The measuring tube was 23 inches long, had a capacity
of ten inches and measured to the nearest tenth inch of rainfall.
METHODOLOGY
The location of the rainfall gauges was determined by the rainfall pat-
tern to be expected in the Roanoke Valley during the testing period.
Rainfalls tend to follow the mountain ridges, especially during the sum-
mer months, and it was necessary to obtain the variation in rainfall
pattern. To accomplish this end, the recording rain gauge was placed
in the Murray Run study area, a non-recording rain gauge was placed in
the Trout Run area and in the 24th Street area, and use was made of the
recording rain gauge located at the U.S. Weather Bureau at Woodrum
Airport north of the City. Data from the gauges were recorded after
each rainfall event and tabulated in appropriate order for future use.
To expand the rainfall data collected during the events measured, the
local climatological data from the U.S. Department of Commerce
were obtained as collected by the local U.S. Weather Bureau for the
past five years.
137
-------
Figure 28. Recording Rain Gauge
Figure 29. Non-recording Rain Gauge
138
-------
PROBLEMS
A six month delivery time for new rain gauging equipment -was not
anticipated. The manufacturers of recording rain gauges are geared
for production of the gauges for only several months each year and
manufacture only those back ordered. Because of this delay, a re-
cording gauge ,was furnished by the FWQA; however, it was an old
gauge that had been used and declared obsolete by the USGS and had a
weekly timing mechanism and 9-inch recording chart. The gauge was
recalibrated by the Belfort Instrument Company and equipped with a
24-hour timing mechanism and a 6-inch chart for use on short duration
rainfalls. It took approximately eight weeks for delivery of the modified
gauge.
The use of the two non-recording rain gauges proved unsatisfactory for
other than simply measuring total rainfall. Due to the greater varia-
tion in rainfall patterns than expected, recorded intensities could not
be satisfactorily correlated with only total rainfall from the non-
recording gauges.
COSTS
Following is a breakdown of the approximate equipment costs in-
volving the hydrological investigation:
Repair old recording rain gauge $27.00
Chart paper 5.00
Non-recording rain gauge 56.00
$88.00
OR
New recording rain gauge $325.00
Non-recording rain gauge 56.00
$381.00
139
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APPENDIX III
GAUGING OF STREAMS AND SEWERS
EQUIPMENT
The equipment used to record the flow in the streams and sanitary
sewers in the three study areas consisted of six continuous water level
recorders manufactured by the Instruments Corporation,, now a part of
Belfort Instrument Company. Also, one pressure type recorder manu-
factured by the Bristol Company of Waterbury, Connecticut, was used.
The operation of each continous water level recorder consisted of a
time element and a stage element. The time element is driven by a
clock weight and regulated to a constant speed by a clock escapement.
Power is transmitted through a driving roll, which unwinds the paper
from a supply 'roll and feeds it onto a take-up roll at the rear of the
instrument case, as a finished record. The stage element is activated
by a float at water level which is connected by a flexible stainless steel
perforated tape and suitable counterweight to a spined float wheel. Any
movement of the float records in a direct ratio of inches of chart to
inches of stage. The rise and fall of the water is plotted as an ordinate
against time as an abscissa. The water level recorders and pressure
gauge are shown by Figures 30 and 31. The Bristol pressure gauge
operates by measuring the pressure due to the depth of liquid by bubbling
a gas such as CO;? through a long tube inserted into the liquid. The
gauge releases the gas at a constant pressure and as the depth of the
liquid changes the pressure differential is recorded on a circular chart
in inches of depth,
METHODOLOGY
All gauges were located as near as possible to the lower end of the
respective study areas. In the Murray Run study are~a, the site for the
stream gauge waa based upon as uniform flow conditions as could be
found in the channel. A 24-inch corrugated standpipe was used as a
stilling well with a continuous level recorder situated on top of the pipe
as shown by Figure 6. Flows were calculated based upon the hydraulic
characteristics of the stream channel. It was impossible to find an
existing manhole in the Murray Run sanitary sewer that could be used
to measure the depth of flow, because of non-uniform flow conditions in
the manholes. A specially designed manhole was constructed over a
section of the sewer having uniform flow, as shown by Figure 7. The
141
-------
Figure 30. Water Level Recorder
V ,"
Figure 31. Bristol Pressure Gauge
142
-------
hydraulic elements of the lower half of the sanitary sewer were used to
determine the dry weather flow. The root masses ia the upper half of
the sewer made it impossible to establish the hydraulic characteristics
when the line was flowing more than one half full. Increases in flow
due to infiltration caused the sewer to surcharge and overflow at man-
holes. Therefore, in order to obtain a more accurate reading of over-
flows, a weir was installed in the side of the manhole wall. The normal
dry weather flow was allowed to continue through the line, but when the
manhole surcharged during a rainfall event, the overflow passed over
the weir into the Murray Run stream, thus giving an accurate measure
of overflow.
In the 24th Street study area, a sharp crested weir plate •was installed
on the upstream face of a box culvert, Figure 10. A 24-inch diameter
corrugated pipe float well was fastened to the head wall. A continuous
stage recorder was installed in a manhole in the sanitary sewer using
an installation similar to Figure 32. This method of measuring the in-
line flow, without the use of a flume or stilling well, proved to be the
most satisfactory and flow was determined by using the hydraulic
characteristics of the sanitary sewer.
In the Trout Run study area, the stream channel consists of a curved
concrete bed with vertical stone sides, giving ideal conditions for
determining flow. However, due to the small quantity of flow and
insufficient depth of flow, a concrete weir was constructed across the
channel. A 9-inch corrugated pipe was fastened to the side wall to
serve as a guide for the float from the water level recorder and also
provide a stilling well for accurate measurement of flow in the stream.
Figure 8 shows the installation in Trout Run stream. The initial gauge
location in the sanitary sewer was unsatisfactory as the sewer sur-
charged during each rainfall event. Other locations were unsuitable due
to physical obstacles.
The gauge was eventually relocated to a manhole in the center of a
street and permanent barricades were maintained. The installation was
similar to Figure 32, and proved quite satisfactory for a wide range of
flows.
A water level recorder was installed at the overflow structure at the
Water Pollution Control Plant, in order to determine the quantity of
sewage bypassed at the plant during rainfall events. Due to a limited
number of recorders, the recorder in the 24th Street stream was re-
located to the plant.
143
-------
FIGURE 32 »ATER LEVEL RECORDER INSTALLATION
IN SANITARY SEWER HANHQLE
WATER LEVEL
RECORDER
144
-------
The stage recorders were left running continuously and had to be checked
about three times a week to wind the clock. At this time, the chart was
removed, dated and appropriately marked for future use. The Bristol
pressure gauge was put in operation only during rainfall events be-
cause the bubbler pipe collected debris and required frequent cleaning,
at least hourly. Because of the maintenance problem the bubbler type
gauge was unsatisfactory when installed in the direct stream flow and
the gauge was replaced with a continuous water level recorder.
PROBLEMS
The problems encountered during the study relating to stream and
sewer gauging were limited to the equipment initially and minor problems
later during gauging. The six continuous water level recorders were
on loan from the FWQA, The recorders had previously been used by
the USGS for gauging rivers and were not geared for the small measure-
ments encountered when gauging small streams and sewer flows. It
was further learned that the instruments were obsolete and had been
replaced by the USGS with a new model of a similar machine. The only
parts readily available were the recording pens and the chart paper •which
were the only items interchangeable with the updated machine. In order
to adapt the machines for use in streams and sewers, it was necessary
to change the gear ratio on the time element to provide maximum paper
travel of 9 • 6 inches per day in lieu of the existing 2.4 inches per day.
Copies were obtained from Belfort Instrument Company of detail draw-
ings of the desired gears. New gears were made locally and installed
in the machines. After this, the water level recorders worked satis-
factorily throughout the remainder of the program. However, the
gauging program was delayed for about 8 weeks.
COSTS
Below is a breakdown of costs required to put the water level recorders
in satisfactory operating condition so that they could be used in the
gauging program.
145
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Equipment Cogjb
12 Gears $200
12 Rolls chart paper 60
6 Floats 135
6 Float counterweights 19
6 Clock weights 6l
Ink, pens, float tape, etc. 73
$548
The cost for six new water level recorders would have been an addi-
tional $1700 or a total of $2248 for gauging equipment. The Bristol
pressure gauge cost about $800, installed and ready for use.
The approximate costs for construction of the weirs and manhole are
as follows:
Location Construction Cost
Trout Run Weir in stream $1140
24th Street Weir in stream $ 900
Murray-Run Manhole $1240
146
-------
APPENDIX IV
WATER QUALITY SAMPLING AND TESTING
EQUIPMENT
The equipment used to obtain samples from the streams and sanitary-
sewers in the three study areas consisted of two Serco samplers for
automatic sampling.
The Serco automatic sampler, Figure 33, works on a vaccuum principle.
The sampler has 24 bottles in which to collect samples. The sample
bottles are all evacuated through the plastic sampling lines and sampling
head by use of a vacuum pump. A vacuum of about 26 inches of mer-
cury can usually be obtained depending on the elevation above sea level,
After evacuation, each bottle is sealed off by means of an individual
switch. The spring driven clock rotates a tripper arm releasing the
individual switches thus drawing a sample into the bottle.
Figure 33. Serco Automatic Sampler
147
-------
Many accessories are available for the samplers such as;
1. Gears or clocks to vary the sampling interval from 5 minutes
to 8 hours.
2. Varying lengths of plastic sampler lines for lifts from 3 feet
to 13 feet.
3 . Vacuum pump.
4. Electric timers .
5. Mechanical refrigeration.
6. Remote starting switch to start the sampling cycle.
The accessories utilized in this study included the following:
1. Two clocks, one timed to collect samples every hour and one
to collect samples every fifteen minutes.
2. Length of sampling hose for 8 feet of lift.
3. Vacuum pump.
4. Remote starting mechanism to start the sampling cycle.
METHODOLOGY
The samples were taken as close to the point of gauging as possible.
Funds were available for only two automatic samplers. These auto-
matic samplers were used as a pair in one study area, obtaining
samples from the stream and sanitary sewer simultaneously during a
rainfall event. During the same event, the other two study areas were
manually sampled at various time intervals. The automatic samplers
were moved from time to time to the other study areas.
Sampling at the Water Pollution Control Plant was done manually with
samples taken from the comminutor room.
After obtaining the samples, they were iced down and transported to the
laboratory for analysis. Tables 51 through 56 give the sanitary sewer
and stream characteristics in tabular form.
148
-------
PROBLEMS
The problems encountered during sampling primarily involved the
equipment. The automatic samplers worked rather well except that
some precautions had to be taken. In the streams, the nozzle could
not be resting on the bottom or sand and grit would be drawn into the
sample bottle. Rags from, the sanitary sewers would block several
of the tube openings during a 24-hour sampling program. Occasionally
a clock would stop and a complete rainfall would be missed. The auto-
matic starting devices proved to be inadequate; therefore, the samplers
had to be started manually at the beginning of each rainfall, which proved
to be time consuming.
149
-------
Previous Page Blank
APPENDIX V
COMPUTER PROGRAM
PROGRAM ABSTRACT
The purpose of this program is to determine the Ideations and potential
rates of overflows from sanitary sewers due to infiltration of surface
water into the sewers during rainfall.
The necessary field data required for input include the length of
collector sewers contributing to flow in the sewer to be analyzed and
the hydraulic characteristics (length, slope and diameter) of each line
in the sewer to be analyzed.
Additional input data required include the characteristics (average in-
tensity and duration) of the design rainfall event, the dry weather flow
(including normal ground water infiltration) of the sewer to be analyzed
and an estimate of the BOD concentration in the sewer during rainfall.
(Data provided by the study contained herein will be a guide to deter-
mining the BOD.) Up to 10 intensity/duration characteristics may be
printed in one pass.
The program assumes that all dry weather flow and surface water infil-
tration are uniformly distributed throughout the sewer and contributing
collectors, and that a sewer has a potential to overflow when flow
exceeds the capacity of the pipe just flowing full, a.s determined by the
Manning Formula.
The resulting output is a tabulation of each lifte, beginning at the up-
stream end and showing manhole number (line designation), capacity,
dry weather flow, wet weather flow, rate of potential overflow, volume
of potential overflow and pounds of BOD overflowing to a surface water
to cause stream pollution, all due to surface water infiltration caused
by the design rainfall event.
Totals for the rates and volumes of potential overflow and pounds of
BOD for the entire sewer are printed at the end of the tabulation.
The printed output can be analyzed for potential overflow in the sewer
and corrective measures taken.
Reruns should indicate the effects of the design changes and any further
changes required to meet the design rainfall event.
151
-------
OPERATING INSTRUCTIONS
IBM 1130 System
SWINF (Surface Water Infiltration)
No switches tested
Card Order:
1. // XEQ SWINF
2. Intensity cards (2 required). Zeroes should be punched in
unused fields.
3. Job title card (1 required).
4. Job dry weather flow, BOD, infiltration multiplier.
5. Manhole deck (160 maximum). Manhole numbers are input
beginning at lower end of system being analyzed.
6. Blank card (1 required) to signify end of manhole deck.
7. Terminate card (1 required), ^punched in card column 80.
Note: Repeat 3-6 for stacked jobs using same intensity com-
parisons. To stack jobs having a new set of intensity cards,
insert a blank card preceding the new intensity cards. This
card is in addition to the blank which signals the end of the
last manhole deck of the previous job. Repeat 3-6 as required,
Files: Temporary - 160 records, 10 words each.
152
-------
// JOB
// FOR
*ONE WORD INTEGERS
*LI5T SOURCE PROGRAM
* IOCS(CARD*1132PRINTER .DISK)
*NAME SWINF
•TRANSFER TRACE
^ARITHMETIC TRACE
*» PROGRAM TO DETERMINE LOCATIONS AND RATES OF POTENTIAL SEWER
** OVERFLOWS DUE TO SURFACE WATER INFILTRATION.
DEFINE FILE 1 (160*10»U»N1)
DIMENSION 10(80)*XINTS( 10) »DURUO)
7 FORMAT(3X»12»9X.F7«4»3F19.4.F15.4»113>
100 READ(2»200MXINTSt I ) »OURU ) »I«l .10)
200 FORMATUOF6.2)
101 1*1
C READ AND PRINT JOB TITLE
READ(2.1)IO
1 FORMAT(BOAl)
IF(IO<1>-23616) 102.999*102
102 IF( I0a»-16448) 103*100.103
103 WRITE<3»2>10
2 FORMAT(1H1,80A1,/)
READ I 2 »5)DWFDA »80D » XMUL
5 FORMAT(F10«2.Fa.2«F^.2)
WRITE(3»9)XINTS(I)iDUR(l)
9 FORMAT*' DESIGN RAINFALL - '»F5.2.« IN/HR AVERAGE INTENSITY1»
1F13.2*1 HOURS DURATION1*/)
C WRITE PAGE HEADINGS
WRITEO.3)
3 FORMAT<• UPSTREAM LINE CAPACITY DRY WEATHER FLOW WET WEAT
1HER FLOW POTENTIAL SEWAGE OVERFLOWS TOTAL BOD')
WRITE<3»4)
4 FORMATS MH NO'«10X»'MGD*»15X*'MGD*»1?Xi'MGD'»12X»'RATE - MGD'«
15X*'VOLUME - MG».TX.'LBS1»/5
C READ ALL INPUT CARDS FOR FILE 1. MANHOLE NO,»DJAMETER.COLLECTQR
C LENGTHS.LINE LENGTH»SLOPE. BLANIC CARD TERMINATES.
Nl-l
20 READ(2»6)MHNO»DIAM»COLL»XLINE*SLOPE
-------
OVERFLOWS DUE TO SURFACE WATER INFILTRATION. PAGE 02
6 PORMAT{I3»F3«0»2F6.0»F8.5)
IFtMHNO>21»300*21
300 TOTMH«N1-1
GO TO 24
21 DIAM*DIAM/12.
WRITEtl»Nl)MMNO»DIAM»COLL«XLlN£*SLOPE
IF(Nl-2)23,22.23
C COMPUTE THE TOTAL LENGTH OF COLLECTORS AND INTERCEPTORS
C CONTRIBUTING TO THE FIRST LINE IN THE SEWER.
22 TOLIN=COLL
GO TO 20
23 TOLINsTOLlN+XLlNE+COLL
GO TO 20
C INFILTRATION RATE FOR THE DESIGN RAINFALL EVENT FROM EQUATION
C DEVELOPED BY ROANOKE POLLUTION STUDY.
24 XINFL=<1.98438*XINTS(I)-0.0870)/10000.*XMUL
C INITIALIZE TOTALS
C KTREM IS NO. LINES PER PAGE
KTREM*5.0
C TRPOF IS TOTAL RATE OF POTENTIAL OVERFLOW
TRPOF=0.
C TPOF IS TOTAL VOLUME OF THE POTENTIAL OVERFLOW
TPOF=0.
C LBBOD IS TOTAL L8S. OF S.O.D. ACTUALLY REACHING AN ADJOINING STR.
LBBOD=0.
C DWFPF IS SYSTEM DRY WEATHER FLOW PER FOOT
DWFPF=DWFDA/TOLIN
C BEGIN INVESTIGATION AT UPSTREAM END
NREC=TOTMH
READ*l'NREC)MHNO»DIAM»COLLtXLINE»SLOPE
TLINE=COLL
C DWF IS DRY WEATHER FLOW THIS LINE
40 DWF*DWFPF#TLINE
C FLOW DUE TO GROUND WATER INFILTRATION
FLOW=XINFL#TLINE
IF(SLOPE)28t28»29
C QFULL IS CAPACITY THIS LINE FLOWING FULL USING MANNING EQUATION
-------
OVERFLOWS DUE TO SURFACE WATER INFILTRATION. PAGE 03
ROUGHNESS COEFFICIENT OF .01,4
28 QFULL«0.
GO TO 30
29 QFULL*<83.3646»U./4.**{2./3.M*DIAM**(8./3.>*SLOPE**.5)*.646
RPOF IS RATE OF POTENTIAL OVERFLOW THIS LINE
30 RPCF*DWF+FLOW-TRPOF-QFULL
IFX1_tttE
25 NREC*NREC-1
IF(NREC)34»34»26
26 READU«NREC)MHNOfDIAM.COLL»XLINE»SLOPE
TLINE«TLINE+COLL
GO TO 40
JOB TOTALS Rourm
34 WRITE(3i8JTRPOF*TPOFtLBBOO
-------
OVERFLOWS DUE TO SURFACE WATER INFILTRATION. PAGE 04
8 FORMAT(/t40X,«INTERCEPTOR TOTALS = • »3X»2F15.4»113)
IF XIWStTt IDUR < 1 )
WRITE(3»3)
WR1TEO.4)
GO TO 24
999 CALL EXIT
END
UNREFERENCED STATEMENTS
31 35 25
i—'
°* FEATURES SUPPORTED
TRANSFER TRACE
ARITHMETIC TRACE
ONE WORD INTEGERS
IOCS
CORE REQUIREMENTS FOR SWINF
COMMON 0 VARIABLES 182 PROGRAM 762
END OF COMPILATION
-------
APPENDIX VI
RAINFALL INTENSITY AND RATE
OF DISCHARGE FOR THE THREE
STUDY AREAS
FIGURES 34 THROUGH 101
157
-------
FIGURE 3H RAINFALL INTENSITY AND RATE OF DISCHARGE
MURRAY RUN STREAM
20
CT
0
5PM
6 FEBRUARY 1969
LEGEND
•- DRY WEATHER FLOW
FLOW DURING RAINFALL
^3 SURFACE RUNOFF
'.W-Ufe'-iM-Ul
7PM
9PM I IPM
TIME, HRS.
1AM
3AM
158
-------
FIGURE 35 RAINFALL INTENSITY AND RATE OF DISCHARGE
MURRAY RUN STREAM
20
CT
E
-10
3PM
CHANGED
TO SNOW
8 FEBRUARY 1969
5PM
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
m*m SURFACE RUNOFF
7PM 9PM
TIME. hrs.
IPM
AM
159
-------
FIGURE 36 RAINFALL INTENSITY AND RATE OF DISCHARGE
MURRAY RUN STREAM
20
•a
£
24 MARCH 1969
2M
4AM
1
I
SAM I2N
TIME, hrs.
4PM
• *• t/y
"3*
8PM
20
P-1
24, 25 MARCH 1969
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
mmm SUFFACE RUNOFF
8PM
.2 ±
oo
12M
4AM 8AM
TIME, hrs
2N
4PM
160
-------
FIGURE 37 RAINFALL INTENSITY .AND RATE OF DISCHARGE
MURRAY RUN STREAM
01
19 JULY 1969
LEGEND
- DRY WEATHER FLOW
FLOW DURING RAINFALL
33 SURFACE RUNOFF
1PM
•sf.
tr
6PM
8PM 10PM
TIME, hrs.
2AM
161
-------
FIGURE 38 RAINFALL INTENSITY AND RATE OF DISCHARGE
MURRAY RUN STREAM
20
TJ
Ol
10
! .31
3 AUG. 1969
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
m^m SURFACE RUNOFF
2PM '
.2
•3
6PM 8PM
TIME, hrs.
0PM
2Mn
to
.5 -
«c
cc
162
-------
FIGURE 39 RAINFALL INTENSITY AND RATE OF DISCHARGE
TROUT RUN STREAM
20
6 FEBRUARY 1969
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
RUNOFF
5PM
7PM
9PM IIPM
TIME, hrs.
TOT
C/J
as
<*:
oc
TAM
163
-------
FIGURE 40 RAINFALL INTENSITY AND RATE OF DISCHARGE
TROUT RUN STREAM
20
-"10
U- v
CHANGED TO SNOW
8 FEBRUARY I 969
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
SURFACE RUNOFF
0.2 £
CO
3PM
5PM
7PM 9PM
TIME, hrs.
PM
AM
164
-------
FIGURE HI RAINFALL INTENSITY AND RATE OF DISCHARGE
TROUT RUN STREAM
DRY WEATHER
FLOW
FLOW DURING
RAINFALL
24 MARCH 1969
SURFACE RUNOFF
oc.
6AM 9AM
TIME, hrs.
20
01
E
LEGEND
DRY WEATHER
FLOW
FLOW DURING
RAINFALL
SURFACE
RUNOFF
f'li':J^;-^i;'';i:'li-:-^"'-'^->1^i1''ii':i^-i^''-J^-'^'-'-i—'-'liji'ji'-ji
3PM
6PM
9PM I2MT
TIME, hrs.
3AM
6AM
165
-------
FIGURE 42 RAINFALL INTENSITY AND RATE OF DISCHARGE
TROUT RUN STREAM
20
TJ
D)
E
10
8, 19 MAY 1969
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
SURFACE RUNOFF
'*** J •*»•«*•'•»•«*•»* H***M •««-xU-^U. Ak'
.2 ^
"•
c
•3£
Ll_
.6 1
8PM
IPM
2AM BAM
TIME, hrs.
SAM
1AM
166
-------
FIGURE H3 RAINFALL INTENSITY AND RATE OF DISCHARGE
TROUT RUN STREAM
30
-o
en
20 -
0PM
12PM
_90
8, 9 JUNE 1969
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
vtmm SURFACE RUNOFF
.2
• V
.5 -
-------
FIGURE 46 RAINFALL INTENSITY AND RATE OF DISCHARGE
TROUT RUN STREAM
80
60
Ol
E
40
20
175 ragd
I .51 in./hr. -
21 JUNE 1969
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
SURFACE RUNOFF
•2
.3
c/>
UJ
.5
3PM
6PM
9PM I2MT
TIME, hrs.
3AM
6AM
170
-------
FIGURE "MS RAINFALL INTENSITY AND RATE OF DISCHARGE
TROUT RUN STREAM
IT"1
5 JUNE 1969
.2
.3
CO
.5
.6
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
mwm SURFACE RUNOFF
7AM 9AM
TIME, hrs.
169
-------
FIGURE 46 RAINFALL INTENSITY AND RATE OF DISCHARGE
TROUT RUN STREAM
80
60
Ol
£
40
20
175 fflgd
I.51in/hr. _
21 JUNE 1969
3PM
LEGEND
.- DRY WEATHER FLOW
FLOW DURING RAINFALL
SURFACE RUNOFF
6PM
9PM I2MT
TIME, hrs.
3AM
I c
2 >•"
c/>
.4
•5 <
or
6AM
170
-------
FIGURE H9 RAINFALL INTENSITY AND RATE OF
TROUT RUN
2 JULY 1969
,3
,6
.7
.8
J
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
SURFACE RUNOFF
'uj at? uju
ui
3AM
BAM 7AM
TIME, hrs.
173
-------
FIGURE 50 RAW ALL INTENSITY AND RATE OF DISCHARGE
TROUT RUN STREAM
30
01
6
.20
APPROXIMATELY 0.5 IN. RAIN
DURATION UNKNOWN
76 mgd.
19 JULY 1969
0«—
3PM
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
^ SURFACE RUNOFF
5PM
7PM 9PM
TIME, hrs.
) 1PM
I AM
174
-------
FIGURE 51 RAINFALL INTENSITY AND RATE OF DISCHARGE
TROUT RUN STREAM
100
80-
60-
Ol
£
2C_
0
9PM
0.79 IN. RAIN
DURATION UNKNOWN
22, 23 JULY 1969
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
iti^Pl SURFACE RUNOFF
I IPM
AM 3AM
TIME, hrs.
SAM
7AM
17$
-------
FIGURE 52 RAINFALL INTENSITY AND RATE OF DISCHARGE
TROUT RUN STREAM __
30
20
u
3 AUGUST 1969
48 mgd
——'v*——
IT
56 in./hr.
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
3 SURFACE RUNOFF
.2
.3 H
oo
LJJ
.5
.6
2PM
6PM 8PM
TIME, hrs.
10PM I2MT
176
-------
FIGURE 53 RAINFALL INTENSITY AND RATE OF DISCHARGE
2Hth STREET STREAM
20
Ul
£
6 FEBRUARY 1969
LEGEND
DRY WEATHER FLOW
FLOW DURING RAIKFALL
teasaad SURFACE RUNOFF
0.
5PM
7PM
9PM MPM
TIME, hrs.
AM
3AM
177
-------
FIGURE 54 RAINFALL INTENSITY AND RATE OF DISCHARGE
2Hth STREET STREAM
T
CHANGED
TO SNOW
8 FEBRUARY 1969
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
SURFACE RUNOFF
20
•2
ce
3PM
5PM
7PM 9PM
TIME, hrs.
I IPM
1AM
178
-------
FIGURE 55 RAINFALL INTENSITY AND RATE OF DISCHARGE
24th STREET .STREAM
20
2M- MARCH 1969
-10
I2MT
SAM
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
SURFACE RUNOFF
6AM 9AM
TIME, hrs.
2N
.2
3PM
•o
en
E
24th STREET STREAM
, 25 MARCH 1969
.2
cc
6PM
9PM
I2MT 3AM
TIME, hrs.
6AM
9AM
179
-------
FIGURE 56 RAINFALL INTENSITY AND RATE OF DISCHARGE
MURRAY RUN SANITARY SEWER
1.0
131
-0.5
1 1
M» . .
MW, . *. . .
•••fc-^i:-X ••'•'
, 1
• > i ;
\P F
1
: i; •
<: ; .» ; ; •
: :: :; - < : : '•:-
Siisrii*-*-* —
1
8 FEBRUARY 1965
:; :; :: ; ; .
I? ' J "
J
I
I
: : : : :•
. < : : :•
"""•-*>*£
\
<"•*
— «
**.
.2
UJ
3PM 5PM
7PM 9PM
TIME, hrs.
MPM I AM
I .0
01
e
0.5 ^
6
_•:
:
|
FEBRUARY 1969
S
EWER SURCHA
i
LEGEND
DRY WEATHER FLOW
lff®&&\ INFILTRATION
RGED ENT RE
— :• -:- •:• :-. < :-: :-. •;.< ; ":<•-
D
1 I
URA
Tip
N ''
:i^:> ;: x :;
f
-C
, 1 ~?
c
.2 >;"
CO
UJ
t—
_J
u_
cc
5PM 7PM
9PM IIPM
TIME, hrs.
I AM SAM
180
-------
FIGURE 57 RAINFALL INTENSITY AND RATE OF DISCHARGE
MURRAY RUN SANITARY SEWER
1.5
.0
'0.5
I I
I2MT
4AM
SAM 12N
TIME, hrs.
4PM
.2
CO
QL
8PM
1 .5
1 .0
24, 25 MARCH 1969
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
INFILTRATION
i'SEWER" REMAiNED'
6PM
2MT
4AM 8AM
TIME.hrs.
2N
4PM
181
-------
FIGURE 58 RAINFALL INTENSITY AND RATE OF DISCHARGE
MURRAY RUN SANITARY SEWER
2. o
I .5
Ol
I .0
0,5
•2
.3
IB, 19 MAY 1969
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
INFILTRATION
•6
or
SURCHARGED
7PM 10PM
AM HAM
TIME, hrs.
7AM
0AM
182
-------
FIGURE 59 RAINFALL INTENSITY AND RATE OF DISCHARGE
MURRAY RUN SANITARY SEWER
I .5
i .0
CT
e
o
^0.5
9 JUNE 1969
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
INFILTRATION
I2M
3AM
6AM 9AM
TIME, hrs.
2N
.2
C/)
.5
.6
.7
.8
.9
i.o
3PM
183
-------
FIGURE 60 RAINFALL INTENSITY AND RATE OF DISCHARGE
MURRAY RUN SANITARY SEWER
I .5
.1.0
TJ
cn
E
0.5
0.91
JUNE 1969
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
INFILTRATION
mm
1111
SURCHARGED
2PM
co
UJ
6PM
8PM
0PM
TIME, hrs.
184
-------
FIGURE 61 RAINFALL INTENSITY AND RATE OF DISCHARGE
MURRAY RUN SANITARY SEWER
5 JUNE 1969
DRY WEATHER FLOW
FLOW DURING RAINFALL
NFILTRATION
fill
7PM
h r s .
185
-------
FIGURE 62 RAINFALL INTENSITY AND RATE OF DISCHARGE
MURRAY RUN SANITARY SEIVER
2.0
I.. 5
-o
01
E
I .0
0.5
0.62
2.25
0.82
J
21 JUNE 1969
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
INFILTRATION
f?'
Ji
<&&£
*$ii$i
*||$ll
<."Xv.'vX"vxX
;.yXy*v;v;v:-
ii>
""I"',-',-',''.- ,"*x'.'^
|i:
SURCHARGED
2 >:
i—
CO
6PM
8PM
10PM I2MT
TIME, hrs.
2AM
4AM
186
-------
FIGURE 63 RAINFALL INTENSITY AND RATE OF DISCHARGE
MURRAY RUN SANITARY SEWER
2.0
I .5
en
E
I .0
0,5
12 JULY 1969
LEGEND
DRY WEATHER FLOW
FLOW DURING ITA1NFALL
INFILTRATION
SURCHARGED
"2MT
2AM
0 J
.2
.3
.1
4AM 6AM
TIME, hrs.
SAM
10AM
CO
187
-------
FIGURE 6<4 RAINFALL INTENSITY AND RATE OF DISCHARGE
MURRAY RUN SANITARY SEWER
2.0
1.5
Ol
i .0
0.5
19 JULY 1969
.50
I .59
LEGEND
— DRY WEATHER FLOW
FLOW DURING RAINFALL
INFILTRATION
SURCHARGED
5PM
7PM
9PM
TIME
IIPM
hrs.
IAM
0 -
i_
• i 7
.2 fc
CO
.3
.1
3AM
188
-------
FIGURE €5 RAINFALL INTENSITY AND RATE OF DISCHARGE
MURRAY RUN SANITARY SEWER
2.0
1.5
T3
Ol
£
1.0
0.5
22, 23 JULY 1969
.06
I .18
LEGEND
DRY WEATHER FLOW
FLOW D.UR ING RAINFALL
NFILTRATION
0-
I ITH"
CO
I AM
3AM
TIME
SAM
7AM
9AM
hrs.
189
-------
FIGURE 66 RAINFALL INTENSITY AND RATE OF DISCHARGE
MURRAY RUN SANITARY SEWER
1.5
• I .0
•o
en
0.5
I .31
J '
3 AUGUST 1969
LEGEND
— DRY WEATHER FLOW
FLOW DURING RAINFALL
m&a INFILTRATION
SURCHARGED
3PM
5PM
7PM 9PM
TIME, hrs.
IPM
0 J
.2 -
t/t
.3
:5
AM
190
-------
FIGURE 67 RAINFALL INTENSITY AND RATE OF DISCHARGE
TROUT RUN SANITARY SEWER
IB, 19, MAY 1969
2.0
I.B-
LEGEND
_ DRY WEATHER FLOW
FLOW DURING RAINFALL
mmm INFILTRATION
T3
oa
-1.0
0-5
•2
C/J
LL.
.5 E
or
.6
8PM
I IPM
2AM 5AM
TIME, hrs.
8AM
AM
191
-------
FIGURE 68 RAINFALL INTENSITY AND RATE OF DISCHARGE
TROUT RUN SANITARY SEWER
[ .5
I1' -0
0.5
8, 9, JUNE 1969
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
INFILTRATION
_L
.2
.3
.5
.6
.7
.8
.9
00
.0
9PM
I I PH
I AM
TIME
3AM
h rs .
5AM
7AM
192
-------
FIGURE 69 RAINFALL INTENSITY AND RATE OF DISCHARGE
TROUT RUN SANITARY SEWER
i .5
.1 .0
0.5
9 JUNE 1969
.2
.3
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
IHFILTRATION
.5
.6
SAM
0AM
2N 2PM
TIME, hrs.
1PM
6PM
193
-------
FIGURE 70 -RAINFALL INTENSITY AND RATE OF DISCHARGE
IBOJT RUN SANITARY SEWER |0
t .5
-ol.
0)
.5
j
15 JUNE 1969
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
INFILTRATION
SURCHARGED
HAM
GAM
SAN 10AM
TIME, hrs.
I2N
. I ^
.c
.2 £
>-
.3 ±
UJ
.5 ^
ZPM
194
-------
FIGURE 71 RAINFALL INTENSITY AND RATE OF DISCHARGE
TROUT RUN SANITARY SEWER
I .5
.0
0.5
21 JUNE 1969
1.51
SURCHARGED
!"*it,'^''!.!.*.'r*X'!-%'.'^'I'M'^V^
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
INFILTRATION
5PM
8PM
IIPM 2AM
TIME, hrs
>AM
.1
.2
.3
UJ
,5
195
-------
1 .0
01
E
0.5
FIGURE 72 RAINFALL INTENSITY AND RATE OF DISCHARGE
TROUT RUN SANITARY SEWER
I, 2 JULY 1969
SURCHARGED
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
INFILTRATION
I i
PM
.2 L.
JZ
.3 •-
>-
u. *~~
*"
LU
.5 z_
.6 <
u_
.7 i
.8
I AM
3AM
TIME,
SAM
h rs .
7AM
9AM
196
-------
FIGURE 73 RAINFALL INTENSITY AND RATE OF DISCHARGE
TROUT RUN SANITARY SEWER
I .0
1*0.5
PM
I
in
T
T
2 JULY 1969
SURCHARGED
LEGEND
_ DRY WEATHER FLOW
FLOW DURING RAINFALL
INFILTRATION
I
.2 --
.3
.5 i
LL.
.6 2
9PM
I IPM
TIME,
iAM
SAM
5AM
hrs.
197
-------
FIGURE 71 RAINFALL INTENSITY AND RATE OF DISCHARGE
TROUT RUN SANITARY SEWER
2.0
1 .5
at
e
I .(_
r
T
.2 .
l_
J=
.3 7
12 JULY 1969
GO
SURCHARGED
.5
.6
.7
.8
.9
LEGEND
DRY WEATHER FLOW
FLOW DURING RA INFALL
INFILTRATION
I
ZM
ZAM
6AM
TiME.hrs.
5AM
TOAM
198
-------
FIGURE 75 RAINFALL INTENSITY AND RATE OF DISCHARGE
TROUT RUN SANITARY SEWER
2.0
.5
jl .0
0.5
I I 1
APPROXIMATELY 0.5 IN. RAIN
RAIHFALL INTENSITY UNKNOWN
19 JULY 1969
SURCHARGED
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
INFILTRATION
UPM
6PM
8PM 10PM
TIME, hrs.
I2M
2AM
199
-------
FIGURE 76 RAINFALL INTENSITY AND RATE OF DISCHARGE
TROUT RUN SANITARY SEWER
I .5
•o
01
E
.1 .0
0.5
I I I
APPROXIMATELY 0.79 IN. RAIN
RAINFALL INTENSITY UNKNOWN
22, 23 JULY 1969
SURCHARGED
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
INFILTRATION
J_
10PM
I2M
2AM
TIME
4AM
hrs.
6AM
BAM
200
-------
FIGURE 77 RAINFALL INTENSITY AND RATE OF DISCHARGE
TROUT RUN SANITARY SEWER
1 .5
.0
T3
Ol
o
io.5
U
3 AUGUST 1969
SURCHARGED
LEGEND
— DRY WEATHER FLOW
PLOW DURING RAINFALL
1 INFILTRATION
I
I
I
2PM
6PM 8PM
TIME, hrs.
I 0PM
.3
M
,5
.6
ZM
201
-------
FIGURE 78 RAINFALL INTENSITY AND RATE OF DISCHARGE
24th STREET SANITARY SEWER
l.(
O)
E0,5
5PM
J
6 FEBRUARY 1969
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
mmm INFILTRATION
•.i
C/j
•a:
cc.
7PM
9PM MPM
TIME, hrs.
1AM
3AM
202
-------
FIGURE IB RAINFALL INTENSITY AND RATE OF DISCHARGE
2Hth STREET SANITARY SEDER
I .0
•CHANGED TO SNOW
8 FEBRUARY 1969
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
INFILTRATION
0.5
I
I
3PM
5PM
7PM 9PM
TIME, hrs.
PM
1AM
203
-------
FIGURE 80 RAINFALL INTENSITY AND RATE OF DISCHARGE
24th STREET SANITARY SEWER
2.0
.5
T3
Ol
ii.o
0.5
2M
24 MARCH 1969
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
INFILTRATION
I
4AM
8AM I2N
TIME, hrs.
4PM
.2
8PM
204
-------
FIGURE 81 RAINFALL INTENSITY AND RATE OF DISCHARGE
21th STREET SANITARY SEWER
1.5
I .0
'0.5
8, 19 MAY 1969
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
INFILTRATION
_L
8PM
PM
2AM SAM
TIME, hrs.
8AM
CO
AM
205
-------
FIGURE 82 RAINFALL INTENSITY AND RATE OF DISCHARGE
2Hth STREET SANITARY
2i. 5
2.0
I .5
T3
01
e
.0
0.5
0
9PM
LEGEND
— •— DRY WEATHER FLOW
FLOW DURING RAINFALL
INFILTRATION
8, 9 JUNE 1969
I
IPM
AM 3AM
TIME, hrs.
SAM
• 3
.6
TAM
,Z06
-------
FIGURE 83 RAINFALL INTENSITY AND RATE OF DISCHARGE
STREET SANITARY SEWER
I .5
en
£
.0
0.5
2.4
SAM 10AM
9 JUNE (969
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
INFILTRATION
.2
,3
.5
cc
I 2N 2PM
TIME, hrs.
1PM
6PM
207
-------
FIGURE 84 RAINFALL INTENSITY AND RATE OF DISCHARGE
2Hth STREET SANITARY SEWER
2.0
.5
00
.0
0.5
21 JUNE 1969
SURCHARGED 3.63 MGD
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
INFILTRATION
.2
.3
3PM
6PM
9PM I2MT
TIME, hrs.
3AM
6AM
208
-------
FIGURE 85 RAINFALL INTENSITY AND RATE OF DISCHARGE
STREET SANITARY SEWER
.5
I .0
CT
0,5
15 JULY 1969
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
t:f?:f;*:fm INFILTRATION
.1 ,>-
GO
.2 2
t—
z
.3 _,
_j
u.
.1 ±
ac.
4AM
6AM
SAM 10AM
TIME, hrs.
12N
2PM
209
-------
FIGURE 86 RAINFALL INTENSITY AND RATE OF DISCHARGE
24th STREET SANITARY SEWER
3.0
2.5
O)
:2,o
I .5
I .0
0.5
0.56
Q.6Q
i, 2, JULY 1969
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
INFILTRATION
>-
h-
.2 -
LU
.3 z
I I PM
AM
SAM 5AM
TIME, hrs.
7AM
9AM
210
-------
FIGURE 87 RAINFALL INTENSITY AND RATE OF DISCHARGE J
24th STREET SANITARY SEWER -
3.5-
3.C-
2.5
2.0
O
_l
LL.
1.0
0.5
r
2, 3, JULY 1969
LEGEND
DRY WEATHER FLOW
FLOW DURING RAINFALL
INFILTRATION
0
7PM
0 .-
LU
.5
0PM
1AM 4AM
TIME, hrs.
7AM
211
-------
FIGURE 88 RAINFALL INTENSITY AND RATE OF DISCHARGE
24th STREET SANITARY SEWER
2,0
I .5
CT
.0
0.5
2 JULY 1969
0.93
\\
LEGEND
DRY WEATHER FLOW
-FLOW DURING RAiKFALL
INFILTRATION
.2
.3
2MT
2AM
1AM 6AM
TIME, hrs.
8AM
0AM
212
-------
89 RAINFALL AW RATE OF QVERROI
WATER POLLUTION CONTROL PLANT
TOTAL RAINFALL I.00 in.
AVERAGE INTENSITY 0.10 in./hr.
DURATION 10,0 hrs,
12,0
10.0
8.0
£
-6.0
o
3-
O
2.0
PEAK I I.3 MGD
24 MARCH 1969
TOTAL
OVERFLOW
2.77 MG
I 2MT
SAM
6AM 9AM
TIME, hrs.
12N
3PM
213
-------
FIGURE 90 RAINFALL AND RATE OF OVERFLOW
WATER POLLUTION CONTROL PLANT
PEAK 13.8
12.0
10.0
8.0
6.0
•o
en
u.
or
TOTAL RAINFALL 1,25 in.
AVERAGE INTENSITY 0.36 in./hr.
DURATION 3.5 hrs.
2.0
21 , 22 JUNE 1969
TOTAL
OVERFLOW
2.85 MG
6PM
8PM
10PM I2MT
TIME, hrs.
2AM
214
-------
FIGURE 91 RAINFALL AND RATE OF OVERFLOW
HATER POLLUTION CONTROL PLANT
TOTAL RAINFALL 0.50 in.
AVERAGE INTENSITY 0.63 in./hr.
DURATION 0.8 hrs.
10.0
PEAK 10.0 MOD
19 JULY 1969
8.0
6.0
TOTAL
OVERFLOW
0.60 MG
2.0
_L
UPM
6PM
8PM 10PM
TIME, hrs.
I2MT
2AM
215
-------
FIGURE 92 RAINFALL AND RATE OF OVERFLOW
WATER POLLUTION CONTROL PLANT
TOTAL RAINFALL 0.60 in.
AVERAGE INTENSITY 0.37 in./.hr,
DURATION I.6 hrs.
22, 23 JULY 1969
PEAK 7:6 MGO
•o
en
O
Ll_
EC
LU
>
O
TOTAL
OVERFLOW
0.69 MG
10PM
I2MT
2AM
TIME
4AM
6AM
SAM
hrs .
Z16
-------
FIGURE 93 RAINFALL AND RATE OF OVERFLOW
WATER POLLUTION CONTROL PLANT
TOTAL RAINFALL 0,50 in.
AVERAGE IKTENSITY O.H in./hr.
DURATION 4.5 hrs.
3 AUGUST 1969
2.5
2.0
1.5
CT
.0
0.5
PEAK 2.4 MGD
TOTAL
OVERFLOW
0.04 MG.
2PM
3PM
4PM 5PM
TIME, hrs.
6PM
7PM
217
-------
FIGURE 94 RAINFALL AND RATE OF OVERFLOW
WATER, POLLUTION CONTROL PLANT
TOTAL .RAINFALL 0.50 in.
AVERAGE INTENSITY 0.26 in./hr,
DURATION 1.9 hrs.
0.8-
•o
en
O
—I
u_
cr
0.6
0.2
5 AUGUST 1969
TOTAL
OVERFLOW
0.02 MG
PEAK I,03 MGD
7PM
8PM
9PM 10PM
TIME', hrs.
I 1PM
12PM
-------
FIGURE 95 STAGE-DISCHARGE-CURVE
MURRAY RUN STREAM
I
10
.1.0
.5
Q_
LLJ
j i i I i i i
5 1 0
DISCHARGE, mgd
50 100
219
-------
FIGURE 96 STAGE-DISCHARGE CURVE
TROUT RUN STREAM
T
Tl
10
i
cc.
'1-0
o
CD
J 1 I 1 II I
i 1 I I I i I I
5 10
DISCHARGE-mgd.
50 100
Z2.0
-------
FIGURE 97 STAGE-DISCHARGE CURVE
2Hth STREET STREAM
5 10
DISCKARGE-mgd.
221
-------
FIGURE 98 STAGE - DISCHARGE CURVE
WEIR IN MURRAY RUN SANITARY SEWER
f i • \ ii i
0 .i ,2
3 .M- .5 .6 .7 .8
DISCHARGE - mgd.
.9 1.0 I
222
-------
FIGURE 99 STAGE DISCHARGE CURVE
TROUT RUN SANITARY SEWER -12" DIA.
I ,2 .3.^.5.6.7.8.9 i.OI.I 1.2 1. 3 i.HI. 5 I.6
DISCHARGE - mgd.
223
-------
FIGURE 100 STAGE DISCHARGE CURVE
STREET SANITARY SEWER 15" BIA,
I I I i I i I i i i i | i i i i i i i i i | i i i i I i i r i | i i i i i i i
Of i i i i
I i i t i I i i i i I i i i i I i i i i I i i i i I i i i i I 1 I i i I i i i
.5 LO 1.5 2.0 2.5 3 = 0 3,5 "*.Q
DISCHARGE -
224
-------
FIGURE 101 STAGE DISCHARGE CURVE
WATER POLLUTION CONTROL PLANT 54" DIAMETER
3.0
o.
LU
O
I ,0
20 30
DISCHARGE, mgd
225
50
-------
Previous Page Blank
APPENDIX VII
SAMPLING DATA FOR STREAMS AND
SANITARY SEWERS OF THE THREE
STUDY AREAS AND THE WATER
POLLUTION CONTROL PLANT
TABLES 51 THROUGH 60
227
-------
TABLE 51
STREAM SAMPLING DATA
MURRAY RUN STREAM
S ctrnpl e
Date Time
6 Feb 1969 6:00 PM
7:00 PM
8:00 PM
M 12: 00PM
10
to
8 Feb 1969 3:50 PM
5:12 PM
6-. 00 PM
6:40 PM
24 Mar 196.9 10:12 AM
10:42 AM
11:12 AM
11:42 AM
12:27 PM
Flow
(mgd)
6.0
6.5
7.2
6.0
5.6
6.0
7.5
9.0
10.0
9.9
9.5
9.3
8.9
BOD
(mg./l.)
13
14
13
26
7
2
11
3
11
14
21
66
16
Total
Solids
(mg./l.)
367
296
771
720
342
263
305
290
340
828
2677
543
358
Total
Volatile
Solids
(rag. /I.)
116
109
127
213
124
61
87
75
92
177
290
130
142
Suspended
Solids
(mg./l.)'
133
80
303
93
60
33
33
27
37
90
147
53
67
Suspended
Solids
Volatile
(mg./l.)
38
24
93
38
21
8
10
7
9
19
15
12
25
Settleable
Solids
(ml. /I.)
1
1
5
2
1
1
1
1
2
5
8
3
1
Coliform
MPN per
100 ml.
(thousands)
15
4
46
2
46
46
15
4
240
240
240
93
240
-------
to
TABLE 52
STREAM SAMPLING DATA
TROUT RUN STREAM
Sample
Date
6 Feb 1969
8 Feb 1969
24 Mar 1969
23 Jvil 1969
3 Aug 1969
Time
6: 55 PM
7:50 PM
8:50 PM
9: 50 PM
3:40 PM
4: 1 0 PM
5: 1 0 PM
6: 1 0 PM
8:45 AM
9:40 AM
10:45 AM
12:40 PM
12:01 AM
12:20 AM
12:40 AM
1:00 AM
1:20 AM
2:20 AM
5:28 PM
5: 44 PM
5: 59 PM
6:45 PM
7:45 PM
Flow
(mgd)
6.2
4.7
2.9
2.0
1.8
4.9
3.2
8.9
13.0
9.5
7.5
5.0
78.0
35.0
16.0
5.0
3.5
2.0
10.0
45.0
14.0
34.0
5.0
BOD
(mg./l.)
20
10
7
4
18
13
16
8
31
25
23
29
22
12
13
20
36
31
17
20
9
23
14
Total
Solids
(mg./l.)
488
273
208
213
607
719
422
445
393
403
361
277
745
745
531
476
456
612
919
492
296
321
186
Total
Volatile
Solids
(mg./l.)
200
122
55
67
169
196
127
140
146
206
115
127
175
134
115
97
131
207
278
139
72
108
76
Suspended
Solids
(mg./l.)
213
70
37
43
167
160
117
110
77
100
90
70
97
110
100
127
80
67
93
107
57
27
30
Suspended
Solids
Volatile
(mg./l.)
79
26
9
13
46
42
35
34
33
5.1
30
31
22
20
21
25
23
22
27
29
13
8
12
Settleable
Solids
(ml. /I.)
5
1
1
1
3
3
2
2
2
2
3
1
4
2
6
2
2
8
4
2
1
2
1
Coliform
MPN per
100 ml.
(thousands)
no
110
110
24
24
46
46
46
11,000
11,000
11,000
11,000
5400
2400
5400
16,000
2400
3500
1100
2800
700
490
9200
-------
TABLE 53
STREAM SAMPLING DATA
24TH STREET STREAM
Sample
Date
6 Feb 1969
8 Feb 1969
24 Mar 1969
Time
6:20 PM
7:20 PM
8:20 PM
9:20 PM
10-.15 PM
4: 45 PM
5:45 PM
6:45 PM
8:30 AM
9:25 AM
10:25 AM
12:30 PM
Flow
(mgd)
0.3
2.2
1.8
1.2
1.0
2.8
3.2
4.0
7.5
7.5
6.0
3.3
BOD
(mg./l,)
39
22
8
23
5
45
35
42
4
4
7
5
Total
Solids
(mg./l.)
705
653
345
379
209
1045
629
648
580
440
298
240
Total
Volatile
Solids
(mg./l.)
193
179
126
132
98
388
230
276
137
121
94
92
Suspended
Solids
(mg./l.)
153
163
97
87
73
167
150
107
87
63
57
37
Suspended
Solids
Volatile
(mg./l.)
46
43
31
30
31
61
53
44
20
15
19
14
Settleable
Solids
(ml. /I.)
3
3
1
2
1
7
4
4
2
1
1
1
Coliform
MPN per
100 ml.
(thousands)
110
46
110
24
24
110
110
110
21
9
4
46
-------
TABLE 54
SANITARY SEWER SAMPLING DATA
MURRAY RUN SANITARY SEWER
Sampl e
Date
6 Feb 1969
8 Feb 1969
24 Mar 1969
Time
6:10 PM
7: 1 0 PM
8: 10 PM
1 2: 1-0 AM
3:50 PM
5:12 PM
6:00 PM
6:40 PM
10:12 AM
10:42 AM
11:12 AM
11:42 AM
12-.27 AM
Flow
(mgd)
1.3*
1.3*
1.3*
1.3*
1.3*
1.3*
1.3*
1.3*
1.3*
1.3*
1.3*
1.3*
1.3*
BOD
(mg./l.)
156
90
96
66
140
96
252
92
420
114
114
108
192
Total
Solids
(mg./l.)
550
302
298
304
705
571
1345
450
1225
513
509
524
418
Total
Volatile
Solids
(mg./l.)
267
41
104
100
284
240
953
212
845
286
221
296
229
Suspended
Solids
(mg./l.)
136
37
83
73
427
410
137
113
70
57
137
97
77
Suspended
Solids
Volatile
(mg./l.)
61
5
27
23
180
168
11
52
47
31
53
56
43
Settleable
Solids
(ml. /I.)
8
0
0
4
1
6
9
11
42
11
27
35
17
Coliform
MPN per
100 ml.
(thousands)
140**
140**
140**
140**
1100**
1100**
1100**
1100**
11,000**
11,000**
11,000**
11,000**
11,000**
* Sewer surcharged - flow indicated is sewer capacity.
**Represents a minimum, value - a more accurate choice of sample
dilutions could have resulted in higher values.
-------
TABLE 55
SANITARY SEWER SAMPLING DATA
TROUT RUN SANITARY SEWER
Sample
Date Time
6 Feb 1969 6:50 PM
7: 50 PM
8:50 PM
9:50 PM
8 Feb 1969 3:40 PM
w 4: 10PM
W 5; 1 0 PM
6; 10 PM
24 Mar 1969 8:45 AM
9:40 AM
10:45 AM
12:40 PM
23 July 1969 1:20 AM
2:25 AM
3 Aug 1969 5:30 PM
5:45 PM
6:00 PM
Flow
(mgd)
*
*
*
*
*
*
•J-
*
*
*
*
&
1 . 5**
1.5**
1.0
1.5**
1.5**
BOD
(mg./l.)
204
150
162
108
162
168
137
168
414
174
294
216
315
108
600
405
360
Total
Solids
(mg./l.)
771
845
658
537
774
832
746
711
853
581
1021
611
1269
2624
1192
1212
1254
Total
Volatile
Solids
(mg./l.)
459
508
341
324
332
342
315
311
535
321
599
259
660
2269
628
676
642
Suspended
Solids
(mg./l.)
210
130
157
280
110
130
133
120
173
130
177
100
123
63
147
167
180
Suspended
Solids
Volatile
(mg./l.)
119
80
75
171
46
51
55
51
102
70
100
41
61
55
76
92
92
Settleable
Solids
(ml. /I.)
11
19
13
8
8
9
7
7
13
12
24
6
17
3
19
26
21
Coliform
MPN per
100 ml.
(thousands)
1100
1100
1100
1100
1100
1100
1100
1100
11,000***
11,000***
11,000***
11,000***
54,000
7900
35,000
54,000
35,000
* Data not available.
** Sewer surcharged - flow indicated is sewer capacity.
##*Represents a minimum value - a more accurate choice of sample
dilutions could have resulted in higher values.
-------
(O
u>
w
TABLE 56
SANITARY SEWER SAMPLING DATA
24TH STREET SANITARY SEWER
Sample
Date
6 Feb 1969
8 Feb 1969
24 Mar 1969
Time
6:30 PM
7:30 PM
8:30 PM
9:30 PM
1 0: 1 5 PM
4:45 PM
5:45 PM
6:45 PM
8:30 AM
9:25 AM
10:25 AM
12:30 PM
Flow
(nigd)
0.8
0.8
1.0
1.0
1.0
1.0
1.0
1.0
1.6
1.7
1.7
1.5
BOD
(mg./l.)
102
98
162
144
120
102
140
88
324
150
156
144
Total
Solids
(mg./l.)
235
410
443
417
394
504
501
320
405
497
432
433
Total
Volatile
Solids
(mg./l,)
39
240
246
211
178
225
251
141
242
295
203
194
Suspended
Solids
(mg./l.)
40
37
50
37
93
70
50
40
47
67
50
33
Suspended
Solids
Volatile
(mg./l.)
6
17
23
17
44
30
24
17
27
39
25
13
Settle able
Solids
(ml. /l.)
7
5
6
3
4
9
9
5
6
9
5
3
Coliform
MPN per
100 ml.
(thousands)
1100
1100
1100
1100
1100
1100
1100
1100
11,000*
11,000*
11,000*
11,000*
^Represents a minimum value - a more accurate choice of sample
dilutions could have resulted in higher values.
-------
NJ
TABLE 57
SAMPLING DATA
WATER POLLUTION CONTROL PLANT OVERFLOW
Sample
Date Time
23 July 1969 1:30 AM
1:45 AM
2:00 AM
2:15 AM
2:30 AM
2:45 AM
3:00 AM
3:15 AM
Flow
(mgd)
7.2
7.5
7.6
7.6
7.4
7.1
6.6
4.2
BOD
(mg./l.)
203
192
218
212
239
293
276
276
Total
Solids
(mg . / 1 . )
941
794
894
870
978
1086
1074
1100
Total
Volatile
Solids
(mg./l.)
562
428
438
449
524
567
570
565
Suspended
Solids
(mg./l.)
137
120
170
117
127
130
103
100
Suspended
Solids
Volatile
(mg./l.)
80
64
83
57
63
65
52
50
Settleable
Solids
(ml. /I.)
12
.11
16
16
25
27
30
31
Coliform
MPN per
100 ml.
(thousands)
160,000
92,000
35,000
35,000
17,000
24,000
35,000
11,000
-------
TABLE 58
SAMPLING DATA
ROANOKE RIVER INTERCEPTOR ABOVE PLANT
Sample
Date
23 July 1969
N>
01 3 Aug 1969
Time
2:00 AM
2:50 AM
6:25 PM
Flow BOD
(mgd) (mg./l.)
* 145
* 84
1.7.5 108
Total
Solids
(mg./l.)
778
587
609
Total
Volatile
Solids
(rag. /I.)
438
235
331
Suspended
Solids
(mg./l.)
83
73
37
Suspended
Solids
Volatile
{mg./l.)
46
29
19
Settleable
Solids
(ml. /I.)
6
6
6
Coliform.
MPN per
100 ml.
(thousands)
92,000
54,000
35,000
*Data not available.
-------
10
Ul
TABLE 59
SAMPLING DATA
SANITARY SEWER DRY WEATHER FLOW
24 HOUR COMPOSITE
Location
Murray Run
24th Street
Trout Run
Date
19 Feb 1969
16 July 1969
16 July 1969
Flow
(mgd)
0.32
0.69
0.86
BOD
(mg./l.)
181
192
342
Total
Solids
(mg./l.)
476
616
890
Total
Volatile
Solids
(mg./l.)
241
325
473
Suspended
Solids
(mg./l.)
91
113
200
Suspended
Solids
Volatile
(mg. /I.)
40
53
98
Settleable
Solids
(ml. /I.)
9
6
8
-------
TABLE 60
SAMPLING DATA
STREAM DRY WEATHER FLOW
24 HOUR COMPOSITE
to
U!
-J
Location
Murray Run
24th Street
Trout Run
Date
17 Sep 1969
1
1
May 1969
May 1969
Flow
(mgd)
4.0
1.2
1.0
BOD
(mg./l.)
8
8
3
Total
Solids
(mg./l.)
248
194
281
Total
Volatile
Solids
(mg./l.)
85
126
147
Suspended
Solids
(mg./l.)
37
20
17
Suspended
Solids
Volatile
(mg./l.)
12
7
8
Settleable
Solids
(ml. /I.)
0
0
0
-------
Previous Page Blank
APPENDIX VIII
SUMMARY REPORT OF LITERATURE SEARCH
PURPOSE
The purpose of this report is to present a summary of literature re-
lated to phases of this project, to support preliminary design criteria,
SCOPE
This report includes a brief summary of all literature and knowledge
found to be pertinent and having important features of direct bearing
on the following:
1. Field investigation
2. Hydrological investigation
3 . Monitoring and sampling
4, Analysis
5. Remedial measures for sanitary sewage overflows
239
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FIELD INVESTIGATION
Larmon (1) ^ reports that the City of South Charleston, West Virginia
used smoke testing to enforce an ordinance banning the connection of
downspouts to sanitary sewers. Equipment consisted of the following:
1. Portable 1500 cfm Homelite blower
2. Sheet of 3/4-inch plywood
3. Canvas air duct
4. Sponge rubber
The plywood was lined with the sponge rubber to ensure a sealed fit
over open manholes. Smoke was introduced by inserting a smoke bomb
into the suction side of the blower. All violations and apparent breaks
or leaks in the sewer were marked for future repair..
Can Tex Industries, Inc. of Cannelton, Indiana suggests the following
for conducting smoke tests. Equipment should consist of;
1, One minute smoke bombs
2. Small blower
3. Test tee
4. Sewer plug
Insert the test tee in the house line, using the plug on the sewer side
of the house connection. After insertion of a lighted smoke bomb into
the blower, watch for smoke to appear at ground level or somewhere
around the house foundation or downspouts. Further emphasis is
placed on the notification of the area residents of the intended plan of
smoke testing.
The National Clay Pipe institute supplied information concerning the
smoke testing of sewers. Their advice concerned primarily the cor-
rect procedure to follow and the violations that may be encountered.
^ Numerals in parentheses refer to corresponding items at the end
of this appendix.
240
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The City of Roanoke's smoke testing crew also provided helpful infor-
mation, in that they had been smoke testing in the city since spring of
1968.
A study conducted by Hayes, Seay, Mattern & Mattern in 1965 on the
sanitary sewers in Roanoke revealed important data concerning the
condition of the sewers and trouble spots that develop during heavy
rainfalls.
HYDRO-LOGICAL INVESTIGATION
Greely and Langdon (2) used a rational approach relating rainfall to
sewage quantities and tributary areas in a study of storm water and
combined sewage overflows near East River of Long Island Sound.
Hourly records of rainfall for five summer months and over the 8-year
period from 1950 to 1957 were obtained. The data were tabulated and
analyzed to establish the number of storms, the total rainfall in the
storm and the duration of the storm. Based upon certain assumptions
the data were translated into a rational analysis of the amount, number
and frequency of overflows .
Benjes, Haney, Schmidt and Yarabeck (3), in a study of storm-water
overflows from combined sewers in Kansas City, Missouri, reported
that runoff of 1 x dry weather flow (DWF) or greater will occur 3.6
percent of the time and that runoff of 2 x DWF or greater will occur
3.2 percent of the time. In arriving at these conclusions, the frequency
of occurence of various rainfall intensities was determined by counting
the number of hours during which each intensite occurred. Measureable
rainfall occurs only about 5 percent of the time at Kansas City. Rain-
storms producing runoff occur only about 3.7 percent of the time. The
data selected for analysis were the official published records of the
U.S. Weather Bureau titled "Hourly Precipitation" for the Municipal
Airport Station, Kansas City, Missouri.
McKee (4) made a detailed study of low-intensity storms using Boston
records for the June through November period for 1934 to 1945. He
found that a rainstorm of 0.04 in./hr. will produce storm runoff equal
to DWF and that 0.03 inch is necessary to wet down the area before
runoff begins. Thus, in Boston, a rainstorm of 0.01 in./hr. after
initial wet-down, will produce runoff equal to DWF.
241
-------
The Corps of Engineers, in 1965, published a report pertaining to
flooding of downtown Roanoke from waters of Lick Run. This report
gives a complete breakdown of their analysis of rainfall and runoff in
the Lick Run drainage area which is adjacent to the Trout Run drainage
area used in this study.
The U. S. Weather Bureau, has published a climatic summary for the
State of Virginia. In this report a history of the total precipitation for
Roanoke is given per month plus the mean number of days with
precipitation between 0.10 and 0.50 inch as recorded at the local
U.S. Weather Bureau at Woodrum Airport.
The Corps of Engineers, in a manual titled "Flood-Hydrograph Analyses
and Computations", describe and illustrate certain methods of deriving
fundamental hydrologic factors by analysing observed hydrographs of
stream flow and related meteorological events and suggests methods of
utilizing these deduced factors in computing hypothetical hydrographs of
runoff for conditions differing, in specified respects, from those pre-
vailing during the observed floods.
Dunbar and Henry (5) report the following results from a study in
Concord, N. H. during the summer months from 16 June through 15
September for the 10-year period 1949 through 1958. Of the 191 storms
that occurred during the 10 summers, all produced runoff sufficient to
cause overflows from interceptors designed for 3 x DWF. The average
frequency was 6.4 times per month and the total average rainfall was
3.03 in./month. The average rainfall that produced runoff after wetting
was 93 percent of the average monthly rainfall or 2.83 in./month. The
average dry weather flow of sanitary sewage at its equivalent of 0.01
in./hr. of rainfall is equivalent to 7.2 in./month. Thus the total
amount of stormwater runoff for Concord is only about 40 percent of the
total sanitary sewage.
MONITORING AND SAMPLING
Burm, Krawczyk and Harlow (6), in a study in 1965 to determine and
compare the chemical and physical qualities of the effluents discharged
from combined and separate storm sewers in the Detroit-Ann Arbor
area, used automatic samplers to obtain their samples. The equip-
ment consisted of submersible pumps which lifted the sample out of the
sewer to an automatic sampling mechanism. The sampling bottles used
were one quart bottles situated on a rotating turntable actuated by a
timing mechanism. Samples were taken at five minute intervals at
242
-------
Ann Arbor and one hour intervals at the Detroit installation.. Methods
of measuring heads in the sewers were incorporated into each site, but
flow calibrations of the sewers were extremely difficult because of the
large discharges involved, as well as the rapidly fluctuating flows.
Cruchley (7) reports that the Road Research Laboratory used a new
instrument during investigation on surface water drainage to record
flow in sewers. The device records variations with time in the rate of
sewage flow and the periods of time during which the flow is in excess
of certain values selected for a particular study. The instrument is
composed of a movement recorder and a time totalizer, the latter con-
sisting of a time base and multiple-contact switch-unit within the move-
ment recorder and a separate box containing a rectifier and a battery
of counters.
Ellis and Johnston (8) report on a field method of measuring and record-
ing flow in sewers. The size, length and slope of a sewer between two
manholes must be determined. For known depths of flow in a sewer,
determine velocities between the upper and lower manholes by using dye
test and stop watch. From the velocity data determine the roughness
coefficient "n" through the Manning formula. Prepare a depth-discharge
curve for the particular stretch of sewer. Using a stage recorder,
continuously record the depth of flow in the sewer for the desired period,
and convert the depth data to flow rate.
Fathmann (9) reports on methods and equipment for the measurement of
sewage flow. To obtain quantitative measurements within a definite
given time, tank measurements are employed, using floats and measur-
ing weirs. Stationary calculations on volume of sewage are carried out
by measurements in pressure pipe lines according to the Venturi
principal or as inductive measurements for the rate of flow.
Weidner, Weibel and Robeck (10) describe a method of sampling and
gaging using an automatic mobile unit. The unit will sample storm-
water runoff from various environments on a time-proportioned or
flow-proportioned basis. The operation of a sampler is dependent on a
sufficient amount of rainfall to start the electrical and cooling systems
and predetermined amount of runoff to activate the sampling section.
In a study of urban runoff in Cincinnati, Weibel, Anderson and Woodward
(11) report that the stormwater flows were measured with a 4-foot
rectangular weir and a continuous water level recorder with 24-hour
chart. Flows up to 25 cfs could be measured with such a set up.
Samples were collected by means of suction hose and small battery
operated centrifugal pump located at a manhole, which was 50 feet
243
-------
upstream of the outfall. The pump discharged to a revolving distributor
and 36 4-liter polyethelene bottles arranged in a housing unit. The
pump was actuated by a float device. The distributing arm rotates
constantly, powered by a spring motor, passing over vertical tubes
arranged in a circle and connected by hoses to the individual bottles.
The arm takes 10 minutes to pass from the center of one tube to the
next, flowing continuously. Plastic bottles with special glass tubing
inlets and^aluminum foil caps collect samples for bacteriological
analyses.
ANALYSIS
Greely and Langdon (2) found that the interception and treatment of the
dry weather flow and the first flushings of storm water will reduce the
volume of sewage discharged through overflows to about 3 percent.of
the total sewage flow. With complete treatment of the intercepted flow,
about 90 percent of the BOD can be removed. Treatment of intermittent
discharges from overflows by retention and chlorination to remove
floating solids and bacterial contamination can also improve conditions
in receiving streams.
Camp (12) reports that the average dry weather flow of sanitary sewage
from combined sewerage systems is approximately equal to the runoff
from a rainstorm having an intensity of about 0.01 in./hr. For inter-
ceptors having a capacity of 2 x DWF, more than 90 percent of the
sanitary sewage is discharged in the overflows with a rainfall intensity
of 0.2 in./hr. or more. With interceptors having a capacity of 5 x
DWF, about 76 percent of the sanitary sewage is lost during rainstorms
having an intensity of 0.2 in./hr. and about 90 percent is lost during
rainstorms having intensity of 0.5 in./hr.
Burm, Krawczyk and Harlow (6), in a comparative study of separate
storm-sewer discharges in Ann Arbor, Michigan, with combined dis-
charges in Detroit, showed that the BOD in the separate storm sewer
discharges was about 20 percent of that in the combined discharges.
Concentrations lessened as discharges increased. Values for total
and volatile suspended solids and for total and volatile setteable solids
were higher in the separate storm sewerage system because of greater
erosion in hillier terrain. Phosphates were higher in combined flows,
but nitrates were lower. In the separate system, BOD was fairly
constant throughout the year, but in the combined system, summer BOD
values were higher.
244
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Weibel, Anderson and Woodward (11) in a field study of sewered storm
water runoff in Cincinnati, noted the following results: the BOD and
suspended solids discharged increased with increasing size of storm;
there was little seasonal change in constituent means concentration,
except for BOD and for high chlorides in winter snow melt; and the
suspended solids and volatile suspended solids discharges were
roughly comparable to dustfall and combustibles in dustfall for the
year, measured at a city air pollution sampling station in the area.
Several of the stormwater runoff constituents discharged over the year
were compared with the computed amounts of the same constituents
that might occur in the raw sanitary sewage produced in the area, all
on a pounds-per-acre-per-year basis, by using the 9 per son-per-acre
population density of the watershed. The comparisons of stormwater
runoff to raw sewage on a percentage basis are: suspended solids from
stormwater runoff, 140 percent of raw sewage production; volatile
suspended solids, 44 percent; COD, 25 percent; BOD 6 percent. It was
concluded that urban storm runoff cannot be neglected in considering
waste loadings from urban sources and that information from a variety of
runoff environments is needed.
Weibel, Weidner and Christiansen (13) report on results of a study at
Cincinnati on the polluting effect of storm water run-off from urban
areas. The rain water was found to contain, on an average, 0.69 mg of
inorganic nitrogen and 0.24 mg of hydrolysable phosphate per litre;
these concentrations exceed the threshold values found by others for the
development of algal blooms. Analyses of the run-off showed its pol-
lution potential, and the concentrations of coliform organisms exceeded
the criterion of 1000 per 100 ml recommended for bathing waters.
Sedimentation alone was not effective in reducing BOD and suspended
solids content. Sedimentation for 20 minutes combined with chlorination
at a dose of 4.62 mg of chlorine per litre killed more than 99 percent of
the bacteria; when the supernatant liquor was dechlorinated, however,
and kept at room temperature for 24 to 72 hours, there was aftergrowth
of coliform organisms, though not of fecal coliform bacteria.
Palmer (14) disclsses the effects of pollution caused by overflowing of
storm water from combined sewers in Detroit. Runoff did not occur
unless precipitation was greater than 0.03 in./hr. and storm water
would not overflow unless precipitation was more than 0.03 in./hr.
plus the capacity of the sewers for storm water. Intercepting sewers
were most effective in preventing overflow when their capacity was
150 percent of the sewage flow and no satisfactory reduction in number
or duration of overflows was achieved by increasing the capacity to any
reasonable extent. The quality of the overflowing liquid varied considerr
ably and would be highly polluting even from a separate system.
245
-------
Weller and Nelson (15) report on the findings of a study in Kansas City,
Missouri concerning stormwater infiltration into sanitary sewers. During
periods of moderate precipitation the major portions of the flow are
from sources other than the water-using plumbing fixtures in the resi-
dences and public buildings within the district. During these periods the
major source of sewer flow is ground water, presumably from foundation
drains used throughout the district.
REMEDIAL MEASURES
Weller and Nelson (16) report on steps taken to divert and treat peak
flows in Johnson County, Kansas and Kansas City, Missouri. They
state that in these two areas the maximal flows may be many times the
average as a result of extraneous flows, defined as liquids entering the
sanitary sewers through sources other than plumbing fixtures or pro-
cess facilities. The peak flows are settled, skimmed and chlorinated
before discharge, thus reducing possible pollution of the,receiving
stream.
Rhodes (17) reports that, in Montgomery County, Dayton, Ohio, a
number of attempts were made to correct the infiltration into a newly
constructed sewerage system. Before any customers were connected
the lines were carrying almost plant capacity due to infiltration. Spot
checks of the system by closed-circuit television in 1962 indicated that
the "poured joints" were allowing the greatest quantity of infiltration.
The remedial methods attempted were:
1 . Relaying of one mile of trunk sewer. This proved to be to costly.
2. The joints of a short section of line were uncovered and a con-
crete collar was poured around them. This also proved to be
too costly.
3. Plastic liners were placed inside the sewer lines. The cost
of the liners was not prohibitive but the reduction in line
capacity could not be afforded.
4. Television inspection and sealing with polymer-type grouting
fluid.
The method that proved successful was inspection by television to pin-
point leaks and sealing with a polymer-type grouting fluid called PWG.
The number of leaks repaired in this manner averaged 7 leaks per
300 feet of sewer line.
246
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Metz (18) describes a procedure for reducing Infiltration by remote
control groutingi The equipment required in the process includes a
van-type truck, chemical grout mixing and pumping equipment, sewer
grouting packers and plugs, air compressor, television inspection
components, winches, down-hold sheaves and communication system.
A winch cable, to which is attached a television camera and sewer
grouting packer, is pulled through the sewer line. The trailing winch
line is attached to the grouting packer, and a communication line is
placed between the two winches and the grouting engineer. The inline
equipment is then moved through the sewer. When a leak is observed
on the television monitor, the grouting packer is set over the leak and
sufficient chemical grout is pumped through the set packer to seal the
leak.
Godbehere (19) describes a method used in Amersham, England to re-
duce infiltration. The sealant is Terra seal which is a form of sodium
alginate. It can be delivered to the site bagged as a coarse brown
powder for mixing with water or as a concentrated viscous solution in
drums for dilution before use. In Amersham, Terraseal was mixed on
site in a 500-gallon tank, agitated and heated to produce a suitable
solution. The prepared solution was transferred to a 100-gallon gauging
tank and pumped into the head of the first length of sewer previously
stoppered at the downstream end. When full the head was then stop-
pered and couplings completed to the reciprocating pump. The solution
was then pumped under pressure and the loss through faults into the
ground monitored by measurement of the depth in the gauging tank.
Further investigation showed that the procedure improved the line by
eliminating about 95 percent of the infiltration in the section of line
tested.
Crane (20) reports on a plan by Buffalo, New York to prevent flooding
from overloaded storm sewers by storing excess storm water in a
disused quarry which has a capacity of 2,350,000 cu. ft. The water
will then be pumped gradually into the sewers and so discharged into
the creek.
Waller (21) reports on the design and operation of one of two retantion
tanks constructed to prevent overflows into Halifax harbor from the
"Arm sewer1', an interceptor sewer which drains the west and northwest
sections of Halifax, Nova Scotia. The tank, which has a capacity of 1
million gallons, is provided with an aerated detritus tank through which
dry-weather flow passes directly to the interceptor sewer after
screening; but when flow in the sewer reaches a maximal level, passage
through the detritus tank is stopped, and the retention tank fills, pro-
viding 15-minute detention at a design peak flow of 150 cu. ft. per
247
-------
second before over-flowing to the "Arm sewer". Arrangements are
made for chlorination to continue as long as the rate of inflow exceeds
the rate of outflow to the interceptor. If the intensity and duration of
the storm are sufficient to fill the tank, the chlorinated sewage is dis-
charged to the harbor.
248
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(1) Larmon, A., "Smoking Out Illegal House Drains11, Wastes
Engineering, 34, 11, 603, November 1963.
(2) Greeley, S. A. and Langdon, P. E., "Storm Water and Com-
bined Sewer Overflows", Proceedings ASCE, 87, SA 1, 1961.
(3) Benjes, H. H,, Haney, P. D., Schmidt, O. J. and Yarabeck,
R. R. , "Storm-Water Overflows from Combined Sewers", Journal
Water Pgllution_Control Federation, 33, 12, 1961.
(4) McKee, J. E., "Loss of Sanitary Sewage Through Storm -
Water Overflows", Journal Boston Society of Civil Engineering, 34,
2, 55, April 1947.
(5) Dunbar, D. D. and Henry, J. G. G. , "Pollution Control
Measures for Stormwaters and Combined Sewer Overflows", Journal
Water Pollution Control Federation, 38, 1, 9, January 1966.
(6) Burm, R. J., Krawczyk, D. F. and Harlow, G. L.,
"Chemical and Physical Comparison of Combined and Separate Sewer
Discharges", Journal Water Pollution Control Federation. 40, 1, 112;
January 1968.
(7) Cruchley, A. E., "New Instrument Can Measure Sewage Flow",
Municipal Engineering, 136, 814-815, 1959.
(8) Ellis, W. and Johnston, C. T., "A Field Method of Measuring
and Recording Flow in Sewers", Public Works, 94, June 1963.
(9) Fathmann, H., "Methods and Equipment for the Measurement
of Sewage Flow", Wasser Luft Betrieb, 10, 668-673, 1966.
(10) Weidner, R. B. , Weibel, S. R. and Robeck, G. C., "Auto-
matic Mobile Sampling and Gaging Unit", Public Works, 99, 1, 78-80,
January 1968.
(11) Weibel, S. R., Anderson, R. J., and Woodward, R. L.,
"Urban Land Runoff as a Factor in Stream Pollution", Journal Water
Pollution Control Federation.36. 914, July 1964.
(12) Camp, T. R. , "Overflows of Sanitary Sewage from Combined
Sewerage Systems", Sewjige &: Industrial Wastes, 31, 4, April 1959.
249
-------
(13) Weibel, S. R., Weidner, R. B. , and Christian son, A. G.,
"Characterization, Treatment and Disposal of Urban Storm Water",
Proc. 3rd. Int. Conf. Water Poll. Res.. Munich, 1966, 1, 329-352,
1967.
(14) Palmer, C. L., "The Pollutional Effects of Storm Water
Overflows from Combined Sewers", Sewage & Industrial Wastes, 22,
154-65, 1950.
(15) Weller, L. W. and Nelson, M. K., "A Study of Stormwater
Infiltration into Sanitary Sewers", Journal Water Pollution Control
Federation, 35, 762, June 1963.
(16) Weller, L. W. and Nelson, M. K., "Diversion and Treatment
of Extraneous Flows in Sanitary Sewers", Journal Water Ppllutipn
Control Federation. 37, 343, 1965.
(17) Rhodes, D. E., "Rehabilitation of Sanitary Sewer Lines",
Journal Water Pollution Control Federation, 38, 2, 215, 1966.
(18) Metz, A., "Remote Control Grouting of Sewer Line Leaks",
Water and Wastes Engineering, 5, 6, 68, June 1968.
(19) Godbehere, J., "Eliminating Infiltration of Ground Water Into
Sewers", Th^__S^r_yeygr__a^d_^an^ipal^Tid....Cpanty Engineer, October 1962,
(20) Crane, F. W., "Retention Basin Eliminates Need for Costly
Storm Sewers", Engine ering News Record, 143, 38-42, December 1949.
(21) Waller, D. H. , "One City's Approach to the Problem of Com-
bined Sewage Overflows", _W^tej^_&_Sewage_Work£, 114, 113-117, 1967.
250
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Subject Field & Group
05B, 05G
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
Organization
Hayes, Seay, Matter n & Mattern, Roanoke, Virginia
Title
ENGINEERING INVESTIGATION QF SEWER OVERFLOW PROBLEM
ROANOKE, VIRGINIA
10
Authors)
Snapp, Wendle R. and
Lemon, Robert A.
16
Project Designation
FWQA Contract No. 14-12-200 (11024DMS)
21
Note
22
Citation
Water Pollution Control Research Series - 11024DMS05/70
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Descriptors (Starred First)
*Sewers, sanitary, *Infiltration, *Overflow, *Water pollution, *Surveys,
^Computer programs, Storm runoff, Flow measurement, sewers, Rainfall-
runoff relationships, Sampling, Construction costs.
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Identifiers (Starred First)
Sewer infiltration, Sanitary sewers
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Abstract
Results are given of investigations, on 25 percent of Roanoke, Virginia's
separate sanitary sewerage system, on the amounts of infiltration for
various storm intensities and durations and the amounts of sewage overflow
from the system. From these results the system was analyzed, using an
in-house developed computer program, to assess the magnitudes and
frequencies of overflows. The generated data from the analysis were used
to develop an optimum design for remedial measures to reduce sewer
overflows. Costs estimates are presented for the various items of work
involved.
Abstractor
Wendle R. Snapp
Institution
Hayes, Seay, Mattern & Mattern
WR:102 (REV, JULY 1969)
WRS1 C
SEND TO: WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U-S. DEPARTMENT OF THE INTERIOR
WASHINGTON, D. C 20240
O, S, GOVERNMENT PRINTING OFFICE : 1970 O - 402-222
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