WATER POLLUTION CONTROL RESEARCH SERIES
11024 EQG 03/71
Storm Water Problems and Control
in Sanitary Sewers
OAKLAND AND BERKELEY, CALIFORNIA
ENVIRONMENTAL PROTECTION AGENCY • WATER QUALITY OFFICE
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HATER POLLUTION CONTROL RESEARCH SERIES
The Water Pollution Control Research Reports describe the results and progress
1n 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 Water Quality Office of the Environmental Protection Agency,
through in-house research and grants and contracts with the Federal, State
and local agencies, research institutions, and industrial organizations.
Triplicate tear-out abstract cards are placed inside the back cover to facili-
tate information retrieval. Space is provided on the card for the user s
accession number and for additional key words. The abstracts utilize the
WRSIC system.
Inquiries pertaining to Water Pollution Control Research Reports should be
directed to the Head, Project Reports System, Planning and Resources Office,
Research and Development, Water Quality Office, Environmental Protection
Agency, Washington, D.C. 20242.
Previously issued reports on the Storm and Combined Sewer Pollution Control
Program:
11034 FKL 07/70
11022 DMU 07/70
11024 EJC 07/70
11020 — 08/70
11022 DMU 08/70
11023 — 08/70
11023 FIX 03/70
11024 EXF 08/70
11023 FOB 09/70
11024 FKJ 10/70
11024 EJC 10/70
11023 — 12/70
11023 DZF 06/70
11024 EJC 01/71
11020 FAQ 03/71
11022 EFF 12/70
11022 EFF 01/70
11022 DPP 10/70
Storm Water Pollution from Urban Land Activity
Combined Sewer Regulator Overflow Facilities
Selected Urban Storm Water Abstracts, July 1968 -
June 1970
Combined Sewer Overflow Seminar Papers
Combined Sewer Regulation and Management - A Manual of
Practi ce
Retention Basin Control of Combined Sewer Overflows
Conceptual Engineering Report - Kingman Lake Project
Combined Sewer Overflow Abatement Alternatives -
Washington, D.C.
Chemical Treatment of Combined Sewer Overflows
In-Sewer Fixed Screening of Combined Sewer Overflows
Selected Urban Storm Water Abstracts, First Quarterly
Issue
Urban Storm Runoff and Combined Sewer Overflow Pollution
Ultrasonic Filtration of Combined Sewer Overflows
Selected Urban Runoff Abstracts, Second Quarterly Issue '
Dispatching System for Control of Combined Sewer Losses
Prevention and Correction of Excessive Infiltration and
Inflow into Sewer Systems - A Manual of Practice
Control of Infiltration and Inflow into Sewer Systems
Combined Sewer Temporary Underwater Storage Facility
To be continued on inside back cover.
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STORM WATER PROBLEMS AND CONTROL
IN SANITARY SEWERS
Oakland and Berkeley, California
by
Metcalf & Eddy, Inc.
Engineers
Boston • New York • Palo Alto
for the
ENVIRONMENTAL PROTECTION AGENCY
WATER QUALITY OFFICE
Program No. 11024 EQG
Contract No. 14-12-407
March 1971
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, B.C. 20402 - Price $4
Stock Number 5501-0095
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EPA/WQO Review Notice
This report has been reviewed by the Water Quality Office and approved
for publication. Approval does not signify that the contents necessarily
reflect the views and policies of the Water Quality Office, nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.
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ABSTRACT
An engineering investigation was conducted on storm water infiltration
into sanitary sewers and associated problems in the East Bay Municipal
Utility District, Special District No. 1, with assistance from the
cities of Oakland and Berkeley, California.
Rainfall and sewer flow data were obtained in selected study subareas
that characterized the land use patterns predominant in the study area.
Results obtained were extrapolated over larger drainage areas. A
computerized flow routing program for the sewer system was used in
this analysis.
Ratios of infiltration to rainfall in the study subareas range from
0.01 to 0.14. Ratios of peak wet weather flow to average dry weather
flow range from 2.1 to 9.1. About 11.1 percent of the rainfall enters
the sanitary sewer system; 30.6 percent of the infiltration is con-
tributed by the 4 percent of the study area that has combined sewers.
Problems associated with infiltration and resulting overflows and
bypasses are: 1) pollution of San Francisco Bay, 2) operational
difficulties at the treatment plant, and 3) danger to public health,
property damage, and nuisance.
Estimated costs for the most feasible combinations of solutions to
these problems, consisting of treatment plant improvements, separation
of remaining combined sewers, partial treatment of overflows, and
sewer improvements, range from approximately $42 million to $94 million.
Specific recommendations for subsequent developmental programs are
presented; complete implementation of the recommended plan will take
about 7 years.
This report was submitted in fulfillment of Program No. 11024 EQG and
Contract No. 14-12-407 under the sponsorship of the Environmental
Protection Agency, Water Quality Office.
Pursuant to Executive Reorganization Plan No. 3 of 1970, effective
December 2, 1970, and Environmental Protection Agency Orders Nos.
1110.1 and 1110.2, all references to the Federal Water Quality
Administration herein shall be to the Environmental Protection
Agency, Water Quality Office.
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CONTENTS
Section Page
1 Conclusions and Recommendations ix
2 Introduction 1
3 Description of the Study Area 9
4 Flow Measuring and Sampling Program 37
5 Analysis and Evaluation of Data 59
6 Estimate of the Volumes of Storm Water 95
Infiltration
7 Problems Resulting from Overflows 117
8 Water Quality Objectives. 131
9 Evaluation of Effects of Overflows on 141
San Francisco Bay
10 Review of Possible Component Solutions to 179
the Problems of Overflows and Bypasses
11 Evaluation and Selection of Alternative 195
Solutions
12 Acknowledgments 221
13 References 225
14 Glossary and Abbreviations 229
15 Appendices 235
111
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FIGURES
Page
1 Vicinity Map of the Study Area i:L
2 Boundaries of EBMUD, Special District No. 1 - 12
Study Area
3 Aerial View of the Study Area 14
4 Groundwater Depths in the Study Area 19
5 Sewage Disposal System for EBMUD, Special District No. 1 22
6 Examples of Faulty Pipe Walls and Joints 24
7 Location Map of the Selected Study Subareas 29
8 Typical Palmer-Bowlus Flume Installation 42
9 V-Notch Weir Plate Details 43
10 Typical V-Notch Weir Installation 44
11 Typical Metering Installations 46
12 Locations and Types of Precipitation Gages 53
13 Diurnal Flow Variation,Pump Station A, 63
Nov.-April 1968-69
14 Extraneous Flow Hydrograph and Rainfall Histogram, 64
Pump Station A
15 Rainfall/Flow/Quality Graph, Pump Station A, 67
Dec. 9-10, 1968
16 Synthesis of Extraneous Flow Hydrograph Using 75
Percolation and Direct Connection Infiltration Ratios,
Capistrano Drive Subarea
17 Comparison of Observed and Computed Extraneous Flow 76
Hydrographs, Capistrano Drive Subarea
18 Graphs of Water Quality Parameters Versus Time During 80
Wet Weather, Benvenue Avenue Subarea
19 Graphs of Water Quality Parameter Trends During 82
Wet Weather
IV
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FIGURES (continued)
Page
20 Intensity-Duration-Frequency Curves, Oakland Airport 85
Gage, 1948-1968
21 Intensity-Duration-Probability Curves, Oakland 86
Airport Gage, 1968-69 Season
22 Frequency of 1968-69 Maximum Storm Event, Oakland 87
Airport Gage
23 Areal Rainfall Distribution Factors 89
24 Marginal Overflow Storm, 1968-69 93
25 Marginal Bypass Storm, 1968-69 93
26 Sources of Extraneous Flow, 1968-69 Season Versus 97
Average Year
27 Disposition of Extraneous Flow, 1968-69 Season Versus 97
Average Year
28 Land Use Distribution, Drainage Area No. 29 100
29 Sanitary Sewer Network, Drainage Area No. 29 102
30 Average Dry Weather Flows and Extraneous Flows 111
Versus Year, EBMUD Water Pollution Control Plant
31 Annual Plant Extraneous Flow and Annual Time of 113
Plant Bypassing Versus Annual Rainfall
32 Locations of Interceptor Overflow and Diversion 125
Structures and of Commonly Reported Manhole Overflows
in Oakland and Berkeley
33 Distribution of Reports on Rat Appearances and 129
Associated Types of Sewer Problems in East Bay
Cities, 1967
34 Water Quality Zones of the San Francisco Bay-Delta 136
Area
35 Diurnal Variation of DO, Entrance to San Leandro 147
Bay, April 10 and 11, 1969
36 Monthly Variation in DO Concentration, East Bay 148
Area, Outfall and South Shore, 1968-69
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FIGURES (concluded)
Page
37 Monthly Variation in DO Concentration, East Bay 148
Area, Emeryville and North Shore, 1968-69
38 Seasonal Variation of Temperature and Chlorosity, 150
North and Central Areas, San Francisco Bay, 1963-64
39 Dye Dispersion Contours at Higher High Water Slack, 152
Injection at Oakland Inner Harbor, End of Cycle 1
40 Dye Dispersion Contours at Higher High Water Slack, 153
Injection at Oakland Inner Harbor, End of Cycle 3
41 Estimated Dispersion Relationships for Pollutants 154
within Oakland Inner Harbor and San Leandro Bay
42 Dye Dispersion Contours at Higher High Water Slack, 155
Injection at Pt. Richmond, End of Cycle 3
43 Estimated Dispersion Relationships for Pollutants 157
Approximately 1-1/2 Miles Off the Emeryville, Berkeley,
Albany Shoreline
44 Grease Removed by Primary Treatment Versus Influent 163
Grease Concentration
45 Probability of Coliform Bacteria Concentration in 172
the Vicinity of the EBMUD Outfall Before and After Post-
Chlorination (1963-64 and 1968-69)
46 Areas of San Francisco Bay that Normally Did Not Meet 174
the Selected Coliform Objectives Before Chlorination
47 Probability of Coliform Bacteria Concentration 175
Approximately 3 Miles Off the Emeryville, Berkeley,
Albany Shoreline, 1963-64
48 Schematic Flow Diagram of the Existing Water Pollution 211
Control Plant Showing Proposed Revisions to Sedimenta-
tion Basins and Sludge Handling Facilities
VI
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TABLES
Paqe
1 Area and Population of the Six Cities in the 10
East Bay Area
2 Climate Characteristics of the East Bay Area 16
3 Distribution of Major Land Uses for the Six Cities 17
in the East Bay Area
4 Results of Sewer Construction and Maintenance 25
Survey, East Bay Area
5 Land Use, Topography, and Sewer Data for 28
East Bay Subareas
6 Locations and Types of Equipment Used in Flow 40
Measuring and Sampling Program
7 Locations and Types of Precipitation Gages Used in 55
Flow Measuring and Sampling Program
8 Areal Contributions of Dry Weather Flow for East Bay 62
Drainage Areas, November-April, 1968-69
9 Summary of Dry Weather Quality Data for East Bay 65
Drainage Areas, March-May 1969
10 Gross Infiltration Ratios for East Bay Drainage Areas, 68
1968-69
11 Ratio of Wet Weather Flows to Dry Weather Flows, 71
1968-69
12 Infiltration Ratios for Percolation and Direct 77
Connections, East Bay Drainage Areas, 1968-69
13 Areal Rainfall Distribution Factors 90
14 Occurrence of Rainstorm Peaks During the Day, 92
Oakland Airport, 1968-69
15 Land Use Products for Pump Station H Area and 104
Drainage Area No. 29
16 Land Use Products for Study Area With and Without 105
Combined Sewer Areas
VII
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TABLES (concluded)
Page
17 Land Use Products Using Direct Connection 107
Infiltration Ratios
18 Land Use Products for North Versus South Interceptor 109
Areas
19 Age Distribution of Infectious Hepatitis in 123
California, 1962
20 Monthly Distribution of Infectious Hepatitis in 123
California, 1962
21 Selected Water Quality Objectives for Evaluating 133
Effects of Overflows
22 Regional Board and Bay-Delta Water Quality Objectives 134
Applicable to San Francisco Bay Vicinity of EBMUD,
Special District No. 1
23 Summary of Data Used to Evaluate Effects of Overflows 143
on San Francisco Bay
24 Effects of Overflows on Dissolved Oxygen in the 160
Near-Shore Waters of Water Quality Zones 3 and 4
25 Summary of Suggested Improvements in Sewer Design 190
and Construction Procedures
26 Estimated Construction Cost of Component Sewer 197
Revisions
27 Estimated Construction Cost of Typical Holding Basin 201
28 Estimated Construction Cost of Typical Overflow 202
Treatment Facilities
29 Estimated Construction Cost of Additions and 208
Revisions to the Water Pollution Control Plant
30 Estimated Construction Cost of Alternative Combinations 215
of Component Solutions
31 Time Schedule for Effectuation of Recommended Alternative 218
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SECTION 1
CONCLUSIONS AND RECOMMENDATIONS
Page
Conclusions
Recommendations
xv
IX
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SECTION 1
CONCLUSIONS AND RECOMMENDATIONS
This engineering investigation of the sanitary sewer systems and
water pollution control facilities of the East Bay Municipal Utility
District, Special District No. 1 was conducted by Metcalf & Eddy, Inc.,
with the assistance of the City of Oakland, the City of Berkeley,
and the East Bay Municipal Utility District in the data collection
phase, under the terms of Contract 14-12-407. The study was directed
toward determining the magnitude and sources of storm water infiltra-
tion and the nature of problems associated with the resulting over-
flowing of sewers and bypassing at the water pollution control plant.
Alternative solutions for controlling these problems were defined,
and preliminary cost estimates were made.
The following conclusions are based on the data collected and
evaluated during this investigation and presented in the body of
the report.
CONCLUSIONS
1. Infiltration ratios (the volume of infiltration to the volume of
rainfall) were defined both for gross infiltration and for infiltra-
tion from each of two sources: percolation and direct connections.
The gross infiltration ratios for selected study subareas ranged
from 0.01 to 0.14, depending upon land use, topography, and age or
condition of the sewer system. The drainage area that contributes
directly to Pump Station A was found to have a ratio of 0.246. About
60 percent of the infiltration was attributed to percolation and
40 percent to direct connections for the eight subareas evaluated.
2. Variations in waste water characteristics during storm conditions
were not well defined, but general trends were detected. Practically
all of the parameters showed a sharp increase in concentration as
the flow rates in the sewer increased. These concentrations returned
to normal, or below normal, by the time the peak flow rate had
reached the sampling station or slightly thereafter. The exception
was the ratio of suspended solids to total solids. This ratio seemed
to increase gradually so long as substantial quantities of extraneous
flow continued.
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3. The average concentrations of pollutants representing the quality
of overflows and bypasses were:
Location
South interceptor
North interceptor
Water pollution
control plant
Grease,
mg/L
105
21
40
Coliform bacteria,
MPN/100 ml
3.7 x 10_
1.5 x 10'
8
4. An analysis of geographic rainfall distribution was made, from
which a correlation was found to exist between rainfall at various
locations (total per storm) and that at the Metropolitan Oakland Inter-
national Airport. Relationships were found for storms having general
rainfall distribution, ranging from factors of 0.9 to 1.55 times the
rainfall at the Oakland Airport. No relationship could be defined for
temporal distribution of rainfall, nor could a pattern be defined for
rainfall during the day.
5. A statistical analysis of rainfall data taken at the Oakland Air-
port indicated that the maximum storm event for the rainy season under
investigation, 1968-69, had a return frequency of about 1.9 years.
6. From an analysis of the first four hours of each of the largest
storms during the season together with recorded overflow occurrences at
two pumping stations and bypasses at the water pollution control plant,
both a "marginal overflow storm" and a "marginal bypass storm" were
defined. The storm conditions were defined by the cumulative rainfall
and the time of rainfall as shown on Figures 24 and 25 on page 93.
These conditions indicate the intensity and duration of a storm that is
needed to cause overflows and bypasses in the East Bay Area.
7. The ratios of peak wet weather flow, measured in the sewers, to
average dry weather flow ranged from 2.1 to 9.1. Ratios were com-
puted for both average daily flow and for average flow for the same
time of day; these are presented in Table 11.
8. The relative magnitude of the major sources of storm water infil-
tration for the study area was concluded to be as follows:
a. The equivalent storm water infiltration ratio for
the East Bay Area is 0.111, i.e., 11.1 percent of
the total volume of rain falling on the area enters
the sanitary sewer system.
b. Approximately 30.6 percent of the total volume of
infiltration is contributed by infiltration and
runoff from those areas which have combined sewers,
composing 4 percent of the study area.
XI
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c. Approximately 3.7 percent of the total volume of
infiltration is contributed by the Pump Station A
drainage area, composing 1.4 percent of the
study area.
d. In the remaining 94.6 percent of the study area,
approximately 26.2 percent of the total infiltration
is contributed via direct connections, and 39.5
percent is contributed via percolation or pipe leakage.
9. During an average year (a year having an average rainfall), the
following conditions were estimated to occur:
a. The total rainfall is 17.57 inches at the Oakland Airport.
b. Bypasses at the water pollution control plant occur an
average of 11 to 12 times per year, and it was concluded
that sewer overflows occur the same number of times,
based on similarities between the storms causing
each condition.
c. Approximately 1,660 MG of extraneous flow (6.8 percent
of the rainfall) reach the water pollution control plant
and 1,040 MG of extraneous flow (4.3 percent of the
rainfall) overflow before reaching the plant.
d. Bypassing at the plant occurs for 110 hours at an
average rate of 168 mgd, resulting in a discharge
of 780 MG of waste water that consists of 480 MG
of extraneous flow and 300 MG of base or dry weather
flow.
e. Approximately 1,180 MG (1,660 - 480) of extraneous
flow reaching the plant are treated before discharge.
f. Overflow volumes were estimated to equal 90.5 MG per
event, with 62.5 MG occurring south and 28.0 MG
occurring north of the plant.
10. Four types of overflows or bypasses were found and are listed
below. The first three contribute to the discharge of untreated com-
bined sewage to the Bay; the fourth involves the overflowing of sewage
within the system resulting in nuisance, property damage, and public
health hazards.
a. Intersystem overflows - occurring at cross-connections
between storm drains and sanitary sewers, resulting at
times in the discharge of raw sewage to the Bay.
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b. System overflows - occurring at specially designed
structures near the interceptor sewer to discharge
excess flow to the Bay.
c. Water pollution control plant bypass - manually con-
trolled bypass around the sedimentation basins to
prevent damage to the plant's mechanical equipment.
d. Intrasystem overflows - occurring at manholes or other
openings and broken sewers.
11. Two operation and maintenance problems were found at the water
pollution control plant which result from storm water infiltration.
a. During wet weather large quantities of fine sand and silt,
which would cause mechanical failure if the flow were not
bypassed, settle in the sedimentation basins. The
additional sand and silt that settles before bypassing
begins is pumped to the digester, hence taking up
digester volume and causing unnecessary cleaning
problems.
b. During periods of bypassing, large volumes of grease
accumulate in the outfall sewer and in the outfall
transition structure. Grease that clings to the wall
of the outfall later breaks loose in sizeable chunks and
contributes to the visible, floating grease. Grease
that accumulates in the structure requires substantial
maintenance effort for cleaning.
12. Based upon a review of the various water quality objectives that
would be applicable to the waters of Central San Francisco Bay, the
following water quality objectives were selected for evaluating the
effects of overflows and bypasses:
Parameter Unit Objective
a. Dissolved oxygen mg/L Minimum of 5.0
b. Floatable material
On water surfaces g/sq m Maximum of 0.02
On shore areas g/sq m Maximum of 0.3
c. Total coliform MPN/100 ml Not more than 20% of
bacteria samples exceeding 1,000.
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13. An investigation of the background concentrations of the selected
water quality objectives produced the following conclusions:
a. Average dissolved oxygen levels in the near-shore
waters are well above the minimum objective of
5.0 mg/L during the rainy season. The levels of
DO that fall below the minimum objective during the
months of January and February were concluded to result
from a combination of storm sewer discharges and
sanitary sewer overflows.
b. Using the guide for floatable grease emissions as set
forth in the Bay-Delta study, the dry weather grease
emissions were found to be acceptable. This guide
would permit 310 pounds per day of floatable grease
in Water Quality Zone 3 and 375 pounds per day in Water
Quality Zone 4.
c. With the exception of the Bay side of Alameda, the
shoreline waters of the East Bay Area were found to
exceed the allowable concentrations of coliform
bacteria. The offshore waters from Albany, Berkeley,
and Emeryville were found to meet the objectives
normally, but to exceed them periodically, probably
because of a combination of sanitary sewer overflows
and storm sewer discharges.
14. The evaluation of the effects of overflows and bypasses on the
selected water quality objectives in the near-shore waters indicated
that only the objectives for floatable materials and coliform bacteria
were exceeded. Except for the possibility of localized problems, the
dissolved oxygen content was not appreciably affected. During and
following overflowing and bypassing, appreciable concentrations of
floatable material (grease) were estimated to persist for six days in
Water Quality Zone 3 and for two days in Water Quality Zone 4. The
mechanisms of floatable grease removal were dispersion and oxidation.
Coliform bacteria were estimated to return to within 10 MPN per 100 ml
of the normal background concentrations within 2.6 days in Water Quality
Zone 3 and 1.5 days in Water Quality Zone 4. Both dispersion and
bacterial die-away were mechanisms in reducing bacterial concentrations.
15. It was concluded that no single action, short of total sewer re-
placement, could be found to solve the infiltration problems. There-
fore, a series of component solutions was evaluated that, when com-
bined, would represent an alternative solution. These component solu-
tions consisted of various improvements to the sewer system, addition
of holding basins or overflow treating facilities, additions and
revisions to the water pollution control plant, and, where applicable,
suggested improvements in sewer design and construction practices.
Estimated costs for each of four alternatives ranged from approximately
$42,000,000 to $94,000,000.
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16. The most practical and the lowest cost combination of component
solutions was concluded to be Alternative No. 3, consisting of the
following steps: 1) complete about 50 percent of the remaining sewer
separation program, 2) provide improvements to the water pollution con-
trol plant, 3) locate and disconnect catchbasins that are presently
connected to the sanitary sewer system, 4) provide partial treatment
for the remaining overflows, and 5) eliminate sewer system bottlenecks.
17. The time period needed to implement the plan of Alternative No. 3
completely was estimated at seven years.
RECOMMENDATIONS
On the basis of the preceding conclusions, the following recommenda-
tions are presented:
1. That Alternative No. 3 of the solutions summarized in Table 30 be
adopted as a plan for solving the problems of storm water infiltration
and overflows. Specific recommendations are presented for the com-
ponent solutions as follows:
a. EBMUD, Special District No. 1 should initiate detailed
studies, including pilot plant testing if necessary,
both for the proposed improvements to the plant and
for new overflow treatment facilities.
b. Each of the six East Bay Area cities should initiate
studies and surveys to locate the remaining combined
sewers, catchbasins attached to sanitary sewers, and
bottlenecks in the sewer system.
c. Each of the participants should undertake final design
and construction of its respective improvements as soon
as funds can be made available.
d. The first phase of construction should include only one
overflow treatment facility. After this facility has
been evaluated and proven, the remaining treatment
facilities should be designed and constructed.
2. That a study of the possible application of electrostatic disinfec-
tion equipment for use at overflow treatment facilities be sponsored by
EBMUD, Special District No. 1 concurrently with other pilot plant
testing or studies.
3. That the City of Oakland sponsor a specific study to determine the
application and limitations of the addition of polymers for increasing
the effective sewer capacity. The recommended site for application of
this process is the Fifth Street trunk sewer, along the south shore of
Lake Merritt. Improvement of the flow capacity of the sewer would help
xv
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relieve the problems during periods of wet weather flows, thereby
minimizing surcharging and overflowing at manholes along the sewer.
This procedure would serve as an interim measure until a more permanent
solution could be achieved. This recommendation would only be
applicable after a substantial improvement in hydraulic capacity of
the interceptor is made.
4. That one of the East Bay Area cities sponsor a study to evaluate
the use of cure-in-place, plastic pipe for lining sewers. The study
would determine the costs and techniques of installation of a glass-
fiber reinforced plastic liner pipe that could possibly substitute for
conventional sewer replacement programs, producing equivalent results
but at a lower cost.
xvi
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SECTION 2
INTRODUCTION
The Problem and the Study Area 2
Historical Background 4
Purpose and Scope of the Study 6
Method of Approach 7
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SECTION 2
INTRODUCTION
THE PROBLEM AND THE STUDY AREA
Infiltration into sanitary sewers has plagued engineers and municipal
officials for many years. Every sewer system is subject to infiltra-
tion to some degree, depending upon the condition of the sewers, the
level of groundwater, and the soil conditions. The extraneous flow
resulting from infiltration into sewers uses up valuable hydraulic
capacity and subsequently reduces the treatment capability of water
pollution control facilities by creating abnormally high flow rates
that upset biological and normal treatment activities.
Infiltration is usually defined as leakage of water into sewers from the
surrounding ground during both dry and wet weather. This study is con-
cerned specifically with infiltration which occurs only during, and as
a result of, wet weather, that is, storm water infiltration, regardless
of the source of the storm water. Therefore, the term, "infiltration,"
as used in this report and when not qualified, refers to the storm water
extraneous flow which enters sanitary sewers only during wet weather
conditions; or, in some places, it refers to the process by which such
extraneous water enters the sanitary sewers. Among the sources of
extraneous water are the following:
1. Groundwater and vadose water that enters the sanitary
sewer system via defects in the sewer.
2. Surface water that enters the sanitary sewer system via
direct connections of roof drains, foundation drains,
surface inlets, catchbasin leads, or other storm water
drains, or via manhole covers or other means.
3. Storm water which is bypassed or overflowed to the
sanitary sewer system from combined sewers or storm
drains.
It might be said that the quantity of storm water infiltration in a
sanitary sewer at any time is computed as the difference between the
actual flow at the time and the quantity which would have been flowing
if the rainstorm had not occurred.
In connection with the storm water - infiltration problem, it is neces-
sary in some instances to mention the dry weather infiltration, which
consists of all infiltration other than storm water infiltration. Where
such usage occurs in this report, either it is qualified or the meaning
is obvious.
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Storm water infiltration results from the use of inadequate construction
materials, poor construction practices, and direct connections. Until
recently, sewer construction materials and practices were frequently
conducive to infiltration because poor joints were produced when the
pipe was laid. Rigid jointing materials fractured during pipe settle-
ment, permitting groundwater to enter or sewage to escape the pipe.
With improvements in construction materials such as flexible plastic
joints, the problem of infiltration in recent sewer construction is
greatly reduced. However, sewers that were built before the improve-
ments in construction materials and methods were developed—around
1960—have many years of useful life remaining, and it is not likely
that they will be replaced before the end of that useful life is reached.
Direct connections, such as roof, yard, and foundation drains, add to
the quantity of infiltration, especially during wet weather. In many
instances, these connections are not only difficult to locate but also
difficult to disconnect because of the political ramifications involved.
For these reasons, the general problem of infiltration will continue
for many years.
The widespread nature and magnitude of the storm water infiltration
problem was illustrated in a 1967 national survey made by the American
Public Works Association for the FWPCA, now called the FWQA. Fifty-
three percent of the jurisdictions reported wet weather infiltration
problems, but only 14 percent reported dry weather infiltration prob-
lems. Moreover, 197 jurisdictions indicated that water pollution con-
trol plant bypassing occurred for an average of 350 hours per year at
each plant during wet weather conditions for the following reasons:
1. The plant was not designed to handle grit and debris
carried by storm flow.
2. High river stages did not permit operation of the
plant without excessive pumping.
3. The receiving stream flow was of such magnitude that
treatment was not deemed necessary by local officials.
4. The plant had insufficient capacity.
Many jurisdictions also reported overflows at locations within the
system other than at bypasses around the plant.
Because the study area selected for this investigation reflects many of
the problems cited above, it is expected that the results will benefit
many cities in addition to those within the study area.
The study area is a portion of the East Bay Area of the San Francisco
Bay metropolitan region in California. The East Bay Area normally
refers to all of the cities located along the east side of the San
Francisco Bay, but, in this report, the term is limited to the six
cities that compose the East Bay Municipal Utility District, Special
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District No. 1: Oakland, Berkeley, Alameda, Albany, Emeryville, and
Piedmont. The City of Oakland, the City of Berkeley, and EBMUD,
Special District No. 1 participated in and contributed materially to
this study. Therefore, the detailed investigations and resulting data
were developed mainly from areas within these two cities and from the
water pollution control plant operated by EBMUD, Special District No. 1.
This plant, located in Oakland near the east end of the San Francisco-
Oakland Bay Bridge, was built in 1948-1951 to serve the entire study
area.
HISTORICAL BACKGROUND
Prior to 1951, the East Bay Area cities were served by individual
systems of combined sewers which conveyed all waste waters together with
storm water runoff from each of the many drainage areas directly into
the near-shore waters of the Bay. By 1940, the pollution state of the
East Bay waters had reached an intolerable condition.
Realizing that action was necessary, the City of Berkeley sponsored a
comprehensive investigation by a board of consulting engineers, of the
collection, treatment, and disposal of sewage and industrial wastes
from seven East Bay cities (the six cities in EBMUD, Special District
No. 1 and Richmond). The results, published in the "1941 Sewage Report"
(1) , provided the basis for most of the improvements that have been
made to date. The four recommendations most pertinent to this study
were that:
1. Dry weather sewage flow from the East Bay cities and from
all areas naturally tributary thereto be collected for
primary treatment and disposal in the vicinity of the
San Francisco-Oakland Bay Bridge.
2. The construction and operation of the recommended sewage
collection system and water pollution control plant be
performed by the East Bay Municipal Utility District.
3. A program be at once developed whereunder existing
combined sewage systems be systematically separated into
sanitary sewers and storm sewers.
4. A program of repair and reconstruction be inaugurated through-
out the East Bay Area aimed at the reduction of the excessive,
unjustifiable amounts of infiltration entering the sewers.
By 1951, the first and second recommendations had been put into effect.
The third recommendation was also subsequently implemented, and by
1969 approximately 96 percent of the sewer separation program had been
completed. The fourth recommendation is the one that has been given
the least attention. Thus, after some 30 years, infiltration problems
still plague the East Bay Area cities.
-------
Because a major part of the sewer separation program was completed
prior to 1960 before the improved jointing methods for vitrified clay
sewer pipe were introduced, many of the problems of leakage and infil-
tration that were previously common to the combined sewer system were
built into the new sanitary sewer systems. Moreover, not all of the
present sanitary sewer system represents newly constructed sanitary
sewers. In many cases, the old combined sewer was converted to a
separate sanitary sewer and a new storm sewer was constructed. There-
fore, the problems inherent in the combined sewer system were carried
into the sanitary sewer system.
Compounding the infiltration problem was the fact that the repair and
reconstruction of sewers was not extensively undertaken. Stopgap
measures were used wherever problems of inadequate capacity were found.
Consequently, the sewer systems of the East Bay Area cities have many
cross-connections between storm and sanitary sewers, direct connections
into sanitary sewers, parallel relief sewers, and overflows directly
to the Bay waters.
Various attempts have been made by EBMUD, Special District No. 1 to
measure the extraneous flow resulting from storm water infiltration.
Because of the many complications within the system, it was never
certain that-all of the extraneous flow actually tributary.to a particu-
lar sewer was measured, nor could all of the problems caused by the
variable hydraulic conditions posed by tide elevation, variations in
pumping rates, and manual operation of diversion structures be overcome.
The conclusions in each case have been that there is a substantial
increase in flow rates during rainfall, but no actual numbers could be
assigned with any degree of confidence.
In view of the complexity of the sewer system and the unsuccessful
previous efforts to define the magnitude of the infiltration problem,
it was concluded for this study that a direct method of measuring all
extraneous flows during rainfall would be extremely difficult and
expensive. No method short of measuring flows in all major storm
sewers and sanitary sewers would portray the complete picture.
Water that overflowed within the system from sanitary sewers into storm
sewers would not be included in flow measurements taken in sanitary
sewers. Also, the differentiation of storm water runoff, storm water
infiltration, and sanitary sewage would be extremely difficult. The
design and construction characteristics of the connections between the
old trunk sewers and the interceptor sewers are not conducive to flow
measurement. Limitation of access, interference by tidal variation,
and the somewhat unpredictable manual operation of the pumping station
and various diversion structures along the interceptor sewer all com-
pound the problem of flow measurement. For these reasons, a different
-------
approach to measurement of extraneous flow resulting from storm water
infiltration was necessary for this study.
PURPOSE AND SCOPE OF THE STUDY
The purpose of this investigation was to define both quantitatively
and qualitatively the magnitude of storm water infiltration in the
sanitary sewer systems of the East Bay Area cities, to define the
problems associated with large volumes of infiltration, to ascertain
what alternative solutions are available to alleviate the problems,
and to provide preliminary designs and cost estimates for the recommend-
ed alternative solutions.
The specific objectives paraphrased from the STATEMENT OF WORK of the
contract were to:
1. Define the study area and select subareas for
intensive study.
2. Collect all existing pertinent data.
3. Measure both dry and wet weather flows in each subarea.
4. Sample both dry and wet weather flows in each subarea.
5. Measure precipitation with sufficient gages to provide
a real definition of rainfall characteristics.
6. Establish the characteristics of both dry and wet
weather discharges to the receiving waters.
7. Define the background water quality and the water
quality objectives for the receiving waters.
8. Define the pollutional effects of overflows and
bypasses on the receiving waters.
9. Develop alternative solutions for controlling or
eliminating overflows and bypasses from the receiving waters.
10. Prepare design criteria and cost estimates for the
alternative solutions.
11. Select and recommend the best alternative solution.
12. Prepare a final project report.
-------
METHOD OF APPROACH
The approach used in this study to accomplish the preceding objectives
entailed the following steps:
1. Selection of subareas that typified various conditions
prevalent in the study area as a whole, such as sizes
and types of sewers; topographic, soil, and groundwater
conditions; and land use categories.
2. Characterization of infiltration in each of the subareas
and the development of infiltration ratios related to
rainfall and land use. Characterization was based on
actual field measurements of rainfall and flows in sewers
and the sampling and analysis of waste water flows.
3. Development of a mathematical flow routing program which
would simulate the dry and wet weather flows in any given
drainage area. The routing program was valuable for defining
the components of infiltration; determining if sewer system
overflows occur and, if so, how much; and evaluating the
effect of holding tanks on the outflow hydrograph. The
routing program further aided in confirming a method of
extrapolating measured or computed volumes of extraneous
flow from a small drainage area to the total drainage area.
4. Evaluation of causes and effects of infiltration and the
development of alternative solutions to the problem. The
evaluation was based on defining the problems caused by
infiltration and determining the pollutional effects of
overflows and bypassed flows on San Francisco Bay from
available data.
5. Development of feasible alternative solutions, cost estimates,
and recommendations.
The project report is divided into three volumes. This volume contains
a description of the study area and of the data collection program,
the development and discussion of the problems and alternative solutions,
and the conclusions and recommendations. The "Technical Supplement"
volume contains a summary of the literature reviews made during this
study to derive the methods used to analyze the data and to develop
the alternative solutions. It also contains a development of the
potential economic benefits. The "Field and Laboratory Data" volume
contains the results of field and laboratory investigations, including
flow rates, quality parameters, and precipitation data, as well as
selected hydrographs and quality plots. These latter two volumes have
a limited publication and are available for inspection only at the
offices of the FWQA and Metcalf S Eddy. Numbers enclosed in parentheses
within the text are the references listed in Section 13.
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SECTION 3
DESCRIPTION OF THE STUDY AREA
Page
Characteristics of the Study Area 10
Principal Features 13
Topography, Geology, and Climate 13
Land Use 15
Groundwater Levels 18
Sewer System 18
Water Pollution Control Facilities 26
Main Pumping Station 26
Grit Chambers 26
Sedimentation Tanks 26
Sludge Digestion Tanks 26
Effluent Pumping Station 27
Outfall Sewer 27
Characteristics of the Study Subareas and Control Areas 27
Berkeley Subareas 27
Benvenue Avenue 27
Carleton Avenue 31
Glen and Spruce Street 31
Oakland Subareas 32
Capistrano Drive 32
High Street 32
Nineteenth Street 33
Pump Station J 33
Skyline Boulevard 34
Trestle Glen Road 34
Control Areas 34
-------
SECTION 3
DESCRIPTION OF THE STUDY AREA
CHARACTERISTICS OF THE STUDY AREA
The six cities of the East Bay Area that form the study area are
located in the northwestern portion of Alameda County on the easterly
side of San Francisco Bay, one of the finest natural harbors in the
world. West of the study area, the headlands of the San Francisco and
Marin peninsulas form the narrow entrance to the San Francisco Bay,
known as the Golden Gate, which itself is probably the fundamental
geographical factor in the area. Eastward through the Golden Gate
come the tide, winds, and fogs of the Pacific, which are decisive
factors in the climatology of the area.
As shown in Figure 1, the cities appear to be a single entity, with no
visible lines of demarcation between them. Together they cover an
urban area approximately 12 miles in length and varying from three to
eight miles in width.
Figure 2 shows the boundaries of the study area: the city limits of
Albany on the north, Berkeley and Oakland on the east, Oakland on the
south, and the San Francisco Bay on the west. The distribution of
area (in acres) and population are listed in Table 1.
TABLE 1
AREA AND POPULATION OF TEE SIX CITIES IN THE EAST BAY AREA
City
Alameda
Albany
Berkeley
Emeryville
Oakland
Piedmont
Total
Total area,*
acres
14,790
3,218
11,585
1,390
49,330
1,090
81,403
Land area,
acres
6,459
1,084
6,503
760
35,520
1,090
51,416
Estimated
population
1968**
70,200
17,200
121,500
2,850
379,500
11,500
602,750
*Includes portions of San Francisco Bay lying within
city limits.
**By the Alameda County Planning Department, as of
January 1, 1968.
10
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EBMUD
SPECIAL
DISTRICT
NO. I
FIG. I VICINITY MAP OF THE STUDY AREA
11
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FIG 2. BOUNDARIES OF EBMUD,
SPECIAL DISTRICT NO.I-STUDY AREA
12
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PRINCIPAL FEATURES
Figure 3 is an aerial view of the study area from a position over the
San Francisco Bay. Following along the shoreline from the north to
the southeast, some important features are: Berkeley Marina, with its
recreation pier and small craft harbor; Aquatic Park on the south
Berkeley waterfront just east of Eastshore Freeway (Interstate Route
80); the recently expanded Oakland Marine Terminal Facility; Oakland
Inner Harbor, which separates the island city of Alameda from the city
of Oakland; the U.S. Naval Air Station on the westerly end of the
island; and San Leandro Bay, a shallow body of water connected to the
main Bay by a natural channel at the southeast end of Alameda. Nearly
all of the shoreline of the East Bay cities runs out westerly in
shallow mudflats on a practically level plain, roughly four miles in
width, to a depth of 15 feet at mean lower low water.
TOPOGRAPHY, GEOLOGY, AND CLIMATE
The East Bay Area includes an alluvial plain lying between the hills
of the Coastal Range along the eastern boundary and the waterfront.
This plain rises gently eastward from the shoreline for a distance
varying from one to three miles, to the foot of the range of hills
forming the eastern boundaries of Berkeley and Oakland. Beyond the
plain, the Berkeley Hills rise rather steeply in a series of ridges
trending southeasterly. The average crest elevation is about 1,200
feet, and the highest point is Bald Peak at 1,913 feet. In the east
Oakland area the highest point is Redwood Peak at 1,619 feet.
Several creeks which traverse the plain from the foothills to the
waterfront govern the layout of the drainage and sewerage systems of
the various cities.
The Temescal Alluvium is an - alluvial plain of simple geologic structure
forming part of the East Bay Area. The predominant geological forma-
tions are undifferentiated Quaternary (recent) deposits which include
sand, gravel, clay, bay mud, recent alluvium and colluvium, and
artificial fill. Artificial fills of varying composition are found in
strips along almost the entire shoreline, usually constructed over
former tidelands.
In the ridge east of Berkeley, the component strata are quite complex,
but in general they are sedimentary and metamorphic formations with
igneous intrusions and remnants. Behind Berkeley proper, the forma-
tions are principally sedimentary sandstones, conglomerates, and
shales. Bald Peak is a basalt cap lying on a conglomerate mass of the
ridge. Proceeding northeasterly from the alluvial plain in the region
of east Oakland, the formation between the approximate elevations of
100 and 200 feet is the San Antonio deposit of alluvial fans. Above
this the Leona Rhyolite rises with quite abrupt slopes to the crest.
The rate of rise is about 1,100 feet in one and one-half miles.
13
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ALBANY
BERKELEY EMERYVILLE
FIG. 3 AERIAL VIEW OF THE STUDY AREA
-------
Appendix Figure 1-1 shows the locations of the various geological
formations and artificial fills in the study area, as well as the major
and minor fault lines. The Hayward Fault zone contains the only faults
known to be active in the area. Appendix Table 1-1 lists the geological
symbols used in the figure.
The climate has three outstanding features: mild year-round tempera-
tures ; abundant rains during the winter; and early morning overcast
with almost no rain during the summer. Prevailing westerly winds from
the Pacific, where temperatures vary little between winter and summer,
keep the winters mild and the summers cool. Sustained periods of
either hot or cold weather occur infrequently.
Approximately 90 percent of the average total annual rainfall of almost
18 inches (measured at the Oakland Airport) falls during a six-month
period, beginning in early November and extending through the end of
April. This period is called the "rainy season" in the report. In the
summer, the cooling sea breezes and early morning overcast combine to
produce a high relative humidity. Although rain usually falls over
the entire East Bay Area during storms, the annual amounts vary from
place to place, the hilly portions receiving larger amounts than the
lower plain.
The characteristics of the climate for the East Bay Area are summarized
in Table 2.
LAND USE
The distribution of major land uses of the cities is listed in Table 3
and shown in detail on maps in Appendix Figure 1-2. Most of the in-
dustrial sites are located on a strip of land approximately one mile
wide extending along the shoreline; in Alameda they are on a narrow
strip along the Oakland Inner Harbor and Estuary. Commercial areas,
other than the downtown areas of Alameda, Berkeley, and Oakland, con-
sist of strip developments along main arterials. Large portions of
the East Bay Area are occupied by the Metropolitan Oakland International
Airport, the Alameda Naval Air Station, the Naval Supply Center and
Depot, the Oakland Army Terminal, the University of California, the
California Schools for the Deaf and Blind, Mills College, and the Oak
Knoll Naval Hospital. The zone between the industrial areas and the
hills consists of commercial and low-to-high density residential use.
The steeper hillsides are usually utilized for low density residential
development. Areas of new developments are few. Development of hill-
side land continues, but bans on Bay filling have curtailed tideland
development. The cities are approaching the saturation level as
measured by today's standards.
Alameda, Albany, and Piedmont are primarily residential cities, whereas
Emeryville is primarily an industrial city. Berkeley has areas of
considerable industrial and commercial importance, but its primary
characteristic and unique feature is that of an educational center.
15
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CTl
TABLE 2
CLIMTE CHARACTERISTICS OF TEE EAST BAY AREA
Precipitation,
inches per month
Length
of record.
years
January
February
March
April
May
June
July
August
September
October
November
December
Yearly
averaqes
Min.
40
0.65
0.02
0.04
T
T
0.00
0.00
0.00
0.00
T
0.00
0.29
.00
Max.
40
8.90
8.53
5.69
4.60
3.42
1.21
0.14
0.34
3.27
8.56
5.66
11.29
Normal
40
3.83
3.21
2.42
1.38
0.65
0.12
T
0.03
0.20
0.78
1.73
3.58
17.93
Normal temperature, deg F
Min.
A
40.6
42.6
44.7
47.7
51.1
54.2
55.9
56.0
55.5
51.1
45.4
41.8
48.9
Max.
*
55.4
58.7
62.5
65.5
68.2
71.3
72.7
72.4
74.6
71.1
63.9
57.1
66.1
Monthly
*
48.0
50.7
53.6
56.6
59.7
62.8
64.3
64.2
65.1
61.1
54.7
49.5
57.5
Average monthly
prevailing winds**
From
21
SE
W
W
W
W
W
WNW
WNW
WNW
WNW
WNW
E
W
MPH
21
6.3
7.0
8.8
9.2
9.9
9.9
9.2
9.0
7.7
6.5
5.9
6.1
7.9
Average
sky cover,
sunrise
to
sunset***
25
6.3
5.9
5.8
5.2
4.8
4.0
3.6
3.9
3.5
4.3
5.9
6.1
4.9
Average monthly
relative humidity,
percent
4 a.m.
5
81%
76
77
77
80
83
85
85
80
79
79
79
80%
4 p.m.
5
71%
67
65
62
64
67
67
67
63
63
69
69
66%
Note: T = Trace, an amount too small to measure.
* Climatological standard normals (1931-1960).
** The prevailing direction for wind is taken from records through 1963.
*** Sky cover is expressed in a. range of 0 for no clouds or obscuring phenomena to 10 for complete sky cover.
Source: U.S. Weather Bureau at Metropolitan Oakland International Airport, Oakland, California.
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TABLE 3
DISTRIBUTION OF MAJOR LAND USES FOR THE SIX CITIES IN THE EAST BAY AREA
Alameda
Major land use
Incorporated area
Water area
Land area
Circulation (streets, f reeways , etc . )
Commercial
Residential
Public use , community facilities,
government installations
Industrial
Vacant
Agricultural
Population
Acres
14,790
8,331
6,459
626
177
1,558
2,127
229
1,546
150
70,
Percent
100
56
44
10
3
24
33
4
24
2
200
Albany
Acres
3,218
2,134
1,084
254
157
448
58
31
135
17
Percent
100
66
34
24
14
41
5
3
13
—
,200
Berkeley
Acres
11,585
5,082
6,503
1,796
267
3,023
819
319
280
—
121,
Percent
100
44
56
27
4
46
13
5
4
—
500
Emeryville
Acres
1,390
630
760
180
12
70
23
375
100
—
2,
Percent
100
45
55
24
2
9
3
49
13
—
850
Oakland
Acres
49,330
13,810
35,520
7,700
1,250
11,050
10,970
1,850
2,700
—
379
Percent
100
28
72
22
4
31
30
5
8
—
,500
Piedmont
Acres
1,126
1,126
223
4
746
123
—
30
—
11
Percent
100
100
20
1
66
11
—
2
—
,500
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Within the city is the original campus of the University of California.
There is a central commercial district and some strip commercial
development along the main traffic arteries. The industrial development
is located in the areas between San Pablo Avenue and the waterfront.
The development of the Berkeley Marina has added recreational use to
the waterfront.
Oakland is, by far, the largest city in the study area and the economic
and transportation center of the East Bay. The entire waterfront area
is involved in industrial use. There is a large commercial downtown
area, as well as strip commercial development along many of the main
traffic arteries. Much of the area around the shores of Lake Merritt
has been developed for either commercial or high density residential
use, with the exception of several public recreational developments.
The foothill and sidehill areas are devoted to medium and low density
residential units.
GROUNDWATER LEVELS
Figure 4 presents the data that were available for defining the ground-
water conditions. Part of the information is a compilation of boring
data collected by the U.S. Geological Survey over the past 30 years
and cannot be given any great weight because of changing conditions.
The most recent and most valid data are those developed during the
foundation investigation made for the Bay Area Rapid Transit System.
Discussions were held with various sewer maintenance and construction
personnel regarding the possible interference of groundwater during
sewer construction. Except in locations near the waterfront, their
experience indicated that water levels were below the normal sewer
depths and did not represent a problem during sewer construction.
Except for local variations, the groundwater seems to be ten feet or
more below the ground, which indicates that groundwater may not repre-
sent a substantial factor in infiltration into the sewer system. This
conclusion seems to be confirmed by the fact that dry weather flow
rates at the water pollution control plant are not abnormally high.
Other factors seem to predominate in the initial volume of infiltration,
for example, direct connections between storm and sanitary sewers and
indirect connections formed by a porous bedding material situated be-
tween leaking storm sewers and broken sanitary sewers. Obviously,
infiltration from groundwater sources cannot be overlooked because this
source probably produces that portion of infiltration that may persist
for one or more days after a storm.
SEWER SYSTEM
Many of the street systems in the cities of the East Bay Area have
been laid out on the familiar rectangular basis, with streets running
directly up the slopes and laterally across them. As a result, most
18
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BASIC «AP REPRODUCED BY
PERMISSION O? THE CALIFORNIA
S2A7£ AUTOMOBILE ASSOCIATION,
BAY
12.5 DEPTH TO FREE WATER SURFACE
12.5 DEPTH TO FREE WATER SURFACE DURING RAINY SEASON.
FIG. 4 GROUNDWATER DEPTHS IN THE STUDY AREA
SOURCE: USGS, SELECTED BORINGS - ALAMEDA COUNTY, 1930-1965 AND BAY AREA RAPID TRANSIT DISTRICT
CONSTRUCTION DATA-BORINGS
19
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of the sewer lines run directly down the slopes on considerable grade
until reaching flat ground. In the more recently developed residential
areas of the middle and upper hills, the streets tend to follow the
contours, with relatively few cross-streets up and down the slopes.
Consequently, there is no difficulty in providing adequate grades for
the sewers in the upper areas.
During early sewer development in the area, sewers were designed to run
directly downhill on the shortest possible lines to discharge at the
shores of the Bay or its estuaries. As a result, a large number of
outlets were discharging untreated domestic and industrial wastes into
the receiving waters. The water pollution control plant was built to
eliminate this problem. Two interceptors—one from the north and one
from the south—collect and carry sewage to the plant. They were
placed as close to the waterfront as possible to connect the existing
outfalls without necessitating reconstruction of the existing system.
The locations of the interceptors, the pumping stations, and the water
pollution control plant are shown in Figure 5.
Appendix Figure 1-3 shows the size, number, and shape of the various
drainage areas tributary to the interceptor sewers. As indicated by
their shape, the drainage areas conform to the natural geographical
conditions.
The interceptor system consists of approximately 21 miles of rein-
forced concrete pipe sewers, varying in size from 12 to 108 inches in
diameter, and 12 pumping stations, varying in capacity from 0.5 to
57 mgd. Two pumping stations at the water pollution control plant
lift the incoming raw sewage from the interceptors into the treatment
units and pump the treated waste from the plant when the flow rate
exceeds the gravity-flow capacity of the outfall line.
The 12 pumping stations are automatically controlled throughout the
year, except during peak storm flows when Pump Station H is manually
operated or shut down to prevent overloading of the water pollution
control plant. The interceptor system is pumped down to minimum levels
each week to create velocities high enough to remove solids deposited
within the system during periods of low flow.
The physical condition of the sewer system can be described by refer-
ence to age, pipe materials, and integrity of pipe walls and pipe
joints. Some of the older sewers in the systems date back almost 100
years. Many of the early sewers were constructed by land developers,
with little or no control by the cities or agencies responsible for
this service; therefore, the quality of construction left much to be
desired. The major system of combined sewers was constructed prior to
1938. As has been mentioned, the sewer separation and reconstruction
began after issuance of the "1941 Sewage Report" (1). The majority of
this work was completed by the early 1960's, although some work has con-
tinued each year. Additional effort is necessary before all of the com-
bined sewers are separated.
21
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ALAMEDA
INTERCEPTOR
LEGEND
A PUMPING
STATION
FIG. 5 SEWAGE DISPOSAL SYS
FOR EBMUD, SPECIAL DISTRICT N
SOURCE* ANNUAL REPORT, WATER POLLUTION CONTROL "DIVISION, EBMUD, SPECIAL DISTRICT N
0. I
22
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Vitrified clay pipe has been used almost exclusively for the construc-
tion of sewers, although some of the large sewers were constructed of
brick or concrete. The joints used in the earlier clay pipe sewers
were made of cement mortar. In addition to being rigid, they ware un-
satisfactory because all too often insufficient care was taken to close
the invert portion of the joint. Later construction made use of
sulphur compound joints, which were also rigid, and pipe settlement
caused failures. Various other jointing compounds were used until the
superior plastic joint became available around 1960. This plastic
joint is now used predominantly.
Figure 6 shows four photographs of sewer failures which were provided
by the City of Berkeley. The pictures are examples from a photographic
survey of the sewers located in Keith Street (between Euclid and Brett
Harte Road) and Keeler Street (between Marin and Forest Hill) in
Berkeley. They illustrate the worst conditions that were found along
those sewers, but these were not all of the failed conditions. Copies
of the survey reports are included in Appendix I. As a result of these
reports, these particular sewer reaches have been replaced. The
question now is how many other reaches of sewer throughout the East Bay
Area are in similar condition?
Sewer construction and maintenance practices found during an interview
survey are summarized in Table 4. Some of the more interesting items
are noted below.
All cities now require that the maximum distance between manholes not
exceed 300 to 400 feet. Prior to 1950, Alameda allowed 450 feet,
Berkeley and Piedmont allowed 600 feet, and Emeryville allowed 1,000
feet.
All cities except Oakland indicated that sewer separation is between
•95 and 100 percent complete. Oakland indicated that its sewer
separation is 90 to 95 percent complete at present, but that progress
is being made each year.
Oakland was the only city to report more than ten catchbasins attached
to sanitary sewers; in fact, Oakland estimated there were more than 100.
Albany and Piedmont were the only cities to report no relief overflows
existing between sanitary sewers and storm drains. Alameda and Emery-
ville reported fewer than five, while Berkeley indicated in excess of
50, and Oakland, 20 or more.
Berkeley
a year-round
failed pipe
ey, Oakland, and Piedmont conduct sewer replacement programs on
•-round basis. Alameda, Albany, and Emeryville only replace
[ nine.
All cities except Emeryville indicated that flooding occurs during
rainstorms; however, in all cases, it was considered a mild problem.
23
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BROKEN JOINT
ROOT INTRUSION THROUGH SEPARATED JOINT
BROKEN 8 OFFSET JOINTS JOINT OFFSET
FKi 6 EXAMPLES OF FAULTY PIPE WALLS AND JOINTS
SOURCE' CITY Of KfKELEV, SEWED MAMTOUMX DCWWTMENT
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TABLE 4
RESULTS OF SEWER CONSTRUCTION AND MAINTENANCE SURVEY, EAST BAY AREA
Question* Albany Berkeley Emeryville
1. Specify vitrified clay pipe as
standard for sewers with plastic joints? XX X
2. Allow asbestos cement pipe?
3. Allow cast iron or corrugated pipe
for special requirements? X
4. Specify special bedding under pipes? XX X
5. Allow curvilinear sewers:
a. horizontal curves?
b. vertical curves?
to
Ul
Oakland Alameda Piedmont
XXX
X
X X
X X
X X
X X
V V V
6. Maximum manhole spacing = 300-400 ft?
7. Disallow roof connections to
sanitary sewers?
8. Test for leaks on new sewer
9.
10.
11.
12.
construction? X X
Specify air testing for sewers?
Infiltration allowance = 500 gallons
per inch diameter per mile per day? X X
Have established maintenance program? X X X
Does flooding occur occasionally
during rainstorms? X X
XXX
X X
X
X X
XXX
Norte: X indicates a yes answer to the question, and a blank indicates either no or some other condition.
*Questions were asked during interviews with public works representatives of each city.
-------
All cities indicated they had few problem areas. Berkeley and Oakland
indicated that tides have an effect on the sanitary sewers, but only
if high tides occur during periods of heavy rainfall.
WATER POLLUTION CONTROL FACILITIES
The water pollution control plant operated by EBMUD, Special District
No. 1 was designed to provide primary treatment for an average dry
weather sewage flow of 128 mgd and a maximum flow of 291 mgd. Facili-
ties are provided for prechlorination, screening, grit removal, sedi-
mentation, and sludge digestion. In 1968 postchlorination facilities
were added. The treated waste water and the digested sludge solids
and supernatant are disposed through an outfall sewer which discharges
into the offshore waters of San Francisco Bay.
Main Pumping Station
Upon arrival at the plant, the sewage flow first enters the main pump-
ing station where it is immediately chlorinated to control odors.
Next, five mechanically-cleaned bar screens with one-inch openings
remove sticks, rags, and other trash from the sewage flow, which is
then lifted by five 42,000-gpm pumping units into the grit chambers.
Grit Chambers
Grit, composed of sand, gravel, and other heavy matter, is settled out
as sewage flows at reduced velocity through the grit chambers. These
chambers consist of five channels, each 60 feet long and 12-1/2 feet
wide, with an average water depth of nine feet. The settled grit is
continuously collected and mechanically removed, and then hauled to a
dump site where it is buried.
Sedimentation Tanks
From the grit chambers, the sewage flows by gravity to ten sedimentatioi
tanks, each 180 feet long and 35 feet wide, with an average water depth
of 11 feet. It is retained in the tanks for approximately one hour
during which the settleable organic solids are removed. The heavier
solids settle to the bottom of these tanks and accumulate in a form of
sludge, which is mechanically collected and pumped to the sludge
digestion tanks for treatment. The floating solids and the oil and
grease that rise to the surface of the tank are skimmed off and in-
cinerated.
Sludge Digestion Tanks
The sludge from the sedimentation tanks is transferred to the sludge
digestion tanks and held at a temperature of 95 deg F for approximately
30 days. During this period, it is converted by biochemical action
into an innocuous humus-like solid residue, liquid, and gas. The
26
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digested sludge is discharged into the outfall sewer. The supernatant
(the liquid residue) is returned to the headworks. The gas is collect-
ed, and some of it is used as fuel to heat the sludge digestion tanks
and plant buildings; the remainder is burned in waste gas burners.
Effluent Pumping Station
The effluent or liquid overflow from the sedimentation tanks flows by
gravity to the effluent pumping station. From here, it either flows
by gravity or is pumped by three 70,000-gpm pumping units into the
outfall sewer.
Outfall Sewer
The outfall sewer is three miles long and has a diameter of 108 inches.
It conveys the effluent and the digested sludge to the point of final
disposal one mile offshore and 45 feet below the surface of San Fran-
cisco Bay. The end of the diffuser is located approximately 540 feet
south of the Bay Bridge. Here the effluent is rapidly dispersed and
diluted by tidal action.
CHARACTERISTICS OF THE STUDY SUBAREAS AND CONTROL AREAS
Ten subareas in Berkeley and Oakland were selected for intensive study:
Berkeley subareas Oakland subareas^
1. Benvenue Avenue 1. Capistrano Drive
2. Carleton Avenue 2. High Street
3. Glen Street 3. Nineteenth Street
4. Spruce Street 4. Pump Station J
5. Skyline Boulevard
6. Trestle Glen Road
These subareas, shown on Figure 7, were selected because together they
typify the various major land use categories, they represent both old
and new sewers, and they include both flat and hillside terrain.
Other considerations were the ease with which samples of flow data
could be collected and the characteristics of the area that would per-
mit generalization of subsequent data to the total study area or to
areas outside the study area. Table 5 lists land use, topography, and
sewer information for the subareas. Additional information on each
subarea follows.
BERKELEY SUBAREAS
Benvenue Avenue
The Benvenue Avenue sanitary sewers consist of predominantly older clay
pipe with cement mortar joints. Direct connections are suspected of
contributing to the infiltration problem during- rainstorms, but a roof
27
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TABLE 5
LAND USE, TOPOGRAPHY, AND SEWER DATA FOR EAST BAY SUBAREAS
Subarea
Berkeley
Benvenue Avenue
Carleton Avenue
Glen Street
Spruce Street
oo
Oakland
Capistrano Drive
High Street
Ninteenth Street
Pump Station J
Skyline Boulevard
Trestle Glen Road
Land
Area, Number of
Category* acres houses
MD RES 106 295
INDUS 28
LD RES 6ll
> 1,820
LD RES 459J
LD RES 95 570
INDUS 78
COMM, HD RES 61
INDUS
LD RES 82 135
LD RES 645 2,600
Use
Number of
buildings
excluding
houses
35
45
—
1
22
90
24
__
—
Roof
area,
acres
25
14
102
20
8
28
17
9
89
Street
and
parking,
acres
11
6
65
23
12
16
7
12
75
Topography
Flat
Flat
Hilly
Hilly
Flat
Flat
Flat
Flat
Hilly
Flat to hilly
Age**
Old
Old
Old
Old
Old
New
Old
Old
New
Old
Sewer Data
Estimated
length'
feet
13,700
4,270
26,620
104,900
18,470
4,560
15,470
~
13,250
148,340
Size,
inches
4-12
6-10
4-15
4-15
6-15
8-12
6-14
8-18
6-8
6-14
*HD RES = High density residential; MD RES = Medium density residential; LD RES = Low density residential; COMM = Commercial;
INDUS = Industrial.
**The term old means any area constructed prior to 1960 when the cities adopted the plastic joint clay pipe as a standard for
sewer construction.
-------
BASIC HAP REPRODUCED BY
PSR-MISSIOS OF THE CAtlFOSSI*
STATE AUTOMOBILE ASSOCIATION,
COPYRIGHT OWHER,
SAN
BAY
LEGEND
STUDY SUBAREA
FIG. 7 LOCATION MAP OF THE
SELECTED STUDY SUBAREAS
29
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leader survey was not undertaken as part of this investigation; there-
fore, this suspicion was not specifically confirmed.
This subarea is located south of the University of California campus
where the soils are usually clayey and shrink or swell with seasonal
moisture changes. Drainage is only fair since there is a slowly per-
meable, clayey subsoil. Slope stability and foundations vary from
poor to fair.
Land use is primarily single-family residential; however, portions are
zoned for restricted two-family residential, restricted multiple-
family residential, and multiple-family residential uses (primarily
rooming houses for students at the University of California). The
area was therefore assumed to fit the category of medium density resi-
dential land use.
Carleton Avenue
The Carleton Avenue sanitary sewers are quite old and have poor joints.
This subarea was selected because it is an isolated industrial area
consisting of manufacturing and pharmaceutical production facilities.
Consequently- most of the sewage is industrial rather than sanitary in
nature. Daily flow in the sewer is subject to the production cycles
of the manufacturers and producers in the area. It is believed that
few illicit connections exist, hence the infiltration problem may not
be as acute as in the residential sections of the city.
This subarea is located on the flat plain east of Aquatic Park in
Berkeley. The soil is a fine-textured alluvium which is deep and
rather poorly drained, with an intermittent water table below 48
inches. There is no erosion hazard with this type of soil, which in-
cludes gravel, sand, and clay as well as Bay mud and artificial fill.
The soil mantle may be as much as three feet thick. The clay shrinks
and swells with seasonal moisture changes and may cause damage to
existing buildings and sewers.
Glen and Spruce Street
The Glen and Spruce Street subareas are identical in land use and
topography. Initially, only one subarea was contemplated, but two
stations were necessary to measure and sample the flow. Throughout
the remainder of this report these areas will be discussed separately.
The sewerage system consists of old clay pipe sewers with poor joints.
Numerous direct connections are suspected of contributing to the infil-
tration problem during rainstorms. During the middle 1950's, a sewer
system study was conducted by the City of Berkeley to determine the
location of roof drain and area drainage connections. When the study
was completed, homeowners were notified to disconnect the roof con-
nections; however, no follow-up study was undertaken, and no check was
made to determine whether all of these connections had been discontinued.
31
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These subareas are located in the northeastern portion of Berkeley near
the crest of the ridge which forms the boundary of EBMUD, Special
District No. 1. This portion is on both the mild and steep slopes of
the Berkeley Hills. Some of the streets are laid out on the familiar
rectangular grid system, but, in the steeper areas, they tend to follow
the contour line. The soil is primarily a loam cover over a sandstone
base, and the depth of the parent rock or sandstone varies from a few
inches to three feet. Drainage varies from good to very good. Since
these subareas are in the immediate vicinity of the Hayward Fault,
ground movement causes sewers to be broken, hence an abnormal condition
of infiltration and root intrusion exists. The sewers are generally
quite shallow. Several springs exist because of the very good drainage
feature of the soil, which could also contribute substantially to the
infiltration problem. During this investigation, a portion of the
sewer system within the subareas was replaced. In that portion many
of the sections of clay pipe had been either crushed or sheared as a
result of land movement or poor installation. The groundwater is near
the surface since the soil layer is fairly thin. The erosion hazard
varies from high to very high because the soils are not cohesive in
nature.
Land use is primarily confined to single-family residential although
there is some two-family residential use. Because the upper reaches of
these subareas are quite steep, the population density decreases toward
the ridge.
OAKLAND SUBAREAS
Capistrano Drive
The Capistrano Drive sewerage system consists of old clay pipe sewers
with poor joints. Numerous direct connections are suspected of con-
tributing to storm water infiltration. The sanitary sewers differ from
those in other subareas in that they generally are not located under
pavement but along back lot lines or outside the travelled way. There-
fore, more joints of these sewers are subject to possible groundwater
infiltration than would normally be the case.
This subarea is located in east Oakland on the south quarter of EBMUD,
Special District No. 1 near San Leandro Creek. It is primarily limited
to single-family residential use. The land is a flat plain having a
loamy surface with poorly draining clay and silt subsoil. There is no
erosion problem.
High Street
The High Street sanitary sewer system consists of new clay pipe with
plastic joints. Few direct connections are suspected since the sewer
has been rebuilt within the last four years (1966). This sewer serves
a new industrial development in addition to the older industries.
32
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The subarea lies along the Oakland Inner Harbor in south central Oakland.
The soil is composed entirely of artificial fill placed over tidal flats
or shallow waters. In general, this type of soil has poor drainage.
The sewers were laid above the groundwater table, hence should not be
subject to continuous infiltration.
Nineteenth Street
The Nineteenth Street sewerage system consists of old clay pipe sewers
with poor joints. Many of the manholes are made of brick. Direct co--
nections are suspected to contribute to the storm water infiltration.
Past studies conducted by the City of Oakland have indicated that il-
legal (forbidden by local Plumbing Code) roof and floor drain connec-
tions exist.
This subarea is in the flat plains southwest of Lake Merritt in central
Oakland. The soil is a clayey mixture with slowly permeable clay sub-
soil in poorly draining loamy sand. Since the land is flat and the
soil exhibits cohesive properties, there is little erosion danger.
Because the location is just inland from the Oakland Inner Harbor, the
groundwater table is influenced by the tides to some degree and by the
water level in Lake Merritt.
This subarea is a concentrated commercial and high density residential
area which is not limited by the characteristics of strip development,
found elsewhere in the study area. It is at the low point of the
drainage shed adjacent to Lake Merritt, a controlled level lake with
beautifully landscaped shores near downtown Oakland, and includes a
portion of the business district, along with several exceptionally fine
hotels and apartments. The land along the lakefront is occupied by
high-rise apartments. This subarea is of particular concern to the
City of Oakland, because overflows from sanitary sewer manholes in the
vicinity of Lake Merritt would flow directly into the lake.
Pump Station J
The Pump Station J subarea is an older, medium-to-light industrial area,
and the sanitary sewers consist of old clay pipe generally below the
groundwater table.
Located in west central Oakland along the Oakland Inner Harbor, this
subarea is generally a flat plain having a loamy-sand surface and sub-
soil which has poor drainage. The water table is subject to tidal
variation. There is no erosion problem except for tidal action.
Industrial areas that could be isolated for purposes of flow measuring
and sampling were difficult to find. For this reason, the Pump Station
J subarea actually consists of two contribution areas. Flow measured
at the Pump Station is a mixture from both areas. Therefore, a second
station was installed to measure and sample the flow from the other
area. This station is on Kennedy Street and will be referred to by that
33
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name. The area contributing to Kennedy consists of a conglomeration of
land uses, so that the volume of flow and mass of pollutants contributed
by the area served by Kennedy must be subtracted from the corresponding
values measured at Pump Station J.
Skyline Boulevard
The Skyline Boulevard sewers are clay pipe with plastic joints installed
since 1965. There are very few direct connections which permit storm
water to enter the sanitary sewer system.
This subarea lies along the crest of the east Oakland Hills at the
south border of EBMUD, Special District No. 1 and is characterized by
steep slopes and sparce vegetation. There is a loam topsoil with a
sandstone base throughout the subarea; the topsoil varies from a few
inches to three feet in thickness. Drainage is good to very good, and
the erosion hazard varies from high to very high. Land use is single-
family residential; development has taken place since 1965.
Trestle Glen Road
The Trestle Glen Road sewerage system consists of old clay pipe with
poor joints. Numerous direct connections are suspected, since the
manholes of the lower section of the sewer system are subject to over-
flowing. Rainfall intensities as low as 0.05 inch per hour may cause
the sewers to overflow. The basements of several homes in the lower
portion of this subarea are subject to flooding, since the basement
drains are connected directly to the sanitary sewers system without
backwater valves.
This subarea is located partly within Piedmont and partly within central
Oakland, east of Lake Merritt. The Oakland portion is relatively flat,
while the Piedmont portion tends toward steep hills. The surface soil
is silt and loam,- the subsoil is a silty-clay loam. Depth to bedrock
is approximately 20 inches. The soil is well drained, and there is a
moderate erosion hazard. This subarea consists of a portion of the
Trestle Glen or Indian Creek drainage area which contributes to the
northeastern arm of Lake Merritt. Overflows from sanitary sewers in
this area have traditionally caused pollution problems in Lake Merritt.
Land use is predominantly single-family residential. Since the upper
reaches of this subarea are quite steep, the population density de-
creases and the lot size increases.
CONTROL AREAS
In addition to the ten study subareas, three large drainage areas were
selected as "control areas" for collecting data needed to substantiate
34
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the procedures used for extrapolating subarea data to the overall study
area. Three major flow measuring and sampling stations were chosen:
1. Pump Station A, located in the northwest corner of Albany.
2. Pump Station H, located near the High Street Bridge in
south central Oakland.
3. The main pumping station at the EBMUD Water Pollution
Control Plant.
These stations serve progressively larger and more complex areas.
Pump Station A serves only one drainage area consisting of Albany and
parts of north Berkeley. Pump Station H serves six drainage areas,
including the Metropolitan Oakland International Airport. The main
pumping station serves all of the drainage areas in the study area.
35
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SECTION 4
FLOW MEASURING AND SAMPLING PROGRAM
Page
Flow Measuring 39
Metering at New Stations 41
Metering at Existing Stations 45
Parkridge Lift Station 45
Pump Station A 45
Pump Station J 47
Pump Station H 47
Water Pollution Control Plant 48
Overflow Structure 49
Sampling and Testing 49
Wet Weather Sampling Procedures 49
Dry Weather Sampling Procedures 50
Laboratory Tests and Procedures 51
Precipitation Gaging 51
37
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SECTION 4
FLOW MEASURING AND SAMPLING PROGRAM
The equipment and procedures used during the flow measuring and sampling
phase of this investigation are described in this section, together
with some of the problems encountered in their use. The resulting
data are discussed in Section 5.
As discussed in Section 2, the approach devised for determining the
amount and effects of storm water infiltration involved the development
of detailed infiltration relationships for the subareas, followed by an
extrapolation or application of these relationships to the whole study
area. Inherent in the selection of the subareas was a consideration
of an available or convenient flow measuring and sampling location.
In several cases other considerations prevailed, and as a result,
several locations were in manholes situated near the centers of
streets, thereby complicating the procedures.
Flow measuring and sampling involved both wet and dry weather con-
ditions. Measurements during wet weather included both the rainfall
and the discharge rate from each subarea so that a relationship be-
tween the two could be determined. Sampling during rainstorms was
done to determine the variation in quality caused by the infiltration
of storm water. Dry weather flow measuring and sampling was necessary
to characterize the normal or base conditions needed for defining the
extraneous flow quantities produced by storm water infiltration and the
effect of extraneous flows on the normal water quality parameters.
Recording flow measuring equipment was installed in manholes at the
point of discharge from each subarea. Recording ammeters were installed
at pumping stations where flow measuring devices did not exist.
Sampling during wet weather conditions was done on a manual basis, ex-
cept at the water pollution control plant. Every effort was made to
begin sampling at the beginning of a substantial storm. This, of
course, was difficult because there was no way to predetermine the
intensity and duration of the rainfall. It was also difficult to
begin the sampling immediately after the beginning of a storm because
of both the distance to be travelled by the sampler and the irregularity
of the storms. Consequently, many samples were taken of relatively
small storms or of only the latter portions of storms. The sampling
period was predetermined to extend five hours after the beginning of a
storm. In some cases, this was extended to cover the duration of the
extraneous flow.
Sampling during dry weather conditions, accomplished by automatic
equipment at regular intervals throughout the day, was done so that
38
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samples taken during storm conditions could be compared and the effects
of storm water infiltration on the quality could be evaluated.
Rain gages, both recording and tube types, were installed in the sub-
areas to provide the detailed data needed to characterize the intensity
and duration of the storms. These data were then used to:
1. Aid in defining the source(s) of infiltration by indicating
the time required to produce infiltration in the sanitary
sewers after significant rainfall began and by indicating
the time required for infiltration to cease once significant
rainfall stopped.
2. Determine the relationships between rainfall and infiltration
in the subareas and, on the basis of this information,
estimate the infiltration outside the subareas.
3. Examine the areal and temporal variations for the storms
occurring during the study period as an aid in selecting
design storms.
Charts from recording rain gages provided the times at which the storm
began and ended as well as the intensity variations in between. These
times were then used to estimate the time of concentration, computed
as the time between the beginning of the storm and the arrival of the
peak rate of flow at the point of discharge from the subarea.
FLOW MEASURING
A preliminary review was made of the sewerage system to select flow
measuring locations that were not likely to have either surcharging or
an intersection of several pipes. This latter requirement was easily
determined by reviewing the as-built drawings and by investigating the
actual location, but the question of surcharging was not so easily re-
solved. A surcharged condition would result in no flow measurement
from almost any kind of standard sewer flow measuring equipment
available.
A search for a new means of measuring flow in the sewer, both under
normal and surcharged conditions, was fruitless. Therefore, standard
types of flumes and weirs were selected, and in locations where sur-
charging was suspected, a weir was used with level measurement on both
sides, so that in case of submergence at least an approximation of the
flow could be made.
Table 6 lists the 16 locations at which flow measurements and samples
were taken, and the types of primary and secondary devices that were
used. The conditions at these stations are described in the following
discussion.
39
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TABLE 6
LOCATIONS AND TYPES OF EQUIPMENT
USED IN FLOW MEASURING AND SAMPLING PROGRAM
Location
Primary devices
Secondary devices
Metering at: New Stations
Berkeley
1. Benvenue Avenue
2. Carleton Avenue
3. Glen Street
4. Spruce Street
Palmer-Bowlus flume
90 deg V-notch weir
90 deg V-notch weir
90 deg V-notch weir
Taylor*
Stevens**
Taylor
Taylor
Oakland
5. Capistrano Drive
6. Nineteenth Street
7. Kennedy Street
8. High Street
9. Skyline Drive
10. Trestle Glen
90 deg
90 deg
90 deg
Palmer
90 deg
Palmer
V-notch weir
V-notch weir
V-notch weir
-Bowlus flume
V-notch weir
-Bowlus flume
Stevens
Taylor
Stevens
Taylor
Taylor
Taylor
Metering at Existing Stations
11. Parkridge Lift Station
12. Pump Station A
13. Pump Station J
14. Pump Station H
15. Water Pollution Control
Plant
16. Overflow Structure
Venturi meter
Pump running time
recorder
Amprobe***
Amprobe
Amprobe
BIF
Taylor
Note: Data from High Street and Parkridge Lift Stations were not usable.
Mention of commercial products does not imply endorsement by the
Federal Water Quality Administration.
*Taylor Pressure Recorder, Series 79J, with 1 or 2 pens, manufac-
tured by Taylor Instrument Company.
**Stevens Model 2A35 liquid level recorder, manufactured by Leupold &
Stevens Instruments, Inc.
***Amprobe Model LAA81 or -82 recording ammeter, manufactured by
Amprobe Instrument Division of Soss Manufacturing Company.
40
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METERING AT NEW STATIONS
Palmer-Bowlus flumes were installed in three (1, 8, and 10 in Table 6)
of the ten metering stations established specifically for this study.
These flumes were constructed of stainless sheet steel and designed to
fit the respective sizes and shapes of the sewers. They were carefully
fitted into the sewers and leaks were stopped by caulking. The flumes
were mounted in the outlet sewer from the manholes so that head measure-
ments could be made at the proper distances upstream from the throats.
Figure 8 shows the typical installation of a Palmer-Bowlus flume in a
manhole with the channel extensions which effectively increased the
throat depth of the flume. Without these extensions the water would
have spread out in the manhole after reaching the spring line of the
sewer, rendering the flume useless.
At the remaining seven new metering stations, 90 degree V-notch weirs
were installed. These weirs, specially designed for ease of installa-
tion, were constructed of marine plywood and covered for additional
water resistance with two coats of polyurethane finish. Figure 9 shows
the design of the V-notch weir in the assembled condition. A channel
closure was provided so that it could be easily slipped down into the
flowing sewage and quickly bolted in position, after installing and
sealing the actual weir plate.
Stevens type 2A35 liquid level recorders were used at three of the
weir locations (see Table 6). These recorders were selected for their
ability to record two liquid levels simultaneously because submergence
of the weir was anticipated. The Stevens recorders were located at
meter installations that were not subject to traffic, since they had to
be mounted directly over the manhole. They were housed in a wooden
enclosure consisting of a rectangular box with two shelves. The entire
enclosure was anchored to prevent loss or damage to the equipment.
Taylor recorders were used at all of the other metering stations. The
liquid level sensing consisted of measuring the back pressure from a
continuously purging bubble system. Nitrogen was used for the gas.
The recorders and auxiliary equipment were housed in a wooden instru-
ment enclosure and mounted behind the curb for protection. Figure 10
shows the installation details for a weir in a manhole with the meter-
ing instrument mounted behind the curb. The flexible plastic tube for
the bubbler was threaded through a buried one-inch diameter conduit
from the instrument enclosure, under the street pavement and out to the
manhole. A one and one-half inch diameter suction pipe was installed
in the same trench with the bubble tube conduit to allow sampling at the
curb, which was accomplished with a positive displacement, manually
operated pump. These suction pipes were provided only at meter loca-
tions where heavy traffic was expected during periods of sampling. In
other locations, the samples were taken manually by insertion of a con-
tainer down through the manhole opening. A third conduit was also
41
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GROUT IN
PLACE
3%f
r
xTRIM TO FIT
[-/
, I AS REQUIRED
J ' "* l2
C:Q>
o
o
i
^^
jr
^
~~~~
-NT-
-.4;.
•/*'
1
J
2%'* ^"CARRIAGE
BOLTS, TYPICAL
SECTION
"RULMER-BOWLUS FLUME
f '-s
2
NOTE;
SPLICE BOARDS FOR CHANNEL SIDES
ONLY IF MANHOLE SIZE PREVENTS
PLACING AS A SINGLE UNIT.
SECTION
FIG. 8 TYPICAL PALMER-BOWLUS FLUME INSTALLATION
-------
-30°
"
— -J
SECTION A- A
3/4" PLYWOOD
CHANNEL CLOSURE
SECTION B - B
2x2x'/4ANGLE SUPPORT
1
w
.
T
' W+12
AS REQUIRED
•• B
ELEVATION
^-CHANNEL CLOSURE (3/4" PLYWOOD )
-2"x 6" BRACE
—WEIR
PLATE
5"x !4" CARRIAGE BOLTS,
TYPICAL
PLAN
-BRACE (3/4" PLYWOOD)
FIG. 9 V-NOTCH WEIR PLATE DETAILS
43
-------
-PLASTIC BUBBLE TUBE
,LAMP HOLE FRAME 8 COVER
-CUT SLOT IN PAVEMENT FOR
METERING AND SAMPLING
PIPES, SEE DETAIL BELOW
REDWOOD
BACKFILL
W/SAND
I "DIA. PIPE
PLASTIC
BUBBLE
DIA. PIPE
CUT SLOT IN
PAVEMENT
PAVEMENT SURFACE
^LEVEL OR
SLOPE TOWARD
MANHOLE
DIA. PIPE
RUBBER AUTOMATIC SAMPLER TUBE
PIPE SLOT DETAIL
FIG. 10 TYPICAL V-NOTCH WEIR INSTALLATION
-------
installed through which "the automatic sampler suction tubing was
later threaded. Figure 11 shows photographs of typical metering
installations.
Liquid levels were extracted from the recording charts at 30-minute
intervals, and the actual flow rates were computed by applying the
head-discharge relationshps for the respective primary device. A
typical base flow curve representing the variation of flow rates during
the day was developed by averaging the values for the same time of day
over ten week days and again over ten weekend days. The extraction of
wet weather flows was similar to that for dry weather flows except
that averaging over several days, of course, was not possible. The
extraneous flows for each individual storm were then computed by sub-
tracting the appropriate period of base flow data from the wet weather
flow rates.
Flow measuring equipment was installed at the High Street subarea. Un-
fortunately, the intermittent discharges from a nearby pumping station
resulted in peak flows that prevented proper interpretation of the
data. Therefore, the flow data from this station was eliminated and no
samples were taken.
METERING AT EXISTING STATIONS
Parkridge Lift Station
The Parkridge Lift Station was considered necessary because it con-
tributed sewage from a newly developing subdivision to the Skyline
Drive subarea. It was expected to contribute substantially to the base
flow of the subarea. As the study progressed, however, it was found
that the flow contribution was negligible. Therefore, the Parkridge
Lift Station will not receive further discussion.
Pump Station A
Pump Station A has four single-speed pumps with equal discharge charac-
teristics. The station is a standard wet well - dry well design with
the pumps mounted in the dry well below the ground level and the motors
mounted directly above, on the ground level floor. In case the pumps
are unable to handle the flow, either because of quantity or mechanical
malfunction, an overflow is provided to discharge the flow to Cerrito
Creek.
The station is equipped with a wet-well liquid level recorder having a
seven-day rotation, circular chart from which flow determinations were
virtually impossible because the only information provided was an
approximation of the increment of time between pump starts and stops.
A determination of which pump or how many pumps were running at any
time was difficult at almost all flow rates. Therefore, a recording
ammeter was attached to the pump electrical leads to record the instan-
taneous current drawn by the pumps. The total number of pumps running
45
-------
INSTRUMENT ENCLOSURE SHOWING
TAYLOR RECORDER AND DRY WEATHER
SAMPLING EQUIPMENT WITH NITROGEN
CYLINDER REMOVED
INTERIOR OF INSTRUMENT ENCLOSURE
FOR STEVENS RECORDER
9T10 V-NOTCH WEIR PLATE INSTALLED
IN MANHOLE
INSTRUMENT ENCLOSURE FOR STEVENS
RECORDER OVER MANHOLE
FIG. II TYPICAL METERING INSTALLATIONS
46
-------
at any given time and their respective running time was then easily
determined. The discharge rate for each pump or combination of pumps
was selected from a system-head curve for the station. This curve was
developed from information on the physical plant layout and discharge
piping, together with the measured head-to-discharge relationship
provided by EBMUD, Special District No. 1.
From the ammeter recordings, the operating time for each pump was de-
termined during each one-hour period throughout the day. Applying the
appropriate pump discharge rate for the running times resulted in
average station discharge volumes for each hour during the day, and
the half-hour values were computed by interpolation. The typical base
flow values were obtained by averaging the rates for the same time of
day over ten week days and again over ten weekend days. These base
flow values were used in computing the extraneous flows. The extrac-
tion of wet weather flows was similar to that for dry weather flows.
The relief overflow at the pumping station handles flows in excess of
the pump capacity during periods of high flow. This overflow consists
essentially of a broad-crested weir formed by boards. A rating curve
for this weir and the wet-well liquid level recorder permitted computa-
tion of overflow quantities. These quantities were then added to the
appropriate wet weather flows. The excess flow drains through a flap
gate into Cerrito Creek, adjacent to the pump station, and directly
into the near-shore water of San Francisco Bay.
Pump Station J
This station is similar in design and construction to Pump Station A,
except that it is substantially smaller. The flows here were deter-
mined in the same way as at Pump Station A; however, the computation
was simplified because there was no overflow or liquid level recorder.
Pump Station H
Pump Station H has a peak pumping capacity of 57 mgd. It is the largest
pump station along the interceptor system, with the exception of the
main pumping station at the water pollution control plant.
The three pumps at this station are driven by two-speed motors. The
normal sequence of operation for the pumps is as follows: one pump at
low speed, one pump at high speed, two pumps at low speed, two pumps
at high speed, three pumps at high speed. Pump Station H is run auto-
matically, as are all the other outlying pump stations, except during
periods of storm flow. It is the only pump station that is operated
manually during wet weather conditions, except the main pumping sta-
tion. Pump Station H may be shut down entirely when the wet weather
flow rates approach the maximum pumping capacity at the plant. When
this occurs, the flow at Pump Station H is backed into the interceptor
and tributary trunk sewers and ultimately overflows at an overflow
47
-------
structure located on Elmhurst Creek near the Oakland - Alameda County
Coliseum complex.
Pump Station H is equipped with both a wet-well liquid level recorder
and a flow recorder. The primary device for the flow recorder is a
Venturi flow tube mounted in the force main downstream from the pumps.
Both the flow rate and the liquid level are recorded on a 24-hour
rotation, circular chart that is changed daily at 8 a.m.
Because the flow meter is mounted on the discharge manifold of the
pumps, it will measure only the pumping rate at any given time and
hence does not directly reflect the variation of influent flow rate
throughout the day. Therefore, instantaneous hourly values were read
from the charts, and half-hour values were derived by interpolation.
These half-hour values of flow rate were further smoothed by averaging
the values for the same time of day over ten week days and again over
ten weekend days. The resulting values were then assumed to represent
the base flow which was subtracted from the wet weather flows to pro-
vide the extraneous flow rates during a storm. Wet weather flows were
derived in a similar manner, in that rates were extracted from the
charts at one-hour intervals and values for the half-hour intervals
were interpolated. This tended to smooth out the erratic flow rate
which reflected the cycling of the pumps.
Water Pollution Control Plant
The influent pumping station at the water pollution control plant lifts
the incoming sewage from the interceptors up into the grit chambers.
The pumps are preceded by one-inch clear opening, mechanically-raked
bar screens. There are five raw sewage pumps; three are driven by
single-speed motors, two by two-speed motors. Each pump discharges
directly into individual grit chambers. With all five pumps operating
at full speed, the pumping capacity is slightly less than 291 mgd.
The station is equipped with individual flow meters on each pump dis-
charge which are connected to a combined flow recorder. The primary
devices for the flow recorder are the discharge weirs in the grit
chambers which reflect the respective pump discharge rates. Although
the pump station has facilities for automatic operation, it is normally
operated on a manual basis. Consequently, it was difficult to deter-
mine a meaningful daily flow variation.
The computation of the flow rates and their variations throughout the
day was similar to that for Pump Station H. The sum of the results of
these computations was compared to the total daily flow normally re-
ported by the operator. These latter values were derived by multiplying
daily pump operating times by the average pump discharge rates. The
ratio of the average daily rates as computed by the above procedures to
those reported was found to be 0.85. This ratio was used to adjust the
recorded flow data, particularly when the data were used with measured
flow.
48
-------
Overflow Structure
This overflow structure is located upstream from Pump Station H at
Elmhurst Creek near the Oakland - Alameda County Coliseum. The overflow
provides a relief for Pump Station H in cases of mechanical failure or
flow beyond its capacity. A flow measuring device was desirable to
provide a means for measuring the volume of water that overflowed.
The flow measuring arrangement consisted of measuring the liquid levels
on both sides of a rectangular tide gate and extracting the flows from
the manufacturer's rating curve. Because of difficulties in installa-
tion and operation, no usable flow measurements were obtained during
periods of overflow. Therefore, estimates of overflow volumes were
derived from the Pump Station H operating records, which indicated
the time period between starting and stopping of the station together
with the flow rate when it was stopped.
SAMPLING AND TESTING
Both wet weather and dry weather samples were taken at most of the
locations listed in Table 6. A total of 926 samples were taken, 787
during wet weather and 139 during dry weather. The wet weather samples
were of the grab type and the dry weather samples were of the composite
type, proportional to time but not flow rate. Eight different labora-
tory analyses were made on each sample. Therefore, except for those
tests in which no results were obtained, approximately 7,400 analyses
were made during the investigation. An evaluation of the data is
presented in Section 5.
WET WEATHER SAMPLING PROCEDURES
The equipment used in taking wet weather flow samples depended on the
location of the metering station. If the station was outside the
travelled way, grab samples were obtained by using a bucket suspended
on a rope. If it was within the travelled way and traffic conditions
rendered manual sampling unsafe, an Edsonl lever action diaphragm pump
was used in conjunction with a previously installed one and one-half
inch suction line. A quarter-drum located at curb-side was used to
receive the first discharge from the pump so that the sample taken
immediately thereafter would reflect the actual condition in the sewer.
The samples were collected in one-gallon plastic containers from which
a six-ounce sample was extracted for separate coliform analyses.
Because of the lapse between the time of sampling and the actual
analyses, the six-ounce samples were immediately placed in an insulated
chest and covered with ice.
-'-Mention of commercial products does not imply endorsement by the
Federal Water Quality Administration.
49
-------
Sampling periods occurred during all times of the day and night.
One or more station wagons were kept loaded and ready with the
necessary equipment in preparation for a storm. The equipment in-
cluded the pumps, buckets, one-gallon containers, six-ounce containers,
ice chests, rubber rain suits, recording equipment, and safety devices.
Many trips were made during which no samples were obtained.
The frequency of wet weather sampling also depended on the location of
the metering station. The initial sampling cycle was: 15-minute
intervals for the first two hours, 30-minute intervals for the next
two hours, and one additional sample at the end of the fifth hour.
This cycle was modified to suit the location once the nature and
characteristics of the contribution from the subarea had been experi-
enced. For example, samples at the water pollution control plant
were obtained at one-hour intervals for a period of 48 hours after the
beginning of the storm. Samples at Pump Station H were taken at
30-minute intervals over the five-hour period. Sampling periods longer
than five hours were also used at Pump Station A and Pump Station H.
It was found that 15-minute intervals for the entire four- or five-hour
period were required for several of the smaller subareas.
DRY WEATHER SAMPLING PROCEDURES
Two types of portable samplers were used to obtain the dry weather
flow samples. Three Hinde Effluent Samplers2 were used; this type
consisted mainly of a positive displacement pump capable of a 20-foot
or higher suction lift. It had a 15- and 30-minute selective time
cycle, a 12-volt DC battery, and a two-gallon storage container. One
Surveyor Automatic Composite Sampler2 was used, consisting of a rubber
vane type pump that could provide only a six-foot suction lift. It
also had an adjustable time cycle and operated on a 12-volt DC battery.
The only real difficulty encountered in using the automatic samplers
was that the suction tubing was so small that stringy and large
size material tended to plug the line. A partial solution was found
with a stilling well arrangement made of 20-mesh galvanized wire fabric.
The suction tubing was placed inside the screened well which prevented
the large materials from reaching the inlet of the tube. It was
necessary periodically to clean the accumulation of debris away from
the wire screen.
The samplers were operated for a period of time which included two
weekends and five week days at each of the metering locations. Because
of the plugging of the suction line, the samplers were operated, in
most cases, for longer times than the anticipated sampling period.
2Mention of commercial products does not imply endorsement by the
Federal Water Quality Administration.
50
-------
No dry weather flow samples were obtained at Nineteenth Street
because the depth of the manhole (24 feet) exceeded the suction lift
capability of the samplers.
Samples were picked up daily. After the sample was mixed in the
storage container, a portion of the liquid was transferred into a
one-gallon container, from which a six-ounce sample was taken for
coliform analyses. The samples were stored in ice chests or in refrig-
erators at approximately 35 to 40 deg F until they were analyzed.
LABORATORY TESTS AND PROCEDURES
All analyses except those for coliform were made in the Metcalf & Eddy
laboratory. A majority (546) of the coliform analyses were made by the
EBMUD Water Pollution Control Plant Laboratory, and the remainder (380)
were made by the Cook Research Laboratories, Inc., Menlo Park, Califor-
nia. All coliform analyses were made by the multiple-tube fermentation
technique and were carried only through the presumptive test. The
EBMUD Laboratory used five tubes with three or more decimal dilutions,
whereas Cook Laboratories used three tubes with three or more decimal
dilutions.
The following analytical tests were conducted on the samples:
1. Total solids
2. Volatile suspended solids
3. Suspended solids
4. Settleable solids
5. BOD
6. COD
7. Oil and grease
8. Coliform bacteria
All of the tests made during this investigation were conducted in
accordance with Standard Methods for the Examination of Water and Waste
Water, 12th edition, published by the American Public Health Associa-
tion (1) .
At the peak of the wet weather sampling, the number of samples collected
exceeded the analytical capacity of the Metcalf & Eddy laboratory.
During this period the samples were kept in a refrigerator at a temp-
erature of 35 to 40 deg F, or were packed in ice in 55-gallon steel
drums until they could be analyzed. Normally, under these conditions,
the samples were held no more than two days, although on two occasions
they were held as long as four days.
PRECIPITATION GAGING
Recording gages giving at least hourly rainfall amounts were needed to
satisfy the requirements for precipitation data. However, in areas
where the temporal variation in rainfall is slight, the temporal
51
-------
distribution from a few recording gages was applied to the rainfall
measured in nonrecording (tube) gages. The distribution of recording
gages depends mainly on the variation in the temporal distribution of
rainfall, whereas the distribution of nonrecording gages depends on
the variation in the areal distribution of rainfall. Therefore, it
was possible to substitute nonrecording gages in some cases where total
daily rainfall was needed to reflect areal distribution only.
For most of the subareas, a recording gage was required within or ad-
jacent to the subarea because the temporal variation of the rainfall
was unknown. The variation of the areal distribution of rainfall
was known to some degree from a map of mean annual precipitation
presently used by the Alameda County Flood Control and Water Conser-
vation District which was established from data covering 30 years of
records. The mean annual precipitation, however, being the total
rainfall for an average year, did not reflect the actual variation in
the areal distribution of rainfall for each storm. Thus, more gages
were considered necessary to define adequately the areal distribution
of storms and to provide sufficient data to construct a map of areal
rainfall distribution.
The locations and types of precipitation gages used are shown on the
map in Figure 12. Table 7 lists the name, location, applicable
subarea, receiver diameter, type, and location of record for each
gage. Official gages are those installed in conformance with U.S.
Weather Bureau standards and checked, periodically by Weather Bureau
personnel. Unofficial gages are the other gages in the area that are
maintained by various agencies and individuals; these may or may not
be as accurate as the official gages.
For this study, five recording gages were added to the existing gages,
bringing the total number of recording gages to 11, or about one for
every 7.3 square miles of area. Three nonrecording gages were also
added, bringing the total number of gages in the study area to 20, or
about one for every 4.0 square miles of area. Data from two additional
gages just outside the study area were collected for describing the
overall rainfall pattern.
The locations of the additional gages were selected to meet the
recommendations of the U.S. Weather Bureau providing: 1) good exposure
to the elements; 2) adequate distance from individual high structures
and trees which could shed more water onto the gage or create eddy
currents; 3) protection from high winds; and 4) security from damage
or disruption by vandalism or foot and automobile traffic. The pre-
vailing local conditions or topography made it necessary to place more
emphasis on one requirement than another,- however, it is considered
that the gages were located in positions that presented the best
available combination of exposure, security, and correlativity.
52
-------
BASIC MAP REPRODUCED By
PERMISSION OF THE CALIFORNIA
STATE A-JTOKOBILE ASSOCTATTOB,
COPYRIGHT OWNER,
FILTERS^ 7..f"
/\ ^f
-------
TABLE 7
LOCATIONS AND TYPES OF PRECIPITATION GAGES USED IN FLOW MEASURING AND SAMPLING PROGRAM
Gage description
Gage name
Berkeley
California School for
the Blind*
Carleton Avenue*
Spruce Street*
Capistrano Drive*
Oakland City Hall*
Pump Station J*
Skyline Boulevard*
Shepherd Canyon*
Piedmont
Oakland International Airport
Meteorological Station
Upper San Leandro Filters
Alameda Naval Air Station
Chabot Filters
Chabot Reservoir
EBMUD Plant
Oakland, Glenwood Glade
Oakland, McMillan
Oakland, Shirley Drive
Oakland, 39th Avenue
Orinda Filters**
Upper San Leandro Reservoir**
Gage location
University of California,
Berkeley
California School for the
Blind, Berkeley
4th and Parker, Berkeley
Shasta Road and Queens Road,
Berkeley
10901 Russet, Oakland
14th Street and Washington,
Oakland
Frederick Street, Oakland
13150 Skyline Boulevard,
Oakland
5921 Shepherd Canyon, Oakland
Vista and Highland Avenue ,
Piedmont
Oakland International Airport
Upper San Leandro Filter
Plant
Naval Air Station, Alameda
Chabot Filter Plant
Chabot Reservoir
EBMUD Water Pollution
Control Plant
172 Glenwood Glade, Oakland
5525 McMillan, Oakland
7200 Shirley Drive, Oakland
4097 39th Avenue, Oakland
Orinda Filter Plant
Upper San Leandro Reservoir
Applicable
subarea
Benvenue Avenue
Benvenue Avenue
Carleton Avenue
Spruce Street
(and Glen Street)
Capistrano Drive
Nineteenth Street
Pump Station J
(and High Street)
Skyline Boulevard
Trestle Glen Road
Trestle Glen Road
Overall Study Area
—
—
—
—
—
—
—
—
—
—
"
Official
or
unofficial
Official
Unofficial
• Unofficial
Unofficial
Unofficial
Unofficial
Unofficial
Unofficial
Unofficial
Unofficial
Official
Official
Unofficial
Unofficial
Unofficial
Unofficial
Unofficial
Unofficial
Unofficial
Unofficial
Unofficial
Unofficial
Type
Tube
Weighing
Weighing
Weighing
Weighing
Weighing
Tube
Tube
—
—
—
Weighing
Tube
Tube
Tipping-
Bucket
Tube
Tube
Tube
Tube
—
Tube
Recording
Yes
No
Yes
Yes
Yes
Yes
Yes
No
No
Yes
Yes
Yes
Yes
No
No
Yes
No
No
No
No
Yes
No
Receiver
diameter,
inches
..
8
8
8
8
8
8
8
8
—
—
—
4
8
8
12
3/4
1
1
4
—
8
Location of record
U.S. Weather Bureau,
San Francisco
Metcalf S Eddy
Metcalf S Eddy
Metcalf S Eddy
Metcalf & Eddy
Metcalf S Eddy
Metcalf S Eddy
Metcalf S Eddy
Metcalf S Eddy
Alameda County Flood
Control District
U.S. Weather Bureau,
San Francisco
EBMUD
National Weather
Records Center, Ashe-
ville, North Carolina
EBMUD
EBMUD
EBMUD Water Pollution
Control Plant
U.S. Weather Bureau,
San Francisco
U.S. Weather Bureau,
San Francisco
U.S. Weather Bureau,
San Francisco
U.S. Weather Bureau,
San Francisco
EBMUD
EBMUD
*Gages installed specifically
"Outside of study area.
for this investigation.
-------
The Benvenue Avenue subarea is located close to the Berkeley Campus and
in similar terrain. A nonrecording tube gage was located within this
subarea at the California School for the Blind. This gage provided the
actual total quantities of precipitation in the subarea. The time
distribution of that precipitation was derived from the recording gage
on the campus.
No existing recording precipitation gages were found within a reasonable
distance of the Carleton Avenue subarea. Accordingly, a recording
gage was installed adjacent to the administration building at Cutter
Laboratories located on Carleton Avenue.
The existing recording precipitation gage nearest to the Spruce Street
subarea is located at the University of California at Berkeley. This
subarea is sufficiently dissimilar, orographically, from the campus that
precipitation in the two areas is not always related; therefore, a
recording gage was located at the fire station at the corner of Shasta
Road and Queens Road to provide a better description of the rainfall
patterns.
The Capistrano Drive subarea is about two miles east of the Metropolitan
Oakland International Airport. No existing precipitation gages were
available so a recording gage was installed within the subarea and
correlated with the official recording gage at the Oakland Airport.
The site selected was inside a fenced industrial yard which offered
good exposure and relatively good security.
A recording gage was installed at the Oakland City Hall. Located only
four blocks from the Nineteenth Street subarea, it was used to develop
the record for that subarea.
The Pump Station J and High Street subareas are orographically similar,
they receive essentially the same mean annual rainfall, and they are
sufficiently close together that it was assumed one recording precipita-
tion gage would adequately describe the rainfall patterns for both
subareas. Because no existing gages were available, one recording gage
was installed at Pump Station J.
The Skyline Boulevard subarea is in a relatively unique location in the
hills above Oakland. No precipitation gages existed close enough to
this subarea to provide an accurate description of the rainfall.
Because it is a newly developing area which was not expected to allow
much infiltration, a nonrecording gage within the immediate vicinity
of the intersection of Brookpark Road and Skyline Boulevard was in-
stalled. The City of Oakland Fire Station, Engine No. 21, on Skyline
Boulevard was selected as the site for the gage because of good security
and exposure characteristics.
56
-------
The City of Piedmont maintains a recording gage at the City Hall,
located reasonably near the Trestle Glen Road subarea. Since the
terrain and orography near the gage is similar to that of the subarea,
the precipitation data were developed from that gage and from a
nonrecording gage located at the City of Oakland Corporation Yard on
Shepherd Canyon Road.
57
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SECTION 5
ANALYSIS AND EVALUATION OF DATA
Presentation of Basic Data 60
Flow Measurements 6°
Diurnal Variations in Dry Weather Flow 60
Extraneous Flow Hydrographs 61
Quality Analyses 61
Dry Weather Data 61
Wet Weather Data 61
Rainfall Gaging 66
Estimate of Relationships Between Infiltration and Rainfall 66
Gross Infiltration Ratios 66
Relative Magnitude of the Two Sources of Storm Water 70
Infiltration
Selection of Flow Routing Program 70
Development of Flow Routing Program 72
Application of Flow Routing Program 73
Results of Flow Routing Program 74
Evaluation of Quality Data 78
Characterization of Quality During Storm Water 78
Infiltration
Determination of Quality Parameters Applicable to 79
Overflows and Plant Bypasses
Analysis of Rainfall Data 84
Frequency Analysis 84
Distribution Analysis 88
Definition of Storms Causing Overflows and Bypasses 91
59
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SECTION 5
ANALYSIS AND EVALUATION OF DATA
The data collected during the flow measuring and sampling program are
too voluminous to be presented in this volume'of the report. In the
first part of this section, data from selected measuring stations are
introduced by means of typical graphs and tables to illustrate the
characteristics of the storm water infiltration. This discussion is
followed by a description of the detailed analyses and evaluations used
in a search of relationships between rainfall and the quantity and
quality of extraneous flow caused by storm water infiltration.
To provide a further definition of the major sources of storm water
infiltration, a flow routing computer program was developed and used
for simulating the measured hydrographs in the sewer system from various
subareas. Much of the data analysis was directed toward developing fac-
tors and coefficients necessary for this program. The use of the compu-
ter program is described briefly here. The computer program is also
used in Section 6 to estimate the overall infiltration quantities in
the East Bay sewer systems.
It would have been useful to include quality routing in the computer
program, but it was realized early in the investigation that development
of a water quality model to that point was beyond the scope of this
study. Therefore, quality relationships needed for evaluation of
effects of untreated overflows on the Bay were selected from data
collected at points along the interceptor that were representative of
the major overflows along the interceptor and the bypass at the water
pollution control plant. The values for selected water quality rela-
tionships are used for evaluating the effects of overflows on San
Francisco Bay in Section 9.
Because rainfall analyses usually involve statistical relationships, it
was not possible to develop all the desired rainfall characteristics
only from the data collected during one season. Historical data were
therefore collected from various sources; the findings and analyses of
both sets of data are included in this section.
PRESENTATION OF BASIC DATA
FLOW MEASUREMENTS
Diurnal Variations in Dry Weather Flow
The diurnal variations developed as part of this data collection pro-
gram represent conditions found in the subareas specifically between
November 1968 and April 1969. The flow variations are not truly unit
60
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flow variations because they represent data for specific sizes of
drainage areas and cannot be directly applied to areas smaller than
those in which they were measured.
Table 8 summarizes the areal contributions of dry weather flow for
each subarea and lists the land area (acres) involved, the respective
land use category, and the diurnal variations. Figure 13 illustrates
the diurnal variations for both week days and weekend days for the
Pump Station A drainage area. The values presented in Table 8 and
Figure 13 are averages of data from up to ten different days, not
necessarily consecutive, and not noticeably influenced by preceding
wet weather conditions.
Extraneous Flow Hydrographs
Extraneous flow hydrographs were developed by subtracting the appro-
priate dry weather flow from the measured wet weather flow; both time
and type of day (week day versus weekend day) were considered. The
area below the resulting extraneous flow hydrograph was measured to
provide the volume of extraneous flow for the respective storm. This
volume was then compared to the volume of rain falling during the storm.
Figure 14 illustrates a typical extraneous flow hydrograph, together
with the rainfall histogram for the Pump Station A drainage area.
The preparation of extraneous flow hydrographs for separate sanitary
sewers representing infiltration of storm water have not been attempted
previously, as indicated by an extensive literature review. Infiltra-
tion rates are normally given for separate sewer systems without regard
either to time distribution or to effect of rainfall.
QUALITY ANALYSES
Dry Weather Data
As has been mentioned, the samples for dry weather quality data were
collected with automatic sewage samplers using either a small positive
displacement or a rubber impeller pump with a small diameter suction
tube. Although the samples were taken at either 15- or 30-minute
intervals and composited throughout the day. the results of the analy-
ses were somewhat erratic. Table 9 shows a summary of the dry weather
quality data consisting of average, minimum, and maximum values com-
piled from both week day and weekend day data. These samples were
taken between March and May 1969 at periods of time least influenced
by preceding rainfall. The data normally represent five samples
collected over a 24-hour period at each subarea.
Wet Weather Data
It was concluded that the best way to illustrate the variations of
quality during wet weather conditions was to plot all of the quality
parameters together with rainfall and extraneous flow versus time on
61
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TABLE 8
Ch
NJ
AREAL CONTRIBUTIONS OF DRY WEATHER FLOW FOR EAST BAY DRAINAGE AREAS,
November-April, 1968-69
Average areal
flow contribution,
gad**
Area description
Subareas
Benvenue Avenue
Carleton Avenue
Glen Street
Spruce Street
Capistrano Drive
Nineteenth Street
Pump Station J
Skyline Boulevard
Trestle Glen Road
Major Drainage Areas
Pump Station A
Pump Station H
Total Drainage Area
EBMUD, Special
District No. 1
Land area,
acres
81
28
61
459
95
61
63
82
645
709
12,259
51,416
Land use*
MD RES
INDUS
LD RES
LD RES
LD RES
HD RES &
COMM
INDUS
LD RES
LD RES
MIXED
MIXED
MIXED
Week
days
3,580
3,930
1,640
1,480
2,840
5,080
3,335
975
2,215
1,495
1,420
1,530
Weekend
days
3,705
1,785
1,310
1,525
2,630
4,590
2,540
975
2,185
1,735
1,155
1,470
Percent
Diurnal variations »
of average flow contribution
Week days
Min.
57%
63
72
64
67
23
54
28
55
35
45
65
Max.
140%
153
130
156
129
185
147
193
151
156
145
140
Weekend days
Min.
60%
88
67
58
57
26
71
28
49
41
51
76
Max.
139%
115
134
144
156
181
128
173
147
171
135
143
*HD RES = High density residential; MD
COMM = Commercial; INDUS = Industrial
**Gallons per acre per day.
RES = Medium density residential; LD RES = Low density residential;
-------
Q
O
EEK DAY DAILY
AVERAGE FLOW
1.06 MGD
M
WEEK DAY
WEEKEND DAILY
AVERAGE FLOW
1.23 MGD
M
9 N 3
WEEKEND DAY
FIG. 13 DIURNAL FLOW VARIATION, PUMP STATION A,
NOVEMBER-APRIL 1968-69
63
-------
55
uJ
Z
<
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TABLE 9
SUMMARY OF DRY WEATHER QUALITY DATA FOR EAST BAY DRAINAGE AREAS,,
MARCH-MAY 1969
Area description
Subareas
Benvenue Avenue
Carleton Avenue
Glen Street
Spruce Street
Capistrano Drive
Pump Station J
Skyline Boulevard
Trestle Glen Road
Major Drainage Areas
Pump Station A
Pump Station H
Total
solids,
mg/L
344
256
503
542
221
884
474
410
682
701
444
1,690
499
380
870
712
353
1,248
406
359
528
435
351
794
547
381
1,289*
880
560
1,186
Suspended
solids,
mg/L
120
46
268
199
55
536
117
51
337
283
108
826
56
31
117
81
34
132
59
33
131
162
57
631
108
64
232
101
67
195
Volatile
solids,
mg/L
88
28
204
125
26
323
81
31
234
182
50
611
37
13
96
63
22
114
46
25
108
122
39
404
88
48
175
79
50
145
Settleable
solids,
ml/L
3.9
0.0
10.0
4.6
0.2
15.5
2.3
0.0
10.3
10.9
0.6
55.9
0.1
0.0
0.5
0.1
0.0
1.4
0.7
0.0
7.6
4.8
0.0
15.2
0.7
0.0
4.5
0.8
0.0
4.6
BOD,
mg/L
89
32
182
1,002
361
1,770
61
27
140
129
30
360
315
125
7,300*
198
127
300
144
85
7,300*
139
84
246
220
110
1,080
294
112
450
COD,
mg/L
260
175
400
1,689
240
3,536
205
116
480
422
167
872
426
194
734
367
246
769
300
213
408
267
188
508
488
235
1,127
542
268
743
Oil and
grease,
mg/L
25.0
4.8
52.6
11.7
4.9
25.6
18.2
7.7
38.5
28.8
8.1
51.1
34.3
14.6
77.6
53.2
14.2
170.1
35.1
20.7
58.1
34.3
23.9
176.3*
30.0
17.9
51.4
41.0
26.7
53.3
Coliform,"
MPNxl03/ml
843
230
2,400
6,530
43
11,000
789
43
4,600
519
43
2,400
2,970
93
11,000
1,500
150
4,600
783
230
2,400
1,320
150
4,600
5,030
430
11,000
6,800
930
11,000
*Excessively high values disregarded in average values.
Note: The top values are averages of all data, the second values are minimums, and
the bottom values are maximums.
65
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a single graph. The rainfall/flow/quality graph for the Pump Station A
drainage area, shown on Figure 15, is a typical illustration of the
variations that were found.
Because it was difficult to begin sampling at the best time so far as
flow was concerned, many of the graphs show quality values during
various periods of the extraneous flow hydrograph. Some are on the
rising limb portion, some cover the peak, and others cover the re-
cession limb portion of the hydrograph.
RAINFALL GAGING
To illustrate the frequency and nature of the rainstorms during the
two peak months of the rainy season, January and February 1969, the
corresponding graphs of rainfall at the Oakland Airport are shown in
Appendix II. Certain historical rainfall data were collected and
analyzed but were not presented in the form of basic data.
ESTIMATE OF RELATIONSHIPS BETWEEN INFILTRATION AND RAINFALL
The sources of storm water infiltration can be described by two general
terms: percolation, which represents the entry of vadose water or
groundwater through poor pipe walls and joints; and direct connections,
which represent the entry of water by any of several sources, such as
roof leaders and catchbasins. The sewers in the East Bay Area are sub-
ject to infiltration from both sources. As previously mentioned, most
of the sewers are old and in poor condition. Also, the maintenance
personnel indicated that direct connections are extensive and must con-
tribute substantially to the infiltration problem. The methods used to
define gross infiltration characteristics and the proportion of infil-
tration applicable to each source are described in the following dis-
cussion.
GROSS INFILTRATION RATIOS
The study area was divided into five types of land use, as shown on
Appendix Figure 1-2. The subareas that were selected contained a
single type of land use and represented four of the five land use cate-
gories : 1) high density residential and commercial, considered as one
because they could not be distinguished; 2) medium density residential;
3) low density residential; and 4) industrial. The fifth category
(cemeteries, parks, military holdings, and undeveloped areas) does not
contribute to dry weather sewage flow. Each of the subareas was further
classified according to its topography (hilly or flat) and age of sewer
system (old or new). Table 10 lists each subarea with its respective
classification. During the flow measuring program, extraneous flow
volumes were measured for several storms for each of the subareas as
well as for the two control areas, Pump Station A and Pump Station H.
66
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COLIFORM XIO6
MPN/ML
OIL AND GREASE
MG/L
SETTLEABLE SOLIDS
ML/L
COD
BOD
MG/L
VOLATILE SOLIDS
MG/L
TOTAL SOLIDS
SUSPENDED SOLIDS-
MG/L
0.8
0.4
0
80
40
0
400
ZOO
0
ZOO
IOO
EXTRANEOUS
FLOW
MGD
RAINFALL
0.1 IN.
I2M IA
2A
FIG. 15 RAINFALL/FLOW/QUALITY GRAPH,
PUMP STATION A.DECEMBER 9-10, 1968
67
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TABLE 10
GROSS INFILTRATION RATIOS FOR EAST BAY- DRAINAGE AREAS*
1968-69
Land use
topography
and sewer age
classification*** Ratio
Area description**
Subareas
Spruce Street
Skyline Boulevard
Capistrano Drive
Benvenue Avenue
Nineteenth Street
Pump Station J
Carleton Avenue
Trestle Glen Road
Major Drainage Areas
Pump Station A
Pump Station H
LD RES, Hilly, Old Sewers
LD RES, Hilly, New Sewers
LD RES, Flat, Old Sewers
MD RES, Flat, Old Sewers
HD RES and COMM,
Flat, Old Sewers
INDUS, Flat, Old Sewers
INDUS, Flat, Old Sewers
LD RES, Hilly, Old Sewers
MIXED
MIXED
0.03
0.01
0.11
0.12
0.14
0.08
0.06
0.07
0.246
0.08
*Gross infiltration ratio is volume of extraneous flow _
volume of rainfall
**For more detailed description, see Table 5.
***HD RES = High density residential; MD RES = Medium density residen-
tial; LD RES = Low density residential; COMM = Commercial;
INDUS = Industrial.
68
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Table 10 does not list a flat, residential area that has new sewers
because there are none within the study area. The flat and most easily
subdivided land was developed prior to 1960.
The volumes of storm water infiltration, defined as extraneous flow,
were plotted against the volume of rainfall for each subarea and control
area. The plots of these points are shown in Appendix Figure II-3. The
points did not plot in straight line positions, but a line of best fit
was drawn visually through the points. Because these plots represent
the first attempt to define the infiltration ratios, the lines were
drawn through the origin of the axes. Technically, these lines should
intercept the vertical axes at some point above the origin because some
rain is required to initiate infiltration. The volume of rain required
was unknown, but it was assumed that the slope of the line would not be
greatly affected. The ratio of extraneous flow to rainfall volume,
computed from the slope of the line, was termed the gross infiltration
ratio. Table 10 lists the gross infiltration ratios for each subarea.
In most of the subareas, there was a substantial variation in the amount
of storm water that entered the sewer. Significant fluctuations in base
flow during periods of rainfall may account for some of the differences
in apparent volumes. The extraneous flow hydrograph was developed from
the total hydrograph by subtracting the average dry weather flow for
the respective time of day.
Two other factors which may account for the variation in infiltration
ratios are the rainfall intensity and duration and the antecedent dry
period, although neither could be confirmed. Data from five subareas
were investigated in an effort to find a definable relationship be-
tween the antecedent dry period and the infiltration ratio, but none
was found. Similarly, data from four subareas were investigated in an
effort to determine the existence of a relationship between rainfall
and infiltration versus antecedent dry period. Again, no relationship
was found.
The normal units used to describe infiltration rates into sewers are
gallons per inch of diameter per mile per day. To provide a means of
comparing the results obtained herein with those published elsewhere,
similar values were computed for two subareas. Because infiltration
during a rainstorm varies with time, some averaging of values was
necessary.
The first infiltration rates were computed for the Capistrano Drive
subarea, which contains 29.62 inch-diameter-miles of pipe, exclusive
of house connections. Assuming that each house is served by a four-inch
sewer and that the distance from the house to the main sewer is 50 feet,
the 570 houses in this subarea add 21.6 inch-diameter-miles of pipe re-
sulting in a total of 51.2 inch-diameter-miles of pipe. The maximum
extraneous flow measured for the storm on February 15, 1969, was 0.87
mgd. This flow is therefore equivalent to an infiltration rate of
17,000 gallons per inch of diameter per mile per day. This infiltration
69
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rate is also equivalent to 9,150 gad. Considering the total 1968-69
season, the extraneous flow measured 1.7 MG during a period of 224
hours. The average storm water infiltration rate was therefore 3,600
gallons per inch of diameter per mile per day or 1,900 gad.
A similar analysis was made for the Skyline Boulevard subarea because
it represents an area of new sewers. Having 24.9 inch-diameter-miles
of sewer including house connections, the maximum infiltration rate
was 5,210 gallons per inch of diameter per mile per day for the storm
on February 15, 1969. The seasonal average was found to be 1,200
gallons per inch of diameter per mile per day- The areal contributions
were 1,600 and 360 gad, maximum and average, respectively.
Another way to describe infiltration rates is to compare the maximum
flow rate during wet weather to the dry weather flow, either for the
same time of day or for the average daily flow. Table 11 gives typical
ratios of wet weather flow to dry weather flow for each subarea.
Further investigation and analyses of these and other data will be
necessary before all of the significant parameters affecting infiltra-
tion are known. Seemingly, the duration of a storm should be considered
with the antecedent dry period, since infiltration is expected to in-
crease as the antecedent dry period decreases. Perhaps the relationship
using the hydraulic parameter of antecedent precipitation index could be
found with the aid of coaxial plots to relate other significant param-
eters. Such an analysis requires more data than were gathered for this
study.
RELATIVE MAGNITUDE OF THE TWO SOURCES OF STORM WATER INFILTRATION
Neither the sources nor the magnitude of storm water infiltration in
sanitary sewers was known prior to the data collection and development
phase of this study. Examination of the extraneous flow hydrographs
indicated that the source of infiltration contributed flow almost imme-
diately after the start of a storm. On the other hand, the examination
indicated that the time of concentration was quite long (several hours) ,
as measured from the beginning of the storm to the peak of the hydro-
graph. This seemed to confirm the previous conclusion that two general
sources of infiltration existed, percolation and direct connections.
To determine the relative magnitude of infiltration from each source,
it was decided to model the hydraulic response of the pipe system to
infiltration by use of a flow routing computer program. The advantage
of such a program was that the hydrographs from the two major components
of infiltration could be computed separately and compared.
Selection of Flow Routing Program
Several methods for routing flow through sewers were investigated: the
Corps of Engineers program using the Muskingum method; the Chicago
method; the Los Angeles method; and the Road Research Laboratory method
(RRL Method). Each of these methods recognizes the available sewer
70
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TABLE 11
RATIO OF WET WEATHER FLOWS TO DRY WEATHER FLOWS
1968-69
Ratio of peak wet weather flows to:
Area description*
Subareas
Spruce Street
Skyline Boulevard
Capistrano Drive
Benvenue Avenue
Nineteenth Street
Pump Station J
Carleton Avenue
Trestle Glen Road
Major Drainage Areas
Pump Station A
Pump Station H
EBMUD Plant
Average daily
dry weather flow
5.2
4.0
5.1
5.1
8.1
4.5
5.0
2.1
9.1
4.0
4.3
Average flow for
the same time of day
3.8
3.8
4.1
4.8
5.2
3.2
6.1
2.3
6.4
3.0
3.7
*For more detailed description, see Table 5.
71
-------
volume as a means of providing storage and thereby dampening the hydro-
graph. The final selection was the KRL Method because of its relative
simplicity, the availability of the basic program, and an indication of
successful use based upon published reports.
A sample form of the RRL program, obtained directly from the Road Re-
search Laboratory in England, was modified to make use of the data that
had been collected and developed during this investigation. The final
program operated under the assumption that the flow in the^ewer was
open channel and could be described by Manning's equation. The pro-
gram routed the flow, allowing for storage in the pipe in a manner simi-
lar to that for routing through a reservoir. It simulated for each pipe
the time distribution and the quantity of dry weather sewage flow by
each type of land use. It also simulated the addition of storm water
infiltration in each pipe length based upon its respective land use.
Initially, the routing program used the gross infiltration ratios
developed previously to simulate storm water infiltration. The sim-
plicity of these ratios aided in the development of the program. How-
ever, the objective was to define the infiltration ratio in terms of
the two sources: percolation and direct connections. Therefore, the
program was later rewritten to accommodate both ratios simultaneously.
The dry weather sewage flow was simulated by considering areal contri-
butions of flow for each land use and for either week days or weekend
days, corrected for diurnal variations by using factors in terms of
average flow for 15-minute intervals throughout the day. The areal
contribution values for week days were identical to those presented in
Table 8. The 15-minute interval factors were derived in the program as
needed by interpolation from the measured 30-minute interval factors.
Development of Flow Routing Program
The flow routing program was first used for the Capistrano Drive sub-
area, an older residential area with relatively flat terrain. The first
step was to evaluate the sensitivity of the program, i.e. , could a
coarse pipe network representing combinations of some of the pipes be
used in lieu of a fine or detailed network which included all or nearly
all of the pipes? Thus, two pipe systems were described: one for a
coarse network having an average drainage area of 1.6 acres and another
for a fine network having an average area of 10.6 acres. The difference
between the computed hydrographs was negligible; therefore, all succes-
sive runs were made using the coarse pipe network.
A routing interval of 15 minutes was chosen on the basis of earlier
studies of parameter sensitivity which were made during the program
72
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development. An examination of the actual rainfall histograms and the
recorded extraneous flow hydrographs for three storms indicated that a
time of concentration of approximately 200 minutes would be in order.
Therefore, an inlet time of 180 minutes was selected, allowing for
travel time in the system of about 20 minutes.
The second step was to evaluate the use of a single value for infiltra-
tion ratio in simulating the measured extraneous flow hydrograph. Con-
stant values for gross infiltration ratio were used for each of three
storms, but the computed hydrographs were found to be flatter near the
peak flow than the observed hydrographs. Also, the rising limb of the
computed hydrographs did not compare favorably with the rising limb of
the observed hydrographs. A gross infiltration ratio that varied as
the sum of the volumes of preceding rainfall was then developed. The
data for the Capistrano Drive subarea were plotted on semilogarithmic
paper, and a line of best fit was drawn through the points. An equation
of this line was inserted into the program in lieu of the single ratio
used previously. The results using this equation produced an exces-
sively high peak and an extended recession curve. Because the use of
infiltration ratios representing only a single source of infiltration
had failed to simulate the measured hydrographs satisfactorily, it was
taken as further evidence that at least a two-phase expression was
needed to describe the infiltration phenomenon.
The third step was to rewrite the computer program to permit use of
two infiltration ratios: percolation and direct connections. A
180-minute time of entry was used for infiltration involving percola-
tion because of the measured time of concentration from beginning of
rainfall. A different time of entry for infiltration ratios involving
direct connections was used, based on storm runoff computations which
use an inlet time of 2 to 15 minutes. The time of entry for direct
connections was selected as 15 minutes because the routing interval
used in the program was 15 minutes (hence the program would not recog-
nize shorter periods of time).
In the development of a program which would simulate an observed hydro-
graph, an allowance had to be made for the rainfall which contributed
to saturating the soil and thus was available for infiltration. The
rainfall which occurs initially will be absorbed into the soil. If
this rainfall is not subtracted in the infiltration analysis, the
resulting computed hydrograph will respond with too much flow after
the start of the rain.
Application of Flow Routing Program
After modifying the flow routing program to permit the use of two
different infiltration ratios, one for percolation and the other for
direct connections, the next step was to determine the relative con-
tribution by each of these two ratios. This was accomplished by
73
-------
running the program for one of the infiltration elements and then
adding the effect of the other. The Capistrano Drive subarea, which
had a gross infiltration ratio of 0.11, was selected for initial in-
vestigation. The results that gave the best fit with the observed
hydrograph were composed of the following:
Percolation infiltration ratio 0.09
Direct connection infiltration ratio 0.02
Gross infiltration ratio 0.11
The 0.02 infiltration ratio for direct connections represented a volume
of storm water equal to the volume that would be collected from an
area equivalent to 10 percent of the roof area—in other words, equal
to 10 percent of the roof drains in the study area connected to the
sanitary sewer system. The program results using the 0.09 percolation
infiltration ratio indicating the results of deducting the first ~~
0.05 inch of rain are shown in the upper graph of Figure 16. The
effect of adding the 0.02 infiltration ratio for direct connections is
shown in the lower graph of Figure 16. The combined curve as compared
to the observed hydrograph is shown in Figure 17. Similar runs were
made for two other storms which confirmed the validity of the two ratios.
Three other subareas were investigated using the flow routing program
and the same arrangement of infiltration ratios: Spruce Street, Pump
Station J, and Benvenue Avenue. In each subarea the relationship
between the two types of infiltration was varied in an attempt to
arrive at the proper one for each type of land use. The program was
run approximately 50 times before reasonable results were found for
these four subareas. The exact duplication of observed hydrographs
was not achieved in all cases because of the many variables involved.
No doubt, other variables affect infiltration characteristics, but it
was concluded that they are either relatively insigificant or are
reflected to some degree in the ratios finally selected for use. The
infiltration values selected indicate that in the four subareas checked,
the major source of infiltration is from percolation and the minor
source is from direct connections.
Results of Flow Routing Program
The results of the several computer runs made for each of these four
subareas were used to determine the relative magnitude of the two
sources of infiltration for the respective land uses they represent.
The ratios thus derived are presented in Table 12. The first six sub-
areas listed in the table were used later in computing hydrographs
from a control area having multiple land uses. The remaining subareas
were used to check the results of the other subareas having the same
types of land uses.
The Spruce Street and Trestle Glen Road subareas were expected to have
the same infiltration ratios because they represent the same type of
74
-------
o.i
UJ
£j
_ii
i
Z
<
a:
Q
o
Z
2
tr
b
u.
Z
RAINFALL , 2/17/69
INITIAL COMPUTED
HYOROGRAPH USING A
0.09 PERCOLATION RATIO,
t
t
HYDROGRAPH AFTER SUBTRACT-\
*" ING FIRST 0.05 IN. OF RAIN \
SYNTHESIZED HYDROGRAPH
AFTER ADDING
0.02 DIRECT
CONNECTION
INFILTRATION
0.09 PERCOLATION RATIO LESSX
THE FIRST 0.05 IN. OF RAIN
"0 2 4 6 8 10
TIME FROM BEGINNING OF RAIN , HOURS
FIG. 16 SYNTHESIS OF EXTRANEOUS FLOW HYDROGRAPH
USING PERCOLATION AND DIRECT CONNECTION
INFILTRATION RATIOS, CAPISTRANO DRIVE SUBAREA
75
-------
O.I
-I? 0.2
O
O
IT
b
E
RAINFALL, 2/17/69
OBSERVED
O.ll GROSS INFILTRATION RATIO
MINUS FIRST 0.05 IN. OF RAIN
TIME FROM BEGINNING OF RAIN , HOURS
FIG. 17 COMPARISON OF OBSERVED AND
COMPUTED EXTRANEOUS
FLOW HYDROGRAPHS, CAPISTRANO DRIVE SUBAREA
76
-------
TABLE 12
INFILTRATION PATIOS FOR PERCOLATION AND DIRECT CONNECTIONS,
EAST BAY DRAINAGE AREAS, 1968-69
Area description
Sub areas
Spruce Street
Skyline Boulevard
Capistrano Drive
Benvenue Avenue
Nineteenth Street
Pump Station J
Carleton Avenue
Trestle Glen Road
Major Drainage Areas
Pump Station A
Pump Station H
Land use,
topography , Percolation
and sewer age infiltration
classification* ratio
LD RES, Hilly, Old Sewers 0.01
LD RES, Hilly, New Sewers 0
LD RES, Flat, Old Sewers 0.09
MD RES, Flat, Old Sewers 0.10
HD RES and COMM, 0.04
Flat, Old Sewers
INDUS, Flat, Old Sewers 0.03
INDUS, Flat, Old Sewers 0.04
LD RES, Hilly, Old Sewers 0.05
MIXED
MIXED
Direct
connection Gross
infiltration infiltration
ratio ratio
0.02 0.03
0.01 0.01
0.02 0.11
0.02 0.12
0.10 0.14
0.05 0.08
0.02 0.06
0.02 0.07
0.246
0.08
*HD RES = High density residential; MD RES = Medium density residential; LD RES = Low density
residential; COMM = Commercial; INDUS = Industrial.
-------
land use and approximately the same sewer conditions. However, the
data available to establish the infiltration ratio for the Trestle Glen
Road subarea were limited to three points, whereas the data for the
Spruce Street subarea included eight points. Therefore, a weighted
average of these two ratios was later used to represent the similar
conditions of land use, terrain, and sewer age. Because of the poor
condition of its sewers, the Spruce Street subarea was expected to
contribute greater amounts of infiltration than were actually measured.
Substantial amounts of extraneous flow may have been discharged to
storm sewers upstream from the gaging station which would therefore
indicate smaller quantities of infiltration. Overflows are known to
exist upstream from the point of measurement, but their extent and
nature are unknown.
EVALUATION OF QUALITY DATA
The evaluation of the quality data collected during this investigation
was directed toward two principal objectives:
1. To characterize the variations in quality during
storm water infiltration.
2. To determine the average values for certain water
quality parameters applicable to overflows and
plant bypasses.
CHARACTERIZATION OF QUALITY DURING STORM WATER INFILTRATION
The wet weather quality data from several sampling stations were
graphically analyzed to determine if any relationships between the
various quality parameters and the time from the beginning of the rain-
fall could be found. The relationship between flow and time after the
beginning of rainfall has been previously established; therefore,
comparisons were also made of each parameter to the variations and
flow rate. These analyses were made for data collected at the Benvenue
Avenue and Capistrano Drive subareas and at the Pump Station A and H
drainage areas. The following nine parameters or ratios of parameters
were investigated:
1. Extraneous flow
2. Total solids
3. Volatile suspended solids
4. Suspended solids
5. Suspended solids/total solids
6. BOD
7. COD
8. Oil and grease
9. Volatile suspended solids/suspended solids.
Plots were prepared for each parameter versus time using all of the
data available for each location. Time was measured from the beginning
78
-------
of rainfall. To aid in comparing the variations in quality with the
variations in flow, the time scale was shifted slightly so that the
rising limbs of the extraneous flow hydrographs were superimposed
on each other. Figure 18 shows the plots for the Benvenue Avenue
sampling station. These are similar to the plots made for each
station, and the various curves typify the results that were observed.
Although two or more sets of data were available for each station
and all of the data were plotted on graphs such as Figure 18,
distinct trends were difficult to define. After reviewing all
of the data, general trends could be detected.
Figure 19 shows a series of unitless graphs with lines depicting
the trends that seemed apparent for each parameter. The plots are
intended to represent the parameter concentrations as they vary
with time after the beginning of a substantial rainstorm. While
these are general trends for the subareas investigated, it should
be realized that individual subareas may show considerable variation
from storm to storm.
Graphs were also prepared for total solids, BOD, and oil and grease
versus extraneous flow for each of the four selected locations (not
shown). Time after the beginning of rainfall was ignored in these
graphs. There were no noticeable relationships between any of these
parameters and extraneous flow.
DETERMINATION OF QUALITY PARAMETERS APPLICABLE
TO OVERFLOWS AND PLANT BYPASSES
It was necessary to determine the expected quality of overflows and
plant bypasses by averaging samples taken in the vicinity of over-
flows and bypasses. These results will be used in Section 9 to
evaluate the effects of overflows on the near-shore waters of
San Francisco Bay.
Upon reviewing the water quality data from Pump Station A and Pump
Station H, the two extreme ends of the interceptor sewer system, a
substantial difference in concentrations of water quality parameters
was noted. For this reason, it was decided to use the average water
quality data from Pump Station A to represent the quality of overflows
occurring along the interceptor north of the water pollution control
plant and that from Pump Station H to represent the quality of over-
flows occurring south of the plant. The quality of water bypassing
the plant was represented by average data taken at the entrance to
the plant during periods of rainfall. Values for coliform bacteria
at the plant were not used because both prechlorination and post-
chlorination are practiced, and the values obtained are of questionable
79
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2-5-69
I 0 -
EXTRANEOUS
FLOW 0.5
MGD
TOTAL
SOLIDS
MG/L
400
ZOO
VOLATILE
SUSPENDED
SOLIDS
MG/L
SUSPENDED
SOLIDS
MG/L
ISO
120
80
40
0
I
100
80
60
SS/TS
% 40
20
0
2-11-69
TIME , HOURS
_J L_
I -I I I 1 L
468
TIME , HOURS
468
TIME , HOURS
468
TIME , HOURS
I i i i i i
J L
468
TIME, HOURS
10
_l I I I I 1 I I I I
FIG. 18 GRAPHS OF WATER QUALITY PARAMETERS
VERSUS TIME DURING WET WEATHER, BENVENUE
AVENUE SUBAREA
80
-------
EXTRANEOUS
FLOW
MGD
BOD
MG/L
120
80
40
400 r
COD
MG/L 20°
24
OIL AND
GREASE
MG/L
100
80
VSS/SS 60
40
20
J L
J L
TIME , HOURS
J_
468
TIME , HOURS
TIME , HOURS
468
TIME , HOURS
TIME , HOURS
FIG. 18 (CONCLUDED)
J I i
I i i i
10
J I
81
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to
o
TIME
V)
TIME
FIG. 19 GRAPHS OF WATER QUALITY PARAMETER
TRENDS DURING WET WEATHER
82
-------
8
UJ
<
cc
X
o
o
o
TIME
TIME
llJ
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TIME
TIME
FIG. 19 (CONCLUDED)
83
-------
significance. The values that were used to evaluate the effects
of overflows on the Bay were:
BOD, Grease, Coliform bacteria,
Location mg/L mg/L MPN/100 ml
South interceptor 370 105 3.7 x 108
North interceptor 105 21 1.5 x 10
Water pollution
control plant 135 40
ANALYSIS OF RAINFALL DATA
FREQUENCY ANALYSIS
In order to relate the rainfall data collected during the 1968-69
season to historical storm events, a statistical analysis was made
of data from the Oakland Airport for periods of maximum storm rain-
fall occurring between 1948 and 1968. A family of curves showing
the relationship between maximum intensity of rainfall and frequency
of occurrence for various values of duration was plotted on Gumbel
extreme probability paper. A graph of intensity versus duration
for various frequencies of storms was plotted from values extracted
from the Gumbel plot and is shown on Figure 20.
A statistical analysis was also made of only the 1968-69 rainfall
data from the Oakland Airport, and a family of intensity-duration-
probability curves was developed. The curves represent data from
the 60 storm events that occurred between November 1968 and April
1969. A storm event was defined as a block of rainfall equal to
or greater than 0.02 inch, separated from another storm event by
at least five hours. A graph of intensity versus duration for
various probabilities of occurrence was plotted from values extracted
from this analysis and is shown in Figure 21. The families of
curves presented in Figures 20 and 21 are not comparable because
the historical data represent annual extreme events, whereas the
1968-69 data represent all events for the season. Figure 21 does
serve, however, to characterize the duration and intensity of the
several storms during the season.
As a means of visualizing the relationship between the storm events of
the 1968-69 season and the historical storm events, a comparison was
made between the maximum event of the past season and the statistical
analysis of historical data. The results are shown graphically in
Figure 22. The comparison shows that the maximum storm event last
season had a return period of 1.9 years, that is, the maximum event
which took place is expected to be equalled or exceeded once every
1.9 years.
84
-------
I 1.5 2 25 3 4 5 6 7 8 9 10
DURATION , HOURS
FIG.20 INTENSITY-DURATION- FREQUENCY CURVES,
OAKLAND AIRPORT GAGE, 1948-1968
SOURCE: BASIC DATA FROM E S S A , HOURLY PRECIPITATION, CALIFORNIA 1946-1968
20
85
-------
PROBABILITY THAT A STORM
OCCURRENCE WAS EQUAL
TO OR LESS THAN
0.03
3 45
DURATION , HOURS
FIG. 21 INTENSITY-DURATION- PROBABILITY CURVES,
OAKLAND AIRPORT GAGE, 1968-69 SEASON
86
-------
FIG. 22
7 8 9 10
DURATION , HOURS
FREQUENCY OF 1968-69 MAXIMUM STORM
EVENT, OAKLAND AIRPORT GAGE
SOURCE' BASIC DATA FROM E S S A , HOURLY PRECIPITATION , CALIFORNIA 1948- 1968
87
-------
DISTRIBUTION ANALYSIS
Two methods were used to describe the areal rainfall distribution over
the study area:
1. An evaluation of total rainfall values for discrete
storms during the 1968-69 season.
2. An evaluation of the mean annual precipitation values
over the study area.
In addition to areal distribution, an attempt was made to describe the
temporal distribution of rainfall over the study area. The methods and
results are described in the following discussion.
In the first method, total rainfall values from each storm during the
1968-69 rainy season measured at each gage were plotted against the
total rainfall values for the same storms measured at the Oakland
Airport gage. A line of best fit was drawn through the points, realizing
that some of the points represented atypical storms. These atypical
points represented rain that fell predominantly in the north end of the
study area (not in the south end). Less importance was placed on these
points because such atypical storms do not cause the worst total in-
filtration conditions. The best fit for all of the points for each
gage was a straight line passing through the origin. The graphs are
shown on Appendix Figure I1-4.
Since the line of best fit was a straight line, the factor needed to
adjust the storm total at the Oakland Airport gage to that at any gage
is a constant value. This factor was plotted on a map showing the
location of all of the gages. Lines were then drawn representing the
equal values of this distribution factor. These values were adjusted
somewhat on the basis of topography and mean annual precipitation.
This procedure minimized the possible gage errors. The plot of the
areal rainfall distribution factors on a map of the study area is
shown in Figure 23.
The second method was based on mean annual precipitation values, which
were derived from an isohyetal map presently used by the Alameda
County Flood Control and Water Conservation District. This map was
based on 30 years of records between 1930-31 to 1959-60. Factors were
computed for each gage location as accurately as the data could be read
from the map. Table 13 presents a tabulation of the factors developed
by the two methods. Some of the differences may be due to the follow-
ing three points:
1. The comparison was made between discrete storm data
versus mean annual data.
2. The comparison was made between measured and
estimated data.
88
-------
FIG. 23 AREAL RAINFALL DISTRIBUTION FACTORS
89
-------
TABLE 13
AREAL RAINFALL DISTRIBUTION FACTORS
Hourly gages*
Factors from
1968-69
Locations storms
Alameda Naval Station
Berkeley (USWB)
Capistrano Drive
Carleton Avenue
EBMUD Plant
Oakland International
Airport Meteorological
Station**
Oakland City Hall
Orinda Filters
Piedmont
Pump Station J
Spruce Street
Upper San Leandro
Filters
0.
1.
1.
1.
0.
1.
1.
1.
1.
1.
1.
1.
92
24
10
05
90
00
03
55
20
00
31
22
Daily gages
Factors from Factors from
mean annual 1968-69
rainfall Locations storms
1.
1.
1.
1.
0.
1.
0.
1.
1.
1.
1.
1.
82
25
15
07
87
00
94
55
26
00
31
32
Chabot Filters 1.20
Chabot Reservoir 1.20
Upper San Leandro
Reservoir 1. 33
California School
for the Blind 1.25
Shepherd Canyon 1.45
Skyline Boulevard 1.35
Oakland, Glenwood Glade 1.35
Oakland, Shirley Drive 2.19
Oakland, McMillan 1.19
Oakland, 39th Avenue 1.23
Factors from
mean annual
rainfall
1.25
1.25
1.48
1.24
1.26
1.37
1.26
1.43
1.17
1.23
*Recording type gages.
**Base gage.
-------
3. A more complete rainfall data collection network was
available for the 1968-69 data than for establishing
the map of the mean annual precipitation values.
The temporal rainfall distribution in the study area was analyzed by
comparing the time at which the storm event began at each gage location.
The results indicated that the storms generally began during the same
hour over the study area. This conclusion is based on those storms
that were general in nature and not on those that covered only certain
portions of the study area. Because the rain gages recorded the rain-
fall variations on graphs with scales that could not be read at inter-
vals much smaller than one hour, a better definition of temporal dis-
tribution was not possible.
DEFINITION OF STORMS CAUSING OVERFLOWS AND BYPASSES
Attempts to describe a "design storm" in the classical sense were
fruitless. The terra design storm involves consideration of intensity,
duration, and frequency of rainfall; and the selection of frequency
involves an understanding of the economic or destructive effects en-
countered when the event is exceeded in magnitude. The knowledge and
understanding of the local citywide and districtwide effects that may
result from overflows were felt to be inadequate for defining the
design storm parameters. Also, no single design storm could be
selected that would account for all of the various problems resulting
from rainfall throughout the study area. An attempt was made, however,
to describe the events that took place during the 1968-69 season by
the storms which caused them. The main events for which records were
available were the pump station overflows and the water pollution
control plant bypasses.
The rainfall data taken at the Oakland Airport between November 1968
and April 1969 indicated that a total of 60 storm events took place.
As mentioned previously, a storm event is defined as a block of rain-
fall equal to or greater than 0.02 inch, separated in time from any
other event by at least five hours.
The first analysis involved an evaluation of the distribution of storm
peaks throughout the day. Table 14 shows the number of storms at the
Oakland Airport that had peaks during each of the six 4-hour periods
of the day. The storms investigated represented 28 of the largest
storms during the season. On the basis of the distribution of storm
peaks indicated in Table 14, it was concluded that there was no need
to define the storm by the period of day during which it occurred.
This conclusion was significant because if the peak of a majority of
the storms had occurred during the early morning hours (12 midnight
to 7 a.m.) when the dry weather or base flow is lowest, the effect
would have been minimized. No other attempts were made to relate
storm peaks or characteristics to various periods of the day.
91
-------
TABLE 14
OCCURRENCE OF RAINSTORM PEAKS DURING TEE DAY,
OAKLAND AIRPORT, 1968-69
4-Hour
interval during Number of peaks
24-hour day during the interval
0:01-4:00 8
4:01-8:00 3
8:01-12:00 7
12:01-16:00 4
16:01-20:00 2
20:01-24:00 4
The next step was to relate the magnitude of the storms to overflows
recorded at Pump Stations A and H. The rainfall was plotted versus
storm duration for the first four hours of the largest storms during
the season. Storms that resulted in overflows at Pump Stations A and
H, as reported by the operating staff, were labeled on the points of
the graph. From these data it was possible to define three zones: an
upper zone in which pump station overflows were certain, a middle zone
in which overflows were questionable, and a lower zone in which over-
flowing would not occur. From the distribution of points in the middle
zone, it was possible to draw in a line which represented storm
conditions that could be on the borderline between causing overflows
and not causing overflows at the pump stations. This borderline storm
was termed the "marginal overflow storm" and is shown on Figure 24.
A similar analysis was made for describing storm conditions causing
water pollution control plant bypassing. The results are shown in
Figure 25. In this case the borderline storm was termed the "marginal
plant bypass storm."
A close observation of Figures 24 and 25 will indicate that the middle
zones for both plots are in essentially the same place and that the
lines representing the two marginal storms are quite similar. For
simplicity, the two marginal storms will be considered identical in
subsequent analyses. This similarity in marginal storms suggested that
the frequency of occurrence of overflows and bypasses is nearly the
same.
Although not completely applicable, an attempt was made to relate the
marginal overflow storm to the frequency or return period. Considering
the marginal storm described in Figure 24 as a maximum event for a year,
and referring to the frequency analysis shown on Figure 20, a return
period of 1.08 years was selected. Therefore, the marginal overflow
92
-------
NO
PLANT BYPASSING
234
TIME OF RAIN , HOURS
FIG. 24 MARGINAL OVERFLOW
STORM, 1968-69
234
TIME OF RAIN , HOURS
FIG. 25 MARGINAL BYPASS
STORM, 1968-69
-------
storm may be expected to be equalled or exceeded at least once every
1.08 years, i.e., equalled or exceeded 92 out of 100 years. The
analogy is not completely proper because the marginal storm in the
last season was not a maximum event. In fact, the marginal storm was
exceeded by 16 other storms. Nevertheless, the analogy offers a
basis for visualizing the characteristics of the marginal overflow
storms.
94
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SECTION 6
ESTIMATE OF THE VOLUMES OF STORM WATER INFILTRATION
Page
Development of Methods for Estimating
Volumes of Overflows 99
The Extrapolation Method 99
Use and Confirmation of the Method 99
Relative Magnitude and Sources of Infiltration 106
The Land Use Method 108
Estimates of Volumes of Overflows and Bypasses 110
Annual Extraneous Plant Flow 110
Annual Plant Bypassing 112
Annual Overflows 114
Overflows at Pump Stations A and H 115
All Other Overflows 115
95
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SECTION 6
ESTIMATE OF THE VOLUMES OF STORM WATER INFILTRATION
In the first part of this section, 1968-69 data were used to develop
and check two methods—the extrapolation method and the land use
method—for estimating extraneous flow from a storm of given charac-
teristics .
The second part of this section deals with the estimation of total
annual quantities of extraneous flows and the disposition of the
various component volumes for the entire study area. The estimations
were made by the land use method and the application of various
historical flow data. The quantities were estimated for the 1968-69
season and for a year having average rainfall.
The significant conclusions developed in this section are outlined
below and graphically summarized on Figures 26 and 27.
1. Relative magnitude of the sources of storm water infiltration:
a. The equivalent storm water infiltration ratio for
the East Bay Area is 0.111, i.e., 11.1 percent of
the total volume of rain falling on the area enters
the sanitary sewer system.
b. Approximately 30.6 percent of the total volume of
infiltration is contributed by infiltration and
runoff from those areas which have combined
sewers, composing 4 percent of the study area.
c. Approximately 3.7 percent of the total volume of
infiltration is contributed by the Pump Station A
drainage area, composing 1.4 percent of the
study area.
d. In the remaining 94.6 percent of the study area,
approximately 26.2 percent of the total infil-
tration is contributed via direct connections,
and 39.5 percent is contributed via percolation
or pipe leakage.
96
-------
40OO
o
5 3000
g
3
u.
t/o
g 2000
^
cc
UJ
t-
0
—
' —
-
—
-
AVERAGE YEAR
P. S . A 100
COMBINED
SEWERS
820
DIRECT
CONNECTIONS
710
PERCOLATION
1070
P. S. A 140
COMBINED
SEWERS
1130
DIRECT
CONNECTIONS
PERCOLATION
1460
—
—
-
P.S. A 3.7 %
COMBINED
SEWERS
30.6 % —
DIRECT
CONNECTIONS
26.2 % ~~
PERCOLATION
39.5 %
100
75
O
U.
O
50
z
UJ
O
£C
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0.
25
FIG. 26 SOURCES OF EXTRANEOUS FLOW, 1968-69 SEASON
VERSUS AVERAGE YEAR
-------
2. Overflows and bypasses during an average year:
a. The total rainfall is 17.57 inches at the
Oakland Airport.
b. Bypasses were found to occur 11 or 12 times, and
it was concluded that overflows would occur the
same number of times.
c. Approximately 1,660 MG of extraneous flow
(6.8 percent of the rainfall) reach the water
pollution control plant and 1,040 MG of
extraneous flow (4.3 percent of the rainfall)
overflow before reaching the plant.
d. Bypassing at the plant occurs for 110 hours at
an average rate of 168 mgd, resulting in a dis-
charge of 780 MG of waste water that consists of
480 MG of extraneous flow and 300 MG of base
or dry weather flow.
e. Approximately 1,180 MG (1,660 - 480) of
extraneous flow reaching the plant are treated
before discharging.
f. Overflow volumes were estimated to equal 90.5 MG
per event, with 62.5 MG occurring south of the plant
and 28.0 MG occurring north of the plant.
3. Overflows and bypasses during the 1968-69 season:
a. The total rainfall was 24.1 inches at the
Oakland Airport.
b. Approximately 2,660 MG of extraneous flow
(8.0 percent of the rainfall) reached the water
pollution control plant, and 1,030 MG (3.1
percent of the rainfall) overflowed before
reaching the plant.
c. Bypassing occurred for 186 hours at an average
rate of 168 mgd, resulting in a discharge of
1,300 MG of waste water that consisted of
300 MG of extraneous flow and 500 MG of base
or dry weather flow.
d. Overflow volumes at Pump Stations A and H
accounted for 3.5 percent of the total overflow
volumes. The remaining 96.5 percent was assumed
to occur at various overflow structures along the
interceptor and within the sewer system.
98
-------
DEVELOPMENT OF METHODS FOR ESTIMATING
VOLUMES OF OVERFLOWS
As mentioned, two methods were used to estimate storm water infiltra-
tion quantities in the study area for a specific storm event that
occurred during the 1968-69 season: 1) the extrapolation method and
2) the land use method. The extrapolation method involved the use of
the flow routing program for computing the outflow hydrograph and the
quantity of sewer system overflows in a pilot drainage area. The
results from this pilot drainage area were then extrapolated to a
larger drainage area, of which it was a part, and finally to the entire
study area. The land use method involved the application of gross
infiltration ratios to the rainfall volumes over each land use category
in the study area. Results from both methods were compared and checked
by measured quantities. The extrapolation method was used to estimate
the relative magnitude of the sources of infiltration. The land use
method could only be used to estimate the total volumes of infiltration,
without regard to source.
THE EXTRAPOLATION METHOD
Use and Confirmation of the Method
The first step in the extrapolation method was to select and describe
the pilot drainage area. Drainage Area No. 29, located in the south
part of Oakland, was chosen because it is part of the total drainage
area (composed of Nos. 29, 30, 31, 32, 33, and 34) that contributes to
Pump Station H, where extensive flow measurements were made during
this investigation. These flow data were thus available for checking
the results. Drainage Area No. 29 is shown in Figure 28. It contains
the seven combinations of land use, topography, and age of sewer for
which infiltration ratios were developed in Section 5. Since this
area stretches from the hillside across Oakland to the waterfront, it
also contains most of the topographic conditions found in the East
Bay Area. The areal rainfall distribution factors for this drainage
area vary from 1.3 at the upper end to 1.0 at the lower end, as can
be seen on Figure 23 in Section 5.
Once the drainage area was chosen and its boundaries determined, the
most difficult task was to describe its pipe network, which is probably
similar to that in many older parts of the East Bay Area. As-built
sewer drawings were obtained from the City of Oakland, but these were
found to be incomplete. One of the major problems in describing the
pipe network was the existence of parallel sewers (new sewers laid
parallel to older sewers to increase the capacity). In some instances,
data regarding the interconnections between these pipes were missing on
the drawings and therefore additional investigations were required. In
other instances, data on invert elevations, on sewer sizes, and even on
pipe locations were also missing.
99
-------
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The final sewer network used in the computer program, as shown on
Figure 29, was made up of 177 pipe lengths, each representing an
average of 5.5 acres of drainage area. Parallel pipes were reduced to
hydraulically equivalent single pipes. The drainage area for each
pipe was further described by the amount of land area involved in each
of the seven types of land use categories and by the areal rainfall
distribution factor.
The second step in the extrapolation method was to select the storm
characteristics for which flow measurements were taken both at Pump
Station H and at the water pollution control plant. Only two discrete
storms having conditions suitable for computation and extrapolation
were found. All other storms were excluded 1) because of interference
by either previous or subsequent storms, or 2) because flows were not
measured at both Pump Station H and the main plant. Of the two suit-
able storms, the one selected for use in the typical computations was
for February 4-5, 1969. This storm, which had 0.48 inch of rain, was
exceeded in total volume 30 percent of the time during the 1968-69
season, but was exceeded in average intensity only 10 percent of the
time.
The third step in the extrapolation method was to run the computer
program for the pilot drainage area. The printout from the program
included the depth of flow in each sewer reach for the peak flow rate,
together with the velocity and the sewer capacity. The listing of
these data permitted a quick review of the oversized sewers as well as
any bottlenecks in the system. The output indicated that 8 of the 177
pipes were surcharged and perhaps overflowing. The question of sur-
charging could not be better defined because of the method, described
below, for computing overflows. Many of the pipes were found to be
flowing less than half full even at the peak flow rate, indicating
that storage capacity might be available, depending upon the ground
elevations. These pipes were in random locations, and the beneficial
use of their natural storage capacity would not be easily effected.
The computer program was written with due consideration for the evalua-
tion of overflows within the sewer system. If the peak flow rate of
the computed hydrograph would not pass through the next downstream
sewer without surcharging, the hydrograph would be recomputed by
making use of more of the available storage volume in the first up-
stream reach of each intersecting sewer. The value stored during each
routing period is released to the downstream sewer during the next
routing period, thus changing the hydrograph. If the. upstream pipes
were full and the resulting dampened hydrograph still could not pass
through the downstream sewer, the program would compute the excess
amount of flow as an overflow, and the remainder of the hydrograph
would be routed on through the system. Overflow quantities thus ob-
tained may not actually occur, however, because nominal surcharging
can increase the hydraulic capacity of the downstream section so that
all of the water may pass on through without overflowing. In spite of
the limiting assumptions and approximations necessary for this method
101
-------
j!v/^: 'a-\;-\<' ;~\ ,<• f'-^i' '" •;*
'SOURCE: OAKLAND SEWER MAINTENANCE DEPART.MEgT . " '^/'^-/ ^\,?*^y^' t?''^\* '•?$'**•.*•*',-ffr
^- It- > ..*.V-,f."l' \'^V \ . ^JP< ^ ""^ xj, ' , S J.,'^ /' - f * x- X *^,VX
102
-------
of overflow computation, the computed volumes seemed to compare well
with the measured volumes when extrapolated to the total drainage
area of Pump station H.
The computed volume of extraneous flow for Drainage Area No. 29 was
1.23 MG, with 0.98 MG reaching the end of the sewer and 0.25 MG over^
flowing within the system. The output from the program could not be
directly checked against measured data because the discharge point
was not one of the measuring stations. Therefore, in order to check
the results, the computed volume of water was extrapolated to the total
Pump Station H drainage area, of which Drainage Area No. 29 is a part.
The final step was to extrapolate the extraneous flow volume computed
for Drainage Area No. 29 to the Pump Station H drainage area. The
computed volume was multiplied by the ratio of the land use product
for the Pump Station H drainage area to the land use product for
Drainage Area No. 29. The development of the land use products is
shown in Table 15. The land use products were computed by multiplying
the infiltration ratio by the land area over which the infiltration
ratio is applicable, and by the areal rainfall distribution factor.
The overall land use product was found by summing the individual pro-
ducts for each land use. (The infiltration ratio for each land use
category is given in Table 12). Consequently, the extrapolation factor
for Drainage Area No. 29 to the Pump Station H drainage area was
10.5 (1,136/108 = 10.5). Multiplying the computed volume of extra-
neous flow from Drainage Area No. 29 by the ratio of 10.5, gave the
volume of extraneous flow estimated for the Pump Station H drainage
area during the February 4-5 storm as 10.2 MG. The measured volume
of extraneous flow at Pump Station H during that storm was 10.1 MG,
which compares reasonably well with the computed value.
Multiplying the computed volume of sewer system overflows, 0.25 MG, by
the ratio of 10.5, gave the volume of water derived from storm water
infiltration that never reached Pump Station H as 2.60 MG. Therefore,
the total computed volume of storm water infiltration for the drainage
area tributary to Pump Station H was 12.8 MG (10.2 + 2.6).
A similar procedure was then used to estimate the extraneous flow for
the total study area from that same storm. The infiltration ratios,
land use areas, and areal rainfall distribution factors used in this
analysis are listed in Table 16, together with the computational steps
needed to develop the total adjusted land use product. The ratio of
the land use product for the total study area as compared to the land
use product for Drainage Area No. 29 was found to be 52.5. Assuming
that the proportion of sewer system overflows is the same for Drainage
Area No. 29 as for the total study area and that no other overflows
are in operation, the total extraneous flow reaching the water pollu-
^Obtained by subtracting average base flow from measured wet weather
flow.
103
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TABLE 15
LAND USE PRODUCTS FOR
PUMP STATION H AREA AND DRAINAGE AREA NO. 29
Gross Land Areal rainfall Product
infiltration area, distribution (l)x(2)x(3),
ratio acres factor acres
Area description (1) (2) (3) (4)
Pump Station H Area
Residential
Low density
Old*, hilly 0.045
New, hilly 0.015
Old, flat 0.110
Medium density 0.120
Commercial 0.090
Industrial 0.085
Totals
Drainage Area No. 29
Residential
Low density
Old, hilly 0.045
New, hilly 0.015
Old, flat 0.110
Medium density 0.120
Commercial 0.090
Industrial 0.085
Totals
4,490 1.26
400 1.40
420 1.17
3,790 1.15
1,050 1.15
2,110 1.05
200 1.26
—
60 1.15
480 1.15
210 1.07
20 1.05
970
254
8
54
523
109
188
1,136
11
—
8
66
21
2
108
*Refers to age of sewer system
104
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TABLE 16
LAND USE PRODUCTS FOP STUDY AREA
WITH AND WITHOUT COMBINED SEWER AREAS
Gross
infiltration
ratio
Area description (1)
Land Areal rainfall Product
area, distribution (l)x(2)x(3),
acres factor acres
(2) (3) (4)
A. Study area less combined sewer areas
Residential
Low density
Old, hilly
New, hilly
Old, flat
Medium density
Commercial
Oakland downtown
Elsewhere
Industrial
Pump Station A
Subtotals
Averages
B. Total study area
Combined sewer areas
Remaining area
Equivalent values
0
0
0
0
0
0
0
0
0
0
0
0
.045
.015
.110
.120
.140
.090
.085
.246
.0812*
.700
.0812
.111***
13,100
400
3,040
8,960
1,700
5,530
8,870
710
42,310
2,060**
40,250
42,310
1
1
1
1
1
1
1
1
1
1
1
1
.30
.40
.05
.13
.10
.08
.03
.20
.20
.20
.20
.20
766
8
351
1,215
262
536
778
209
4,125
1,730
3,920
5,650
*Computed value: 0.0812 = 4,125/1.2x42,310.
**Four percent of the total area: 2,060 = 0.04x51,416 acres.
***Computed value: 0.111 = 5,650/1.2x42,310.
105
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tion control plant would be 51.1 MG and the sewer system overflows
would be 13.0 MG. The volume of extraneous flow measured at the plant
during that storm was 50.5 MG. The close agreement of the computed
extraneous flow and the amount observed for this storm supports the
validity of the extrapolation method.
Relative Magnitude and Sources of Infiltration
In developing the land use product for the total study area, special
consideration was given to the Pump Station A drainage area and to the
portions of the study area that still have combined sewers. The method
used in accounting for these areas is shown in Table 16. These two
areas were given special attention because their infiltration was
known to be greater than would be indicated by use of the infiltration
ratios developed in the study subareas. Flow data from Pump Station A
gathered during the 1968-69 season indicated a gross infiltration ratio
of 0.246, which is substantially greater than any other ratio measured
during the season. The estimate that 4 percent of the study area has
combined sewers was based on reports from personnel of EBMUD and the
various cities. These combined sewer areas were assumed to have an
"infiltration ratio" of 0.70 (i.e., equivalent to a storm water runoff
coefficient).
Considering the additional infiltration contributed from both the
Pump Station A drainage area and the combined sewer areas, the
equivalent infiltration ratio for the total study area was found to
be 0.111, as shown on Table 16. This figure is significant because it
indicates that 11.1 percent of the total volume of rain falling on the
study area enters the sanitary sewer system, the only exceptions being
those portions that do not contribute to sanitary sewers.
It is important to note from the land use products in Table 16 that
the combined sewer areas, consisting of only 4 percent of the study
area, account for about 30.6 percent of the total amount of water
defined as infiltration (1,730 x 100/5,650 = 30.6%).
It is also important to note that the Pump Station A drainage area,
consisting of only 1.4 percent of the study area, accounts for 3.7
percent of the total amount of infiltration (210 x 100/5,650 = 3.7%).
Therefore, these areas, the combined sewers and Pump Station A, should
be given priority when considering ways of reducing storm water infil-
tration in the East Bay Area.
Table 17 develops the land use products using only the direct connec-
tion infiltration ratios in a manner similar to that using the gross
infiltration ratios in Table 16. The adjusted land use product in
Table 17 excludes the Pump Station A drainage area and the combined
sewer areas. Comparing the direct connection land use product to the
total land use product, it will be seen that direct connections con-
Obtained by subtracting average base flow from measured wet weather flow.
106
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TABLE 17
LAND USE PRODUCTS USING
DIRECT CONNECTION INFILTRATION RATIOS
Area description
Residential
Low density
Old, hilly
New, hilly
Old, flat
Medium density
Commercial
Direct
connections Land
infiltration area,
ratio* acres
(1) (2)
0.02 13
0.01
0.02 3
0.02 8
Oakland downtown 0.10 1
Elsewhere
Industrial
Totals
Combined sewers
Adjusted product
Percent of total
0.05 5
0.05 8
41
2
39
infiltration volume
contributed by direct connections
Percent of total
infiltration _
,100
400
,040
,960
,700
,530
,870
,600
,060*
,540
This
Areal rainfall Product
distribution (l)x(2)x(3),
factor acres
(3) (4)
1.30 342
1.40 6
1.05 64
1.13 202
1.10 187
1.08 298
1.03 458
1,557
1,480**
product 1,480x100 _ 9R 9?.
Total product 5,650
(3,9:
contributed by percolation
20 209) 1,480 1 on — TO z>°.
5,650 " 10° 39'b
*See Table 12.
**1,480 = (39,540/41,600) x 1,557.
***See Table 16.
107
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tribute approximately 26.2 percent of the total infiltration volume.
Table 17 also shows that the percolation source of infiltration over
the total study area, excluding the Pump Station A drainage area and
the combined sewer areas, amounts to 39.5 percent of the total infil-
tration volume. This indicates that the percolation source of infil-
tration contributes 51 percent more water than the direct connection
source of infiltration ((39.5-26.2)100/26.2 = 51%).
Table 18 shows the relative proportions of infiltration quantities ex-
pected north and south of the water pollution control plant. It was
assumed that the ratio of the land use products for the areas north
and south of the water pollution control plant are indicative of the
relative quantities of infiltration and also of overflows north and
south of the plant. As shown in Table 18, 31 percent of the extran-
eous flow will occur north of the plant and 69 percent will occur south
of the plant.
THE LAND USE METHOD
The land use product, as used previously, is expressed in units of
acres. Because the land use product contains an adjustment for rain-
fall distribution and for infiltration ratios, the direct multiplication
of rainfall quantity by land use product should equal the total volume
of infiltration from any given storm. The storm used for the previous
computations contained 0.48 inches of rain. Using the total land use
product of 1,136 acres for the Pump Station H drainage area, multiply-
ing by the rainfall of 0.48 inches and correcting the units, the esti-
mated total volume of infiltration in the Pump Station H drainage area
would be 14.8 MG (0.48 x 1,136 x 0.0271 = 14.8). The volume computed
by the extrapolation method was 12.8 MG. The difference of 2.0 MG was
partly caused by not considering the loss of the first 0.05 inch of
rainfall for the percolation portion of the infiltration which was done
in the flow routing program. Considering this loss, the difference
between the two methods is reduced to 0.9 MG, which may be attributable
to the mechanics of the routing program, the method of handling the
surcharged condition, and the computation of resulting overflows.
A similar procedure was then used to estimate the extraneous flow for
the total study area from the same storm. By using the equivalent land
use product developed in Table 16, applying the rainfall of 0.48 inch
and correcting the units, the total infiltration quantity was 73.5 MG
(5,650 x 0.48 x 0.0271). Recomputing the infiltration volume leaving
out the first 0.05 inch of rain that enters via percolation, the
total expected infiltration by the land use method was 67.5 MG, which
may be compared to the total of 64.1 MG found by the extrapolation
method.
These calculations indicated that the land use method would provide
results comparable to those from the extrapolation method, although
somewhat higher. The land use method is quicker and less time
consuming than the extrapolation method, but it provides a gross estimate
108
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TABLE 28
LAND USE PRODUCTS FOR NORTH VERSUS SOUTH INTERCEPTOR AREAS
North South
Gross Land Areal rainfall Product Land Areal rainfall Product
infiltration area, distribution (l)x(2)x(3), area, distribution (l)x(5)x(6),
ratio acres factor acres acres factor acres
Area description (1) (2) (3) (4) (5) (6) (7)
Residential
Low density
Old, hilly
New, hilly
Old, flat
Medium density
Commercial
Oakland downtown
Elsewhere
Industrial
Pump Station A
Totals
Percent of total
0.
0.
0.
0.
0.
0.
0.
0.
045 4,760 1.30 278 8,340 1.30
015 400 1.40
110 700 1.17 90 2,340 1.01
120 2,420 1.15 334 6,540 1.12
140 1,700 1.10
090 2,290 1.10 227 3,230 1.07
085 1,510 1.05 135 7,360 1.03
246 710 1.20 209
1,273
31%
487
8
260
878
262
312
645
2,852
69%
-------
of total volumes, with no indication of the fraction of sewer system
overflows. Had time been available during this study, the extrapola-
tion method could have been used to estimate the actual shape of the
infiltration hydrograph at all points along the interceptor, and thus
provide a more complete picture of the events of overflowing and by-
passing.
ESTIMATES OF VOLUMES OF
OVERFLOWS AND BYPASSES
Estimates of storm water infiltration quantities for the average year
were derived by the same land use method that was used to derive the
volumes of discrete storms described in the foregoing discussion. This
method, however, will not provide an indication of the disposition of
the various portions of infiltration. The procedures used for defining
the volumes and disposition of the total annual volume of_infiltration
are described in the discussion that follows.
The mean seasonal precipitation at the Metropolitan Oakland Interna-
tional Airport is 17.57 inches. Using the equivalent land use product
developed in Table 16, which accounts for land area, gross infiltra-
tion, and areal rainfall distribution, the average annual volume of
storm water infiltration in the study area was estimated to be 2,700 MG
(17.57 x 5,650 x 0.0271). This estimated volume was based on the
assumption that the average infiltration ratio for the study area is
0.111, which is actually applicable to only those conditions that
prevailed during the 1968-69 season. The value will be expected to
change as combined sewers are eliminated and as other improvements are
made to reduce infiltration in the sewer system. Nevertheless, this
value of infiltration ratio will be assumed applicable for the next
several years.
ANNUAL EXTRANEOUS PLANT FLOW
Data were gathered and analyzed to determine the amount of extraneous
flow which actually reaches the water pollution control plant as a
result of storm water infiltration. The plant records of total
monthly flow for the period from 1959 to 1969 were analyzed. Seasonal
contributions of waste water from local canneries were found to add
substantially to the average dry weather flows. Lines of best fit
were drawn through plotted values of dry weather flow for both the
canning and non-canning season. The dry weather flow months were
selected from those that had an insigificant amount of rainfall,
usually April, May, June, and July. The canning season months were
assumed to be August, September, and October.
These lines of best fit were straight and parallel, as shown in
the upper curve of Figure 30. The uniform slope of the line
indicates a constant annual increase in dry weather flow. No
annual increase in cannery waste water flow was indicated
because the lines were parallel. A second graph was constructed
110
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n r 1 1 1 r—
AVERAGE DRY WEATHER FLOW
o
=! 3
m
O
I
AVERAGE DRY WEATHER FLOW
DURING CANNING SEASON
AVERAGE DRY WEATHER FLOW
DURING NON-CANNING SEASON
CANNING SEASON
NON- CANNING SEASON
CD
I- 2
I
WET WEATHER EXTRANEOUS FLOW
EXTRANEOUS FLOW VOLUME
AVERAGE DRY WEATHER FLOW,
WITH AND WITHOUT CANNERY FLOW
_L
I960 1961
1962
1963
1964
YEAR
1965
1966 1967
1966
FIG. 30 AVERAGE DRY WEATHER FLOWS AND
EXTRANEOUS FLOWS VERSUS YEAR,
EBMUD WATER POLLUTION CONTROL PLANT
SOURCE: EBMUD WATER POLLUTION CONTROL PLANT ANNUAL REPORTS, 1959-1968
111
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from the data for all months that had significant rainfall, as shown
in the lower portion of Figure 30. That portion of the monthly flow
falling above the dry weather flow conditions determined above was
assumed to represent extraneous flow caused by the infiltration of
storm water.
The flow data recorded during 1968-69 at the water pollution control
plant, compared to the results of a more detailed analysis, appeared
to be high. The actual values of flow were estimated to be approxi-
mately 85 percent of those recorded from pump running time computations
(see Section 4 for discussion). It was assumed that this factor of
85 percent was applicable to previous years as well.
Therefore, the values for extraneous plant flow during 1959 through
1969, as derived from the lower curve of Figure 30, were adjusted by
the factor of 85 percent. The resulting values were plotted versus
annual rainfall measured at the Oakland Airport, and are shown in the
lower curve of Figure 31. The curve drawn through these points indicates
that, as expected, the ratio of extraneous flow to total annual rain-
fall tends to decrease during years of very high rainfall. This
relationship is noted by the flattening out of the curve. The reason
for this is that during periods of high rainfall, much more water is
overflowed via system overflows, hence never reaches the plant.
Referring again to the lower curve of Figure 31, the average annual
extraneous plant flow was found to be 1,660 MG for a mean seasonal
precipitation of 17.57 inches measured at the Oakland Airport. From
the same curve, the amount of extraneous plant flow during the 1968-69
season was found to be 2,660 MG, based on a total precipitation of
24.1 inches at the Oakland Airport.
ANNUAL PLANT BYPASSING
From the water pollution control plant records, it was found that the
plant was bypassed a total of 186 hours during the 1968-69 season,
amounting to about 1,300 MG, of which 500 MG was the base or dry
weather flow (both the extraneous flow and the base or dry weather flow
are bypassed). Therefore, the amount of extraneous flow bypassed was
800 MG. This amount of excess flow bypass results in an average flow
rate during bypassing of 168 mgd.
Again, using the plant data for the 1959-69 period, a relationship
between hours of plant bypassing and annual rainfall was developed, as
shown in the upper curve of Figure 31. It is noted that mean annual
precipitation is normally recorded for calendar years, whereas the
reference in Figure 31 is to mean annual precipitation based on the
fiscal year, July through June. The average annual duration of plant
bypassing can be read from the curve as 110 hours based upon the annual
precipitation of 17.57 inches. If the average bypass flow rate found
for the 1968-69 season is assumed to represent average annual condi-
tions, the average annual plant bypass is 780 MG (110 x 168/24). Again,
112
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20°
c
CD
100
o
UJ
3000
o
2000
1000
I
I
0 10 20 30 40
TOTAL SEASONAL RAINFALL AT OAKLAND AIRPORT, IN.
FIG. 31 ANNUAL PLANT EXTRANEOUS FLOW AND ANNUAL
TIME OF PLANT BYPASSING VERSUS ANNUAL RAINFALL
SOURCE: BASIC DATA FROM EBMUD WATER POLLUTION CONTROL PLANT ANNUAL REPORTS, 1958-1969
113
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assuming 1968-69 season conditions of 110 hours of plant bypassing at
an average base flow rate of 66 mgd, approximately 300 MG of dry
weather flow would be bypassed (110 x 66/24). The difference between
the total plant bypass amount (780 MG) and the dry weather flow bypass
amount (300 MG) of 480 MG represents the amount of extraneous flow
which is bypassed annually.
The average number of yearly bypass occurrences can be determined by
an analysis of the marginal overflow storms discussed in Section 5.
The number of occurrences was found by counting the number of storms
during the period from 1951-52 to 1968-69 in which the cumulative
rainfall for each of the four hours of highest rainfall intensity was
greater than the marginal overflow storm. The average number of occur-
rences was found to be 11.5 per year,- i.e., 11 or 12 times per year.
The average annual volume of plant bypass per occurrence was found to
be 68 MG (780/11.5 = 68). The assumptions used to determine this
amount, however, do not take into account future changes. For example,
it is known that the average annual dry weather flow in the future will
not be equal to that in 1968-69. In fact, Figure 30 indicates that the
future dry weather flow is likely to increase at a rate of about 1.8
mgd per year. An increase in the dry weather flow would decrease the
amount of infiltration because of the reduced carrying capacity of the
various sewers, but it would increase the amount of pre-plant over-
flowing, the number of times in which overflowing and bypassing take
place and their duration, the volume of bypassing, and the amount of
dry weather flow in the volume bypassed. The effect of the increasing
dry weather flow on these values cannot be easily estimated. An
attempt was made to determine the effect of increasing dry weather
flow on the extraneous plant flow and the hours of bypassing for the
water pollution control plant data from 1959 to 1969, but no relation-
ship could be found.
ANNUAL OVERFLOWS
As previously discussed, the equivalent infiltration ratio computed in
Table 16 representing total infiltration over the study area was 0.111.
A similar computation was made indicating that the annual plant ex-
traneous flow could be represented by an equivalent infiltration ratio
of 0.08. The difference between these two infiltration ratios, 0.031,
represents the volume of rainfall assumed to have overflowed prior to
reaching the water pollution control plant. Therefore, the estimated
quantity of storm water infiltration suspected of overflowing prior to
reaching the plant was 1,030 MG (0.031 x 2,660/0.08 = 1,030) for the
1968-69 season. Similarly, the average annual overflow volume was
estimated to be 1,040 MG per year, assuming that the 1968-69 relation-
ships continue to exist. This value was found by subtracting the
amount of extraneous plant flow expected annually (1,660 MG) from the
total amount of infiltration found by application of the land use
method (2,700 MG).
114
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The average number of times per year that overflowing is expected to
occur is the same as for bypasses, i.e., 11.5. This conclusion is
based on the fact that the marginal overflow storms are nearly identical.
It was assumed that the largest volume of overflow ahead of the plant
would occur at the same time that pump stations overflow. Therefore,
the number of all pre-plant overflows is assumed to be the same as that
for pump station overflows. It is noted, however, that some pre-plant
overflows will take place before pump station overflowing begins, and
also at times when no pump station overflowing occurs. The average
overflow amount per occurrence was estimated to be 90.5 MG (1,040/11.5).
The amount of overflowing that occurs from the areas north and south of
the water pollution control plant, respectively, is not actually known.
It was assumed that the volumes of overflow would be proportional to the
ratios of infiltration between the two areas. The ratios of infiltration
were computed in Table 18 as 31 percent north and 69 percent south of
the plant. Therefore, of the 90.5 MG of average annual overflow, 28.0
MG overflow in the area north of the plant, and 62.5 MG overflow in the
area south of the plant.
Overflows at Pump Stations A and H
The flow data gathered for Pump Station A for the 1968-69 season indi-
cated that 1.22 MG of overflow occurred between December 8 and Febru-
ary 17. During this period, 14.46 inches of rain fell at the Oakland
Airport. If 24.6 percent of the rain infiltrated, a total volume of
82 MG of infiltrated flow would have -resulted. Of this 82 MG, 1.22 MG
were indicated as overflowing, which is 1.5 percent of the total infil-
tration. If this percentage of overflow were to hold for the rest of
the season during which overflows were not measured, a total of 2.5 MG
would be expected to overflow. This 2.5 MG of overflow represents
0.24 percent (2.5 x 100/1,030 = 0.24%) of the total estimated overflow
for the study area during 1968-69.
The plant records indicate that 34 MG overflowed at Pump Station H
during the past season. This volume represents 3.3 percent
(34 x 100/1,030 = 3.3%) of the total amount of overflow for the
study area during 1968-69.
All Other Overflows
The quantity of overflows during the 1968-69 season from other than
the pump stations accounts for 994 MG. This figure represents 96.5
percent of the total amount of overflows during 1968-69.
115
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SECTION 7
PROBLEMS RESULTING FROM OVERFLOWS
Page
Intersystem Overflows 118
System Overflows 119
Water Pollution Control Plant Bypass 120
Silt Problems 120
Grease Problems 121
Intrasystem Overflows 122
Public Health 122
Property Damage 124
Nuisance 127
Rodent Control 127
117
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SECTION 7
PROBLEMS RESULTING FROM OVERFLOWS
The problems that result from overflows in the East Bay Area may be
categorized according to the type of overflow or bypass involved. Four
types of overflows were found:
1. Intersystem overflows - occurring at cross-connections
between storm drains and sanitary sewers.
2. System overflows - occurring at specially designed
structures near the interceptor sewer to discharge
excess flow to the Bay.
3. Water pollution control plant bypass - manually
controlled bypass to prevent damage to the plant's
mechanical equipment.
4. Intrasystem overflows - occurring at manholes or other
openings and broken sewers.
Intersystem and system overflows and plant bypasses ultimately result
in discharging untreated sewage to San Francisco Bay. The problems
associated with discharges to the Bay will be considered in detail in
Section 9.
Intrasystem overflows, which commonly occur throughout the East Bay
cities, do cause serious problems (involving public health, community
hygiene, property damage, and nuisance), but they do not have a signifi-
cant direct pollutional effect on San Francisco Bay. Therefore, these
problems are not considered in the evaluation of pollutional effects in
Section 9 but alternatives for their correction are discussed in Sec-
tion 10.
INTERSYSTEM OVERFLOWS
Several problems are associated with the intersystem type of overflow.
Raw sewage is discharged into storm drains that lead directly to the
Bay, producing an uncontrollable source of pollution. The overflow
from sanitary sewers tends to hydraulically overload storm sewers that,
in turn, cause problems of surcharging and possible property damage.
Excess water from storm sewers discharged into sanitary sewers con-
tributes to overflowing downstream and bypassing at the treatment plant.
Each of these problems involves the discharge of pollutants to the Bay.
It would be impossible to enumerate and describe all of the intersystem
overflows that exist in the East Bay Area, simply because they are
118
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unknown. However, several types of intersystem overflows are described
in Appendix III.
As described earlier, the sewer system in the East Bay Area is extremely
complex because it was originally designed as a combined sewer system,
and this was later converted to separate sanitary and storm sewer sys-
tems. In some areas, the sanitary sewers were designed and constructed
specifically for conveying domestic, commercial, and industrial waste
waters. In other areas, the sanitary sewer system is a converted com-
bined sewer, complicated by the construction of parallel or relief
sewers which were required because of unexpected growth in the service
area and excessive infiltration rates. Also, with increasing infiltra-
tion rates through poor joints, the need for relief at critical loca-
tions in the sewer system became mandatory.
Having limited funds, the various maintenance personnel did their best
to relieve the problem of overflowing sewage. Various forms of bypasses
were connected from the sanitary sewers to nearby storm sewers that
could carry the additional extraneous flow. Each new intersystem bypass
or overflow added to the problem, however, until it reached the propor-
tion that exists today. Similar bypasses and overflows were constructed
on the storm sewer lines to discharge into oversized sanitary sewers,
and these contribute to the problem of system overflows and bypassing
of the plant.
Another condition that contributes to overflows is the connection of
subsurface drains to sanitary sewers. In areas where groundwater or
perched water causes difficulties in roadbed stability, a system of
perforated pipes is placed in the ground to drain away the water.
These underdrain systems normally discharge into storm sewers; however,
in several cases, they were connected into the sanitary sewer system.
If the discharge of pollutants to the Bay is to be stopped by treating
or otherwise handling the flow in the sanitary sewer system, the over-
flows into the storm sewers must be eliminated. If they are not
eliminated, the storm sewers will operate as combined sewers, hence
their flow may also require treatment prior to discharge into the Bay.
Because of the large sums of money that have been spent to date for
separating sanitary and storm sewers, it would seem logical that every
effort should be made to take advantage of that separation. This would
mean elimination of all overflows from sanitary sewers into storm
sewers, so that storm water can be discharged into the Bay without
treatment.
SYSTEM OVERFLOWS
System overflows occur at locations along the interceptor sewer at
points where the trunk sewers are intercepted. The problem associated
with these overflows is that of discharging untreated sewage to the
Bay during periods of wet weather. The following discussion concerns
the purpose of these overflows and their design features.
119
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When the water pollution control plant was constructed in 1951, assur-
ances were obtained from the contributing cities that there would be
complete separation of storm and sanitary sewers. For this reason the
interceptor sewer and treatment facilities were designed large enough
to handle only the expected sanitary and industrial sewage flow, plus a
reasonable allowance for infiltration. This peak design flow was
291 mgd. No allowance was made for large quantities of extraneous
flow into the sanitary sewer system.
Five combined sewers, serving large areas at the time of the construc-
tion of the interceptor sewer, were allowed to be connected, with the
understanding that they would also be converted to sanitary sewers as
soon as possible. These sewers were connected to the interceptor by
way of diversion structures which would direct all of the dry weather
flow into the interceptor and divert storm water diluted sewage into
the original outfall sewers that discharge directly to the Bay waters.
These diversion structures were designed to permit a flow equal in rate
to the design dry weather flow to discharge into the intercepting sewer.
The flows beyond this were to continue along the original outfall and
into the Bay. The existing outfalls were fitted with tide gates to
prevent Bay waters from entering the interceptor sewer. Each diversion
structure includes a gate that is shut to bypass all or any part of the
storm water flow through the existing outfall sewer, thus bypassing the
sewage treatment facilities.
In addition to the five diversion structures, three overflow structures
were constructed on the interceptor sewer. These are fitted with tide
gates to permit sewage to overflow automatically when the intercepting
sewer becomes surcharged; no slide gates are involved. Figure 32 shows
the approximate locations of all overflow and diversion structures along
the intercepting sewer.
WATER POLLUTION CONTROL PLANT BYPASS
There are two basic problems caused by extraneous flows at the water
pollution control plant: 1) operation and maintenance problems caused
by large quantities of silt and grease which will be discussed here,
and 2) bypassing of raw sewage to the Bay, which will be evaluated in
Section 9.
Shortly after the water pollution control plant was placed in operation,
it became evident that rainfall resulted in abnormally high flow rates
together with large quantities of silt and floatable grease. The de-
position of large quantities of silt damages the sedimentation basin
equipment, and floating grease accumulates in the outfall and related
structures.
SILT PROBLEMS
The greatest problem was caused by large amounts of fine sand and silt
(particles with diameters of less than 0.2 millimeter) being carried
120
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into the plant. This sand and silt was not removed in the grit cham-
bers, which were designed to remove only particles with diameters
greater than 0.2 millimeter. During storms, the fine sand and silt
collected in the sedimentation basins in sufficient quantity to cover
the sludge collectors completely and to stop the mechanism. After
storms when the flow had returned to normal, it was necessary to de-
water the channels one at a time and to remove the excess sludge by
hand before the chain and flight collectors could be restarted. In
addition, pumping sand-laden sludge wore out sludge pump impellers,
resulting in high maintenance costs.
When large volumes of sand-laden sludge are pumped into the sludge
digesters, they must be frequently taken out of service for cleaning.
This problem is both expensive and detrimental to the overall operation
of the plant. For this reason sand-laden sludge was bypassed around
the digesters and to the outfall for disposal to the Bay.
To eliminate the operational difficulties produced by the large quan-
tities of silt, a bypass was constructed to divert the total wet weather
flow around the sedimentation basins. The basis for operating the by-
pass channel was the objective of a substantial study by the staff of
the water pollution control plant (1).
The purpose of the study was to define the point at which bypassing
should begin. Based upon laboratory tests and field measurements of
both dry and wet weather flows, a value for the electrical resistance
of the waste water above which the bypass gate would be opened was set
at 1,350 ohms. This represented about a twofold dilution of the
sewage, which averaged about 800 ohms. A resistance of 1,350 ohms was
equivalent to a plant flow rate of approximately 120 mgd.
Operating experience has confirmed the validity of the study because
only acceptable amounts of fine sand and silt are collected in sedimen-
tation basins with flow rates of less than 120 mgd. In actual practice
it is this flow rate, not the resistance measurement, that is used to
gage the correct opening time for the bypass gates. Use of this crite-
rion involves judgment on the part of the operator; if it appears that
the maximum flow rate might only slightly exceed 120 mgd, the bypass
gates may not be opened.
Obviously, if improvements could be made in handling or removing the
large volumes of sand and silt that are carried into the plant, the
bypassing of raw sewage around the sedimentation basins during wet
weather could be stopped, or at least substantially reduced. A study
of this solution to the problem of bypassing will be undertaken in
Sections 10 and 11.
GREASE PROBLEMS
Large volumes of grease also represent a problem at the plant, particu-
larly in the outfall system. During bypassing, the grease passes around
121
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the sedimentation basins and tends to float at both the effluent pumping
station and at the outfall transition structure. Grease also clings to
the wall of the outfall sewer and accumulates until it begins to break
loose in chunks. These chunks of grease, although broken up to a large
degree by turbulence in the outfall, contribute to the visible floating
material during the rainy season. Cleaning and disposing of the grease
that accumulates in the effluent pumping station and in the transition
structure requires a substantial amount of personnel time. For example,
during the months of January and February 1969, grease and other float-
able matter was removed from the outfall transition structure on six
different occasions requiring a total of 108.5 man-hours.
If bypassing could be stopped, the problems caused by grease accumula-
tion in the outfall would be reduced. A large portion of the grease
would then be removed in the sedimentation basins where provision has
been made for its removal.
INTRASYSTEM OVERFLOWS
Four kinds of problems are associated with intrasystem overflows:
1) public health, 2) property damage, 3) nuisance, and 4) rodent control.
These problems are caused by overflows at manholes or other openings and
broken sanitary sewers.
PUBLIC HEALTH
The concern of public health is the transmission of water-borne dis-
eases. Sewage is known to carry many of the microbial agents of dis-
eases, including typhoid fever bacteria and other members of salmonellae,
the viruses of poliomyelitis and hepatitis, and various other intestinal
parasites (2,3). Normally, ingestion of infective material is necessary
to transmit these diseases. In the case of infectious hepatitis, the
infective material may be either fecal matter or blood from an infected
person, both of which find their way into the sanitary sewer system.
Although most epidemiological cases involve contaminated water supplies,
there still remains the possibility of ingestion as a result of improper
personal hygiene coupled with contact with infected matter. This pos-
sibility is the source of the public health problem involved with intra-
system overflows. One of the pleasures of children is wading or other-
wise playing in rainwater that has collected in street gutters. This
in itself is probably not harmful, but if that gutter water contains
the remains of sewage discharged from a nearby manhole and if proper
hygiene is not practiced, there is the risk of ingestion of contaminants
during subsequent eating or drinking.
Fortunately, the probability of contacting a water-borne disease is not
high, as indicated by the infectious hepatitis data presented in
Tables 19 and 20. Table 19 shows the age distribution for cases of
hepatitis in California during 1962. The number of cases for children
between one and nine years of age was 875, only about 20 percent of the
122
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TABLE 19
AGE DISTRIBUTION OF INFECTIOUS HEPATITIS
IN CALIFORNIA, 1962
Age
Under 1
1-4
5-9
10-14
15-19
20-24
Over 25
Total
Cases
9
163
712
525
503
689
1,935
4,536
Source: Safety Committee, California
Water Pollution Control Associa-
tion (3).
TABLE 20
MONTHLY DISTRIBUTION OF INFECTIOUS HEPATITIS
IN CALIFORNIA., 1962
Month Cases
January 487
February 410
March 440
April 390
May 460
June 287
July 319
August 351
September 298
October 470
November 327
December 297
Total 4,536
Source: Safety Committee, California Water
Pollution Control Association (3).
123
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total. The evidence does not appear to indicate a disproportionately
high occurrence of cases among children. Table 20 shows the monthly
distribution for the same data. The six winter months from October
through March (50 percent of the calendar year) had 54 percent of the
cases. Hence there does not seem to be a significant increase in
occurrence during the rainy season. Nevertheless, the possibility of
infection exists, and good community hygiene is necessary in controlling
or reducing the possibility.
Fortunately, also, the distribution of the locations of the intrasystem
overflows indicates that many of them take place in areas involving
other than residential land uses. Figure 32 shows the reported loca-
tions of commonly occurring overflows from manholes throughout the
Oakland and Berkeley systems. The data were collected from maintenance
personnel and records from these two cities. These are locations where
overflows occur consistently and are to be expected during each sub-
stantial rain. No doubt overflows occasionally occur in other locations
if storm conditions are right or if some additional problem occurs
downstream. Similar data were not collected for the four other cities
in the study area; however, the following quote from an engineering
report by M. Carleton Yoder, consulting engineer on the Piedmont
sewer system, indicates similar problems:
Other sewers, while not actually overflowing during the past
winter (1962-63), had indications that they operated under
surcharged conditions during storms. The danger here is that
storms of greater intensity than those of last winter could,
conceivably, result in overflow of these sewers. Also, sur-
charging of some sewers caused backing up of sewage into the
basement of homes. In several locations, 8-inch sewers run
directly into 6-inch sewers causing overflow to the surface
and/or surcharging of the line (4).
PROPERTY DAMAGE
A review of Figure 32 and the above quote indicates that property
damage is very likely a problem associated with intrasystem overflows.
The damage can arise not only from sewage backing up into basements,
but also from sewage overflowing from sewers located in sideyard and
rear-lot easements. These areas are difficult for maintenance per-
sonnel to reach.
Claims against the cities for property damage caused by overflowing or
backed-up sewage indicate the scope of this problem. Berkeley officials
indicated that about four or five such claims are made each year;
Oakland officials indicated about 25. The dollar value of these claims
was not readily available. Even if it were available, the value would
be misleading because much of the clean-up work resulting from overflows
on private property is done by city maintenance crews, and their costs
would not be included in the claims. Also, inconveniences are caused
in some cases where claims are not made.
124
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i ,/ \ ELMHURST CREEK
"ERFLOW STRUCTURE \ ...
. 5 AiWERFLOW /
TO IERRITO CREEK
MERGENCY OVERFLOW
STRUCTURE '
* '
GENCY OVEftFLOVy
STRUCTURE (NORMALLY LOCKED)
, OVERF__..
STgUCffe (I'DiA.)'
\
TEMESCAL CREEK OVERFLOW^
,1 STRUCTURE'S-3
^WEBSTER^'wATER^5^
nd a GROVE—T^^'JijtG^' .•-. iv''"' '
LEGEND
» OVERFLOWING MANHOLE
a OVERFLOW STRUCTURE
• DIVERSION STRUCTURE
FIG. 32 LOCATIONS OF INTERCEPTOR OVERFLOW
AND DIVERSION STRUCTURES AND OF COMMONLY
REPORTED MANHOLE OVERFLOWS IN
OAKLAND AND BERKELEY
125
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NUISANCE
The problem of nuisance considerations is obvious. No one appreciates
the idea of sewage flowing from manholes and along the street gutters,
even when it is diluted with extraneous flows. Knowledge of its pres-
ence is repulsive.
An example of the reaction that may be found was a situation in Oakland.
Shortly after completion of the Kaiser Center, overflowing sewage was
detected in the gutters around the building during rainstorms. A
demand was immediately made for correction of the problem and persisted
until the condition was alleviated.
RODENT CONTROL
The appearance of rats is very often an indication of a problem in the
sanitary sewer system. An opening in the system may offer rats an
access to sewage as a source of water, or may permit rats to escape
the sewer during an extermination program.
An annual program of rodent extermination in the sewer system is con-
ducted by the local health departments. Rat poison is introduced at
selected locations in the sewer system, and the resulting appearances
of dead rats are reported by residents. The health department then
investigates and recommends corrective action.
Figure 33 shows the distribution of the appearances of dead rats and
the reported types of sewer problems in the six East Bay cities for
1967. The data are divided on the basis of census tracts for Oakland,
Piedmont, and Emeryville; the data for Berkeley, Alameda, and Albany
are for each city as a whole.
The reports revealed that approximately 78 percent represented broken
sanitary or building sewers; 6 percent, stopped or plugged sewers;
14 percent, seeping sewage; and 2 percent, flooded basements. Although
the distribution of findings was not available from Berkeley, it was
assumed that it was similar to that in other areas. These data indicate
both the widespread and the general nature of the failures associated
with sanitary sewers.
It should not be concluded that these reports represent all of the cases
because many are not reported. Only those broken sewers that are asso-
ciated with the appearance of rats are indicated by these reports.
Because house connections are often broken or plugged, it can be con-
cluded that they may not only contribute to rat infestation but may
also cause property damage or nuisance during periods when the sewers
are surcharged with extraneous flows. The data further indicate that
house connections can contribute to the problem of infiltration.
127
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SAY
TYPES OF PROBLEMS FOUND UPON INVESTIGATION OF REPORTS
TOTAL * BROKEN STOPPED SEEPING FLOODED
REPORTS SEWER SEWER SEWAGE BASEMENTS
NO. 197 101 8 17 2
% 100 * * 78 6 14 2
* INCLUDES 69 REPORTED PROBLEMS FROM BERKELEY WHICH WERE NOT DEFINED.
** ASSUMES DISTRIBUTION OF PROBLEMS IN BERKELEY ARE SIMILAR TO THAT IN OTHER AREAS.
FIG. 33 DISTRIBUTION OF REPORTS ON RAT APPEARANCES AND
ASSOCIATED TYPES OF SEWER PROBLEMS IN EAST BAY CITIES, 1967
SOURCE •• COMPILATION OF DATA FROM ALAMEDA COUNTY HEALTH DEPARTMENT
AND BERKELEY AND ALBANY CITY HEALTH DEPARTMENTS.
129
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SECTION 8
WATER QUALITY OBJECTIVES
Page
Selected Objectives 132
The Regional Board and Bay-Delta Objectives 132
Selected Parameters 137
Dissolved Oxygen 137
Floatable Materials 137
Coliform Bacteria 138
Other Parameters 138
Biostimulants 138
Relative Toxicity 138
Miscellaneous 139
131
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SECTION 8
WATER QUALITY OBJECTIVES
SELECTED OBJECTIVES
To determine the effects of overflows on the quality of the Bay water,
water quality objectives must first be established. In this study, the
objectives adopted by the San Francisco Bay Regional Water Quality
Control Board were used except where they were deficient in numerical
limits. These objectives were part of Resolution No. 67-30, "Water
Quality Control Policy-Tidal Waters Inland from Golden Gate," and will
be hereinafter referred to as the Regional Board Objectives (1). In
order to establish numerical limits, the objectives recommended by the
San Francisco Bay-Delta Water Quality Control Program (2) were used.
These objectives have been subsequently considered by the Regional
Board for adoption, but no action has been taken to date. These
objectives are hereinafter referred to as the Bay-Delta Objectives.
The objectives were evaluated to determine 1) which parameters could
be selected for use in assessing the effects of overflows, and 2) what
rational values could be used for the selected parameters. Three water
quality parameters were selected: dissolved oxygen (DO), floatable
materials, and coliform bacteria. These parameters are consistent with
the data gathering program of the study and can be used with available
data and evaluation procedures for making a reasonable assessment of
pollution effects. The selected objectives are given in Table 21. The
following discussion elaborates further on why these parameters were
selected (and why others were not) and describes the rationale used
in establishing numerical values.
THE REGIONAL BOARD AND BAY-DELTA OBJECTIVES
The excerpt below from Resolution No. 67-30 indicates the Regional
Board's awareness of the problem of overflows and indicates their
policy toward its solution.
This Regional Board has considered the discharge of untreated
sewage onto public streets and into waterways from overloaded
sanitary sewer systems during periods of rainfall the same as
any other sewage discharge as defined in the California Water
Code. The Regional Board has prescribed requirements or pro-
hibited these discharges on a case-by-case basis; however,
these problems have generally been given a lower priority
over other pollution problems because of their intermittent
nature (1) .
132
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TABLE 21
SELECTED WATER QUALITY OBJECTIVES FOR
EVALUATING EFFECTS OF OVERFLOWS
Parameter
(1) Dissolved oxygen
Unit
mg/L
Value
Minimum of 5.0
(2) Floatable materials
On water surfaces g/sq m Maximum of 0.02
On shore areas g/sq m Maximum of 0.3
(3) Total coliform bacteria MPN/100 ml Maximum of 1,000*
*In a 30-day period the total coliform MPN must not be greater than
1,000/100 ml more than 20 percent of the time. No samples are to
contain more than 10,000 coliform per 100 ml when verified by
another sample within 48 hours.
Sources: (1) and (3) Regional Board Objectives (Ref. 1).
(2) Bay-Delta Objectives (Ref. 2).
On the basis of the Regional Board statement, the determination of the
effects of overflows on the Bay waters may be made using the water
quality objectives normally used for continuous discharges. In the
past, this type of discharge has been given a lower priority because of
the more pressing problems of continuous discharge. At the present
time, however, consideration of requirements is imminent for both inter-
mittent discharges and overflows.
Table 22 lists the two sets of water quality objectives that were con-
sidered applicable for the East Bay waters. Column 1 lists the
Regional Board Objectives, which apply at the outer limit of the rising
waste plume or beyond a limited dilution area as determined by the
Regional Board on a case-by-case basis. If the dilution zone is small
in area, these objectives could apply to the water being discharged,
although their intent is for measurement of receiving water quality.
Several parameters are not quantified under the Board's present policy.
It would therefore be difficult to determine the adverse effects of
the pollutional matter discharged to the Bay using these parameters.
The only parameters with specific limits are DO, coliform bacteria,
and pH.
Column 2 summarizes the Bay-Delta Objectives, which were recommended
for Water Quality Zones 3 and 4 (hereafter referred to as Zones 3 and
4), shown on Figure 34.
More of the parameters listed under the Bay-Delta Objectives have
numerical limits. In addition, two new parameters--biostimulation and
relative toxicity—are introduced. Neither of these could be used
133
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TABLE 22
REGIONAL BOARD AND BAY-DELTA WATER QUALITY OBJECTIVES
APPLICABLE TO SAN FRANCISCO BAY VICINITY OF EBMUD, SPECIAL DISTRICT NO. 1
Water Quality
Parameter
(1)
Regional Board Objectives
(2)
Bay-Delta Objectives
(Zones 3 and 4)
Dissolved oxygen
Minimum of 5 mg/L; when natural factors cause
lesser concentrations, then controllable water
quality factors shall not cause further re-
duction. . .
median > 7 . 5 = mg/L
95 percentile > 6.5 = mg/L
Floatable materials
None other than of natural causes.
Floatable materials shall not be present in
concentrations which cause interference with
identified beneficial uses, particularly esthetic
enjoyment and recreational uses. (Suggested
guide - Max. concentration of oil materials not
to exceed 0.02 g/sq m on water and 0.3 g/sq m
on shore areas).
Coliform bacteria
To meet Sees. 7957 and 7958, Title 17 of
California Administrative Code in designated
areas.*
median i 70 MPN/100 ml
95 percentile 5 230 MPN/100 ml
Biostimulants
Relative toxidity
Toxic materials
None present in concentrations deleterious
to beneficial uses; none at levels which
render aquatic life or wildlife unfit for
human consumption.**
Limit flows of primary or secondary effluents
to 1980 levels. Transport flows above projected
amounts from zone or provide-tertiary treatment
to remove 90 percent of the biostimulants with
discharge locally.***
40 ml/L****
Temperature
Turbidity
(Clarity or transparency)
See Appendix Table III-l.
No significant variation beyond present
natural background levels.**
See Appendix Table III-l.
Maintain present transparency pending studies
to evaluate the effects of changes on algal
populations and other organisms.
-------
Table 22 (concluded)
Color
Bottom deposits
Nutrients
Radioactivity
pH
Oil or materials of
petroleum origin
Odors
Pesticides
Methylene blue active
substances
No significant variation beyond present
natural background levels.**
None other than of natural causes.**
None causing deleterious or abnormal growths.
See Appendix Table III-l.
7.0 - 8.5
None floating in quantities sufficient to
cause an iridescence, or none suspended or
deposited on the substrate at any place.
None other than of natural causes at any place.
No pesticide or combination of pesticides shall
reach concentrations found to be deleterious to
fish or wildlife at any place.**
5 percentile s 7.5
95 percentile < 8.5
None objectionable which are man-induced
and/or controllable.
No quantitative objective - recommend that the
manufacture, sale and use of persistent
pesticides, particularly the chlorinated
hydrocarbons, be regulated to eliminate insofar
as possible their entry to the aquatic en-
vironment.
median *0.5 = mg/L
95 percentile < 0.75 = mg/L
*In a 30-day period the total coliform MPN must not be greater than 1,000 per 100 nil more than 20 percent of the time. No
samples are to contain more than 10,000 coliform per 100 ml when verified by another sample within 48 hours.
**The water quality objective will generally apply at the outer limit of the rising waste plume or beyond a limited dilution
area as determined by the Regional Board on a case-by-case basis.
***Design criteria pending studies to develop water quality objectives for biostimulation.
****Relative toxici.ty concentration calculated from amounts and locations of discharges assuming concentration of
discharged relative toxicity = 1,000 ml/L.
Sources:(1) San Francisco Bay Regional Water Quality Control Board, Resolution No. 67-30 (1967) and Resolution No. 69-6 (1969) .
(2) San Francisco Bay-Delta Water Quality Control Program, final report, preliminary edition, March 1969.
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Ul
CTv
RICHMOND-SAN RAFAEL BRIDGE
RICHMOND
EMERYVILLE
• PIEDMONT
OAKLAND
ALAMEDA
FIG. 34 WATER QUALITY ZONES
OF THE SAN FRANCISCO
BAY-DELTA AREA
SCALE IN MILES
SOURCE SAN FRANCISCO BAY REGIONAL WATER QUALITY CONTROL BOARD, DECEMBER 1968
-------
because they were developed and recommended after the initiation of
this study and adequate data were not accumulated. Nevertheless, they
will be defined and discussed in this section.
For this study, the water quality objectives for DO and coliform
bacteria were selected from the Regional Board Objectives, and the
objective for floatable materials was selected from the Bay-Delta
Objectives.
SELECTED PARAMETERS
DISSOLVED -OXYGEN
In Column 1 of Table 22 the Regional Board Objective for DO content
is listed as not less than 5 mg/L, whereas the Bay-Delta Objective
(Column 2) is for a median value of not less than 7.5 mg/L with a
95 percentile value of not less than 6.5 mg/L. Although the Bay-Delta
Objective appears to be substantially higher than the Regional Board
Objective, it seems to be more in line with the actual DO content of
the major water masses in the Bay. Therefore, the Bay-Delta Objective
is an attempt to establish and maintain the present DO level.
In reality, the two objectives may not be as different as they first
appear. The Bay-Delta Objective establishes a median value for DO
together with a lower limit, whereas the Regional Board Objective
establishes only a minimum value. Because most of the available data
provide mean values of DO rather than extreme values, the Bay-Delta
Objective is more applicable to this investigation.
The Regional Board Objective of a minimum of 5.0 mg/L DO was selected
for use in this study because it is actually in effect, whereas the
Bay-Delta Objective is only a recommendation at this time.
FLOATABLE MATERIALS
In the Bay-Delta Program it was assumed that the objectionable portions
of the floatable materials are related in some way to oil and grease.
Based on this assumption, the maximum concentration of oily material
was recommended not to exceed 0.02 gram per square meter on water
surfaces or 0.3 gram per square meter on shore or beach surfaces.
Obviously, not all floating materials contain grease or can be indicated
by measuring oil and grease. Also, very little data are available to
support this approach or to aid in its application. -However, because
oil and grease tend to aggregate other solid matter and form an objec-
tionable float or scum, this objective for floatable material seems to
be a reasonable approach. For this reason and because extensive data
on oil and grease were collected during this study, this objective was
selected for evaluating the pollutional effects of overflows.
137
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COLIFORM BACTERIA
The Regional Board Objective for coliform bacteria is based on total
coliform concentrations. The coliform test involved in this objective
is the presumptive test as described in Standard Methods (3). This ob-
jective for coliform presently meets the California Health Department
requirements for water contact sports (4).
The Bay-Delta Objective for coliform bacteria is based on fecal coli-
forms. The determination for fecal coliforms requires an additional
step beyond the standard presumptive test, involving incubation of
media innoculated from the positive tubes in the presumptive test for
24 to 48 hours at an elevated temperature, usually between 43 deg C
and 48 deg C (5). This objective meets the U.S. Public Health Service
criteria for shellfish harvesting areas (6).
Because all of the coliform analyses made as part of this investigation
were by the presumptive test, the Bay-Delta Objective could not be used.
Therefore, the Regional Board Objective will be used in this study as a
means of defining the effects on the Bay waters from overflows.
OTHER PARAMETERS
BIOSTIMULANTS
The term biostimulants is intended to encompass all of the nutrient
material that may be discharged to a receiving water. Nutrients are
those materials that increase the rate of eutrophication or aging of
the water mass. The concept of the term recognizes that eutrophication
is not the result of any single nutrient, such as phosphorus or nitro-
gen, but involves the combined effect of all nutrients, including those
trace elements necessary to sustain biological life and reproduction.
It was presented in the Bay-Delta Program report with an explanation of
limitations and the need for extensive study and definition. The
concept of biostimulation provides a means for assessing and comparing
the total relative amounts of biostimulants or nutrients discharged from
various sources in the future.
The recommended water quality limits set forth in Table 22 for bio-
stimulants in Water Quality Zones 3 and 4 require limiting flows of
primary or secondary effluents to 1980 levels. Therefore, biostimula-
tion resulting from overflows in the East Bay Area is assumed to be not
critical at this time, but it will become more critical as the projected
flow rates for 1980 are approached.
RELATIVE TOXICITY
The relative toxicity of a particular waste stream is defined as its
flow rate divided by the 48-hour median tolerance limit (TL ) expressed
as a fraction. (The TL is the concentration of a waste, expressed as
a percent or decimal fraction, which kills one-half of the test fish in
138
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the given exposure time). For example, if the effluent flow rate
from the EBMUD Water Pollution Control Plant averaged 70 mgd and
had a TLm of 66 percent, the relative toxicity would be 106 mgd
(70 mgd/0.66 = 106 mgd). Thus, the parameter takes into account both
the amount and toxic strength of the waste. The Bay-Delta Program
report states:
Field studies have demonstrated a relationship between the
calculated concentrations of relative toxicity in the
southern region of the Bay and the observed effects on the
benthos (bottom animals). These studies show that an
adverse effect is discernible when the ratio of dilution
water to relative toxicity is less than 25 to one (40
milliliters of relative toxicity per liter of dilution
water). The benthos must be considered as a critical
ecological element since these animals represent 85 per-
cent of the total protein in the San Francisco Bay
waters. They are an integral and necessary part of the
food chain of fish and it is almost certain that any
conditions adverse to benthic biota will also harm fish (2).
Relative toxicity represents a new approach to evaluating the effects of
waste waters, and substantial research effort will be required to define
more precisely the causes and effects. In addition, more information is
needed on the dispersion patterns of waste discharges so that areas of
effect can be delineated. When more information is known in the future,
it is probable that relative toxicity will be used extensively as a
measure of adverse effects of waste discharges.
MISCELLANEOUS
Several other water quality parameters were considered for evaluating
the effects of overflows on the Bay, including temperature, pH,
methylene blue active substances, pesticides, odors, color, and bottom
deposits. Either because of the limited state of knowledge, lack of
quantitative values, or lack of available data, these water quality
parameters could not be used. It should be noted, however, that on
February 13, 1969, the Regional Board adopted specific numerical
temperature objectives for the water quality zones inland from the
Golden Gate (Resolution No. 69-6). These temperature objectives,
presented in Appendix Table III-l, supersede those adopted as part^of
Resolution No. 67-30. They recognize both a seasonal and geographical
variation in temperature levels and do not apply to tide flats or other
very shallow portions of the system. The waters in these areas may be
naturally warmer than the main water masses.
It is interesting to note the temperature data taken by EBMUD from
their north and south interceptors during the months of January,
February, and March 1969, when substantial amounts of the season's
rain fell. The minimum temperatures were substantially lower than
those recorded during the other months of the year. The average
139
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combined minimum temperature for these three months was approximately
57 deg F, which is only slightly higher than the 95 percentile temper-
ature limit of 56 deg F for Water Quality Zone 3. Therefore, tempera-
ture should not be a controlling parameter although overflows occur
along the shoreline where minimum dilution is provided.
140
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SECTION 9
EVALUATION OF EFFECTS OF OVERFLOWS ON SAN FRANCISCO BAY
Page
Conclusions 142
Dissolved Oxygen 145
Background Dissolved Oxygen Levels 146
Estimates of Dissolved Oxygen Depression
Caused by Overflows 149
Mass of Organic Material Discharged 149
Dispersion Characteristics 151
Procedure for Computing Dissolved Oxygen
Depression 156
Computation of Dissolved Oxygen Depression 159
Floatable Materials 159
Background Grease Loading 161
Floatable Grease Emission During Dry Weather 161
Assimilative.Capacity of the Receiving Waters 162
Estimates of Quantity, Duration, and Areal Distribution
of Grease from Overflows 166
Coliform Bacteria 168
Bacterial Die-Away 169
Bactericidal Action 169
Sedimentation 170
Dilution 171
Background Coliform Bacteria 171
Estimates of the Effects of Overflows on Coliform Counts 173
141
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SECTION 9
EVALUATION OF EFFECTS OF OVERFLOWS ON SAN FRANCISCO BAY
This section is devoted to an evaluation of the effect of overflows on
each of three selected water quality objectives. For this purpose,
pollution will be assumed to exist if the computed values of the water
quality parameters exceed the selected water quality objectives.
It should be understood that an extensive sampling of the Bay to deter-
mine the background quality and to determine the effects of overflows
accurately was beyond the scope of this investigation. The intent of
this section is to provide an order-of-magnitude type of analysis by
using existing available data, together with procedures supported by
previous work reported in the literature. Results and findings de-
veloped here are used in Sections 10 and 11 to evaluate the various
alternative solutions to overflows that are available.
A summary of the quantity and quality of overflows and their frequency
is presented in Table 23. This table includes the data that were de-
veloped in Sections 5 and 6 and that are used in the computations in
this section.
CONCLUSIONS
The evaluation produced the following significant conclusions:
• Results of the computations made on each of the three
selected parameters indicated that only floatable materials
and coliform bacteria exceed the selected objectives during
or just after overflows.
• Dissolved oxygen (DO) is the least affected of the three
parameters that were evaluated. Although the DO is depressed
by overflows, the combined effect of overflows and storm
sewer discharges is required to produce conditions that
violate the objectives. Available background DO data show
that this condition does occur during the rainy season, but
usually only within the months of January, February, or
March (see Figures 36 and 37).
• The duration or persistence of floatable materials in the
near-shore waters was found to be six and two days for
Zones 3 and 4, respectively. These time periods were based
on the time duration required for the floatable grease
concentrations to return to within 0.01 gram per square
meter of the selected objective which was 0.02 gram per
142
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TABLE 23
SUMMARY OF DATA USED TO
EVALUATE EFFECTS OF OVERFLOWS ON SAN FRANCISCO BAY
Item
Water Pollution
Zone 3 Zone 4 Control Plant Bypass
Quantity:
Number of storms per year
producing overflows and
bypasses
Volume of overflow or bypass
per storm, MG
Distribution of plant bypass,
percent
Quality:
BOD*, mg/L
Grease, mg/L
Coliform bacteria,
MPN/100 ml
11.5
62.5
50
370
105
11.5
28
50
105
21
3.7xl08 1.5xl07
11.5
68
135
40
*5-day Biochemical Oxygen Demand.
143
-------
square meter. The floatable materials were estimated to
affect 22 square miles of water surface area, considering
both Zones 3 and 4.
• Coliform bacteria discharged during overflows were found to
produce concentrations above the selected objective for
approximately 2.6 and 1.5 days after each overflow event
for Zones 3 and 4, respectively. Therefore, the objective
for coliform bacteria would be exceeded in the East Bay
waters as a direct result of overflows for about 23 days
per year. The computations considered only bacteria
discharged in numbers beyond those normally discharged during
dry weather. This was done because the background count in
the near-shore waters usually equals or slightly exceeds
the selected objectives. Persistence was based on the
time for the bacteria either to disperse in the Bay or to
die-away until their concentrations returned to within
10 MPN per 100 ml of the normal background counts. The
area of effect was assumed to be equal to that for floatable
materials.
• Coliform bacteria concentrations and their time of persis-
tence beyond the selected objectives would also be substan-
tially increased by storm sewer discharges. Although the
evaluation of storm sewer contributions is an important
consideration, it was assumed that their effects would be
lessened by implementing the recommendations of this report.
• From the preceding findings it was concluded that any
alternative solutions for alleviating the pollutional
problems by treating the extraneous flow prior to overflow
should be directed at reducing the grease and the coliform
bacteria. Because of the inherently high DO levels during
the rainy season of the year, organic material from
overflows alone will normally not depress the DO levels
below the selected objective.
Other pertinent conclusions are as follows:
1. Average DO levels are well above the minimum objective of
5.0 mg/L during the rainy season.
2. Localized and short-lived DO levels were noted to fall
below the minimum objective during the rainy season.
3. The low values of DO found during the rainy season were
considered to be the result of the combined effects of
overflows and storm sewer discharges.
144
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4. The background concentration of floatable materials in the
East Bay waters presently equals or slightly exceeds the
objective of 0.02 gram per square meter.
5. The allowable floatable grease emission was found to be
310 pounds per day into Zone 3 and 375 pounds per day
into Zone 4.
6. A relationship between grease concentration and percent of
floatable grease was derived from grease removal data in
the sedimentation basin at the plant.
7. From existing background coliform bacteria data, it was
found that the objective is presently exceeded in the
shoreline waters between Albany and North Alameda and
throughout the Oakland Inner Harbor but is being met along
the Bay side of Alameda.
8. The East Bay waters offshore from Albany, Berkeley, and
Emeryville normally meet the objective for coliform bacteria
and likely exceed it only because of a combination of over-
flows and storm sewer discharges during the rainy season.
9. The East Bay waters offshore from southern Alameda normally
meet the coliform objective. Again, the limitations are
similar to those waters offshore from Berkeley and Emeryville.
DISSOLVED OXYGEN
An adequate level of oxygen dissolved in water is necessary for pro-
tection of aquatic life. The fish are usually among the first to be
affected by a reduction in DO levels. Next are the smaller organisms
that provide the food supply for the fish. Lower oxygen levels may
result in a change in the type of bacterial population both in the
water and in the bottom sediments. At zero DO levels the anaerobic
organisms, which include such organisms as the methane bacteria, would
predominate. Fortunately, this condition, which is normally accom-
panied by the presence of gas bubbles at the surface of the water, has
not prevailed since the construction and operation of the interceptor
sewers and the water pollution control plant.
DO may be the oldest parameter used for measuring pollution in re-
ceiving waters. Reduced DO levels indicate the discharge of excessive
amounts of organic matter to the receiving waters. This causes the
bacterial population to increase and its combined metabolism to
exert a demand on the DO quantities in the water, resulting in a re-
duction of the oxygen resources. Similar effects can be noted in the
Bay waters. For this reason, the DO objective, although set to protect
or enhance aquatic organisms, will be used as a measure of the allow-
able organic material that may be discharged to the Bay via overflows.
145
-------
Limited data are available for determining the background DO concen-
trations in the East Bay waters to which the overflows are added.
However, by using data collected during the 1963-64 "Comprehensive
Study of San Francisco Bay" made by the University of California (1),
and 1967-69 receiving waters data from EBMUD, an estimate of back-
ground levels was made. Dispersion data developed in the Bay Model
by the Corps of Engineers and BOD data collected during this investi-
gation were used to estimate the effects of overflows on the back-
ground DO levels. BOD measurements indicate the amount of oxygen
required to stabilize the organic material discharged, hence provide
a means for estimating the effect on the oxygen resources in the
receiving waters.
BACKGROUND DISSOLVED OXYGEN LEVELS
Because there is a background of organic and nutrient materials in
the Bay waters, a substantial population of algae is maintained at all
times. Algae and various other forms of chlorophyll-containing plank-
ton require the presence of sunlight to carry on their metabolic
processes. These organisms produce oxygen by photosynthesis during
the daylight hours but consume oxygen at night, thereby causing the
oxygen level in the receiving water to vary throughout the day.
Figure 35 shows the indicated diurnal variation of DO, derived from
data taken during the daylight portions of April 10 and 11, 1969, .near
Doolittle Bridge at the mouth of San Leandro Bay. The points shown
on this graph are the average values based on two days of sampling.
It may be seen that the DO levels were quite high, averaging 9.4 mg/L.
Using the water temperatures and chlorosity levels prevalent in that
area, the DO level at saturation was 9.0 mg/L; therefore, the average
DO content was approximately 7 percent above the saturation level.
Figure 35 indicates that there is a difference of approximately 2 mg/L
between the high and low DO values in the Bay waters. This variation
is significant and should be recognized in the conduct of Bay sampling
programs.
Figures 36 and 37 represent the variation in DO level for four
different locations in the East Bay waters during the 1968-69 fiscal
year. The mean DO in the EBMUD outfall area remained well above the
objective of 5.0 mg/L during the rainy season. The mean DO levels
along the south shore (Alameda) varied from a low of 6.1 up to a high
of 9.4 and down to 8.7 in that same period of time. It will be noted
from Figure 36 that the mean DO levels during the dry season are sub-
stantially below the selected objective DO. A similar occurrence ap-
pears on Figure 37 for the north shore stations (Emeryville and
Berkeley). This low DO level during the late summer season may be
attributable to three factors: higher salinity values, higher water
temperatures, and greater organic loading on the Bay resulting from
cannery discharges.
146
-------
II.0
10.0
9.0
MEAN D 0 9.4 MG/L
MEAN D 0 9.4 MG/L
SATURATION DO = 9.0 MG/L
CHLOROSITY I6.6G/L(CI~)
TEMPERATURE 12.0° C
I2M I 2 3 4 5 6 7 8 9 10 II I2N I 2 3 4 5 6 7 8 9 10
TIME, HOURS
o
Q
z
UJ
x
o
Q
UJ
>
o
to
Q -
8.0
I2M
FIG. 35 DIURNAL VARIATION OF DO, ENTRANCE TO
SAN LEANDRO BAY, APRIL 10 AND II, 1969
147
-------
10
CXI
UJ
o
LJ
o
CO
-AVG. D 0 - SOUTH SHORE
-WIN. DO - SOUTH SHORE
RAINY SEASON
D J F
MONTHS
N 0 J
MONTHS
FIG. 36 MONTHLY VARIATION IN DO
CONCENTRATION, EAST BAY AREA,
OUTFALL AND SOUTH SHORE, 1968-69
FIG. 37 MONTHLY VARIATION IN DO
CONCENTRATION, EAST BAY AREA,
EMERYVILLE AND NORTH SHORE, 1968-69
SOURCE: MONTHLY REPORTS, WATER POLLUTION CONTROL
CT NO. I, 1966- 1900
-------
Temperature and chlorosity vary throughout the year in a manner simi-
lar to that shown in Figure 38. Both of these curves were developed
by combining data collected during 1963-64 for the north and central
San Francisco Bay areas.
While discharges from canneries in the East Bay Area do affect the
DO levels, the canning season is concluded by the time the rainy season
starts, so cannery discharges should produce no effect on the receiving
waters to overshadow or compound the problem of overflows. The only
possibility would be an abnormally early rain from a high intensity
and substantially long duration storm.
It will be noted that the minimum DO levels are substantially below
the mean values during the rainy months of January and February. These
differences probably indicate the effect of intermittent discharging
of oxygen demanding materials to the Bay waters during these two
months.
ESTIMATES OF DISSOLVED OXYGEN DEPRESSION CAUSED BY OVERFLOWS
Will the organic material discharged by overflows alone cause a deple-
tion of the DO resources to a level below that prescribed by the water
quality objectives? To answer this question the following steps were
necessary:
1. The total mass of organic material (BOD) discharged to the
receiving water by overflows and bypasses was computed.
The BOD is then distributed throughout the receiving waters
by tidal action or dispersion.
2. The dispersion characteristics for the north shore and
south shore waters were defined.
3. The procedure was developed for equating biological decom-
position to DO depression.
4. DO depression was computed, considering both dispersion
and biological decomposition.
Mass of Organic Material Discharged
t
The concentration of BOD in the overflows and in the bypassed sewage
will be assumed equal to the BOD values measured during this investi-
gation at Pump Stations A and H and at the water pollution control
plant. As developed in Section 6, the average frequency of overflows
will be taken as 11.5 per year evenly spaced over the rainy season and
the amount of sewage discharged at each overflow occurrence will be
62.5 MG into the Oakland Inner Harbor, 28 MG into the north shore
waters, and 68 MG into the outfall dispersion area. This latter num-
ber is based on bypassing sewage at the rate of 168 mgd for a period
149
-------
20
O
o
15
UJ
or
tr
UJ
o.
5
UJ
10
TEMPERATURE
CHLOROSITY
20
,5
O
tr
o
10
o
J A SOND|JFM AM J
1963 1964
MONTH
FIG. 38 SEASONAL VARIATION OF TEMPERATURE
AND CHLOROSITY, NORTH AND CENTRAL AREAS,
SAN FRANCISCO BAY, 1963-64
SOURCE- COMPOSITE OF MEAN TEMPERATURES FOR CENTRAL AND NORTH SAN FRANCISCO BAY, STORRS,
ET AL ( I )
150
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of 9.6 hours at the plant via the outfall. It will be assumed, on the
basis of float studies made in the "1941 Sewage Report" (2) , that 50
percent of the bypassed flow would enter Zone 3 and 50 percent would
enter Zone 4. It will also be assumed that 30 percent of the BOD dis-
charged into each zone will enter the respective near-shore waters
and will effectively combine with the BOD discharged in the overflows.
This latter assumption is admittedly weak; however, the 30 percent
figure seems to be conservative and will serve to indicate the overall
effect of overflows and bypassing until more exact relationships can
be determined in the future by either mathematical modelling or tests
in the Bay Model.
Dispersion Characteristics
Dispersion data in the East Bay waters are limited to dye studies made
by the Corps of Engineers in the San Francisco Bay Model. A compre-
hensive study requiring dye release points at several locations
throughout the Bay Area was made for the U.S. Public Health Service (3).
Figures 39 and 40, taken from these studies, show dye dispersion con-
tours for releases near Government Island, Oakland Inner Harbor,
after one and three tidal cycles, respectively. In addition to these
two conditions, data were developed for up to 40 tidal cycles.
Figure 41 is a plot of dye concentration versus time at several
stations within the Oakland Inner Harbor and the San Leandro Bay
system. As seen on the plot, there is no distinct dispersion of the
dye from the Inner Harbor until almost ten cycles have elapsed. At that
point a definite dispersion rate seems to occur. Although there are
several points of overflow into Oakland Inner Harbor,- the fact that
there is no distinct dispersion for ten tidal cycles after the overflow
permits all discharges to be evaluated as a single discharge. Con-
sidering the Oakland Inner Harbor and San Leandro Bay as a single entity,
an average concentration was selected between the first and tenth
tidal cycles equal to 400 ppb per gram of dye released. The concentra-
tion of dye after ten cycles seems to follow the relationship:
C = 1.82 x 105 t~2'66 for values of t >_ 10
where C is in units of ppb/g.
This relationship, together with an allowance for decay, was used to
compute the concentration of BOD in the receiving water at any time
after the occurrence of an overflow within the Oakland Inner Harbor-
San Leandro Bay system.
The Bay Model studies do not include dye release for a point along the
north shore, so the dispersion characteristics had to be estimated.
Richmond was nearest the dye release point for which data were avail-
able. Within one tidal cycle, substantial dye reached the waters off-
shore from Berkeley and Emeryville. Figure 42 shows the dye concen-
trations after three tidal cycles. This figure is typical of the dye
151
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NOTES-
Ul
NJ
I CONTOURS REPRESENT DYE CONCENTRATIONS IN
PARTS PER BILLION PER GRAM OF DYE RELEASED
(PPB/G).
2. BASE TEST WAS CONDUCTED FOR PUBLIC HEALTH
SERVICE AND MARITIME ADMINISTRATION - AEC
FLUSHING STUDIES.
3. FRESH WATER INFLOW AT CHIPPS ISLAND = 16000 CFS.
DYE TRACER •
CONCENTRATION = 1000 PPM
VOLUME - 6 LITERS
QUANTITY = 6.0 GRAMS
LEGEND
x
X
X
INJECTION STATION
AUTOMATIC FLUOROMETER A
RECORDER
T-5 FEET BELOW WATER SURFACE
M- MIDDEPTH
B-5 FEET ABOVE CHANNEL
BOTTOM
FIG. 39 DYE DISPERSION CONTOURS AT HIGHER HIGH WATER SLACK , INJECTION AT
OAKLAND INNER HARBOR, END OF CYCLE I
SOURCE'• CORPS OF ENGINEERS , ( 31
-------
Ln
NOTES
I. CONTOURS REPRESENT DYE CONCENTRATIONS IN
PARTS PER BILLION PER GRAM OF DYE RELEASED
(PPB/G).
2. BASE TEST WAS CONDUCTED FOR PUBLIC HEALTH
SERVICE AND MARITIME ADMINISTRATION - AEC
FLUSHING STUDIES.
3. FRESH WATER INFLOW AT CHIPPS ISLAND = 16000 CFS.
DYE TRACER ••
CONCENTRATION = 1000 PPM
VOLUME = 6 LITERS
QUANTITY = 6.0 GRAMS
LEGEND
A r
x
X
X
INJECTION STATION
AUTOMATIC FLUOROMETER 8
RECORDER
T-5 FEET BELOW WATER SURFACE
M- MIDDEPTH
B-5 FEET ABOVE CHANNEL
BOTTOM
FIG. 40 DYE DISPERSION CONTOURS AT HIGHER HIGH WATER SLACK , INJECTION AT
OAKLAND INNER HARBOR, END OF CYCLE 3
SOURCE ' CORPS OF ENGINEERS , 1 3 )
-------
I 1 —I—
OAKLAND INNER HARBOR , NORTH OF GOVERNMENT ISLAND
ESTERN INLET TO SAN LEANDRO BAY
SOUTH END OF SAN LEANDRO BAY
AVG. C= 400 PPB/G. FOR 1
NORTH INLET TO
SAN LEANDRO BAY
10
4 5 6 7 8 9 10
TIME IN TIDAL CYCLES
20 30 40 50 60 70 8O 90 100
FIG. 41 ESTIMATED DISPERSION RELATIONSHIPS FOR POLLUTANTS
WITHIN OAKLAND INNER HARBOR AND SAN LEANDRO BAY
SOURCE. CORPS OF ENGINEERS (S)
154
-------
•S*41! iU \ \v
NOTES-'
I CONTOURS REPRESENT DYE CONCENTRATIONS IN
PARTS PER BILLION PER GRAM OF DYE RELEASED
(PPB/G).
2. BASE TEST WAS CONDUCTED FOR PUBLIC HEALTH
SERVICE AND MARITIME ADMINISTRATION - AEC
FLUSHING STUDIES.
3. FRESH WATER INFLOW AT CHIPPS ISLAND = 16000 CFS.
DYE TRACER :
CONCENTRATION = IOOO PPM
VOLUME = 6 LITERS
QUANTITY - 6.0 GRAMS
LEGEND
x
x
X
INJECTION STATION
AUTOMATIC FLUOROMETER B
RECORDER
T-5 FEET BELOW WATER SURFACE
M- MIDDEPTH
B-5 FEET ABOVE CHANNEL
BOTTOM
FIG. 42 DYE DISPERSION CONTOURS AT HIGHER HIGH WATER SLACK , INJECTION AT
PT. RICHMOND, END OF CYCLE 3
SOURCE: CORPS OF ENGINEERS, (3)
-------
concentration distribution over the next 37 cycles. The greatest con-
centration is seen near the shore, with the lesser concentrations toward
the deeper portions of the Bay, similar to what one would expect if
the dye had been released along the shoreline.
Figure 43 is a plot of dye concentrations at several points in the
north shore waters versus time. After reaching a point of maximum
concentration, it can be seen that lines drawn through the data points
were reasonably parallel, indicating a general trend in dispersion
rate. Because these data points represented only a small portion of
the dye actually released at Point Richmond, they could not represent
the actual concentration of dye if it had been released along the
Berkeley or Emeryville shoreline. However, if an initial concentration
could be established, the same rate of dispersion could be reasonably
used.
To compute the initial dye concentration that might occur if released
along the shoreline, it was assumed that the dye concentration at the
end of one tidal cycle would be zero at a point three miles from
shore (west end of Berkeley Pier) and would be maximum at the shore-
line. Hence, the average dye concentration would occur at a point
one and one-half miles offshore. Using the soundings presented on a
USC&GS map of the San Francisco entrance, the volume of water in the
prototype between the San Francisco-Oakland Bay Bridge on the south and
Point Isabel on the north and a width of three miles was found to be
Q
48 x 10 cubic feet. One cubic foot in the Bay Model is equal to
1 x 10 cubic feet in the prototype; therefore, the corresponding
volume of water in the model at this location would be 48 cubic feet
or 1,460 liters. Injecting one gram of dye would produce a concentra-
tion of 685 ppb per gram of dye in this volume. Therefore, the esti-
mated concentration of dye after one tidal cycle at a point located
one and one-half miles offshore would equal 685 ppb per gram of dye
released. Plotting this value on Figure 43 and drawing a line through
it with a slope equal to that of the lines drawn through the data
points previously plotted, yields the estimated dispersion rate for dye
if released along the Berkeley or Emeryville shoreline. The equation is:
C = 685 t"1-13 for values of t _> 1.0
where C is in units of ppb/g.
Because of the gross nature of the dispersion equation, no attempt
could be made to evaluate single or individual overflows. In this
zone the need to evaluate single overflows is not great, because the
major overflow does occur at a single point.
Procedure for Computing Dissolved Oxygen Depression
The equation for BOD concentration in the receiving water from over-
flows (considering dispersion only) was developed in the Bay Model
156
-------
ESTIMATED CONCENTRATION OF DYE
AFTER I TIDAL CYCLE AT A POINT
LOCATED I-/, MILES OFF SHORE
ESTIMATED DISPERSION RATE
BASED UPON DISPERSION OF DYE
DISCHARGED FROM PT. RICHMOND
PLOTS OF DISPERSION
DATA AT 3 POINTS
IN THE WATER OFFSHORE
FROM BERKELEY
(DYE DISCHARGED @ PT. RICHMOND)
40 50 60 70 80 90 100
TIME IN TIDAL CYCLES-AVERAGE
FIG. 43 ESTIMATED DISPERSION RELATIONSHIPS FOR POLLUTANTS
APPROXIMATELY I- '/2 MILES OFF THE EMERYVILLE,
BERKELEY, ALBANY SHORELINE
SOURCE CORPS OF ENGINEERS (3)
157
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studies (3) and is as follows:
LS = C (ppb/g) x 4.54 x 10~6 x BOD discharged
(1,000 Ibs)
where LS = BOD (5 day, 20 deg C), mg/L
C = dye concentration at the point in question,
ppb/g of dye released
4.54 x 10~6 = factor for converting model units to
prototype units
BOD discharged = 8.33 x overflow volume (MG) x BOD (mg/L).
To determine the total BOD concentration in the receiving waters, the
background BOD concentrations must be added to the above computed con-
centrations. Values of receiving water BOD in the outfall area during
1968-69 varied from less than 0.1 mg/L to 1.9 mg/L. Values for the
months of November through March were distinctively lower than those
for the other months of the year, averaging about 0.35 mg/L. For
purposes of these computations, a value of 0.5 mg/L of background BOD
was assumed.
Having the expression for evaluating dispersion on BOD concentrations
in the receiving water, the Streeter-Phelps equation may be used con-
currently to estimate the resulting oxygen depression:
k,L
D, = (10~klt-10~k2t) + D 10~k2t
t *-
where Dt = oxygen deficit at reference point at time t, mg/L
Da = initial DO deficit in the receiving water immediately
after mixing with the waste water, mg/L
La = ultimate first stage BOD, 1.46 x LS , mg/L
L5 = BOD (5 day, 20 deg C), mg/L as computed by
expression for dispersion
t = time, days after overflow
k-L = deoxygenation constant, 0.10 at 20 deg C, days"1
k2 = reaeration constant, 0.24 at 20 deg C, days"1
T = temperature, deg C.
158
-------
The Streeter-Phelps formulation assumes that BOD removal consists only
of aerobic biological degradation, and that reaeration is simply ab-
sorption of atmospheric oxygen. Also inherent in this equation is the
assumption that the rate of removal of oxygen by benthic demand and
plant respiration is equal to the rate of addition of oxygen by photo-
synthesis .
To be usable, the deoxygenation and reaeration constants, k-|_ and k2,
must be adjusted for temperature. This adjustment may be made using
the following equation:
kT = k2QaT-20.
It was assumed that the value of a is constant and is equal to 1.047
for the deoxygenation constant and 1.016 for the reaeration constant.
It should be noted that in the foregoing equation the value for La is
a variable. This variability takes place because dispersion occurs in
the receiving waters, hence reducing the BOD concentration with time.
However, if the value of La is recomputed for each time period,
using the dispersion relationships as determined above, the variability
can be accounted for.
Computation of Dissolved Oxygen Depression
To illustrate the magnitude of the oxygen deficit resulting from the
average overflows, a series of calculations was made for each of the
two water quality zones for the average overflow conditions. The
results are tabulated in Table 24. The typical conditions selected
for these computations are noted at the bottom of the table.
Table 24 indicates that organic materials discharged by overflows alone
do not normally cause depression of DO levels below those permitted by
the selected objective. This conclusion does not indicate that over-
flows, together with storm sewer discharges (during storms), will not
depress the oxygen levels below those recommended. In fact, Figure 37
shows that DO values below 5.0 mg/L occasionally occur during the
months of January, February, and March. Also, storms that are larger
than normal might produce unacceptable DO levels from overflows for a
short time, particularly near the shore in the immediate vicinity of
the discharges.
FLOATABLE MATERIALS
Floatable materials may consist of any substance or objects that will
float on the surface of the water. They may be derived from many
sources, including spilled motorboat fuel, bilge pumping, storm sewer
discharges, overflows, and sewage treatment plant effluents. Floating
materials are most objectionable when they are foreign to their sur-
roundings. For example, floating globules of grease or matrixes of
159
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TABLE 24
EFFECTS OF OVERFLOWS ON DISSOLVED OXYGEN
IN THE NEAR-SHORE WATERS OF WATER QUALITY ZONES 3 AND 4
Water Quality Zone 3
Time after beginning of
overflow and bypass, days 1 2 3 4 5 10
Initial DO deficit*, mg/L 0.50 0.50 0.50 0.50 0.50 0.50
Imposed DO deficit*, mg/L 0.37 0.28 0.22 0.18 0.14 0.06
Total DO deficit, mg/L 0.87 0.78 0.72 0.68 0.64 0.56
Saturation DO*, mg/L 9.50 9.50 9.50 9.50 9.50 9.50
Median DO, mg/L 8.63 8.72 8.78 8.82 8.86 8.94
Objective:
Minimum DO, mg/L 5.0 5.0 5.0 5.0 5.0 5.0
Water Quality Zone 4
Time, days 12345
Initial DO deficit*, mg/L 0.50 0.50 0.50 0.50 0.50
Imposed DO deficit*, mg/L 0.09 0.07 0.05 0.04 0.03
Total DO deficit, mg/L 0.59 0.57 0.55 0.54 0.53
Saturation DO*, m-/L 9.50 9.50 9.50 9.50 9.50
Median DO, mg/L 8.91 8.93 8.95 8.96 8.97
Objective:
Minimum DO, mg/L 5.0 5.0 5.0 5.0 5.0
*Computation based on chlorosity of 15 grams per liter and
temperature of 10.5 deg C.
160
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grease and other particulate matters are very objectionable in the
water environment. The presence of sticks, leaves, and other natural
detritus, although undesirable, is not nearly as objectionable as is
the presence of oil and grease (hereafter referred to as grease).
Because of this factor and because a measurable parameter was needed,
grease was selected as a measure of floatable materials. As discussed
previously, the water quality objective for floatable materials was
based on a measure of the mass of the floating grease in units of
grams per square meter.
Very few data are available to determine the background grease concen-
trations in the East Bay waters to which the grease from overflows is
added. Also, very few data are available to substantiate the selected
permissible, floatable emissions in the East Bay Area. However, by
using certain assumptions made in the Bay-Delta Program report, data
from the EBMUD Water Pollution Control Plant, and dispersion charac-
teristics developed in the Bay Model by the Corps of Engineers, esti-
mates were made of the background grease concentrations relative to
the water quality objectives and the increases in grease content
immediately after the occurrence of an overflow.
BACKGROUND GREASE LOADING
Grease normally entering the water pollution control plant is partly
removed in the sedimentation basins either by floating or by settling.
The grease and other materials that float to the surface, called scum,
are removed and disposed of by incineration. The grease that settles
is removed from the sedimentation basins together with the sludge and
pumped to the digesters where anaerobic digestion takes place. Not
all of the grease is broken down during the period of digestion;
therefore, grease is discharged to the outfall with the digested
sludge. The grease that is not removed in the sedimentation basins
together with that from the digesters, passes to the outfall and is
discharged to the receiving waters.
Floatable Grease Emission During Dry Weather
Between 1960 and 1967, the average grease concentration in the effluent*
from the sedimentation basins was 32.9 mg/L and the average flow through
the plant was recorded as 74.6 mgd. Therefore, 20,500 pounds per day
of grease were discharged to the receiving waters after passing through
the sedimentation basins. Furthermore, during this period, an average
of 3.00 MG per month of digested sludge with a grease content of 0.5
percent was discharged to the outfall. This additional discharge of
grease averaged 4,100 pounds per day. Thus, the total amount of grease
discharged to the receiving waters from the plant averaged 24,600
pounds per day, and the average concentration of grease in the effluent
was 39.5 mg/L, based on an average flow rate of 74.6 mgd.
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Obviously, not all of the grease that is discharged to the receiving
waters—either in raw sewage from overflows or from the water pollution
control plant—rises to the surface as floating material. To provide a
means for estimating the fraction of discharged grease that will appear
as floating material, an analysis was made of the influent grease con-
centrations versus removal in the sedimentation basins, together with
an analysis of the fraction of grease removed in the form of scum.
The results are shown graphically on Figure 44.
The data consist of monthly averages for raw sewage, settled sewage,
weight of scum removed, and percent of grease in the scum. Because
the data were somewhat erratic, they were grouped into ranges based on
raw influent concentrations, and the average values from these ranges
were plotted on Figure 44. Curve A describes the overall removal of
influent grease in the sedimentation basins. Curve B indicates the
fraction (in percent) of the grease that was removed in the sedimen-
tation basins (Curve A) where it appeared as scum or as floatable
material. Curve C is the product of Curves A and B so that the percent
of raw grease that will float could be read directly. The data seem
to indicate that for influent grease concentrations below 30 to 40 mg/L,
the majority of grease is removed by floating. Concentrations of in-
fluent grease above 40 mg/L tend to be removed by a combination of
settling and flotation, with settling predominating in ranges above
60 mg/L.
In order to estimate the amount of floatable grease discharged to the
Bay each day, it was assumed that the grease in the plant discharge
would settle or float in a manner similar to that of the influent
grease depicted in Figure 44. However, certain limiting assumptions
were also made. First, only the grease that would be discharged with
the digested sludge would react in the manner described in Figure 44.
The grease in the sedimentation basin effluent would remain in the
suspended state. Second, because salt water is conducive to congealing
grease, the percentages of floatable grease indicated by Figure 44
should be increased by 50 percent.
The average concentration of grease in the plant effluent attributable
to digested sludge is 6.6 mg/L. Using the nearest influent oil con-
centration on Figure 44, 10 mg/L, the probable proportion of grease
discharged that would rise as floatable matter would be about 18 per-
cent. Increasing this figure by 50 percent, and applying that to
the mass of grease discharged, indicated a floatable grease emission
of 1,100 pounds per day (0.18 x 1.50 x 4,100).
Assimilative Capacity of the Receiving Waters
Does a discharge of 1,100 pounds per day of floatable grease exceed the
water quality objective established for floatable materials? To
answer this question, it was necessary to define the assimilative
capacity of the receiving waters.
162
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A. INFLUENT
GREASE REMOVED AS
SCUM AND SLUDGE
B. FRACTION OF GREASE REMOVED AS SCUM
C. INFLUENT GREASE
REMOVED AS SCUM
ONLY (AxB =
20 30 40 50 60 70 8090100
3 4 5 6789 10
GREASE REMOVED, %
FIG. 44 GREASE REMOVED BY PRIMARY TREATMENT
VERSUS INFLUENT GREASE CONCENTRATION
SOURCE BASIC DATA FROM E6MUD, SPECIAL DISTRICT NO I WATER POLLUTION CONTROL PLANT ANNUAL REPORTS, 1960-1968
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In the Bay-Delta Program report, the principal removal mechanism for
grease was assumed to be biological oxidation, occurring on the shore-
line between the mean low water and mean high water and in the one-half
mile of water nearest the shore. It was also assumed that the rate of
removal, both from the water and the shore, is 3.5 percent per day.
This rate was based on studies of biological oxidation of motor oils in
water at a temperature of 10 deg C.
The second removal mechanism was assumed to be the net daily tidal ex-
change. Between 15 and 20 percent of the tidal prism in San Francisco
Bay was estimated to be replaced by new ocean water during each tidal
cycle. This is the single most important mechanism by which pollu-
tants are ultimately removed from the Bay.
These two mechanisms were used to estimate the allowable grease load
on the receiving waters during dry weather conditions.
On the basis of the previously mentioned assumption that the pollu-
tional materials discharged in the vicinity of the EBMUD outfall would
disperse almost equally between the north and south directions, approx-
imately 550 pounds per day of floatable grease would be discharged
into the easterly portions of Zones 3 and 4.
Studies were also made for the "1941 Sewage Report" using free-floating
bottle floats. Of 54 bottle floats released in the vicinity of the
present outfall, 29 were recovered. About 90 percent of those found
in Zone 3 were along the shoreline of northern Alameda and the Oakland
Middle and Outer Harbors. Obviously, the direction and velocity of
the wind during the float studies played a very important role in their
distribution, probably more important than the tidal currents. About
65 percent of those floats recovered in Zone 4 were located along the
shoreline between Emeryville and Point Isabel; the others were located
in remote parts of the central San Francisco Bay.
From the results of these studies it was assumed that tidal currents
have a greater effect on floating material in Zone 4 than in Zone 3
when the material is discharged in the vicinity of the EBMUD outfall.
Therefore, it was assumed that 80 percent of the floatable material
discharged into Zone 3 and 60 percent of that discharged into Zone 4
from the outfall will reach the near-shore waters or shoreline.
Considering only that portion of the East Bay waters lying within
Zone 3 (south of the San Francisco-Oakland Bay Bridge), the shoreline
available for accumulation of floating materials was estimated to be
20,000 meters in length. Assuming this shoreline is basically three
meters in width plus the large areas (mud flats) that are exposed during
low tidal conditions, the estimated shore area available for accumula-
tion of grease and its biological oxidation is approximately 6.7 million
square meters. This amount includes the mud flats within San Leandro
Bay and along the northerly line of Bay Farm Island and the Bay side of
Alameda.
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Using a projected length of the shoreline and a one-half-mile width of
water surface, the water surface area available for assimilation and
oxidation of grease was estimated to be 13.6 million square meters.
Applying an areal loading of 0.02 gram per square meter on the water
surface and 0.3 gram per square meter on the shore between mean high
water and mean low water, a maximum allowable accumulation of grease
is found to be 5,500 pounds. Assuming a decay rate of 3.5 percent per
day for grease on both surfaces together with a tidal exchange rate of
20 percent applied only to grease on the water surface, the maximum
allowable floatable grease emission into Zone 3 was found to be 310
pounds per day -
The actual floatable grease emission into the near-shore waters of
Zone 3 is about 140 percent of the allowable grease emission (0.80 x
550 x 100/310 = 140%).
Turning to Zone 4, a similar set of calculations was made to determine
the permissible load and the daily emission of floatable materials from
the East Bay system. Three assumptions were made for these calcula-
tions that were different from those in Zone 3: 1) the tidal exchange
rate was only 15 percent; 2) the near-shore waters were considered to
reach to the westerly end of the Berkeley Pier, or about three miles;
and 3) only 60 percent of the floatable materials discharged from the
EBMUD outfall would reach the near-shore areas. A lower value for
tidal exchange was assumed because more of the north shore area has
shallow water and mudflat exposure during low tides. Also, a definable
current pattern does not exist in these waters during the ebbing and
flooding of the tides.
Float studies made at the end of the Berkeley Pier in the "1941 Sewage
Report" showed that, from that point, there was very little movement
into or away from the shore during the various tidal positions. For
these reasons the near-shore waters were assumed to reach to the end
of the Berkeley Pier, or approximately three miles from the north
shoreline. The assumption regarding the accumulation of floatable
materials discharged in the vicinity of the EBMUD outfall was based on
the free-floating bottle study described previously.
On the basis of the above assumptions, the permissible floatable grease
emission into the East Bay portion of Zone 4 was 375 pounds per day.
The actual load was computed to be 330 pounds per day, which is 88 per-
cent of the permissible loading.
In the Bay-Delta study the overall comparison of present floatable
emissions and assimilative capacities for Zones 3 and 4 indicated that
the emissions (1965) were 212 percent of the acceptable discharges in
Zone 3 and 305 percent of the acceptable discharges in Zone 4. These
computations took into account both the eastern and western shores of
the zones and all of the major municipal and industrial waste dis-
chargers. It should be noted that floatable grease may also be con-
tributed to Zone 3 by the City of San Leandro, the Oro Loma Sanitary
165
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District, and the Hayward sewage treatment plants, and to Zone 4 by
the City of Richmond and the Stege Sanitary District sewage treatment
plants. To a much lesser degree, dischargers on the west side of the
Bay may also add to the floatable concentrations in the East Bay
waters. Of course, the reverse is also true. Having no better data
to substantiate assumptions, it will be assumed that the interchange
of floatable materials between the east and west shore dischargers is
equal and will not substantially change the floatable emissions com-
puted above.
The inherent assumption that other dischargers along the east shoreline
would have no effect on the floatable emissions in the near-shore
waters of EBMUD, Special District No. 1 may not be applicable. The
three dischargers located south of Bay Farm Island may not contribute
substantially to the problem because of the natural barrier provided
by Bay Farm Island and because the prevailing winds are toward shore,
tending to maintain the floatable materials within the one-half mile
zone.
This may not be the case in Zone 4 along the north shoreline. Dye
studies made in the Corps of Engineers' Bay Model indicate that pollu-
tants will be carried quickly from the vicinity of the Richmond out-
fall into the waters offshore from Albany, Berkeley, and Emeryville.
Also, the discharge from the Stege plant will tend to contribute
because it discharges directly into these waters. However, use of
this plant will soon be discontinued and the sewage will be pumped
into the EBMUD interceptor for disposal through their plant. There-
fore, it may be reasonable to assume that the floatable emissions and
accumulations in the waters along the north shore are presently equal
to the permissible levels of the water quality objective.
Although the floatable emission exceeds the permissible level in Zone 3,
substantial quantities of grease and related floatable materials are
not presently noticeable in these waters. Therefore, for purposes of
this investigation and for evaluating the effects of overflows on the
receiving waters, it will be assumed that the present grease concen-
trations in both Zones 3 and 4 are acceptable during dry weather, but
that grease discharged by overflows and bypasses during wet weather
will exceed the water quality objective.
ESTIMATES OF QUANTITY, DURATION, AND AREAL DISTRIBUTION
OF GREASE FROM OVERFLOWS
It was assumed that no grease would be discharged from the digesters
during periods of bypassing. Because the sedimentation basins are out
of service during bypassing, no sludge would be pumped to the digesters
and no supernatant or digested sludge would be displaced.
The weight of floatable grease discharged in Zone 4 was computed in a
way similar to that for Zone 3, except that only 60 percent of the
grease discharged from the plant entered the near-shore waters.
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Using the procedures outlined for floatable grease emissions during
dry weather, the quantity of materials discharged during an average
storm condition and expected to float was found to be 12,900 pounds
to Zone 3 and 4,600 pounds to Zone 4.
To compute the duration of time that grease concentrations would ex-
ceed 0.01 gram per square meter (greater than the objective for
floatable material), it was assumed that the grease would be removed by
both tidal exchange and biological oxidation. The tidal exchange
characteristics were assumed to be equal to those depicted on Figures
42 and 43, which show variations in dye concentrations measured in the
Bay Model versus time for both Zones 3 and 4. In Zone 3 the dye con-
centrations presented on Figure 41 apply only to areas within the
Oakland Inner Harbor and San Leandro Bay System. In Zone 4, the con-
centrations apply at points approximately one and one-half miles
offshore between Point Isabel and San Francisco-Oakland Bay Bridge. It
was also assumed that grease globules or particles would be distributed
throughout the water in a way similar to that portrayed by the dye
releases. The distributed grease would then float in quantities pro-
portional to the uniform grease concentration suggested by the dye
dispersion data. The floatable fraction would be determined from
Figure 44. It was further assumed that biological oxidation would
occur at a rate of 3.5 percent per day. These assumptions resulted in
the following general equation:
FT = G0 (C x 4.54 x 10~6) (0.305d) (l.SRf) (1.00 - 0.035)T
where FT = floating grease concentrations at time T, grams per
square meter
G = weight of grease discharged in 1,000 pounds
C = 400 ppb/g for Zone 3 for t<10
= 1.82 x 105 t~2'56ppb/g for Zone 3 for tXLO
= 685 t"1-13 ppb/g for Zone 4 for t>_l
d = depth of water at mean high water, feet
(approximately 12 feet)
Rf = ratio of floatable grease to total grease dis-
charged (read directly from Figure 44 for the
grease concentration in the overflow)
t = time, tidal cycles (approximately 2 per day)
T = time, days
4.54x10"^ = factor for converting model units to prototype units.
167
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From the above formulation, the areal grease concentrations resulting
from an average wet weather condition, as defined in Section 5, was
found to persist for a period of six days in Zone 3 and two days in
Zone 4. The area assumed to be affected by floating grease in Zone 3
is equal to the one-half mile of near-shore waters along a projection
of the south shore line, which is a total of 7.5 square miles. The
area affected by floating grease in Zone 4 is equal to the three-mile
width of near-shore waters between Point Isabel and the San Francisco-
Oakland Bay Bridge, which is a total of 14.5 square miles. Therefore,
the surface area of the East Bay waters that are adversely affected by
floatable materials is about 22 square miles (7.5 + 14.5).
The values of areal and temporal floatable grease distribution on the
receiving waters should be used, not with a high degree of certainty,
but rather with a realization of the nature and number of assumptions
necessary. Obviously, the computations could be improved substantially
by using a two-dimensional mathematical model for defining the disper-
sion from both inflows and outflows. Also, additional dye releases
could be made in the Bay Model to show the dispersion from the overflows
in Zone 4 and from the EBMUD outfall. Additional research is needed
to define the fraction of grease discharged that may be expected to
float, and also the rate of biological oxidation that may be expected
to occur in this environment.
COLIFORM BACTERIA
The main purpose of establishing a water quality objective for bacteria
in the receiving waters is to protect the recreational users of that
water from enteric diseases. The indicator organisms selected for
measuring the safety of the waters for recreational users has his-
torically been the coliform group of bacteria. The Standard Methods (4)
definition of this group suggests the test procedures necessary for
their identification:
The coliform group includes all of the aerobic and
facultative anaerobic, Gram-negative, nonspore-forming,
rod-shaped bacteria which ferment lactose with gas
formation within 48 hours at 35 deg C.
The greatest shortcoming of the coliform test is not that it will fail
to indicate a state of pollution, but rather that it may indicate
pollution where none exists. For this reason more definitive tests
are commonly being proposed for water quality objectives, but with each
degree of refinement, the cost of monitoring the water increases.
Because the usual testing procedure for the coliform group involves
multiple-tube fermentation procedures and not a direct enumeration of
organisms, a statistical procedure is commonly used for estimating the
number of coliform organisms that existed in the sample. This esti-
mated number of organisms or the most probable number is usually iden-
tified by the abbreviation MPN. It should be understood that this is
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merely an index to the number of coliform bacteria which, more probably
than any other number, would give the same results as a more direct
laboratory examination. It is not an actual enumeration of the coliform
bacteria in any given volume of sample.
Most of the data that were available for evaluating the effect of over-
flows on the coliform counts in the Bay were from the presumptive coli-
form test, with the exception of those made by the EBMUD Water Pollution
Control Plant Laboratory which were confirmed tests.
BACTERIAL DIE-AWAY
Coliform bacteria are living organisms and as such are subject to their
environmental conditions. Transferring them from the protected envi-
ronment of the host to a more antagonistic environment, such as that of
the Bay waters, will usually cause a substantial decay or die-away of
the organisms. Although several investigators have looked into the
mechanics of bacterial die-away in receiving waters, there still is no
simple and sure method for estimating the concentration of organisms
that will persist in receiving waters.
Bactericidal Action
In 1956 Orlob (5) summarized the literature that had been published.
The major mechanism of mortality seemed to be that of bactericidal ac-
tion or biological action in sea water. The general expression that
was presented for mathematically describing the die-away characteris-
tics was a first order equation established by Chick's Law (6) written
as follows:
Nt = N010~k(t~to)
where N = the number of surviving organisms after time t
N = the initial bacterial population at t = 0
t = the lag time between the discharge of bacteria into
the receiving water and the beginning of a definitive
die-away
k = die-away constant.
This equation should be used only for relatively short periods because
of a pronounced decline in mortality rate after about a 90 to 99 per-
cent mortality.
Orlob pointed out that lag time and die-away constant will vary sub-
stantially with temperature and the presence of varying amounts of nu-
trient materials. Other minor bacteriological factors that may be
present in the marine environment include predation by zooplankton,
salinity, sunlight, pressure, bacteriophage, and heat-labile bactericidal
169
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substances. For practical purposes it may be assumed that these fac-
tors operate universally in marine waters, hence may be combined into
the one single factor of die-away constant.
It was also noted that bacterial mortality in sea water is susceptible
to chlorination, pasteurization, and filtration, but its action is not
completely destroyed by any one of these treatments. It would seem
likely that the addition of chlorine would have the greatest effect on
those organisms with the least resistance and would result in discharg-
ing the most resistant organisms. For this reason the assumption will
be made in subsequent calculations that the die-away phase will be pre-
ceded by a lag time of 1.0 day when the effluent is chlorinated. The
lag time for unchlorinated discharges will be assumed to equal 0.3 day,
which is supported by the various results reported by the investigations
and summarized by Orlob.
Die-away constants found by Orlob for incubation temperatures similar
to those found in the East Bay waters and for the total coliform group
ranged from 0.69 up to 1.59 per day. Gunnerson (7), in his study of
existing outfalls in Santa Monica Bay, indicated a die-away constant of
1.35 per day. Vacarro (8) observed coefficients of mortality to be as
high as 1.25 per day. On the basis of these references, the value of
the die-away constant that will be used in this study to describe death
rates due to bactericidal action alone will be 1.25 per day.
The only component that could be identified separately was predation by
zooplankton. On the basis of work done by Ketchum, Ayers, and Vacarro
(9) together with reported zooplankton concentrations in the central
portion of San Francisco Bay of 8,530 per cubic meter, the k value
for predation only was computed to be 0.13 per day.
Sedimentation
Orlob concluded that substantial die-away rates may be contributed to
by sedimentation of organic materials with absorbed bacteria. He felt
that this mechanism would not contribute to die-away beyond a limited
zone of sedimentation. Gunnerson indicated that sedimentation is a
major cause of coliform disappearance from surface waters. The con-
siderable difference between coliform die-away rates in primary and
secondary effluent suggests sedimentation as the cause, and this seems
to be confirmed by later studies. Rittenberg (10) showed a progressive
sinking of the zone of maximum coliform density and maximum turbidities
as a sewage field moved away from an ocean outfall. However, Weiss (11)
showed that bacteria previously absorbed on silt particles were found
to be desorbed when placed in saline water, depending upon the type of
silt, size of particles, and the chloride concentration. In comparing
computed die-away rates to measured rates, Vacarro attributed the
greater die-away rate in the measured results to sedimentation for
which he had not accounted, based upon an accumulation of bacteria on
the bottom silts. He also concluded that the apparent die-away from
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sedimentation was more important than either dilution (in that case) or
predation, but much less important than bactericidal action.
The die-away constant for reduction due to sedimentation can be esti-
mated from the data presented by Vacarro to be 1.0 per day. However,
Gunnerson in the Santa Monica Bay study found k values can be as
high as 4.53 for primary effluent and 1.14 for secondary effluent. Be-
cause of the shallow water location of several of the discharges in the
East Bay and the relatively high tidal currents in the vicinity of some
of the discharges, it appeared that a die-away constant value similar
to that for secondary effluent would be both conservative and more
realistic. Therefore, the die-away constant value assigned to sedi-
mentation for this study will be 1.15 per day. Combining the die-away
constants for bactericidal action and for sedimentation results in an
overall constant of 2.40 per day.
Dilution
The initial dilution of the effluent and subsequent dispersion of coli-
form organisms throughout the Bay is a third major factor in total coli-
form die-away. In this study, the dilution and dispersion was computed
using the data from the Bay Model as described previously in this
section.
BACKGROUND COLIFORM BACTERIA
Three sources of data were used for determining the background coliform
concentrations in the East Bay waters: 1) the EBMUD Water Pollution
Control Plant, 2) the 1963-64 University of California study (1), and
3) miscellaneous data from the Regional Board. Unfortunately, most of
the available data were prepared prior to the time that EBMUD began
chlorinating its effluent. Prior to January 1968 the EBMUD plant
practiced prechlorination for odor control and some suppression of
coliforms. Since that time, both prechlorination for odor control and
postchlorination for bacterial reduction have been practiced.
Figure 45 is a probability plot of coliform concentrations in the
vicinity of the EBMUD outfall. The upper line represents the results
of coliform samples taken bimonthly during the 1963-64 study. The
sampling point was located approximately 4,000 feet north of the end
of the outfall. The lower line represents the data collected by the
EBMUD staff during the fiscal year 1968-69. Although more data were
available, only two sampling points are represented in the lower line
located approximately 3,000 feet north and south of the outfall, re-
spectively.
These two plots show the effect of postchlorination in the vicinity of
the outfall, because median coliform counts were reduced from an MPN of
9,000 per 100 ml down to an MPN of 400 per 100 ml. Looking at the lower
plot, the MPN value for which 80 percent of the values are lower is
slightly in excess of 1,000 per 100 ml. Therefore, the coliform counts
171
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IOO.OOO
90,000
80,000
70,000
60,000
50,000
40,000
100
80 85 90
95
98%
FIG. 45
IN THE
PERCENT EQUAL TO OR LESS THAN
PROBABILITY OF COLIFORM BACTERIA CONCENTRATION
VICINITY OF THE EBMUD OUTFALL BEFORE AND AFTER
POSTCHLORINATION (1963-64 AND 1968-69)
« SOURCE. BASIC DATA FROM STATION NO 3, CENTRAL SAN FRANCISCO BAY, STORRS , ET AL ( I )
* * SOURCE BASIC DATA FROM STATION NO. 8, EBMUD WATER POLLUTION CONTROL PLANT LABORATORY DATA
172
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in the vicinity of the outfall do not always meet the Regional Board's
objective for recreational waters.
It was noted in reviewing the available data that coliform counts in
the immediate vicinity of the outfall were often lower than those at
greater distances away. Conclusions are difficult to draw with reason-
able confidence, but these data do illustrate the impact of chlorina-
tion on the receiving waters.
Figure 46 shows a generalized map of the central part of San Francisco
Bay showing those areas that normally did not meet the coliform objec-
tive established for recreational waters before chlorination. This map,
based upon data taken in 1964-65, was made available by the Regional
Board and confirmed to a large degree by more recent background sampling
done by EBMUD. It may be seen that coliform counts along the shoreline
of Berkeley and Emeryville did not meet the coliform objective. However
the near-shore waters north and south of the Berkeley Pier were normally
within coliform limits. The waters along the south shore of Alameda
as well as waters for some distance away from shore normally meet the
coliform objective. Few data exist for waters within the Oakland Inner
Harbor and San Leandro Bay. However, from limited data developed by
EBMUD in 1965, it was concluded that these waters did not normally
meet the water quality objective.
Figure 47 is a probability plot of data developed during the 1963-64
Bay study at a point located approximately one and three-fourths miles
north of the Berkeley Pier and approximately three miles offshore. It
was assumed that data collected at this point were representative of
the entire area within that zone normally meeting the coliform objec-
tive. In this figure only about 70 percent of the samples fall within
the MPN limits of 1,000 per 100 ml, indicating that the water quality
objective is probably not met during only one or two months out of the
year. Reviewing the available data, both from the 1963-64 studies and
from EBMUD, the coliform counts are substantially greater for January
and February than for other months. This may indicate that the reason
occasional months do not meet the objective involves rainy season con-
ditions, namely overflows and storm drainage.
In general, it can be seen that the only waters along the shoreline
that presently meet the coliform objective for recreational waters are
those along the south shore of Alameda. The near-shore waters adjacent
to Alameda and Albany-Emeryville are normally within the objective.
The additional loading due to untreated discharges from sanitary sewers
and storm drains may be the reason for periodically exceeding the ob-
jective. All other waters do not normally meet the water quality ob-
jective.
ESTIMATES OF THE EFFECTS OF OVERFLOWS ON COLIFORM COUNTS
As indicated in the preceding paragraphs, the water quality objective
for coliforms is presently being met in portions of the offshore waters
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LEGEND
WATERS NORMALLY MEETING
COLIFORM OBJECTIVES
WATERS NOT MEETING
COLIFORM OBJECTIVES
FIG. 46 AREAS OF SAN FRANCISCO BAY THAT NORMALLY DID NOT MEET
THE SELECTED COLIFORM OBJECTIVES BEFORE CHLORINATION
SOURCE BASIC DATA FROM REGIONAL WATER POLLUTION CONTROL BOARD, 1964-1965
174
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_J
s
o
o
0.
z
(E
UJ
H
U
ffi
cr
o
o
o
10000
9000
8000
7000
6000
5000
4000
3000
2000
1000
900
800
700
600
500
400
300
20C
i
100
90
80
70
60
50
40
30
20
10
_L
2% b 10 15 20 30 40 50 60 70 80 90 95 98%
PERCENT EQUAL TO OR LESS THAN
FIG.47 PROBABILITY OF COLIFORM BACTERIA CONCENTRATION
APPROXIMATELY 3 MILES OFF THE EMERYVILLE, BERKELEY,
ALBANY SHORELINE, 1963-64
SOURCE: BASIC DATA FROM STATION NO. 2 , NORTH SAN FRANCISCO BAY, STORRS, ET AL (I)
175
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in the East Bay, except during one or two months of the year. These
are believed to be the months during the peak of the rainy season,
namely January and February. The question, then, is whether or not
elimination of overflows would result in the offshore waters meeting
the coliform objective during all 12 months of the year. Unfortunately,
this question cannot be answered directly and with great assurance be-
cause of the many environmental factors involved.
The large quantities of storm drainage that occur simultaneously with
overflows contribute large numbers of coliforms. Also, the persistence
of coliforms during these periods of high turbidity and turbulence in
the Bay cannot be predicted with assurance. The die-away rate of bac-
teria is subject to available organic material in the water needed for
metabolism, together with the advective of large volumes of relatively
fresh water into the near-shore Bay waters, possibly altering the nor-
mal bactericidal effects. However, using the normal die-away equation
and die-away constants for bactericidal effects and sedimentation, to-
gether with the dispersion characteristics defined in the discussion
on dissolved oxygen, estimates were made for the number of coliforms
discharged to the receiving waters and the time necessary for the coli-
form counts to return to less than 10 per 100 ml above the normal back-
ground counts.
Because prechlorination and postchlorination are continued at the plant
during periods when flow is bypassed around the sedimentation basins,
and because the volume of water bypassed during a storm is normally not
more than twice the average daily discharge, the overall increase in
coliform discharge to the Bay during bypassing would be less than a
factor of ten. Therefore, in computing the coliform counts in the
receiving waters resulting from overflows, the additional coliform dis-
charged through the outfall will be disregarded.
Estimates for coliform concentrations discharged via overflows to re-
ceiving waters were based upon samples taken at Pump Station A and
Pump station H. This was done because samples at the EBMUD main plant
were taken after prechlorination and therefore did not indicate actual
coliform concentrations in the overflows. The coliform concentrations
found for each zone were:
Zone 3: 3.7 x 108 MPN/100 ml
Zone 4: 1.5 x 107 MPN/100 ml.
Using the data developed in Section 5 for the average number and
volume of overflows per year (11.5, producing an overflow of 62.5 MG
in Zone 3 and 28 MG in Zone 4), the MPN of coliform discharged per
overflow was estimated as:
Zone 3: MPN = 87.5 x 1016 coliform organisms per overflow
Zone 4: MPN = 15.9 x 1015.
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Distributing the coliforms in the volumes of near-shore waters, respec-
tively, the average concentrations were found to be:
Zone 3: NQ = 31.0 x 105 MPN per 100 ml
Zone 4: NQ = 11.7 x 103 MPN per 100 ml.
The following equations were then used to estimate the time required
before coliform counts returned to normal:
Zone 3: Nt = N010~2'4(t"°-3) , for values of t less than 5 days
Zone 4: Nt = N 10~2'4(t~°-3> (2t)"1-13
where Nfc = coliform concentrations at time t, MPN/100 ml
NQ = coliform concentrations at time t = 0, MPN/100 ml
t = time, days.
From these equations it was found that coliform counts contributed from
overflows would be reduced to below an MPN of 10 per 100 ml in about
2.6 days in Zone 3 and 1.5 days in Zone 4. Based on the occurrence of
11 or 12 overflows per year, the East Bay waters would exceed the coli-
form objective for about 23 days per year (2 x 11.5).
It should be noted that the above computations were made for the average
number of overflows per year and the average volume for each overflow.
No accounting was made for extreme conditions, such as those that oc-
curred during the 1968-69 rainy season. Obviously, the rain does not
occur each year at equal intervals throughout the rainy season. A dis-
proportionate number of storms will occur during the two months of
January and February, resulting in greater numbers of overflows during
these two months. It was therefore concluded that overflows contribute
substantially to the high coliform counts normally found in the re-
ceiving waters during the months of January and February.
It would be difficult to conclude that elimination or disinfection of
overflows would result in coliform counts lower than the water quality
objective in the two near-shore areas, because storm sewer discharges
also contribute large numbers of bacteria during the rainy season.
However, the results of a bacteriological investigation of separate
storm and sanitary sewer discharges by Burm and Vaughan (12) indicate
that discharges from combined sewers (similar to sewage overflows) will
contain about ten times more coliforms than discharges from storm
sewers. Furthermore, the fecal coliform concentration in combined
sewage will approach that of the total coliforms, whereas in storm
flows the fecal coliforms seldom exceed 20 percent of the total
coliforms.
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Assuming that storm flow volumes from storm sewers in the East Bay Area
exceed those from overflowing sanitary sewers by a ratio of five to one,
the results of the preceding study suggest that overflows will contrib-
ute twice as many coliforms as will storm sewers. Almost ten times
more fecal coliforms could be contributed by overflows than by storm
sewer discharges. Also, overflows are known to contain fecal matter of
human origin, whereas storm sewer discharges contain wastes that are
primarily of non-human origin. Therefore, elimination or disinfection
of sewage overflows is recommended, although storm sewer discharges
would continue without disinfection.
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SECTION 10
REVIEW OF POSSIBLE COMPONENT SOLUTIONS
TO THE PROBLEMS OF OVERFLOWS AMD BYPASSES
Component Solutions Presented in the Literature 180
Reduce Infiltration to Control Overflows 181
Disconnect Direct Connections 181
Inspect and Repair Faulty Sewers 182
Improve Hydraulic Design to Control Overflows 183
Sewer Modifications 183
Holding Facilities 185
Provide for Treatment for Overflows 186
Flow Separation Devices 186
Conventional Treatment Devices 187
Additional Component Solutions 188
Revisions and Additions to the Water
Pollution Control Plant 188
Improved Sewer Design and Construction Practices 189
Application of Multipurpose Concepts 192
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SECTION 10
REVIEW OF POSSIBLE COMPONENT SOLUTIONS
TO THE PROBLEMS OF OVERFLOWS AND BYPASSES
The problems resulting from storm water infiltration that have been
described in this study may be summarized in the order of their impor-
tance as follows:
1. Pollution of San Francisco Bay caused by discharging
floatable grease and large numbers of coliform bacteria
via sanitary sewer overflows (intersystem and system)
and water pollution control plant bypasses.
2. Operational problems at the water pollution control
plant resulting from large quantities of grease, sand,
and silt carried by extraneous flows. The deposition
of sand and silt is the main reason for plant bypassing.
3. Property damage, public health hazards, and general
nuisance caused by sewage overflowing (intrasystem
overflows) onto streets from sewer manholes and appur-
tenances within the sewer system. These problems
result from high flow rates that exceed the capacity
of the sewers.
As the study progressed it became apparent that no single solution
would resolve all of these problems. Therefore, a series of possible
component solutions was developed from which combinations could be
selected and further evaluated for use in alleviating the problems in
the East Bay Area.
This section is devoted to a brief review of all of the possible com-
ponent solutions derived from 1) an extensive literature review and
2) observations made and ideas developed during this investigation.
Those component solutions that show promise for application to the
problems in the East Bay Area are evaluated further in Section 11.
COMPONENT SOLUTIONS PRESENTED IN THE LITERATURE
The many approaches found in a review of the literature for solving the
problems of excess wet weather flow fall into three general categories:
1) reduce infiltration to control overflows, 2) improve hydraulic de-
sign to control overflows, and 3) provide treatment for overflows.
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REDUCE INFILTRATION TO CONTROL OVERFLOWS
Storm water infiltration may occur from many different sources,
including:
1. Illicit connections.
a. roof leaders
b. basement drains (both pump and gravity)
c. foundation and window well drains
d. catchbasins and paved areas.
2. Submerged manhole covers.
3. Street catchbasins.
4. Groundwater or vadose water entering into broken or
damaged sewers.
The two main solutions found for reducing or eliminating these sources
were to 1) disconnect direct connections and 2) inspect and repair
faulty sewers.
Disconnect Direct Connections
The first phase of a program to disconnect direct connections involves
locating each direct connection, including illicit connections. This
process usually requires an intensive type of survey, several of which
were described in the literature. They ranged from house-to-house
visual observations to the use of various tracers including marked
objects, liquid dyes, and smoke testing. The results of these surveys
depend largely upon the sincerity and initiative of the individuals
involved.
The second phase of the program involves the actual disconnecting.
Where private property is concerned, a frequently used approach is to
submit a letter to the property owner that has been signed by the
mayor, or other individual of similar authority, requesting the correc-
tion of the illicit connection. The letter normally describes the
ordinance by which the request is made and stipulates a time limit
during which the disconnection is to be accomplished. Results obtained
from this kind of approach have been mixed. Some cities have had a
reasonable degree of success, while others, lacking cooperation from
their citizens, have had total failure.
Disconnections of direct connections found in public rights-of-way do
not involve the political ramifications associated with disconnections
on private property. There are many street drains or catchbasins
connected to sanitary sewers, although a storm sewer is available. The
disconnection of these catchbasins would substantially reduce the
quantity of storm water entering the sanitary sewers.
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From the experiences described in the literature it was concluded that
a successful program for disconnecting illicit sewer connections
involves:
1. Available funds and personnel.
2. Complete cooperation of the citizenry.
3. Persistency by the agency in charge of the sewer system.
From the experiences of several of the East Bay cities, it was concluded
that complete cooperation of the citizenry would be difficult to obtain.
Also, the topography is such that many houses were constructed with
basements, garages, and patios situated at elevations below the level
of the street, so it would be difficult to conform in every case to the
present city plumbing codes. These codes require that roof drains be
discharged onto splash blocks. Although these codes are sound, com-
plete conformance would present difficulties because water would flow
down the slope from one property onto the adjacent property, particular-
ly in the hilly areas. This situation would not be satisfactory.
Furthermore, as seen from the results of the mathematical flow routing
model (Section 5), the contribution from direct connections was found
to be less than that from infiltration through pipe walls and other
similar means, i.e., percolation.
In view of these considerations, embarking upon a program of completely
eliminating illicit or direct connections from private property would
not be a practical solution, although a selective program would be of
value. But a program should be undertaken to disconnect all catch-
basins from sanitary sewers that are located in public rights-of-way
and reconnect them to storm sewers.
Inspect and Repair Faulty Sewers
The procedures for sewer inspection and repair may be used on both new
and existing sewer systems. In a new sewer system, inspection pro-
cedures may provide the basis for accepting or rejecting new construc-
tion work. In an existing sewer system, they may be used to determine
the actual location of leakage and the extent to which repairs are re-
quired. Repairs may be necessary in either case, and their extent
would be defined during the inspection. For purposes of this discussion,
the use of sewer inspection and repair will be limited to existing
s ewe r sy s terns.
Sewer inspection techniques now include hydrostatic testing, smoke
testing, low pressure air testing, photography, and closed circuit tele-
vision. Each has advantages and disadvantages, and some are more
applicable to existing sewer systems than others. The determining
factor in the selection of the technique is whether or not it will pro-
vide the necessary information for making the sewer repairs. For in-
stance, if the pavement surface must be cut and the trench opened to
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expose the broken or damaged sewer, the location of the failure must be
known within close limits. Simple hydrostatic testing or smoke testing
procedures will not necessarily provide this kind of accuracy. Air
testing or closed circuit television, however, can easily provide the
detail required.
There are three generally accepted methods for repairing sewers:
1) excavate and replace, 2) internal sealing, and 3) external sealing.
The method finally selected for use will depend upon the condition of
the sewer as determined by the inspection or by the character of com-
plaint that may have been registered for that reach of sewer. Com-
plaints may result from street failures caused by soil leaching or
from flooding caused by debris accumulation at broken, offset joints.
The method selected will also depend on whether the repairs are made on
a "crisis" basis or on a properly scheduled program of repairs.
In many portions of the East Bay Area, the sewer systems are less than
25 years old. Their expected service life should be at least another
30 years. Therefore, the initiation of a total replacement program for
this category of sewer would not be logical. The City of Oakland has
initiated a 60-year replacement program for its sanitary sewer lines,
with the older, problem sewers scheduled for replacement first. Ob-
viously, this type of program will not provide an immediate solution
for infiltration problems, but it is the only ultimate approach to the
overall problem. Such a program would not be economically feasible if
it were accelerated to completion in a short period of time because of
the tremendous cost involved. Therefore, the judicious use of an in-
terim program of inspection and sewer sealing could provide a sub-
stantial reduction in infiltration in the very near future.
IMPROVE HYDRAULIC DESIGN TO CONTROL OVERFLOWS
Two general solutions were found in the literature for improving the
hydraulic capacity of the sewer system and thereby controlling inter-
system overflows: 1) sewer modifications and 2) holding facilities.
The objective is either to increase the capacity of the sewer so that
the entire combined flow can be contained, or to provide sufficient
storage capacity to dampen the peak flow so that overflowing would not
occur.
Sewer Modifications
These procedures include any special design, chemical addition, or
modification that would substantially increase the capacity of the sewer
system, thereby reducing the number and quantity of overflows. It
excludes any form of treatment for the water- The sewer modifications
considered were:
1. Reduce the friction factor by chemical addition.
2. Increase the sewer capacity at constrictions.
3. Construct relief sewers.
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4. Provide means for flow regulation.
5. Make use of natural system storage.
The addition of chemicals to reduce the friction factor in a sewer to
improve its capacity was recently investigated by The Western Company,
Richardson, Texas. This alternative should be considered as a solution
only for local problems. It would not seem practical to add chemicals
simultaneously in all areas of the sewer system because of the physical
limitations and the cost involved. Therefore, chemicals would be added
only at locations where major constructions occur, or where replacement
of a long reach of large sewer would otherwise be required. This al-
ternative, then, is very similar to enlarging the sewer at locations
where constrictions are present. However, the general concept of im-
proving the sewer capacity by either reducing friction or by enlarging
the pipe section to increase its capacity in a critical area is
definitely a possible solution to local problems.
Construction of relief sewers may be necessary in those areas where the
downstream capacity is inadequate to carry the combination of dry
weather flow and extraneous flow. Such a sewer may be either parallel
with the existing sewer or connected to a different sewer having a
greater capacity. Again, this alternative would be applicable to local
problems.
Flow regulation can be provided by installing either manually or auto-
matically operated regulating devices in the sewer system. These
devices help make use of the natural storage in the sewer system.
Obviously, the best application of this alternative would be where
sewers are large but do not flow full, except possibly at high flows
which occur infrequently. This additional storage capacity could be
utilized to reduce the peak of the discharge hydrograph. This procedure
is presently being used to some degree in the East Bay system. During
periods of high flow, as the capacity of the treatment facilities is
approached, various actions are taken to reduce the flow into the plant.
These may involve the closing of control gates or the stopping of
pumping stations which cause portions of the interceptor and adjacent
trunk sewers to fill to the overflow position. If flow to the plant
cannot be resumed because of a continuation of high extraneous flow,
then overflowing must take place.
Natural storage is the volume remaining within the sewer above that
required for dry weather flow. Regulation, mentioned above, is simply
the attempt to control and make full use of this natural storage. The
presence of constrictions in a sewer system inherently makes use of the
natural storage occurring upstream from that point. Of course, natural
storage can be used only if it is available. Because the problems under
consideration in this investigation involve an existing sewer system,
the natural storage has been previously established and is fixed.
Therefore, the available storage may or may not be in the most advan-
tageous locations within the system. Some authorities contend that
sewers should be initially overdesigned to provide additional storage
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capacity, inferring that the additional capacity is available at a
reasonably low cost. New sewer system design is not involved in this
investigation; therefore, a complicated and extensive system of flow
regulation, necessary to make use of the natural storage in the existing
sewer system, would not be a practicable solution.
Each of the above solutions is applicable in reducing the number of
overflows that occur locally within the sewer system. However, except
for flow regulation, these sewer modifications do not present a general
solution to the complex sewer system of the East Bay. Flow regulation
may be applicable to a problem of this magnitude but would be technic-
ally difficult to apply in this case. Moreover, seven different
jurisdictions are involved in the sewerage systems. Obtaining complete
agreement by all parties as to the facilities needed, the operational
requirements, and the financing would be difficult. Therefore, the
applicability of flow regulation would also be questionable for the
East Bay Area.
Holding Facilities
Holding facilities are devices designed to provide storage capacity
necessary for dampening the hydrograph peak. They provide a substan-
tial period of quiescence for the water, causing a natural separation
of settleable and floatable material. Any treatment of combined flow
obtained with these facilities would be incidental to the prime ob-
jective of dampening the peak flow rate. There are two types of holding
facilities: on-line and off-line.
On-line facilities are those which receive both dry weather and wet
weather flow. The advantage of an on-line holding basin is that
normally the hydraulic gradient can be maintained so that pumping of
either the overflow or the accumulated sludge would not be required.
The disadvantage is that it must be constructed along the existing
sewer and therefore land must be available. The land area requirement
is substantial and this limits its applications to those locations
where trunk sewers are constructed in relatively open areas.
Off-line holding facilities are those which do not receive flow during
dry weather; in other words, they are used only during wet weather
conditions. Off-line facilities have been used more commonly in the
United States than any other type of overflow control. The greatest
limitation to this alternative, as in the case of the on-line facilities,
is the land area requirement. Off-line holding basins may receive
overflow from the trunk sewer either by gravity or by pumping, and may
be built either above grade or below grade, depending on the soil and
geological conditions.
Thus, the application of holding facilities, either on-line or off-line,
will depend upon the availability of adequate land area. It appears
that land may be available in certain areas along the trunk sewers dis-
charging into the north interceptor and in areas along the most south-
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erly reach of the south intercepter. Although limited to these areas,
holding basins definitely represent an alternative solution to the
problem of overflows in the East Bay Area.
PROVIDE TREATMENT FOR OVERFLOWS^
Two general methods were presented in the literature for treatment of
overflows: 1) the use of flow separation devices and 2) the use of
conventional treatment devices.
Flow Separation Devices
Several types of flow separation devices have been designed and built
to remove pollutants from overflows. Most of these have been on-line
units. The use of such devices in the United States has been relatively
limited, but several have been under investigation in Great Britain.
These devices include:
1. Low side-weir overflow
2. Stilling pond overflow
3. Vortex with central overflow
4. High side-weir overflow with storage
5. Spiral flow separator and overflow
The advantage of the low side-weir, stilling pond, high side-weir, and
spiral flow separator overflow facilities is that pumping of either the
through-flow or the overflow would not be required if they have been
designed properly. Unless substantial elevation differentials are
available or unless upstream sewers can be surcharged several feet, the
vortex overflow may require pumping of either the overflow or the under-
flow. The low side-weir device was found to be less efficient than the
other devices, both from the hydraulic and the solids removal stand-
point. The results of solids removal studies reported for the stilling
pond design varied substantially. Certain variations in design pro-
duced improvements whereas others apparently did not, and the differen-
ces were difficult to explain.
The vortex with a central overflow is not satisfactory unless it is
designed with an appreciable storage capacity. The advantage of the
vortex unit with storage capacity is that the first flush from a short-
duration storm enters the storage chamber before overflowing begins.
This means that the greatest quantity of polluting material is collect-
ed and held in the vortex unit. This is an attractive characteristic
but one that can also be obtained with other devices.
The high side-weir overflow with storage capacity is also designed to
capture the first flush before overflowing occurs. This is accomplish-
ed by limited storage capacity provided either in a section downstream
from the overflow weirs or by increasing the height of the overflow
weirs. The dry weather flow normally passes through the unit via an
outlet at the downstream end of the storage chamber. During wet
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weather flow, this outlet acts as an orifice, permitting a portion of
the flow to continue along the sewer, forcing the remainder to overflow.
The performance of this type of unit has been found to be better than
the types discussed previously.
The spiral flow separator involves a channel with either a single or a
double curve. The channel section is designed so that the main flow
passes along the main channel and the overflow passes over the wall of
the channel, but the curve in the sewer causes solid material to settle
out in a quiescent zone produced along the inside of the bends. The
settled material is continuously removed by the flushing action devel-
oped by water being drawn off through slots located in the settling
zone. Because of the simplicity of the design and the results reported
in the literature for this device, it is a possible alternative in
those areas where partial treatment is necessary but large land areas
are not available.
It should, be noted that each of the preceding overflow devices was
designed specifically for the removal of settleable materials. In this
investigation, the problem of floatable materials is greater than the
problem of settleable solids. Each device, however, can be fitted with
scum boards or baffles that will tend to reduce the overflow of float-
ables. Unfortunately, the results reported from the little work done
along this line were not encouraging. The question of most concern is
whether the detention time is sufficient to permit the floatable
materials to rise to the surface before being swept over the weirs.
More experimental work is needed to fully answer this question. Also,
if flow separation devices were used and the underflow sent to the
treatment plant, the existing grit removal and handling facilities
would require additional study and modification..
The available evidence does not warrant recommending the use of flow
separation devices.
Conventional Treatment Devices
Very few of the conventional treatment methods have been applied to the
treatment of overflows in the past because dilution was considered to
be satisfactory. Another reason was the inherent cost in the treatment
of large intermittent volumes of combined sewage. The following list
of unit processes received attention as treatment methods for combined
sewage overflows.
1. Screening
2. Filtering
3. Flotation
4. Sedimentation
5. Disinfection
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6. Ponds
a. aerated lagoons
b. stabilization ponds
7. Flow through biological systems.
Physical conditions, such as availability of land in the East Bay Area,
limit further consideration to only four of these processes: screening,
flotation, sedimentation, and disinfection.
Fine screening, flotation, and sedimentation processes are being eval-
uated for other locations in the United States, under the sponsorship
of the FWQA. In most cases these evaluations are being made on com-
bined sewer systems that have waste discharge characteristics some-
what similar to those found in this study. Each of these methods is
applicable to removal of grease and floatable materials and should be
considered as a possible solution to problems in the East Bay Area.
However, past experiences with fine screening at the EBMUD Water
Pollution Control Plant indicated a problem of severe blinding because
of grease. Improvements in design and recent experience at other
installations have indicated that by proper design and selection of
equipment, screening can be considered as an applicable process.
Flotation processes have the added requirement of process control,
including recycle rates, recycle pressures, etc.
Disinfection of overflows is necessary to reduce the coliform counts
so that the receiving waters are maintained within the water quality
objectives or, at least, so that overflows are not the cause of the
objectives not being met. This, of course, would not account for
storm sewer discharges that also carry large quantities of coliform
bacteria.
ADDITIONAL COMPONENT SOLUTIONS
In addition to the component solutions described in the literature,
three other approaches were developed for application to the East Bay
Area conditions: 1) revisions and additions to the water pollution
control plant, 2) improved sewer design and construction practices,
and 3) application of multipurpose concepts.
REVISIONS AND ADDITIONS TO THE WATER POLLUTION CONTROL PLANT
None of the component solutions presented in the literature review in-
volving treatment of the overflows would reduce the quantity of
settleable material discharged to the water pollution control plant.
Each of those alternatives simply helps to reduce the pollutional
characteristics of the water discharged to the Bay, but in so doing
would discharge most of those pollutants to the existing treatment plant.
As discussed earlier in this report, one of the problems of the existing
plant during high extraneous flow is that of large quantities of sand
and silt settling in the sedimentation tanks. The sludge is deposited
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in such large quantities and at such high rates that the sludge collec-
tion equipment cannot cope with it and must be stopped before failure
occurs. To avoid mechanical failure, the flow heretofore has been by-
passed around the sedimentation tanks when the combined flow reaches
approximately 120 mgd.
As indicated in Section 6, prevention of bypassing at the water pollu-
tion control plant would prevent an annual discharge of 780 MG of an
essentially untreated combined sewage. This volume amounts to about
43 percent of all the combined sewage and extraneous flow discharged by
overflows and plant bypassing annually. However, this percentage is
not directly indicative of the relative effect of bypasses on the
pollutional problem, because of the dilution and dispersion produced by
discharging through the outfall to deep water. Correction of the
single problem of grit removal and handling would almost completely
eliminate bypassing, thereby ensuring primary treatment of a major
portion of the extraneous flows before it is discharged to the Bay.
If the settleable material, previously discharged to the Bay via over-
flows, is to be discharged to the plant, the total quantity of settle-
able material will be substantially increased during periods of over-
flow. If no additions or corrections were made at the plant, it would
follow that bypassing would be necessary at even lower rates than
before.
IMPROVED SEWER DESIGN AND CONSTRUCTION PRACTICES
A summary of suggested sewer design and construction procedures that
would contribute to reducing infiltration is presented in Table 25.
Many of the recommendations are applicable only to new sewer design
and construction, hence apply to projects in the East Bay Area involv-
ing extensive sewer replacement.
In addition to design practices, two problem areas were discussed in
which construction procedures should be reviewed with the aim of reduc-
ing infiltration: 1) inspection, and 2) administration. The inspection
problem involves a shortage of competent inspectors. During the peak
construction season, the Public Works Department often cannot provide
the number of inspectors necessary; therefore, inexperienced men may
be used who may sincerely conclude that certain work is satisfactory
although it does not completely meet the specifications. For this
reason, inexperienced personnel should be provided with sufficient
training to give them a better understanding of the requirements of
their position.
Administration problems involve contract administration and departmental
jurisdiction. Contract administration difficulties arise if a non-
technical governing board refuses to support the recommendations of
the technical staff. In such cases the bargaining position of the
technical staff is seriously impaired. Departmental jurisdiction
problems center around the question of which department is in charge of
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TABLE 25
SUMMARY OF SUGGESTED IMPROVEMENTS IN SEWER DESIGN
AND CONSTRUCTION PROCEDURES
Problem
Recommendation
Soils investigation
• Laying pipe on unstable soil, permitting excessive
movement of the pipe during compaction or in sub-
sequent long-term settlement.
• Inability to compact pipe beddinq because of
"pumninn action.'
• Unrealistically high compaction requirements,
causing excessive compactive efforts and
possible damage to pipe.
Selection of pipe materials
• Inability of pipe to withstand overburden of
trench backfill and/or live loads.
• Inability of pipe to resist chemical attack.
The subsurface investigation must be sufficiently comprehensive to
provide the design engineer with the necessary information to
prepare a safe, workable, and economical design. The investigation
should include information on:
1. The presence and location of rock.
2. The elevation of groundwater.
3. The nature of the soil relating to
a. compactive characteristics
b. stability of trench walls
c. bearing strength of subsoil.
Physical and chemical characteristics of pipe- materials should br
compatible with the physical, chemical, hydraulic, and economi'
requirements of the system.
Consider joint design availability when selecting pipe material.
Consider bedding and backfill materials when selecting pape
materials and strencrth classifications.
^election of pipe jointing materials
• Leakage, root intrusion, and cave-ins from
soil leaching.
• Failure of barrel if flexibility :.s not
available.
• The joint should be standard, with the pipe material specified;
be simple, requiring very little skill and time to make; and
give a positive indication when it is made and properly seated,
(for example, a tell-tale sound that indicates positive seating
or a mark that identifies proper insertion) .
• The completed joint should be tight and should offer reasonable
flexibility but must be capable of transmitting shear loads to
prevent offsetting at joints.
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TABLE 25 (concluded)
Problem
Recommendation
Selection of bedding materials
• Differential settlement under load
resulting in broken pipe.
Selection of details for appurtenances
a. Manholes
Use crushed stone with a gradation of 3/4- to 1/4-inch
(1.9- to 0.6-cm), ASTM No. 67. Do not use sand or smooth surface
gravel.
• Leakage at joints in the vertical
barrel sections.
• Leakage into manhole covers.
• Leakage caused by settling and breaking
of oipe at the manhole.
b. Mouse lateral connections
• Failures because of inadequate support
near the main sewer.
• Imnroper connections with the main sewer.
Preparation of plans and specifications
• Problems may be numerous and depend
comoletelv uoon the individual case.
• Use precast bases with rubber ring type joints for the barrel.
• Use covers with no vent holes and with pick holes located along
perimeter so that opening is closed by the seating surface of
the ring. Do not locate manhole at the bottom of a depression.
• Design connection piping with short, flexible jointed sections
adjacent to the manhole.
Use care in placing the backfill and use crushed stone
supporting base.
Use specially designed connections where stub is unavailable, for
example, the Shewer Tap System by Smith & Loveless.*
Provide sufficient detail on drawings to describe work required
without question. Specify sufficient authority to the inspectors
to permit control of the project.
*Mention of commercial products does not imply endorsement by Federal Water Quality Administration.
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controlling the connecting of house laterals to sewer mains. Neglect-
ing to define this area of jurisdiction promotes uncertainty between
the departments and may result in little if any control over the type
or quality of connections being made.
Miscellaneous construction procedures involve the correction of house
connections during the replacement or repair of main sewers. In
addition to replacing the house connection, a new alternative involving
a product called Cychem6, manufactured by the American Cyanamid Company,
may be available. Cychem is a new plastic pipe which may be drawn
into a house lateral or sewer in a deflated condition and then inflated
and cured in place. The lining would be a tough, glass-fiber reinforc-
ed polyester pipe and would be continuous from the building out to the
main sewer. This pipe could also be used to line the main sewer,
forming a single continuous piping system. Because of its continuous
nature it would minimize leakage and root intrusion. The simplicity of
installation and the result may outweigh the legal problems of main-
tenance responsibility; hence this alternative should not be overlooked.
APPLICATION OF MULTIPURPOSE CONCEPTS
The areas of the East Bay that offer sufficient land for the construc-
tion of holding basins are located along the waterfront and in publicly
held land, such as neighborhood parks. Except for the Albany area, the
land use along the waterfront zone is mainly industrial, heavy commer-
cial, and residential. The residential areas generally consist of
older dwelling units of stereotype construction. Most of the residents
are in lower-middle and lower income groups, and a high percentage are
in minority groups. If sufficient land area must be placed under public
jurisdiction for the purpose of constructing storm water holding tanks,
it would be desirable to incorporate aesthetically appealing landscap-
ing and possibly recreational facilities, such as playgrounds or tennis
courts. The added cost of landscaping or recreational facilities would
not be high from the standpoint of the project, but would substantially
increase the social acceptance and social value of the project. This
concept would, of course, be applicable only for holding tanks that
could be placed underground and that require sufficient land area to
make the site desirable for recreational activities. Also, the site
would have to be in or near a residential neighborhood. Any such
facilities designed and constructed within an industrial or commercial
area would probably be suitable only for such uses as public parking.
For either or both of the above reasons, it is desirable that better
arrangements for grit removal and handling be considered for the
existing water pollution control plant.
^Mention of commercial products does not imply endorsement by the
Federal Water Quality Administration.
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CONCLUSIONS
On the basis of the foregoing discussion, the following list of compon-
ent solutions could be effectively used to solve problems of overflows
and bypasses in the East Bay Area:
1. Improve the sewer system.
a. Complete the sewer separation program immediately.
b. Initiate a comprehensive program of sewer repair
and replacement.
c. Initiate a comprehensive program of sewer inspection
and sewer repair by sealing to reduce infiltration
and subsequent overflows.
d. Institute a program for locating and disconnecting all
street drains from the sanitary sewers.
e. Initiate a program for correcting local problems
produced by overflowing sewage, both through manhole
covers and intersystem overflows.
2. Provide new holding basins or overflow treatment facilities.
a. Provide either on-line or off-line holding facilities
to improve the hydraulic capacity of the sewer system
and thereby control overflows.
b. Provide treatment of the remaining overflows using one
or more of the following facilities together with
disinfection; 1) flotation, 2) sedimentation, and
3) screening.
3. Provide additions and revisions at the water pollution
control plant to eliminate the need for bypassing the
sedimentation facilities during wet weather flow.
4. Where needed, improve sewer design and construction practices
for extensive sewer replacement programs.
5. Consider application of multipurpose concepts for design
of holding or overflow treating facilities.
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SECTION 11
EVALUATION AND SELECTION OF ALTERNATIVE SOLUTIONS
Evaluation of Component Solutions
Improvements to the Sewer System
Complete Sewer Separation Program
Repair and Seal Remainder of Sewer System
Locate and Disconnect Catchbasins
Replace Selected Sections of Sewer to
Eliminate Bottlenecks
New Holding Basins and Overflow Treatment Facilities
New Holding Basins
Overflow Treatment Facilities
Dissolved Air Flotation
Fine Screens
Plain Sedimentation
Disinfection
Conclusion
Improvements to the Water Pollution Control Plant
Lengthen Existing Grit Chambers
Add New Grit Removal Facilities
Heavy-Duty Detritus Tanks
Aerated Grit Chambers
Modify Sedimentation Basins and Add Sludge
Handling Equipment
Selection of Alternative Combinations of Component Solutions
Time Schedule for Recommended Alternative
Miscellaneous Recommendations
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SECTION 11
EVALUATION AND SELECTION OF ALTERNATIVE SOLUTIONS
On the basis of the discussion in Section 10, the following categories
of component solutions will be further developed in this section, and
cost estimates will be presented so that comparisons can be made.
1. Improvements to the sewer system.
2. New holding basins or overflow treatment facilities.
3. Improvements to the water pollution control plant.
This evaluation will be followed by the selection of the most feasible
combination of component solutions and the development of a schedule
for implementing the recommended plan.
EVALUATION OF COMPONENT SOLUTIONS
IMPROVEMENTS TO THE SEWER SYSTEM
The estimated length of sanitary sewers in the study area is approxi-
mately 1,700 miles. This estimate was based on discussions with the
engineering departments of each of the six East Bay cities, and does
not include the interceptor sewer which is approximately 21 miles long.
In addition, the total length of house connections or building sewers
was estimated at 1,500 miles, based on an average length of 50 feet per
building and 156,600 buildings. As discussed previously, an estimated
4 percent of the area is presently served by combined sewers. There-
fore, approximately 68 miles of combined sewers still exist in the
study area, and most of these lie within the commercial-industrial
portion of the city of Oakland. The remainder are located in isolated
areas throughout most of the study area.
The estimated construction cost for each of the component sewer revisions
is shown in Table 26. No estimate was included for repairing or re-
placing house connection sewers. Even if all of the work outlined in
Table 26 were accomplished, there would still be substantial contribu-
tions of infiltration from roof leaders and house connections. However,
based on conclusions drawn in Section 6, the reduction in flow provided
by the sewer revisions would probably permit the sewers to handle the
increase in flow during wet weather.
The benefits of repairing all house connections to eliminate gross
infiltration completely may not presently be worth the cost, when it is
considered that the component sewer revisions are expected to eliminate
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TABLE 26
ESTIMATED CONSTRUCTION COST OF COMPONENT SEWER REVISIONS*
1. Complete sewer separation program
a. 12-in. diameter sewer, 68 miles @ $32.00 $11,500,000
per If, including repaving
b. Manholes @ 300 feet apart, 1,200 @ $750 900,000
c. Reconnect house connections, 12,000 @ $250 3,000,000
Subtotal $15,400,000
Contingencies (2 5%+_) 3,850,000
TOTAL $19,250,000
2. Repair and seal remainder of sewer system
a. Replace about 15 feet "per 300 feet of $13,750,000
sewer, 430,000 If @ $32.00
b. Clean, inspect, test, and pressure grout 8,600,000
seal (hilly areas only) 2,870,000 If @
$3.00/lf**
c. Clean, inspect, test, and pressure grout 24,700,000
seal (flat areas only) 5,740,000 If @
$4.30/lf***
Subtotal $47,050,000
Contingencies (25%+_) 11,750,000
TOTAL $58,800,000
3. Locate and disconnect catchbasins
a. 500 catchbasins @ $650 $ 315,000
Contingencies (25%+_) 85,000
TOTAL $ 400,000
4. Replace selected sections of sewer to
eliminate bottlenecks.
Note: Estimate based on extrapolation
of detailed estimate made for Drainage
Area No. 29.
Sewer improvements for Drainage Area No. 29 $ 215,000
Sewer improvements for remainder of study area
(42,000-1,000)/1,000 x $215,000 $ 8,800,000
Subtotal 9,015,000
Contingencies(25%+) 2,255,000
TOTAL $11,270,000
*Estimating prices based on late 1972 values (ENR Index S.F. = 1900)
**Based on an average sewer size of 8-in. diameter.
***Based on an average sewer size of 12-in. diameter.
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enough flow to alleviate the problem. The estimated cost for repairing
house connections by replacement with new pipe, using a cost per
connection of $500, was about $78,300,000 (156,600 x $500).
Complete Sewer Separation Program
The cost estimate for completing the sewer separation program that was
initiated as a result of the "1941 Sewage Report" was based on an
average pipe diameter of 12 inches. Presently the combined sewers
serving these areas are larger than 12 inches. However, with the
separation of the two flows, the sanitary sewer should be smaller than
the combined sewer. Also, the sewers in the commercial-industrial
area may range in size up to 18 inches, but the sewer revisions in the
isolated areas would likely require a size of eight inches. Manhole
spacing was assumed to be an average of 300 feet. Because the new
sewer is proposed to be the sanitary sewer, the present house connec-
tions would have to be either shortened or lengthened and connected to
the new sanitary sewer. A contingency factor of 25 percent was applied
to each estimate. The total cost estimate for completing the sewer
separation program was $19,250,000 based on construction costs in 1972
(ENR Index S.F. = 1900), the approximate mid-point of construction if a
program were started immediately. This estimate does not include ad-
ministration and engineering costs, which will be applied when the
combination of components are compared, nor does it include a cost for
traffic and business interference, as is normally the case.
Repair and Seal Remainder of Sewer System
The estimate for repairing and sealing the remainder of the sewer
system (96 percent) was based on the pressure grout sealing method.
The average sewer size was assumed to be eight inches; in the flatter
areas, it was assumed to be 12 inches. All of the sewers involved in
sealing would be cleaned and inspected. Because the sewers in most of
the areas are quite old, it was assumed that several joints of pipe
between each manhole reach would require replacing before sealing could
be effective. This amount was assumed to be 15 feet for every 300 feet
of sewer. It should be noted that the 15 feet of sewer would not
necessarily be consecutive sections, nor would each manhole reach require
sewer replacement. The cost for sealing was based on estimating prices
from a local sealing contractor. The total estimated cost for repair-
ing and sealing the remainder of the sewer system was $58,800,000.
Locate and Disconnect Catchbasins
The estimated cost for locating and disconnecting catchbasins that are
presently connected to sanitary sewers was intended to include only
those within a reasonable distance from a storm sewer. Catchbasins
that are presently located within the combined sewer areas are not
included in these figures, because it was assumed that the storm sewer
would be the "existing sewer" after construction of new sanitary sewers;
hence the catchbasins would already be connected to the proper sewer.
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The number of catchbasins to be disconnected was estimated on the basis
of counts made in a given area and then projected over the study area.
The accuracy of the number is questionable but was believed to be
indicative of actual conditions. The total estimated cost for dis-
connecting these catchbasins was $400,000.
Replace Selected Sections of Sewer to Eliminate Bottlenecks
Replacement of selected sections of the sewer system in order to
eliminate bottlenecks would first involve a careful investigation of
each drainage area to locate the problems. Such a study was made in
Drainage Area No. 29 as part of this investigation. In that area
several reaches of sewer required enlarging so that the peak flow could
pass through the pipe without surcharging and overflowing. These
revisions were estimated to cost $215,000. It was then assumed that
similar revisions would be necessary throughout the study area in con-
junction with the use of overflow treating facilities. Therefore, the
total estimated cost for replacing selected sections of sewer (usually
replaced with larger sizes) was derived by prorating on the basis of
relative areas; hence the total estimated cost was $11,270,000.
NEW HOLDING BASINS AND OVERFLOW TREATMENT FACILITIES
New Holding Basins
Holding basins are limited in application as component solutions to
infiltration problems because they can only act to dampen the peak
flow rate, thereby helping to prevent sewer overflows. During a storm
of an abnormally long duration, a holding basin would be of little
value. Fortunately, there is sufficient time between storms to permit
rising and falling flow rates to dampen.
A holding basin installation was investigated for application to
Drainage Area No. 29. The selection of the holding basin dimensions
was made by using the flow routing model (described in Sections 5 and
6) to compute an inflow hydrograph, followed by using a storage model
for computing the holding basin effect on the hydrograph. The result-
ing outflow hydrograph was then reintroduced into the flow routing
model and routed through the remainder of the system. A series of
trial runs was made in order to find the dimensions needed to eliminate
sewer system overflows.
Certain sewer modifications were found to be necessary, either upstream
or downstream from the holding basin, to make the connections to the
holding basin. Therefore, the construction cost estimates for holding
basins include the estimated cost for the necessary sewer connections
or revisions.
The location of the holding basin in Drainage Area No. 29 was selected
because the peak flow was exceeding the sewer capacity in that area
and because land was available for installation of the facility. A
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local park was assumed to be available for this purpose. If holding
basins are used, a study of available land would be made in other
drainage areas throughout the East Bay Area. The best way to determine
the required sewer revisions and the proper size of holding basin would
be by use of the computerized flow routing model developed during this
investigation and used for Drainage Area No. 29.
Two different designs of holding basins were considered for application
to Drainage Area No. 29. Each design included a fixed roof. Such a
roof could then be incorporated into the existing recreational facilities
of the park, e.g., tennis or basketball courts. The alternative designs
consisted of:
1. Rectangular units with mechanical cleaning equipment.
2. Self-cleaning arrangements using sewage for flushing
the settled solids.
The design involving mechanical cleaning equipment may take several
different configurations. However, based on estimated mechanical
equipment capital and operating costs, the different basin designs are
essentially equal. Therefore, the final selection would depend upon
structural design considerations and characteristics of the specific
items of mechanical equipment. Because the roof span would be greater
for square tanks than for rectangular tanks, the latter would be pre-
ferred. Also, the use of a low-head moving bridge type of cleaning
equipment would be preferable because less maintenance would probably
be required during the summer season. For these reasons, the rectang-
ular shaped holding basins with moving bridge cleaning equipment are
recommended for consideration as a component solution.
The self-cleaning design for a holding basin would be arranged to
operate without mechanical cleaning equipment. The basin would consist
of one or two parallel channels constructed with bottom slopes of not
less than 5 percent beginning with an Ogee spillway at the head-end of
the channel. This spillway would be arranged to assist the hydraulic
flushing of the solids. Initial and final flushing action would be
derived from the sewage flow itself. The solids would be flushed into
a pumping sump at the back end of the channel. The pumps would meter
the water back into the main sewer as well as return the solids to the
sewer to continue on to the plant. The disadvantage of this design is
that a substantial hydraulic gradient is necessary to provide the
flushing action needed to wash the settled sludge to the pumping sump,
resulting in generally deep construction.
The inlet to the basin would be so arranged that water would enter only
after the level in the sewer reached a predetermined level. This could
be accomplished by side channel weirs set, for example, at the normal
depth for peak dry weather flow or by a more positive flow control
device.
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The estimated cost for a typical holding basin is shown in Table 27.
It was concluded that the two designs discussed above would have about
the same construction cost, although the self-cleaning arrangement would
be slightly lower. The cost estimate includes the complementary sewer
improvement. The total cost for providing holding basins in strategic
locations throughout the study area was estimated by extrapolating the
estimated cost for Drainage Area No. 29 by the ratio of the two areas.
Therefore, the total cost for holding basins in the East Bay Area would
be $19,700,000 ($470,000 x 42,000 acres/1,000 acres).
TABLE 27
ESTIMATED CONSTRUCTION COST OF TYPICAL HOLDING BASIN*
Note: Design based on Drainage Area No. 29
serving about 1,000 acres.
Structural concrete and earthwork $165,000
Mechanical 60,000
Electrical 25,000
Site improvements 45,000
Sewer revisions 80,000
Subtotal $375,000
Contingencies (25%)^ 95,000
TOTAL $470,000
*Estimating prices based on 1972 costs (ENR Index S.F. = 1900).
Overflow Treatment Facilities
Of the several methods reviewed for the treatment of overflows, none
seemed more suitable for removing floatables than either dissolved air
flotation, fine screening, or plain sedimentation, each in combination
with disinfection. The preliminary design parameters used for each of
these alternatives are included in Appendix Table IV-1.
Dissolved Air Flotation. Because the dissolved air flotation process is
known for its effectiveness in removing floatable materials, its appli-
cation to overflow problems seems natural. However, the necessary
equipment causes the cost of this alternative to be quite high. Also,
no experience is available for the application of this process to the
treatment of overflows such as those of the East Bay Area. Equipment
is now being installed in San Francisco for the treatment of combined
sewer overflows and data should soon be available on this application.
A cost estimate for the installation of an air flotation system was
made for a typical overflow site. The results are tabulated in Item 1
of Table 28.
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TABLE 28
ESTIMTED CONSTRUCTION COST OF TYPICAL OVERFLOW TREATMENT FACILITIES*
Note: Designs based on an average flow rate of 23 mgd and maximum
flow rate of 35 mgd.
1. Dissolved air flotation
a. Structural concrete and earthwork $ 380,000
b. Mechanical equipment 280,000
c. Electrical 125,000
d. Influent and effluent sewers 250,000
e. Site improvements 100,000
f. Miscellaneous piping 65,000
g. Land 60,000
Subtotal $1,260,000
Contingencies (25%)+_ 320,000
TOTAL $1,580,000
2. Fine screens (traveling water screens)
a. Structural concrete and earthwork $ 250,000
b. Mechanical equipment 280,000
c. Electrical 100,000
d. Influent and effluent sewers 250,000
e. Site improvements 125,000
f. Land 50,QOQ
Subtotal $1,055,000
Contingencies (25%) +_ 265,000
TOTAL" $1,320,000
3. Plain sedimentation
a. Structural concrete and earthwork $ 430,000
b. Mechanical equipment 190,000
c. Electrical 90,000
d. Influent and effluent sewers 250,000
e. Site improvements 115 QOO
f. Miscellaneous piping 75 QOO
g. Land 65,000
Subtotal $1,215,000
Contingencies (25%) -f 305,000
TOTAL" $1,520,000
*Estimating prices based on 1972 costs (ENR Index S.F. = 1900).
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The air flotation installation was sized on the basis of an average
flow rate of 23 mgd and a maximum flow rate of 35 mgd. The rate is
based on 1,040 MG of overflow per year and 11.5 occurrences per year,
each over a period of 9.5 hours. A total of ten sites would be required
if no sewer separation is accomplished, nine if about half of the re-
maining program is completed, and seven if total sewer separation is
accomplished. The surface area was selected for a 3-gpm per square
foot overflow rate, and the recycle pump and pressurization equipment
were sized for a 33 percent recycle rate.
The chlorination equipment estimate was based on the use of a sodium
hypochlorite solution with variable discharge feed pumps which would
diffuse the chlorine solution at the head-end of the flotation unit.
The hypochlorite holding tank was estimated as a glass-fiber reinforced
polyester tank sized so that it would contain enough chlorine solution
for five average overflows. Feed rates were based on applying 25 mg/L
of available chlorine to each overflow.
The air flotation unit would be preceded by a one-inch opening, mechan-
ically cleaned bar screen and sewage pumps to lift the raw sewage into
the treatment facilities. Special arrangements would be required in
most instances to insure the prevention of reverse flow through the
units caused by tidal variations, i.e., tide gates. Because each of
these units would be constructed in a more or less densely populated
area, the land area was estimated as small as possible to contain the
unit. Assuming that public land, either in part or in whole, would be
available in some instances, the average land cost was estimated to be
$40,000 per acre.
This installation would be located near the waterfront where foundation
conditions are very poor and where space for construction is limited.
Therefore, adjustments were made in the cost estimates to account for
groundwater, shoring of the excavation, and pile foundations. Also,
in some locations an outfall to the Bay might be necessary.
The appropriate location for overflow treatment facilities would be in
the vicinity of the present overflows or diversion structures and in
certain locations where large trunk sewers meet the interceptor, even
though an overflow structure does not now exist.
Fine Screens. Several types of fine screens are available that could
be applicable to the treatment of sanitary sewer overflows. These vary
from revolving drum and vibrating units to vacuum units with disposable
filter media. A broad spectrum of screen sizes is available together
with different materials of construction. In general, cost increases
as the screen size decreases. All of these factors make selection of
a specific screen at this phase of the investigation difficult. There-
fore, cost estimates are presented here as an aid in evaluating the
applicability of alternative component solutions, using the screen
that appears to be most acceptable.
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Two types of screens offered promise for the treatment of overflows: a
traveling water screen and a fixed, self-cleaning screen. The travel-
ing water screen would require the use of steam sprays to maintain the
mesh free from grease build-up. It is also possible that steam sprays
might be needed on the fixed screens. The advantage of the traveling
water screen is that a lower pumping head would be satisfactory, whereas
the entire flow would have to be pumped up and uniformly distributed
over the fixed screen. Neither of these screens has been used in this
service, but their features make them promising enough to be considered
for additional study.
Item 2 of Table 28 presents the cost estimate for the most promising
screening alternative—traveling water screens. On the basis of first
cost, this installation would be more attractive than dissolved air
flotation. However, before any final design is attempted, a pilot
study should be conducted to define the acceptability of screening and
the design parameters.
The screening installation estimate was based on a mechanically cleaned
bar screen followed by two parallel traveling water screens. Both
screens would be fitted with steam sprays as necessary to keep the
screen free from grease. All of the screens would be located inside a
building. Chlorination was based on a system similar to that described
previously for air flotation, except that covered chlorine contact tanks
were necessary. In some cases, part or all of the necessary contact
time may be obtained in the outfall sewer, between the screen installa-
tion and the point of discharge into the Bay. Therefore, the tank was
sized to provide ten minutes of holding at peak flows, assuming the
remaining five minutes would be obtained in the outfall sewer.
Plain Sedimentation. Plain sedimentation has the advantage of simplicity.
However, simplicity does not mean that all mechanical equipment can be
eliminated because the remaining sludge and scum in the tank must be
removed. The sedimentation basin was sized for 30 minutes of holding,
providing time for substantial fractions of the floatable material to
rise to the surface. This holding time should be evaluated for
desirable floatable removals before any final design is undertaken.
The same number of installations would be necessary as for screening
and air flotation. Also, their locations would be about the same,
except for necessary changes to obtain more land area. Chlorination
and pumping equipment would be similar to that for air flotation.
Item 3 of Table 28 presents the estimated cost for this alternative
component solution. The cost estimates for plain sedimentation and
air flotation were almost equal.
Disinfection. Each of the preceding alternatives for removing float-
ables was estimated including Chlorination for disinfection. As
indicated, the chlorine would be in the form of sodium hypochlorite
solution. Liquid or gaseous chlorine was considered to be a potsntial
public safety hazard and therefore a last choice.
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An estimated cost of chlorine per treatment installation would be about
$2,700 per season, based on a 25 mg/L dosage of available chlorine,
23-mgd design flows for 9.5 hours at each event, 11.5 events per year,
and $0.14 per pound of available chlorine. Although hypochlorite is
safer than other forms of chlorine, there is a time limit beyond which
it substantially loses its strength. Therefore, some planning and
handling problems are inherent in its use.
An alternative to the purchase of hypochlorite solution is to generate
an equivalent solution on-site as needed. Although no precedent has
been established, an electrolytic treatment device is presently being
evaluated for marketing that is claimed to make this alternative
possible. The equipment is manufactured by the Pacific Engineering
and Production Co. of Nevada.^
Probably the most ideal application of this type of equipment exists
along the East Bay shoreline because of the availability of high
chloride content Bay water. The water could be pumped from the Bay,
through the electrolytic unit, changing some of the chlorine in the salt
to the hypochlorite state. The solution would then be added to the
screened or otherwise treated waste flow exactly as the sodium hypo-
chlorite solution discussed previously. Although this technique is
new, it should be studied as an alternative to purchasing and handling
other forms of chlorine. A pilot plant could be established simul-
taneously with any other studies that might be made on overflow treat-
ment facilities.
Conclusion. The construction estimates for the three different types
of overflow treatment facilities in Table 28 are for single-units. It
was estimated that the equivalent of nine such units would be necessary
to serve the entire study area if only 50 percent of the remaining
combined sewers were separated. However, if all sewers were separated
the required number would be reduced to seven. Therefore, on the basis
of using fine screening, the total estimated cost for providing treat-
ment facilities for the overflows in the total study area would be:
1. Before completing sewer separation, 9 @ $1,320,000 = $11,900,000.
2. After completing sewer separation, 7 @ $1,320,000 = $9,200,000.
It should be noted that the number of units selected here is presented
as a means for estimating the cost of this alternative component solu-
tion. In the final analysis, it may be concluded that only two or
three units would be desirable. In that case the flow rates would be
adjusted accordingly, and some savings may be realized because of the
increase in scale.
^Mention of commercial products does not imply endorsement by Federal
Water Quality Administration.
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The fine screening alternative offers the lowest capital cost, the
most reliable and positive results, and the smallest overall site.
Therefore, fine screening is recommended as the most feasible means
of treating overflows. However, pilot studies should be conducted
prior to final design in order to better define the design parameters
and operational problems involved in fine screening and to determine
the effluent quality. If very strict standards are established on oil
and grease in the effluent or in the receiving waters, then it is con-
ceivable that the cost and operating problems of such fine screens may
dictate the use of dissolved air flotation or some modification thereof.
IMPROVEMENTS TO THE WATER POLLUTION CONTROL PLANT
As discussed previously, the main reason that wet weather conditions
present problems at the water pollution control plant is the influx of
large quantities of sand and silt that settle in the sedimentation
basins and damage the equipment. A secondary problem is that these
large quantities of sand and silt are pumped into the digesters, thereby
reducing the digester capacity. The present means of alleviating this
problem is to bypass the flow during wet weather when the flow rate
reaches approximately 120 mgd.
The continual upgrading of water quality standards may require conver-
sion of the water pollution control plant from its present status as
a primary plant to that of a secondary plant in the very near future.
Therefore, any additions or modifications to the treatment plant pro-
posed as solutions to infiltration problems should take this into
account. A detailed engineering investigation has not been made of the
existing facilities to date, so there is no sure way of knowing what
type of treatment may be required or used in the future. However,- a
majority of the secondary treatment plants presently being planned or
constructed use some variation of the activated sludge process. There-
fore, that process was assumed applicable in this case for purposes of
evaluating the alternative revisions to the plant.
Three basic alternative revisions were considered:
1. Modify the existing grit chambers.
2. Add new grit removal facilities.
3. Modify sedimentation basins and add sludge handling
equipment to accept large quantities of sand and silt.
A summary of the design parameters used for sizing the various units
involved in the revisions is included in Appendix Table IV-1.
Lengthen Existing Grit Chambers
The present grit chambers consist of five channels approximately 60
feet long and 12.5 feet wide, having the chain and bucket type of grit
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removal equipment. The discharge from the channel takes place over a
12.5-foot long rectangular weir. Each channel was designed to receive
the discharge from a constant speed pump. The only exception is that
two of the pumps have two-speed motors, but the variation in discharge
is only about 10 to 12 percent. Because of this design there is no
significant change in flow rate between dry weather and wet weather
conditions. The reduced grit removal during wet weather conditions
seems to be caused by an increase in particle sizes smaller than the
chambers were sized to remove. Although the chambers can separate sub-
stantial quantities of grit, the grit removal equipment is so placed
that only part of the grit can be removed unless the chamber is taken
out of service. As the chain and bucket conveyors reach the head-end
of the channel, they must rise vertically through the incoming stream
of flow immediately after the discharge from the pump. This causes a
large part of the grit contained in the bucket to be washed out and
returned to the bottom of the channel.
It was estimated that the channels would have to be lengthened by about
90 feet, to a total length of 150 feet, in order to remove grit sizes
between 100 and 65 mesh (0.15 and 0.21 mm). Although these dimensions
are theoretically satisfactory, they are not very practical from the
grit removal equipment standpoint. Extremely heavy equipment would be
needed to collect and remove grit from a channel this long.
Item 1 in Table 29 shows the estimated cost for lengthening the exist-
ing grit chambers. This cost includes replacing all of the chain and
bucket collection equipment in the existing channels with heavy-duty
equipment. The estimate does not include a revision of the head works
of the grit chambers where the grit is removed from the channel.
Therefore, even if the channels are lengthened in accordance with
this alternative, there will still be unsatisfactory operating charac-
teristics. Modifications necessary to change this configuration of
the chambers would greatly increase the cost estimate, thereby further
reducing the desirability of this alternative.
Although the additional length to the grit removal channels would
relieve the sedimentation basins of large volumes of sand and silt, no
particular improvement to floatable materials would be accomplished.
Therefore, two additional bays would be necessary in the primary sedi-
mentation basins to reduce the overflow rate and to improve floatable
grease removal. Each bay is equivalent to two channels, 17.5 feet wide
by 180 feet long. These additional bays would reduce the peak flow
overflow rate from 4,600 gpsf per day to 3,800 gpsf per day, theoret-
ically improving removals by as much as 20 percent.
Although the capital cost is attractive, this alternative for improving
the grit handling capability of the plant is not recommended. The in-
herent problems of grit removal from the lengthened channels, the un-
certain results and complexity of such a design, and interference with
normal plant operation during construction were the major arguments
against its selection.
207
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TABLE 29
ESTIMATED CONSTRUCTION COST OF ADDITIONS
AND REVISIONS TO THE WATER POLLUTION CONTROL PLANT*
1. Enlarge existing grit chambers**
a. Grit chambers
(1) Structural concrete and earthwork
(2) Mechanical equipment
(3) Electrical
(4) Relocate bypass pipes
Subtotal
b. Additional sedimentation basins
(1) Structural concrete and earthwork
(2) Mechanical equipment
(3) Electrical
(4) Piping
(5) Miscellaneous
Subtotal
Total
Contingencies (25%) +
TOTAL
2. Add new grit removal facilities
a. Aerated grit chambers
(1) Structural concrete and aeration
and grit removal equipment
(2) Blowers, air headers and
blower building
(3) Electrical
(4) Yard piping
(5) Miscellaneous
Subtotal
b. Additional sedimentation basins
Total
Contingencies (25%) +
TOTAL
3. Modify sedimentation basins and add
sludge handling equipment
a. Modifications
(1) Structural concrete and earthwork
(2) Mechanical equipment
(3) Electrical
(4) Piping and valves
Subtotal
b. Additional sedimentation basins
Total
Contingencies (25%) +
TOTAL
$ 440,000
350,000
50,000
160,000
$1,000,000
$ 630,000
190,000
115,000
125,000
80,000
$1,140,000
$2,140,000
540,000
$2,680,000
$1,270,000
190,000
50,000
50,000
40,000
$1,600,000
1,140,000
$2,740,000
690,000
$3,430,000
$ 710,000
630,000
130,000
160,000
$1,630,000
1,140,000
$2,770,000
690,000
$3,460,000
*Estimating prices based on 1972 costs (ENR Index S.F. = 1900).
**Estimate does not include revisions to grit handling equipment at the
head-end of the chambers.
208
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Add New Grit Removal Facilities
This alternative plant improvement would involve constructing additional
or substitute grit removal facilities just north of the present grit
chambers. Two arrangements were considered:
1. Heavy-duty detritus tanks
2. Aerated grit chambers.
Heavy-Duty Detritus Tanks. As in the case of extending the existing
grit chambers, the detritus tank installation was sized for removing
grit sizes ranging between 100 and 65 mesh, based upon the manufacturer's
recommendations. This removal was based on an average storm flow
condition of 256 mgd, which was twice the design peak dry weather flow
rate of 128 mgd. The selected configuration consisted of two 65-foot
square units constructed in parallel.
The installation would include two 65-foot square, heavy-duty detritus
tanks with integral grit classifiers. It would require the relocation
of the existing storm water bypass which could be reconstructed as a
part of the new grit facilities. As in the case of lengthening the
existing grit chambers, two bays would be added to the sedimentation
basins. The cost estimate for this alternative was similar to that for
aerated grit chambers and was not included in Table 29.
The advantages of this alternative are that the construction would not
disrupt normal operations of the plant and the equipment would not
have to be used continuously but could be used as a supplemental grit
removal facility during storm conditions. The disadvantages are that
the bypass must be relocated and experience with the standard designs
of such tanks has indicated some deficiencies in hydraulic distribution
and resulting grit removal characteristics. Although the estimated
cost is attractive, the uncertainties introduced from experience over-
ride the advantages. Therefore, this alternative is not recommended.
Aerated Grit Chambers. To be applicable as an alternative improvement
to the plant for improving grit removal and handling capability,
aerated grit chambers must be designed for the maximum wet weather flow
rate. If this flow rate is not used in the design, the grit chambers
will remove too little grit during the peak flow conditions. If it is
used during dry weather flow conditions, the system would ensure
particularly good removals.
The preliminary design consists of four tanks 60 feet long, 18 feet
wide, and 15 feet deep. Because large volumes of grit will accumulate
in relatively short periods during storms, a clam-shell type of grit
removal mechanism is recommended.
Item 2 in Table 29 shows the estimated cost of .the proposed aerated
grit chambers. The estimate includes necessary air diffusers, air
209
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headers and blowers together with clam-shell grit removal equipment,
all necessary yard piping, structures, and excavation. It does not
include a superstructure over the grit chambers but does include a
separate structure for the blower equipment. Although the cost of the
blower building is included in this estimate, it could possibly be in-
cluded in the blower building for future secondary facilities.
As in the preceding alternatives, aerated grit chambers will not effec-
tively remove floatable materials; therefore, the cost of additional
sedimentation basins was included. The estimated cost is identical to
that used previously.
This plan would be applicable to future conversion of the plant to an
activated sludge system because sufficient grit would be removed to
permit continuation of the present method of handling the primary
sludge, i.e., digestion without sludge degritting. Waste-activated
sludge could be thickened separately by flotation and combined with the
primary sludge either before or after digestion. If sludge incinera-
tion is considered, the primary sludge should be sufficiently free of
grit to permit vacuum filtration without further degritting.
These aerated grit chambers would permit year-round operation since
they have substantially more detention time during the normal dry
weather flow. If it were considered desirable to have all removal and
handling facilities in one location, the floors of the existing grit
chambers could be raised sufficiently to increase the sewage velocity
and prevent settling of grit. This modification may actually be
necessary to preserve the hydraulic capacity through the system without
further structural and mechanical revision. Because the future plans
for expansion at the plant have not been completed, further detailed
conclusions could not be drawn.
This alternative has merit and should be considered equally with the
following alternative which involves modifications to the sedimentation
basins. The final selection between these two alternatives for recom-
mentation should be based both on capital and operating costs and
overall compatibility with the plans for future plant expansion.
Modify Sedimentation Basins and Add Sludge Handling Equipment
The merits of this plan are based on the probability that the water
pollution control plant will be expanded to include secondary treatment
and that future sludge handling will include dewatering and incineration
for disposal in lieu of digestion. It was further assumed that waste-
activated sludge would be thickened separately and then blended with
primary sludge for disposal. In preparation for dewatering, particularly
by centrifuging, it would probably be desirable to degrit the primary
sludge. This alternative improvement therefore is presented to take
advantage of that probable need for primary sludge degritting.
Figure 48 is a schematic flow diagram for this alternative improvement.
210
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NORTH INTERCEPTOR
SOUTH INTERCEPTOR
ODOR CONTROL
BAR SCREENS
CHLORINATORS \
I
SCREENINGS
PUMPS ]
i
i
INCINERATOR
i
LANDFILL
GRIT CHAMBERS
BYPASS
HOSING
WATER
GRIT
SEDIMENTATION BASINS
PUMP
DISINFECTION
SCREEN
— SCUM-
-SLUDGE
•SUPERNATANT-
.. THICKENED SLUDGE
WASTE
t
*4-
GRIT--
BUILDING HEAT
•GAS
HEAT EXCHANGERS
<—GAS
4— GAS
SLUDGE
PRIMARY DIGESTERS
SECONDARY DIGESTER
SUPERNATANT LIQUOR
f
EFFLUENT PUMPS
| \
OUTFALL
FIG. 48 SCHEMATIC FLOW DIAGRAM OF
THE EXISTING WATER POLLUTION CONTROL
PLANT SHOWING PROPOSED REVISIONS
TO SEDIMENTATION BASINS AND
SLUDGE HANDLING FACILITIES
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The chain and flight collectors located in the sedimentation basins
would be fitted with two-speed motor drives, and the cross-collectors
would be replaced by heavy-duty, cross-collector equipment. These
revisions would permit the operator to increase the speed of the chain
and flight collectors, hence preventing excessive accumulation of sand
and silt during periods of infiltration. In order to provide adequate
capacity during storm flows, another complete bay would be added to the
sedimentation basin. The sludge from each sedimentation channel would
be pumped by individual pumps to cyclone-type degritters. Each cyclone
would be sized to receive the discharge from two sludge pumps; therefore,
six cyclones would be necessary. Based upon a solids concentration of
less than 0.5 percent during dry weather conditions and approximately
1.0 percent during wet weather conditions, the cyclones would receive
600 gpm of flow. Each cyclone would have its own grit classifier.
Grit from the classifiers would be discharged to a common conveyor and
then to a truck or other container for ultimate disposal.
Because the sludge would be pumped from the sedimentation basins at
low solids concentrations, sludge thickening would be necessary before
pumping to the digesters, probably by the gravity thickening method.
For this reason, gravity thickeners were sized and included in the
equipment estimate. The thickened sludge would be pumped either to
dewatering facilities for disposal by incineration or to the existing
digesters for biological degradation.
Item 3 in Table 29 indicates the estimated cost for mechanical and
electrical equipment, structures, and piping necessary for the sedi-
mentation basin modifications and sludge handling equipment.
The advantages of this alternative are that 1) the scheme can be incor-
porated in the planning for future improvements to the plant, 2) the
existing bypass channel would not be relocated, and 3) the equipment
would be usable and applicable throughout the year. The disadvantage
is the cost for operation and maintenance of the mechanical equipment
involved. However, most of this equipment may become necessary in the
near future. It was therefore concluded that this plan for improving
the grit handling capability of the plant should be considered as an
equal alternative to aerated grit chambers, hence should be selected on
the basis of compatibility with plans for future plant expansion.
Because the cost estimates are almost identical, either alternative
could be chosen without affecting the combined cost estimates for
selected combinations of component solutions.
SELECTION OF ALTERNATIVE COMBINATIONS
OF COMPONENT SOLUTIONS
Drawing on the conclusions and cost estimates of the various component
solutions in the preceding discussion, several alternative combinations
were selected as being applicable to the problems of infiltration in
the East Bay Area. It should be realized that each of these alternative
solutions will allow some increase in flow during the storm or wet
212
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weather conditions. The objectives in formulating the alternative
solutions were:
1. To reduce infiltration or otherwise provide containment of
the volume of water that enters the sewer during wet weather.
2. To provide sufficient treatment of any overflows to prevent
pollution of the receiving waters.
3. To reduce greatly or eliminate bypassing at the water
pollution control plant.
Using the objectives outlined above, the following combinations of
component solutions were selected for consideration and comparison:
Alternative No. 1
1. Complete the sewer separation program.
2. Provide a series of holding tanks at strategic locations.
3. Provide plant improvements to prevent bypassing.
4. Locate and disconnect catchbasins presently connected
to the sanitary sewers.
Alternative No. 2
1. Complete the sewer separation program.
2. Provide plant improvements to prevent bypassing.
3. Locate and disconnect catchbasins presently connected
to the sanitary sewers.
4. Conduct sewer repairing and sealing program for all the
remaining sanitary sewers.
Alternative No. 3
1. Complete about 50 percent of the remaining sewer
separation program.
2. Provide plant improvements to prevent bypassing.
3. Locate and disconnect catchbasins presently connected
to the sanitary sewers.
4. Provide treatment of overflows.
5. Eliminate sewer system bottlenecks to prevent intersystem
overflows.
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Alternative No. 4
1. Complete sewer separation program.
2. Provide plant improvements to prevent bypassing.
3. Locate and disconnect catchbasins presently connected
to the sanitary sewers.
4. Provide treatment of overflows.
5. Eliminate sewer system bottlenecks to prevent intersystem
overflows.
Table 30 summarizes the combined construction cost estimates for each
of the alternative solutions, including an addition to cover administra-
tive and engineering costs. Alternative No. 3 had the lowest capital
cost. This alternative was based upon completing only about one-half
of the remaining sewer separation program and installing overflow
treatment facilities. The bulk of the combined sewers to be separated
were assumed to be located in the commercial-industrial areas of the
city of Oakland.
Alternative No. 1 had the second lowest capital cost. As discussed
earlier in this section, the components of Alternative No. 1 (holding
tanks) would be applicable to all storms that produce a typical rise
and fall in flow rate, allowing the peak rate to be dampened by
storage. However, under conditions of extended rainfall, storage would
not adequately reduce the peak flow rate. In fact, the holding basins
might become somewhat of a bottleneck in the system under those
conditions. Because of this inherent weakness, it was concluded that
Alternative No. 1 would not satisfy the needs of the East Bay Area.
Alternative No. 4 had the third lowest estimated cost. This alternative
was similar to Alternative No. 3, except that all the remaining combined
sewers were to be separated. This would permit the elimination of two
overflow treatment facilities. The reduced treatment cost would not
offset the increase in construction cost for the new sewers; hence only
partial separation would be more economical as indicated in Alternative
No. 1.
Alternative No. 2 was found to have the highest estimated capital cost.
It should be noted, however, that this alternative would not add to the
overall operation and maintenance costs for sewage collection in the
East Bay Area. On the contrary, it would tend to reduce the annual
maintenance cost because:
1. Less maintenance effort would be required during
wet weather.
2. The frequency of sewer cleaning would be reduced in some areas.
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TABLE SO
ESTIMATED CONSTRUCTION COST OF ALTERNATIVE COMBINATIONS OF COMPONENT SOLUTIONS*
1.
2.
3.
4.
5.
6.
7.
8.
Alternative
Item description No. 1
Sewer separation $19,250,000
Provide a series of holding 19,700,000
tanks
Provide plant improvements 3,430,000
Locate and disconnect catch- 400,000
basins on sanitary sewers
Conduct sewer repairing and
sealing program
Provide treatment of overflows
Eliminate sewer system
bottlenecks
Subtotal $42,780,000
Administration and 6,420,000
engineering (15%)
TOTAL CAPITAL COST $49,200,000
Alternative Alternative
No. 2 No. 3
$19,250,000 $ 9,600,000
—
3,430,000 3,430,000
400,000 400,000
58,800,000
11,900,000
11,270,000
$81,880,000 $36,600,000
12,280,000 5,490,000
$94,160,000 $42,090,000
Alternative
No. 4
$19,250,000
—
3,430,000
400,000
—
9,200,000
11,270,000
$43,550,000
6,530,000
$50,080,000
*Estimating prices based on 1972 values (ENR Index S.F. = 1900), and include an allowance
for contingencies.
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3. No new treatment equipment would be added throughout the
area; hence there would be no additional maintenance personnel
and power costs (both for power consumption and minimum
demand charges)-
4. The inevitable sewer replacement program, such as that
presently adopted in Oakland, could be postponed.
A brief review of the relative operation and maintenance costs for
these alternatives was made, and it was found that they were not great
enough to change the relationship of the alternatives.
A definite factor in the selection of any one of the preceding combina-
tions of component solutions involves the question of equality of
results. Probably Alternative No. 2 would produce the best overall
results because all flows could be directed through the treatment
facilities at the plant. This assumes that a sewer repairing and
sealing program, together with sewer separation and additional grit
removal facilities at the plant, would sufficiently reduce the peak
flow rates and the grit problems so that the sewage would receive at
least primary treatment and possibly some could receive secondary
treatment (split flow basis). The complete accomplishment of a sewer
sealing program could require from 10 to 15 years. Without this
component, the remainder of the alternative cannot produce the desired
results. Therefore, the disadvantages of this alternative, timing and
excessive cost, prohibit recommendation as a feasible alternative.
Alternatives No. 3 and No. 4 would be about equal in their results.
The determining factor is the ability of the treating device to
accomplish the necessary removals of grease and similar floatable
materials. In those areas south of the water pollution control plant,
the measured grease concentration was 105 mg/L during wet weather
flows. A tentative resolution was recently submitted to the City of
San Francisco by the Regional Water Quality Control Board, setting
forth requirements for discharges from several wet weather diversion
structures in that city. The requirements stipulate that grease con-
centration not exceed 25 mg/L and settleable matter not exceed
1.0 ml/L/hr at any time, as measured in the waste stream. If this
limitation would be placed on discharges in the East Bay Area, those
facilities south of the plant would require 80 percent grease and
settleable matter removals to be acceptable. However, facilities
located north of the plant would require only sufficient treatment to
maintain the present average grease concentrations but enough to meet
the settleable matter limitation. An additional comment was included
in the resolution to the effect that this limit is to be considered as
a goal until the costs for accomplishing these ends can be assessed.
Based upon the belief that the necessary requirements can be met with
proper equipment selection and appropriate design, either Alternative
No. 3 or No. 4 would satisfy the requirements and would be a good
solution to the storm water infiltration problems in the East Bay Area.
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The ability of Alternative No. 1 to satisfy the requirements is the most
uncertain of the several alternatives. The steps by which this alterna-
tive would produce results are similar to those described for Alternative
No. 2, i.e., elimination of overflows. Because this investigation was
very broad and general in its approach and conclusions, an absolutely
positive statement cannot be made about the effectiveness of the pro-
posed holding basins. The basin configuration and location studied
during this investigation indicated good results, except during ex-
tended storms, but a gross extrapolation of this solution to the total
study area may be optimistic. Also, the fact that extended storms can-
not be effectively coped with by this design is an indication that
positive results are not assured. Therefore, this alternative could
not be recommended without additional extensive study.
On the basis of the foregoing discussion, Alternative No. 3 is recommend-
ed to the six East Bay cities and to EBMUD, Special District No. 1 for
serious consideration and additional study as a solution to the problems
of storm water infiltration.
It should be realized that the adoption and effectuation of Alternative
No. 3 would not eliminate the need for a long-term sewer repair and
replacement program. Unless such a program is initiated and followed,
the infiltration quantities could increase until even the facilities
described as part of Alternative No. 3 would be inadequate.
TIME SCHEDULE FOR RECOMMENDED ALTERNATIVE
In view of the impending action of regulatory agencies, the time schedule
that would be necessary to put Alternative No. 3 into effect is im-
portant. The time schedule that appears to be most realistic in terms
of present conditions is shown in Table 31. This schedule assumes that
very little time will elapse before the East Bay cities and EBMUD
approve the plan outlined in Alternative No. 3 and take the necessary
action to initiate the work. It was assumed that the cities would
undertake the necessary surveys needed to outline the design work for
completing sewer separation, disconnecting catchbasins,and eliminating
sewer bottlenecks as soon as funds could be made available to the
departments involved. The design and construction of these phases of
the program could be conducted simultaneously, producing several
contracts rather than only one large one.
The most time-consuming phase of the program would be the overflow
treatment facilities. The time schedule was based on the assumption
that EBMUD would take almost immediate action toward the initiation of
design studies on the type of facilities needed to actually meet the
anticipated water quality requirements. Financing for such a study
could possibly be developed through federal or state aid programs. It
was taken for granted that EBMUD, Special District No. 1 would be the
agency involved directly in the construction and operation of these
facilities because this is presently its function in the East Bay
sewage collection and treatment system.
217
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TABLE 31
TIME SCHEDULE FOR EFFECTUATION OF RECOMMENDED ALTERNATIVE
NJ
M
00
Item description
Acceptance of plan by participants
Developinq financing
Complete sewer separation
a. Location survey
b. engineering design
c. Construction
Provide plant improvements
a. Pilot plant studies, if required
b. Engineering design
c. Construction
Locate and disconnect catchbasins on
sanitary sewers
a. Location survey
b. Engineering design
c. Construction
Provide treatment of overflows
a. Preliminary pilot plant studies
b. Engineering design of one unit
c. Construction of one unit
d. Evaluation of first unit
e. Engineering design of remaining units
f. Construction of remaining units
Eliminate sewer system bottlenecks
a. Location survey
b. Engineering design
c. Construction
Time in years after submittal of report
1
2
__ _
3
4
5
6
7
8
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Although preliminary studies would be undertaken for final selection of
equipment, it would not be wise to design and construct all of the
proposed facilities until after one unit has been put in operation and
fully evaluated. Unfortunately, this extends the time of completion
substantially.
The improvements to the water pollution control plant would be most
efficiently accomplished by being constructed as part of, or immediately
after, any near-future revisions to the plant. For this reason,
initiation of this phase of the program was shown as beginning about
two years after submittal of this report, in general it appears that the
entire program could be completed in about seven years.
MISCELLANEOUS RECOMMENDATIONS
During the conduct of this study two recent developments were consider-
ed to have promise for some of the problems in the East Bay Area:
friction reducing chemicals and special pipe designed for relining
existing pipes.
The addition of certain polymers to waste water in sewers has been
shown to be effective in reducing friction and hence increasing the
effective capacity of the sewer. Dosage rates in the range of 50 to
150 mg/L were found necessary to increase the apparent capacity by
100 percent. The techniques for feeding and handling the volumes of
polymer necessary to be effective in a large installation have not
been fully developed. Therefore, the use of this technique would
actually be a test installation and as such might justify federal or
state funds as a process demonstration.
Although other locations exist, one specific trunk sewer that would
benefit from the application of polymers is the Fifth Street sewer,
i.e. , the one that runs along the south shore of Lake Merritt. At a
point near the interceptor a definite constriction occurs. This bottle-
neck apparently causes surcharging in the sewer, the lifting of man-
hole covers, and overflowing. Therefore, further study of the interim
use of polymers is recommended until a more permanent correction can
be made.
A glass-fiber reinforced plastic pipe has been developed and used to
reline older pipes, particularly for the gas and chemical industries.
Although certain material and installation problems would have to be
resolved, this liner pipe appears to be a good way to repair sewers in
place. It would be applicable to both street sewers and house connec-
tions either separately or together. The liner pipe is normally placed
in the old pipe in a continuous length and in a flattened condition.
The length could be as much as several hundred feet. The pipe is then
inflated and cured with steam under pressure. The repair could be con-
sidered equivalent to, or better than, replacing the old sewer with new
pipes, both from the standpoint of usable life and leakage rates. The
pipe walls are thin and would not materially reduce the hydraulic
capacity; in fact, they might improve it because of the smooth interior.
219
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It was concluded that this pipe could be used as a means to repair house
laterals from a point near the building out to the sewer. This in-
stallation would entail digging one hole near the building and one at
the connection to the street sewer; the remainder of the yard or
paving would be left untouched. An appropriate cement would be used to
seal each end of the liner to the existing and remaining sewer. The
house lateral would then be a single continuous unit from the house out
to the sewer, minimizing both infiltration and future maintenance
problems.
An alternative to the above use would be to reline both the street
sewer and the house laterals during one operation. This would result
in an almost bottle-tight system. The sewer would be relined from
manhole to manhole with a single length of pipe. Each house lateral
connection would then be made by cementing a saddle type unit directly
to the wall of the sewer liner. Because the liner pipe has structural
integrity, both crushing and internal pressure, a short length of the
new pipe could be exposed between the end of the old house lateral and
the wall of the street sewer without concern.
It is therefore recommended that a study area be selected, perhaps one
of those used in this investigation, and a controlled installation of
this liner material be evaluated in conjunction with the manufacturer,
American Cyanamid Co. Two types of installations should be studied:
one with only house laterals lined and another with both street sewer
and house laterals lined. The objective of this test would be to
determine the techniques of installation and the cost, as well as the
possibility of relining in lieu of replacing sewers. Costs are sus-
pected to be higher than for sewer sealing techniques but lower than
for total replacement. Again, this further study would be in the
category of research and development and might qualify for federal or
state financial assistance.
Two other areas of interest were discussed in Section 10: improvements
in sewer design and construction practices, and the application of the
multipurpose concept. Both of these items merit the attention of the
designers and should be used where applicable.
8Mention of commercial products does not imply endorsement by Federal
Water Quality Administration.
220
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SECTION 12
ACKNOWLEDGMENTS
221
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SECTION 12
ACKNOWLEDGMENTS
Execution of the project depended upon close cooperation among the City
of Oakland; City of Berkeley; East Bay Municipal Utility District,
Special District No. 1; and Metcalf & Eddy, Inc., contractors for the
study. Metcalf & Eddy, Inc., gratefully acknowledges the contributions
of these organizations and, in particular, the efforts of the following
individuals:
City of Oakland
1. James E. McCarty, Director of Public Works.
2. Weston E. Follett, Assistant City Engineer.
3. Jefferson Billiard, Supervising Civil Engineer.
4. Charles Bryant, Senior Engineer.
5. William Muck, Sewer Maintenance Superintendent.
City of Berkeley
1. Roy E. Oakes, Director of Public Works.
2. Harold M. Fones, Assistant Director of Public Works.
3. Henry McGraw, Public Works Maintenance Superintendent.
4. Robert Hemphill, Public Works Maintenance Supervisor.
5. Joseph DiSilva, Public Works Maintenance Supervisor.
East Bay Municipal Utility District, Special District No. 1
1. Elmer E. Ross, Manager, Water Pollution Control Division.
2. John D. Foster, Senior Civil Engineer.
3. Edward Chow, Senior Sanitary Chemist.
4. Glenn H. Davis, Superintendent, Water Pollution Control Plant.
5. Robert Howard, Mechanic Foreman.
The following agencies were consulted while accumulating data concern-
ing the locations and characteristics of current precipitation stations
in the study area:
1. Alameda County Flood Control District, Hayward.
2. Alameda Naval Air Station, Alameda.
3. California Department of Water Resources, San Francisco
Bay District, Vallejo.
4. East Bay Municipal Utility District, Oakland.
5. Oakland International Airport Meteorological Station, Oakland.
6. San Francisco Water Department, San Francisco.
7. U.S. Army Corps of Engineers, San Francisco District,
San Francisco.
222
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8. U.S. Weather Bureau Climatological Office, San Francisco.
9. University of California, Geography Department, Berkeley.
The advice and assistance of the following officials of the Federal
Water Quality Administration is also acknowledged:
William D. Bishop, Project Officer
John C. Merrell, Director, California-Nevada Basins Office
Key personnel of Metcalf & Eddy, Inc., participating in the conduct
of the study were:
Dean F. Coburn, Senior Vice President
Franklin L. Burton, Project Manager
Joseph White, Project Manager - Development phase of study
Charles E. Pound, Principal Investigator
Dennis A. Sandretto, Sanitary Engineer - Flow Routing Program and
Literature Reviews
William G. Smith, Sanitary Engineer - Data Collection and
Analysis Program
Charles A. Kohlhaas, Engineer - Economic Benefits Evaluation
223
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SECTION 13
REFERENCES
225
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SECTION 13
REFERENCES
SECTION 2
(1) Hyde, Charles G., Gray, Harold F., and Rawn, A. M., "Report
upon the Collection, Treatment and Disposal of Sewage and
Industrial Wastes of the East Bay Cities, California,"
June 30, 1941 (referred to as the "1941 Sewage Report").
SECTION 3
(1) Hyde, Charles G., Gray, Harold F., and Rawn, A. M. , "Report
upon the Collection, Treatment and Disposal of Sewage and
Industrial Wastes of the East Bay Cities, California,"
June 30, 1941 (referred to as the "1941 Sewage Report").
SECTION 4
(1) American Public Health Association, Standard Methods for the
Examination of Water and Wastewater, 12th edition, New York,
1960.
SECTION 7
(1) Chanin, Gerson, Chief Sanitary Chemist, East Bay Municipal
Utility District, Oakland, California, "Storm Water Flows at
the Sewage Treatment Plant," unpublished inter-office
memorandum report, 1954.
(2) Sedgwick, William T., Principles of Sanitary Science and the
Public Health, Macmillan, New York, 1903, pp. 123-220.
(3) California Water Pollution Control Association, Safety Committee,
"Report on Hepatitis," Journal of Water Pollution Control
Federation, Vol. 37, No. 12, Dec. 1965, pp. 1629-1634.
(4) Yoder, M. Carleton, "Report to the City of Piedmont (California),
A Study Regarding Sewerage and Storm Drainage," Oct. 1, 1963.
226
-------
SECTION 8
(1) San Francisco Bay Regional Water Quality Control Board, "Water
Quality Control Policy for Tidal Waters Inland from the Golden
Gate within the San Francisco Bay Region," Resolution No. 67-30,
1967, Oakland, California.
(2) Kaiser Engineers, Oakland, California, "San Francisco Bay-Delta
Water Quality Control Program," Mar. 1969, final report,
preliminary edition, for California Water Resources Control
Board.
(3) American Public Health Association, Standard Methods for the
Examination of Water and Wastewater, 12th edition, New York,
1960.
(4) California Department of Public Health, "Laws and Regulations
Relating to Ocean Water Contact Sports Areas," excerpts from
the California Health and Safety Code and the California
Administrative Code, 1958, Berkeley, California.
(5) Federal Water Pollution Control Administration, "Sanitary
Significance of Fecal Coliforms in the Environment," WP-20-3,
Nov. 1966, Cincinnatti, Ohio.
(6) U.S. Public Health Service, "National Shellfish Sanitation
Program Manual of Operations," Part 1, "Sanitation of Shellfish
Growing Areas," 1965 Revision, U.S. Government Printing Office.
SECTION 9
(1) Storrs, P.N., Selleck, R. E., and Pearson, E. A., "A Comprehen-
sive Study of San Francisco Bay. 1963-64, North Central and
Lower S.F. Bay Areas," fourth annual report, SERL Report No. 65-1,
Apr. 1965, University of California, Berkeley.
(2) Hyde, Charles G. , Gray, Harold F., and Rawn, A. M., "Report upon
the Collection, Treatment and Disposal of Sewage and Industrial
Wastes of the East Bay Cities, California," June 30, 1941
(referred to as the "1941 Sewage Report").
(3) U.S. Army Corps of Engineers, "Comprehensive Survey of
San Francisco Bay and Tributaries, California, Appendix 'H'
Hydraulic Model Studies," Volumes I and III, Mar. 1963,
San Francisco, California.
(4) American Public Health Association, Standard Methods for the
Examination of Water and Wastewater, 12th edition, New York,
1960.
227
-------
(5) Orlob, Gerald T., "Viability of Sewage Bacteria in Sea Water,"
Sewage and Industrial Wastes, Vol. 28, No. 9, Sept. 1956,
pp. 1147-1167.
(6) Chick, H., "Investigation of the Laws of Disinfection," Journal
of Hygiene, Vol. 10, No. 3, 1910.
(7) Gunnerson, C. G., "Sewage Disposal in Santa Monica Bay,"
Transactions, American Society of Chemical Engineers, Vol. 124,
1959, pp. 823-851.
(8) Vacarro, R. P., et al, "Viability of Escherichia Coli in Sea
Water," American Journal of Public Health, Vol. 40, No. 1257,
1950.
(9) Ketchum, B. H., Ayers, J. C., and Vacarro, R. F., "Processes
Contributing to the Decrease of Coliform Bacteria in a Tidal
Estuary," Ecology, Vol. 33, No. 247, 1952.
(10) Rittenberg, S. C., "Studies on Coliform Bacteria Discharged
from the Hyperion Outfall, Final Bacteriological Report," 1956,
Allan Hancock Foundation, University of Southern California,
Los Angeles.
(11) Weiss, C. M., "Adsorption of E. Coli on River and Estuarine
Silts," Sewage and Industrial Wastes, Vol. 23, No. 2,
Feb. 1951, pp. 227-236.
(12) Burm, R. J. and Vaughan, R. D., "Bacteriological Comparison
Between Combined and Separate Sewer Discharges in Southeastern
Michigan," Journal of Water Pollution Control Federation,
Vol. 38, No. 3, Mar. 1966, pp. 400-409.
228
-------
SECTION 14
GLOSSARY AND ABBREVIATIONS
Page
Glossary 230
Abbreviations 233
229
-------
SECTION 14
GLOSSARY AND ABBREVIATIONS
GLOSSARY
AREAL RAINFALL DISTRIBUTION FACTOR - The ratio of the rainfall in a
selected area to that measured at Oakland International Airport.
BUILDING SEWER - Same as house connection.
BYPASS - (noun) - An arrangement of pipe, conduit, gates, pumps and
valves, whereby the flow may be passed around a hydraulic structure
or treatment facility.
(verb) - The act of causing flow to pass around a hydraulic structure
or treatment facility.
COMBINED SEWAGE - A sewage containing both sanitary or domestic sewage
and surface water or storm water, with or without industrial wastes.
COMBINED SEWER - A sewer receiving both surface runoff and sewage.
DIRECT CONNECTION - Any opening, pipe, or other arrangement permitting
storm water to directly enter the sanitary sewer.
DISPERSION - The mixing of polluted fluids with a large volume of water
in a stream, estuary, or other body of water.
DOMESTIC SEWAGE - Sewage derived principally from dwellings, business
buildings, institutions, and the like. (It may or may not contain
groundwater, surface water, or storm water.)
DRY WEATHER FLOW - The combination of sanitary sewage, and industrial
and commercial wastes normally found in the sanitary sewers during
the dry weather season of the year,- sometimes referred to as base flow.
EXTRANEOUS FLOW - That portion of the liquid carried in the sewer that
is not normally classified as sanitary, commercial, or industrial
waste or sewage. This investigation emphasizes the extraneous flows
attributed to storm water infiltration.
GROSS INFILTRATION - The total infiltration entering a sanitary sewer
by direct connections and by percolation through the soil.
GROUNDWATER (noun) - Subsurface water occupying the zone of saturation.
In a strict sense the term applies only to water below the water table.
230
-------
GROTjNDWATER TABLE - The free surface of the groundwater, that surface
subject to atmospheric pressure under the ground, generally rising and
falling with the season, the rate of withdrawal, the rate of restora-
tion, and other conditions. It is seldom static.
HOUSE CONNECTION - In plumbing, the extension from the building drain
to the public sewer or other place of disposal.
INDUSTRIAL WASTE - The liquid wastes from industrial processes as
distinct from domestic or sanitary sewage.
INFILTRATION - The process by which water, other than that classified
as sanitary sewage or commercial and industrial wastes, enters the
sewer system through any one of many different routes. In this inves-
tigation, infiltration includes all extraneous water during wet
weather, i.e., groundwater and surface water from both direct and
other connections.
INTERCEPTOR SEWER - A sewer which receives dry weather flow from a
number of transverse sewers or outlets and conducts such waters to a
point for treatment and disposal.
OVERFLOWS - The overflowing of trunk or interceptor sewers resulting
from the combination of extraneous flows and normal flows that exceed
their capacities. This investigation deals only with those overflows
that occur during periods of wet weather and not those caused by
power or mechanical failures.
OUTFALL SEWER - The outlet, structure, or sewer through which sewage
is finally discharged.
PERCHED WATER - Groundwater that is separated from the main body of
groundwater by unsaturated material.
PERCOLATING WATER - Subsurface water which passes through the soil or
rock, along the line of least resistance and under the force of
gravity, whose limits are not particularly defined by less permeable
formations, and which does not of itself form a part of any definite
body of subsurface water or flow in any subterranean channel.
PERCOLATION - The movement or flow of water through the interstices
or the pores of a soil.
SANITARY SEWAGE - Same as domestic sewage.
SANITARY SEWER - A sewer which normally carries domestic sewage and
into which storm water, surface water, and groundwater are precluded,
so far as possible, unless intentionally admitted.
SEWER - A pipe or conduit generally closed, but normally not flowing
full, for carrying sewage and other waste liquids.
231
-------
SEWERAGE - A system of sewers and appurtenances for the collection,
transportation, and pumping of sewage and industrial wastes.
STORM SEWER - A sewer which carries storm water and surface water,
street wash and other wash water, or drainage, but excludes sewage
and industrial wastes.
STORM WATER - Water resulting from precipitation which either
percolates into the soil or runs off from the surface and is captured
by storm drainage facilities.
SURFACE WATER - Rain water that falls onto the surfaces of roofs,
streets, ground, etc. and not absorbed by that surface, thereby
collecting and running off.
VADOSE WATER - Groundwater suspended or in circulation above the
normal groundwater table.
232
-------
ABBREVIATIONS
EBMUD - East Bay Municipal Utility District
ESSA - Environmental Science Services Administration
FWPCA - Federal Water Pollution Control Administration
FWQA - Federal Water Quality Administration, formerly FWPCA
USC&GS - United States Coast & Geodetic Survey
BOD - biochemical oxygen demand
cf - cubic foot
cfm - cubic feet per minute
cu m - cubic meter
COD - chemical oxygen demand
DO - dissolved oxygen
fpm - feet per minute
g - grams
gad - gallons per acre per day
gpd - gallons per day
gpm - gallons per minute
gpsf - gallons per square foot
If - linear feet
mg - milligram
MG - million gallons
mgd
mg/L
ml
MPN
ppb
psf
sq ft
sq in.
sq m
ss
tss
tvs
vss
million gallons per day
milligrams per liter
milliliter
most probable number
parts per billion
pounds per square foot
square foot
square inch
square meter
suspended solids
total suspended solids
total volatile solids
volatile suspended solids
233
-------
SECTION 15
APPENDICES
Page
I. Description of the Study Area (Section 3)
Table 1-1: Key to Geological Symbols on Figure 1-1 236
Figure 1-1: Geological Formations of the East Bay Area 237
Figure 1-2: Land Use in the East Bay Area 239
Figure 1-3: Sanitary Sewer Drainage Districts of 247
the East Bay Area
Copy of Sewer Survey Report for Keith Street, Berkeley 249
Copy of Sewer Survey Report for Keeler Street, Berkeley 250
II. Analysis and Evaluation of Data (Section 5)
Figure II-l: Hourly Rainfall Record-Oakland 251
International Airport, January 1969
Figure IT-2: Hourly Rainfall Record-Oakland 253
International Airport, February 1969
Figure II-3: Rainfall Volume versus Infiltration 255
Volume for Study Subareas, 1968-69 Storms
Figure II-4: Rainfall at Oakland Airport versus 260
Rainfall at Other Locations,
1968-69 Storms
III. Problems Resulting from Overflows (Section 7)
Description of Intersystem Overflows and Connections 265
Table III-l: Revisions to Water Quality Objectives 267
for Tidal Waters Inland from Golden
Gate Within San Francisco Bay Region
IV. Evaluation and Selection of Alternative Solutions
(Section 11)
Table IV-1: Preliminary Design Data 268
235
-------
TABLE 1-1
KEY TO GEOLOGICAL SYMBOLS ON FIGURE 1-1
gb Gabbro.
Jk Knoxville Formation, shale, sandstone and minor conglomerate.
Kjfc Chert and shale.
Kjfg Greenstone.
Kjfm Metamorphic rocks, undifferentiated.
Kjfs Sandstone and shale, some chert, greenstone, serpentine,
metamorphic rocks.
Kjm Sandstone, shale, conglomerate.
Ko Oakland Conglomerate.
Kr Sandstone.
Ks Shale.
Ku Undifferentiated Upper Cretaceous rocks; may include unrecognized
Eocene rocks.
Qac Alluvium and colluvium.
Qaf Artificial fill.
Qg Unnamed gravel, sand and clay.
Qm Merritt sand.
Qsl San Antonio Formation lower member, gravel with silty clay matrix.
Qsu San Antonio Formation upper member, clay, silt, sand and gravel.
Qtb Material contemporaneous with Qtc and Qts deposited by streams
flowing from Berkeley Hills.
Qtc Temescal Formation, dark alluvium.
Qts Alluvial material derived from the San Antonio Formation.
Qu Undifferentiated Quoternary deposits.
Sp Serpentine.
Tb Briones Sandstone.
Tbp Bald Peak Formation, predominantly basalt.
Tc Claremount Shale.
Tec Contra Costa Group, undifferentiated. Includes unnamed
sedimentary rocks.
Tern Markley Sandstone, predominantly clay shale.
Tes Unnamed Eocene sandstone and shale.
Th Hambre Sandstone.
Thl Hercules Shale member.
Tk Kirker Tuff.
Tku Paleocene siliceous shale and Upper Cretaceous sandstone units,
undifferentiated. Predominantly sandstone unit, with minor amounts
of siliceous shale too small to be shown on map.
Tl Leona Rhyolite.
Tm Moraga Formation, basalt, andesite and intercalated clastic rocks.
Tmz Martinez Formation, sandstone and siltstone.
Tn Northbrae Rhyolite.
To Oursan Sandstone.
Tor Orinda Formation, conglomerate, siltstone, sandstone, claystone.
Tp Siliceous Shale.
Tr Rodeo Shale.
Ts Siesta Formation, silty claystone and sandstone.
Tso Sobrante Formation, sandstone and silt stone.
Tsp San Pablo Formation, predominantly sandstone.
Tsr San Ramon Sandstone.
Tt Tice Shale.
Contact.
Fault.
Concealed fault.
? Doubtful.
236
-------
°y
•»*•-••.;
' *i»a
'3
V- ^f'S-S.S0 i *"
c# ) v /\ L'"'^S3
L;'-r'V(/'1' \
\\\
* ' \
rf\ \S \
\* ^, ^
#
, 1
^"
J^
/
V
/
/
rf ^
FIG. I-l GEOLOGICAL FORMATIONS OF
THE EAST BAY AREA
SOURCE: RADBRUCH, D. AND CASE, J E , "GEOLOGIC MAP AND ENGINEERING SEOLOGIC INFORMATION,
OAKLAND AND VICINITY, CALIF." U.S. GEOLOGICAL SURVEY, OPEN-FILE REPORT, 1967.
237
-------
LEGEND
LOW DENSITY RESIDENTIAL
MEDIUM DENSITY RESIDENTIAL
HIGH DENSITY RESIDENTIAL AND COMMERCIAL
INDUSTRIAL
PUBLIC, MILITARY, OR VACANT
FIG. 1-2 LAND USE IN
THE EAST BAY AREA
239
-------
LEGEND
LOW DENSITY RESIDENTIAL
SS&Si MEDIUM DENSITY RESIDENTIAL
'////. HIGH DENSITY RESIDENTIAL AND COMMERCIAL
V.\V INDUSTRIAL
PUBLIC, MILITARY, OR VACANT
. . . . , . -
I1.41J. . . . , ,
........
FIG. 1-2
(CONTINUED)
241
-------
.\v.v.\v,
* •*•••****
v.v.'
v
•
:-:->: •:•:
I *-*»* A*.**A "a *******.. . -i -*..'
&;:Xv' v:-:-:- •:•:•:•:-,
:^->:-:-:-:-..-.-. '-/:-:• --:•>:->:
•:•:•:•:•:•:•:-.....-.. ... .•.".-.-.-.'.
LOW DENSITY RESIDENTIAL
SSSSISi MEDIUM DENSITY RESIDENTIAL
'//// HIGH DENSITY RESIDENTIAL AND COMMERCIAL
INDUSTRIAL
PUBLIC, MILITARY, OR VACANT
1
FIG. 1-2
(CONTINUED)
243
-------
LEGEND
Illlllll LOW DENSITY RESIDENTIAL
iSSSS. MEDIUM DENSITY RESIDENTIAL
'//// HIGH DENSITY RESIDENTIAL AND COMMERCIAL
•'///. INDUSTRIAL
[ I PUBLIC, MILITARY, OR VACANT
-. -.V.V. v./x-x*:*:*:-:-:/,--:::
* . , ^ . .
* ....
• i. i i i >
-L . . »
''":il||i;i
*• s- i ut .7
i '
T
r\
FIG. I-2
(CONCLUDED)
245
-------
SAN
FIG. 1-3 SANITARY SEWER DRAINAGE DISTRICTS
OF THE EAST BAY AREA
247
-------
COPY OF SEWER SURVEY REPORT FOR KEITH STREET, BERKELEY
Submitted By Pacific N.W. Pipeline Survey Co., Inc., Vacaville, Calif.
July 22, 1968
REPORT Roll 21
This report covers the 10 inch sanitary sewer line on Keith between
Euclid and Brett Harte Road in the City of Berkeley, as shown in the
diagram on the cover page. The picture interval is 2 feet. The
camera was pulled backward with the lens facing Manhole A.
All measurements should be made from 2 feet past the center cf Manhole A.
The general condition of this line is poor. The pipe is relatively
sound, but will take extensive help to bring up to standards, due to
poor alignment and major offsets.
The grade is fair. A hillside installation is indicated by fast water,
and is the only reason why the grade is acceptable. At 598 feet there
is a pocket of water standing.
The alignment is very poor. While the line is normally quite curved
in this installation, very abrupt changes are evident at numerous
places, especially near the end of the run.
Side sewers are located at 301 RP, 339 RP and 372 1/2 R feet.
There are cracks at 3,49, 389, 417, 424, 457, 476 to 478, 493, 495, 497,
and 554 feet.
Breaks are located at:
From 6 to 13 feet the pipe is broken, displaced, and crushed oval, from
128 1/2 to 130 1/2 the pipe is broken. Other breaks are at 161 1/2,
259, 312 1/2, 320, and 429 1/2 feet, where a chip is missing.
Joint separations were noted at:
15, 31, 75 1/2(major), 97, 105, 117 1/2(major), 141, 587, 589, 591, 596,
and 609 feet.
Joint offsets were listed at:
4 1/2, 15, 31, 65, 70 1/2, 75 1/2(major), 81, 87, 99(major), 105, 113
(major,with void), 123(major), 133, 157, 295, 349, 415 1/2, 432 1/2,
596, and 609 feet.
There are intrusions at 75 1/2, 301(roots at side sewer, as well as at
joint), 339(roots at side sewer installation), 429 1/2, 445, 457 1/2,
483, 485, 487, 565, 569 1/2, and 572 1/2 feet.
There is no infiltration apparent, but quite logical at bad joints,
breaks, and intrusions.
Remarks: New pipe appears installed from 33 to 70 1/2 feet.
249
-------
COPY OF SEWER SURVEY REPORT FOR KEELER STREET, BERKELEY
Submitted By Pacific N.W. Pipeline Survey Co., Inc., Vacaville, Calif.
April 19, 1968
REPORT Roll 14
This report covers the 6 inch sanitary sewer line on Keeler between
Marin and Forest Hill in the City of Berkeley, as is shown in the dia-
gram on the cover page. The picture interval is 2 feet. The camera
was pulled backward, with the lens facing manhole A.
All measurements should be made from 3 feet past the center of Manhole A.
The general condition of this line is fair.
The grade appears good, except for one dip between 308 and 316 feet.
Alignment: The pipe tends to wander, causing minor offsets.
Side sewers are located at 57 L, 104 L, 151 L, and 231 1/2 LP feet.
There are cracks visible at 87, 109, 111, 306 1/2, 315, and 331 feet.
Breaks: At 107 the spigot appears chipped. At 244 feet the pipe is
crushed, displaced and oval. Also from 325 to 327 feet the pipe is
crushed, displaced, and oval shaped.
Joint separations were noted at 242 1/2, 244 1/2, 306 1/2, and 329 feet.
There are joint offsets at 9, 11, 15, 46, 52, 60 1/2, 89, 91, 105, 113,
134, 153, 183, 199, 206, 300 1/2, 302 1/2, 303 1/2, 306 1/2, 318 1/2,
321, 323, 329, 331, and 344 feet.
Root intrusions were listed at 11, 15, 29, 48, 57, 64 1/2, 68, 111, 113,
115 1/2, 117 1/2, 119 1/2, 121 1/2, 123 1/2, 125 1/2, 127 1/2, 134, 189,
191, 193, 195, 197, 206, 238, 242 1/2, 244 1/2, 246 1/2, 250 1/2, 255,
257, 259, 265 1/2, 267 1/2, 269 1/2, 271 1/2, 273 1/2, 276, 278, 280,
282, 284, 286, 288, 290, 300 1/2, 325, and 329 feet. Massive ones are
underlines.
Infiltration seepage is noticeable at most areas of intrusion.
The pipe appears out of round at 9, 11, 15, 17, 25, 46, 48, 59, 113,
115 1/2, 134, 148, 183, 185, 228, 242 1/2, 244 1/2, 246 1/2, 261, 278,
294 1/2, 331, and 344 feet.
Remarks: A root intrusion problem exists in this line. Broken pipe
areas could completely fail at any time, causing stoppages. It is our
opinion that the joints in this line are predominently faulty, due
possibly to the type of sealant used.
250
-------
FIG.H-I HOURLY RAINFALL RECORD
JANUARY 1969
OAKLAND INTERNATIONAL AIRPORT
251
-------
FIG.H-2 HOURLY RAINFALL RECORD
FEBRUARY 1969
OAKLAND INTERNATIONAL AIRPORT
253
-------
600
400 —
UJ
o
Ul
3
200 —
a
I
(T
300
200
100
1 I I I T
1 T
TRESTLE GLEN ROAD
I I I I I
8
12
*
16
INFILTRATION VOLUME , ACRE - IN.
* DEFINED AS EXTRANEOUS FLOW DUE TO RAINFALL
20
FIG.H-3 RAINFALL VOLUME VERSUS INFILTRATION
VOLUME FOR STUDY SUBAREAS, 1968-69 STORMS
255
-------
100 —
UJ
a:
o
UJ
20
<
a:
NINETEENTH ST.
2468
INFILTRATION VOLUME , ACRE-IN.
10
FIG. H-3 (CONTINUED)
256
-------
150 —
CAPISTRANO AVE
2468
INFILTRATION VOLUME , ACRE-IN.
10
FIG. H-3 (CONTINUED)
257
-------
PUMP STATION J
I 2 3
INFILTRATION VOLUME , ACRE-IN.
FIG. TJ-3 (CONTINUED)
258
-------
1200 —
800 —
z
I
(T
O
400 —
IOO
200
300
400
500
20,000
10,000
• •
PUMP STATION H
400 800 1200 1600
INFILTRATION VOLUME, ACRE-IN.
FIG. IT-3 (CONCLUDED)
2000
259
-------
TOTAL RAMFALL AT ALAMEDA NAS
FOR \*RIOUS STORMS, M.
TOTAL RAINFALL AT BERKELEY USWB FOR VARIOUS STORMS, IN
TOTAL RAHFALL AT CAP1STRANO DRIVE FOR VWWOUS STORMS, IN- TOTAL RAINFALL FOR CARLETON AVE FOR VftRIOUS STORMS, IN
FIG. E-4 RAINFALL AT OAKLAND AIRPORT VERSUS RAINFALL
AT OTHER LOCATIONS FOR 1968-69 STORMS
260
-------
UPPER SAN LEANDRO FILTERS
TOTAL RAMFALL AT SKYUNE BU/D. FOR VWVOUS STORMS, M.
OS 10
TOTAL RAMM-L AT UPPER SAN LEANDRO FILTERS
FOR VARIOUS STORMS, IN-
8
3
I
SCHOOL FOR THE BLIND
TOTAL RAMBU.L AT SCHOOL FCR THE BLMO
FOR VARIOUS STORMS, M.
TOTAL RAINFALL AT SPRUCE AVE. FOR VKRIOUS STORMS, IN.
FIG. H-4 (CONTINUED)
261
-------
I ' 1 '
WATER POLLUTION CONTROL PLANT
OAKLAND CITY HALL
TOTAL RAINFALL AT EBMUD PLANT FOR VUHOUS STORMS, IN- TOTAL RAINFALL AT OAKLAND CITY HALL FOR VARIOUS STORMS, IN
I I I I I I
TODtt. RAKFAU. AT PUMP STA. J FOR YftfflOUS STORMS,
TOTAL RAMBUJ. AT PIEDMONT FOR WWIOUS STORMS, IN
FIG. E-4 (CONTINUED)
262
-------
TOTAL RAWFALL AT MeMLLAN FDR VARIOUS STORMS, IN.
TOTAL RAINFALL AT ORINDA FILTERS FOR VARIOUS STORMS , IN-
TOTAL RAINFALL AT 39TH AVE. FOR MW10US STORMS, IN-
TOTAL RAWFALL AT SHEPHERD CANTON ROAD FOR VARIOUS STORMS, IN.
FIG. n-4 (CONTINUED)
263
-------
i 1 ' T
SHIRLEY DRIVE
U> US 2.0 Z3
RAMFNJ. AT SHIRLEY DRIVE FDR VARIOUS STORMS, IN
'^ I ' I
GLENWOOO GLADE
LO 15 2-0
RAINFALL AT OLENWOOO OLAOE FDR VMIOUS STORMS, M.
—i 1 1 1 1 1 ' T
UPPER SAN LEANDRO RESERVOIR
RAMFALL AT UPPER SAN LEANDRO RESERVOIR FOR VARIOUS STORMS , IN.
RAHFALL AT CHABOT FOR MWKXIS STORMS, IN
FIG. H-4 (CONCLUDED)
-------
DESCRIPTION OF INTERSYSTEM OVERFLOWS AND CONNECTIONS
The following is a description of the six main types of intersystem
overflows and connections found on the sanitary sewer systems of the
various cities comprising EBMUD, Special District No. 1.
1- Improperly converted combined sewers. Intermittent reaches
of old combined sewers are converted to separate storm and
sanitary sewers, respectively. That portion of the sewer
remaining was abandoned by plugging. Each end of the
connecting reach of sewer was plugged at existing manholes.
The pipe between the plugs was filled with sand. The
sanitary portions of these sewers subsequently surcharged
and, at times, overflowed onto the streets during periods
of rainfall. Removal of the top few inches of both the
plugs and the sand provided a relief overflow for the
sanitary sewer to the storm sewers and stopped the over-
flowing onto the street.
2. Common manholes. Common manholes are used for both storm
and sanitary sewers. At these locations, the manhole is on
the storm line. The sanitary sewer is piped directly through
the manhole with the invert of the sanitary line above the
crown of the storm sewer. The upper one-fourth of the
sanitary sewer pipe in the manhole is removed to provide
access to the sanitary sewer and to act as a relief overflow
during excessive sanitary flow.
3. Direct overflows to storm sewers. Direct overflows from
sanitary sewers to storm sewers exist at manholes. These
are generally located so that the sanitary sewer must sur-
charge to reach the invert of the overflow pipe. The
invert of the overflow pipe is usually above the crown of
the storm sewer. In cases where it is not, a flap valve
is placed on the outlet of the overflow pipe to prevent
storm flow from entering the sanitary sewer.
4. Direct connections of storm sewers to sanitary sewers. Direct
connections from isolated storm sewers to sanitary sewers
exist at several locations in the East Bay. In these cases,
the storm sewers terminate at sanitary manholes. These provide
for storm runoff from several catchbasins on each line to
flow directly into the sanitary system.
5. Subsurface drains. Subsurface drains connected to sanitary
sewers provide another method of entry for storm water. These
drains are found primarily in the hillside areas of Oakland
and Berkeley where excess groundwater seeps to the surface or
causes slippage and movement of the soil mass. This land
265
-------
movement causes other local problems, such as cracked,
broken, or displaced sewers.
Subsurface drains are usually made of perforated steel pipe
which collects groundwater and thereby relieves the soil
pressure. These drains collect water continuously throughout
the year, but the quantities increase during the rainy
season.
Overflows to natural drainage channels. Overflows were found
between sanitary sewers and natural drainage channels.
Here, the sanitary sewer must surcharge before reaching the
overflow connected directly to a nearby creek or lake. The
surface runoff in the creek or lake dilutes and transports
the overflowing sewage to the Bay.
266
-------
TABLE III-l
REVISIONS TO WATER QUALITY OBJECTIVES
FOR TIDAL WATERS INLAND FROM GOLDEN GATE
WITHIN SAN FRANCISCO BAY REGION
, .__ or.LITY
- • ^' 1C ATOR
TempevGCi.re
D
Radioactivity
UNIT
«*
January
February
March
April
May
June
July
August
September
October
-w-
November
December
WATER QUALITY ZONE
1
1
2
3
4
5
6
7
8
No significant variation beyond following levels
57
51
57
51
59
54
64
59
71
65
76
70
79
73
78
73
75
70
70
65
64
59
59
54
56
51
56
51
58
53
62
57
67
62
72
67
75
70
75
70
73
68
69
64
64
59
59
54
56
52
55
51
56
52
59
55
63
59
67
63
69
65
70
66
69
65
66
62
63
59
59
55
53
52
50
49
53
52
55
54
58
57
60
59
63
62
64
63
63
62
61
60
59
58
55
54
55
51
56
52
58
54
61
57
65
61
68
64
70
66
70
66
68
64
64
60
60
56
57
53
54
50
54
50
57
53
61
57
66
62
69
65
71
67
71
67
68
64
64
60
59
55
56
52
53
49
53
49
56
52
61
57
66
62
70
66
73
69
72
68
69
65
64
60
59
55
55
51
The concentrations of radioactive materials shall not exceed those
specified in California Administrative Code, Title 17, Chapter 5,
Subchapter 4, Section 30355, Table II, Column 2; and shall not
result in accumulations of radioactive materials in edible plants
and animals that would present a hazard to consumers.
52
48
53
49
56
52
61
57
67
63
72
68
74
70
74
70
70
66
65
61
59
Ts
55
51
E
"OTF.S: A. The water quality objective will apply to the main body of water by zone. Future determinations
of temperature of the main body of water will be generally consistent with the procedure used in
the CISFB&CEW.
In prescribing requirements for a particular waste discharge, the Regional Board may specify
receiving water quality limits, other than the water quality objective contained herein, to apply
at control points at or near the outer edge of the designated dilution areas if time of exposure
and other considerations indicate that adequate protection of beneficial uses is assured;
B. A significant variation will be any level of water quality which has an adverse and unreasonable
effect on beneficial water uses or causes nuisance; stated objectives will be periodically reviewed
and revised, if necessary, as additional background levels are determined and as the thermal
requirements of and the effects of thermal wastes on the beneficial water uses are determined;
C. The upper number ig the 95%-ile, lower number is mean temperature;
D. Inasmuch as any unnecessary human exposure to ionizing radiation is considered undesirable, the
concentration of radioactive materials in natural waters should be maintained at the lowest
practicable level;
E. The concentrations of radioactive materials in water used as a source of drinking water shall not
exceed one-third of those specified in California Administrative Code, Title 17, Chapter 5,
Subchapter 4, Section 30355, Table II, Column 2; except that Che concentrations of radium-226 and
strontium-90 shall not exceed 3 and 10 picocuries per liter, respectively. This objective will
apply beyond a limited dilution area as determined by the Regional Board on a case-by-case basis.
Source: State of California, Regional Water Quality Control Board No. 2,
San Francisco Bay Region, "Resolution No. 69-6, Statement of Policy
Regarding Revisions to Water Quality Objectives for Tidal Waters
Within the San Francisco Bay Region," February 1969.
267
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TABLE IV-1
PRELIMINARY DESIGN DATA
WATER POLLUTION CONTROL PLANT REVISIONS
Design flows
Average Peak
Sedimentation basin revisions and
additional sludge handling equipment
Plant flow 128 291
Sludge collector speed, fpm 3 12
Sludge pumps
Number 10 10
Capacity, gpm 300 300
Solids concentration pumped, % 0.5- 1.0+
Cyclones
Number 5 5
Capacity, gpm 600 600
Classifiers, number 5 5
Sludge thickeners
Primary sludge to thickener, Ib/day 176,000 376,000
Solids loading required, psf/day 20 40
Total area required, sq ft 8,800 9,400
Number of tanks 2 2
Tank dimensions
Diameter, ft 80 80
Sidewater depth, ft 10 10
Area per tank, sq ft 5,000 5,000
Total tank area, sq ft 10,000 10,000
Solids loading, psf/day, average 17.6 37.6
Required total feed flow, mgd 4.32 4.32
Aerated grit chambers
Flow, mgd 128 291
Number of tanks 4 4
Tank dimensions
Length, ft 60 60
Width, ft 20 20
Average water depth, ft 14 14
Unit area, sq ft 1,200 1,200
Total area, sq ft 4,800 4,800
268
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TABLE IV-2 (continued)
Design flows
Unit volume
cf
gal.
Total volume
cf
gal.
Number of tanks in service
Detention time, minutes
Overflow rates, gpsf/day
Air supply range, cfm/ft
Total air supply range required, cfm
Number of blowers
Unit capacity range, cfm
Grit handling, cf grit/MG
Grit removed, cf/day
Heavy-duty detritus tanks
Flow, mgd
Detention time, minutes
Total volume required, cf
Number of tanks
Tank dimensions
Diameter, ft
Water depth, ft
Unit area, sq ft
Total area, sq ft
Unit volume, cf
Unit volume, gal.
Total volume, cf
Total volume, gal.
Number of tanks in service
Detention time, minutes
Overflow rates, gpsf/day
Grit handling, cf/mi/gal.
Grit removed, cf/day
Average
20,400
152,500
81,500
610,000
4
7
26,700
1-5
240-1,200
2
120-600
4
511
260
1.65
39,800
2
65
6
3,320
6,640
19,900
148,700
39,800
297,400
2
1.65
39,200
4
1,040
Peak
20,400
152,500
81,500
610,000
4
3
61,000
1-5
240-1,200
2
120-600
4
1,175
292
1.47
39,800
2
65
6
3,320
6,640
19,900
148,700
39,800
297,400
2
1.47
44,000
4
1,170
269
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TABLE IV-1 (concluded)
HOLDING BASINS
Design flow
Flow, mgd 2.6
Number of channels 2
Channel dimensions
Length, ft 100
Width, ft 18
Water depth at peak flow, ft 6.7
Unit area, sq ft 1,800
Total area, sq ft 3,600
Unit volume, cf 12,100
Unit volume, gal. 90,200
Total volume, cf 24,200
Total volume, gal. 180,400
Detention time at peak flow, hr 1.6
OVERFLOW TREATMENT FACTLITIES-AIR FLOTATION
Design flows
Average Peak
Flow, mgd 23 35
Number of tanks 3 3
Tank dimensions
Length, ft 100 100
Width, ft 18 18
Depth, ft 88
Unit area, sq ft 1,800 1,800
Total area, sq ft 5,400 5,400
Unit volume
cf 14,400 14,400
gal. 141,000 141,000
Total volume
cf 43,200 43,200
gal. 323,000 323,000
Recycle rate, percent 33 33
Recycle pumps
Number 3 3
Capacity, each, gpm 1,800 1,800
Detention time, minutes
Hydraulic 20 13
Effective 26.7 17.3
Overflow rate, gpsf/day 4,320 6,480
Air supply, cfm 50 50
Number of blowers 2 2
Chlorine dose rate, mg/L 25 25
270
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\
Ac cession .Vumber
5
O
Subject
Field Sf Croup
SELECTED WATER RESOURCES AlSTIACTf
INPUT TRANSACTION FORM
Organization
Metcalf & Eddy, Inc., Palo Alto, California
Title
STORM WATER PROBLEMS AND CONTROL IN SANITARY SEWERS,
./-, Authoifs)
Pound, Charles E.
11 ,
16
Dale
j~ Paftes
Project Number
PWQA Contract No. 14-12-4
(1.102U EQG)
, «- Contract Number
2| Note
07
2 2 j Citation
Water Pollution Control Research Series - .11024 EQ.G 3/71
23
Descriptors (Starred first)
*Infiltration, *Sewerage, *Overflows, *Flow measurements,
*Computer models, Sampling, Sewage treatment, Storm water
25 ! Identifiers (Starred h'irst)
' "Hydrology, Estimated costs
r~.
27
. Abstract
An engineering investigation was conducted on storm water infiltration into sanitary
sewers and associated problems in the East Bay Municipal Utility District, Special
District No. 1, with assistance from the cities of Oakland and Berkeley, California.
Rainfall and sewer flow data were obtained in selected study subareas that
characterized the land use patterns predominant in the study area. Results
obtained were extrapolated over larger drainage areas. A computerized flow routing
program for the sewer system was used in this analysis. Ratios of infiltration to
rainfall in the study subareas range from 0.01 to 0.14. Ratios of peak wet
weather flow to average dry weather flow range from 2.1 to 9.1. About 11.1 percent
of the rainfall enters the'sanitary sewer system; 30.6 percent of the-infiltration
is contributed by the 4 percent of the study area that has combined sewers.
Problems associated with infiltration and resulting overflows and bypasses are:
1) pollution of San Francisco Bay, 2) operational difficulties at the treatment
plant, and 3) danger to public health, property damage, and nuisance. Estimated
costs for the most feasible combinations of solutions to these problems, consisting
of treatment plant improvements, separation of remaining combined sewers, partial
treatment of overflows, and sewer improvements, range from approximately $42
million to $94 million. Specific recommendations for subsequent developmental
programs are presented; complete implementation of the recommended plan will
take about 7 years.
>tbsfracror
Charles E. Pound
Institution
Metcalf & Eddy, Inc.
WR;102 (REV. OCT. IBeet
WRSCC
0
WASHINGTON. DC. 20240
U. S. GOVERNMENT PRINTING OFFICE : 1671 O - 439-698
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Continued from Inside front cover
11022 — 08/67 Phase I - Feasibility of a Periodic Flushing System for
Combined Sewer Cleaning
11023 — 09/67 Demonstrate Feasibility of the Use of Ultrasonic Filtration
in Treating the Overflows from Combined and/or Storm Sewers
11020 — 12/67 Problems of Combined Sewer Facilities and Overflows, 1967
(WP-20-11)
11023 — 05/68 Feasibility of a Stabilization-Retention Basin in Lake Erie
at Cleveland, Ohio
11031 — 08/68 The Beneficial Use of Storm Water
11030 DNS 01/69 Water Pollution Aspects of Urban Runoff, (WP-20-15)
11020 DIM 06/69 Improved Sealants for Infiltration Control, (WP-20-18)
11020 DES 06/69 Selected Urban Storm Water Runoff Abstracts, (WP-20-21)
11020 — 06/69 Sewer Infiltration Reduction by Zone Pumping, (DAST-9)
11020 EXV 07/69 Strainer/Filter Treatment of Combined Sewer Overflows,
(WP-20-16)
11020 DIG 08/69 Polymers for Sewer Flow Control, (WP-20-22)
11023 DPI 08/69 Rapid-Flow Filter for Sewer Overflows
11020 DGZ 10/69 Design of a Combined Sewer Fluidic Regulator, (DAST-13)
11020 EKO 10/69 Combined Sewer Separation Using Pressure Sewers, (ORD-4)
11020 — 10/69 Crazed Resin Filtration of Combined Sewer Overflows, (DAST-4)
11024 FKN 11/69 Stream Pollution and Abatement from Combined Sewer Overflows •
Bucyrus, Ohio, (DAST-32)
11020 DWF 12/69 Control of Pollution by Underwater Storage
11000 — 01/70 Storm and Combined Sewer Demonstration Projects -
January 1970
11020 FKI 01/70 Dissolved Air Flotation Treatment of Combined Sewer
Overflows, (WP-20-17)
11024 DDK 02/70 Proposed Combined Sewer Control by Electrode Potential
11023 FDD 03/70 Rotary Vibratory Fine Screening of Combined Sewer Overflows,
(DAST-5)
11024 DMS 05/70 Engineering Investigation of Sewer Overflow Problem -
Roanoke, Virginia
11023 EVO 06/70 Microstraining and Disinfection of Combined Sewer Overflows
11024 — 06/70 Combined Sewer Overflow Abatement Technology
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