WATER POLLUTION CONTROL RESEARCH SERIES • H022 ELK 12/71
Maximizing Storage in
Combined Sewer Systems
U.S. ENVIRONMENTAL PROTECTION AGENCY
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WATER POLLUTION CONTROL RESEARCH SERIES
The Water Pollution Control Research Series describes the
results and progress in the control and abatement of pollution
in our nation's waters. They provide a central source of.
information on the research, development and demonstration
activities in the Environmental Protection Agency, through
inhouse research and grants and contracts with Federal, State,
and local agencies, research institutions, and industrial
organizations.
Inquiries pertaining to VJater Pollution Control Research
Reports should be directed to the Chief, Publications Branch
(Water), Research Information Division, R&M, Environmental
Protection Agency, Washington, D.C. 20^60.
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MAXIMIZING STORAGE IN COMBINED SEWER SYSTEMS
by
Municipality of Metropolitan Seattle
410 West Harrison Street
Seattle, Washington 98119
for
Office of Research and Monitoring
ENVIRONMENTAL PROTECTION AGENCY
Project No. 11022 ELK
Contract No. 13-Wash-l
December 1971
For sule hy tho Suitcrintoiident of Documents. I'.S. (Jovernmont Printing Ollice, Washington. D.C. 20402- I'ricc $1.75
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EPA-Review Hotice
This report has been reviewed by the Environmental Protection
Agency and approved for publication. Approval .does not
signify that the contents necessarily reflect the views and
policies of the Environmental Protection Agency nor -does
mention of trade names or commercial products constitute
endorsement or recommendation for use.
ii
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ABSTRACT
Since the first Metropolitan Seattle sewers were constructed, combined
wastewater has been discharged into salt water or estuaries along the
Seattle waterfront. Beginning in 1958, plans were developed to make
use of storage available in the collection system before combined
sewage overflows occur. The initial plans included: (1) interception
and treatment of raw sewage flowing to salt water points, (2) regulation
of lines, and (3) construction of temporary storage tanks at fresh water
overflow points. In 1968, a $70 million sewer separation project was
approved to increase system storage by reducing storm inflow. Metro
funds originally earmarked for storage tanks have been applied to the
separation project.
All required construction has been completed in a project to demonstrate
the feasibility of applying computer-control concepts to make maximum
use of all available storage within a collection system. Automatic and
manual sampling programs are monitoring overflows and adjacent waters.
Background data, which has been accumulated and analyzed to establish
control conditions before computer activation, show dramatic improve-
ments in receiving water quality resulting from interception and treat-
ment phases of construction. Analysis of monitoring data projects a
50% to 70% reduction in pollutant loading to fresh water after sewer
separation projects have been finished.' Overflow volume, frequency,
and quality factors are monitored to serve as a basis for measuring the
performance of the control system as it leaves the instrumented local
control phase and begins the totally computer-managed phase.
This report is submitted in partial fulfillment of Project Number
11022 ELK, Contract 13-Wash-l, under the sponsorship of Water Quality
Research, Environmental Protection Agency.
iii
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CONTENTS
Section
I
II
III
IV
V
VI
VII
VIII
IX
X
XI
Abstract
List of Figures
List of Tables
Conclusions
Recommendations
Introduction
Factors Affecting Storage
in the Seattle Sewer System
Maximizing Storage by Computer
Water Quality Studies
/*
Demonstration Grant Planning
Acknowledgments
References
Glossary of Terms and Abbreviations
Appendices
Page
iii
vi
ix
1
5
7
13
39
81
137
141
143
147
153
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FIGURES
Fig.
No. Page
1 Facilities Expansion 14
2 Examples of New Facilities 15
3 Summer Rainfall Intensity 19
4 Interceptor Capacity and Overflow Frequency 19
5 Interceptor Capacity and Overflow Quantity 20
6 Storage Gained by Gated Regulators 22
7 Typical Gate Regulator 22
8 Underground Regulator 25
9 Dexter Overflow Reduction Hydrograph 27
10 West Duwamish System Schematic 28
11 Lake City Tunnel Schematic 29
12 Combined Sewer Separation Areas 32
13 Separation Construction Status (March 1971) 33
14 Sewer Infiltration from Broken Brick Arch Section 36
15 Summer Rainfall Distribution Patterns 40
16 CATAD Theory 41
17 Computer Terminal Locations 44
18 CATAD Console 46
19 Real-Time Process Control Implementation 47
20 CATAD System Schematic Diagram 48
21 Central Computer and Equipment 53
22 Computer Delivery Through Second-Floor Window 53
23 CATAD Central Control Floor Plan 55
vi
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FIGURES (Continued)
Fig.
No. Page
24 Console Sections 56
25 CRT Display Formats 58
26 Wall Map Legend 59
27 West Point Remote Console 59
28 Telemetry Control Unit 62
29 Congested Regulator Station 64
30 Remote Transmitting Terminals 66
31 Interface Testing Equipment 66
32 Force Main Calibration Chart 69
33 Remote Telemetering Depth Sensors 70
34 Metro Rain Gaging Sites 72
35 Rain Gage Equipment 73
36 CATAD Control Model Block Diagram 76
37 CATAD Simulation Model Block Diagram 78
38 Overflow and Storm Sampling Stations 82
39 Automatic Overflow Samplers 85
40 Sample Overflow Chart 87
41 Flow and Nutrient vs. Time 96
42 Flow and Solids vs. Time 97
43 Flow, BOD and COD vs. Time 99
44 Nutrient Concentration vs. Time 100
45 Sample Separation Charts 104
46 Typical Equipment and Setup for Separation Study 105
vii
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FIGURES (Continued)
Fig.
No. Page
47 Storm Runoff with Rainfall and Nitrate Nitrogen 112
48 Overflow with Rainfall and Ammonia Concentration 113
49 Receiving Water Sampling Stations 117
50 Metro Sampling Boat Fleet 119
51 Autoanalyzer in Operation 120
52 Coliform Concentrations at Elliott Bay Shoreline 122
53 Coliform Levels and Standard 123
54 Dissolved Oxygen Levels in Bay at River Mouth 124
55 Dissolved Oxygen Levels in Elliott Bay 125
56 Automatic Water Quality Monitor System 127
57 Duwamish River System Flow 129
58 Minimum River Dissolved Oxygen 130
59 River Total Coliform Count 131
60 River Ammonia Concentration 133
61 River Phosphorous Concentration 134
62 River Bottom Chemical Oxygen Demand 135
63 Planning and Progress Chart 138
64 Tidal Variations in Puget Sound 139
viii
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TABLES
No. Page
1 Unintercepted Combined Sewer Trunks (1958) 17
2 CATAD Storage Potential 23
3 Infiltration Specifications 35
4 Typical Telemetry Scan Message Content 60
5 Overflow Sampling and Monitoring Stations 84
6 Volume Calculation Program—Sample Output Data 88
7 Bacterial Density Summary—Overflows 90
8 BOD and COD Summary—Overflows 91
9 Solids Constituent Summary—Overflows 93
10 Nutrient Concentration Summary—Overflows 94
11 Regression Correlations Between
Rainfall Volume and Overflow Volume 95
12 Regulator Station Overflow Data (1970) 101
13 Separation Study—Station Data 102
14 Bacterial Density Summary—Storm Sewers 106
15 Nutrient Concentration Summary—Storm Sewers 107
16 BOD and COD Summary—Storm Sewers 109
17 Solids Summary—Storm Sewers 109
18 Pollution Loading to Lake Washington 109
19 Estimated Effects of
Separation in a Combined Sewer Area 110
20 Individual Correlations 114
21 Urban Freeway Drainage Water Quality 116
22 Total Coliform Concentrations—Elliott Bay 121
ix
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TABLES (Continued)
No. Page
~~ J —•..•K.—
23 Water Transparency Readings—1970 126
24 Adult Salmon Returns 136
25 Trawl Catches of English Sole 136
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SECTION I
CONCLUSIONS
1. Application of various storage improvement techniques has visibly
improved receiving water quality even though overflow sampling analyses
are inconclusive.
2. Reductions in coliform levels following the August 1970 inter-
ception of major Elliott Bay outfalls by gated regulators range from
63 to 98 percent.
3. Duwamish River minimum dissolved oxygen levels have increased
nearly 200% from an average of 2.5 mg/1 to 4.5 mg/1. The improvement
cannot definitely be attributed to interception until an additional
summer's data can be compared.
4. Decreases in ammonia-nitrogen concentrations at certain stations
on the Duwamish River are a result of improved nitrification techniques
being utilized at the Renton secondary treatment plant discharging
into the river upstream of those stations.
5. Following interception of all major outfalls, improved trawl
fish catches indicate larger populations of certain fish species,
including English sole and Chinook salmon, in the lower Duwamish
River.
6. Monitoring of Elliott Bay indicates an improvement of between
two and three mg/1 of dissolved oxygen in the bay as a result of
interception and regulation of 12 former raw sewage outfalls.
7. Automated chemical methods are a precise and useful tool if
used for many repetitions of a single analyses or if sufficient
accessories are on hand to run different tests in parallel.
8. Samplers and recorders, to be effective, require regular
surveillance and maintenance. The smallest failures can reduce
valuable data to a level that is unusable for certain statistical
analyses.
9. Sampler and recorder data have not only provided valuable
data about combined sewer overflows, but also have aided Metro in
the operation of the collector system by: (a) allowing early detection
of station controller malfunctions and (b) pinpointing hydraulic
design weaknesses where, for example, certain stations overflow
much more often than others.
10. The best sampling equipment is generally the least complex,
is portable, does not require power, is not susceptible to plugging
of small suction lines, constrictions, or bends, and is not likely
to become damaged when submerged (a large order).
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11. Development of an "overflow priority table" will not be a simple
task. At Metro regulators, coliform density values would establish
a "least desirable" overflow priority station sequence as follows:
40-13-37-36; while BOD and COD levels would reorganize the table
thus: 36-17-10-14. A combination of factors would place station
36 (which drains a commercial-residential area but receives many
oils and solvents) as the least desirable.
12. Weather studies in the Seattle area indicate a high correlation
between peak intensity and total volume of rainfall, so improved con-
trol efficiency can be expected by obtaining as much current rain gage
data as possible to develop early estimates of flow input to a computer
control model.
13. The collected overflow sequential sampling data is too sparse
to draw any conclusions other than to iterate the oft-described
"first-flush" effects.
14. Water quality data was used to predict overall reduced loading
to receiving water of 50% to 65% for solids, nutrients, and BOD and
37% for COD following partial separation. However, stormwater will
drain to new areas where storm drains never existed before, and this
may influence receiving water quality in some local areas.
15. An exception to the above separation prediction was evidenced
at one station where suspended solids actually increased in a storm
drain as compared to a combined overflow. However, the low volatile
suspended solids (15%) indicate that the increased solids were probably
a result of soil erosion and construction materials being washed
to the drains by storms.
16. Sequential sampling in storm drains showed a strong inverse
relationship between flow and ammonia-nitrogen concentrations.
17. In comparing combined sewers with storm drains, the combined
sewers showed a greater degree of correlation between nutrient concen-
trations and rainfall or various flow parameters.
18. In storm drains, the most significant nutrient correlations
were with meteorological data other than rain (e.g. air temperature
and wind direction) or historical factors such as antecedent dry
weather period and volume and intensity of previous storm flow. The
correlation was found somewhat different at combined sewer stations,
where the greatest nutrient correlations were with current conditions
such as volume of overflow, rain volume, and meteorological factors.
19. At present, programmer inexperience and turnover can be expected
to influence all computer process control applications in the wastewater
field, generally delaying any schedule for completion.
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20. This project is one of a few nationwide attempts to apply computer
process control principles in the wastewater field. At this time,
there are no standard programming formulas to follow. Each application
in each city seems unique, demanding a completely separate program of
design and construction.
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SECTION II
RECOMMENDATIONS
1. It is recommended that municipalities entering the process control
field aim toward standardizing control requirements based somewhat
on the experience of this and other research efforts so that computer
and control firms can develop a package to satisfy most needs. Stand-
ardization could improve the product and the customer's satisfaction
while reducing the municipalities' time and cost investment through
competition between commercial firms.
2. The attainment of a reduction in the amount of human effort
required to maintain a reliable sampling and monitoring system is a
difficult task. The industry again should attempt to standardize on
specifications. By now, sufficient data and experience should be
available to proceed toward this goal.
3. It was premature to develop and publish in this report cost
or operational data related to computer process control. A similar
absence of such data has been noticed in other published reports
on this subject. More economic information should be generated by
installations using computer systems for wastewater collection and
treatment control purposes.
4. There is a need for more studies and development in the use
of water quality monitors within sewage collection systems to base
the selection of overflow points on current data rather than a pre-
dictive model. A secondary benefit would be the ability to trace the
source of waste material discharges to the sewer system that are
harmful to the collection system or treatment processes.
5. Investigate all potential applications of computers in the waste-
water field. In general, a computer that is large enough to perform
some control function will not be continuously occupied with any one
task and can become a definite asset in the performance of other control
functions and routine common engineering and data processing problems.
The following recommendations refer specifically to the demonstration
grant project in the Seattle Metro area but might also be applied
to other municipalities :
6. It is recommended that a thorough evaluation be made of the
relative contributions of interception, regulation, separation, and
computer control based on some loading factor such as BOD. This
should be followed with a study of the economic relationships of
the above, to include the cost effectiveness for each level of
reduction.
7. Generate more statistical data on overflows, including volume
calculations. This may be done by shifting emphasis of monitoring
programs from the sewer separation studies to overflow studies.
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8. The separation study should be continued, on a reduced scale,
to observe whether effects on the receiving water occur as predicted
after all pipeline construction is completed.
9. It is recommended that an effort be made to study changes in
West Point Treatment Plant influent characteristics and flow levels
as a result of computer control under CATAD.
\
10. Study the possibility of wastewater quality modeling to auto-
matically update an "overflow priority table."
11. The possibility of expanding computer applications should include
the Renton Treatment Plant process control, addition of control to
new stations being built or remodeled, inclusion of a river water
quality model (related to recommendation 10) and the inclusion of
additional rain gages supplied by Metro or the City of Seattle.
12. Complete the sewer separation construction program as presently
scheduled, but also study if further separation is needed based on
the accomplishments of the CATAD system and alternative treatment and
control methods.
13. Economic evaluations should be made to analyze whether the
CATAD system provides actual cost benefits to Metro in the form of
reduced pumping and treatment or system enlargement costs. An attempt
should be made to relate these findings to improved water quality
benefits.
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SECTION III
INTRODUCTION
This document, "Maximizing Storage in Combined Sewer Systems," is
an interim report of the development and present status of a federally
assisted demonstration project being administered by the Municipality
of Metropolitan Seattle (Metro). Aimed at eliminating or minimizing
overflows in a combined sewer system, the Metro project is based on
computer control of sewage collection, treatment, and disposal. The
system is designed to: (1) continuously monitor water depths and
other factors needed to compute flows and capacity in the sewers and
treatment works, (2) receive and process meteorological data and predict
runoff intensity and volume on the basis of historical records, and
(3) reduce flow and store sewage in portions of the pipeline system to
permit increased flow from areas experiencing high runoff rates. Other
computer functions include the processing of data from an extensive
water quality monitoring program and performance of administrative
recordkeeping and related data processing jobs.
The combined sewer overflow, a result of excessive amounts of stormwater
entering sewer systems of limited design capacity, is an example
of the ecological problems receiving extensive attention in an effort
to reduce man's adverse impact on the environment. The storm overflow
pollution problem in the Seattle combined sewer system is typical
of the problem elsewhere; however, Seattle's solution is unusual.
A computer-controlled system such as the one in Seattle offers promising
solutions to other cities. Construction and basic programming of
the entire system is now complete, and operation is about to begin.
Metro experience related in this document should be helpful in suggest-
ing ways to speed the difficult process of merging a complex computer
system with a combined sewage collection system.
SCOPE
This report describes the procurement and installation of a computer
system capable of controlling a large sewer system. Important factors
covered are control devices, monitoring equipment and measurement
parameters, telemetry methods and data processing requirements,
computer programming and data storage details, and human element
considerations.
A final report, to be published in 1973, will complete the demonstration
grant requirements and describe a representative period of operation
of the nation's first computer-controlled sewage collection, treatment,
and disposal system.
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BACKGROUND
Between 1956 and 1958 an areawide sewerage and drainage survey resulted
in a comprehensive plan for the collection, treatment, and disposal
of wastes from Seattle and other communities within the drainage
basin. (1)
Following completion of the sewerage and drainage plan in 1958,
Seattle-area voters approved the formation of the Municipality of
Metropolitan Seattle (Metro) , a regional agency responsible for the
collection, treatment, and disposal of waste water. (2) Consulting
engineers were hired to begin preliminary design work to implement
the comprehensive plan. (3) The proposed treatment and interceptor
system (now completed) was designed with sufficient capacity to
accommodate all predicted population and industrial growth within
the entire drainage area. For this reason, considerable storage
capacity is still available within the interceptors and trunk lines.
Regulation, and other ideas to improve storage and reduce the storm
inflow and resultant combined system overflows, were recommended
and accomplished during this 10-year program.
Despite improvements brought about by the basinwide construction
plan, Seattle itself was still plagued by overflows from the 60-
year-old combined sewer system. A combination of ideas within the
Metro agency staff and its consulting engineers plus the interest
of the federal government culminated in a research and development
demonstration grant (4), awarded in 1967. The demonstration project
is expected to achieve the ultimate in system storage and control
in a combined sewer system through computerized "total system manage-
ment." This revolutionary concept in the field of sanitary engineering
has become known as the "Computer Augmented Treatment and Disposal
System," or CATAD.
WATER QUALITY STANDARDS
Appendix A details Washington State water quality standards developed
In 1967. To meet these standards, combined sewer separation and new
sewage collection and treatment facilities were required. Even
greater corrective measures are under consideration today as federal
agencies enforce existing regulations (5) and begin a new series
of discussions of even stricter standards.
As a result, Metro has planned for additional facilities as a part
of a second-stage construction program. (6) Appendix B shows second-
stage construction costs.
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ALTERNATIVE SOLUTIONS TO THE PROBLEM
A wide variety of solutions to the overflow problem of combined
sewers has been listed in the past by numerous authorities. (7,8,9)
The solutions can be characterized as three methods:
1. Increase the total capacity of the system;
2. Provide automatic control and management of the system;
3. Treat any overflow or bypass resulting after steps 1 and
2 have been completely accomplished.
Storage Capacity
Storage capacity can be gained by reducing inflow or by expanding
the system. Total separation has often been considered the ideal
solution to the combined sewer problem; but, apart from its tremendous
cost, there is increasing concern that other problems may develop
as a result of separation. (7,10) Many cities have begun separation
projects of limited size. Seattle and Washington, B.C., have begun
major projects to separate large portions of their combined sewer
systems. The various degrees of partial separation make it difficult
to compare costs from city to city, but nearly all cities agree that
financing is the major problem in a separation program. (8)
s
Other methods to increase capacity by reducing storm inflow center
on ways to limit infiltration. Included in this area are techniques
such as reconstruction (11,12) or use of sealants (13) to repair
broken or cracked sewers, replacement or redesign of manhole covers
with excessively large ventilation holes, and a number of methods
for locating and reducing the number of illegal connections that
allow stormwater to enter the system. (14,15)
System Expansion
The second method to increase system capacity is simply by expanding
the system itself. Construction of new sewer lines or tunnels (16)
either in series or parallel to existing systems and construction
of storage tanks (17) or other holding basins (18) are the two most
common ways of increasing storage within the system.
Instrumented Controls
Within any combined sewer system, storage capacity can be increased
by a number of control techniques. Regulating structures can increase
system capacity by restricting flow while using available storage from
a trunk sewer entering an interceptor line (19). Motorized gates,
weirs, or other flow regulating devices can restrict flow and thereby
store sewage within interceptors and trunk lines. Successful use
of computers and instrumentation in various industries has led to
the application of these techniques to the pollution control field
to gain storage in combined sewer systems.
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In the Netherlands, remote control of pump stations has been used
to store peaks of sewage flow in the interceptor system, thereby
maintaining a more uniform flow at the sewage treatment plant. (20)
This has resulted in improved sewage treatment efficiency.
Demonstration grants are in progress now in various cities around
the country in an effort to show how remote control of gates and
other devices within a collection system can be used to maximize
storage or to route flows through systems that contain large sewers
or a grid network. In either case, the maximum storage available
in a combined sewer system is employed through the use of instrumen-
tation at various points. In such instrumented systems, it is likely
that computer control and system models are included or planned for
future installation when conditions or funds permit such action. The
complexities involved suggest that it would be helpful to go into addi-
tional detail on the various demonstration grants involving instrumental
control systems to distinguish the unique features of each.
Nationwide System Control Projects
Monitoring to detect unusual or unnecessary overflows is the primary
feature of the Cincinnati studies. (21) The Minneapolis-St. Paul
Sanitary District has adopted a more sophisticated approach by tele-
metering data from river monitors, mechanical gate diversion points,
and sewer flow and level sensors to a central point where a computer
assists a dispatcher in routing and storing stormflows to make efficient
use of the interceptor capacity. (.22) The Detroit project involves
even further system control refinements. This project includes rain
gages, level sensors, overflow detectors, and a central console for
controlling pumping stations and selected regulator gates. Computers
are employed to test such pollution control techniques as "storm
flow anticipation," "first flush interception," "selective retention,"
and "selective overflowing." (23)
The Metro setup incorporates all the main features of the other control
projects plus additional water quality monitoring functions into one of
the most advanced waste transmission and treatment monitoring and
control systems in existence today. The Metro CATAD control system is
described in greater detail in succeeding chapters of this report. The
descriptions of the projects mentioned above have been brief; further
details about these demonstration grants can be found in other publica-
tions. (24,25,26)
Overflow Treatment
Many cities are engaged in attempts to treat stormwater overflows
from combined sewer systems using a combination of methods. A few
cities have actually incorporated overflow treatment into regular
operating procedures for an entire collection system. Portland,
Oregon, has experimented with a rotating fine screen system to separate
settleable solids from the overflow stream. Cleveland has investigated
10
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both biological and chemical oxidation followed by sedimentation
as a treatment procedure for overflows. Philadelphia is testing a
combination of micros training, chlorination, and ozonation. Excess
mixtures of stormwater flow and sewage are settled, skimmed, and
chlorinated in holding tanks of the Mission township district of
Johnson County, Kansas. (27) Other techniques such as dissolved
air flotation and crazed resin filtration are being studied to test
the feasibility of adopting such techniques for full-scale municipal
application.
The Seattle area has also considered proposals for treating overflows.
In 1970, a consulting firm presented a detailed study for a proposed
screening and chlorination installation. (25) The construction
cost was estimated as $800,000 for a facility with the capacity for
treating 25 mgd. Considering the construction costs and unknown
operating costs and other factors, City of Seattle officials declined
the proposal and elected to invest funds into separation projects
where considerably more benefit could be obtained for a given amount
of money. It is expected that separation projects, together with
computerized storage control, will eliminate or reduce overflows
to a level so that receiving water quality standards can be met.
11
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SECTION IV
FACTORS AFFECTING STORAGE IN THE SEATTLE SEWER SYSTEM
It would be difficult, if not impossible, to make an accurate evaluation
of the success or failure of the effort to maximize the storage within
the Seattle combined sewer system if we did not first study all the
factors that presently affect storage within the system. These related
factors in order of presentation are:
1. System expansion,
2. Improved regulation techniques,
3. Storm inflow reduction.
Historically, system expansion has preceded the other storage improvement
techniques; therefore, this aspect is discussed first.
SYSTEM EXPANSION
Implementation of the metropolitan area comprehensive sewage collection
and treatment plan of 1958 began in 1960 with numerous independent trunks
and small sewage treatment plants. The first-stage construction program,
completed in 1970, added the interceptor lines and new facilities shown
in Figure 1.
Over the total Seattle area, some 87 miles of sewers between 8 and 108
inches and averaging 56 inches in diameter, all constructed to the design
size specified for ultimate flow within the drainage basin, constitute a
large portion of the increased system storage potential.
Major features of the expansion are represented pictorially in Figure 2.
Pipeline size and construction problems are illustrated by photographs A
and B. Photos C and D show the smallest and largest of the four primary
treatment plants along Puget Sound, which borders Seattle to the west.
Photograph E is representative of the 14 regulator stations already con-
structed (four more are being planned for future construction). Some
18 pump stations similar to photograph F complete the expansion of the
sewer system.
The added facilities together with the existing 1,029 miles of combined
sewers in Seattle, including the large North Interceptor sewer and many
tributary trunk lines, complete the comprehensive sewage collection
system as it exists today. Another method of gaining in-system storage—
stormwater holding tanks—has also been considered.
Storage Tanks
A number of cities have studied and built temporary or permanent storm-
water storage tanks in some form as a means of preventing stormwater
overflows from combined sewer systems to local receiving waters. Columbus,
Ohio, and Washington, B.C., are well known examples of this technique.
Seattle also planned the construction of storage tanks to remedy a situ-
ation along Lake Washington where overflows periodically occured at
nearly 60 separate points, as shown in Appendix C.
13
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Figure 1. Facilities Expansion
14
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A, Pipeline Laying
B. Tunnel Construction
C. Richmond Beach Treatment Plant D. West Point Treatment Plant
E. Regulator Station
F. Pump Station
Figure 2. Examples of New Facilities
15
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The Brown and Caldwell report (1) recommended, as an interim solution
prior to sewer separation, that some 34 storage tanks averaging
1.2 million gallons each be constructed underground along the western
shoreline of Lake Washington at points where tributary drainage areas
connect .to the main interceptor line. The planned stormwater holding
tanks were essentially a "stop-gap" measure until sewer separation
was financially feasible. (28).
Storage holding tanks will have to be considered as one of the alterna-
tive approaches to regaining system storage in the future when popula-
tion and industrial growth have encroached upon the current excess
capacity built into the collection system.
System Expansion Design
Of the expansion projects actually undertaken, a major problem confront-
ing Metro in 1960 was the sizing of interceptors to serve the combined
sewer system within the City of Seattle. Former studies have shown
that, for the Seattle area, a combined sewer interceptor to handle
the flow from storms with recurrence intervals of one per summer
needs to have a capacity, depending upon the time of concentration,
of some 30 to-60 times the average dry-weather flow. To construct
an interceptor of such dimension would be physically and economically
unrealistic. As a matter of comparison, interceptors for a separate
system are usually designed for peak flows of two 'to four times
the average dry-weather flow. The interceptors had to be'designed
to afford the maximum utilization of their capacity and to minimize
stormwater overflows, keeping in mind the following considerations:
1. Construction of an interceptor having a capacity sufficient
for the flow.
2. Partial or complete separation of a portion or all of the
tributary area.
3. Construction of holding tanks at overflow points to store
excess flow during periods of rain.
Deficiencies
Combined sewer systems have two major deficiencies or drawbacks:
1. The cost of interception, conveyance, and treatment is many
times greater than a separate sanitary sewage system.
2. Only the provision of extremely large interceptor sewers
and excessive hydraulic capacity in collection, treatment, and disposal
works would prevent periodic overflows of diluted sewage in stormwater
and resultant pollution of adjacent waters.
For these reasons, the design criteria were based on the assumption
that all new areas will be developed with separate sanitary systems
and older combined systems eventually will be separated partially
or totally. The combined sewer trunks listed in Table 1 had to
be intercepted.
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TABLE 1
Unintercepted Combined Sewer Trunks (1958)
Sewer
Service Area
(acres)
Trunk Size
(inches)
150 x 100
96
72
48
36
49
48
72
30
20
42
30
48 x 30
18
42
42
15
DWF refers to dry-weather flow; PWWF, peak wet-weather flow.
Interceptor Capacity Analysis
The design capacity for combined sewer interceptors is based on the
sum of peak domestic sewage flow, peak industrial flow, and an allow-
ance for infiltration and stormwater inflow. Detailed population and
loading studies established the ultimate design flows for domestic and
industrial wastes. The Seattle area has allowed a maximum stormwater
and infiltration inflow of 3,200 gallons per acre per day (gpad) under
winter conditions in existing sewer lines. Inflow allowances have
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
Hanford Street
Lander Street
Connecticut Street
King Street
Madison Street
University Street
Vine Street
Denny Way
Prospect Street
Garfield Street
32nd Avenue West
Avalon Way
Chelan Avenue
West Michigan Street
8th Avenue South
10th Avenue South
Misc. small trunks (7)
Total - (24 outfalls)
2,900
610
640
156
17
63
60
1,170
140
210
1,400
480
1,825
210
180
130
309
10,500
Flow
DWF
4.6
1.5
1.6
2.0
0.4
2.0
0.1
2.5
0.3
0.3
2.0
0.9
3.0
0.9
0.5
0.3
1.1
24.0
(MGD)a
PWWF
308
200
110
48
40
130
45
66
49
210
147
65
114
33
29
21
13
1,430
17
-------
been reduced to 1,100 gpad maximum for new sewer construction.
Detailed rainfall analyses assist the engineers in determining over-
flow frequencies and volumes and, therefore, probably have the greatest
significance in interceptor design.
In view of the importance of overflows to the subject matter of this
report, some additional detail concerning the interceptor capacity
analysis will be repeated from the Brown and Caldwell report. ((1)
The rainfall analysis shown in Figure 3 and the assumed average values
for time of concentration and per capita sewage flow provide the basis
for calculating the frequency of overflow from interceptor sewers of
various capacities. The effect of interceptor capacity on frequency
of overflow is then plotted in Figure 4.
To establish the quantity as well as the frequency of overflow, a
statistical study is summarized in Figure 5 (valid for interceptors
or holding tanks). The summary shows the percentage of sewage overflow,
occurrence of rainfall, and percentage of total sewage not intercepted
for the full year. As shown,, the total quantity not intercepted is
relatively small, even with an interceptor designed to carry only two
times the average dry-weather flow of sanitary sewage and ground water.
To the engineer, it is also evident that the increase in percentage
of sewage intercepted with larger interceptors is slight. By increasing
the interceptor capacity from two to five times the dry-weather flow,
the quantity of sewage intercepted will be increased during summer con-
ditions only from 98.4 to 99.4 percent while the interceptor capacity
has increased to 50 percent. To the design engineer, there is no
economic justification for increasing interceptor size to prevent the
last small portions of overflow. To the water quality purists, ecologists,
and the growing number of concerned individuals, the "minor" overflows
remaining are a significant source of pollution.
The Recommendation
After careful analysis of all design considerations, the engineers recom-
mended that the large interceptors to be built between 1960 and 1970
should have a capacity of approximately three times the dry-weather
flow. This recommendation was qualified by stating the policy that
future additions to the system must be separated and that the existing
combined sewer areas should also be gradually separated. The effect
is that the interceptor will have many sanitary sewage systems
directly tributary to it and will therefore contain a higher percentage
of sanitary sewage than the combined sewer trunk lines that are also
tributary. Therefore, the engineers stated that when overflows did
occur from the combined sewer portions, such overflows would be
from the stormwater trunk rather than the interceptor itself. This
then leads to a discussion of the method of connecting trunk sewers
to interceptors.
18
-------
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' """"•• .
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£ 0 13 30 45 60 75 90 103 120
OURAT ON , MINUTES
Figure 3. Summer Rainfall Intensity
(T
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^-TIME OF CONCENTRA-
TION IN DRAINAGE
AREA, MINUTES
\
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^-.*>>^'--
CD 1 2 3 4 5 6 7 8 9 10 20 30 40 60 60 80 100
RATIO OF INTERCEPTED FLOW
TO AVERAGE DRY WEATHER FLOW
Figure 4. Interceptor Capacity and Overflow Frequency
19
-------
PER CENT OF TOTAL SEWAGE
NOT INTERCEPTED
0.03 0.04 0.05 O.06 O.Oi 0.10 0.20
RAINFALL INTENSITY, INCHES PER HOUR
0.90 0.40 0.50 OK) O.«0
Figure 5. Interceptor Capacity and Overflow Quantity
REGULATION INCREASES STORAGE
The regulator at the physical location of overflow release from a
combined sewer system might not be contributing to the overfloxj problem.
The APWA report entitled Problems £f Combined Sewer Facilities and
Overflows—1967 (9) points out that deficiencies in the sewer system
may be such that improvement of the regulator facility alone will
not significantly reduce pollution. However, few systems will function
effectively with minimum pollution impact if the regulator facilities
have not been properly chosen and adequately maintained. A more
recent report entitled Combined Sewer Regulator Overflow Facilities
(19) indicated that the above statements are true whether the regulator
is simple or highly complex or whether it is used strictly as a relief
point or functions in conjunction with system storage.
As is common practice in the design of combined systems, Seattle
sewers have overflow and bypass structures whereby wet-weather flows
in excess of intercepting sewer and pumping station capacities are
diverted to convenient points of disposal. Regulators in the Seattle
system reflect most of the various designs that have been developed
during the history of combined sewer systems. Stationary regulators
are represented by the simple short weir in the bottom of an overflow
manhole and the more complex side weirs, leaping weirs, and orifice
plate design. More sophisticated mechanical regulators and electronic
controls are also installed at various locations in the system. Although
20
-------
the majority of these structures are incorporated in trunk lines lead-
ing to intercepting sewers, some are also located on the interceptors.
Pre-1960 Regulators
Theoretically, overflow weirs in use in Seattle are designed to
function when the flow in the sewer reaches from five to nine times
the average dry-weather flow. (1) Because the overflow weir crests
generally are set at a height of about 1/4 depth of the upstream
sewer, overflowing easily begins when the ratio of stormflow to
sanitary flow reaches 2:1, or even less. Mechanical regulators of
the Brown and Brown type (29) were first introduced in the Elliott
Bay Interceptor line about 1938. In addition to the unsatisfactory
maintenance practice established after years of operating these
float-controlled regulators, engineering studies in 1960 (3) showed
that two regulators allowed less than 3% of the total trunk flow
to enter the interceptor even under perfect operating conditions,
an amount considerably beneath interceptor capacity. It would appear
that storage was not a major consideration in the design of these
older regulator facilities. Figure 6 illustrates the storage volume
that can be gained by replacing a weir regulator with a motorized
gate regulator station such as the one shown in Figure 7.
Sluice Gate Regulators
The simplest, least expensive means of intercepting combined sewer
trunks is by means of overflow weirs. Because the peak sanitary
sewage flow is only about 5% of the total flow in the trunk under
stormflow conditions, the usual weir design would permit overflows
to occur before the capacity of the interceptor is reached and before
the storage capacity available in the trunk was fully utilized. The
problems of fixed weir overflows in Seattle are compounded by tidal
fluctuations (11 feet mean and 19 feet maximum), which dictate that
any such weir be high enough to prevent the entry of salt water to
the interceptor. This situation almost precludes the use of fixed
weirs because of the extreme difficulty in relieving the combined
sewer system during storms while preventing salt water backflow into
the system during dry weather and high tides.
To provide fully for the maximum use of interceptor capacity and
minimum occurrence of stormwater overflows requires a design using
positive mechanical means of control. The design adapted by Metro
for interception of combined sewers provides this control. Thus,
it is now possible to make maximum use of the trunk storage capacities
as shown in Table 2. Interceptor storage potential for selected lines
are shown for comparison.
21
-------
OVERFLOW
OUTFALL
*— AVAILABLE STORAGE
BEFORE OVERFLOW
A. SIDE SPILL WEIR REGULATOR
DWF
*—AVAILABLE STORAGE
BEFORE OVERFLOW
B. SLUICE GATE REGU-
LATOR
Figure 6. Storage Gained by Gated Regulators
Figure 7. Typical Gate Regulator
22
-------
TABLE 2
CATAD Storage Potential
I. Trunk Storage
Maximum Safe Average Dry- Maximum Storage
Station Storage (MG) Weather Flow (MGD) Time (hours)a
Eighth Avenue South
West Michigan Street
Chelan Avenue
Harbor Avenue
Norfolk
Michigan
Brandon
Hanford
Lander
Connecticut
King
Denny Way
Lake City Tunnel
II. Interceptor
West Marginal
East Marginal
Duwamish
Inter bay
Matthews Park
0.5
-
0.4
-
0.4
1.2
0.5
3.8
1.4
0.8
0.1
0.8
6.5
Storage Upstream
0.3
1.2
2.0
9.3
2.6
0.8
0.9
3.0
0.9
5.8
1.0
1.3
4.6
1.5
1.6
2.0
2.5
10.0
from Pump Stations
3.6
16.8
24.0
35.0
8.0
15.0
0.2
3.2
0.5
1.7
28.8
9.2
19.9
22.4
12.0
1.2
7.7
15.8
0.8
1.7
2.0
6.4
7.8
For DWF only—Storage will reduce as average flow increases
23
-------
The regulator station at each combined trunk sewer to be intercepted
is provided with two automatically operated sluice gates of the modu-
lating type. Figure 8 illustrates the typical underground regulator
stations which were first constructed where the Elliott Bay Interceptor
meets the Norfolk Street, Michigan Street, and Brandon Street trunk
lines.
The location and function of these gates are as follows:
1. Regulator Gate. This gate is located on a line connecting
the trunk to the interceptor. It is designed to regulate flow from
the trunk so as not to exceed a selected depth in the interceptor.
Under dry-weather flow conditions, the gate is fully opened and all
sewage flow in the trunk is diverted to the interceptor. Under stormflow
conditions, the gate is closed to the extent necessary to maintain
the preset water level in the interceptor.
2. Outfall Gate^. This gate is located on the stormwater overflow
line from the trunk. It is designed to retain sewage in the trunk
to utilize the full potential for storage. Thus, when the flow in
the trunk is equal to or less than that being diverted to the interceptor
through the regulator gate, the outfall gate remains closed. As
the flow in the trunk increases, the gate remains closed until the
preset water level in the trunk is reached, at which time it opens
as necessary to maintain this level. Under peak storm conditions,
the gate will be fully open. An overriding control prevents the
gate from opening when the tidal elevation exceeds the water surface
elevation in the trunk.
Control of the gates is based on water level elevations in the incoming
trunks and in the interceptor. Air bubblers or other level sensors
are used to sense the water level. This information is then transmitted
to a controller which converts the pneumatic signal to an electronic
signal. The gates are then actuated, either to close or open in
increments, in response to changes in the water surface elevation
in the trunk or interceptor. Electric motor drives or hydraulic
cylinders are used to move the gates.
Benefits From Sluice Gate Regulators
An example of the effectiveness of the sluice gate regulator in reducing
overflows is demonstrated by an engineering study (30) performed
in 1969, which recommended construction of this type of regulator
station at Dexter Avenue. The upstream trunk has a capacity of roughly
162 mgd. Downstream of the 30-foot-long side spill weir, the interceptor
sewer has a capacity of 38 mgd. Overflow begins to occur when sewer
flow reaches about 32 mgd and all flow in excess of the capacity
of the downstream pipe is discharged to Lake Union at the foot of
Galer Street. The 1969 study assumed a regulator station would be
constructed near the side weir to store, if necessary, in the large
(84-inch) interceptor upstream of the existing weir.
24
-------
LOCAL ytONTROLiOSTRUCTURE
RECEIVING
Figure 8. Underground Regulator
25
-------
Depth of flow in the interceptor was monitored just upstream from
the overflow site; the results of these measurements are plotted
in Figure 9. During the study period, the flow exceeded the 38-
mgd capacity of the downstream section eight times on five separate
days and overflowed more than 6.4 million gallons of combined sewage
into Lake Union. The mass hydrograph diagram was then constructed
from flow calculations, assuming that a regulator station would be
allowed to store all flows in excess of 38 mgd, up to the capacity
available in the upstream trunk assuming a 4-foot surcharge at the
regulator. All volumes in excess of this amount would be overflowed
to Lake Union. The mass hydrograph showed that a gated regulator
station would have eliminated all but one overflow, a reduction in
frequency of 87.5%. The quantity overflowed to the lake would have
been reduced to 2.7 million gallons or 42% of the quantity released
over the existing simple weir. These percentages cannot be applied
indiscriminately to all locations because of dissimilarities in
sewer capacities, overflow levels, upstream sewer reaches, and the
characteristics of the tributary area.
West Duwamish Interceptor System
The West Duwamish Interceptor system is an example of how regulator
storage might be increased by constructing regulator gate structures
that provide no storage themselves but, by controlling trunk flow,
allow extra capacity at other stations within the system. The West
Duwamish system, shown schematically in Figure 10, consists of four
regulators, one pump station, and interceptor sewers that serve about
6,200 acres of residential area and 1,400 acres of industrial area.
Table 1 indicates that the four main tributary trunk sewers have
a hydraulic capacity in excess of 250 mgd. However, interceptor
design was based on sanitary flow, which was computed as 36 mgd.
Either separation or regulation was necessary to divert excessive
stormflow to nearby receiving waters. The final enginneering design
allowed for either or both of these alternatives at each regulator
station. When separation has been completed in tributary drainage
areas, connections can be made to existing pipe stubs to bypass the
then unnecessary regulator stations, or the stations could continue
to function as merely an emergency release point in cases of sewer
line damage or plugging and to regulate flow during dry weather for
peak flow attenuation.
The Eighth Avenue South regulator, also shown in Figure 10, was con-
structed to divert sanitary flow from two outfalls at 8th Avenue
and 10th Avenue into the interceptor. Some 15 hours of storage time
at dry-weather flow is available at this regulator, as shown by
Table 2. The Chelan Avenue regulator also has a relatively flat
tributary drainage area where considerable storage is available.
The system design between the Harbor Avenue regulator and Chelan
Avenue regulator is unique in that the interceptor passes through
the latter after being regulated at Harbor Avenue. This unusual design
26
-------
to
CAPACITY OF TRUHK DOWHSTREiU F/tOH
OVERFLOW STRUCTURE - 38 MffO
OV€RFLOtriH6 SCGINS *T FLOW
OF 51 USD IN SrSTFH
5 I 6 I 7 I a I 9 I 10 I I
DECEMBER 1966
19 It IT 19 U ZO 21 22 23 24 23 26 27 28 29 30
NOVEMBER 1968
Figure 9. Dexter Overflow Reduction Hydrograph
-------
8fthlAVE' S0y/Tr .W,MICHIGAN R.S.
/"STEEP
y HILLSIDE
\
I
CHELAN R.S.-I\ I
Siphon to
P.S and
Treatment
LEGEND
OUTFALL +>
Figure 10. West Duwamish System Schematic
was brought about because engineers found that existing combined
sewers could be tapped and could adequately handle flow from Harbor
Avenue without requiring the construction of a new interceptor line
the entire distance between the two stations. Both the Harbor Avenue
and West Michigan Street regulator stations are located at the bot-
tom of relatively steep hillsides where essentially no storage is
available. Mechanically operated gates at these two locations could
reduce overflows during a local storm in either of the watersheds.
This would be accomplished by storing behind other regulators, thereby
allowing greater flows into the interceptor from either of these
two locations where no storage is available. Because of the limited
storage upstream at Harbor Avenue and West Michigan Street, periods
of frequent overflows often result. Therefore, to justify construction
of these control stations, the overall optimum, storage within a total
system must be considered. Other factors may affect such a decision.
For example, at Harbor Avenue, a regulator was also needed because
of the low residential area lying directly north where flooding would
occur if a combined sewer relief point were not provided.
It was decided that each of the four regulators would have mechanically
operated regulator and outfall sluice gates so that precise computed
flow measurements could be made in the future at all four points,
28
-------
even though computer control was not contemplated at West Michigan
or.Harbor Avenue. Also, tidal effects at three stations require that
outfall gates be constructed. At West Michigan an outfall gate was
not required for tidal purposes, but was installed mainly to reduce
the amount of grit and other inorganic materials that otherwise
would•contribute to pipe damage and reduced treatment process efficien-
cies. Each station was provided with a bypass line which is used
mainly when heavy maintenance is being done on sluice gates; the
bypass lines are also available for use in the future when sewer
separation is completed.
Gate Station Storage
It was previously pointed out that the new interceptor system construc-
tion shown in Figure 1 had been built with sufficient size to adequately
carry the ultimate flow of the tributary drainage area. At no point
in the Metro sewage collection system is this more evident than in
the Lake City tunnel system, shown schematically in Figure 11.
KENMORE PUMP
STATION
MATTHEWS PARK
PUMP STATION
KENMORE INTERCEP.
FUTURE
REGULATORS
LAKE CITY TUNNEL
REGULATOR
LEGEND
X SANITARY FLOW
1 COMBINED FLOW
Figure 11. Lake City Tunnel Schematic
29
-------
The Lake City tunnel was completed in 1968 to accept separate sanitary
flow from the tributary area north and northwest of Lake Washington.
Extending for 17,200 feet, the 96-inch-diameter tunnel has a hydraulic
design capacity of 160 mgd, but actually now carries only 40 mgd at peak
wet-weather flow and an average 10-mgd dry-weather flow. Thus three-
fourths of its capacity is unused, making in effect a long narrow reser-
voir that could be used for temporary storage of sanitary sewage,
when necessary.
At present flows, by closing the regulator gate at the south tunnel
portal and making use of the 6.5 million gallons of available storage,
all 10 mgd of dry-weather flow through the tunnel can be stored
for approximately 16 hours without making use of other available
upstream storage. By shutting down the two pump stations upstream
of the Lake City regulator, storage times of 45 hours and 74 hours
can be obtained. Such storage times would be more than adequate
to allow the downstream interceptor to return to normal flow levels
following a storm, thereby reducing the probability of overflows
in that downstream interceptor.
With these facts in hand, Metro approached the FWQA in July of
1967 with a request to use demonstration grant contingency funds
to construct the Lake City gate control structure at the south
end of the tunnel. The station is now in operation.
The North Interceptor provides additional storage potential,
and, on the basis of a detailed hydraulic study of that system
(30), design of four additional sluice gate regulator stations
has been authorized. Construction is expected within the next
5 years.
STORAGE FROM REDUCED STORM INFLOW
Through system expansion and optimum application of regulation
techniques, it has been demonstrated that engineers have extracted
a great deal of storage out of the existing Seattle combined
sewer system. However, the improvements that have been discussed
thus far have mainly affected the large trunk lines and interceptor
lines, which now are the responsibility of Metro. The City of
Seattle owns and operates the many small trunk lines and collector
sewers, many of which have points of overflow that have not been
affected by the improvements made to the system. Overflows still
are common from the smaller systems at many points; therefore,
all the'innovative design and optimum operation and maintenance
efforts are somehow dulled by subsequent adverse effects on the
receiving water. It follows then that any effective plan to
eliminate or reduce the frequency of combined sewer overflows
throughout the entire city must provide additional capacity in
the sewage system by eliminating all possible sources of storm
drainage through a combination of infiltration reduction methods
30
-------
and some degree of sewer separation. Any effort to reduce storm inflow
to the combined sewer system will improve the storage availability in
both the local sewer area and the metropolitan collection system, there-
by benefitting the entire population by reducing or even preventing
these overflows.
Sewer Separation
Construction
Seattle voters in 1968 approved a bond issue to provide for separation
of sanitary sewage and storm drainage in the city's combined sewer
system over an area of 18,000 acres. The approved separation
area covered about half the total combined sewer system and slightly
less than a third of the city's total land area of 52,000 acres
(31). The areas to be separated are shown on Figure 12. Cost
details for 1958 for two different areas can be found in Appendix
D. Design of additions was predicated on, as a minimum, the City
£f_ Seattle Standard Plans and Specifications. (32)
Present Status
About 330 miles of storm drains will be installed. Of the 35
construction contracts awarded since the, program began, 23 are
complete. Of the 35 contracts, the city prepared plans for 9 and
design consultants, 26. Cooperation among the agencies and private
businesses involved has aided progress. (33) The present status
of individual projects is summarized in Figure 13.
The new storm drains are sized to carry 100% of the design storm,
even though the partial separation now being done intercepts only
70% of the stormflow. For a cost increase of 12%, storm drains
will have sufficient capacity to pick up the remaining 30% of stormflow
from roof and foundation drains, if studies indicate this action
is necessary. However, the cost to connect these individual drains
is estimated to be equal to or greater than the cost of the project
now under way.
Beginning in 1953, the City of Seattle has enacted a series of ordinances
that require all new construction or modernization of existing structures
to provide for separation of storm and sanitary drainage. Therefore,
as land use changes, complete separation will gradually be accomplished.
While the separation program is in progress, studies are being planned
to investigate whether it is possible to raise or plug various combined
sewer overflow weir points as a result of the decreased stormflow
following completion of partial separation.
31
-------
CITY LIMITS
LEGEND
L ok* Wo »h. South
ol
Loke Wain.
Lake Wa*h.
Uni vtr tit>
Magnolia
Quttn Anni
Lake Union
Longfellow
Witt S*att<*
Bollard
Lak* Union North
D iago na I Oahora
me nt Program Artoi
Not Includtd In N a mt Area*.
North
Nifthegit
Wtii
South
Alkl
0 I
SCALE IN MILES
Figure 12. Combined Sewer Separation Areas
32
-------
CITY LIMIT*
LEGEND
Completed
I///1 In Progress
IS£S1 Complete by 1974
I ^
I '/, 0
SCALE IN MILES
Figure 13. Separation Construction Status (March 1971)
33
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Infiltration Reduction
The Problem Defined
Sewer system designers have long provided surplus capacity for ground
water infiltration whether the capacity be provided in the form of an
allowance based on an acreage of area served or the length of the line
and its cross-sectional size. Typical infiltration specifications are
presented in Table 3 from the book Sewers for a_ Growing America. (34)
Permissible infiltration rates are the result of a balance between
the cost of requiring tighter joints in a small sewer and the cost
of a larger sewer with leaking joints. Actual infiltration rates
are estimated based on the type of sewer pipes and mechanical joints,
and are influenced by the age and physical state of repair of the
pipeline and the number of illegal stormflow connections to a sanitary
sewer. Figure 14 shows excessive infiltration that can lead to collapse
of a sewer.
On an acreage basis, the Seattle metropolitan area has a wide variety
of storm inflow and infiltration rates into various sanitary systems.
The Bothell area of about 5,000 acres has an infiltration of about
5 gallons per acre per day (gpad) under the worst storm and runoff
conditions. On the other end of the scale, the Lake City sewer area
has an infiltration rate of as high as 2,000 gpad. Improved materials
and quality control largely account for the improved infiltration
experience of the former system, which was built about 10 years after
the Lake City system. Metro experience indicates tighter joint speci-
fications can be attained in practice, as modern construction techniques
often limit infiltration to rates far below those allowed. Present
Metro design allowable rates are stated as 300 to 600 gpad for infiltra-
tion and 0 to 500 gpad for stormwater inflow (lower of the two rates
is for summer conditions; higher, winter).
Obviously, the waste of sewer capacity by excessive infiltration is
a serious matter not only because overflows and sewer backups may
result but also because allowances for infiltration require the use
of larger and more expensive sewer lines and will result in more expensive
pumping and treatment costs. The first problem then is to locate
the source of excessive infiltration in a combined or sanitary sewer
system.
Most infiltration and storm inflow enters sewers through loose joints
and abandoned house connections, leaky manholes and manhole covers,
and illicit sewer connections. Inspection on new construction work
will generally limit illicit stormwater connections; older illicit
connections have often been found using smoke tests and dye release
tests. Such studies located many sources of illicit storm connections
to the Lake City sanitary sewer. Corrections have already been made.
A regular program of inspection, either by specially trained inspectors
or film or television cameras, depending on sewer size, will locate
other sources of storm or ground water infiltration to the sewer system.
34
-------
TABLE 3
Infiltration Specifications
Allowable infiltration (gal./mi./24 hr.)
Source
Greeley & Hansen
Metcalf & Eddy
Havens and Emerson
Consoer, Townsend & Assoc.
Gannett, Fleming, Corddry, &
Carpenter
William A. Goff
Buck, Seifert and Jost
Whitman, Requardt & Assoc.
O'Brien and Gere
John Baffa
Nussbaumer, Clarke 6. Velzy
Miami, Fla.
Milwaukee, Wis.
Minneapolis, Minn.
Portland, Ore.
Seattle, Wash.
Syracuse, N. Y.
Tampa, Fla.
Tulsa, Okla.
Topeka, Kans.
Stamford, Conn.
Allegheny County (Pa.)
San. Auth.
Washington (D.C.) Suburban
San. Commission
Nassau County (N. Y.)
Conditions
(A) Consulting
Average ground
Wet, perv. ground
Average
Any short section
-
-
.
-
-
-
-
Average
-
(B) Cities and
-
-
-
-
-
-
-
-
-
-
-
_
Per in.
dia.
Engineers
-
500
1,000
500
200
500
-
-
250
-
-
500
Districts
1,000
-
-
0.5b
-
200
-
-
1,500
-
150
-
8- in.
pipe
5,000
10,000
4,000
8,000
4,000
1,600
4,000
5,000
7,000
2,000
1,400
4,000
4,000
8,000
5,800
3,500
5,100
3,200
1,600
10,000
25,000
12,000
1,160
1,200
5,000
10-in.
pipe
5,000
10,000
5,000
10,000
5,000
2,000
5,000
6,300
8,800
2,500
1,750
5,000
5,000
10,000
7,250
3,500
6,350
3,800
2,000
10,000
-
15,000
1,300
1,500
6,000
12- in.
pipe
5,000
10,000
6,000
12,000
6,000
2,400
6,000
7,500
10,500
3,000
2,100
6,000
6,000
12,000
8,700
3,500
7,600
4,400
2,400
10,000
-
18,000
1,600
1,800
7,000
24- in.
pipe
5,000
10,000
12,000
24,000
12,000
4,800
12,000
15,000
21,000
6,000
2,450
12,000
12,000
24,000
17,400
3,500
15,200
10,000
4,800
10,000
-
36,000
-
3,600
12,000
0.4 4,000
5,000 6,000 12,000
Short sections may be 100 per cent in excess.
Per 100 feet.
Reference: Sewers for a Growing America (34)
35
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Figure 14. Sewer Infiltration from Broken Brick Arch Section
It has been found that as much as 150 gallons per minute may leak
through a manhole cover. (35) Until recently the standard city manhole
lid in Seattle contained as many as 30 separate ventilation and lifting
holes, which allowed as much as 0.1 million gallons per day (mgd)
of stormwater to enter the sewer from each lid with a depth of only
1 inch of water above the lid. (30)
Clean-Up Still Incomplete
Even with the sewer projects thus far accomplished, including the
original local sewer system, the recently expanded interception lines
and treatment plants, advanced automatic regulator operation, and
stormwater separation projects, some pollution sources still remain
today. Heavy localized storms continue to cause overflows, even within
the larger Metro collection system. Power outages and other mechanical
failures periodically result in a bypass of combined sewage to a nearby
receiving water.
Storm drainage pollution, even in separated areas, may assume greater
significance as the combined sewer overflow problem is reduced. Chlori-
nation plants such as those being installed by the City of New Orleans
(36), and methods of screening, sedimentation, and chemical-biological
treatment are being studied for the Seattle area.
36
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One large reservoir of system storage that may be utilized to prevent
overflows still remains intact. The technique that must be used to
obtain this last measure of storage is becoming known as "total system
management." The simplest method of describing these small unused
pockets of storage within a large combined sewer system is to describe
the dynamic situation of an intense storm localized in one small drainage
area within the system. The drainage area beneath the cloudburst is
immediately saturated so that the regulator that transfers sewage
from the full trunk line to the interceptor is forced to overflow
to relieve the combined sewer system. Meanwhile, the adjacent drainage
area with only partially full trunk lines is transmitting its entire
flow to the nearly full interceptor.
Theoretically, by either routing flow from the saturated area to the
dry drainage area before regulation or by making use of storage in
the dry area, thereby allowing additional flow from the wet area into
the interceptor, it will be possible to make maximum use of all storage
within the system and minimize overflow to nearby waters. The diffi-
culties in manually locating these pockets of storage within a total
sewer system and of making flow calculations and predictions followed
by manual adjustments of mechanical equipment are nearly insurmountable.
Metro is now engaged in a 6-year study to determine whether a real-
time computer and highly instrumented automatic pumping and regulation
network will solve this problem of total system management and in
effect maximize the storage available within a combined sewer system.
This federally sponsored demonstration grant is described in following
sections of this report.
37
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SECTION V
MAXIMIZING STORAGE BY COMPUTER
REVIEW OF EXISTING CONTROLS
A review of the control procedures for motor-driven sluice gate regulator
stations in the Seattle area will help to explain how storage within
the combined sewer system can be maximized. The relationship between
interceptor and trunk water levels and regulator outfall gate positions
is outlined in Section IV, "Sluice Gate Regulators." Setpoint control
elevations were also briefly discussed. The important point here
is that the trunk setpoint is being manually established at a regulator
station so that at the worst possible combination of high tide, heavy
stormflow in the trunk, and a fully laden interceptor line would still
permit combined flow from the trunk line to escape from the sewer
system via a fully opened outfall gate without any resultant flooding
or backup conditions upstream in the trunk sewer drainage area. Once
the setpoint has been established, it remains essentially fixed through
the various seasons, unless manually altered.
It would be difficult and time-consuming to have a person or persons
visit each of the widely separated regulator sites to make adjustments
in the setpoint to compensate for thef dynamically changing water level
conditions occurring during each storm. But if it were possible to
do this, adjustments in the setpoint could allow a higher water elevation
in many instances so that additional storage could be gained and overflows
reduced or prevented.
By enlarging upon some basic rainfall information, it can be shown
how computer control of an entire sewage collection system might be
applied to gain additional internal storage. Figure 15 is a bargraph
of actual rainfall data for two summer storm types that occurred in
the Seattle area during 1967. Storm A illustrates the traveling storm.
Notice that although the total rainfall is fairly uniform over the
five districts, the peak intensity (most critical for overflows) struck
initially in the southwest and occurred nearly 2 hours later in the
northeast. Storm B illustrates the localized storm, where rainfall
was measured in the southeast and southwest districts only.
Figure 16 is a schematic explanation of how storage is maximized in
a representative system of three regulators, assuming that rainfall
intensities vary considerably from one drainage area to another. All
regulators would normally appear physically nearly alike, but only
one outfall line is shown for clarity. The illustration exaggerates
storm conditions by concentrating all rainfall in the drainage area
tributary to only one trunk. But, the theory can be logically extended
to cover any situation where rainfall intensities are significantly
different over separate drainage areas.
39
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N.W N.E.
.20 1
to
T
27th. Day z
A,"'
0
.20-,
INCHES
.10-
27th. Day
^m
0200 O 0200
HOURS
CENTRAL
27th. Day
A
6 0200
HOURS
S.W. 20-
26th 27th Days
r^
.10-
[z SE
x 27th Day
z
"A
2200 0 0 0200
HOURS
A. TRAVELING STORM
APRIL 27, 1967
N.W. N.E.
20-
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UJ
X
No Rain in z
this Region |0_
No Rain in
this Region
I2'00 I2'00
20 CENTRAL
Ul
x No Rain In this Region
z
.10" ~
12*00
HOURS
"S.w.w-«n
u
X
z
.10-
p
- S.E.
^
1200 1200
HOURS
8. LOCALIZED STORM
AUG. 23, 1967
Figure 15. Summer Rainfall Distribution Patterns
Part 1 of Figure 16 shows a storm concentrated in one area. Under
local control, gates operate to permit all trunks connected to the
interceptor to divert the flow from each trunk into the interceptor
and gradually fill the interceptor until storage is exhausted, resulting
in an overflow from the trunk that is filled by the increased stormflow.
With the proper application of computer control demonstrated by Part
2 in Figure 16, the regulator gates in all trunk lines not affected
by increased stormflow are closed to store water in the trunks, thereby
40
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PART I INDEPENDENT LOCAL CONTROL
PART 2 COMPUTER CONTROL
Trunk 8
I. DRY WEATHER FLOW
All gates open < 6\,t i ,
Z. LOCAL STORM TRUNK C, WATER RISES RAISING INTERCEPTOR AT C
2. LOCAL STORM TRUNK C, WATER RISES, RAISING INTERCEPTOR AT C
Regulator
gate open
Outfall
gate closed
Gates at A and B closed
J. LOCAL CONTROLS CLOSE REGULATOR GATE, STORING WATER IN TRUNK
3. COMPUTER CLOSES GATES A AND B TO STORE WATER IN TRUNKS
Regulator
gate open
Outfall
gate closed
Gates at C and B
closed
8
4. INTERCEPTOR FULL — OVERFLOW FROM TRUNK C
4. INTERCEPTOR NOW ACCEPTS MORE FLOW AT C PREVENTING OVERFLOW
Figure 16. CATAD Theory
-------
reducing flow into the interceptor and allowing greater amounts of
sewage and storm water to drain from the trunk that is filled with
storm runoff. The effective use of storage thus reduces or prevents
overflow from trunk lines that carry the largest portion of stormflow
to the interceptor.
This concept of maximizing storage throughout the system can be extended
to interceptor lines where substantial storage capacity has been made
available because the basic collection system is designed for ultimate
projected sanitary flows. By considering the interceptor system as
a number of trunk lines emptying into a common point, each of the
branch interceptors could be gated so that sewage is stored in areas
where total flow is small. The end result is the same as that suggested
in Figure 16.
The Metro system is designed so that in some instances motorized gates
and control structures have actually been installed in interceptor
lines. However, storage can also be generated by controlling the pump
stations that lift sewage from a low elevation to a higher elevation
on a pipeline to allow continuation of gravity flow. By slowing or
stopping the pumps at a station, the effect is the same as if a gate
were being modulated to control flow and maximize storage within the
interceptor itself.
Thus, with the proposed system of computer, control of regulator station
gates, interceptor gates, and pump station flow, it should be possible
to make the ultimate maximum use of all storage within a combined
sewer system. All these promising ideas were ultimately incorporated
in the federal demonstration grant program proposed in 1966.
DEVELOPMENT OF CATAD SYSTEM
Mr. A.M. Rawn, former chief engineer with the Los Angeles County Sanita-
tion Districts, has been credited with the original ideas for the
use of trunk storage in combined sewer systems. His idea included
a central console with pushbuttons to control some 50 storm gates
in the Los Angeles County area to gain additional storage and prevent
overflows.
Although the Rawn plan to gain storage through centralized control
was not incorporated in the Metro first-stage, 10-year construction
program begun in 1961, engineers did take into consideration the potential
for future centralized controls. Considered during design of one
of the first Metro construction projects (the Elliott Bay Interceptor
south of the deactivated Diagonal Avenue sewage treatment plant) was
a proposed plan for a small IBM 1620 computer (in a control room to
be located near the construction site). The computer was to monitor
and control the three regulators and one pumping station upstream
of the treatment plant. However, engineers were skeptical about
the costs and reliability of computer process control systems, then
42
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in their infancy. After much deliberation, the computer system idea
was shelved, and pneumatic controllers were built into each station
with provisions made for future remote control.
The plan to develop a system of computer-controlled mechanical regula-
tors to make the maximum use of storage within the Elliott Bay-Duwamish
River combined sewer system was formulated in 1965. The primary features
of the Computer Augmented Treatment and Disposal system (CATAD), at that
time, included the following: (1) five automatic regulator stations,
(2) a central computer, (3) central command console, (4) water quality
monitoring equipment, and (5) controls and wiring for an automatic
storage and regulation system. The proposed plan was presented to
various federal agencies for possible grant consideration. In late
1966, the newly formed Federal Water Pollution Control Administration
approved the grant proposal and awarded federal funds totaling $1.4
million.
Since the original proposal, many improvements have changed the appear-
ance of the original CATAD demonstration grant concept. In June 1967,
a plan for obtaining additional interceptor storage was formulated
with the request to use demonstration grant funds to construct the
Lake City tunnel regulator gate station to develop large amounts of
storage in the Lake City tunnel.
Another important influence on the CATAD control system was the rapid
development taking place in the computer and instrumentation field.
During this period, vastly improved third-generation computers were
being developed, and the improvements were incorporated in the design
of the central computer for the Metro control system. The new, improved
computers allow Metro to consider a large and rapid system that can
function as both a real-time process control computer and a background
business and engineering type of computer. Such a dual-purpose applica-
tion could not have been considered if the CATAD system had been built
as few as 5 years earlier. The outstanding features available with
the new generation computers provide Metro with a great deal of additional
computer capacity and many potential uses that are just beginning
to be realized.
In 1968, consultants completed the design specifications for the computer-
controlled regulator system, incorporating provisions for additional
future stations. The future additions are shown in Figure 17. They
consist of: (.1) the West Seattle system of five pump and regulator
stations and a small primary treatment plant, and (2) the Renton system,
including nine pump stations and one major secondary treatment plant.
A primary feature was the main central console, which was to cover
the entire wall of a large control room with a separate cathode ray
tube for displaying operating data from each station within the CATAD
system.
43
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Figure 17. Computer Terminal Locations
-------
The final and most visible changes took place during 1969 when the
contractor who undertook the construction of the CATAD system proposed
additional design changes and improvements. Metro accepted a number
of these suggestions; as a result, the CATAD system now includes an out-
standing command control console similar to a console complex built for
the NASA Houston Space Center. The main features of the console are
shown in Figure 18. They consist mainly of an active lighted wall map
display and operator console. The map display graphically shows the
entire Metro sewage collection system and its operating facilities. Now,
data from seven or fewer stations is being displayed on the CRT's at any
given time. An operator seated at the control console, immediately in
front of the map display, can observe data output from the various sta-
tions , manually enter control commands, and quickly order a hard copy
record of all operating information from the 37 regulator and pump
stations in the CATAD system. (Refer to Appendix E.)
Basically, the CATAD system has not changed to any degree since the 1968
contract was awarded and initial change orders approved, though some
stations originally labeled "future" are now operating within the system.
The extreme flexibility of CATAD, as it was originally designed, has
allowed Metro to include many features that at first were not even
envisioned. The features of the system as it exists and is operated at
this time are detailed in succeeding sections of this chapter.
COMPUTERIZED TOTAL SYSTEM MANAGEMENT
Real-Time Control
The development and implementation of computers within sewage collection
and treatment agencies and municipal public works is small in comparison
to other industries, even though objectives are similar and management
processes are nearly the same. Many unrelated industries have placed
primary emphasis on computer control in a determined effort to improve
product quality and reduce production costs. Such industries as petro-
leum, gas, chemicals, cement, power, iron and steel, and paper have made
tremendous strides in the use of computer process control for automating
and managing their plants. (37)
The sewage collection and treatment field, although entering the realm
of computers relatively late, is now beginning to make use of this tool
in the management and control of plants and personnel. Computer appli-
cations in this industry are rapidly expanding as a result of increases
in federal funding, growing concern over water quality conditions, and
partly as a result of the tremendous success other industries have had
with real-time control systems.
The term "real-time control" is worthy of some additional explanation.
Real-time can be defined as the method of processing data so fast that
virtually no time passes between inquiry and result. Real-time process
control implies, or more correctly requires, the use of a digital
45
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Figure 18. CATAD Console
computer in the control loop, as pictures in Figure 19. The three
diagrams in Figure 19, adapted from the APWA report Feasibility of Com-
puter Control of Wastewater Treatment (38), show the progressive develop-
ment of a real-time or immediate responding control system from off-line
computers to on-line computers to actual computer control.
Metro CATAD Control System
Metro is in the process of assembling a real-time process control system
with the primary objective of maximizing storage within the sewage col-
lection system and minimizing combined sewage overflows. The CATAD sys-
tem can be divided into the following main components:
1. A central digital computer and internal control program.
2. A console where human-oriented information is communicated.
3. A series of remote terminals where information is generated and
control functions are accomplished.
46
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A. Process Operation
Assisted by Off-
Line Computer
Operating
Instructions
B. Process Operation
Assisted by On-Line
Computer
C. Process Operation
Controlled by Computer
Recorders
On Line
Computer
Log
Figure 19. Real-Time Process Control Implementation
4. A telemetry network for high-speed transmission of data be-
tween the computer and the remote terminals.
Figure 20 shows schematically how the various components relate to each
other in the basic CATAD operating system. Information will first be gen-
erated at block 1 on the diagram, from a bubbler, rain gage, or other
sensor. Spread throughout the Metro area are various analog sensors and
alarm contacts that develop information about water levels or equipment
status in the form of varying voltages or contact positions. At block 2
in the diagram, information from block 1 is converted to digital data,
47
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CENTRAL CONSOLE
PERIPHERAL
TYPEWRITER
CARD READ
LINE PRINT
PAPER TAPE
PLOTTER
ETC.
16
MAIN PLANT
CONSOLES
14
LEGEND
r—-j
-^-{CRT'SK
I I
COMPUTER
(Including
Control
Model)
I \
*-lCONTROLSp
I I
CONTROL
PUSH-
BUTTONS
10
INTERFACE
LOGIC
FUTURE
EXPANSION
ENCODERS 8
DECODERS -
TRANSMIT 8
REGULATOR AND PUMP STATIONS
REMOTE TERMINALS
On Line
Telemetry
Off Line
GATE
OPERATOR
II
INLET WATER
ELEVATION
12
Figure 20. CATAD System Schematic Diagram
48
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placed in a coded message, and converted to frequencies suitable for
transmission over the telemetry system.
The telemetry system consists of duplex voice-grade phone lines with
special security procedures and conditioning added to minimize the type
of electrical interference that might destroy or alter the coded message
between central and remote terminals. Following successful transmission,
at block 3, receivers and encoders convert the coded message to data
that can be transmitted through special interface logic at block 4 to
the main digital computer at block 5.
Once inside the computer, the data is acted upon by a series of
coded instructions (or programs) that convert the data into information
suitable for output to either a visual display represented by
a cathode ray tube (CRT), shown as block 6, or a logging type printer,
shown by block 7. At the same time, programming within the computer
generates alarms in the form of flashing lights, printed messages,
or audible alerts (blocks 7, 8, and 9). Once information or alarms
have been output at the central console, an operator can respond
to the conditions through the control pushbuttons, labeled block
10 in the diagram. His instructions are transmitted to the computer,
then back through interface logic, encoders, and the telemetry
system to remote terminals where blocks 11 and 12, which symbolize
control operations, react to the control command. Information
about the manner and speed of equipment reaction is transmitted
back over the same lines to restart the cycle.
In addition to the main features of the CATAD system, Figure 20 also
includes some additional features to illustrate the capacity and
flexibility of a computer system. Block 13 is a general reference
to some of the future remote process control functions currently
under consideration. Water quality information is transmitted
to the central computer over phone lines from monitors at five
separate locations along the Duwamish River, as symbolized by
block 15. In case of mechanical or electronic problems with the
central console or during periods when the central console is not
being operated, monitoring and control is transferred to the two
main plant consoles, symbolized by block 13. The last operation
represented on the diagram is the peripheral equipment listed in
block 16. Initially, the computer will be occupied with its process
control tasks for only 30% of the available processing time. Therefore,
it is expected that considerable use will be made of available
background time for common managerial applications such as information
reporting, accounting, engineering, and mathematical problems.
Block 16 lists some peripheral devices that will be physically
attached to the computer for these purposes.
49
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Computer Learning Process
The development of a complex computer control system can be likened
in many respects - to the development of intelligence or its equivalent
within the animal kingdom. The more complex the animal brain and
physical system is, the longer 'it takes for the animal to achieve
its full mental potential. The same situation exists in computer
systems; a large, complicated computer-system intended to control
many interrelated functions requires many weeks and months of engineering
and programming time to fully implement its potential. This in
part explains the projected length of the 6-year development period
for the Metro CATAD control system.
The developmental phases of the CATAD system can be compared with
the development of intelligence within the human species. The
digital computer is initially provided with the basic "instincts"
for inputting and outputting information in some form. The computer
manufacturer has provided the computer with a basic form of intelligence
that allows it to control the input and output of data and interpret
the various forms the data may take. Memory cells are provided
so that the computer can accept prepared instructions and data
and store this information temporarily or permanently in various
forms of storage. At this point the computer might be compared
with a new-born infant.
An instrumentation and electronic contractor, Philco-Ford Corporation,
Western Development Laboratories, is presently taking the CATAD
system'through-what might be/termed its' "childhood" phase. Programs
have been written and are being'integrated to instruct the computer
in how to interpret specially coded ;inf ormation transmitted over
telemetry lines and convert this basic data into dot patterns that
form visible letters on cathode ray tubes or hammer instructions
that will print information on teletype printers. These programs
enable the computer to energize relays; turn on lights and other
signals, and interpret-pushbutton patterns, which are instructions
from a human operator. In effect,-the1 computer is being taught
how to read, write, and communicate with both instruments and human
operators.
The last phase in the CATAD system development will be the "adult"
or final application stage. Metro's consulting engineers are preparing
to guide the computer system through this final control stage. Very
complex and sophisticated control, Calculation, and simulation
programs have been designed and are being written so that in the
next 2 years, it is expected that the computer will be fully educated
and, in effect, have its "college degree11 as a completed on-line
process control computer.
50
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SYSTEM COMPONENTS AND PROBLEMS
In the computer control field, there is a boundary or interface between
hardware and software. Software consists of programs made up of com-
puter instruction sequences and data to be used by these instructions
in the performance of some action. Hardware comprises the physical
circuitry equipment and electronic,components that make up the computer,
A typical program (200 instructions) using both hardware and software
during execution will be finished about one-thousandth of a second
after it is started.
Also in process control systems, but on the other end of the spectrum,
are what might be termed "slow-ware," which comprise the motors,
sensors, gages, and other devices that, when compared to computer
hardware and software, are extremely slow-acting equipment. With
slow-ware, minutes or seconds may pass before discernible differences
can be detected. The timing problem is complicated because the
central computer, operating at extremely high rates of speed, is
necessarily communicating with a multitude of relatively slow-
acting devices.
Central Computer
The heart of the CATAD system is a high-speed digital computer
manufactured by Xerox Data Systems and called the Sigma 2. Detailed
information about the computer is presented in Appendix L.
The Sigma 2 computer system was selected because of its fine record
in process control applications and its excellent hardware and
software protection features. For the CATAD application, the computer
is divided into foreground and background areas by a boundary that
can be automatically adjusted when program size requires this change.
The computer system is continuously performing one of three tasks:
1. Foreground data acquisition or control tasks.
2. Background programs and input-dutput operations.
3. Idling in a state awaiting foreground or background job
requests.
Foreground operations consist of such tasks as scanning all stations
for data at timed intervals, printing a complete system log each
hour, or checking on a common operation to generate alarms in case
of failure. Each of these operations is started by a countdown
clock that is unique for each foreground task. Each countdown
clock is initially set to some value, then is decremented by a master
real-time clock that keeps time for the system, until the countdown
clock reaches zero, triggering the foreground task and resetting
the triggered clock to its initial value. Foreground tasks are
all assigned a higher priority than background jobs and are also
protected by hardware and software so that background problems
cannot affect any of the foreground operations.
51
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Because of the extreme high speed of the computer system, the amount
of core memory, and the high-rate input-output equipment available,
foreground tasks occupy only about a third of the available computer
time. Therefore, the computer can be assigned many background jobs
such as accounting or engineering problems.
One useful feature is that, in cases where both foreground and
background programs take up the entire available core memory, the
background job can be interrupted and its program status and all
register contents instantly written onto the bulk memory device.
The foreground operation is then completed and the background job
replaced in core memory and restarted, all in such a short time
as to be nearly unnoticed by the computer operator. This background
interruption procedure is called checkpointing.
Background programmers have many alternative peripheral devices
to select from. Figure 21 illustrates some of the main computer
units on the control room floor. Additional details about these
units can be found in Appendix L.
Universal Computer Startup Problems
Problems and delays in getting computer systems operational are
universal. The CATAD system probably has had more than its share
of these problems, but possibly the experience gained from this
system can be helpful to other agencies contemplating a similar
computer control project. Difficulties can be categorized as either
physical (hardware) problems or programming (software) problems.
CATAD hardware has had a fine record of operation in the 2 years
since it was initially assembled. Electronic components have failed,
but such failures have been average or less frequent than normal,
considering the state of the art of solid-state electronics. Surpris-
ingly, the most vexing problems have been that of heat removal,
air conditioning, and simple physical installation considerations.
Failures with circulating fans have caused some electronics overheating
and subsequent failure. The air conditioning system for the computer
room itself has been revised and reinstalled twice by the contractor;
even now, modifications are needed to satisfy insurance requirements.
Size and weight of the equipment contributed to two additional problems.
First, the computer system could be moved into its permanent location,
an office building, only by removing a building window and lifting
components by crane through the opening (see Figure 22). Once
inside the building, certain computer elements were of such extreme
weight that they had to be located over structural beams so that
floor damage would not occur. The maze of signal and power cables
required construction of a special combination equipment platform
and cableway to enclose the cables and conduits.
52
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Figure 21. Central Computer and
Equipment
Figure 22. Computer Delivery
Through Second-Floor Window
The problem of maintenance responsibility for equipment from different
suppliers is a difficult one to resolve. Even if it were possible
to assign the maintenance responsibility for all equipment initially
purchased to one firm or individual, later additions to the computer
system or to the total control system will increase the maintenance
requirements, and responsibilities will overlap and conflicts will
develop. Metro requested bids for a maintenance contract as part
of the original CATAD specifications. As a result, the prime contractor
has assumed responsibility for essentially all of the computer,
communication, and interface equipment. However excluding the two
telephone companies, ten different agencies are performing some
level of maintenance on parts of the CATAD system, four groups act
as subcontractors to the prime contractor.
Contrary to most business computer systems provided by manufacturers
to commercial firms or large industries, CATAD, as with many other
real-time applications, became enmeshed in complicated programming
problems that forced delays in planned schedules. One of the major
contractor problems was that very few experienced and competent
real-time system programmers were available. Those who are competent
are often attracted to other firms, and the resulting turnover
has undesirable effects on control system schedules. The CATAD experi-
ence was that programmer turnover led to a delay in completion of
at least 1 year.
Another problem in computer control systems is that few manufacturers
provide executive programs that are particularly directed to real-
time process control systems. The contractor on the CATAD system
found it necessary to develop an executive program to augment the
basic foreground-background operating system provided by the computer
manufacturer. The computer manufacturer would not allow his customer
53
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(the contractor) to modify the basic executive program, but the
contractor still had to overcome certain system deficiencies.
This led to extensive programming time and purchase of additional
core to meet foreground time use restrictions of 30% imposed by
the contract specifications. The extra core memory provided was
to Metro's benefit, but the time delays were not.
One important feature of the specifications was the provision that
a large benchmark program had to be executed by the contractor-
supplied operating system in background at the same time foreground
was operating. The benchmark program pointed out deficiencies
in the operating system because the same program that could be
run in a minimum of 14,000 words of core memory could also run
on a more efficient executive system with only 8,000 words of core
memory. Because of the benchmark provision of the specifications
the contractor had to provide the larger core memory.
One problem that affected both software and hardware was the requirement
that the CATAD system be able to restart itself automatically in
case of a power failure. Some elaborate programs had to be written
and certain hardware modifications incorporated to provide an automatic
restarting capability. Emergency power was not contemplated for
the CATAD system because all remote terminals being controlled
have emergency power systems and, in case of power failure to the
central computer or telemetry failures between the computer and
any remote stations, provisions were made so that remote terminals
will automatically return to local control systems until power
is restored to the central computer. In designing future systems
similar to CATAD, a consideration should be given to providing
emergency power to a central computer and developing 100% reliable
communications systems, thereby reducing control systems required
at remote terminals, and the interfacing problems that result directly
from these complex independent control systems.
Operator's Console
Immediately adjacent to the computer equipment is the operator's
console and wall map display, which will serve as the interface
between the human operator and the control system. The relationship
between the console and computer areas is illustrated by the floor
plan in Figure 23.
The operator's console consists of three main parts: a desk-type
control console, alarm and events teletype printing units, and lighted
wall map display. These combine to enable the human operator to
either control or strictly observe the various functions of each
of the remote stations. The various control and display sections
of the console are pictured in Figure 24. At the front of the
console, proceeding from left to right, are the following functional
areas:
54
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Ul
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
MAINTENANCE
AND
EQUIPMENT
AREA
XX XXX
MAP DISPLAY BOARD
FEET
OPERATORS
CONSOLE
-TELETYPE
COMPUTER
AND I/O
AREA
z o
o tu
o
ENCLOSURE
A VIEWING AREA
;
•N
*
XXX X
Figure 23. CATAD Central Control Floor Plan
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Figure 24. Console Sections
1. The control panel, for entering or cancelling various types
of commands.
2. The command panel, for selecting the type of command desired.
3. The West Point station selector, for selecting the station
to which the command will be directed.
4. The alarm panel, which displays the type of alarm or alarms
at any selected station.
5. The status panel, which, indicates the status of all commands
in progress.
6. The Alki and Renton station selectors, which function similar
to the West Point selector.
7. The segment selector, which is used to select which part
of the total CATAD system will be displayed on the seven operating
cathode ray tubes immediately above the control panel. (Only seven
of the 37 total stations can be displayed at any one time. One
cathode ray tube is a spare and is not wired into the system.)
8. The last section on the far right of the console is the
communication section, where radio and telephone communication can
be maintained with mobile units and other maintenance and operation
personnel.
56
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Above the console area is the bank of seven cathode ray tubes, which
display quantitative data from the pumping and regulator stations.
The seven or fewer stations displayed at any one time are located within
a common area arid are operationally related. Displayed data will include
such information as water levels and gate positions plus computed
information such as sewage flow rates and storage volumes. Formats
for these information displays are flexible, but an example of
typical formats for the different types of stations is shown in
Figure 25.
Visible also in Figure 24 is the wall map display, which pictures
the Metro collection system and future extensions to the system
within the entire drainage area. The wall map supplements the
operator's console by associating each cathode ray tube (CRT) display
and each alarm with its geographic location. Within the symbol
for each regulator or pump station is a four-segment lamp to indicate
the condition at each station. An explanation of the wall map and
lamp features is outlined in the,wall map legend shown in Figure 26.
Figure 27 illustrates one important extension to the central operator
console. This is a photograph of the West Point remote console.
The CATAD system was designed to permit operator attendance at the
control center for a single 8-hour shift on weekdays. During these
normal working hours, the majority of' system observations, modifications,
and maintenance will be accomplished. At other times, the system
will be monitored at satellite terminals installed at the two main
sewage treatment plants, which are operated twenty-four hours a
day. The remote consoles will receive all system alarms as a visual
display and a printed hard copy from the teletype. The plant operator
will be able to request a display on the cathode ray tube of the
conditions at any selected remote station. A limited number of control
actions can also be accomplished from the remote consoles pictured
in Figure 27.
Telemetry System
In any real-time process control system, a method of communicating
between the control computer and remote points must be decided
upon. Construction and operating costs, ownership, and security
factors will influence the final selection of a hard-wired, telephone
line, telegraph line, microwave, or radio wave system. After a
thorough analysis of the different communication alternatives and
numerous discussions with telephone company personnel regarding
security precautions, it was decided that the telephone system
would be used for CATAD. Metro consultants recommended that a high
degree of security be maintained in message telemetry and that
remote stations be specially controlled to prevent unnecessary overflows
in case of telemetry failures. In the normal scanning operation,
a command is issued sequentially to each remote station from the central
computer to begin transmission of the coded message groups from the
remote site. A list of typical data transmitted is presented in Table 4.
57
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LANDER ST. REGULATOR STATION
INTERCEPTOR
INTERCEPTOR LEVEL 00.0
REGULATOR SET- POINT 00.0
FLOW SET- POINT OO.O
DIVERTED FLOW 00.0
FLOW DOWNSTREAM 00.0
REGULATOR POSITION 00.0
INTERBAY PU
STATION
INFLOW 1 0000
INFLOW 2 0000
OUTFLOW 0000
INLET CHANNEL LEVEL 00.0
STORAGE RATE 0000
SETPOINT LEVEL 00.0
CONTROL LEVEL Oo.O
CONTROLLER OUTPUT 00.0
TRUNK
LEVEL UP-STREAM
REGULATOR SET- POINT
TRUNK IN- FLOW
STORED FLOW
BY PASSED FLOW
TIDE LEVEL
OUTFALL GATE
MPING STATION
PUMPS
MODE
SPEED 1
SPEED 2
SPEED 3
SPEED 4
SPEED 5
SPEED 6
00.0
00.0
00.0
oo.o
00.0
00.0
00.0
0000
0000
0000
0000
0000
oooo
0000
Figure 25. CRT Display Formats
58
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WALL MAP LEGEND
SYMBOL
DEFINITION
EXISTING SEWER LINES
FUTURE SEWER LINES
INTERIM SEWER LINES
METRO BOUNDARY
METRO DRAINAGE AREA
PUMPING STATION
REGULATOR STATION
TREATMENT PLANT
LAMP CODE
(WHITE)
STATION BE-
ING DISPLAYED
ON CRT
(IF BLINKING)
STATION SELECTED
FOR ACTION
(ORANGE)
WATER LEVEL
ALARM
(RED) STATION
IN ALARM CON-
DITION
(IF SLINKING)
NEW ALARM
NOT YET AC-
KNOWLEDGED
(GREEN) STATION
UNDER REMOTE
CONTROL MODC
Figure 26. Wall Map Legend
Figure 27. West Point Remote Console
59
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TABLE 4
Typical Telemetry Scan Message Content
Number of
Item Description Similar Items
1 Command status relays 12
2 Power on/off relays 2
3 Equipment status or alarm 6
4 Spare contact inputs 60
5 Pulse counters 2
6 Spare pulse counters 2
7 Reference voltage 1
8 Water levels 3
9 Equipment operating position 4
10 Operating levels 2
11 Spare analog inputs 2
To provide the highest degree of security, each telemetered control
or data message will contain a parity bit (indication of even or
odd number) and will be doubly transmitted. Each message is checked
at the receiving point and compared for parity, bit by bit, with
the first message. If an error is detected or the first two messages
do not agree, the data will be retransmitted.- Unsuccessful transmission
after three tries will trigger a station telemetry alarm.
The data transmission rate is 1,200 bits per second over the leased
telemetry facilities. A separate transmit and receive pair of
conductors has been installed to each station. Special security
measures have been ordered by the telephone company to protect
all circuit terminals against unintentional disconnections. Balancing
coils, amplifiers, radio frequency isolators, and special loop-
back devices have been incorporated into the telemetry system by
the telephone company in a determined effort to provide a minimum
amount of interference and a maximum response to possible telemetry
problems. .
The initial experience of operating the CATAD system with telephone
circuits has been promising, and only time will tell if maintenance
responsibility and ownership boundaries between phone companies
and those using the service will eventually result in disputes
and operating problems. As an example of the reliability and high
60
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speed of the CATAD system, the entire sequence from beginning to
end of a scan of all 37 stations takes about 40 seconds. Scan intervals
can be ordered from the operator console at any interval from 1
to 10 minutes. It is expected that scan intervals will be widely
spaced during the summer dry season in contrast to winter storm
periods when scanning may be as frequent as 1-minute intervals.
Parallel Alarm System
Since 1966, Metro has had an operating telemetering alarm system
to each remote station in the collection and treatment system.
The system, called "Metrotel," now includes some 60 remote transmitters
that send three general alarms, using a frequency shift principle,
via voice-grade telephone lines to two receiving and recording stations
located at the West Point and Renton treatment plants.
When the reliability of the CATAD system has been proved over a
period of time, perhaps a year or two, it is planned to remove the
Metrotel station alarm system at facilities where CATAD monitors
are being installed. The Metrotel system will continue to function
at smaller stations and other points within the collection system
where the investment for a CATAD telemetry terminal is not warranted.
In the distant future, this parallel system may be interfaced to
feed directly into the CATAD system.
Remote Units
At each remote station, an additional element of the high-speed
computer system is labeled a telemetry control unit (TCU). The
unit, pictured in Figure 28, is built with solid-state electronic
components similar to the computer. It converts data and transmits
information between the station equipment and the computer via
telemetry lines. The TCU contains a modem, analog-to-digital conversion
circuits, encoding and decoding circuitry, pulse counters, and
other equipment in the form of small integrated circuit modules
that plug into a terminal board. The TCU design makes any single ,
unit interchangeable with any other station by simply rearranging
the circuit modules and changing a hard-wired address code.
Problems can exist within the station that may not be sensed by
the telemetry control unit and subsequently by the computer. Any
operator or maintenance man who observes a serious problem within
the station can, by simply throwing a single switch on the TCU,
disconnect the computer system from station control, thereby returning
the station to the local control system to manually override computer
commands at the station site.
61
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Figure 28. Telemetry Control Unit
Maintenance Considerations
One other important feature is visible at the telemetry control unit
the bottom of the equipment box is the computer maintenance
^sponsibility boundary. Computer systems specialists are not familiar
th sewage collection pumping and regulator stations, just as
iewage treatment specialists are unfamiliar with computer electronics
Therefore, a boundary had to be decided upon; it was placed at
the bottom on the TCU box where a plug connected to station equipment
with a socket receptacle permanently installed in the TCU.
The description and reason for the seven separate cables interfacing
int will be explained in the next section of this report
:cept for the telephone and power plugs, which enter the top of
box, this is the point where the computer system terminates
and local station electronics and controls begin.
REMOTE TERMINAL MODIFICATIONS REQUIRED
Interfacing
Construction of the sewage collection system, including pipelines,
egulator stations, and pump stations, has been described in this
report as well as the computer control system and telemetry system
62
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that will transmit monitored data and commands between the two
elements. However, it is not a simple task to take information
developed at each station and merely plug data cables into a transmitter
and expect to have any type of logical information develop. A given
signal voltage representing a gate position or water elevation must
be converted through various electronic devices into information
that can be understood and relayed to the computer for further
operation. This "mating" of station signals to computer signals,
called interfacing, is no simple task. Switching between various
voltages, common ground requirements, and analog-to-digital and
pneumatic-to-electronic conversions are difficult even under the
most advantageous conditions. The situation in the Metro system
was even further complicated because of the many differences in
the remote stations; many changes in instrumentation had been made
during the 8-year period between 1962 and 1970.
Although there are experts in the computer control field and design
engineering experts in the sewage collection control station field,
there are few highly qualified experts at interfacing these two
systems together. Any agency starting out on a similar system should
be ready to accept the trials and mistakes that will arise when
attempting this phase of a process control system. Of prime importance
are the qualities of understanding the systems being interfaced,
of coordination, both written and oral, between the various personalities
ajid agencies iqvplved, $nd of an honest awareness of the difficulties
}.n, attempting such a project;. Supervisors must be prepared to
accept 3 flexible dea^ine because unforeseen problems in interfacing
are the rule rather than.£he exception. Although the continual
delays are frustrating, the end rewards are sufficiently gratifying
to justify the money and effort expended.
Space Considerations
When much of the coordination and preliminary engineering requirements
have been established, space considerations become a serious limitation,
as illustrated by Figure 29. The photograph shows the Brandon
Street regulator station and shows a congested appearance caused
by the many instrument cabinets required to interface a regulator
station to a computer many miles away. The Brandon Street station
is one of the earlier regulator installations constructed within
the Metro system, and, although future centralized control was
allowed for, there was very little awareness of the amount of instru-
mentation that might be required. In newer stations, all the electronics
are being installed in spacious instrument panels, resulting in
much less difficulty in the operation and maintenance of these
local control systems.
63
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Figure 29. Congested Regulator Station
Changes to Station Controls
CATAD system control procedures are well documented in an article
published in Water and Waste Engineering. (39) In summary, electronic
equipment was needed in each remote station to perform several
system control functions:
1. All remote control is done indirectly. That is, the computer
or operator will impose a calculated water level setpoint elevation,
which the station local control system will follow with its own
control sequences.
2. Remote control of the setpoint is accomplished by transmission
of a contact command signal to the remote terminal. The signal
operates a contact in a circuit from a variable-rate pulse generator
to a stepping motor. The stepping motor drives a potentiometer,
which produces a proportional voltage output signal. The voltage,
an analog signal, is transmitted back to the computer until it
reaches the desired voltage level, whereupon the computer terminates
the process.
3. A control-restoring sequence is provided in case of loss
of signal from the computer. The restoring circuit equalizes the
remote control setpoint with a constant signal from a manual setpoint
device at a prescribed rate through a closed-loop balancing circuit.
4. Three-pen chart recorders provide a basis for comparing
station operation and responses to information available at the
computer and for recording events that transpire when a station
is in local control and computer logs cannot be generated.
64
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To obtain the signal quality and precision needed in keeping with
the computer process, some modifications were required to existing
station controls and sensors. The goal was to obtain signal quality
that would have a minimum of interference or noise while maintaining
a tolerance of 2% or less from the point the signal is generated
to its storage and output location at the central computer terminal.
Such precision can be obtained in many cases only by replacing
existing signal cables with larger shielded cables or'by replacing
gate position indicators with newer, more sensitive devices. Cables
and connectors were specified to provide a path for some 184 separate
conductors (including an average of 22 spares for future applications)
between the station control system and the telemetry control unit.
Figure 30 illustrates the differences between interfacing equipment
required at a regulator station and that at a pumping station.
Maintenance Inventions
To prevent the age-old habit of one person pointing a finger at
another when a problem exists, and to reduce the time needed to
determine the source of a signal problem and on whose side of the
interface boundary the problem originated, the persons responsible
for maintenance on either side of the interface developed a device
to isolate any potential problems. By quickly disconnecting the
seven cables that link the computer system to the station controls,
an instrument technician can reconnect the cables to a special instru-
ment, called a simulator, and quickly locate the source of any problem.
Because there is no guarantee that an instrument technician will
arrive first at a troubled station, Metro maintenance personnel
have a similar device to isolate problems in their system. Figure 31
shows the two different simulator units in operation.
The simulation equipment has been an invaluable tool in the location and
correction of problems in both the computer system and the remote sta-
tion control systems prior to the physical connection of the two systems.
It would appear that some duplication of effort exists in the two simu-
lator devices and that some funds and personnel might be saved by com-
bining the two maintenance functions. At this time, Metro and its
consultants feel that the technicians and engineers responsible for the
computer controls and those responsible for local station controls are
unprepared to assume maintenance responsibility for the entire system.
The initial period of dual maintenance responsibility possibly will indi-
cate whether a single maintenance group can gradually take on the mainte-
nance responsibility for the entire system as technology develops.
FLOW MEASUREMENT STUDIES
Early phases of program development revealed that continuous flow measure-
ments were needed throughout the collection system to provide sufficient
data input to a simulation model for use by the computer to properly
control the CATAD system. The Metro collection system was analyzed to
65
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imp Station-C.C.U. B. Regulator Station-A. C.U.
Figure 30. Remote Transmitting Terminals
A. Pump Station Simulator B. Telemetry Unit Simulator
Figure 31. Interface Testing Equipment
66
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determine where flow data could best be acquired. Many of the existing
structures in the system provided convenient locations for the gathering
of flow parameters. Remote depth telemetering stations are being con-
sidered at critical points where flow data cannot otherwise be continu-
ously obtained.
Available Measuring Points
One group of structures being used to transmit flow data are the
existing regulator stations. In a regulator, sewage passes control
devices such as weirs and gates where flow can be determined with
sufficient accuracy by using the appropriate weir or orifice discharge
formula and knowing the depth of flow at these control sections.
The data collection system provides the needed depth of flow.
The existing pumping stations provide another location where flows
can be calculated. By combining pump speed and head data, both
supplied by the data collection system, with manufacturers' certified
pump curves, which are available for every pump in the system,
a flow can be determined fairly accurately for a newly installed
pump. However, a number of factors have reduced the accuracy of
the pump curves. Because this is a combined sewage system, grit
and other materials in the sewage have caused wear of the impellers.
Also, repairs and other adjustments have been made to the pumping
equipment after installation. Thus, the certified pump curves
are no longer a satisfactory method by which flow can be calculated.
Force Main Calibration
The pump station force main can be used as a primary device for
flow measurements. The problem is selecting a satisfactory and
flexible method to calibrate the force mains. One means of calibration
is the total count method using radioisotopes. This method was
decided against because of the frequent difficulty in obtaining
a usable range of flows in the force mains. Sufficient flow is
dependent upon rainstorms in the area and would tie up a radiological
safety officer or some other person trained in the use of isotopes
for a long period of time. The highly trained individuals and
elaborate equipment needed indicated that total count procedures
would not be readily repeatable by the Metro maintenance crews.
The method finally selected was an adaptation of the "Allen Salt
Velocity Method of Water Measurements." (40)
The use of the salt velocity method requires that the force main
head be kept constant between the time salt is injected until it
is sensed at the discharge end of the force main. In many cases,
this requires a period of half an hour or longer. The rate of
flow can be calculated by dividing the volume of water displaced
in the force main by the length of time that passed while displacing
the known volume. The volume is computed from "as-built" drawings.
The time is determined by injecting salt into the suction side
67
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of the pump and then measuring with a conductivity meter at the
discharge end of the force main to determine when the salt slug
has reached the end of the pipe. Stop watches are used to measure
the time for the salt slug to travel between the two known reference
points. The salt is injected into the sewage pump suction from
a container holding five to seven pounds of salt. The container
is pressurized with compressed air, and a quick-acting valve is
actuated, blowing the dry salt into the pump suction.
Force main pressure is held constant during a calibration run by the use
of a pressure sensing system that has been calibrated to acceptable
limits. This system consists of a pressure transmitter having an accur-
acy of 0.15% of full scale, a range of zero to 100 pounds per square
inch gage (psig) with an output signal of zero to 5 volts dc proportional
to the pressure. The recorder is a laboratory model with an equivalent
accuracy. Conversion of the raw data results in a calibration chart such
as that shown in Figure 32. These calibration techniques are being used
on all CATAD pumping station force mains. The data collection system
will transmit force main pressures to the central computer for flow
calculation.
Additional Flow Measurements
Other structures in the system provide locations that would yield flow
information. One such point is the Fremont Siphon on the North Intercep-
tor. It is believed that knowledge of the head on this inverted siphon
can lead to calibration of flow through the siphon. Figure 33 shows
the design of the depth recorder to be used. A sonic sensor, accurate
to +^ 1% of scale, relays water depth to an above-ground enclosure where
telemetry equipment sends a modulated signal over a standard voice-grade
line to a nearby regulator station. At this location, the analog input
is converted to digital output to the data collection system. Similar
flow depth recording equipment is being contemplated at other points in
the Metro system. The cost of one of these self-contained depth record-
ing stations is estimated to be $8,500.00.
WEATHER ANALYSES
A series of weather analyses were begun late in 1969 to determine
what types of meteorological quantities would provide the best
information for predicting storm intensities and actual wet-weather
flows in the combined sewer system. Theoretically, with a lead
time in excess of 2 hours, any excess storage being used in the
Seattle collection system to level sewage load to the major treatment
plants could be quickly released and the system drawn down to the
fullest extent possible to gain the maximum amount of storage in
preparation for the predicted rainfall. The study was divided
into two main sections. The first was based on precipitation data
only and covered a 3-year period from 1965 through 1967. The second
section considered wind speed and direction data in addition to
precipitation. Weather data was provided by observers at three airfields
68
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in the Puget Sound Basin: (1) Seattle-Tacoma International, 10
miles south of the center of Seattle, (2) McChord Air Force Base,
22 miles south-southwest of Seattle-Tacoma International, and (3)
Paine Field, 32 miles north of Seattle-Tacoma International.
Analyses Performed
Precipitation studies to correlate data from the three airfields
indicated that between 40% and 50% of all storms greater than 0.10
inch began at either of the two distant stations, McChord and Paine
Fields, between 2 and 3 hours before rainfall began in the Seattle
area.
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Figure 32. Force Main Calibration Chart
69
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TELEMETER TRANS-
MITTER EQUIPMENT
SONIC WATER
LEVEL SENSOR
.f T* l_ t V l_ I- OUII^WR
M—
•xpL.-^
4
UNDERGROUND POWER AND
TELEPHONE CONDUITS
NORTH INTERCEPTOR
/ ////////////// / / 7 /
SEWAGE FLOW nr
//////77s
//////////
/ / /
/ / / / / / / //I
Figure 33. Remote Telemetering Depth Sensors
A second study was performed to determine the relationships between
the peak storm intensity and the total volume of rainfall during
a storm. Statistical analyses indicated a definite mathematical
relationship between these two factors. By gaining the earliest
information available on the peak intensity of the storm, the total
rainfall volume could be readily estimated. In over half of the
storms analyzed, the peak intensity was reached within 4 hours
after the beginning of the storm period. By continuously checking
the intensity values from distant or local raingages, the computer
would be able to estimate storm volumes and predicted flows for
each drainage area tributary to the Metro system.
70
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Wind directions were next analyzed to see if they could be associated
with rainfall patterns to provide even better predictions of storm
potential. It was found that during certain months in summer,
every storm with a total rainfall of 0.10 inch or more was preceded
by windshifts from a northerly to southerly direction. Studies
of wind directions for 1965 showed that consideration of wind shift
not only increased lead times on many storms but also predicted
two storms during the test period when rainfall began first in
Seattle. One additional finding was that persistence of wind from
a particular direction was definitely related to total volume. Heaviest
storms were associated with long periods of soi^therly winds, while
light storms occurred in conjunction with a high, percentage of
northerly winds. The end conclusion was that the combination of
wind direction and rain gaging from remote stations would provide
advance information to enable the CATAD program to determine optimum
flow regulation and storage levels within the sewage collection
system.
Actions Taken
Rather than duplicate much meteorological work being accomplished
by the weather bureau, Metro decided to reduce the weather sensing
portion of the CATAD program to the three following procedures:
1. Long-range precipitation forecasts, would be entered into
the computer program by obtaining the chance of rain (COR) prediction
issued by the weather bureau at 6-hour intervals. This COR prediction
would be incorporated into the model so that higher COR percentages
would reduce allowable storage factors within the collection system.
2. Medium-range raingage data would be provided by rain gages
at Metro stations located to the farthest north or south extent
of the collection system. The first amount of rain detected by
these gages would signal the immediate release of all stored sewage
and draw down of those trunks and interceptors in a manner described
at the beginning of this chapter.
3. Short-term weather prediction would be obtained by rain
gages located throughout the Metro drainage area at points indicated
in Figure 34.
The map shows locations for the six telemetering rain gages initially
planned for the Metro CATAD system. Each rain gage is located adjacent
to a pump or regulator station. A tipping bucket signals a counter
inside the telemetry control transmitter unit within the nearby station.
Figure 35 shows rain gage equipment at a remote terminal site. The
computer senses changes in the counter during the next scan and com-
putes rainfall intensity.
It is planned to run -correlation studies in the future to determine
if the six locations are sufficient to establish relationships between
rain intensities and drainage areas. If it appears that the six
stations are not sufficient, additional stations may be purchased
or a parallel manually controlled raingage system owned and operated
71
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Paine Field
Snohomlvh County
P.S. King County
IPJU'J--1 j
Me Chord Field
Figure 34. Metro Rain Gaging Sites
72
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Figure 35. Rain Gage Equipment
by the City of Seattle and consisting of 27 stations (41) may be
tied to the Metro computer to expand its sources of rainfall data.
Three raingages are provided and checked by the Seattle Engineering
Department as well as being tied directly to the Metro CATAD computer
system. Data collected by the two agencies from these cooperatively
operated gages will be compared and checked for accuracy. All meteoro-
logical data is being processed and forwarded to the U.S. Weather
Bureau for further analysis and distribution. Rainfall data from
selected Seattle stations for recent years is summarized in Appendix K.
73
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PROGRAM FOR A SYSTEM MODEL
General Theory
At the same time equipment was being built and installed, there was need
for a parallel effort in the development of computer executive
programs, which are designed to make the hardware work properly.
That is, all equipment must operate according to specifications;
the console must respond to operator command actions; and the map
display must light, blink, and otherwise function as specified.
Most important, Metro-provided data from stations in the field
must be brought without modification to a specific location in
computer memory so that further programming actions can take place.
When station data has been monitored, transferred to the central
computer, and placed in a specific addressable location, another
series of system programs, generally called the mathematical model,
take over to calculate and combine various bits of information to
simulate the system and issue control commands that the executive
program must execute properly. The executive program also provides
the Metro programs with a means of interrupting other less critical
computer1 functions so that tasks can be accomplished in the order
of their priority relationship to other system functions.
Hydraulics and Hydrology
Regulation of storage by the CATAD system controls will be accomplished
By the use of rule curves, which define the 'permissible storage volume
in relation to time. This technique is used extensively in river
system storage regulation in which storage reservoirs are drafted
and refilled in accordance with rule curves. The reservoirs are
drawn down prior to a seasonal flood to a level that provides adequate
space for anticipated flood flows; at the end of the flood period,
the reservoirs are permitted to refill. Rule curves are initially
based on past records. The curves are not inflexible but serve as
a guide in effective use of available storage. The mathematical
model will be used to study system operation with different rule
curves under various runoff conditions and the effect of this operation
on the volume and duration of overflows.
The task remains of developing storm hydrographs for the various
trunk lines. At first a synthetic unit hydrograph, perhaps triangular
in shape, will be used. Monitoring of the sewer system by the CATAD
system is expected to furnish information that will permit refinement
of the initial hydrographs. Storm hydrographs will be routed through
the sewer system by a procedure similar to that used for routing
floods down a river as suggested by B.R. Gilcrest in Chapter X of
Engineering Hydraulics. (42)
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Programming Requirements
Computer programs and subroutines needed to effect computer-directed
remote control of regulator and pumping stations are currently being
prepared and compiled by consulting engineers specializing in hydraulic
and control systems. Two main computer programs are required: a
modeling and a control program. The modeling program simulates
the operation of the system based on a rule curve or inflow hydro-
graph selected by the engineer.
The control program will operate the system under an assumed rule
curve based on measured variables. Under this program, the trunk
inflow is calculated from measured variables. Thus, the program
can be used to accumulate inflow hydrograph data for correlation
with precipitation data. Many program routines will be common to
both the simulation and control models.
Control Model
The method of controlling the CATAD system during periods of storm
conditions is illustrated in the block diagram in Figure 36. The
approach uses a mathematical model of the Metro interceptor system
to simulate the movement of sewage from selected entry points to
final disposal in the receiving waters of Puget Sound.
Four different types of inflow are considered, as shown in Figure 36.
They are: -(1) sanitary flow, which includes sanitary wastes and
seasonal ground water infiltration; (2) infiltration, which represents
ground water inflow resulting from recent rainfall; (3) measured
rainfall, as determined by the Data Collection System; and (4) forecast
rainfall, which may be a combination of operator input and information
provided by the data collection system. Pump stations and regulator
gates represent hydraulic devices used to inhibit the progress of
sewage toward its ultimate treatment and disposal. Because the
volume of flow in the system depends to a great extent on the nature
and extent of rainfall, the need to inhibit flow and store sewage
behind regulator gates varies proportionately to the amount of rainfall.
Hence, forecast and measured rainfall data are used to prepare rule
curves to govern the behavior of various pump and regulator stations
in the system.
The rule curves provide a master plan for operating the system during
periods of rainfall. It is also necessary to monitor the actual
progress of the storm to optimize the available capacity of the
system. Hence, rainfall, infiltration, and sanitary flow are combined
into unit hydrographs, which are relationships of equivalent rainfall
against time for the various tributary drainage areas. The unit
hydrographs can readily be converted into projected runoff entering
the system at the 50 or so flow entry points. The projected runoff
for 30 minutes from a given point in time can be checked with the
75
-------
A
o -
J
I
mOLOGC MODEL
1
> SAN
I F
1 ID
L_
REG
~~" f
'.
L ]
r^ 1
INFI
LTRATION • —
TARY
W.F) '
L
RUNOFF FACTOR 1
ADJUSTMENT |
L
MEASURED
RAINFALL
FORE
RAINF
I I
UNIT
HYDROGRAPH
1
'I
PROJECTED
RUNOFF
ACTUAL
RUNOFF _,
0
o
2
a
JLATOR
LOW
3
<
1C
Q
>.
T T
- ui PUMP
j m -* FLOW
j >
1 "Y
S
J
1
J
t
INTERCEPTOR/
_ TRUNK
FLOW
ROUTING
MODEL
CONTROL
- CONTROL
TRUNK
(
°SEMWAG" TREATMENT
OVERFLOW
TREATED
EFFLUENT
Figure 36. CATAD Control Model Block Diagram
actual recorded runoff after the 30 minutes have elapsed. The recorded
value can be used to modify future values of the projected runoff.
Runoff entering the system is routed through the system by the routing
model to eventual discharge either through the treatment plant or,
if necessary, through outfalls .directly to the receiving waters as
combined sewage overflow. The progress of the sewage is subject
to regulator control, which, where possible, follows the selected
rule curve of storage against time. In a similar fashion, flow to
a pump station is controlled by pump control.
76
-------
From time to time, levels in the trunks or interceptors may exceed
the maximum safe level allowed. In this event, it will be necessary
to amend one or more of the rule curves to relieve the condition.
It is the task of the interceptor trunk control program to detect
such occurrences. The water quality control program will then modify
the appropriate rule curves to provide optimum usage of the system
storage and also establish a priority system for planned overflows.
In theory, at some time in the future, the water quality control
program may be adjusted automatically by the data collection system,
which could be sensing such physical data as river flow, tide level
and direction, dissolved oxygen concentration, and other water quality
parameters for which sensors can be obtained.
Simulation Model
A block diagram of the simulation model showing control of the CATAD
system under programmed storm conditions is shown by Figure 37.
Rainfall from a simulated storm is combined with infiltration and
normal sanitary flow into a unit hydrograph at various points in
the Metro region. Drainage area characteristics such as inlet time,
runoff coefficients, and acreage will determine the projected runoff
at each entry point in the collection system.
Flow entering the interceptors through regulator stations is modulated
by regulator control to follow a preset rule curve (the rule curve
is developed from data about the storm) . High water levels in the
trunk or interceptor, detected by interceptor/trunk control, will
point out program faults. Water quality control will amend the
appropriate rule curve to provide optimum use of the system storage
and establish a priority system for planned overflows.
A thorough engineering analysis of the system along with tne flow
calibration and weather analyses previously described can lead to
a period of trial testing and program modification to develop refined
rule curves for use in actual control of the system during precipitation
events. Alternatively, the model can be used to rerun previous storms
and to refine the accuracy of the routing model to provide better
flow projection for future storms.
Present Status
CATAD mathematical model programming has been proceeding in parallel
with the executive system programming by using a separate computer
so that the two programming groups would not interfere with each
other. Coordination between the two program teams has been less
than perfect so that some delay is a result of not having the two
programming groups working in harmony on the same computer. For
example, the prime contractor scheduled his software development
in such a sequence that an executive program which was required by
the consultants writing the control model, was one of the final programs
to be finished. This scheduling could not be modified, and, as a result,
77
-------
INFILTRATION
SANITARY
FLOW
(D.W.F.)
RAINFALL
UNIT
HYOROGRAPH
PROJECTED
RUNOFF
ROUTING
MODEL
COMBINED
SEWAGE
OVERFLOW
REGULATOR
CONTROL
PUMP
CONTROL
INTERCEPTOR/
TRUNK
CONTROL
WATER
QUALITY
CONTROL
TREATMENT
TREATMENT
EFFLUENT
Figure 37. CATAD Simulation Model Block Diagram
early completion of the model was impossible. It is unreasonable
to expect complete cooperation and coordination between different
persons working on parts of a single program, so delays can be expected
irrespective of the size of the programming group.
At this time, model subroutines (described in Appendix F) are being
compiled and tested on the Metro CATAD computer. It is expected
that in the late summer of 1971, the mathematical model can begin
to run in a simulation mode while system reaction to various supervisory
commands and storm conditions is monitored and analyzed for use
in updating rule curves and other model programs. If weather conditions
provide enough different types and intensities of storms so that
most conditions can be predicted based on actual monitored data,
78
-------
it is expected that the control program can begin to direct collection
system stations beginning with one station and proceeding deliberately
until there is sufficient confidence to place the entire system
under computer control. Each step of the assumption of this control
will be closely monitored both at the central command console and
at remote station terminals where physical observation will verify
whether proper equipment responses are taking place and whether central
console information displays match what is observed at the site
itself.
79
-------
SECTION VI
WATER QUALITY STUDIES
Since 1963, the Municipality of Metropolitan Seattle (Metro) has
been engaged in a comprehensive water quality monitoring program
throughout the entire metropolitan drainage area. At the inception
of the computer demonstration grant in 1967, additional specialized
water quality monitoring studies were added to the existing program
to concentrate on certain areas within the collection system that
contribute to combined sewer overflows. The portion of the comprehensive
monitoring program and the special studies relating to the purpose
of the demonstration grant will be described in this section.
The objectives of the demonstration grant water quality studies were
two-fold. First, new water quality studies were begun or old programs
modified to show how receiving water quality and other dynamic system
parameters have changed during the periods of expansion, interception,
regulation, and separation. A second objective was to establish
a base level for various parameters that could be used as a tool
for measuring the results of the CATAD demonstration project. The
studies have been divided into two general areas related to either
the collection system itself or the receiving waters adjacent to
the municipality. Weather and other pertinent environmental factors
are correlated with data from the two main study categories.
STUDIES ORIENTED TO COLLECTION SYSTEM
Collection system studies for the demonstration grant centered upon
combined sewer overflows. Because of the importance of the storm
water portion of combined sewage and the potential impact of the
large sewer separation program being undertaken by the City of Seattle,
two parallel studies have been included in this report section: (1)
a 3-year study of the effects of sewer separation and (2) a short
preliminary study of the quality of freeway drainage. The map in
Figure 38 locates the sampling stations referred to in the discussion
of the collection system studies".
OVERFLOW SAMPLING
jScope of Study
A demonstration project to reduce overflow frequency and volume and
to improve receiving water quality, all as a direct result of some
special new device or technique, must by its own nature include
a detailed analysis of combined sewer overflow physical, chemical,
and biological measurements. This concentrated study of overflows
is generally intended to determine relationships of overflows to
various rainfall and other meteorological factors, how overflow charac-
teristics change with respect to time, rainfall intensities, and
historical data such as dry periods before a storm or the intensity
of the last previous storm. Another objective is to establish the
81
-------
STATION LEGEND
H SEPARATION ITUOT
D OVERFLOW (TUOT
DRAINAK tTUOY
Figure 38. Overflow and Storm Sampling Stations
82
-------
loading value of various pollution indices to nearby receiving waters
and relate this information to water quality data from routine receiving
water sampling information. The last comparison to be made will
relate different overflows to the characteristics of the tributary
drainage areas and collection system features.
Overflow sampling was divided into three categories: physical and
chemical sampling, bacteriological sampling, and overflow volume
computation. Figure 38, summarizes all overflow sampling stations
included in the study. Physical and chemical sampling stations numbered
seven when the study began in 1969 and were expanded to 13 in 1971.
Samples were automatically taken by either a composite or sequential
automatic sampler installed at each regulator station. Bacteriological
sampling was accomplished at 16 stations during manual sample collection
runs by water quality teams, which were on call during areawide
storms. Volume measurements were taken initially at six stations.
The number of volume stations was increased to 12 in 1971 and will
be expanded to 13 by 1972 with the addition of the Norfolk Street
Regulator Station. Volume measurements were based on three-pen recorder
charts, which indicated tide level, trunk level, and gate opening
from which volume is calculated by a computer program. Table 5 summarizes
all the overflow sampling and monitoring stations.
Equipment and Analyses
Programmed automatic refrigerated samplers were designed and built
as part of the demonstration grant to simplify the sample collection
tasks at the widely separated overflow stations in the project. Six
compositing and seven 24-bottle sequential samplers were installed
to operate whenever the adjacent outfall gate is in the open position.
The samplers all operate on a vacuum principle drawing overflow samples
up as much as 17 feet to a bottle of at least 1-liter volume.' Samples
are then refrigerated until a technician collects samples and replaces
the full sample bottles. Figure 39 shows the main features of the
two different types of samplers. With either sampler, a section containing
programmers, timers, and other control devices rests above a refrigerator
section. The enclosure is heated and contains air circulation fans
to reduce interior corrosion from condensation. Additional details
are available from the equipment manufacturer's instruction manual.
(43)
The connotation of the term "automatic" used to describe these samplers
is somewhat deceiving; considerable manual effort is involved in
collecting samples, replacing bottles, and testing and repairing
the various :electrical components. Originally the samplers were
supervised, maintained, and serviced by different personnel. On
the newly designed samplers, there was a 6-month period during which
the samplers were broken in and various parts changed or modified.
During 1970, a single technician was assigned the supervision, servicing,
and some maintenance responsibility for each of the automatic samplers
and since then the performance record of these units has been satisfactory.
83
-------
TABLE 5
Overflow Sampling and Monitoring Stations
No.
8
10
13
14
15
16
17
18
20a
23a
25a
36a
30
31
32a
33
34
36
37
38
40
Station
Name
Magnolia
32nd Avenue
Denny-Elliott
Denny-Lk. Union
Vine
University
Madison
Washington
King
Connecticut
Lander
Hanford
Harbor
Chelan
Longfellow
Diagonal
Brandon
Michigan
W. Michigan
Eighth South
Norfolk
Type
Combined
Storm
Combined
Combined
Combined
Combined
Combined
Combined
Combined
Combined
Combined
Combined
Combined
Combined
Storm
Storm
Combined
Combined
Combined
Combined
Combined
Automatic
Sampler
None
None
Composite
Sequential
None
None
None
None
Composite
Sequential
Composite
Sequential
Composite
Sequential
None
None
Composite
Sequential
Composite
Composite
Sequential
Regulation by:
Orifice Mech. Gate
X
-
X
X
X
X
X
X
X
X
X
X
X
X
-
-
X
X
X
X
X
station 1971
84
-------
A. Composite B. Sequential
Figure 39. Automatic Overflow Samplers
An average of 30 samples are collected and analyzed each week
analyses throughout this report were performed according to "Standard
Methods." (44) The following tests are performed on each sample:
settleable, suspended, and volatile suspended solids; ammonia and
total nitrate nitrogen; total phosphate; and biochemical and chemical
oxygen demand. This information is transferred to punch cards for
computer statistical analyses.
At least twice a week, each sampler is visited to collect samples
and perform minor maintenance. Most sampler malfunctions have been
caused by conditions that were simple to correct; rarely has the
manufacturer been called in to make major repairs.
A number of sampler problems might be explained to assist others
in the specification and purchasing of sampler equipment. The electrical
system on these samplers was complicated; on the first model, wiring
was difficult to maintain. Fuses were often inadequate and, for
a period of time, required frequent replacement. A number of electrical
components have been found to be relatively marginal and have failed
during continuous operation. Such things as timers, microswitches,
relays, and reed switches have had to be replaced by instrument tech-
nicians. In sequential samplers, a float switch frequently failed
to turn off the vacuum pump, resulting in water being drawn up into
the pump even though water trap protection was provided. Despite
an automatic purging feature, the 3/8-inch-diameter sampling tubes
85
-------
often become plugged with rags and other debris, requiring constant
checking. Debris can usually be cleaned off with a hose or by manually
lifting and cleaning the sampler tubes.
During periods of extreme high flows, the sampler tubes are often
flushed over emergency overflow weirs and left hanging high and dry
when the flow subsides. Guy wires were installed to hold them in
place and to facilitate retrieval of sample tubes whenever they are
found out of position. Shortly after purchasing the initial set
of samplers, a number of modifications were added to simplify the
testing of these devices by the water quality technician. As a rule,
when any sampler, no matter how simple or complex, is properly maintained,
it will work well and sample each overflow according to design specifica-
tions.
To establish overflow volumes, three-pen strip chart recorders were
installed in 12 regulator stations. In the first seven stations,
the recorders were tied to instruments that converted pneumatic signals
to electronic signals for computer interfacing. Each chart records
the levels* of sewage in the trunk, the tide level, and the outfall
gate opening, as shown by a sample chart on Figure 40. A computer
program was written to determine the volume of sewage that escapes
during an overflow by treating the gate as an orifice that may become
submerged due to tidal action. The flow can be computed according
to King's hydraulic handbook (.45) by the equation:
Flow = (constant) x (area) x ,/(head)
or
Q = k A
The volume of overflow is the rate of flow multiplied by the duration
of the overflow. The computer program (described in Appendix F)
must take into account the level and scale factors that are necessary
for converting strip chart readings to levels relative to the invert
of the outfall sewer. Strip charts are graphically divided into
uniform areas and transferred to a worksheet (see Table 6 for sample
data) for punching onto data cards to be read by computer programs
that integrate these areas into a flow computation.
Operating experience with these recorders was similar to the sampler
equipment in that after a specific individual had been assigned
the duty of overseeing and servicing the recorders the units have
proved reliable and helpful in determining operational problems at
various stations. Several sample charts that indicate regulator instru-
mentation problems have been included in Appendix H.
The chart recorders have been useful in regulator stations . Their
first use and the reason they were initially installed is to record
86
-------
CO
100
90
0300
0400
0500
0600
0700 0800
TIME, HOURS
0900
1000
1100
10
1300
Figure 40. Sample Overflow Chart
-------
TABLE6
Volume Calculation Program—Sample Output Data
Time
Station Date Overflow Duration Volume Flow
Began
Michigan
Michigan
Michigan
Michigan
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
70- 9-17
70- 9-17
70- 9-17
70- 9-17
70- 9-17
70- 9-17
70- 9-17
70- 9-17
70- 9-17
70- 9-17
70- 9-17
70- 9-17
70- 9-17
70- 9-17
70- 9-17
70- 9-17
70-11- 8
70-11- 8
70-11- 8
70-11- 8
70-11- 8
70-11- 8
70-11- 8
70-11- 8
70-11- 8
70-11- 8
70-11- 8
70-11- 8
70-11- 8
70-11- 8
70-11- 8
70-11-19
70-11-19
70-11-19
70-11-19
70-11-19
70-11-19
70-11-19
70-11-19
70-11-19
70-11-19
70-11-19
70-11-19
70-11-23
70-11-23
70-11-23
70-11-23
70-11-23
70-11-23
70-11-23
70-11-23
70-11-23
70-11-23
70-11-23
70-11-23
70-11-23
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
18
18
18
18
18
18
18
18
18
18
18
18
15
15
15
15
15
15
15
15
15
15
15
15
15
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.2
0.2
0.2
0.1
1.7
0.1
0.1
0.1
0.2
0.2
0.2
0.2
0.3
0.1
0.1
0.2
0.2
0.1
0.1
2.3
0.1
0.1
0.1
0.1
0.2
0.2
0.2
0.2
0.2
0.2
0.1
1.9
0.1
0.1
0.1
0.1
0.1
0.1
0.2
0.2
0.2
0.1
0.1
0.1
1.6
61.8
110.7
120.2
105.3
85.3
74.4
47.5
28.6
31.7
9.4
10.7
29.9
30.2
29.9
9.5
785.1
9.9
19.8
33.8
92.7
92.1
92.7
123.3
203.1
58.9
77.7
244.5
154.2
74.4
31.7
1309.0
9.3
18.8
21.0
18.4
57.1
56.6
54.8
54.3
53.3
51.9
9.4
405.2
6.0
12.4
21.9
20.0
20.2
23.0
66.2
68.5
72.1
36.7
40.7
25.0
412.6
28.7
51.4
49.7
48.9
39.6
30.7
22.1
13.3
13.1
4.4
4.4
4.5
4.5
4.5
4.4
4.6
9.2
14.0
13.8
13.7
13.8
18.3
22.9
27.4
32.1
36.4
35.8
30.7
13.1
4.3
8.7
8.7
8.6
8.5
8.4
8.2
8.1
7.9
7.7
3.9
2.8
5.7
9.0
9.3
9.4
9.5
9.8
10.2
10.7
11.4
11.6
7.7
Total
Total
Total
Total
88
-------
information for accurate manual or computer determination of overflow
volumes and durations. A second asset is that the recorders have
assisted operations personnel in locating station instrumentation
problems and solving these problems before a long period of unnecessary
overflow or further equipment damage transpires. Lastly, the recorders
will have a use even after the computer automatically determines
overflow volumes; they will provide information to check computer
computations and also to continue the data base in case of telemetry
or othef computer failures that might cut off the automatic source
of overflow volume information.
Data and Results
This section presents the results of laboratory tests performed on
storm water and combined storm water and sewage taken from the sampling
stations of Figure 38. Although some water quality data is available
from as early as January 1970, for the purpose of this report, the
analysis summary will cover the period of October 1969 to December
1970 when flow data from most stations became available for comparison.
These concentrations are based on the average of each event sampled
from the 16 test areas.
Bacteriological
The membrane filter technique (44) was used for the total coliform,
fecal coliform, and fecal streptococci tests. Bacteria samples were
taken manually during overflow conditions and on a less frequent
basis than the other parameters, collected by automatic samplers.
Table 7 gives the summary for this data. Stations 8 and 33 are the
only storm drains being sampled. Station 8 (Magnolia) is the only
truly separated storm sewer and is the lowest in coliform density.
The high densities recorded from station 33 (Diagonal) reflect frequent
combined sewage overflow into this "storm" sewer from the Metro Hanford
Street No. 1 regulator and three City of Seattle regulators. Stations
15 through 18 drain the Seattle Central Business District and indicated
low coliform averages when compared to other overflow points. Station
31 at the Chelan Street regulator has shown only one overflow since
the start of the project, and this overflow was not sampled for bacteri-
ological analysis.
Organic
Biochemical oxygen demand (BOD) and chemical oxygen demand (COD)
were measured to show organic concentrations of the overflows. This
data is summarized in Table 8. Station 36 (Michigan) had, by far,
the highest BOD and COD concentration. The most likely explanation
for this is the design of this particular station. At Michigan Street,
the outfall gate and the regulator gate are about 800 feet apart.
This situation creates a stagnant condition in this section of line
along with a high buildup of solids. As the regulator gate closes
and the outfall gate opens the stagnant sewage flushes out first,
89
-------
TABLE 7
Bacterial Density Summary—Overflows
(October 1969 to December 1970)
vo
o
Station
Number
8
10
13
14
15
16
17
18
30
31
33
34
36
37
38
40
Total Coliform/100 mis
Mean Min. Max.
18000
2400000
6500000
4400000
34000
1300000
500000
140000
2000000
-
1400000
700000
4400000
4600000
980000
7000000
1500
1600
4700000
1500000
2300
16000
2000
26000
1100000
-
120000
425000
850000
850000
590000
4200000
59000
16000000
38000000
6600000
3100000
8600000
1000000
1100000
5000000
-
7100000
1100000
6900000
7900000
2600000
8200000
Fecal
Mean
6000
340000
320000
540000
3600
110000
18000
7500
410000
-
24000
46000
530000
780000
320000
340000
Coliform/100 mis
Min. Max.
800
250000
150000
7000
20
500
1000
1800
2500
-
16000
7800
290000
290000
36000
250000
10000
710000
4200000
4200000
140000
280000
35000
340000
1000000
-
600000
93000
4400000
5400000
590000
2800000
Fecal Streptococcus /100 ml
Mean Min. Max.
40000 1900 46000
51000
29000
43000
500
6000
3800
34000
23000
_
29000
12000
54000
24000
42000
150000
24000
23000
21000
380
150
1600
650
100
_
270
8100
18000
24000
7500
28000
350000
790000
110000
85000
46000
6000
260000
100000
—
65000
30000
90000
74000
380000
210000
-------
TABLE 8
BOD and COD Summary—Overflows
(October 1969 to December 1970)
Station
Number
8
10
13
14
15
16
17
18
30
31
33
34
36
37
38
40
j,
Mean
27
79
62
68
34
51
148
27
49
15
42
33
236
66
19
66
SW AU^/ J_
Min.
10
17
81
3
18
4
148
11
6
15
17
7
5
6
18
1
Max.
41
228
73
200
216
318
148
39
198
15
330
129
2700
366
20
264
*
Mean
266
295
196
353
371
288
736
100
210
160
96
250
817
211
200
272
-IW *U|^/ J.
Min.
56
16
120
37
110
10
736
56
28
160
16
32
20
40
200
20
Max,
842
860
272
1389
936
542
736
296
1200
160
440
1320
3472
1184
200
1555
followed by high concentrations of solids that had built up in this
section. Samples are taken at the outfall gate at station 36 and
reflect this condition in their BOD and COD values.
A similar outfall configuration exists at station 34 (Brandon);
however, the distance separation is less and the drainage area is
considerably smaller in size and different in other characteristics,
Corrective action to alleviate the stagnant sewage condition is
planned at both of these stations. A low weir will be built in
the outfall line at the regulator and the outfall sewer relined
to provide a rising invert from the regulator gate to the outfall
gate.
91
-------
Station 17 also indicates relatively high BOD and COD values, but
this is the result of only one observation so should not be considered
as representative when comparing all stations.
The average BOD concentrations from the 16 sampling stations ranged
from a low of 15 mg/1 at station 31 to a high of 236 mg/1 at station
36. Average COD concentrations ranged from a low of 96 mg/1 at station
33 (storm drain) to a high of 817 mg/1 at station 36.
Solids
Three solids categories were measured including settleable, suspended,
and volatile suspended solids. Averages of these categories can
be found in Table 9. Considerable variation is found in all three
categories. Settleable solids ranged from a low of 0.1 ml/1 from
the storm drains of station 16 and 33 to a high of 8.8 ml/1 at station
14 (Denny-Lake Union). Station 14 was also highest in suspended
solids (1464.0 mg/1). Diagonal storm drain was the lowest at 34
mg/1. Michigan Street regulator, station 36, had the highest percentage
of volatile suspended solids concentration, with a value of 85.2%.
Station 8 (.Magnolia storm drain) had the lowest percentage of volatile
solids, with a value of 18.4%, indicating that solids from this
storm drain are essentially of- a non-organic sandy nature. This
is also an indication of good separation construction with few if
any cross connections.
Nutrients
Average values for three nutrients are given in Table 10. They include
ammonia-nitrogen, nitrate-nitrogen, and total soluble phosphate.
Ammonia-nitrogen ranged from a low of 0.23 mgN/1. at station 8 to
a high of 6.25 mgN/1 at station 40. Station 31 had the lowest nitrate-
nitrogen value of 1.52 mgN/1. Total soluble phosphate ranged from
0.34 mgP/1 at station 8 to 3.46 mgP/1 at station 40. As with the
solids analyses, nutrients tests pointed out the reduced loading
from storm drains.
Volume of Overflow
There was enough acceptable overflow data collected during 1969 and 1970
to run a stepwise regression analysis on overflow volume and rainfall
information from four regulator stations. The volume figures were used
as the dependent variable and were correlated with seven independent
rainfall variables including: volume of rain, duration of rain, duration
of antecedent rain, and intensity of antecedent rain. These rainfall
measurements accounted for 85% of the variability in overflow at station
41, 73% at station 30, 92% at station 36, and 86% at station 37. Volume
of rain, as expected, in each case correlated the highest with volume of
overflow, with values as shown in Table 11.
92
-------
TABLE 9
Solids Constituent Summary—Overflows
(October 1969 to December 1970)
Station
Number
8
10
13
14
15
16
17
18
30
31
33
34
36
37
38
40
Settleable ml/1
Mean Min. Max.
0.8
3.3
1.0
8.8
0.2
0.1
0.9
0.2
4.0
5.5
0.1
2.7
3.8
3.4
1.4
6.3
0.1
2.5
0.5
2.0
0.1
0.1
0.1
0.1
0.1
5.5
0.1
0.1
0.1
0.1
0.3
0.7
3.0
5.5
1.5
19.0
2.5
1.2
1.7
0.3
35.0
5.5
2.0
40.0
241.0
34.0
1.8
33.0
Suspended mg/1
Mean Min. Max.
339.6
168.0
212.0
1464.0
53. 0
64.0
280.0
90.0
207.1
200.0
34.0
194.2
777.4
313.2
191.8
244.9
26.0
31.0
148.0
90.0
38.0
15.3
280.0
34.0
2.0
200.0
14.0
16.0
5.0
20.0
66.0
2.0
1305.0
580.0
276.0
11105.0
575.0
148.0
280.0
180.0
970.0
200.0
1350.0
952.0
8099.0
1620.0
293.0
1290.0
Volatile Suspended mg/1
Mean Min. Max. % Volatile
62.6
86.2
80.0
553.3
34.0
30.0
105.0
19.0
103.7
90.0
17.0
101.0
662.0
135.5
50.4
129.0
8.0
24.0
64.0
60.0
10.0
4.0
105.0
8.0
2.0
90.0
4.0
8.0
4.0
20.0
24.0
0.1
255.0
230.0
96.0
8965.0
145.0
144.0
105.0
86.0
760.0
90.0
220.0
736.0
6102.0
1350.0
66.0
792.0
18.4
51.3
37.7
37.8
64.2
46.9
37.5
21.1
50.1
45.0
50.0
52.1
85.2
43.3
26.3
52.7
-------
TABLE 10
Nutrient Concentration Summary—Overflows
(October 1969 to December 1970)
VO
Station
Number
8
10
13
14
15
16
17
18
30
31
33
34
36
37
38
40
Ammonia
Nitrogen mg N/l
Mean Min. Max.
.23
1.87
1.98
5.08
.78
1.36
1.34
.36
2.18
.91
.38
2.75
3.00
2.50
1.58
6.25
.03
.20
1.20
1.50
.05
.08
1.34
.09
.30
.62
.04
.60
.04
.60
.70
.50
.76
3.60
2.75
10.80
2.20
3.10
1.34
.60
6.80
1.20
.71
10.00
18.23
9.80
3.90
22.20
Nitrate
Nitrogen mg N/l
Mean Min. Max.
.27
.58
.34
.51
.54
.54
1.52
.84
.44
.21-
.33
.22
.33
.82
-
.42
.12
.30
.34
.26
.39
.42
1.52
.70
.06
.10
.24
.10
.02
.04
-
.04
.40
.86
.34
.86
.70
1.20
1.52
.98
.64
.32
.42
.38
2.66
4.54
-
2.20
Total Soluble
Phosphate mg P/l
Mean Min. Max.
.34
2.38
2.45
3.29
1.36
.52
1.10
.73
1.54
1.72
.55
1.31
1.56
1.80
1.13
3.46
.14
1.60
2.40
.35
.85
.15
1.10
.28
.11
.44
.32
.45
.10
.25
.26
.30
.76
3.60
2.50
9.20
2.10
2.40
1.10
1.00
6.40
3.00
1.08
3.60
5.63
7.90
2.70
22.00
-------
TABLE 11
Regression Correlations Between Rainfall Volume and
Overflow Volume
Station "r value"a
14 .5467
30 .5633
36 .6664
37 .7241
Q
See Glossary (Section X) for explanation of
"r value".
The equipment problems referred to in the preceding "Equipment and
Analyses" section prevented the gathering of sufficient amount of volume
data with corresponding overflow quality data for 1969 and 1970. These
statistical analyses wjll be given in the final 'report.
Sequential Sampler
The sequential samplers at stations 14, 36, and 40 have generated
a fair amount of information on concentration versus time. Some
of this data has been plotted with flow and rainfall intensity. Figures
41 through 44 show this sequential data.
The next three charts show an overflow that occurred on November
23, 1970, at station 36. Nutrient values are plotted on Figure 41.
All nutrient values have an apparent direct relationship with overflow
volume; that is, they are gradually diluted as storm runoff enters
the combined sewer system. Dilution effects are more pronounced
with ammonia than with other nutrients. The highest volume peak
in the overflow occurred approximately 1 hour after the greatest
rainfall intensity.
Solids have an initial "first flush" peak after the flow reaches
a maximum, followed by gradual dilution of solids concentrations,
as illustrated in Figure 42. Studies of longer sequentially sampled
overflows indicate that, following the surge, solids levels diminish
to baseline levels as slower wastewater velocities probably promote
upstream sedimentation. Analysis of dry-weather flow concentrations
would be helpful to describe differences in amplitude of solids
levels following overflow conditions and during dry-weather flows.
95
-------
vO
Station 36
Nov. Z3, 1970
TIME
OVERFLOW
BEGAN
TIME (HOURS)
Figure 41. Flow and Nutrient vs. Time
-------
VD
Figure 42. Flow and Solids vs. Time
-------
BOD and COD concentrations shown in Figure 43 show a similar inverse
relationship to flow. One interesting observation showed a high
correlation of nutrient data with tide level at some sequential
sampling stations. This discovery may indicate the possibility of
a "salt wedge" of sea water backing up into the trunk and being sampled
during overflow periods when outfall gates are wide open.
Nutrient parameters measured during an extended 15-hour overflow
are shown in Figure 44. This overflow occurred at station 40 (Norfolk
regulator) on October 12, 1970. Placement of the rainfall intensity
is impossible as there is no way of measuring the time of overflow
nor overflow volume at this station. Because of space limitation
inside this underground station and because the regulator is scheduled
to be rebuilt above ground within 2 years, a flow chart was not
built in this station.
Table 12 presents a summary of laboratory analyses from confirmed
over-flows along with rainfall information and sample and overflow
volumes for 1970. Similar overflow data for other stations appears
in Appendix I. As can be seen from these tables, more volume data
is needed. A flow chart has not yet been installed at station 40.
Data being collected in 1971 is more complete and will give the
needed matching of overflow volume and laboratory analyses.
SEWER SEPARATION STUDY
Scope of Study
In March 1968 shortly after the City of Seattle passed a $70 million
bond issue to partially separate all of the combined sewer system
tributary to Lake Washington, Metro decided to embark upon a cooperative
study with the City of Seattle to:
1. Determine the present effect of combined sewer overflows
and storm drainage on Lake Washington receiving waters.
2. Record changes in combined sewer quality, volumes, and
overflows as separation progresses.
3. Predict the future effect on the receiving water as partial
separation is completed.
4. Determine the impact of separation projects throughout
the city on the CATAD computerized storage management system.
As partners in this separation study, the City of Seattle provided
access to sampling sites in addition to detailed rainfall data from
areas tributary to the sites, and Metro provided manpower, sampling
equipment, and laboratory facilities. Four representative sampling
sites were selected as the primary sampling locations. Table 13
points out certain details about each sampling site (the sites
are shown in Figure 38). Sand Point,and Cooper Street sampling
stations are on storm sewers draining small areas that have been
separated for many years. Windemere and Henderson Street are sample
98
-------
11.0
10.0
_9JL
100
90
RAINFALL
.-
I
0.5 1
FLOW
\
10
X
u
7.0
U-
o
o
6.0
5.0
> — cop
\
10
Station 36
NOV. 23, 1970
-I
TIME
OVERFLOW
BEGAN
tl
TIME (HOURS)
Figure 43. Flow, BOD and COD vs. Time
-------
0-01
—
b
7 8 9 10
TIME (HOURS)
14 15 16 17
Figure 44. Nutrient Concentration vs. Time
-------
TABLE 12
Date
Rain Sample
Total Max. Rate Volume
(in.) (in./hr.) (liters)
4-19 0.37
12-28 0.66
10-12
11-19
11-30
12- 6
12-19
12-28
1- 9
1-13
1-19
1-26
2- 5
2-15
3- 6
3-12
4- 9
4-24
4-27
6-29
10-17
11- 8
11-15
11-19
11-23
11-30
12- 3
12-28
0.05
0.14
0.23
1.69
0.24
0.64
0.19
1.50
0.61
1.18
0.16
1.08
1.20
0.34
0.80
0.19
0.28
0.47
0.26
0.53
0.22
0.30
0.80
0.21
0.20
0.48
0.10
0.13
0.05
0.03
0.07
0.16
0.07
0.09
0.09
0.22
0.11
0.13
0.04
0.12
0.16
0.13
0.12
0.07
0.18
0.28
0.21
0.10
0.06
0.06
0.09
0.06
0.05
0.09
2
1
1
3
10
4
6
12
12
12
10
7
12
12
12
6
8
12
8
10
4
12
12
12
8
12
Regulator Station Overflow Data (1970)
Overflow Solids
Volume Settleable Suspended Volatile BOD COD ""3 "-2"1W3 *~4
(gal. x 1000) (ml/1) (mg/1) (mg/1) (mg/1) (mg/1) (mg N/l) (mg N/l) (mg P/l)
NH.
P°
Station 13 Denny Way - Elliott Bay
1.5
0.5
276
148
96
64
84
62
272
120
1.20
2.75
Station 14 Denny Way - Lake Union
255.7
35651.0
55768.8
1126.2
297.0
1164.4
1315.9
75.6
Station 30 Harbor Avenue
0.25
0.23
2.50
2.40
10.3
11.5
4.0
8.0
8.8
9.4
1580
370
180
400
2273
425
92
320
175
252
1874
260
12
200
191
110
32
70
105
210
480
758
264
419
4.35
6.40
•6.60
4.67
5.20
3.69
0.30
0.49
0.37
0.49
0.27
0.37
0.37
9.20
4.57
3.38
3.23
2.66
3.0
1.8
2.1
0.6
20.0
3.0
4.0
2.0
4.0
1.5 .
2.0
3.0
11.5
1.2
3.5
1.5
0..3
1.3
3.2
2.5
210
200
142
152
200
120
308
142
154
106
280
160
36
50
2
295
108
198
550
294
114
100
60
54
106
46
128
44
82
32
80
140
-
20
2
170
86
128
305
120
72
54
-
-
76
36
51
42
42
18
54
63
20
6
-
10
26
41
32
48
248
119
136
-
504
344
368
120
216
112
184
224
128
335
838
140
28
168
207
223
3.40
1.60
0.50
0.60
3,90
1.90
1.80
2.00
1.50
0.30
2.00
5.00
2.25
1.00
1.70
1.85
2.35
1.80
2.50
2.55
0.50
-
0.55
0.91
0.55
0.55
0.20
0.40
0.30
0.01
0.05
0.27
0.27
0.19
0.25
0.37
0.39
0.26
0.24
0.28
1.60
1.45
1.10
0.57
2.90
0.70
1.50
1.10
1.00
0.50
1.30
2.50
-
0.35
1.30
6.40
0.75
1.15
1.40
1.95
-------
TABLE 13
Separation Study—Station Data
Station Drainage Area Pipe Diameter
Number Name Type Acres (inches)
4901 Sand Point Separated 183 36
4902 Windemere Combined3 448 36
(overflow)
4903 Henderson Combined 539 84
(overflow)
4904 Cooper Separated 103 60
a
Includes 215 acres served by separated sewers.
stations located at side-spill weirs where combined sewage frequently
overflowed to Lake Washington and where separation was being planned
in the near future.
It was not planned so initially, but the separation study turned into
an extended research project into the efficiency of various types of
samplers and flow recorders. It also was a large drain on manpower
because the study, which extended from April 1968 to May 1971, required
generally at least three persons for any manhole entry (samplers
were located in manholes), extensive safety equipment and attention
to safety procedures, plus considerable travel time; all this added
up to a great deal of manpower during the 3-year life of the study.
Equipment and Analyses
Equipment used in the §tudy can be divided into two groups: that
used during the research period, and equipment finally selected
to complete the study. Initially, one vacuum-operated sequential
sampler and three battery-driven compositing samplers were combined
with specially designed compressed air bubbler depth recorders and
installed at the four manhole sampling sites. For the 12 months
following the first installation in May 1968, the sampling equipment
and recorders were studied and found to haye serious problems that
required correction. The compositing samplers needed frequent battery
changes and were continuously becoming plugged with solids from
the sewers. - The bubbler-type depth recorders, after an extended
calibration period, were found to be insufficiently sensitive for
the minimal changes in sewer depth that were found to occur.
102
-------
During the summer of 1969, the separation project was expanded.
Additional personnel were added and three more vacuum-operated sequential
samplers were purchased. A float-type, direct-reading level recorder
was installed at each station and connected to a scow float that
rode on the surface of the rapidly moving sewage stream. Two more
changes occurred. The scow float was replaced by a plastic ball
float, which operated much more effectively, and the vacuum-operated
samplers had a special clock starter device attached so that entry
to the manhole was not required to initiate a sequential sampler
cycle. As has been indicated by others C9) sampling equipment must
be designed to cqpe with the violence and unexpected flooding conditions
that occur in sewer lines.
As it was finally established, the sampling procedure began at the
onset of rainfall in the Seattle area. Water quality technicians
would rapidly travel to each sampler site, remove a manhole cover,
and release a pneumatic device to start the clock motor on the sequential
sampler. At the same time, the technician would take a manual sample
for bacteriological examination. The day following the storm, techni-
cians would visit each sampler site and remove the sequential sampler
from the manhole. The four samplers would be transferred to the
central laboratory for solids and chemical nutrient tests. Samplers
would then be recharged and returned to their manhole locations in
preparation for the next storm.
Each week, another crew would replace the sewage level recording
chart at each site. These charts were then converted into punch
card data for computer calculation and volume computation using
Mannings' formula. The sharp peaks shown on a typical level recording
chart, reproduced in Figure 45, 49, show how difficult it is to
convert these data into elevations and then volumes. However, even
with these limitations, the calculated volumes correlate well with
recorded rainfall information as indicated by the data presented
in the following sections. Figure 46 shows the installation and
sampling equipment used during the sewer separation study.
In addition to the volume calculation, study parameters included
such physical analyses as settleable solids and total suspended
solids. Volatile suspended solids tests were added following a prelim-
inary study report issued in April 1970 (46) that indicated high
solids loading from storm sewers. Biochemical and chemical oxygen
demand tests were also added following the preliminary report. Chemical
analyses included total phosphate and ammonia nitrate. Total and
fecal coliform and fecal streptococcus bacteriological counts complete
the list of analyses performed as part of the study.
Data and Results
Analyses performed on overflows and storm drainage are summarized
in Tables 14 through 17. As stated, stations 4901 and 4904 are
storm sewers, whereas stations 4902 and 4903 are combined overflows.
103
-------
Station 4902
72"Dia.
Nov. 1970
UJ
10
I!
DAYS
A. COMBINED SEWER OVERFLOW
12
Station 4901
48" Dia.
Nov. 1970
24 25
DAYS
8. STORM SEWER
26
27
Figure 45. Sample Separation Charts
104
-------
• FLOAT (FIBERGLASS)
•SAMPLING HEAD
SEWAGE FLOW
A. Site
B. Sampler
' $Mk;
IP?
S.-v:**
C. Recorder
Figure 46. Typical Equipment and Setup for Separation Study
105
-------
Even though stations 4901 and 4902 are in the north end of Seattle
and stations 4903 and 4904 are in the south end, both storm sewers
seem to compare relatively close in concentrations, as do the combined
overflows.
Bacteriological
The reduction in coliform concentration in going from a combined
sewer to a storm sewer can easily be seen in Table 14. The reduction
ranges from 60 to 140 times.
TABLE 14
Bacterial Density Summary—Storm Sewers
(October 1969 to December 1970)
Station
Number
4901 median
min.
max.
na
Total Fecal Fecal
Coliform/100 mis Coliform/100 mis Streptococcus/100 mis
24,000
20
1,900,000
40
3,200
20
110,000
38
2,400
20
12,000
20
4902 median
min.
max.
n
1,400,000
130,000
4,400,000
24
150,000
1,200
4,200,000
25
180,000
7,600
570,000
16
4903 median
min.
max.
n
1,200,000
60,000
10,000,000
18
160,000
35,000
1,300,000
19
46,000
2,000
380,000
10
4904 median
min.
max.
n
8,800
180
380,000
41
2,300
20
68,000
39
7,600
1,200
720,000
24
n - number of individual tests
106
-------
Nutrients
A nutrient summary is given in Table 15. Here again the difference
in storm and combined overflows is evident. Ammonia-nitrogen is
seven to eleven times lower in the storm overflow, nitrate-nitrogen
1.3 to 2.0 times lower, and total phosphate five to eight times lower.
Organics and Solids
Tables 16 and 17 summarize BOD, COD, and solids. Storm sewer data
compares favorably with findings of other researchers. Pollution
indices in combined sewers are generally 2 to 5 times larger than
for similar parameters in storm overflow. One exception is found
at station 4901 in suspended solids. Suspended solids at this storm
drain were three times higher than the nearby combined station 4902.
This results from a fine clay silt that drains from a sidehill into
the storm drains and from construction of a new apartment house
in the area, which washed large amounts of clay and construction
materials into the storm drain after the slightest rainfall. Unusually
low volatile percentages reinforce this conclusion.
TABLE 15
Nutrient Concentration Summary—Storm Sewers
(October 1969 to December 1970)
Station
Number
4901 mean
min.
max.
n
4902 mean
min.
max.
n
Ammonia
Nitrogen mg N/l
.18
.02
1.80
319
2.05
.14
7.00
75
Nitrate Total Soluble
Nitrogen mg N/l Phosphate mg P/l
.66
.21
1.80
158
.87
.06
2.40
46
.35
.12
1.54
317
1.97
.36
8.10
75
4903 mean
min.
max.
n
.26
.22
.70
73
1.11
.09
5.70
51
1.78
.54
4.10
73
4904 mean
min.
max.
n
.18
.01
.98
121
.51
.02
2.40
86
.20
.06
.69
123
107
-------
Estimates of Pollutional Loadings
The pollutional loading values in Table 18 were computed from average
concentrations and total overflow volume from each station for 1970.
Flow data and, therefore, loadings are unreasonably low at station
4904 because the sewer slope is rapidly changing from 0.0142 to
0.168 at the point where depth measurements are being recorded.
Unfortunately, there was no alternate sampling site. By estimating
the slope effect in Manning's formula flow calculations, one could
increase computed flows by a factor of two to four.
By averaging together the above data from each separated area and
repeating the procedure for the combined sewer areas, and making
adjustments based on data from other references, such as Storm Water
Pollution from Urban Land Activity (26) , some estimates can be made
about the effects of separation on the receiving waters (Lake Washington,
in this case). The following assumptions were made and should be
taken into consideration when referring to the estimates presented
in Table 19: (1) The basic data are representative of the entire
area. (2) Since separation diverts an estimated three-fourths of
total storm flow x*est to saltwater, overflow contribution to the
lake will be reduced to one-third of previous levels (Note: no
data are available to verify this assumption. We expect overflow
volume to decrease to about one-fourth, but because sewage would
Be less dilute, we selected a value of one-third.) (3) A hypothetical
5QO-acre drainage area is being considered; to estimate total effect
on the lake, multiply loading figures as follows:
loading \ /. ^ •,..,*. ... \ /New loadingX
.. \ (total tributary separation area, acres) / ,. \
from 1 . I from 1
I x ~-~—^~———^—~•—"^^——• = I I
500-acre I /cnn \ I separated I
/ (500 acres) \ /
area / \areas /
or
x » . L
C500)
(4) To gauge the total effect to the lake, in addition to the above,
other existing pollutant sources must be totaled and factored into
the equations.
In light of all the previously discussed factors, Table 19, shows
that separation should be expected to reduce essentially all pollution
loadings to less than half their former levels, with the exception
of COD, which is diminished by only 37%.
108
-------
TABLE 16
BOD and COD Summary—Storm Sewers
(October 1969 to December 1970)
Station
Number
4901
4902
4903
4904
Mean
05.5
39.0
41.5
09.6
BOD (mg/1)
Min.
0.3
3.8
1.8
0.1
Max.
34.5
96.0
264.0
70.5
Mean
76.5
124.2
164.6
56.9
COD (mg/1)
Min.
8.0
14.0
53.0
15.0
Max.
398.0
364.0
344.0
273.0
TABLE 17
Solids Summary—Storm Sewers
(October 1969 to December 1970)
Station
Number
4901
4902
4903
4904
Station
Number
4901
4902
4903
4904
Settleable
Mean
0.8
2.0
1.7
0.3
Volatile
Solids ml/1
Min. Max.
0.1 15.8
0.1 7.5
0.1 11.5
0.1 3.5
Solids mg/1
Mean Min. Max.
46.7
53.2
110.4
15.4
3.6 570.0
0.1 140.0
-0- 550.0
0.1 140.0
Suspended Solids
Mean Min .
305.3 2.8
93.4 8.0
285.8 11.6
53.8 0.3
% Volatile
15
57
38
28
mg/1
Max.
3390.0
260.0
1300.0
675.0
TABLE 18
Pollution Loading to Lake Washington
(Representative sample stations - data in pounds per year)
Station
Number
4901
4902
4903
4904a
Susp.
Solids
54,000
55,800
144,200
205
BOD
970
19,100
20,900
128
COD
13,500
60,900
83,100
760
Ammonia
Nitrogen
32.0
1,010.0
640.0
2.4
Nitrate
Nitrogen
117.0
430.0
560.0
6.8
Total
Phosphate
62.0
970.0
900.0
2.7
aFlow data is questionable at this station. See text for explanation.
109
-------
TABLE 19
Estimated Effects of Separation in a Combined Sewer Area3
Source
Combined
Sewer
Storm
Sewer
Total
Type
BOD
S.S.
COD
NH4
N03
P04
BOD
S.S.
COD
N03
P04
BOD
S.S.
COD
NH4
N03
POA
Loading in Pounds
Before Separation
20,000
100,000
70,000
820
500
950
-
-
_
-
"•
20,000
100,000
70,000
820
500
950
to Lake Washington
After separation
6,700
33,000
23,000
270
170
320
3,000
3,000b
21,000
45
62
32
9,700
36,000
44,000
315
232
352
% Decrease
(increase)
67
67
67
67
67
67
:-
-
—
-
..."
52
64
37
62
54
63
See text for assumptions made in preparation of this table.
Data based on reference (25)
110
-------
Sequential Sampler Data
Figure 47 shows how nitrate nitrogen at station 4901 varies when
plotted against time, flow, and rainfall intensity. As soon as
the overflow begins, a relatively high amount of nitrate nitrogen
is flushed off. There also appears to be some dilution, as shown
by the peaks in overflow and corresponding depressions in nitrate
nitrogen. As the storm continues, nitrate nitrogen declines on
a gradual scale. Other sequential sampler data show that a pollution
parameter will finally reach a baseline concentration from which
it will fluctuate very little if rainfall intensity remains relatively
constant.
Combined overflow (station 4902) sequential sampling results are
illustrated in Figure 48. Ammonia nitrogen was plotted against
time, flow, and rainfall intensity. Here, concentration takes on
an inverse relationship to flow. As shown in the statistical analysis
that follows, ammonia has an "r value" of -0.643 when correlated
to flow at station 4902. This means that an increase in flow would
result in a corresponding decrease in ammonia about 64% of the time,
a strong correlation.
Pollution Parameter Correlations
Nutrient data was available in sufficient quantity for valid statistical
analysis. Therefore, it was possible to run a series of stepwise
regression analyses to determine single and multiple correlation
values with overflow and rainfall characteristics. Ammonia-nitrogen,
nitrate-nitrogen, and total phosphate were the dependent variables.
The independent variables were:
1. Air temperature
2. Wind direction
3. Volume of overflow
4. Duration of overflow
5. Intensity of overflow
6. Time siace last overflow
7. Volume of antecedent overflow
8. Duration of antecedent overflow
9. Intensity of antecedent overflow
10. Volume of rain
11. Duration of rain
12. Intensity of rain
13. Time since last rain
14. Volume of antecedent rain
15. Duration of antecedent rain
16. Intensity of antecedent rain
Results of individual correlations are summarized in Table 20. A
large "r value" indicates a significant correlation. Negative "r
values" show inverse relationships. The table shows that seemingly
unrelated factors such as nutrient concentration and wind direction
111
-------
00
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ALL
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, Q
1.0
1.0
t .5
Station 4901
Oct. 19-20, 1970
ITRATE
1400
1600
BOO 2000
2200 2400
HOUR OF DAY
0200 040O 0600 0800
Figure 47. Storm Runoff with Rainfall and Nitrate Nitrogen
-------
Station 4902
Dec- 10, 1970
(Heaviest storm of year)
1000 1200
HOUR OF DAY
1600
1800
2000
Figure 48. Overflow with Rainfall and Ammonia Concentration
-------
TABLE 20
Individual Correlations
Nutrient Parameter Station
Ammonia-nitrogen
4901
(storm)
Overflow or Rainfall
Characteristic
Air temperature
Time since last storm flow
Volume of antecedent storm flow
Time since last rain
4902 Volume of overflow
(overflow) Time since last overflow
Duration of antecedent rain
Nitrate-nitrogen
Total phosphate
4903
(overflow)
4904
(storm)
4901
(storm)
4902
(overflow)
4903
(overflow)
4904
(storm)
4901
(storm)
4902
(overflow)
4903
(overflow)
4904
(storm)
Time since last overflow
Intensity of rain
Wind direction
Volume of antecedent storm flow
Air temperature
Air temperature
Volume of overflow
Intensity of overflow
Intensity of rain
Wind direction
Duration of overflow
Volume of rain
Wind direction
Time since last storm flow
Volume of rain
'r value"
0.397
0.485
-0.490
0.463
-0.638
0.420
-0.455
0.378
-0.375
-0.452
0.516
0.441
-0.472
-0.305
-0.389
-0.484
-0,451
0.451
0.375
0.415
0.467
-0.346
Time since last storm flow 0.334
Volume of antecedent storm flow -0.474
Intensity of antecedent storm flow -0.377
Time since last rain 0.467
Volume of overflow -0.423
Volume of rain -0.365
Duration of rain -0.355
Time since last overflow 0.507
Volume of rain -0.337
Wind direction -0.471
Duration of antecedent storm flow 0.368
Intensity of antecedent rain -0.339
114
-------
or air temperature often correlate well. This is likely the result
of the high correlation in the Seattle area between storms and various
meteorological factors.
Data derived from the stepwise regression analyses can be found
in Appendix J. The statistical analyses show that by taking all
significant independent variables into account, 50% to 85% of the
nutrient variation is explained at the storm drain stations (4901
and 4904). At the two combined sewer overflow stations (4902 and
4903) analysis of the independent variables explained between 55%
and 98% of the nutrient variation.
The most significant independent variables for each nutrient in
the regression analyses are the same as those presented in Table
20. All the above statistical analyses were done using standard
"Biomedical" programs on the University of Washington CDC 6400 computer.
FREEWAY DRAINAGE STUDY
As part of the overall Metro study of the effects of separated stormwater
on environmental water quality, a preliminary survey (47) was initiated
in February 1970 to assess the quality of stormwater drainage from
the Seattle freeway system. An elevated portion of Interstate 5
was chosen (see Figure 38) based on the relative noninterference
from outside drainage sources.
s
Essentially, only two complete periods of rainfall could be sampled
during the time allotted for the study. One of these periods was
preceded by a rather lengthy dry spell C12 days) while the other
was preceded by 3 days of dry weather. The latter storm was character-
ized by a much higher rainfall intensity.
Runoff samples were analyzed for settleable solids, chemical oxygen
demand (COD), biochemical oxygen demand (BOD), nitrate-nitrogen
(N02 + N03 as N), total hydrolyzable phosphates (P), free ammonia
(NH3 as N), oil, and gasoline additives.
Findings
A summary of the data collected is presented in Table 21. Mean
concentrations of the constituents analyzed are listed in relation
to time after start of runoff. Because of the short duration of
the study, it is necessary to consider the data presented as only
preliminary, and conclusions should be drawn with this in mind.
The "first-flush" contained relatively high concentrations of contam-
inants, particularly suspended solids, COD, BOD, and oil. Nutrient
levels were relatively low.
115
-------
TABLE 21
Urban Freeway Drainage Water Quality
Total
PO,
Free
NH0
Date
Time After Suspended Settleable
Time Since Start of Solids Solids COD BOD Nitrogen Soluble ""3 Oil
Last Rain Runoff mg/1 mg/1 mg/1 mg/1 mg N/l mg P/l mg N/l mg/1
2-17-70
3- 2-70
3 hrs.
12 days
0-15 min.
0-15 min.
15-30 min.
30-40 min.
559
1494
25
11
0.8
31.0
<0.1
<0.1
1617
909
893
198
181
162
0.56
2.52
2.50
2.45
3- 3-70
3- 6-70
3 days
16-16.5 hrs.
0-20 min.
4 hrs.
8 hrs.
12 hrs.
60
504
177
228
141
0.2
1.1
0.2
0.7
0.2
384
222
185
150
103
44 1.85
22
21
9
12
0.58
1.00
0.38
0.51
.51
.37
.18
.16
.14
.33
.28
.20
.16
.51
.44
.18
.20
.09
.11
56.8
.01 55.0
.01 16.0
.01 18.0
25.0
55.0
47.0
27.0
30.0
The concentrations of these contaminants show a high correlation
to rainfall intensity and duration as well as antecedent rainfall.
Concentration levels diminished rapidly in the first 15 to 30 minutes.
Nutrient concentrations were also lower under conditions of a shorter
antecedent dry spell and more intense rainfall.
Gasoline additives probably contribute to stormwater contamination.
One such byproduct was found and identified as calcium bromide,
which originates in the gasoline additive ethylene bromide. This
particular byproduct turned the samples a yellow color.
In general it appears that some effect on receiving water quality
can be expected from freeway drainage, particularly in regard to
aesthetic effects. Even though the stormwater does not carry a high
level of nutrient concentration, its first-flush flow does contain
rather high levels of other contaminants. This warrants a closer
look to determine the need for separation or treatment, especially
of the first-flush contaminants. On-site rain gaging should be
performed in any future studies to provide more accurate rainfall
data for volume and loading figures.
STUDIES ORIENTED TO RECEIVING WATERS
Metro's comprehensive monitoring program has included many analyses
of all waters that receive drainage from the Seattle metropolitan
area. Additional details about the entire program can be found in
various reference reports (48) (49). Two principal receiving water
bodies are being studied as part of this demonstration grant. They
include the Green-Duwamish River and Elliott Bay. Sampling stations
include shore stations, surface stations, and automatic river monitoring
stations, as indicated on the map in Figure 49. The analyses discussed
in this section of the report include bacteriological, physical,
chemical, and ecological analyses.
116
-------
DIAGONAL T.P.
(Closed 1969)
LEGEND
• CHEMICAL **0 OK CIOLOEICAL STA.
O BACTERIOLOSICAL STATION
9 COUaiNEO STATION
A AUTOMATIC MONITORS
Figure 49. Receiving Water Sampling Stations
117
-------
Elliott Bay Sampling
Scope
The objectives of the Elliott Bay sampling are mainly to show how
the expansion and interception of trunks by Metro has improved the
local receiving waters and also to demonstrate to regulatory agencies
the degree of local compliance with their established water quality
standards. On a weekly basis, sampling runs are made along shore
stations. Biweekly, offshore sampling runs are made by a sampling
boat operated under a cooperative agreement with the United States
Geological Survey. Samples are taken for analysis of total and
fecal coliform, dissolved oxygen, temperature, transparency, and
chloride content. Figure 50 shows the boats and typical tests used
by Metro crews in sampling the receiving waters.
Automated Wet Chemistry Analyses
To speed the analysis of the many samples being brought to the Metro
laboratory, a Technicon autoanalyzer was purchased in 1969. This
unit was tested out during a 6-month period and found to give extremely
reliable results from the automated analysis procedure. Unfortunately,
a scarcity of available information resulted in inadequate planning,
and an autoanalyzer was purchased with a single-channel recorder
and a number of interchangeable "plattered manifolds" (tubing arrange-
ments specific for each chemical test). This meant that the autoanalyzer
could be used for a variety of tests, but it required a time-consuming
change of the manifolds to run a second test. It was found that,
for the rate that samples requiring multiple analyses were brought
to the lab, it was easier and less time consuming to run chemical
analyses in the standard manual manner rather than calibrate and
set up the autoanalyzer for each test.
After the trial period at the Metro central laboratory, the autoanalyzer
was transferred to the Renton Treatment Plant, where a different
demonstration grant was in progress. This demonstration grant required
multiple repetitions of total phosphorous tests on many samples,
and the autoanalyzer proved ideal for this application. (50) Figure 51
shows the autoanalyzer being operated at the Renton Treatment Plant.
The Minneapolis Sanitary District has also found much success with
the autoanalyzer in their analyses of sewage samples (51). It is
expected that as tests multiply and the Renton Treatment Plant purchases
an analyzer for plant use, the Metro central laboratory will add
accessories to the original autoanalyzer for use specifically on
the CATAD demonstration grant.
Bacteriological
Probably the most striking improvement found in the receiving water
of Elliott Bay is in the total coliform concentration resulting
from diversion of several large raw sewage outfalls from the bay
118
-------
A. Chemical and Biological Sampling
Equipment in the "Hydor"
B. Shore Sampling from "Boston Whaler"
C. Trawl-Caught Fish Counts Using 16-Foot Craft
Figure 50. Metro Sampling Boat Fleet
119
-------
1 * '
* 1
' <
'.
<• -«j
Figure 51. Autoanalyzer in Operation
to the West Point Treatment Plant. Table 22 shows median coliform
concentrations of shore and offshore stations both before and after
diversion. August 1969 to March 1970 represents the condition before
interception and August 1970 to March 1971 represents the conditions
after. This same data is graphically presented in Figure 52. The
data plotted in Figure 53 compares total coliform counts during summer
periods (quarters) of 1968 and 1970. Figures 52 and 53 show that
coliform counts now fall relatively close to the standard, even
during winter periods.
Dissolved Oxygen
Low dissolved oxygen has never been a problem in Elliott Bay, which
experiences good tidal flushing and the flushing effect of the Green-
Duwamish River. Some improvements can be seen, however, as a result
of the closure of the Diagonal Treatment Plant and the diversion
of all major raw sewage outfalls from Elliott Bay. Stations 301
and 184 are geographically the closest offshore stations to the
old raw sewage outfalls. Figures 54 and 55 show both the surface
and bottom dissolved oxygen levels from 1968 through the beginning
of 1971. This data reveals several small changes. Saline waters
near the bottom often had higher DO values than the less saline
surface waters until about November 1969. This may be explained
partially by high biochemical oxygen demand of the effluent from
120
-------
TABLE 22
Total Coliform Concentrations—Elliott Bay
(Before and After Raw Sewage Diversion
to the West Point Treatment Plant)
Median Total Coliform Concentration (Organisms per 100 mis)
Station August 1969 to March 1970 August 1970 to March 1971
230 4800 1800
231 4900 1500
232 5000 1200
233 12000 2200
234 11000 2500
235 20000 2600
236 28000 6400
237 1800 200
238 260 180
301 19000 2800
305 16000 6400
181 430 64
182 540 63
183 7000 230
184 13000 450
188 17000 1400
the Diagonal Treatment Plant, which depressed oxygen levels in surface
waters where it was principally being carried. Most of this water
then flows through the East Waterway and into Elliott Bay, flowing
over the more dense salt water in the bay and creating lower DO
concentrations in the surface waters. After the Diagonal plant
was closed, surface DO concentrations then exceeded concentrations
on the bottom.
DO values on the surface at both stations were higher in the August-
to-November period of 1970 (following diversion of raw sewage outfalls
in the East Waterway) when compared to the same periods of 1968
and 1969. At station 184, the difference was about 2 mg/1, and at
station 301, the difference was 2 to 3 mg/1. Bottom values at station
301 were not significantly different in 1970 compared to 1968 and
1969. DO values from 50-meter depths at station 184 were slightly
higher in the August-to-November period of 1970 than the same periods
121
-------
4.8
4.9
5.0
SEATTLE
.0
ELLIOTT BAY
20.0
28,0
LEGEND
Before Diversion Pre Aug. 1970
After Diversion Post Aug. 1970
Station •
Total Coliform / lOOmls. x 1000
Figure 52. Coliform Concentrations at Elliott Bay Shoreline
122
-------
1968
YEAR
1970
100,000
*
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tr 10,000
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230 233 235 236 2St
STATIONS
230 £33 233 23« 23*
STATIONS
Figure 53. Coliform Levels and Standard
123
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1968 1969 1970 1971
Figure 54. Dissolved Oxygen Levels in Bay at River Mouth
-------
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1968 1969 1970 1971
Figure 55. Dissolved Oxygen Levels in Elliott Bay
-------
of 1968 and 1969. The slightly higher DO values at 50 meters at
station 184 in 1970 may be the result of lower oxygen demand of bottom
waters in the area as a result of less settling of particulate matter
from surface waters, specifically as a result of the removal of
raw sewage discharges.
Water Transparency
Unfortunately, secchi disc readings were not taken prior to 1970,
which leaves no historic base for comparison. Water transparency
readings were taken in 1970; Table 23 gives monthly averages for
three Elliott Bay stations.
Based on visual observations and comments from people working along
the Seattle waterfront, it can be stated that there has been a major
improvement in water transparency during the summer of 1970 as compared
to previous years.
Further improvement in all water quality indicators of Elliott Bay
is expected as the CATAD system permits better regulation of combined
sewage and stormwater overflows.
TABLE 23
Water Transparency Readings—1970
(All depths in feet)
Station
188
Station
184
January
February
March
April
May
June
July
August
September
October
November
December
4.9 8.7
7.7 8.2
17.5 18.6
9.5 11.6
8.7 8.2
16.8 14.7
11.8 12.3
(diversion completed)
21.5 18.0
24.2 22.6
24.3 27.5
19.7 26.2
15.1 19.7
Station
301
5.4
8.8
7.7
4.4
3.4
9.8
8.3
8.6
16.1
17.7
18.0
19.5
126
-------
Duwamish River Studies
Scope
The major objective of the Duwamish-Green River studies is to maintain
a continuous surveillance of water quality conditions as they relate
to the migration and propagation of fish life. (The name of the
river changes about 11.5 miles upstream from the mouth. The lower
portion is the Duwamish; upper reaches are known as the Green.) Another
objective is to demonstrate compliance with state water quality standards
and to observe improvements in water quality conditions as brought
about by Metro construction or>operational adjustments. Metro is
a partner with United States Geological Survey in a cooperative
study of the Duwamish River using continuous monitoring stations
at five strategic points on the river. At each remote site, an
automatic monitoring unit, shown in photograph A of Figure 56, telemeters
information over phone lines to a central receiving data logger,
shown in photo B. Information, which is transmitted hourly, is
converted to punch card or tape storage for further statistical
analyses.
In addition to the automatic monitoring stations, an extensive manual
sampling program is being carried out to augment the automatic equipment.
Data is collected from 18 shore and river sampling stations shown in
Figure 49.
A. Remote Monitoring Unit
B. Central Data Logger
Figure 56. Automatic Water Quality Monitor System
127
-------
Equipment and Analyses
Automatic monitoring equipment measures dissolved oxygen, pH, tempera-
ture, solar radiation, turbidity, and conductivity. The other manual
sampling stations add BOD and nutrient investigations to the list
of analyses.
Data and Results
Riverflow, water temperature, and conductivity have not changed signifi-
cantly from their normal fluctuations and ranges. Riverflow in cubic
feet per second is illustrated through 1970 in Figure 57.
Dissolved Oxygen
The first major change in dissolved oxygen observed since Duwamish
River monitoring began in 1961 occurred in the summer of 1970. This
change was noted in bottom waters at the 16th Avenue South automatic
monitor site. As demonstrated in Figure 58, the bottom dissolved
oxygen level did not drop as low in the late summer of 1970 as in
previous years. Minimum values in 1970 approached maximum values
in 1969. The fall in DO during July was caused by diversion of
raw sewage upstream to Diagonal Avenue during construction of the
Hanford Street regulator.
One factor possibly contributing to the increased DO was the greater
tidal exchange in 1970 than in previous years. The increase also
correlates well with the interception of the raw and treated sewage
outfalls previously discharging to the river estuary. Assuming normal
tidal exchange, 1971 and 1972 records will demonstrate whether the
increased DO is merely a tidal exchange phenomenon or an improvement
trend resulting from interception.
Bacteriological
Figure 59 shows median fourth quarter total coliform concentrations
for the Duwamish-Green River for the past three years. A fivefold
reduction in coliform concentration was recorded in the lower estuary.
This is i primarily the result of closing of the overloaded Diagonal
Treatment Plant, which discharged its effluent to the river. This
reduction was noticed immediately after plant closure in the fall
of 1969. The figure also shows a gradually increasing coliform concen-
tration traveling downstream until reaching station 306, a result
of numerous industrial and some domestic pollution sources. The
reduced coliform between station 306 and 307 is most likely a result
of salt water dilution.
Nutrients
The study of chemical nutrients in the river have included such param-
eters as ammonia-nitrogen, nitrate-nitrogen, and total hydrolyzable
128
-------
N5
VD
(Si
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1962-63 1963-64 1964-65 1965-CG 1966-67 1967-68 1966-69 1969-70 1970-
Figure 57. Duwamish River System Flow
-------
U)
o
7 14 21 28 4 II
JAN FEB
18 23 4 II 18 23 I 8 IS 22 29 6 13 20 27 3 10 17 24 I 8 13 22 29 5 12 19 26 Z 9 16 23 30 7 14 21 28 4 II IB 25 2 9 16 23
MAR APR MAY JUN JUL AUG SEPT OCT NOV DEC
Figure 58. Minimum River Dissolved Oxygen
-------
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DRIVER
^^
^
FLOW DIRE
_i
J
t-
o
a
(E
STA. 3106
\\ STA. 310
IS
STA 3IO7 \^
\
:TION
\
\ \
%. \
Nx\
\^ Ny
^J
LEGEND
OCT. DEC.
ii H
STATIONS
II II
968
qcq
I97O
36 307 309 310 311 315
Figure 59. River Total Coliform Count
131
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phosphate. In comparing 1970 with 1967, it was found that ammonia
concentrations have decreased greatly at station 309 during the
months of July, August, and September (Figure 60). The ammonia
concentration at this station was lower than recorded in previous
years because of modified plant operation which allows greater nitrifi-
cation of the Renton Treatment Plant effluent (see Figure 49). Nitri-
fication reduces the nitrogenous biochemical oxygen demand loading
of the effluent. A slight decrease in ammonia is also apparent
at stations 305 and 307 for. the same time comparison. Similarly,
phosphate-phosphorous concentrations were generally lower in 1970
than in 1967, but the pattern is not consistent or of as great a
significance (Figure 61).
Biochemical Oxygen Demand
Recent biochemical oxygen demand studies of the river have been performed
by the U.S. Geological Survey branch located in Tacoma, Washington,
but the data has not yet been published.
Bottom Sediments
Studies of benthal deposits in the Duwamish River estuary have been
continued to assess the changes resulting from increased effluent
discharges from the Renton Treatment Plant and the removal of various
raw and treated sewage outfalls in the lower Duwamish River estuary.
Physical characteristics of the stretch of river under study have
not changed significantly since the start of the study in 1963.'
The upper undredged section of river has remained sandy, with corre-
sponding low chemical oxygen demand (COD) values. This indicates
that the Renton Treatment Plant has not contributed to any sludge
buildup in this section of river.
In the lower dredged section of the river, a significant decrease
in the COD of benthal sediments was recorded at the station (Figure 62)
below the Diagonal Treatment plant between 1968 and 1969. During
this period, a land filling project near the discharge point was
in progress at the time of the plant closure. Observation of sediments
during 1969 indicated that significant amounts of sand were mixed
with the fine organic sediment usually found at this station. The
sand presumably entered the river through erosion from the nearly
filled site. Although the presence of the sand contributed to the
decrease in benthal COD, it is safe to assume that the elimination
of the Diagonal Treatment Plant discharge contributed to the decrease
in COD levels at one station.
Aquatic Life
The Green-Duwamish River continues to support significant runs of
salmon. Data from the Washington State Department of Fisheries (Green
132
-------
.84.
v-87
.60
40
.20
AMMONI
L
\
1970 /
/
/
/
.60
AMMONI
STA. 3
.20
1967-
.40
AMMON
STA. 3<)5
.20
1967
S
\
1970
JUNE JULY AUG SEPT
PiOv
5EC
Figure 60. River Ammonia Concentration
133
-------
.60
PHOSPHORUS
STA. 3C9
.40
.20
1970-
z
1967
.40
PHOSPHORUS
STA. 307
.20
• 1970
Z_
1967
.40
.20
PHOSPHORUS
STA. 305
1970
/ 1 3 I U
1967
JUNE JULY AUG SEPT OCT NOV DEC
Figure 61. River Phosphorous Concentration
134
-------
160
Oi
Former Diagonal Treatment
Plant Oitehang* Point
CL
UJ
Q
a:
LU
S 6 7
MILES FROM RIVER MOUTH
Figure 62. River Bottom Chemical Oxygen Demand
-------
River Hatchery) for various years are shown in Table 24. These pollu-
tion-sensitive fishes have been able to maintain, and in one case
apparently increase, their population during the past few years.
Another example of the effects of improved water quality on the
increase in a fish population is shown in the Duwamish trawl study.
The results are shown in Table 25.
These data illustrate the significant increase in the number of
English sole at all three sampling stations. Small numbers of English
sole are caught at station KW probably because the species is intolerant
to large salinity changes; such changes occur at this station because
of tidal fluctuations and the resulting effect on salt water intrusion
into the estuary.
The removal of raw and treated waste discharges from the lower Duwamish
River estuary has improved water quality and benefited the continued
growth and survival of salmon and other aquatic life.
TABLE 24
Adult Salmon Returns
(Green River Hatchery)
Year Chinook Salmon Coho Salmon
1967 5,038 12,736.
1968 8,114 50,856
1969 6,650 36,000
1970 9,000 70,868
TABLE 25
Trawl Catches of English Sole
(average number for various years)
Station
Station
Year 1st Avenue So. 16th Avenue So. KW
1967 8.7 7.0 0.4
1968 15.5 2.4 0.4
1969 10.9 9.2 3.9
1970 32.6 50.2 11.7
136
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SECTION VII
DEMONSTRATION GRANT PLANNING
IMPLEMENT THE CATAD SYSTEM
This report was prepared to indicate how the storage capacity of
combined sewers can be maximized to prevent and possibly eliminate
overflows. The progress of the Seattle area toward this goal has
now been defined; therefore, the task remains to demonstrate whether
the specific application of on-line computers to automatic control
of a collection system is the ultimate solution to achieving this goal.
Figure 63 relates the planned schedule and the progress thus far attained
toward implementing the Metro CATAD computerized total management system.
Filled-in areas on the bar graph indicate work already completed.
Unfilled areas show scheduled work. The planning chart shows that all
facilities and hardware have been purchased and are in use. As of June
1971, the tasks remaining include: (1) continued sampling and monitoring
of quantity and quality indicators, (2) refinements to the control and
simulation model programs to allow a gradual change from local to super-
visory to computer control (one station at a time) , and (3) an evaluation
of the merits of the system, including a final report.
MONITORING
Plans call for the receiving water monitoring program to continue at
about the present levels with a few exceptions; these include an increase
in Lake Washington Ship Canal sampling, where much regulator construction
work is planned in the next 5 years. Collection system monitoring will
show a major shift in emphasis as the separation and storm drainage
studies are completed and more effort is diverted to overflow studies.
More automation is planned, beginning with automatic chemical analyses
and proceeding to automatic overflow volume calculations, river water
quality plots, and possibly computer-directed overflow sampling operations.
MODELING
As pointed out in Section VI, the CATAD mathematical model is now passing
through a transitional phase where monitored data, relating system
response to measured rainfall and manual control actions, will be chang-
ing model program coefficients and algorithms (computational methods)
until the model performs its duties without significant error. Further
model revisions or additions are being studied.
Both the regional United States Geological Survey and River Basin
Coordinating Committee—Water Resources Management Study (RIBCO-
WRMS) are engaged in extensive research to develop water quality
models for Seattle area river systems. For the Duwamish River estuary,
this work is highly complicated because of the gradual mixing of fresh and
salt water and the complex tidal variations, pictured in Figure 64, which
range from -3 feet to +13 feet. When a model is finally available, it is
137
-------
TASK RELATIVE
FACILITIES
CONSTRUCTION
CATAO 8 REMOTE
MONITORING
nvrRnnw^AMPiiKirc IIIM
REPORT OUTLINES PRE- 111]
PARED S APPROVED
EVALUATE CONSTRUCTION I !J
AND LOCAL CONTROL
WRITE - PUBLISH
INTERM REPORT
PROGRAM
REFINEMENTS TO
CONTROL MODEL
COMPUTER MONITORS
RAINFALL 8 FLOW
SUPERVISORY CONTROL
COMPUTER CONTROLS
SYSTEM
EVALUATE COMPUTER
CONTROL
WRITE - PUBLISH
FINAL REPORT
PROGRESS
..
,
III!
|™
liilin
AJOJAJOJA J 0 J A J 0 J A J 0 J A J OJAJO
1967 1968 1969 1970 1971 1972 1973
Figure 63. Planning and Progress Chart
138
-------
Figure 64. Tidal Variations in Puget Sound
to tie in some version of the Metro automatic river monitoring system so
that effects of overflows or other stream loadings can be predicted and
used to keep stream factors within established limits by automatically
limiting or eliminating any discharge.
At the same time, new modeling techniques such as those recently com-
pleted by Lager, Metcalf, Eddy, et al. (52) and those being initiated by
San Francisco and by Battelle for Cleveland (53) will be studied to
determine whether refinements can be made to the CATAD system to further
improve its ability to optimize all facets of the collection and treatment
system, including operation and planning and design of additions to upgrade
or expand the present system.
NEW APPLICATIONS
Also being planned are various ways to capitalize on the great number
of alternative potential uses that become available as a result of
Specifying a real-time computer system that can be time-shared by the
foreground or background programs. For example, a remote terminal simi-
lar to the West Point console has been specified for the Renton Treatment
Plant. (54) This terminal will have as a major component a mini-computer
that will eventually allow development of a secondary treatment process
control program. Other foreground applications include an on-line preven-
tive maintenance management system and automatic receiving water quality
monitoring, plotting, and alarming functions. The possible background
uses for the new generation digital computers are too numerous to describe
in this report.
139
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SUMMARY
It would appear that municipal utility agencies are generally heading
toward computer usage at some level to improve their service to the com-
munities they support. Computer assistance can take the form of improved
efficiency in record keeping and billing procedures or improved operating
procedures to reduce costs. The Municipality of Metropolitan Seattle and
EPA-WQO have made a large investment in an attempt to gain a foothold in
the application of computers to real-time control of sewage collection
systems. Regardless of the final results of this demonstration grant,
many cities will profit from this research effort: Metro in that a
highly adaptable computer system is available for many purposes and
other cities in that such information will be on hand to serve as a
starting point to begin the solution of their own unique problems.
140
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SECTION VIII
ACKNOWLEDGMENTS
Appreciation is extended to the following persons and their organizations
for their assistance and cooperation during the course of this study:
1. PROJECT GUIDANCE
Municipality of Metropolitan Seattle
Charles V. Gibbs, Executive Director
Theodore W. Mallory, Director, Engineering and Water Quality
Water Quality Office, Environmental Protection Agency
William A. Rosenkranz, Jr., Chief, Storm and Combined Sewer
Pollution Control Branch, Division of Applied Science
and Technology
James C. Willmann, Project Officer, Research and Develop-
ment Office, Pacific Northwest Region
George A. Kirkpatrick, Project Manager, Storm and Combined
Sewer Pollution Control Branch
2. ENGINEERING DESIGN
Metropolitan Engineers, Consultants for the Municipality
David H. Caldwell, PhD, Project Manager
Roger F. Wilcos, Chief Engineer
Stuart M. Alexander, Executive Engineer
James F. Lynch, Project Engineer
City of Seattle, Department of Engineering
Harvey W. Duff, Senior Supervising Engineer, Head of
Sewerage and Drainage Section
Patricia A. Flynn, Senior Engineer
Municipality of Metropolitan Seattle
Richard L. Hibbard, Superintendent Design and Construction
(Now Executive Assistant)
3. WATER QUALITY AND PROGRAMMING
Glen D. Farris, Superintendent Water Quality and Industrial
Wastes, Metro
Cecil M. Whitmore, Senior Water Quality Analyst, Metro
Raymond Dalseg, Senior Bacteriologist, Metro
Bruce Burrows, Water Quality Technician, Metro
James E. Stapleton, Programmer, Metro
4. PHOTOGRAPHY AND DRAFTING
Roy Montgomery, Senior Engineering Associate, Metro
George Fields, Engineering Associate, Metro
5. SECRETARIAL
Jean Blair, Senior Clerk Stenographer, Metro
141
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6. MAINTENANCE AND OPERATION
Thomas G. Rice, Superintendent, West Point Division, Metro
H. Dennis Brown, Assistant Superintendent of Maintenance,
West Point Division, Metro
Gary D. Isaac, Superintendent, Renton Division, Metro
Edwin R. Sironen, Maintenance Supervisor, Electrical and
Instrumentation, Renton Division, Metro
7. COMMERCIAL FIRMS
Philco-Ford Corporation, Western Development Laboratories,
Palo Alto, California
Xerox Data Systems, El Segundo, California
142
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SECTION IX
REFERENCES
1. Brown, K.W., and Caldwell, D.H., Metropolitan Seattle Sewerage and
Drainage Survey, City of Seattle, King County and the State of Wash-
ington Report, Metropolitan Seattle Area (1958).
2. Municipality of Metropolitan Seattle, The Metro Enabling Act, Reprint
of State of Washington Revised Code, Chapters 35.58, 35.95, and
39.33 (1970).
3. Metropolitan Engineers, Predesign Report on First Stage Construction
of Comprehensive Sewerage Plan, Municipality of Metropolitan Seattle,
Washington (1958).
4. Duwamish River-Elliott Bay Storm Water Control System, Grant Applica-
tion 11022-ELK to Federal Water Pollution Control Administration
(1966).
5. Guidelines—Water Quality Management Planning, Environmental Protec-
tion Agency—Water Quality Office, Washington, D.C. (1971).
6. Metropolitan Engineers, Predesign Report on Second Stage Construction
of Comprehensive Sewerage Plan. Municipality of Metropolitan
Seattle, Seattle, Washington (1970).
7. Environmental Pollution Panel, Restoring the Quality of Our Environ-
ment, The White House, Washington, D.C. (1965).
8. Public Health Service, Pollutional Effects of Stormwater and Over-
flows from Combined Sewer Systems, Public Health Service Publication
No. 1246 (1964).
9. American Public Works Association—Research Foundation, "Problems of
Combined Sewer Facilities and Overflows—1967," Federal Water Quality
Administration Publ. No. WP-20-15, U.S; Department of the Interior
(1969).
10. De Felippi, J.A., and Shih, C.S., Characteristics of Separated Storm
and Combined Sewer Flow, Paper presented to 43rd Water Pollution
Control Federation Meeting, Boston, Mass. (1970).
11. "Island City Solves Tough Sewerage Problem," Public Works, 101, No. 2,
p 95 (1970).
12. "Sewer Improvements Call for Trunk," Water and Sewage Works, 116,
No. 10, pp 406-407 (1969).
13. Western Company of America, "Improved Sealants for Infiltration
Control," Federal Water Pollution Control Administration Publ.
Report No. 11020-DIH (1969).
143
-------
14. Llewellyn, I.E., "Massive Sewer Infiltration," American City 83.
No. 10, pp 90-91 (1968).
15. Musgrave, G.W. and Holtan, H.N., "Section 10-Infiltration," Handbook
of Applied Hydrology. McGraw-Hill Book Company, New York (1964).
16. Keifer, C.J., Tholin, A.L. and Sulowaz, M., Combined Overflow
Storage Plan for Pollution and Flood Control in the Chicago Metro-
politan Area, City Bureau of Engineering, Dept. of Public Works (1969)
17. "Underwater Storage Tanks an Aid to Pollution Abatement," American
City, 84, No. 9, pp 30-34 (1969).
i !
18. Escritt, L.B., "A Re-examination of the Storm Tank Problem," Water
and Waste Treatment, 12, No. 9 (1969).
19. American Public Works Association-Research Foundation, "Combined
Sewer Regulator Overflow Facilities," Federal Water Quality Adminis-
tration, Publ. No. 11022-DMU (1970).
20. Wammis, J.W.C., "The Trunk Sewer System and the Sewage Treatment
Plant of the Town of Utrecht," Ingenieurs Grav.. 77, pp 23-31 (1965) .
21. Cester, A.D., and Stein, W.J., "Pollution From Combined Sewers
Cincinnati, Ohio," American Society of Civil Engineers Preprint
No. 1090 (1970) „
22. Anderson, J.J0, "Real-Time Computer Control of Urban Runoff,"
Proceedings, American Society of Civil Engineers Hydraulics Division
- No. 7028 (1970).
23. Brown, J.W., "Sewer Monitoring and Remote Control—Detroit,"
American Society of Civil Engineers Preprint No. 1035 (1969).
24. Rosenkranz, W.A., "Storm and Combined Sewer Demonstration Projects,"
Clearinghouse No. PB190799 (1970).
25. Cywin, 0., and Rosenkranz, W.A., "Storm and Combined Sewer Research
and Development," American Society of Civil Engineers Preprint
No. 1039 (1969).
26. "Combined Sewer Overflow Abatement Technology," Federal Water Quality
Administration Publ. No. 11024 06/70 (1970).
27. Report on Sanitary Sewer Capacity and Surface Drainage Survey for
Mission Township Main Sewer District No. 1, Johnson County Kansas
(1959).
28. Gibbs, C.V., "Steps to Success in Water Pollution Control," Public
Works Magazine, 101, No. 5, pp 62-67 (1970).
144
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29. Babbitt, H.E., and Baumann, E.R., Sewerage and Sewage Treatment—
8th Ed., John Wiley and Sons, Inc., New York (1958).
30. Metropolitan Engineers, Engineering Study Reduction of^ Combined
Sewage Overflows North I_nt_erc_eptor System, Seattle, Washington (1969)
310 Forward Thrust, Inc., Developing a Capital Improvement Plan for King
County/Part III; Recommendation, Seattle, Washington (1967).
32. City of Seattle—Standard Plans and Specifications—8th Edition,
Seattle Engineering Department (1967).
33. Flynn, P., Progress of Seattle's Sewer Separation Program, paper
presented to Pacific Northwest Pollution Control Association (1970).
34. Cohn, M.M., Sewers for a Growing America, Certain-teed Products
Corporation (1966).
35. Rawn, A.M., "What Cost Leaking Manholes," Water Works and Sewerage,
_84 p 459 (1937).
36. Storm Water Pollution—New Orleans Louisiana, Sewerage and Water
Board of New Orleans (1970).
37. American Public Works Association—Research Foundation, "Public
Works Computer Applications," APWA Special Report No. 38, Chicago,
Illinois (1970).
38. American Public Works Association—Research Foundation, "Feasibility
of Computer Control of Wastewater Treatment," Environmental Protec-
tion Agency Contract 14-12-580 (1970).
39. Gibbs, C.V., and Alexander, S.M., "CATAD System Controls for
Regulation of Combined Sewage Flows," Water and Wastes Engineering
6,, No. 8, pp 46-49 (1969).
40. Allen, C.M., and Taylor, E.A., "Salt Velocity Method of Water
Measurement," American Society of Mechanical Engineers Journal, 46,
No. 1, pp 13-51 (1924).
41. Duff, H.W., and Hsieh, G.C.C., "Seattle Rain-Gaging Program and
Rainstorm Data," American Society of Civil Engineers Preprint
No. 1089 (1970).
42. Rouse, H., Engineering Hydraulics, John Wiley and Sons, Inc., New
York (1950).
43. Leiser, C.P., and Tompe, C.K., Sewer-Test Vary-Sampler Field Manual,
Sirco Controls Products, Limited, Vancouver, B.C. (1969).
145
-------
44. Standard Methods for the Examination of Water and Wastewater—12
Edition, American Public Health Association, New York (1965).
45. King, H.W., Handbook of Hydraulics—4th Edition. McGraw-Hill Book
Company, Inc., New York (1954).
46. Dalseg, R.D., and Leiser, C.P., Characteristics of Storm Sewers and
Combined Sewer Overflows Discharging into Lake Washington, Preliminary
Report to Municipality of Metropolitan Seattle (1970).
47. Dalseg, R. D., and Farris, G.D., The Quality of Rainfall Runoff from
Interstate 5 at Seattle, Municipality of Metropolitan Seattle (1970) .
48. Gibbs, C.V., and Isaac, G.W., "Seattle Metro's Duwamish Estuary Water
Quality Program," Journal Water Pollution Control Federation, 40,
pp 385-394 (1968).
49. Gibbs, C.V., "Receiving Water Monitoring," Water Works and Wastes
Engineering, 1, No. 9, pp 52-55 (1964).
50. "Phosphate Removal in an Activated Sludge Facility," Federal Water
Quality Administration Grant Proposal No. WPRD 247-01 (1969).
51. Anderson, J.J., et al., Application of the Autoanalyzer to Combined
Sanitary and Storm Sewer Problems, presented to Technicon Symposium,
New York (1967).
52. Lager, J.A., et al., Triumvirate Model for Storm Water Management,
Report presented to 43rd Water Pollution Control Federation
Conference, Boston, Mass. (1970).
53. Oleson, D., and Cearlock, D., Unpublished Report on Cleveland Model
System, Battelle Northwest, Richland, Washington (1971).
54. Metropolitan Engineers, Specifications for Contract No. 71-2. Renton
Treatment Plant Enlargement, Seattle, Washington (1971).
146
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SECTION X
GLOSSARY OF TERMS AND ABBREVIATIONS
access time - time required by computer to locate a word in core memory
and transfer the word to a register.
A.C.U.- auxiliary control unit: cabinet containing electronics, relays,
etCo located between x.C.U.an^ station local control system.
address - name or number which identifies a particular storage location
in the computer.
analog - the representation of a numerical quantity by some physical
variable, e.g., translation, rotation, voltage or resistance.
as-built - engineering drawing completed after a facility is constructed,
shows original design plus revisions made during construction.
autoanalyzer - copywritten term referring to equipment which automates
chemical tests on samples. After initial set-up of equipment and sampl-
ing unit, no further human effort is needed other than interpreting a
strip chart.
background — a low priority, unprotected processing area in a computer
where batches of programs are compiled, tested and run without affecting
other protected control and processing areas.
benchmark — a test program written to test the speed, performance and
capacity of a computer and often to compare the results of a run on
different computers.
benthal sediments - deposits on the bottom of a stream, often containing
decaying material which removes oxygen from the stream.
binary - the representation of a numerical quantity by use of the two
digits 0^ and _1.
bit - abbreviation of binary digit: smallest possible unit of computer
storage.
BOD - biochemical oxygen demand, a standard test used in assessing waste-
water strength. The quantity of oxygen used in the biological-chemical
oxidation of organic matter in a specified time under standard conditions.
CATAD - computer augmented treatment and disposal system.
C.C.U. - CATAD control unit: cabinet same as A.C.U but located at pumping
stations.
cfs - cubic feet per second, unit of quantity of liquid flow
147
-------
checkpoint - a point in time where computer processing is stopped, all
machine variables, registers and background area copied to a rapid
magnetic storage device so that a large foreground program can temporarily
use all or a part of what is normally called background area.
COD - chemical oxygen demand, a standard rapid test of the strength of a
wastewater. The COD determination provides a measure of the oxygen
equivalent of that portion of the organic matter in the sample that is
susceptible to oxidation by a strong chemical oxident.
core - computer storage area where binary data is represented by the
direction of the magnetic field in each unit of an array of tiny donut-
shaped rings (generally).
Coliform - bacteria found only in intestines of mammals, therefore used as
an indication of the pollution level of a sample or body of water.
composite - placing samples from a continuously changing stream into one
common storage point to test for an average value.
C.P.U. - central processing unit: that portion of computer excluding
input-output and external storage units, where arithmetic, logical,
storage and control functions are centered.
CRT - Cathode Ray Tube: television, for visual data presentation.
J)C - direct current, a form of electrical power.
DO - dissolved oxygen, the amount of gaseous oxygen dissolved into a
liquid sample.
digital - the use of discrete numbers to a given base to represent all
quantities in a problem or calculation. Most often all information is
stored, transmitted or processed by a dual state condition; e.g. on-off,
open-closed, true-false.
dwf - dry weather flow: normal sewer flow from domestic and industrial
sources only.
executive - a program, often supplied with a computer, which controls
loading and relocation of all software (much unknown to the programmer)
required to execute a job entered by a programmer.
fecal coliform, fecal streptococcus - bacteria associated with humans,
refinements to coliform tests to eliminate animal sources when assessing
the pollution level of a water sample.
first flush - heavy load of material, previously settled in sewers, which
is washed along by the initial flow resulting from a storm.
148
-------
fps - feet per second, a measure of velocity.
force main - a pressure pipe joining the pump outlet at a wastewater
pumping station with a point of gravity flow.
F value - a number corresponding to the degree of confidence of a certain
statistical correlation. A correlation with an "F" less than one is
generally discounted.
gpad - gallons per acre per day, a measure of infiltration or leakage
between a pipeline and its surroundings.
hardware - the physical equipment and devices which comprise a computer
or computer system component.
head - distance in feet from a free liquid surface to some reference
point (which may be a different liquid surface).
hydrograph - a graphical representation of liquid flow versus time with
time as the horizontal axis.
interceptor - sewer which receives water from various traverse sewers and
carries water to a point for treatment and disposal.
interface - a common boundary between parts of a computer system.
interrupt - a special signal which temporarily halts the normal operation
of some computer job for the purpose of accomplishing another more
important short task, after which normal operation resumes.
loading - the dry weight, in pounds, of some material that is being added
to a process or disposed of to a receiving water.
logic - the science of combining electronic components in order to define
the interactions of signals in an automatic data processing system.
mathematical model - the characterization of a process or concept in
terms of mathematics, which allows the simple manipulation of variables in
an equation to determine how the process would act in different situations.
mg/1 - milligrams per liter, or the concentration of some chemical in a
liquid. If a letter appears after "mg" it represents the chemical symbol,
e.g. N, for nitrogen; P, for phosphorous.
mgd - millions gallons per day, a common term for quantity of wastewater
flow.
modem - device which converts between computer recognized signals and
tones transmitted over telemetry lines.
149
-------
NH
,, NCL - chemical shorthand for ammonia and nitrate in solution.
nutrient - is a major ingredient of a water or wastewater sample, e.g.
ammonia nitrogen, nitrate-nitrite nitrogen, phosphate phosphorous, or
silica which may serve as growth media for microorganisms, phytoplankton
or zooplankton.
off-line - system and equipment under human operator control, not C.P.U.
control.
O.G.C. - outfall gate controller: cabinet containing controllers and
recorders relating to the outfall gate at a mechanical regulator station.
on-line - system and equipment under continuous automatic C.P.U. control.
orifice plate regulator - a machined hole in a metal plate (usually
horizontal) allows a flow only slightly in excess of trunk dry weather
flow to enter the interceptor.
overflow - undesirable emergency relief of sewer system by direct
transmission to receiving water generally without treatment.
outfall - pipeline which carries raw or treated sewage from the collection
system or treatment plant to the receiving body of water.
parity - a term relating to whether a given word or character (group of
digits) is even or odd. A single bit denoting the parity of a word is
usually attached to that word so that quick tests can be made as to the
validity of the data.
partial separation - removal of some portion of all the elements of
storm drainage into a combined sewer; e.g. streets and parking areas
only, leaving roof and foundation drainage to enter the combined sewer.
peripheral - specialized machines connected electrically to the computer
for converting between binary and other data forms, e.g. cards, tapes,
typed pages.
jjH - a measure of the degree of acidity or alkalinity of a solution.
PO, - chemical shorthand for phosphate in solution.
priority - degree of importance assigned to some computer task.
psig - pound per square inch, gage: a measure of the pressure of a fluid
or gas based on atmospheric pressure.
purging - the act of reversing flow or using high pressure liquid or gas
to clear a pipeline of a plug of solids.
150
-------
rational method - a means of computing storm drainage flow rates by use
of the formula Q=ciA; where £ is a coefficient describing the physical
drainage area, i_ is the rainfall intensity and A is the area.
real-time control - control of a system by using computers and timing
such that the speed of response to the input information is fast enough
to effectively influence the performance of that system.
register - device consisting of miniature electronic components including
transistors, where a specific number of bits are stored and operated upon.
regulator - structure which controls amount of sewage entering an
interceptor by storing in a trunk line or diverting some portion of flow
to an outfall.
routing - storing, regulating, diverting or otherwise controlling the
peak flows of wastewater through a collection system according to some
prearranged plan.
rule curves - a set of curves which relate storage and discharge for a
given reservoir under different control conditions.
r value - individual correlation value; indicates the degree of correla-
tion between two variables.
R value - multiple regression value: the correlation value to many
independent variables with a single dependent variable, e.g. air
temperature and solar radiation on water temperature.
sag curve - a curve which describes the gradual drop to some minimum
value followed by an increase to normal levels of the dissolved oxygen
in a flowing stream following the addition of some oxygen demanding
material such as sewage.
salt wedge - a wedge shaped volume of salt water beneath a body of fresh
water.
secchi disk - a disk, painted in four quadrants of alternating black
and white, which is lowered by rope into a body of water. The measured
depth at which the disk is no longer visible from the surface is a
subjective measure of relative transparency.
sequential - samples taken at known time intervals and stored in separate
labeled containers.
side weir - a regulator which is essentially a long slot cut into the side
of a sewer. Normal dry weather flow continues through the sewer while
the increased depth during a storm will allow excessive flows to exit
through the slot to some alternate point as an overflow.
151
-------
scan - the collection and storage of data from all points at all stations
in system by computer.
scan time - time set by operator which establishes the interval from the
beginning of one scan to the next.
simulation - representation of physical systems and phenomena by computers,
models and other equipment.
siphon - a u-shaped pipe used to carry wastewater under some obstacle such
as a stream or another pipe.
sluice gate - a vertically sliding gate of any shape used to control or
shut off flow in a sewer or other channel.
software - the programs or instructions which often control the hardware
to perform some computer operation or extend the capabilities of the system.
stepwise regression - a statistical technique whereby a sequence of linear
regression equations are computed in a stepwise manner, i.e. each
independent variable is entered into the equation as it becomes the
greatest remaining effect upon the variability of the dependent variable.
storage - unfilled, enclosed volumes within or connected to a sewer system
capable of accepting and retaining wastewater for a period of time.
subroutine - a compact set of instructions to perform some repetitive task
quickly and return to a main program.
telemetry - data transmission over long distances via telephone or
telegraph lines by electro-magnetic means.
T.C.U. - Telemetry Control Unit: interchangeable electronic cabinets,
convert between telemetry and station control signals (from A.C.U. or
C.C.U.).
time sharing - use of a computer or device for two or more purposes
during the same overall time interval, done by interspersing component
actions in time.
trunk - large sewer which receives wastewater from tributary branch
sewers serving generally one drainage area.
trawl - a fish catching technique using nets pulled along a river bottom
(net sometimes also reaches to the surface) by boat.
wastewater - the spent water of a community, including domestic, industrial
and commercial water-carried solids plus storm or other water sources.
Replacing the term sewage.
word - a set of 16 or more bits stored and transferred as a unit by the
computer.
152
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SECTION XI
APPENDICES
A. Washington State Water Quality Standards 155
B. Metro Second-Stage Construction Program Costs 167
C. Combined Sewer Overflow Points 169
Table C-l: Overflow Points Within Separation Area 169
Table C-2: Overflow Weir Elevation Outside Separation Area. 173
D. Separation Cost Examples (1958 data) 177
Figure D-l: Separation Plan—Southwest Seattle District . . 178
Table D-l: Estimated Construction Costs—
Southwest Seattle District 179
Figure D-2: Separation Plan—East Central Seattle 182
Table D-2: Estimated Construction Costs—
East Central Seattle. 183
E. CATAD Station Information 187
Table E-l: Regulator Stations 188
Table E-2: Pump Stations 190
F. List of Model Subroutines 193
G. Flow Calculation Programs 195
Table G-l: Manning's Program—Input Data 197
Table G-2: Manning's Program—Output Data 201
Table G-3: Chart Conversion Factors 203
Table G-4 : Sluice Gate Program—Input Data 204
Table G-5: Sluice Gate Program—Output Data 209
H. Chart Problem Examples 211
Figure H-l: Denny Regulator (10/21/70) 212
Figure H-2: West Michigan Regulator (01/17/71) 213
Figure H-3: Michigan Regulator (07/01/70) ... 214
Figure H-4: Michigan Regulator (12/15/70) 215
Figure H-5: Michigan Regulator (12/16/70) 216
I. Overflow Water Quality Data 217
Table 1-1: Stations 34 and 36 218
Table 1-2: Stations 37 and 38 219
Table 1-3: Station 40 . . . 220
J. Stepwise Regression Analyses 221
Table J-l: Station 4901 221
Table J-2: Station 4902 222
Table J-3: Station 4903 223
Table J-4: Station 4904 224
K. Area Rainfall Distribution 225
Table K-l: 1969 Monthly Rainfall Distribution. 225
Table K-2: 1970 Monthly Rainfall Distribution 225
Figure K-l: City Engineering Dept. Rain Gage Locations. . . 226
L. Condensed Computer System Specifications 227
153
-------
Appendix A
Washington State Water Quality Standards
BEFORE THE WATER POLLUTION CONTROL COMMISSION
STATE OF WASHINGTON
IN THE MATTER OF PROMULGATING )
REGULATIONS RELATING TO THE )
ESTABLISHMENT OF WATER QUALITY ) PROMULGATION
STANDARDS FOR THE INTERSTATE AND ) OF
COASTAL WATERS OF THE STATE OF ) REGULATION
WASHINGTON AND A PLAN FOR IM- )
PLCMENTATION AND ENFORCEMENT )
OF SUCH STANDARDS )
I. INTRODUCTION
The Water Pollution Control Commission following the procedures
set forth in Chapter 34.04 RCW and after giving notice as required by
Chapter 42.32 RCW, and by virtue of the authority vested in it by Chapter
90.48 RCW, hereby promulgates the following regulation relating to water
quality standards for the interstate and coastal waters of the State of
Washington and a plan for implementation and enforcement of such standards
as set forth in Section II through V hereof; said regulation remaining
in effect until amended or rescinded. This regulation is promulgated to
comply with Section 10 of the Federal Water Pollution Control Act as
amended. (PL 84-660, as amended.)
155
-------
II. CRITERIA AND CLASSIFICATION
The water quality criteria and the classification of
interstate and coastal waters set forth in this section are
established in conformance with present and potential water uses
of said waters after giving due consideration to the natural
potential and limitations of the same.
A. WATER QUALITY CRITERIA
The following criteria shall be applicable to the
various interstate and coastal waters of the State of Washington:
156
-------
1. Class AA Extraordinary
a. General Characteristic
Water quality of this class markedly and uniformly exceeds the
requirements for all or substantially all uses.
b. Characteristic Uses
Characteristic uses include, but are not limited to, the
following:
Water supply (domestic, industrial, agricultural)
Wildlife habitat, stock watering
General recreation and aesthetic enjoyment (picnicking,
hiking, fishing, swimming, skiing and boating)
General marine recreation and navigation
Fish and shellfish reproduction, rearing and harvest
c. Water Quality Standards
Total Coliforrn Organisms shall not exceed median values of 50
(FRESH WATER) or 70 (MARINE WATER) with less than 10% of samples
exceeding 230 when associated with any fecal source.
Dissolved Oxygen shall exceed 9.5 mg/1 (FRESH WATER) or 7.0 mg/1
(MARINE WATER).
Temperature No measureable increases shall be permitted within
the waters designated which result in,water temperatures exceeding
60°F (FRESH WATER) or 55°F (MARINE WATER) nor shall the cumulative
total of all such increases arising from nonnatural causes be per-
mitted in excess of t= 75/(T-22) (FRESH WATER) or t= 24/(T-39)
(MARINE WATER); for purposes hereof "t" represents the permissive
increase and "T" represents the resulting water temperature.
£H shall be within the range of 6.5 to 8.5 (FRESH WATER) or 7.8 to
8.5 (MARINE WATERS) with an induced variation of less than 0.1 units.
Turbidity shall not exceed 5 JTU.
T_qxic_, Radioactive or Deleterious Material Concentrations^ shall be
less than those which may affect public health, the natural aquatic
environment, or the desirability of the water for any usage.
Aesthetic Values shall not be impaired by the presence of materials
or their effects, excluding those of natural origin, which offend
the senses of sight, smell, touch or taste.
157
-------
2. Class A Excellent
a. General Characteristic
Water quality of this class exceeds or meets the requirements for
all or substantially all uses.
b. Characteristic Uses
Characteristic uses include, but are not limited to, the
following:
Water supply (domestic, industrial, agricultural)
Wildlife habitat, stock watering
General recreation and aesthetic enjoyment (picnicking,
hiking, fishing, swimming, skiing and boating)
Commerce and navigation
Fish and shellfish reproduction, rearing and harvest
c. Water Quality Standards
Total Coliform Organisms shall not exceed median values of 240
(FRESH WATER) with less than 20Z of samples exceeding 1,000 when
associated with any fecal source or 70 (MARINE WATER) with less than
10% of samples exceeding 230 when associated with any fecal source.
Dissolved Oxygen shall exceed 8,0 mg/1 (FRESH WATER) or 6.0 rag/1
(MARINE WATER).
Temperature No measureable increases shall be permitted within the
waters designated which result in water temperatures exceeding 65°F
(FRESH WATER) or 61°F (MARINE WATER) nor shall the cumulative total
of all such increases arising from nonnatural causes be permitted
in excess of t- 90/(T-19) (FRESH WATER) or t- 40/(T-35) (MARINE
WATER) ; for purposes hereof "t" represents the permissive increase
and "T" represents the resulting water temperature.
pjl shall be within the range of 6.5 to 8.5 (FRESH WATER) or 7.8 to
8.5 (MARINE WATER) with an induced variation of less than 0.25 units.
Turbidity shall not exceed 5 JTU over natural conditions.
Toxic. Radioactive or Deleterious Material Concentrations shall be
below those of public health significance, or which may cause acute
or chronic toxic conditions to the aquatic biota, or which may
adversely affect any water use.
Aesthetic Values shall not be impaired by the presence of materials
or their effects, -excluding those of natural origin, which offend
the senses of sight, smell, touch or taste.
158
-------
3. Claas B Good
a. General Characteristic
Water quality of this class exceeds or meets the requirements for
most uses.
b. 'Characteristic Uses
Characteristic uses include, but are not limited to, the following:
General recreation and aesthetic enjoyment (fishing,
swimming, skiing and boating)
Fishery and wildlife habitat
Industrial and agricultural water supply
Stock watering
Commerce and navigation
Shellfish reproduction and rearing, and Crustacea (crabs,
shrimp, etc.) harvest.
c. Water Quality Standards
Total Coliform Organisms shall not exceed median values of 1,000
with less than 20% of samples exceeding 2,400 when associated with
any fecal source.
Dissolved Oxygen shall exceed 6.5 mg/1 (FRESH WATER) or 5.0 mg/1
(MARINE WATER), or 70% saturation whichever is greater.
Temperature No measureable increases shall be permitted within the
waters designated which result in water temperatures exceeding 70°F
(FRESH WATER) or 66°F (MARINE WATER) nor shall the cumulative total
of all such increases arising from nonnatural causes be permitted
in excess of t- 110/(T-15) (FRESH WATER) or t= 52/(T-32) (MARINE
WATER); for purposes hereof "t" represents the permissive increase
and "T" represents the resulting water temperature.
2H shall be within the range of 6.5 to 8.5 (FRESH WATER) or 7.8 to
8.5 (MARINE WATER) with an induced variation of less than 0.5 units.
Turbidity shall not exceed 10 JTU over natural conditions.
Toxic. Radioactive or Deleterious Material Concentrations shall be
below those which adversely affect public health during the exercise
of characteristic usages, or which may cause acute or chronic toxic
conditions to the aquatic biota, or which may adversely affect
characteristic water uses.
Aesthetic Values shall not be reduced by dissolved, suspended,
floating or submerged matter, not attributable to natural causes,
so as to affect water usage or taint the flesh of edible species.
159
-------
4. Class C Fair
a. General Characteristic
Water quality of this class exceeds or meets the requirements of
selected and essential uses.
b. Characteristic Uses
Characteristic uses include, but are not limited to, the following:
Commerce and navigation
Cooling water
Boating
Fish passage
c. Water Quality Standards
Total Coliform Organisms shall not exceed median values of 1,000
when associated with any fecal source.
Dissolved Oxygen shall exceed 5.0 mg/1 (FRESH WATER) or 4.0 mg/1
(MARINE WATER), or 50% saturation whichever is greater.
Temperature No measureable increases shall be permitted within the
waters designated which result in water temperatures exceeding 75°F
(FRESH WATER) or 72°F (MARINE WATER) nor shall the cumulative total
of all such increases arising from nonnatural causes be permitted
in excess of t- 125/(T-12) (FRESH WATER) or t- 64/(T-29) (MARINE
WATER); for purposes hereof "t" represents the permissive increase
and "T" represents the resulting water temperature.
j>H shall be within the range of 6.0 to 9.0 (FRESH WATER) or 7.0 to
9.0 (MARINE WATER) with an induced variation of less than 0.5 units.
Turbidity shall not exceed 10 JTU over natural conditions.
Toxic, Radioactive or Deleterious Material Concentrations shall be
below those which adversely affect public health during the exercise
of characteristic usages, or which may cause acute or chronic toxic
conditions to the aquatic biota, or which may adversely affect
characteristic water uses.
Aesthetic Values shall not be interfered with by the presence of
obnoxious wastes, slimes, or aquatic growths or by materials which
will taint the flesh of edible species.
160
-------
B. CLASSIFICATION
Interstate and coastal waters of the State of Washington are
classified as follows:
1. Columbia River Class A
Mouth to the Washington-Oregon border (River Mile 309)
Special Conditions
Temperat u r e No measureable increases shall be per-
mitted within the waters designated which result in
water temperatures exceeding 68°F nor shall the
cumulative total of all such increases arising
from nonnatural causes be permitted in excess of
t= 110/(T-15); for purposes hereof "t" represents
the permissive increase and "T" represents the
resulting water temperature.
Below Interstate Highway No. 5 bridge
Total Coliform Organisms shall not exceed median values
of 1,000 with less than 20% of samples exceeding 2,400
when associated with any fecal source.
2. Columbia River Class A
Washington-Oregon border (River Mile 309) to Grand Coulee Dam
(River Mile 595)
Special Conditions
Washington-Oregon border (River Mile 309) to Priest
Rapids Dam (River Mile 397)
Temperature No measureable increases shall be per-
mitted within the waters designated which result in
water temperatures exceeding 68°F nor shall the
cumulative total of all such increases arising
from nonnatural causes be permitted in excess of
t« 110/(T-15); for purposes hereof "t" represents
the permissive increase and "T" represents the
resulting water temperature.
3. Walla Walla River Class B
Mouth to Lowden (River Mile 15)
161
-------
30. Quinault River Class AA
Mouth to River Mile 2
31. Queets River Class AA
Mouth to River Mile 3.0
32. Hoh River Class AA
Mouth to River Mile 0.8
33. Strait of Juan de Fuca and Puget Sound Class AA
Through Admiralty Inlet and South Puget Sound, South and West to
Longitiude 122° 52' 30" W (Brisco Point) and Longitude 122° 51' W
(Northern tip of Harstene Island), Hood Canal, Possession Sound
south of Latitude 47° 57' N (Mukilteo) and all North Puget Sound
West of Longitude 122° 39* (Whidbey, Fidalgo, Guemes and Lurami
Island) except as otherwise noted.
34. Port Angeles Class A
South and West of a line bearing 152* true from buoy "2" at the
tip of Ediz Hook
Special Conditions
Total Coliform Organisms - Shall not exceed a median value
of 240 with less than 20% of samples exceeding 1,000 when
associated with any fecal source.
35. Sequin Bay Class A
Southward of entrance
36. Port Townsend Class A
West of a line between Point Hudson and Kala Point
37. Port Gamble Class A
South of latitude 47° 51' 20" N.
38. Elliott Bay Class A
East of a line between U. S. Navy Supply Depot and Duwamish Head
Special Conditions
Total Coliform Organisms - Shall not exceed median values
of 1,000 with less than 20% of samples exceeding 2,400
when associated with any fecal source.
39 • Duwamish River Class B
Mouth south of a line bearing 254* true from the NW corner of Berth 3,
Terminal No. 37 to the confluence with the Black River (Tukwila).
162
-------
40. Duwamish River Class A
Upstream fron the confluence with the Black River to the limit
of tidal influence.
Special Conditions
Total Colifonn Organisms - Shall not exceed median values
of 1,000 with less than 20% of samples exceeding 2,400
when associated with any fecal source.
41. Dyes and Sinclair Inlets Class A
West of Longitude 122° 37' W
Special Conditions
Sinclair Inlet and Port Washington Narrows West of Longitude
122° 37' W and south of Latitude 47° 35' 20" N
Total Coliform Organisms - Shall not exceed median values
of 1,000 with less than 20% of samples exceeding 2,400 when
associated with any fecal source.
42. Commencement Bay Class A
South and east of a line bearing 258° true from "Brown's Point"
and north and west of a line bearing 225° true through the
Hylebos Waterway light.
Special Conditions
Total Coliform Organisms - Shall not exceed median values
of 1,000 with less than 20% of samples exceeding 2,400
when associated with any fecal source.
43. Inner Commencement Bay Class B
South and east of a line bearing 225° true through the Hylebos
Waterway Light except the Port-Industrial and City Waterways
south and east of south llth street.
44. Port-Industrial and City Waterways Class C
South and East of south llth street.
45. Puyallup River Class B
Mouth to River Mile 1 (from mouth)
46. Puyallup River Class A
River Mile 1 to limit of tidal influence
47. Chambers Creek Class A
Mouth to the limit of tidal influence.
48. Nisqually River Class A
Mouth to River Mile 9 (Muck Creek confluence)
163
-------
C. GENERAL CONSIDERATIONS
The following general guidelines shall be applicable to the
water quality criteria and classifications set forth in the sections
II A and II B hereof:
1. At the boundary between waters of different classifications, the
water quality criteria for the higher classification shall prevail.
2. In brackish waters of estuaries, where the fresh and marine water
quality criteria differ within the sane classification, the criteria
shall be interpolated on the basis of salinity except that the
marine water quality criteria shall apply for dissolved oxygen when
the salinity is one (1) part per thousand or greater and for total
coliforn organisms when the salinity is ten (10) parts per thousand
or greater.
3. The water quality criteria herein established, except for the
aesthetics values, shall not apply within immediate dilution areas
of very limited size adjacent to or surrounding a wastewater dis-
charge. In determining the size of an immediate dilution area,
consideration will be given to the quality of the effluent or waste-
water discharged and the nature and condition of the receiving waters.
No such areas will be established for a waste discharge unless
authorized under a permanent permit:
a. The waatewater discharge has been provided with all known,
available and reasonable methods of treatment,
b. The wastewater treataent facilities are operated and maintained
to the satisfaction of the Commission and,
164
-------
c. The treated wastewater is provided with initial diffusio.
at the point of discharge into the receiving water to the
satisfaction of the Commission.
4. The criteria established in Section I1A for any of the various
classifications of this regulation may be modified by the Director
for limited periods when receiving waters fall below their natural
water quality condition due to natural causes which are unusual
and not reasonably foreseeable if in the opinion of the Director
the protection of the overall public interest and welfare requires
such modification.
5. Regardless of the water quality criteria as herein established,
wherever existing receiving waters of a classified area are of a
higher quality than the criteria assigned for said area, the
existing water quality shall constitute water quality criteria.
Likewise existing water quality conditions shall constitute the
criteria for Interstate and coastal waters not specifically
classified herein.
165
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D. CHARACTERISTIC USES TO BE PROTECTED
The following is a nonlncluaive list of uses to be protected
by the various classifications:
USES
FISHERIES
Salmonid
Migration
Rearing
Spawning
Warn Water Game Fish
Rearing
Spawning
Other Food Fish
Commercial Fishing
Shellfish
WILDLIFE
RECREATION
Water Contact
Boating and Fishing
Environmental Aesthetics
WATER SUPPLY
Domestic
Industrial
Agricultural
NAVIGATION
LOG STORAGE & RAFTING
HYDRO-POWER
WATERCOURSE CLASSIFICATION
AA A B C
F M
F M
F
F
F
F M
F M
M
F M
F M
F M
F M
F
F M
F
F M
F M
F
F M
F M
F
F
F
F M
F M
M
F M
F M
F M
F M
F
F M
F
F M
F M
F
F M
F M
F
F
F M
F M
M
F M
F M
F M
F M
F M
F
F M
F M
F
F M
F M
F M
F M
F
F M
F M
F
** F - Fresh Water
M - Marine Water
166
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Appendix B
Metro Second-Stage Construction Program Costs
FAT II (TV
r Av< 1 LI 1971 1972 1973.1974 1975 1976 1977 (97(
Renton Plant - Enlargement No 1 ""linn HM
" " Enlargement No. 2
East Green River Valley Interceptor UJ.ui.i2
West Soos Creek Trunk ?i,,,,,,,
Cedor River Trunk
May Creek Trunk uif 1111,11 , , m^j^g
Vasa Park Force Mam ^^m^^^ma4t6
Issaquoh Creek Interceptor (Sections 1 and 2 ) mmmmmmtiMS
(Section 3) H " ll_lt
Beaver Lake Interceptor
Tibbetts Creek Interceptor
Redmond Interceptor (I-A) ^^mi^mcua
Stage 1 - Redmond - Bothell Interceptor mini m.ljj' " > > HIM,
Evans Creek Interceptor
Novelty Creek Interceptor
Cottage Lake Interceptor • ' trnVm
1979
I96C
••
^H
1
— 1
1 f f y
• 1961
^m
3M>
EjE
w-
~
West Point Sludge Disposal iimnim iMMnf5J)tf
Bothell - Woodinville Interceptor mum ""i > n I lidjjjd
Woodinville Interceptor P" MM ' i u n nrmjc »/p
East Woodinville Interceptor "f * <
Lower Bear Creek ETTT.
i North Creek Interceptor mi < i "if MI
Matthews Park Pumping Station m^mm^mmiito
East Marginal Way Pumping Station m^m^ma/so'
Reconstruction of Seattle Pumping Stations mm^mma?* '
West Seattle Interceptor """iiiiinna/ / > iiui"uuiUn.Jt''LJ'"">
CONSTRUCTION EXPENDITURE BY YEARLY TOTALS S.4K) B.M7 MIS MM7 «*T I&SM BJT» KZfr
4JM1
4.794
|
19621963
1 f
mm
-- •
j»
i
^~
_
111,
««M
im
i/r.M
Txn
If3l
_
rm
1964
1969
AND
IMS
K«M
2nd STAGE TOTAL CONSTRUCTION EXPENDITURE _» 166.895
mm\ HATE* OWU.ITY (*33.T9») OHO COKC FtCIUTf I*77,O73 I
NOTE : Figurti are in millions of dollori
exrtNsioH I'ss.oi*
167
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Appendix C
Combined Sewer Overflow Points
No,
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
Table C-l
Overflow Points Within Separation Area
Location
Lake Washington South of
Union Bay
38th and Alaska
Cooper
Perry
Grattan (Lift Station)
57th Avenue South
Brighton & 57th
Alaska
Snoqualmie
Alaska
40th Avenue
50th Avenue
Lake Wash. Blvd.
Alaska and 38th
Horton
College
Massachusetts
Charles
Dearborn
Main
Blaine
Park
Alder
James
Pike
Pine
Denny
Lee
Lee
Diam.
Size In.
20
15
12
16
-
-
12
20
-
15
72
24
12
12
16
20
12
8
12
16
15
16
16
24
8
20
20
Weir*
Elevation
22.2
25.6
19.5
-
15.0
9.0
-
17.5
-
-
11.5
10.3
22.2
17.6
19.9
15.0
18.8
16.7
16.5
14.2
10.0
13.0
12.6
12.0
7.6
11.8
5.1
2.5
169
-------
Table C-l (cont'd.) Lake Washington S.
No.
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
Diam.
Location Size In.
Lynn
39th Avenue
Lake Washington Ship Canal
Brooklyn Avenue
Brooklyn Avenue (Pump Station)
Montlake Blvd.
Lake Washington North of Union
55th & 40th
38th Avenue (Storm)
41st & 38th
Belvoir Place
N.E. 31st (Lift Station)
38th
43rd
Kenilworth
Windemere
Amble side Road
60th
64th (Lift Station)
Park
Park
Park
Henderson System
Rainier North
Rainier South
50th
48th
46th
Ren ton
42nd
24
—
12
15
84
Bay
60
60
-
21
8
30
10
15
36
15
27
15
18
15
12
72
36
10
8
12
10
60
Weir
Elevation
8.7
1.4
7.2
9.5
17.2
94.1
3.4
19.7
10.0
7.8
17.4
16.8
13.0
13.5
8.0
4.9
22.5
7.5
9.7
8.8
14.1
18.3
15.7
17.4
29.7
32.4
41.9
170
-------
Table C-l fcont'd.) Salmon Bay Waterway
No. Location
56 Burke
57 Densmore
58 Woodland Park
59 Carr Place
60 Stoneway
61 2nd Avenue
62 1st Avenue
63 8th Avenue (Pu
64 llth Avenue
65 45th & 8th
66 24th Avenue
67 24th Avenue
68 20th Avenue
69 28th Avenue
70 N.W. 57th (Pum
71 32nd
72 16th
73 17th
74 17th
75 Prospect
76 Spokane
77 W. Michigan
78 8th Avenue
79 104th
80 98th
81 Brace
82 Director
Diam Weir
Size In. Elevation
12
8
& 34th 24
8
30
30
60x80
mp Station) 8
60
IS
30
18
36
48
ip Station)
Magnolia
24
16
42
30
30
Duwamish Waterwav
15
36
36
West Seattle
8
10
10
60
.
-
16.7
-
15.4
11.6
-
4.8
9.0
13.2
25.0
8.4
8.0
14.2
10.0
10.0
-
-
6.4
1.2
-
-
-
22.0
- 3.8
171
-------
Table C-l (cont'd.) West Seattle
No.
83
84
85
36
87
88
89
90
91
92
93
94
95
96
97
98
99
100
Location
Cloverdale (Lift Station)
Lowman Beach (Purip Station)
Alaska
Lov/man Beach (Punp Station)
Bruce (Lift Station)
Spokane
Alki T.P.
53rd (Lift Station)
23rd & Darton
Atlantic Street
Jersey
Jersey
California
.Maryland Place
Georgia Street
Fairmont Avenue
Myrtle & 24th
Webster & 28th
Diam.
Size In.
20
72
54
48
24
66
42
60
12
20
24
10
30
12
12
42
30
VJeir
Elevation
-5
5.0
-
4.0
-1.3
C T5
-J . ' >
-
-l.C
326. n
-n.2
-1.3
-
-
-4.°
-O."1
-4 .?
-
* City of Seattle Datum is 6.05 above MSL set USGS after
1947 adjusted.
172
-------
Table C-2
Overflow Weir Elevation Outside the Separation Area
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Location
N. of Sand Point
Thornton (lift)
103rd
105th (Storm)
113th (Pump)
127th (Lift)
119th (Pump)
130th (Lift)
106th (Punp)
107th
144th
140th
126th
N. of West Point
Carkeek Park
Bedford Crt. (Pump)
N. Beach (Pump)
32nd (Lift)
71st (Lift)
68th (Lift)
77th (Lift)
S. of West Point
W . Raye
W . Raye
Elliott Bay
Denny Way
Denny Way
Vine
Diam.
Size In.
18
12
72
12
12
12
8
15
12
12
12
12
33
8
15
8
8
8
8
24
12
96
72
48
Weir*
Elevation
9.8
16.1
13.6
15.3
14.9
15.6
8.0
13.1
14.0
14.0
14.0
14.0
4.0
18.0
-
2.7
-6.6
-5.6
3.4
4.0
- .7
-1.2
1.3
173
-------
Table C-2 (cont'd.) Elliott Bay
No.
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
Location
University
Madison
Columbia
Washington
King
Connecticut
Massachusetts
Stacy (Raw)
Lander
II an ford
Spokane (Raw)
Salmon Bay
Cramer
Ewing
Aurora
Ship Canal North
Latona
Sunnyside (Pump)
Duwamish River
Oregon Siphon
Diagonal
Oregon and Ohio
Diagonal and Colo.
Diagonal and 1st
8th and Hanford
Brandon
Michigan
Brighton
E. Marginal (Pump)
Othello
Norfolk
Diam.
Size In.
49
24
12
24
48
72
12
12
96
150x100
16
20
39x60
8
18
8
36
30
30
30
8
96x84
50x78
70x102
30
36
24
84
Weir
Elevat
-5.4
-1.8
-4.3
-6.7
-1.4
-4.1
0.8
-2.0
-6.0
-6.8
™"
-5.8
6.4
"
9.31
8.0
-10.0
-.55
.95
.87
-7.45
-3.2
-5.3
-8.4
-10.9
-4.5
2.6
174
-------
Table 02 (conf d.) Diam> Weir
Size In. Elevation
NO,
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
Location
Harbor Island
Spokane (Pump)
E. Han ford
Massachusetts
13th
W. Hanford
Lander
13th and Lander (Pump)
Florida
Lake Union
Crokett
Galer
Valley
Fairview
Yale
Garfield
Newton
Lynn
Louisa
Roanoke
Hamlin
Shelby (Pump)
Shelby (Pump)
Allison
Eastlake
Allison
16th
W. Park
Mont lake
Shelby (Pump)
39th (Pump)
12 -1.5
8
8
8 -1.6
8
8
24
8
8
42 27.8
18 9.2
24 7.4
8 5.9
18 16.3
8 4.2
21 10.0
8 8.0
24 29.1
10 34.7
8 3.3
18 8.9
8 5.12
10 43.4
8 6.1
30 7.1
18 9.5
60 32.7
21 9.8
8 -1.4
*City of Seattle Datum is 6.05 above MSL set USGS after
1947 adjusted.
175
-------
Appendix D
Separation Cost Examples
A. Southwest Seattle
Figure D-l
Table D-l
B. East Central Seattle
Figure D-2
Table D-2
177
-------
Figure D-l
Separation Plan - Southwest Seattle District
r~
I t=. Tl
/
7
178
-------
Table D-l
Estimated Construction Costs - Southwest Seattle
Number
Design
flow, cfs
Description
Construction
cost, dollar!;
Partial separation3
Relief sanitary sewers
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
15, 30b 300 ft of 21-in. RC at 1.0*
0.7. 2.8b 100 ft of 8-in. cone at 1.5%
0.5, 1.7b 230 ft of 8-in. cone at 1.0%
1.5, 6.5b 80 ft of 8-in. cone at 2.2%
0.5, 1.7b 70 ft of 8-in. cone at 1.0%
3.9 80 ft of 15-in. RC at 0.4% to replace existing 12-in
1.5, 3.9b 260 ft of 10-in. cone at 0.5%
2.0 90 ft of 15-in. RC at 0.2% to replace existing 8-in
0.3,
1.1 - 1.8b 690 ft of 8-in. cone at 0.4 - 0.6%
1.2, 5.2b 280 ft of 8-in. cone at 3.1%
0.4, 1.7b 610 ft of 8-in. cone at 0.3 - 0.9%
2.8, 4.1b 240 ft of 15-in. RC at 0.3%
0.9, 2.1b 240 ft of 10-in. cone at 0.3%
1.0, 3.1b 290 ft of 8-in. cone at 0.9%
0.5, 1.5b 340 ft of 8-in. cone at 0.7 - 1.0% ,
2.0, 6.2b 220 ft of 8-in. cone at 12.9%
1.4, 3.5b 370 ft of 10-in. cone at 0.9%
0.7-1.0,
2.7 - 3.0b 660 ft of 8-in. cone at 2.4 - 2.8%
1.3, 2.1b 380 ft of 10-in. cone at 0.4%
0.5, 1.4b 280 ft of 8-in. cone at 0.6%
0.8, 2.9b 240 ft of 8-in. cone at 0.9%
1.3, 2.7b 240 ft of 10-in. cone at 0.4% ._
0.3, 1.7b 300 ft of 8-in. cone at 0.4%
0.5, 4.3b 330 ft of 8-in. cone at 9.7%
0.4, 3.1b 290 ft of 8-in. cone at 4.8%
1.0, 2.1b 320 ft of 8-in. cone at 0.9%
0.2, 1.3b 340 ft of 8-in. cone at 0.8%
0.4, 1.0b 280 ft of 8-in. cone at 0.4%
0.4-0.8,b
1.6 300 ft of 8-in. cone at 0.4 - 0.9%
0.2, 1.0b 290 ft of 8-in. cone at 0.4%
0.9, 1.6b 360 ft of 10-in. cone at 0.4%
58 - 66 1,100 ft of 30-in. RC at 3.2 - 6.0% to replace existing 42 - 48-in. which is
to be used as storm drain
50-55 1,200 ft of 27-in. RC at 3.0 - 15% to replace existing 36 - 42-in. which is
to be used as storm drain
46-47 640 ft of 24-in. RC at 5.6 - 33% to replace existing 36-in. which is to be
used as storm drain
— Reconnect 80 house connections
6.600
800
1,600
500
500
1,100
2,200
1,600
4,800
2,600
4,200
3.300
2.000
2,000
2,400
1,200
3,100
7,200
4.900
3,000
1,700
2,000
3,200
2.300
2,000
1,800
2,400
1.900
2,000
2,000
4,600
26,000
29,700
13,300
3,200
179
-------
Table D-l (cont'd.)
Number
Design
flow, cfs
Description
Construction
cost, dollars
Reconnect 64 manholes 6,400
Reconnect 9 lateral sewers 1,800
Subtotal, relief sanitary sewers ~ 161,900
Trunk storm drains
A-l 220-225 600 ft of 54-in. RCatl.8% _ 27,600
A-2 86-100 1,140 ft of 30-ta. RC at 4.5 - 7.0% 21,300
A-3 80-83 1,560 ft of 48-in. RC at 0.3 - 0.6% 55.200
A-4 44-66 1,200 ft of 33-in. RC at 0.7 - 3.9% 27,300
B-l 32-36 1,680 ft of 21-in. RC at 5.6 - 10.5%.. „ 22,800
C-l 60 860 ft of 36-in. RC at 1.0 - 20%._ 21,800
C-2 32 1,170 ft of 27-in. RC at 1.2 - 18% _ 20,100
C-3 27-32 1,280 ft of 18-in. RC at 7.5 - 17% 14,100
C-4 15 -17 1.260 ft of 18-ta. RC at 2.6 - 5.1% 15,300
D-l 25 - 30 520 ft of 24-in. RC at 1.6 - 5.0% 8,300
D-2 23-25 710 ft of 18-ia. RC at 6.2 - 15% 8,700
- - Connections to Misting trunk to be utilized as storm drain 2,000
Subtotal, trunk storm drains :.... 244.500
Local storm drains
25,200 ft of 8-in 125,800
17,600 ft of 10-in 103.900
17,700 ft of 12-in 148,200
24,200 ft of 15-in. ._ 238,500
9,800 ft of 18-in. 113,500
5,700 ft of 21-in ,. 81.200
600 ft of 24-in 9,600
227 intersection crossings, includes catch basin recomtectiona 80,900
Subtotal, local storm drains 901,600
Total contract cost, partial separation 1,308,000
Engineering and contingencies, 25 pet cent 427,000
Total construction cost, partial separation 1.735,000
Complete separation0
Relief sanitary sewers*'
3.0-4.5 2,940 ft of 15-in. RC at 3.0 - 33% to replace existing 36-48-in. which is to
be utilized as storm drain 42,600
1.9 - 2.4 1,200 ft of 12-in. RC at 3.8 - 7.0% to replace existing 42 - 48-in. which is
to be utilized as storm drain 13,109
1.5 - 1.9 1.480 ft of 12-in. RC at 0.3 - 0.6% to replace existing 48-in. which is to be
utilized as storm drain 16,000
15 new house connections 4 500
Reconnect IB lateral sewers 3,600
Subtotal, relief sanitary sewers „..._.. 80,700
180
-------
Table D-l (cont'd.)
Number
Design
flow, els
Description
Trunk storm drains
A-l 365 - 375 600 ft of 63-in. RC it 1.8% 32.400
250-260 710 ft of existing 42 - 48-in
60. 240b 390 ft of 30-in. RC at 3.2% to parallel existing 42-in 8.300
215 - 225 670 ft of existing 42-in
190-200 540 ft of 45-in. RC at 3.0% to replace existing 36-in 16,800
170- 190 630 ft of 39-in. RC at 5.6-9.2% to replace existing 36-in. 16.700
A-2 135-165 1,220 ft ol existing 42-in
A-3 100-135 1.750 ft of existing 42-48-in
A-4 68 - 80 930 ft of 39-in. RC at 0.7 - 3.9% 25,300
B-l 45 - 50 1,680 ft of 27-in. RC at 5.6 - 10.5% 32,500
C-l 100 860 ft of 42-in. RC at 1.0 - 20% 45,300
C-2 55-100 1,170 ft of 33-in. RC at 1.2 - 18% 33,400
C-3 50-55 1,280 ft of 24-in. RC at 7.5 - 17% 20.300
C-4 28 - 30 1,260 ft of 24-in. RC at 2.6 - 5.1% 21,700
D-l 40-45 520 ft of 27-in. RC at 1.6 - 5.0% 10,600
D-2 35 710 ft of 21-in. RC at 6.2 - 15% 11,000
Connections to existing trunk to be utilised «s storm drain 6,000
Subtotal, trunk storm drains 280,300
Local storm drains
37.600 ft of 8-in 226,700
11.800 ft of 10-in 84.800
17,300 ft of 12-ia 170,100
19,300 ft of 15-in 224,100
19,700 ft of 18-in 264,600
6,000 ft of 21-in 98,900
6,900 ft of 24-in 125,500
240 ft of 27-in 4,600
340 ft of 30-in 7,900
227 intersection crossings, includes catch basin reconnections 80,900
3,825 new house connections 1,147,500
Subtotal, local storm drains... 2,435,600
Total contract cost, complete separation ~ 2,796,600
Engineering and contingencies, 25 per cent 699,200
Total construction cost, complete separation 3,495,800
Construction
cost, dollars
d.
Partial separation provides for removal of all street drains
from sanitary sewers and for continued discharge of roof
leaders and foundation drains to sanitary sewers. See Fig.
C-l for facility location.
First flow is required relief capacity, second is total
design flow.
Complete separation provides for removal of all storm drainage,
including roof leaders and foundation drains, from sanitary
sewers.
Routes approximately same as above.
181
-------
Figure D-2
Separation Plan East Central Seattle
JQ*»O
'— * *
182
-------
Table D-2
Estimated Construction Costs - East Central Seattle
Number
Design
flow.cfs
Description
Construction
cost, dollars
Partial separation*
Relief sanitary sewers
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
64-65 2.120 ft of 39-in. RC at 0.50 - 0.70%, to replace existing 54 - 60-in. which
is to be used as storm drain 119.000
44 - 49 880 ft of 30-in. RC at 1.4 - 2.3%, to replace existing 48-in. which i* to be
used as storm drain, includes 880 ft of 8-in. lateral parallel to trunk to
avoid making house connections to trunk 31,300
1.2, 2.7b 330 ft of 8-in. cone at 1.4% 2.000
1.7, 9.0b 210 ft of 10-in. cone at 1.3% 1.500
2.4, 7.0b 310 ft of 8-in. cone at 4.4 - 8.1% 1.900
0.4-1.0.
2.0-4.0" 720 ft of 8-in. cone at 1.0 - 4.0% 4.300
3.0, 13b 210 ft of 12-in. RC at 0.8% 3,900
5.3, 7.4b 60 ft of 15-in. RC at 0.9% 1.300
2.7. 6.0b 470 ft of 10-in. cone at 2.4% 6,200
0.7, 2.5b 320 ft of 8-in. cone at 2.1 - 3.3% 1.900
1.1.
4.0-5.3b 510 ft of 8-in. cone at 5.4 - 11.8% 3.100
2.8, 4.0b 270 ft of 12-in. RC at 1.0% 2.900
1.3. 3.4b 470 ft of 10-in. cone at 0.9% 6,200
0.7-1.3.
2.7-2.9b 850 ft of 8-in. cone at 1.0 - 1.4%.. 5.100
0.4, 2.0b 60 ft of 8-in. cone at 1.6% 400
0.3-0.6.
1.0- 1.5b 690 ft of 8-in. cone at 0.4 - 1.1% 4.100
2.4, 3.7b 60 ft of 10-in. cone at 1.1% 400
2.4, 3.9b 80 ft of 12-in. cone at 0.4% 900
3.6. 28b 80 ft of 8-in. cone at 11.6% 500
1.1, 3.1b 390 ft of 10-in. cone at 0.30% 2,800
0.8, 2.6b 350 ft of 8-in. cone at 0.70% 2,100
0.4, 2.4b 60 ft of 8-in. cone at 0.80% 400
1.0, 2.2b 390 ft of 10-in. cone at 0.30% 2,800
0.4, 2.1b 90 ft of 8-in. cone at 0.60% 500
0.5-0.7.
1.7-2.0b 450 ft of 8-in. cone at 0.60 - 1.45% 2.700
3.5. 22b 100 ft of 8-in. cone at 7.7% 600
0.6. 2.2b 330 ft of 8-in. cone at 0.5% 2.300
1.2, 2.1b 230 ft of 10-in. cone at 0.6% 1,900
0.3-0.8
1.0-1.6" 640 ft of 8-in. cone at 0.3 - 0.4% 4,500
0.6-0.8.
1.5-2.3° 890ft of 8-in. cone at 0.8 - 1.5% 6,200
2.7. 18b 410 ft of 12-in. RC at 0.9*. 5,000
0.4, 2.0b 230 ft of 8-in. cone at 1.9% 1,400
183
-------
Table D-2 (cont'd.)
Number
Design
flow, cfs
Description
Construction
cost, dollm
33 11, 17b 170 ft of 30-in. RC at 0.06%. includes 170 ft of 8-in. lateral parallel to trunk
to avoid making house connections to trunk 5,100
34 0.7. l.lb 50 ft of 10-in. cone at 0.11% «00
35 6.9. 8.6b 60 ft of 27-in. RC at 0.07%. 1.300
36 4.2. 8.6b 330 ft of 15-in. RC at 0.45%.- 4.600
37 1.2-1.6.
4.7-5.2b 660 ft of 8-in. cone at 1.2 - 1.6% 4.000
38 0.8. 2.0b 310 ftof 8-in. cone at 0.5 - 0.7% 1.900
39 1.7, 2.1b 600 ft of 12-in. RC at 0.25% 7.300
40 0.7. 1.7b SO ft of 8-in. cone at 0.7% 300
Reconnect 132 house connections 6.500
Reconnect 89 manholes „ 8.900
Subtotal, relief sanitary sewers 270,400
Trunk storm drains
A-l 100 320ft of 36-in. RCat2.2% 6,900
A-2 59-66 600 ft of 30-in. RC at 8.8 - 16.7% 10,500
A-3 42-53 1,020 ft of 30-in. RC at 7.7 - 16.7% 17,800
A-4 11-16 560 ft of 15-ia. RC at 2.9 - 6.7% 5,700
A-5 22 250 ft of 24-in. RC at 0.80% 4,100
A-6 17 420 ft of 21-ia. RC at 1.3 - 1.4% _ 5,700
A-7 26 270 ft of 27-ia. RC at 0.8 - 5.8% 4,900
A-8 15 890 ft of 24-iu. RC at 0.6 - 15.3% 13,000
A-9 34-37 3,600 ft of 24-in. RC at 2.3-10.0% 59.400
- - Connections to existing trunk to be utilised as storm drain 1,500
Subtotal, trunk storm drains .,..„.„„«...,« .._..,.....,.......,... .„ 129,500
Local storm drains
22,000 ft of 8-ta. 102,100
19,000 ft of 10-in. 112,700
13,000 ft of 12-in. 106,300
17,000 ft of 15-in „ 169,900
8,000 ft of 18-in _ 91,300
1,000 ft of 21-ia. ._ 12,800
800 ft of 24-in 13,100
700 ft of 27-in.._ 12,000
900 ft of 30-in _ 17,400
212 intersection crossings, includes catch basin reconnections 74,700
Subtotal, local storm drains 712,300
Total contract cost, partial separation 1,112,200
Engineering and contingencies, 25 per cent 278,000
Total construction cost, partial separation 1,390,200
184
-------
Table D-2 (cont'd.)
Number
Complete seporatio
Relief sanitary s
Trunk storm drai
A-l
A-2. A-3
A-4
A-S. A-6
A-6
A-7
A-8
A-9
Design
flow,cfs
nc
ewers
3.5 - 4.5
is
180-210
179
163
62-100
19-28
32
26
44
22
54-58
Description
1,940 ft of 15-in. at 0.48 - 0.70%, to replace existing 54 - 60-in. which is to
be used as storm drain
490ft of 54-in. RC at 0.8 - 1.45".
350 ft of 51-in. RC at 0.8%
320 ft of 42-in. RC at 2.2%
1,620 ft of 30-in. RC at 7.7 - 16. 7%
560 ft of 18-in. RC at 2.9 - 6.7% . ...
460 ft of 30-in. RC at 0.8 - 1.3%
210 ft of 24-in. RC at 1.4%
270 ft of 33-in. RC at 0.8 - 5.8%
890 ft of 24-in. RC at 0.6 - 15.3%
3,600 ft of 30-in. RC at 2.3 - 10.0%
Connections to existing trunk which is to be utilized as storm drain
Subtotal, trunk storm drains
Local storm draii
IS
34,100 ft of 8-in.
15,600 ft of 10-in. . .
15,600 ft of 12-in.
19,600 ft of 15-in.
10,100 ft of 18-in.
4,200 ft of 21-in
1,600ft of 24-in.
620 ft of 27-in
1,000 ft of 30-in.
600 ft of 33-in
170 ft of 48-in
212 intersection crossings, includes catch basin reconnections
2,930 new house connections
Subtotal, local storm drains
Total contract cost, complete se
Engineering and contingencies.
paration
25 per cent ..
Total construction cost, complete separation
Construction
cost, dollars
62.3PO
35. 500
2.1. -100
13. 000
A:,:OO
8,300
10,500
3.300
6,700
14.100
100,300
1,500
248,800
182,400
Q7.300
139.600
210.400
126.700
57,000
24,600
11,000
19,500
13,300
6.000
74.700
879,000
1.841,500
2,152.600
538,200
2,690,800
d.
Partial separation provides for removal of all street drains
from sanitary sewers and for continued discharge of roof
leaders and foundation drains to sanitary sewers. See Fig.
C-l for facility location.
First flow is required relief capacity, second is total
design flow.
Complete separation provides for removal of all storm drainage,
including roof leaders and foundation drains, from sanitary
sewers .
Routes approximately same as above.
185
-------
Appendix £
CATAD Station Information
Table E-l Regulator Stations
Table E-2 Pump Stations
187
-------
oo
oo
Table E-l
REGULATOR STATIONS
Facility
Station Name No. Segment Location
Brandon (3)
Chelan
Connecticut (2)
Denny-Lk. Union0
Denny-Local0
Dexter Avenue
Eighth Avenue So.
Hanford #1
Hanford #2 (2)
Harbor
King Street
Lk. City Tunnel (2)
Lander
Michigan (3)
Norfolk
W. Michigan
220
420
560
620
bOO
800
470
500
530
400
580
710
540
240
260
450
S. Elliott Bay
W. Duwamish
H. Elliott Bay
N. Elliott Bay
N. Elliott Bay
North Trunk
W. Duwamish
Hanford-Elliott
N. Elliott Bay
W. Duwamish
N. Elliott Bay
Lake City
N.Elliott Bay
S. Elliott Bay
S. Valley
W. Duwamish
Computer
Reference
10
5
16
19
18
21
1
13
14
4
17
25
15
9
7
3
Telemetry
Circuit
2
1
6
6
6
4
1
6
6
1
6
4
6
2
N/A
1
Floor Space
Square Feet
180
140
410
390
390
1530
170
190
480
200
220
780
800
220
215
130
Construction
Cost-dollars
68,200b
70,600
191,000
240,000
240,000
454,000
63,700
110,000
343,000
75,400
114,000
137,400
305,000
71,100b
63,300b
56,700
Contract
Yr . Compl .
1964
1967
1971
1969
1969
1971
1967
1968
1971
1967
1971
1969
1971
1964
1964
1967
a. Numbers in parenthesis refer to no. of units, if station components are at multiple locations
b. Cost does not include facilities from 1935 construction, stations to be remodeled 1971-72.
c. Both stations at one physical site, cost and floor space allocated evenly.
-------
00
Table E-l (cont'd.)
REGULATOR STATIONS
Connecting Sewer Diameter-Inches
Station Name
Brandon
Che Ian
Connecticut
Denny-Lake Union
Denny-Local
Dexter Avenue
Eighth Avenue S.
Hanford #1
Hanford #2
Harbor
King Street
Lk. City Tunnel
Lander
Michigan
Norfolk
W. Michigan
Trunk Outfall
40x66a 50x78a
54 54
72 72
60 60
42 42
84 48
48 36
150xlOOa 120
15QxlOOa 150xlOOa
36 54
48 48
96 N/A
96 96
72xl02a 72xl02a
84 84
24 24
a. Horseshoe shaped sewer
b. Dimension of opening -
c. Gates
are actually all
Interceptor
60
42
96
102
102
48
36
N/A
96
21
96
108
96
60
42
42
cross -section
no gate
rectangular.
Transfer
12
36
36
21
18
N/A
24
N/A
48
N/A
30
N/A
36
24
42
10
Size refers
Gate
Regulator
20x20
36d
36x36
2 Id
18x18
84x84
24x24
N/A
48x48
24x24
30x24
96x96
36x36
20x24
60x24
lOd
to opening
Size-Inches0
Outfall
48x48
54x54
84x60
48x48
24x24
48x360b
36x36
96x84
144x96
54x54
60x36
N/A
84x60
96x60
54x48
24d
behind gate
Bypass
N/A
30x54b
72d
24xl84b
24x48b
84x66
28x36b
40x96b
96x84
48x84b
24xl20b
N/A
96x84
N/A
N/A
24db
which
Drive
Mechanism
Motor
Motor
Hydraulic
Motor
Motor
Hydrauli:
Motor
Hydrauli:
Motor
Motor
Motor
Hydrauli:
Hydrauli:
Motor
Motor
Motor
is the critical dimension for computing flows.
-------
Table E-2
PUMPING STATIONS
Facility Computer Telemetry Floor Space
Station Name
Bellevue
Belvoir Place
Duwamish
E. Marginal
E. Pine
Heathfield
Henderson
Interbay
Juanita Heights
Kenmore
Kirkland
Matthews Park
N. Mercer Island
Rainier Avenue
Renton S.T.P.
S. Mercer Island
Sweyolocken
Thirtieth Ave.N.E.
W. Marginal Way
Wilbur ton
West Point S.T.P,
'a. Cost includes
b. Estimated cost
No. Segment Location Reference
1160 East Side S. 30
100 Green Lake 23
200 S. Elliott Bay 11
250 S. Elliott Bay 8
130 Green Lake 22
1130 East Side S. 34
150 S. Valley 6
650 N. Elliott Bay 20
1020 East Side N. 36
740 Lake City 27
1090 East Side N. 37
720 Lake City 26
1210 East Side S. 32
140 Hanford-Elliott 12
1230 East Side S. 29
1220 East Side S. 33
1150 East Side S. 31
110 Green Lake 24
440 W. Duwamish 2
1140 East Side S. 35
660 N. Elliott Bay 28
Circuit
5
3
2
2
N/A
5
N/A
6
4
4
5
4
5
H/A
5
5
5
3
1
4
3
estimated value of facilities constructed in
plus value of new pumps not yet installed,
c. Estimated value of pumping facilities within sewage
Square Feet
1020
1500
4900
1790
700d
400
1000d
9000
1480
500
1420
20,000
2700
1100
30,000
940
1490
2100
2080
940
35,800
1940's.
stations to be
Construction Contract
Cost-dollars Yr.
160,000
374,000a
1,134,000
192,100
62,000b
163,000
64,000b
1,486,100
259,000
207,500
167,800
3,493,000
712,900
64,200b
3,500,000°
179,800
216,200
385,000a
262,000
154,900
4,000,000°
remodeled 1971-73
Compl.
1965
1971
1969
1964
1932
1965
1934
1967
1969
1966
1966
1967
1970
1932
1965
1965
1965
1971
1967
1965
1966
,
treatment plant.
d. Estimated floor space, drawings not available.
-------
Table E-2 (cont'd.)
PUMPING STATIONS
No . Pumps
Station Name Initial
Bellevue
Belvoir Place
Duwamish
E. Marginal
E. Pine
Heathfield
Henderson
Interbay
Juanita Heights
Kenmore
Kirkland
Matthews Park
N. Mercer Island
Rainier Avenue
Renton S.T.P.
S. Mercer Island
Sweyolocken
Thirtieth Ave. N.E.
W. Marginal Way
Wilburton
West Point S.T.P.
3
3
3
2
2a
2a
2a
3
3
3a
3
3
3
3a
3
3
3
3
3
2
4
Installed
Ultimate
3
3
3
3
-
:
3
4
-
3
6
4
6
3
4
3
3
3
4
Total Pumping Capacity - MGD Rated Pump
Initial Ultimate Head, Feet
13.8
15.0
150.0
20.0
4.3
6.0
7.2
180v.O
11.0
12.0
12.0
93.0
7.8
11.8
192.0
18.0
20.4
18.0
24.3
8.0
432.0
13.8
15.0
150.0
44.0
-
_
180.0
16.0
-
12.0
186.0
10.5
513.0
18.0
27.2
18.0
24.3
12.0
432.0
90.0
23.0
17.5
16.4
90.0
180.0
19. Ob
39.0
122.0
32.0
187.0
77.0
149.0
30. Ob
42.0
63.3
75.0
42.0
20.0
110.0
17.7
Bypass
Dia. -Inches
24
36
2 3 36
36
24
8
60
72
N/A
N/A
48
5 @ 24x24
24
N/A
96
24
30
36
N/A
24
2 @ 84
a. No ultimate data included, station due for remodeling
b. Estimated head, plans not available
-------
Appendix F
List of Model Subroutines
The subroutines at present under development have the
following functions to perform: storage, flow, regulation, and
checking. Under storage functions the following subroutines
are included: STRG1, CLOOO, PLOWP and FLOWR. Flow determination
utilizes subroutines AREAH, AREA1, OTFL1, OTFL3, OTFL4 and INTER.
Regulation involves subroutines PUMP1, OTFL2, FLOS1, PUMP2,STPT1
and REGL1. Checking subroutines include SBMR and CHECK.
A brief description of the functions of the various subroutines
and the current status of the programs is shown below:
(1) Subroutine: STRG1
Function:
(2) Subroutine:
Function:
(3) Subroutine:
Function:
(4) Subroutine:
Function:
(5) Subroutine
Function:
(6) Subroutine:
Function:
(7) Subroutine:
Function:
(8) Subroutine:
Function:
Using the input of regulator (or pump)
discharge and sewage level upstream of the
regulator (or pump wet-well) this subroutine
gives values of storage in the sewer and
flow entering the sewer.
ARE AH
This program calculates the area and wetted
perimeter of horseshoe sections.
AREA!
This subrbutine calculates the areas and
wetted perimters of circular sewer sections.
PUMPQ
This subroutine provides a common means of
calculating either pump speed or pump dis-
charge, given a known static head and one
of the other variables.
CALDX
This subroutine computes the length of sewer
for which the sewage depth drops 0.2 feet.
OTFL1
This subroutine computes the free discharge
from a rectangular gate opening.
FLOWP
This subroutine calculates flows and storage
for a pump station.
FLOWR
This subroutine computes flow and storage
for a regulator station.
193
-------
(9) Subroutine:
Function:
(10) Subroutine:
Function:
(11) Subroutine:
Function:
(12) Subroutine:
Function:
(13) Subroutine:
Function:
(14) Subroutine;
Function:
(15) Subroutine:
Function:
(16) Subroutine:
Function:
(17) Subroutine:
Function:
(18) Subroutine:
Function:
OTFL2
This subroutine, using input of discharge
and upstream sewage level, gives the gate
opening appropriate for delivery of the
required discharge.
OTFL3
This subroutine gives the outfall discharge
including that from an overflow weir if
used.
OTFL4
This subroutine gives an estimation of sub-
merged flow through the regulator.
INTER
This subroutine computes the interceptor
flow downstream of the regulator.
SBMRG
This subroutine furnishes
submergence.
FLOS1
a check of regulator
For regulator station without interceptors.
This subroutine computes trunk inflow, storage,
overflow, downstream flow and gate positions.
FLOS2 (For Hanford No. 1 Regulator Station)
This subroutine gives trunk inflow, level
upstream, overflow, diversion flow and gate
positions.
CHECK
This subroutine combines flows from several
upstream tributary stations and compares their
total flow (plus an allowance for interflow)
with the observed flow at a downstream station.
It alarms on an excessive discrepancy.
PUMP 2
From the pump discharge pressure in the
force mains this subroutine calculates the
pump station discharge.
REGL1
This subroutine operates to control regulator
or pump stations by a rule curve.
194
-------
Appendix G
Flow Calculation Programs
1. Manning's Formula Program
Metro has installed Leupold & Stevens depth recording instru-
ments in four sewers. The recorders plot depth of sewage vs.
time on gridded graph paper. The purpose of this program is to
calculate the volume of sewage that flows through the station
during an overflow or a storm.
Manning's formula was used in the calculations. Rather than
go into a detailed description of the formula (See King's Hand-
book of Hydraulics) suffice it to say that the slope, radius, and
depth of flow are all that is needed to calculate the flow. The
volume is, of course, the flow in a unit of time multiplied by
the duration.
Since many of the overflows are recorded as spikes by the
instrument, the depth and duration figures are often subjective.
Also, Manning's formula is not meant to be used to calculate surge
but rather steady state flows. Even with these limitations,
however, the volumes calculated correlate well with recorded
rainfall.
The program read the data from cards with the format shown
on the sample data sheet of Table F-l. The stations numbers are:
4901 Sand Point 4903 Henderson
4902 Windemere 4904 Cooper
The date is a six digit number: Month, Day, Year: e.g. 032170
for March 21, 1970.
The time is expressed as a two digit military time number
referring to the hour that the overflow started, for example:
13(00) means the flow started at 1:00 PM.
Duration is the length of time in hours that the overflow
occurred. The decimal point must be punched.
The depth is the number of scale divisions in the vertical
direction during an overflow. Again, punch the decimal point.
Referring to the chart for Sand Point (4901) on March 21st,
the data card should read:
4901 032170 10 00.5 04.7
Duration Date Time Duration Depth
195
-------
For the more complicated overflow occurring on March 23
beginning at 1600, two cards could be used:
4901 032370 16 1.75 07.5
4901 032370 16 5.00 15.0
Note that the time is the same on both cards. This indicates
that only "one" overflow occurred. Also note the subjective
nature of the parameters of depth and duration.
A copy of the program listing follows a sample of input
and output.
196
-------
Table G-l
Manning's Program-Input Data
STATI9N
1-4
4901
4901
4901
4901
4901
4901
4901
4901
4901
4901
4901
4901
4901
4901
4901
49Q1
4901
49jl
49jl
49ol
49jl
4901
4901
49Q1
49C1
49ul
49G1
4901
4901
4901
49^1
49U1
49W1
49C1
49wl
49J1
49ul
4901
4901
4901
4901
4901
4901
4901
4901
4901
4901
5-6
09
09
09
09
09
10
10
10
10
10
10
11
11
11
11
11
11
11
11
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
01
01
01
01
01
01
01
01
01
01
01
01
01
DAY
7-8
24
25
27
29
30
07
08
09
09
27
28
02
03
04
06
15
20
23
27
03
04
J8
09
10
10
12
16
17
18
19
20
2Q
22
23
25
08
09
09
13
17
18
18
20
21
22
24
26
31
YEA=i
9-10
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
69
36
69
69
73
7D
7j
7-
7:
7C
73
70
70
70
70
70
70
THE
11-12
08
14
12
04
08
14
16
08
18
01
23
23
20
33
16
04
05
02
12
31
J7
04
14
14
21
J8
11
16
05
10
1*
23
3e
14
2-;
12
04
JS
07
03
01
21
02
01
10
05
08
04
"jllK
13-16
02*0
02.0
06*0
06«U
Cfa.O
O&tO
02 »U
02.0
04*0
IctU
OH-U
Cb.O
OQ.i>
4giO
02.0
20 «w
19. u
24.0
00»3
1 0 • ^
03-0
12.0
06*0
Q4. U
3fetw
3ft. U
12.0
Cg.O
14.U
ic.u
02.0
24. U
29. U
C8«w
18.0
12. 0
Cfe.O
Ife.w
72. u
21. w
26.0
26.0
ic.o
14.0
24.0
4s»u
4C«U
la.o
DtPTH
17-20
10.0
Ob.O
05.0
04. 0
06.0
J5.0
03.0
03.0
04t 0
J3.0
04,0
J4.0
03.0
J5.0
03.0
Ob.O
Jb.O
Jb.O
J5.0
J4.Q
^/6. 0
J4.0
Jl .5
Jl.b
wfa . 0
JD.O
Jc . 0
J3.u
Jc. 0
03.0
Jl.O
J3.0
Jb.O
w J . 0
J3. G
J4.0
•J'jt C
Ob.C
J5.C
04. 0
JJ.O
Jb.O
J3.0
J4.0
Jb.O
J4,0
J7.Q
J3.0
197
-------
Harming's Formula Program
j«F-ltu>
PE:?I*1«2t ,)••?•( PI -THtTA)
r A •*l,6667«P£t? !"!«*{ «, 666?)
EfO
B
JOU6 d
JOOA 3
'J003 0
EXTERN
U010 8
txTE«\
UOOC B
5lN
(.J33E3
SUE" J093 »
* DATA SIZE • J018 •
SIZE • ooao »
e.XT£«\ u:33Ul
L:33i11
ATANii
<\
uOOL &
iN
-15P6P
3008 3
33
i>!33-?3
_;33S3
198
-------
INTE3E9 CR«U?
IMTE3ER
REAL
DATA C**uP/105*108/
DATA RK*R/3.0,.iJO*7,it0.b,l2f9,2./l.:>,3t J,2tb/
IPAGE"!
2 F8=MAT(H142X, J2,////,
1 43H STATI9N DATE
1 25X*5HH9'J:«S,5X,SHTH3j 3AL//)
LlMt«6
5
10
ISTA-SSTA
38 12 I«lj3
12 IDATE(I)«MDATEtI
15
28*14
15,2.8
IF
16 IF(\3ATE(2)»lDATE{eJ))lB,
17
IB
20
2, IX,
IF(.1\E«50)25,1,1
25 IF(N5TA)30/30,10
29 FB^ATdiHlMS SUCH STATISN)
30
31
CAu
END
0025 R £5
OOOF 3 «<
EXTERN L.I
tXTERN Li
TV8L
JSTA
EXIT
002? 9
0031 B
0039 B
9030 B
EXTERN
U021 8
U017 B
EXTERN
0027 B
U02F B
0033 3
0038 B
wOO-s - NDATL
b IPACiL
L:CBF
u:33ul
B I
IT1ME
.Q
L«33A3
u03F a
,.!33=!3
.S3313
• PROGRAM SI2E* J17A *
199
-------
» DATA SIZE «
£T«JOW,?3
200
-------
Table G-2
Manning's Program-Output Data
3TATI8N DATE
4901 9*24-69
4901 9-25-69
4901 9-27-69
4901 9-29-69
4901
4901
4901
4901
49G1
49ul
4901
4901
49C1
49^1
4901
49^1
4901
4901
4901
49cl
4901
4901
9-30-69
10-
10-
10-
10-
ic-
10-
li-
11-
11-
11-
11-
11-
11-
il-
ia-
12-
12"
7-69
8-69
9-63
9-69
27-69
28-69
2-69
3-69
4-69
6-69
15-69
20-69
23-69
27-69
3-69
4-69
8-69
TIME
8
14
12
4
8
14
16
8
18
1
23
23
2D
3
16
4
5
2
12
1
7
4
DUKAT1BN
2.0
2.0
6*0
6*0
6.0
6*
2*
0
0
2.0
«•
12*
tit
5*
3
0
3
0
V8LUME
TH9U QAt
180*1
41.8
125.3
77.9
184.6
125*3
U*0
14.0
51*9
84*2
103.9
6**9
.5 3*5
48*
2*
20.
19.
24*
•
3
0
0
•3
0
5
1D.O
3.
12.
•J
0
1002*8
14.0
417*8
396*9
501.4
lr,«4
129.8
98.3
155.8
201
-------
2. Sluice Gate Flow Program
Strip charts are installed in eight of ?ietro's regulator
stations. On these charts are recorded the level of sewage in
the trunk, the tide level and the outfall gate opening. The
purpose of this program is to compute the volume of sewage that
escapes during an overflow.
The outfall is treated as an orifice in these calculations.
The tide level can become high enough so that the outfall becomes
a submerged orifice; this is taken into account in computing the
head. The flow through an orifice is given by the equation:
A = K x (Area) x head
The volume is, of course, the flow multiplied by the duration of
the overflow.
The regulator stations and their numbers which have the
recorders are:
0013 Denny Local
0014 Denny Lake Union
0030 Harbor
0031 Chelan
0034 Brandon
0036 Michigan
0037 W. Michigan
and 0038 8th Avenue South
The outfall at W. Michigan is never influenced by "the tide,
hence, tide level is not recorded on its chart. The chart at Denny
Local is scheduled to be installed in the summer of 1971 and no
charts are available yet.
The programs read cards with the format shown on the sample
data sheet of Table F-2. Time is a two digit military time re-
ferring to the time the overflow started. Trunk level, gate
opening and tide level are all two digit numbers that correspond
to the scale divisions on the strip charts. "Duration" must have
the decimal point punched in the card.
If, during an overflow, the gate or trunk level changes,
another card must be punched to reflect these changes. If the
time the overflow started is not changed, the volume calculated
will be the total volume of the overflow.
Internal to the program are many level and scale factors that
are necessary for converting the strip chart readings to levels
relative to the invert of the outfall. Factors are variable
depending upon calibration but the accepted values are presented
in Table F-3.
Typically, on the charts the tide level is red, the trunk
level is blue and the outfall gate opening is green. The charts
at Denny deviate from this scheme.
202
-------
Table G-3
Chart Conversion Factors*
No.
13
14
20
23
25
26
30
31
34
36
37
38
Station Name
Denny Local
Denny Lake Union
King
Connecticut
Lander
Hanford #2
Harbor
Che Ian
Brandon
Michigan
W. Michigan
8th Avenue
Tide
Factor
-
.15
.06
.12
.12
.12
.06
.09
.15
.14
-
.1
Corr.
-1.8
.5
.5
.5
1.4
-1.0
- .75
2.25
-
- .71
-
.25
Trunk
Factor
-
.17
.06
.12
.12
.12
.09
.12
.08
.08
.05
.1
Corr.
.5
.5
.5
.5
.5
.5
1.0
2.25
.5
.5
.5
2.05
OG Factor
.04
.05
.03
.05
.05
.08
.045
.045
.04
.05
.02
.03
*Note: To compute differences in feet relative to invert:
D = (factor) * (Chart Reading) + Corr.
203
-------
Table G-4
Sluice Gate Program-Input Data
1-4
0037
0037
0037
0037
0037
0037
0037
0037
^037
0037
0037
0037
0037
0037
0037
0037
0037
0037
0037
0037
0037
0037
0037
OD37
0037
0037
U037
OC37
0037
0037
0037
0037
OOJ7
0037
0037
C037
0037
OJ37
00 -7
OOJ7
0037
0037
0037
OOJ7
0037
0037
i-6
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
71
15VTH
7.8
01
02
02
02
02
02
02
02
02
02
02
03
03
03
03
03
03
03
03
03
03
03
03
j3
33
03
03
03
03
03
03
J3
03
J3
03
03
J3
03
j3
j3
03
03
03
03
03
03
03
03
DAY
9-10
18
12
14
14
14
15
15
15
.15
18
24
07
10
10
10
10
11
11
11
11
11
11
11
11
11
22
22
23
23
23
23
23
23
26
26
26
26
27
29
29
30
30
3j
3 ".
30
30
30
30
T HE
11-12
18
20
08
12
19
00
•03
J9
12
23
05
12
13
13
13
13
17
17
17
17
17
17
17
17
17
05
05
03
10
10
10
U
1C
03
03
03
03
18
31
jl
22
22
c.2
22
22
22
22
22
13.14
3U
42
35
35
34
40
3£
37
41
51
52
49
37
36
27
3fc
34
29
33
37
27
dU
37
37
31
27
36
34
26
27
36
32
26
31
29
Jy
31
3U
3e
26
26
3b
26
3w
32
35
26
2
-------
Sluice Gate Flow Program
ASlN(X)
Pl2«lt573796326
ASI\»PJ2
2 JF(X*lt )
-------
u STA\A1U*12>
INTE3E-* STAT*STA(12),DATE<3),XDATE.<3)*UiE**TIflE*c-
-------
w I~ •"UC-,I3A\ THEN GO C81PJTE AREA F3R Cl*Cu.A-<
lF(I-8) 15*20*15
15 AR£A«33»«l.>Tr|( J )
39 T9 25
* CHCJLA3 9^IC£ AT w. MICHIGAN
2U AREA»(o9«l. )»SUi?T< J9*(2.-G
C C9-IPJTP EFFECTIVE HEAD
25 IF(T3LVL«.5*39) 27/27/28
C EXPBSED
27
38 T9 30
w SJdlE^jtJ- 9RFICE
2e
C C9«1PJTE FLdK (CFS)
30 J«4.31«A^EA»SS
- C91PJTE VgUJ^E IN 1H3USAVDS 3F 3AULB\S
31
C JP3ATE. T9TAL
READ
IX*
3F12.1./ »
ANJ !>U*ATI9\
DATE (.
C IS IT A
IFl
35 IF
39 IF
44 IF(STA(I)
C IF STATI3N IS
45 IF(STAT)50/
51 FB^AT(lHl)
CALL IXIT
^003 9
0063 d
OUF3 3
0133 B
0117 B
0121 3
STA
XTME
I=>A3E
33
0123 B TM3;OC
EXTERN u!
0133
ASI\
T-PSOS
(STA\A>i(jf
1/1
- EXIT
,:01B 3
U07B S
U10B B
U119 B
TNCB*
a
0093 D
0111 D
W12X b
TDFAC
STANAM
XDATt.
uP
L:INP
U123 B
U12F 9
LXTEr
-------
,. V8u
LJ0P
SUE? 02AF «
» JATA SUE « 01*7 *
* C3"I*19N SUE. » JU
ET-090t52
E3D
T-090.63
208
-------
Table G-5
Sluice Gate Program-Output Data
MICHIGAN!
MICHIGAN
lICHIGASJ
1IC1IGAN
MICHIGAN
MICHIGAN
MICHIGAN
STATI9N
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
DATE
70-10-22
70-10-22
70-10-22
70-11- 8
70-11- 8
70-11- 8
70-11- 8
70-11-11
70-11-11
70-11-11
70-11-19
70-11-19
70-11-23
70-11-23
70-11-23
70-11-24
70-11-24
70-12- 5
70-12- 5
70-12- 5
70-12- 5
70-12- 5
70-12- 5
70-12- 5
70-12- 5
70-12-10
7C-12-10
70-12-10
7o-12-30
70-12-30
71- 1-15
TIME
23
23
23
3
3
3
3
10
10
10
18
18
15
15
15
9
9
5
5
5
5
5
5
5
5
12
12
12
7
7
0
H9URS
i«0
7,0
8,0
,7
1,0
,5
2.2
.8
,3
1,1
.8
,8
1.0
,3
1,3
' •«
.8
1.0
,3
1,0
1.0
1,0
1*0
,3
3.6
.6
.3
.9
2.5
£.5
6.5
VBLJHE
TH8U GAL
206.8
3517.2
3724.0
458.3
368.2
485.5
1312.0
485.3
103,6
588.9
170.7
170.7
274,7
92.3
367.0
363.9
363.9
122*4
576.2
5110,6
8*18.6
8383*8
1041,0
105*7
23558.2
280,0
171*8
*5l*7
1923.5
1923.5
9587.7
7.7
18.7
22.7
13.7
36.1
22.6
12.8
7.9
10.2
16.9
4.6
71.4
190.0
305.5
311.7
38.7
13.1
17.3
21.3
28.6
54.8
T9TAL
T9TAL
T9TAL
T3TAL
T9TAL
T9TAL
T3TAL
T8TAL
T9TAL
209
-------
Appendix H
Chart Problem Examples
211
-------
to
\' ~"i too"' \ T~~r
.,v,.^_- dr-.:
-4--1- \ iffi
9 A.M.
L-Gate Position
-Tide Level
Figure H-l
Denny Regulator
Date: 10/21/70
Comment: Normal overflow. Outfall gate opened at 9 A.M. and
remained open until about 8 P.M. Then the regulator
gate (not shown) opened and the trunk level returned
to normal. The tidal backwater effect is noticeable
from 9 A.M. to about 3 P.M.
-------
K>
. IT M ~~ 1~ZTT T "-"
ioa
_9c-f--r=^
i--60-T
rrf-60-rer
riooT
-hj-
: : I i - i •"
> ori^--;
,--..; JO—p rr—i
-70-
• - • ---,---..-,- -> J -. -- 4 4 ^ T ^J - •
W7^
Gate position
1200
TIME
Figure H-2
West Michigan Regulator
Date: 01/17/71
Comment: Probably outfall gate controller malfunction
which never repeated itself January 17, 1971.
-------
to
Gate position
•Tide level
Figure H-3
Michigan Regulator
Date: 07/01/70
Comment: Emergency repair in July 1970.
Outfall gate was opened for eight hours
at a time to allow workmen to repair site.
Trunk flow stopped with sandbags.
-------
t o
M" " -r ~r'" "T"i .•••r-ri '•"•'•• ^:~r"
r -90—^ ; i^—•' '"~Qn 1-=
2*200
-Trunk level
-Tide level
Gate position
TIME
Figure H-4
Michigan Regulator
Date: 12/15/70
Comment: Probably an outfall gate controller malfunction
that was never repeated. Regular checks indicate
controller returned to normal operation.
-------
t J
! - ! - •
M --•. .-. i
: • : • j ;
|
i
i i : ; I
_ ,in • • _/u-\ .
I ,/ '\
•Tide level Gate position
0900
Trunk level
Figure H-5
Michigan Regulator
Date: 12/16/70
Comment:(continued from previous page)
TIME
-------
Appendix I
Overflow Water Quality Data
217
-------
Table 1-1
Regulator Station Overflow Data
1970
Station 34 Brandon Street
Rain
Date
1-13
1-18
1-26
2-15
3-6
3-12
4-9
4-24
to 4~27
H 4-29
00 6-29
9-3
11-8
12-30
Total
Inches
1.59
.63
1.34
1.08
1.75
.36
.84
.23
.35
.19
.14
.29
.78
.91
Max. Rate
in./hr.
.26
.11
.17
.12
.46
.13
.12
.09
.21
.07
.10
.10
.12
.24
Sample
Volume
Liters
12
12
12
12
12
8
12
9
12
3
12
9
12
3
Overflow Solids
Volume Sett.
gal. x 1000 ml/1
1.8
.7
.3
40.0
1.5
1.0
.8
2.5
1.5
.1
2.0
1.0
.3
.3
Susp.
mg/l
200
162
172
380
368
32
148
840
144
14
144
76
50
178
Vol.
mg/l
100
52
54
292
92
8
76
156
36
8
132
34
-
50
BOD
mg/l
54
—
—
80
32
21
21
38
49
10
46
39
24
7
COD
mg/l
119
100
_
424
144
120
184
816
104
32
200
-
51
34
NH3
mg N/l
4.00
1.00
.60
3.20
2.60
2.90
3.00
1.40
1.60
1.20
5.40
2.70
2.30
.60
NO, +N03
mg N/l
_
.12
.19
.05
.15
.10
.06
.01
.35
.25
.07
.25
.14
.07
P04
mg P/l
1.63
1.10
.50
2.30
1.60
1.00
1.00
1.90
.70
.60
2.90
1.50
.45
.45
Station 36 Michigan Street
1-13
1-18
4-9
4-27
4-29
9-17
9-20
11-8
11-19
12-5
12-28
1.59
.54
.84
.35
.19
..70
.44
.78
.57
1.64
.67
.26
.09
.12
.21
.07
.15
.15
.12
.10
.19
.10
1
15
13
6
1
4
5
9
7
1
1
-
—
-
-
_
1653.8
755.2
6748.4
170.7
23558.2
-
.1
.5
.7
2.3
.1
9.9
1.9
1.7
2.4
1.2
.2
3700
728
367
178
28
73
95
73
200
45
55
3520
666
308
115
20
43
27
23
136
-
30
600
-
78
213
66
-
-
41
58
6
22
-
1215
758
490
320
300
398
333
522
69
68
2.80
1.60
1.80
3.90
7.10
2.09
1.63
4.61
4.25
1-55
5.60
-
.36
.34
.20
.25
.22
.13
.07
.27
1.77
.01
5.63
1.40
1.20
2.60
1.30
.87
.93
1.33
1.56
.90
1.45
-------
Table 1-2
Regulator Station Overflow Data
1970
Station 37 West Michigan Street
NJ
Rain
Total Max. Rate
Date
1-19
3-6
3-12
4-1
4-9
9-6
9-16
9-17
9-20
10-17
11-8
11-30
12-3
12-6
12-28
Inches
.70
1.52
.40
.23
.94
.42
.13
.84
.47
.31
.96
.28
.26
1.69
.60
in./hr.
.13
.17
.14
.14
.16
.13
.10
.17
.22
.21
.15
.08
.07
.15
.09
Sample
Volume
Liters
12
12
8
5
12
9
12
12
12
8
12
12
12
12
12
Overflow
Volume
sett.
qal. x 1000 ml/1
^
476.9
90.0
-
-
6.4
4.6
86.5
118.9
62.9
125.2
232.6
.7
2483.8
143.2
4.0
2.0
1.8
34.0
.7
1.5
5.0
1.0
.3
1.3
1.6
1.5
.8
.5
1.1
Solids
Susp.Vol.
rcg/1
162
256
206
404
156
129
J45
-
112
116
-
268
510
20
334
mg/1
56
70
40
244
50
40
200
-
68
-
-
86
105
20
58
BOD
mg/1
__
33
42
306
6
180
84
-
-
31
-
24
30
6
16
COD
mg/1
100
192
128
744
120
300
-
140
130
64
-
144
126
142
154
NH3
mg N/l
1.90
1.50
2.20
4.90
.80
3.20
4.52
5.20
.75
3.35
1.80
2.15
2.05
1.15
1.60
N02 + N03 POA
ing N/l
.10
.15
.45
.30
.25
.28
.39
.03
.30
.42
.22
.34
.32
3.03
.42
mg P/l
2.00
1.70
4.30
2.40
.06
1.60
2.20
2.60
.25
.70
.50
1.64
.82
1.85
1.30
1-19
1-26
3-6
3-12
.70
.41
1.52
.40
.13
.22
.17
.14
Station 38 8th Avenue South
2
8
2
1
_
-
-
1.8
.3
1.8
1.8
120
252
228
293
58
52
52
66
^
-
20
18
8
-
200
200
.80
1.00
1.50
3.90
.05
.14
.05
.05
.80
.86
1.30
2.70
-------
Table 1-3
Regulator Station Overflow Data
1970
Station 40 Norfolk Street
to
N5
o
Date
1-9
1-13
1-19
1-26
2-5
2-17
3-3
3-6
3-12
4-1
4-6
4-9
4-24
4-27
4-29
5-8
6-29
9-3
9-17
9-20
10-4
10-11
10-17
10-19
11-30
12-1
12-10
12-15
12-28
Rain
Total Max
Inches in
.22
1.50
.66
1.18
.14
.20
.10
1.53
.32
.31
.23
.85
.28
.20
.19
.21
.13
.27
.84
.39
.20
.11
.23
.19
.18
.19
.75
.50
.51
. Rate
./hr.
.10
.24
.11
.15
.04
.07
.04
.19
.11
.11
.07
.12
.09
.16
.04
.07
.06
.09
.18
.13
.09
.04
.15
.04
.05
.06
.15
.08
.10
Sample
Volume
Liters
3
8
14
3
9
7
3
6
7
1
-
10
8
4
3
2
6
3
15
12
10
19
7
22
23
20
24
23
22
Overflow Solids
Volume Sett.
gal. x 1000 ml/1
11.8
6.8
4.0
1.7
8.4
6.1
7.3
8.9
9.4
3.5
4.2
4.9
2.3
4.2
3.2
8.1
5.2
8.3
8.5
3.4
11.7
6.1
14.5
5.0
5.1
5.2
6.0
5.5
6.9
Susp.
mg/1
366
317
50
149
228
189
269
421
151
288
132
136
198
173
95
208
317
340
134
90
338
446
309
261
159
101
111
138
312
Vol.
mg/1
215
228
36
69
98
81
173
139
46
128
110
55
41
87
55
190
222
122
67
83
245
254
25
10
96
40
93
72
91
BOD
rag/1
146
86
-
-
74
26
114
74
33
60
-
55
28
202
70
-
54
130
-
-
35
29
39
20
78
61
68
68
14
COD
rag/1
833
206
241
-
296
249
808
254
257
400
160
366
188
205
347
400
243
-
576
492
182
97
214
140
207
388
224
122
239
NH3
mg N/l
9,00
7.60
7.20
1.90
8.50
7.00
16.20
7.30
4.70
8.70
8.60
3.30
3.20
12.80
8.80
8.60
11.90
13.73
4.81
3.80
6.25
7.12
4.72
4.94
7.23
9.50
6.14
4.36
3.64
N02+NO3
mg N/l
.19
-
.61
.60
.29
.24
.30
.27
.39
.30
.24
.49
.54
.29
.31
.18
.19
.22
.30
.25
.22
.05
.07
.42
.58
.60
1.34
.81
.59
P04
mg P/l
6.80
4.00
3.80
.76
5.50
2.20
6.30
4.00
3.80
3.30
8.30
1.10
1.60
5.00
3.10
8.60
3.80
5.00
2.87
1.63
3.25
3.79
1.32
1.23
4.10
3.58
3.66
2.81
2.34
-------
Appendix J
Stepwise Regression Analyses
Table J-l
Station 4901
Nutrient Parameter
Ammonia Nitrogen
as rag N/l
Independent Variable
Multiple R
Nitrate Nitrogen
as mg N/l
Total Phosphate
as mg P/l
Volume antecedent stormflow .4899
Time since last stormflow .6209
Intensity of Rain .7288
Air temperature .7475
Wind Direction .7770
Volume of Rain .7881
*Intensity of antecedent stormflow.8004
Air temperature .4407
Intensity of stormflow .4615
*Volume of rain .5099
Volume of antecedent stormflow .4736
Time since last rain .5951
Volume of stormflow .6484
Intensity of rain .6949
Duration of antecedent rain .7179
Duration of antecedent stormflow .7400
Intensity of stormflow .7646
Duration of stormflow .8013
Time since last overflow .8178
*Air Temperature .8274
F Value
9.4750
6.8686
8.6947
1.6848
2.9517
1.1449
1.3049
7.2326
.6910
1.7763
8.6757
5.8277
,2063
.2593
.7415
.7839
.1325
.6984
1.7777
1.0.521
3.
3.
1.
1,
2,
3.
*Although more variables correlated increase the "R"
low "F" values beneath this point lead the statistician
to ignore lower variables.
221
-------
Table J-2
Station 4902
Nutrient Parameter
Independent Variable
Multiple R
F Value
Ammonia Nitrogen
as mg N/l
Volume of Overflow .6377
Duration antecedent rain .7211
Intensity antecedent overflow .8341
Air Temperature .8741
Intensity of rain .8898
*Intensity of overflow .9080
8.9122
2.8327
6.3530
2.8973
1.1980
1.4903
Nitrate•Nitrogen
as mg N/l
Total Phosphate
as mg P/l
Intensity of rain .4845
Air temperature .6025
Volume of overflow .6543
*Volume of antecedent overflow .6763
Volume of overflow .4233
Time since last overflow .5193
*Duration of rain .5493
3.9874
2.4158
1.2532
.5402
2.8383
1.4856
.5062
*Although more variables correlated increase the "R",
low "F".values beneath this point lead the statistician
to ianore lower variables
222
-------
Table J-3
Station 4903
Nutrient Parameter
Independent Variable
Multiple R
F Value
Ammonia Nitrogen
as mg N/l
Time since last overflow
Intensity of rain
Duration antecedent Rain
Air Temperature
Duration of rain
Duration of overflow
Intensity antecedent rain
Volume antecedent overflow
*Volume overflow
.3781
.7457
.8572
.9170
.9439
.9554
.9668
.9763
.9834
1.8352
9.3721
6.0085
5.3338
.2239
,4909
.6935
.5707
3.
1.
1,
1.
1.2696
Nitrate Nitrogen
as mg N/l
Total Phosphate
as mg P/l
Wind Direction .4513
Duration of overflow .5389
Duration of antecedent rain .6534
Air temperature .7339
*Intensity rain .7673
Time since last overflow .5065
Intensity of rain , .8034
Volume of antecedent rain .8270
Volume of antecedent overflow .8788
Wind Direction .9242
Duration antecedent rain .9528
*Volume of overflow .9594
2.8136
1.2226
2.1435
1.9377
.8530
3.7966
10.9700
.0946
,1055
3.9302
3.4903
.8004
1,
3.
* Although more variables correlated, increase the "R".
low "F" values beneath this point lead the statistician
to ignore lower variables
223
-------
Table J-4
Station 4904
Nutrient Parameter
Independent Variable
Multiple R
F Value
Ammonia nitrogen
as rag N/l
Nitrate Nitrogen
as mg N/l
Total Phosphate
as mg P/l
Duration antecedent overflow .5160
Intensity antecedent rain .6725
Wind Direction .7768
Intensity rain .7997
*Intensity of overflow .8546
Time since last overflow .4672
Wind direction .5853
Volume of rain .6135
Volume of antecedent overflow .6476
Intensity of overflow .6817
Duration of overflow .7215
Intensity antecedent overflow .7611
Intensity antecedent rain .8135
*Duration of antecedent overflow .8385
Wind Direction .4712
Intensity Antecedent Rain .6194
Volume Antecedent overflow .7073
Intensity antecedent overflow .7653
Intensity rain .8596
*Time since last rain .8709
7.2564
6.4536
6.8644
1.7019
5.3817
5.5838
3.5925
.9757
,2594
.3532
.7505
.9532
3.1719
1.6709
1.
1.
1.
1,
5.7089
4.9801
4.2013
3.5026
9.3880
1.2191
*Although more variables correlated, increase the "R",
low "F" Values beneath this point lead the statistician
to ignore lower variables
224
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Appendix K
Area Rainfall Distribution
Table K-l
1969 Monthly Rainfall Distribution
Station *(See Fig K-l for Map Location)
3
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Year Total
(Inches)
6
5.81
3.43
2.22
3.99
2.34
1.85
.20
.24
6.57
1.89
3.70
8.00
40.24
14
4.12
3.28
1.67
2.95
2.27
1.06
.21
.19
4.94
1.33
1.83
5.97
29.82
15
6.65
4.04
1.83
3.51
2.44
.92
.18
.38
5.49
1.26
.81
7.07
34.58
17 18 19
6.02
3.91
1.17
3.78
3.05
1.40
.45
.30
5.83
1.67
2.16
6.94
37.38
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Year
Total
(Inches)
7.36
1.77
3.06
2.89
1.22
.40
.61
-
1.81
1.83
4.14
7.68
34.09
Table K-2
1970 Monthly Rainfall Distribution
7.78
1.86
2.99
2.40
.85
1.00
.45
.07
1.77
3.12
4.45
7.65
6.51
2.21
3.78
3.15
1.04
.26
.53
.04
2.32
3.25
5.46
9.21
9.35
2.34
3.81
3.55
1.25
.66
.63
.24
2.96
3.49
5.59
9.13
34.40
37.76
43.00
8.92
2.11
3.54
3.73
1.04
.67
.62
.06
2.49
2.94
5.15
8.37
39.64
8.46
2.33
3.64
3.25
1.21
.94
.67
2.40
3.63
5.01
9.02
40.56
225
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Figure K-l. City Engineering Dept. Rain Gage Locations
226
-------
Appendix L
CondensecM^omputer System Specifications
Computer Main Frame (XDS Sigma 2)
Core Memory words installed:
Core Memory words maximum:
Access Time:
I/O Transfer Kate:
I/O Channels, peripherals
direct
Word Size
Byte Size:
Hardware Registers, General Purpose:
I/O channel:
Memory Protect:
Arith. & Control:
45,056
65,536
920 nanoseconds
400,000 bytes/sec.
12 ea.
1 ea.
16 bits
8 bits
8 ea.
16 ea.
16 ea.
3 ea.
Fixed-Head, Rapid-Access Magnetic Disk Bulk Memory
Capacity, words:
Transfer rate:
Average Access Time:
Rotational speed:
Peripheral Devices
a. Card Reader
b. Card Punch
c. Tape Reader
d. Tape Punch
e. Buffered Line Printer
f. Drum Plotter
g. Magnetic Tape Drive
h. Keyboard-Printer
1,474,560
180,000 bytes/sec.
17 milliseconds
1780 rpm
400 cards/min.
300 cards/min.
300 characters/sec.
120 characters/sec.
800 line/min.
300 increment/sec.
30,000 byte/sec.
10 characters/sec.
227
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1
5
Ac cession Number
i) Subject Field & Group
05F
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
Organization
Seattle, Municipality of Metropolitan
Title
MAXIMIZING STORAGE IN COMBINED SEWER SYSTEMS
10
Aulborfs)
Leiser, Curtis P.
16
21
Project Designation
EPA-WQO Contrac.t No. 1.3 -WASH- 1
Project No. 11022-ELK
Note
22
Citation
23
Descriptors (Starred First)
*Wastewater storage, *Water pollution control, *Regulation,
*Computer programs, overflow, infiltration, flow separation, sampling,
computer models, storm runoff, storage tanks, construction, telemetry,
monitoring, calibrations, rainfall intensity, water pollution sources,
water pollution effects, operations, maintenance, wastewater treatment
25
Identifiers (Starred First)
*Combined sewers, *Seattle, Washington, *Computer control, system
control, control consoles
27\ Abstract^ major portion of the Seattle Metro area's comprehensive sewage
collection and treatment plan launched in 1958, included improvements to
an existing combined sewer system within Seattle's city limits. Initial
plans included: (1) interception and treatment of raw sewage flowing to
saltwater points, (2) regulation of combined flows to utilize all available
trunk storage and (3) construction of temporary storage tanks at freshwater
overflow points. In 1968, a $70 million sewer separation project was
approved and will enlarge system storage by reducing storm inflow. All
construction has been completed in an effort to demonstrate the feasibility
of applying computer-control concepts to theoretically make maximum use of
all available storage within a collection system.
Automatic and manual sampling programs are monitoring overflows and
adjacent waters. Accumulated and analyzed data shows dramatic improvements
in receiving water quality resulting from interception and treatment phases
of construction. Analysis of separation monitoring data, projects a 50-70%
reduction in pollutant loading to fresh water from combined sewer overflows.
Overflow volume, frequency and quality factors are established to serve as
a basis for measuring the performance of the control system as it leaves
the instrumented local control phase and begins the totally computer-managed
— jjiinnn -
Abstractor
Curti
c*
.^
Lei
Lfiejc
Institution
Muni
cipal
_i
±X-
Of
Metropo
litan Seattle
WR:I02 (REV. JULY 1»69)
WRSIC
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON. O. C. 20240
4U.S. GOVERNMENT PRINTING OFFICE: 1972 484-484/131 1-3
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