WATER POLLUTION CONTROL RESEARCH SERIES • DAST 29
Control of Pollution
by
Underwater Storage
U.S. DEPARTMENT OF THE INTERIOR • FEDERAL WATER POLLUTION CONTROL ADMINISTRATIO1S
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HATER POLLUTION CONTROL RESEARCH SERIES
The Water Pollution Control Research Reports describe the results
and progress in the control and abatement of pollution of our
Nation's Waters. They provide a central source of information on
the research, development and demonstration activities of the
Federal Water Pollution Control Administration, Department of the
Interior, through in-house research and grants and contracts with
the Federal, State, and local agencies, research institutions,
and industrial organizations.
Triplicate tear-out abstract cards are placed inside the back
cover to facilitate information retrieval. Space is provided on
the card for the user's accession number and for additional key-
words. The abstracts utilize the WRSIC system.
Water pollution Control Research Reports will be distributed to
requesters as supplies permit. Requests should be sent to the
Publications Office, Department of the Interior, Federal Water
Pollution Control Administration, Washington, D.C., 20242.
Previously issued reports on the Storm and Combined Sewer Pollu-
tion Control Program:
WP-20-11 Problems of Combined Sewer Facilities and Overflows -
1967.
WP-20-15 Water Pollution Aspects of Urban Runoff.
WP-20-16 Strainer/Filter Treatment of Combined Sewer Overflows.
WP-20-17 Dissolved Air Flotation Treatment of Combined Sewer
Overflows,
WP-20-18 Improved Sealants for Infiltration Control.
WP-20-21 Selected Urban Storm Water Runoff Abstracts.
WP-20-22 Polymers for Sewer Flow Control.
ORD-4 Combined Sewer Separation Using Pressure Sewers.
DAST-4 Crazed Resin Filtration of Combined Sewer Overflows.
DAST-5 Rotary Vibratory Fine Screening of combined Sewer
Overflows.
DAST-6 Storm Water Problems and Control in Sanitary Sewers,
Oakland and Berkeley, California.
DAST-9 Sewer Infiltration Reduction by Zone Pumping.
DAST-13 Design of a Combined Sewer Fluidic Regulator.
DAST-25 Rapid-Flow Filter for Sewer Overflows.
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CONTROL OF POLLUTION
BY
UNDERWATER STORAGE
Feasibility of providing temporary underwater storage
of storm overflow from a combined sewer system.
FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
DEPARTMENT OF THE INTERIOR
by
UNDERWATER STORAGE, INC.
SILVER, SCHWARTZ, LTD.
JOINT VENTURE
1028 Connecticut Avenue, N.W.
Washington, D.C., 20036
program No. 11022 DWF
Contract No. 14-12-139
December, 1969
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F.W.P.C.A. Review Notice
This report has been reviewed by the Federal
Water Pollution Control Administration and
approved for publication. Approval does not
signify that the contents necessarily reflect
the views and policies of the Federal Water
Pollution Control Administration.
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ABSTRACT
A pilot plant was designed, constructed and operated to assess the
feasibility of providing a facility for the collection, treatment,
storage and final disposition of a portion of the storm overflow
from a combined sewer system serving a thirty-acre drainage area
in Washington, B.C.
A Parshall flume was installed in the overflow line for measurement
of flow rates and determination of total overflow volume. A por-
tion of the overflow was diverted to the pilot plant through grit
chambers and a comminutor. Flow was stored in two 100,000-gallon
underwater bags fabricated of nylon reinforced synthetic rubber and
fastened to the river bed by a system of patented anchors. During
the period of storage, compressed air was delivered to the tanks
for agitation of the solids. Following cessation of the storm,
contents of the bags were pumped to the interceptor sewer for
delivery to the District of Columbia Sewage Treatment Plant at Blue
Plains. Flow into and out of each underwater storage tank was
metered and recorded. Samples of the combined sewage overflow
discharged to the bags and pumped discharge from the bags were
collected and subjected to laboratory analyses.
During the operation period from January through September, 1969,
a total of 1,600,000-gallons of diverted overflow from 38-storms
was stored in the tanks. In addition, 600,000-gallons of river
water was pumped into the underwater storage tanks for testing
during dry weather periods. The total amount stored was pumped to
the interceptor sewer in 26-separate pump out periods.
The cost of the pilot plant was $341,480.00, or $1.70 per gallon of
storage. This included facilities for testing, samples and flow
measurement. Estimates for larger installations, without these
special requirements range from 28.2C to 14.6C per gallon for plants
with storage from two to twenty million gallons.
The project demonstrated that temporary storage of overflow from
combined sewers in underwater rubber storage tanks is feasible and
may, under suitable conditions, be effective in eliminating direct,
untreated discharge of combined sewage into surface waters during
storm periods. Drainage area to be served, land use, nature
of storm events,and other factors must be considered when planning
an underwater storage facility.
This report is submitted in fulfillment of Contract No. 14-12-139
between Federal Water Pollution Control Administration and Under-
water Storage, Inc., Silver, Schwartz, Ltd., Joint Venture.
iii
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i •
«)
STORM OVERFLOW PROJECT
UNDERWATER STORAGE INC. & S I L_VER, SCHWARTZ l_TD.
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CONTENTS
SECTION NO. TITLE PAGE NO.
Abstract iii
Figures ix
Tables xi
1 Conclusion 1
2 Recommendations 11
3 Introduction 15
4 Site Selection 17
5 General 25
6 Design 29
7 Plant Equipment 41
8 Construction Cost 51
9 Operational Description 59
10 Sample Collection and Analysis 75
11 Hydrology 87
12 Discussion 101
13 Acknowledgements 129
14 References 131
15 Patents and Papers 133
16 Appendix 135
VII
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FIG. NO.
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FIGURES
TITLE
Flow Diagram
Cost Per Gallon
Side View of Pump House
Rear View of Pump House
Marker Buoys Locating Underwater
Storage Tanks
Rendering of Multiple Tank
installation In a cluster
Rendering of Multiple Tank
Installation In a Line
Site Selection Plan
Project Location Plan
Project Area Plan
Main Sewage Pump
Sludge Pump
Air Compressor
Comminutor
Main Header Line from Comminutor
Chamber Showing Pump Bypass
Line
Main Header Line Showing Branch
Runouts to Underwater Storage
Tanks
Forward and Reverse Meter
Installation in Main Header
Line
Forward and Reverse Meter
Recording Station
Underwater Storage Tank Ready
for Submergence
Plant Operational Plan
Repair of Large Tear in Tank
Repair of Large Tear in Tank
Clamps for Repair of Small
Openings in Tank
Overflow Manhole Graph; 12/22/68
Overflow Manhole Graph; 1/18/69
Overflow Manhole Graph; 2/ 8/69
Overflow Manhole Graph; 6/ 2/69
Overflow Manhole Graph; 7/22/69
Overflow Manhole Graph; &/ 9/69
PAGE NO.
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FIGURES
FIG.
NO.
30
31
Overflow
Overflow
TITLE
Manhole
Manhole
Graph ;
Graph ;
8/20/69
9/ 8/69
PAGE NO.
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Discharge Hydrograph, Hyetograph
and Overflow Waste Water Sample
Analysis
12/22/68
12/22/68
12/22/68
1/18/69
1/18/69
1/18/69
2/ 8/69 - 2/9/69
2/ 8/69 - 2/9/69
2/ 8/69 - 2/9/69
6/ 2/69 - 6/3/69
6/ 2/69 - 6/3/69
6/ 2/69 - 6/3/69
7/22/69
7/22/69
7/22/69
8/ 9/69
8/ 9/69
8/ 9/69
8/ 9/69
8/20/69
8/20/69
8/20/69
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TABLES
TABLE NO.. . . ^ TITLE _ PAGE NO.
I Construction Cost Estimates 3
II Estimated Annual Operation and
Maintenance Costs 5
III Estimated Total Annual Cost 6
IV Time in Minutes Needed to Fill
100,000-Gallon Tank 40
V Pilot Project Cost 57
VI History of Operation 66 - 68
VII Summary of Laboratory Analyses 78 - 86
VIII Rainfall Summary 88
IX History of Rainfall and Flow
Through Parshall Flume 98, 99
XI
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SECTION 1
CONCLUSIONS
A holding facility eliminates many of the problems encountered with
other means of controlling water pollution from overflow sewers.
The holding facility can be above ground, below ground, or under
water. The underwater holding facility lends itself, under certain
conditions, in meeting the problem for the following reasons:
1. Since overflow is always near a river, stream or lake, space
is either available or can be made available by dredging to
install an underwater holding facility.
2. Land area along a river bank or other body of water is
frequently inadequate for an above ground holding facility,
and acquisition of shore line real estate for such use is
generally costly and time consuming.
3. There are no significant odor problems in underwater install-
ations .
4. Beautification along our waterways is greatly enhanced by
the avoidance of large land structures. Storage facilities
are out of sight, permitting unhindered development of shore
line property for industrial, residential or public use.
5. Underwater storage offers an economical solution for control
of pollution. The maintenance of the system is minimal. The
system components remain serviceable for years with little
upkeep.
A further advantage of underwater holding tanks is found in con-
struction flexibility in the fact that tanks can be installed in
multiple units at each overflow, thereby permitting work to be
accomplished in phases. This further allows expansion of the
system as required, permitting capacity to keep pace with munici-
pal growth. In addition, the storage tanks are portable, float-
able, replaceable, collapsible, washable, odor free and flexible.
The construction cost of the project included many items not
required for an actual operating installation and is, therefore,
not indicative of actual anticipated construction costs. Con-
struction estimates, based on ENR Construction Cost Index of 1300,
from two to twenty million gallons storage, as shown on Table I
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are more realistic for actual requirements. These estimates are
"based on the use of 500,000-gallon and 1,000,000-gallon underwater
storage tanks in lieu of 100,000-gallon tanks as utilized (costs
for the larger tanks are considerably less than costs for equal
capacity of smaller tanks) in the demonstration project. These
estimates include grit chambers, comminutor, pump house, metering
station, pumps, piping, air compressor, Parshall flume, instrumen-
tation, electrical work, earthwork and all underwater work of tanks,
installation and dredging. These estimates assume certain ground
conditions that may not require extensive costs in ground work,
excavation, sheet piling, dewatering, etc., as was encountered in
the pilot plant. Even with all these unknown variables, it is
seen in Figure 2 that as the storage capacity of the project
increases, the cost per gallon of storage will level off at approx-
imately twelve cents per gallon. This cost does not include auto-
mated computerized control.
Reference is made to Section 8, Construction Costs, page 51 for
explanation of the various line items of cost indicated in the
Estimates of Table I.
As a result of this pilot project, it was determined that many
cost savings could be realized in such areas as in the use of tank
flotation systems, installation of quick-connect fittings for
underwater work, replacement of underwater bolting with shackles,
installation of nets for hold-down of tanks and change in venting
system on tanks. It was also determined that the cost per gallon
of underwater storage tanks decreased as the capacity increased.
The cost of a 500,000-gallon tank is less than ten cents per gallon
and the cost of a 1,000,000-gallon tank is estimated at eight cents
per gallon, whereas the cost of a 100,000-gallon tank is 14.4 cents
per gallon.
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TABLE I
CONSTRUCTION COST ESTIMATES
Storage Capacity
1. General Conditions
2 . Bond and insurance
3. Earthwork*
4. Sheet Piling and Dewatering*
5 . Lawn and Planting
6. Timber Piles on Shore*
7. Off-Shore Work*
8. Concrete
9. Miscellaneous Metal
10. Structural Steel
11. General Construction
12 . Painting
13. Mechanical Equipment
14. Pipe and Fittings
15 . Electrical
16. underwater Storage Tanks
and Piping
TOTALS
Cost per Gallon - Total
Installation
Cost per Gallon - Storage
Only
2 M Gal.
$2,000
4,500
25,000
33,000
800
20,000
78,000
35,000
6,000
20,000
10,000
3,000
60,000
20,000
7,000
240,000
$564,300
28.2*
16.9*
3 M Gal.
$2,000
6,000
30,000
36,000
1,000
24,000
92,000
40,000
6,000
28,000
10,000
3,000
68,000
24,000
8,000
350,000
$758,000
25. 3
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COST PER GALLON
C
0
S
T
P
E
R
G
A
L
I,
0
N
S
•
30C
Cost per Gallon - Total
Cost per Gallon - Storage
M
10 12 14 16 18 20
Only
nstallation
to
GALLONS STORAGE
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Annual operation and maintenance costs for the underwater storage
project have been estimated based on experience gleaned in the
demonstration facility. The items of labor and supervision include
the necessary disposal of screenings and pump station operation.
Actually, labor need only be provided for operation during overflow
conditions. Materials and supplies for operation are minimal.
Power includes that required for pump and comminutor operation.
Maintenance costs allow for general upkeep of plant equipment and
periodic inspection of tanks and underwater piping. Miscellaneous
costs include telephone, charts, etc.
TABLE II
ESTIMATED ANNUAL
OPERATION AND MAINTENANCE COSTS
Storage Capacity
Labor and Super-
vision
Materials and
Supplies
Power
Maintenance
Miscellaneous
Total Annual
Operating and
Maintenance Cost
2 M Gal.
$7,500
500
2,000
5,000
600
$15,600
3 M Gal.
$8,500
500
2,800
6,000
600
$18,400
5 M Gal.
$10,000
500
4,500
8,000
600
$23,600
10 M Gal.
$12,000
500
8,500
10,000
600
$31,600
20 M Gal.
$12,000
500
16,000
14,000
600
$43,100
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Total annual cost is the total of annual operating and maintenance
cost and cost of amortizing the capital expenditure. The useful
life of the project is estimated to be in excess of twenty years.
However, for the purpose of this report, twenty years is selected
with interest rate of 6.0%. On this basis, the capital recovery
factor is established at 8.4%.
TABLE III
ESTIMATED TOTAL ANNUAL COST
Storage Capacity
Capital Project
Cost
Amortization Cost
Operating and
Maintenance
Costs
Total Annual Cost
2 M Gal.
$564,300
47,400
15,600
$ 63,000
3 M Gal.
$758,000
63,700
18,400
$ 82,100
5 M Gal.
$987,000
82,900
23,600
$106,500
10 M Gal.
$1,754,500
147,400
31,600
$ 179,000
20 M Gal.
$2,923,000
245,500
43,100
$ 288,600
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Side View of Pump House
Fig. 3
Rear View of Pump House
Fig. 4
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Marker Buoys Locating Underwater Storage Tanks Fig. 5
5
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It is noted by observation and by analyses at this site that a
major portion of the polluting material is contained during the
initial flush of the overflow. During this period of several hours
duration, it is important to capture and store all of the overflow.
The balance of the overflow has less polluting effect on the
receiving waters; therefore,complete storage may not be absolutely
required. This conclusion may be an important factor where limited
funds necessitate partial storage at the outset of a program.
In order to properly establish the capacity of holding facility,
it is necessary to estimate the assimilated pollution capacity of
a particular receiving body of water as related to rainfall and
to provide storage capacity for that rainfall in excess of the
receiving water requirement, but no less than the initial flush of
the overflow.
Under the above conditions, the capacity of a holding facility for
storm sewer overflow could be planned to control anywhere from
25% to 50% of actual overflow discharge during heavy rains, and
100% during light rains.
These findings will also offer additional flexibility in the possible
design of on site sewage treatment facilities. By storing the
initial flush of storm water overflow for subsequent pumping, it
may be possible to treat the diluted low content pollutant flow with
a lesser treatment facility than would be required for a sewage
treatment plant to serve the entire flow.
The pilot facility has demonstrated that it is possible to divert
combined sewer overflow to underwater rubber storage containers
and to return the stored waste water to the interceptor sewer at a
time when the flow in the combined sewer is such that the stored
waste water can be accepted. This may occur shortly after the
storm ceases.
The demonstration has proven conclusively that combined sewer
overflows need not be discharged into rivers, lakes and waterways,
but can be received, treated, stored and pumped to final disposal,
and this major cause of water pollution can be controlled.
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SECTION 2
RECOMMENDATIONS
It is recommended that existing overflow from combined sanitary and
storm sewer systems be controlled wherever feasible. Each munici-
pality or sewage authority should analyze the costs and problems
of various methods presently available or proposed to achieve this
purpose. In analyzing various proposed alternatives, it is
necessary to view the entire picture, not just direct costs, but
side effects and costs such as tearing up of streets, interference
with traffic, operational problems, system reliability and equip-
ment durability, effectiveness, system flexibility and esthetics.
It will be found in many cases that underwater storage will be the
answer to this critical problem.
It is recommended for the future that consideration be given to
additional treatment in connection with underwater storage over-
flow installations. Inasmuch as storage provides the key factors
of hydraulics and time that is a prerequisite for treatment plant
operation, the amount of treatment for one or more overflow
systems need not be of the full capacity of the overflow, but may
be a fraction of the flow. The relationship of treatment capacity
to storage capacity should be a matter of economics. If more
storage is provided, then lesser treatment capacity would be
necessary. If, in future studies for additional treatment, it is
determined that full pumping back to the interceptor sewer is not
required, then as many overflows as possible, within economic
reason, should be served by a single installation.
Where many overflows occur in a municipal system, it is recommended
that installations be automated to operate from a central computer-
ized control. This not only would reduce operating cost, but would
eliminate potential human error.
It is recommended that underwater storage tanks be provided with
built in flotation facilities for raising and lowering the tanks.
It is recommended that quick-connect connections be used on all
piping below water, not just on air and vent lines. In the demon-
stration project, flanged connectors were used on the main lines;
as a result, costs for piping connections were excessive because
of labor costs of divers. These high costs were also reflected
in disconnecting lines when raising tanks.
11
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Another area in which it was found that installation of discon-
necting costs can be reduced was in the use of plate clamps or
shackles, rather than bolted connections, for securing underwater
storage tank supports to the anchoring system.
It is recommended that underwater storage tanks be provided with
marine nets for hold-down purposes and to enable uniform pressure to
be exerted on the tanks as well as controlling tank configuration.
In addition the use of underwater diaphragm purge valves for venting
air and gas from the underwater storage tanks have proven extremely
effective and should be utilized on all underwater projects. These
vents also control internal tank pressures.
Multiple tank installations can be installed in a cluster as shown
in rendering Figure 6, or in a line from a single header as shown
in rendering Figure 7. The in-line arrangement can also be
installed with a single branch runout to each tank as was accom-
plished in the pilot project.
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Rendering of Multiple Tank Installation
in a Cluster
Fig. 6
Rendering of Multiple Tank Installation
In a Line
Fig. 7
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SECTION 3
INTRODUCTION
In cities where combined sanitary and storm sewer systems exist,
dry weather flow of raw sewage is processed by the sewage treatment
plants. During periods of heavy rainfall, the flow is increased to
such an extent by the addition of storm water in the system that
the interceptor sewers are often hydraulically incapable of handling
the cascade of water that floods into the lines. During periods of
light rainfall, the problem is found to exist when the storm sewer
flow is coincidental with the peak sanitary sewage flow. The in-
crease in flow in the interceptors because of storm water depends
on the area served, population density, green space, and the
characteristics of the sewer system. Under these conditions of
sanitary and storm water flow, present sewage treatment plants do
not have sufficient capacity to treat the increased flow. To
relieve the system and to protect the sewage treatment plant opera-
tion, overflows are customarily employed to direct all excess flow
to the rivers, lakes and waterways through overflow structures.
This expedient reduces pressure on the main sewer interceptor and
aids in avoiding backup into the streets. However, as a result,
much of the sanitary waste (as much as 90%) never reaches the sew-
age treatment facility. The overflow combined sewer, unprocessed
and bacteria-laden,pours directly into the river, lake or waterway.
The storm water alone is contaminated with coliform organisms,
nutrients and other foreign matter such as oil, grease and debris
it accumulates on its way to the gutter and storm sewer. Once in-
side the combined sewer, it mixes with the raw sewage already in
the line. As the interceptor fills to capacity during a rainfall,
the torrent inside flushes out the sediment that has been accumu-
lating in the lines for days, weeks, or even months. Especially
during the first few hours of a storm, this overflow may have a
biological oxygen demand of 400 or more milligrams per liter of
combined sewer flow at the point of discharge* well above average
for domestic waste. Settleable solids during this period may
range from 10 to 60 milliliters per liter and suspended solids from
200 to 1,000 milligrams per liter. All this leads to the inevitable
and obvious result pollution.
If the sewage treatment plants were of adequate size to accommo-
date the peak flows existing in combined sewers, they would have to
be tremendously enlarged at prohibitive land and construction costs.
15
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One solution that has been advanced and widely used to resolve
the problem of combined sewer overflow is to separate the systems;
i.e., to retain the existing combined sewer for storm water flow
and to provide a new and independent system for sanitary sewer
flow. The problems inherent with this separation concept are many
and complex. Besides being extremely costly, the installation of
separate sanitary sewer lines entails tearing up of streets, inter-
ference with other underground utilities, tying up of traffic and
the complete revamping of individual building connections. Even
with the separation of the systems taking place,there is still the
problem of storm water pollution; which, though not as extensive,
is still a major factor in the overall problem.
Other solutions to the combined sewer overflow situation take into
account some form of holding facility to retain the overflow for
separate treatment or for treatment by the municipal sewage plant
during periods of low flow. With either situation it is necessary
to provide adequate storage at the holding facility to enable the
sewage plant to effectively treat the stored overflow over a
period of several hours to several days, depending upon plant
capacity, during off peak hours.
Some of the holding systems which have been proposed with treat-
ment at the facility have been retention and sedimentation basins,
above ground holding tank and deep tunnels. With off-shore reten-
tion basins there is the problem of blocking off large water areas
to receive the flow. The above ground holding facility requires
large land structures, results in potential odor problems, and
necessitates the need for costly and time consuming acquisition of
shore line real estate. The deep tunnel project is costly;
present estimates range from $.40 to $.45 per gallon of storage,
based only on preliminary studies.
It is desirable to find an economical system for holding of com-
bined sewfer overflow that is not costly, that removes the
necessity of tearing up streets, that is esthetically acceptable
and out of sight, that permits unhindered development of shore
line property for industrial, residential or public use, that is
flexible for expansion to keep pace with municipal growth, that
provides some means for primary and possible secondary treatment,
and that is equally or more effective in reducing pollution than
those methods presently in use or being considered. This report
deals with the feasibility of one such possible alternative.
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SECTION 4
SITE SELECTION
A preliminary investigation was made by studying the "Sewerage
System" map of the District of Columbia (See Figure 8 on Page 23 )
in conjunction with the Sewer Separation Program - 1966, report
by the District Sanitary Sewer Department. There are approxi-
mately fifty outfalls of combined sewers along the Potomac and
Anacostia Rivers, all of which had potential as sites for the
pilot plant. investigation revealed most of them as unusable
for compliance with contract requirements as to size of drainage
area, availability of work space during testing period, accessi-
bility and interferences, all as hereinafter discussed.
The outfalls into the Washington Channel and Anacostia River be-
tween the Twelfth Street and South Capitol Street Bridges were
immediately eliminated because the sewer system in this area
was in the process of being converted from a combined system to
a separate system.
Elimination of the above group of sewers left two groups to be
investigated. The sewers of Group 1 outfall into the Potomac
River between Three Sisters Islands and the Arlington Memorial
Bridge. The sewers of Group 2 outfall into the Anacostia River
between the South Capitol Street Bridge and the John Philip
Sousa Bridge.
Within Group 1 were further eliminated the outfalls between Rock
Creek and the Arlington Memorial Bridge because they drained
areas that were either too large or too small for the study, and
they outfell on existing improved Park Service property. Again,
to the West of Rock Creek, the elimination of four outfalls was
concluded because of the size of drainage area served. The
remaining outfalls that showed possibility in Group 1 then, were
as follows: 21-inch outfall at 30th Street, 24-inch outfall at
31st Street, 24-inch outfall at Wisconsin Avenue, and a 4-foot
by 4-foot outfall West of Key Bridge near 36th Street.
The outfalls at 30th and 31st Streets respectively did not serve
large enough areas unless they were connected in some manner for
the project. More important, however, interference from barges
serving industry at these locations was anticipated, and there
was indication that there would be a lack of work space available
during certain phases of the project. These locations, therefore,
17
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were taken out of further consideration.
The two remaining sites of Group 1 are discussed herein in con-
junction with any possible sites of Group 2 sewers after reviewing
that group.
Within Group 2 along the Anacostia River, use of the outfalls
within the U. S. Navy Yard area would be far less than ideal since
another Government agency would be involved, not to mention ship
interference, site accessibility problems, etc., so these loca-
tions eliminated themselves.
On the East side of the Anacostia River there were three combined
sewer outfalls, but two of these were located within the turning
basin of the U. S. Navy Yard and, therefore, would have been
involved with interference from many more large ships and boats
than upstream. In addition, all of the sites on the East side
were on newly reclaimed Park Service property, and construction
here for the pilot plant would not be desirable unless absolutely
necessary.
The remaining four sewer outfalls of Group 2 were located on the
West Bank of the Anacostia River between the Anacostia and Sousa
Bridges. Of these, two of the outfalls served very large drainage
areas and another served a very small drainage area; therefore,
these were eliminated. The fourth sewer, outfailing closest to
the Sousa Bridge,was found to be the best possibility of Group 2
sewers and will be discussed along with the two sites available
from Group 1.
Three sites remained for final consideration and are referred to
hereinafter as the "Key Bridge" site, the "Wisconsin Avenue" site,
and the "Sousa Bridge" site; the first two being located on the
Potomac River and the latter on the Anacostia River.
Key Bridge Site (Group 1)
a. The area drained by the sewer network is about seventeen
acres at this site.
b. The depth of water in the Potomac River near the outfall of
this sewer is about ten-feet.
c. The only use of the waterway in this area is that of the
small boat and pleasurecraft.
18
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d. Ample work space is available at this site as well as good
accessibility.
e. It is assumed that property and right-of-way rights, as well
as all required permits, will be readily available to the
Contractor at this location.
f. There should be no problem in making the installation com-
patible to the surroundings at this site.
9- Highway: Future extensions of the Whitehurst Freeway as a
depressed roadway or tunnel will remove any underwater
installation from the River. This highway work could take
place in about two or more years.
Wisconsin Avenue Site (Group 1)
a. The drainage area served by the sewer at this site is about
eight acres.
b. The depth of water of the Potomac River at this sewer out-
fall is approximately 36-feet.
c. The waterway at this site is available to large boats and
barges as well as small boats and pleasurecraft.
d. The work space available at this site is more than enough for
the project needs and access is excellent.
e. There does not appear to be any problem in securing property
and right-of-way rights or construction permits at this site.
f. An installation at this site could easily be made to fit
into the surrounding area even considering proposed
beautification of these surroundings.
g. Highway; The future extension of the Whitehurst Freeway
will not interfere with the installation. It could, however,
substantially alter the shape and area of the drainage basin
served. This highway work could take place in about two
years.
19
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Sousa Bridge Site (Group 2)
a. The area of land drained by the sewers of this site is
about 28-acres.
b. The indicated water depth at this site is thirteen-feet,
however, increased depths upstream and downstream were
noted.
c. No large boats are known to travel as far upstream as this
site/ however, the area is used extensively by small boats
and pleasurecraft.
d. This site has ample work space available and access to the
site poses no problem.
e. It was not anticipated that there would be any problem in
securing the necessary right-of-way or property rights or
permits for construction at this site.
f. There were no problems anticipated in making an installation
at this site fit the surrounding conditions as they are now
or may be in the future.
g. Highway; Design of the extension of 1-295 is in the final
stage, but the new road work would not interfere with the
proposed installation. It is not likely that the shape and
area of the drainage basin served would be substantially
altered by this road work.
After a study of all the factors involved, it was recommended that
the "Sousa Bridge" site on the Anacostia River be chosen as the
location for the proposed water pollution control project. This
site came closest to meeting the requirements for the required
size of drainage area, at about 28-acres. Also, it was antici-
pated that because of the smaller size of the Anacostia River,
the problems of river and tidal currents and their effects on
the installation would be less than at the other sites. With
all other criteria for the site being more or less equal at all
locations, the other factors which influenced the final site
selection were (1) anticipated lower installation costs; (2)
a more evenly and well-defined drainage pattern; and (3) less
interference from new highway construction.
20
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Because the "Sousa Bridge" site was selected for the pilot
plant does not preclude the other sites, either separately or by
grouping, as not being adaptable to the underwater storage of
combined sewer overflow.
21
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PAGE NOT
AVAILABLE
DIGITALLY
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SECTION 5
GENERAL
The pilot plant on the Anacostia River in Washington, B.C. was
built under Contract No. 14-12-139 with the Federal Water Pollu-
tion Control Administration to determine the feasibility of
storing overflow of combined sewers in inflatable tanks anchored
to the bottom of the river bed. The entire project was installed
under permit No. 6:830:106 obtained from the National Capitol
Park Service on a piece of property 50-feet by 105-feet adjoining
the river at the Sousa Bridge. Application was made and approved
by the U. S. Army Corps of Engineers for dredging and by the
U. S. Coast Guard for installation of navigational aids. The con-
struction of the pilot plant began in May, 1968, was completed in
November, 1968 and was in continuous operation until October, 1969.
The overflow sewer selected served approximately thirty-acres of
mixed residential and commercial area. The combined sanitary and
storm sewer normally discharges into a 72-inch interceptor
sanitary sewer, with overflow through a 33-inch line into the
Anacostia River during heavy sewer flow. The site proved suitable
conditions for dredging and installation of underwater storage
tanks and anchorage system to stabilize the tanks.
Patents 3,114,384, 3,114,468, 3,155,280 and 3,187,793 issued to
Harold G. Quase, assigned to Underwater Storage, Incorporated,
were used for the storage system,tank cradle supports and anchorage
No interferences resulted to waterway users, ample work space was
available and the site was readily accessible.
Two 100,000-gallon synthetic rubber-coated nylon fabric tanks
were installed in the bed of the river through a patented system
of anchors. The existing 33-inch diameter combined sewer over-
flow from a 30-acre site was diverted through a Parshall flume
for purposes of measuring total flow. Flow to the underwater
storage tanks passed through a concrete grit chamber where oil
and grease floated to the top and grit, sand, etc., fell to the
bottom, in addition, a motor-operated comminutor was provided
in the flow channel to shred all solids down to 3/8-inch. Flow
to the underwater tanks was by gravity. In the main header pipe
from the comminutor to the underwater tank, a meter was provided
to determine the actual flow in and out of each tank. When tank
or tanks were filled, the remaining overflow was allowed to take
25
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its normal course of flow into the river. If 100% storage could
have been provided, no flow would have been allowed to discharge
into the river.
Between the hours of midnight and 8:00 A.M., after rainfall, when
the sewage treatment plant operation was at a minimum, the under-
water storage tanks were pumped out by the main sewage pump through
a force main to discharge the contents into the interceptor
sewer.
A good portion of the solids flowing into the underwater storage
tanks remained in suspension and could be readily pumped out.
The balance of solids was agitated by compressed air to assist
in the pumping operation. The tanks were vented to the atmosphere
and were protected from river debris by an underwater fence
enclosure. A water pump was used for pumping river water into the
tanks for test purposes during dry periods, and also for washing
down water channels when desired. A sludge pump was provided to
dispose of pumpable solids from the grit chamber.
To test the pilot plant during the operational period, meters and
recorders were provided to measure total flow runoff of the over-
flow sewer and the amount of flow into and out of each tank.
Facilities were provided for sampling of all flow for laboratory
analysis for determination of BOD, pH, bacteria, TOC, settleable
solids, suspended solids, coliform and industrial waste.
Facilities were set up for automatic sampling in sterilized
bottles which were refrigerated prior to testing.
26
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SCAA-E: \'= 20o'
Project Area Plan
28
Fig. 10
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SECTION 6
DESIGN
After site selection was completed, a survey was made to deter-
mine conditions of the ground on both sides of the seawall.
Soundings were also taken of the river bed.
From the boring log, it was determined that all structures would
have to be erected on pilings, because of the ground and water
conditions.
Design was predicated on anticipated and past records of rain-
fall and water flow in the 33-inch diameter District of Columbia
combined sewer overflow line.
A Parshall flume 4-foot in size was selected to handle a minimum
of 570 GPM and a maximum of 30,000 GPM at free flow. The exist-
ing 33-inch sewer would be diverted into the Parshall flume where
meters would record flow in a meter house built above the flume.
Leaving the flume, the system design would incorporate flexibility
to divert the storm overflow to storage tanks or back to the out-
fall in the river.
A structure to house grit chambers, comminutor, supplemental
chambers, sewage pump, sludge pump, river water pump, air
compressor, and operators' console was designed of reinforced
concrete, because of ground and water conditions. A United
States Park Service directive would allow only five-feet of any
structure above grade; design of this building was carefully
plotted to keep within this directive.
Storage of 200,000-gallons of water in the river bed was
mutually decided upon with provisions for future expansion to
300,000-gallons.
A complete piping system was then designed to take storm overflow
from the Parshall flume to the grit chambers, and then from the
comminutor discharge to the storage tanks through metering
facilities. Water being pumped out of the storage tanks is piped
back through the metering device into the sewage pump where it
is then pumped uphill to a 6-foot interceptor sewer which flows
to the sewage treatment plant. Grit chambers can be cleaned by
pumping out through the sludge pump. River water can be pumped
into the system for test purposes. An air compressor and a
29
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piping system to the tanks is used for agitation to prevent build-
up of solids at tank base. All valving, pumping and metering are
accomplished within one room.
A metering station was designed adjacent to the overflow manhole
at Barney Circle (See Site Plan, Appendix A), which would record
the height of all water running through the manhole. The first
8-inches of this water goes into the interceptor sewer, and all
above 8-inches flows into the 33-inch storm overflow line.
Principal items of design were:
a. Storage Tanks: Flexible synthetic rubber-coated nylon
fabric with a tensile strength of 1500 psi.
b. Pumps; Horizontal double volute self-priming centrifugal
type. Pumps to have replaceable check valve, wearplate,
impeller, and mechanical shaft seats. Motors to be non-
overloading type.
c. Comminutor; Readily installable in a straight rectangular
sewage channel. Replaceable steel cutters. Design for
minimum flow of 4 MGD, average flow of 11 MGD, and a maximum
of 19 MGD.
d. Air Compressor; Heavy duty, adjustable, complete with
compressor, motor, controls, starter and tank. All A.S.M.E.
approved.
e. Piping:
1. Pump House: Schedule 40 black steel.
2. Underground: Extra-heavy cast iron.
3. Force Main: Mechanical joint.
4. In River: Rubberized hose.
f. Slide Gates; Aluminum, rising-stem type.
g. Controls; Metering and recording equipment, Foxboro and
Hersey-Sparling.
A steel cradle was designed to hold the tank and enable lowering
tanks into river to be fastened to steel "H" piles driven to
anchoring depth.
30
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Basic to the design of a storage system to handle storm sewage
overflow is the quantity of storage required and the necessary
rate of acceptance. Statistical analysis of records for many
years of rainfall of a single storm or rainfall per day, or
rainfall per hour, will give the percent of total sewage overflow
a given sized system will store and return for processing. This
percentage could be considered the system efficiency if we
believed that drainage and sewage mixed uniformly during a storm.
This form of calculation would be of great value in the design of
a final system and in the evaluation of the performance of a
pilot plant; however, other considerations such as increased
operating experience overshadow optimum design for pilot plants.
With flow over short distances, the flow rates are determined by
precipitation rates over rather short time periods such as ten
minutes, particularly in an area such as Washington, B.C. that is
subject to an average of some thirty odd thunder storms per year.
The storm rain rates for the specific area considered were un-
available; therefore, the largest hourly race of recent record was
used to calculate the required flow rate. The resulting rate of
just over 2 feet3 per second per acre compared favorably with
handbook values (p. 44, WPCF Design and Construction of Sanitary
and Storm Sewers).
Design Parameters
The size of the system is determined by: the area served,
drainage characteristics, rain rate and storm duration. Most of
the system components, however, must be determined from rates of
flow rather than total quantity. Discharge rates can be calcu-
lated for the defined service area of thirty-acres. Investiga-
tion of official weather records for the last twenty-years
showed the greatest hourly rate to be 2.9-inches per hour; how-
ever, for computational purposes 3.0 will be used. Based on
visual inspection of the area served, with regard to the amount
of paved area and the imperviousness of the soil/ the runoff
factor was assumed to be 0.75. The average design flow rate (Q)
into the storage system is calculated as:
Q = (runoff factor)(rain rate)(sq.ft./acre)(number of acres)
Q= (0.75)(3/12)(43,560)(30)
= 255,025 ft.3/hr.
=68.1 ft.3/sec.
31
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Return Pump Rate
The District of Columbia, Department of Sanitary Engineering
established an operating procedure whereby the only permitted
time for pumping out of storage tanks would be between the hours
of 12:00 Midnight and 8:00 A.M. on the day following the sub-
siding of a storm. To compute the pumping rate to meet this
requirement, it is assumed pumping to start at 12:00 Midnight,
and end at 4:00 A.M. the following morning.
Total Volume 200,000 gallons (two tanks)
Pumping Time Four hours, or 240-minutes
The required pump rate is:
Pump Rate = Volume = 200,000 = 830 gallons per minute
time 240
A 1,000 gallon per minute pump was selected for the project. If
a third storage tank were used, the additional pumping time
would be:
Time = Volume = 100,000 = 100 minutes
Pump Rate 1,000
Therefore, the time interval to pump three tanks would be from
12:00 Midnight to 5:40 A.M., well within the time allowable for
pumping.
Return Pump
From observation of the proposed site, the following pump require-
ments were estimated: The suction would require an eight (8)
foot lift when returning directly from the underwater storage
tanks, allowing for a low tide. The discharge would require a
net head of 41-feet to reach the interceptor sewer. Pipe losses
of one foot of head were assumed on suction, and 20-feet of
head on discharge, resulting in a total suction lift of 9-feet
and a discharge head of 54-feet. The velocity head in the pipe
was neglected. The return pump specifications are:
Capacity 1,000 gallons per minute
Suction Lift 9-feet
Discharge Head 61-feet
32
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Sludge Pump
The sludge pump is used to pump effluent going through the floor
drains of the comminutor room, out to the intercept sewer.
Capacity 200 gallons per minute
Suction Lift 5 -feet
Discharge Head 65-feet
Drains From Grit Chamber
These pipes are arbitrarily set at 4-inch diameter because of no
flow requirements.
Water Pump
The water pump is used to pump water from the river to the storage
tanks and the grit chamber for testing purposes. It is also used
for washing purposes for the grit chamber and the storage tanks.
Capacity 200 gallons per minute
Suction Lift 5 -feet
Discharge Head 25-feet
Air Compressor
The air compressor is used to supply compressed air to the storage
tanks through three parallel 3-inch pipes installed at the base of
each tank with fifty 1/32-inch holes per 100-foot run on top of
pipes. The purpose of the compressed air is to agitate the sludge
in the tank to prevent settling of the sludge material.
Capacity 175 CPM (Actual)
20 PSI, 25 HP
213 CFM Piston Displacement
Sump Pump
The submersible sump pump is used to pump water from the floor
of the grit chamber to the intercept main. This will prevent
seepage water from accumulating.
Capacity 10 gallons per minute
Suction Lift 3 -feet
Discharge Head 67-feet
33
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Return Line to Intercept Sewer
A length of 400-feet, change in elevation of 34-feet and a head
loss of 20-feet, requires the installation of a 6-inch diameter
return line. This 6-inch return line is installed inside the
33-inch overflow sewer up to the manhole near Barney Circle.
From there it is buried underground and connected to the inter-
cept sewer.
Anchor Forces
From the dimension of each storage tank, which is 124-feet by
24-feet by 5.5-feet, and a maximum river velocity of three knots
(5-feet per second) (based on information obtained from the
Corps of Engineers) the uplift force on each tank is as follows:
Hydrodynamic Lift:
Where:
A
P
V
~)
C-j-Ap V /2 from Fluid Mechanics by Richard Pao
Coefficient of Lift
Area of Bottom Surface of Tank in Square Feet
Density in Slugs per foot = 1.94 for fresh water
Maximum Current Velocity
2 IT sin a from lift characteristics of a
typical Joukowsky profile as found in
Mechanics of Fluids by Hunter Rouse
The Angle of Attack of the Current on the
Storage Tank
(2 TT sin 15°) (124 x 24) (1.94) (5) 2/2
117,500 pounds
34
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Buoyancy Lift (Based on 10% Buoyance of Tank):
FB = 10% x V x D
Where:
V = Volume of Tank in Cubic Feet
D = Specific Weight of Water in Pounds per Cubic Foot
F = 10% (124 x 24 x 5.5) (62.4)
B = 102,000 pounds
Total Uplift = Hydrodynamic Lift plus Buoyancy Lift
= 117,500 pounds plus 102,000 pounds
= 219,500 pounds per tank
= 109,750 pounds per side
= 885 pounds per foot
Three rows of seven (7) piles were driven. The two outboard rows
each served one side of a tank and the center row served the load
from both tanks. 8BP36 steel piles were used throughout.
Area of pile = 10.6 square inches
Maximum pile capacity at 20 kips per square inch
= 212 kips (tension)
Length of pile 40-feet; 37-feet was driven into river bed.
Based on report dated March 6, 1968 obtained from Schnabel Engin-
eering Associates, Foundation and Soil Mechanics Consultants,
Washington, B.C., the cohesion for the initial 24-feet of pile
would be expected to be 300 pounds per square foot and for the
lower 13-feet of pile would be expected to be 1,500 pounds per
square foot.
35
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Pile Surface = 4 by 8-inches
= 32-inches
2.67-feet
Initial 24-feet = 2.67 x 0.3 x 24-feet = 19.2 kips
Final 13-feet = 2.67 x 1.5 x 13-feet = 52.0 kips
Total = 71.2 kips
Seven (7) piles per side:
Force = 124-feet x 0>885 k (uplift)
6-spaces
= 18.3 kips per pile
Safety Factor (outer row of tank)
71.2
18.3
3.9
Safety Factor (inner row of tank)
1.95
Drag:
FD
C ApV2/2 from Fluid Mechanics by Richard Pao
Where:
C = Coefficient of Drag
AD = Frontal Area of Tank in Square Feet
P = Density in Slugs per Foot
V = Maximum Current Velocity
C = 1.20 based on Value of L/D = 124/24 = 5.2
D from Mechanics of Fluids by Hunter Rouse
FD = 1.20 (24 x 5.5)(1.94)(5)2/2
3,850 pounds per side
36
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FD (Two Tanks) = 7/700 pounds
With 7 Piles = 1,100 pounds per pile
Based on cantilever of 6-feet on pile:
Momentum = 1,100 x 6
= 6,600 pounds per foot
= 79,200 pounds per inch
Stress = 79,200 pounds per inch/29.9 (section Modulus
of pile)
= 2,640 psi
2,640 psi (actual stress) _ 13 2%
20,000 psi (allowable stress)
This is satisfactory, since actual stress is less than 15% of
allowable stress.
Stresses on Piles:
Bending Stress = 2,640 psi
Tension = 18.3 kips/pile x 2 (tanks)
10.6 square inches (area of pile)
= 3,450 psi
37
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Parshall Flume
A Parshall flume is a specially shaped open channel flow section
which is installed to measure the rate of flow of water. Since
it was estimated that a maximum flow of 68-feet^ per second would
exist at the overflow, a 4-foot Parshall flume was chosen to be
the most economical for the project.
There are two water levels recorded in the Parshall flume; one
upstream and the other downstream. For a free flow, the upstream
head (H=) will be the determining factor, while the downstream
ct
head (Hb) will have a zero reading. However, whenever there is
backed-up water from downstream, submergence occurs. This occurs
when the water surface downstream from the flume is far enough
above the elevation of the flume crest to reduce the discharge.
Parshall flumes tolerate 50% to 80% submergency before the free-
flow rate is measurably reduced. Submergency ratio is the ratio
of downstream reading Hb to upstream reading Ha, or Hb/Ha.
During free flow, the discharge depends solely upon the width of
the throat, W, and the depth of water. Ha, at the gauging point.
Calibration tests show that the discharge is not reduced until the
submergency ratio Hb/Ha, expressed in percent, exceeds 70% for a
4-foot flume. When submergence occurs, a correction factor must
be subtracted from the free flow discharge rate. For all practical
purposes, the flow rate may be determined from a table (U. S.
Department of the interior, Bureau of Reclamation, Water Measure-
ment Manual , Department of the Interior, Denver, Colorado,
second edition, 1967, pp. 274-277.) specifying the head reading
Ha and a throat width of 4-feet.
The range of a 4-foot Parshall flume is 1.26 to 62.93-feet3 per
second. This rate corresponds to head readings of 0.20-feet and
2.50-feet respectively. Readings outside this range will not be
accurate, and also are beyond the range of the table. Therefore,
for a 4-foot flume, the minimum Ha reading should be at least
0.20-feet.
Unfortunately, during much of the time, the readings in the
Parshall flume were less than 0.20-feet. Since extrapolation
would be erroneous, these lower readings had to be disregarded,
since only readings 0.20-feet and above were considered. There
was no other way to determine the rate, unless, of course, a
Parshall flume smaller than one-foot were constructed. However,
the upper range of this smaller Parshall flume would then be
38
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drastically reduced. It is interesting to note here that for
1-foot to 4-foot flumes, only readings 0.20-feet and above are
considered.
One factor that confuses readings in the Parshall flume is the
presence of backed-up water in the float pipes for the Parshall
flume recorders. This back-up may be caused by stagnant water,
ground seepage, or other factors such as tide water and waves
from boats outside on the river lashing back into the seawall and
flowing back into the sewer pipes. It is, therefore, difficult
to differentiate between these factors as to which is causing
readings on the Parshall flume. One characteristic of waves from
boats outside is that this often occurs during Saturday afternoons
and Sundays.
One way to measure the amount of water going into the comminutor,
and hence to the underwater tanks, is to determine from the
reports exactly when the 24-inch butterfly valve was opened to
let water into the tank. This time could then be compared
against the Parshall flume chart to determine the total amount of
water that is let into the tanks.
Since the Parshall flume readings contain data from factors other
than storm overflow, one way to avoid backed-up water and to make
sure that the reading is only from storm overflow, is to put a
one-way gate where the sewer pipe meets the seawall. This would
prevent waves or tide water from flowing back into the sewer pipe.
Table IV indicates the flow through the Parshall flume in cubic
feet per second and in gallons per minute for corresponding head
reading at the upstream water level and no submergence. For manual
operation, to assist the operator, time is indicated for filling
each 100,000-gallon underwater storage tank for the various flow
rates.
39
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TABLE IV
TIME IN MINUTES
NEEDED TO FILL 100,OOP-GALLON TANK
4-Foot Parshall
Flume Reading
(Feet)
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
Ft.3/Sec.
1.26
1.80
2.39
3.06
3.77
4.54
5.36
6.23
7.15
8.11
9.11
10.16
11.25
12.38
13.55
14.76
16.00
17.28
18.60
19.94
21.33
GPM
566
809
1,075
1,375
1,695
2,040
2,410
2,800
3,220
3,640
4,090
4,570
5,050
5,560
6,080
6,640
7,190
7,760
8,350
8,960
9,540
Time Needed
(Minutes)
177
124
93
73
59
49
42
36
31
27
24
22
20
18
16
15
14
13
12
11
10.5
NOTE: This Table is applicable only when the Parshall flume is
not either fully or partially submerged.
40
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SECTION 7
PLANT EQUIPMENT
Parshall Flume: Leopold "Leo Lite" for channel flow measure-
ment.
Gate_s: Aluminum gates were provided for flow control at grit
chamber and at bar screen. Inlet to the plant was controlled
by a Lunkenheimer butterfly valve.
Comminutor; Worthington Corporation type 36-C unit to operate con-
tinuously and automatically to screen, cut or shred coarse solids
directly in the flowing raw sewage without requiring removal of
the screenings from the channel. The comminutor was provided
with a two horsepower vertical, squirrel cage induction motor
wound for 208 volts, three phase, 60 cycle and is of size for
flow range of 5 MGD to 19 MGD. The comminutor consists of
stationary, vertical semi-circular screen with horizontal slots
and an oscillating cutter that passes through a stationary cutter
or cutters located along the screen for the purpose of comminuting
sewage screenings. The screenings were reduced to a size that
would permit them to pass through the screen slots. The rate of
comminution was such that no undue accumulation of screenings
would result on the screen and cause excessive upstream head con-
ditions. The comminutor was provided with permanent oil lubrica-
tion. The screen consisted of replaceable steel sections and the
comminutor was so designed that the cutters could be removed for
sharpening or replacement. The stationary cutters are adjustable
so that proper rubbing contact may always be maintained. See Fig. 14,
Bar Screen; Manual screen comprised of 2-inch by 1/4-inch bars,
1-inch on center was provided for use in the event comminutor
was out of service.
Grit Chamber; A concrete structure to slow down the velocity of
flow and to remove sand and heavy particles by settling. Oils
and floating materials could be skimmed off the surface. For the
purpose of this demonstration this was accomplished by hand. In
a full scale project this could be mechanized.
Sewage Pumps; Gormann Rupp self-priming centrifugal pumps of
horizontal double volute construction, fitted with replaceable
suction check valves, replaceable wear plates, open type impeller
and double face grease lubricated mechanical shaft seal. The
41
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sewage pump has a capacity of 1000 gpm at 70-foot total head
and 9-foot lift. It is equipped with a 40-horsepower, 1750 rpm,
three phase, 208 volt motor. pumps are shown in Figures 11 and 12
The water pump has a capacity of 200 gpm at 30-foot head and
5-foot lift. It is equipped with a three horsepower, 1750 rpm,
three phase, 208 volt motor.
The main pump was used for pumping out the storage tanks to the
interceptor sewer. The sludge pump, designed for solids hand-
ling was used for pumping out grit chambers to the interceptor
sewer. The water pump was used to provide river water for test
purposes, and for wash down. This pump could also be utilized
for flushing of the underwater storage tanks.
Sump Pump; Piqua submersible pump has a capacity of 10 gpm at
70-foot head. It is equipped with a single horsepower, three
phase, 208 volt, 60 cycle motor, and a level sensor to auto-
matically control operation. This pump was installed in a pit
and was designed for pumping out any leakage on pump house
floor.
Air Compressor; Worthington Corporation package radial, air
cooled vertical, single stage, belt driven compressor has a
delivery of 175 CFM at 20 psi and is equipped with a 25-horse-
power, 1800 rpm, three phase, 208 volt motor. The compressor
provided plant air for instrumentation and for agitation of
underwater storage tank contents. Figure 13 shows air compressor.
Exhaust Fans and Louvers: Manufactured by Power Line Fan
Company were provided for forced ventilation in pump house and
in meter house.
Unit Heaters; Berko electric unit heaters were provided in pump
house. Control was provided by remote thermostats.
Electric Service Equipment; Equipment provided consisted of
Square D panelboards. Grouse Hinds heavy duty switches, plugs
and lights.
Instrumentation; Hersey-Sparling flow meters, transmitters and
recorders, and Foxboro measuring station. Belfort Instrument
Company continuous recording twelve-hour rain gauge. Figure 17
shows forward and reverse meter installation in main pipe header
line in pump house. Figure 18 shows meter recording station.
42
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Main Sewage Pump
Fig. 11
Sludge Pump
Fig. 12
43
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Air Compressor
Fig. 13
Comminutor
Fig. 14
44
-------
Main Header Line from Comminutor Chamber
Showing Pump Bypass Line
Fig. 15
Main Header Line Showing Branch Runouts
to Underwater Storage Tanks
Fig. 16
45
-------
Forward and Reverse Meter Installation
in Main Header Line
Fig. 17
Forward and Reverse Meter Recording
Station
Fig. 18
46
-------
Hose; Goodyear Rubber Company "Diversipipe" with flanged ends
was used in water for main sewage flow. Small diameter hose for
vent and air lines was Goodyear "Ortac" with quick acting couplings
matching connections at the underwater storage tanks.
Piping: Piping in pump house is Schedule 40 black steel, ASTM 120.
Underground piping is extra heavy cast iron. Compressed air
piping installed in the underwater storage tanks is PVC, Schedule
40 perforated with ends plugged. See Figures 15 and 16 for pump house
Underwater Storage Tanks: In order to obtain shortest delivery
period to meet stringent construction time schedule, standard
pillow shaped tanks were utilized. The synthetic rubber-coated
nylon fabric tanks were furnished by the Goodyear Tire and
Rubber Company. These tanks are an adaptation of the tanks that
have been used by the United States Air Force for 25-years for
oil storage.
The general specification of the pillow tank falls within
MIL-T-12260B, Amendment No. 1, with specific requirements being
as follows:
A. Physical Characteristics of the Coated Fabric
1. Weight, ounces per square yard 60 + or - 5.0 oz.
2. Breaking strength, pounds per inch
minimum both warp and fill 600 by 600 pounds
3. Adhesion (cloth to compound) pounds
per inch minimum 20 pounds
4. Tear strength, warp and fill minimum 20 by 20 pounds
5. Coated fabric thickness .065 + or -
.005 inches
B. Physical Characteristics of Coating Compound
1. Tensile Strength 1500 psi
a. Original psi minimum
2. Ultimate elongation 300%
3. All seams have a tensile strength
equal to the tensile strength of the
coated nylon fabric.
Each 100,000-gallon pillow tank was equipped with a 10-inch
flanged stainless steel inlet connection which served as both
the inlet and outlet fitting. This fitting was located on the
47
-------
bottom of the tank. Also located on the bottom of the pillow
tank was a 1-1/2-inch fitting for connection to the 3-inch PVC
aeration tubes. Air was pumped through these tubes to keep any
solids from settling to the bottom of the pillow tank. On the
top surface of each was located a 1-1/2-inch stainless steel vent
fitting. This was later changed to six (6) 1-inch vents as
described hereinafter under Section 9, Operational Description.
A 20-inch stainless steel manhole located on top of the tank
allowed easy access into the tank. All connections on the tank
were connected to the on-shore fittings with rubber hose.
The pillow tanks were strapped to a fabricated steel cradle for
permanent installation. The cradles were attached to steel piles
driven to bed rock on the bottom of the river by a patented
system of anchors to a depth of 37-feet below the river bed.
Installation of the pillow tank was easily accomplished. Nearly
1,100 yards of rubber fabric was used in the manufacture of the
tanks. The shipping crate measured 140-inches by 54-inches by
34-inches and weighed approximately 3,000 pounds. The pillow
tank was located in the center of the cradle and unrolled. Con-
nections were made, the hold-down straps connected and the tank
was ready for lowering and attachment of the cradle to the piers.
Each tank was 124-feet long by 24-feet wide and 5-1/2-feet high
when inflated. Tanks used for this project cost $14,400.00 each.
Cost included all fittings on the tank, including manhole, to
meet the requirements of the pilot plant.
Figure 19 shows one of the underwater storage tanks held in place
by cranes ready for submergence.
48
-------
Underwater Storage Tank Ready for
Submergence
Fig. 19
49
-------
SECTION 8
CONSTRUCTION COSTS
A contract was entered into on May 10, 1968 with the low bidder,
W. M. Schlosser Company, Inc. of Hyattsville, Maryland for the
construction of the Demonstration Underwater Facility in accord-
ance with plans prepared by Silver, Schwartz, Ltd. for the sum
of $341,486.00. Breakdown of contract is as follows:
1. General Conditions $1,900
2. Bond and Insurance 2,750
3. Earthwork 21,540
4. Sheet Piling and Dewatering 33,110
5. Lawn and Planting 750
6. Timber Piles on Shore 19,500
7. Off Shore Work 68,450
8. Concrete 30,860
9. Masonry 2,576
10. Miscellaneous Metal 6,770
11. Structural Steel 11.098
12. Miscellaneous General Construction 9,865
13. Painting 4,825
14. Mechanical Equipment 47,942
15. Pipe and Fittings 16,600
16. Electrical 5,500
17. Off Shore Tanks, Cradles, Hoses
and Belts 57,450
Total $341,486
1. General Conditions: Includes construction sign, temporary
toilet, telephone and field office.
2. Bonds and Insurance; Includes performance and payment
bonds as required to meet contract requirements.
3. Earthwork: Includes all shore excavation and backfill.
4. Sheet Piling; It was necessary to sheet pile the entire
shore construction area because of latent conditions
observed at the site.
5. Lawns and Planting; A requirement of the National Park
Service was to maintain green area around the project.
51
-------
6. Timber Piles on Shore: Required for the entire construction
because of soil conditions.
7. Off Shore Work; Includes dredging, installation of steel
piles, setting of tank and cradle assemblies.
8. Concrete; Includes all work necessary for construction of
flume, channels, grit chambers, pump house and meter house.
9. Masonry: Includes structure over meter house.
10. Miscellaneous Metal; Includes circular stair to pump house,
gratings and louvers.
11. Structural Steel; Includes cost of steel piles in river, and
tank anchorage system.
12. Miscellaneous General Conditions; Includes waterproofing of
structures, caulking as required, hollow metal and hardware.
13. Painting: Includes painting of exterior of pump house to
fulfill National Park Service requirements, painting of
pumps, piping and equipment.
14. Mechanical Equipment; Includes comminutor, bar screen,
pumps, meters, compressor, instrumentation, channel gates,
flume liner, automatic sampler.
15. Pipe and Fittings; Includes all lines and valves in pump
house for sewage flow, force main, compressed air, water.
16. Electrical; Includes all lighting, wiring, conduit and
outlets.
17. Off Shore Tanks and Belts; Includes underwater storage
tanks, cradles, piping and hoses in river and web belting
around tanks.
52
-------
Construction Change Orders - Charges
1. Addition of Manhole 602.51
2. Supports and Modifications to Tanks 15,472.00
3. Added Dredging 2,730.00
4. Cable Instrumentation 465.46
5. Added Grading 3,378.00
6. Spar Buoys 950.00
7. Dock Repair 450.00
8. Sewer Changes 3,000.00
9. Chains and Closures 185.00
10. Signs 117.42
11. Sodding 405.00
12. Modifications to Pillow Tanks 3,550.00
13. Raising and Lowering of Pillow Tanks 21,896.00
Total Charges $53,201.39
Construction Change Orders - Credits
1. Deleted Manhole 1,731.50
2. Deleted Concrete Wall Section 45.00
3. Butterfly Valves and Aluminum Gates 4,778.00
4. Deleted Parging 144.00
5. Deleted Explosion-Proof Motor 40.00
Total Credits $ 6,738.50
Net Construction Changes $46,462.89
53
-------
Explanation of Charges^
1. Added Manhole: A manhole was added over the baffle section
of the Parshall flume in order to provide a cleanout for
anticipated build-up of sewage and rubbish.
2. Tank Supports and Modifications; Includes various items of
concern during installation:
a. Added a 24-gauge galvanized decking in tank
cradles to support storage tanks $5,600
b. Added sprayed urethane on metal decking of
pillow tanks and around perimeter of steel
cradle to protect against pillow tanks rubbing
against decking and sides during inflation
and deflation 6,005
c. Provided a six-foot high chain link fence and
posts around cradle to protect against river
debris from damaging pillow tanks 3,027
d. Field conditions necessitated installation of
brackets to support ten-inch pipe connections
at pillow tanks to prevent sagging through
bottom of galvanized decking and installation
of suspension cables for tank manholes to
support weight of manholes when tanks are in a
deflated condition 84°
Total $15,472
3. Added Dredging; The original contract was based on 700-
cubic yards of dredging. Actual dredged material amounted
to 1,225-cubic yards. The charge is based on the additional
dredging of 525-cubic yards at $5.20 per cubic yard.
4. Instrumentation: Revisions were made to instrumentation for
transmitting flow readings to the pump house.
5. Added Grading; Additional backfill and grading was required
when it was decided to extend the grading line around the
pump house structure beyond property limits.
6. Spar Buoys; Two spar buoys were installed as per Coast
Guard requirements.
7. Dock Repair; It was necessary to repair the existing dock
and to provide safety rails for the safety of visitors to
the project.
54
-------
8. Sewer Changes: Revision was made to the force main from the
pump house to the interceptor sewer manhole.
9. Chains and Closures; It was necessary to add posts and
chains around the comminutor well to provide safety for
visitors to the installation and to provide closures at the
bar screen and comminutor to prevent solids from entering
underwater storage tanks.
10. Signs; Three "No Trespassing, Government Property" signs
were provided at the site.
11. Sodding: An additional 450-square yards of sodding was
provided beyond limits as required by the National Capitol
Park Service.
12. Modifications to Pillow Tanks; A 100-foot long wire mesh
screen in the form of cylinders approximately 12-inches in
diameter was installed down the center of each underwater
storage tank for the purpose of preventing the collapse of
the tank over the suction inlet during a pump out period.
In addition, various air vents were installed along the top
of the tanks to improve the air relief system.
13. Raising and Lowering of Pillow Tanks; During construction,
it was noted the inboard pillow tank was physically wider
than the outboard tank. Time did not permit obtaining a
replacement unit. When this tank was lowered into place in
the river bed, it was noted that the top protruded out of
the river during periods of low water condition. It was
also noted that the belts had apparently slipped and twisted,
creating a potential pressure problem on the surface of the
tank. In a meeting with representatives of Federal Water
pollution Control Administration, it was decided to raise
the inboard tank to visually inspect the tank and determine
if any damage resulted.
Following this inspection, it was found that corrective
measures were necessary to both tanks as outlined herein-
before in Change Order 12. In addition, all belts were
realigned and adjusted. Breakdown of costs for raising and
lowering tanks is as follows:
55
-------
a. Crane and Barge Rental
$1,744 per day for nine days $15,696
b. Cost to Unload Barge of Steel Piles
Prior to Bringing the Barge to the
Site 500
c. Overtime for Crane Personnel 300
d. Tug Rental, Two days at $450 900
e. Divers Cost, Nine days at $500 4,500
Total $21,896
Explanation of Credits
1. Deleted Manhole; Manhole shown on plans adjacent to rail-
road property was deleted since it interfered with railroad
communications system.
2. Deleted Concrete Wall Section; It was found that concrete
wall in grit chamber was not required for the operation of
the plant.
3. Butterfly Valves and Aluminum Gates; Substituted butterfly
valves and aluminum gates for the Armco gates originally
specified because of delivery problems.
4. Deleted parqing; Parging on concrete walls below grade at
comminutor and pump house was not required since pitch was
provided.
5. Deleted Explosion-Proof Motor; Substituted explosion-proof
comminutor motor with a fan cooled weatherproof motor
because of problems in delivery schedule.
56
-------
TABLE V
PILOT PROJECT COST
1.
a.
b.
c.
d.
e.
f .
g-
2.
a.
b.
c.
d.
3.
a.
b.
c.
d.
e.
f .
4.
Design and Construction
Detailed Plans and Specifications
Field Engineering and Inspection
Design Consultants
Construction
Construction Change
Plant Modifications
Project Management
Sub-Total
Plant Operation and Maintenance
Plant Labor
Plant Supervision
Electric Power
Plant Materials
Sub -Total
Test and Evaluation
Program Management
Program Planning
Testing and Data Collection
Laboratory Analyses
Evaluation
Reports
Sub -Total
Fee
Total program Cost
$20,364
30,750
6,652
341,486
46,463
24,630
71,260
25,800
5,526
1,271
7,538
21,050
3,250
4,740
5,982
3,820
13,376
$545,475
40,135
52,218
30,000
$667,828
NOTE: These figures are actual costs expended for this pilot
installation which includes those items not normally
reflected in an actual operating installation.
57
-------
SECTION 9
OPERATIONAL DESCRIPTION
During a severe rainstorm, the water level in the combined sewer
manhole rose above 8-inches. In this case, sewage automatically
overflowed into a 33-inch line and thence into the Anacostia
River. A recorder measured the height of the water at the man-
hole.
Overflow was diverted through a 4-foot Parshall flume for flow
measurement. Automatic recordings of the flow rate were made
continuously, 24-hours a day.
On the downstream end of the Parshall flume, an inlet line was
installed to allow a portion of the overflow to enter the grit
chamber of the pilot plant. When the meter in the line to the
underwater storage indicated full capacity in the tanks, the
24-inch butterfly valve at the inlet to the grit chamber was
closed, and the influent allowed to flow freely into the Anacostia
River. During dry weather, the 24-inch butterfly valve was placed
in the open position, ready to accept the next wet weather flow.
Inside the grit chamber, particles were reduced by the comminutor
to a maximum of 3/8-inch. However, when the comminutor was not
in use, particles 2-inches and larger were removed by a bar
screen. Drains allowed settled materials in the grit chamber to
flow to a sludge pump, discharging into a new 6-inch force main
inserted inside the 33-inch main to the interceptor sewer.
Liquid from the grit chamber flowed by gravity into the under-
water storage tanks. Liquid entering or leaving the storage
tanks was metered and recorded. After the storm subsided and
during non-peak hours, liquid was pumped from the tanks by
the sewage pump into the interceptor sewer.
Storm water in excess of the pilot plant capacity of storm water
overflow, when the system wa s shut down, took its normal course
of flow through the existing tide gate into the Anacostia River.
In order to prevent undue settlement of solids in the storage
tanks, compressed air was forced into the tanks for the purpose
of agitating any settled sludge and to enable possible pumping
out of all the contents of the storage tanks to the interceptor
main.
59
-------
The facility was manually operated to fill and empty the under-
water tanks. Samples of effluent from the sewer overflow and
from the tank discharge to the interceptor were taken at
frequent intervals during the operational period.
The samples were analyzed for the following characteristics:
a. pH
b. Suspended Solids
c. Suspended Solids - Volatile
d. Settleable Solids
e. Biochemical Oxygen Demand
f. Coliform Bacteria
g. E Coli Bacteria
h. Petroleum Products
Volumetric data was taken, recorded and analyzed at the follow-
ing points:
a. Storm water flow passing through the 33-inch overflow line.
b. Water volume passing through Parshall flume.
c. Water volume passing into or out of pump house.
The quantitative and qualitative data obtained by metering and
analysis at the facility by the rain gauge installed in the
drainage area, and the instrumentation installed in the sewers
and facility was assembled and analyzed to record the effects of
rainfall on the 33-inch outfall and the ability of this facility
to minimize discharge of storm water overflow to the Anacostia
River.
Testing without rainfall was also accomplished by introducing
river water into the system by means of a water pump. These
tests approximated tests during rainfall.
60
-------
General Operating Procedure
1. Rain charts were changed every morning if it had rained the
day before. If no rain was recorded, the charts were
changed every third day.
2. Dates were placed on all charts every day at 12:00 Midnight.
3. When sewage pump was used, electric meter reading was
recorded.
4. When overflow sewage reached the Parshall flume, the operator
was instructed to assure that the 24-inch valve was in open
position and to allow gravity flow to the underwater storage
until parshall flume recorders read "zero" if tanks did not
fill up, or to 100,000-gallons per tank, whichever came sooner,
5. Grit chambers were cleaned after each rain. Caution was
taken to make sure comminutor was turned off while cleaning.
6. Samples were taken according to the Parshall flume chart.
Two bottles were taken on each maximum and minimum point on
recorder.
Plant Operating Procedure
Operating procedure outlined herein was furnished to plant
personnel. It can be followed on Figure 20.
1. Check and read 10-inch meter for forward reading and start
recorder. Note on recording charts date and time of starts.
2. Open valves 1, 3 and 6. Make sure valve 7 is closed.
3. Open gates 16, 18 and 21 in comminutor room.
4. Make sure that 24-inch chain operated butterfly valve is in
open position to allow storm water to enter building.
5. Start comminutor.
6. Gates 20 and 22 should be closed when comminutor is in
operation.
61
-------
7. When meter and recorder reads 100,000 gallons more than
original reading, close valve 6.
8. Check and read 10-inch meter and recorder for forward read-
ing.
9. Open valve 7 for second tank.
10. When meter and recorder reads 100,000 gallons more than
second reading, close valves 7 and 1.
11. Close 24-inch chain operated valve and turn off comminutor.
12. During the filling procedure, either first or second grit
chamber may be used. When comminutor is out of service,
third chamber may be used for manual screening of particles
in the storm overflow.
13. After filling procedure is completed, grit chambers shall be
cleaned. For cleaning water, 4-inch river water pump shall
be used.
14. Before starting 4-inch pump, open valves 12 and 13.
15. Start river water pump.
16. Any one hose bibb in the grit chamber area may be used for
cleaning.
17. In order to get rid of dirt, gravel, etc., in grit chambers,
sludge pump shall be used.
18. To clean first grit chamber, open valves 9, 11 and start
sludge pump.
19. To clean second grit chamber, open valves 10, 11 and start
sludge pump.
20. When grit chambers are clean, turn off sludge pump and close
valve 9 or 10. Valve 11 may be left open at all times.
21. Close all gates and valves previously opened.
22. Before discharging the liquid from tanks, start compressor
and open air valves 24 and 25 for agitation.
62
-------
CAUTION: Discharging of liquid line into District of
Columbia sewers shall only be accomplished from 12:00 Midnight
to 6:00 A.M.
23. Open valves 6, 3, 2 and 5.
24. Check and read 10-inch meter for reverse reading and start
recorder.
25. Start sewage pump.
26. When meter and recorder reads 100,000-gallons more than
original reading, open valve 7 and close valve 6.
27. Check and read 10-inch meter for reverse reading.
28. When meter and recorder reads 100,000-gallons more than
second reading, turn off pump and close valves 7 and 2.
29. Stop air compressor.
63
-------
"1
H-
•Q
K)
o
METER
PARSHALL FLUME
OVER FLOW
SEWER
AIR
COMPRESSOR
EAR bCREEN
BUTTERFLY VALVE
GRH CHKMBER*L
PUMP
TO STORAGE
'
COMMIKIUTOR
3/4M WOSE
BIBB ' B)BE>
STORIM WATEK OVEFSFLOW DEMON 5T R A>T \ ON
NOT TO 5CA.LE
-------
Metering System
Using two meters in Parshall flume at different depths enables
measurement of the total flow from the combined overflow sewer.
The meters transmit the water level information to the recorders
in the pump room. With the use of a diagram furnished by the
meter manufacturer, it was possible to compute the submerged
flow.
A separate metering system in the pump room measured the amount
of flow into and out of the underwater storage tanks.
Sampler Operating Instructions
1. Be certain all bottles and tubing are clean.
2. Set rubber stoppers securely in the 24-bottles.
3. Place vacuum head over sampling head and start the vacuum
pump. Hold vacuum head in place until all bottles are
vacuum sealed. Vacuum is assured in each bottle if each of
the rubber tubes is collapsed (flattened).
4. Seal off each bottle by setting the switches on the switch
plate.
5. Release the vacuum head and check to see if all bottles are
evacuated and holding vacuum. Check the rubber tube to see
if each remains collapsed.
6. Set tripping arm to desired position.
7. Drop sampling head into manhole. Make sure head is sub-
merged in liquid.
8. Start sampler.
9. Record the bottle number of the first sample.
10. After sampling period, remove bottles and cover with screw
on caps. Place bottles in refrigerator.
11. For cleaning; Back flush each line with water from the
rubber stopper end and allow to dry for future use. Make
sure all solids are flushed or blown with compressed air
from sampling head and plastic pipes.
65
-------
TABLE VI
HISTORY OF OPERATION
Date
1968
12/10
12/16
12/23
12/30
1969
1/15
1/18
1/20
1/21
1/22
1/24
1/25
2/3
2/8
A./ U
2/9
2/15
2/16
2/17
2/18
2/22
2/23
2/26
3/6
3/7
3/9
3/15
3/16
3/22
3/23
3/24
3/25
3/29
3/30
Total
Rainfall
( inches^ _
F low to
Tanks
(gallons)
Began operation of
Trace
0.6
0.1
Underwater storage
0.3
0.2
0.5
0.1
Trace
0.0
Trace
0.3
78,000
5,000
Samples taken from
0.0
0.0
0.0
0.0
Realized
50,000 RW
30,000 RW
a tear ex]
Pumped
from Tanks
(qallons)
Storage in Tanks
inboard
^qallons)
Parshall flume (sample
system in place.
|
68,000
inside both
60,000
128,000
.sted in the
is discussed in detail in this
5,000
Outboard
(qallons)
1 \
s only) .
78,000
10,000
Number of
Samples
Taken
•7
i
2
15
5
7
/
A
*T
2
*•
7
7
/
tanks through manhole.
35,000
-93,000
inboard tc
t>u,uuu
ink. This
section under oper-
ational problems. Inboard tank out of s<
through April 29, 1969.
Trace
0.2
Trace
Trace
0.1
Trace
0.0
0.0
0.0
0.0
0.2
0.2
Trace
Trace
54,000 RW
53,000 RW
20,000 RW
54,000
53,000
srvice
54,000
53,000
20,000
4
"X
2
4
5
7
2
2
2
_
RW indicates river water pumped into tanks.
66
-------
TABLE VI - Continued
HISTORY OF OPERATION
Date
4/5
4/7
4/8
4/9
4/12
4/13
4/16
4/18
4/19
4/20
4/22
4/26
4/27
4/28
4/29
5/9
5/10
5/12
5/19
5/20
5/28
6/1
6/2
6/3
6/8
6/15
6/18
6/28
6/29
Total
Rainfall
(inches)
0.3
0.0
0.0
0.0
0.0
0.0
0.2
Trace
0.3
0.0
0.3
0.0
0.0
Flow to
Tanks
(gallons)
6,000
22,000 RW
24,000 RW
100,000 RW
18,000
15,000
86,000 RW
Pumped
from Tanks
(gallons)
52,000
120,000
12,000
88,000
Storage in Tanks
Inboard
(gallons)
Developed a problem in the main sewage pump
This is discussed in this section under
operational problems . Pump out of service
through May 21, 1969.
0.2
0.1
0.6
0.0
0.0
0.4
0.2
0.0
0.1
1.2
0.1
0.5
0.6
0.4
0.0
0.0
5,000
5,000
37,000
63,000 RW
1,000
6,000
9,000
11,000
7,000
35,000
2,000
78,000 RW
48,000
4,000
29,000
46,000
151,000
37,000
100,000
52,000
53,000
49,000
55,000
64,000
29,000
36,000
71,000
73,000
113,000
Outboard
(gallons)
26,000
48,000
72,000
20,000
120,000
18,000
6,000
21,000
107,000
19,000
24,000
29,000
38,000
Number of
Samples
Taken
1
6
4
2
3
7
1
1
6
11
6
4
10
4
4
7
10
67
-------
TABLE VI - Continued
HISTORY OF OPERATION
Date
7/5
7/6
7/9
7/12
7/15
7/19
7/20
7/22
7/23
7/26
7/27
7/28
7/29
7/30
8/1
8/2
8/3
8/4
8/5
8/9
8/10
8/11
8/14
8/19
8/20
8/21
8/22
8/23
9/2
9/3
9/4
9/8
9/9
9/17
9/30
Total
Rainfall
(inches)
0.2
0.2
0.0
0.2
0.0
0.4
1.8
2.0
0.0
0.0
0.8
2.3
0.0
0.0
0.3
2.4
0.6
0.0
0.3
1.0
0.8
0.0
0.0
0.2
0.2
1.8
0.0
0.0
0.2
0.2
1.7
2.6
0.0
0.4
Flow to
Tanks
(qallons)
15,000
11,000
7,000
17,000
54,000
141,000
196,000
16,000 RW
68,000
96,000
49,000
30,000
38,000
53,000
50,000
63,000
12,000
19,000
115,000
17,000
12,000
75,000
114,000
24,000
Pumped
from Tanks
(qallons)
26,000
7,000
16,000
84,000
96,000
127,000
60,000
43,000
94,000
115,000
218,000
24,000
Storage in Tanks
Inboard
(qallons)
15,000
26,000
101,000
16,000
84,000
38,000
63,000
75,000
94,000
17,000
29,000
104,000
24,000
Outboard
(qallons)
7,000
17,000
55,000
95,000
96,000
49,000
89,000
53,000
103,000
43,000
115,000
114,000
Number of
Samples
Taken
3
4
7
10
6
26
6
7
8
4
6
9
4
7
3
2
2
6
8
4
68
-------
Operational Problems
in order to expedite construction and operation of the demonstra-
tion facility, it was decided to use a standard type underwater
pillow tank as manufactured by Goodyear Tire and Rubber Company.
Since the tanks had no flotation devices or hold-down facilities,
it was necessary to fabricate steel cradles to support the tanks
as well as to provide the means for connection to the patented
system of anchors in the river bed. The tank cradles were not
designed for raising and lowering as was necessary during demon-
stration and during tank repair. Not only is this an expensive
proposition, but may result in damage because of improper crane
handling or to uneven stresses exerted on the frame.
The use of the cradle for support of the underwater storage tanks
necessitated installation of nylon straps laced diagonally across
the top of tank and fastened to the cradle. Underwater storage
tanks were installed and ready for operation in January, 1969.
It was found after a few weeks of operation that only one-half of
the design straps were installed and that those which were in
place had pulled apart, interlacing between straps, at each cross-
over point, where the straps could have been sewn would have pre-
vented the condition from occurring. When the straps pulled apart
because of the strap problem and because of air vent problems
within the tank, several air pockets developed and top of tank
sections appeared above the water surface. This was remedied at
the time by the addition of air vents at the air pockets.
Originally, this problem would not have existed if a cargo type
net were used for hold-down in lieu of the web straps.
In December, 1969 a 2-inch, 9,000-pound test nylon net, double-
stitched at each crossover point was installed over each tank.
The nets were each provided along the periphery with 74 3/4-inch
diameter triangular rings (31 per side and 6 per end). The rings
were connected underwater to the tank cradle by 5/8-inch shackles
to the existing "D" rings welded to the frame. This installation
proved successful and indicated that in future installations there
would be no need for strapping . Cost of installation of nets
was $7,500.00.
After several weeks of operation it was found that the top of the
underwater storage tanks were not level and that high points
appeared because of the strapping problem, because of the com-
pressed air used in the tank for aeration and agitation, and
because of inadequate air venting on the top of the tanks. As
69
a
-------
result of this situation it was necessary to add six (6) air vent
fittings along the top of each tank and to extend air vent piping
to Urethane floats on top of the water. This was not effective
since floats broke away because of floating debris. As a result
of this problem, it was apparent that underwater air vents would
be required to be installed within the tank to relieve air directly
into the surrounding waterway.
Six (6) equally spaced underwater diaphragm purge valves were
installed in December, 1969 on the top of tanks. These valves are
designed to operate against the pressure head of the water above
the tanks. The valves open on internal tank pressure to expel air
and gases within the tank, and further, prevents water flow from the
river into the tanks.
It was found during a pump out process on February 18, 1969, one
month after tanks were in operation, that an extensive tear existed
in the inboard storage tank. The size of the tear was too large
for an underwater repair job. Divers attempted to install clamps,
which would have been feasible if the tear had been noted earlier.
A second attempt to use large lever type scissor clamps proved
unsuccessful because of the fact that the rubber at the tear had
folded back under the tank and it was impossible to exert enough
pressure to pull the flap back into position. It was then decided
to raise the tank and to make all repairs above water. When the
tank was raised, it was noted that the tear occurred near the man-
hole location. It was presumed that the material at this point
had been weakened because of a previous force exerted by a crane
cable connected to the top of the manhole. In addition, it was
found that air binding could have occurred at the tear location
and this could have been causing additional pressure to the weak
spot, thereby causing the rupture. The installation of the new
air vents and the net over the tanks, as well as protection of the
manhole from cable or crane attachment will prevent a future
occurrence of this situation.
The repair to the tear was performed above the water between April
20, and April 29, 1969 with sheet rubber material applied with a
base material and cured with heat, much like a vulcanizing process.
Because of the size of the tear, and because of the limited
number of electric iron assemblies available, it was necessary to
set up nine times to patch the entire area. Each patch was
cured in approximately three-hours. The cost of raising the tank
from shore with two ninety-ton cranes and repairing the tear was
$9,600.00. Figures 21 and 22 show the repairs being made to the
tank tear. Figure 23 shows the clamps used in repairing small open-
ings in tanks.
70
-------
Fig. 21 Fig. 22
Repair of Large Tear in Tank
Clamps for Repair of Small Openings
in Tank
Fig. 23
71
-------
A standard type non-clogging self-priming sewage pump was used
to pump from the underwater storage tanks to the interceptor
sewer. It was noted during a pump out on April 27, 1969 that the
pump was vibrating and clattering. Investigation found that the
inlet check valve diaphragm had broken away and had clogged the
pump impeller. This subsequently was repaired by the manufacturer
on May 21, 1969 when it was found to be a defect aggravated by
some floating solid that caught up in the check valve. This is
not a normal type problem and should be a rarity for the type pump
used.
The automatic sampler at the Parshall flume was found to be in-
adequate for the requirements of the testing laboratories. The
equipment was purchased prior to construction and before any
arrangements were made for testing. Actually, during the initial
operation testing was performed in part by the F.W.P.C.A.
Analytical Services Laboratory at District of Columbia Pilot plant
and in part by The C. W. England Laboratories. The sampling
quantities required were four-times greater than that originally
contemplated. As a result, samples were taken partly with the
automatic sampler, and primarily by hand in accordance with
schedule set forth for the project. The alternate would have been
to change gears on the sampler to sample four (4) bottles at a
time. This would have reduced the effectiveness of the sampler
and would have resulted in extensive outage time because of
delivery and installation of gears. It is felt that an advanced
sampling method should be considered in future installations, such
as pump operating on a programmed time clock to operate with a
series of solenoid valves installed in each branch feeder to a
sampling container.
An altitude gauge was installed in the underwater storage tank to
record height of tank at various conditions of operation. This
gauge proved ineffective because of unevenness of top of tank and
because of variations in pressure in the tank. A possible method
for recording tank height would be a sonar device at the sea wall
for the inboard tank and one underwater for the outboard tank to
scan the tank configuration and transmit to a screen in the pump
house. This would be extremely costly and is not recommended for
the value received.
During the test period of October, 1968, it was noted that at the
conclusion of the pumping period, there existed cavitation noises
at the suction of the pump. It was also noted that pump suction
pressure had increased. This indicated a blockage in the suction
72
-------
line. The divers verified the conclusion that the tank had
collapsed over the suction inlet of the tank. As a result, the
tanks were raised on October 16, 1968 and 6-inch by 6-inch welded
woven wire mesh formed in an 18-inch diameter cylinder were
installed the length of each tank. This proved successful in pre-
vention of tank collapsing during pumping.
Site Restoration and Renovation
Inasmuch as the 33-inch overflow sewer was to be abandoned by the
District of Columbia Department of Sanitary Engineering because of
the installation of a new highway in the vicinity of the overflow
manhole, it was agreed that the pilot plant was of no further
service as a holding facility for combined sewer overflow. It was
decided that the facility, with minor modifications, could be used
by the National Capitol park Service as a holding facility and
pumping station for various marinas and industrial facilities exist-
ing or contemplated in the vicinity of the pilot plant. As a result,
various measuring equipment, instrumentation, Parshall flume, meter
house and sundry piping external to the pilot plant were removed
and the site was regraded for use by the National Capitol Park
Service.
73
-------
SECTION 10
SAMPLE COLLECTION AND ANALYSIS
During and after every rainstorm, samples were taken of combined
sewer overflow flowing through the Parshall flume. The time of
sampling had been developed as being spaced in accordance with
the stage hydrograph. In general, one sample was taken every
fifteen minutes during the first hour of rain; one sample every
thirty minutes during the second hour; and one sample every hour
thereafter until there was no overflow in the line.
Analyses carried out in the laboratory were: Coliform bacteria,
Escherica Coli bacteria, BOD (biologican oxygen demand), TOC
analysis, suspended solids, settleable solids, volatile suspended
solids, pH value and petroleum products.
From December, 1968 through June, 1969 samples of the effluent
were analyzed by the following laboratories:
1. Coliform and petroleum products tests by The C. W. England
Laboratories, Inc., Washington, D.C.
2. BOD, TOC, pH, settleable solids, suspended and volatile
suspended solids tests were made by the Analytical Services
Laboratory at the Federal Water Pollution Control Adminis-
tration Pilot Plant, Washington, D.C.
From July, 1969 through September, 1969 all testing was performed
by The C. W. England Laboratories, Inc. In this latter period
no TOC tests were performed since facilities were not available.
The results of the analyses have been plotted against time.
Sample test results and graphs are shown in Table VII,
and Figures 32 through 56 inclusive.
A complete listing of dates, rainfall and number of samples taken
during the period of operation from December, 1968 to October,
1969 may be found in Section 9, under sub-heading "History of
Operation," Table VI.
Tests were made by "Standard Methods for Examination of Water
and Waste Water," 12th edition, 1965, except as otherwise noted
herein.
75
-------
1. Total Coliform - Standard Test A.
2. Coliform - E Coli - Standard Test A with the E Coli
identified by selecting a representative number of
colonies into E. C. Medium.
3. Biochemical oxygen demand - Section III with oxygen
determined - Section III method A (Azide Modification) .
4. pH - Electrometrically adjusted to 25° C.
5. Suspended Solids - Section III, part C, using a glass
mat.
6. Settleable Solids - (Residue) - Section III, method
F 1.1 by volume using Irahoff cone.
7. Volatile Settleable Solids - (Residue) - Section III,
method D.
8. Petroleum Products - Section III, method B (grease) .
9. Total oxygen consumed - chromatographic method.
During the initial stage of the project, samples of the overflow
were taken at random, and not according to the required schedule.
However, the latter samples conformed to the schedule and showed
some basic trends. Two characteristic trends were observed.
First, bacteria count, etc. increased abruptly during the initial
onset of rain. They then decreased during the duration of the
rain, and tapered off. This verifies the assumption that during
a rainstorm, the bacteria concentration build up in the sewer is
washed down into the overflow main during the initial phase. If
this flow is diverted into a temporary storage tank during the
initial stages of rainfall, river contamination would be greatly
reduced.
Second, it was observed that bacterial count always increased
during peak sanitary sewage usage hours. This occurs in the
morning at approximately 7:30 A.M. and in the evening at
approximately 7:00 P.M. During these peak hours, bacteria con-
centration is always at its highest, particularly during light
rains. If storage during these peak periods of sanitary sewer
overflow were accomplished, a major reduction of river pollution
would result.
Biological oxygen demand was found to be greater than average
for domestic waste at the outset of the overflow period.
Samples of 400 to 600 milligrams per liter of combined sewer
overflow were recorded. Following the initial phase of approx-
imately 60-minutes of the overflow, BOD concentration dropped
to well below domestic waste average. The general range during
this period was 60 to 100 milligrams per liter. Sampling of
flow from the underwater storage tank indicated an initial BOD
76
-------
of approximately 100 milligrams per liter falling to approximately
20 milligrams per liter during the latter stages of the pumping
cycle. Higher BOD concentration in the initial draw from the tanks
is attributable to the fact that pump suction was taken from
bottom of the tank. High concentration of solids were also noted
in the initial flow from the tank.
Settleable solids were found to fall in the range of 10 to 60
milliliters per liter at the outset of overflow and dropped
rapidly to the range of 0.1 to 1.1 milliliters per liter, well
below the range of domestic sewage flow because of dilution.
Suspended solids followed the same pattern, 200 to 1,000 milli-
grams per liter at the start and 100 to 150 milligrams per liter
following the initial flush.
77
-------
TABLE
SUMMARY OF LABORATORY ANALYSES
Date
and
Time
12/22
1968
1730
1850
1915
1940
2015
2045
2115
1/18
1969
830
1020
1045
1115
1215
1300
1335
1700
1845
1900
2015
2100
2200
2230
2300
Total Coli
1,000 per
100 ml
14,000
12,000
3,500
5,100
5,700
1,600
1,400
850
240
140
40
390
80
70
60
20
81
43
11
110
64
480
E. Coli
1,000 per
100 ml
6,200
5,800
1,200
1,400
1,600
200
500
660
210
40
30
210
9
6
11
14
32
10
2
14
32
21
BOD
mg/1.
106
80
53
43
37
49
39
657
433
122
119
186
119
138
72
168
202
64
63
72
99
202
PH
7.20
7.15
7.35
7.26
7.25
7.28
7.33
6.56
7.12
7.26
7.45
7.48
7.12
7.47
6.65
7.42
7.43
7.50
7.50
7.50
7.50
7.12
Settleable
Solids
ml/1.
4.0
1.8
0.4
0.8
0.2
0.1
0.1
40.0
60.0
1.0
1.0
1.5
5.0
0.2
1.0
0.6
0.3
0.8
0.1
1.2
2.5
7.0
Suspended
Solids
mg/1.
248
148
80
62
80
151
40
1,196
1,068
100
100
240
176
152
108
132
120
108
68
78
112
480
VSS
mg/1.
NR
NR
NR
NR
NR
NR
NR
970
850
60
64
150
108
108
60
103
100
44
48
78
112
300
Petro
Products
mg/1.
52.9
41.1
27.3
25.6
24.1
84.8
24.2
161.0
-
-
• -
-
35.0
-
-
-
-
-
-
-
78.0
"
TOG
mg/1.
126
76
46
33
29
138
35
800
460
140
125
180
126
134
126
180
220
75
70
90
95
270
•J
00
-------
TABLE VII - Continued
StTMMARY OF LABORATORY ANALYSES
Date
and
2/1
1969
0630
0700
0730
[~2/2
1969
2000
2100
2200
2300
2/8
1969
2015
2035
2240
2300
2315
2345
2400
1 2/9
1969
0200
0300
1000
1400
Total Coli I
1,000 per
100 ml
52
56
30
3
3
3
520
130
54
21
19
11
4.2
3.8
6.1
5.7
4.3
E. Coli
1,000 per BOD
100 ml mq/1.
12 150
16 45
9.3 80
3 9
3 7
3 7
3 5
470 540
120 360
33 210
11 105
11 26
8.2 27
2.2 33
2.6 23
2.9 19
2.2 4
2.3 24
pH
7.10
6.98
7.13
6.70
6.88
7.21
6.61
6.58
6.90
6.96
7.02
7.02
7.01
6.88
.93
6.97
7.47
7.45
Settleable
Solids
ml/1.
.D
0.7
4.5
OT
. 1
0
0
0
70 • U
35.0
18.0
3.5
0.8
0.4
0.6
NR
NR
0
0.8
Suspended
Solids
mq/1.
A 1 Q
150
198
46
46
30
1 "iOO
844
524
656
162
124
128
86
90
108
VSS
mq/1.
NR
NR
NR
NR
NR
NR
NR
1,040
530
305
249
NR
72
60
NR
NR
NR
NR
Petro
Products
mq/1.
20
11.0
.33
51
TOC
mq/1.
135
42
66
15
12.6
11.4
12.6
740
300
210
165
39
35
39
27
26
9
26
-------
TABLE VII - Continued
SUMMARY OF LABORATORY ANALYSES
Date
and
Time
2/9
1969
Tank*
4/18
1969
2130
4/19
1969
2040
4/20
1969
0127**
0134**
0147**
4/22
1969
0300
0320
0345
0415
1735
1745
1750
Total Coli
1,000 per
100 ml
58.0
76.0
370
440
1,400
610
230
1,600
340
54
56
1,200
450
230
E. Coli
1,000 per
100 ml
56.0
62.0
29
110
570
180
28
780
110
16
27
210
56
70
BOD
mq/1.
640
118
58
136
111
16
18
400
47
28
23
320
350
57
PH
6.62
6.83
6.79
7.00
7.00
7.06
7.05
6.55
6.73
6.73
6.65
7.32
7.23
7.27
Settleable
Solids
ml/1.
38.0
0.5
0.8
1.0
5.0
0.3
0.1
32
2.5
0.8
0.2
4.0
10.0
0.5
Suspended
Solids
mg/1.
1,716
192
800
164
560
112
92
768
248
548
196
1,116
2,580
440
VSS
mq/1.
1,100
115
112
108
190
28
10
71
53
13
31
42
32
14
Petfo
Products
mg/1.
65
438
24
61
21
68.0
14.0
289.0
16.0
TOC
mg/;.
820
102
•..-.....!.
80
106
128
22
18
408
63
44
29
480
520
60
00
o
laboratory Analysis of Samples Taken from Inboard Underwater Storage Tank.
**Laboratory Analysis of Samples Taken from Outboard Underwater Storage Tank,
-------
SUMMARY OF LABORATORY ANALYSES
00
M
Date
and
Time
5/9
1969
0915
0930
0945
1005
1150
1220
5/19
1969
0815
1030
1045
1100
1130
1205
2130
2145
2200
2215
2230
2430
0145
0200
0215
0225
0330
Total Coli
1,000 per
100 ml
840
520
170
25
65
35
59
680
540
63
89
88
870
810
550
1,300
1,100
470
870
310
540
280
460
E. Coli
1,000 per
100 ml
290
250
80
4
43
24
12
270
180
50
62
71
440
380
220
400
320
80
600
90
70
130
110
BOD
ma/1.
350
125
85
43
82
83
90
120
115
115
58
130
200
140
100
100
100
34
380
60
40
20
18
PH
6.64
6.90
7.23
6.96
7.32
7.40
7.43
6.60
6.43
6.62
6.73
6.68
6.98
7.05
7.16
7.19
7.12
6.90
6.58
6.96
6.94
6.85
7.00
Settleable
Solids
ml/1.
25
3.0
5.5
1.5
4.5
0.7
1.2
6.0
3.0
8.5
0.75
0.75
2.0
2.0
7.0
7.0
NR
NR
30.0
7.0
2.5
1.3
0.8
Suspended
Solids
mg/1.
1,308
484
1,468
212
312
200
152
276
228
372
148
156
236
312
252
264
136
72
2,528
1,724
476
288
164
VSS
mg/1.
49
34
22
22
33
20
45
52
46
50
38
50
66
58
57
47
50
50
41
23
24
15
17
Petro
Products
ma/1.
-
-
51.0
-
-
24.0
-
24.0
-
-
29.0
-
-
42.0
-
-
21.0
-
-
-
-
15.0
—
TOC
mej/1.
470
156
190
50
72
46
80
252
114
158
71
94
172
166
112
102
90
33
456
168
69
39
40
-------
TABI£ VII - Continued
SUMMARY OF LABORATORY ANALYSES
Date
and
Time
6/1
1969
1930
1945
2000
2015
6/2
1969
2015
2030
2045
2100
2115
2130
2220
2235
2250
2305
6/3
1969
0050
0100
0115
0130
Total Coli
1 , 000 per
100 ml
—
—
—
-
3,000
2,200
_
1,600
1,800
3,000
2,000
..
1,500
500
100
40
300
100
E. Coli
1,000 per
100 ml
_
-
600
850
-
700
400
800
850
_
250
90
35
20
80
35
BOD
mg/1.
1,040
1,200
800
580
330
360
390
370
380
350
170
300
200
170
12
12
12
13
pH
6.15
6.14
6.46
6.72
5.50
6.08
6.90
7.08
7.45
7.17
6.53
6.25
6.35
6.53
7.11
6.92
7.20
7.20
Settleable
Solids
ml/1.
13.0
10.0
1.2
0.2
3.0
2.5
3.0
2.5
2.0
2.0
5.0
17.0
8.0
5.0
0.3
0.4
0.1
0.1
Suspended
Solids
mg/1.
1,560
1,360
300
120
328
344
316
260
224
212
716
2,820
2,540
1,930
92
88
44
40
VSS
mg/1.
640
530
100
16
161
150
136
112
108
108
243
740
762
365
O f\
20
20
12
16
Petro
products
mg/1.
—
-
-
—
—
—
—
—
—
—
—
—
~
™
•~
TOC
mg/1.
840
880
630
410
T O (\
290
280
270
300
250
240
130
240
230
260
1 fi
J.O
•"* n
21
16
15
00
N)
-------
TABLE VII - Continued
SUMMARY OF LABORATORY ANALYSES
Date
and
Time
6/15
1969
1345
1400
1415
1430
1445
1500
1515
6/18
1969
1305
1320
1350
1415
2215
2230
2245
2300
2315
2330
Total Coli
1,000 per
100 ml
1,600
740
590
190
46
73
72
3,800
2,700
240
230
910
840
570
980
480
360
E. Coli
1,000 per
100 ml
750
320
330
74
13
21
24
940
540
100
90
180
300
180
320
110
150
BOD
mcr/1.
500
480
530
290
280
80
70
340
410
50
54
110
95
100
110
90
70
PH
6.37
6.33
6.35
7.16
7.11
6.95
6.95
6.88
6.43
6.75
6.83
6.64
6.70
6.70
6.67
6.67
6.72
Settleable
Solids
ml/1.
11.0
16.0
17.0
1.2
1.5
1.8
1.5
20
40
1.5
0.5
6.5
5.5
4.5
6.5
3.0
3.0
Suspended
Solids
mg/1.
1,456
1,332
1,428
264
220
508
500
544
1,844
228
136
296
316
536
732
812
728
VSS
mg/1.
35
36
40
33
29
20
25
76
60
39
33
51
38
32
38
27
25
Petro
Products
mq/1.
62.0
—
—
—
11.0
"
1 o r\
130
—
12
—
—
34
—
—
23
"
TOC
mg/1.
c f^r\
DUU
575
375
204
196
140
70
A AC
*±Uo
700
51
44
118
92
108
138
120
112
03
W
-------
TABLE VII - Continued
SUMMARY OF LABORATORY ANALYSES
Date
and
Time
7/1
1969
1530
1545
1600
1615
7/20
1969
1345
1400
1415
1730
1745
1800
1815
7/22
1969
1730
1745
1800
1830
1900
1930
2000
2030
2100
2200
Total Coli
1,000 per
100 ml
530
1,200
1,300
2,100
2,400
2,100
2,900
1,300
1,100
1,900
2,900
3,600
1,200
1,600
1,400
640
200
140
680
360
450
E. Coli
1,000 per
100 ml
180
460
410
620
920
840
410
160
380
240
410
700
260
280
460
170
30
10
220
20
60
BOD
mg/1.
388
335
429
175
316
139
183
222
66
35
188
54
65
25
45
19
75
65
60
65
80
PH
6.28
6.30
6.42
6.20
6.82
7.21
6.82
6.58
6.62
6.42
6.68
6.52
6.58
6.50
6.28
6.08
6.15
6.22
6.20
6.22
6.41
Settleable
Solids
ml/1.
16.0
12.0
15.0
6.0
12.0
2.0
3.5
7.5
2.5
2.0
7.5
6.0
0.8
0.8
0.7
2.0
0.5
0.5
1.0
0.5
0.7
Suspended
Solids
mg/1.
1,020
888
940
216
1,112
316
366
602
598
582
898
1,492
382
462
232
448
262
322
158
266
136
VSS
mg/1.
584
510
536
48
552
210
212
180
168
160
352
260
84
276
62
140
194
86
40
70
88
Petro
Products
mg/1.
54
-
—
15
—
-
13
-
—
—
3
""
—
8
—
—
-
—
3
—
"
TOC
mg/1.
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
00
-------
CD
TABLE VII - Continued
SUMMARY OF LABORATORY ANALYSES
Date
and
Time
8/9
1969
2115
2130
2200
2300
2330
2400
8/10
1969
0100
0130
0230
0330
0430
0500
0530
0600
0700
8/19
1969
1900
1915
1930
1945
Total Coli
1,000 per
100 ml
970
400
800
920
920
840
6,100
5,300
6,200
6,500
6,500
5,300
6,600
6,500
7,100
620
930
360
300
E. Coli
1,000 per
100 ml
170
160
120
70
50
120
810
760
810
510
790
540
840
710
460
360
410
160
160
BOD
mg/1.
180
50
60
80
40
80
120
140
90
60
90
110
70
70
60
640
530
110
120
PH
6.50
6.57
6.49
6.41
6.38
6.42
6.70
6.71
6.68
6.70
6.71
6.75
6.70
6.72
6.72
5.98
6.02
6.12
6.09
Settleable
Solids
ml/1.
1.3
0.4
1.1
1.2
0.7
1.1
0.1
1.1
0.1
0.1
1.0
2.5
0.1
0.1
0.1
29.0
24.0
1.4
0.9
Suspended
Solids
mq/1.
712
218
266
364
586
386
90
102
44
48
112
74
60
52
54
11,062
8,212
1,030
632
VSS
mq/1.
218
98
126
182
182
160
c n
DU
64
24
28
80
54
32
24
30
3,774
1,230
172
184
P«tro
Products
mg/1 .
—
8
—
—
5
^
~
7
_
—
w
4
•"
"
—
69
""
TOC
mg/1.
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
-------
TABLE VII - Continued
SUMMARY OF LABORATORY ANALYSES
Date
and
Time
8/20
1969
0230
0315
0345
0445
0545
0645
0730
8/21
1969
0005
0030
0130
9/9
1969
0100
0115
0130
0145
0200
0230
Total Coli
1,000 per
100 ml
110
90
80
60
70
50
40
160
190
130
380
260
340
70
80
20
E. Coli
1,000 per
100 ml
30
20
30
40
40
20
20
60
80
60
90
40
90
1
0.8
0.3
BOD
mg/1.
130
90
100
100
90
80
80
40
70
60
85
25
45
35
25
95
PH
6.32
6.52
6.68
6.78
6.85
6.82
6.82
6.42
6.22
6.31
6.32
6.30
6.28
6.22
6.32
6.19
Settle able
Solids
ml/1.
0.2
15.0
9.5
1.1
23.0
3.4
29.0
0.1
0.1
0.1
3.0
1.5
0.9
0.8
0.8
0.3
Suspended
Solids
mg/1.
148
2,372
802
418
1,302
684
2,970
18
28
36
706
548
288
176
158
122
VSS
mg/1.
112
234
164
118
338
134
326
0
16
24
168
176
136
74
86
58
Petro
Products
mg/1.
21
-
-
25
-
-
54
-
19
—
—
17
-
-
-
19
TOC
mq/1.
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
NR
03
-------
SECTION 11
HYDROLOGY
Collection of rainfall data was taken by a recording rain gauge
placed on the roof of the building housing the grit chambers and
comminutor. The gauge was manufactured by the Belfort Instrument
Company and was of the continuous recording type. Twelve
hour strip charts were changed daily. These strip charts were
used directly in obtaining rainfall intensity and duration for
the construction of the hyetographs found in Figures 32 to 56.
It must be noted here that only in the last four months of the
demonstration period was rainfall sufficient to run meaningful
sampling and testing. Table VIII summarizes rainfall activity
during the operation of the project. Original termination date
for the project was June 30, 1969. This was extended to Septem-
ber 30, 1969 to take advantage of the summer rains. The rainfall
summary chart indicates the decision was wise.
A liquid level recording station was located near Barney Circle
beside a manhole to measure the height of water in the storm
sewer. During dry weather flow, the water level was normally
found to be below 8-inches. In this case, the water flowed into
the existing 72-inch interceptor sewer and thence to the treat-
ment plant. However, during peak usage hours or during a heavy
rainstorm, the water level was found to rise well above 8-inches.
In this case, the water overflowed into a 33-inch pipe, through
the par shall flume, and then either to the comminutor room or to
the river.
A circular chart with a capacity of seven-days measured the
height of the water on a continuous basis, 24-hours a day. The
chart was changed at least once a week. From the chart, could
be determined the time of day when the water level was above
8-inches.
The record of stage in the overflow manhole not only shows when
overflows occur, but could be used to estimate the flow diverted
from this manhole to the interceptor sewer.
The recording meter was run by nitrogen gas in a tank. Since
there was frequent trouble with the nitrogen tank, such as leak-
age, etc., readings on the chart were sometimes erratic or not
recorded. It could be gathered from the charts that during peak
usage hours, the water level in the pipe always was at its peak.
87
-------
TABLE VIII
RAINFALL SUMMARY
Month
December, 1968
January, 1969
February, 1969
March, 1969
April, 1969
May, 1969
June, 1969
July, 1960
August, 1969
September, 1969
Total Rain-
fall (inches)*
2.22
1.69
2.08
1.60
1.71
1.20
3.46
9.44
6.98
5.07
Record Mean
(inches)
2.89
2.70
2.58
3.45
2.88
3.88
3.30
3.85
4.84
3.15
Rainfall
(inches)**
0.8
1.40
2.85
1.60
1.8
1.9
3.6
5.95#
6.3
5.30
* From local climatological data, U. S. Department of Commerce
** Site data
# Rain gauge out of order part of the month.
88
-------
To determine overflow condition, a recording device measures the
height of the water in the overflow manhole. The results of the
data are then plotted against a consecutive time interval. This
indicates how intensity of rainfall affects the amount of overflow
effluent from the 33-inch pipe. An indication that a rain storm
always causes overflow to the river will again justify diversion
of the overflow to temporary storage in the underwater tanks.
However, other factors may also cause an overflow. It seems that
usage at peak hours (0700 to 0800, and 1800 to 1900) even during
"dry" days will also affect overflow, and hence increase pollution
to the river.
Figures 24 to 31 show the plotting of the height with respect to
time in the overflow manhole for various overflow conditions.
& rain gauge was installed at the site to record the amount of
rainfall in the area. Table IX indicates total rainfall, total
anticipated flow from the drainage area, based on a runoff factor
of 0.75 and actual combined sewer flow through the Parshall flume.
It is to be noted that flow through the flume, normally is less
than total expected flow, since excess is carried by the interceptor
sewer.
At times the flow through the flume exceeds anticipated flow. This
phenomenon can be attributed to abnormal water usage, particularly
during summer months, for lawn sprinkler systems, pools, air con-
ditioning, and fire-fighting.
Based on the information of Table IX , the total discharge flow
through the Parshall flume is practically the total estimated flow
from the drainage area.
The total storage during the operational period of the pilot plant
from January through September, 1969, was 1,600,000-gallons of
diverted overflow or approximately 10% of the total flow. If
2,000,000-gallons of storage were provided instead of the 200,000-
gallons that was used for this pilot project, no overflow would
have reached the Anacostia River. Two million gallons of storage,
which can be obtained with the installation of four 500,000-gallon
tanks would be of sufficient size to accommodate the maximum con-
dition of September 8, 1969 at which time 2.6-inches of rain fell
with a flow of 1,850,000-gallons measured at the Parshall flume.
89
-------
1500
1700 1600
Q.OQQ 1\QQ
TIME
23OO 24QO OlOO
OVERFLOW MANHOLE
FIG. 24
90
-------
r
o
UJ
X
1.
90
e>o
70
6O
50
40
30
20
IO
o
/
/
7
/
J
*sj
0900 f2
W
\
XN
k
IV
/\.
i i
,OO ' I7OO 2lOO OIOO O5OO
TIME
OVERFLOW MANHOLE
FIG. 2.5
91
-------
UJ
X
1.
.90
• 80
.70
.40
• 3O
.20
.10
.0
P-^HMM^*
/"
/
_/—
A
h/ ^
I
1
V
2OOO 22OO 24OO 02OO O4OO IOOO
TIME
OVERFLOW MANHOLE
MOO
1200
DATE^S!^^
FIG. 26
92
-------
2 FT
1.6
.1.4
X
.1.0
.08
.04
,02
.0
4000
2IOO
11OO
2300
TIME
24OO
01OO
O2OO
OVERFLOW MANHOLE
DATE
FIG. 2.7
93
-------
UJ
X
I7OO >80Q ' »9OO 20 OO 2IOO
TIME
OVERFLOW MANHOLE
2.2OO
FIG. 26
94
-------
t-
z
UJ
I
z.o
1.6
i.fe
- 1.4
. 1.2.
I.O
.08
.06
-02
o
1
7
A
A
^
A
A
A
V.
\
^-.
— —
2.IOO 2^00 23OO24OO OlOOOQOO O3QO O4OO O50O OfcOO
TIME
OVERFLOW MANHOLE
DATE
FIG.
95
-------
I FT
OVERFLOW MANHOLE
8-20-49
FIG. 30
96
-------
u.
i
OIOO
0130
02 OO
0230
03OO
0330
TIME
OVERFLOW MANHOLE
97
FIG. 31
-------
TABLE IX
HISTORY OF RAINFALL AND FLOW THROUGH PARSHALL FLUME
Date
1969
1/18
1/20
— •/
1/21
^~f ^ ^
1/22
2/8
/
2/23
3/24
3/25
4/5
/
4/16
* / ^ ^
4/22
4/28
* / ^ »*
4/29
5/9
™* /
5/19
** f ^
5/20
6/1
^**
6/2
V/ "-
6/3
%^/ ^
6/8
6/15
6/18
Total
Rainfall
(inches)
0.3
0.2
0.5
0.1
0.3
0.2
0.2
0.2
0.3
0.2
0.3
0.2
0.1
0.6
0.4
0.2
0.1
1.2
0.1
0.5
0.6
0.4
Total Area
Drainage
(gallons)
180,000
120,000
300,000
60,000
180,000
120,000
120,000
120,000
180,000
120,000
180,000
120,000
60,000
360,000
240,000
120,000
60,000
720,000
60,000
300,000
360,000
240,000
Flow Through
Flume
(gallons)
280,000
85,000
220,000
25,000
170,000
35,000
102,000
80,000
125,000
45,000
102,000
64,000
35,000
245,000
170,000
90,000
42,000
600,000
38,000
235,000
280,000
320,000
98
-------
TABLE IX - Continued
HISTORY OF RAINFALL AND FLOW THROUGH PARSHALL FLUME
Date
7/5
7/6
7/12
7/19
7/20
7/22
7/27
7/28
8/1
8/2
8/3
8/5
8/9
8/10
8/19
8/20
8/21
9/2
9/3
9/4
9/8
9/17
Totals
Total
Rainfall
(inches
0.2
0.2
0.2
0.4
1.8
2.0
0.8
2.3
0.3
2.4
0.6
0.3
1.0
0.8
0.2
0.2
1.8
0.2
0.2
1.7
2.6
0.4
27.8
Total Area
Drainage
(gallons)
120,000
120,000
120,000
240,000
1,080,000
1,200,000
480,000
1,380,000
180,000
1,440,000
360,000
180,000
600,000
480,000
120,000
120,000
1,080,000
120,000
120,000
1,020,000
1,560,000
240,000
16,680,000
Flow Through
Flume
(gallons)
146,000
160,000
115,000
212,000
1,700,000
1,350,000
275,000
1,400,000
240,000
1,200,000
280,000
80,000
380,000
395,000
86,000
135,000
1,250,000
125,000
150,000
1,650,000
1,850,000
230,000
16,796,000
99
-------
SECTION 12
DISCUSSION
The purpose of the project was to divert a part of the combined
sewer overflow into the Anacostia River to temporary storage in
two 100,000-gallon underwater storage tanks. After a storm sub-
sides and at non-peak usage hours, waste water in the storage tanks
is pumped back through a force main to the sewage treatment plant.
Application of this kind of process could reduce and eventually
eliminate contamination of the river.
A Parshall flume was installed along the path of the overflow main
to measure the flow rate of the combined sewer. Analyses as to the
contents of the effluent were also performed. These characteristics
were analyzed: Coliform Bacteria, Escherica Coli Bacteria, sus-
pended solids, settleable solids, percent of volatile suspended
solids, BOD and TOC count, and pH value of the effluent.
One purpose of the analyses was to determine whether or not there
was a significant increase in the pollution characteristics
immediately after the beginning of a rainfall when the additional
rain water helps overflow the pipe. If this increase were sig-
nificant, then diverting the overflow sewer, at least during the
initial part of a storm, to the underwater storage tanks instead
of to the river would greatly reduce river contamination.
Graphs were prepared to show the various reading of bacteria
count, etc., against the time the samples were taken during and
after a rainfall. From the graph, fluctuations as to the various
readings can be observed with respect to time. On the graphs
were shown the discharge hydrograph and rainfall curve in order
to study how the character of the overflow fluctuates according
to the intensity and duration of rainfall. The effectiveness of
the diversion of the overflow sewer to temporary storage in the
underwater tanks will thus be demonstrated.
Measurements were also taken of the height of water in the over-
flow sewer manhole. During regular days, when the level is
below 8-inches, combined sewer flows to an interceptor main and
then on to the treatment plant. However, during peak usage hours,
or during a severe rainfall, the water may rise above 8-inches,
and overflow into the river. However, in this facility flow has
been diverted through a Parshall flume, a comminutor room, a
pump house, and then to temporary storage into two underwater
tanks until the storm subsides.
101
-------
Figures 32 to 56 show discharge hydrographs, hyetographs and
corresponding fluctuations in Coliform bacteria, Escherica Coli
bacteria, BOD, TOG, suspended solids, settleable solids, volatile
suspended solids and pH value.
It is noted that except for pH values, fluctuations of water sample
characteristics are fairly uniform. For purpose of discussion,
only the BOD fluctuations are analyzed; the others are similar.
BOD Analysis
12/22/68
1/18/69
2/8/69
6/2/69
7/22/69
The sharp drop in BOD from 110 to 35 milligrams
per liter is noted during initial overflow. The
sharp increase that occurred at 9:00 P.M. can be
attributed to the coincidence of sanitary flow
and rainfall.
The sharp drop in BOD from 600 to 120 milligrams
per liter is noted during the initial overflow.
Decrease to 70 milligrams per liter over the
ensuing seven hours of overflow is erratic, but
continuous. Between 6:00 P.M. and 7:00 P.M.
there was a sharp increase to 200 milligrams per
liter because of domestic sewage flow.
BOD decreased continuously from 600 to less than
10 milligrams per liter over the entire period
of overflow. A slight rise in BOD to 20 milli-
grams per liter is noted during morning hours of
February 9, 1969.
Decrease of BOD from 8:30 P.M. to 11:00 P.M. was
moderate (from 380 to 180 milligrams per liter)
because of minimal overflow. Drop off to
12 milligrams per liter was severe during balance
of overflow.
Overflow occurred from 5:30 P.M. to 10:00 P.M.
BOD is erratic between 20 and 80 milligrams per
liter because of concurrence of overflow with
domestic sewage flow.
102
-------
8/9/69
8/20/69
9/8/69
BOD decreased from 180 to 50 milligrams per liter
during initial overflow. Increase to 80 milli-
grams per liter is noted at start of second over-
flow peak and further increases to 150 milligrams
per liter at third overflow peak. Continuous
drop off then occurs over balance of the overflow.
This behavior pattern between the hours of 9:30
P.M. and 1:30 A.M. cannot be attributed to
coincidental domestic flow, but to heavily laden
lines which were not completely flushed with the
initial overflow.
BOD decreased from 140 to 80 milligrams per liter
in a steady pattern during the overflow from
2:30 A.M. to 7:00 A.M.
BOD decreased from 85 to 25 milligrams per liter
during initial overflow; the increased sharply
during second surge.
TOG Analysis
It was noted the pattern was the same as for BOD, therefore, no
further discussion is warranted.
103
-------
DISCHARGE HYDROGRAPH, HYETOGRAPH
AND OVERFLOW WASTE WATER SAMPLE ANALYSIS
a
K
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OD
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50
45
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SO
25
20
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74
7.2
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12-22-
TIME
Fig. 32
104
-------
DISCHARGE HYDROGRAPH, HYETOGRAPH
AND OVERFLOW WASTE WATER SAMPLE ANALYSIS
EMDED
:
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soo
40G
IOC
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toe
7O
BO
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JU6PEVDED SOL ID 2
SEAJTLEA6LE SOLIDS
SOLIDS
4.0
3.0
2.0
1.0
6.6
O. 7
0.&
0.6
0.4
:..-
O.I
-,
•
- j
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s
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Fig. 33
105
-------
DISCHARGE HYDROGRAPH, HYETOGRAPH
AND OVERFLOW WASTE WATER SAMPLE ANALYSIS
.
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• :
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106
Fig. 34
-------
DISCHARGE HYDROGRAPH, HYETOGRAPH
AND OVERFLOW WASTE WATER SAMPLE ANALYSIS
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DISCHARGE HYDROGRAPH, HYETOGRAPH
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Fig. 53
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DISCHARGE HYDROGRAPH, HYETOGRAPH
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Fig. 54
-------
DISCHARGE HYDROGRAPH, HYETOGRAPH
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127
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DISCHARGE HYDROGRAPH, HYETOGRAPH
AND OVERFLOW WASTE WATER SAMPLE ANALYSIS
-
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Fig. 56
128
-------
SECTION 13
ACKNOWLE DGEMENTS
This demonstration facility was carried out by the Underwater
Storage, Inc., Silver, Schwartz, Ltd. Joint Venture under con-
tract No. 14-12-139 for the Federal Water Pollution Control
Administration, Department of the Interior.
The particular concept of underwater storage of combined sewer
overflow as herein reported was originally conceived by
Dr. Harold G. Quase, President of Underwater Storage, Inc.
Proprietary items used in the formulation of this project are
based on patents assigned to Underwater Storage, Inc., by
Dr. Quase.
Acknowledgement is made of the support and assistance of those
who participated directly in this effort:
Mr. Grover E. Steele and Mr. Robert Viklund of the National
Capitol Park Service, Department of the Interior, for their
efforts in all aspects of construction and operation of the
project.
The Goodyear Tire and Rubber Company, Industrial Products Divi-
sion for the expeditious manner in which the underwater storage
tanks were fabricated and delivered to the site.
Commander John A. Dearden, United States Coast Guard,for his
assistance in establishing navigational aids at the project.
Mr. G. J. Maliszewski of the Potomac Electric power Company for
his personal efforts in providing electric service to the site on
short notice.
Dr. Harold M. Windlan of The C. W. England Laboratories, Inc. for
giving the project immediate service in processing of chemical
analysis of waste samples.
The Analytical Services Laboratory at the Federal Water Pollution
Control Administration Pilot Plant, Washington, D.C. for its
assistance in chemical analyses through the initial phase of the
project.
129
-------
Mr. Howard L. Keller of Scullen, Keller and Marchigiani for
structural design of land structures.
Mr. Duncan Gray, Consulting Engineer, for structural design of
underwater facilities.
Mr. James J. Schnabel of Schnabel Engineering Associates for his
report on soils and foundations.
Mr. Herbert G. McDonald of McDonald, Williams and Marshall for
architectural design of pump house.
Penniman and Browne, Incorporated for test borings and river
soundings.
Special thanks are given to Mr. George Kirkpatrick and
Mr. William Rosenkranz of Federal Water Pollution Control Admin-
istration for their comments during the course of the program,
which provided valuable guidance in the evaluation of the system.
The project was administered and supervised by Underwater
Storage, Inc.; Dr. Harold G. Quase was Project Director, and
Mr. H. C. John Russell was Project Supervisor.
The project was designed and operated by Silver, Schwartz, Ltd.
Mr. Sidney A. Silver, P.E. was Chief Engineer; Mr. Harold
Schwartz, P.E. was Design Engineer, and Mr. Irving T. Read was
the Field Engineer.
130
-------
SECTION 14
REFERENCES
American Public Health Association. Standard Methods for
Examination of Water and Wastewater. New York, 1965.
Babbitt and Baumann, Sewerage and Sewage Treatment. New York,
John Wiley, 1967.
Construction Cost Index. Engineering News Record, November,
1969.
D. C. Sanitary Sewer Department. Sewer Separation Program, 1966.
Laurenson, Schulz and Yevdjevich, Research Data Assembly for
Small Watershed Floods. Colorado State University,
September, 1963.
Pao, Richard H.F., Fluid Mechanics. New York, John Wiley, 1961.
Rouse, Hunter, Mechanics of Fluids. New York, John Wiley, 1946.
Seelye, Elwyn E., Data Book for Civil Engineers, Vol. I, "Design",
New York, John Wiley.
Sullivan, Richard H., "Problems of Combined Sewer Facilities and
Overflows", Journal, Water Pollution Control Federation,
Vol. 41, January, 1969.
U. S. Bureau of Reclamation, Water Measurement Manual, 1967.
U. S. Federal Water Pollution Control Administration. Problems
of Combined Sewer Facilities and Overflows, 1967.
Water Pollution Control Federation. Design and Construction of
Sanitary and Storm Sewers. Manual of Practice No. 9.
131
-------
SECTION 15
PATENTS AND PAPERS
Patent No. 3,114,468 - H. G. Quase assignor to Underwater
Storage, Inc. "Collapsible Container," dated
December 17, 1963.
Patent No. 3,114,384 - H. G. Quase assignor to Underwater
Storage, Inc. "Underwater Storage System," dated
December 17, 1963.
Patent No. 3,155,380 - H. G. Quase assignor to Underwater
Storage, Inc. "Buoyant Flexible Container and Underwater
Anchorage Therefor," dated November 3, 1964.
Patent No. 3,187,793 - H. G. Quase assignor to Underwater
Storage, Inc. "Amphibious Underwater Storage System,"
dated June 8, 1965.
Paper prepared by Underwater Storage, Inc., "Underwater Storage
of Overflow from Combined Sanitary and Storm Water Sewers."
Paper prepared by Underwater Storage, Inc., "Demonstration
Underwater Storm Sewer Overflow and Storage Facility."
133
-------
SECTION 16
APPENDIX
Grading plan
Borings and Tank Location Plan
Storage Tank Pile and Frame Layout
Meter and Pump House Elevations
project Piping Distribution
Overflow Sewer Plan and Site Plan
parshall Flume Plan and Sections
parshall Flume Details
Comminutor and Pump House Plans
Pump House Piping and Valve Plan
pump House Electrical Plan
Comminutor and Pump House Structural Plans
Beam and Pile Cap Schedules
135
-------
Grading Plan
DOOPs S> U O K
MS fa. i a>LJC.J<
oo c.ojcR.£Te
136
-------
F
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137
-------
Borings and Tank Location Plan
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139
-------
Storage Tank Pile and Frame Layout
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140
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141
-------
Meter and Pump House Elevations
(PP.OUT)
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144
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145
-------
Overflow Sewer Plan and Site Plan
SE\A/ER
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Beam and Pile Cap Schedules
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BIBLIOGRAPHIC: Underwater Storage, Inc., Silver, Schwartz, Ltd., Joint Venture.
Controf of Pollution by Underwater Storage FWPCA Publication DAST 29.
ABSTRACT: A pilot plant was designed, constructed and operated to asses the feasibility of
providing a facility for the collection, treatment, storage and final disposition of a portion
of the storm overflow from a combined sewer system serving a thirty-acre drainage area
in Washington, D.C. A Parshall flume was installed in the overflow line for measurement
of flow rates and determination of total overflow volume. A portion of the overflow
was diverted to the pilot plant through grit chambers and a commirtutor. Flow was
stored in two 100,000-gallon underwater bags fabricated of nylon reinforced synthetic
rubber and fastened to the river bed by a system of patented anchors. During the period
of storage, compressed air was delivered to the tanks for agitation of the solids. Follow-
ing cessation of the storm, contents of the bags were pumped to the interceptor sewer
for delivery to the District of Columbia Sewage Treatment Plant at Blue Plains. Flow
into and out of each underwater storage tank was metered and recorded. Samples of the
combined sewage overflow discharged to the bags and pumped discharge from the bags
were collected and subjected to laboratory analyses. During the operation period from
January through September, 1969, a total of 1,600,000-gallons of diverted overflow from
38-storms was stored in the tanks. In addition, 600,000-gallons of river water was pump-
ed into the underwater storage tanks for testing during dry weather periods. The total
amount stored was pumped to the interceptor sewer in 26-separate pump out periods, The
cost of the pilot plant was $341,480.00, or $1.70 per gallon of storage. This included
facilities for testing, samples and flow measurement. Estimates for larger installations,
without these special requirements range from 28.24 to 14.6* per gallon for plants with
storage from two to twenty million gallons. The project demonstrated that temporary
storage of overflow from combined sewers in underwater rubber storage tanks is feas-
ible and may, under suitable conditions, be affective in eliminating direct, untreated
discharge of combined sewage into surface waters during storm periods. Drainage area
to be served, land use, nature of storm events, and other factors must be considered
when planning an underwater storage facility.
II
~ ~ _. ^ _ _ _ _-
't^
BIBLIOGRAPHIC: Underwater Storage, Inc., Silver, Schwartz, Ltd., Joint Venture.
Control of Pollution by Underwater Storage FWPCA Publication DAST 29.
ABSTRACT: A pilot plant was designed, constructed and operated to asses the feasibility of
providing a facility for the collection, treatment, storage and final disposition of a portion
of the storm overflow from a combined sewer system serving a thirty-acre drainage area
in Washington, D.C. A Parshall flume was installed in the overflow line for measurement
of flow rates and determination of total overflow volume. A portion of the overflow
was diverted to the pilot plant through grit chambers and a comminutor. Flow was
stored in two 100,000-gallon underwater bags fabricated of nylon reinforced synthetic
rubber and fastened to the river bed by a system of patented anchors. During the period
of storage, compressed air was delivered to the tanks for agitation of the solids. Follow-
ing cessation of the storm, contents of the bags were pumped to the interceptor sewer
for delivery to the District of Columbia Sewage Treatment Plant at Blue Plains. Flow
into and out of each underwater storage tank was metered and recorded. Samples of the
combined sewage overflow discharged to the bags and pumped discharge from the bags
were collected and subjected to laboratory analyses. During the operation period from
January through September, 1969, a total of 1,600,000-gatlons of diverted overflow from
38-storms was stored in the tanks. In addition, 600,000-gallons of river water was pump-
ed into the underwater storage tanks for testing during dry weather periods. The total
amount stored was pumped to the interceptor sewer in 26-separate pump out periods The
cost of the pilot plant was $341,480.00, or $1.70 per gallon of storage. This included
facilities for testing, samples and flow measurement. Estimates for larger installations,
without these special requirements range from 28.2* to 14.6* per gallon for plants with
storage from two to twenty million gallons. The project demonstrated that temporary
storage of overflow from combined sewers in underwater rubber storage tanks is feas-
ible and may, under suitable conditions, be effective in eliminating direct, untreated
discharge of combined sewage into surface waters during storm periods. Drainage area
to 6e served, land use, nature of storm events, and other factors must be considered
when planning an underwater storage facility.
ACCESSION NO:
KEY WORDS:
Storm Overflow
Combined Sewers
Underwater Storage
Hydrology
Pumping Stations
ACCESSION NO:
KEY WORDS:
Storm Overflow
Combined Sewers
Underwater Storage
Hydrology
Pumping Stations
BIBLIOGRAPHIC: Underwater Storage, Inc., Silver, Schwartz, Ltd. Joint Venture
Control of Pollution by Underwater Storage FWPCA Publication DAST 29.
ABSTRACT: A pilot plant was designed, constructed and operated W asses the feasibility of
providing a facility for the collection, treatment, storage and final disposition of a portion
of the storm overflow from a combined sewer system serving a thirty-acre drainage area
in Washington, D.C. A Parshall flume was installed in the overflow line for measurement
of flow rates and determination of total overflow volume. A portion of the overflow
was diverted to the pilot plant through grit chambers and a comminutor. Flow was
stored in two 100,000-gallon underwater bags fabricated of nylon reinforced synthetic
rubber and fastened to the river bed by a system of patented anchors. During the period
of storage, compressed air was delivered to the tanks for agitation of the solids. Follow-
ing cessation of the storm, contents of the bags were pumped to the interceptor sewer
for delivery to the District of Columbia Sewage Treatment Plant at Blue Plains. Flow
into and out of each underwater storage tank was metered and recorded. Samples of the
combined sewage overflow discharged to the bags and pumped discharge from the bags
were collected and subjected to laboratory analyses. During the operation period from
January through September, 1969. a total of 1,600,000-gallons of diverted overflow from
38-storms was stored in the tanks. In addition, 600,000-gallons of river water was pump-
ed into the underwater storage tanks for testing during dry weather periods. The total
amount stored was pumped to the interceptor sewer in 26-separate pump out periods. The
cost of the pilot plant was $341,480.00, or $1.70 per gallon of storage. This included
facilities for testing, samples and flow measurement. Estimates for larger installations
without these special requirements range from 28.2* to 14.6* per gallon for plants with
storage from two to twenty million gallons. The project demonstrated that temporary
storage of overflow from combined sewers in underwater rubber storage tanks is feas-
ible and may, under suitable conditions, be effective in eliminating direct untreated
discharge of combined sewage into surface waters during storm periods. Drainage area
to be served, land use, nature of storm events, and other factors must be considered
when planning an underwater storage facility.
ACCESSION NO:
KEY WORDS:
Storm Overflow
Combined Sewers
Underwater Storage
Hydrology
Pumping Stations
* U. S. GOVERNMENT PRINTING OFFICE : 1970 O - 376-9
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