WATER POLLUTION CONTROL RESEARCH SERIES
11022 DPP 10/70
Combined Sewer Temporary
Underwater Storage Facility
U.S. DEPARTMENT OF THE INTERIOR • FEDERAL, WATER QUALITY ADMINISTRATION
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WATER POLLUTION CONTROL RESEARCH SERIES
The Water Pollution Control Research Reports describe the results and progress
1n the control and abatement of pollution of our Nation's waters. They provide
a central source of Information on the research, development and demonstration
activities of the Federal Water Quality 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 facili-
tate information retrieval. Space 1s 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 Project Reports System,
Office of Research and Development, Department of the Interior, Federal Mater
Quality Administration, Washington, D.C. 20242.
Previously issued reports on the Storm and Combined Sewer Pollution Control
Program:
11000 — 01/70 Storm and Combined Sewer Demonstration Projects -
January 1970
11020 FKI 01/70 Dissolved Air Flotation Treatment of Combined Sewer
Overflows, (WP-20-17)
11024 DOK 02/70 Proposed Combined Sewer Control by Electrode Potential
11023 FDD 03/70 Rotary Vibratory Fine Screening of Combined Sewer
Overflows, (DAST-5)
11024 DMS 05/70 Engineering Investigation of Sewer Overflow Problem -
Roanoke, Virginia
11023 EVO 06/70 Microstraining and Disinfection of Combined Sewer
Overflows
11024 — 06/70 Combined Sewer Overflow Abatement Technology
11034 FKL 07/70 Storm Water Pollution from Urban Land Activity
11022 DMU 07/70 Combined Sewer Regulator Overflow Facilities
11020 — 08/70 Combined Sewer Overflow Seminar Papers
11022 DMU 08/70 Combined Sewer Regulation and Management - A Manual
of Practice
Continued on inside back cover....
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COMBINED SEWER TEMPORARY
UNDERWATER STORAGE FACILITY
by
Melpar
An American-Standard Company
7700 Arlington Boulevard
Falls Church, Virginia 22046
for the
FEDERAL WATER QUALITY ADMINISTRATION
DEPARTMENT OF THE INTERIOR
Program #11022DPP
Contract* 14-12-133
October 1970
For sate by the Superintendent of Documents, U.S. Government Printing Office
Washington, D.C. 20402 - Price $1.75
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FWQA Review Notice
This report has been reviewed by the Federal
Water Quality Administration and approved for
publication. Approval does not signify that the
contents necessarily reflect the views and
policies of the Federal Water Quality Adminis-
tration, nor does mention of trade names or
commercial products constitute endorsement
or recommendation for use.
ii
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ABSTRACT
A pilot plant underwater storage facility was designed, constructed, operated
and evaluated as a method of temporarily storing storm overflow from the com-
bined sewer of the Choptank Avenue drainage basin, Cambridge, Maryland.
Combined sewage in excess of the sewer capacity, which would normally be
discharged directly into the Choptank River, was intercepted and pumped into a
nominal 200,000 gallon flexible underwater storage container located 1300 feet
offshore. The stored overflow was later returned from the tank at a rate which
could be accommodated by the intercepting sewer and treatment plant.
The facility was tested with overflow both from four naturally occurring rain-
falls and using fresh water simulation. The overflow samples were analyzed in
a field laboratory for the following characteristics: pH, suspended solids,
volatile suspended solids, settleable solids, 5 day biochemical oxygen demand,
and chemical oxygen demand.
The pilot plant facility was capable of collecting 96 percent of the average annual
overflow from the drainage basin at a cost of less than $1.85 per thousand
gallons. The facility could prevent the annual discharge of 7,136 pounds BOD
into the Choptank River.
Underwater storage facilities could be used effectively for many combined
sewer areas. Site selection, however, has proved to be a critical factor.
Care must be exercised to prevent public disturbance, and factors such as
land use, tidal conditions, or the types of storms, must also be considered.
This report was submitted in fulfillment of contract number 14-12-133 under the
sponsorship of the Federal Water Quality Administration.
Key Words: Storm overflow, combined sewers, underwater storage, hydrology,
pumping station.
iii
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CONTENTS
Section Title Page
ABSTRACT iii
LIST OF FIGURES vii
LIST OF TABLES ix
I. PROJECT CONCLUSIONS AND RECOMMENDATIONS 1
Conclusions 1
Recommendations 1
II. INTRODUCTION 3
III. CHARACTERISTICS OF THE SELECTED SITE 5
^
IV. DESIGN PHASE 15
The Upstream Flow Meter 15
Bar Screen Overflow Meter, and Diversion
Manhole 17
The Wet Well and Pumping Station 19
The Transfer Pipe 19
The Storage Module 19
The Return Flow Line 21
The Control Trailer 22
V. CONSTRUCTION PHASE . 23
Offshore Construction 23
Onshore Construction 24
Summary 28
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CONTENTS (Continued)
Section Title Page
VI OPERATIONAL PHASE 29
Operation of Pilot Plant 29
Normal Mode of Operation 29
Simulated Mode of Operation 31
Sampling of the Combined Sewer Overflow 32
Flushing of the Storage Tank 32
Monitoring of the Rainfall 33
Characterization of Combined Sewer Effluent 33
VII DISCUSSION 35
General Testing 35
Public Attitude and Acceptance 46
VIII REMOVAL OF PILOT PLANT FACILITY 49
DC COSTS 55
X ACKNOWLEDGEMENTS 59
XI BIBLIOGRAPHY 61
vi
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FIGURES
Figure Page
1 Geographic Location and Outline of Drainage Basin Q
2 Aerial View, Lower Section of Drainage Basin 7
3 Choptank Avenue Combined Sewer Outfall 8
4 Choptank Avenue Diversionary Structure 9
5 Rainfall Intensity Duration Curve 12
6 Estimated Overflow Volumes for Choptank Avenue 13
7 Schematic Diagram of Combined Sewer Underwater Storage
Plant 16
8 Upstream Flume Manhole 18
9 Underwater Storage Container 20
/*
10 Installation of the Pumping Station and Wet Well 25
11 Construction of Bar Screen and Flume Manholes 26
12 View of Site after Installation of Facility 27
13 Valving in the Pumping Station 30
14 Close-up View of Storage Tank after Removal 50
15 Internal View of Storage Tank after Removal 51
16 Submersible Pump and Gate Valve after Removal 52
vii
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TABLES
Table Page
I. Estimated Overflow Volumes for Choptank Avenue Drainage
Basin 14
II. Analytical Results of Overflow Discharge of June 19, 1969 -
Simulated Overflow, Test No. 1 36
III. Analytical Results of Overflow Discharge of June 24, 1969 -
Simulated Overflow, Test No. 2 37
IV. Analytical Results of Overflow Discharge of June 26, 1969 -
Simulated Overflow, Test No. 3 38
V. Analytical Results of Overflow Discharge of July 5, 1969 -
Natural Overflow, Test No. 4 39
VI. Analytical Results of Overflow Discharge of July 7, 1969 -
Natural Overflow, Test No. 5 40
VII. Analytical Results of Overflow Discharge of July 10, 1969 -
Simulated Overflow, Test No. 6 41
VIII. Analytical Results of Overflow Discharge of July 12, 1969 -
Natural Overflow, Test No. 7 42
DC. Analytical Results of Overflow Discharge of July 28, 1969 -
Natural Overflow, Test No. 8 43
X. Summary of Rainfall and Overflow 45
XI. Total Cost for Combined Sewer Overflow Facility 56
XII. Estimate of Annual Operation and Maintenance Costs 57
lx
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SECTION I
PROJECT CONCLUSIONS AND RECOMMENDATIONS
Conclusions
The construction of an offshore underwater temporary storage facility at
Cambridge, Maryland, has demonstrated the feasibility of utilizing this concept
as a means of abating pollution resulting from storm overflow from a combined
sewer. Unfortunately, adverse public reaction to the pilot project limited the
contractor's ability to accomplish a thorough evaluation of both the mechanical
aspects of the system and those analytical parameters of interest to monitoring
the biological and chemical characteristics of the overflow handled by this
system.
The impact of public non-acceptance upon projects such as this cannot be dis-
missed, for Cambridge is typical of many older communities located adjacent
to national water resources. Frequently, the sewage treatment facilities are
only primary in nature and have not kept pace with the needs of the growing
population. Invariably, such systems allow any overflow to discharge directly
into the nearest water course. The expense of replacing combined sewers with
separate dual systems is generally prohibitive, even if it is physically possible
to accomplish such construction.
Public resentment of this demonstration project was such that it became neces-
sary to curtail the operation of the facility prior to satisfactory evaluation, and
to completely remove the installation. Had it been possible for the sewage
treatment facility at Cambridge to have retained the installation for permanent
use, it would certainly have been of long-range public benefit.
During the operation of the facility, it was determined that the use of flumes as
metering devices for the discharge of the drainage basin was ineffective, espe-
cially for the conditions of the tidal river. The tide caused surcharged condi-
tions within the sewer, thus flooding the measuring devices, and causing in-
accurate readings.
Mechanically, the combined sewer temporary underwater storage facility
operated as designed. It was capable of storing 200,000 gallons of storm
overflow (approximately 4.5% of the daily capacity of the Cambridge Treatment
Plant), which could then be pumped into the sewer system at rates up to 48, 000
gallons per hour at such time as capacity to treat the stored overflow was once
more available.
Recommendations
It is recommended that future demonstration projects of this type place emphasis
upon site selection, not only from a practical engineering standpoint, but also
with respect to public acceptance giving preference to locations that are not
adjacent to residential areas. It would be desirable to accept both the increased
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facility costs and the inconvenience of rerouting the overflow sewage line to a
remote location, rather than to jeopardize the success of the project through
public resistance.
Additionally, it is recommended that a number of design changes be incorpora-
ted into future systems of this type, as follows:
1. Protective devices should be installed around the eductors of the
circulation system in the storage module to prevent damage to the flexible
cover.
2. Additional ventilation hose should be added to the flexible cover.
Seven ventilators are recommended for the system described in this report.
An ell should be installed at the junction of the center hose and flexible cover
to prevent kinking of the hose.
3. Better methods for measuring flow rates in sewers should be de-
vised.
4. It is recommended that interface instrumentation be utilized for
the synchronization of rainfall-runoff data collection to provide more accurate and
precise results and conclusions.
5. The samplers utilized on the project are not recommended for the
sampling of sewage from combined sewers. A more advanced and efficient
sampling method should be developed for future programs.
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SECTION H
INTRODUCTION
Recognition of the Nation's increasing concern over the magnitude of the
water pollution problem came in the Water Pollution Control Act of 1948. This
act was the first national effort to treat the pollution control problem. In 1956,
Congress extended and strengthened the 1948 Act, in part by increasing the
effort on pollution research. Subsequent amendments in 1961, 1965, and 1966
were made to strengthen the procedures for abating pollution. Since 1956 an
intensified research effort has been enforced nationally to eliminate water pol-
lution and restore our waterways to usable quality standard. Many new and
innovative techniques are being evaluated in an effort to achieve this goal. This
report concerns a demonstration project to minimize pollution from the discharge
from combined sewers during periods of rainfall runoff.
The combined sewer carries sanitary sewage and other waste-water to points
of treatment during dry weather. During storm periods this sewer serves as
the collector of storm water from streets and other sources and conveys the
mixture of sanitary sewage-storm water to points of treatment or discharge.
Overflow pipes or channels transmit the excess flow from combined sewers
directly to the receiving waters. Sanitary engineers and public health officials
long believed that combined sewer overflow water was so dilute that its dis-
charge would not degrade the receiving stream. Today, these officials are in-
stalling signs warning of bacterial contamination caused by the discharging of
sanitary wastes into receiving waters via the combined sewer outfalls. These
discharges adversely affect all known water uses in the receiving water courses.
These wastes contain pathogenic organisms that can cause diseases such as
typhoid, dysentery, and infectious hepatitis. The wastes provide nutrients,
particularly nitrogen and phosphorus, for algal growth and promote eutrophi-
cation if discharged in a body of still water. More and more lakes are exper-
iencing ecological unbalances because of the pollutional loads.
A multitude of old cities, both large and small, having combined sewers with
overflows discharging in the nearest water course are faced with a requirement
for pollution abatement in their community by legislation. These cities are
confronted with the complex problem of combined sewers existing in the most
fully developed, highly congested parts of the city where land is simply not
available. To replace the combined sewers with a separate dual system would
be extremely expensive, if not prohibitive, and would produce immeasurable
disruption to an entire community. To assist these communities in their dev-
elopment of pollution control, it is necessary to have a national effort for
evaluating the feasibility of the many approaches offered; separation within the
sewer lines, stilling ponds, and storage tanks are a few of the measures being
studied.
The objective of this program was to design, construct, operate and evaluate,
and remove (if necessary) a pilot underwater storage facility that would
function as a surge tank on a combined sewer system. The purpose of the
facility was to retain the flow in excess of the sewer capacity and later return
it for processing at a rate which the sewer system and treatment plant could
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handle. This approach was unique in that the storage reservoir was a flexible
tank placed in the adjoining waterway in such a manner that it did not require
the use of expensive land in a congested area. The design of the storage tank
and its accompanying systems is considered an optimum balance between eco-
nomics, simplicity, dependability, adaptability to a modular type installation,
and future use potential.
This project was installed on the Choptank Avenue drainage basin in Cambridge,
Maryland. The drainage basin is 20 acres in size and is sewered by one com-
bined sewer running north down Choptank Avenue to the Choptank River. The
basin is fully developed for residential use.
The project was divided into four distinct phases; design, construction, oper-
ation and evaluation, and removal, which are described in detail in the subse-
quent sections of this report. The interception and storage system evaluated
in this project consisted of metering manholes, a diversion manhole, wet well,
pumping station, transfer lines, and flexible storage module. Except for the
storage module the other pieces of hardware were items of standard manu-
facture. The storage module basically was a steel tank with a rubber diaphragm
top which either inverted into the tank or expanded above the tank.
The basic purpose of this pilot project was to assemble the individual compon-
ents as a single integrated unit to demonstrate that storm overflow from a
discharge sewer could be stored for later sewage treatment. Appropriate
instrumentation and analytical techniques were also included to allow the
evaluation of the characteristics (both quality and quantity) of the water that
overflows from a combined sewer system and the changes which might occur
during storage.
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SECTION HI
CHARACTERISTICS OF THE SELECTED SITE
After surveying sites in Virginia, Maryland, Washington, D.C., Pennsylvania,
and Delaware, the Choptank Avenue drainage basin in Cambridge, Maryland,
was selected as the site for this demonstration project, and approval from all
governmental agencies concerned was obtained. Figure 1 shows the geograph-
ic location and outline of the drainage basin within the city limits of Cambridge.
The basin is 20. 0 acres in size and is sewered by one combined sewer running
north down Choptank Avenue to the Choptank River. The basin is fully develop-
ed for residential use as illustrated in figure 2. The residential development
is typical of an older community with the homes built on narrow lots and loca-
ted close to the street. The imperviousness of the entire drainage basin was
estimated and set at 60 percent. The outfall drain, shown in figure 3, is a
18-inch diameter pipe extending 290 feet out into the Choptank River.
At the selected site the Choptank River is approximately 2 miles wide with a
narrow channel in the center, which is deep enough to allow the passage of
ocean going vessels up to the city harbor. The river is relatively shallow with
a gentle slope from the shoreline to the edge of the center channel where the
depth is approximately 12 feet.
Prior to the middle nineteen thirties, the entire sewer system of the city of
Cambridge discharged into the Choptank River. During the middle nineteen
thirties, an interceptor was designed and built to intercept the dry weather
flow from the combined sewers along the waterfront to transmit the flow to the
municipal sewage treatment plant. Simultaneously, 18 diversionary structures
were built with each structure equipped with an overflow weir and tide gate.
The Choptank Avenue diversionary structure, with elevations, is shown in
figure 4. The diversion manhole on the Choptank Avenue sewer atHambrooks
Avenue is designed so that a maximum flow of 850 gpm is intercepted when &e
outlet end has a free fall condition. This, however, is not fee case when a
storm exists because the sewer system upstream contributes to the total flow
in the Hambrooks Avenue sewer surcharging the sewer and submerging the
Choptank Avenue diversion line. This reduces the discharge capacity of the
diversion line to approximately 350 gpm.
A flow of 350 gpm represents the flow equivalent to the maximum dry weather
flow (DWF) and the runoff from a rainfall of 0.05 in. Ar. This is based-on
the average dry weather flow of 30 gpm, a maximum daily rate of 2.5 times
the DWF and a runoff flow of 54 gpm/0.01 in./hr of rainfall from the Choptank
Avenue drainage basin. The Choptank Avenue drainage basin represents about
6 percent of the total area of fully developed land that is served by the city's
combined sewer system.
An evaluation of meteorological records was made of several surrounding
United States Weather Bureau (USWB) stations. The results of the evaluation
established certain criteria that were directed toward the development and
sizing of the pilot plant facility for the retention of overflow water from the
Choptank Avenue combined sewer system.
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Figure 1. Geographic Location and Outline of Drainage Basin
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YACHT CLUB
STORAGE TANK
UNDERGROUND
PUMPING STATION
CITY OF CAMBRIDGE
II
Figure 2. Aerial View, Lower Section Drainage Basin
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Figure 3. Choptank Avenue Combined Sewer Outfall
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8" TO INTERCEPTOR
Lc:
15' COMB.
SEWER
EL +1.80
15" COMB.
SEWER
\
INV EL. +1.84
\
r*
J
18" OVERFLOW
PLAN
M.H.
M.H.
EL. +2.50
I/ 3
TIDE GATE
EL. +2.00
EL. +1.80
x
SEC. A - A
18" OVERFLOW
Figure 4. Choptank Avenue Diversionary Structure
9
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Precipitation records were obtained from the Office of Hydrology, USWB. The
following stations with reliable periods of record were considered:
Station Daily Hourly
Cambridge, Maryland 65 yrs.
Washington National 60 yrs. 25 yrs.
Baltimore, Maryland 60 yrs. 25 yrs.
Georgetown, Delaware 13 yrs. 7 yrs.
Leonardtown, Maryland 25 yrs. 12 yrs.
The criterion for selection of the station to be used for analysis of the hourly
data was that it be one which most nearly resembled the Cambridge precipita-
tion regime. Consequently, monthly precipitation totals were selected as a
description of the regime and correlation coefficients were calculated between
the Cambridge monthly totals and the totals for the other nearby stations with
the following results:
Station January April July October
Washington National 0.88 0.92 0.22 0.66
Baltimore 0.81 0.86 0.54 0.33
Georgetown 0.78 0.86 0.59 0.44
Leonardtown 0.90 0.81 0.68 0.78
Leonardtown precipitation showed the highest overall correlation with that at
Cambridge, and therefore it was used to evaluate the hourly precipitation data
for purposes of relating it to Cambridge.
Ten years of hourly records of Leonardtown data have been analyzed on the
basis of storms. A storm is hereafter defined as a period of precipitation dur-
ing which the total accumulation is 0.10 inches or greater and during which
the intensity of precipitation was greater than 0.05 inches per hour for at
least one hour. A single storm begins when the intensity is greater than 0. 01
inches per hour and ends when the precipitation ceases.
By this definition, the average number of storms will be less than the average
number of days per year that precipitation is recorded. In this case, for the
last 18 years of record, Cambridge, Maryland, has recorded precipitation on
88 days a year. However, based on the above definition of a storm, there are
only an average of 55 storms per year. Since the Hambrooks interceptor,
shown in figure 7, will accept the runoff flow from a storm of 0. 05 inches per
hour or less, by the above definition the overflows resulting from such a
storm were considered. In accordance with this criteria there will be an
10
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average of 55 overflows per year.
The precipitation for each storm was idealized, and the resultant intensity
duration curve for 10 years of Leonardtown data is presented in figure 5.
Using the results of this curve and based on a runoff of 54 gpm/0.01 in./hr of
rainfall and the interception of the first 0.05 in./hr of rainfall, the anticipated
overflow volumes are tabulated and totalized in Table I and shown graphically
in figure 6 for storms up to the 18 hours duration. The tabulation and figure
indicated that on the averate 19 storms per year will generate an overflow of
200, 000 gallons or more. Only the overflow in excess of 200, 000 gallons
would have to be bypassed around the pilot plant. The amount of runoff, 54
gpm/0. 01 in. /hr of rainfall, was determined through the use of the "rational
formula" (Q=CIA). As previously mentioned a value for the coefficient of
imperviousness for the basin was set at 0.6.
On the average, 36 storms per year would be completely contained within a
200. 000 gallon container. During an average year an underwater storage sys-
tem of this size for the Choptank Avenue drainage basin would have been sub-
jected to 55 operational cycles. Of these, 19 overflow conditions would have
equaled or exceeded the container: however, the sewer system would be fairly
well flushed out and any additional overflow would be of weaker pollutional
strength.
11
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0.30 Q. 30
LLJ
5 0.20
z
- 0.10
HI
0.0
LEONARDTOWN, MD STORM DATA
10 YEAR RECORD
8 10 12
DURATION HOURS
Figure 5. Rainfall Intensity Duration Curve
12
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350
300
250
o
o
o
o
1 200
=5
O
tx.
LJ
150
100
50
10
20
30
40
50 55
NUMBER OF STORMS OVERFLOW IS EQUAL TO OR
GREATER THAN INDICATED VOLUME
Figure 6. Estimated Overflow Volumes for Choptank Avenue
13
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TABLE 1
ESTIMATED OVERFLOW VOLUMES
FOR
CHOPTANK AVENUE DRAINAGE BASIN
Period of
Rainfall
hr.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Rainfall
Intensity
in/hr.
0.23
0.18
0.15
0.13
0.12
0.11
0.10
0.10
0.09
0.09
0.085
0.08
0.08
0.075
0.07
0.065
0.06
0.06
Number of
Storms/ Yr
55
45
37
30
24
19
15
12
10
8
7
5
4
4
3
3
2
2
Estimated
Gallons
58,300
42,100
32,400
25,900
22,700
19,400
16,200
16, 200
13,000
13,000
11,300
11,300
9,700
8,100
6,500
4,800
3,200
3,200
Overflow
Total to Hour
Gallons
58,300
100,400
132,800
158,700
181,400
200,800
217,000
233,200
246,200
259,200
270,500
281,800
291,500
299,600
306,100
310,900
314,100
317,300
14
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SECTION IV
DESIGN PHASE
The pilot plant for the underwater temporary storage of combined sewer over-
flow was designed to be compatible with a multiplicity of conditions for the
particular tidal estuary demonstration site. The purpose of this pilot plant
was to provide temporary storage for the excess flow from the 15 inch
Choptank Avenue combined sewer, and later return it to the Hambrooks inter-
ceptor sewer when the treatment plant was prepared to process it. The key
item of the pilot plant was a flexible storage module which was to be located in
the Choptank River some 1300 feet offshore where the river was 8 feet deep at
mean low tide. When not in use, the storage module would not protrude more
than one foot above the existing natural river bottom. The items listed below
were required to support the storage module and to transfer the overflow water
to it and back to the sewer system.
* The upstream flow meter
* The bar screen, overflow meter, and diversion manholes
* The wet well and pumping station
* The transfer pipe
* The storage module
* The return flow line
* The control trailer
These items are shown on the schematic diagram presented in figure 7.
These individual items can be grouped into two basic installations, the onshore
facilities and the offshore facilities. The onshore facilities consist of all the
items except the transfer pipe and the storage module. The offshore facilities
include the transfer pipe and the storage module, which is in a direct line with
Choptank Avenue. The transfer pipe interconnected the onshore and offshore
facilities.
A description of the pilot plant is given in the subsequent paragraphs. Refer-
ences are made to appropriate Melpar drawings which are on file at the
Federal Water Quality Administration, Storm and Combined Sewer Pollution
Control Branch.
The Upstream Flow Meter
A 15 inch Leopold Lagco flume (F.B. Leopold Co., Inc., Zelienople, Pa.) and
15
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LINE LEGEND:
--- EXISTING
15" INTERCEPTOR SEWER
ALONG HAMBRQOKSAVE.
NEW
15" SEWER
ALONG CHOPTANK
AVE.
0>
y V\ DIVERSION
UPSTREAM >y A\ DOWNSTREAM MANHOLE &
FLUME // \. FLUME TIDE GATE
r_£, ^\
~{* , ~* ~"l - J T RAc""^
1 • *•"• ~ 1 BAR ^^^
DIVERSION SCREEN
^ MANHOLE
*• — \ 8" RETURN LINE
3" WATER LINE
.»..».
15" 0
L/
1 PLOW
WET DRY
WELL PU*
d 1 A
l. CHOPTANK
j RIVER
<'
\ J
VER- |
SEWER
-* SHORE LINE
-i 1
/ 12" TRANSFER
-> ^ IS 1 URAUt
1 1, ~ \TANK>
WELL 1 " X /
(PING I |
TION /*— 1300' -H
CONTROL
TRAILER
POWER AND SIGNAL
CABLES
Figure 7. Schematic Diagram of Combined Sewer Underwater Storage Plant
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a Stevens Type F water-level recorder (Leopold & Stevens Instruments, Inc.,
Portland, Ore.) were installed in a test manhole located upstream of the
existing city diversion manhole. Figure 8 shows the flume in place, looking
downstream. The flume and recorder monitored the total flow generated
from the drainage basin before any flow was diverted to the interceptor or to
the overflow line.
The flow chart was intended to record the daily flow of sewage and
storm water from the drainage basin. Sampling of the flow at this location
was intended to allow for the characterization of the entire flow generated in
the drainage basin. Surcharging conditions in the sewer eventually eliminated
the use of this test manhole.
Bar Screen, Overflow Meter, and Diversion Manhole Bar Screen
A bar screen (Melpar Dwg. No. R453025) was constructed upstream of the
overflow meter and diversion manhole. This was a hand cleaned screen used
to prevent large objects from clogging the flume and from entering the pilot
plant and endangering either the pumps or the storage container's recircula-
tion system. The size and nature of the drainage basin and sewer system did
not warrant installation of a mechanically cleaned bar screen or a comminutor.
Overflow Meter
An 18 inch Leopold Lagco flume (F. B. Leopold Co., Inc., Zelienople, Pa.)
and a flow transmitter (Style ML, Badger Meter Mfg. Co. , Milwaukee, Wise.)
were installed immediately downstream of the bar screen. A receiver and
recorder (Style X701E, Badger Meter Mfg. Co., Milwaukee, Wise.) for the
transmitter was located in the remote control panel of the trailer. This flow
meter system (Melpar Dwg. No. R453025) which was placed ahead of the diver-
sion structure, monitored all of the overflow water from the drainage basin
regardless of whether or not it was taken into the pilot plant.
Diversion Manhole
A new diversion manhole (Melpar Dwg. No. R453136) was constructed just
ahead of the seawall. The purpose of this structure was to divert the overflow
water from existing outfall sewer into a supply tank (wet well), and then to the
pumping and storage facilities. The existing outfall sewer that extended be-
yond the new diversion manhole served as the pilot plant bypass or overflow
line. When the pilot plant was not in operation or had reached its storage ca-
pacity, the gate on the diversion line was manually closed and the water flow-
ing in the overflow sewer was directed out the existing outfall pipe. Under
plant bypass conditions the overflow sewer functioned in the same fashion as in
normal operation.
A tide gate was installed on the downstream side of the bypass port of this
diversion structure to ensure that river water would not flow through the out-
fall pipe and into the pilot plant.
17
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Figure 8. Upstream Flume Manhole
18
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The Wet Well and Pumping Station
The water directed to the pilot plant flowed from the diversion manhole to a wet
well just ahead of the pumping facilities. The pumping station was designed to
function as the master unit for flow into and out of the storage container and
other parts of the pilot plant. These units were built by Schmieg, Richmond,
Va., reference Melpar drawing Nos. R452995 and R453034.
The pumping station consisted of two, two-speed (600-1000 gpm) pumps, pump
controllers, and the necessary valving. The maximum full flow capacity of the
pumping station was 2000 gpm.
On the flow to the storage container cycle, the pumps operated on automatic
control (with manual override provisions) that programmed the operation of the
pumping stages to match the rate of flow into the wet well from the sewer sys-
tem. This was accomplished by five liquid level sensors (Type ENP-10, Flygt
Corp., Stamford, Conn.) in the wet well. The pumps were stepped up and
down automatically as the level in the wet well fluctuated, and they were shut off
when the flow into the wet well ceased.
The valving and piping in the pumping station provides for the suction side of the
pumps to be connected to the transfer line to the storage container. This also
allowed the pumps to function as discharge pumps and to pump the water from
the container back to the sewer system. During this operational cycle, the
pumps discharged through an eight-inch cast iron pipe that interconnected the
pumping station to the interceptor sewer. The normal return flow operation
was 600 gpm.
A 3-inch fresh water supply line, with approved backflow devices, was installed
on the top of the wet well. This water line provided a source of clean water
that was used in a clean-out and flushing operation of the storage container. It
also served as a source of water to operate the pilot plant during periods when
there was no storm flow.
The Transfer Pipe
The transfer pipe served as the connecting link between the onshore facilities
and the storage module. A single 12-inch cast iron pipe was installed in a
trench along the river bottom. The power line running to the recirculation
pump and the leads running to the pressure sensing elements and warning lamps
were laid on top of the pipe. The transfer pipe was used to transfer the liquid
wastes to and from the storage tank.
The Storage Module
The storage module included the 200, 000 gallon (nominal capacity) container,
the inlet and outlet piping, the flushing system, the anchorage system, and the
pressure sensing device. The storage container, shown under preliminary test
in figure 9, consisted of a lower half of epoxy coated steel and an upper half of
neoprene coated nylon fabric material. In a collapsed condition the flexible top
folded into the steel bottom section. The storage container had a circular con-
19
-------
Figure 9. Underwater Storage Container
20
-------
figuration with a 55 foot diameter and a designed height of 14 feet including both
the steel bottom and fabric top. The steel tank was constructed by American
Welding Co. Inc., Baltimore, Maryland. The flexible neoprene coated fabric
cover was fabricated by Uniroyal Plastics Products, Mishawaka, Indiana.
After American Welding Co. installed the flexible cover to the steel tank, the
storage module was filled with air by a large air compressor to check for air
leaks. See figure 9. Upon completion of the leak testing, the storage container
was towed by tugboat from the Baltimore Harbor via the Chesapeake Bay to
Cambridge, Md. The storage container was placed in the Choptank River
approximately 1300 feet out from shore where the depth was 8 feet at mean low
water. The tank rested in a depression excavated in the bottom of the river to
a depth of seven feet below the natural river bottom. The elevation of the con-
nection between the steel bottom and the flexible top therefore corresponded to
the elevation of the existing river bottom. The flexible top when filled raised
an additional seven feet above the top of the steel tank.
The recirculation system consisted of a recirculation pump (Crane-Deming,
Type 7360, Burnet Engineering Co., Richmond, Va.) mounted to the steel
bottom with necessary intake and discharge piping. The suction line of the re-
circulation pump was connected to the drain on the storage tank. The discharge
header consisted of a pipe running around the entire perimeter of the tank at the
bottom of the steel portion of the tank with fifteen circulating tank eductors
(Penberthy, Prophestown, Illinois) equally spaced and mounted on the pipe. The
recirculating water aided suspension of the solids carried into the tank.
Access to the inside of the tank was gained through a manhole port on the side of
the steel tank with a hatch placed at the surface of the river bottom. This pro-
vided an access near the bottom of the tank so the position of the flexible top
would not be a hindrance or problem.
An air bleed valve on the top of the flexible portion of the storage module provid-
ed a means of escape for any gases that might have become trapped in the con-
tainer. If not released these gases would have reduced the capacity of the tank
or resulted in excessive positive pressure on the inside of the tank.
A differential pressure sensing element was installed on the storage tank to
monitor the location of the top when in a near full condition. The differential
reading between the two levels of the flexible cover would indicate how high the
fabric top raised off the steel bottom. It was necessary to measure differential
pressure to compensate for the fluctuations in water level due to tides and storm
conditions.
The Return Flow Line
The return flow line connected the pumping station with the city diversion man-
hole for the purpose of returning the water from the pilot plant back to the
interceptor sewer. This line discharged into the Choptank Avenue sewer ahead
of the original diversion line. By returning the flow upstream of this point, the
diversion manhole functioned as a throttle on the return flow to the system. Re-
turn flow in excess of the diversion capacity overflowed the existing weir and
continued down through the outfall sewer into the wet well. The level monitor in
21
-------
the wet well indicated when the return pumping rate was in excess of the sewer
capacity.
The Control Trailer
The control trailer (Coastal Model M-30, Brandywind, Md.) was used as a
central location for the control of the pumping station operation and the housing
of the meter readouts. An indication panel was installed in the trailer for visual
display of the events occurring in the pumping station and wet well. The larger
section of the trailer was modified for laboratory space and equipped with the
necessary laboratory supplies to perform the chemical analyses of combined
sewer overflow samples. The trailer was located nearby in the city park.
22
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SECTION V
CONSTRUCTION PHASE
The objective of this phase was to construct one complete pilot plant for control
of water pollution from the Choptank Avenue outfall in the Choptank River at
Cambridge, Maryland. The combined storm and sewage overflow from the
Choptank Avenue combined sewer was intercepted and stored in a collapsible
storage tank located in the river. A pumping station and other necessary diver-
sion and control devices were located onshore at the foot of Choptank Avenue.
Primarily, the construction was divided in two parts.
* Offshore Construction
* Onshore Construction
The potential subcontractors were allowed to submit bids on either the offshore
or onshore construction or both. The successful bidders were Smith Brothers
Pile Driving, Inc., (Galesville, Maryland) for the offshore construction and
Norris E. Taylor Contractors, Inc. (Easton, Maryland) for the onshore con-
struction. The work began in September 1968 and was completed in April 1969.
Offshore Construction
The offshore construction consisted of the entire offshore portion of the pilot
plant, including:
* Installation of the storage tank
* Installation of the 12-inch cast iron pipe line
* Installation of the electrical equipment
* Installation of the piles and wire rope
Excavation of approximately 1400 cubic yards of the river bottom was required
to prepare the offshore site for the storage tank. This step included excavation
of the river bottom to the generally required configuration, and placement of the
excavated material on the Great Marsh peninsula (about 2500 feet from the site)
as fill material. The excavation included a trench in which the transfer pipe and
electrical cables were buried near the natural river bottom elevation.
Following the excavation, guide piles were drived around the sides of the exca-
vation. These piles protruded above the surface of the water and were used to
locate the storage tank over the excavated area. After the guide piles were in
place, the tank was towed into place, sunk, and secured to the guide pilings.
After the tank was lowered to the bottom and secured, additional piles were
driven around the outer edge and the storage module was secured to these pil-
ings. A total of 6 fifty foot piles were installed.
23
-------
After the storage tank was installed, the transfer pipe was connected to the tank.
In conjunction with this the power cables for the circulation pump and navigation
lamps were connected to one of the piles. The cables were terminated in a
watertight junction box located on the piling.
A 3/8-inch galvanized wire rope was installed around the periphery of the tank
and supported by the piles. The rope was used to support the electric cable
that supplied power to the six navigation lamps which were mounted on top of
each pile.
Onshore Construction
The onshore construction consisted of the entire onshore portion of the pilot
plant. This included the following major subsystems:
* Installation of pumping station and wet well
* Construction of bar screen, flume and transmitter, and
diversion manholes
* Installation of 3-inch fresh water line
* Installation of 8-inch return line
* Provisions for necessary utility connections to control trailer
* Electrical installation
The pumping station and wet well were ordered from a manufacturer as package
units and were delivered to the site as self contained working modules. The in-
stallation of these units required the sheeting and excavation of the proposed
area, the pouring of a concrete foundation slab, the installation of the units to
the concrete slab, and the connection of the inlet and outlet piping and power lines.
Figure 10 shows the construction for the installation of the pumping station and
wet well.
The other onshore facilities were built or installed in place. These facilities in-
cluded the bar screen, flume and transmitter, and diversion manholes. These
structures were built independently of the other and the piping connected as they
were completed. Figure 11 shows the bar screen and flume manholes being
constructed.
After the installation of the pumping station and wet well, the pumping station
and the city diversion manhole were interconnected with an eight-inch cast iron
pipe line, which served as the return line for the stored overflow waste-water.
A three-inch fresh water line was installed between the city's four-inch main
and the wet well. The connection of the line to the wet well included a shut-off
valve, a city water meter, and a doucle check valve to prevent back flow.
All excavated areas were back filled and the street paved. Figure 12 shows the
street after the completion of all construction.
24
-------
Figure 10. Installation of the Pumping Station and Wet Well
25
-------
Figure 11. Construction of Bar Screen and Flume Manholes
26
-------
Figure 12. View of Site After Installation of Facility
27
-------
Summary
Icy conditions on the river, tidal conditions, and high winds presented the main
problems encountered by the subcontractor during the installation of the offshore
portion of the facility. Otherwise, the offshore construction continued efficient-
ly and smoothly.
The onshore contractor experienced many difficult situations other than the pro-
blem of inclement weather. Problems of the type encountered will occur if the
appropriate construction procedures are not properly enforced on the project.
For example, during the initial stages of construction, there was the need for
full time on-site supervision and better public relations. The excavation for the
installation of the pumping station and wet well collapsed and undermined a large
area of the street, sidewalks, curbs, and adjacent portions of private properties.
The primary reason for the collapse was the weak and insufficient bracing used
to support the interlocking steel sheeting. The contractor's small type pumps
proved to be inadequate for keeping the excavation area pumped clear of the
infiltrating tide water. Eventually adequate pumps and a well point system of
sufficient capacity were installed to accomplish the task of dewatering the area
of excavation.
28
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SECTION VI
OPERATIONAL PHASE
Operation of Pilot Plant
The operation of the pilot plant was characterized by two basic modes of opera-
tion; (1) the normal routine for a rainfall generated overflow condition and
(2) a test routine for an artificially generated overflow condition. The latter
was necessary to ensure that a sufficient number of mechanical tests could be
performed on the pilot plant during the contract period.
Normal Mode of Operation
After each use of the pilot plant, it was returned to a normal mode condition in
anticipation of the next storm. This involved opening the sluice gate into the
pilot plant at the new diversion manhole, if it was closed to bypass part of the
previous storm. The volume of liquid remaining in the storage container dur-
ing the previous cycle was calculated after each use of the pilot plant. The
valves in the pumping station were properly opened and/or closed to direct the
pumped flow out to the underwater storage container. The valving arrange-
ment for pumping in and out of the storage container is shown in figure 13.
The underwater storage system was now ready to receive any overflow, be it
rainfall runoff or just normal surcharging of an overloaded sewer system.
When the rain started and the flow in the Choptank Avenue sewer exceeded the
height of the diversion dam, the water overflowed the dam and flowed down the
outlet pipe toward the Choptank River. The overflow liquid next passed
through a manually cleaned bar screen used to protect all downstream units
from any large objects. As the flow passed through the Lagco flume it was
monitored totally and as a function of time. The flow next came to the new
diversion manhole where it was directed away from the overflow sewer to the
pilot plant. The flow continued by gravity from the diversion manhole into the
wet well.
The wet well contained five mercury switches located at uniform increments of
height above the bottom of the well. The switches were enclosed in waterproof
weighted bags. These bags were so designed that they changed their attitude
in a predetermined manner as water rose up under them. As this occurred,
the mercury switch was actuated, signaling that a particular water level had
been attained. When any or all of these switches had been actuated, corres-
ponding indicator lamps were illuminated on both the pumping station and trail-
er control panels; in the automatic mode, they also provided the pump control.
When the pump controls were set for automatic operation, the pumps operated
as follows:
* Switch No. 1 (lowest) closed, no pumping action (standby/cutoff)
* Switch No. 2 closed, pump No. 1 starts on low speed (600 gpm)
29
-------
WET WELL
M»-
KNJ
VI
TO CITY SEWER
-*i
12'
(PIIM
6"
f
I PUM
6"
RETURN LINE
P, ^
)
„ A
P 2 J
5" /s
V
f \/1
V-Y 1
5" /S
V
CV2
>
v
2
V2
<-
\-7
^V3
MODE 1: WET WELL TO STORAGE TANK
V, = OPEN
V2 = OPEN
V3 = CLOSED
V4 = CLOSED
MODE 2: STORAGE TANK TO CITY SEWER
V, = CLOSED
V2 = CLOSED
V3 = OPEN
V4 = OPEN
Figure 13. Valving in the Pumping Station
-------
recording system is actuated
* Switch No. 3 closed, pump No. 1 starts on high speed (lOOOgpm)
* Switch No. 4 closed, pump No. 2 starts on low speed (IGOOgpm)
* Switch No. 5 closed, pump No. 2 starts on high speed (2000gpm)
This sequence was reversed after the runoff subsided and the liquid level in
the wet well was being lowered.
As the water filled up the wet well, the level sensors activated the pumps to
keep pace with the incoming flow up to the maximum capacity (2000gpm) of
the facility. The flow rate into the storage tank from the pumps was sensed
by a magnetic flow meter 1800 series (The Foxboro Co., Foxboro, Mass.);
this information was transmitted to an associated Foxboro receiver and re-
corder (9650 series) remotely located in the trailer control panel. A timer
was associated with the recorder that, in combination with a mechanical inte-
grating device, determined the total volume flow. This total volume was
indicated on a totalizer (a six place digital counter). Attached to this counter
was a switch that was set to open when a predetermined total was reached.
This switch was normally set to open at the nominal 200, 000 gallon capacity of
the storage tank. Flow in excess of this 2000 gpm rate or in excess of storage
tank capacity surged in the upstream sewer until its head exceeded the level of
the river and tide at which time it would open the tide gate and discharge into
the river. Under a full scale operation this would not occur unless a storm
flow in excess of the design storm occurred. All of these events could occur
with the station in an unattended condition.
An operator came on duty at the beginning of each storm to monitor the filling
operation. These duties included ensuring shutdown if the storage module
filled up or shutting off the pilot plant from the overflow sewer should a mal-
function occur in the system. The operator placed the sampler in position
during an overflow to take periodic samples of the incoming flow. The opera-
tor also was responsible for analyzing the samples, changing charts, placing
the system in "stand-by" mode, and all other general maintenance.
At the conclusion of a storm event, the operator recorded the totalized flow
measurements and prepared the pumping station flow pattern for returning the
flow to the sewer system. The recirculation system on the storage module
was turned on to keep the solid contents in suspension. After the stored con-
tents were pumped back to the sewer system, the pilot plant was returned to a
standby mode.
Simulated Mode of Operation
The simulated test runs followed the same operating procedure with the excep-
tion of start up.
To perform a simulated test run, the outlet sewer pipe in the overflow manhole
at Hambrooks Avenue was sealed off with an inflatable plug. This diverted all
31
-------
upstream flow to back up and flow through the overflow line to the pilot plant.
At no time during these simulated tests was the flow allowed to exceed the
plant capacity and result in a discharge into the river. The simulated tests
were sampled and monitored in the same manner as the naturally occurring
overflows.
The system was debugged and ready for operation on June 19. 1969. Simulat-
ed tests were performed with cooperation from the City Water Department.
Two simulated tests were performed between me hours of 9 a.m. to 1 p.m.
and one simulated test was conducted between the hours of 12 midnight and
1:30 a.m.
After numerous complaints were received from the local residents because of
low water pressure during the day and too much noise from the flowing
hydrants during night hours, the simulated tests were ceased after July 14,
1969.
From this time, the storage module was operated only during periods of rain-
fall. The one exception to this was the final fill and draw cycle which was
carried out to assist in a full inspection of the diaphragm portion of the stor-
age module. After inspection of the module, the contents were pumped out
and the system was permanently isolated from the sewer system.
Sampling of the Combined Sewer Overflow
The required volume per sample was 1020 ml to perform all required analy-
ses. The standard SERCO Model NW-3 Automatic Sampler (Sanitary
Engineering Research Co., Minneapolis, Minnesota) would collect approxi-
mately 330 ml of sample per bottle when operating with a five-foot lift and
26-inches Hg internal vacuum and an atmospheric pressure of 30-inches Hg.
Therefore, it was necessary to fill four bottles at a time (1300 ml) for
adequate sample volume. A newly designed and fabricated tripper arm was
installed on the SERCO sampler. The tripper arm simultaneously actuated
four sampling line switches.
The SERCO units have gearhead provisions for sampling at 5-, 10-, and 15-
minute intervals, as well as at hourly intervals. The 15-minute gearhead
was utilized for the tests to provide a sampling interval that would not over
tax the field laboratory beyond its capacity.
Flushing of the Storage Tank
A three-inch water main was coupled to the wet well and was controlled by a
gate valve outside the well. The pilot plant system was set for pumping into
the storage tank. The wet well was filled four times with city water and
emptied into the tank. This quantity of water was enough to provide sufficient
coverage of the tank bottom and to allow the circulating pump to properly rinse
the tank sides and bottom. The circulating pump was allowed to operate for
several minutes and during the time the tank was pumped out. The water from
the tank was returned through the 8-inch return line to the upstream side of
the city diversion juncture.
32
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Monitoring of the Rainfall
Precipitation in the Choptank Avenue drainage basin was measured and recorded
with a Universal Rain Gauge (No. 5-780, Belfort Instrument Co., Baltimore,
Maryland). The instrument was provided with an 8-day chart drive movement
and a 12-inch dual-traverse chart. Interfacial instrumentation was not provided
for the automatic synchronization of rainfall and runoff data.
Characterization of Combined Sewer Effluent
Samples of effluent from the combined sewer overflow and of sewage as it was
pumped back from the storage tank to the city sewer system were analyzed to
determine the following characteristics: pH, suspended solids, volatile sus-
pended solids, settleable solids, 5-day biochemical oxygen demand (BOD), and
chemical oxygen demand (COD). Analytical techniques employed for the analysis
of the samples were in accordance with procedures outlined in the twelfth edition
of "Standard Methods for the Examination of Water and Wastewater, "1 except
for the subsequent changes. The procedure for the pH determination was as set
forth in "Standard Methods ... I Water," rather than the procedure of "Standard
Methods ... HI Wastewater, " since it was performed at 25°C instead of at the
20°C temperature of the latter procedure. Under field conditions it was easier
to maintain the 25 °C temperature in the trailer laboratory. In addition, the use
of the third (intermediate) buffer, pH = 6.86, provided a greater degree of
accuracy and precision. Procedures for suspended solids and volatile suspend-
ed solids conformed exactly to "Standard Methods..., " except that ignition was
for 30 minutes, instead of 15-20 minutes, to more adequately assure the thor-
oughness with which the volatiles are driven off.
33
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SECTION vn
DISCUSSION
General Testing
After the installation of the pilot plant facility, a debugging phase was employed
to test the overall reliability of the facility. Initial tests indicated problems in
the magnetic flow metering system and leaks in the offshore system.
The electrical system functioned properly except for the Foxboro flowmetering
system that monitored the flow to and from the storage container. The receiver
and recorder of the metering system was remotely located on the control panel
in the trailer. After exhaustive testing indicated that the system would not
function reliably under the remote conditions, the receiver and recorder unit
and the associated timer were removed from the trailer control panel and in-
stalled in the pumping station, where satisfactory results were achieved.
The offshore system was tested for leaks by pumping a concentrated solution of
uranine dye from the wet well into the system. Leaks were detected in the
vicinity of the storage tank. An underwater inspection, performed by a diver.
revealed three rips in the flexible cover. Each rip was located over aneductor,
which protruded inward of the tank. Metal plates were fabricated and coated
with gum rubber to conform with the configuration of the damaged area on the
flexible rubber cover. These plates, which were installed by two scuba divers.
were successfully used to sandwich the ripped areas of the rubber cover. Pro-
tective devices, that were fabricated of steel rods, were installed by divers
around each eductor. Consequently, no further damage occurred to the rubber
cover.
The full scale test runs started with a simulated run on June 19, 1969. During
the next month and one-half, four rainfalls were captured and monitored and
three additional simulated runs were performed. In addition the facility was
mechanically used when water entered the overflow sewer from other than a
rainfall or simulated test. During these periods no sampling was carried out.
Prior to any simulated run, the tank was pumped relatively clear of its contents.
The characterization of the water pumped in each test run is presented in tables
H - DC.
The data from the simulated runs cannot be considered in describing the charac-
ter of combined sewer overflows because it is made up primarily of fresh water
discharged from a fire hydrant. Although it is flushed across the street to the
sewer it is concentrated across one path which becomes very clean in a hurry.
The higher pH on these runs identifies the source of the water as treated water
as opposed to sewage and rainfall runoff water.
One noteworthy observation of the simulated runs is that the first sample is
35
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TABLE II
ANALYTICAL RESULTS OF OVERFLOW DISCHARGE OF JUNE 19, 1969 -
SIMULATED OVERFLOW, TEST NO. 1
Time
10:55
11:10
11:25
11:40
11:55
12:10
Temp.
°C
26.0
25.5
25.7
25.5
24.5
24.5
pH
8.1
8.4
8.2
8.6
8.4
8.3
Sett. Solids
ml/1
4.0
1.0
9.0
1.0
0.5
0.1
T.S.S.
mg/1
8.0
9.0
32.0
10.0
9.0
16.0
V.S.S.
mg/1
6.0
4.0
23.0
10.0
9.0
10.0
COD
mg/1
—
—
—
—
—
—
BOD
mg/1
300.0
190.0
275.0
80.0
50.0
25.0
ANALYTICAL RESULTS OF STORED OVERFLOW
*RETURN FLOW JUNE 20, 1969
Sample
No.
1
2
3
4
24.0
24.0
24.0
24.0
7.9
7.9
7.9
7.9
Trace
Trace
Trace
Trace
1.0
1.0
1.0
6.0
1.0
1.0
1.0
4.0
—
—
—
—
100.0
90.0
150.0
130.0
*Return samples taken after every 20,000 gallons
36
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TABLE III
ANALYTICAL RESULTS OF OVERFLOW DISCHARGE OF JUNE 24, 1969 -
SIMULATED OVERFLOW, TEST NO. 2
Time
11:05
11:27
11:42
11:50
12:05
12:20
Temp.
°C
28.0
26.0
26.0
26.0
26.0
25.0
PH
8.0
8.2
8.3
8.2
8.2
8.3
Sett. Solids
ml/1
9.0
0.4
0.4
0.4
0.2
0.1
T.S.S.
mg/1
40.0
4.0
2.5
2.5
2.0
1.5
V. S.S.
mg/1
36.0
4.0
2.5
2.5
2.0
1.5
COD
mg/1
568.0
37.0
80.0
43.0
25.0
31.0
BOD
mg/1
205.0
15.0
15.0
10.0
15.0
20.0
ANALYTICAL RESULTS OF STORED OVERFLOW
*RETURN FLOW JUNE 24, 1969
Sample
No.
1
2
24.5
24.5
7.6
7.8
Trace
Trace
3.0
2.5
3.0
2.0
37.0
37.0
20.0
20.0
*Return samples taken: No. 1 after return of 15,700 gallons and No. 2 after
55,000 gallons
37
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TABLE IV
ANALYTICAL RESULTS OF OVERFLOW DISCHARGE OF JUNE 26, 1969 -
SIMULATED OVERFLOW, TEST NO. 3
Time
11:15
11:25
11:35
11:50
12:05
12:20
Temp.
°C
26.5
24.5
25.5
24.0
24.5
23.5
pH
8.6
8.3
8.3
8.4
8.4
8.3
Sett. Solids
ml/1
21.0
3.5
0.2
0.2
0.1
0.1
T. S.S.
mg/1
10.5
7.0
6.5
5.0
2.5
2.8
V.S.S.
mg/1
90.0
7.0
6.5
4.5
2.5
4.0
COD
mg/1
728.0
31.0
31.0
31.0
12.0
31.0
BOD
mg/1
—
12.0
20.0
22.0
20.0
23.0
ANALYTICAL RESULTS OF STORED OVERFLOW
*RETURN FLOW JUNE 27, 1969
Sample
No.
1
2
25.0
25.0
8.0
8.0
Trace
Trace
8.5
8.0
6.0
6.5
12.0
18.0
32.0
23.0
*Return samples taken: No. 1 after return of 50, 000 gallons and No. 2 after
92,500 gallons
38
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TABLE V
ANALYTICAL RESULTS OF OVERFLOW DISCHARGE OF JULY 5, 1969 -
NATURAL OVERFLOW, TEST NO. 4
Time*
-
-
-
Temp.
°C
24.5
24.5
25.2
pH
7.0
7.3
7.4
Sett. Solids
ml/1
3.0
0.8
1.3
T.S.S.
mg/1
13.5
9.5
7.0
V.S.S.
mg/1
12.5
9.5
5.0
COD
mg/1
446.0
217.0
132.0
BOD
mg/1
—
105.0
55.0
*Samples taken at 15 minute intervals
ANALYTICAL RESULTS OF STORED OVERFLOW
"RETURN FLOW JULY 7, 1969
Sample
No.
1
2
27.0
27.0
7.4
7.4
1.0
2.5
15.5
20.0
9.5
14.5
157.0
290.0
120.0
105.0
*Return samples taken No. 1 after return of 3, 000 gallons and No. 2 after
6, 000 gallons.
39
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TABLE VI
ANALYTICAL RESULTS OF OVERFLOW DISCHARGE OF JULY 7, 1969 -
NATURAL OVERFLOW, TEST NO. 5
Time
11:25
11:40
11:55
12:10
12:25
12:40
Temp.
°C
25.5
26.0
25.5
24.5
25.5
26.0
pH
7.4
7.4
7.4
7.4
7.5
7.7
Sett. Solids
ml/1
1.5
1.2
0.7
0.5
0.3
Trace
T.S.S.
mg/1
1.0
4.5
8.5
6.5
4.0
4.5
V.S.S.
mg/1
1.0
4.5
1.0
4.5
4.0
4.5
COD
mg/1
120.0
102.0
102.0
84.0
96.0
108.0
BOD
mg/1
280.0
220.0
215.0
200.0
195.0
235.0
ANALYTICAL RESULTS OF STORED OVERFLOW
RETURN FLOW JULY 8, 1969
Sample
No.
1
2
26.0
26.0
7.0
7.0
0.5
0.5
21.0
15.0
12.0
10.5
147.0
235.0
235.0
215.0
40
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TABLE
ANALYTICAL RESULTS OVERFLOW DISCHARGE OF JULY 10, 1969 -
SIMULATED OVERFLOW, TEST NO. 6
Time
0039
0054
0109
0124
Temp.
°C
25.0
23.5
23.0
23.0
pH
7.8
8.1
8.2
8.2
Sett. Solids
ml/1
28.0
0.2
0.1
Trace
T.S. S.
mg/1
40.0
7.0
6.5
5.0
V.S.S.
mg/1
37.0
7.0
6.5
5.0
COD
mg/1
200.0
40.0
17.0
17.0
BOD
mg/1
—
—
35.0
—
ANALYTICAL RESULTS OF STORED OVERFLOW
*RETURN FLOW JULY 10, 1969
Sample
No.
1
2
25.0
25.0
7.7
7.7
1.0
Trace
26.0
15.5
13.0
11.0
130.0
40.0
—
40.0
*Samples taken: No. 1 after return of 17,000 gallons and No. 2 after
35, 000 gallons
41
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TABLE VIII
ANALYTICAL RESULTS OF OVERFLOW DISCHARGE OF JULY 12, 1969 -
NATURAL OVERFLOW, TEST NO. 7
Time
Temp.
°C
25.5
26.0
25.0
24.0
24.0
24.0
PH
6.9
6.9
7.2
6.9
7.1
7.3
Sett. Solids
ml/1
1.0
6.0
12.0
2.0
2.0
0.1
T.S.S.
mg/1
8.5
14.0
7.0
5.0
5.0
2.5
V.S.S.
mg/1
6.5
10.5
2.0
5.0
4.5
2.5
COD
mg/1
71.0
118.0
71.0
82.0
53.0
71.0
BOD
mg/1
—
90.0
65.0
60.0
45.0
60.0
RETURN FLOW - NO RETURN SAMPLES
42
-------
TABLE EX
ANALYTICAL RESULTS OF OVERFLOW DISCHARGE OF JULY 28, 1969 -
NATURAL OVERFLOW, TEST NO. 8
Time*
1700
1705
1745
1800
1830
Temp.
°C
24.0
24.0
24.0
26.0
26.0
PH
6.6
6.6
7.0
7.3
7.3
Sett. Solids
ml/1
7.0
7.0
2.5
Trace
Trace
T.S.S.
mg/1
16.0
15.0
18.0
15.0
15.5
V.S.S.
mg/1
13.0
13.0
15.0
13.0
11.0
COD
mg/1
—
—
—
—
—
BOD
mg/1
90.0
35.0
35.0
45.0
50.0
*Manual actuation of sampler
RETURN FLOW - NO RETURN SAMPLES
43
-------
comparable to the storm flow. Once the sewer has been flushed however, the
monitored values quickly drop to minimum levels in terms of pollution sources.
The four natural occurrence overflows were runs No. 4, 5, 7, and 8. The first
one, No. 4, was a very short rainfall that generated an insignificant quantity of
overflow water. Even then a decrease in all of the measured paramters was
evident. This decay indicates that the sewage in the line has been flushed out
and the storm flow has taken over as the major contributor. The return flow
samples are close to averaging out the values for the incoming flow. This
means that once in the tank the water has been homogeneously mixed and has
not measurably changed its state.
The second rain was of a longer duration and therefore allowed the collection
of samples over a 1-1/2 hour period. In contrast to the previous rain all the
measured parameters remained relatively constant during this storm period.
The initial first flush was not as high, but this was due to the fact that a pre-
vious storm and a simulated run on the two previous days had cleaned out the
sewer. Generally, the dry-weather sewer sludge accumulations are scoured
from the combined sewer by higher velocities and turbulences of flow during
rain storms or simulated storm events. A summary of the rainfall and over-
flow data are presented in Table X.
The use of flumes as metering devices for the discharge of storm overflow from
the drainage basin was ineffective, especially for the conditions of the tidal
river. For each natural overflow occurrence during the operational period, the
tide caused surcharged conditions within the sewer, thus flooding the measuring
devices, and causing inaccurate readings; therefore, discharge hydrographs
are not available.
In terms of biochemical oxygen demand (BOD), chemical oxygen demand (COD),
and settleable solids, the return flow from the storage tank appears unchanged
from the incoming flow of sewage. However, the total solids and volatile frac-
tion did increase significantly. This would indicate that some previously de-
posited material was scoured up by the large turnover of liquid and was flushed
out. This material was not of sufficient quantity however to have a noticeable
effect on the BOD.
The next rainfall was run No. 7. This runoff followed the pattern of the first
storm with the samples showing a decay in pollutional strength with time. The
level of strength was comparable to run No. 5 in terms of COD and total sus-
pended solids (T.S.S.) but was only half the strength in terms of BOD. No
samples were available on the return flow.
The fourth rain storm, run No. 8, indicated a first flush in terms of BOD but
not in terms of T.S.S. In this case the T.S.S. remained at a level comparable
to the high point for previous storms. The BOD however started at me level
of the previous storm and then showed a significant reduction.
In an overall view the BOD and COD levels characterized a flow comparable to
typical sewage.
44
-------
TABLE X
SUMMARY OF RAINFALL AND OVERFLOW
Date
6/19
6/24
6/26
7/5
7/7
7/10
7/12
7/28
7/29
Activity
(storm)
simulated
simulated
simulated
natural
natural
simulated
natural
natural
simulated*
Total
Rainfall
(inches)
-
-
-
0.45
0.75
-
1.15
0.85
-
Overflow
Pumped to Storage
(gallons)
91,700
111,400
108, 100
20,600
44,300
43,400
55,200
121,000
184,000
Overflow
Pumped From Storage
(gallons)
96,700
119,600
113,500
20,600
47,700
47,000
58,800
-
-
*This simulation was conducted to fill the storage tank to maximum capacity
for visual inspection.
45
-------
In contrast the total suspended solids were consistently low. With the limited
amount of data it is impossible to determine if this was due to analytical pro-
cedures or was actually a characteristic of the runoff from this particular basin.
Regardless of what form it was in, the runoff did carry with it a significant
pollutional load in terms of oxygen demanding material. The flow when allowed
to be regularly discharged will have a noticeable effect in the quality of the
waterway.
The volumes of runoff water generated from this small basin indicate that
efforts to contain the total combined sewer flow in any single container may be
close to impossible; however, multiple tank installations could be used to pro-
vide sufficient capacity. During the short operational period, what might be
considered typical storms for the area were experienced. These storms gener-
ated overflows in excess of the pilot plant's pumping capacity of 2000 gpm and
in excess of the capacity of 18" overflow line. A projection to an overall full
scale operation for the entire city of Cambridge would require a reservoir sys-
tem capable of storing approximately 3.5 million gallons, to handle the major
portion of the polluting material.
Public Attitude and Acceptance
One of the criteria for a successful program was the development of a system
which was compatible with the surrounding buildings and which would not create
a nuisance condition to the neighborhood. In terms of engineering knowledge it
is believed that this had been accomplished. The onshore facility, once install-
ed, was visible only as two low rising manholes. The offshore facility was
marked by buoy lights to warn boaters of its underwater presence, but other-
wise it wf<5 not visible. The local boating community did not see this as an
invasion of their waterway, but on the other hand they were curious and interes-
ted observers. One unfavorable aspect of this program which manifested itself
from the beginning of the work, but for which we were unable to fully plan ahead
was the repercussion this project had on the neighborhood.
After the selection of the Choptank Avenue site, approval was sought and obtain-
ed from all concerned governmental agencies. This included the City Council
of Cambridge, Maryland, the State Health Department of Maryland, the State
Water Resources Commission of Maryland, the State Board of Public Works of
Maryland including the Chesapeake Bay Affairs Commission, and the U.S. Army
Corps of Engineers. After approvals for the installation and operation of the
proposed project at the selected site was received from the agencies, a public
hearing was held in Cambridge. The City Council approved the project and
granted permission to Melpar to continue work on the project. During the same
meeting, Melpar made the following concessions: relocation of the trailer and
a power pole and lowering of the pumping station and wet well manholes, in an
attempt to promote harmony.
The attitude of the residents immediately adjacent to the demonstration project
indicated a feeling that any sewer problems which might be experienced were a
direct result of having the facility located there.
An exceptionally large quantity of sea lettuce was present in the harbor and on
46
-------
the shoreline of the park. After a storm sufficiently intense to cause combined
sewer overflow, raw sewage discharged near the shoreline of the park and bulk
head near the Yacht Club on Water Street and further out into the water at West
End Street. The outfalls in this area should be in deeper water where the more
favorable current conditions prevail. The receiving waters at the outfall near
the park have always remained polluted for a period of one to five days after
each rainfall. The sewage from the outfalls adjacent to and including the
Choptank outfall decomposed and provided nutrients to the obviously large quan-
tities of algae which eventually washed ashore. Highly objectionable odors did
emanate from the putrid sewage and sea lettuce. Public complaints concerning
the foul odor were understandable: although, it was sometimes difficult to ex-
plain and convince people that the causes were not from the demonstration
project.
As background to the reactions of the residents it must be remembered that
Cambridge is an old seashore fishing village. Life is slow moving and quiet in
a tranquil environment. The families have lived in the same homes for genera-
tions and any change is a disruption of their way of life. Out of this backdrop
came such comments as "we fully support your idea and the need to stop pollu-
tion, but why can't you do it on the next street?" This background possibly
explains why the running of an open fire hydrant in the night made too much
noise in the neighborhood and caused them to call city officials requesting that
the water be turned off. This water was being used to simulate a rainfall. The
operation of the pumping station and storage facility itself did not apparently
disturb the neighborhood. This is encouraging because in a normal application
the facility itself would not be a disturbance to the neighborhood. It was, how-
ever, these research related disturbances which started to generate a commun-
ity environment that was best handled by a discontinuance of any further tests.
47
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SECTION VHI
REMOVAL OF PILOT PLANT FACILITY
The project site was restored to an appearance compatible with the surrounding
area as it existed prior to construction of the pilot plant facility. Both the off-
shore and onshore work was performed under contract with Smith Brothers Pile
Driving, Inc. (Galesville, Maryland). The cost for removal and site restora-
tion was $28,670.00.
The collapsible offshore storage tank and all its appurtenances were removed
from the Choptank River. After the removal of the storage tank from the
river bottom, the flexible cover was removed and an inspection was made of
the tank. Figure 14 shows a close-up view of the side of the steel tank. Numer-
ous marine crustaceans were attached to the tank's steel bottom (and also the
flexible cover). No apparent damage was observed as a result of the presence
of marine life.
The U-clamps, which were used to secure the storage tank to the wood pilings,
had rusted because they were not coated with a protective vinyl, an obvious
oversight before the installation of the tank. One of the clamps is shown in
figure 14.
The inside of the steel tank was relatively free of sludge deposits. This indicates
that the flushing procedure and circulation system was effective in keeping the
tank clear of settieable solids. Figure 15 shows an internal view of the storage
tank. The silt that was observed in one area of the tank was the result of the
discharge of external sedimentation from the flexible top into the tank during the
removal of the flexible cover.
The submersible pump and gate valve are shown in figure 16. The gate valve
and the mounting plate for the pump were damaged during the removal of the
storage tank. The deposits, both marine crustaceans and rust, could have a
deleterious effect on the heat transfer characteristics of the submersible pump.
During the course of the program, no problems were encountered with the opera-
tion of the pump nor with the protective heater element.
In general, the flexible cover was believed to be in good condition. After the
initial repairs, damages were not observed on the flexible cover as a result of
system performance and the presence of saline water and marine crustaceans.
The patches were intact on the torn areas of the cover. The metal plates of the
patches did not cause damage to the cover. Hard rubber plates should be sub-
stituted for the metal plates and assembled with plastic nuts and bolts. The
presence of saline water was obviously detrimental to the metal components of
the patches used in repairing the cover; however, time and the urgency to begin
program testing did not allow for time consuming design, selection of materials,
and testing.
49
-------
Figure 14. Close-up View of Storage Tank After Removal
50
-------
Figure 15. Internal View of Storage Tank After Removal
51
-------
Figure 16. Submersible Pump and Gate Valve After Removal
52
-------
The onshore restoration was performed as smoothly and efficiently as the off-
shore restoration. Inspection of the onshore equipment did not reveal any
damage, other than normal wear, except to the upstream recorder. The record-
er was damaged by water that infiltrated in the unit during a surcharged sewer
condition.
53
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SECTION K
COSTS
The costs for the pilot plant facility to store combined sewer overflow from the
Choptank Avenue drainage basin are summarized in Table XI. The onshore and
offshore subsystems were fabricated and constructed by subcontractors. The
value given in the table for the construction and installation of the offshore sys-
tem also includes the cost for pilings (6), 12-inch cast iron pipe (1300 ft.) and
electrical cables (1300 ft.). Similarly for the onshore elements of the system,
the sewer pipe, manhole materials, electrical cables and conduits, and the 8-
inch cast iron pipe were furnished by the onshore subcontractor and these costs
are included in the value given for the onshore construction.
A municipality could expect to duplicate the pilot plant facility at a similar site,
for slightly more than $150, 000. The total cost depends upon the obvious
variables of local labor rates, the distance of the storage tank from the shore
line, and individual onshore construction requirements. In addition, the assoc-
iated costs of site surveys, detailed design, and inspection could increase the
total cost of such a facility. These costs are not included in Table XI, for
municipalities would frequently assign these functions to the normal work load
of existing off ices; i.e., City Engineer, Sanitary Engineer, Planning, etc.
The annual operation and maintenance costs for the pilot plant facility are tabu-
lated in Table XII. The costs are based on labor and supervision supplied by
the city only during overflow conditions and costs realized during the perfor-
mance of this demonstration project. Maintenance costs include two under-
water inspections of the storage module and general maintenance of the
equipment.
The cost of replacing the combined sewer in the Choptank Avenue drainage
basin with a complete separate dual system would be $262,000. This figure
is based on the cost data published by the U.S. Department of Interior.*
The nominal design capacity of the pilot plant underwater storage facility was
200, 000 gallons. The flexible cover actually contained a larger volume than
expected, resulting in a total capacity of 248,000 gallons. The storage capacity
of the pilot plant, then, was sufficient to allow total containment of the runoff
from more than 40 of the 55 storms which are anticipated during a given year
(see Table I). The facility could totally contain some 75 percent of the individual
rainfall events.
The average annual runoff from the Choptank Avenue drainage basin is estimated
to be 8.9 million gallons. The pilot plant facility could contain 8.6 million
gallons of this runoff, or approximately 96 percent of the total yearly overflow.
The storage and treatment of this quantity of combined sewer overflow would
prevent the annual discharge of 7,136 pounds BOD, based upon an average five
day BOD of 100 ppm. The discharge of all but 299 pounds BOD would be pre-
vented.
55
-------
TABLE XI
TOTAL COST FOR COMBINED SEWER OVERFLOW FACILITY
Task
Total Costs
OFFSHORE
Subsystems and Supplies
Steel tank
Flexible cover
Installation of flexible cover to tank
Miscellaneous supplies
Construction
$
27,175.00
13,254.00
2,039.00
3,368.00
Subtotal $ 45,836.00
$ 46,830.00
Subtotal $ 92,666.00
ONSHORE
Subsystem and Supplies
Pumping station and wet well
Remote control panel
Miscellaneous supplies
Construction
$ 22,550.00
6,200.00
3,097.00
Subtotal $ 31,847.00
$ 31,488.00
Subtotal $ 63,335.00
MAINTENANCE - REPAIRS
LABOR (OPERATING, SAMPLE COLLECTION,
WATER QUALITY ANALYSES)
$
865.00
$ 2,167.00
TOTAL
$ 159,033.00
56
-------
TABLE XII
ESTIMATE OF ANNUAL OPERATION AND MAINTENANCE COSTS
Labor and Supervision
Maintenance
Power
Materials and Supplies
$4,500
1,100
1,400
300
Total Annual Cost
$7,300
57
-------
The approximate cost of storage and return per one thousand gallons is $1.85
based upon prorating the facility cost over a ten year life expectancy for the
system; increasing to $2.71 when the estimated annual operation and mainte-
nance costs are added to the installation cost for the same ten year period. The
approximate costs per pound of BOD are $2.22 and $3.25, respectively, on the
same basis. The ten year life expectancy is considered to be a conservative
estimate, and the annual operational costs may well be a part of other sewage
department labor assignments. The actual cost of storage and return could be
less than $1.50 per thousand gallons, with a cost per pound of BOD less than
$2.00, if the underwater storage facility was an integral part of an overall
sewage treatment system.
58
-------
SECTION X
ACKNOWLE DGEMENTS
Melpar wishes to express its appreciation to the several organizations and many
individuals who made extensive contributions during the course of this program.
Melpar is especially indebted to the City of Cambridge, Maryland and to the
Honorable Mayor Osvrey C. Pritchett and the City Council. Mr. Robert L. Dodd,
Director of the Department of Public Works, rendered valuable assistance and
furnished valuable data and information relative to the program. Melpar is in-
debted also to Mr. Bernard W. Dahl, Consulting Engineer, Rockville, Maryland,
for his capable and valuable assistance and consultation. The service provided
by the following subcontractors was of considerable value to the conduct of this
project:
American Welding Co., Baltimore, Md., Steel Tank
Schmieg, Division of Sydnor Hydrodynamics, Inc., Richmond, Va.,
Wet Well and Pumping Station
Uniroyal Plastics Products, Mishawaka, Ind., Rubber Cover
Smith Brothers Pile Driving, Inc., Galesville, Md., Offshore Con-
struction
Norris E. Taylor Contractors, Inc., Easton, Md., Onshore Con-
struction
B. C. Langley
T. P. Meloy
59
-------
SECTION XI
BIBLIOGRAPHY
1. "Standard Methods for the Examination of Water and Wastewater, "
12th Ed., American Public Health Association, Inc., New York
(1965).
2. "Problems of Combined Sewer Facilities and Overflows 1967."
U. S. Department of Interior, FWPCA, Publ. WP-20-11, U. S.
Government Printing Office, Washington, B.C. (1967).
61
-------
SECTION XII
APPENDIX
Choptank Avenue and Park
Flexible Cover Fabrication
Fabric Back-up Plate
Storage Tank
Storage Tank Sub-Foundation
Storage Tank Installation
63
-------
PAGE NOT
AVAILABLE
DIGITALLY
-------
BIBLIOGRAPHIC:
Melpir, an American-Standard Company. Combined Sewer Temporary Underwater
Slonfi Facility. Frofram No. II022DPP, Contract No. 14-12-133. October 1970.
A pilot plant underwater atorap facility waa deufned. i
sat1
ieidte. Maryland. Combined etwafe in net. of Ike .ewer capacity, which would
(ed directly into Ike Choptank River, waa intercepted and pumped
ilainer located 1300 feel offahore. The a
th from four naturaDy oecurrinf ramfalb and uainf
e analyzed in a field laboratory tor the fouowinf
landed aolida. actlleabk eoUa. 5 day biochemical
into a nominal
waa later returned from the lank at a rate"which could be accommodated by the mtereeptinf arwer
and treatment plant
The facility wa. teated with overflow both from four
freah water aunulabon. The overflow aamplea were
craracterMka: pH, auapended aolida, volatile .upendedaoUda. eettleable aobaWSday
oiyetn demand, and chemical o.yien demand.
The piot planl facihly waa capable of eoleeuBf 96 percent of the avenfe annual overflow
me annual diaduufe of 7,136 pounda BOD into'the^hoptank Rner. "°" '"""
Underwater atorafe faciliuea could be uaed effectively for many combined aewer
areaa. Site aeketton, however, haa been proved to be a critical factor. Care mat be enroled la
prevent public aMurbanee, and faetora euch aa land uae, tidal condition* or the type, of atorma,
muatalaobeconaiderci.
Thia report waa aubmittcd in fuKlhnent of contract number 14-12-113 under the aponaor-
ahip of the Federal Water Quality/
ACCESSION NO.
KEY WORDS:
Hydrotoiy
hrnpinfMMIon
BIBLIOGRAPHIC:
Melpar, an American-Standard Company, Combined Sewer Temporary Underwater
Storafe FadHty. Pnpam No. 11022DPP. Contract No. 14-12-133. October 1970.
ABSTRACT
ACCESSION NO.
KEY WORDS:
A pilot plant underwater alorafe facility wu di
draina*baaiaiCanalirie]B*. Maryland. Combined aewafe ill
normally be diedtanjed directly into the Onptank River. •
200.000 faBon flelible underwater atora(e container local.
icted, operated and evaluated
ewer of the Choptank Avenue
ledwd of temporarily atorinf atorm overflow from the combined aewer o
"" ----- ... rafemeseeaaof the aewer capacity, which would
iver, waa intercepted and pumped into a nominal
:r located 1300 feet offahore. The atored overflow
waa later returned from the tank at a rale which could be accommodated by the mtereeplinf aewer
and treatment plant
The facility waa teated with overflow both from four naturally occurriraj ninfalla and uainf
freah water aimulaoon. The overflow aamplea were analyaed in a field laboratory for the foUowuif
characttrietiei: pH, auapended aolida, volatile auapended MUda. acttkabk aolidi, 5 day biochemical
capable of cotketinf 96 percent of the averafe annual overflow
himuWdraia»iehiaaaatacoatre- The atored overflow
waa later returned from the lank at a rale which could be accommodated by the Merceptinf arwer
and treatment plant
The faculty waa teated with overflow both from four n
freeh water aimuteioeu The- overflow aampleat " *
cfcanetnMIn: pH. auapended aobda. volatile n
«vfen demand, and chemical oiyfen demand.
The pilot plant facility «raa capable of coUeetinf % percenl of the averafe inoual overflow
frc^UMdrairor haemal a coat of leaa than tl.Urxrdiouaandailona. ThefadUtyc
the annual dlackarfe of 7.1 36 pounda BOD into the Choptank Rrm.
" " f | adfcitieB « "" - - - - -
ACCESSION NO.
KEYWORDS:
Storm ovajrflow
. both from four naturally occuninf ramfalla and utinf
i were analyaed m a fleU laboranrr for the fotowinf
auapended aobda. aettleabk aokda. 5 day bwchemkal
• could he uaed effectively for many combined aewer
areaa. Site adection.laowe.er.haa Wen proved to be a critical factor. Care aaual be eierciaed to
prevent public dianirbanee, and facton auch aa hnd uae, tidal condibona, or the type, ofatorma,
mudakobeeoriaklered.
Thla report waa «jbnitted In fulfiUmenl of contract number 14-12.133 under the aponaor-
ahipof the Federal Water Quality AdniUuatration.
-------
i Accession Number
c Organization
o 1 Subject
*• \ Field* Group
05D
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
MELPAR, an American-Standard Company
7700 Arlington Boulevard
Falls Church. Vireinia 22046
0 Title
COMBINED SEWER TEMPORARY UNDERWATER STORAGE FACILITY
J2.
22
Authors)
Meloy, T. P.
Langley, B. C.
11
Date
October 1970
16
12
Patfea
79
Project Number
21
i F Contract Number
14-12-133
Note
Citation
23 I
— '
Descriptors (Starred First)
storage overflow
combined sewers
underwater storage
hydrology
pumping station
25 i Identifiers (Starred First)
Abstract
A pilot plant underwater storage facility was designed, constructed, operated and
evaluated as a method of temporarily storing storm overflow from the combined sewer
of the Choptank Avenue drainage basin, Cambridge, Maryland. Combined sewage in
excess of the sewer capacity, which would normally be discharged directly into the
Choptank River, was intercepted and pumped into a nominal 200,000 gallon flexible
underwater storage container located 1300 feet offshore. The stored overflow was later
returned from the tank at a rate which could be accommodated by the intercepting sewer
and treatment plant.
The facility was tested with overflow both from four naturally occurring rainfalls
and using fresh water simulation. The overflow samples were analyzed in a field
laboratory for the following characteristics: pH, suspended solids, volatile suspended
solids, settleable solids, 5 day biochemical oxygen demand, and chemical oxygen demand.
The pilot plant facility was capable of collecting 96 percent of the average annual
overflow from the drainage basin at a cost of less than $1.85 per thousand gallons. The
facility could prevent the annual discharge of 7,136 pounds BOD into the Choptank River.
Underwater storage facilities could be used effectively for a number of combined
sewer areas. Site selection, however, has been proven to be a critical factor. Care
must be exercised to prevent public disturbance, and factors such as land use, tidal conditions,
or the types of storms, must also be considered.
This report was submitted in fulfillment of contract number 14-12-133 under the
sponsorship of the Federal Water Quality Administration.
Abstractor
T. P. Meloy
Inttitution
Melpar, an American-Standard Company
WR;10a (REV. OCT. <••!)
WR1IC
(END TO! WATER REIOURCEI SCIENTIFIC INFORMATION CENTER
U f. DEPARTMENT OP THE INTERIOR
WA1HINOTON. O.C. aO*40
•ft D. S. GOVERNMENT PRINTING OFFICE : 1970 O - 410-209
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Continued from Inside front cover....
11022 — 08/67 Phase I - Feasibility of a Periodic Flushing System
for Combined Sewer Cleaning
11023 — 09/67 Demonstrate Feasibility of the Use of Ultrasonic
Filtration 1n Treating the Overflows from Combined
and/or Storm Sewers
11020 — 12/67 Problems of Combined Sewer Facilities and Overflows,
1967, (WP-20-11)
11023 — 05/68 Feasibility of a Stabilization-Retention Basin 1n Lake
Erie at Cleveland, Ohio
11031 — 08/68 The Beneficial Use of Storm Water
11030 DNS 01/69 Water Pollution Aspects of Urban Runoff, (WP-20-15)
11020 DIH 06/69 Improved Sealants for Infiltration Control, (WP-20-18)
11020 DES 06/69 Selected Urban Storm Water Runoff Abstracts, (WP-20-21)
11020 — 06/69 Sewer Infiltration Reduction by Zone Pumping, (DAST-9)
11020 EXV 07/69 Strainer/Filter Treatment of Combined Sewer*Overflows,
(WP-20-16)
11020 DIG 08/69 Polymers for Sewer Flow Control, (WP-20-22)
11023 DPI 08/69 Rapid-Flow Filter for Sewer Overflows
11020 DGZ 10/69 Design of a Combined Sewer Flu1d1c Regulator, (DAST-13)
11020 EKO 10/69 Combined Sewer Separation Using Pressure Sewers* (ORD-4)
11020 — 10/69 Crazed Resin Filtration of Combined Sewer Overflows, (DAST-4)
11024 FKN 11/69 Storm Pollution and Abatement from Combined Sewer Overflows-
Bucyrus, Ohio, (DAST-32)
11020 DWF 12/69 Control of Pollution by Underwater Storage
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