HYDRO BRAKE STORMUATER DETENTION
SYSTEM DEMONSTRATION IN CLEVELAND, OHIO
Dual Combined Sewer Overflow
Pollution Control and Basement
Flooding Relief
by
Timothy M. Matthews
Paul D. Pitts, Jr.
R. Charles Larlham
Snell Environmental Group, Inc.
Stow, Ohio 44224
Grant No. G005370
Project Officer
Ralph G. Christensen
Great Lakes Demonstration Program
Great Lakes National Program Office
Chicago. Illinois 60604
Technical Advisors
Richard P. Traver
Douglas C. Ammon
Municipal Environmental Research Laboratory
Cincinnati. Ohio 45268
This study was conducted in cooperation with the
Municipal Environmental Research Laboratory
United States Environmental Protection Agency
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DISCLAIMER
This report has been reviewed by the Municipal Environmental Research
Laboratory and the Great Lakes National Program Office, U.S. Environmental
Protection Agency, and approved for publication. Approval does not signify
that the contents necessarily reflect the views and policies of the U.S.
Environmental Protection Agency, nor does mention of trade names or com-
mercial products constitute endorsement or recommendation for use.
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ABSTRACT
This research project was initiated with the overall objective of determining
the ability of the Hydro Brake flow control device, in conjunction with offline
underground storage, to limit the rate of stormwater flow into combined sewers.
The .intended result of this control was the reductions of overflows (CSO) and
street and basement flooding during storm events.
Three underground storage tanks were constructed and outfitted with Hydro
Brakes of different flow rates. The storage tanks were filled, and their rates
of discharge were measured to establish discharge curves for the Hydro Brakes.
The Hydro Brakes were then monitored for performance during actual storm events.
During the study, each Hydro Brake was downsized and retested for discharge
rates, permitting the evaluation of six sizes of Hydro Brakes. Homeowner surveys
were also undertaken to evaluate the effects of the Hydro Brake/storage instal-
lations on flooding.
Results of the draindown tests were evaluated in terms of their comparison
with discharge curves of orifices of equivalent size. Measured storm flows were
similarly evaluated. In addition, one year, two year, five year and ten year
return period storm flows were identified from storm frequency tables, and
discharge hydrographs and storage needs were then calculated from those storm
flows and the observed discharge curves.
It was demonstrated that the Hydro Brakes did release storm flows to
combined sewers more slowly, and at a rate more nearly independent of head,
than orifices of equivalent size. The use of off-line storage tanks appeared
to reduce the incidence of street and basement flooding.
This report was submitted in fulfillment of Grant No. G005370 by Snell
Environmental Group, Inc. under the sponsorship of the U.S. Environmental
Protection Agency. This report covers the period from September, 1980 to
August, 1981, and work was completed as of January 31, 1982.
IV
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CONTENTS
Foreword -Hi
Abstract -..,. iv
Figures ". vii
Tables viii
Abbreviations and Symbols ix
Acknowledgment x
1. Introduction 1
2. Conclusions 7
3. Recommendations 9
4. Method of Approach 11
General Procedures n
Description of Hydro Brake Control Devices H
Description of Installations 12
Simulation of Design Conditions 15
Storm Flow Monitoring 18
Precipitation Records l9
Water Quality Sampling 19
Survey of Service Area Population 20
Data Analysis 20
5. Results 22
Discharge Curves 22
Storm Hydrographs 29
Storm Water Quality 33
Homeowner Surveys 37
6. Design and Performance Evaluation 42
Design Concept ^2
Design Criteria 42
Storm Simulation and Design 43
Evaluation of Original Design . , , 44
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Hydro Brake Redesign 46
Evaluation of Hydro Brake Redesign 47
7. Comparative Evaluation of Flow Regulator • 52
Installations 52
Rochester, New York 52
Nepean Township, Ottawa> Canada 56
Borough of York, Ontario, Canada 62
Comparison of Installations . . ^ 62
8. Alternative Evaluation 67
General Screening of Alternatives 67
Description of Viable Alternatives 68
Cost Estimates of Viable Alternatives 68
References 70
Bibliography 71
Appendices 72
A. Formulae, Head vs. Volume Tables 72
B. Homeowner Survey 78
C. Water Quality Data , 80
D. Photographs and Sediment Measurements 87
E. Design Storm Hydrographs 100
F. Cleveland Design Report 112
G. Hydro Brake Demonstration Project
Santee Drainage Area - Rochester, New York 147
(O'Brien and Gere Engineers, Inc., 1981)
VI
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FIGURES
Number Page
1 Study Area Location Map 3
2 Drainage .Area and Control Structure Locations 4
3 Overflow Chamber M-15 5
4 W. 170th Street Installation 13
5 W. 177th Street Installation 14
6 Puritas Avenue Installation 16
7 W. 170th St. Head-Discharge Curves: Original Design . . 23
8 W. 170th St. Head-Discharge Curves: Redesign 24
9 W. 177th St. Head-Discharge Curves: Original Design . . 25
10 W. 177th St. Head-Discharge Curves: Redesign 26
11 Puritas Ave. Head-Discharge Curves: Original Design . .. 27
12 Puritas Ave. Head-Discharge Curves: Redesign 28
13 Hydrographs at W. 177th St. Control Structure -
Storm of June 8-9, 1981 32
14 Hydrographs at W. 177th St. Control Structure -
Storm of July 13, 1981 34
15 Hydrographs at W. 170th St. Control Structure -
Storm of July 13, 1981 35
16 Hydrographs at W. 170th St. Control Structure -
Storm of August 7, 1981 36
17 Basement Flooding Survey Responses 40
18 Street Flooding Survey Responses ^
19 Head-Discharge Curves - Santee Drainage Area 53
20 Head-Discharge Curve - Santee Hydro Brake 54
21 Storm of May 11, 1981 - Santee Drainage Area 55
22 Inflow-Outflow Hydrographs - Nepean Twp.
Area 1 - October 30 -31, 1976 57
vii
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23 Inflow-Outflow Hydrographs - Nepean Twp.
Area 2 - May 23, 1977 58
24 Inflow-Outflow Hydrographs - Nepean Twp.
Area 2 - June 25, 1977 59
25 Inflow-Outflow Hydrographs - Nepean Twp.
Area 2 - June 29, 1977 60
26 Inflow-Outflow Hydrographs - Nepean Twp.
Area 2 - July 1, 1977 > 61
27 Comparison of Hydro Brake Discharge Curves 64
TABLES
Number Page
1 Hydro Brake Drainage Areas 31
2 Summary of Sampling Results 38
3 Combined Sewer Overflow Reduction at M-15 43
4 Original Hydro Brake Design - 5 year Design
Storage and Discharge Requirements 45
5 Comparison of Hydro Brake Discharge Rates -
Original Design vs. Redesign 47
6 Design Hydrograph Parameters - 1/2 hour storm
Rainfall and Intensity 49
7 Comparison of Hydro Brake Discharge Rates and
Storage Volumes for Original Design vs. Redesign 49
8 Summary of Hydro Brake Control/Retention for 1/2 hour
Duration Design Storms 51
9 Analysis of Peak Flow Attenuation for 2 in. Unit 56
10 Comparison of Rated and Actual Hydro Brake Discharges ... 65
11 Cost Comparisons of Storm Flow Control Alternatives .... 69
vm
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LIST OF ABBREVIATIONS AND SYMBOLS
ABBREVIATIONS
CFS/cfs — cubic feet per second
cm — centimeter
cm/hr — centimeters per hour rainfall intensity
CMP — corrugated metal pipe
CSO — combined sewer overflow
ft^ — square feet
ft3 — cubic feet
ha — hectare
in — inch
in/hr — inches per hour rainfall intensity
km — kilometers
L — liter
L/s — liters per second
mm — millimeter
M — meter
ml/1 — milliliters per liter
mg/1 — milligrams per liter
RCP — reinforced concrete pipe
ix
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ACKNOWLEDGMENTS
During the course of this evaluation, special assistance was provided by
the City of Cleveland's Divisions of Utilities Engineering and Water Pollution
Control, the Northeast Ohio Regional Sewer District and the National Weather
Service. Their cooperation is sincerely appreciated.
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SECTION 1
INTRODUCTION
BACKGROUND
The City of Cleveland has long been plagued with most of the well-
documented problems which beset urban centers served by combined sewer sys-
tems. Such systems are subject to overflow problems as a matter of design.
Combined sewer overflows (CSC) are designed into these systems as the
primary method of relief when flows exceed the capacity of the receiving
sewers. However, while it provides hydraulic relief for receiving sewers
and sewage treatment plants, CSO often carries heavy loads of pollutants
to streams and water bodies. This is especially true of the "first flush"
waters from an intense storm.
CSO occurrences can be eliminated, or their impacts attenuated, by a
variety of documented, generally effective and acceptable methods. However,
these methods are not always effective in relation to another set of prob-
lems often associated with combined sewer systems - basement and roadway
flooding. Those CSO problem solutions which include flow retardation may
exacerbate flooding problems.
In addition, CSO itself often provides relief only for areas downstream
from most of the sewer system. Upstream areas have no external area to which
overflow may be routed. Thus, the system is relieved by surcharging into
basements, or to the ground (usually the roadway) surface. Surcharging and
flooding represent very evident health hazards. Structural damage as a
result of hydrostatic pressure and/or wash-out, as well as damage to per-
sonal possessions, are also frequent occurrences.
For all of these reasons - water quality, health, safety and property
damage - control of CSO and combined sewer surcharging has become very
important in recent years.
Over the past several years, numerous investigations have been under-
taken to determine cost effective methods of abatfng CSO without making
flooding worse, or to abate flooding and surcharging without increasing
CSO. Much of this effort has concentrated on upstream stormwater, and
methods of retaining it without worsening local flooding.
One method has been to provide storage of upstream stormwater, with
release to receiving sewers after downstream stormwater has drained.
This approach avoids upstream flooding by not allowing stormwater into
sewers until capacity is available, and avoids downstream surcharging
and CSO by permitting downstream flow to be conveyed away before upstream
flows can arrive.
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Various approaches to upstream storage have been devised: roof storage,
roadway storage, in-line or off-line storage with reduced discharge orifices
and offline storage with discharge pumps.
The City of Cleveland and the EPA Great Lakes Demonstration Program under-
took the investigation of the effectiveness of off-line storage with release con-
trolled by a proprietary device, the Hydro Brake, which purportedly permits
discharge at a relatively constant rate.
PROBLEM DEFINITION
The Puritas Avenue - Rocky River Drive area of the City, chosen for
this Investigation, encompasses approximately 115 (46.6 ha) acres. Of this, 9.0
acres (3.6 ha) contribute flows to the Hydro Brake Structures (Figures 1 and 2).
This area is served entirely by combined sewers. The area was primarily developed
during the 1920's as a medium density residential neighborhood.
The combined sewers in the neighborhood carry sanitary flows, as well as
roof drain, weeping tile, driveway drain and street flows. All flows from the
area are ultimately conveyed to a CSO chamber (M-15 - Figure 3) via a 42 inch
(1.1M) sewer, from which a 36 inch (0.9M) sewer conveys flows which do not
exceed its capacity to the Southerly Sewage Treatment Plant. Flows in excess
of the capacity of this sewer are discharged into a 60 inch (1.5M) CSO sewer,
which connects to a 78 inch (2.0M) sewer discharging to the Rocky River.
River.
Downstream of M-15, 507 acres (205 ha) of land are tributary to the 78 inch
(2.0 M) sewer. Land uses are industrial and residential, and during storms which
produce CSO from M-15, backwater from this area affects performance of
the Puritas Avenue area sewers.
Overland storm drainage within the demonstration area is discontinu-
ous, resulting in street flooding at low road points during sewer system
surcharge. Basement flooding also occurs throughout the area during severe
rainfall events.
During the design phase of this project, an actual storm event with
cumulative rainfall approximately equal to a five-year storm was used in a
sewer system response simulation to further define the extent of the CSO and
combined surcharge problems. The Simulation indicated that the Puritas Avenue
42 inch (1.1H) sewer was surcharged at an average loading ratio of 2.0, (i.e.,
it was subjected to a flow rate double its capacity). Tributary sewer ratios
averaged 1.5, and ranged from less than 1.0 to 3.0. An analysis of this storm
indicated that some basement floodings would occur every six to nine months,
with CSO occurring every four to six months.H'
OBJECTIVES
The primary objective of this investigation was to evaluate the abi-
lity of the Hydro Brake to effectively regulate specific design flows from
stormwater storage structures to such an extent that receiving sewers could
be protected from surcharging and creating CSO conditions.
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CLEVELAND
HOPKINS
AIRPORT
LEGEND
(NO SCALE)
STUDY AREA
• RAIN GAUGE LOCATIONS
FIGURE-I
STUDY AREA LOCATION MAP
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^ r
-^~-"
*s
o
CD
»•
>
h-
N
Jf
NQIANA AVE.
FAIRVILLE
OVERFLOW CHAMBER
M-15
LEGEND
(NOT TO SCALE)
LJ COMBINED SEWER DRAINAGE
I.J CONTROL STRUCTURE DRAINAGE AREA
LOCATION OF STRUCTURES
FIGURE 2 DRAINAGE AREA AND CONTROL STRUCTURE LOCATIONS
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INV. 768.66
—TOP 772.00
FIGURES OVERFLOW CHAMBER M-15
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The secondary objective of this investigation (although undoubtedly the
primary concern of the residents of the study area) was to reduce
flooding in the study area.
SCOPE OF STUDY
Three off-line underground stormwater storage units were installed in
the study area, and a Hydro Brake was installed in each. The following moni-
toring and evaluation tasks were then performed:
1. Five storm events were monitored for inflow, hydraulic level in the
unit and discharge. Discrete and composite water quality samples
were taken from the storage tanks and analyzed, and observations
of sedimentation were made. Discharge curves were developed and
analyzed for the three devices.
2. In addition to the above monitoring and analysis, observations
of the operating characteristics of the devices were made, home-
owner interviews were undertaken, and other similar installations
were comparatively analyzed from reports.
3. From the above information, an analysis of the efficacy and cost
effectiveness of the off-line storage/Hydro Brake system as a CSO
attenuation and flooding relief approach has been prepared.
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SECTION 2
CONCLUSIONS
This study has examined the performance and design concept of the
Hydro Brake method of inlet control for regulation of peak runoff rates
and temporary storage of storm flows. This application was evaluated in
relation to its ability to reduce combined sewer surcharge and resultant
combined overflows.
This evaluation offers the following conclusions:
1. The Hydro Brake device does regulate flow rates at relatively
constant levels once an effective operating head has been de-
veloped. Conversely, the device behaves as an orifice below
the effective range of heads. Hydro Brake flow rates above the
effective operating head are substantially lower than those
for an orifice or other clear opening of the same size.
2. The flow regulating capability of the Hydro Brake causes re-
ductions in combined sewer overflow peak rates and total
volumes by reducing the stormwater inflow rate to the sewers
upstream of the control point and by delaying the drainage of
storm runoff.
3. By removing the peak rate surge from the sewer system, combined
overflow pollutant loadings are reduced because the first flush
effect is dampened.
4. Hydro Brake regulation of peak inflow rates is effective in
alleviating sewer surcharge and basement flooding problems.
5. Percentage reduction in peak flow rates by the Hydro Brake
device is dependent upon the percentage of total runoff which
can be intercepted, as well as the level of control and dis-
charge rate desired. Discharge rates may be lower than avail-
able excess capacity in receiving sewers, depending upon the
availability of surface storage and/or the feasibility and
expense of additional below grade storage.
6. Inlet control for purposes of storm water flow rate regulation
may be accomplished with orifices, but the orifice size must
be smaller than the Hydro Brake that would be required for the
discharge rate desired. The use of an orifice results in a
larger range of discharge rates and a higher peak discharge
rate over a given range of heads when compared with a Hydro
Brake of the same size as the orifice.
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7. For effective application of the Hydro Brake control/storage
technology, it is important that the design approach includes
accurate characterization of drainage areas and sewer hydraulics
to properly identify site specific release rate requirements.^
The level of control desired determines the required storage
volume, and the characteristics of the site determine whether
to employ above grade or below grade storage, or a combination
.thereof.
8. Where surface ponding is an acceptable form of stormwater storage,
the application of Hydro Brakes aloneris more cost-effective
than Hydro Brakes used in conjunction-with off-line, below
grade storage structures. Both applications» however, are more
cost-effective than other combined flow alternatives where both
surcharging and overflows are the prevailing problems.
9. The design of inlet control/storage systems and the construction
of below grade storage structures and related appurtenances are
the major cost elements in the application of these systems.
The cost of the Hydro Brakes is a small portion of the total
project cost.
10. Because the Hydro Brake is a specialty item, sufficient lead
time must be allowed for manufacturing and delivery delays.
' Installation of the device is relatively simple where the proper
clearances have been provided in control structures.
11. During the first 18 months of operation, the Hydro Brake control/
retention structures exhibited minimal maintenance requirements.
Solids deposition in the storage tanks is almost negligible and
should not increase through time.
12. Fouling of small diameter Hydro Brake control devices with stormwater
debris is possible where inlets and catch basins are not trapped.
This occurred in both the Rochester and Cleveland projects.
13. The minimum practical size of Hydro Brake devices appears to be
approximately 2 inches (5 cm), provided that inlet structures
are trapped or otherwise constructed to capture debris this size
and larger. 2 inch (5 cm) units were used in catch basins in
Cleveland without any reported incidents of plugging. Smaller
sizes of Hydro Brakes are possible where stormwater flows are
relatively clean, as has been suggested for downspout control/
rooftop storage systems.
In summary, the Hydro Brake is an effective and feasible means of con-
trolling storm water flows. Applications are practical and inexpensive
because the inlet control concept makes optimum use of existing facilities.
Flexibility in stormwater storage options allows the concept to be adapted
to account for site differences and varying levels of control. Finally,
potential cost savings through use of the Hydro Brake technology offers
methods of stormwater control where other alternatives are prohibitive
in cost.
8
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SECTION 3
RECOMMENDATIONS
As a result of this study, certain design, evaluation and opera-
tional recommendations are proposed for existing and future Hydro Brake
control/storage technology applications.
1. Design of Hydro Brake control/retention systems must include
accurate simulation of storm inflow effects on receiving sewers
to properly identify maximum allowable Hydro Brake discharge
rates. Receiving sewers should be monitored to check the
validity of hydraulic modeling efforts and to verify the proper
selection of Hydro Brake discharge rates.
2. Design storm runoff characteristics must be properly identified
in relation to selected Hydro Brake discharge rates. An inflow/
outflow continuing relationship is necessary to determine the
optimum size stormwater storage requirements.
3. Identification of site specific characteristics is necessary to
properly identify runoff characteristics as well as the best
combination of surface and subsurface stormwater storage.
4. Surcharge indicators and receiving sewer level recorders should
be utilized as necessary to identify potential applications
and measure the effectiveness of existing installations.
5. Surface ponding effects of potential Hydro Brake control/storage
applications should be evaluated by selective installation of
control devices in catch basins prior to detail design.
6. Hydro Brake control/storage designs should be evaluated for use
in existing separate storm sewer systems for sediment control
and receiving stream flooding relief.
7. Hydro Brake control/storage applications should be considered
in storm sewer design for cost savings through pipe size
reduction, and to avoid transferring upstream flooding
problems to downstream areas.
8. Hydro Brake regulated catch basins should be inspected frequently
and cleaned as necessary to remove deposited debris.
9. Hydro Brake, regulated catch basins, as well as unregulated inlets
and catch basins, tributary to retention sturctures should be
designed to trap and prevent large debris and floatables from
interfering with Hydro Brake control devices. Traps should also
be employed to control the release of odors from combined sewers.
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10. Retention tanks should be inspected after every major storm event
to establish a history of debris and silt accumulation to deter-
mine ongoing maintenance and inspection requirements and verify
unobstructed entry to Hydro Brake control devices.
11. Hydro Brake control/storage project construction inspection should
include flooding or pressure testing of plugs inserted in abandoned
catch basin leads where stormwater flows are to be rerouted to
control/storage structures. Faulty plugs reduce stormwater
capture and effectively counteract the regulated release function
of the Hydro Brake.
12. Periodic inspection is necessary to check the structural integrity,
corrosion and performance of all control/storage structures and
appurtenances. Leaks in structures and abandoned catch basin
leads should be identified and sealed to insure the control/
storage system is operating as designed.
10
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SECTION 4
METHOD OF APPROACH
GENERAL PROCEDURES
Various data collection and analysis tasks were undertaken to accom-
plish the evaluation objectives of this study. The methods described here
were directed towards measuring the performance of the Hydro Brake device
as well as evaluating its applicability in relation to other methods of
storm water control.
Field tasks were devised to record the ability of the Hydro Brake
devices and storage structures to reduce peak storm flow rates and delay
storm drainage, thereby reducing receiving sewer surcharging and decreasing
the frequency and magnitude of combined sewer overflows. Additional tasks
included water quality monitoring to determine runoff pollutant loadings
to receiving sewers, and sedimentation measurements in the storage struc-
tures for evaluation of maintenance requirements. Homeowner surveys were
performed as well to further document the effectiveness of storm water
control obtained.
Data analysis efforts involved desk top modeling to evaluate design
conditions and measured storm events, and the derivation of discharge curves
from field simulation of design storm conditions. Further analysis was per-
formed to provide cost comparisons with alternate storm water control methods
and an evaluation of other applications of the Hydro Brake device.
DESCRIPTION OF HYDRO BRAKE CONTROL DEVICES
The Hydro Brake is a proprietary flow regulator device which purpor-
tedly acts as an energy dissipator by imparting." cvortex pattern to the flow
passing through the device. It is a static device which is said to develop
control energy from the head above the unit, and its physical geometry. The
resistance to flow is described as increasing with increasing head, thereby
reducing the rate of increase of the discharge from the device. This head-
discharge relationship results in a much "flatter" rating curve when compared
with the discharge from unrestricted openings or orifices of the same size.
The Hydro Brake units examined in this study are described as the
"horizontal conical" type. Each unit is constructed as a frustum of a cone,
having a sealed lower base and an open upper base, which is the discharge
side of the device, the diameter of which describes the size of the unit.
The cone is oriented horizontally such that its axis defines the effective
direction of flow. Flow entry is accomplished through a slot along the face
of the cone between the two bases. The orientation of this entry slot and
the conical shape combine to produce the spiral flow pattern inherent with
the flow regulating capability of the Hydro Brake. Photographs of the Hydro
Brakes presently in use in the study area may be found in Appendix D.
11
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During the course of this evaluation, it was determined that a reduc-
tion in the size of the Hydro Brake control devices was required, in order
to reduce the discharge rates. This subject is discussed in detail in
Appendix F, Cleveland's Redesign Report. This study, therefore, discusses
both the original design Hydro Brakes and the redesigned units. All data
collection and evaluation tasks were performed for both the original design
and redesign conditions.
DESCRIPTION OF INSTALLATIONS
Each Hydro Brake installation consists gf- a storm water retention struc-
ture located at the low point of a drainage area with a Hydro Brake regula-
tor device installed at the effluent end of each structure. Discharge is
to the existing combined sewers. Minor storm sewer construction and plug-
ging of cath basin lead was accomplished in the immediate vicinity of the
Hydro Brake structures to direct runoff to these units. Catch basins
located in more remote locations of each drainage area were modified through
installation of .05 cfs (1.4 L/s and .25 CFS (7.1 L/s) Hydro Brake devices.
When surface runoff rates exceed these values, storm flows bypass the catch
basins, flow along the street gutter system, and drain to the retention
structures.
West 170th Street Installation
The W. 170th Street Hydro Brake control structure consists of one 48
inch (1.2 M) diameter round corrugated metal pipe, (CMP), 163 feet (50M)
long, sealed at both ends to form a tank. The storage volume is approxi-
mately 2,000 ft3 (57M3). Catch basins are connected through an 18 inch (.45M)
pipe at both ends as shown in Figure 4.
The tank is buried about seven feet (2.1M) to the invert.
The Hydro Brake is located at the discharge end of the tank and is
inserted in a twelve inch (.30M) pipe which discharges to the 21 inch
(.53M) combined sewer. There is no manhole at the junction of the 21 inch
(.53M) combined sewer and the twelve inch (,30M) effluent line.
The original Hydro Brake unit had a manufacturer's discharge rating
of 2.0 cfs (57 L/s). On July 21, 1981, a new unit rated at 1.25 cfs (35.4 L/s)
was installed.
West 177th Street Installation
The W. 177th Street Hydro Brake control structure consists of two 156
foot (47.5M) long, 87" x 63" (2.2 M x 1.6M) cross section corrugated metal
arch pipes, buried about eight feet (2.4M) to the invert, with a total volume
of 10,000 ft3 (283M3). The tanks have a series of catch basins connected
to them as shown in Figure 5. The two tanks are also connected together
by a 24 inch C.61M) CMP. The tanks drain through an 18 inch (.46M) CMP to
a manhole where another 18 inch (.46M) RCP pipe is connected, tying in a
series of catch basins. The Hydro Brake unit is inserted in the 12 inch
(.30M) effluent line from this manhole and is drained to the 18 inch (.46M)
12
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%
LEGEND
(NOT TO SCALE)
COMBINED SEWER
STORM SEWER
CATCH BASIN
DIRECTION OF FLOW
YDROBRAKE LOCATION
63'-48"(49.7m- 122cm.)
21" COMBINED SEWER
/
(53cm.)
W 170 ST.
PLAN VIEW
T!
I
I
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LEGEND
(NOT TO SCALE)
COMBINED SEWER
STORM SEWER
CATCH BASIN
DIRECTION OF FLOW
HYDROBRAKE LOCATION
W 177 ST.
156'- 87 "X 63" (47.5m.-22!XI60cm.) O
156'— 87 "X 63" (475m.-221X 160cm.) Q
PLAN VIEW
i w
PROFILE VIEW
*• J? J/_7_ ST.
iri
H
i|
^w
IT
_J!
I ' 1
HYDROBRAKE LOCATION
FIGURE 5 W. 177 ST. INSTALLATION
14
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combined sewer on denshire Avenue.
The original Hydro Brake unit that was installed had a manufacturer's
rating of 1.5 cfs (42 L/s). A replacement unit was installed with a rating
of 0.25 cfs (7.1 L/s), on July 21, 1981.
Puritas Avenue Installation
The Puritas Avenue Hydro Brake control structure is located under the
eastbound curb lane on Puritas Avenue between" W. 170th and W. 172nd Streets.
The storage tank is a corrugated arch pipe 170- feet (52M) long with a cross
section of 95" x 67" (2.4M x 1.7M). It is buried about ten feet (3M) to
the invert. Total volume is 5,800 ft3.(164M3). At the downstream end
the tank there is an 18 inch (.46M) spiral corrugated pipe leading to a man-
hole containing the Hydro Brake unit. This manhole has an invert approximately
3.3 feet (1M) below the invert of the tank. An 18 inch (.46M) effluent line
from the Hydro Brake manhole discharges to the 3' 6" (1.1M) brick combined
sewer. There is no manhole at that point, making access to the 18 inch (.46M)
effluent line very difficult. An illustration of this control structure can
be seen in Figure 6.
The original installation consisted of 7.0 cfs (197 L/s) rated Hydro
Brake. On August 1, 1981, a new unit rated at 1.0 cfs (28 L/s) was instal-
led.
SIMULATION OF DESIGN CONDITIONS
Introduction
In order to simulate design storm conditions (full storage utilization
and maximum head on the Hydro Brake) and to field calibrate the Hydro Brake,
each storage tank was filled from street fire hydrants and a record of the
drain down time was made. Data collected was used to derive discharge
relationships as described below.
The total storage volume at each location was calculated, and then was
reduced to incremental volumes for each one-inch (2.5 cm) reduction in water
depth. Since two of the storage tanks were corrugated arch pipe, and the
third was corrugated round pipe, geometric formulae were used to calculate
incremental volumes (Appendix A).
All influent lines were plugged, as was the Hydro Brake, in each tank,
and the tank was filled from fire hydrants. After filling, water levels
in each structure were observed. If the water level was observed to drop
prior to pulling the Hydro Brake plug, leaks in the system or in the plug
were identified and corrected, if possible. The Hydro Brake plug was then
pulled, and the time for each one-inch (2.5 cm) drop in water level was
recorded, using a surveyor's level rod inserted in each storage tank at
the discharge point and a digital totalizing stop watch. Automatic level
recorders simultaneously recorded the fill and;drain procedures. The effluent
elevation was taken as the invert elevation of each Hydro Brake device. Each
installation was tested in this manner, and retested when revisions were made
in Hydro Brake sizes.
15
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LEGEND
(NOT TO SCALE)
COMBINED SEWER
STORM SEWER
CATCH BASIN
DIRECTION OF FLOW
PU RITAS AVE.
42"(
07cm) COMBINED SEWER
Q 170'- 95" X 67" (52m.-24IXI70cm.) QJ
-HYDROBRAKE LOCATION
PLAN VIEW
PURITAS AVE.
rr~
ii
HYDROBRAKE LOCATION
FIGURE 6
II
PROFILE VIEW
STORAGE TANK
1701-95"X67"(52m.-24IX170cm.)
M
I I
I L
42."{l07ctn)COMBINED SEWER
~rr
PURITAS AVENUE INSTALLATION
16
-------
Before performing discharge tests for each Hydro Brake structure,
head vs. volume relationships were computed for each retention tank.
Manufacturer's standard arch pipe cross sections were used for the Puritas
Avenue and W. 177th Street locations. The W. 177th Street tank is a
48 inch diameter round pipe. All three tanks were constructed with a
sTope of 0.5%.
. For calculating incremental volumes, it was assumed that the water
surface in the retention structures would be .horizontal during storm
water storage conditions. Profile drawings o-Tthe tanks were oriented
at a slope of 0.5% and horizontal planes, representing one inch (2.54 cm)
increments in water depth, were constructed passing through the tanks.
Cumulative volumes were then computed by increments through the full
depth of the tanks, primarily by using the formula for an ungula of a
cylinder. The circular cross section defines a simple cylinder, and in
the case of the arch pipe tanks, the cross section defines a volume which
is a composite of partial cylinders having three different radii. Sec-
tions through manholes and connecting storm pipes were accounted for as
required. Formulae and head vs. volume tables may be found in Appendix A.
Calculating incremental volumes of water lost as a function of time
for incremental changes in head produced a discharge rate curve for each
installation. This curve was, of course, a variable head test curve, based
upon a full head in the tank, and no additional water input during the test.
Each installation was tested in this manner, and retested when revi-
sions were made in Hydro Brake sizes.
Discussions of Calibration Procedures
Uest 170th Street Installation:
For the calibration tests of the original unit as well as the new unit,
the Hydro Brake had to be removed from the tank to gain access to the pipe.
A sewer plug was allowed to fall into the combined sewer when it was released
to avoid obstructing the flow in the effluent pipe during the drain down
test. Calibration was then performed in accordance with procedures described
previously. In both cases the 48 inch (1.2M) CMP was filled to the crown.
A catch basin on Martha Avenue leaked during the first test. The leakage
occurred at the plug intended to isolate it from the combined interceptor.
West 177th Street Installation:
In the manhole on denshire where the 12 inch (.30M) effluent line
meets the 18 inch (.46M) interceptor a 12 inch (,30M) sewer plug was
installed. A plug was also installed in the 18 inch (.46M) RCP in the
Hydro Brake manhole to isolate the catch basins. Calibration was then
performed. There were no leaks within the tanks.
17
-------
After the new Hydro Brake unit was installed, a recalibration was per-
formed. The 18 inch (.46M) RCP from the catch basins was not plugged for
this test, and the additional volume associated with these structures was
calculated from construction plans when the discharge curve was calculated.
Subsequently, a catch basin at the northeast corner of Glenshire and W. 177th
was found to have a bad plug at the point where it was isolated from the
combined sewer. This severe leak allowed the tanks to be filled only to
about 3* 2" (.96M). Therefore, only a partial discharge curve was measured.
This causes calculated discharge values to be too high for the higher head
value.
Puritas Avenue Installation:
The calibration of the original unit was done by wrapping foam rubber
around an 18 inch (.46M) sewer bag and inserting it into the spiral corru-
gated pipe. While this plug leaked slightly around the corrugations of
the pipe, the tank was still able to be filled to six feet (1.8M). Cali-
bration was then performed as previously described.
A recalibration was performed on the new 1.0 cfs (28 L/s) Hydro Brake
unit, installed on August 1, 1981. The 18 inch (.46M) effluent line at the
combined sewer was plugged and the tank was filled.
As the level in the tank approached 1.7 feet (.52M) the plug blew.
Following reinstallation, the maximum safe air pressure was exceeded during
an attempt to better seal the discharge line. The filling proceeded to
about 2.6 feet (.79M) when the plug blew out again. At this level there
was approximately 6 feet (1.8M) of head on the Hydro Brake. The filling
was stopped at that level and calibration was continued.
STORM FLOW MONITORING
Equipment
Bristol bubbler level recorders were installed in each tank and at CSO
chamber M-15. At West 170th and West 177th Streets, strip charts set for
one-half inch (1.3cm) per hour were used. Twenty-four hour circular charts
were used at the Puritas tank and at the Puritas overflow. ISCO 1870
bubbler level recorders replaced the Bristol meters at West 170th and 177th
Streets for approximately the last two months of the study, because of re-
current problems with the air supply systems in those two meters. All
equipment was installed in concrete meter vaults which were placed on tree
lawns adjacent to the storage structures and connected to the structures
with underground 3 inch (7.6cm) PVC conduit. Each structure was equipped
with hinged, locking steel access doors. Monitoring lines were secured in
the storage structures at the invert elevation of the Hyrdo Brakes at the
discharge end of each storage structure, and were connected to the monitoring
equipment through the PVC conduit. In the Puritas Avenue structure, monitoring
lines were installed in the invert of the storage tank at the effluent end,
approximately 3.5 feet (1.1M) above the invert elevation of the Hydro Brake
control device.
18
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Data Collection
Charts were pulled weekly or after storm events, and field observations
and equipment adjustments were noted. The zero level point for each level
recorder was adjusted so that the level record represented depth of storm
water above the invert elevation of the Hydro Brake devices. In the Puritas
Avenue structure, the zero level point was set at the effluent end invert
elevation of the storage tank. At CSO M-15, the difference in elevation
of the bubbler tube and the overflow weir wall was measured so that a chart
correction could be applied to the level recordings to accurately define any
potential overflow hydrographs. Charts and field notes for each meter were
maintained in a common file.
Analysis
Using the derived discharge curves for each location, outflow hydrographs
were prepared for significant storm events. These hydrographs were com-
pared with inflow hydrographs derived from recorded rainfall data to
evaluate peak storm flow rate attenuation and storage utilization.
PRECIPITATION RECORDS
Equipment
A Bel fort recording rain gauge with a twelve inch (30 cm), double
traverse, eight-day chart was installed at Fire Station No. 43 on Rocky
River Drive, approximately .25 mi (.4 km) from the center of the study-
area.
Data Collection
Charts were pulled weekly or after storm events, and concurrent storm
information was obtained from the National Weather Service and the Northeast
Ohio Regional Sewer District (NEOP.SD) for storm events. This supplemental
rainfall information was used during the Summer, 1981 monitoring period.
Analysis
Hyetographs of rainfall data were converted into run-off (inflow)
hydrographs for correlation with level and discharge data from the in-tank
level recorders.
UATER QUALITY SAMPLING
Equipment
ISCO 1680 programmable sequential samplers were installed in the same
manner as the flow level records in each end of the West 170th Street and
the Puritas Avenue storage tanks, and at the discharge end only of the West
177th Street tank, because the influent line entered at that end also.
Level actuated Mercury float switches initiated a variable time contact
closure sequence to pulse the samplers.
19
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Data Collection
Upon initiation, the samplers collected discrete samples at intervals
of 2.5, 5, 10, 15, 30 and 60 minutes. At the end of the first hour, a
relay eliminated intervening signals and only 30 minute samples were col-
lected for the duration of the storm, up to a maximum of eleven hours unless
the 28 bottle collector was replaced.
To accomplish the designated sample frequency, a timer was developed
which would activate sampling equipment on the..variable time schedule
described above. The timing mechanism was activated by a mercury level
switch which closed a circuit when storm flows were detected in the storage
structures.
Analysis
Discrete samples were analyzed for biochemical oxygen demand (BODs),
volatile suspended solids and total suspended solids. Samples were com-
posited and analyzed for total organic carbon, chemical oxygen demand,
chlorides, sulfates, copper, cadmium, chromium, lead and zinc.
Results were compiled and evaluated to determine whether storm water
retention and peak attenuation could be shown.to have an effect on receiv-
ing water quality.
SURVEY OF SERVICE AREA POPULATION
Data Collection
Two survey questionnaires (Appendix B) were developed for the home-
owners of the study area. The surveys were conducted as house-to-house
surveys. Residents were asked for information on flooding history prior
to construction. The second survey was conducted at the end ot the study,
and residents were asked about flooding during the study period.
Analysis
Homeowners' pre and post-construction responses were mapped and an
assessment of flooding conditions was developed. Although post-construc-
tion responses indicate a reduction in flooding of basements and streets
during the study period, it is not possible to prepare a definitive
analysis of project effectiveness after only one year.
DATA ANALYSIS
As noted previously, discharge hydrographs were computed using water
level records from actual storm events and the stage discharge curves deve-
loped for each Hydro Drake. Calculations of inflow hydrographs, represent-
ing surface runoff from the drainage area contributing to each retention
structure, were performed using the linearized subhydrograph modification
of the rational method proposed by Chien.(2)
20 '
-------
One-half hour duration storms were selected for evaluating the level
of control provided by each unit because the time of concentration for
each drainage area approximates this duration. Rainfall amounts were
determined from the U.S. Weather Bureau Technical Paper #40, "Rainfall
Frequency Atlas of the United States" for 1/2 hour storms having return
periods of one, two, five and ten years. The standard time distribution
of storm rainfall (Huff, 1967)(3> was used to provide rain increment input
into the linearized sub-hydrograph method for computation of inflow hydro-
graphs for each retention structure. Discharge hydrographs for these design
storms were then computed using the discharge" curves for each Hydro Brake
and the storage continuity equation:
I - 0 = ds
It
Where: I is inflow rate
0 is outflow (discharge) rate
ds/dt is the change in storage per time increment
A more thorough discussion of the methods introduced here and the
formulae involved are presented with the discussion of results presented
in Section 6.
21
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SECTION 5
RESULTS
DISCHARGE CURVES
Data collected in the variable head tests described in Section 4 were
used to construct discharge curves for both original and replacement Hydro
Brake control units. A plot of head v.s. flow-rate was contructed from
the field record of falling head v.s. time and calculations of partial volumes
v.s. incremental changes in head. The head values used were averaged for each
increment of volume discharge, and flow rates were computed from measured time
increments for each corresponding volume increment. The datum point for each
Hydro Brake was taken as the invert of each control device. Best fit curves
were derived for each set of Hydro Brake test values using a commercially
available curve fit program. Head discharge data pairs were input and
regression analysis produced coefficients defining the equation of the best
fit curvilinear relationship between head and discharge valves. For each
Hydro Brake, a discharge curve for an orifice having the same size opening was
calculated, using the equation: Q = .6a (2gh)l/2.
Where: .6 is an orifice coefficient
a is the cross sectional area of the orifice
g is the force of gravity
h is the head on the orifice
Figures 7 and 8 represent the discharge curves developed for the
W. 170th Street structure, before and after redesign of the Hydro Brake
control unit, respectively. The curve for the original device indicates
a considerably higher discharge rate than the manufacturer's 2.0 cfs
(57 L/s) rating. This can be explained in part by the faulty catch
basin plug on Martha Avenue, which would increase the apparent discharge
rate for the higher head values. Repairs accomplished by the City of
Cleveland corrected this problem as indicated by the discharge curve
for the redesigned control unit, which is rated at 1.25 cfs (35.4 L/s).
Discharge rates at the higher heads indicate the new device is performing
close to its rating.
The W. 177th Street discharge tests resulted in the discharge curves
presented in Figures 9 and 10. The original Hydro Brake device exhibits
a lower discharge rate than an orifice of the same size (7 in. - 17.8 cm)
but considerably higher than the manufacturer's rating of 1.5 cfs (42 L/s).
This is also the case for the redesigned unit, rated at .25 cfs (7.1 L/s),
but a leaking catch basin plug on Glenshire Avenue, discovered during
the second test, produces significant errors in the range of higher heads,
heads, causing the discharge rates through the Hydro Brake to appear to be
too high.
22
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-(300)
10-
9-1
-(250)
7-
~- 5-
^
OC
UJ
£4-
3-
_(200)
-(150)
9" (23cm.) ORIFICE
^ 9" (23cm.) HYDROBRAKE
CATCH BASIN LEAK
MANUFACTURERS RATING
2.0 cfs (57L/S)
\
I
FIGURE 7
I
2' 3'
(.61) (.91)
HEAD IN FEET (METERS)
W.I70 ST. HEAD-DISCHARGE CURVES : ORIGINAL DESIGN
(.30)
I
4'
(1.22)
I
5'
(1.52)
23
-------
2 —
CO
LU —-
X « -
S U- ^
co °
S
-(75)
^r- 6"(l5cm.) ORIFICE
6"(l5cm.) HYDROBRAKE
-(50)
--(25)
MANUFACTURER'S RATING
125 cfs( 35.4 L/S)
I
FIGURE 8
1 ^
2' 3'
(.61) (.91)
HEAD IN FEET (METERS)
W.I70 ST HEAD-DISCHARGE CURVES: REDESIGN
(.30)
I
4'
(1.22)
I
5'
(1.52)
24
-------
7 (18cm.) ORIFICE
7" (18cm.) HYDROBRAKE
' -75
-50
MANUFACTURERS RATING
tr co
a,!*
CD *-
-25
1.5 Cts (42L/S)
I
I'
(.30)
I I
2' 3'
(.61) (.91)
HEAD IN FEET(METERS)
I
4'
(1.22)
I
5'
(1.52)
FIGURE 9
W. 177 ST. HEAD- DISCHARGE CURVES : ORIGINAL DESIGN
25
-------
1.5-1
1.4-
-(40)
1.3-
-(35)
1.2-
-(30)
1.0-
0.9-
-(25)
0.8-
co
o
~ o.7-r
0.6 H
oen
cou.
0.5-
0.4-
0.3-
-(20)
-(15)
-(10)
3"( 7.6cm.) ORIFICE
^ 3" (7.6cm.) HYDROBRAKE
(CATCH BASIN LEAK)
MANUFACTURER'S RATING
0.2-
-(5)
0.1-
0.25 cfs (71 L/S)
(.30)
I 1
2* 3'
(.61) (.91)
HEAD IN FEET (METERS)
FIGURE 10
W. 177 ST. HEAD- DISCHARGE CURVES
26
4
(1.22)
REDESIGN
5
(1.52)
-------
14 —
ra-
10 —
8 —
tO
LJ
:_ 7
-400
— 350
—300
-250
-200
I6"(4lcm) ORIFICE
. 16" (41cm) HYDROBRAKE
MANUFACTURER'S RATING
CO
o
4 —
3 —
2 —
I
-1-50
I
70cts (I97L/S)
\ I
12
(.30) (.61)
1
3
(.91)
I I
45
(1.22) (1.52)
I I
67
(1.83) (2.13)
I T^
89
(2.44) (274}
10
FIGURE II
HEAD IN FEET (METERS)
PURITAS AVE. DISCHARGE CURVES : ORIGINAL DESIGN
27
-------
5.5" (14cm) ORIFICE
-. 5.5"(l4cm) HYDROBRAKE
4-
-f —
v>
iLl
UJ
< o
x g"
o c~
(f>
I-
-100
- 50
MANUFACTURER'S RATING
1.0 CFS (28L/S)
I I
I 2
(.30) (.61)
I
3
(.91)
I
4
(1.22)
I
5
(152)
I
6
(1.83)
7
(2.13)
1 I
8 9
(2.44) (2.74)
HEAD IN FEET (METERS)
FIGURE 12 PURITAS AVE. DISCHARGE
28
CURVES — REDESIGN
-------
Figures 11 and 12 illustrate the discharge curves for the Puritas
Avenue structure. The downstream end of the retention tank is approxi-
3.5 feet (1.1 M) above the invert of the Hydro Brake control unit (see
Figure 6), so the effective operating range of heads on the control
unit is 3.5 - 9.0 feet (1.1 - 2.7 M). Essentially no control occurs between
0 f 3.5 feet (0-1.1 M) of head because the volume involved is negligible
(44 ft3 - 1245 L).
The discharge curve in Figure 11 indicates that the original
control device performed close to its rating of 7.0 cfs (198 L/s) for
actual heads of 4 to 8 feet (1.2 - 2.4 M). Data points from the second
discharge test (Figure 12) indicate that the discharge rate began to
stabilize around 2.0 cfs (56.6 L/s)5 when the head on the control unit
was 5-6 feet (1.5 - 1.8 M) or 1.5 - 2.5 feet (0.4 - 0.8 M) depth in
the storage structure. No measurements above this level were taken
because of the problems encountered during the field test.
STORM HYDROGRAPHS
In order to assess the performance of the Hydro Brake structures
and control devices under actual operating conditions, rainfall and
depth of flow measurements were performed for several storms.
Measured Storm Events
Field records of actual storm events during the Fall, 1980 and Summer,
1981 monitoring periods were disappointing in that the rain events were not of
sufficient intensity to cause appreciable response in the storage/control
structures. Before sampling equipment was installed for the Summer, 1981
monitoring period, three moderate rainfall events were recorded on the rain
gauge at Fire Station 43 on Rocky River Drive. Total rainfall of 1.87"
(4.75 cm) occurred June 8-9, 1981, 1.03" (2.62 cm) occurred June 22, 1981
and .78" (1.98cm) was recorded for June 25, 1981. Peak intensities were
approximately 2.3 inch/hour (5.8 cm/hr), 0.5 inch/hour (1.3 cm/hr) and 0.4
inch/hour (1.0 cm/hr), respectively. All three storms caused slight short
duration overflows at the combined sewer overflow M-15 on Puritas Avenue,
but it was not possible to estimate the involvement of the Hydro Brake control
structures during these storms. The-drainage areas which directly contribute
flows to the retention/control structures account for less than 10 (ten)
percent of the total drainage area tributary to this overflow point. No over-
flows at M-15 occurred while sampling equipment was in place at the control
structure.
Three storm events which best represent the response of the Hydro
Brake structures to peak flow rates were selected for illustrative
purposes. These events occurred June 8-9, July 13 and August 7, 1981.
The Puritas Avenus structure is not discussed here because none of the
storms caused any appreciable response in this unit. Storm intensities were
not of sufficient magnitude to produce stormwater inflow rates significantly
storms caused any appreciable response in this unit. Storm intensities were
not of sufficient magnitude, to produce stormwater inflow rates significantly
greater than the Hydro Brake discharge rate. Therefore, records of stormwater
levels in the storage tank indicated negligible amounts of storage.
29
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Hydrographs were constructed for the W. 177th Street unit for the
first and second storms. The 1.5 cfs (42 L/s) control device from the
original design was in place for these events. The W. 170th Street
unit was evaluated for the second and third storms. The 2.0 cfs -
(57 L/s) device was in place for the July 13 storm and the 1.25 cfs
(35.4 L/s) unit was in use for the August 7 storm.
Rainfall Data
In attempting to construct hydrographs far actual storm events to
illustrate inflow/outflow relationships for the'Hydro Brake installations,
it was found that the 8 day rain records from the Rocky River Drive
location could not be used to identify short duration rainfall increments.
Subsequently, rainfall records were obtained from the National Weather
service for Cleveland-Hopkins Airport and from Northeast Ohio Regional Sewer
District for recording stations at John Marshall High School and Brookpark
City Hall (See Figure 1). Though these locations are 2-4 miles from the study
area, they were expected to exhibit similar rainfall patterns and provided
records which could be reduced to five minute increments for use in con-
structing inflow hydrographs.
Inflow Hydrographs
A modification of the rational method was used to calculate inflow
hydrographs for each drainage area, similar to the linearized sub-
hydrograph method proposed by Chien.^2) Five minute rainfall increments
were applied to the drainage area tributary to each structure to con-
struct subhydrographs, which were then superpositioned with a five minute
delay between successive subhydrographs to construct the total inflow
hydrograph.
The formula used to construct each subhydrograph is:
Q = CIA (2 tr)/(tr + tc)
Where Q = peak flow rate in cfs at time = tr
C = runoff coefficient
I = rainfall intensity in in/hr
A = contributing drainage area in acres
tr = time duration of rainfall increments
tc = time of concentration of contributing drainage area
The base of each subhydrograph is the sum of tr and tc.
From Cleveland's redesign report (Appendix F), the runoff coefficient and
time of area was estimated to be .5 and 25 minutes, respectively. Drainage
areas were calculated as the sum of street surface and a 30 foot (9.1 M) setback
to residential structures. Table 1 summarizes these values for each Hydro Brake
structure.
30
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TABLE 1. HYDRO BRAKE DRAINAGE AREAS
Total Area Area to Hydro Brake
Location Acres (hectares) Acres (hectares)
W. ^70 St.
W. 177 St.
Puritas Ave.
5.7
7.5
7.9
(2.3)
(3.0)
(3.2)
2.4
3.1
3.5
(1.0)
(1.2)
(1.4)
The difference between total area and area "directly contributing
to the Hydro Brake structures is the roof area and yard area which
drains to the combined sewers by means of area drains, downspout con-
nections and footer drains.
Discharge Hydrographs
Discharge hydrographs were constructed from values of head vs.
time recorded during storm events and the head-discharge curves which
were derived for each Hydro Brake. Inflow and outflow hydrographs
were then plotted for comparison purposes for the selected storms
mentioned previously. Volumes were calculated by summing the areas
of trapezoidal sections under each curve.
Figure 13 shows hydrographs at the W. 177th St. structure for the
storm of June 8-9, 1981. The original design Hydro Brake (1.5 cfs -
42 L/s) was in place for this storm event. The rainfall pattern represents
an average of the records from Cleveland Hopkins Airport and John Marshall
High School, because this produces an invlow hydrograph which best matches
the outflow pattern observed at the study area which is between these two
rain gauge locations. Because of problems with the level recorder, the
outflow hydrograph constructed from the field record indicates too small a
volume for the rain observed for this event. Therefore, a discharge hydrograph
was also calculated to illustrate the probable outflow pattern for this storm.
This was accomplished using the calculated inflow hydrograph and the storage
continuity equation:
I - 0 = ds/dt
Where I = inflow
0 = outflow
ds = change in storage
dt = time increment
31
-------
.-(5)
-(75)
2.5-
2.0-
o
I
1.5-
1.0-
0.5-
RAINFALL INTENSITY
IN/HR.(cm./HR.)
•INFLJOW
(8382 FT. -237,400 L)
-MEASURED OUTFLJOW
(4905 FT.3-138,900 L)
•CALCULATED OUTFLOW
(8181 FT.3-231,700 L)
-(50)
-(25)
2400
1
0100
TIME OF DAY
I
0200
0300
FIGURE 13
HYDROGRAPHS AT W.I77ST CONTROL STRUCTURE
STORM OF JUNE 8-9,1981 -1.5 CFS (42 L/s) HYDROBRAKE
32
-------
These problems aside, this storm was selected to illustrate the
ability of the Hydro Brake control device to significantly reduce high
storm flow rates (the second peak in Figure 13), while lower flow rates
pass through the unit with little control evident.
-, Figures 14 and 15 present hydrographs at the W. 177th Street Ind
W. 170th Street locations, respectively, for the storm of July 13, 1981.
The original design Hydro Brakes were still in use at this time.
Rainfall records varied considerably among the four gauging locations,
such that inflow and outflow hydrographs did no.t correlate well.
It was noted that the depth of flow in all three retention structures
reached a maximum of only 1-1.5 feet (.30 - .45 M), well below the
optimum operating range of the control devices (approximately 3-5 feet
(0.9 - 1.5 M)). Though some flow attenuation occurred, it appears
that only sustained high intensity storms will produce any substantial
peak rate reduction and storage volume utilization. This is because
of the relatively small drainage areas tributary to the control points,
and the high rate operating ranges of the Hydro Brake devices. Low
to moderate intensity storms (less than 1 in/hr or 2.5 cm/hr) will
exhibit unimpeded flow through the control structures, as was the case
with most of the storms observed during the monitoring periods.
Figure 16 shows hydrographs at the W. 170th Street location for
the storm of August 7, 1981, with very little control of the storm flow
occurring. This is as expected when the rainfall record (Cleveland
Hopkins) is examined. Intermittent high intensity rainfall is evident,
but is not sufficient to generate a high rate of surface runoff.
The August 7 storm occurred after installation of the redesigned
Hydro Brake control devices. The flow record from the Puritas Avenue
structure shows insignificant response to this storm, and no records
were available from the W. 177th Street structure. Shortly after the
installation of the redesigned control unit at W. 177th Street in mid July,
1981, the device became plugged with a styrofoam cup, and the retention
structure was 30% full of water for the remainder of the monitoring period.
It was not possible to clear the unit before the termination of field investi-
gations in August, 1981.
STORM WATER QUALITY
Sampling Results
It was originally intended to collect discrete samples of influent
and effluent flows for storm events at the three Hydro Brake structures.
as described in Section 4 Frequency of sampling was 2.5, 5, 10, 15 and
30 minutes after the onset of a storm event, to observe any first flush
effects and loadings on the receiving combined sewer system. Subsequent
samples after the initial sequence were taken every half hour.
33
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2- '(5)
3-
-(75)
2.5-
2.0-
15-
1.0-
.5 —
-(50)
-(25)
0500
FIGURE 14
RAINFALL INTENSITY
IN/HR.(cmyHR.)
(JOHN MARSHALL)
INFLOW
(4338 FT0-122,800 L)
—OUTFLOW,
(2460FT. -69^700L)
0600
0700
I
0800
0900
TIME OF DAY
HYDROGRAPHS AT W.I77ST CONTROL STRUCTURE
STORM OF 7-13-81 - I.5CFS(42LA) HYDROBRAKE
34
-------
RAINFALL INTENSITY
IN/HR.(cm/HR.)
(BROOKPARK)
INFLOW
(6738 FT. -190,800 L)
OUTFLOW
(8304FT-235.200L)
0600
0800
TIME OF DAY
0900
1000
FIGURE 15 HYDROGRAPHS AT W. 170 ST. CONTROL STRUCTURE
STORM OF 7-13-81 — 2CFS (57L/s) HYDROBRAKE
35
-------
UJ
I
2-
1.0-
0.9-
08-
ci 0.7-
0.6'
0.5-
0.4
0.3--
0.2-
0.1'
U
(5)
•(30)
(20)
(10)
u
RAINFALL INTENSITY
(CLEVELAND HOPKINS)
IN/HR.(cm./HR.)
INFLDW(3765 FT -106,600 L)
.OUTFLOW (3179 FT3- 90,000 L)
1500
1600
1700
1800
1900
FIGURE 16 HYDROGRAPHS AT W.I70ST CONTROL STRUCTURE
STORM OF AUGUST 7,198I-2CFS (57L/s) HYDROBRAKE
36
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Sampling Results
Samples were collected for storm events as summarized in Table 2. Data
presented includes the range and average of values measured at the locations
indicated. Complete sampling results are presented in Appendix C.. All values
represent samples taken at the effluent end of each storage structure, immediately
upstream of the Hydro Brake control devices.
Due to the low levels and short duration of flows in the, storage structures,
in addition to occasional equipment malfunctions, it was not possible to collect
samples from all locations for all storm events. In all but one case, the
analyses of the samples collected did not show any significant first flush
effects. -The loading on the combined sewers appears representative of normal
stormwater flows, as the comparison in Table 2 indicates.
The sampling also provides no indications of removals or deposition within
the storage structures, nor was it possible to use the sampling data to project
potential solids deposition problems. This is partly because the structures
have multiple influent points, and in the W. 170th Street and W. 177th Street
locations, part of the influent flow enters the storage structures immediately
adjacent to the effluent point.
Sediment Observations
In addition to the sampling results, field observations and measurements of
the depth of solids, sediment and water along the length of each storage tank
indicate that solids deposition and debris accumulation should not be a problem
in the storage structures. The only exception is the redesigned Hydro Brake
control unit at W. 177th Street, which could become clogged with debris, as was
the case shortly after this unit was installed in July, 1981. This is apparently
due to the small clear opening in this device. The Hydro Brake has an opening
approximately 3 inches (7.16 cm) in diameter, and became plugged with a styro-
foam cup on or about July 21, 1981. This size opening is smaller than the
openings in the other Hydro Brake control devices and is, therefore, more sus-
ceptible to plugging. Subsequent installation of catch basin traps by the City
of Cleveland should correct this problem.
Photographs taken in each control structure during Fall, 1981, along
with a record of solids depth measurements are presented in Appendix D.
These data were recorded after ths structures has been operational for
approximately 18 months, and indicate minimal accumulation of solids in the
retention structures over this time period.
HOMEOWNER SURVEYS
Two house-to-house surveys were conducted during the investi-
gation. The first survey was conducted prior to completion of con-
struction, and requested information on past flooding experience.
The second survey was conducted during the first week of October,
1981, and requested information on post-construction flooding.
37
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TABLE 2 - SUMMARY OF SAMPLING RESULTS
STORM WATER PARAMETERS FROM
AND COMPARISON WITH
SELECTED LOCATIONS.
to
oo
LOCATION
Cleveland W 170
Cleveland W 170
Cleveland W 170
Cleveland W 177
Cleveland W 177
Ann Arbor, MI
Castro Valley, CA
Des .Moines, Iowa
Durham, N.C.
Los Angeles, CA
Madison, WI
New Orleans, LA
Roanoke, VA
Sacramento, CA
Tulsa, Oklahoma
Washington, D.C.
DATE
7/21/81
8/8/81
8/17/81
7/13/81
7/28/81
1965
1971-72
1969
1968
1967-68
1970-71
1967-69
1969
1968-69
1968-69
1969
BOD5
AVG.
51
19
20
49
21
28
14
36
31
9.4
-
12
7
106
11
19
mg/1
RANGE
51
12-28
16-23
34-59
10-29
11-62
4-37
12-100
2-232
-
-
-
-
24-283
1-39
3-90
S.S.
AVG.
91
150
65
85
71
2,080
-
505
-
1,013
81
26
30
71
247
1,697
mg/1
RANGE
91
100-210
48-90
79-98
35-110
650-11,900
-
95-1,053
-
-
10-1,000 '
-
-
3-211
84-2,052
130-11,280
COD
AVG.
100
110
53
39
40
-
-
-
224
-
, -
-
-
58
85
335
mg/1
RANGE
-
-
-
-
-
-
-
-
40-660
-
-
-
-
21-176
12-405
29-1,514
-------
Basement Flooding
Figure 17 shows pre and post-construction survey responses with
respect to basement flooding. The distribution of responses indicates
that, at least for Glenshire Avenue and W. 170th and 172nd Streets,
the basement flooding problem may have been improved. This conclusion
is further supported when the expository comments on the questionnaire,
which indicated flooding historically occurred during any heavy (or
even moderate) rainfall, are considered in light of a two-inch rainfall
which occurred during a two-hour period July 9^ 1981. In addition.
one Puritas Avenue resident indicated to field personnel that he had
had no basement flooding, only siSce the installation of the redesigned
Hydro Brake control device in July, 1981. This information was noted
August 8, 1981, one day after the August 7 storm.
Street Flooding
As shown by survey responses illustrated on Figure 18, street
flooding problems on Glenshire and Martha Avenues have evidently been
alleviated to some degree. However, W. 172nd Street apparently still
experiences some flooding. Also, storm water ponds around a catch
basin and yard area on W. 168th Street, where .05 cfs (1.4 L/s) Hydro
Brakes had been installed in the catch basins. The City of Cleveland
has since removed the control device from the problem area.
On balance, it can be concluded that both street and basement
flooding have been reduced in the study area. Basement flooding has
been reduced because combined sewer surcharging has been alleviated through
the use of Hydro Brake control devices, which reduce peak storm inflow
rates to the combined sewers. Street flooding has been reduced through surface
drainage improvements and the construction of below grade stormwater storage
structures. However, it is expected that sustained high intensity storm
would cause some street flooding (of a temporary nature) because the entry
points to the combined sewers are restricted to eliminate surcharging of
the combined collection system.
39
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M
LEGEND . '
NO SCALE
PRE-CONST POST-CONST
A YES • YES
• NO 9 NO
iiliii: STORAGE TANKS
FIGURE 17 BASEMENT FLOODING SURVEY RESPONSES
-------
LEGEND '
NO SCALE
PRE-CONST. POST-CONST.
A YES • YES
• NO O NO
i$8:|:$;:$:i::$ STORAGE TANKS
FIGURE 18 STREET FLOODING SURVEY RESPONSES
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SECTION 6
DESIGN AND PERFORMANCE EVALUATION
INTRODUCTION
This section presents a summary of the design elements employed by Thiel
and Candaras d) in the original design of the~..Cleveland Hydro Brake control/
storage system in addition to an evaluation of the design and performance of
this system. During the course of this study, it became apparent that the
system was not performing as intended. Therefore, the City of Cleveland under-
took a redesign effort to modify the system to better respond to actual con-
ditions in the study area. The elements of this redesign are also presented
here. All study tasks were duplicated and an evaluation parallel to that of
the original design was then performed. ,
ORIGINAL DESIGN CONCEPT
The Hydro Brake application in Cleveland is based on the idea of
regulating the inflow of surface runoff into the existing combined sewers
so as not to exceed the capacity of the collector system. This is
a radically different concept compared to the traditional drainage
design approach of building collectors capable of handling the peak
flow rates generated by some five or ten year design storm.
The Hydro Brake device is the means by which flow rates are regu-
lated, with any excess flows stored in below grade structures or by
surface ponding. In a residential area such as the Puritas study area,
the practical limit to surface storage is between curbs on the streets.
ORIGINAL DESIGN CRITERIA
In order to design the flow regulation and retention structures
constructed in the study area, the surface runoff parameters and
combined sewer flow patterns were modelled using the proprietary Dorsch
Hydrologic Volume Method.0) This model was selected because it purportedly
accounts for sewer surcharging and backwater effects from downstream
areas that would result from critical storm events over the drainage
area. This allowed simultaneous simulation of surface runoff and sewer
system response.
Surface Runoff Parameters
Drainage areas were divided into sub-basins, all of which were
assigned runoff parameters for land use, imperviousness, surface slope
and roughness, depression storage, infiltration rate and flow path.
Separate hydrographs were generated for different types of surfaces
as well as total surface runoff hydrographs. This was necessary where
certain portions of the drainage area, such as roof areas, would be
routed directly to the combined sewers.
42
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Design Rainfall
The rainfall of July 19, 1972 was selected for design purposes
because the greatest number of flooding complaints occurred during this
storm event and it approximated a five year return period rainfall.
Thi-s corresponds with the City of Cleveland's storm sewer design standard
for a five year return frequency rainfall. This storm event consisted
of three high intensity, short duration peaks, with each occurring ap-
proximately one hour apart. Peak intensities (based on five minute
rainfall increments) ranged from 3.1 to 3.8 in/hr (7.9 - 9.8 cm/hr),
with a total accumulation of 1.96 in. (4.98 cm).
STORM SIMULATION AMD DESIGN
Model Ing Methodology
Using records of the July 19, 1972 storm described above, the
Dorsch HVM model was employed to simulate the response of the existing
sewer system, after which the simulation was repeated considering only
roof area and private area drain inflow sources to the sewer system.
Surface hydrographs were developed for the remaining area to identify
storm flows which would be regulated into the collection system. Finally,
inflow regulation rates were determined through a series of successive
iterations such that flow levels were maintained below basement ele-
vations. These flow regulation rates are the discharge rates of the
Hydro Brake devices to be installed, and are based on the available
excess capacity at those points in the sewer system where inflow regu-
lation is required. An analysis of the surface hydrographs in relation
to these flow regulation rates produced the required storage volume at
each inflow regulation point.
Control Device and Storage Sizing
As a result of the design storm simulation, recommendations were
made for storage tank sizes and Hydro Brake discharge rates, as sum-
marized in Table 3. The design allowed for some surface ponding between
curbs on street surfaces.
TABLE 3. ORIGINAL HYDRO BRAKE DESIGN
5 YEAR DESIGN STORAGE & DISCHARGE REQUIREMENTS
Peak Hydro Brake Retention Surface
Inflow Discharge Tank Volume Storage
Location
W. 170
U. 177
St.
St.
Puritas Ave.
cfs
4.
5.
13.
3
8
0
(L/s)
022)
(164)
(368)
cfs
2.0
1.5
7.0
(L/s)
C57)
(42)
(198)
ft*
2074
8984
6024
(1000 L)
(58.7)
(254)
(170)
ft3 (1000 L)
1676
1246
246
(47
(35
(7.
.5)
.3)
0)
43
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The estimated surface storage is only practical on lightly traveled
residential streets, where it is not likely to be a traffic hazard and
is very temporary in nature. Draindown of this volume occurs in ap-
proximately fourteen minutes for the W. 170th and W. 177th Street
locations, and less than a minute on Puritas Avenue.
EVALUATION OF ORIGINAL DESIGN
Combined Sewer Overflow Reduction
The original design approach for the study" area resulted in recom-
mendations for a two phase plan to install seven Hydro Brake control/
retention structures, catch basin Hydro Brakes in the areas tributary to
the control structures and storm sewers. Modifications to overflow
chamber M-15 were also recommended to improve flow patterns. Only Phase
I was implemented, involving the control structures at W. 170th Street,
W. 177th Street and Puritas Avenue, in addition to catch basin Hydro Brakes
on W. 168th Street and the overflow chamber modifications. As part of a
separate project, storm sewers and catch basin Hydro Brakes were installed
in the Mil burn Avenue area north of Puritas Avenue.
Because all the recommendations were not implemented, the actual
reduction in overflows at M-15 is less than projected in the original
design report. Overflow volume and peak rate reductions are a result
of the improvements made in the subject study area and the Mil burn Avenue
area. Estimates of the reduction in combined overflows at M-15 which
can be attributed to these improvements are presented in Table 4. These
estimates take into account the removal of the Grayton Road lift station
discharge which previously contributed flows to the Puritas Avenue sewer
upstream of the study area. These flows were included in storm flow
projections in the original design study. Peak flow rates were estimated
to be 8.4 cfs (238 L/s). In the Spring of 1981, this flow was rerouted
to a sewer on Rocky River Drive which is not tributary to the Puritas
Avenue trunk and overflow M-15.
Because a large percentage of the overflows at M-15 is related to
backwater effects from downstream areas, it is difficult to estimate
overflow peak rate and volume reductions without using a surface runoff
and sewer system hydraulics model. This effort is beyond the scope of
this evaluation, so estimated reductions are based on the pre and post-
design simulation from the original design study for those areas where
flow controls were installed.
As presented in Table 4, simulation of sewer system response to
the five year design storm indicates that the peak rate of overflow
from chamber M-15 is approximately equivalent to the influent flow rate
to this control point. This is true even with full implementation of
the design study recommendations, apparently because of backwater ef-
fects from areas downstream of M-15. Therefore, estimates of overflow
rates resulting from Phase I improvements reflect the same relationship.
44
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TABLE 4. COMBINED SEWER OVERFLOW REDUCTION AT M-15
BASED ON DESIGN STORM SIMULATION - ORIGINAL DESIGN
Overflow No Stormwater Phase I S II Phase I
Parameter Control Implementation Implementation
Peak Inflow 122 (3455) 47 (1311) 89 (2520)
(cfs - L/s)
Peak Overflow 110 (3115) 38 flD76) 77 (2181)
(cfs - L/s)
Overflow Vol. 189,400 (5364) 53,790 (1523) 121,300 (3435)
(ft3 -1000 L)
For all practical purposes, the same volume of storm water enters
overflow chamber M-15 under all three levels of control, but the overflow
rate and volume is reduced because of peak rate reduction at various
inlet points to the system as well as flow retardation until capacity is
available after the subsidence of backwater effects.
Reduction in Flooding and Surcharging
Based upon the results of the surveys of study area residents,
which were presented in Section 5, it is apparent that some reduction
in basement flooding has occurred as a result of the Hydro Brake controls
now in place. This indicates some lesser degree of sewer surcharging
than was prevalent before the control/retention structures were con-
structed.
To further examine the effectiveness of these controls in relation
to sewer surcharging, the design simulation results for individual sewer
segments were compared to pipe capacities. Simulation flow values were
adjusted to reflect only the Phase I improvements described previously.
This analysis indicates that peak flow rates in the sewers in the im-
mediate area of the Hydro Brake controls are generally less than pipe
capacity, with a few segments at or slightly above capacity.
It appears that some surcharging will still occur under design storm
conditions, particularly in the Phase II areas where controls have not
been installed. This is the case in the U. 174th Street-Ponciana-Flamingo
area. The Puritas Avenue sewer also exhibits surcharging at all points
between U. 174th Street and overflow chamber M-15. It is not known if
this condition causes any significant problems in the areas noted.
45
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Evaluation of Control/Retention Sizing
In the early stages of this evaluation, particularly during the
Fall, 1980 field monitoring, it became apparent that only the most severe
storm events would cause any appreciable response in the control/retention
structures. Subsequent review of the original design criteria seemed
to indicate that a large percentage of the drainage areas tributary to
each retention structure was used in simulating response of the system to
a five year design storm. However a significant portion of the runoff from
residential sites actually enters the combined sewers directly by way of
area drains, footer drains and downspout connections. It appeared that
because of an oversight in the original design only roof areas were accounted
for in routing flows directly to the sewers.
Once this apparent error had been identified, the City of Cleveland
prepared new runoff computations for the drainage areas associated with the
W. 170th, W. 177th and Puritas structures (See Appendix F). Given the
rainfall pattern employed in the original design, it was determined that
a large portion of the subject drainage areas would have to be contributing
runoff to be able to generate the peak rates and volumes which were the basis
of design of discharge rates and storage volumes.
There are several implications of these findings. It would appear
that the storage tanks which had been constructed would rarely be fully
utilized, especially up to the five year design level. For the original
discharge rates, the storage tanks were apparently significantly over-
designed. Furthermore, if too small a proportion of total runoff were
routed to the combined sewers, the available capacity for storm release
rate determinations would be too large. Therefore, the Hydro Brake re-
lease rates would be too high and could negate the intent to reduce
surcharging and basement flooding. Finally, if a smaller proportion of
total runoff were actually controlled through the retention structures,
combined sewer overflow reduction would be overestimated.
Time constraints and the scope of this evaluation did not allow
computer simulation of system hydraulics to check the validity of these
concerns, nor was it possible to observe these effects in the field
beyond the noted lack of response of the control/retention structures
to significant rainfall events. No storms resembling a five year design
storm were recorded, and it was not possible to estimate the response
of the combined sewers receiving storm flows.
HYDRO BRAKE REDESIGN
Design Concept
After the Fall, 1980 monitoring period, during which insufficient
amounts of data were collected, the City of Cleveland initiated a pro-
ject to redesign the Hydro Brake discharge rates at the three retention
structures. The intent of the redesign effort was to define runoff
parameters for representative design storms having various durations
and return periods, and to reduce the Hydro Brake discharge rates such
46
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that the storage facilities would have a more frequent, higher percentage
utilization in relation to these storms. A discussion of this effort
has been prepared by the City of Cleveland and is included in Appendix F.
Design Criteria
•v
The areas which drain directly to the control/retention structures
were defined as the area between building set back lines, which includes
streets, sidewalks, driveways, tree!awns and front yard areas. These
areas are presented in Table 1, Section 5. A.runoff coefficient of .5
was used with a time of concentration of 25 minutes (See Appendix F).
Rainfall distributions representative of the Cleveland area were used in
defining runoff parameters.
Hydro Brake Sizing
Runoff volumes were calculated and inflow hydrographs were con-
structed for each location. Hydro Brake discharge rates were selected
which maximized storage of five and ten year design storms while main-
taining a safe level of control over surface flooding. Table 5 presents
a comparison of original design and redesign Hydro Brake discharge
rates.
TABLE 5. COMPARISON OF HYDRO BRAKE DISCHARGE RATES
Original Design Redesign
Discharge Rate Discharge Rate
Location
W. 170th Street
W. 177th Street
Puritas Ave.
cfs
2.0
1.5
7.0
(L/s)
(57)
(42)
(197)
cfs
1.25
.25
1.00
(L/s)
(35)
(7.1)
(28)
The new control devices were to be delivered and installed prior
to the start of the Summer, 1981 monitoring period. Various delays in
delivery of the new Hydro Brakes and their installation postponed operations
under redesign conditions until July, 1981. Therefore, data collection
during 1981 represents "before" and "after" redesign.
EVALUATION OF HYDRO BRAKE REDESIGN
Combined Sewer Overflow Reduction
It was assumed that the combined reduction of 8.0 cfs (226 L/s)
in Hydro Brake discharge rates would result in a reduction of peak
inflow rates to 81 cfs (2294 L/s) at overflow chamber M-15. From com-
parisons with values in Table 4, the estimated peak overflow rate is
69 cfs (1954 L/s) with an overflow volume of 106,400 ft.3 (3013 x 103 L).
This represents an estimated 37% reduction in the peak rate of combined overflow
over the previous conditions of no stormwater control. Overflow volume reduction
is estimated at 44%.
47
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Reduction in Flooding and Surcharging
By reducing Hydro Brake discharge rates, it was expected that flow
rates in the receiving combined sewers should be reduced by a similar
amount. It was not possible to determine from survey results whether
th-is difference would be noticed by homeowners when compared to pre-
vailing conditions with the original Hydro Brakes.
As noted previously for the original design Hydro Brakes, no sur-
charging in the vicinity of the control devices is apparent when the
sewer system simulation results are examined. .As indicated above, this
condition should be further improved with lower rate devices in place.
Those sewers on Puritas Avenue and H. 174th Street, which would ap-
parently be surcharged under design conditions with the original Hydro
Brakes in place, would still be surcharged but to a lesser degree.
With the redesigned Hydro Brakes in place, it is also expected that
the potential for surface ponding during severe storm events is somewhat
increased. An evaluation of design storm conditions presented below
indicates that any surface flooding which might occur will be relatively
minor.
Evaluation, of Redesigned Hydro Brake Devices Using Storm Simulation Techniques
In an effort to evaluate the performance of the redesigned Hydro
Brake control/retention structures in relation to design storm conditions,
storm hydrographs and runoff volumes were calculated using the design
criteria proposed by the City of Cleveland and the hydrograph construction
methods presented in Section 4. As noted previously, one-half hour
duration storms were used because they would generate the highest peak
flow rates over the drainage areas of interest. This was done to il-
lustrate the highest probable level of control (i.e. peak rate attenuation)
that could be provided by the Hydro Brake control devices. However,
larger storage volume requirements are possible from longer duration
storms having the same return frequency as the 1,2,5 and 10 year
storms examined.
After construction of inflow hydrographs, discharge hydrographs
were computed using the storage continuity relationship presented in
Section 4. These calculations were performed for the original Hydro
Brake discharge rates for comparison with design values, and for the
redesigned discharge rates in order to project the expected performance
of these units. The head-discharge curves used were the calculated
relationships from the field calibration tests of each Hydro Brake
device. Hydrographs are presented in Appendix E.
48
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Table 6 summarizes rainfall parameters for the one-half hour
duration storms examined.
TABLE 6. DESIGN HYDROGRAPH PARAMETERS - 1/2 HOUR
STORM RAINFALL AMD INTENSITY
Storm
Return
Frequency
1
2
5
10
Total
Rainfall
in. ( cm . )
.76
.91
1.19
1.37
(1.93)";
(2.31)
(3.02)
(3.48)
Peak
Intensity
in/hr. (cm/hr)
4.0
4.7
6.2
7.1
(10.2)
(11.9)
(15.7)
(18.0)
Table 7 presents comparisons of Hydro Brake discharge rates and
required storage volumes for a five year design storm as computed by
simulation during the original design and by methods employed in this
evaluation. Note that the drainage areas and design storms used in the
two methods are not equivalent.
TABLE 7. COMPARISON OF HYDRO BRAKE DISCHARGE RATES
AND STORAGE VOLUMES FOR 5 YEAR DESIGN STORMS
Original Design
Location
W. 170th Street
W. 177th Street
Puritas Avenue
Location
W. 170th Street
W. 177th Street
Puritas Avenue
Peak
Inflow
Rate
cfs (L/s)
4.3 (122)
5.8 (42)
13.0 (368)
Post- Construct! on
Peak
Inflow
Rate
cfs (L/s)
3.4 (96)
4.4 (125)
5.0 (142)
Peak
Discharge
Rate
cfs (L/s)
2.0 (57)
1.5 (42)
7.0 (198)
Evaluation
Peak
Discharge
Rate
cfs (L/s)
3.1 (88)
1.7 (48)
7.0 (198)
Storage
Required
ftj (1000 L)
3,750 (106)
10,230 (289)
6,270 (178)
Storage
Required
ft3 (1000 L)
380 (11)
3,470 (98)
None
49
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Table 8 presents a summary of the expected performance of the
control/retention structures for various one-half hour design storms
with the redesigned Hydro Brake devices in place. It is projected that
storage capacity would be exceeded at the W. 170th Street structure for
the 5 and 10 year return storms. For the 5 year storm, there would
be 340 ft3 (9630 L) and for the 10 year storm, a 930 ft3 (26,340'L)
of stormwater in excess of storage capacity. For surface ponding at an
average depth of 4 inches (10 cm) on a 24 foot (7.3 M) wide road surface,
flooding would occur over a distance of 42 feet and 116 feet (12.8 m and
35.4 M), respectively, and drain down at the indicated peak discharge rates
would occur in 4.5 and 11.5 minutes. This condition appears to be of
minor consequence considering that it would rarely occur and is of very
short duration.
50
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TABLE 8. SUMMARY OF HYDRO BRAKE CONTROL/RETENTION FOR
1/2 HOUR DURATION DESIGN STORMS
Design
Control Storm
Structure Return
Location Period
W. 170th St. 1
2
5
10
W. 177th St. 1 '
2
5
10
Puritas Ave. 1
2
5
10
Peak Inflow
(Runoff) Rate
To Retention
cfs (L/s)
2.15
2.58
3.40
3.90
2.80
3.35
4.38
5.10
3.17
3.78
4.96
5.70
(61)
(73)
(96)
(no)
(79)
(95)
(124)
(144)
(90)
(107)
(140)
(161)
Peak
Discharge
Rate
cfs (L/s)
1.12
1.19
1.30
1.35
.43
.45
.48
.50
1.78
1.89
2.05
2.12
(32)
(34)
(37)
(38)
(12)
(13)
(14)
(14)
(50)
(54)
(58)
(60)
Retention Storage
Inflow Volume
.Volume Required
ff3 (1000 L) ft3 (1000 L)
3,340 (95)
3,940 (112)
5,220 (148)
6,000 (170)
4,280 (121)
5,130 (145)
6,670 (189)
7,730 (219)
4,810 (136)
5,800 (164)
7,700 (218)
8,710 (247)
1,280 (36)
1,690 (48)
2,640 (75)
3,230 (91)
3,350 (95)
4,120 (117)
5,550 (157)
6,540 (185)
1,570 (44)
2,220 (63)
3,570 (101)
4,430 (125)
Percent
Storage
Utilization
55
75
115
140
35
40
60
70
25
35
60
70
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SECTION 7
COMPARATIVE EVALUATION OF FLOW REGULATOR INSTALLATIONS
Flow regulator devices have been used and evaluated in several communities
in the United States and Canada. Evaluations have included emperical observa-
tions vs computer simulated performance of Hydro Brake devices, and evaluations
of such devices compared to straight orifice reduction, as well as evaluation
against uncontrolled discharge. - .
Applications varied, as did the sizes of drainage areas and the types of
unit configuration.
PROJECT SUMMARIES
Rochester, New York
In Rochester, an off-line storage tank for stormwater retention was con-
structed for comparative evaluation purposes. A Hydro Brake Standard 5-B-7
unit and a three-inch (75 mm) orifice were tested under controlled head con-
ditions. A variable head test and a static head test were run for each.
Unfortunately, size and rating data were not available for the Hydro Brake,
making comparison of results something of a matter of faith.
Head-discharge curves demonstrated that the Hydro Brake device success-
fully retarded the discharge rate as heads increased. The observed orifice
discharge rate was nearly in linear relationship to the head, as would be
expected; for.a simple orif1ce> flow rate is proportional'to the square root
of the head. The Hydro Brake discharge rate tended strongly to be asymp-
totic in relationship to the head. Figure 19, redrawn from O'Brien and Gere,
demonstrates th edischarge curves. Figure 20 illustrates the relationship
between discharge rates derived during testing and discharge rates as
described by the manufacturer. The difference is attributable to experi-
mental error, when compared to the difference between the Hydro Brake and the
three-inch orifice, according to the study report.
Additionally, the performance of the Hydro Brake during a storm, which
occurred fortuitously during the testing period, was evaluated. Inflow and
outflow were monitored and plotted, (Figure 21), demonstrating that the Hydro
Brake effectively retarded peak flows and maintained relative discharge
constancy throughout the discharge period.
52
-------
en
oo
0.6 -
-(15)
0.5-
0.4-
-(10)
0.3-
o
0.2-
0.1-
0.
-(5)
(.30)
3" (7.6cm) ORIFICE
HYDROBRAKE
(STD. 5-B-7)
2 3' 4' 5'
(.61) (31) (1.22) (1.52)
HEAD IN FEET (METERS)
6'
(1.83)
FIGURE 19
HEAD - DISCHARGE CURVES SAIMTEE DRAINAGE AREA CALIBRATION
-------
0.5-
0.4-
0.3-
0.2-
0.1-
-(10)
-(5)
AS DETERMINED IN TEST ON
MAY 13,1981'
AS PER HYDROSTORM
DIFFERENCE ATTRIBUTED TO EXPERIMENTAL
ERROR
I I I ! I
12345
(.30) (.61) (.91) (1.22) (1.52)
HEAD IN FEET (METERS)
FIGURE 20 HEAD-DISCHARGE CURVE, S ANTE E HYDROBRAKE
-------
trt
en
,00 -J
.80-*
.60-
Ig -40H
.20-
-(25)
-(20)
-(20)
-(10)
-(5)
20
VOLUME = 2,000 CU. FT.
(56,410 L)
UNCONTROLLED DISCHARGE (INFLOW)
—HYDROBRAKE CONTROLLED DISCHARGE
(OUTFLOW)
VOLUME =1,700 CU.FT.
(47,949 L)
1
40
60 80
TIME (WIN.)
100
120
140
FIGURE 21 STORM OF MAY II, 1981 - SANTEE DRAINAGE AREA
-------
Toward the end of this study, it was noted that the Standard 5-B-7
Hydro Brake was showing discharge curves that were not appreciably different
from an orifice of similar diameter. Debris in the entry slot was discovered
to be the cause. Although the piece of lath had not blocked the flow, as had
the styrofoam cup in the W. 177th Street (Cleveland) installation", it had
affected the flow regulating characteristics of the unit.
The Rochester, New York, application of the Hydro Brake parallels the
Cleveland project. The Rochester demonstration project report is presented
in Appendix 6 to provide supplemental information pertinent to the application
of this technology.
Nepean Township, Ottawa, Canada ^ '
This evaluation consisted of the installation of two oversize catch
basins, in which Hydro Brakes were installed. One catch basin drained 1.28
acres (0.519 ha), of which .39 acres (0.158 ha) was 86.67 ft3 (2,450 L)
and was outfitted with a Hydro Brake of 0.6 in. (15 mm) diameter orifice.
The other catch basin drained 0.61 acres (248 ha), of which 0.34 acres
(0.139 ha) was impervious surface. This basin contained a storage capacity of
75.6 ft3 (2,135 L) and was outfitted with a Hydro Brake of 2.0 in (50 mm)
diameter orifice. Water levels in the catch basins were monitored by means of
continuous recording water level sensing units. Outflow was calculated from
the water level and rainfall data by first calculating inflow, and then using
discharge curves supplied by the manufacturer, deriving discharge volumes.
The Hydro Brakes demonstrably attenuated the peak flows (Figures 22,
23, 24, 25, and 26, redrawn from Gore and Storrie), but the 0.6 in (15 mm)
diameter device proved to be too small for the storage volumes provided.
It was replaced with a 4.0 in (100 mm) device, but storm events during the
study period did not produce great enough peak flows to exceed this unit's
pass-through capacity. Table 9 shows the peak flow reductions obtained by the
2.0 in (50 mm) device for several storms. As was the case in Cleveland,
accurate sizing of Hydro Brake devices during design proved to be a problem.
No problems with debris in regards to Hydro Brake operation were reported
in this study. However, it was noted that solids buildup in the catch basins
did occur, and that odor was a problem. Attempts to trap solids in mesh bags
were unsuccessful.
TABLE 9 ANALYSIS OF PEAK FLOW ATTENTUATION FOR 2 IN. UNIT
Storm Event
May 23,
May 28,
June 25
June 29
July 1,
1977
1977
, 1977
, 1977
1977
Peak Rate
of Runoff
L/s cfs
5.60
2.94
2.95
.12
6.20
. .198
.104
.104
.145
219
•^'3 K<
Attenuated
Peak
L/s cfs
1.20
1.05
0.85
1.10
1.17
.042
.037
.030
.039
.041
% Reduction
of Peak
78.5
64.3
71.2
73.3
81.1
-------
tn
.125-
.100-
.075-
o
.050-
.025-
0.6" (15mm.) HYDROBRAKE
INFLOW
OUTFLOW
0.009 CFS
(0.25 L/S)
0.005 CFS
'(0.14 L/S)
I0:00pm 12:00 2'OOam 4:00
6:00 8=00
TIME OF DAY
10:00 12=00
T i r
2:00pm 4:00
FIGURE 22 INFLOW-OUTFLOW HYDROGRAPHS NEPEAN TWP AREA I - OCTOBER 30/31, 1976
-------
01
00
.250-
.200-
.150
"•& .100-
.050-
L(6)
-(5)
-(4)
-(3)
-(2)
3=00pm 3^30
4=00
2" (50mm) HYDROBRAKE
INFLOW
OUTFLOW
0.198 CFS'
(5.6(L/S)
I 0.042 CFS
[I.2L/S)
4=30
I
5'00
TIME OF DAY
5=30
6--00
I
6:30
FIGURE 23 INFLOW-OUTFLOW HYDROGRAPHS NEPEAN TWP AREA 2 - MAY 23, 1977
-------
en
.125-
-(3)
.100-
.075-
V)
.050-
.025-
-(2)
-(I)
IQiOOatti 11=00
-0.104 CFS
(2.95 L/S)
-0.030 CFS
(0.85 L/S
2" (50mm.) HYDROBRAKE
INFLOW
OUTFLOW
12:00
I
I'OO
TIME OF DAY
I
2=00
I
3=00
4=00
5=00
FIGURE 24 INFLOW-OUTFLOW HYDROGRAPHS NEPEAN TWP. AREA 2 JUNE 25, 1977
-------
CTI
O
.150-
-(4)
.125-
-(3)
.100-
.075-
£
.050-
.025-
-(2)
-(I)
2" (50 mm.) HYDROBRAKE
• INFLOW
--- OUTFLOW
-0.145 CFS
(4.12 L/S)
r 0.039 CFS.
/ (I.I L/S)
\
7=00 8=00 9=00 10=00 11=00 12=00 hOOpm 2=00 3=00 4=00 5=00 6=00 7=00
TIME OF DAY
FIGURE 25 INFLOW-OUTFLOW HYDROGAPHS NEPEAN TWP AREA 2 JUNE 29, 1977
-------
.250-
.200-
.150-
CO
I;
100 -J
.050-
-(7)
-(6)
-(4)
-(3)
-(2)
-(I)
3:00om
I
4=00
-0.219 CFS (62 L/S)
2" (50 mm.) HYDRO BRAKE
INFLOW
OUTFLOW
-0.041 CFS (I.I7L/S)
I
5:00
I
6:00
TIME OF DAY
I
7=00
I
8:00
9=00 IO--00
FIGURE 26 INFLOW—OUTFLOW HYDROGRAPHS NEPEAN TWR AREA 2 — JULY I, 1977
-------
Borough of York, Ontario, Canada (6)
This study does not include evaluations of Hydro Brakes In situ.
Rather, it uses as a given the ability of the device to regulate flow to
a desired maximum discharge. Based upon that ability, four areas of the
Borough of York are evaluated.
The results of those evaluations were translated into required storage
capacities and regulated discharge rates for each area, presented for 2,
5 and 10 year frequency storms. Discharge rates are calculated from runoff
coefficients and existing sewer capacities to-p.rovide zero surcharge flow
in existing sewers.
Hydro Brake installation in the four areas is expected to permit the existing
sewers to carry the design flow without system modification other than con-
struction of off-line storage, or implementation of roof storage in one
industrial area.
Euclid, Ohio
Although no formal evaluation of the effectiveness of the City's Hydro
Brake installations has been performed, telephone interviews with Mayor Anthony
Giunta and Mr. John Piscitello, Service Director, elicited some informa-
tion. Hydro Brakes were installed directly in catch basins in areas which
experience basement flooding, in effect utilizing street retention of
storm waters upstream of flooded areas. Both the Mayor and the Service
Director feel that the devices have worked well, and that flooding problems
have been greatly reduced, albeit not entirely eliminated.
COMPARISON OF INSTALLATIONS
Introduction
Comparisons among the Hydro Brake installations described above and
between those and the Cleveland installation are difficult. Hard data is,
for the most part, extremely limited in the few reports published to date.
Although results are ascribed to various factors, it is not possible to
compare their derivations, since such basic data as Hydro Brake orifice
diameter, calibration of storage structures, discharge calibration, etc.
are each missing from one or another of the reports. Much of this lack of
data is probably ascribable to the fact that the reports available are
intended to apprise a client of results, rather than to qualify the
report for journal publication.
In addition, each installation is different from the others, and only
the Santee Drainage Area in Rochester, New York, installation is similar
to the Cleveland project.
62
-------
Finally, although Hydro Brakes have apparently been installed in at
least a dozen locations, follow-up studies are, for the most part, unavail-
able. Thus, quantitative evaluations and comparisons are limited to only
those described above.
DT-scussion of Calibration
The Rochester, New York installation is most similar to the Cleveland
project. An underground, off-line storage structure with a Hydro Brake
regulator was installed to accept the flow from approximately 50,000-55,000
ft2 (.465-.512 ha) as compared to the Cleveland installations. Those
installations drained approximately three acres (1.215 ha) each. The
Cleveland falling head calibrations of Hydro Brake discharge were, in fact,
modeled after the Rochester study. Unfortunately, physical problems with
the sewer plugging efforts limited the usefulness of some of the results
(see Section 4). However, it was noted that the discharge curves that
were developed did not indicate so dramatic a flow attenuation as did
the discharge curve developed in Rochester.
Figure 27 displays the Cleveland calibration curves against the
Rochester calibration curve for the Hydro Brake Standard 5-B-7. Although
various sizes of Hydro Brakes are included, a consistent pattern of attenua-
tion (discharge independent of head) should be evident for all. As can be
seen, this seems to be the case. However, as shown in Table 10, (which
includes data from the Nepean Twp. Ottawa Project) local conditions may
affect Hydro Brake performance.
As can be seen, observed flow rates in the Nepean Twp. and Rochester
studies more closely approximated the expected rates than did the observed
Cleveland rates. The 1.0 cfs (28.3L/s) and 2.0 cfs (26.6 L/s) units in
the Cleveland study units were especially high in relationship to the
expected flows. The difference shown for the 2.0 cfs (56.6 L/s) unit is
not explainable by available data, although the leakage described in
Section 4 may have contributed significantly. In any case, it is' pparent
that some attenuation of flow occurs for all sizes of Hydro Brake.
The Nepean Twp. installations were somewhat different from the Cleveland
and Rochester installations, in that the storage volume provided was much
less per unit area of drainage. However, if street storage is assumed
equivalent to off-line storage, the ultimate function of the units is
quite similar. Calibration data is included in Table 10, but the flows
were too low to be effectively displayed in Figure 27.
Discussion of Rainfall Event Monitoring
Although differences in monitoring and calculation methodologies among
the studies make quantitative comparisons unuseable, it is apparent that
in Rochester, Nepean Twp. and Cleveland, the Hydro Brakes did reduce peak
flows. Thiseeffect in turn increased storage; thereby delaying entry of
stormwater into the sewer system. Therefore, it can be said that in all
three cases, additional sewer capacity was made available during the moni-
tored storm events. Comparative flow rate analyses of ordinary orifices,
63
-------
7_ -(200)
D ^™
-(150)
4 ——
s
oo
to
2—
-(100)
I6in.(4lcin.) HYDROBRAKE
(PURITAS AVE.)
9in.(23ctn.) HYDROBRAKE
W. 170 ST.
5.5in.(l4cm.) HYDROBRAKE
7in.( 18cm.) HYDROBRAKE
W. 177 ST
6in.(l5cm) HYDROBRAKE
W. 170 ST
3"(76cm.) HYDROBRAKE
. W.I77ST
5-B-7 HYDROBRAKE
I (.30)
I
2 (.61)
HEAD IN FEET (METERS)
\
4(1.22)
50.52)
FIGURE 27 COMPARISON OF HYDROBRAKE DISCHARGE CURVES
64
-------
en
TABLE 10
COMPARISON OF RATED AND ACTUAL
HYDRO BRAKE DISCHARGES
Hydro Brake
Size
. in. (cm)
.6
2.0
3.0
3.0*
3.0
5.5
6.0
7.0
9.0
16.0
(1.52)
(5.08)
(7.62)
(7.62)
(7.62)
(13.97)
(15.24)
(17.78)
(22.86)
(40.64)
Manufacturer's
Rating (cfs)
cfs L/s
.005
.05
.24
.25
1.00
1.25
1.50
2.00
7.00
(.142)
(1.42)
(6.80)
(7.08)
(28.32)
(35.40)
(42.48)
(56.64)
(198.23)
Observed
Flow (cfs) at
3 ft. .Head
cfs L/s
.006
.04
.21
.44
.40
2..95
1.30
1.85
4.40
7.70
(.17)
(1.13)
(5.95)
(12.46)
(11.53)
(83.54)
(36.81)
(52.40)
(124.60)
(218.05)
Observed
Flow (cfs) at
5 ft. Head
cfs . L/s
--
—
.27
.58
—
3.95
1.45
2.50
5.50
9.10
—
—
(7.65)
(16.42)
—
(111.86)
(41.06)
(70,. 80)
(155.75)
(257.70)
Location
Nepean Twp.
Nepean Twp.
Rochester
Rochester
Cleve./W. 177
Cleve./Puritas
Cleve./W. 170
Cleve./W. 177
Cleve./W. 170
Cleve./Puritas
*Straight Orifice
-------
similar in size to the Hydro Brake devices, strongly suggest that the Hydro
Brakes were able to retard flow, using a larger outlet than would have been
possible with a standard orifice.
In addition ,the Cleveland study indicates that by making additional
sewer capacity available, basement flooding and some street flooding was
re'duced. The City of Euclid reports apparently similar results. By the
use of Hydro Brakes in catch basins, Euclid utilizes street storage,
thus reducing catch basin surcharging, and consequently basement flooding
caused by back-up flows from those catch basins.
In summary, it would seem that the method of storage is relatively
unimportant. As suggested in the study prepared for the Borough of York,
street, roof and parking lot, or buried off-line tank storage should be
determined from the uses and needs of the project area; with the Hydro
Brakes designed to best serve the chosen storage method.
The Hydro Brakes themselves seem to have two outstanding advantages.
By retarding flow while permitting a larger outlet, they seem less likely
to become fouled by refuse than would the smaller orifice. However, as
demonstrated by the redesigned 177th Street Hydro Brake in Cleveland,
small orifice Hydro Brakes may themselves become fouled. This does not
negate the likelihood that the even smaller orifice required for the same
level of control would incur a proportionately greater risk of fouling.
In addition, their flexibility of design allows for a variety of appli-
cations, which increase their attractiveness as control devices for older,
overloaded sewer systems that may otherwise require the alternatives of
replacement or relief sewer construction.
Debris in two Hydro Brakes affected performance. In the W. 177th
Street installation (Cleveland), a styrofoam cup wholly blocked the flow
of stormwater. In the Standard 5-B-7 installation (Rochester) a piece of
lath apparently interrupted the vortex within the unit, and thereby
permitted stormwater flow to occur at a rate equal to a 3.5 in (8.9 cm)
orifice.
Generally speaking, maintenance was not described as a problem,
although the Nepean Township catch basin installations were subject to
solids depositions. Regular clean-out was necessary because of odors.
66
-------
SECTION 8
ALTERNATIVE EVALUATION
GENERAL SCREENING OF ALTERNATIVES
Some alternatives for alleviating detrimental combined sewer over-
flow effects are not practical for handling upstream sewer surcharge
problems. These control methods were identified and eliminated from
further consideration.
Combined Sewer Relief Regulators
This method of alleviating combined sewer overloads is not viable
in areas similar to the Puritas Avenue study area. There is no where to
relieve the combined sewers without extensive interceptor construction,
and this option compounds the health and water quality degradation problems
of conventional combined overflows.
In-Line Storage
Where there is available trunk and interceptor capacity, this is
a simple, cost-effective means of controlling storm flows through in-line
regulators. There is no excess capacity in the sewers of the subject
study area.
End of Pipe Methods
Interception and transportation of combined flows at the point of
overflow does not relieve surcharging upstream of the control point,
and requires large interceptor construction to carry flows to some
point for treatment. Likewise, end of pipe treatment does nothing for
problems upstream and usually has lower pollutant removal efficiencies
compared with centralized treatment facilities. Controls in upstream
problem areas reduce the pressure on downstream control points, in large
part eliminating the need for peak flow rate transportation or treatment.
Off-Line Combined Storage with Gravity Discharge
Grades in the study area are not sufficient to allow a workable
gravity influent/gravity effluent combined flow storage approach. To
take advantage of gravity return from off-line storage here would require
high capacity lift stations capable of handling peak runoff rates.
The reliability of such a system would also be jeopardized by power outages,
so that back-up power would also be requird.
67
-------
DESCRIPTION OF VIABLE ALTERNATIVES
Inlet Control
The simplest control requires only regulation of peak flows at com-
bined sewer inlet points. Hydro Brake control devices inserted in catch
basins has been successfully implemented in several areas, as noted
in Section 7. This option is contingent upon the availability and
safety of surface ponding to accommodate storm water storage require-
ments.
Inlet Control and Storage
This alternative is the central issue of this evaluation. A
combination of inlet controls and below grade storage was used for storm
flow regulation. Relatively shallow storage facilities are required to
allow gravity discharge to the combined sewers. This approach offers
considerable design and flow regulation flexibility, depending on the
level of control desired.
Off-Line Combined Storage with Pumped Discharge
Storage facilities must be deeper than the combined sewers, and
require pumping to return flows to the collection system. Storage
volume and flow regulation rates are flexible, with the pump discharge
being the flow rate control mechanism. Compared to surface runoff storage,
combined flow storage may have higher maintenance requirements because
of solids deposition and decomposition problems.
Sewer Separation
This option eliminates combined sewers but only with very
extensive construction and at great expense. Sewer construction in
fully developed urban areas is often beyond the means of both residents
and public agencies.
COST ESTIMATES OF VIABLE ALTERNATIVES
Project cost summaries have been compiled from the City of Cleveland's
project cost summarie for the Puritas Avenue and Mil burn Avenue projects,
the Santee Drainage Area/Hydro Brake Demonstration Project report (O'Brien
& Gere) (?) and EPA construction cost summaries. All costs were adjusted
to an ENR index of 3700 (January, 1982) and are reported as cost per acre
for rough comparability, although project scales are different.
For estimation of off-line combined flow storage costs, it was assumed
that one retention dewatering lift station rated at 0.5 - 1.0 cfs (14 -
28 L/s) would be required for a 10 acre (4 ha) drainage area. The only
difference between the Hydro Brake storage tanksand the combined flow
storage is depth; costs were based on Hydro Brake storage costs plus 25%.
Table 11 presents a comparison of the costs for the various alter-
natives discussed. The obvious benefit of the Hydro Brake concept is
its cost-effectiveness when compared with other alternatives.
68
-------
TABLE 11. COST COMPARISONS OF STORM FLOW CONTROL ALTERNATIVES
Alternative
Inlet Control
(Cleveland)
Inlet Control &
Project
Cost
$ 4,300
$345,000
Drainage
Area Cost Per
Acres (hectares) Acre ($/hectare)
31 (12.5)
25 (10. 1)
$ 140
$13,800
($350)
($34,200)
Storage (Cleveland)
Inlet Control m 8,400
(O'Brien & Gerer '
Inlet Control $22,100
Storage (O'Brien & Gere)(7)
Combined Storage
(a) Retention
(b) Pumping
(c) TOTAL
Sewer Separation
35 (14.2) $ 240 ($590)
1.25 (.5)
(.4)
(.4)
(.4)
1 (.4)
$17,700 ($44,200)
$13,500 ($33,300)
8,500 ($21,000)
$22,000 ($54,300)
$3(1.000- ( 74.100-
45,000 11KOOO)
69
-------
REFERENCES
1... Theil, Paul E., and A.M. Candaras, Paul Theil Associates Limited, Design
of the Hydro Brake Stormwater Detention Tank Assemblies for the Control
of Combined Sewer Overflow Pollution, EPA Demonstration Grant No. S005370,
April, 1981. (unpublished in-file report).
2. Chien, Jong-Song, and K.K. Saigal, Urban Runoff by Linearized Subhydro-
graphic Method. Journal of the HYD. Div., ASCE, HY 8, Aug., 1974.
3. Terstriep, Michael L., and John B. Stall, The Illinois Urban Drainage
Area Simulator, ILLUDAS.
4. O'Brien & Gere Engineers, Inc., Hydro Brake Demonstration Project -
Santee Drainage Area Progress Report, June, 1981.
5. Gore & Storrie Limited, Evaluation of the "Hydro Brake" Flow Regulator,
Report SCAT-7 for Canada Mortgage and Housing Corporation.
6. Paul Theil Associates Limited, Borough of York Sewer Surcharging and
Flooding Relief Study by Implementing Hydro Brake System, June, 1977.
7. O'Brien & Gere Engineers, Inc., Hydro Brake Demonstration Project -
Santee Drainage Area - Rochester, New York, February, 1981.
70
-------
BIBLIOGRAPHY
Contractors Data Report - Nationwide Tabulated Bid Results - Ohio Listings.
Dames & Moore Water Pollution Control Engineering Services„ Construction
Costs for Municipal Wastewater Conveyance Systems: 1973-1977, EPA
Technical Report 430/9-77-014, May, 1978.
Field, Richard, Anthony N. Tafuri and Hugh E\ Masters, Urban Runoff Pol-
lution Control Technology Overview, Storm and-Combined Sewer Section -
Municipal Environmental Research Laboratory, EPA - 600/2-77-047, March,
1977.
Freeman, Peter A., Peter A. Freeman Assoc., Inc., Evaluation of Fluidic
Combined Sewer Regulators Under Municipal Service Conditions, EPA Demon-
stration Grant No. 11022 FWR, EPA - 600/2-77-071, August, 1977.
Mallory, C.W., The Beneficial Use of Stormwater, EOA - R2-73-139, January,
1973.
Sarikelle, Somsek, Overview of Hydrograph and Routing Techniques and Intro-
duction to Modeling, in Proceedings of Urban Runoff Seminar, University
of Akron, December 10, 1976.
Sullivan, Richard H., et. al., American Public Works Association, The
Helical Bend Combined Sewer Overflow Regulator, EPA - 600/2-75-062,
December, 1975.
71
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1.
APPENDIX A
FORMULAE, HEAD VS. VOLUME TABLES
Ungula of a cylinder - calculation of volume increments for head
vs. volume relationships.
Figure A-l. Ungula of a cylinder
Volume = ^ [a(3R2-a2) + 3R2 (b-R) VI ]
Where b = depth of water measured at downstream end of storage tank
r = radius of storage tank
2a = width of water surface
h = length of volume section (varies with b and slope of tank)
2w = central angle of chord defined by b and r
72
-------
2. Construction of Sub-Hydrographs (design storm evaluation)
1
TIME
Figure A-2. Design Storm Sub-Hydrograph
Q = CIA (2tr)/(tr + tc), tr«tc
Where Q = Peak flow rate in cfs
C = Runoff coefficient
I = Rainfall increment intensity in in/hr
A = Drainage area in acres
tr = Duration of rainfall increment
tc = Time of concentration of drainage area
73
-------
3. Hydrograph Routing - Design storm discharge simulation
For convenience in hydrograph routing, it is assumed that the
"average of flows at the start and end of a small time increment is
equivalent to the average flow during this increment.
Therefore, the storage continuity equation:
May be rewritten as:
II + 12 - DI + 02 = S2 - Sj
2 2 dt
Where 0} = discharge at time tj
02 = discharge at time t%
\l = inflow at time t^
I 2 = inflow at time t2
S2 = storage at time t2
S1 = storage at time t}
dt = t2 - ti
Rearranging yields:
Q!) = 2S2/dt + 02
All terms on the left side of the equation are known, so the value
of the right side may be calculated. From known relationships for
H vs. S and H vs. Q, a graph of 2S/dt + 0 vs. 0 may be constructed.
To solve the routing problem, successive inflow values are input to
determine corresponding discharge values (O^). These discharge values
are then used to repeat the calculation until all influent flows have
been input through the relationship to construct the corresponding
discharge hydrograph.
74
-------
4. Head vs. Volume Relationships
Table A-l presents cumulative volumes in cubic feet for one
inch incremental changes in water depth in each Hydro Brake retention
structure. Depth is measured at the downstream end of each structure
and includes volumes for catch basin leads; manholes and storm sewer
segments where applicable.
TABLE A-l
Depth* Cumulative Volume in Cubic Feet
(Inches)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
22
24
W. 170 St.
0.5
2
7
13
23
37
54
75
100
129
163
200
242
287
337
391
451
516
585
610
675
743
811
880
W. 177 St.
1
6
15
30
51
80
116
161
214
275
346
426
516
615
723
842
970
1109
1257
1414
1578
1746
1914
2084
75
Puritas Ave.
1
5
15
30
52
83
121
169
226
293
368
451
540
633
730
830
932
1037
1143
1250
1359
1469
1579
1690
-------
Depth
(Inches)
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
Cumulative
W. 170 St.
951
1021
1091
1161
1230
1298
1365
1429
1492
1553
1611
1667
1721
1773
1824
1874
1923
1971
2015
2067
2108
2146
2181
2214
2240
2261
2279
2293
2304
2311
2316
2318
Volume in Cubic
W. 177 St.
2260
2439
2622
2807
2993
3180
3369
3557
3746
3923
4123
4311 .
4498
4684
4868
5053
5236
5418
5598
5777
5955
6131
6305
6477
6647
6815
6980
7143
7303
7460
7614
7765
Feet
Pun'tas Ave.
1801
1914
2026
2139
2252
2365
2478
2590
2702
2814
2926
3037
3095
3257
3366
3474
3581
3688
3794
3899
4002
4105
4207
4307
4406
4503
4600
4694
4787
4878
4968
5055
76
-------
Depth
(Inches)
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
Cumulative Volume in Cubic
U. 170 St. W. 177 St.
2319 7912
8056
8195
8330
8461 _
8586 ~ -
8706
8819
8925
9023
9114
9196
9271
9338
9398
9452
9498
9539
9573
9601
9624
9642
9655
9665
9670
9673
9675
Feet
Pur Has Ave.
5141
5224
5305
5384
5460
5533
5603
5671
5734
5794
5850
5900
5945
5983
6015
6042
6062
6078
6089
6096
6100
6101
'b" in Figure A-l .
77
-------
APPENDIX B
HOMEOWNER SURVEY FORMS
PURITAS AREA QUESTIONNAIRE
(PRE-CONSTRUCTION)
ADDRESS
1. Have you experienced basement flooding?
If so, when and how often?
2. What is the deepest that the water has ever appeared in
your basement:
3. Does your street experience street flooding during a storm
or during a rainy season?
If so, when and how often?
If the street does flood, at what location is the water
present?
78
-------
PURITAS AREA QUESTIONNAIRE
(POST-CONSTRUCTION)
ADDRESS:
1. Have you experienced basement flooding in recent months?
If so, when, how deep?
2. Does your street experience street flooding during a storm or
during a rainy season?
If so, where?
3. Do you have any sewage odor problems?
Explain when.
4. Are these odors more noticeable during rain storms?
79
-------
SAMPLING LOC.: W177
APPENDIX C
STORM WATER QUALITY SAMPLING RESULTS
DATE OF SAMPLE: July 13, 1981
Time of Sample Taken (min.)
PARAMETERS 2.5 5.0
BOD mg/1 34 48
Suspended Solids mg/1 98 80
Volatile Suspended
Solids mg/1 15 13
Cadmium mg/1
Total Chromium mg/1
Chloride mg/1
Copper mg/1
Lead mg/1
Sulfate mg/1
Zinc mg/1
Total Organic
Carbon mg/1
COD mg/1
Settleability ml /I
10 --- 15 30 Composite
52 59 51
79 88 80
14 10 10
0.01
LT 0.01
6.3
0.02
0.10
8.5
0.16
12
39
LT 0.18
LT = Less Than
80
-------
SAMPLING LOG.: W170 DATE OF SAMPLE: July 21, 1981
Time of Sample Taken (min.)
PARAMETERS 2.5
BOD mg/1 51
Suspended Solids mg/1 91"""-
Volatile Suspended Solids mg/1 32
Cadmium mg/1 0.01
Total Chromium mg/1 0.01
Chloride mg/1 13
Copper mg/1 0.03
Lead mg/1 LT 0.01
Sulfate mg/1 8.6
Zinc mg/1 0.15
Total Organic Carbon mg/1 7
COD mg/1 100
Settleability ml/I LT 0.32
LT - Less Than
81
-------
SAMPLING LOG.: W177 DATE OF SAMPLE: July 28, 1981
Time of Sample Taken (min.)
PARAMETERS 90 JI20 J50 JSO _2JO Composite
BOD mg/1 10 29 17 19 21
Suspended Solids mg/1 61 56 40 /" 58 35
Volatile Suspended
Solids mg/1 13 10 7 16 10
Cadmium mg/1 — — — — — 0.01
Chromium mg/1 — -- — -- — 0.01
Chloride mg/1 -- — — -- -- 9
Copper mg/1 — — — -- — 0.03
Lead mg/1 — — — -- — 0.01
Sulfate mg/1 - - -- 27
Zinc mg/1 — -- — -- — 0.18
o
Total Organic
Carbon mg/1 — — -- -- -- 26
COD mg/1 — — — -- — 40
Settleability ml/1 — LT 0.18
LT - Less Than
82
-------
SAMPLING LOG.: W177
%
PARAMETERS 2.5
BOD mg/1
Suspended Solids mg/1
Volatile Suspended
Solids mg/1 16
DATE OF SAMPLE: July 28, 1981
Time of Sample Taken (min.)
5.0 10 15 30 60
27
74
22
82
17
69 >/
18
56
15
110
13
72
15
14
15
16
12
83
-------
SAMPLING LOG.: W170 DATE OF SAMPLE: August 8, 1981
Time of Sample Taken (min.)
PARAMETERS id Ii2 J£ li Composite
BOD mg/1 21 28 12 13 —
Suspended Solids mg/1 210 180 .\-100 110
Volatile Suspended Solids mg/1 65 60 30 30
Cadmium mg/1 -- -- -- -- 0.01
Total Chromium mg/1 — -- -- -- 0.01
Chloride mg/1 — — — — 11
Copper mg/1 . -- ~ -- ' -- 0.05
Lead mg/1 — — — — 0.12
Sulfate mg/1 — -- — — 12
Zinc mg/1 — — -- -- 0.26
Total Organic Carbon mg/1 — -- -- — 36
COD mg/1 - - — - 110
Settleability ml/1 -- — — — 1.2
84
-------
SAMPLING LOG.: W170
PARAMETERS
BOD mg/1
Suspended Solids mg/1
Volatile Suspended Soilds mg/1
DATE OF SAMPLE: August 17, 1981
Time of Sample Taken -(min.)
30 60 90 120
19 19
58 "- 83
21 18
16
70
24
19
61
20
85
-------
SAMPLING LOG.: W170
PARAMETERS
BOD mg/1
Suspended Solids mg/1
Volatile Suspended Solids mg/1
Cadmium mg/1
Total Chromium mg/1
Chloride mg/1
Copper mg/1
Lead mg/1
Sulfate mg/1
Zinc mg/1
Total Organic Carbon mg/1
COD mg/1
Settleability ml/I
DATE OF SAMPLE: August 17, 1981
Time of Sample
2.5 5.0 10
23 22 21
90 62 - - 50
31 24 20
—
—
—
—
—
—
—
—
—
~_ _«. __
Taken
15
20
48
20
—
—
—
—
—
—
—
—
—
„_
(min.)
Composite
—
—
—
0.02
LT 0.01
28
0.33
0.07
21
0.22
50
53
0.98
LT = Less Than
86
-------
APPENDIX D
STORAGE TANK PHOTOGRAPHS AND SEDIMENT RECORDS
Photographs were taken in November, 1981, after the Hydro Brake
control/retention structures had been in operation approximately 18 months.
Each series of photographs starts at the downstream end of the structures
and proceeds up the tanks at approximately 25 foot {7.6 M) intervals.
Each photograph includes descriptive comments using the following format:
Picture No.
(a) Location or approximate distance from downstream bulkhead, etc.
{b) Sediment measurements, comments - September, 1980
(c) Sediment measurements, comments - November, 1981
Note that construction timbers were still in place in the Puritas
and W. 177th Street structures.
Puritas Avenue~ ~
#1. (a) View of 16" (41 cm) Hydro Brake in place
(b) --
(c) --
87
-------
#2.
#3.
(a) West Bulkhead
(b) 1" (2.5 cm) standing water
(c) 1" (2.5 cm) standing water
a) 25 feet (7.6 M)
b) 1" (2.5 cm) standing water
c) 1" (2.5 cm) standing water
-------
#4.
(a)
b)
c)
50 feet (15 M)
1" (2.5 cm) standing water
1" (2.5 cm) standing water
#5. (a) 75 feet (23 M)
(b) 1" (2.5 cm) standing water
1" (2.!
(c)
,5 cm) standing water
89
-------
#6. (a) 100 feet (30.5 M)
(b) 1" (2.5 cm) standing water
(c) 1" (2.5 cm) Standing water
#7. (a) 125 feet (38.1 M) - View of East Bulkhead
(b) 1" (2.5 cm) standing water
(c) Dry
S
90
-------
W. 170th Street
#1. (a) Downstream Manhole with 9" (23 cm) Hydro Brake in place
(b) 3" (7.6 cm) sediment
(c) 1" (2.5 cm) sediment
#2.
a) 25 feet (7.6 cm)
b) 3" (7.6 cm) sediment
(c) 1" (2.5 cm) sediment
91
-------
#3.
(a) 50 feet (15 M)
(b) 3" (7.6 cm) sediment
(c) 1" (2.5 cm) sediment
#4. (a) 75 feet (23 M)
(b) Dry
(c) 1" (2.5 cm) sediment
92
-------
#5.
100 feet (30.5 M)
b) 1" (2.5 cm) standing water
(c) 1" (2.5 cm) sediment
#6. (a) 125 feet (38.1 M)
(b) 2" (5.1 cm) standing water
(c) 3" (7.6 cm) sediment & water
\
93
-------
H. 177th Street
#1. (a) 7" (18 cm) Hydro Brake in place
(b) --
(c) --
(a) 25 feet (7.6 M) - East tank
(b) 1" (2.5 cm) standing water
(c) 3" (7.6 cm) sediment
94
-------
#3. (a) 50 feet (15 M)
(b) 1" (2.5 cm) standing water
(c) 2" (5.1 cm) standing water
\
#4. (a) 75 feet (23 M)
(b) 2" (5.1 cm) standing water
(c) 1" (2.5 cm) sediment
95
-------
#5. (a) 100 feet (30.5 M)
b) 1" (2.5 cm) standing water
c) 1" (2.5 cm) sediment
#6. (a) 125 feet (38.1 M) view of South Bulkhead (East tank)
(b) 2" (5.1 cm) standing water
(c) 2" (5.1 cm) standing water
96
-------
#7. (a) North Bulkhead (West tank) - effluent pipe to Hydro Brake
Manhole
(b) 2" (5.1 cm) standing water
(c) 2" (5.1 cm) standing water
#8. (a) 25 feet (7.6 M)
(b) 1" (2.5 cm) sediment
(c) 2" (5.1 cm) sediment and water
97
-------
#9.
#10.
a) 50 feet (15 M)
b) 1" (2.5 cm) standing water
c) 1" (2.5 cm) sediment
a)
.b)
(c)
75 feet (23 M)
1" (2.5 cm) standing water
1" (2.5 cm) standing water
98
-------
#11.
(a)
(b)
(c)
100 feet (30.5 M)
1" (2.5 cm) standing water
1" (2.5 cm) standing water
#12. (a) 125 feet (38.1 M) view of South Bulkhead (West tank)
(b) 1" (2.5 cm) standing water
(c) 1" (2.5 cm) standing water
99
-------
APPENDIX E
1/2 HOUR DURATION DESIGN STORM HYDROGRAPHS
RAINFALL INTENSITY
IN/HR.(cm./HR.)
INFLOW
OUTFLOW
{6in./l5cm. HYDROBRAKE)
\
\
\
\
\
\
liliiiiiiiin^ I i i i
6 12 IB 24 30 36 42 48 54 60 66 72 78 84 90 96 102
TIME (MINUTES)
FIGURE E-l W. 170 ST. DESIGN STORM HYDROGRAPHS
10 YR. RETURN- 1/2 HR. DURATION (l.37ia-3.48cm.)
100
-------
_. 3-
u.
o
I
LJ
RAINFALL INTENSITY
IN/HR(cm./HR.)
INFLOW
OUTFLOW
(6in./l5cm. HYDROBRAKE)
2—
\
\
\
\
\
i r i i i i i i^ i i i > i i I
6 12 18 24 30 36 42 48 54 60 66 72 78 84 90
TIME (MINUTES)
FIGURE E-2 W. 170 ST. DESIGN STORM HYDROGRAPHS
SYR. RETURN-1/2 HR. DURATION(U9ia-3X>2cm.)
101
-------
RAINFALL INTENSITY
IN/HR.(cm./HR.)
INFLOW
OUTFLOW
(6in./!5cm. HYDROBRAKE)
iI I r
18 24 30 36
42
TIME (MINUTES)
1 I I T
48 54 60 66
T r
72 78
t
84
FIGURE E-3 W. 170 ST. DESIGN STORM HYDROGRAPHS
2YR. RETURN-1/2 HR. DURATION (.91 in.-2.3lcm.)
102
-------
5-
5
U-
o
UJ
2—
(5)
(10)
RAINFALL INTENSITY
IN/HR.(cm./HR.)
(15)
• INFLOW
-(75)
OUTFLOW
(6in./l5cm. HYDROBRAKE)
2.15 CFS(60.9L/s)
» I I T
24 3O 36 42 48
TIME (MINUTES)
I I
54 60
66
FIGURE E-4 W.I70ST DESIGN STORM HYDROGRAPHS
IYR. RETURN-1/2 HR. DURATION (.76in.-l.93cm.}
103
-------
RAINFALL INTENSITY
IN/HR.(cm./HR.)
INFLOW
OUTFLOW
(3ia/7.6cm. HYDROBRAKE)
\
l I 1
468 474 480
FIGURE E-5
TIME (MINUTES)
W. 177 ST. DESIGN STORM HYDROGRAPHS
10 YR, RETURN-l/2 HR. DURATION(l37ia-3.48cm.)
104
-------
fe
RAINFALL INTENSITY
IN/HR.(cm./HR.)
INFLOW
OUTFLOW
(6ia/l5cnn HYDROBRAKE)
I I
24 30 36 42 48 54
I I
420 426
TIME(MINUTES)
FIGURE E-6 W. 177 ST. DESIGN STORM HYDROGRAPHS
SYR. RETURN-1/2HR. DURATION (I.l9in.-3.02cra)
105
-------
5-
4—
3—
tn
LL.
o
I
1 *-
LL.
-(5)
(10)
-(100)
I
6
RAINFALL INTENSITY
IN/HR.(cm,/HR.)
3.35 CFS (94.9 L/s)
INFLOW
OUTFLOW
{6ta/l5cm. HYDROBRAKE)
12
18
I
24
I
30
1 I
36 42
TIME (MINUTES)
\
48
I
54
60
330 336 342
FIGURE E-7 W. 177 ST. DESIGN STORM HYDROGRAPHS
2YR. RETURN-1/2HR. DURATION (.91in.-2.31cm.)
106
-------
RAINFALL INTENSITY
IN/HR.(cm;/HR.)
cc
INFLOW
OUTFLOW
(6in/l5cm. HYDROBRAKE)
I
12
18 24 30
I
36
1
42
1
48
1
54
60
I I I
288 294 300
TIME (MINUTES)
FIGURE E-8 W. 177 ST. DESIGN STORM HYDROGRAPHS
IYR. RETURN- 1/2 HR. DURATION (76in.-1.93cm.)
107
-------
RAINFALL INTENSITY
!N/HR.(cm./HR)
INFLOW
OUTFLOW
(5.5in./l4cm. HYDROBRAKE)
_J
to
i
UJ
S3
ST.
I
FIGURE E-9
I I i 1 i \ \ I r
24 30 36 42 48 54 60 66 72 78 84
TIME (MINUTES)
PURITAS AVE. DESIGN STORM HYDROGRAPHS
10YR. RETURN- 1/2 HR. DURATION (l.37in.-3.48cm.)
108
-------
RAINFALL INTENSITY
IN/HR.(cm./HR)
INFLOW
- OUTFLOW
(5.5in./14cm. HYDROBRAKE)
TIME (MINUTES)
FIGURE E-IO PURITAS AVE. DESIGN STORM HYDROGRAPHS
SYR. RETURN-1/2 HR. DURATION (U9in.-3.02cm.)
109
-------
RAINFALL INTENSITY
IN/HR.(cm./HR.)
INFLOW
OUTFLOW
(5.5in./|4cm. HYDROBRAKE)
I I I I I I II II
6 12 18 24 30 36 42 48 54 60 66
TIME(MINUTES)
FIGURE E-ll PURITAS AVE. DESIGN STORM HYDROGRAPHS
2YR. RETURN- 1/2 HR. DURATION (.9lin.-2.31cm.)
110
-------
to
fe
RAINB\LL INTENSITY
IN/HR.(cm./HR.)
ni 2-
INFLOW
• OUTFLOW
(5.5in./|4cm. HYDROBRAKE)
\ I f I I I I
18 24 30 36 42 48 54 60
TIME (MINUTES)
FIGURE E-12 PURITAS AVE. DESIGN STORM HYDROGRAPHS
IYR. RETURN - 1/2 HR. DURATION (76in.-1.93 cm.)
m
-------
APPENDIX F
HYDRO BRAKE/RETENTION
APPLICATIONS IN CLEVELAND, OHIO
DESIGN CRITERIA
AND
PROJECT SUMMARIES
by
City of Cleveland
Department of Public Utilities
Narrative Sections
by
J. Christopher Kocsan
Technical Sections
by
Francis Toldy, P.E.
112
-------
INTRODUCTION
The purpose of this appendix is three (3) fold. First, the City of
Cleveland has recently constructed many projects which are similar in nature
to the evaluated grant project. The City intends, at this point, to present
descriptions of each of these similar projects, including pertinent statistical
data, and to compare and contrast these similar projects to the evaluated grant
project.
*" v
Secondly, during the evaluation of the grant project, it became obvious
to all concerned parties that the underground retention tanks which had been
constructed were not being fully utilized as far as their storage capacities
were concerned. Accordingly, new more restrictive Hydro-Brake flow regulators
were installed within these tanks during the summer of 1981. The manner in
which these new sizes were determined by the City, is presented within this
section of the appendix.
The final section of this appendix contains a Design Manual for Storm
Water Retention Facilities. The City has taken one of its similar projects,
and by using that project as an example, it has demonstrated on a step-by-step
basis the manner in which an interested party would proceed with designing
this type of Storm Water Retention Facilities. It is believed that the
information contained within this section will prove quite valuable to those
readers who are interested in constructing projects similar to the one which
has just been evaluated.
COMPARISON OF SIMILAR PROJECTS
A comparison of the similar projects which have been constructed by the
City of Cleveland since the time when the evaluated grant project became opera-
tional will now be presented.
1. Southwest Sewer Project - Phase I
The Southwest Sewer Project - Phase I is a project in which the City
of Cleveland utilizes an existing creek within the project area to
receive excess storm water flow which has been created by heavy rains.
The City has achieved this by installing thirteen (13) 4-inch Standard
Hydro-Brake flow regulators within the existing catch basins which are
located at the uphill ends of Kirton Avenue. The flow out of these
catch basins has been greatly reduced because of the installation of
this patented control device. Accordingly, since during periods of
heavy storms, the flow into these combined sewers is retarded by the
installed Hydro-Brakes, and since these catch basins are also located
at the uphill ends of Kirton Avenue, a majority of the storm water
run-off is bypassing the uphill catch basins and flowing into
the catch basins which are located in the low point area of Kirton
Avenue. These catch basins discharge their flow directly into the
existing creek.
113
-------
The Hydro-Brakes which were recently installed possess a discharge
rating of .25 CFS at three (3) feet of head. A total of $8,450 was
expended by the City for the purchase of Hydro-Brakes concerning
this project, as these Hydro-Brakes cost $650 each,including installa-
tion. The total drainage area along Kirton Avenue which is effected
by the installation of these Hydro-Brakes is approximately four (4)
acres.
Since the project contained a number of different improvements in addi-
tion to the Hydro-Brake installations, it is not appropriate to discuss
a per cubic foot cost as far as storage space is concerned. The con-
struction cost of this project was $83,487. In addition, because of
the referenced additional improvements, it is also not appropriate to
quote a figure concerning the cost per acre required in order to
implement this project.
The major element of the additional improvements which were made,
above and beyond the installation of the referenced Hydro-Brakes, was
the rebuilding of sixteen (16) existing catch basins located within
the low point areas of three streets - Kirton Avenue, Carrington
Avenue and Erwin Avenue. The storm flow from these catch basins was
rerouted from the existing combined sewer system into a nearby creek.
This obviously reduced the level of flow to the combined system within
the area. In addition, a small playground within the area was enlarged
and landscaped, and it is now used as an above ground storm water re
tention basin during periods of intense rainfall and sewer system sur
charging.
2. Southwest Sewer Project - Phase II
The Southwest Sewer Project - Phase II is quite similar to the eval-
uated grant project. In this project, the City constructed four
(4) underground storm water retention tanks within the project area,
as well as utilitizing the available roadway surface for purposes
of storm water storage during periods when intense rainfalls cause
the combined sewer system in the area to become surcharged. A summary
of the characteristics of the four undergound retention tanks which
were constructed is as follows:
LOCATION
1. Crossburn Ave.
2. Crossburn Ave.
3. Bennington Ave,
4. Bennington Ave.
DIMENSIONS CAPACITY
353' Long
48" Dia.
400' Long
48" Dia.
400' Long
48" Dia.
371' Long
48" Dia.
114
4,436
Cu. Ft.
5,026
Cu. Ft.
5,024
Cu. Ft.
4,662
Cu. Ft.
OUTLET
REGULATOR
6" Standard
Hydro-Brake
6" Standard
Hydro-Brake
6" Standard
Hydro-Brake
9" Standard
Hydro-Brake
OUTLET
DISCHARGE
RATE
0.6 CFS @
5 Ft. of Head
0.6 CFS G>
5 Ft. of Head
0.6 CFS @
5 Ft. of Head
1.5 CFS @
5 Ft. of Head
-------
All tanks were constructed of corrugated steel pipe, are circular in
diameter, and were positioned at low points on their respective streets.
A total of 13 catch basins along Crossburn Avenue now have their storm
flow diverted into the two newly constructed retention tanks instead
of directly into the combined sewer system. A total of 14 catch basins
along Bennington Avenue have their storm flow diverted in a similar
manner. All of the retention tanks eventually discharge their storm
flow through the Hydro-Brakes and into the existing combined sewer
system at the controlled rate of discharge which is regulated by the
Hydro-Brake.
A total of five (5) existing catch basins within the pro.iect area
have been equipped with four-inch Standard Hydro-Brakes in order to
increase the level of storm water runoff flowing towards the low
points of the referenced streets. At this point, the surface runoff
from the area is dischargeed directly into the retention tanks
through the low point catch basins. These Hydro-Brakes have discharges
which are rated by the manufacturer at .25 CFS at 3 feet of head.
The construction cost of the entire project was $175,860. The pro-
ject effects a total drainage area of 38.6 acres. Thus, the project
cost $4,556 per acre in order to construct. The total volume of
storage which is available within the constructed retention tanks is
19,175 cubic feet. Thus, the project cost $9.17 for every cubic foot
of storage space created.
The costs pertaining to the purchase of the required Hydro-Brakes for
this project, including installation, were as follows:
Description Quantity Price Extension
9" Standard Hydro-Brake 1 $2,300 $2,300
6" Standard Hydro-Brake 3 1,675 5,025
4" Standard Hydro-Brake 5 915 4.575
Total $11,900
Thus, a total of $11,900 was expended by the City within the applic-
able construction contract for the purchase and installation of
Hydro-Brakes concerning this project.
115
-------
3. Southwest Sewer Project - Phase III
This project, as far as scope of work is concerned, is a combination
of the preceding two phases of this four phase series of projects.
Within this phase, the City constructed one underground retention
facility along West 127th Street between Astor and Crossburn Avenues.
The referneced tank is 209 feet long, is 66 inches in diameter, and
has a capacity of 4,965 cubic feet. The tank's outlet is equipped
with a 6-inch Standard Hydro-Brake-which has a discharge rating of
.7 CFS at 5 feet of head.
A total of seven (7) catch basins in the area have their flow diverted
into the newly constructed retention tank. In addition, four other
catch basins within the project area have also been equipped with 4-inch
Standard Hydro-Brakes which possess discharge ratings of .25 CFS at
3 feet of head. This further relieves the level of storm flow which
enters the combind sewer system during periods of sewer surcharging.
Because of the implementation of this system, the number of incidents
of surcharging within the project area have been effectively reduced.
The total drainage area which is tributary to the constructed reten-
tion tank is 3.3 acres.
The total expenses incurred by the City for the purchase of Hydro-Brakes,
including installation, concerning this project is as follows:
Description
6" Standard Hydro-Brake
4" Standard Hydro-Brake
Quantity Price
1
4
$1,800
1,050
Total
Extension
$1,800
4,200
$6.000
Thus, a total of $6,000 was expended for the purchase and installa-
tion of Hydro-Brakes concerning this project.
Along Longmead, Milligan and McGowan Avenues, which are adjacent
streets located within the project area, thirteen (13) existing catch
basins were reconstructed with their storm flow being rerouted from
the area's existing combined sewer system into a nearby creek. This
further reduces the storm flow entering the combined system within t
he area.
Because of these additional improvements, it is improper to quote a
project cost based upon per acre of drainage area effected. It is
also improper to quote a cost per cubic foot of storage space created.
The construction cost of the project was $83,267, while the total
drainage area effected by all elements of the project is 8.5 acres.
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4. Southwest Sewer Project - Phase IV
Within this project, the City constructed two (2) underground storm
water retention tanks at low points along Carrington Avenue. The
first of these tanks is 300 feet long, 48 inches in diameter, and
has a volume of 3,770 cubic feet. The tank is not equipped with, a
Hydro-Brake regulator, but with a discharge pipe which is six-inches
in diameter and which discharges its storm flow into an existing
18-inch combined sewer.
The second tank is slightly smaller. It is 250 feet long, 48 inches
in diameter, and has a volume of 3,142 cubic feet. This tank is
also equipped with a discharge pipe which is six-inches in diameter,
but which discharges its flow into a 20-inch combined sewer. Both
tanks are constructed of corrugated steel pipe. A total of eight
catch basins now discharge their storm flow into these two retention
tanks.
None of the catch basins which are located uphill from the two reten-
tion tanks constructed along Carrington Avenue are equipped with
Hydro-Brakes.
The total storage volume created by the project is 6,912 cubic feet,
with a cost per cubic foot of storage space created equaling $7.60.
The total drainage area effected by the project is 16.1 acres. The
cost per acre effected was $3,621. No funds were expended for the
purchase of Hydro-Brakes concerning this project.
5. Retention Catch Basin Demonstration Project
Phase I-A
This project is a continuation of the Storm Water Quality Control
Program which was implemented by the City of Cleveland under the
authority of this grant.
This project included the installation of 12 Hydro-Brakes in existing
Catch Basins just north of the area affected by the evaluated grant
project. These Hydro-Brakes were installed within catch basins located
along Milburn Avenue, West 168th Street, West 171st Street, West 173rd
Street and West 176th Street. The purpose of these installations was
to allow the excess storm runoff to bypass the uphill catch basins so
that the runoff is collected at the street's low point. Eventually,
this flow will be directly discharged into the new storm sewer refer-
enced within the following paragraph.
The project also included the installation of a new storm sewer in Mil-
burn Avenue and West 168th Street. This new sewer was connected into an
existing 78 inch sewer, thus eliminating the need for constructing
underground retention facilities along either street. A total of 12
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catch basins were rerouted from the combined system into the newly
constructed storm sewer, thus providing relief to the existing-combined
sewer system and reducing the number of incidents of sewer surcharg-
ing in the area. The construction cost of the entire project was
$100,508, and the drainage area serviced by the project is 12.8 acres.
As stated previously, a total of 12 Hydro-Brakes were installed with-
in existing catch basins in order to utilize the roadway surfaces
for storm water ponding, thus reducing combined sewer surchagring.
The expenses incurred by the City within the applicable construction
contract for the purchase and installation of these Hydro-Brakes
were as follows:
Description Quantity Price Extension
4" Standard Hydro-Brake 2 $600 $1,200
2" Standard Hydro-Brake 10 290 2.900
Total $4,100
Thus, a total of $4,100 was expended by the City for the purchase
and installation of Hydro-Brakes concerning this project. Because
of the additional improvements above and beyond the installation of
the referenced Hydro-Brakes, the quoting of costs based upon per acre
of area serviced or cubic foot of storage created concerning this
project is irrelevant.
Summary of Projects 1 through 5
The sewage flow from all five project areas is eventually discharged into
the 8 foot combined sewer which services West 130th Street and which flows in a
northerly direction. This sewer terminates at Brook!awn Avenue where the excess
flow from the combined sewer is allowed to overflow into a dual 12 foot by 8 foot
storm sewer. This occurs during periods when the 8 foot combined sewer is sur-
charged. During dry weather, when no excess flow exists, the flow from the 8
foot combined sewer flows directly into a No. 5C sanitary line. (Please see
Table C)
The Southwest Sewer Projects - Phases I through IV, are geographically
located near the Brooklawn Avenue Combined Sewer Overflow. This means that these
four projects, some of which include the storage of storm water and thus reduce
the level of flow within the West 130th Street sewer, should have had a positive
impact upon the quality of water which is routed into the streams and rivers within
the area. It is believed that these projects have reduced the number of overflow
occurrences, as well as reducing the volume of combined sewage which overflows at
this location. Although the City assumes this to be the situation, because it
is the most logical result of the implementation of these projects, it has not
been verified, as neither formal monitoring of the overflow nor a post construc-
tion evaluation study have been undertaken concerning these projects. The City
does not presently plan to undertake a post construction evaluation of Projects
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1 through 5 as funds are rather limited and are not currently available for these
purposes.
The sewage flow effected by the Retention Catch Basin Demonstration Project
Phase 1-A is also eventually routed into the West 130th Street sewer. However,
because the location of this project is somewhat removed from the overflow in
question, its impact upon that overflow is not quite as profound or measurable as
the impact of the Southwest Sewer Projects, Phases I through IV. Nevertheless,
the effect of this project on water quality within the area should not be
underestimated as the project directly effects tlie combined sewer overflow which
is located near the intersection of Puritas Avenue and Interstate 71 (M-15), as
well as indirectly effecting the performance of the Brook!awn Overflow.
It does appear that the basement flooding within these areas has been
drastically reduced by the construction of these projects. While the City used
to receive many complaints from the residents of these areas, the present rate
of complaints from these areas regarding basement flooding has been reduced
to a minimal level. It also does not appear that street flooding has become a
problem in the areas where Hydro-Brakes were installed within the existing catch
basins in order to utilize surface storage technology. Overall, the projects
seem to have had a positive impact upon the areas which they service and
the City is quite pleased with the results which have been generated by the projects,
6. Hamlet Avenue Sewer Project - Phase II
The City of Cleveland constructed one retention tank in the sidewalk
area of Hamlet Avenue within the scope of this project. The tank
which was constructed is 467 feet in length, 48 inches in diameter,
and contains a volume of 5,868 cubic feet of storage space for
purposes for storing storm water runoff. The tank discharges through
an outlet pipe which is 6-inches in diamter and into an existing
No. 3 brick sewer. (Please see Table C) The tank is constructed of
corrugated steel pipe and a total of five catch basins presently have
their flow routed into the referenced tank.
The project services a drainage area which encompasses two acres.
The project's construction cost was $46,509, while the project
cost $7.93 for every cubic foot of storage space created. The project
can also be considered to cost $23,255 per acre of area serviced.
No funds were expended for the purchase of Hydro-Brakes concerning
the project, as none were installed at this location.
7. Adolpha Avenue Retention Facility
Approximately one year after the completion of the Hamlet Avenue Sewer
Project - Phase II, it became apparent to the City that the completion
of the referenced project had not solved all of the basement and street
flooding problems which were present within the area. At that time,
the City's Department of Public Utilities began to research different
alternatives which would lead to the elimination of all of the prob-
119
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lems present within the area. It was at this time that the City de-
veloped and decided to construct a project which is now known as the
Adolpha Avenue Retention Facility.
The Adolpha Avenue Retention Facility is an underground storm water
retention tank which was constructed in two sections. The first
section is 280 feet in length, 48 inches in diameter, and has a
storage volume of 3,518 cubic feet. The second section is 232 feet
in length, 60 inches in diameter, and has a storage volume of 4,555
cubic feet. Total storage volume of the entire tank is 8,073 cubic
feet and the entire tank is constructed of Corrugated Steel Pipe.
The tank discharges its flow through a 12-inch outlet which is equipped
with a 4-inch Standard Hydro-Brake. This flow regulator has a dis-
charge rating of .25 CFS @ 3 feet a head. The total amount expended
by the City within the construction contract for the purchase of this
Hydro-Brake was $300, including installation. The tank discharges its
flow into an existing No. 5 brick sewer. (Please see Table C)
A total of seven catch basins, five of which were existing and two of
which were recently constructed, have their flow routed into the re-
ferenced retention tank. The total drainage area which is tributary
to the retention facility is 2.9 acres. The project's construction
cost was $58,260. Thus, to express expenses in comparative terms,
the project cost $20,090 per acre of area affected or $7.22 per
cubic foot of storage space created.
Summary of Projects 6 and 7
The retention tanks constructed in Hamlet and Adolpha Avenues discharge
their flows into the existing Hamlet - Adolpha Sewer. This sewer then carries
the flow into the No. 12 sewer running along East 65th Street. (See Table C)
The East 65th Street Sewer is the main interceptor sewer for the area and
it flows in a northerly direction.
There is a combined sewer overflow located .7 of a mile north of the point
where the Hamlet - Adolpha Sewer introduces its flow into the East 65th Street
Sewer. This overflow is located at the intersection of East 65th Street and Selma
Avenue. However, because of the large capacity available within the East 65th
Street Sewer, and because of the large number of small sewers which are tributary
to the East 65th Street Sewer, it is nearly impossible to measure the positive
effects which these two projects have had upon the overflow under consideration,
and formal attempts to do so have not been undertaken.
It does appear that the basement and street flooding problems which were
prevelant within the area have been reduced by the construction of these two
projects, as complaints to the City of this nature have been reduced to minimal
levels within the past year. Prior to this, complaints of this nature were quite
common as levels of street and basement flooding sometimes reached 18 inches.
Thus, the City is quite pleased with the results of the two projects, as a severe
problem has been eliminated with minimal capital expense to the City.
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8. East 99th Street and Carr Avenue Area Retention
Facilities
This project is also quite similar in nature to the evaluated grant
project. The project included the construction of three storm water
retention tanks at low points within a 12.3 acre drainage area. Two
tanks were constructed along Carr Avenue, while one tank was construc-
ted along East 99th Street. All three tanks were constructed of
corrugated steel pipe and the totak.storage volume created by the
construction of these tanks is 8,467/cubic feet.
The two tanks constructed along Carr Avenue both discharge their flow
into a common manhole with a 12-inch outlet pipe which is equipped
with a 7-inch Standard Hydro-Brake. This Hydro-Brake has a discharge
rating of .9 CFS @ 5 feet of head and the City expended $1,220 for
the purchase of the subject Hydro-Brake, including installation,
within the project's construction contract.
The larger of the two tanks constructed along Carr Avenue is 230 feet
in length, 48 inches in diameter, and has a volume of 2,880 cubic feet.
The smaller of the two tanks is 100 feet long, 48 inches in diameter
and has a storage volume of 1,257 cubic feet. The total storage volume
which discharges through a 12-inch outlet pipe, and which is regulated
by a 7-inch Standard Hydro-Brake, is 4,147 cubic feet. A total of six
(6) catch basins now have their flow routed into the two retention tanks
which are under consideration. The tanks in question discharge their
storm flow into an existing No. 6 brick sewer. (Please see Table C)
The tank which was constructed along East 99th Street is 220 feet in
length, 60 inches in diameter, and has a storage volume of 4,320 cubic
feet. A total of three (3) catch basins located along East 99th Street
now have their storm flow diverted away from the combined sewer system
and into the referenced retention facility. The tank dishcarges its
flow through a 12-inch outlet pipe which is equipped with 5-inch
Standard Hydro-Brake. This Hydro-Brake has a discharge rating of
.5 CFS @ 5 feet of head and cost the City $950 to install, including
installation. The flow from the referenced facility is discharged
into an existing No. 3 brick sewer. (Please see Table C)
The total cost incurred by the City for construction of this project
was $83,202. A total of 12.3 acres of drainage area was effected by
the construction of the project. This project cost the City $6,474
per acre of drainage area effected. The project also cost the City
$9.83 per cubic foot of storage space created.
A post-construction evaluation of the referenced project has not been
undertaken. However, preliminary indications are that the project
has had a positive effect upon the combined sewer system within the
area and that basement flooding has been drastically reduced.
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9. Parkridge Avenue Retention Facility
Within this small project, the City of Cleveland constructed one (1)
underground storm water retention tank along Parkridge Avenue. The
tank which was constructed is 300 feet in length, 48 inches in diameter,
has a storage volume of 3,770 cubic feet, and is constructed of Corru-
gated Steel Pipe. The flow from two catch basins within the area has
been routed away from the combined sewer system and into the referenced
retention tank.
The tank discharges its flow through an outlet pipe which is 6-inches
in diameter and into an existing 15-inch combined sewer. The tank's
outlet is not equipped with a Hydro-Brake.
The project cost $29,018 to construct while the total drainage area
which is tributary to the referenced tank is 4 acres. Thus, the pro-
ject cost $7.70 per cubic foot of storage space created and $7,254
per acre of drainage area effected. The City has received many posi-
tive responses from the area's residents concerning this project.
10. Lakeview Road Area Retention Facilities
The last of the projects which will be analyzed within this appendix
is the Lakeview Road Area Retention Facilities. Once again, this pro-
ject is very similar to the evaluated grant project. The project in-
cluded the construction of three underground storm water retention
tanks along cross streets which intersect Lakeview Road. The project
also included the strategic placement of Hydro-Brakes within exsiting
catch basins in order to take advantage of the roadway surface storage
capacity which is available within the project area.
The first of these tanks, which was constructed along Ohlman Avenue, is
384 feet in length, 48 inches in diameter, has a storage capacity of
4,826 cubic feet, and is constructed of Reinforced Concrete Pipe.
The flow from six (6) catch basins has been diverted into this tank.
The tank discharges its flow through a 12-inch outlet pipe which is
equipped with a 5-inch Standard Hydro-Brake and into a 15-inch com-
bined sewer. The tank's Hydro-Brake has a discharge rated at .5 CFS
@ 5 feet of head and cost $1.075, including installation.
Two catch basins located along Ohlman Avenue which are uphill from
the retention tank have been equipped with Standard 2-inch Hydro-Brakes
in order to allow additional storm water runoff to be captured by the
catch basins located within the low points of Ohlman Avenue. The dis-
charge of these Hydro-Brakes is rated at .06 CFS @ 3 feet of head and
the subject Hydro-Brakes cost $500 each, including installation.
The second tank, which was constructed along Saywell Avenue, is 428
feet in length, 48 inches in diameter, has a storage capacity of
5,378 cubic feet and is constructed of Corrugated Steel Pipe. The
flow from six (6) catch basins within the area is discharged into
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the referenced tank instead of entering the combined sewer system.
The tank discharges its flow through a 12-inch outlet pipe which has
been equipped with a 5-inch Standard Hydro-Brake and into an existing
18-inch combined sewer. The tank's Hydro-Brake has a discharge rated
at .5 CFS @5 feet of head by the manufacturer and cost $1,075', in-
cluding installation.
In addition, two catch basins located along Saywell Avenue have also
been equipped with Standard 2-inch^Hydro-Brakes in order to allow
additional storm water runoff to be captured at the catch basins
located within the low point of Saywell Avenue. These Hyrdo-Brakes
have a discharge rated at .06 CFS @ 3 feet of head and cost $500 each
including installation.
The third tank was constructed along Fairport Avenue. This tank is 325
feet in length, 48 inches in diameter, has a storage capacity of 4,084
cubic feet, and is constructed of Reinforced Concrete Pipe, A total
of 6 catch basins now have their flow diverted into the retention tank.
The flow from the retention tanks is then discharged through a 12-inch
outlet which is equipped within a 5-inch Standard Hydro-Brake and
into an existing 15 inch combined sewer. The Hydro-Brake which has
been utilized has a discharge rated at .5 CFS @ 5 feet of head and
cost $1,075 including installation.
As with the other two streets, two catch basins along Fairport Avenue
were equipped with 2-inch Standard Hydro-Brakes in order to aid in
the capturing of additional surface runoff in the low point area of
Fairport Avenue. The Hydro-Brakes which were installed have a dis-
charge rating of .06 CFS @ 3 feet of head and cost $500 each includ-
ing installation.
The construction cost of this project was $177,143. A total of 19.3
acres of drainage area are effected by the project. The total volume
of storage space now available because of the construction of the
three retention tanks is 14,288 cubic feet. Thus, the project cost
$12.40 for every cubic foot of storage space created, and $9,178 per
acre of drainage area effected.
Summary of Projects 8 through 10
These three projects are somewhat different than the previously considered
projects in that the effect which these projects have upon Combined Sewer Overflows
is minimal. The construction of the East 99th Street and Carr Avenue Retention
Facilities did not effect the level of combined sewage flowing into Lake Erie
in any manner, as the storage capacity which was created by the project is not
sufficient to have any effect upon the nearest Combined Sewer Overflow, which
is located 1,050 feet to the west along East 88th Street. The project was under-
taken with the intention of reducing basement flooding in an area where this
problem was being experienced on a wide spread scale. With thevconstruction of
the project, this problem has been almost completely eliminated, as virtually no
complaints are being received from this area concerning this problem which has
plagued this area in the recent past.
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The construction of the Parkridge Avenue Retention Facility also has a
minimal effect upon the level of combined sewage overflowing into Lake Erie. The
nearest Combined Sewer Overflow is located 1,300 feet south of the project, where
a 48 inch combined sewer intersects with the six (6) foot Big Creek Interceptor.
The retention capacity created by the construction of a single retention tank on
Parkridge Avenue does not create enough storage volume to have a significant impact
upon the referenced overflow. Once again, the intention of the City in construct-
ing this project was to eliminate basement flooding in an area which was badly
affected by this problem, and the elimination or reduction of combined sewer over-
flows was only a secondary consideration.
The construction of the last project to be considered, the Lakeview Road
Retention Facilities, most probably had a profound effect upon the nearest Combined
Sewer Overflow, which is located at the intersection of Lakeview Road and Hopkins
Avenue, just three blocks north of the project area. Because of the large volume
of storage capacity created by the project, it is anticipated that the level of
and the number of occurances of combined sewer overflows at this location has been
drastically reduced. However, without the benefit of a post - construction eval-
uation concerning the referenced project, it is impossible to quantify and verify
that a reduction in the level and the number of overflows occuring at this location
has taken place.
As with the other two projects, the construction of the Lakeview Road Area
Retention Facilities has virtually eliminated the basement flooding problem which
was prevelant within the project area prior to construction. Due to lack of funds,
an evaluation of the effect which this project has had upon the nearest Combined
Sewer Overflow can not be undertaken at this point in time.
General Comments
It may appear from the information given within the preceeding text, as
well as from the information given within Table A and Table B, which immediately
follows these comments, that the installation of Hydro-Brakes significantly in-
creases the cost of a project as far as the acreage of drainage area effected, as
well as the cost per cubic foot of storage space created. For example, from the
projects which are cited, those projects which do not utilize Hydro-Brakes cost
approximately $7.50 per cubic foot of storage space created, while the cost per
cubic foot of storage space created for those projects which do utilize Hydro-
Brakes ranges from $9 to $12. In addition, for those projects cited, the cost
per acre of drainage area effected for projects which utilize Hydro-Brakes is
generally higher than the cost per acre of drainage area effected for projects
which do not utilize Hydro-Brakes.
This may lead the reader to believe that the utilization of Hydro-Brakes
within a project significantly increases the cost of that project. In fact,
this is not the case. The reader should notice from the text of the appendix,
as well as from the information contained within Table A, that the actual cost of
Hydro-Brake regulators on a per unit basis is rather insignificant. It should
also be noted that concerning those projects in which multiple Hydro-Brakes have
been utilized, the cost of these units is rather insignificant when compared to
the total construction cost of the project. Therefore, it is purely coincidental
that the cost per acre of drainage area effected, as well as the cost per cubic
124
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foot of storage space created, appears to be significantly higher for those pro-
jects which utilize Hydro-Brakes than for those projects which do not.
The reader may have also noted from the text of this appendix, as well as
from the information given within Table A, that it appears that from project to
project, the price of Hydro-Brakes flucuates widely even though the sizes of
Hydro-Brakes used within the projects may be equivalent. The reason for this
phenomenon is the fact that the prices quoted for Hydro-Brakes within this report
are the prices which were bid by the various contractors who constructed the
projects. The prices for these units within eSch of the applicable construction
contracts contain may different elements such as the actual cost of the device,
overhead, profit, etc. The inclusion of these considerations within the prices
quoted by the various contractors for the purchase and installation of these
control devices makes it impossible to quote the actual price which was paid for
the purchase and installation of Hydro-Brakes within each of these projects.
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TABU_A
COMPARATIVE SUMMARY
W"
EVALUATED PROJECTS
ro
PROJECT TITLE
1. Southwest Sewer Project
Phase I
Z. Southwest Sewer Project
Phase II
3. Southwest Sewer Project
Phase III
4. Southwest Sewer Project
Phase IV
5. Retention Catch Basin
Demonstration Project
Phase IA
6. Hamlet Avenue Sewer Project
Phase II
7, Adolpha Avenue Retention
Facilities
4
1
2
1
1
METHOD
OF
STORAGE
Surface
Ponding
Retention Tanks
Plus
Surface Ponding
Retention Tank
Plus
Surface Ponding
Retention Tanks
Plus
Surface Ponding
Surface Ponding
Retention Tank
Retention Tank
VOLUME
OF
STORAGE
H/A
19,148
Cu. Ft.
4,965
Cu. Ft.
6,912
Cu. Ft.
N/A
5,868
CU. Ft.
8.073
Cu. Ft. .
OUTLET
REGULATOR
N/A
One 9" Standard
Hydro -Brake
and
Three 6" Standard
Hydro-Brakes
One 6" Standard
Hydro-Brake
Two 6" Orifices
N/A
One 6" Orifice
One 4" Standard
Hydro-Brake
COST
OF
REGULATOR
N/A
$ 2,300
Each
1,675
Each
$ 1,800
Each
N/A
N/A
N/A
$ 300
Each
CATCH
BASINS
REGULATED
13
5
4
0
12
0
0
CATCH
BASIN
REGULATOR
4" Standard
Hydro-Brakes
4" Standard
Hydro-Brakes
4" Standard
Hydro-Brake
N/A
Two 4" Standard
Hydro-Brakes
and
Ten 2" Standard
Hydro-Brakes
N/A
N/A
/
COST
OF
REGULATOR
$ 650 Each
$ 915 Each
$ 1,050 Each
N/A
$ 600 Each
$ 290 Each
N/A
N/A
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TABLE A
PROJECT TITLE
8. East 99th Street & Carr Ave.
Retention Facilities
9. Parkrldge Avenue
Retention Facilities
10.
Lake view Road Area
Retention Facilities
COMPARATIVE SUMMARY
EVALUATECTPROJECTS
(Continued)
METHOD
OF
STORAGE
3 Retention Tanks
1 Retention Tank
3 Retention Tanks
Plus
Surface Ponding
VOLUME
OF
STORAGE
8,467
Cu. Ft.
3,770
Cu. Ft.
14,288
Cu. Ft.
OUTLET
REGULATOR
One 7" Standard
Hydro-Brake
and
One 5" Standard
Hydro-Brake
One 6" Orifice
Three 5" Standard
Hydro-Brakes
COST CATCH CATCH COST
OF BASINS BASIN OF
REGULATOR REGULATED REGULATOR REGULATOR
$ 1,220 0 N/A $ N/A
Each
$ 950
Each
N/A 0 N/A N/A
$ 1,075 6 2" Standard $ 500 Each
Each Hydro-Brake
f\>
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TABLE B
PROJECT TITLE
1. Southwest Sewer Prolect
Phase I
2. Southwest Sewer Project
Phase II
3. Southwest Sewer Project
Phase III
4. Southwest Sewer Project
Phase IV
5. Retention Catch Basin
Demonstration Project
Phase IA
6. Hamlet Avenue Sewer Project
Phase II
7. Adolpha Avenue Retention
-> Facilities "
tvi
00 8. East 99th Street & Carr Ave.
Retention Facilities
9. Parkridge Avenue Retention
Facilities
10, Lakevlew Road Area Retention
Facilities
COST SUMMARY
EVALUATED~PROJECTS
PROJECT
COST
$ 83,487
$ 175,860
$ 83,267
$ 53,503
$ 100,508
$ 46,509
$ 58,260
$ 83,202
$ 29,018
$ 177,143
DRAINAGE AREA
EFFECTED
4.0 Acres
38.6 Acres
8.5 Acres
16.1 Acres
12.8 Acres
2.0 Acres
2.9 Acres
12.3 Acres
4.0 Acres
19.3 Acres
PROJECT COST STORAGE SPACE
PER ACRE CREATED
N/A N/A
$ 4,556 19,148 Cu. Ft.
N/A 4,965 Cu. Ft.
$ 3,621 6,912 Cu. Ft.
N/A N/A
$ 23,255 5,868 Cu. Ft.
$ 20,090 8,073 Cu. Ft.
$ 6,474 8,457 Cu. Ft.
$ 7,254 3,770 Cu. Ft.
$ 9,178 14,288 Cu. Ft.
COST PER CUBIC FOOT OF
STORAGE SPACE CREATED
N/A
$ 9.18
N/A
$ 7.60
N/A
$ 7.93
J 7.22
$ 9.84
$ 7.70
.' $ , 12.40
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TABLE C
COMPARISON BETWEEN CITY OF CLEVELAND EGG SHAPED BRICK SEWER SIZES
AND
PRESENT DAY SEWERS WHICH ARE CIRCULAR IN DIAMETER
WATER WAY AREA
EGG SHAPED SEWER IN ... EQUIVALENT CIRCULAR
REFERENCE NUMBER SQUARE FEET .. ^ SIZE IN INCHES
1 1.00 ' 15
2 2.52 21
3 4.33 27
4 6.35 33
5 8.55 36
6 10.90 42
7 13.39 48
8 16.00 54
9 18.72 60
10 21.54 N/A
11 24.46 66
12 27.47 72
13 30.57 N/A
14 33.74 78
Letter suffixes which are added to sewer reference numbers denote the
following type of construction:
A - 1 Ring of brick around
B - 1 Ring of brick around, 1 extra ring on arch
C - 2 Rings of brick around
D - 2 Rings of brick around, 1 extra ring on arch
E - 3 Rings of brick around
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HYDRO BRAKE RESIZING DECISION
As stated previously within the main body of this report, during the
course of the post-construction evaluation of the demonstration grant project,
it became evident to all concerned parties that the retention facilities which
had been constructed were not being utilized in an efficient manner. Specifi-
cally, a large percentage of the storage volume created by the construction of
the three retention tanks was never being utilized. This situation was verified
by the fact that during the course of 1980, the storm water which was captured
and stored within these retention tanks never reached a depth which exceeded a
few inches.
It was apparent to the City that one of the following three factors was
adversely effecting the performance of the referenced retention tanks:
A) The retention tanks which were constructed were too large and
were oversized.
B) The drainage areas which were tributary to each of the retention
tanks were too small to capture enough storm flow to utilize the
storage space available within these tanks.
C) The Hydro-Brakes which had been installed within each of the tanks'
outlets at the recommendation of the designer did not restrict the
discharge of the tanks sufficiently in order to take advantage of
the storage capacity which had been created.
It was fairly obvious that since the facilities had already been constructed,
Factors A and B could not be altered except at great expense to the City. For that
reason, Factors A and B were considered as given.
Because of this situation, the City decided to attempt to modify Factor C
so that the retention tanks which had been constructed would be utilized more
efficiently, thus taking advantage of the storage capacity which had been created.
In order to do this, the City decided that the Hydro-Brakes within each of the
tanks' outlets should be removed and replaced with Hydro-Brakes which were more
restrictive in terms of their discharge. This decision was made early during
1981, with the installation of the more restrictive Hydro-Brakes tentatively
scheduled for May 1, 1981.
As indicated within the main body of this report, problems were experienced
with the delivery of the new Hydro-Brakes which were selected by the City for
installation within the retention tanks. After numerous delays, these devices
were finally received and installed in mid-summer of 1981. This provided the
City and its consultant a minimal period for evaluating and monitoring the per-
formance of the referenced Hydro-Brakes. It should be pointed out, however, that
during the period of time in which the Hydro-Brakes were being evaluated, much
meaningful data was gathered. This data has subsequently been considered within
preceeding sections of this report.
130
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Prior to the City's decision to select alternative sizes of Hydro-Brakes
for installation, it was necessary for the City to make a number of assumptions
in order to be able to select those Hydro-Brakes which were of a proper size and
which possessed an appropriate discharge rating. The assumptions which were made
are as follows:
1. The areas from building set-back line to building set-back line
are tributary to the retention tanks.
2. The discharge of all Hydro-Brakes was .assumed to be relatively constant.
3. The Hydro-Brakes which were installed within the existing catch basins,
and which discharge their flow directly into the combined sewer system,
were not taken into consideration during the course of this evaluation.
The reason why these Hydro-Brakes which had been installed within the
existing catch basins were not taken into consideration is because the
level of impact which these units have upon the volume of storage space
utilized within the constucted retention tanks is minimal.
4. The volumes of the retention tanks as computed by Snell Environmental
Group were assumed to be correct.
Having made the preceeding assumptions, the City then used the following
methodology in order to arrive at its decision to request that the manufacturer
replace the originally selected Hydro-Brakes with Hydro-Brakes which were smaller,
and more restrictive, in terms of their discharge rating.
1. Areas which are tributary to each of the retention tanks were
calculated. (Table D)
2. The various drainage areas effected by the project were evaluated
for various storm frequencies of one (1) hour duration. (Table E).
Following this analysis, the drainage areas were then evaluated for
ten (10) year storms of various durations. (Table F). The one (1)
hour, ten (10) year storm produced the largest volume of storage util-
ized within the retention tanks. It was determined that using this
storm as a design criteria was far superior to using any other design
criteria which had previously been recommended.
3. Hydrographs for a ten (10) year, one (1) hour storm were then developed
for each drainage area. (Figures 1, 2, 3). A relationship between hydro-
graph volume and the rate of discharge was then developed to utilize the
existing storage volume of the retention tanks located within the drainage
areas.
4. Hydrographs for a five (5) year, one (1) hour storm duration were then
developed for comparative purposes. (Figures 4, 5, and 6).
-------
From the various hydrographs which were developed, the City was able to de-
termine which Hydro-Brake discharge rates would provide maximum utilization of
the storage space which is available in the constructed retention tanks. In order
to make this determination, a 10 year storm of one hour duration was selected as a
design criteria for the previously mentioned reasons.
Having selected the design criteria, the Engineering Section of the City's
Division of Water Pollution Control moved forward with its attempt to determine
the sizes and discharge rates of Hydro-Brakes inhich would utilize the storage
space which had been created in an efficient manner. A trial and error methodo-
logy was used in that calculations of the volumes of storage space utilized for
each retention tank were computed under Hydro-Brakes of various sizes and possess-
ing various discharge ratings. Results were compared, and those Hydro-Brakes
which provided the largest volume of storage space utilization, that is, those
Hydro-Brakes which stored the greatest volume of storm water runoff without creat-
ing a maintenance problem, were chosen for installation.
The characteristics and capacities of each retention tank were considered
independently during the course of the analysis. The Engineering Section of the
Division of Water Pollution Control arbitrarily determined that any Hydro-Brake
which possessed a discharge rating of less than .25 CFS would be a maintenance
problem because of clogging and possible blockage. Taking these factors into
consideration, the existing retention tanks were modified by the installation
of new Hydro-Brakes. The following is a summary of the characteristics of these
retention tanks after the new Hydro-Brakes had been installed, including a summary
of the tank's expected level of performance during a ten year storm of one hour
duration.
1. West 177th Street Tank
Regulator: 3" Hydro-Brake
Discharge rating: .25 CFS
Capacity of Retention Tank:
Volume of water stored:
Excess capacity:
Puritas Avenue Tank
Regulator: 5.5" Hydro-Brake
Discharge rating: 1.0 CFS
Capacity of Retention Tank:
Volume of water stored:
Excess capacity:
West 170th Street Tank
Regulator: 6" Hydro-Brake
Discharge rating: 1.25 CFS
Capacity of Retention Tank:
Volume of water stored:
Excess capacity:
8,984 cubic feet
7,900 cubic feet
1,084 cubic feet
6,024 cubic feet
5,000 cubic feet
1,024 cubic feet
2,074 cubic feet
1,900 cubic feet
174 cubic feet
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This completes the analysis of the methodology used by the City of Cleveland
in computing the sizes and discharge ratings of the Hydro-Brakes which are currently
in place within the referenced retention tanks. The figures and tables which
are referenced in this section will now be presented.
TABLE D
Calculation of Drainage Areas
West 177th Street Tank
(Right-of-way set backs) + (Right-of-way) = Drainage Area
(50'+30'+30')1135' + (40'x290') = 136,450 Ft.2
Drainage area =3.1 Acres
Total area involved is 7.5 acres.
Puritas Avenue Tank
(Right-of-way set backs - W. 172) + (Right-of-way set backs - W. 170) +
(Right-of-way set backs - Puritas) + (Right-of-way - W. 172 & W. 170)
(40'+30'+30')518' + (40'+30'+30')222' + (80'+30'+30')504' + 40'(78'+78')
51,800 Ft.2 + 22,200 Ft.2 + 70,560 Ft.2 + 6,240 Ft.2
Drainage area = 150,800 Ft.
Drainage area =3.5 acres
Total area involved is 7.9 acres.
West 170th Street Tank
(Right-of-way set backs - Martha Rd.) + (Right of way - W. 170)
(401 + 30')504' + (40' + 30' + 30')679'
35,280 Ft.2 + 67,900 Ft.2 = 103,180 Ft.2
. Drainage area =2.4 acres
Total area involved is 5.7 acres.
133
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TABLE E
Effect
West 177th Street Tank
Frequency
Depth
Total Volume
Run-off Volume
Puritas Avenue Tank
Frequency
Depth
Total Volume
Run-off Volume
West 170th Street Tank
Frequency
Depth
Total Volume
Run-off Volume
of Project on Storms of One
6 Mo.
.66"
7,500
3,750
6 Mo.
.66"
8,300
4,150
6 Mo.
.66"
5,600
2,800
1 Yr.
.90"
10,200
5.100
1 Yr.
.90"
11,300
5,650
1 Yr.
.90"
7,700
3,850
3 Yr.
1.30"
14,800
7,400
3 Yr.
1.30"
16,300
8,150
3 Yr.
1.30"
11,100
5,500
Hour Duration
5 Yr.
1.50"
17,000
8,500
5 Yr.
1.50"
18,800
9,400
5 Yr.
1.50"
12,900
6,450
10 Yr.
1.80"
20,400
10,000
10 Yr.
1.80"
22,600
11,300
10 Yr.
1.80"
15,500
7,750
Volumes are stated in cubic feet.
134
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TABLE F
Effect of Project on 10 Year Storms of Various Durations
West 177th Street Tank
Duration 15 min. 30 min. 1 Hr; 2 Hr. 4 Hr. 6 Hr.
Depth 1.13" 1.55" 1.80" 2.10" 2.20" 2.30"
Total Volume 12,850 17,600 20,400 23,800 25,000 26,000
Run-off Volume 6,425 8,800 10,200 11,900 12,500 13,000
Puritas Avenue Tank
Duration
Depth
Total Volume
Run-off Volume
West 170th Street Tank
Duration
Depth
Total Vol ume
Run-off Volume
15 min.
1.13"
14,200
7,100
15 min.
1.13"
9,700
4,850
30 min.
1.55"
19,500
9,750
30 min.
1.55"
13,300
6,650
1 Hr.
1.80"
22,600
11,300
1 Hr.
1.80"
15,500
7,750
2 Hr.
2.10"
26,400
13,200
2 Hr.
2.10"
18,000
9,000
4 Hr.
2.20"
27,600
13,800
4 Hr.
2.20"
18,900
9,450
6 Hr.
2.30"
28,900
14,450
6 Hr.
2.30"
19,800
9,900
Volumes are stated in cubic feet.
135
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TIME - MINUTES
A « 3.1 Ac.
C « 0.5
T.C. « 25 MIN.
INFLOW
OUTFLOW 3" HYDROBRAKE
TANK CAPACITY 8984 C.F.
120
640
FIGURE 1 WEST 177 STREET TANK
HYDROGRAPH 10 YEAR STOKM, 1 HR. DURATION
136
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6.13
6_
A « 3.5 Ac.
C - 0.5
T.C. « 25 MIN.
INFLOW
OUTFLOW 5.5" HYDROBRAKE
TANK CAPACITY 6024 C.F.
I
20
r
40 60
TIME - MINUTES
80
100
120
FIGURE 2 PURITAS AVENUE TANK
HYDROGRAPH 10 YEAR STORM, 1 HR. DURATION
137
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5 -
A
C
T.C.
2.4 Ac.
0.5
25 MIN.
4.19
4 -
INFLOW
— OUTFLOW 6" HYDROBRAKE
TANK CAPACITY 2074 C.F,
2-
1 -
i
20
) 60
TIME - MINUTES
80
100
120
FIGURE 3 WEST 170 STREET TANK
HYDROGRAPH 10 YEAR STORM, 1 HR. DURATION
138
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5-
4.64
to
u
2 .
1 -
A • 31. Ac.
C - 0.5
T.C. « 25 MIN.
INFLOW
OUTFLOW 3" HYDROBRAKE
TANK CAPACITY 8984 C.F.
40
60
TIME - MINUTES
80
100
120
580
FIGURE 4 WEST 177 STREET TANK
HYDROGRAPH 5 YEAR STORM, 1 HR. DURATION
139
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1 -
A - 3.5 Ac.
C " 0.5
T.C. - 25 MIN.
INFLOW
_ OUTFLOW
TANK CAPACITY 6024 C.F.
20
40 60 80
TIME - MINUTES
FIGURE 5 PURITAS AVENUE TANK
HYDROGRAPH 5 YEAR STOBM, 1 HR. DURATION
140
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5.
3.51
A - 2.4 Ac.
C » 0.5
T.C. - 25 HIM.
INFLOW
OUTFLOW 6" HYDROBRAKE
TANK CAPACITY 2074 C.F.
2-
1-
i
20
40 60
TIME - MINUTES
100
120
140
FIGURE 6 WEST 170 STREET TANK
HYDROGRAPH 5 YEAR STORM, 1 HR. DURATION
141
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Guidelines For Design of Storm Water Retention Facilities
The third and final section of this appendix demonstrates the manner in
which an interested party should proceed when designing Storm Water Retention
Facilities which are similar in nature to those constructed under the auspices
of the evaluated grant project. Our analysis will proceed by using one of
the comparable projects which has previously been described within this
appendix as an example. The manner in which thjs project, known as the
Southwest Sewer Project - Phase II, was designedly the City of Cleveland
will be considered in detail. It is hoped that from this description, other
agencies which desire to implement this type of storm water control technology
will be able to proceed with construction of their own facilities. It should be
noted thaj: additional, more detailed information concerning the design of these
types of storm water retention facilities is available directly from the City of
Cleveland's Department of Public Utilities, Division of Water Pollution Control.
The projects which were described within the preceding sections of this appendix
were designed by the City of Cleveland for construction in areas of the City
where both combined sewers are located and basement flooding problems are prevelant.
The purpose of these projects was to provide the residences within the respective
project areas protection from basement flooding up to the level of a five year
storm of one hour duration.
Utilizing this design criteria, the following methodology was used by the
City of Cleveland in designing the Southwest Sewer Project - Phase II.
1. The volume of storm flow which discharges directly into the existing
combined sewer system from the house connections located within the
project area was calculated using the Rational Method. The following
methodology was used to make this calculation.
a. The roof areas, and those yard areas (A) which drain into the house
connections which are located within the project area, were estimated.
b. Run-off Coefficients (C) for both the roof and yard areas within
the project area were estimated.
c. The time of concentration at the proposed discharge point, in this
case a manhole, where the volume of flow can be checked for retention
purposes, was estimated.
d. Intensities (i) were obtained from rainfall intensity curves.
e. The peak rate of flow was calculated using the Rational Method
Equation. (Q=CiA)
2. The capacity of the existing sewer was calculated using Manning's
Equation for calculating velocity of flow.
(R2/3 S1/2)
Q (capacity) = velocity x cross-sectional area of pipe = vA
142
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3. A hydrograph at the subject manhole was constructed. The volume of flow
which was used in constructing the referenced hydrograph included all
storm run-off tributary to the referenced manhole.
4. The capacity of the existing sewer was compared with the peak flow
of the house connections as calculated in step number one. Because the
capacity of the existing sewer was greater than the peak flow, the peak
flow was subtracted from the referenced capacity. The difference be-
tween these two figures was utilized /for Hydro-Brake design.
The Construction of the Southwest Sewer Project - Phase II enabled the City
of Cleveland to utilize Hydro-Brake Control Technology for two purposes.
A. To control the flow from the constructed retention tanks into the
existing combined sewer system.
B. To control the flow from regulated catch basins into the existing
combined sewer system. This was accomplished by the installation of small
Hydro-Brakes in existing catch basins within the project area. These
installations forced portions of the storm run-off within the area
to bypass the regulated catch basins, which are connected to the existing
combined sewer, and to flow directly into the catch basins which are
.onnected to the constructed retention tank. The implementation of this
technology also provided for additional storage of storm water run-off,
as run-off is stored on the surface of the street, as well as within the
constructed retention tanks.
In order to complete the storage tank design, a new hydrograph was constructed
based upon existing hydrographs. This new hydrograph took into account the flow
calculation computed in accordance with Step No. 1. The revised hydrograph also
considered the amount of run-off which was to be routed into the proposed retention
tanks and discharged through the Hydro-Brakes. It was determined that all volume
not accounted for would be stored on the surface of the pavement.
Accordingly, the available surface storage areas were surveyed and the volume
of storm water run-off which could be stored on the surface without causing serious
street flooding problems was calculated. After this calculation had been made, the
volume of required storage, as determined by the revised hydrograph, was computed.
The volume of water to be stored on the surface was subtracted from the total
storage required, thus yielding the volume of storm water to be stored within the
retention tanks. These retention tanks are usually constructed and installed within
a sidewalk or treelawn area.
143
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As stated previously the Southwest Sewer Project - Phase II is to be utilized
as example of the demonstrated storm water control technology. Accordingly the
reader's attention is drawn to the following calculations which were generated
using the data available concerning the Bennington Avenue Area, a sub-section of
what is now known as the Southwest Sewer Project - Phase II.
1. Calculation of storm flow which discharges directly into the Combined
Sewer System.
Description
68 Homes
34 Garages
34 Yards
Area x Run-off .Coefficient
[68(25'x30')]x0.9
[34(20'xlO')]x0.9
[34(20'x25')]x0.5
Total (CA)
45,900 Sq. Ft.
6,120 Sq. Ft.
8,500 Sq. Ft.
60,520 Sq. Ft.
Time of concentration
Intensity (5 yr. frequency)
t= 15 minutes
i=3.4 inches per hour
Q=CiA=60,520 x 3.4
Q=CiA=205,768
Conversion to CFS
_ 205,768 =
' 43,560
2. Calculation of the capacity of the existing combined sewer system.
Size of pipe = 18" Vitrified Clay Pipe
Grade = .5 %
Roughness Coefficient, N = 0.015
Hydraulic Radius
R =
Area
Permitneter
K *~ w~™ - ~ U • o / D
144
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Velocity v = ( -^i )(R 2/3 S 1/2)
v=(^f5)(-3752/3X.0051/2)
v = 3.65 FPS
Capacity vA = '(3.65) (1.77)
vA = 6.5 CFS
3. The total volume of flow as determined by the revised hydrograph is
22,350 cubic feet.
Utilizing this information, it was determined that the retention tank
to be constructed would be controlled with a 6 inch Hydro-Brake which possessed a
discharge rating of 0.6 CFS. The determination was also made to regulate four
additional catch basins which are located upstream away from the referenced
retention tanks. Three regulated catch basins were modified by installing 4"
Hydro-Brakes, with discharge ratings of .25 CFS.
With these modifications, the total discharge into the existing combined
sewer system within the area was calculated as follows:
4.7 CFS + 0.6 CFS + (4 x .25)CFS = 6.3 CFS
This level of discharge is less than the maximum discharge rate of the system
.which was calculated previously. Thus, the design of the referenced retention
tank was continued with the following calculations being generated.
1. Volume discharged into the system through the Hydro-Brakes.
V = 1.5 x 70 x 60 = 6,300 Cubic Feet.
2. Volume discharged into the system through house connections.
V = ( 4'7xfx6° ) = 7,755 Cu. Ft.
3. Total volume to be stored.
V = 22,350 - 6,300 - 7,755 = 8,295 Cubic Feet.
145
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4. Estimate of volume required to flood an area, 220' x 30', with an
average depth of 6".
V = 200' x 30' x 0.5' = 3,300 Cubic Feet.
5. Total volume to be stored in retention facility.
V = 8,295 - 3,300 = 4,995 Cubic Feet.
In order to store the volume of water required, it was decided that 400 feet
of reinforced concrete pipe, 48" in diameter, would be used. This yields the
following available capacity for storage purposes.
V = 400 Lineal Ft. x 12.56 Cubic Ft. = 5,024 Cu. Ft.
The final calculation which needed to be made was the drain down time required
to discharge the entire volume of storm flow.
Tank: 5,024 Cu. Ft. * 0.6 = 8,373 seconds = 140 minutes
Street: 3,300 Cu. Ft. * 0.6 = 5,500 seconds = 92 minutes
Total drainage time = 140 minutes + 92 minutes = 232 minutes.
This is equivalent to 3.9 hours.
CONCLUSION
This concludes Appendix F which has been authored by the City of
Cleveland for the purpose of relating the experiences which it has had concerning
the type of storm water control technology which has been evaluated during the
course of this demonstration grant project. The City welcomes constructive
comments from other interested parties who have have similar experiences related
to this type of technology. These comments should be addressed as follows:
Commissioner, Division of Water Pollution Control
City of Cleveland
1825 Lakeside Avenue
Cleveland, Ohio 44114
Attention: Engineer of Sewer Design
146
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APPENDIX 6
HYDRO BRAKE DEMONSTRATION PROJECT
SANTEE DRAINAGE AREA - ROCHESTER, NEW YORK
by
O'Brien & Gere Engineers, Inc.
Syracuse, New York 13221
February, 1982
147
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HYDRO-BRAKE DEMONSTRATION PROJECT
SANTEE DRAINAGE AREA - ROCHESTER, NEW YORK
GENERAL
The concept of inlet control to reduce downstream sewer system
surcharging and resultant CSO discharges was demonstrated in the Santee
Drainage Area in the City of Rochester, New York.
Past practices of removing stormwater runoff as quickly as possible
have resulted in moving flooding and pollution problems downstream,
potentially inducing more serious damage. By providing inlet control
such that the rate of stormwater inflow does not exceed the capacity of
the existing collection system, problems such as basement back-ups,
shock loadings to downstream treatment facilities, and CSO discharges can
be minimized or eliminated.
Inlet control practices by their nature, increase the frequency and
extent of surface flooding. Surface flooding, however, is usually limited
to short term ponding. In most instances this is preferable to the
significant damage that may result from uncontrolled stormwater inflows.
One type of inlet control method recently introduced into the United
States is a device known as the Hydro-Brake. This flow regulator was
developed in Denmark and is marketed in North America by Hydro Storm
Sewage Corporation. The Hydro-Brake is constructed of non-corrosive
stainless steel, is self-regulating, contains no moving parts, and requires
no power to operate. The movement of water through the Hydro-Brake
involves a radial motion which dissipates energy to control the rate of
discharge through an orifice. As the hydraulic head on the unit
increases, the radial motion or angular velocity increases, thereby
decreasing the coefficient of discharge through the orifice. At lower
148
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heads, the angular velocity decreases, thereby increasing the coefficient
of discharge through the orifice. In this way, discharge through the
orifice is kept relatively constant under a varying range of heads. A
schematic of a Hydro-Brake regulator is presented in Figure 1.
An advantage of the Hydro-Brake unit, one that was investigated in
this study, is that for a given sized orifice, an equally sized Hydro-Brake
(diameter of Hydro-Brake orifice outlet = diameter of orifice) will
discharge less flow at identical hydraulic heads.
PROJECT DESCRIPTION
This demonstration study consisted of two separate and independent
investigations.
1. The concept of off-line storage detention with controlled release
using a Hydro-Brake regulator. (Off-Line Storage Tank
Study)
2. The concept of utilizing increased surface/street ponding of
stormwater to reduce inflow to an existing combined sewer
system. (Catchbasin Study)
Each concept offered a viable methodology to reduce the rate of inflow
into the sewer system using flow restrictors. Such flow restrictors or
regulators could be Hydro-Brakes, or specifically sized orifices used to
throttle flow.
The demonstration study area is located on the west side of the City
of Rochester and comprises 35 acres of primarily single family residential
houses. The entire area is served by a combined sewer system which is
tributary to the West Side Trunk Sewer. There are about 250 houses and
8 commercial establishments within the drainage area, many of which have
roof leader connections to the combined sewer system. Sixty-two
catchbasins within the area are presently connected directly to the
149
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OUTLET
ORIFICE
(Typical 3.5 inch
Diameter)
DIRECTION
OF FLOW
INLET
Typical 5 inch
Figure 1. Schematic of Hydro-Brake Regulator
150
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combined sewer system. A schematic of the demonstration site is
presented in Figure 2.
A field survey was conducted in the Santee Drainage Area to acquire
necessary system information. The information obtained included sewer
sizes and slopes, manhole inverts, the number and location of
catchbasins, the number of house roof drain connections to the sewer
system, and approximate street surface grades.
The Hydro-Brake units required for this study were ordered from
Hydro Storm Sewage Corporation in December, 1980. After a series of
unmet delivery dates, the Hydro-Brake units were finally received in late
April, 1981. The Hydro-Brake designated for the off-line storage facility
was installed within a week after delivery; however, modifications to the
catchbasin Hydro-Brakes were required and installation of these units was
not completed until June, 1981. These delays prevented the evaluation of
early spring storms.
OFF-LINE STORAGE TANK STUDY
Background
The purpose of the off-line storage tank study was to evaluate the
effectiveness of off-line storage in conjunction with Hydro-Brake
regulated outflow, on the reduction of downstream sewer surcharge
potential.
Using a reference storm with a return frequency of 2 years (60
minute duration, total rain = 0.75 inches, peak intensity = 1.5 in/hr), a
plot of cumulative runoff volume vs. time was developed. This plot,
shown in Figure 3, was used to determine a proper Hydro-Brake
discharge rate and the capacity of the off-line storage tank. A Hydro-
Brake discharge rate of 0.25 cfs at 50 inches of head, and an off-line
storage tank capacity of 4700 gallons were selected. The original design of
the off-line storage tank was subsequently modified, increasing the
capacity of the tank to 5700 gallons.
151
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en
(Q
c
(D
ro
to
o
zr
(D
O)
ct-
»j.
O
O
-h
a.
o
i
en
3
o
o
ft-
3
ft-
o'
CO
n>
t
-N —
of
QC
K
! CURLEW S
i
i-
U)
z
i
&
z
•
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1
-------
1.0 T
2 YEAR FREQUENCY STORM
DURATION =60 minutes
TOTAL RAIN = 0.75 inches
PEAK INTENSITY = 1.5 in./hr.
0.8 •
X
I
o
0>
t «r
E
3
O
0.4 • •
Q2 <•
10
20
30
40
60
TIME
Figure 3. 2 Year Storm - Cumulative Runoff Volume vs. Time
153
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The off-line storage tank was constructed using sections of 54-inch
diameter reinforced concrete pipe. The pipe was laid end-to-end to
create a tank 48 feet long. A manhole was installed at each end of the
tank to provide access to facilitate maintenance and monitoring. The tank
was sloped at 0.008 to allow for drainage.
Figure 4 presents a layout of the ;off-line storage facility area
including the number and location of catchbasins tributary to the storage
tank. In addition, the piping route connecting these catchbasins to the
storage tank, and the route of the outlet pipe from the storage tank to
the combined sewer system at Villa and Santee Streets, are shown in the
figure. Discharge from the off-line storage tank is controlled by a
Hydro-Brake (Standard 5-B-7) regulator, as shown in Figure 5. The
Hydro-Brake regulator has a 3.5-inch diameter outlet orifice.
In order to restrict flow in the outlet pipe from the existing storage
tank until the Hydro-Brake regulator was installed, a 3-inch diameter
orifice, constructed from 0.75-inch plywood, was installed at the tank
outlet. Figure 6 presents an overall plan and profile of the off-line
storage facility.
Orifice Head-Discharge Tests
Prior to the installation of the Hydro-Brake, head-discharge tests
were conducted on the orifice in the off-line storage tank. These tests
led to the development of a head-discharge curve for the 3-inch orifice on
the outlet pipe from the storage tank. The tests used to develop the
head-discharge curve, are discussed below.
Variable Head Test --
The 6-inch diameter outlet pipe from the off-line storage tank was
temporarily plugged at the manhole at Villa and Santee Streets. Using a
nearby fire hydrant, the storage tank was filled. The temporary plug in
the 6-inch outlet pipe was then removed and the level in the tank was
154
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MICHIGAN
Catch Basins
New Piping Between
Catch Basins and Off-
line Storage Tank
Row
Monitoring Location
• Flow Direction
VILLA STREET
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DEMONSTRATION STUDY
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Storage Control
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Figure 4. Schematic of Off-line Storage Facilities Area
155
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Figure 5. Hydro-Brake Regulator Installed in-Off-Line
Storage Tank
-156
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monitored at one minute intervals. The change in volume over each one
minute interval (discharge) was plotted against the average head on the
orifice during the one minute interval. The average head here was
interpreted as the average between head at the beginning of the interval
and head at the end of the interval. A curvilinear relation with a
correlation coefficient equal to 0.94, was fitted to this data and is shown
in Figure 7.
Static Head Test —
In this test, the depth in the off-line storage tank, and therefore
the head on the orifice, was held constant at three different hydrant
discharge rates. These three points were added to the plot of variable
head test data for comparison. The three observations fit well into the
expected variance about the curve developed for the variable head test,
and therefore tended to confirm the results of that test.
Head-Discharge Curve —
The head and discharge data collected in the variable head test were
transformed by taking their logarithms. A linear regression function was
then fitted to the plot of Log h vs. Log Q; where h = Head, Q =
Discharge. The resulting equation was:
Log Q-= -0.6135+ 0.5394 Log h
By taking antilogs of this equation, the following expression is obtained:
Q = 0.2435 h °-5394
The standard equation for discharge through an orifice is:
Q = CA >/2gh~
158
-------
8
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-------
where Q = Discharge
A = Area of orifice
g = Acceleration of gravity
h = Head on orifice
C = Coefficient of discharge
A comparison between the two equations, can be made.
Test Data Equation (Q) Standard Orifice Equation (Q)
0.2435 h °-5394 = CA/2gh
0.2435 h °'5394 * CA/2B h0'5000
In the standard equation, h is raised to the 0.5000 power. The equation
obtained from the variable head test data shows h raised to the 0.5349
power, consistent (within experimental error) with the value in the
standard equation. To solve for C, the coefficient of discharge, h is
factored from the equation.
0.2435 - CA>/2g~
For this test data, C * 0.62, which is consistent with most reported values
of C - 0.60. As a result of this observation, the test procedures
described above were considered to be appropriate in the evaluation of
discharge from the off-line storage tank.
Hydro-Brake Head-Discharge Tests
Head-discharge tests were conducted on a Hydro-Brake Standard 5-
B-7 unit installed in the off-line storage tank in the Santee Drainage
Area. These tests led to the development of a head-discharge curve for
this Hydro-Brake. The tests used to develop this curve were the same as
those used to develop the head-discharge curve for the 3-inch orifice.
Data from these tests (variable head and static head) are presented in
160
-------
Figure 8. A curvilinear relation with a correlation coefficient equal to
0.80, was fitted to the variable head test data. Again, the three
observations taken in the static head test fit well within the expected
variance about this curve.
Head-Discharge Curve —
As for the orifice, head and discharge data collected in the variable
head test were transformed by taking logarithms. A linear regression
function was then fitted to the plot of Log h vs. Log Q; where h = Head,
Q = Discharge. The resulting equation was:
Log Q = -0.7897 + 0.3290 Log h
By taking antilogs, the following equation was obtained:
Q = 0.1623 h °'3290
In a general comparison with the orifice equation, in which discharge
is dependent on head to the 0.5000 power, it is seen that discharge from
the Hydro-Brake depends on head raised to the 0.3290 power. This
indicates that compared to an orifice, the Hydro-Brake will tend to
dampen discharges associated with higher heads. The curve, fit to the
variable head test data in Figure 8, shows this effect.
Hydro Storm Head-Discharge Curve —
Figure 9 shows the head-discharge relationship for a Hydro-Brake
(Standard 5-B-7),with a 3.5-inch outlet orifice, as defined by data
supplied by Hydro Storm Sewage Corporation. The curve developed from
the Hydro-Brake testing at the off-line storage tank is presented for
comparison.
Generally the relationship provided by Hydro Storm slightly
underestimates discharge at given heads. This is not considered to be a
161
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serious discrepancy as differences between the developed and Hydro
Storm curves can be attributed to experimental and roundoff errors, as
well as minor variations in the manufacturing process.
Storm Monitoring Results
Fifteen storms were monitored during the period from May 11 to
August 11, 1981 at the off-line storage tank in the Santee Drainage Area.
On August 5th, additional discharge tests were conducted on the Hydro-
Brake regulator. These tests resulted in the development of a discharge
curve that was strikingly similar to a discharge curve for a 3.5-inch
orifice. Upon further investigation at the site, a 15-inch long piece of
lath was found lodged inside the Hydro-Brake. The lath was found
positioned in a manner that would have prevented flow from developing a
radial motion within the Hydro-Brake. The development of this radial
motion is necessary in order to dissipate energy in the flow and reduce
the coefficient of discharge through the Hydro-Brake's 3.5-inch outlet
orifice.
On September 4th, subsequent to the removal of the piece of lath,
further tests were conducted on the Hydro-Brake regulator. The
discharge curve developed as a result of these tests compared well with
the initial discharge curve, shown in Figure 8, developed in May.
Four of the fifteen monitored storms at the off-line storage tank
occurred in August, during the period of time that the Hydro-Brake was
determined to have been rendered ineffective due to the lodged piece of
lath. Of the remaining eleven storms, five filled the storage tank to at
least 20% of its maximum depth. These five storms were considered
significant, and the impacts of these storms were analyzed in more detail.
On the evening of May 11, 1981 over a one hour-45 minute period,
0.37 inches of rainfall was recorded at the Rochester-Monroe County
Airport. Runoff from this storm was monitored at the off-line storage
tank. Using the developed head-discharge curve for the Hydro-Brake in
164
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the storage tank, inflow (uncontrolled) and outflow (Hydro-Brake
controlled) hydrographs were developed. These hydrographs are shown
in Figure 10.
The inflow hydrograph was developed using the equation:
where I = inflow
E = outflow
As _ change in storage tank volume with respect
At "to change in time.
Values of outflow (E) were obtained from the Hydro-Brake head-discharge
curve using average values of head on the Hydro-Brake. Values of -|-|
were developed from monitoring data at the storage tank.
During each interval, average head was interpreted as the average
between head at the beginning of the interval and head at the end of the
interval.
The hydrographs presented in Figure 10 show that peak discharges
to the combined sewer system are reduced by the Hydro-Brake installed
in the off-line storage tank. The peak discharge rate of 1.038 cfs,
representing the peak uncontrolled discharge to the sewers, was reduced
by 75%. The peak discharge rate through the Hydro-Brake was observed
to be 0.260 cfs. Total volume discharged to the sewers in the first 50
minutes of this storm (that portion of the storm where inflow to the tank
exceeded outflow) was reduced by 60%.
Storms on June 4th, July 2nd, July 9th, and July 20th were analyzed
in the same manner as discussed above. The results of these analyses are
summarized in Table 1. Figures 11-14 show the inflow (uncontrolled) and
outflow (Hydro-Brake controlled) hydrographs for each of these storms.
165
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-------
TABLE 1. STORM MONITORING RESULTS AT OFF-LINE STORAGE TANK
en
Date
5-11-81
6-04-81
7-02-81
7-09-81
7-20-81
Total Rain*
(Inches)
0.37
0.04
0.52
0.21
1.27
Peak Uncontrolled
Discharge (cfs)
1.038
0.331
0.996
0.536
0.327
Peak Hydro-Brake
Discharge (cfs) % Reduction
0.260 75.0
0.146
0.213
0.186
0.180
55.9
78.6
65.3
45.0
Total Uncontrolled
Discharge (gallons)
13,616
2,658
4,865
3,947
6,061
Total Hydro-Brake
Discharge (gallons)
12,716
2,366
5,296
3,937
5,990
Total Hydro-Brake Discharge ,«\
Total Uncontrolled Discharge *•*'
93.4
89.0
108.9
99.7
98.8
*As recorded at the Rochester-Monroe County Airport.
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As in the storm on May 11, peak discharge rates from these storms were
substantially reduced by the Hydro-Brake regulator. The percent
reductions ranged from 78% on July 2, to 45% on July 20.
Relatively little correlation can be seen between total rain and peak
discharges. This is probably due, at least in part, to the 4-mile distance
between the rain gage at the Rochester-Monroe County Airport and the
Santee Drainage Area.
Discrepancies between the total uncontrolled discharges and the total
Hydro-Brake discharges are due primarily to experimental and roundoff
errors.
Operation and Maintenance
The maintenance required at the off-line storage tank was minimal.
Over the four month demonstration period (May-August), only 2-3 inches
of fine debris built up at the lower end of the tank. Although these
depositions did not affect the normal operation of the Hydro-Brake unit, a
larger piece of stromwater debris did become lodged in the Hydro-Brake,
temporarily rendering the unit ineffective. Upon removal of the debris,
operation of the Hydro-Brake returned to normal. Given the nature of
stormwater debris, it may be good practice to check the Hydro-Brake
after every major storm to ensure its normal operation.
Installation Costs
The following represent the construction costs incurred installing
the off-line storage facility described above:
172
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Costs Attributable Costs Attributable
Total to Storage Tank to Collection System
Labor $ 7,450 $4,800 $ 2,650
Storage Tank 2,320 2,320
Piping 5,250 5,250
Equipment Rental 2,450 1,500 950
(Dump Truck, Crane,
Operator)
Materials 2,065 500 1,565
(Gravel, Ready-Mix
Concrete, Stone)
Restoration 855 150 705
(Binder, Top Asphalt,
Topsoil)
1 - Hydro-Brake Unit
(5-B-7) 525
$20,915 $9;795 $11,120 (ENR = 3510)
The costs of this alternative method to reduce the rate of inflow into
an existing collection system, are comparable with costs of other off-line
storage alternatives as outlined in the 1978 Needs Survey: Cost
Methodology for Control of Combined Sewer Overflow and Stormwater
Discharges (NTIS PB-296 604). The costs of this alternative, about $1.72
per gallon of storage, compare favorably with the $2.05 per gallon of
storage figure taken from the 1978 Needs Survey (ENR = 3510).
173
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CATCHBASIN STUDY
Background
The purpose of the catchbasin study was to evaluate the
effectiveness of reduced inflow rates to the..combined sewer system on the
frequency of surcharge conditions. A reduction of inflow rates was
accomplished by sealing a number of selected catchbasins in the Santee
Drainage Area. Hydro-Brake regulators were then installed in the
remaining catchbasins in the drainage area. This combination allowed for
limited surface/street ponding of stormwater, thereby reducing the rate
of runoff into the combined sewer system.
Homeowner Survey
A complaint analysis was conducted to identify the existing flooding
problems within the study area. Information was obtained through
distribution of a homeowner survey, as shown in Figure 15, and review of
previous complaint records filed with Monroe County. About 25 percent
of the total number of surveys (241), which were hand distributed to
homeowners in the study area, were returned. Table 2 presents the
street location, number of responses, and the number of responses which
indicated basement flooding problems.
TABLE 2. SANTEE HOMEOWNER SURVEY RESULTS*
No. of Responses No. of Responses
Street Received w/Basement Flooding
Michigan
Curtis
Emerson
Kestrel
Curlew
Santee
14
16
14
3
3
6
6
2
3
0
0
0
*Based on a 25% survey response.
174
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FLOODING SURVEY
1) Does your basement flood during rains?
D Yes D No --..
2) Have you previously filed a complaint?
D Yes D No .
3) How many times per year does basement flooding occur?
4) How does your basement flooding frequency compare with some of your
neighbors?
B about the same (3 more than
less than
5} Is Street flooding a problem in your area?
n Yes D No
6} Does basement flooding always occur along with Street floodina?
D Yes D No
7) Does Street flooding ever encroach on your property?
D Yes D No
8) Has your street ever been closed due to flooding?
D Yes D No
9) In your opinion, what location in your immediate area experiences the
worst basement and/or street flooding.
10) Comments:
Owner's Name:
(address if different)
Date:
Building Address:
Reach: (Office Use Only)
MH to MH
Figure 15. Homeowner Survey Questionnaire
175
-------
A review of the Monroe County complaint records indicated several
occurrences of basement flooding in the Santee Drainage Area over the
last three years. The complaint records, however, were so brief that it
was difficult to determine the impact that surcharging of the combined
sewer system may have had on basement flooding.
Study Description
In order to determine the extent of sewer surcharging conditions
prior to the sealing and installation of Hydro-Brakes in selected
catchbasins, sewer flows in the study area were monitored. Monitoring
was accomplished using level sensing equipment at five locations within
the drainage area. Monitoring equipment used in this study consisted of
Manning Level Recorders (L-3000A), and NB Electronic Manhole Meters
(GS). The flow monitoring locations are listed below and are shown in
Figure 16.
- Emerson and Robin
- Curtiss and Santee
- Curttss - 2 MH west of Santee
- Michigan - 2 MH west of Santee
- Villa and Santee
Storm flows at these locations were monitored in 1980, prior to the
sealing of any catchbasins or the installation of Hydro-Brakes.
Preliminary stormwater modeling of the sewer system in the Santee
Drainage Area was conducted to help determine the number and location of
catchbasins to be fitted with Hydro-Brake regulators. A field survey of
street surface grades was also conducted in order to locate areas of
natural depression that would facilitate stormwater ponding. The results
of this survey and the preliminary stormwater modeling indicated the need
for Hydro-Brakes at 11 catchbasin locations.
176
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The flow monitoring conducted in the Santee Drainage Area during
1980 showed frequent surcharging in the 12-inch combined sewer along
Emerson Street. To reduce the frequency and magnitude of surcharging
in this sewer stormwater inflow had to be restricted. A reference storm
with a return frequency of 2 years (60 minute duration, total rain = 0.75
inches, peak intensity = 1.5 in/hr), was predicted to produce stormwater
inflow from roof leader connections on Emerson Street at an estimated rate
of 1.25 cfs. When combined with the normal dry weather flow rate,
estimated to be 0.07 cfs, the remaining capacity in the Emerson Street
sewer was determined to be 0.50 cfs. Inflow from each of the two Hydro-
Brakes on Emerson Street was therefore restricted to 0.25 cfs. Hydraulic
computations for the remainder of the Santee Drainage Area showed that
an inflow rate of 0.25 cfs through the remaining Hydro-Brake installations
was appropriate. Since the average depth from street surface to
catchbasin invert was approximately 50 inches, and since it was desirable
to standardize the units selected, Hydro-Brake Standard 5-B-7 units with
a discharge of 0.25 cfs at 50 inches of head were specified for each of the
11 catchbasin locations in the Santee Drainage Area.
In the spring of 1981, the necessary catchbasins were sealed and
Hydro-Brakes were installed in the 11 catchbasins. Figure 16 shows the
location of the sealed catchbasins and the catchbasins with Hydro-Brakes
installed. Early into the monitoring program in 1981, a number of
residents in the neighborhood, inconvenienced by street ponding at the
ends of their driveways, opened certain catchbasins in order to prevent
ponding in their areas. These catchbasins are also shown in Figure 16.
In 1981, subsequent to the sealing of catchbasins and the installation
of Hydro-Brakes, flow monitoring was resumed in the same locations used
during 1980.
Storm Monitoring Results
Information on existing system conditions was obtained by monitoring
depths of storm flow, at the previously indicated locations, from May
178
-------
through September 1980. For each storm at each location, the maximum
depth of flow in the sewer was plotted against the maximum 15-minute rain
intensity.
In 1981 monitoring began in June, after the delivery and installation
of the Hydro-Brakes, and continued through mid-August. As was done
in 1980, for each storm the maximum depth of flow in the sewer was
plotted against the maximum 15-minute rain intensity.
At each location, 1980 results were compared to those in 1981.
Figures 17-21 present these comparisons for each of the monitoring
locations. At Villa and Santee, Curtiss, and Emerson and Robin (Figures
17-19), maximum flow depths obtained in 1981 for given rainfall intensities
were generally lower than those observed in 1980. At Emerson and
Robin, a 12-inch sewer, although sewer flows were generally reduced as a
result of the study, surcharge conditions during most rainfall events still
persisted.
At Michigan (Figure 20) and Curtiss and Santee (Figure 21) no
improvement in 1981 data over 1980 data was seen. These results may be
attributed primarily to the open catchbasins, shown in Figure 16, near
these locations.
It is encouraging to note, that at Villa and Santee (Figure 17),
downstream of each of the other monitoring locations, flows in 1981 were
lower than those in 1980, Thus, although the study may not have shown
consistent improvements in each of the upstream sewer sections, the
combined effect was a reduction in peak runoffs from the drainage area as
a whole.
Follow-Up Homeowner Survey
During the last month of the study, a follow-up complaint analysis
was conducted. This survey concentrated on those homeowners who
indicated basement flooding problems before the start of the study and on
179
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1981 Line of Best Fit
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Figure 17. Monitoring Results - Villa & Santee Streets
180
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Figure 18. Monitoring Results - Curtiss Street
181
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Figure 19. Monitoring Results - Emerson & Robin Streets
182
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Figure 20. Monitoring Results - Michigan Street
183
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Figure 21. Monitoring Results - Curtiss & Santee Streets
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those homeowners closest to the larger street ponding locations. The
results of the survey were mixed, with some howeowners noticing definite
improvements and others indicating no change in the frequency of
basement flooding. It was therefore difficult to show a definite
correlation between the fevel of sewer flow and the extent of basement
flooding. The inconsistent results may b,e primarily attributed to the
inability to isolate stormwater runoff from roof leaders connected to
individual house laterals. The catchbasins opened by neighborhood
residents inconvenienced by street ponding, may further explain the
inconsistent results obtained.
Operation and Maintenance
In preparation for the monitoring program in 1980, each catchbasin
in the Santee Drainage Area was cleaned. Throughout the 1980
monitoring period, only minor amounts of debris accumulated in each
catchbasin. In the spring of 1981, prior to the sealing of catchbasins and
the installation of Hydro-Brakes, the catchbasins were again cleaned.
During the 1981 monitoring period, only minor amounts of debris
accumulated in the catchbasins. This accumulation of debris did not
interfere with the normal operation of the Hydro-Brakes. Larger pieces
of debris, however, as at the off-line storage tank, may render the
Hydro-Brakes ineffective. In order to ensure the normal operation of the
Hydro-Brakes, it may be good practice to check each unit on a regular
basis, especially following major storms. The catchbasins themselves,
should be cleaned at least once every other year.
Installation Costs
The costs incurred in developing the inlet control system for the
catchbasin study described above are the following:
Labor $ 765
12 Hydro-Brake Units (5-B-7) @ $600/ea. 7,200
$7,965 (ENR = 3510)
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The costs of this alternative, about $230 per acre, are very
favorable when compared to the conventional alternative - sewer
separation, at approximately $42,000 per acre, as estimated in the 1978
Needs Survey (ENR = 3510).
CSO REDUCTIONS
By attenuating peak stormwater runoff, sewer surcharging and
combined sewer overflow can be reduced. Both methods demonstrated in
this study reduced the rate of inflow into the combined sewer system.
These reduced inflows can result in reducing the frequency and
magnitude of surcharging in the immediate localized tributary drainage
area, and in the reduced frequency and volume of CSO further
downstream in the combined sewer system.
i
At the off-line storage tank facility, peak discharge rates and total
volume of flow during peak runoff periods were reduced. The peak
discharge rate during the storm of May 11, 1981, was reduced by 75% and
the total volume of flow discharged to the sewers during the peak runoff
period was reduced by 60%. These types of reductions tend to reduce
overflow from the combined sewer system. Since peak stormwater flows,
especially during a first-flush, are generally associated with higher
concentrations of pollutants, any reduction in peak discharge rates and
resulting overflows may show significant Improvements in pollution
control. Although the off-line storage demonstration was conducted over
a small drainage area, similar results would be expected using properly
sized facilities with larger tributary drainage areas.
The mixed results obtained as part of the catchbasin study and
confirmed in the follow-up homeowner survey can be attributable in part
to the indeterminate and uncontrolled amount of stormwater runoff from
roof-leaders connected directly to the combined sewer system. Due to the
resulting surface ponding, many homeowners did not perceive the Hydro-
Brakes to be an effective solution to their flooding problem. In order to
change this perception and to eventually gain acceptance of future Hydro-
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Brake implementations, it may be necessary to educate neighborhood
residents on the concept of inlet control through the use of Hydro-
Brakes. Hydro-Brakes are able to reduce sewer flow only at the expense
of increased surface ponding. The catchbasin study, in some cases, did
show reduced levels of sewer flow and surcharging. It is felt that this
will subsequently result in the reduced occurrence of overflow from the
combined sewer system.
SUMMARY AND CONCLUSIONS
Two different methods to reduce the rate of inflow into the combined
sewer system were evaluated as a part of this project. The concept of
off-line storage in conjunction with Hydro-Brake controlled discharge,
serves to regulate downstream sewer flows after stormwater runoff has
entered the collection system. In contrast, the surface/street ponding
concept with Hydro-Brake controlled inflows, serves to regulate the rate
of stormwater runoff before it enters the collection system.
Conclusions developed as a result of the off-line storage evaluations
are presented below:
1. The Hydro-Brake regulator field performance curve agreed closely
with the performance curve supplied by the Hydro Storm Sewage
Corporation. The field unit indicated flowrates approximately 6
percent higher than the design curve at 50 inches of hydraulic head.
2. Although it performed reasonably well through a number of storms,
during one period of time the Hydro-Brake was rendered ineffective
by debris present In normal stormwater runoff.
3. During the period when the Hydro-Brake was rendered ineffective
by debris, it failed to offer any improvement in flow restriction over
a simple orifice of the same diameter.
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4. Compared to an equally sized orifice, the Hydro-Brake passed less
flow at given hydraulic heads when operating as designed (i.e. with
flow not impeded by debris).
5. The equation of discharge obtained for the Hydro-Brake Standard 5-
B-7 regulator with a 3.5-inch diameter outlet orifice was as follows:
Q = 0.1623 h0'3290
where Q = Discharge in cfs
h = Hydraulic head in feet
6. Used in conjunction with off-line storage, the Hydro-Brake regulator
effectively reduced peak stormwater runoff rates into the combined
sewer system by as much as 78 percent.
7. Utilization of Hydro-Brakes to reduce inflow into combined sewer
systems can result in a reduction in the frequency and magnitude of
combined sewer overflows. In localized drainage areas, sewer
surcharging can be reduced at the expense of additional surface
ponding.
Conclusions developed as a result of the catchbasin control
evaluations are presented below:
1. The combination of surface/street ponding and Hydro-Brake
regulated inflow to the combined sewer system may not result in
significant impacts in the immediate localized tributary area.
However, impacts may be felt further downstream as the combination
did reduce peak runoffs from the drainage area as a whole.
2. In drainage areas where roof leaders are connected directly to house
laterals, the effectiveness of restricting inflow from street runoff
through use of catchbasin inlet control devices is reduced, since the
fraction of runoff from roofs is not controllable by the catchbasin
inlet control devices.
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3. Even though the hydraulic grade line of the collection system was
reduced by means of inlet control devices, the perception of
homowners in the demonstration area failed to support significant
improvements. The existance of surface ponding and problems
unrelated to collection system conveyance capacity contributed to
this perception.
in general, it should be noted that the implementation of the Hydro-
Brake as a feasible static control device is significantly limited by the
present capacity of the supplier to deliver units and provide field
installation assistance. (Supplier now claims that delivery problems have
been corrected.)
RECOMMENDATIONS
1. The design of the Hydro-Brake should be reviewed to develop
modifications which would minimize the impact of stormwater debris
on the optimal operation of the unit.
2. Use of the Hydro-Brake should be evaluated in conjunction with
surface retention basins. These results should be compared to those
obtained from the Hydro-Brake's use with off-line storage,
particularly on a cost-benefit basis.
3. Further studies on the effectiveness of Hydro-Brakes in reducing
peak stormwater flows and the frequency of basement flooding,
should be conducted by EPA at other locations, in drainage areas
where roof leaders are not connected to house laterals.
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