United States Office Of Water EPA 832-R-95-007
Environmental Protection (4204) August 199E
Agency
4»EPA Sanitary Sewer
Overflow Workshop
-------
FINAL REPORT
SANITARY SEWER OVERFLOW WORKSHOP
Held April 26-28, 199$
Renaissance Downtown Hotel
Washington, D.C.
Presented to the
Urban Wet Weather Flows Advisory Committee
SSO Subcommittee
August 17, 1995
Sponsored by:
U.S. Environmental protection Agency
Office of Wastewater Management
Mail Code 4201
401 M Street, S.W.
Washington, D.C. 20460
-------
-------
TABLE OF CONTENTS
Executive Summary . . . . . . . . . . ... ... . . .ES-1
Chapter 1: Introduction . 1-1
Chapter 2: Workgroup 1 - Preventive Maintenance ............... . . . . . . . 2-1
Summary of Group Presentation . ............. ... . . . . .2-1
Recommendations for Further Research 2-4
Question and Answer Session ....................... 2-5
Chapters: Workgroup 2 - Peak Inflow .... ........... . . '. . . . .... . . .3-1
Summary of Group Presentation .3-1
Recommendations for Further Research ................. 3-6
'.' Question and Answer Session ....................... 3-7
Chapter 4: Workgroup 3 - Rainfall Induced Infiltration . . . . . .... . . . . , . . . ... 4-1
Summary of Group Presentation . . 4-1
Recommendations for Further Research 4-5
Question and Answer Session . . 4-5
Chapter 5: Workgroup 4 - Laterals .5-1
Summary of Group Presentation ...................... 5-1
Recommendations for Further Research 5-6
Question and Answer Session .... . . . 5-6
Chapter 6: Workgroup 5 - Treatment Options for Wet Weather Flow 6-1
- Summary of Group Presentation . 6-1
Recommendations for Further Research 6-6
Question and Answer Session . . . 6~*>
Chapter 7: Workshop Summary and Conclusions 7-1
Chapter 8: Research Needs and Recommendations .....' . . 8-1
Appendices
Appendix A: Agenda and Workgroup Assignments A-l
Appendix B: Workgroup Reports ........ .-'. ... . . . ... . . . . B-l
Appendix C: List of Workgroup Members and Observers . . . . . . . . C-l
Appendix D: Useful Definitions D-l
-------
-------
TECHNICAL WORKSHOP ON SANITARY SEWER OVERFLOWS
EXECUTIVE SUMMARY
Due to growing concerns about the health and environmental effects of sanitary
sewer overflows (SSOs), the Office of Wastewater Management (OWM) has established an
Advisory Subcommittee to assist EPA, in addressing the problem. In response to the
Subcommittee's request for additional technical information, the U.S EPA Office of
Wastewater Management (OWM), in cooperation with the EPA Office of Research and
Development, conducted a two-day technical conference on SSOs in April, 1995.
OWM also invited a number of national wet weather and wastewater treatment
experts and committee members to participate in a workshop on SSOs hi Washington, DC,
April 26-28, 1995, immediately following the conference. The workshop focused on five '
specific, areas: 1) preventive maintenance, 2) peak inflow, 3) rainfall induced infiltration
'(RII), 4) laterals, and 5) treatment options for wet weather flow. Following is a summary
of the findings and recommendations of the workshop.
KEY FINDINGS: .
While workshop participants did not resolve all of the technical issues related to the
S SO problem, they did reach consensus on a number of key issues. The group agreed that
SSOs are a widespread problem throughout most of the nation and that SSOs are causing
adverse public health and environmental effects. The group further agreed that: 1) while
infiltration and inflow (I/I) are major contributors to the SSO problem, poor sewer
maintenance is also a major factor; 2} to be. effective, I/I reduction programs must address
both publicly and privately-owned portions of the collection system; 3) almost all dry
weather SSOs can be eliminated and most wet weather SSOs can be significantly reduced;
and 4) where wet weather SSOs cannot be eliminated, cost-effective storage and treatment
options, similar to those used for Combined Sewer Overflow (CSO) control, are available
or could be developed. However, participants also agreed that in order to resolve some of
the remaining technical issues, additional research or study will be needed.
For each focus area, workshop participants identified guidance for addressing key
issues:
Preventive Maintenance: Workshop participants agreed that the sanitary sewer industry
should be managed as an enterprise operation, and they outlined guiding principles for the
industry. These principles stressed the need for systematic implementation of operation and
maintenance (O&M) programs, preservation and protection of infrastructure investments, a
concise inventory of the infrastructure, O&M staff involvement and input during all stages
of the process, and cooperation between federal, state, and local organizations.
-------
In addition to these principles, workshop participants identified four elements of an
effective O&M program: 1) education, -2) program development and implementation, 3)
local enforcement, and 4) clearly defined roles for regulators and professional organizations.
Participants generally agreed that educating the public about the need for and benefits of
preventive maintenance is the most important element.
t- -..
Peak Inflow: One goal of the workshop was to prepare a comprehensive .methodology for
inflow removal. Workshop participants developed a methodology for predicting a
collection system's response to storm events too great to be monitored. Participants agreed
that a comprehensive methodology should include six essential elements: 1) data gathering,
2) system modeling, 3) inflow source identification techniques, 4) inflow removal
guidelines, 5) a system for evaluating inflow removal success, and 6) estimated costs of
inflow removal. This methodology has proven to be effective in identifying and removing
inflow and in reducing SSOs after sewer system rehabilitation and relief sewer construction.
The definition of peak inflow used for the purposes of the workshop emphasized
that peak inflow includes inflow from rainfall as opposed to inflow from tidal, estuary, or
-cooling tower sources. Peak inflow was. defined as sewer system flow in direct response to
rainfall events, where system response (flow) is due to sources (defects) that activate almost
instantaneously when rainfall occurs. -,
i1 , -
RII: Workshop participants defined RII as storm water entering a separated sanitary sewer
system through defects in manholes, mams, laterals, or private service lines. While the
peak flow characteristics of RII are similar to those of inflow, participants agreed that
inflow is a separate and distinct source.
Workshop participants concluded that the RII quantification methodology must
incorporate preventive maintenance, peak inflow, laterals, and treatment options if a cost-
effective SSO control program is to be developed. Participants identified modeling and
field work as two key methods for identifying and controlling RII. The RII quantification
methodology presented to the workshop participants (Exhibit 4-1) connects modeling and
field work, and illustrates the interdependence of RII with each of the other Workshop focus
areas. The methodology included four main steps: 1) monitoring and assessing peak flow,
2) determining the extent of RII, 3) identifying sources of RII, and 4) developing options
and associated costs to control RII. Participants agreed that in the hydraulic modeling
process, differentiation between RII and inflow is unnecessary until a control option needs
to be selected and the associated costs determined.
* ' '''"
Laterals: The workshop also covered issues surrounding SSOs occurring on private
property because of defects in laterals. Workshop participants defined a lateral as a service
line from a structure to a sanitary sewer conveyance system, including all appurtenances
attached both directly and indirectly. Participants discussed where responsibility for
maintenance and rehabilitation of such service lines lies, and explored the role that public
education plays_ in the proper management of collection systems.
ES - 2
-------
Participants agreed upon eight areas that should be addressed when examining the
problems surrounding laterals: 1) social- and geographic ramifications, 2) education, 3)
economic issues, 4) legal issues, 5) politics, 6) health impacts, 7) enforcement and
inspection, and 8) technology. Participants concluded that inspection of laterals is essential,
although they wanted to avoid entry to private property, if possible. Because defects in
laterals account for a major portion of SSOs, a systematic approach for handling laterals
must be developed and property owners must be educated about those areas for which they
are responsible. .
Treatment Options: Workshop participants agreed that SSOs can be controlled using CSO
control methods because both SSOs and CSOs are mixtures of municipal sewage and storm
water. The difference between the two is that the average ratio of sanitary sewage to storm
water is higher in SSOs. Workshop participants concluded that to develop a cost-effective
solution, several demonstrated approaches to handling SSOs should be considered, including
some combination of the following: 1) removing inflow, 2) performing only cost-effective
rehabilitation, 3) inspecting the interceptor and sewer systems, 4) maximizing flow to
publicly owned treatment works (POTWs), 5) maximizing POTW treatment capacity, and
6) installing satellite treatment facilities.
Workshop participants were hi agreement that the first three approaches to handling
and treating SSOs (inflow elimination or reduction, cost-effective sewer rehabilitation, and
collection system inspection) must be performed in all cases; an integrated economic and
feasibility analysis using a combination of maximizing both flow to POTWs and treatment
capacity must be considered for controlling the remaining SSO. Workshop consensus was
that these first five options are preferable to the use of satellite storage.
KEY RECOMMENDATIONS: -
For each focus area, workshop participants identified areas for further investigation
or research by EPA or other environmental organizations:
Preventive Maintenance. Develop 1) performance and evaluation criteria, 2)
- standards for debris removal O&M activities, 3) a national clearinghouse for
program successes in O&M, and 4) educational materials for the public and elected
officials. .
Peak Inflow. Undertake further research on 1) quantification of inflow defects, 2)
impacts of rainfall data on inflow projections, 3) storm event (design storm)
selection, 4) preventive measures, and 5) Manning's ("n") and Hazen Williams ("c")
coefficients of friction.
ES - 3
-------
RII. Investigate 1) flow projection methodology, 2) the effectiveness of
rehabilitation approaches, 3) future engineering design and construction practices,
and 4) the use of unregulated, long-term stream records instead of monitoring
groundwater conditions as an alternative approach for calculating RII.
' - f " i,
Laterals. Focus future research efforts on 1) examining case studies of programs
and successes, 2) developing educational materials, 3) exploring municipal takeovers
of laterals, and 4) expanding enforcement options for National Pollutant Discharge
Elimination System (NPDES) permit holders.
Treatment Options. Develop effective national requirements for treatment options
by 1) demonstrating, improving, and evaluating emerging technologies, and 2)
determining particle size removal requirements for adequate disinfection by various
disinfection technologies, including ultraviolet disinfection.
ES-4
-------
CHAPTER. 1: INTRODUCTION
Sanitary sewer collection systems are designed to collect municipal and industrial
wastewaters, with allowances. for groundwater infiltration and unavoidable stormwater that
enters the system, and transport those flows to a sewage treatment plant. Sanitary sewer
overflows (SSOs) are untreated sewage overflows from sanitary sewer collection systems .
SSOs can contain high levels of pathogenic microorganisms, suspended solids, toxic
pollutants, floatables, nutrients, oxygen-demanding organic compounds, oil and grease, and
other pollutants. SSOs can discharge to areas where they present high risks of human
exposure such as streets, private property, basements, and small streams. In addition to
health risks, SSOs can contribute to exceedances of water quality standards and water
quality impairment.
\ -.',.,. ". ., . ...
SSOs occur when flows exceed the capacity of a sewer and the sewers surcharge.
This problem .can be caused by high flows during wet weather conditions, blockages,
bottlenecks, and/or undersized pipes. Usually, SSOs are most prevalent during wet weather
conditions, when flows are at peak levels due to inflow and infiltration (I/I). It is thought
'that in most sanitary sewer systems, I/I is the primary factor causing peak flows. However,
SSO's are not always the result of I/I or insufficient capacity. Sewer system maintenance
issues such as root intrusions, grease build up, and debris also play a significant role in
initiating SSO's in many utilities. These SSO's are not necessarily wet weather related. In
addition, cracked and leaking sanitary sewers can also exfiltrate raw sewage during dry
weather periods or during certain surcharged conditions causing potential groundwater
contamination.
Over the years, many sanitary sewer lines have deteriorated with age, neglect, and
lack of proper preventive maintenance programs. Many systems now contain defective
sewer joints, cracked lines and manholes, displaced manholes, missing manhole covers, etc.,
which during wet weather allow rainfall runoff to enter the sanitary sewers. In some
systems, lines soon become overloaded and uncontrolled overflows occur at unspecified
locations throughout the system. Since most sanitary sewers have no overflow structures
designed into the systems, the overflows often occur through manholes and defective lines
and often occur in residential neighborhoods. The surcharged lines also sometimes cause
backups into homes. In comparison to a combined sewer overflow (CSO), SSOs generally
contains higher percentages of raw sewage arid a lower percentage of stormwater,
There are many circumstances which can give rise to systems with chronic SSO \
problems, including: infrastructure deterioration due to insufficient planned system
rehabilitation and replacement programs, inadequate preventive maintenance programs^
insufficient pipe capacity, poorly performing or undersized pumps, and insufficient planning
for new development.
1-1
-------
The efforts to eliminate excessive I/I under" the construction grants program have not
always been successful due to many factors, including:
a. Technical Factors
Estimates of infiltration reduction were based on a flawed concept that
elimination of a specific infiltration source would result hi a
corresponding reduction in the infiltration rate. This was later found
to be incorrect due to groundwater migration and the fact that the
repair was not absolute or adequate.
Extreme cases of rainfall induced infiltration were not always
anticipated, and hence were not properly identified and corrected.
.... ,. . i
Some sanitary sewer evaluation surveys (SSES) were poorly
conducted.
Peaking factors for I/I were greatly underestimated.
Inflow was not always adequately addressed.
Flow from private sources were not addressed.
b. Non-Technical Factors
' I/I programs are costly and take a long time.
Lateral connections to buildings, which typically represent about 50
percent of the infiltration to a sewer system, were generally excluded
from rehabilitation programs because they were not grant eligible and
sanitary districts may have limited jurisdiction to enter private
properties where lateral connections to buildings are located.
Some grantees inappropriately certified I/I non-excessive in order to
quickly obtain grant funding without conditions for plant construction.
To assist the Agency hi addressing these issues, The Office of Wastewater
Management (OWM) has established a Federal Advisory Committee on Sanitary Sewer
Overflows (SSOs). The SSO Advisory Committee, which is composed of selected
stakeholders (municipalities, environmental groups, States and EPA), held an initial scoping
meeting on December 5th and 6th. One of the Committees first observations was a need
for additional technical data.
The attached report summarizes the results of a recent workshop on SSO technical
issues, held in Washington, DC on April 26-28, 1995. The workshop was held in response
to the Committees request for additional technical data on SSO identification, control,
treatment and costs.
1-2
-------
The workshop was divided into five workgroups. Each group was assigned a
specific technical area to address. The scope for each workgroup, and a list of the
workgroup members is included in the Appendix. The original working reports for each
committee is also included in the Appendix. The oral.presentations presented by the grow
leaders are summarized in Chapters 2 through 6. An overview of the key workshop
findings is included in Chapter 7. In addition to the findings, the workgroups developed a
list of recommendations. The recommendations are summarized in Chapter 8 and identify
needs for additional technical information or research by the EPA or other organizations
1-3
-------
'r
-------
CHAPTER 2: WORKGROUP #1 - PREVENTIVE MAINTENANCE
Summary of Group Presentation and Q&A Session for Workgroup #1
Preventive Maintenance for the Elimination of SSOs in Sanitary
Sewer Systems
Albert Gallaher presented the report for workgroup 1. He began by outlining the
guiding principles that the group had developed, The group felt that these principles could
be applied to each of the five workgroup areas and to the sanitary sewer industry as a
whole. Group members emphasized that the sanitary sewer industry should be managed in
a forward thinking manner like a well run enterprise operation. The group agreed that
addressing the following principles and communicating their importance would assist the
industry in meeting the goals identified by the group. The guiding principles included the
following: . -
'...'-* "
Systematic Implementation of Operation and Maintenance (O&M) will reduce
SSOs.
Preservation, protection of infrastructure investments, as well ,as asset
management will prevent future liabilities. .
. Adequate allocation of human and material resources.
Meeting communication needs can be facilitated by Federal and. State
government and professional organizations.
A concise inventory of the infrastructure is essential. (Everyone needs to
know what exists in their system before they can develop a plan to fix it.)
It is crucial to have O&M staff involvement and input during the planning,
design, and implementation process.
Federal, State, and Local cooperation should be developed.
In addition to the guiding principles, the group identified four goals or elements of
an effective O&M program:
(1) Education; .
(2) Program development and implementation;
(3) Local enforcement; and
(4) Clearly defined roles for regulators and professional organizations.
The necessary foundation for the accomplishment of these goals should be training.
. . '' ' ' . 2-1. . ' - .
-------
The mission of these goals is to extend basic system O&M and provide general guidelines
that are targeted toward assisting the local service provider/state to implement an O&M
program. ; -'-
" ' * ,' "'"-'., , . . - . ,
Implementing the goals serves to protect the public's investment hi the existing
system and provides asset management to prevent future liabilities. Achieving the goals
will also enable the collection system's manager to provide a public service and
accommodate growth within the system while ensuring its reliability in the future.
Addressing O&M issues will also facilitate the protection of public health and natural
wildlife. As a result of O&M activities, system servers will be able to maximize their
conveyance capabilities,and establish standard operating procedures for emergency
conditions. .
The group addressed and developed the following strategies for achieving the four
goals: »
Education. The workgroup identified four categories of individuals that would
benefit from education: the general public, local officials, system managers, and technical
field staff. The group also identified the specific areas each category of individuals should
know about.
The general public should be made aware of general system operations and
understand the nature of the capital investment. The local official should be made aware of
the processes involving priority setting, budgetary issues, planning, and recognition of
capital investment. System managers should understand short-term and long-range
budgeting and program administration. Technical staff and field crews should be trained in
procedural and record-keeping requirements.
, O&M Program Development and Implementation. The group identified 11 key
components necessary to develop and implement an effective O&M program.
(1) Coordinate administratively -Administrative coordination is essential to
help prevent future problems. Before developing an O&M program, the
group recommended conducting a review of existing city building standards,
material specifications, and acceptable construction and design practices to
minimize potential storm water effects. All of these elements help to
determine the life cycle cost of capital improvement projects as part of design
process. Life cycle costs should include both O&M and capital costs for
increasing necessary treatment plant capacity for existing or new facilities.
(2) Establish performance and evaluation criteria - The group recommended
that developing performance criteria would help focus the goal of each O&M
program. Suggested components for these criteria include: flow monitoring,
event notification systems, inspection records and videos, and compliance
2-2 . ,
-------
monitoring and tracking.
; , ^
(3) Develop system mapping and inventories - System maps should be
developed after a system inventory has been performed.
(4) Formulate management structures, staffing needs -.Formulation of
management structures can be a result of educating the system managers
about expected requirements. The basic problems .that prevent good O&M
are lack of motivation, 10% pay, and loss of trained personnel.
(5) Develop inspection and record keeping procedures - Inspection and record
keeping procedures should be incorporated into the education process for
technical staff. Some of the standard inspection procedures include:
Internal television inspection;
. Physical inspection; .
manhole/street/ROW surface inspection;
internal manhole inspection; and
- other methods (private sector).
(6) Itemize and prioritize corrective and preventive activities -
Some of the standard corrective/preventive "maintenance activities include:
«* "' * " .
' Cleaning;
mechanical; and ' ~
: - hydraulic;
Maintenance of ROW and structures for access; -
- spot repairs;
manhole rehabilitation; ,
pipe relining; -
private sector inspection/monitoring; ,
- root control; *
- , vandalism control;
- reporting; .
- flow monitoring; and ,
- information recording/management.
(7) Develop O&M manuals (lift stations, collection systems) - O&M manuals
should be continuously refined so that best practices can continuously be
improved upon. ^
(8) Determine Equipment Requirements - The group emphasized that the best
equipment does not always mean the fanciest; it is important not to overlook
'. " ' ' " 2-3 ' ...
-------
the basics. , - .
(9) Develop financing plan - As they had indicated earlier, the group felt it was
important to keep hi mind that the system needs to be viewed as an
enterprise. Operating and mauitaining the system up front is an essential
investment.
(10) Inter/Intra-departmental coordination on capital projects - See (1).
(11) Formulate short-term/long-range Capital Improvement Projects (CIP). -
The general consensus of the group was that it is necessary to identify
potential funding sources.
Local enforcement - The group felt it was essential to provide enforcement
measures for any O&M program. Some enforcement activities could include establishing
building standards or discharge limits, assigning areas of public/private responsibilities, or
developing ordinances protecting facilities.
** ' /
Clarify and define the role of regulators and professional organizations. The
group recommended that the role of State/Federal Enforcement Activities (CO's, F&O's)
should be to define enforcement parameters and develop tiered enforcement approaches.
This could be accomplished by: ,
Integrating Performance Criteria for Collection System Operation as part of
both the permitting process and the construction approvals process;
Developing certification programs for collection system operators;
» - Recognizing successful initiatives and "local heroes;"
Developing standard specifications and project protocols;
Developing education programs and training materials; and
Funding and conducting research on emerging technologies.
Summary
The group report concluded by emphasizing that the public sector is accountable for
a longer period of time than the private sector and that some long term goals may be
intangible, but should not be overlooked. It is essential to educate the public about the
need for and benefits of preventive maintenance.
Recommendations for Further Research
2-4
-------
. Workgroup #1 outlined four areas for further EPA research:
Establish performance and evaluation criteria for O&M activities;
Develop standards for how to handle debris removed during O&M activities;
Develop a national clearinghouse for program successes in O&M; and
Develop educational materials for the public and elected officials.
These areas, and the areas outlined by the other workgroups are also identified in Chapter 8,
Research Needs and Recommendations.
Question and Answer Session for Workgroup #1
Following the groups presentation, workshop participants were invited to ask
questions. Some of the issues raised included the following questions:
Ql: Are the costs of O&M proportional to the value of the infrastructure?
Al: The group consensus was that proactive O&M practices are more cost effective than
reactive solutions. For example, for every dollar spent proactively now on the
system, five dollars would need to be spent if the response were reactive: Graham
Knott added that in Portland, for example, they spend $4.5 to $5 million annually on
O&M. He noted that this represents only one half of one percent of the total value
of the entire system. Another participant suggested that WEF had prepared draft
costs for O&M organized by population and crew needs.
Q2: Mike Wallis asked if the group had discussed how to determine the percent of the
system that would need to be flow monitored or cleaned?
/ -..'.-
A2: An example was given that a manageable mini-system in Charlotte would be
approximately 7.5 miles. Currently in a system of that size, there are 12-15 flow
monitors every 2,500 miles; the number of monitors will increase to approximately
5,0 for every 2,500 miles (or 1 per 50 miles) in the future. Another individual
suggested that 20% of the system would be a reasonable rule of thumb. This was in
agreement with Predos Law which states that 80 percent of the problem is in 20
percent of the system. Therefore the key to eliminating SSOs is to identify that
particular 20 percent. Another participant indicated that a rough percentage might
not always be a good estimate. Each system should be evaluated on a case-by-case
basis. He felt that in order to evaluate each system, it is essential to understand the
specific elements unique to the system. It is important to know not only what
exactly is in the ground, but what condition the system is in as well.
'2-5
-------
On the issue of flow monitoring, Graham Knott commented that it is also
important to integrate flow monitoring into an analysis of basic trends in the system.
The data gathered can be used to help develop questions for the city; it can act also
as an indicator. Ralph Petroff added that typical numbers for his system include
one-tenth to one-half of one percent per the value, of the system. For every dollar
spent on collection systems, $5 to $10 are spent on treatment plants.
Q3: Roy Orkin wanted to know how to address regulatory issues hi terms of
implementation?
A3: Graham Knott mentioned at this point everything new should be phased in. Nothing
has been determined as an amount required per year. The philosophy should be if
you have a program of any sort hi place, EPA should not "come after you."
Developing a program shows that a city is trying to do something to prevent SSOs.
Albert Gallaher also added that in some communities a regulatory approach tp the
SSO problem might be seen as a relief by some local officials. He used the analogy
.of a hammer coming down from outside sources and explained that the hammer
gives the local official some power to enforce. When something is regulated, there
is a shift in how a program is perceived.
David Crouch expanded on the issue of the local official, noting that
regulators need to take into consideration the local officials and the politics of their
administration as well as the budget limitations they face. Sewer system managers
need to counsel local officials about the importance of avoiding dry weather SSOs.
Roy Orkin rephrased his question to focus on the hammer and asked whether
the hammer of regulation should be coming down on the collection system owner or
the NPDES owner. The workgroup had not discussed that aspect of the issue but
Rick Arbour gave an example from Minnesota, which has CSO requirements. He
stated that when there is no CSO requirement, nothing in NPDES requires reporting
or enforcement, so the owner of the source of the inflow is not in violation of the
Clean Water Act. He noted further that the hammer should have some power and
that there is a need for regulatory reform.
Rick Arbour also cited that the members of the workshop, their colleagues,
and the Agency have a responsibility to make a concerted effort to help elected
officials understand the nature of the SSO problem and how to make effective and
educated decisions about where to start solving the problems. Collection system
managers and consultants need to start developing good data and understanding
more about the consequences of ignoring preventive maintenance activities.
Q4: Did the group discuss the specific structure of a typical preventive maintenance
program?
2-6
-------
A4: The group came to a consensus that it was more important to establish a preventive
maintenance structure and to assist communities in understanding the need to '
develop a preventive maintenance plan. Since each community and collection
systems varies, it would be difficult to develop the general elements of a preventive
maintenance plan. ,
Following up on this idea, Reggie Rowe asked how it would be possible to ,
determine the adequacy of proposed preventive maintenance plans. In response, it
was suggested that since communities vary so much, any justification or approval of
the plan needs to come from a regulatory agency.
Q5: Keith Benson suggested that enforcement agencies reevaluate the need to apply
fines, since the fines only serve to take away resources that otherwise could be
allocated to solving the problems. ';'.' .
' f " '
A5: One workgroup participant stressed the need to give state and local governments the
flexibility to impose fines and negotiate with those companies being fined. He
shared the.example from Ohio where some cities have been to set allowable goals.
In one instance, a company was subject to larger fines according to the books, than
what was actually imposed. This allows the state to recognize/reward those
companies that try in earnest to comply and make good faith efforts towards
implementing preventive, maintenance programs. This question opened up a
discussion on the value of fines. Some individuals felt that fines we, re necessary as
a wake up call, or as a negative incentive. Others were in agreement that fines were
needed to jump start any type of preventive maintenance program.
Mr, Benson acknowledged the importance of fines, but noted that the fine
' will only be passed back to the rate payer. In response to that, one individual noted
that the fines also would be passed on to the rate payer if the system were to go into
decay. '
Q6: How does a regulatory agency view a collection system? Is this part of the problem
with asking officials and community boards to focus attention on the need for
preventive maintenance for the system as a whole?
A6: The general consensus was that in most cases the agency focus is on the treatment
plant facility. Even when licensing requirements are in place, no stringent
involvement is required of the licensed parties. No priority is placed on allocating
money for a preventive maintenance program, because its value has not been
recognized. In addition, licensed parties are not required to provide annual reports
or inspection records. .
2-7
-------
Further, the group felt that agency inspectors do not really understand how
the collection system as a whole-functions. The question was raised that perhaps the
agencies should be required to write permits for the entire collection system as
opposed to simply permitting the treatment plant. This might help agencies to
understand the need to maintain the entire system. One participant noted that in
New Jersey, where the state agency does not have enough staff, treatment plant
inspectors only examine the terminal manhole and the pump station records.
This discussion then expanded into the area of agency training. Some
participants suggested training agency staff on collection system operations and how
the systems decayed to then* present state. This training might also include a brief
overview of how blockages and grease affect flow as well as how poor or ongoing
construction affects the system operations.
One participant tied the discussion of training to the question of how much
money is actually spent on O&M. He noted the importance of making agency staff
aware that on average the cost of O&M is less than one hundredth of the value of
the system. This makes O&M costs an easy target for cuts in the collection system
budget. The workgroup discussed this issue and felt very strongly that sanitary
sewer collection systems should be insulated from the political process and run more
like a utility or business enterprise.
* i1 .','', '
*' *
Q7: Mike Wallis asked the group about guidelines currently available on O&M. ,
\ ' *.'.,' , i
. i , ' ' - ' - . - , \ , ' ',
A7: Albert Gallaher mentioned the California State manuals and suggested that manuals
like these be refined and updated on a regular basis. Such documents could be used
as a standard reference or as part of a tiered training. Another participant suggested
that training and education specifically for system operators was a priority. He
suggested using videos, and training operators on how to operate equipment.
Participants felt that this type of training should be ongoing, and that the role of the
professional organizations should be examined with respect to specific training
needs.
* , ,''('
Another suggestion involved developing a nationwide clearinghouse. This
would be useful because a lot of systems are not currently under administrative
order, and information on these systems and their successes should be made
available. Some participants cautioned that focusing too much on training often
does not leave enough time to get actual work done.
Richard Field also suggested a number of references developed through an
old Wastewater Research Program. These potential references include APWA
documents:
2-8
-------
Control of Infiltration/Inflow hito Systems; , '
'',-'"-.' / : . " '" ' '*'
Manual of Practice for Prevention and Control of Inflow into Systems;
and.. - . . ' . "-- ..'..-;'''.'. / , . ;
' Sewer System Evaluation, Rehabilitation and Construction Manual
(this document is even 7 years older than the other two).
Kevin Weiss mentioned that John Golden is compiling a listing of available
resources and needs input from individuals like those at the workshop. Gordon
Gartner also mentioned that the AWPA has focused on the Best Management
Practices for maintenance of sewers and drains and for developing a self certification
process. For the second area AWPA has focused on identifying elements necessary
to develop a good certification program. The biggest problem that AWPA has had
with developing this self certification program is determining just how much weight
a certification from a professional organization should carry in the industry.
To conclude the session Buddy Morgan reminded the group that regulations
have been on the books for a number of years and that the problem does not lie with
the regulators. He strongly encouraged collection system managers and consultants
to improve their dialogue with local builders and the general public and to increase >
their hands on experience with their systems. Moreover, he stressed the need to
educate local community boards about the importance of preventive maintenance and
the general operations of the collection systems.
2-9
-------
-------
CHAPTERS: WORKGROUP -#2 - PEAK INFLOW
Summary of Group Presentation and Q&A Session for Workgroup #2
Peak Inflow Evaluation and Rehabilitation
The charge of this workgroup was to prepare a comprehensive methodology plan for
inflow removal., The report was presented by Richard Nogaj of RJN Group, Inc. The
group determined that a comprehensive plan should include six essential elements: 1) data
gathering, 2) system modeling, 3) inflow source identification techniques, 4) inflow removal
guidelines, 5) a system for evaluating inflow removal success, and 6) estimated costs of
inflow removal. The group also identified five main areas for further EPA investigation:
1) quantification of inflow defects, 2) impacts of rainfall data on inflow projections, 3)
storm event (design storm) selection, 4) preventive measures, and 5) Mannings ("n") and
Hazen Williams ("c") coefficients of Friction."
A major theme throughout the conference was the need to clearly define the terms
.involved with SSOs. Several members of the group suggested that peak inflow and rainfall
induced infiltration were mutually interactive and might best be addressed together.
However, after a lengthy discussion, the group developed the following definition for peak
inflow for the purposes of then- workgroup.
Definition: Peak inflow is sewer system flow usually in direct response to rainfall
eventsj where system response (flow) is due to sources (defects) that activate almost
instantaneously to rainfall. !
The group agreed that this definition emphasized rainfall induced inflow as opposed
to inflow from tidal, estuary, or cooling tower sourqes. The group identified elements that
are always inflow sources. These included manhole covers, frame seals, and cone (corbel)
defects. The group felt that all "pipe to pipe" inflow sources could be divided into two
categories, public sector sources and private sector sources. The public sector sources
include catch basins, inlets, and direct storm to sanitary cross connections. Sources in the
private sector include downspouts; roof leaders; area, stairwell, or patio drains; open clean
outs; and foundation drains, sump pumps, and crawl space drains. Some of the non-rainfall
induced sources that are always inflow include cooling towers, tidal flooding, street wash,
and drains from creeks and rivers. The group also noted that inflow sources sometimes
include indirect storm or sanitary cross connections where the soil seam has become a void
(direct path). The workgroup noted that inflow is normally transmitted through "holes" as
opposed to cracks and joints. ,
Once the peak flow is^defined, the next step in developing a plan to reduce peak
flow is to determine what the "peak" flow is. - Since peak inflow cannot be monitored if the
system surcharges, it is difficult to measure directly. Therefore, a methodology should be
developed to project the collection system response to storm events that are too great to be
3-1
-------
monitored. In addition, information should be gathered on a larger number of monitored
storm events to help improve the reliability of any response'projections. The group
suggested that virtual rainfall data might improve the reliability of projections and they
included this under their recommendations for further EPA research topics.
The Six Elements of a Comprehensive Methodology for Inflow Removal
Data Gathering. In order to develop a system model to project peak inflow, one
needs to look at the existing system and gather as much hard data as possible for input into
the model. The data gathering can be accomplished through map reviews, interviews with
local operators, exhaustive studies of system records, and other investigative activities.
Additional information can be compiled by performing flow monitoring or rainfall gauging.
A parallel goal is to identify the data gaps in the existing information and understand how
those will affect the model.
System Modeling. To develop the model, one should review and select the most
appropriate type of model, either paper or computer based. The group agreed that this step
is essential. Part of the model input should also include characterization data such as the
soil conditions, elevations, slopes, capacity, connectivity of the network, and groundwater
information. Modeling is important to allow:
Prediction of system performance;
Prediction of effects of rehabilitation;
Identification of system hydraulic limitations (bottlenecks);
Prediction of future SSOs;
Conducting "what if scenarios; and
Ongoing collection system planning.
Modeling normally includes flow monitoring/rainfall gauging, physical inspection
data (from existing data/models) and source defect listings with quantified inflow. System
inventory is often supplemented with elevation data, slope data, and system continuity
checks.
To supplement the physical data, a system inventory should be performed. To make
the model as accurate as possible, the group unanimously agreed that calibration and
verification is essential, especially in light of the lack of research available on the
coefficients of friction for free flow (Mannings "n") and surcharge situations (Hazen-
Williams "c").
\ ' : ,.
Inflow Source Identification. The group suggested prioritizing the system to be
able to identify "worst" to "least" areas. The following criteria examined as a whole could
be used to help make such judgments:
3-2
-------
Unit inflow rate ("gpd/idm" approach);
Unit inflow rate in proportion to remaining system capacity; and
Existing information on SSO occurrence.
There was an indication that several members of the group had suggested that an
"equivalent length dimensional unit" was a more appropriate measure of I/I than the "unit
flow rate" suggested by the group. Information on this alternative method is included in
Appendix D. , .
In addition to these criteria, the group also stressed the need to perform field
techniques to identify inflow sources with critical aspects. Some of the routine techniques
include smoke testing, dye flooding, and manhole inspection, and building inspection hi the
private sector. The group developed a list of issues to consider when choosing each
technique. ^ ;
Smoke Testing. If the selected technique is smoke testing then the following
elements should be considered:
--.. dual blower or high intensity blower;
proper ambient conditions (low groundwater and no rainfall);
test single manhole to manhole segment at a time (300 ft); arid
always record "suspect" sources that have a likelihood of direct connection to
sanitary sewer, but dp not actually smoke, as candidates for follow-up dye
water flooding.
Techniques that deviate from these guidelines need to be substantiated with
independent tests hi the relationship between the smoke testing technique and the number of
inflow defects identified.
Dye Flooding. This technique is crucial as a follow up to smoke testing. Dye
flooding is generally used because with it one can:
test "suspect" sources that are "trapped" such as yard drains and roof leaders;
and
follow up the smoke testing to pinpoint and quantify the defects.
Factors to consider when performing the dye flooding to quantify defects include:
" take wier measurements and/or depth/velocity in sanitary sewer before and
after dye flooding;
observe dye water at outlets; and
3-3
-------
utilize dye in conjunction with TV inspection to pinpoint exact location of
defect or multiple defects..
Manhole Inspection: Another field technique that can be used is manhole inspection.
A number of steps can be taken when performing this technique to improve the
accuracy of the results, including:
perform full descent inspection; ,
use lamping lines during full descent to help locate routs, deterioration, and
debris as well as provide a guide for the TV;
ideally perform manhole inspection during wet weather conditions;
.',""*' ' '
use a trained eye since defects (i.e. frame seals) are not always obvious;
may help to use surface flooding or dye injection around manhole to locate
defect;
keep in mind that smoke immediately around a manhole during smoke testing
may indicate a defective frame seal; and
, " ' ' ' , i - -
may need to simulate how defects will activate after storm events.
Building Inspection. A fourth field technique that can also be used in the private
sector is building inspection, either internal or external inspections. Internal
inspections help locate foundation drains, sump pump connections, and crawl space
drains. They are used specifically in areas with basements. External inspections, are
sometimes conducted during smoke testing and crews must walk the backyards and
streets. External inspection are used to determine patio, area, and yard drains as
well as foundation drains.
In addition to the results gathered from field techniques, there are some additional
factors to consider when quantifying inflow. First, individual defects respond to rainfall
intensity and duration. Second, inflow responses from individual defects can be estimated.
Since most defects that emit inflow are glorified orifices, based on the head the quantity of
flow emitted to the system can sometimes be estimated. The group agreed that finding or
developing methods for accurately quantifying inflow is an area where EPA should support
further research. Improvements in quantification accuracy can be coupled with improved
accuracy in flow monitoring. The flow monitoring data can also be used to "balance" the
sum total of source flow from quantified defects against the actual flow. Members of the
group differed in their opinions as to how much quantification of inflow is required to
eliminate SSOs.
3-4
-------
Inflow Removal Guidelines. The group agreed that inflow removal guidelines
would be useful, however, they did not discuss what specific elements should be included.
The group did agree on a three-tiered approach to inflow removal. '
Step 1: The first step is to remove all inflow sources that are obvious "Find It-
Fix It" defects." -/
Step 2: Some group members felt that after the "Find It-Fix It" repairs have
_been made, the defects should be quantified as a target for setting
4 removal goals. If no removal goals are required, then quantification
may not be a high priority.
Step 3: The third step in the process is to identify the appropriate removal
'techniques. , .
Evaluation of Inflow Removal Success. After inflow sources have been identified
and removed, the next element of a comprehensive program is a plan for evaluating the
success of the correction activities. The evaluation should be both qualitative and
quantitative in nature, in order to help manage the system as a whole. In addition, the
group advised keeping an unrehabilitated area as a control area for comparison purposes.
The group agreed that monitoring is an effective tool to help evaluate collection
systems. Specifically, post rehabilitation flow monitoring is essential to develop ah
effective evaluation methodology. Three additional evaluation methods include: (1)
recording changes in frequency and duration of SSOs, (2) requiring effectiveness testing by
rehabilitation contractors to ensure the integrity of individual repairs, and (3) utilizing
pump station and treatment plant meters or event recorders. The group also suggested that
using unregulated stream flow records rather than rainfall could be an effective alternative.
Post Rehabilitation Monitoring. The group identified a number, of elements that
should be considered when performing or planning to perform post rehabilitation
monitoring: ' '
match manhole locations for pre- and post- rehabilitation monitoring;
match seasons and groundwater conditions;
continue and follow up with rainfall monitoring;
meter as required, with either temporary or permanent flow meters;
apply existing evaluation techniques before and after analysis.
Cost of Inflow Removal. Another charge to the workgroup was to develop cost
estimates both for identifying and removing inflow sources. The group estimated
'. '''- ' V -':, 3-5. ' - ' , . .--
-------
identification program costs, but concluded that further research was needed to develop
nationwide guidelines for actual removal costs. Exhibit 3-1 presents the estimated program
costs for source identification proposed by the workgroup.
EXHIBIT 3-1
Estimated Costs for Inflow Source Identification
Technique
Flow Metering/Rainfall Gauging
Modeling
Smoke Testing
Manhole Inspection
Dye Flooding/TV
Building Inspection (internal)
TOTAL SYSTEM
Cost/unit
$50 - $150 per meter day
$0.05 - $0.25 per foot
$0.20 - $0.40 per foot
$50 - $100 per foot
$100 - $1,000 per set up
$40 - $70 per building
$0.50 - $3.00 per foot
Recommendations for Further Research
' The group identified a number of areas where further research is necessary:
Quantification of inflow defects including best removal methods, life cycle of
repair, migration potential, and best identification methods.
I
Impacts of rainfall data on inflow projections including virtual rainfall data
and depth/velocity scatter graphs.
Storm event (design storm) selection including ambient (antecedent)
conditions and rainfall/inflow projections and allowable frequency of SSOs.
Preventive measures for preventing future inflow defects from entering or
reentering system.
1 . . . '*.
Mannings ("n") and Hazen Williams ("c") coefficients of Friction.
These issues are discussed in more detail in Chapter 8, Research Needs and
Recommendations.
3-6
-------
- Summary
The methodology addressed in this summary has been proven to be effective in
identifying,and removing inflow and in reducing SSOs after sewer system / .
rehabilitation/relief sewer construction. Additional research needs were identified to
improve the prediction accuracy of several components of the methodology. These
additional research needs would enhance the prediction methodologies, while recognizing
the numerous success stories that have been documented using the existing methodology.
Question and Answer Session for Workgroup #2 '-'
Following the presentation, participants raised, questions "about costing, metering, and
modeling issues. ;
Ql: Ralph Petroff asked what happens when removal activity involves taking storm
water out and putting SSO into the stormwater sewer. His concern was that the
" sump pump goes overland and may create icy conditions in the certain areas.
Al: The group indicated that each municipality would have to deal with that issue
individually and emphasized performing comprehensive removals. The group
- discussed whether or not the associated costs should be included as part of the
removal cost. , . .
Q2: Buddy Morgan inquired when an inflow source is not cost effective to remove?
A2: A participant hi the group indicated that inflow removal might not be cost effective
when the defect is from a foundation drain in an 8-foot deep basement. Buddy
responded that if basements are involved then there might be a need to bring in the
individuals that deal with stormwater.
Q3: Another topic raised by a number of participants was the nature of the flow metering
suggested in the group's plan. Some individuals questioned whether it was
necessary, for permanent meters to be installed.
A3: The group had discussed the issue at length and felt that the decision to pick
permanent meters over temporary meters depended on a number of factors including
the size of the system and the needs of the community. They stressed that for the
program the group,had developed they did not intend to make permanent metering
mandatory, nor to imply that permanent meters are necessary. They concluded that
flow meters arc an effective measuring technique, but a program should not require
permanent meters.
3-7
-------
Q4: Another participant asked if it was ever appropriate not to do system modeling.
A4: Henry Gregory mentioned that hi smaller communities it is not cost effective to
develop computer models of system response. The smaller systems simply can not
afford to model on the computer all of the time. In fact, he added that modeling on
the computer often does not solve their problem. The group seemed to agree that
then* use of modeling referred to models both on computers and done by hand. The
group felt that for very new systems or for very small systems computer modeling
was inappropriate.
Q5: Following up on the issue of modeling," another group member asked if there were
any alternatives to modeling.
'." ^ ;',." .." ; ^ ».... " .'"'.' \ ,
A5: The general consensus was that the "Find It-Fix It" method was appropriate for
infrequent SSOs.
V . ','..' .
Q6: Lam Lim also raised the issue that peak flow is not a hew concept and the
techniques mentioned hi the group's plan are not new either. Specifically, he
questioned why inflow sources have not been eliminated if we have already been
applying these techniques.
A6: The group answered that every time these techniques are applied it is in a different
place with individual limitations. Sometimes the techniques have been applied using
short cuts because of low funding. A general consensus seemed to indicate that
although the techniques and methods are available, they have not always been
applied or evaluated systematically.
3-8
-------
CHAPTER 4: WORKGROUP #3 - RAINFALL INDUCED INFILTRATION (RII)
""..''"'- ".
Summary of Group Presentation and Q&A Session for Workgroup #3
Peak Rainfall Induced Infiltration Evaluation and Rehabilitation
Mike Wallis presented the report for the workgroup and began the presentation by
defining rainfall induced infiltration (RII) and how it relates to areas the other groups at the
workshop focused on. The group developed the following definition:
Definition: RII is stormwater entering a separated sanitary sewer system through
defects in manholes, mains, laterals, or private service lines. RII peak flow
characteristics are similar to inflow. However, inflow is considered, a separate and
distinct^source from RII.
-. ' . «--' ' ~
The group developed a methodology to quantify RII and select appropriate SSO
control options. The group felt'that it was essential to incorporate their methodology with
the issues that each of the other four groups were handling. They noted that interaction
with the other groups is required in order to develop a cost-effective SSO control program.
They identified two key elements that should or ;can be Used to help identify and control
rainfall induced infiltration:
(1) Modeling; and '
(2) .Field Work.
The methodology developed by the group is summarized in Exhibit 4-1, which connects the
model with the field work and illustrates the interdependence of mis group with each, of the
other groups. ._.".
- " ' ' . " - /
This model shows the relationships between the groups and indicates the importance
of continuous interaction between the field work data and the modeling process. Each of
the four main sections of the model describes how the group addressed the specific
objectives and key questions described* above. The group's model included four steps:
(1) Monitoring and assessing peak flow; ,
(2) Determining the extent of RII; '
(3) Identifying sources of RII; and '
(4) Developing options and associated costs to control RII.
4-1
-------
EXHIBIT 4-1
R II Methodology
Group 1 ^N Mtlntermnca ^
' Patterns
Inflow
Private Property
I/I Condltons
Records of
I/I Source*
^ Overflow . ^
Control
Options
Malntananoo
Practices
Monitor/Assess Peak Flows
Rll
Extent of Peak R!l
Sources of Peak Rll
Options to Control Rll
Costs to Control Rll
Field Work
9 Smoke Test
Dye Rood
Building Inspection
MH Inspection
Flow Isolation
Rainfall Simulation
TV
Vacuum/Pressure Test
Work Groups
1-Prev«nflve Maintenance
; 2-P*ak Inflow ' '
3-PeakRII
4»Privato Property
6=OV9rtlow Control Options
4-2
-------
Monitoring and. Assessing Peak Flow. The group determined that the first step in
the process to control RII is to assess the extent of RII in the system. This could be done
using .flow and rainfall rnonitoring and developing hydrographs and rainfall hyetographs for
actual events. Several members of the group suggested that RILmight.be better addressed
by using unregulated long term stream flow records. This could eliminate the need for
monitoring fluctuating ground water condition. The group could not reach agreement on
this approach and suggested additional research was needed. The group unanimously
agreed that the most cost effective and reasonable action is to undertake inflow
investigations first. The investigations and correction activities for inflow removal are
significantly less expensive than the investigation techniques for RII.. The group also
cautioned that while it is best to remove inflow sources first, inflow corrections can result
in an increase in RII when the stormwater is redirected to the ground surface where it may
eventually enter defects in mains, lower-laterals, or private service lines.
If the source is determined tp.be inflow, this is the best case scenario and~the
methodology for RII removal could be applied to the inflow; The,group indicated that for
the purposes of the workshop, if the source was determined to be inflow, then the problem
should be solved by group 2. Further if the source turned out to be inflow on a service line
in the private sector, then they deferred to group 4. Additionally, the group recognized that
the input of group 1 regarding improved preventive maintenance strategies would be
effective and useful both at the .beginning of the process as well as throughout all of the
steps. " . . -. ' ' .
Determining the Extent of RII. In order to determine the extent of RII, peak RII
must be differentiated from peak inflow. The major benefit of such differentiation is that
the cost to correct, the sources of peak inflow is substantially less than the cost to remove
RII. The same field techniques can be used to gather data to help with the differentiation.
The group investigated two methods for gathering data:
Flow Monitoring. Flow monitoring data can be used to help distinguish between
the two sources. One distinction should become apparent when looking at data for
areas with distinct dry and wet seasons. In such cases, zero antecedent- soil moisture
indicates inflow or a minimal response to rainfall. Conversely, the presence of
.antecedent soil moisture results in a higher response to rainfall. The difference
between the two responses is RII.
-"'".- " . ,
Other considerations for the flow data are. that for the use of flow projection
in hydraulic modeling, there is no benefit or need to distinguish RII from inflow at
this point. There is, however, a need to develop a method for estimating' the volume
and rate of upstream SSOs. Additionally, the group noted that fluctuating
groundwater conditions are important and expensive to measure in the field.
Physical Inspection Data. Physical inspection data should be used as input for the
..-'.: 4-3 /. . . . .
-------
model. This type of data can be acquired by using either smoke testing, manhole
inspections, flow isolation, dyed--water flooding, and rainfall simulation. Television
inspection, vacuum and pressure testing, and. building inspection also provide
alternative sources of field data. The group added that it would also be useful to
review maintenance records for blockages, collapses, and pipe materials.
. . ' : . . r . "''. '.',.., ..'',' ;...>. v . - ,
,,;; , : .. . ,_,,_; ' . , ; i .: : t. .' . ;, " ',
Sources of RH. The group identified four main types of RII sources. .They
suggested that investigations to determine which source is responsible for the overflow in
each situation should involve working with maintenance crews and reviewing records of
inflow and infiltration sources. The sources of RII identified by the group include:
, , ' 'i, " ,' , " ' , ' '',;_,,,', , ' ,
All manhole, and pipe defects from mains to lower laterals and private sector
service lines;
Stormwater percolating mrough the soil to reach the defects;
Leakage from storm sewers hi common trenches with sewers; and
* ' ' .. '.'.'', j - '; ' f ' '.:.'.', .' .
Leakage from sewers crossing drainage channels or placed within drainage
ways or in parallel to drainage ways.
« Options and associated, costs to control RII. After identifying the sources of RII,
the group then identified a number of options to control RII and developed rough cost
estimates for these options. These estimates can be used to help determine whether it is
be,tter to apply a transport/treatment/storage solution or to perform rehabilitation techniques.
The group noted that if the treatment option is selected, then it becomes part of the issues
dealt with in group 5. In addition, the group indicated when decisions are made regarding
ways to control existing RII, it is an opportune time to consider long-term maintenance
practices and incorporate actions recommended by either group 1 or group 4 that would
facilitate less overflows or better monitoring in the future on both public and private sector
service lines.
The group emphasized that the level of SSO control required is governed by local
conditions, and that any eventual SSO policy or guidance should be flexible and allow for
local definition of the level of control required. The group recommended that to achieve a
70 percent reduction of peak inflow and infiltration, a comprehensive rehabilitation program
should include mains, lower laterals, and private service lines. A program that needs "less"
of a reduction, maybe 30 to 40 percent, may only need to include rehabilitation of mains
and lower laterals. The group noted that a method for determining the effectiveness of the
rehabilitation should also be put into place. Further, they recommended that EPA perform
additional research on ways to determine rehabilitation effectiveness.
; t '.'''' v' .'''' '" ''' "i!" ' ' " '' .: ,'' . ;
The group suggested five steps to help determine the cost effectiveness of each
rehabilitation option and to facilitate the decision making process:
. ' . . . . i ,. ...,*.'" .1. ',.!,.
; , ; 4-4 ' ' ' '
-------
(1) Project overflow volume and'rate;
(2) Assess water quality impacts; ,
(3) Define level of SSO control required based on local conditions;
(4) Develop engineering solutions for the selected control levels; and
(5) Develop the most cost-effective alternative.
;-' - Summary
Chris Kahr concluded by summarizing the group's consensus that in the hydraulic
modeling process, there is no benefit or need to differentiate between RII and, inflow. The
distinction is important later, when it comes tune to choose a control option and the
associated cost;becomes a significant factor. .
Recommendations foe Further Research
The group also recommended four areas where EPA should undertake further studies
and develop technical guidelines:
Flow Projection Methodology;
Effectiveness of Rehabilitation Approaches;
Future Engineering Design and Construction Practices; and ,
Use of unregulated long term stream records instead of monitoring
groundwater conditions as an alternative approach for calculating RII.
Each of these areas is discussed in more detail in Chapter 8, Research Needs and
Recommendations.
Question and Answer Session for Workgroup #3
Ql: One participant commented on the inclusion of private sector lines in the group's
model and asked if that implied that the group had come to a consensus that private
property issues were a major issue to be addressed?
Al: - The group explained that they had concluded that private property issues needed to
be looked at, but.had not discussed whether or not the private service lines were a
major source of inflow or RII. ,
Q2: Richard Nogaj commented on the field techniques listed on the group's diagram
siting that building inspection and other techniques were not explicitly mentioned.
He inquired as to whether this implied mat they were not appropriate for RII?
A2: The group responded that the flow diagram only included a sampling of the field
; '.. ' ' 4-5 - * .
-------
techniques available to identify sources. Other techniques are certainly appropriate
everi if they are not included on-the diagram itself. The diagram's emphasis is on
the need to have continual interaction between the data gathered from field work and
the development of an accurate model.
Q3: Following up on the question about techniques another participant noted that the
techniques for identifying RII were similar to those used to identify inflow.
; Specifically, he asked if the group methodology could be applied to inflow.
A3: Henry Gregory reminded the group that all five of the workgroup areas were
interconnected and encouraged that a goal of field work should be to inspect for RII
and inflow at the same tune. Mike Wallis added that the model was intended to
apply to both RII and inflow. The first step of the model implies that the field work
should be used to monitor and assess the peak flow and determine whether it is
inflow or RII. If it is inflow, then the rest of the methodology still applies even
though there will be different options and associated costs for the removal of inflow
sources as compared to RII. The data gathering and model development process in
general applies to both inflow and RII. The distinction results from the specific
options and costs included in the model since inflow sources are cheaper to fix than
RII sources.
Q4: Will cost-effective analyses be built into this methodology?
A4: Yes, eventually. The group will investigate this area further.
Q5: Is one objective of this methodology to ensure that we do not overlook RII as a
potential source as we have done in the past?
i. I » , . .- , ; . f
A5: Yes. This question instigated a discussion about the need to be able to distinguish
inflow from RII for communication purposes. The group indicated that there is a
basic definition problem. Henry Gregory recommended that EPA establish standard
definitions for. these terms. Ralph Petroff asked if the group had determined a way
to differentiate inflow from RII. Mike Wallis responded that one way to attempt to
make this distinction is by using field work to determine the inflow sources,
addressing these sources, and then declaring the rest of the problem RII. He
recommended smoke testing as the inexpensive methods to gather all information.
Richard Nelson added that RII and inflow can not be differentiated based on
hydrograph or by examining the SSO as it occurs. He stressed the need for field
work as a tool to help determine and quantify sources.
n '!' ' i ii ' ' i , l ,, -'',"'' ,. ' ' ' >. '
Q6: Henry Gregory questioned whether smoke testing would take into consideration
ground water issues that are associated with coastal locations such as Miami? He
added that smoke testing will not help individuals in these areas to identify the
defects.
4-6"
-------
A6: Mike Wallis clarified that smoke testing is One option; the model presented does not
suggest using any method independently. Appropriate field methods should be used -
in conjunction with one another. Chris Kahr added that the group consensus .was
that the goal is to identify inflow from the start. There is a need to continue with
the proposed steps only if you suspect RII is present. The method used in box 1 of
Exhibit 4-1 does not solve for RII, it identifies inflow sources. If inflow sources
turn out to be the only problem, then that is the best case scenario and there is no
need to continue to model and try to .control RII.
Q7: Allen Hollenbeck then asked if creating a division between RII and inflow confused
the education process? "
A7: ~ Mike Wallis responded that there is a significant portion of rainfall dependent flow
that comes through numerous leaks along the links of pipes and laterals that can not
be fixed using a point by point fix to get flow reduction. Making this distinction
may confuse the education process, but it is essential to help make the cost-e'ffective
decisions surrounding which removal options to choose to reduce flow.
4-7
-------
ii'itliilll ;:: '
't
-------
CHAPTER 5: WORKGROUP #4 - LATERALS
Summary of Group Presentation and Q&A Session for Workgroup #4
Maintenance and Rehabilitation of Building Sewers Located Inside
Private Properties
The workgroup examined the issues surrounding SSOs due to defects on laterals on
private property. They discussed several issues, including determining where responsibility
for maintenance and rehabilitation of such service lines lies, and exploring the role that
public education plays in the proper management of collection systems. T.R. "Buddy"
Morgan, presented the reportout for the group. He began by presenting the following
working definition for laterals.
Definition: A lateral is a service line from a structure to a sanitary sewer
conveyance system, including all appurtenances attached directly or indirectly.
The group outlined the following eight areas that need to be addressed when
examining the problems surrounding laterals:
- " ' /- '
- Social and geographic ramifications;
Education;
-.-' Economic issues; "
Legal issues; ,
- Politics; ,
-l Health impacts;
Enforcement and inspection; and
- Technology. ./
Social and Geographic Ramification. The group mentioned that one limitation to
their discussions was the absence of any participant from the northeast or northwest who
could provide insight into the problems associated with basements. The group felt that
geography and local issues were at the heart of the lateral issue. Each city or locality
draws the line of responsibility in a different place. Buddy Morgan presented two different
scenarios for where a city might draw the line. ,
He explained that in Alabama the private owner's responsibility for the sewer line
begins at the tap and continues to the house or structure. Since the managers of public
collection system-cannot control what the private homeowner puts into the systenv the
owner must take responsibility for that portion of the line from the tap to the house. In
other states, the cities take responsibility from the right of way (ROW) to the top of the
main.
5-1
-------
Education. The group stressed that the key element in any plan to deal with laterals
should be education of all the individuals involved. One of the reasons for emphasizing the
need for education, is that often the decision makers hi the states are not familiar with the
operations of a sanitary sewer system. Buddy Morgan gave the example of a recent «<
decision by the Mayor in Montgomery, Alabama, to move all sewer lines behind the curb
Hne. This requires that an individual on one side of the street dig up his own yard and his
neighbor's yard across the street in order to repair or rehabilitate any part of the private
service line. This example illustrates the need to educate and work with elected officials
who make decisions affecting the collection system.
The group also suggested educating the public using simplified examples describing
the Clean Water Act hi a comic book form (Sewerman). This would help explain the
impact of laterals on private property. It is important to educate citizens concerning what
impacts their activities could have on water quality. The group stressed the importance of
educating rural citizens as well.
Economic Issues. The group indicated that when identifying and controlling SSOs
on private property, there was a need to be concerned with the economic issues. The
general consensus was that laterals do not fail because of technology. The group noted that
laterals tend to have more problems hi older neighborhoods, where residents are on fixed
incomes or economically disadvantaged. Buddy Morgan outlined one way that
Montgomery, Alabama, handles this situation.
He described that repairs are funded in Montgomery to take into account the
economic situation of the individuals affected. As described earlier, in Montgomery the
section of the system from the tap to the house is considered privately owned. If during the
course of an inflow/infiltration study, a defect is found on the privately owned part of the
collection system, the private owner is sent a letter stating that the city will fix the problem
at a cost not to exceed $1,200. In addition, the city will provide an opportunity for the cost
of the repairs to be financed at a zero percent interest rate over a 4-year period. The city
does this because it places a priority on fixing and maintaining the system.
If the private owner chooses not to fix the problem, then they are sent a 10-day
warning letter which indicates that if the problem is not fixed within 10 days, the water will
be shut off. If after receiving this letter, the private owner still has not done anything in
response to either letter, the water service is terminated.
Further, if the lateral on private property causes a street failure and poses a health
problem, and the private owner cannot afford to make the repair, the city will make the
repair and charge the owner only the actual cost of the repair and allow the owner to
finance the payments at zero percent interest.
,, ' ' " '" ! i ''''"' i '' ',''*' , ' ' ' ' ' \'
Another issue that the group discussed at length, was the issue of how to fund
repairs on private laterals. Bill Sukenik brought up the issue that in Houston public bond
if . ' '.....'. , '. ; i' i . ' .. /'.
: ", . .. 5-2
-------
funds cannot be spent on private property. However, he emphasized that it may be possible
to allocate O&M funds to be spent for repairs on private property.
Legal Issues. The group also discussed the legal responsibility associated with
managing a collection system. The mam issue that the group addressed was going onto
private properties versus pressuring the private owner to take responsibility for the service
lines on his/her property. They discussed the question of how a collection system manager
can legally gain access to laterals on private property. Suggestions for methods to help
investigate private property include cameras, flow testing, and smoking machines. The
group cautioned that an initial pass with a smoking machine does, not reveal all the
problems; smoke testing is a repetitive process.
The workgroup concluded that there is no "one size fits all" solution. Specifically
Buddy Morgan described the situation hi Montgomery, Alabama, where the collection
system covers 1,000 miles of public land and connects with 1,500 or more miles where the
city has no control. He estimated that 90 percent of the problems occur on private land and
are due to problems such as missing cleanout caps and cracked pipes.
The group characterized a homeowner as a "city without an NPDES permit." This
is especially the case when the private land is used for more than just a single house. This
private land might contain apartments or a trailer park. Buddy Morgan suggested the
following approach to handling .such situations. The city, or homeowner without an NPDES
permit should have to report their average water consumption over 5 years. Based on that
figure and dividing by 12 months, the city should be able to determine a monthly allowance
for the owner. This type of program would incorporate a "pay to play" philosophy. This '
would, in turn, present the owner with two options. An owner could either decide that it is
more cost effective to deal with the inflow or infiltration problem individually, or that it is
more cost effective to pay the city to deal with any problems. This result of this process
would be to clearly define who the responsible party is before the problems arise.
Politics. The group realized that politics plays a role, but did not discuss specific
ways to deal with political issues. These will vary on a regional basis and collection -
system managers need to work in cooperation with community boards and councils and
elected officials. -
Health Impacts. The group identified this as one of the issues that needs to be
examined with regard to laterals on private property, however, they did not report out on
this issue.
Enforcement and Inspection... One part of the problem with laterals stems from the
way systems are permitted. Permits are issued only for Publicly Owned Treatment Works
(POTWs), not for the collection systems as a whole. To exacerbate the problems with
enforcement, often multiple municipalities each with their own lateral regulations use the _
same collection system.
. ' ' 5-3 '" ', '.-..';.- "
-------
The group agreed that hi order to have an effective enforcement program as well as
to be able to manage the collection system, each collection system needs to have a sound
inspection program. Buddy Morgan mentioned that Alabama required its inspectors to have
'a'Jjyiilding science degree because technology has changed so drastically. The inspectors
need to be able to understand^ the specifics of the collection system. One way to improve
the inspection program might be to reevaluate the certification process.
In addition to establishing an effective inspection and certification program, the
group felt that building codes and ordinances are necessary to ensure the conditions of the
sewer system. Specifically, it was suggested that municipalities adopt ordinances requiring
a lateral inspection at the time of sale of the property. The group recognized that the
constitutional issues involving property rights cannot be ignored. It is essential to educate
the public about the importance of lateral inspections and,build public support.
' " ' '" ' ' ' ' '". ' ' ! ' -. '''''.' "'" ' "'., '',"'' '' ' '.''
Technology. The group identified this as one of the issues that needs to be
examined with regard to laterals on private property. To illustrate the variety of techniques
-that could be used to identify and remove defects on laterals, the group presented the
following summary table. Exhibit 5-1 illustrates ten typical lateral defects, associated
inspection and identification methods, and recommended rehabilitation techniques.
EXHIBIT 5-1
Lateral Defects
Inspection/Identification
Methods
Rehabilitation
Techniques
lateral (building service)
smoke, dye, TV, pressure test,
sonic, and radar
replace,
point repair,
lining,
grouting,
sanipour
cleanout
smoke, dye, building inspection
- replace cap,
- riser pipe (brass/other
material),
- 2-way cleanout (for
older systems)
5-4
-------
EXHIBIT 5-1
downspouts and roof
drains
smoke, dye, building inspection
- disconnect and
reconnect to storm
- overland discharge
area drains
smoke, dye, building inspection
- disconnect and
reconnect to storm
- overland discharge
patio, driveway, window
well drains
smoke, dye, building inspection
- disconnect and
reconnect to storm
- overland discharge
foundation drains and
basements ;
smoke, dye, building inspection
disconnect and
reconnect to storm
overland discharge
treat foundation seal
sump pumps
dye, building inspection
disconnect and
reconnect to storm
overland discharge
purchase property
cooling systems
(blowdown sent directly
into the system may
contain solvents)
building inspection
disconnect and
reconnect to storm
Hammer taps, protruding
tap, break in the
connection
TV (educate the plumber and
coordinate)
- reinstate service tap
(exterior)
Abandoned building
(especially in
subdivisions) and .open
service laterals'
smoke, dye, building inspection
plug at main
In addition the group noted that Donna Renner Would submit the estimates for
- ' . '. /' - - 5-5
-------
costing each option at a later date. This information can be found in the workgroup report
in Appendix C.
Roy Orkin added that the group had also discussed the possibility of developing a
third agency for the private sector to borrow money from. The agency would lend money
specifically for collection system repairs required on private lines. He mentioned that other
avenues might already exist in the form of tax or credit incentives.
Summary
The group concluded by summarizing that inspection and education are essential.
They also agreed that if it could be avoided, no one wanted to be on private property.
However, defects in the laterals account for a-major portion of SSOs. Therefore, a
systematic approach to handle laterals must be developed and private owners must be
educated about those areas where they are responsible.
'.','. Recommendations for Further Research
The group also identified areas where EPA should focus future research or develop
materials. .These areas included the following:
li ' ' : ' ' ' ' - '
Case studies of programs and successes;
Educational material;
City take overs of laterals; and
Expanding enforcement options for NPDES owners.
,,, . I ', ' , , ,, , '..,.,,' ,..
These areas are described in more detail in Chapter 8, Research Needs and
Recommendations.
Question and Answer Session for Workgroup #4
Ql: Richard Field asked who is responsible for the connection point when it is affected
by traffic loads, especially since this loading will continue after the repair?
Al: Buddy Morgan responded that the answer will vary depending on how the city has
drawn the lines of responsibility. If Ihe city is responsible only up to the Y, then if
the Y has collapsed, the city will make repairs; otherwise, it is the private owners
responsibility. If mis occurs in a city that is responsible from the top of'the main to
the ROW, then the city would be responsible for the lateral that failed and must fix
it. He added that the situation will vary depending on how the boards are set up in
a municipality. The cost of repair will vary also depending for example on how
deep the affected lateral is in the ground. The cost may range from $3-4,000 to
$18,000.
' ' . . 5-6
-------
Henry Gregory added that in Houston, as in Montgomery, the city found a lot
of defects in the laterals. Since they did not have access problems, the city fixed the
defects.
Q2: Is there a way to remove the cultural barriers that may arise when public money is
spent to remove defects on private laterals?
A2: The group response indicated it is essential to educate the public that the alternative
to not fixing the defect at the private lateral is much more expensive for everyone.
At this point Gordon Garner outlined two ways to look at the lateral issue.
He suggested that it can be seen as an I/I issue and as a customer service issue. As
an I/I issue, he cautioned: that we need to guard against the idea that the problem can
never be resolved if the, defect (i.e., a sump pump or basement drain) is on a private
property. He noted that this attitude will not solve anything because in the end any
flow that does not get fixed is eventually "owned" by the collection system when it
enters the system. The goal should be to gain a better understanding of this
phenomena and integrate it as a part of the design process,'so that when engineers
design an interceptor or treatment plant, they can make .realistic design assumptions
that take into account the quantity of flow that occurs because of defects from
private laterals. : :
As a customer service;issue, the industry needs to look at and understand that
crews currently cross a property line in efforts to help the customer. For example,
when the system floods private property on a regular basis due to geography, the
collection system managers need to provide some form of protection. Often, the
crews must cross the property line to install backflow preventers or other protection
devices. He introduced the concept of giving private owners the opportunity to pay
,up front, maybe $2/month, for the city to take care of the lateral on their property.
Then there would be no legal battle with the public, although it might cause, a battle
with the plumbing community.
Buddy Morgan suggested a strategy for working cooperatively with the
plumbing community. The city can ask the plumbing community to work with them
to provide a customer service. For example, an Emergency Response Plan might
include jpre-approved costs and rates, estimated times to repair, and a list of
materials used for numerous contractors. With this information, an individual can
call any of the contractors to make the repair. He emphasized that after the
plumbing repairs have been made, it is important to go back and inspect the repair
work.
Albert Gallaher observed that privatization has been occurring in O&M
practices for at least 30 years, but that it is a new concept for collection system.
management. ,
''"-' . '' ' ' ' 5-7 ' '
-------
practices for at least 30 years, but that it is 'a new concept for collection system
management. ''."'..
David Crouch emphasized the need to take advantage of both new
technologies and new concepts to reevaluate the construction process. If the city
owns parts of the service lines, then there are opportunities to look for ways to share
a common line or the cost of a common manhole.
He also added that there is a need 19 look at available surface area at the
treatment plant from open top tanks and drying beds. During an emergency
situation, it may be possible to divert that pipe flow from the headwork of the
treatment plant. * .
5-8
-------
'- * , - ' ' ' -
CHAPTER 6: WORKGRGIJP #5 - TREATMENT OPTIONS FOR WET
WEATHER FLOW
Summary of Group Presentation and Q&A Session for Workgroup #5
Proper Handling of Wet Weather Flows Remaining After I/I Control
Richard Field presented the report for Workgroup 5. He outlined the group's
approach to SSO control and observed that SSO can be controlled using the CSO control
methods since both SSO and CSO, are mixtures of municipal sewage and stormwater. The
difference between the two is that the average sanitary sewage to stormwater fraction is
higher for SSO,, The group focused on developing a cost effective solution considering
several demonstrated approaches available to handle and treat SSO. He noted that the
available approaches include taking some combination of: . '
Removing inflow;
Performing only cost effective sewer rehabilitation on a continuing basis;
Inspecting the interceptor and sewer system for blockages, siltation, and
pumping station and structural failures which cause SSO (clean out or repair
these as necessary);;
» Maximizing flow to the publicly owned treatment works (POTWs) by using
surge or storage facilities or increasing interceptor flow carrying capacity.
Maximizing POTW treatment capacity by retrofitting, installing parallel
process trains, or constructing new high-rate POTWs; and
Installing satellite treatment facilities.
He noted that the group unanimously recommended that the first three approaches
, must be performed in all cases; and an integrated economic and feasibility analysis using a
combination of maximizing flow to the POTW and maximizing treatment capacity must be
considered for controlling the remaining SSO. ,
He began by summarizing the group's discussions and some of the group's
recommendations for national requirements. Then he outlined the group's discussion with
respect to maximizing flow to the POTW, maximizing POTW treatment capacity, and
installing satellite treatment facilities. Then he mentioned the costs associated with the:
requirements and some of the references available. He concluded by suggesting two areas
for further EPA research and development.
6-1
-------
The group first addressed three issues:
(1) Design flows and volumes;
(2) SSO quantity and quality monitoring; and
(3) Quality aspects of the monitoring.
Design Flow and Volume. The group suggested that design flow rates and volumes
should be determined using long-term simulation, data analysis, and statistical modeling.
SSO Quality and Quantity Monitoring. They agreed that SSO quantity and
quality monitoring should begin immediately and be used in conjunction with the models,
either in the development of the model or to help improve an existing model. The
monitoring should also be used for calibration and verification purposes. Flow estimates
for, the future inflow/infiltration reductions (or., additions) should be subtracted (or added) to
design flow values.
Quality Aspects of the Monitoring. Monitoring samples analyses should include
particle settling velocity and size distribution and dissolved solids fraction as related to
pollutants of concern. In addition the group indicated that it is important to consider
correlating historical POTW quality data with rainfall records to assist in developing a wet
weather flow (WWF) quality database.
,, ' \ " '' i ' i ' '
The workgroup consensus was that no more than one to two SSOs per year should
be allowed into the, receiving water. However, about half of the workgroup recommended
elimination of all SSOs as a goal. Since the SSO event volumes and flow rates as well as
the long-term volumes and average flow rates are significantly lower than the comparable
values for CSOs, the group felt that elimination of all SSOs would be economically
feasible, but in the worst case allow no more than one SSO per year. The group also
recommended that suspended solids (and associated pollutants) removal by directing the
excessive SSOs through a storage facility should be considered.
* National Requirements (Policy and Standards). The group suggested that national
requirements for SSO treatment should combine of a technology-based approach with more
stringent human health and receiving water quality risk-based requirements. In other words,
if the applied treatment technology results in receiving water quality impairments, then
higher treatment levels would be required. Richard Field noted that exceptions should be
allowed based on the community's ability to meet certain criteria. For example, the
exceptions should provide:
No additional water quality impairment and no heath risks; and
'''',' -1 - - -l ' '
Economic affordability that would give the community a longer
compliance time without affecting the standard.
6-2
-------
EPA should develop affordability guidelines'and encourage compliance using a
granting mechanism. The technology-based approach should be based on national - ..
guidelines with the above exceptions. .
-.-'..'-,-. ' .:'' . i '- _ '. . ^
Maximizing flow to the publicly owned treatment works (POTWs). Maximizing
flow to the POTW can be accomplished by two basic methods: 1) utilizing storage
facilities, and/or 2) increasing interceptor flow carrying capacity. \
Storage facilities.. An important part of SSO control system planning is determining
the economic break-even point between the required storage volume and the
treatment capacity. The multi-purpose functions of SSO storage facilities should be
used wherever possible and include: *
- sedimentation treatment for excessive SSO;
dry weather flow equalization;
- flood protection; and
- sewer line relief. '..'",''
Sedimentation treatment in storage facilities can either relieve POTW solids
burden or remove, a significant pollution fraction of an excessive wet weather flow
which causes a storage facility overflow. If the storage basin is used for dry
weather flow (DWF) equalization, then it should be compartmentalized for DWF
capture to reduce sludge handling problems. .
The group noted that storage can be applied upstream, midstream, or down-
stream at the SSO point (either at the remote SSO location or at the POTW). They
, , also noted that upstream storage can sometimes provide the dual benefit of drainage
and flood relief/control. The types of storage recommended by the group included:
- , unused capacity in the existing interceptor and sewer lines;
conventional concrete tanks and lined earthen basins;
minimum land requirement tunnels and underground tanks; and
abandoned facilities. .
Additionally, new sewers can be designed to handle larger quantities of wet
weather iflow for conveyance and storage. Of these options, in-sewer storage .and
storage in abandoned facilities will be the least expensive and should, therefore, be
considered first. Earthen basins are also relatively inexpensive and should be
considered next.
Increasing interceptor flow carrying capacity. The group recommended the
following methods for increasing .interceptor flow:
increasing pumping capacity for surcharges interceptors; (Note: The
- ' '"" ; ' ' 6-3 ' '. , "-. '
-------
hydraulic gradeline should be'reviewed to determine the practical
amount of increased flow before increasing pump capacity. The
increased flow achieved may not justify the cost.)
removing any bottlenecks;
installing parallel sewers;
replacing existing sewers with larger pipes;
- lining pipes to reduce pipe roughness;
installing larger or parallel interceptors; or
- ' applying polymer injection liner to reduce pipe friction. (Note: Any
! economic analysis should incorporate the relatively short bench life for
polymer storage.)
Maximizing POTW treatment capacity. The group presented approaches to
accomplish maximizing POTW treatment capacity that included: 1) increasing hydraulic
loading to existing primary/secondary treatment processes, 2) retrofitting, or 3) installing
parallel process trains. ..
Increasing hydraulic loading. Increasing the loading to existing primary/secondary
treatment processes without modifications should be based on stress testing. This
method will be the least expensive and should be considered first.
Retrofitting. As another way to maximize POTW treatment capacity, the group
suggested retrofitting the primary settling tanks with plate settlers, chemical addition
, facilities, or dissolved air flotation (DAF). They noted that a designers should
consider an automated switching process for converting from settling during low-
flow to DAF during high-flow conditions to save power costs.
1 i
Installing parallel process trains. The group presented some examples of ways to
install a parallel process train. These included:
primary physical treatment;
secondary biological treatment for new POTW installations;
disinfection; and
natural treatment systems.
The parallel treatment process train effluent can either be discharged directly
to the receiving water, directed back to the existing POTW influent, or sent to both
by means of flow splitting. If the effluent is directed back to the POTW influent,
i ' , " ' .
6-4
-------
then a flow equalization basin could be needed.' The selection of a flow discharge
option will depend on water quality impacts and permit requirements.
Primary physical treatment. Options for primary physical parallel treatment
processes include microscreens; plate settlers; screening/dual-media high-rate
filters; DAP; conventional primary settlers; and if treatment efficiency
requirements are low, swirl degritters. Chemical addition should also be
considered. All of these processes; have been successfully demonstrated for
treating CSO.
'"-"'>" '"','-."-:'
Secondary biological treatment for new POTW installations. The group
recommended seven options for this type of treatment method, including:
(1) Contact stabilization during wet weather flow periods;
(2) Automatically switching to conventional activated sludge during dry
weather flow periods;
i " . , . i - -.-_.,,
(3) High-rate trickling filtration (deep honeycomb plastic media);
(4) Having two filters in parallel during wet weather flow periods that
automatically switch to series operation during dry weather flow
periods (series operation will keep the biological slime active and
improve dry weather flow efficiency);
(5) Rotating biological contactors (shaft-mounted rotating disks);
(6) Upflow biological aerated filtration (fixed film reactor); or
(7) Biological fluidized bed filtration.
The first two processes have been successfully demonstrated to treat SSO,
and the first and last three processes have been successfully demonstrated to
treat CSO.
Disinfection. If the existing unit cannot provide adequate disinfection, the
group recommended the use of parallel high rate disinfection processes since
these processes require smaller contact tank volumes. High-rate processes
that have been successfully demonstrated to work for CSOs include higher
dosing, static and dynamic (mechanical) mixing, the use of more rapid
oxidants, two-stage dosing, or combinations of these. Ozone and chlorine "
dioxide are relatively rapid oxidants and high intensity mixing is
accomplished by mechanical-flash mixers.: Slower static mixing should also
be considered. Adequate suspended solids concentration and particle size
.'.(''. ' ' 6-5 '-.''".' "'-'
-------
reductions are essential to accomplish a successful microorganism kill.
\ '
Natural Treatment Systems. The use of natural treatment systems to provide
some additional treatment of excessive wet weather flows should be
considered. Some examples of natural treatment systems include:
" ;J :' ,l , . --...> , ... . . " , . .
(1) Constructed wetlands; and
(2) Land application.
Other Considerations The group suggested that consideration should be given to
bypassing secondary treatment and just providing primary physical treatment and
disinfection. Any decision to select" this" option should be based on the receiving
water quality impacts and the BOD dilution in the. influent.
Consideration should also be given to innovative, advanced, and evolving treatment
technologies. The group did not expand further on this option during the
presentation.
Installing satellite treatment facilities. The group recommended that, if needed,
satellite treatment should only be implemented as an automatic physical process with
remote monitoring to reduce the labor requirements. Since maintenance issues will be
pronounced and potential failures and associated water quality impacts will exist at the
remote locations, physical treatment processes at satellite locations should only be used in
cases where the POTW cannot handle all of the wet weather flow. As described
previously, the satellite storage should be used for dual purpose of treatment by settling for
wet weather flow volumes greater than the storage volume. The group recommended that
satellite treatment should only be considered as a last resort.
Location issues, such as sensitive receiving stream segments* and neighborhood
aesthetics need to be considered as well.
Costs. The cost information for the options recommended by the group is available
in the report for Workgroup #5 in Appendix C.
Bibliographies. The bibliographic information for the options recommended by the
group is available in the report for Workgroup #5 in Appendix C.
Summary
In all cases, inflow elimination or reduction, cost effective sewer rehabilitation, and
collection system inspection (with associated clean out and repair) must be performed. The
selected treatment action should be part of an integrated economic and feasibility analysis
using a combination of maximizing flow to the POTW and maximizing treatment capacity
6-6
-------
for the remaining SSO. The group consensus was that these options are preferable to the
. use of satellite storage.
-.-: Recommendations for Further Research
The group identified two areas where further research needs to be performed in
order to help develop effective national requirements:
Demonstrate, improve, andsevaluate .emerging technologies; and
Determine particle size removal requirements for adequate disinfection by
various disinfection technologies, including ultraviolet disinfection.
... ... ,..,..,._, :-- (
' ' , ' - ft ' ; ' '
Question and Answer Session for Workgroup #5
Ql: Roy Orkin questioned the .group's comment that an acceptable number of SSOs in a
given year was only one to two events. r
Al: The group clarified that they were referring to one to two facility overflows, such as
discharges from a satellite treatment facility. ,';'.'
Q2: Roy Orkin also, questioned the group's technology approach and asked if the group
had considered a hydrograph control release program.
A2: The group had not examined that approach.
Q3: Roy Orkin followed up with a third question. He stated that based on his :
experiences and observations, after you get past the first flush, the inflow acts like
rain water. Was any consideration given to developing a lower level, of NPDES
permit to address a secondary or tertiary treatment requirements. - - . '
A3: There was no consensus in the group about establishing lower level NPDES permits.
The group had addressed technologies at various different treatment levels on a case-
by-case basis. Kevin Weiss added that the group.had recommended that greater
emphasis ;be placed on the frequency of the discharge as opposed to the
concentration of the discharge. The group also agreed that priority should be given
to getting the flow to the existing POTW facility.
Q4: Did you consider seasonal variation?
A4: Seasonal variation was not a main focus of the group's discussion, but the group
recommended basing disinfection practices on the current events in the sanitary
sewer system. Herb Kaufman added that the group addressed this issue by placing a
.- . : '''' 6-7 " ..-' . - . '
-------
priority on maintaining the existing uses of'receiving water. The receiving water
uses may vary regionally or seasonally, but the group felt it was essential to
maintain the existing uses of the receiving water. ,
Q5: S. Wayne Miles emphasized the importance of the group's recommendation to focus
on long-term continuous simulation in sizing storage facilities. He stressed the need
to look at rainfalls over 40 to 50 years to take into account the yearly fill. The use
of a single design storm does not take into account constant fill. Herb Kaufman
. , added that stream flow may, in fact, be a better design criteria than rainfall.
Q6: One participant questioned the group's recommendation to perform only cost
effective maintenance regularly - is this a caution to keep the regulators from
requiring things?
A6: Lamont Curtis suggested that the group was referring to cost effective rehabilitation
not cost effective maintenance. Maintenance should be routine. Herb Kaufman
added that there is a need to define the phrase cost effective I/I method. Another
participant emphasized that cost effective does not mean easy. Albert Gallaher
concluded the session with an observation that one way to define cost effective is
that it equates to intelligent management.
6-8
-------
CHAPTER 7: SUMMARY A~ND CONCLUSIONS
. The U.S. Environmental Protection Agency (EPA) is currently addressing the need
for additional technical data on the issues surrounding sanitary sewer overflows (SSOs). This
report summarizes the results of an EPA-sponsored workshop on SSO technical issues held in
Washington, DC, April 26-28, 1995. The workshop comprised five workgroups, each of
which focused on a specific topic:
. 'Workgroup-1: Preventive Maintenance
Workgroup 2: Peak Infl6w
Workgroup 3: Rainfall Induced Inflow (RD)
Workgroup 4: Laterals
Workgroup 5: Treatment Options for Wet Weather Flow
Each workgroup met in small discussion groups during the 2 days of the workshop,
and the workgroups presented their findings to the entire workshop during a summary
session. The conclusions summarized in this chapter are based on the workgroup
presentations and the workshop discussions following each report.
Workgroup 1: Preventive Maintenance
Participants from the preventive maintenance workgroup emphasized that the sanitary
sewer industry should be managed as an enterprise operation, and they outlined guiding
principles for the industry. These principles stressed the need for systematic implementation
of operation and maintenance (O&M) programs, preservation and protection of infrastructure
investments, a concise inventory of the infrastructure, O&M staff involvement and input
during all stages of the process, and cooperation between federal, state, and local
organizations. In addition to these principles, workshop participants identified four elements
of an effective O&M program:
(1) Education;
(2) Program development and implementation;
(3) Local enforcement; and
(4) Clearly defined roles for regulators and professional organizations.
Participants generally agreed that educating the public about the need for and benefits of
preventive maintenance is the most important element. Workgroup participants also
suggested.developing:
; Performance and evaluation criteria; :
_."'.. Standards for debris removal O&M activities;
.-'-.... A national clearinghouse for program successes in O&M; and
Educational materials for the public and elected officials.
7-1
-------
Workgroup 2: Peak Inflow "
The workgroup designated to examine peak inflow issues developed a definition of
peak inflow for the purposes of the workshop, emphasizing that peak inflow includes rainfall
induced inflow as opposed to inflow from tidal, estuary, or cooling tower sources. They
defined peak inflow as sewer system flow in direct response to rainfall events, where system
response (flow) is due to sources (defects) that activate almost instantaneously when rainfall
occurs. ;
The workgroup also developed a methodology for predicting a collection system's
response to storm events too great to be monitored. Workshop participants agreed with the
workgroup that a comprehensive methodology should include six essential elements:
(1) Data gathering;
(2) System modeling;
(3) Inflow source identification techniques;
.(4) Inflow removal guidelines;
(5) A system for evaluating inflow removal success; and
(6) Estimated costs of inflow removal.
This methodology has proven to be effective hi identifying and removing inflow and hi
reducing SSOs after sewer system rehabilitation and relief sewer construction.
Workgroup participants also suggested that EPA undertake further research on:
Quantification of inflow defects;
Impacts of rainfall data on inflow projections;
Selection of storm events (design storm);
Preventive measures; and
Mannings ("n") and Hazen Williams ("c") coefficients of friction.
Workgroup 3: REE
RII workgroup participants defined RII as stormwater entering a separated sanitary
sewer system through defects in manholes, mains, laterals, or private service lines. While
the peak flow characteristics of RII are similar to those of inflow, the workgroup agreed that
inflow is a separate and distinct source.
Members of the RII workgroup felt that the RII quantification methodology must
incorporate preventive maintenance, peak inflow, laterals, and treatment options if a cost
effective SSO control program is to be developed. Workgroup participants identified
modeling and field work as two key methods for identify ing and controlling RII. The RII
quantification methodology presented to the workshop participants (Exhibit 4-1), connects
modeling and field work and illustrates the interdependence of RII with each of the other
1 ' . ' , !
. 7-2 " ' , '
-------
workshop focus areas. The workgroup's methodology included four main steps:
(1) Monitoring and assessing peak flow;
(2) Determining the extent of RII;
(3) Identifying sources of RII; and .
(4) Developing options and associated costs to control RII.
Workgroup participants agreed that in the hydraulic modeling process, differentiation
between RII and inflow is unnecessary until a control option needs to be selected and the
associated costs determined. The workgroup recommended that EPA further investigate:
Flow projection methodology;
The effectiveness of rehabilitation approaches;
Future engineering design and constructionpractices; and
, The use of unregulated, long-term stream records instead of monitoring
groundwater conditions as an alternative approach for calculating RII.
Workgroup 4: Laterals
Workgroup 4 focused on issues surrounding SSOs occurring on private property
because of defects hi laterals. Participants defined a lateral as a service line from a structure
'to a sanitary sewer conveyance .system, including all appurtenances attached both directly and
indirectly. Participants discussed where responsibility for maintenance and rehabilitation of
such service lines lies, and explored the role that public education plays in the proper
management of collection systems.
Participants outlined eight areas to be address when examining the problems
surrounding laterals: \ >.
(1) Social ramifications;
(2) , Education;
(3) Economic issues;
(4) Legal issues; . .
(5) Politics; .
(6) Health impacts; ,
(7) Enforcement; and
(8) Technology. ,
Participants concluded that inspection is necessary, although actions on private
property should be avoided if possible. Because defects in laterals account for a major
portion of SSOs, the workgroup felt that developing both a systematic approach for handling
laterals and a process to educate property owners about those areas for which they are
responsible is essential.
,7-3
-------
The workgroup recommended that EPA focus future research efforts on:
Examining case studies of programs and successes;
Developing educational materials, for property owners;
Exploring municipal takeovers of laterals; and
Expanding enforcement options for National Pollutant Discharge Elimination
System (NPDES) permit holders.
Workgroup 5: Treatment Options for Wet Weather Flow
Workshop participants noted that SSOs can be controlled using combined sewer
Overflow (CSO) control methods because both "SSOs and CSOs are mixtures of municipal
sewage and stormwater. The difference between the two is mat the average ratio of sanitary
sewage to stormwater is higher in SSOs. Workgroup discussions focused on developing a
cost effective solution considering several demonstrated approaches to handling SSOs,
'including some combination of the following:
(1) Removing inflow;
(2) Performing only cost-effective rehabilitation;
(3) Inspecting the interceptor and sewer systems;
(4) Maximizing flow to the publicly owned treatment works (POTWs);
(5) Maximizing POTW treatment capacity; and
(6) Installing satellite treatment facilities.
Participants also addressed design flows and volumes as well as the quantity and quality of
current SSO monitoring.
Workshop participants recommended that the first three approaches to handling and
treating SSOs (inflow elimination or reduction, cost-effective sewer rehabilitation, and
collection system inspection) must be performed in all cases; an integrated economic and
feasibility analysis using a combination of maximizing both flow to POTWs and treatment
capacity must be considered for controlling the remaining SSOs. Workshop consensus was
that these first five options are preferable to the use of satellite storage.
The workgroup recommended that EPA develop effective national requirements for
treatment options by:
Demonstrating, improving, and evaluating emerging technologies; and
Determining particle size removal requirements for adequate disinfection by
various disinfection technologies, including ultraviolet disinfection.
Chapter 8: Research Needs and Recommendations, presents more detailed descriptions of
the recommendations from each workgroup.
7-4 .
-------
CHAPTERS: RESEARCH NEEDS AND RECOMMENDATIONS
Following the presentation by Workgroup #l,,.Michael Cook briefly outlined funds
currently available from EPA for research opportunities. Gordon Garner added that these
funds apply to research in areas including SSOs, NPDES, CSOs and other wet weather flow
conditions. He emphasized that EPA needs to examine all wet weather flow phenomena
together, rather than compartmentalizing each condition. Michael Cook agreed and added
that even though there are budget limitations, EPA still wants to hear about all areas where
workshop participants feel more information is needed. Even if EPA cannot perform all of
the research itself, associations such as WEF or ASCE, may be able to follow up in certain
areas. Kevin Weiss added that the availability of funds is a moving target and suggested
that interested individuals speak with Lam Lim in September to find out actual fund
availability.
David, Crouch stressed that the group effort illustrated by the SSO workshop and
conference and the openness of EPA to suggestions for research areas from industry
represents a positive approach and increases confidence in EPA's willingness to work
cooperatively with private industry.
Throughout the presentations, each workgroup identified areas for further EPA
research or technical guidance; some groups developed more detailed recommendations.
Each area identified by the workgroups is highlighted below.
Recommendations for Further Research from Workgroup #1
Workgroup #1 outlined four areas for further EPA research:
Establish performance and evaluation criteria for O&M activities;
Develop standards for how to handle debris removed during O&M activities;
Develop a national clearinghouse for program successes in O&M; and
Develop educational materials for the public and elected officials.
Recommendations for Further Research from Workgroup #2
Workgroup #2 described a number of areas where EPA should focus future research
efforts-
Quantification of inflow defects. The group suggested that EPA help identify and
quantify inflpw defects by developing technical guidelines for areas including:
Determining "peak" inflow;
' Best removal methods and associated costs (on a regional basis);
Expected life cycle of repairs; "
-. Migration potential; and
' ' .. . '8-1 " .' " , -
-------
Best identification methods. -
Impacts of rainfall data on inflow projections. The group felt that gathering more
data including virtual rainfall, depth and velocity, and scatter graph data would help
project the effects of rainfall on inflow. In addition, EPA should help develop a
methodology to project system response in general;
Storm event (design storm) selection. The group suggested collecting better data
on design storms including, ambient (antecedent) conditions data and rainfall/inflow
projections. EPA should monitor a larger number of storm events to improve the
reliability of projections.
Preventive measures. Another potential research topic involves identifying
methods for preventing the occurrence..of future inflow defects from connections to
the systems.
Mannings ("n") and Hazen Williams ("c") coefficients. EPA should conduct
further studies on these coefficients in existing sewers. Using improved coefficient
factors based on the existing conditions will make modeling and design assumptions
more accurate. Data based on current conditions is essential for verification and
calibration.
Recommendations for Further Research from Workgroup #3
Workgroup #3 recommended three areas where EPA should undertake further
studies and develop technical guidelines: flow projection methodology, effectiveness of
rehabilitation approaches, and future design and construction practices.
« .. Flow projection methodology. The group suggested that EPA develop technical
guidelines, including case studies, for methods to project design flows from flow
monitoring data. Specifically EPA could:
(1) Describe alternative methods and approaches for projecting flows for larger
storms based on flow monitoring results from smaller storms. The guidelines
should describe the advantages and disadvantages of each method. Possible
methods for inclusion .are:
unit hydrograph;
linear or log normal relationships to rainfall;
- defect models;'
antecedent soil moisture conditions; and
three dimensional relationships including storm duration.
(2) Describe the extent of rainfall data to be collected.
' 8-2
-------
(3) Develop information on uncertainties associated with rainfall and flow and
flow projections. EPA should use this information to assess the impact of
these uncertainties on facility sizing. In addition, EPA should provide
guidance on the resolution and duration of rainfall and flow measurements.
(4) Develop data analysis techniques such as, hydrographs, scatter plots, and
hyetographs.
Effectiveness of rehabilitation approaches. To help evaluate the effectiveness of
rehabilitation methods, EPA should:
(1) Develop a summary of national' data on I/I reduction resulting from multiple
rehabilitation approaches. Data could be compiled for three categories:
mains only, mains and lower laterals, .or comprehensive rehabilitation (mains,
lower laterals, and private sector service lines).
v
(2) Quantify types of I/I reduction by peak flow or flow volumes.
(3) Relate I/I to RII and groundwater infiltration.
(4) Define other system variables including size and type of repair performed.
(5) Develop cost data for rehabilitation, including cost per foot of pipe (either
based on system-wide length of pipe or based on feet of pipe rehabilitated) or
cost per gallon of I/I removed.
(6) Collect cost data on sewer system replacement activities. Areas to examine
include annual investment in rehabilitation (percent of system value) and
expected design life of the sewer system. The analysis should examine
whether annual investment matches expected design life.
(7) Develop generalized guidance on the minimum cost of system rehabilitation
for I/I reduction. The group questioned whether this was possible and
suggested identifying, for example, the minimum cost per foot of pipe in the
system. ,
The group cautioned against developing cost curves, noting that the curves
are inaccurate due to variability of local conditions.
Future engineering design and construction practices. The group suggested that
EPA develop technical guidance on engineering and construction practices for new
facilities in an effort to minimize I/I in the future. The group emphasized that these
construction practices could be accomplished at zero or low cost compared to the
costs required by retroactive corrections.
: ' '. - 8-3- . . " , ' ' ' " '
-------
The guidance should cover pipe and'manhole materials, backfill
specifications, joint design, and designing laterals to be accessible to TV inspection.
Three additional suggestions included: 1) making TV inspection results available to
private owners and recommending repairs when appropriate, 2) prohibiting backyard
easements, and 3) designing permanent monitoring stations for larger systems.
* Long-term stream records. The group suggested that EPA evaluate the use of
unregulated, long-term stream records an alternative approach for calculating RII.
The investigation should examine whether such records could take the place of
monitoring groundwater conditions as a basis for estimating RII.
Recommendations for Further Research from Workgroup #4
Workgroup #4 identified four areas where EPA should focus future research or
develop guidance materials:
Case studies of program and successes. Specifically, the group suggested
developing case studies on the private, voluntary program in Fairfield, Ohio, as well
as on any other incentive or city assisted programs.
Educational material. The group felt that EPA's role should be to help develop
and disseminate education materials on the benefits of rehabilitating laterals. In
particular, mechanism for disseminating the information to municipal officials, home
owners, and school children should be developed.
City take-overs of laterals. EPA should look at opportunities for city take-overs.
However, most cities do not want to own the part of the sewer from the ROW to the
house.
Expanding enforcement options for NPDES owners. Specifically, EPA should
develop more enforcement options for NPDES permit owners with respect to
unpermitted cities and private citizens.
Recommendations for Further Research from Workgroup #5
Workgroup #5 identified two areas where research is needed to help develop
effective national requirements:
Demonstrate, improve, and evaluate emerging technologies.
Determine particle size removal requirements for adequate disinfection. This
determination should be made for various disinfection technologies, including
ultraviolet disinfection.
8-4
-------
APPENDIX A
-------
-------
..-,. United States
Environmental Protection Agency
Office of Wastewater Management
Sanitary Sewer Overflows (SSOs) Workshop
Renaissance Washington DC Hotel-^Downtown
Washington, DC
April 26-28,1995
Agenda
WEDNESDAY APRIL 26
3:15PM Workshop welcome and introductions
3:30PM Instructions to workgroups ". ,
'4:OOPM Individual workgroup sessions
5:30PM- AD J OURN - ' '
THURSDAY APRIL 27. "".
8:30AM General discussion
9:OOAM Individual workgroup sessions (continued)
.. 12:OOPM LUNCH '. '. '
1:OOPM Individual workgroup sessions (continued)
3:15PM ,B RE AK ,
3:30PM Workgroup reports
5:30PM ADJOURN. '
. FRIDAY APRIL 28
8:30AM Workgroup reports (continued)
. . 10:30AM B RE AK . '
10:45AM Workgroup repoirts (continued)
11:45AM General discussion
12:30PM .ADJOURN
' Printed on Recycled Paper
-------
-------
Workgroup #1
Subject:
Objective:
Background:
Key Question:
Output:
Preventive maintenance (PM) for controlling SSO in sanitary sewers.
To develop an effective maintenance program for eliminating
unintended SSO in sanitary sewers. .'--.' . *
Recent reports from the field indicate that municipalities across
the country are experiencing SSO, and that SSOs occur during
both wet and dry weather periods. Primary causes of SSOs
appear'to be excessive inflow/infiltration (I/I) and poor system
maintenance.
What constitutes effective system maintenance for preventing SSOs?
In response to this question, the work group will develop a discussion
paper addressing key components of a system maintenance program
necessary for controlling SSO. For example:
As built sewer maps and inventories;
Maintenance records showing system conditions;
System design and construction including pumping stations;
Power supply and back-ups;
. Preventive maintenance procedures;
. Resources and organizational structures;
System inspection, evaluation, and rehabilitation; and-
« Building sewer maintenance. -
The workgroup should also address poorly maintained sewer systems
which'may require special efforts in order to restore sewer integrity.
A summary report containing the following:
Brief discussions of various key components and procedures
for an effective PM program, including costs and options.
- A comprehensive system maintenance strategy for a site-
specific, sewer system.
-------
-------
Workgroup #2
Subject:
Objective:
Background:
Key Question:
Output:
Peak inflow evaluation and rehabilitation.
To develop a methodology for 1) determining peak inflows in a sewer
system; 2) evaluating options for removing these inflow sources; and
3) assessing the costs of these options.
Peak inflows are major causes of wet weather SSO. This is generally
the case because sanitary sewers do not have the designed hydraulic
capacity to handle storm flows. Experiences under the EPA
construction grants program show that a properly designed inflow
reduction program can be cost effective because most of these inflow
sources can be economically identified and removed (e.g., vented
manhole covers, abandoned building sewer clean outs, roof and
surface drains and storm sewer cross connections). However,
foundation drains and some hidden cross connections may be difficult
to locate and,costly to remove.
How can an effective inflow reduction program be designed so mat
wet weather SSO can be brought under control? While it is recognized
that all inflow sources may not be eliminated from a sewer system, the
workgroup members should jbcus their efforts on developing a.
methodology for the identification and removal of major inflow
spurces that can cause the flow to exceed the hydraulic capacity of the
sewer system, and thereby result in SSO during storm events. Such a
methodology should include state-of-the-art techniques for:
* Designing system hydraulic modeling; "......'
Identifying and quantifying inflow sources; ,
Removing inflow source and costs; and
Evaluating the results of an inflow rehabilitation program.
- _ /'',.,
The workgroup should also evaluate costs for various techniques
proposed in the methodology.
A summary report containing the following: '
A comprehensive methodology or plan for conducting system
inflow evaluation and rehabilitation.
A plan for evaluating successes of an inflow correction
program.
Costs associated with various techniques proposed in the plan.
-------
-------
Workgroup #3
Subject:
Definition:
Objective:
Background:
Peak rainfall induced infiltration evaluation and rehabilitation!
For purposes of this exercise, rainfall induced infiltration (RII) is
defined as infiltration characterized by instant flow peaking and
subsidence in response to storm events similar to those of inflows.
To,develop a methodology for 1) assessing the extent of RII in a
sewer system; 2) differentiating peak RII from peak inflows; 3)
identifying sources of RII; and 4) evaluating available options and
their costs for controlling RII.
Flow data from East Bay Municipal Utility District (EBMUD)
and a number of systems have shown that RII may be the
major factor responsible for peak flows in some sewer systems.
In fact, the similarity in flow characteristics between inflows
and RII has caused confusion in identifying one from another.
Because of this, it is necessary to develop techniques for
= differentiating these two I/I sources, so that appropriate
rehabilitation techniques can be effectively applied
Key Question: How can peak RII be properly identified and controlled?
The workgroup will develop a methodology incorporating techniques
for determining the following:
Extent of peak RII in a sewer system.
Sources of peak RII.
Options for controlling RII.
Costs associated1 with various available options identified.
Output:
A summary report containing a comprehensive methodology or plan
for evaluating RII as explained above.
-------
-------
Workgroup #4 -
Subject: , Maintenance and rehabilitation of building sewers located inside private
properties.
Objective: To address the institutional and legal issues associated, with building sewers
and their maintenance.
Background: Historically, building sewers are poorly maintained because
major portions of these sewers are privately owned.
Municipalities inspect and maintain only the portion of building
sewers between the street connections and the property lines.
It is estimated that about 50 percent of I/I originates from building
sewers, ,
Success of an I/I correction program is limited if building sewer
rehabilitation is excluded.
Municipalities are looking for ways to overcome these institutional
and legal barriers.
'',';- Technologies for inspecting and rehabilitating building sewers are
costly and not up to date.
Key Question: ; How can building sewers be properly maintained?
Obviously, problems associated with maintenance of building sewers are both
technical and institutional in nature. To resolve these issues, the workgroup
needs to address the following:
Maintenance programs in other utilities such as gas, electric, and
telephone companies.
Options available for overcoming the existing institutional barriers in
; sanitary sewers districts.
Experiences and successes of some sanitary districts in dealing with
these problems. . - -
State-of-the-art technologies available for inspecting and rehabilitating
building sewers. .
Output: A summary report containing:
-------
Options for municipalities to overcome institutional and legal
barriers in order to ensure physical integrity of building sewers.
Description and costs of available technologies for inspection
and rehabilitation of building sewers.
-------
Workgroup #5
Subject:
Objective:
Background:
Key Question:;
Output:
Proper handling of wet weather flows.
To identify and evaluate treatment and storage technologies and other
schemes available for handling of wet weather flows in order to
prevent SSO and bypasses. . ,
Because not all I/I can be economically eliminated, some
portions of I/I are expected to remain in the system after a
rehabilitation program, these remaining flows will continue to
cause SSO and'bypasses if not properly handled.
How to properly convey »and treat the remaining I/I to prevent SSO
and bypasses?
. The remaining I/I in a system can continue to cause SSO and
bypasses. For this reason, proper handling of these I/I, especially
during storm events must be addressed. This workgroup will look into
available options and technologies for handling wet weather flows.
These may include:
Continuing sewer maintenance to maintain sewer integrity.
Retrofitting existing facilities with treatment processes for
handling excess flows during storm events.
On-site and off-site storage facilities.
. Underground storage.
Relief sewers.
A summary report containing:
Available options and schemes to store or properly convey the
wet weather flows to a treatment facility.
List of treatment technologies that can be used to retrofit
existing facilities for handling and treating wet weather flows.
Costs associated with these various options and technologies.
-------
-------
APPENDIX B
-------
-------
WORK GROUP # 1
PREVENTIVE MAINTENANCE (PM)
FOR ELIMINATION OF SSOs IN
SANITARY SEWER SYSTEMS
APRIL 28,1995
-------
-------
WORK <2ROUP #1 SUMMARY
INTRODUCTION/PURPOSE
The subject of discussion for the work group was preventative maintenance for
controlling SSOs into sanitary sewers. The work group objective was to
develop an effective maintenance program for eliminating unintended SSOs in
sanitary sewers. . ; > , ...-..
BACKGROUND
i . ' . " '
Recent reports from the field indicate that municipalities are experiencing SSOs
across the nation, and that SSOs occur during both wet and dry weather
periods. Primary causes of SSOs appear to be excessive I/I and poor system
maintenance.
. - t -
ATTENDANTS
Rick Arbour, Richard Arbour and Associates, Inc.
Dwight Culberson, City of Fairfield, Ohio
Albert Gallaher, Charlotte-Mecklenburg, (Group Leader)
John Gresh, RJN Group, Inc.
Graham Knott, Brown and Caldwell
Reggie Rowe, CH2M Hill
Joe Mauro, U.S. EPA, Office of
Wastewater Management
' r .} *
WORK GROUP OVERVDSW
The session started out with everybody introducing themselves and indicated
issues and concerns that they expected to be discussed at these work group
sessions. The main issue being how to shift communities from doing only
emergency repairs to a regular preventative maintenance program, and what is
a good preventative maintenance program. The group suggested.that the basic
prolems that prevent good O&M are lack of motivation and loss of trained
personnel. For example, municipalities spend as much as a year training key
personnel only to have them leave after several years for higher pay which
cannot be matched within a rigid civil service organization. Other issues
included standardization for tracking and recording information, methodologies
WG 1-1 V
-------
'*, * ' ,
for encouraging appropriate spending of money; ie: equipment and people, and
the lack of clear understanding of the sanitary sewer system and the associated
resources needed by both general public and public officials.
The last issue discussed was the role of the EPA/regulators in the operation and
maintenance of the sanitary sewer system. Here it was pointed out that many
communities will not prepare a maintenance program unless they are required
to, or deal from the customer service point of view. One suggestion was to put
some requirements into the NPDES permit specific to the sanitary sewer
collection system. Some of the requirements suggested included; .certification of
an operator for the system, establishment of a preventative maintenance
program and the application of proper technology. Other less extreme ideas
were sited such as an outreach program by the EPA or other professional
groups; WEF etc; production of training and information videos, research
projects with information being available to all and establishment of a clearing
house so that large communities who do research have a way of sharing the
information with smaller communities.
WORK GROUP #1 REPORT
, p ." .- x '
Collection systems should be managed as a well run enterprise operation
"(business)/investment in a forward thinking manner. The following conclusions were
developed and should be crafted into basic goals:
\ ' " ' ' -
Systematic Implementation of Operation and Maintenance will reduce
SSOs.
r . . , ''''.'
Preservation and protection of infrastructure investments, through asset
management will prevent future liabilities.
Adequate allocation of Human and Material Resources
Meeting communication needs can be facilitated by Federal and State
government and professional organizations.
' ' "
Inventory of the infrastructure is required.
Operation and Maintenance staff involvement and input should occur
during the planning, design, and implementation process.
Federal, State, and Local co-operation should be developed.
The foundation of the accomplishment of these goals should be training and education.
WG 1-2
-------
Mission and Goals:
SSOs extension of basic system Operations and Maintenance
(O&M) provide general guidelines to be targeted toward local
service provider/state^
- Protect investment, asset management prevents future liabilities.
- Provide public service and accommodate growth.
- Ensure reliability of sanitary, facilities.
- Protect public health / wildlife.
-Maximize conveyance system capabilities.
- Establish standard operating procedures for preventative maintenance
and emergency conditions , ,
.-."." i
Education (applied at different levels.)
- General Public- general system operation and recognition of capital
investment.
- Local Official - priority-setting, budgetary issues, planning, and
recognition of capital investment.
- Managers - short term and long range budgeting, program
administration. .
- Technical Staff and Field Crews- procedural , record-keeping
requirements
Program Development and Implementation.
- Establish initial system evaluation and plan for on-going condition
assessment. '
- Administrative Coordination /Preventing future problems. Review
of municipal building standards, material specifications, acceptable
construction practices, and design to minimize potential stormwater
effects. .
WG 1-3
-------
- Determine life cycle costing on capital improvement projects as part of
design process. Note: -Life cycle costs on both O&M costs and capital
costs for necessary treatment plant expansions could indicate. There
are cases where significant costs, which have been of likely to be
incurred as a result of I/I, were omitted from total like cycle costs.
,-... , . ' *.,-. \ . - "f
- Assigning areas of public/private responsibilities through municipal
ordinances.
- Developing system mapping and inventories.
- Formulate management structures, staffing needs (number of staff and
educational requirements). .
- Develop standard inspection procedures and record keeping. (See
Attachment 1)
- Itemizing and prioritizing corrective and preventive activities.
(See Attachment 2)
- Develop O&M manuals (lift stations, collection systems).
- Determine Equipment Requirements
- Develop financing plan (enterprise orientation).
- Inter/Intra-departmental coordination on capital projects.
- Formulate short-term / long range Capital Improvement Projects. (CIP)
Establish Performance Standards and Criteria
- Flow monitoring/integrate with hydraulic modeling.
- Event Notification Systems.
- Inspection records / videotapes.
- Complaint monitoring / tracking.
WG 1-4
-------
Role of regulators and professional organizations.
- State/Federal Enforcement Activities (CO's, F&O's) define enforcement
parameters and tiered enforcement approaches
- Integrate Performance Criteria for Collection System Operation as part
permitting process and construction approvals
-Develop certification programs for collection system operators
-Recognition of successful initiatives and "Local Heroes" through WEF,
AMSA and other professional organizations.
- Development of Standard Specifications and Project Protocols
/ '
- Develop Education Programs and Training Materials
- Fund and Conduct Research on Emerging Technologies
WG 1-5
-------
-------
Attachment 1
Standard Inspection Procedures
Internal .Television Inspection.
.Physical Inspection...
Manhole/Street/ROW Surface Inspection.
Internal Manhole Inspection.
Other (Private Sector)
Attachment 2
Corrective / Preventive Maintenance Activities
' Cleaning.
Mechanical.
Hydraulic.
Maintenance of ROW and structures for access.
Spot repairs. ,
Manhole rehabilitation.
" Pipe relining.
!.,''
Private sector inspection/monitoring.
Root control. >
Vandalism control.
Reporting. .
Flow monitoring.
Information Recording / Management.
-------
-------
WORK GROUP #2
REDUCING PEAK INFLOW
FOR ELIMINATION OF SSOs IN
SANITARY SEWER SYSTEMS
APRIL 28,1995
-------
-------
WORK GROUP #2 SUMMARY
INTRODUCTION/PURPOSE
The subject of discussion for the work group was how to develop a methodology
for: 1) determining peak inflows in a sewer system; 2) evaluating options of
removing these inflow sources; and 3) assessing the costs of these options for
controlling SSOs from sanitary sewers. =The work group objective was to develop
an effective inflow control program for eliminating unintended SSOs.
BACKGROUND ..
Recent reports from the field indicate that municipalities are experiencing SSOs
across the nation, and. that SSOs occur during both wet and dry weather periods.
r Primary causes of SSOs appear to be excessive I/I and poor system maintenance.
Peak inflows are major causes of wet weather SSO. This is generally the case
because sanitary sewers do not have the designed hydraulic capacity to handle
storm flows. Experiences under the EPA construction grants program show that
a properly designed inflow reduction program can be cost effective because most
of these inflow sources can be economically identified and removed. For example:
vented manhole^ covers, abandoned building sewer clean outs, roof and surface
drains and storm sewer cross connections. However, foundations drains and some
hidden cross connections may be difficult to locate and costly to remove.
ATTENDANTS
Keith Benson, Hampton Roads Sanitation District s
Gordon Garner, Louisville and Jefferson County
Metropolitan Sewer District
Henry Gregory, City of Houston
Alan Hollenbeck, RJN Group, Inc.
S. Wayne Miles, COM, Inc.
Richard Nogaj, RJN Group, Inc. (Group leader)
Ralph Petroff, ADS Environmental Services, Inc.
John Smith, J«M. Smith and Associates, Inc.
Norbert Huang, U.S. EPA, Office of
Wastewater Management
WG2-1
-------
WORK GROUP OVERVIEW
The session started out with everybody introducing themselves and indicated
issues and concerns that they expected to be discussed at these work group
sessions. The main issue being how to design an effective inflow reduction
program so that wet weather SSOs can be brought under control. The work
group recognized that all inflow sources can not be eliminated from a sewer
system, so the group focus on the effort in developing a methodology for the
identification and removal of major inflow sources that can cause the flow to
exceed the hydraulic capacity of the sewer system and thereby result in SSO
during storm events. It was agreed that such a methodology should include state-
of-the-art techniques for: , *
designing system hydraulic modeling
identifying and quantifying inflow sources
removing inflow source and costs
evaluating the results of a inflow rehabilitation program
The group also agreed that they could provide some limited information to
evaluate costs for various techniques proposed in the methodology.
; ' , , :
At the beginning of the meeting, several members disagreed with the EPA
position that inflow should not include Rainfall Induced Infiltration (RII).
One member suggested that they are mutually interactive and might be better
addressed together to make an impact on SSO's. To illustrate this point, an
example is included in attachment 1. However, the majority felt that, even
though in some cases the RII did enter the system very rapidly when the soil
was dry and cracked, RII should be evaluated separately (also see work group
, #3 report on reducing peak infiltration.
The group concluded that in many cases peak inflow can be identified based on
certain criteria and economically removed from the system. The group identified
the following as the key inflow sources:
vented manhole covers and frame seals
pipe to pipe defeats
yard drain
foundation drains
sanitary sewer/storm sewer cross connection
»
* Inflow normally transmitted through "holes", not from cracks/joints
WG 2-2
-------
The group also identified the following techniques for identifying inflow:
1. Smoke test many approaches; for appropriate application, smoke test should
be done at low flow and no precipitation
2. Dye flooding
- done w/TV to pinpoint for repair
weir measurement for flow quantification
3. Manhole inspection ' ' .. .
- full depth manhole inspection (below grade)
ideally, during wet weather
4. Building inspection
a. internal
sump pump
- footing drain
b. external (smoke test)
foundation drains
- yard drains
A lengthy discussing followed concerning how to quantify inflow and
determine the costs to remove inflow.
,- . - Wayne Miles suggested doing before and after monitoring to
determine the amount removed through SSO control actions
- Keith Benson suggested removing all inflows, big or small
(search and destroy)
All agreed flow monitoring w/metering is essential
Comprehensive evaluation may not be needed for the entire
system, but important for the most severe areas
Ralph Petroff suggested sub area monitoring be done. Such
monitors are vital to the execution of the work after the
initial determination of excessive I/I. Since they remain in
place throughout the SSES and rehabilitation, these
" WG 2-3
-------
monitors provide a pulse for the system and give the earliest
symptoms of significant changes in the subarea. Thus, they are ideal
in checking the rehabilitation reductions and supplying a means of
tracking system deterioration after the SSES.
Important to compare flow monitoring with rainfall data
EPA needs to support more research on methods to quantify
inflow
System modeling is essential for a comprehensive approach to
control inflows
Some unit costs for inflow, reduction are available in literature.
However, EPA needs to update the numbers.
Program costs (not including actual inflow removal) range $0.5-
$3.0/ft, which include flow metering, modeling, smoke testing
manhole inspection, building inspection, etc., are available in
literature, but need to be updated. May be a subject for EPA
research.
The group also discussed how to evaluated past and future inflow removal
effectiveness. Key elements included:
Post rehab monitoring
Ralph Petroff suggested that any comparison of the system
before and after rehabilitation would be apples and oranges and
therefore not truly representative because of fluctuating water
tables, differing precipitation activity, continued system
deterioration, and many other factors.
Monitor a control area match location, season (ground water
level)
Herb Kaufman suggested that follow up monitoring could be
effectively done using unregulated stream flow records rather
than rainfall (see attachment 2 for more details).
. r '
Existing methodologies contain significant degree of
uncertainties. A subject EPA's future study can try to improve.
WG2-4
-------
WORK GROUP #2 REPORT
Introduction , ..'..-,
Definition: Peak inflow is sewer system flow usually in direct response to rainfall
events, where system response (flow) is due to sources (defects) that activate
almost instantly to rainfall (This definition emphasizes rainfall induced inflow as
opposed to tidal, estuary, cooling towers,etc.).
Inflow Sources Always Include; .-.,."
"Pipe to Pipe" Defects
T Public Sector
Direct StormVSanitary cross connections
Catch basinsMnlets
- Private Sector
Downspouts, roof leaders
Area, stairwell, patio draws
Open cleanouts
Foundation drains, sump pumps, crawl space drains
Non-Rainfall Induced Sources
Cooling towers
Tidal flooding
- - Street Wash
Drains from creeks, rivers .
Inflow Sources Sometimes Include:
Indirect storm\sanitary cross connection where soil seam has become void
(direct path) '", '
."'--, Inflow is normally transmitted through "holes" as opposed to
cracks\joints
Methodology for Determining "Peak" Inflow
Key Issues:
- Cannot be monitored, if the system surcharges
- Need methodology to project system response to storm events that can be
monitored ,
Need large number of monitored storm events to improve reliability
of projections
: - . - WG2-5 ' ..-'.:. . "".-
-------
Virtual rainfall data may improve reliability of
projections (another topic for EPA Research)
Data Gathering
A. See Attachment 3
System Modeling
A. Management -> Control of System
B. Modeling -> Predictions-of System Behavior
C. Modeling is essential to a successful* methodology
D. Modeling is important for the following reasons:
1. Predicting system performance
2. Predicting effects of rehabilitation done
3. Define system limitations
4. Determine system capacity or under
capacity (Identify Bottle Necks)
5. Predict future SSO's
6. Needed .for "What if scenarios
7. .Needed for planning
E. Modeling is an "umbrella" over system flows and individual source
defects
F. Modeling normally includes the following key activities:
1. Flow MonitoringYRainfall data
' 2. Physical inspection data (from existing data - models)
3. Source defect listing each qualified flow and rehabilitation cost
for each defect
4. System inventory after supplemented from field inspection
activities
- Elevation data
- Slope\capacity data
- System continuity\network
G. Smaller systems may use "Paper" or desktop model
WG2-6
-------
H. Calibration of models is critical and verification is essential. Engineers
should establish at least four calibration points covering a wide range of
depths, and should conduct both instantaneous calibration and dye travel
calibration. After a satisfactory calibration curve for each location is
established, the depth data can be converted.
Inflow Source Identification includes the following key activities;
A. Smoke Testing Techniques
1. Dual blower or high intensity single blowers
2. Proper ambient conditions - low ground water and no rainfall
3. Test single manhole to manhole segments at a time (up to 300+ feet)
4. Need better guidelines based on independent research in controlled
laboratory approach
5. Always record "suspect" sources that have likelihood of direct connection
to sanitary sewer but did not smoke (these are good candidates for follow
' up dye flooding
B. Dye Flooding
1. Can test "suspect" sources that are "trapped" - yard drains, roof leaders,
etc> '-' ..' .'.'''
2. Follow up smoke testing to pinpoint and quantify defects ... ' '
3. Take weir measurements or depth\velocity readings in sanitary sewer
before and after dye flooding to quantify defect(s)
4. Observe dye water at outlets
5. IJtilize TV with dye to pinpoint exact location of defect\multiple defects to
allow repair
. . . - s ' . ,
C. Manhole Inspection
\ . .
1. Full descent inspection into manhole is the best procedure to properly
locate and quantify defects
2. Lamping during full descent inspection also helps locate,roots,
deterioration, debris and is a guide for TV inspection
3. Ideally descent inspections should be performed in wet weather
4. Defects (i.e. frame seals) are not always obvious and need trained eye
(inspectors) ~
5. May use surface flooding on dye injection around manhole to locate
defects .
6. Smoke seen immediately around manhole during smoke testing generally
indicates a defective frame seal
7. Need to simulate how defects1 will react after the storm events
',.'.' WG 2-7 ; ' ' . '
-------
8. Manhole monitoring: Advantages and disadvantages of key manhole
monitoring is included in- attachment 4.
D. Building Inspection (Private Sector)
1. Internal Inspections
Location of foundation drains, sump pump connections, crawl space
drains
Other connections specific to areas with
basements
2. External Inspections
Sometimes conducted during smoke testing (crews must walk
backyards and streets looking for smoke)
1 - Determine patio, area and yard drains
along with foundation drains
E. Steps to quantifying Inflow include the following:
1. Individual defects respond to rainfall intensity and duration
2. . Inflow response from individual defects can be estimated
3. EPA needs to support research on quantification of individual inflow
defects
4. Flow monitoring data can be used to balance against sum total of
quantified defects tributary to flow meter
The justification for intensive monitoring is that savings in cost of cleaning
and TV inspection in those reaches found to have low I/I more than offset
monitoring costs. One monitoring station for each 10,000 to 20,000 linear feet
(3048 - 6096 m) of main and lateral sewers (excluding service connections) is
reasonable for the preliminary survey, but the final survey should allow about
4,000 feet (1210 m) per monitoring station.
New Inflow Removal Guidelines Need To Be Developed
WG 2-8
-------
Evaluation of Inflow Removal Success Include the Following;
1. Qualitative and/or quantitative
2. Post rehabilitation flow monitoring
3. Based on need to manage system . '
4. Modeling is the tool
5. Should have a non rehabilitated area as a "control" area for comparison
6. Require rehabilitation effectiveness testing by rehabilitation contractor to
ensure effectiveness of individual repairs
7. Record change in frequency arid duration of SSO's
8. Utilize pump stationUreatment plant running time meters and/or flow
meters for recorders
9. Post rehabilitation monitoring should always (guidelines):
Fair evaluation of a rehabilitation program demands that inspectors compare
conditions existing before arid after rehabilitation. Because no two rainfalls
have exactly the same characteristics, it is extremely difficult to correlate pre-
rehabilitation and post-rehabilitation flows; only through long-term
monitoring can the flows be averaged to the point where significant
conclusions can be drawn.
-Match same manhole as pre-rehabilitation metering
- Match same seasons\ground conditions
- Utilize same rainfall monitoring approach
- Post monitor as required can be:
temporary /
; permanent
Note: Specific benefits to be derived from long-term monitoring include:
1. Allows the continuous evaluation of I/I conditions.
2. Provides a basis for implementing additional I/I removal, as needed.
3. Provides a constant check on system deterioration, arid thus avoids a
large "one time" expenditure to update the system,
4. Allows pricing of a system's requirements throughout its life.
5. Identifies areas which are "top priority" for future maintenance.
6. Help to determine if a project has met I/I removal standards.
Long-term flow monitoring involves three phases: preparation of locations,
purchase and installation of equipment, and evaluation of the project before and
after completion. The first two phases are discussed below:
WG 2-9
-------
10. Apply existing (same) evaluation techniques to before\after analysis
Cost of Inflow Removal
1. EPA needs to gather and publish National data on rehabilitation
including:
-Narrative or description of common defects
- Quantify range of inflow from the common defects
- Removal method(s)
' - Cost for removal should include regional variations
- Life of repairMife cycle cost to include potential for migration
2. Estimated Program (Plan) Costs
- Flow meters\rainfall gauges $50 to $150 per meter per day
- Modeling $0.05 - 0.25 per foot of sewer
- Smoke testing - 0.20 - 0.40 per foot of sewer
- Manhole inspection - $50 - 100 per manhole
- Dye floodingVTV - $100 - $1000 per setup
- Building Inspections (Internal) - $40 - 70 per building.
Total System $0,50 - $3.00 per foot of sewer
' ' - '" ., "^ ' .
Recommendations for EPA Sponsored Research
1. Quantification of inflow defects expanded to include:
- Best removal methods available
- Expected life cycle of repairs
- Migration potential
- Best identification methods available
2. Impacts of rainfall data on inflow projection:
- virtual rainfall data
- depthWelocity
- scatter graphs, etc.
3. Storm event (design storm) selection including:
- Ambient (and antecedent) conditions
- Rainfall\inflow projections
- Allowable frequency of overflows
4. Preventive measures for controlling future inflow defects from connecting
to the system
5. Refine Mannings "N" and Hazen Williams "C" factors in operating
sewer systems
WG 2-10
-------
ATTACHMENT 1
ALTERNATE APPROACH USING GROUND WATER INDEX
Narratative ...'.,. -....-. . ,
Attached are two plates entitled "1974 Daily Extraneous Flow and Rainfall -
Plate 14" and "Effect of Antecedent Rainfall on Extraneous Flow Patterns - Plate
14"? selected at random from separate reports. The effect of antecedent rainfall
has far more impact on I/I peaks than the individual rainfall events. Two
rainfalls, each totalling about 3.5 inches/day are shown in the "Effect" plate. One
follows a dry period and results in a peak I/I of about 75 mgd and a much lower
total. The second follows a wet period and results in a peak of about 210 mgd
and a much greater total. This is also supported by the plate presenting the 1974
daily data showing total extraneous fikrtv (I/I), rainfall per day, plant bypass, and
overflow. Comparing the data from the middle of March through April, when the
groundwater was high due to a series of earlier smaller rainfalls and lower losses
from consumptive use and evaporation, with that of early September, when there
were fewer but still significant rainfalls in August, and higher losses. On March
29, 30, 31, rainfalls of 0.7, 0.75, and 0,25 respectively occurred. On those same
dates, rainfall responsive infiltration was 0.0, 8.0 and 23 mg respectively, and
inflow 0.0, 14 and 22 mg respectively. For September 1 through 4, rainfalls
equalled 1.95, 0.05, 3.0 and 0.2 inches respectively, while rain responsive
infiltration was 0.0, 6.0, 10.0 arid 41.0 mg respectively, and direct inflow 0.0, 16.0,
30.0 and 12.0 mg respectively. In the last three days of March, 1.7 inches of
rainfall produced 36 mg of inflow, while in the first four days of September 5.2
inches of rainfall produced 58 mg of direct inflow. Each inch of rainfall in March
produced about 21 mg of inflow, while in September, 11 mg. Inflow was not
proportional nor was it activated "almost instantly" by rainfall. ,
In comparing the total I/I for the periods compared, it appears that the more
dominant influence is continuous infiltration, which is determined by groundwater
level. In a number of systems, good correlation was made between long term
unregulated stream flow records, readily available from the Weather Bureau, and
I/I. It is suggested this correlation results since the dominant influence on both is
groundwater level, Relating instantaneous I/I measurements to long term stream
flow records through use of the Ground Water Index (GWI) described in the
attached paper entitled "New Tool for Infiltration/Inflow Analysis and
Quantification" permits estimating both average and peak I/I flows and the
success of an I/I reduction program.
WG 2-11
-------
BERGEN COUNTY UTILITIES AUTHORITY
22O
too-
035-
; ago-
INFILTRATION/INFLOW ANALYSIS AND
SEWER SYSTEM EVALUATION REPORT
jliliiliL
"ii». CAM. N en*. Ma CAM. N«RM. M
AHUL 9, mo . APWL to, isao
I 7
. t iih
i i
O B
MARCH
4 12
I960 APRIL
LOO-
ars-
oso-
Q2S-
L.nl.lll .Illllll
Sfe
Mia 8AM. N 6PM Mia 6AM. N S^M. MIX
OCT. 29, 1973 OCT. 30,197%
RAINFALL HYETOGRAPH
20 26
SEPT.
14 20 26 31
1973 OCT.
ANTECEDENT PRECIPITATION
APRIL
OCT.
EFFECT OF ANTECEDENT RAINFALL ON
EXTRANEOUS FLOW PATTERNS
CLINTON BOGERT ASSOCIATES
-------
-------
-------
ATTACHMENT 2
PAPER SUBMITTED AT WPCF CONFERENCE
OCTOBER 10, 1990
NEW TOOL FOR INFILTRATION/INFLOW ANALYSIS AND QUANTIFICATION
Herbert L Kaufman, Partner and David H. Hull, Associate
Clinton Bogert Associates
INTRODUCTION
Results of infiltration/inflow (I/I) correction programs have too often been below
expectations. After completion of programs for I/I reduction, wet season peaks nave been
experienced which far exceed those developed using currently accepted peak to average ratios
for separate sewer systems. This has resulted from the much higher rates for LI compared
to sanitary waste. The failure to effectively analyze and quantify peak to average ratios for
I/I has resulted from reliance primarily on spot readings and failure to recognize I/I as a
variable with a peak to average range of up to 15 to 1, compared to a maximum of about 3
to 1 for municipal wastewater. Such peaks have been experienced in separate systems where
I/I may comprise as much as 80 percent of the a-ntwal flow. Reducing the amount of I/I to
40 percent of the flow would still result in a peak to average ratio for I/I of from 6 to 1 for
large flows to about 8 to 1 for very small flows. The wide divergence in peak factors for
sanitary compared to I/I flows should be recognized and provided for in the peak design flows
when rehabilitating separate systems. It also provides a much greater incentive for effective
I/I reduction, .
, , <* - - - ' .
Traditionally, interceptor and trunk sewers have been sized based on design peak
flow determined by a single curve setting forth the ratio of peak to average flow, with a lower
ratio for higher average flows. Harmon's ratio and curves in the various sewer design
manuals are typical examples of design standards which do not account for the different-peak
to average ratios applicable to the base sanitary and I/I components of the waste flow.
Sanitary trunk and interceptor sewers in separate systems, with capacities determined by
these curves, have frequently been overloaded during rainfalls concurrent with high
grbundwater. Sewer overflows have occurred although the tributary population and
, 1
-------
contributing water consumption have been less than provided for in the design. Such
overflows in systems with & relatively large average infiltration component in the flow can
continue for days after a moderate rainfall when-the groundwater level is high.due to a wet
period. " ...
To more reliably predict the required design peak capacity, analysis has been
made of continuous flows at a number of systems for long periods - as much as 30 years. The
relative pattern of I/I flows to sanitary base sewage flow was determined. A similar pattern
has emerged for a number of systems, some very large and some smaller. They include
systems serving the Bergen County Utilities Authority, Orangetown, NY,. Asbury Park, KJ,
the Raritan Township Municipal Utilities Authority, NJ, and the Princeton, NJ Sewer
Operating Committee. , . -;
PEAK FLOW CHARACTERISTICS
The flow pattern appears typical for the areas investigated which contain
relatively small percentages of impervious area and where the water table is normally below
the sewer. The base sanitary component of the flow appeared to be relatively stable from day
to day. Analysis of the diurnal patterns indicated the peak daily sanitary flow component
at the downstream end of large systems seldom exceed 1.5 times average, and at the upper
end of system, seldom exceed 2 times average, and never exceed 3 times average, except in
predominantly industrial or commercial areas. -On the other hand, throughout the periods
analyzed, the I/I component would range from essentially 0 to over 13 times the long term
average I/I component Plate 1 presents, on/log probability paper, the total time during the
period when the I/I rate exceeded specific multipliers of the average I/I. The multiplier
experienced for less than 10 percent of the time is well defined. I/I exceeded 3 times average
about 5 percent of the time, 5 times average about 1 percent of the time, and 10 times
average about 0.1 percent of the time.
In separate sewer systems, the major subcomponent of high I/I variation is
intermittent^ variable infiltration. While direct inflow can have a very high peak to average
ratio, it constitutes only a small portion of the a-rm^i i/i JQ most separate systems.
-------
Following very wet -periods, the intermittent, variable infiltration subcomponent, which may
equal about 92 to 95 percent of the average I/I, can have .a peak to average ratio of up to 10
to 1 four days after all precipitation and direct inflow has ended. The critical variable for
determining ihe design peak to average ratio is the percentage of average I/I in the average
flow. The series of curves shown in Plate 2 use as criteria a peak flow to be exceeded no
more frequently than 2.4 hours per year. At such times, the peak sanitary flow component
is expected to equal the average flow times a multiplier indicated in the 0 percent curve. The
I/I component would equal 13.3 times average LT in the system. At a point in the system
where the.average flow is 1.0 MGD, with I/I constituting about 55 percent of the average
flowythe peak to average ratio would be S.45, and the design flow would be 8.45 MGD. If the
' \ -".-- '' ' . ' '
I/I averaged 80 percent of the flow, the pSak flow would be 11.25 MGD. The traditional
Harmon's ratio is similar to an interpolated curve on Plate 2 for I/I constituting about 6
percent of the average flow and would yield a corresponding peak to average ratio of 2.95.:
The benefit of infiltration reduction offers substantial incentive. '
The average percent LT in a separate sewer system has a major impact on work
required to upgrade existing separate sewer systems. Compared to sewers designed using
current accepted standards, the sewers should be (1) larger to accomodate:the high peak, and
(2) constructe'd at steeper slopes to provide adequate cleansing velocities when infiltration is
low. The high peak to average ratio, assuming minimal surcharging of the sewers, may also
be reduced in certain instances if it becomes permissible to allow occasional overflows when
infiltration and groundwater, and consequently streamflows are high. As an example, for
the average flow of 1 MGD of which 55 percent is infiltration, the peak flow would be 5.9
MGD if the flow can be exceeded 24 hours per year. The I percentage curve to be used would
be 31.35 rather than 55 (0.57 times 55). However, with the allowance for this occasional
overflow, the peak design flow would still be twice .that projected by Harmon's ratio.
DETERMINATION OF I AVERAGE .
It is necessary to determine the infiltration percentage in the average flow to
calculate the peak design flow. The infiltration determined in any single measurement can
-------
be converted to the -average infiltration, and the peak flow multiplier -then determined. A
methodology for doing so has been developed. The method accounts for the following:
.1. The I/I admitted to a static system will vary considerably from month
to month,, year to year, and even from decade to decade based on changeo in
precipitation and groundwater level, as shown in Plate 3.
2. Systems are not static since new pipes can be added and older pipe
joints deteriorate.
3, There are periods "when well maintained .meters can. record
systematically higher or lower than actual or breakdown entirely.
Average I/I cannot be reasonably determined by simple subtraction of the
estimated sanitary flow from the metered flow using several spot measurements since the
variation in infiltration would not be addressed. However, such spot measurements for a
number of selected short periods **»" be used to develop the long term average infiltration
rate for the system. The infiltration on any specific day or period may be obtained by
subtracting the estimated sanitary base component from the total metered flow. Since the
infiltration in the system on any specific day may vary from 0 to more than 10 times its long
term average rate, an indicator of relative groundwater is required to convert spot measured
infiltration to long term average infiltration. The factor by which the spot-metered
infiltration is divided to determine the long term average infiltration has been called the
groundwater index. The following equation is used to estimate the average infiltration in a
sewer system:
-------
Where: . . ... .... .. ,': ' . ,
1 (avg.) = Average Infiltration
Q. = Metered Flow at a Specific Time
JJ. = Sanitary Waste Component of Qj '
GWI. « Ground water Index at the ..lime of Measurement
The groundwater index at a specific time is .similar for systems within a region
with similar development characteristics and having essentially similar patterns of
precipitation. The flow in basically unregulated streams in the region also varies linearly
with the groundwater index on days without significant precipitation. This linearity is most
pronounced from autumn through mid-spring in the eastern portion of the nation when the
rainfall events generating the groundwater are reasonably uniform over large areas.
Continuous long term streamflow records or calibrated system records can be used to1
estimate the local groundwater index on any date provided periods .of significant rainfall and
snow-melt are deleted, ._.,._
As shown in Table 1, the infiltration in a specific period is determined by
subtracting the estimated base flow from the metered flow. The infiltration can then be
correlated for given periods with flows in the stream used as a guide. An example is sb own
in Plate 4. The groundwater index can be equated to streamflow by the following: -
. Where: . . ' ' . . , ".,'.
k equals the streamflow when infiltration equals zero
m is the measured streamflow at a given time period
- " c is a constant
GWl is the groundwater index corresponding to streamflow m
By determining the average streamflow over a long period with times of
significant rainfall or snow melt excluded, the average infiltration can be determined from
a correlated curve such as shown in Plate 4. Equation 1 can then be used to, determine, the
Average GWI, and the constant c of Equation 2 determined. For any value of
-------
except for periods previously excluded, the GWI can be calculated. The average infiltration
obtained from the ^calibrated curve is then confirmed by using the GWI for corresponding
periods of recorded I/I and stream flows to calculate the average I/I based on recorded values.
The individual average I/I values for specific periods so calculated can be expected to vary
somewhat due to errors inherent in sewer flow measurements and the usual small variations
in base flow. However, the average should reasonably confirm that obtained using the
average streamflow.
CONFIRMATION PROCEDURE
The sensitivity of some of the inputs to Equations 1 and 2 should be considered
to insure acceptable results. Measured § values should be selected when the average
metered flow is relatively constant and between 2 to 3 times the base flow. A 2 percent error
in measurement would result in a 4 to 6 percent error in the estimated infiltration, while a
5 percent error in the base flow would result in a 3 percent error in the estimated infiltration.
In both cases the errors should be plus and minus, and should be largely compensating, "with
a sufficient number of actual measurements, m should be a reliable value since its usual
source would be long term USGS records, k should be reasonably valid, with an acceptably
correlated curve: The value of c should be reasonably correct since the input should not
contain significant error. A large difference between the calculated infiltration based on
observed metered flows and that calculated from streamflows would suggest that either the
extent of the sample and the average streamflow used, or both, should be reviewed to
determine what adjustments are indicated to achieve an acceptable confirmation.
DETERMINATION OF I/I REDUCTION
The methodology developed herein for determining average infiltration in a
sanitary sewer system can be used to determine the effectiveness of an infiltration
elimination program. Upon completion of work in a subsystem, flow measurements can be
made at the terminal manhole. Measurements made before the work have determined the
average infiltration in that subsystem. A similar measurement after completion of the work,
when related to riverflow, should result in a lower Q. This lower Q value introduced in
-------
Equation 1 will permit calculation of the new average I/I, and will yield'the percentage of I/I
remaining and the effectiveness of the work. . . . .
SOURCES OF INFILTRATION .', , -. = " .
Unit I/I rates in subsystems are frequently expressed and compared in terms of
flow per diameter-length,'ie. GPD per inch-mile. However the I/I in" sewer system
subdivisions may originate from the following sources:
; a. Porous manholes
b. Porous collector sewer joints ' .'-'>'
: c. The junction of collector and building sewer
oL Broken collector sewer barrels
- ' e. The building sewer
f. Building via basement and foundation drains
1 ' " ' , " .'' ' ' : '
The proportionality assumed with the use of diameter-length only may neglect the
substantial I/I originating from manholes, joints, connection points, and connected buildings.
Although a subsystem with closely spaced joints, building connections and manholes has an
intrinsically higher potential for I/I than a subsystem with distant spacing of these sources,
the diameter-length would be the same. : .'
- The synthetic equivalent length dimensional unit (EQL) is a common unit of I/I
potential winch can be applied to quantify all the potential sources in the subsystem. The
unit EQL is defined as "The I/I admitted by one foot of 8-inch collector sewer including
one-third of a sewer joint based on,a three foot joint spacing typical of day sewers." The EQL
of the subsystem equals the sum of the Relative EQL (H) estimated from each of the potential
sources m^.rplied by the number of each source in the subsystem.
When R* %IfI , (3)
100 (NxEQL)
-------
Subsystem EQL =
(R manhole x number of -manholes) +
(R collector sewer joints x number of joints adjusted for diameter) +.
(R building connection x number of building connections) +
(R collector sewer x collector sewer length adjusted for diameter) +
(R building sewer x building sewer length) +
(R building x number of connected buildings)
In assessing the relative I/I severity of various subsystems, the I/I per EQL is a
more meaningful term fo^m I/I per inch-mile. The term I/I per EQL takes .into account the
spacing of joints, manholes and connected buildings as well as sewer din meter and lenglh.
« ' »
Estimates of the Relative EQL (R) of each source may be based on the following
distribution of I/I in a typical reach. The typical reach indicated herein includes two.
manholes, 300 ft. of 8-inch collector sewer with three foot joint spacing, six building
connections, each with 58 foot sewer length. The following allocations for percent reach I/I
is based on current experience. Further studies in specific areas could prove different basic
allocations are justified. ' '
Typical Sewer Reach I/I Distribution
I/I Source
a. Manholes (2)
b. Collector sewer joints (100)
c. Lower building itwer (48 ft.) and junction* (6)
-------
In this typical system, 1EQL unit (a foot of pipe and one-third joint) would contribute
0.167 percent (50%/300 ft.) of the total reach I/I. Conversely, this typical system has an E$L
of 600 ft. Based on the assumed I/I.distribution in the typical sewer reach, and the
assumption that EQL is proportional to pipe and joint diameter, the following R may be
assigned to each source: . " --- / ^:;--.. '" . . ,
Relative Equivalent Length for Sources
I/I Source
a. Per manhole
b. Per collector iewer joint
c. Per building connecaon
d. Foot of collector sewer barrel
e. Foot of upper building Sewer
f. Per connected building
R
60 ,
-------
d. Spot excavation and replacement of the more severe videotaped sewer cracks and
breaks may eliminate 70 percent of the I/I originating from broken collector sewer
pipes, ..
e. At present, only a small portion of the I/I originating from the upper building sewer
may be cost effectively eliminated.
f. At present, only a small portion of the I/I originating from the connected building may
be cost effectively eliminated.
The estimated subsystem I/I removable by any of these repair procedures may- be
calculated by the following equation:
Potential IflXtducdon*IIIxRxtfxEfEQL _ W)
where:
III s I/I in the subsystem
R - Relative EQL weight for the source repaired by procedure
N ss Number or quantity of source addressed by repair procedure
E s Efficiency of repair procedure
EQL = Equivalent Length of the Subsystem
Depending on the spacing of the joints, buildings, and manhole, the estimated I/I
reduction may vary substantially. For example, the typical subsystem noted previously with
an I/I rate of 1000 GPD, a program of manhole grouting may eliminate 120 GPD:
120 GPD*l600GP£x60x2x0.6/600 (5)
A standard test-and-seal contract in the typical subsystem may eliminate 400 GPD:
400 GPD »1000 GPD x2.4x 100x1/600 <&
However, for a similar subsystem with no building connections and asbestos cement-
pipe with 12.5 foot joint spacing, the subsystem EQL would decrease to 237.6. The estimated
I/I removal from manhole grouting would increase to 303 GPD:
1000 GPD x 60x2x0.6/237.6 . <^
10
-------
The I/I reduction from a test-and-seal contract in the similar subsystem would reduce
to 242 GPD because of the fewer number of joints' which may be admitting I/I
242 GPD* 1000 GPDx2.4.x24x 1/237.6 (8)
SUMMARY : - .--', -^ .-'! ;'- * : . J ;' '. _ _' '.'.;.. ' '. ' '.''. :
The methodology discussed herein permits reliable determination of average quantities
of infiltration which can be validated based on long term records. The peak flows associated
with various percentages of infiltration in the waste flow can be calculated. The conventional
basis for design of separate sanitary sewers in systems where infiltration is a factor should
be reviewed since peak to average ratios, if overflows are to be prevented, are much higher
than those forecast by the currently accepted methodology of sewer design. .
11
-------
Metercd
PSOCFlow
(mgd).
450
5.60
3.70
5.60
550
4.70
5.40
4.40
4.10
550
550
3.70
5.00 -.
5.50
520
"455
5.45
5.40
5.40
4.60
650
5.30
6.00
550
650
625
625
720
Eit.
Sue How
(»gd)
2.04
2.04
2.04
2.04
2.04
2.04
2.04
2.04"
1.74
2.04
2.04
2.04
2.04
2.04
2.04
2.04
2.04
2.04
2.04
2.04
2.04
2.04 '
1.74
2.04
2.04
2.04
2.04
1.74
EJC
i/i
(mgd)
Prior to Repairs
256
356
1.66
356
3.46
2.66
356
136
256
321
356
1.66
256
3.46
3.16
251
3.41
3.36
336
256
4.76-
326
426
3.46
426
481
421
5.46
Ground
Water
Index (1)
^^^^^^
1.14
151
055
129
129
129
1.18
1.04
050
051
124
050
1.04
1.49
' 127
1.07
057
255
1.70
1.32
156
154
1.61
151
154
352
155
258
Cl»'
AvgLl
(ingd)(2)
251
156
1.75-
2.76
2.49
2.18
255
223
252
354"
3.10-
2.06
256
254
2.49
2.63
352-
1.43-
158
154
256
2.43
257
151-
220
157"
3.12-
257
Date
Jan 5-15,1973
Apr 11-15,1973
Oct 18-19,1974
Jan 31-Feb 1,1975
Feb22-ilar 1,1975
Mar 31-Apr 1,1975
May 1-3,1975
May 22-23,1975
Jun 10-11,1975
Oct 1-5,1975
Nov 16,1975
Dec 5.1975
Jan 16-20,1976
Feb 16-20,1976
Mar 19-21,1976
Apr 4-5,1976
Apr 10-11,1977
Dec S-9,1977
Jan 23-24,1978
Feb 3-5,1978
Mar 24-25,1978
Apr 6-10,1978
May 28430,1978
Dec 11-12,1978
Jan 31-Feb 1,1979
Mar 1-2,1979
Apr 16-20,1979
May 2S50,1979
Average
Average excluding 4 high and 4 low values noted*
2.43
2.42
. NOTES:
(1) GWI based on (0.0183 x Mancsquan Rivw Flow cfc)-0.189
' (2) Avg. I/I - Est 1/1 divided by GWI * . ,
-------
TABLE2
I/I DISTRIBUTION IN A TYPICAL PSOC CLAY PIPE REACH
Percentage of Reach I/I
".'-.' Probable to
PartofReach '.; Total . Eliminate
MANHOLES - .'. : -/ 15 9
BRANCH SEWERS ' - 50 47 ,
(from otherwise sound joints) (40) (40)
(from other pipe defects) (10) (7)
CONNECTIONS AND LOWER BUILDING SEWERS 15 12
UPPER BUILDING SEWERS "AND BUILDINGS 20 - 0
(building sewers, aU but lower 8 ft.) (15) , (0)
(building and foundation drains) (5) (0)
TOTAL 100 6S
-------
-------
- PLATE 1
DURATION (DAYS PER AVERAGE YEAR)
0.1 0.512 51020 50 100
1 I ! i
200
100.0
10.0
D! LO
£ °-5
0.1
0.5
5 5 1 5 1 ! | |
< : i :::£= i : i :
! ! i-::E: I 'N 5
! .lifiill 1 HI!;
1 iliiii
Ill
iii
V!P
! M 1 1 i
Mil!
iii!
1 -III
1- HI
^rr-nts: rrmt
^BM::=: : : : ':'':
n%-=i j riiji
I ji:?ry_ 1 s sfi
niiiiirHl i ill!
inn win
iiiiiil ! inSi
iililfi 1 Mil?
{ j!!!i!f! I i iii;
~ .. ; :::::-. :"i : :~
:: :>:;!:
f
H 1
ii i i
ii j 1
1 ' M
i i '
L 1 i
i !
| !
i i
! i
5
ii , ; j ; ; j j-
::
» i ! "I
H : : :
ii i 1 I
jj : | ;
< 1 1 1
!! N I i i
!i M
11 Nil
! j ^ 1
> i !::::= : : : i:
Him i i III!
i 'iiiiiil ! iiiit
1 HIM IHlii
i illlil
1 111
i !MM
K :
I; iii
!! I I I
; ill
II ! ! 1
: : :
; ' !
! ! i
I i !
i i i
] i
: j
i -.
"s: ?
:N : 2
! l\
i i I ^
LEGEND
0 ACTUAL D ATA POD*
\ SMOOTH CURVE OF
.NBESTFrr
ALTERNATIVE PEAK
MULTIPLIERS
ANNUAL EXCEEDENCI
2.4 HOURS
12 HOURS
A 24 HOURS
"^^^^^^^^^^^^"""^^"T^1!
t
i
1 MM ! Iii!
H ! i ii!
II! j I
ill ii P
I j Ji
Mill. S!
= ' j ' ?1?
: i :
: t ;
I j
: : :
1 H
I 1 i
1 1
""" - * *"
: l'.:-l s:::i ; ; 1
i
-1 1 1 V!
BASED ON CONTINUOUS|
BCUA DATA 1970-1984
TYPICAL
t-rrrrr i , =. f ; j r
; i i ;; i i ; i.u
! flHfeB i Nil
I 5 : ? :::|i S 5 «T
1 IIMW
i Hill
i HSl
! i!i!:
al I I
0.01 ai L<
i iiiii
iiilii
T/T 1?
1/Ir
! iiilii
) 1C
t rrt
| { i
I ! 1
i i
I!
i
: : i si::
Hi i ilii
iiiJ.i- ii
ill! ! Ii
Ii i i 1 »i
]!!!! l- III
ifiiill
iuw4
ii-14-4 £A
f!U i l!ii!
!! ! Hi!
ii JH|
ihM iiH
5 1 i
J ;
1 1
Ii
: :
! i
M
| |
t :
'V : "
4v-
1 1 ; >
!!
LOW EXCEEDENCE CURVE
if!!
! 1 !
]
iji ; |ii;
MM Hi
: ;
|
rs
«
i
i
i
.
i
!
.
W
! iii
XO 50.0 9a095.0 99.0 99.S
Xf
DURATION (PERCENT OF TOTAL TIME)
-------
PLATE 2
LEGEND
EQUATIONS FOR 7 FOR ALTERNATIVE CRITERIA:
EXCEEDENCE
DURATION FREQUENCY
2.4ERS/YR. «-TEARS 7
INFILTRATION/INFLOW
TOTAL AVERAGE FLOW
0.68 INFILTRATIONflNFLOW
TOTAL AVERAGE FLOW
O.S7 MTLTRATIONflNFLOW
TOTAL AVERAGE FLOW
PEAK TO AVERAGE FLOW RATES
VERSUS I/I PERCENTAGE
0.1
as LO 2.0 5.0 mo 20.0
AVERAGE SEWAGE FLOW (MGD)
50.0 100.0
-------
PLATES
RETURN FREQUENCY
is
TO
6- -
3
: 1
! j !
i :
J. - 1
i i
i i 1
. : :
i |
; :
: j
1
!
i
:
I : i
: : :
!
i ::
j : ;
i :
I
I \\
I ' : !
j f
{ |
1 i
i H
: i : :
| |
' i i
i
1
-,
1/2YR. 1YR 2YRS.
i i ! i ! i i i ! i ! iiiii
i : Is i 1 : : i Hi:
I. ! UL ,, H MI iiii.. _.
i i iii i ; Ml! ii i i!
1 i ill 1 1 .HI! !!!
l iij l1 ii - n i HI i
.- -Wli«- Jl l- IIU
II M 1 iii ! i i i !
.- II ill Jl Ml. J
1 Jl 1 II 1 1 If 1 1 1
It II if 1 i iiii
i ill i il MI 1 il i i l
I ill 1 IK 11 i HIM
j ! M! i ! i ' M . i i LJb-rr
iiiiLi H' ji Lksn
i nTi ^ll/li|il i 1
i M i JjSi lili! i !
I H. Jmll : [IIII
i Mijni iiii l iii I I I
! ILKii iili ill I I J
I *1J i M 1 ii ii i
! Ml. ! j 1 ! I : : : :
1 li! .! Mil iiii ii I
MM 5 1 Mil iiii ' -'
M i 1 1 i i
Ml ii ! f Ml! iiii i !
! i i { .if ]t iiii i ii
MM ii j Jj iiiii
i 1 : ! :!!!!:::: i
|il 1 i iii iii i
-ih "T ii i 1111 Iii
IP 1 r M iiii i
ill ii 1 M I Mil ij
i IH _:l ill 111.11
i -I.I ! 1 1 II 111 1
5 3 7 S 910 20 30
I/I RECURRENCE INI
5YRS. - 10YRS. 2C
| i i 1 iiiii
I !. 1 1 1 iiiii
.5 ! Hi
ii T- I ..JH-
1 . TT- i i
i iii
: : i >
l,lF- 1 IHi
f ! =i 1 ! !!!
Jl nil!
IIII ;"-= tJJi
jji4^HT ii!
i i i ' h 1 Mil
l 'hi' j i|lj
1 ! I ! Hi i
1 1 1 liiii'
iii 1 ' ilii
i ! ; - i » « :
i i i 1 i i
1 i 5 1 1 ! !!!!=
I !j|l|.
- 1 ' h!l|i
M i hil
I 1 ill!! 1
' M iiiii i
i ! 1 ' ITJltl
1 li Illlll
i 1 I : 1 i! 1
* ! ! i If:
i i i j 5 i ' « hit
IYRS:
iiill i
iliiiiii
ilil! ! i
Hi!!
iii! in
Usfi iii
iiiiiil
li i
iiiii iii
22
-
-s.
11
Sb
il
-------
-------
ATTACHMENTS
COMPREHENSIVE METHODOLOGY PLAN FOR INFLOW REMOVAL
1.) Data Gathering
a.) Map Reviews
b.) Interviews
c.) Records\Studies
d.) Identify Needs - Gaps
e.) Flow Monitoring and Rainfall Gauging
2.) System Modeling
a.) ReviewXSelect Model
b.) Characterization " »' ' '
c.) Impact Physical
d.) System Inventory
. , ' '>-. d ''-'.'
3.) Inflow Source Identification , ,.
a.) Prioritize worst to least areas
b.) Performing Field Techniques
c.) Phased Implementation (Fund Limitations)
10 Using the''inch/diameter/mile"Approach
2.) In proportion to remaining capacity
3.) Occurrence of SAO's
4.) Inflow Removal Guidelines
a.) Remove all sources or implement FIND IT-FIX IT"
b.) Quantity (estimate) Defects - highly desirable as a target
c.) Removal technologies.
5.) Evaluating Inflow Removal Success
a.) Correction Components f
b.) Post rehab (Removal)
c.) Monitoring Conditions
6.) Cost of Inflow Removal
a.) Program Costs
b.) Removal Costs by Source
7.) Recommendations for EPA Sponsored Projects
a.) Establish specific scopes
b.) Prioritize for Cost, benefits, etc.
-------
-------
ATTACHMENT 4
KEY MANHOLE MONITORING
Key manhole monitoring breaks the .collection system into a series of definable
subsystems. There is some controversy as to length of pipe within each subsystem to
maximize the effects of this type of monitoring which will be discussed later. The
advantages are:
1) Flow monitoring may help to eliminate some of the subsystems from further
study. ^ ,:
2) This type of flow monitoring can set priorities for the subsystems relative to
I/I severity. ..
3) More data is available to identify hydraulic restrictions.
4) Flow monitoring, if performed regularly, can build a foundation for a data
base which can be used in the future to evaluate the sewer system as the -
population increases and the sewers become older.
5) SSES completion time may be reduced by eliminating subareas from further
study.
6) Better correlation of flow, e.g., leaks found vs. monitored flow may be
obtained.
7) The reaction of each subsystem to the entire system for a particular storm can
be identified; this reaction is particularly important when rainfall varies in
intensity across the collection system or monitoring area.
8) Peak wet-weather flows are less travel-time dependent, making the
hydrograph easier to interpolate. .
9) A more effective maintenance program can be implemented; the program
places emphasis on the subsystems, where most of the I/I originates.
Some of the disadvantages to key manhole monitoring are: -
1 Multipoint monitoring is initially more expensive.
2) Resources required to monitor and maintain flow monitors increase in direct
proportion to the number of monitors used.
-------
ATTACHMENT 4
KEY MANHOLE MONITORING -CONTINUED
3) Some difficulty can be expected in balancing flows where one subsystem flows
through another, due to travel time, monitor accuracy, and varying rainfall
patterns.
4) . Eliminating some subsystems from further study overloads I/I point sources in
these subsystems that could be eliminated cost-effectively.
5) Unexpected surcharging of sewers make flow depth data useless. Anticipated
surcharging cam be handled by the. use of appropriate equipment.
Although initially much more expensive than single point flow monitoring, in most
cases key manhole monitoring will be the most economical approach because time will
not have been wasted looking for leaks which do not exist during a rehabilitation
project.
-------
WORK GROUP # 3
REDUCING PEAK INFILTRATION
FOR ELIMINATION OF SSOs IN
SANITARY SEWER SYSTEMS
APRIL 28,1995
-------
1 ff
-------
WORK GROUP #3 SUMMARY
INTRODUCTION/PURPOSE
The subject of discussion for the work group was to explore ways to reduce
peak infiltration for controlling SSOs into sanitary sewers. The work group
objectives were to develop a methodology for 1) assessing the extent of rainfall
induced infiltration (RII) in a sewer system; 2) differentiating peak RII from
peak inflow; 3) identifying the sources of RII; and 4) evaluating available
options and their costs for controlling unintended SSOs in sanitary sewers.
BACKGROUND
Flow data from EBMUD and a number of other systems have shown that RII
may be the major factor responsible for peak flows in some sanitary sewer
systems. In fact, the similarity in flow characteristics between inflows and RTI
has caused confusion in identifying one from another. Because of the similarity
in peaking characteristics between inflows and RII, it is necessary to determine
the causes and .sources of these peaking flows so that appropriate measures can
be taken to control these flows. In order to reduce the peak flows caused by
RII, it is necessary to develop techniques for differentiating these two I/I
sources so that appropriate rehabilitation techniques can be effectively applied.
ATTENDANTS
David Crouch, City of Fairfield
Steve Donovan, Hamilton County Municipal
Sewer District
Phil Hannan, Washington Suburban Sanitary
Commission / -1
Gisa Ju, Montgomery/Watson
Christine Kahr, Greater Houston Wastewater
Program
Tim Krasus, Louisville and Jefferson County
Metropolitan Sewer District v
Richard Nelson, Black and Veach
Michael Wallis, East Bay Municipal Utility
District (Group leader)
Lam Lim, U.S. EPA, Office of
Wastewater Management
s , * '
WG3-1
-------
WORK GROUP OVERVIEW
The session started out with everybody introducing themselves and indicated
issues and concerns that they expected to be discussed at these work group
sessions. The main issue being how to develop a methodology incorporating
techniques for determining the following:
- extent of peak RII in a sewer system
- sources of peak RE
- options for controlling RII
- costs associated with various available options identified
'
At the beginning of the meeting, one member disagreed with the need to
differentiating RII from inflows (alsq see work group #2 report on reducing
peak inflow). However, the majority justified such a need for purposes of cost
analyses and selection of rehabilitation techniques. The group suggested that
the purpose of distinguishing between RII and the other two traditional
components of extraneous flows (infiltration and inflow) is to determine
whether I/I remains elevated after a storm event because of residual inflow
from indirect sources, surged infiltration caused by elevated groundwater over
the sewer pipe, or both. This determination is performed based on the flow
monitoring results to direct the conduct of the SSES. If the cause of RII is
residual inflow then the inflow investigation will require activities such as
internal building inspections and more extensive dye testing of ditches. If the
cause of RII is infiltration surge then part of the investigation will need to be
coordinated with the end of rainfall events. If RII is caused by both residual
inflow and infiltration surge then the inflow investigation woiald need to be
performed first to isolate it as a component, to be followed by the infiltration
investigation. More detailed information is included in attachment 1. The
group also reported out a methodology for assessing RII outlined in figure 1.
The group concluded that in many cases RII can be identified and economically
removed from the system.
WORK GROUP #3 REPORT
Work Group 3 was assigned the task of discussing rainfall, induced infiltration
(RII). There was some disagreement among the members, but the definition
which follows was utilized for purposes of the workshop,
WG3-2
-------
Definition: RII is storm water entering a separated sanitary sewer system through
defects in manholes, mains, laterals, or private service lines, RH peak
flow characteristics are similar to inflow. However inflow is considered
a separate and distinct source from RII.
The significance of recognizing RII separately is related to the cost-effectiveness
of controlling it compared to inflow.
Work Group 3 established the following methodology to quantify RII and select
appropriate SSO control options. Interaction with each of the other Work
Groups will be required to effectively develop cost-effective SSO control
programs. Two key elements in identifying and controlling RH include:
Comprehensive System Modeling (flows, hydraulics, alternative
analyses for selecting cost-effective solutions).
Field Work.
Objectives:
Work Group 3 was assigned four specific objectives. Each objective is discussed
in the text below.
Objective 1; Assess the extent of RII in the sewer system
The following activities represent the key elements in determining the cause
of peak flows in sewer systems. ;
- Start with flow and rainfall monitoring.
- Develop flow hydrographs and rainfall hyetographs for actual events.
- Undertake inflow investigations first, since both the investigation and
inflow correction are less expensive than RII investigation and correction.
-. Inflow investigations rely primarily on smoke testing, dye flooding,
building inspection.
. Smoke testing of 100% of the system should eventually be done.
- Complete immediately in areas targeted for inflow or peak RII
correction. ,
WG3-3
-------
- Good maintenance practices will include smoke testing of the
entire system on an appropriate cycle (possibly every 5 to 10
years).
- Inflow correction has the potential to cause imcreases in RII
when storm water is redirected to the ground surface where it
may eventually enter defects in mains, lower laterals, or private
services.
Subsequent analytical steps become expensive; the process outlined in
Objectives 2 through 4 below is sometimes not affordable or necessary
when:
For small systems with fixed annual budgets, it may be prudent to simply
prioritize areas for rehab or relief based on flow measurements and
limited field data; these systems would invest annually in construction
and could not afford the cost for extensive planning and investigation;
these systems would have SSOs which require control, but no large
public health or water quality problems.
For larger systems with limited SSOs, an extensive flow monitoring study
and engineering, analysis would also not be justified; such systems should
be required to develop effective preventive maintenance programs and
reasonable system replacement schedules.
Objective 2; Differentiate peak RII from peak inflow
The general approach to defining peak flows and providing a basis for
evaluating management strategies is to create a comprehensive computer
model of the sewer system that predicts its response to rainfall and
groundwater. The following outlines the rationale and activities in
differentiating RII from inflow and developing the necessary model to
evaluate impacts and correction strategies.
- Purpose: the cost for correcting the sources of peak inflow is generally
substantially less than the cost for correcting diverse system defects which
cause peak RII; to properly evaluate the cost of removing RII,. it is
important to distinguish it from inflow.
- Use of flow monitoring data.
WG 3-4
-------
Figure 1
R 11 Methodology
I/I Sources
Monitor/Assess Peak Flows
Control
Options
Future
Long-term
Maintenance
' Practices
RII
Extent of Peak
Sources of Peak Rll
Options to Control Rll
Costs to Control Rll
Field Work
Smoke Test
Dye Rood
Building Inspection
MH Inspection
Flow Isolation
« Rainfall Simulation
TV
Vacuum/Pressure T
Work Groups
(^Preventive Maintenance
Z=Peak Inflow
SaPeakRII
4»Private Property
Control Options
WG 3-5
-------
. For areas with a distinct dry and wet season:
- Minimal antecedent soil moisture data indicates inflow
(minimum response to rainfall).
- . . * ' ' ^
- Increasing antecedent soil moisture results in higher response to
rainfall; difference is RII.
- Flow Modelling.
. Many approaches are currently utilized throughout the industry for
projecting flows from actual events to selected design conditions
through the use of the comprehensive model; at a minimum, the model
must be able to predict peak flows and estimate overflow volumes for
a variety of rainfall, groundwater, and base flow conditions. See
Recommendation I below.
Flow
Rainfall
Figure 2
- Flow projections.
. In hydraulic modeling, there is no benefit or need to distinguish RII
from inflow.
WG3-6
-------
. Need a method for estimating the volume and rate of upstream SSOs.
. Fluctuating groundwater conditions are important and expensive to
measure in the field (in some cases RH may be bether addressed by
using unregulated, long term stream flow records. This could
eliminate the need and expense of measuring fluctuating groundwater
conditions).
. Future growth and 1/1 assumptions.
--,-,'. ',','/. ' '
- Use of physical inspection data.
. Smoke testing.
-'', . - " * " . . '
. Manhole inspection.
. Flow isolation.
f " ' ' ' V ' . , ;
'. Dyed water flooding.
. Rainfall simulation.
. Television inspection.
. Vacuum and pressure testing.
. Building inspection.
. Review maintenance records for blockages/collapses and pipe materials
Reference Water Environment Federation (WEF), Manual of Practice
(MOP), Existing Sewer Evaluation and Rehabilitation, FD-6, 1994.
Objective 3; Identify RII sources
Field investigations are needed to identify RII sources to determine cost
effectiveness of rehabilitation.
- RII sources include all manhole and pipe defects (mains, lower laterals,
private service lines).
- Storm water percolating through soil to reach the above defects.
- Leaking storm sewers in common trenches with sewers.
WG3-7 ' -.'-'
-------
- Sewers crossing drainage channels or placed within drainage ways or
running parallel to drainage ways.
y ,''''. '' '
Objective 4: Identify options available for controlling RII and
their costs
Evaluating the options for controlling RII involves comparing the cost and
effectiveness of sewer rehabilitation with transport, storage, and treatment
needed to protect water quality and public health. Typically, a model is used
to predict the effectiveness of rehabilitation on reducing peak flows and
volumes; that information is used in developing corresponding transport,
treatment, and storage elements.
- Comprehensive rehabilitation including mains, lower laterals, private
services to achieve 70% +/- reduction of peak I/I.
- Rehabilitation of mains and lower laterals for "less" reduction of peak I/I
(say 30 - 40%). See Recommendation 2 below.
- Cost-effectiveness Analysis.
. Project overflow volume and rate:
- Must utilize historical system response data over a long period
of time to ensure accuracy.
- Include future flow projections based on land use planning
information.
- 1/1 will increase over a long period of time; future 1/1
conditions must be defined.
- Possibly cap I/I at current levels by instituting aggressive long
term preventive maintenance programs.
i '
- Consider future design and construction practices.
See Recommendation 3 below.
- Capping I/I at current levels or providing an allowance for
additional system deterioration must be based on a realistic
assessment of the level of reinvestment in the sewer system.
- Consider relating future 1/1 conditions to overall system age
(which varies with the investment in rehabilitation and
WG 3-8
-------
.restoration); if a municipality fails to invest enough each year
in rehabilitation to maintain the current system age, then an
allowance for future additional 1/1 must be included in design
flow projections.
- It is difficult to predict future 1/1 conditions related to
continuing system deterioration; an allowance for future
deterioration may be offset by conservative design assumptions.
: . Design for no surcharge; capacity is gained when the system
actually surcharges.
. Conservative pipe sizing (roughness coefficient, etc.);
- Assess water quality impacts.
- Define the level of SSO control required; Work Group 3
believes that the level of SSO control required is governed by
local conditions-, M eventual SSO policy or guidance shall be
flexible and allow for local definition of the level of control
required. ,
- Develop engineering solutions for the selected control levels;
. Rehabilitation to remove 1/1 (model must include varying
levels of 1/1 reduction associated with various rehabilitation
approaches: mains only, mains and lower laterals,
comprehensive).
- Rehabilitation methods can vary in effectiveness and cost
depending on local conditions.
. Grouting can be effective in certain conditions; costs must
include replacement; design life for grout is shorter than
other rehab methods such as sliplining, etc.
.Manhole rehabilitation is generally effective for 1/1 reduction:
- Liners
- Coatings
- Joint Sealers
- Replacement
WG 3-9
-------
. Grouting and manhole 'rehabilitation must include all joints
and leaks (must be comprehensive) to be effective due to
migration of 1/1 from one defect to another.
. Other rehabilitation methods:
- Sliplining - -
- Cured in place pipe (CIPP)
- Remove and replace
- Pipe bursting
- Fold and form liners
Methods such as CIPP and fold and form liners may not
achieve the sam levels of I/I reduction since no correction is
made to the connection point between the lateral and the main.
- Transport and treat to appropriate levels (secondary or less)
- Store and treat
- Combinations of the above
Develop the most cost-effective alternative; complete financial
affordability analysis.
Model compares cost per gallon of 1/1 removed to cost per gallon to
transport/treat/store.
Costs vary tremendously depending on local geographic areas, size
and depth of facilities, etc.
Do not utilize cost curves due to local variability in costs.
Recommendations
Work group #3 recommends that the following studies be undertaken by the
appropriate contractor or by EPA:
WG 3-10
-------
Recommendation 1: Flow Projection Methodology
Provide technical guidance on methods to project design flows from flow
monitoring data.
- Describe alterative methods and approaches for projecting flows for larger
storms based on flow monitoring results from small storms; advantages
and disadvantages of each:
- Unit hydrography
- Linear, log normal relationships of flow to rainfall
-Defect models ,
- Antecedent soil moisture conditions
- 3 dimensional relationships including storm duration
- Develop data analysis techniques
- Hydrographs ,
- Hyetpgraphs
- Scatter Plots
- Describe the extent of rainfall data to be collected and the application of
newer technologies including radar detection and rainfall determination
techniques.
- Develop information on the uncertainties associated with rainfall and
flow projections and their impact on facility sizing; provide guidance on
the resolution and duration of rainfall and flow measurements.
- include case studies.
Recommendation 2: Effectiveness of Rehabilitation Approaches
- Develop a summary of national data on 1/1 reduction resulting from
multiple rehabilitation approaches: "
WG 3-11
-------
- Mains only ~-
- Mains and lower laterals
- Comprehensive rehabilitation (mains, lower laterals, private services).
- Quantify type of 1/1 reduction:
- Peak flows
- Flow volume
- Relate I/I reduction to source
" '
- RII
- GWI
- Define other system variables:
- Size
- Type of repair made at connections (lower lateral to main, private
service to lower lateral).
- Develop cost data for rehabilitation:
- $/foot of pipe (based on system-wide length of pipe)
- S/foot of pipe (based on feet of pipe rehabilitated)
- $/gaIIon of 1/1 removed.
- Collect cost data on approach to replacement of sewer systems:
- Annual investment in rehabilitation = x% of system value
- Expected design life of sewer system = 50 years? 100 years?
- Does annual investment match expected design life?
- Cost data are useful; do not develop cost curves (they are inaccurate due to
the variability of local conditio ns).
WG3-12
-------
- Is it possible to develop any generalized guidance on the minimum cost of
system rehabilitation for 1/1 reduction? (e.g., minimum $/total feet of pipe
in the system).
Recommendation 3; Future Design and Construction Practices
Develop technical guidance on engineering and construction practices for new
facilities to minimize I,/K in the future and facilitate study and analysis.
- Pipe and manhole material
r <
- Backfill specifications
V Joint design » ,
- Make laterals accessible to TV inspection
. Cleanouts
. Common laterals serving multiple dwelling units
. - During rehabilitation of public lines, TV laterals; make results available to
private property owners and recommend repair when appropriate.
- Prohibit backyard easements.
- For large systems, design permanent monitoring stations.
- These construction practices can be accomplished at zero or low cost when
compared to retroactive correction.
\ . '..'
Additional Reference: In 1990 EPA completed a report entitled Rainfall
Induced Infiltraton - A Report to Congress (EPA 430/09-90-005) which includes
much of the information summarized above and specific case studies. Refer to
Attachment 3 for more details.
WG 3-13
-------
-------
Identification and reduction of excessive flow in sewer systems is a complex
problem just beginning to be understood by the technical community.
Inflow Distribution in
Wastewater
Systems
A- cross connection initially identified by
dyed-water flooding must be subsequent-
ly located by T.V. inspection'with concur-
rent dyed-water flooding.
by AJai J. Hollenbeck P.E.
and Richard J. Nogaj P.E.
Identification and elimination of in-
filtration and inflow (I/I) sources in
sanitary- sewer systems has turned out
to be far more complex than originally
anticipated by authors of the federal
Water Pollution Control Act Amend-
ments of 1972:
The, 1980 U.S. EPA report1 on the
effectiveness of the I/I program has
been interpreted by many to conclude
that the entire I/I rehabilitation pro-
gram has been ineffective. The EPA
report has also been used as justifica-
tion for aband9ning or scaling down
implementation of a nationwide I/I
rehabilitation effort. At the same time
that the engineering profession is de-
veloping the necessary experience and
technology" to improve" rehabilitation
programs, pressures have developed to
reduce both the cost and time required
for sewer system evaluation survey
projects.
.Comparative flow monitoring data
was the major basis for the conclusion
in the EPA report that rehabilitation ,
programs completed ,to-date have been
ineffective. Typical comparative data
from the EPA report are shown in
Table 1. Consistent flow monitoring
criteria, however, complete with stan-
dard definitions for peak infiltration
and peak inflow-have yet to be imple-
, mented throughout the profession.
Such standard criteria are essential for
proper evaluation of I/I programs.
In many areas and especially in the
Midwest, the inflow component of I/I
causes many of the apparent problems.
Careful evaluation of .inflow is there-
fore necessary to avoid misleading
conclusions. It is interesting to note
that the EPA report states:
"The methods used to estimate in-
flow during the SSES [Sewer System
Evaluation Survey] work were inexact
and the method used to calculate in-
flow during the study may be question-
able. Thus, it is scientifically unsound
If intensive monitoring is used to eliminate 80 percent of the field survey, then inflow
sources such as building downspouts would not be identified.
Tatoto "t- *-x£
I/I RahabtHtatlon EffoetH
;%' -' ' ^
fvVQv
According to 198O EPA ftoport
I/I Reduction
Municipality Predicted
Mt. Holly, PA 60
Castle Rock, WA 82
Centralia, WA 60
Dunsmuir, CA 99
New Buffalo. Ml 85
Amity, PA 85
Sussex, Wl 92
Conyngham, PA 92
Average 82
Achieved
23
60
- 3
0
1
24
7
17
17
r . --v.,'-v:_;
' "" Ti
StUtfrATM
.
^,*:yjjjj8t
toteJl^ilP
.. ... k~ -TV- "^
Total
, Peak Inflow
Municipality
Arrowhead
Marengo
Belvidere
St. Charles
Villa Park
Population
2,500
4.500
15,000
17.000
12,000
(mgd)
1.4
4.2
10.0
18.4
14.9 .
fjgjiiijg^e ,,M
'JJKJ*:''A' - '"">£<' -
itifl^lfe^:^-'.
'^jjjSSSg-^'
Main Sewers
(tt)
50,000
95,000
325,000
440,000
187,000
Average
Age
(years)
15
30
20
20
20
Reprinted from the January 1983 issue of WATER/Engineering & Management
-------
to state that inflow removal in the 18
sewer systems that were studied was or
was not effective."
Concern over the cost and time to
complete a typical SSES project has
led to the use of flow monitoring as a
basis for eliminating large portions of
the collectipn system from field survey
activities such as manhole inspections.
smoke testing, dyed water flooding,
building inspection and television in-
spection. Installation of flow monitors
at an interval of approximately 4.000 ft
has been proposed to eliminate large
sections of the collection system from
further field survey. Achieving a suc-
cessful I/I rehabilitation program
where large parts of a collection sys-
tem are not surveyed is dependent,
however, on the assumption that a
large percentage of the total infiltra-.
lion and inflow is concentrated within
a small portion of the system.
The results of an analysis of actual
field-verified inflow data for sev-
eral sewer system evaluation surveys
conducted by RJN Environmental As-
sociates pointed to certain conclusions
about the inflow component of I/I.
The sewer systems evaluated con-
tained a wide range of pipe materials,
age and construction techniques. Four
of the five study areas had older cen-
tral sections as well as newer outlying
subdivisions. An SSES was conducted
for each of these communities with the
aid of computerized data management
and analysis procedures. Characteris-
tics of Jhe study areas are shown in
Table 2.
During the SSES studies, flow moni-
toring was performed at intervals of
approximately 25,000 ft in the piping
system. Continuously recording rain
gauges were also placed in each study
area so that peak inflow could be
determined relative to rainfall intensi-
ty. A determination of peak inflow as a
function of rainfall intensity for each
basin was made on the basis of a one-
yr storm event as the reference storm
in accordance with previously pub-
lished procedures.2 Inflow sources
. were identified from manhole inspec-
tions, smoke testing, dyed water flood-
ing and building inspections.
All field data was entered into a
computer. Peak inflow was quantified
by individual inflow source and 'then
assigned to the specific manhole-to-
manhole line segment on which the
source was located. The next step was
balancing peak inflow obtained from
flow monitoring with flow obtained
from quantification of the inflow
sources that were identified during
field surveys. An acceptable balance
between total monitored inflow by ba-
sin, and total identified inflow by ba-
sin ensured that essentially all of the
inflow was actually identified. If an
acceptable flow balance was not
achieved, then additional field survey
activities were performed to locate re-
maining inflow sources.
Since all inflow sources were quan-
tified and assigned to a line segment, a
computer model could be used to ana-
lyze the distribution of inflow as it
actually existed in the system. The RJN
Environmental computer program de-
veloped for sewer system studies, re-
ferred to as "CASS," includes the abil-
ity to simulate the use of a wide range
of flow monitoring intervals. An im-
portant aspect of the approach is that
the data base used in the computer
analysis is developed from both flow
monitoring and field survey data. Re-
sults of- this analysis are therefore
based on the actual location and mag-
nitude of each identified inflow
sourcenot on flow monitoring data
alone.
The first level of, the evaluation
shows the distribution of inflow
sources based on the use of a flow
monitoring interval of approximately
25,000 lin ft as used during the SSES
studies. This interval indicates that an
average of 68 percent of each collec-
tion system must be surveyed in order
to identify 80,percent of total system
inflow (Table 3). Consequently, only 32
percent of the collection system would
be eliminated from any field survey.3
There have been published reports
that flow monitoring at this interval
should normally result in eliminating
60 percent of a collection system from
field studies, as compared to the aver-
age of 32 percent identified for the
projects surveyed here.
The next step was to look at data
obtained using 4,000 ft monitoring in-
tervals. Often referred to as intensive
monitoring, this interval requires that
one flow meter be installed at approxi-
mately every 15 manholes in the col-
lection system. The cost-effectiveness
of intensive flow monitoring is depen-
dent on the ability to eliminate major
parts of the collection system from the
field survey work. Previous claims'
have been made that use of intensive
flow monitoring should result in elimi-
nating 80 percent of a collection system
from any field survey because the
remaining 20 percent of the system is
said to contain 80 percent of the total
inflow*. Results from this study, how-
ever, indicate that if a 4.000 ft monitor-
ing interval was used, it would still be
necessary to perform field tasks in 50
percent of the collection system if 80
percent of the inflow was to be identi-
fied (Table 4). Thus, implementation of
an intensive flow monitoring program
would only have resulted in eliminat-
ing approximately 50 percent of the
collection system from field work.
The final evaluation phase involved
simulating a flow meter at every man-
hole (approximately 250 ft). This ap-
proach applied to an entire collection
system would obviously be too expen-
sive, but it is interesting to note the
results that could be expected. The
data analyses indicate that the installa-
tion of a flow meter at every manhole .
does not result in eliminating 80 per-
cent of a collection system from a field
survey. On the average, approximately
30 percent of the system would still
t^XKaflM^^^^El^EiSKJC^&^V^ra^^^^^^^l^^^Hl^^HRR
^BBK
Hh^^
jf^^B^^^lrW'^|M|j^^^^^^^SjP
&s|3SaEJP*gK
K*'*J4W.'
RS?
!?5tKS1355?§H
-s8*?Hm
i - ---.f* .- .-*.*.#**, ' . .* '^fc^p^sa^^^M
n^HUHMBB^HBi^TCira^
System Surveyed (%)
. UunldpaHy Total Inflow (%)
Arrowhead
Merango
BeMdere ' '
StCbarte. .$£.
We, Park '»;*'£ '
. . AyW*^ACF _ ,""--.
4O
33
35
24
22
22
27
6O
50
52
40
38
48
. .46
80
73
73
64
58
74
68
System Surveyed {%}
Municipality Total Inflow <%J
Arrowhead
Marengo
BeMdere
St Charles
vmaPark
Average . ....
40
29
25
19
14
15
_ 20
60
44
40
30
20
28
32
80
' 62
65
50
32
44
51
-------
to state that inflow removal in the 18
sewer systems that were studied was or
was not effective."
Concern over the cost and time to
complete a typical SSES project has
led to the use of flow monitoring as a
basis for eliminating large portions of
the collection system from field survey
activities such as manhole inspections,
smoke testing, dyed water flooding,
building inspection and television in-
spection. Installation of flow monitors
at an interval of approximately 4,000 ft
has been proposed to eliminate large
sections of the collection system from
further field survey. Achieving a suc-
cessful I/I rehabilitation program
where large parts of a collection sys-
tem are not 'surveyed is dependent,
however, on the assumption that a
large percentage of the total infiltra-.
tion and inflow is concentrated within
a small portion of the system.
The results of an analysis of actual
field-verified inflow data for sev-
eral sewer system evaluation surveys
conducted by RJN Environmental As-
sociates pointed to certain conclusions
about the inflow component of I/I.
The sewer systems evaluated con-
tained a wide range of pipe materials,
age and construction techniques. Four
, of the five study areas had older cen-
tral sections as well as newer outlying
subdivisions. An SSES was conducted
for each of these communities with the
aid of computerized data management
and analysis procedures. Characteris-
tics of'the study areas are shown in
Table 2.
During the SSES studies, flow moni-
toring was performed at intervals of
approximately 25,000 ft in the piping
system. Continuously recording rain
gauges were also placed in each study
area so that peak inflow could be
determined relative to rainfall intensi-
ty. A determination of peak inflow as a
function of rainfall intensity for each
basin was made on the basis of a one-
yr storm event as the reference storm
in accordance .with previously pub-
lished procedures.2 Inflow sources
were identified from manhole inspec-
tions, smoke testing, dyed water flood-
ing and building inspections.
All field data was entered-into a,
computer..Peak inflow was quantified
by individual inflow source and then
assigned to the specific manhole-to-
manhole line segment on which the
source was located. The next step was
balancing peak inflow obtained from
flow monitoring with flow obtained
from quantification of the inflow
sources that were identified during
field surveys. An acceptable balance
between total monitored inflow by ba-
sin, and total identified inflow" by ba-
sin ensured that essentially all of the
inflow was actually identified. If an
acceptable flow balance was not
achieved, then additional field survey
activities were performed to locate re-
maining inflow sources.
Since all inflow sources were quan-
tified and assigned to a line segment, a
computer model could be used to ana-
lyze the distribution of inflow as it
actually existed in the system. The RJN
Environmental computer program de-
veloped for sewer system studies, re-
ferred to as "CASS," includes the abil-
ity to simulate the use of a wide range
of flow monitoring intervals. An im-
portant aspect of the approach is that
the data base.used in.the computer
-analysis is developed from both flow
monitoring and field survey data. Re-
sults of this analysis are therefore
based on the actual location and mag-
nitude of each identified inflow
sourcenot on flow monitoring data
alone.
The first level of the evaluation
shows the distribution of inflow
sources based on the use of a flow
monitoring interval of approximately
25,000 lin ft as used during the SSES
studies. This interval indicates that an
average of 68 percent of each collec-
tion system must be surveyed in order
to identify 80 percent of total system
inflow (Table 3). Consequently, only 32
percent of the collection system would
be eliminated from any field survey.3
There have been published reports
.that flow monitoring at this interval
should normally result in eliminating
60 percent of a collection system from
field studies, as compared to the aver-
age of 32 percent identified for the
projects surveyed here.
The next step was to look at data
obtained using 4,000 ft monitoring in-
tervals. Often, referred to as intensive
monitoring, this interval requires that
one flow meter be installed at approxi-
mately every 15 manholes in the col-
lection system. The cost-effectiveness
of intensive flow monitoring is depen-
dent on the ability to eliminate major
parts of the collection system from the
field survey work. Previous claims
have been made that use of intensive
flow monitoring should result in elimi-
nating 80 percent of a collection system
from any field survey because the
remaining 20 percent of the system is
said to contain 80 percent of the total
inflow4. Results from this study, how-
ever, indicate that if a 4,000 ft monitor-
ing interval was used, it would still be
necessary to perform field tasks in 50
percent of the collection system if 80
percent of the inflow was to be identi-
fied (Table 4). Thus, implementation of
an intensive flow monitoring program
would only have resulted in eliminat-
ing approximately 50 percent of the
collection system from field work.
The final evaluation phase involved
simulating a flow meter at every man-
hole (approximately 250 ft). This ap-
proach applied to an entire collection
system would obviously be too expen-
sive, but it is interesting to note the
results that could be expected. The
data analyses indicate that the installa-
tion of a flow meter at every manhole
does not result in eliminating 80 per-
cent of a collection, system from a field
survey. On the average, approximately
30 percent of the system would still
'
Tot* Mow (%)
-'&"-''-'-..
"'%*"i :." -
yjp!?,""-?"'' ' ' .
Ssfet'ih^ '*' - -
lp^5' " :'" '*''
£*&- -^-' * »*-
Syrta
4O
33
36
24
22
22
27
Sunwyad
. «O
so :
52
40
38
48
._^6
(%)
80
73
73
64
58
74 '
68
SyatamSurvay^(%)
Municipality
Anownaad
Marango
nmhtlrtowm
D8JTVKJMW
StOwtoa
VBtaPark
Avaraga
Total Inflow <%^> 4O
29
- 25
19 -
14
15
.- -.-"20
60 .,80
44 62
'40 65
30 50
20 32
28 44
32 51
-------
Muntoipattty
Arrowhead
Marenoo
Beivkiera
St. Charles
VTMaPark
Average
System Surveyed (%)
Total Inflow (%) 4O 6O 80
8 19 32
10 20 40
8 18 29
5 10 16
8
8
14
16
26
29
Municipality
Arrowhead
Marengo '
Behridare
StChartoe
Vina Park
Average
Basin
Number
8
3
6
4
7
2
9
1
5
fc*n-
BasJn
Size
(Wm>*
124
117
49
68
168
149
27
97
76
Peak
Inflow
(mod)
2.7
1.8
0.7
0.9
1.7
1.4
0.2
0.4
0.3
Unit
Inflow Rftte
(gpd/Mmr
21.900
15.000
14.600
12.600 *
9.80O
9.600
6.600
4.300
3.900
Priority
1
2
a
2
3
3
4
4
4
Figure 1. Average Inflow Distribution by
Monitoring Interval.
require field survey to identify 80 per-
cent of the inflow, even if flow meters
were installed at every manhole to iso-
late the inflow (Table 5).
A plot of the average inflow distri-
bution data for the flow monitoring
intervals analyzed is shown on Fig. 1.
In all cases a relatively even distribu-
tion of inflow is evident. The 4.000 ft
interval resulted in a distribution of
inflow sources corresponding to ap-
proximately an 80/50 rule as compared
to the 80/20 rule previously reported.
Inflow distribution data at the same
4.000 ft interval plotted for each proj-
ect does not suggest a high concentra-
tion of inflow (Fig. 2). The St. Charles
system showed the highest degree of
Inflow concentration, while the AT-
Figure 2. Inflow Distribution for Intensive
Monitoring.
rowhead system showed the lowest.
None of the projects approached 80
percent of system inflow in 20 percent
of the total system.
Although inflow may not be highly
concentrated in small sections of a
sewer system, experience shows that
large individual sources do exist. Typi-
cal examples include low-lying defec-
tive manholes, cross connections with
sanitary sewers, and defective sanitary
sewers that pass through storm sewers.
The fact that these large sources exist
does not imply, however, that they are
concentrated in a small part of the col-
lection system. An analysis was per-
formed to determine the extent that
flow monitoring would isolate the larg-
est inflow sources in each of the five
Number of
Intanaiv*
Monttom
12
33
57
79
32
%of 10
Largeet Inflow
40
70
30
40
80
52
study areas. Intensive flow monitors
were simulated for an average flow
monitoring interval of 4.000 ft. The
results show that if 80 percent of the
collection system is eliminated from
field survey activities, then, on the
average, only 52 percent of the ten
largest inflow sources in all of the
study areas would be identified. Some
of the large sources which would have
been missed contribute in excess of _50
gpm per source. A summary of the sim-
ulated intensive flow monitoring data
is show in Table 6. Based on the results
of this analysis, it can be stated that the
implementation of an intensive flow
monitoring program may result in only
about one-half of the largest inflow
sources identified. swith the balance
never identified or rehabilitated.
The fact that inflow is relatively
evenly distributed in the collection
systems analyzed is further evidenced
by the .widespread identification of
certain sources. For example, an aver-
age of approximately 75 percent of the
manholes in the study areas had defec-
tive frame seals. It is this widespread
occurrence of sources that results in an
essentially even distribution of inflow
throughout the collection system. Such
a distribution prevents the isolation of
a large percentage of inflow into a
small part of the system.
Attempts to reduce the cost of SSES
projects have normally concentrated
on eliminating as much of the field
survey work as possible. The increased
application of this approach will most
probably lead to further dissatisfaction
with the results from I/I reduction pro-
grams. Large percentages of total sys-
tem inflow cannot effectively be reha-
bilitated when only a small part of the
system is surveyed. Since I/I will not
disappear just by the effect of regula-
tions or funding limitations, alternative
approaches to high initial first cost
SSES studies still need to be found so
that effective results can be obtained
from I/I rehabilitation.
One method, the priority approach,
would be to apply the results of
flow monitoring of an interval of ap-
proximately 25,000 ft to rank the drain-
age basins of a collection system in
descending order by unit inflow rates.
By assigning priorities to the basins.
-------
annual field survey program which
includes manhole inspections, smoke
testing, building inspections, dyed wa-
ter flooding and television inspection
could be used. Priority ranking is an
approach that can be integrated.with
an annual operation and maintenance
program, In one example (Table 7), a
field survey could be initiated in the
Priority 1 basin during the first year.
followed by system rehabilitation in
the second year. A field survey could
then be conducted in Priority 2 basins
sometime during the second year and
similarly for the balance of the basins
and their corresponding priority.
Four major conclusions were drawn
from the analysis of the data collected
in this study. ' - ..
Inflow is generally not highly con-
centrated hi small parts of a collection
system but rather evenly distributed. It
is independent .of the flow monitoring
interval used to isolate inflow
sources.. ,
Elimination of large parts of a
sanitary sewer system from field sur-
vey activities could result in not identi-
fying up to 50 percent of the largest
inflow sources.
Inflow reduction is proportional
to the extent of the field survey work
performed.
Rehabilitation- by priority can be
part of an annual operation and main-
tenance program.
The identification and reduction of
excessive flow in a sewer system is
complex and is just beginning to be
understood by the technical communi-
ty. Therefore, it would be inappropri-
ate to abandon the program or search
for shortcuts that will not accomplish
the stated goals and desired objectives
of the I/I reduction and rehabilitation
efforts.
REFERENCES
1. "Evaluation of Infiltration/Inflow Program. Fi-
nal Report Draft;" U.S. EPA duly. 1980).
2. Nogaj. R.'|. and A. |. Hollenbeck. "One Tech-
nique For Estimating-Inflow With Surcharge
Conditions." Journal WPCF (April. 1981).
3. Tharp. E. L. and L. P. Lawson. "Improve I-
I/SSES Accuracy and Cut Costs." Water fr
Wastes Engineering (July. 1980).
4. DeCoite. D.C.W.. R. A. Tsugita and R. Petroff.
"Infiltration/Inflow Source Identification by
Comprehensive Flow Monitoring." presented
at the 52nd annual Water Pollution Control
Federation Conference. Houston, Texas (Octo-
ber. 1979).
About the Authors
Alan f. Hollenfaeck, department head, and
Richard J. Noga/. president, are with RJN
Environmental Associates. Inc.. consulting
engineers. Wheaton. Illinois. This paper
Was presented by Mr. Hollenbeck at the
55th annual meeting of the Central States
Water Pollution Control Association in
fllcomingdaie, Illinois. May ,19, 1982.
-------
-------
WORK GROUP #4
MAINTENANCE AND REPAIR OF
PRIVATE BUILDING SEWERS
FOR CONTROLLING SSOs
APRIL 28,1995
-------
-------
WORK GROUP #4 SUMMARY
INTRODUCTION/PURPOSE
The subject of discussion for the work group was how to address the
institutional and legal issues associated with Maintenance and rehabilitation of
building sewer located on private properties. The work group also needed to
address costs of available technologies for inspection and rehabilitation of
building sewers
BACKGROUND
Historically, building sewers are poorly maintained because major portions of
these sewers are privately owned. Municipalities inspect and maintain only the
portion of building sewers between the street connections and the property
lines. It is estimated that about 50% of I/I is originated from building sewers.
Success of an I/I correction program to reduce SSOs would be of limited value
if building sewer rehabilitation were not addressed. Municipalities need to
develop ways to overcome the institutional and legal barriers to maintaining
and repairing privately owned building sewers. ' .,
ATTENDANTS
Rodolfo Fernandez, RJN Group Inc.
Stephen Jenkins, City of San Marcos
Ralph Johnson, GWR Engineers
T.R. "Buddy" Morgan, City of Montgomery (Group leader)
Jay Reynolds, City of South Portland
Bill Sukenik, Greater Houston Wastewater Program
Jacqueline Townsend, Charlotte-Mecklenburg
Utility Department
Charles Vanderlyn, U.S. EPA, Office of
Wastewater Management
WG 4-1
-------
WORK GROUP OVERVIEW
The session started out with everybody introducing themselves and indicated
issues and concerns that they expected to be discussed at these work group
sessions. The main issue being problems associated with maintenance of
building sewers of both a technical and institutional in nature. To resolve these:
issues, the work group agreed that they needed to address the following: '
- Maintenance programs in other utilities such as gas, electric and telephone
companies.
- Options available for overcoming the existing institutional barriers in sanitary
sewers districts. .
- Experiences and successes of some sanitary districts in dealiing with these
problems.
- State of the art technologies available for inspecting and rehabilitating
building sewers.
- The costs associated with the various inspection and rehabilitation options.
WORK GROUP # 4 REPORT
SUMMARY
The group discussed various ways to define the lateral. Buddy Morgan explained that
in 'the City of Montgomery the entire line from the top of the main to house is
considered to be a private line. The health department has to tell the home owner
they have a problem with their building sewer. If the lateral fail at the "Y"
connection then the city takes responsibility.
The discussion continued with a general agreement reached that in most municipalities
the lateral is owned by the home owner. The municipality notifies home owners to
repair. After notification, the home owners have 60 days to make repairs. The home
owner is generally responsible for the lateral from curb to the house. In some new
subdivision, however, the lateral may run three feet inside curb.
Buddy, also described part of the city's incentive program. For lateral failures in
older houses in low income areas, the municipality fixes the system (attachment 1
describes the City of Montgomery program 1-5 in more detail). Maximum cost to the
home
WG 4-2
-------
owner is $1,200. The city pays any additional costs and will finance the 1,200, up to 4
years with a no interest loan. The city will provide pictures with flags to indicate I/I
points to home owner. After 60 days the city sends a follow up letter and requests
that the water utility disconnect the water service to the home, for non compliance.
The city can opt to use a private plumber or utility personal to fix lateral house. Most
houses older than 20 years no clean outs.. Most new subdivision have capacity fees.
The group suggested that the Federal Government can help water quality standards
with tax credits for I/I relieve over a base amount. The issue was raised about the
expenditure of public funds for use on private property. The group suggested the
following possible options:
- Special grants for rehabilitation of lateral.
' , * ' , "
- Block grants -
- State funds, etc.
The group suggested some penalty on the POTW if I/I was not removed. However,
several problem with this approach were identified.
- Permits are on POTW, but POTW may not own the collection system.
- Multiple municipalities may use the same collection system, and each with
different lateral regulations.
The group agreed that in order to reach the objects, several Issues of concern would
have to be addressed. These major issues of concern included:
- Social
- Economic
- Legal
- Political
-Health related
- Education
- Enforcement
WG 4-3
-------
- Technical
- Financial
The municipality needs to do something. EPA may require a plan of action to make
something happen. The group suggested the following actions:
- Economic; . ,-
- Phased scheduling reliefattack the most serious problems in the
collection system first.
- Delegated states should receive guidance to take care of immediate
needs. Frequently changing -ownership.
- Health Related;
- Health Department inspections to evaluate conditions of the house,
because lateral can be cause for making house uninhabitable.
- Back flow values.
- Political;
- One entity needs to take complete control.
- Financial;
- Use of SRF funds for lateral repair.
- Tax exemption for municipal bonds (currently have limited for use on
private property).
- Legal;
Explore IRS issue, if there are limits on use of tax exempt bonds for
environmental improvements on private property.
Provide local communities with tools needed to connect lateral
problems; i.e. are illegal connections covered by CWA?
WG4-4
-------
- Technical; -
- Distinct definition of laterals could be:
"line from a structure to a sanitary collection system eventually
trying in the building lateral".
- 10 States Standards are good for designing flow capabilities, but good
standards for pipe installation are needed.
-Develop minimum standards for collection systems.
* '"". . - " ' "'"."
- Enforcement; "-_',"
- Use of lenders to inspect laterals, when homes are sold. Could be low
term solution. Problem is older homes that are causing biggest
problem, but these homes do not turn over rapidly. With no change of
ownership they are an ongoing maintenance problem.
- Social;
- RegionalMocal differences.
- Educational;
- EPA needs to develop educational materials on the benefits of
rehabilitating laterals. Municipalities need a mechanism to get the
- . . ' word out. ,.
-Benefits to home owner.
-Information to address wet weather concerns.
- Need to educate the kids and municipal officials.
RECOMMENDATIONS
.x '
The group indicated a need for extensive dialogue between various Governmental
agencies to discuss SSO lateral problem and how to resolve private lateral issues. The
group also agreed that there was a need to develop linkage between private and public
responsibilities.
WG 4-5
-------
The work group developed the following list of needs. Many of these need will require
additional research on the part of EPA or other outside organizations such as the
WEF, AMSA, etc.
- Need to educate everyone involved on the house lateral SSO issues.
. The City of Fairfield has developed an educational video tape.
. Case study for Fairfield, OH and Montgomery, AL.
- Need for good preventive maintenance - so that SSO problems will not occur.
Why should high wet weather flows be tolerated by the community?
* ' ' '
- Need to do TV lateral observations during wet weather.
.- Need to look at customer records of sewer problems - backups, blockages, etc.
- Need to thoroughly analyze what the off line structures are going to do.
BenefitVcost analysis.
- Need to take care of immediate needs.
WHG 4-6
-------
ATTACHMENT 1
Data Handling Procedures Expedite Sewer Evaluation and Repair of Service Laterals
Co-authored by - ' "'
Reggie Rowe, P.E., CH2M HiU and
Danny Hohnberg, P.E., Assistant Genera) Manager
The Montgomery Water Works and Sanitary Sewer Board
Introduction
Communities across the nation are re-examining the issue of service laterals as a significant source of
extraneous infiltration/inflow. This renewed interest has been prompted by the current industry-wide
emphasis on correcting sanitary sewer overflows (SSQs), the increasing concerns of the public about
water quality, and the need for maximum water system efficiency mandated by tight operating budgets
and limited capital improvement funds.
Traditionally, lateral problems have been avoided or ignored primarily because of the reluctance of
public officials to tackle the administrative and legal issues associated with a public or semi-public
governmental body doing work on private property; However, the potential Liabilities of regulatory non-
compliance, the possibility of related civil actions, and an increased public awareness and concern over
water quality and public health issues have provided a strong impetus for addressing the lateral :
rehabilitation issue.
This paper presents a case study review of the recent efforts of the Water Works and Sanitary Sewer ,
Board of the City of Montgomery to encourage and expedite the process of service lateral rehabilitation
by private property owners. It describes how the Board has introduced new technology and field
procedures to significantly improve the overall efficiency of lateral problem detection, reporting, and
rehabilitation activities.
What are Service Laterals?
Service laterals are that component of the sewer collection system that connect a house or commercial
building with the collector sewer. Depending on the region of the country, they can be called service
laterals, house, sewers, service mains, house services, or building sewers ~ all describing the same house-
to-sewer system connection.
-------
The service lateral pipe forms the connection between the collector sewer and the house or.building
drain. This pipe (with appurtenances) is further divided into two segments; the upper lateral comprised of
the pipe between the house, and the public/private easement boundary, and the lower lateral segment
which completes the connection from the easement boundary to the collector sewer. Figure 1 shows the
service lateral, the upper and lower lateral boundaries, and the typical lateral components such as cleanout
and service wye or tee. Some communities also require two cleanout points, one at the house or building,
and the other'at the easement.
Figure!
Defective Laterals are a significant source of infiltration/inflow and contribute to SSOs.
The extraneous flow contribution of service laterals has not been widely documented. Despite the
considerable network of installed sewer and service lateral pipe, very little specific data is available which
distinguishes between the wet weather flow contributions of a service lateral, and the flow contributions
of the other collection system components. Typically, prior to an area system rehabilitation project, the
combined lateral and collection system flow for that area is monitored and documented. Then, either the
collector sewers or laterals are repaired, and a deduction made for flow contribution of the non-
rehabilitated systems by comparing pre-to post- rehabilitation flow rates.
Perhaps the primary reason that service laterals have seldom been monitored is the shear quantify of
connections. Also, it is difficult to physically isolate service laterals from a collector sewer for
installation of flow monitors, and placing a flow rate meter in an existing lateral typically requires
significant and often expensive lateral modifications.
-------
Most communities now recognize that problems with service laterals can significantly contribute to a
collection systems' extraneous wet weather flow problems, and have undertaken studies to measure
the specific extraneous flow contributions of the service lateral Kurz (1995) reports that a study done
by Bible (1991) in the Nashville subdivision area of Oak Valley resulted in an infiltration reduction value
from 50% reduction to 75%, simply by renewing the lower lateral and collector sewer connection.
Similarly, Wallis (1989) reports that in California's East Bay Municipal^ Utility District,
infiltration/inflow(I/I) reductions ranged from 52% to 86% in three community subbasins where the sewer
collectors and lower and upper lateral were completely rehabilitated. In two subbasins where the sewer
collectors and lower laterals only received rehabilitation, the I/I reductions were 45% and 87%. In
* , '
subdivisions where only portions of the laterals and sewers were repaired, the I/I reductions results ranged
from a gain of 100% to a reduction of 89%.
Variations in the effectiveness of I/I reductions can be caused by a number of factors; and determining the
cost-effectiveness of lateral rehabilitation will vary from community to community. However, based on
an analysis of over three million linear feet of sewer pipe serving Montgomery, Alabama, it was
determined that for fully 86% of the collection system, it was cost-effective to rehabilitate inflow type
sources. Some rehabilitation decisions were obvious. For example: Replacing a missing 4-inch clean out
cap, identified through physical observation or smoke testing, was clearly very cost effective. A
significant I/I problem was detected and remediated with little expense. Of course, other methods like
flow isolation or closed-circuit television inspection are more costly, and require more preliminary
rehabilitation value analysis. ;
Findings of Montgomery Board's Lateral Service Testing Program show that service laterals are a
large percentage of overall collection system defects.
In Montgomery, the Board has produced engineering reports and documentation on smoke testing
conducted over the past three years for approximately 865,000 linear feet of pipe. These areas represent
only portions of the Board's overall collection system improvements program. The smoke tested areas
include 14 subbasins covering approximately 6,155 sewer acres. This work showed, as indicated in
Tables 1-1 through 1-3, that of the 1,338 collection system defects observed, 1,239 (93%) were service
lateral problems. Of the 1,239 service lateral problems, approximately 591 (48%) were upper lateral and
648 (52%) were lower lateral related. Almost a quarter of these service lateral problems (24%) were
-------
simply a matter of restoring or replacing missing cleanout caps. On average, the Board found a service
lateral problem for every 700 linear feet of sewer.
*(!
Table 1-1
Catoma Basin; Genetta Ditch
Area Smoke Test Results
Subbasin
11
13
15
16
17
Total
Sewered Area.acres
Linear Feet Sewer.ft
No. Smoke Defects(AII Types)
No. Lower Lateral Defects
No. Upper Lateral Defects
No. Cleanout Defects
Percent Lateral Defects,%
Percent Cleanout Defects,%
Ratio Ft Sewer/Lateral Defect
588
88,704
106
24
71
31
90
29
248
47,890
-97
71
23
10
97
10
860
130,258
263
195
53
33
94
13
656
111,619
143
89
48
18
96
13
317
54,648
119
61
48
10
92
8
2,669
433,119
728
440
243
102
94
14
634
Table 1-2
Towassa Basin Smoke Testing
Results
Subbasin
2
10
11 Total
Sewered Area.acres
Linear Feet Sewer.ft
No. Smoke Defects(AII Types)
No. Lower Lateral Defects
No. LlDoer Lateral Defects
No. Cleanout Defects
Percent Lateral Defects.%
Percent Cleanout Defects.%
Ratio Ft Sewer/Lateral Defect
97
21,042
52
4
48
45
100
87
93
12,778
24
4
20
12
100
50
239
51.533
49
27
22
13
100
27
32
8,336
105
66
38
29
99
28
929
134.690
69
47
19
1?.
96
17
588
88,704
2
1
1
1
100
50
1,890
317,033
299
148
147
111
99
37
1075
-------
Table 1-3
Econchate Basin: Ann Street Area
Smoke Testing Results
Subbasin
Total
Sewered Area.acres
Linear Feet Sewer.ft
No. Smoke Defects(AII Types)
No. Lower Lateral Defects
No. Upper Lateral Defects
Nor Cleanout Defects
Percent Lateral Defects,%
Percent Cleanout Defects,%
Ratio Ft Sewer/Lateral Defect
32
'8.336
91
10
65
52
82
57
569
87.226
170
28
115
- 26
84
15
515
69.115
50
22
21
'4
86
8
2.815
362,000
311
60
201
82
84
26
1.387
Recent Service Lateral Testing prompts development of new policy and procedures.
X
In early 1994, after reviewing the field reports of recent source detection work in Subbasin 6 (the Caney
Creek Area of the Catoma Basin) it was noted that of the 258 smoke defects, 247 (96%) were a matter of
missing or broken cleanout caps on sen/ice laterals. (Please reference Table 2) It was also observed that
there were no storm drains in the area, and that the cleanouts were serving as storm .water drains. A
review of the flow monitor hydrographs indicated that the area responded rapidly to storm .events.
Table 2
Catoma Basin: Caney Creek Area Smoke Test Results
(Subbasin 6)
Subbasin Total
Sewered Area,acres
Linear Feet Sewer.ft
No. Smoke Defects(AII Types)
No. Lower Lateral Defects
No. Upper Lateral Defects
No. Cleanout Defects
Percent Lateral Defects.%
Percent Cleanout Defects,%
Ratio Ft Sewer/Lateral Defect
569
87,226
258
11
247
247
100
96
338
-------
Board's Lateral Repair Policy
Shortly after reviewing the Caney Creek data, discussions were held with the Boaird's staff to advise them
of the significant impact that the lateral defects appeared to be having on this area and on other sectors of
the collection system. This initiated a comprehensive re-examination of Board lateral policy.
The Board's lateral rehabilitation policy, historically, placed sole responsibility for lateral maintenance
from the collector to the house with the private property owner. When lateral service problems were
discovered, the property owner was notified and directed to make the correction. The Board had made
provision for repairs to the lower lateral, if the lateral repair was associated with a capital improvements
rehabilitation project. However, initial capital improvement projects failed to address the upper portion
of lateral service defects.
After advising the Board's staff of the urgent need to address the upper lateral problems if their goal of
significant I/I reductions was to be realized, it was agreed that the Board's policy should be revised. A
more aggressive policy was recommended and approved. Private property owners would make Ifl
repairs detected on their laterals, or risk having their water service terminated. The Board gave the
property owner the option of permitting the Board's staff to make the repair to the lower lateral if the
repair cost was reimbursed by the property owner. If the owner elected to use Board restoration services,
any other lower lateral defects discovered in the course of the work would also be repaired.
* * s .' ' ' ' '
A maximum cost ceiling to the property owner for lower lateral repairs was established at $1,200, with
the Board assuming the remainder of any cost over that amount. The Board also decided to offer
-1 ;" . t. '
property owners interest-free financing for owner-incurred lower lateral repair costs up to the maximuim
amount, with repayment to be made over a four year period. In addition, as further incentive to property
owners to resolve lateral problems, the Board would replace missing or broken cleanout caps for a cost of
$13.52 far below local area plumber fees for the same simple procedure.
Under the present policy, a property owner retains the option of repairing any private defect himself. If
he chooses that option, the Water Works Board will go to the site and conduct a visual inspection of the
work performed. If the repair is complete and of acceptable quality, a Thank You .Letter is sent to the
property owner. If the repair is not acceptable or another defect is located, a second notice is generated
stating what needs to be done to bring the owner up to Board standards.
-------
Notices to property owners. When a property owner fails to respond to an initial 60-day notice of lateral
repair requirements, a second 10-day notice is generated advising of possible interruption of service. If
the property owner has not responded within the specified time frame, water service is terminated.
A schematic of the revised lateral property owner notification decision tree is shown in Figure 2 below.
Board Colects &
Processes Field Data
Board Generates 1 st Notice
To Property Owner
Board
Completes Repair
Board Sends
Thar* You Letter
No
Board Generates
Second Notice
Cycle
f) to (1
<; or ;:
0 to U
If Repair Is Unacceptable
Board Disconnects
Owners Water
Figure 2
-------
Board recognizes need for improvements in defect documentation.
Concurrent to formulating these policy revisions, an improved approach to lateral defect identification
and documentation was developed so that this important data could be gathered and processed, and the
appropriate repairs performed quickly and cost-effectively.
It was apparent that the method of recording the noted defects in an engineering report needed to be
improved. Engineering reports were not being prepared until the field activities for multiple subbasuis
were complete a long and costly time lapse. The Board realized that it was missing major
opportunities to make significant I/I reductions through actions as simple and inexpensive as replacing
missing cleanout caps.
Subsequent discussions on improving data, collection, reporting, and property owner notification
procedures focused on options for computerization and automation of the process. The Board was
already midway through a major modernization of their customer information system, and was
incorporating a department-wide geographical information system. They had experienced the benefits of
. computerization and wanted to extend this concept into the field.
At that time, the data handling process involved field crews recording field information on hard copy
forms, and then bringing the information back to the office where it was uploaded into a software
database. Multiple Polaroid photos of each observed field defect were taken, and Polaroid film duplicates
attached to copies of the hard copy form in the office for later distribution to the Board's staff. Because
*, ' '' ,.",'
the database summaries and the field data information were included as a part of the engineering report,
this information was taking from 6 to 8 weeks to reach the Board.
A new field data documentation method is approved and implemented.
The field crews were provided with lap top computers to directly enter inspection observations into the
database while still at the site. The Polaroid cameras were replaced with digital ones. Now,
photographs of a defect could be inserted into the appropriate electronic inspection form, and all of these
data processing functions accomplished in the field.
After initial field testing, the new systems and equipment have worked well. Each day, the field
crews upload their date into the master database. Then, about once each week, the database sorts the
-------
work for service lateral defects. Information acid photos of these defects are electronically transmitted to
the Board from CH2M HILL's office. " . .
Field Crews use new computerized, field-based, form systems.
CH2M HILL's field crews perform the inspection work and record the information into the computerized
database loaded on the laptops. Figures 3 and 4 show two of the computer interfaces that the crews use
for Smoke, Setups and Smoke Defects. The interface was designed so that it can be used much like a
paper form. Built in scroll bar menus are provided for as many of the entry cells as possible. This allows
more information to be accessed from a smaller screen, and tends to reduce error and expedite data entry.
For example, on Figure 3, all of Montgomery street addresses, have been loaded into the database. A
crew member need only type the first few letters in the street address and the scroll bar advances to the
general area of the street on the street list. On the next setup, the same street address remains in the cell;
\ .
therefore, the crew member need only change the address number for the next task when working on the
same street. When the crew member is ready to record the observed smoke defects, he simply activates
the "Defect" button.
Microsoft Acce
£<»t yiew Be cords yflndow Ijelp
Figure 3: Smoke Test Setup Screen
-------
Microsoft Acces
£lle Edit JOew Becords aimdow Help
SMOKE SETUPS
Smoke detected in driveway
Smoke detected in roof gutter .
Smoke detected in storm drain
Smoke detected in abandoned lateral
Smoke detected over main ine h easement
Smoke detected in yard grate
Cleanout cap mitring and standpipe shattered
Figure 4: Smoke Test Defect Screen
In Figure 4, information on the observed smoke defect is recorded. A scroll down menu lists the standard
defects options. Highlighting and pushing the enter button automatically records the selection into the
database. Also, this screen has a button for pictures and sketches. These buttons activate subprograms
that allow a digital photo or scanned image to be inserted in this screen. Multiple photos can be attached.
Qirrently, field sketches showing dimensions and other information to locate the problem are being
drawn on paper forms and later scanned and attached to the record. When the crews are in the office,
standardized sketches with minor field drawing using computer software packages are being evaluated.
Each day the field crews download their laptops to a central database in the office. At the end of die
week, the central database is sorted, checked, and transmitted to the Board.
Production of board-generated forms and letters is simplified through computerization.
When the Board receives data, it is directly uploaded into the database. A first notice is generated by
bringing up a Microsoft Access screen called Generate Customer Correspondence (Figure 5.) This
screen provides the user with overall control of a variety of actions depending on where the property
owner is in the repair process! For instance, pushing the "Generate First Notice" button opens up the
screen shown in Figure 6. This screen displays data buttons and menus that allow the Board to access
information on all the locations that were sent a first notice. Another button allows the Board to find out
the status and history of a specific location. This screen is shown in Figure 7. This record is where
-------
detailed information about the defect is located. For instance, the administrative issues and repair costs
taken from field work orders are retrievable-from this screen. If a property owner contacted the Board
regarding the status of work, the data could be quickly accessed on this screen.
Figure 5: Customer Correspondence Screen
J-lle Edit yiew Hecords y£lndow Help
Figure 6: First Notice Screen
-------
Die Edit jfiew fiecords Window Help
Figure 7: Lateral Defects and Repairs by Location Screen
Response of the Montgomery area public to new lateral repair policy is positive.
The Board has been using this process since the Fall of 1994 with a surprisingly favorable level of
participation from the public, and very minimal customer resistance. Table 3 shows the areas that have
been smoke tested, but not yet documented in an engineering report similar to the data included in the
previous tables. The data indicates that after just the first notice to property owners, 475 (69%) out of a
total of 684 defects were repaired through the process described above. Approximately 93% of the
individual laterals evaluated revealed only one defect The remaining 7% of owners with multiple
defects is possibly due to the absence of adequate lateral air pressure from the missing or broken cleanout
cap. Defects discovered during the initial repair must also be repaired. The 209 property owners (31%)
who did not respond to the first notice received a second notice. But under the risk of having their water
service discontinued, each of these 209 customers corrected their defects. In addition, it should be noted
that the cleanout cap problem for these areas is considerably higher than the 24% frequency average
reported in Tables 2-1 through 2-3. The average shown in Table 3 is 97%.
-------
Tables
Private Property Lateral Response/Repair Status as of April 1995
Subdivision Area
Woodcrest1
Hopehull1
Southlawn1
Carriage Hills
Brighton Estates
Halcyon
Regency Park
Totals
Total* * *1st #2nd f Board # Owner
Smoke Cleamout Notices Notices Repairs Repairs
Defects Cap
Defects -.
7
36
215
61
151
24
190
684
6
36
205
61
145
24
188
665
. 7
36
215
61
151
24
190
684
4
9
61
27
1 42
2
64
209
3
21
111
18
63
7
;. 103
326
4
15
104
43
88
17
87
358
. Total #
Repairs
7
36
215
61
151
24
190
684
Catoma Basin, Si'bbasln 6
Post rehabilitation flow monitoring is currently underway in the Board's system; therefore, I/I reduction
values are not yet available. There are strong expectations and indications that noticeable reductions will
be measured, particularly downstream of subdivision areas like Southlawn and Brighton Estates.
s
Conclusions
Despite the strong evidence that service laterals should be included in the SSO rehabilitation plan, many
communities are still reluctant to open up the proverbial "public/private can-of-worms". However, the
Board's experience in Montgomery, to date, has been revealing and encouraging particularly regarding
service area systems that are less than 30 years old, where a high percentage of lateral defects are in the
upper segment with many of those consisting of easy to repair items like missing or broken cleanout caps.
Communities that have been unwilling to pursue service lateral rehabilitation would be well served to
review the data on Montgomery's experience and note the significant inflow/infiltration reduction
benefits achieved through relatively inexpensive and cost-effective innovations in policy, procedure, and
the application of new technology.
-------
REFERENCES
'* f
Kurz, George E., et al, "Successful Sewer System Rehabilitation." The Alabama Water Environment
Association , Orange Beach, AL, (1995).
CH2M HELL, "Catoma Interceptor Improvements Program, Phase II Source Detection Program, Genetta
Ditch Area." Prepared for The Water Works and*Sanitary Sewer Board of the City of Montgomery,
Montgomery, AL, (July 1992). .
r
CH2M HELL, "Towassa Interceptor Improvements Program, Phase II Source Detection Program."
, Prepared for The Water Works and Sanitary Sewer Board of the City of Montgomery, Montgomery, AL,
(July 1993).
CH2M HILL, "Ann Street Interceptor Improvements Program, Phase II Source Detection Program."
Prepared for The Water Works and Sanitary Sewer Board of the City of Montgomery, Montgomery, AL,
(February 1992).
CH2M HILL, "Environmental Compliance Assessment Source Detection Study, Maxwell Air Force
Base." Prepared for The Mobile District Army Corps of Engineers, Mobile, AL, (January 1994).
Bible, D., "Results from Sewer Rehabilitation Test Areas". Water Pollution Control Federation 64th
Conference, (1991)
Wallis, Michael, "East Bay Municipal Utility District Infiltration/Inflow Program". Water Pollution
Control Federation Conference, San Francisco, California (October 1989).
-------
WORK: GROUP #5
OPTIONS FOR TREATING THE
THE REMAINING SSOs FROM
SANITARY SEWER SYSTEMS
APRIL 28, 1995
-------
-------
WORK GROUP #5 SUMMARY
INTRODUCnON/PURPQSE
The subject of discussion for the work group was how to identify and evaluate
treatment and storage technologies and other schemes available for handling
wet weather flows in order to prevent SSO and treatment plant bypasses
elimination of inflows from the sanitary sewers. The work group objectives
were to develop: 1) available options and schemes to store or properly convey
the wet weather flows to a treatment facility; 2 ) identify treatment technologies
that can be used to retrofit existing facilities for handling and treating wet
weather flows; and 3) develop costs associated with these various options and
technologies. .
BACKGROUND
Because not all I/I can be economically eliminated, some portions is expected to
remain in the system after a rehabilitation program. These remaining flows
will continue to cause SSO treatment plant and bypasses if not properly
handled. Since CSOs and SSOs are both mixtures of sanitary wastewater and
storm water, both exhibit similar pollutant characteristics. Because of this
similarity many of the demonstrated CSO treatment techniques are expected to
also effectively treat SSOs.
ATTENDANTS
Lament Curtis, URS Consultants, Inc.
Richard Field, U.S. EPA (Group leaded)
Art Hamid, Montgomery Watson
Herbert Kaufman, Clinton Bogert Associates
Terry Krause, Metcalf and Eddy, Inc.
Tricia Sheet, Cahaba River Society
Kevin Weiss, U.S. EPA, Office of
Wastewater Management
Jim Wheeler, US EPA, Office of
Wastewater Management
WG 5-1
-------
WORK GROUP OVERVIEW
The session started out with everybody introducing themselves and indicating
issues and concerns that they expected to be discussed by the work group
sessions. The main issue raised was how to properly convey and treat the
remaining I/I in the system after rehabilitation, to prevent SSOs and bypasses.
The group agreed that the remaining I/I in a system would continue to cause
SSO treatment plant and bypasses. For this reason, proper handling of these
I/I, especially during storm events must be addressed. The group discussed the
available options and technologies for handling of wet weather flows. These
options included: - -
Continuing sewer maintenance to. maintain sewer integrity
" v r '
Retrofitting existing treatment facilities with treatment processes
for handling excess flows during storm events
On-site and off-site storage facilities
Underground storage
Relief sewers
WORK GROUP # 5 REPORT
.Summary ,
SSO can be controlled using CSO control methods. SSO and CSO are both
mixtures of municipal sewage and storm water, although the average sanitary
sewage to storm water fraction is generally higher for SSO.
Must plan a cost-effective solution considering all approaches to handling and
treating of SSO including:
Removing inflow.
Performing only cost-effective sewer rehabilitation on a continuing
basis.
WG 5-2
-------
- Inspecting the interceptors,-collection sewer systems, and pumping
stations for blockages, siltation and structural failures which cause
SSO, and clean out of repair the systems as necessary.
Maximizing flow to POTW by using surge\storage facilities or by
increasing interceptor flow capacity.
Maximizing POTW treatment capacity by retrofitting, installing
:.'.-'.. parallel process trains, or constructing new high-rate
POTW's.
, - Installing satellite treatment facilities.
Inflow elimination or reduction, cost-effective sewer rehabilitation and collection
system inspection with associated clean out and repair must be done in all cases.
This includes an integrated economic and feasibility analysis using a
combination of maximizing flow to the POTW and maximizing treatment
capacity for handling any remaining SSOs.
Design flow rates and volumes should be determined by long-term simulation,
regression analysis and statistical modeling. SSO quality and quality
monitoring should begin immediately and be used in conjunction with the
models for their development, improvement, or calibration and verification.
Flow estimates for future inflow\infiltration reduction or addition should be
subtracted or added to design flow values, should flow change due to changes in
service area, population, flow rates, and industrial flows.
Samping and analysis should be conducted for suspended and dissolved solids,
BOD, nutrients, and others pollutants of concern. Some sample analysis should
include particle settling velocity and size distribution analysis. This will provide
us with more positive treatment process selection and design parameters. In
addition we should consider correlating historical POTW quality data with
rainfall records to assist in developing a wet weather flow (WWF) quality data
bases, particularly as it relates to solids and BOD.
The work group consensus was that a minimum number of SSOs per year
should be allowed into the receiving water, however, about 1/2 of the work
group recommended elimination of all SSOs as the goal. Since SSO event
volumes and flow are significantly lower than the comparable values for CSOs,
it was felt that it should be economically feasible to eliminate most SSOs The
exact number of allowed SSOs would be based on water quality considerations.
Also providing partial treatment by directing the excessive (one to two SSO per
year) through a storage or satellite treatment facility, should be strongly
considered. In those instances where an overflow causes environmental damage
or public health problems, and a National standard of treatment requirements
should be adopted.
WG 5-3
-------
RECOMMENDED NATIONAL POLICY AND STANDARDS
The group agreed that setting National treatment requirements for SSOs was
beyond the scope of the work group. However, there was a general agreement
that any National SSO treatment requirements should be a technology-based
approach coupled with stringent human health, receiving water quality, risk-
based requirements. In other words, if the applied treatment technology results
in receiving water quality impairments, than higher treatment levels would be
required. However, the work group suggested that exceptions should be
allowed based on the community's showing of (1) no additional water quality
impairment and no health risks and (2) economic affordabiliity which would
give the community a longer compliance time, but not effect the standard. EPA
will need to develop affordability guidelines. These guidelines should
encourage compliance with previous--federal grant conditions or requirements.
The technology-based approach should be based on national guidelines with the
above stated exceptions.
MAXIMIZING FLOW TO THE POTW
Maximizing flow to the POTW, after cost effective rehabilitation to reduce or
remove infiltration and inflow, can be accomplished by two basic method: (1)
storage and.(2) increasing interceptor flow capacity. These methods can be
supported based on previously demonstrated and evaluated CSO or SSO
projects. An important part of SSO control system planning is the
determination of the economic break even point between the required storage
volume versus treatment capacity. The SSO storage facilities should be
designed for multi purpose use, where .possible, including: storage of SSO dry
weather flow (DWF), equalization or storage of wet weather flows (WWF), and
satellite treatment before discharge, as a last resort.
Compartmentizing the storage basin for capture of DWF can reduce sludge
handling problems and still provide flood protection and sewer line relief.
- Storage Options;
Storage can be applied upstream, midstream, or downstream at the SSO
point (either at remote SSO location, or at the POTW). Upstream
storage can offer the dual-benefit of drainage and flood relief control.
Storage can include: (1) unused capacity in the existing interceptors and
sewer lines; (2) conventional concrete surface basins, tanks and lined
earthen basins; (3) tunnels and underground tanks; amd (4) abandoned
treatment facilities.
WG5-4
-------
Tunnels and underground basins have the advantage of minimizing land
requirements in urban areas. New sewers can be made larger for wet-
weather flow (WWF) storage. In-sewer storage and use of abandoned
facilities for storage will be the least expensive types of storage and
therefore should be considered first.
.'.,., - Increasing interceptor flow carrying capacity; r
This can be accomplished by either: (1) increasing the pumping capacity
for surcharged interceptors, where possible (not all systems have
extensive pumping); (2) installing parallel interceptors or sewers; (3)
replacing existing sewers with larger sewers, if cost effective; (4) applying
polymer injection to increase the flow; (5) removing bottle neck, if they
exist; or (6) lining to reduce pipe roughness.
Several members of the group noted that before increasing pump
capacity, the proposed hydraulic grade line should be reviewed to
determine the practical amount of increased flow. The increased flow
achieved may not justify the cost. They also noted that polymer in
storage has a relatively short benchlife. The economics of its use should
be evaluated against alternatives.
MAXIMIZING POTW TREATMENT CAPACITY
POTW treatment capacity can be maximized with a variety of technologies or
combinations of technologies. The processes described below have been
demonstrated to treat WWF at relatively high hydraulic and organic loadings.
- Increasing hydraulic loading to existing primary\secondary treatment
processes without modifications based on stress testing. This will be
the least expensive method and should be considered as a first step in
most cases.
- Retrofitting primary settling tanks with plate or tube settlers, chemical
addition facilities, or dissolved air flotation (DAF). Consider an
automated switching process for converting from settling during low-
flow to DAF during high-flow conditions. One member of the group
noted that conversion to interim DAF during high flow conditions may
not be easy, since it could require two effluent and two solids removal
systems plus an air bubbler system to operate in the DAF mode.
WG5-5
-------
Installing parallel process trains*.- The parallel process train effluent
can be either discharged directly to the receiving water, if water
quality standards can be met, directed back to the existing POTW
influent, or both by flow splitting. If it is directed back to the influent
flow equalization could be needed. If discharged directly, '
consideration should be given to blending the effluent from the wet
weather treatment processes and the normal treatment plant effluent.
These flow discharge options should depend on water quality impact,
human health and other permit requirements.
- Primary physical treatment technologies for new and existing
POTW installations;
- microscreens -.
- plate or tube settlers. ([Plate settlers in a primary settling
tank may not provide significant improvement in larger
plants).
- screening plus dual-media high-rate filters. (Provision
would have to be made for the disposal of high rates of
backwash water with dual media high rate filters. This
could adversely impact the plant).
- screening plus DAF
- conventional primary settlers (additional)
- primary effluent filters
> swirl degritters (if treatment requirements are
low)
- Chemical addition to the primary clarifiers
- Secondary biological treatment technologies for new POTW
installations;
- contact stabilization during WWF periods automatically
switching to conventional activated sludge during DWF
periods. (The advantages of contact stabilization are that
it limits loss of biomass during high flow periods and can
WG 5-6
-------
produce an acceptable effluent quality. However, when
switching from standard activated sludge to contact).
. stabilization, about 18 hours may be required for
achieving process stability. Where I/I caused high flows
are a factor, the plant could be operated continuously in
the contact stabilization mode. Changing the modes of
operation with the frequency that may be required is
complex mechanicaly and can expect to result in poor
treatment during the change over).
- high-rate trickling filtration having two filters in parallel
during WWF periods automatically switching to series
operation during DWF periods (series operation will keep
biological slime, active and improve DWF treatment
efficiency).
- rotating biological contactors.
- Upflow biological-aerated-filtration.
- biological-fluidized bed filtration.
Disinfection processes for new and existing POTW
installations: .
- Where existing disinfection unit cannot provide adequate
disinfection, parallel high-rate disinfection processes
may be appropriate to optimize contact tank volume.
Ozone and chlorine dioxide are relatively rapid oxidants
and can also decrease needed contact time.
- High-intensity mixing with mechanical-flash mixers or
static mixing should also be considered. Adequate SSO
concentration and particle size reductions are necessary
for satisfactory microorganism disinfection. High-rrate
processes have been successfully demonstrated to work for
CSO. These include:
. higher dosing
. static and dynamic mixing
. using more rapid oxidants (ozone or chlorine
dioxide, etc.)
', ' "' : WG 5-7 '.-'''.
-------
. two-stage dosing
. combinations of the above
- Natural treatment systems
- .(' . - Consideration should be given to using natural systems
such as:
. Constructed Wetlands
,. . Land application
. linfiltration ponds
- Other Considerations
\ ~' ' ' ' '
- Consideration should be give to bypassing secondary
treatment (primary physical treatment plus disinfection)
based on receiving water quality impacts and BOD
dilution in the influent.
. :
- Consideration should also be given to innovative,
advanced, and evolving treatment technologies.
SATELLITE TREATMENT
Satellite treatment should be automatic physical processes with remote
monitoring to reduce manpower requirements. The treatment process must be
designed to produce an effluent quality which will not cause environmental
damage or public health risks. Maintenance issues will be more pronounced
and potential failures at remote locations along with associated water quality
impacts at remote location will exist. Accordingly physical treatment processes
at satellite locations should only be used as a last resort, if the POTW cannot
handle all of the WWF. As previously stated satellite storage should be used
for dual-purposes by providing storage for DWF flows, as well as wet weather
peak flow volumes that can be stored and released without treatment by
optimizing the collection system and POTW. Only after the exising system is
optimized and the available storage is fully utilized would the treatment and
discharge function be utilized.
WG 5-8
-------
Location issues such as sensitive receiving stream segments and neighborhood
aesthetics should be considered:
COSTS
Cost information is available from the literature and is summarized in
attachment 1.
BIBLIOGRAPHY
Most of the stated technologies have references relating to demonstration and
evaluation project(s) which are listed in Attachment 2.
RECOMMENDATIONS -
The work group developed the following list of needs. Many of these need will
require additional research on the part of EPA or other outside organizations
such as the WEF, AMSA, etc.
- Need protocol to demonstrate, improve, and evaluate emerging
technology.
- Need methodology to determine particle size removal requirements for
adequate disinfection by various disinfection technologies including
uy. ' ,, -.-...- ;
- Need design criteria for satellite treatment processes.
- Need better data on wet weather overflow quality as a
function of rainfall to determine impact of wet weather
infiltration and inflow.
- Need to determine the relationship between stream flows and I/I
qua titles to confirm whether the approach broader applicaton Refer
to attachment 3 for more details.
WG 5-9
-------
-------
a
«o
H
«O
eg
«
O)
T8
O) _ «
* S «
1*1
o
10
TO
O
r«- " *-" «T «*.
r7 C<4
i/» (O
1
3
en
a
I
ft..-.
rUJ
r
Eg
55
o> o
S3
o =
p
= -o
* f^ ^
_ a
? E
5 0
o -^
o<
< .
5
I :
&
1
. . 2
"3
£
1
I 'SS
1 i
i «
^*i
1
°e~
o
?
I
U
1
5
TS
8
JB
1
|
1
^
8
'
-------
-------
s1
«^ w"
v. O*
tf> it)
O ?*
eo <»
Woi
"**
ft
Of*
co" (6 '* «
o> e>
A 2k Ci
5 5 8S£
O, rf «
fS
8.
S
3
d 0' W W -.'
v*. (O
c *
2s «3 «> «g
o $ S S.i
§§s §
O e»
i* 0.1; *r «o
O 0 Q O
i* J5 r»
*- ^ «n
in
4
pi o> «M «> o» . 8 *^
S 2 S S5SS S
S S °. . °. n".- d
vn
m
CM
O
«o
<7 *
i? 2
m v o
S 8" 5
20- n
O %3 *?
I
1
8
11
S
3S;
o
O
U
CO
T3 i «»
e ~
. S
I gl
.< .&
2 I
« .v
£e =
"8 "'
1 l till
Z O O W « W I-
i * 3
- * tf
I J «
s-
I
B
e
S5
78
i
K
3 att S" w
a c.^!^
LILLE!
_ _ An J. _
Q. Q..CL O. 0.
Jt
S
wv
.o
f-
w
2 n s e
o
I
-------
JiS
2::
t*
« w
to
11
ii
o u
75 i»
*c M
TS Z
il
i£
rt
s
1
i
eo
o
* ° ' w
JB 1 >
1 i 3
i !
iSs*
if 2|^-
O * * »
o» o
iiil=-!
:f ^Z f fB »^ _**
S 75 T5
*» oi o*
W W2
f *5 ** "S* 3"o" 1
5lUJ(-£2.2.S,i2.tUllJUJ
rsss
-------
sneet4
cost summary or selected screening Aitemanvesa
ENR
5450
Prelect
Location
Type of
Screen
Screening capital
Capacity Cost
(MGD) (S)
Annual
cost. o&M Costs
(S/MGD) (1/1000 gal)
Belleville. Ontario (1) Rotary Screen
Static
screen
Cleveland. OH(?) " , Drum screen
R. Wayne.lN
Ml. Clemens, Ml(3)
Philadelphia. PA
Racine, Wl
Seattle, WA(4)
Syraaisci. NY (5) ~
Static screen
Drum scraon
Rotary screen '
Microstratncr
Microstrainerwnn cnemicai addition
Mlcrostrainer without chemical addition
Drum
1.8 91.233
5.4 280,178
7.2 349,890
0.75 40.548
3.9 260.510
7.6 358,212
25 1.658.217
50 2.419.146
100 4.755.670
700 9 107.377
18 742.290
18 692.913
18 1.593.362
47.524
48.632
48,505
54.173
49.595
47,416
63.272
48.287
47.S24
45.453
41.202
38.368
41.965
0.23
0,23
0.23
0.12
0.12
0.12
0.06
0.11
.. 0.12
71,305 71,395
7.4 247.430
7.4 403.300
33.463
54.300
Rotary screen
Rotary screen
Drum screen
3.9 61.585 15.805
25 1.635.000 65.400
5 352.833 70.523
10 700.325 70.087
0.13
0.13
0.27
0 Estimated costs for several sizes of facilities.
" Estimates include supplemental pumping stations ana appurtenances.
(1) Opeiutiuiial Data for me Belleville Screening Project. Ontario Ministry of the environment. August 6,1976.
(2)EPA11023EY!04/72 '
(3) EPA^FQy2.75-01Q
(4) EPA11023FDD03A70 ,
(5) EPA'COO/2-76-206
Mgal/dx 0.0438 «m3/c;$/1000 gal x 0.264 *$/m3; (EPA^OQ/8.77.014)
bar sr/Aftns (>25.4 mm (>i in.) openings), coarse screens (2S.4-4.6 mm
(1-3/16 in.)), fine screens (4.6*0.1 nun (3/10-1/230 in.)), and mlcroscreens (<0.1 mm (<1/2SO in.)).
Page i
-------
-------
,c e> o «- w
c f* « » «
= «M r» ou p-
M
m 9 r«. *
CM
-------
-------
c-
55 8
vlrf in
s. g
1:11
v t **
P. 06
in CM
CM. ».
flA
-------
-------
I
CO
g-
V
V
§
ra
e
l
ei x
M l
-------
-------
J= «
S» ^
= O
S
o «-'
pi
w
111
tw «» m
«. r. i^.
«o f. «vi
SO 00
K. *r cj
«. «-. in c>j
Sm «M of
8 3 g
I
fj
r
.
S.
8
.I'*'
g^l
O U 5
1
5
i
i
CO
o
o
r
if
i
ll
« V)
T3 ft)
W" f^t
1 «
sl
a<5
ta
O
g
I
1
i
ll
1
i
s ° w
8
«- «n w>
.S T» O
S?
2§J?
t|l
11|
5 2&
r=- o
O w
£ =
a re
%,i
= B
T54
55
. c ^
|1|
§
«:
j|-
1^
TO
! I 5
-------
-------
3
li
11
s
£
S
S
i
o
2
"5.
a
O
.
I.
ii
O UJ
-------
-------
ATTACHMENT 2
BIKLTQGRAPHY; STfYEAfiF. £Nj) TREATMENT Qf EXCESSIVE;
.WET-WEATHER FLOWS TO SANITARY SEWER SYSTEMS
Agnew, R. W., et at., 1975, "Biological Treatment of Combined Sewer Overflow ait
Kenosha, Wisconsin,* USEPA, ORI), Report # EPA-670/2-75-019, NTIS PB 242 126.
Benedict, A. H. and Roelfs, V. L., 1981, "Joint Dry/Wet Weather Treatment of Municipal
Wastewater at Clatskanie, Oregon," USEPA, ORD, Report if EPA 600/2-81-061, NTIS PB
81-1872(52.
Cesareo. D.J. and Field. R.. 1975. "infiltration-inflow Analysis,e Journal of the
Environmental Engineering Division, ASCE, Vol; 101, No. EES, Proc. Paper 11645.
October, 1975, pp. 775-785.
Chandler, R. W., and Lewis, W. R., 1977, ."Control of Scwcr Overflows by Polymer
Injection,' USEPA, ORD, Report #JSPA-600/2-77-189, NTIS PB 272 654.
Derick, C. and Logic, K., 1973, "How Augmenting Effects of Additives on Open Channel
Flows," USEPA, .Office of Research and Monitoring, Report # EPA-R2-73-238, NTIS PB"
222911.
Homack, P.H. a aL. 1973, "UUHration of ITrickling Filters for Dual 'lYeatment of Dry and
Wet Weather Flows/ USEPA. ORD. Report #EPA-670/2-73-071. NTIS PB 231 251.
Innerfeld, H., et al., 1979, "Dual Pmcess High-Rate Fillratiun of Raw Sanitary Sewage and
Combined Sewer Overflows,* USEPA, ORD, Report # EPA-COO/2-79-015, NTIS PB 296
626.
Western Company, The, 1969, "Polymers for Sewer Flow Control," Federal Water Pollution
- Control Administration, Report if 11020DIG08/69, NTIS PB 185 951.
Welborn, H. L., 1974, "Surge Facility for Wet and Dry Weather Flow Control,* USEPA,
ORD, Report #EPA-670/2-74-075; NTIS PB 238 905.
Welsh, KL., and Stucky, U.J., "Combined Sewer Overflow 'Iteatment by the KotaHng
Biological Contactor Process," USEPA, ORD, Report» EPA-670/2-74-050, NTIS PB 231
892. '.--'..
Wolf, H.W., 1977, "Bachman Trealincnl Facility for Ex«»sivc Storm Flow in Sanitary
Sewers," USEPA, ORD, Report » EPA COO/2-77-128, NTIS PB 209 128.
-------
-------
APPENDIX G
-------
'r.
-------
©EPA
United States
Environmental Protection Agency
Office of Wastewater Management
Sanitary Sewer Overflows (SSOs) Workshop
Renaissance Washington DC HotelDowntown-.
Washington, DC -.-'"'..
April 26-28,1995 -
Final List of Experts (by Workgroup)
Workgroup 1 - O&M
Rick Arbour
Richard Arbour and Associates, Inc.
P.O. Box 458
JHopkins, MN 55353
612-939-9188
Fax:612-939-9658
Dwight Culberson
Director of Public Utilities
CityofFairfield
5350 Pleasant Avenue
Fairfleld, OH 45014
513-867-5375 '
Fax:513-867-5329
Albert Gallaher
Research & Competition Manager
Research & Competition Strategic
Business Unit " . . .
Charlotte-Mecklenburg
Utility Department
4100 West Tyvola Road
Charlotte, NC 28202-6746
704-357-6064
Fax: 704-357-8581
John Gresh
RJN Group, Inc.
7100 Baltimore Boulevard
Suite 203
Baltimore, MD 20740
301-864-5400
Fax:301-864-4908
Graham Knott
Principal Engineer
.Brown and Caldwell Consultants
100 West Harrison Street
Seattle, WA 98119
' 206-281-4000
Fax: 206-286-3510
Joe Mauro
Environmental Engineer
Municipal Technology Branch
Office of Wastewater Management
U.S. Environmental Protection Agency
401M Street, SW (4204)
Washington, DC 20460
202-260-1140
Fax: 202-260^0116
James McGregor
Senior Associate
Killam Associates
27 Bleaker Street
P.O. Box 1008
Mfflbum, NJ 07041
201-912-2635
Fax: 201-912-2632
Reggie Rowe
Client Service Manager
CH2MHffl
2567 Fairlane Drive
Montgomery, AL 36116
334-271-1444
Fax: 334-277-5763
Unable to Attend:
John Larson
Central Contra Costa Sanitary District
5019 Imhoff Place
Martinez, CA 94553
510-229-7150
Fax:-510-838-2950
Richard Thomasson
Washington Suburban .
Sanitary Commission
14501 Sweitzer Lane
Laurel, MD 20707-5902
301-206-8600 .
Fax: 301-206-7005
1 Printed on Recycled Paper
-------
Workgroup 2 - INFLOW
Keith Benson
Director
Hampton Roads Sanitation District
P.O. Box 5911
Virginia Beach, VA 23455-0911
804-460-2261
Fax:804-460-0637
Gordon Garner
Executive Director
Louisvflle & Jefferson County
Metropolitan Sewer District
400 South Sixth Street
Louisville, KY 40202-2397
502-540-6346
Far 502-540-6106
Henry Gregory
Deputy Assistant Director
Utility Maintenance Technical
Services Section
City of Houston
306 McGowen Street - 2nd Floor
Houston, TX 77006
713-525-9999
Fax:713-525-9996
Alan Hpllenbeck
Senior Vice President
RJN Group, Inc.
200 West Front Street
Wheaton, IL 60187
708-682-4700 ,
Fax:708-682-4754
Norbert Huang
Environmental Engineer
Municipal Technology Branch
Office of Wastewater Management
U.S. Environmental Protection Agency
401M Street, SW (4204)
Washington, DC 20460
202-260-5667
Fax:202-260-0116
S. Wayne Miles
Environmental Engineer
Camp Dresser & McKee Inc.
5400 Glenwood Avenue
Suite 300
Raleigh, NC 27612
919-787-5620
Fax: 919-781-5730
Richard Nogaj
President
RJN Group, Inc.
200 West Front Street
Wheaton, IL 60187 ,
708-682-4700
Fax:708-682-4784
Ralph Petroff
President
ADS Environmental Services, Inc.
5025 Bradford Boulevard
Cummrngs Research Park
Huntsvffle.AL 35805
205-430-3366
Fax: 205-430-6446
John Smith
President
JM Smith & Associates
7373 Beachmont Avenue
Cincinnati, OH 45230
513-231-6800
Fax: 513-231-6847
-------
Workgroup 3 - DWILTRATION (KH)
David Crouch
Special Project Coordinator
Public Utilities Department
CityofFairfield
5350 Pleasant Avenue
Fairfield, C-H 45014
513-867-6069
Fax:513-867-8809
Steve Donovan
Civil Engineering Technician
Hamilton County Metropolitan
Sewer District
225 West Galbraith Road
Cincinnati, OH 45215
513-352-4909
Fax:513-352-4910
Philip Hannan
Maintenance Reconstruction
Division Manager
Washington Suburban Sanitary
"Commission
14501 Sweitzer Lane
Laurel,MD 20707-5902
301-206-4354
Fax: 301-206-4383
GisaJu
'Principal Engineer,
Montgomery Watson ..
355 Lennon Lane
Walnut Creek, CA 94598-2427
510-9.33-2250 ....
Fax:510-945-1760
Christine Kahr
Program Manager
Greater Houston Wastewater Program
City of Houston
2525 S/Sgt Macario Garcia
Houston, TX 77002
713-646-9731
Fax:713-659-5518
TiraKraus
Louisville & Jefferson County
Metropolitan Sewer District
400 South Sixth Street
Louisville, KY 40202-2397
502-540-6246
Fax:502-540-6365
Lam Lim
Environmental Engineer
Municipal Technology Branch
Office of Wastewater Management
U.S. Environmental Protection Agency
401M Street, SW (4204)
Washington, DC 20460
202-260-7371
Fax:202-260-0116
Richard Nelson
Director of Systems Planning
Black &Veatch
8400 Ward Parkway
P.O. Box 8405
Kansas City, MO 64114
913-339-3510
Fax:913-339-3626 '
Michael Wallis
Director of Wastewater
East Bay Municipal Utility District
P.O. Box 24055 (MS: 702}
Oakland, CA 94623-1055
510-287-1615-
Fax: 510-287-1351
Unable to Attend:
Joseph Niehaus
Sewers Chief Engineer
Metropolitan Sewer District of
Greater Cincinnati
1600 Gest Street
Cincinnati, OH 45204
513-557-7102
Fax:513-244-1399
-------
Workgroup 4 - LATERALS
Rodolfo Fernandez
RJN Group, Inc.
2201 Corporate Boulevard - Suite 101
Boca Raton. FL 33431
407-241-2400
Fax:407-241-1044
Stephen Jenkins
Director, Environment and
Engineering Department
City of San Marcos
630 East Hopkins
San Marcos, TX 78666
512-353-4444
Fax: 512-396-4656
Ralph Johanson
Vice President
GR\A? Engineers
250 East Fifth Street
1500 Chicruita Center
Cincinnati, OH 45202
'513-762-7653
Fax: 513-721-4628
TJl. "Buddy" Morgan
Executive Director
Water Works and Sanitary Sewer Board
City of Montgomery
P.O. Box 1631
Montgomery, AL 36102-1631.,
334-206-1607
Fax: 334-240-1616
Donna Evanoff Renner .
Project Manager
RJN Group, Inc.
12160 Abrams Drive - Suite 206
Dallas, TX 75243
214-437-4300
Fax:214-437-2707
BillSukenik -
Greater Houston Wastewater Program
City of Houston
1100 Louisiana - Suite 1100
Houston, TX 77002
713-646-9707
Fax: 713-659-5518
Charles Vanderlyn
Environmental Protection Specialist
Municipal Technology Branch
Office of Wastewater Management
US Environmental Protection Agenisy
401M Street, SW (4204)
Washington, DC 20460
202-260-7277
Fax:202-260-0116
Unable to Attend:
Jay Reynolds
Program Manager
Engineering Department
City of South Portland
25 Cottage Road
South Portland, ME 04106
207-767-3383
Fax 207-767-7646
Jacqueline Townsend
Planning & Analysis Engineer
Charlotte-Mecklenburg
Utility Department
5100 Brookshire Boulevard
Charlotte, NC 28216
704-399-2221
Fax: 704-393-2219
-------
Workgroup 5 - TREATMENT
Lamont Curtis
Vice President
URS Consultants, Inc.
5606-B Virginia Beach Boulevard
Suite204
Virginia Beach, VA 23462
804-499-4224
Fax: 804-473-8214
Richard Field
Chief
Storm and Combined, Sewer Overflow
Pollution Control Program
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
2890 Woodbridge Avenue
(MS-106)
Edison, NJ 08837-3679
908-321-6674
Fax: 908-906-6990
ArtHamid
Vice President
Montgomery Watson ..
1300 East Ninth Street
Cleveland, OH 44114
216-621-2407 . .
Fax:216-621-4972
Herbert Kaufman
Partner *
Clinton Bogert Associates
270 Sylvan Avenue
Englewood Cliffs, NJ 07632
201-567-7979
Fax: 201-567-8886" :
Terry Krause
Vice President
Metcalf & Eddy, Inc.
One Pierce Place - Suite 1500, W
Itasca, E, 60143-2641
708-775-0300
Fax: 708-875-3210
Larry Roesner
Chief Technical Officer
Camp Dresser & McKee Inc.
1950 Summit Park Drive
Suite 300 - .
Orlando, FL 32810
407-660-2552
Fax:407-875-1161
Kevin Weiss
Permits Division
Municipal Technology Branch
Office of Wastewater Management
U.S. Environmental Protection Agency
401M Street, SW (4203)
Washington, DC 20460
202-260-9524
Fax: 202-260-1040
Unable to Attend:
Gregory Anderson
Project Engineer
URS Consultants, Inc.
5606-B Virginia Beach Boulevard
Suite 204
Virginia Beach, VA 23462
804-499-4224
Fax: 804-473-8214 .
Dick DiTuIlio
Camp Dresser & McKee Inc.
-ten Cambridge Center
Cambridge, MA 02142-1401
617-252-8000 .
Fax:617-621-2565
Barrel Gavle
Vice President
Baxter and Woodman Engineers, Inc.
8678 Ridgefield Road
Crystal Lake, E. 60012
815-459-1260
Fax:815-455-0450
Stephen Maney
Principal
RJN Group, Inc.
200 West Front Street
Wheaton, E, 60187
708-682-4700
Fax: 708-682-4754
-------
-------
vvEPA
-United States
Environmental-Protection Agency
Office of Wastewater Management
Sanitary Sewer Overflows (SSOs) Workshop
Renaissance Washington DC HotelDowntown..
Washington, DC
April 26-28,1995 , . , , . . .
Final List of Observers
Watson Allen
Town Manager
329 Sixth Street
P.O. Box 152
West Point, VA 23181
804-843-3330
. Fax: 804-843:4746
John Dombrowski
Office of Enforcement and
Compliance Assurance
U.S. Environmental Protection Agency
401M Street, SW(2224A)
Washington, DC 20460
202-564-7036
Fax:202-564-0037 ' , .
Hormoz Ferkhan
Project Manager .-'-.'
Water Environment
Research Foundation
601 Wythe Street
Alexandria, VA 22314
703-684-2470
Fax: 703-684-2492 , .
Jonathan Golden
Project Manager
Metcalf& Eddy, Inc.
30 Harvard Mill Sojiare
P.O. Box 4071
Wakefield, MA 01880-5371
617-246-5200
Fax: 617-224-6546
Raynetta Curry Grant
Manager of Research Projects
Water Environment'
Research Foundation
601.Wythe Street
Alexandria, VA 22314-1994
703-684-2470 . '
Fax:703-684-2492
Randall Haddock
Field Director -
Cahaba River'Society
2717 Seventh Aveflue, S
Suite 200
Birrningham, AL 35233-
205-322-5326
Fax:205-324-8346
John Harkins
Environmental Engineer
U.S. Environmental Protection Agency
345 Courtland Street, NE
(MC4WM-WFB)
" Atlanta, GA 30365
404-347-3633 .
Fax:404-347-1798
Roy Herwig
Engineer
U.S. Environmental Protection Agency
345 Courtland Street, NE
Atlanta, GA 30365
404-347-4793
Fax:404-347-1797
Jey Jeyapalan
American Ventures, Inc.
2320 85th Place, NE
Bellevue, WA 98004
206-462-6261
Fax: 206-462-6316
John Jurgens
Gelco Services
20606 84th Avenue, S
Kent, WA 98035
206-487-3325 ' . '
Fax:206-487-3702 , '
David Klunzinger
Northeast Ohio Regional Sewer District
3826 Euclid Avenue
Cleveland, OH 44115 . . ,-
216-881-6600
Fax: 216-881-2738
Jeff Lape
Associate Partner
Woolpert Consultants
1800 Diagonal Road - Suite 600
Alexandria, VA 22314-2840
703-684-4417
Fax:703-684-1603
Daniel Murray
Environmental Engineer
Center for Environmental
Research Information
U.S. Environmental Protection Agency
26 West Martin Luther King Drive (G-75)
Cincinnati, OH 45268
513-569-7522
Fax: 513-569-7585 .
Monika Oakley
Principal Engineer
Mill Creek Project Office
Montgomery Watson
3101 Euclid Avenue - Suite 800
Cleveland, OH 20785
216-432-0777
Fax: 216-432-1091
Ray Orvin
Executive Director
Western Carolina Regional
Sewer Authority
561 Mauldih Road
Greenville, SC 29607
803-299-4000
Fax:803-277-5852
DanSchecter
Manager, Regulatory Compliance
Water Environment Federation
600 Wythe Street
Alexandria, VA 22314
703-684-2423
Fax: 703-684-4657
1 Printed on Recycled Paper
-------
Final List of Observers (continued)
Tritia Sheets Patrick Stevens
Director of Administration Regional Senior Vice President
Cahaba River Society ADS Environmental Services, Inc.
2717 Seventh Avenue, S 6330 East 75th Street
Suite 205 . Suite-200 " .
Birmingham, AL 35233 Indianapolis, IN 46250
205-322-5326 317-578-0789
Fax 205-324-8346 Fax:317-578-0791 . - -
Unable to Attend:
Peter Lehner GregSchaner
Natural Resources Defense Fund Manager of Technical Services &
40 West 20th Street Regulatory Affairs .
New York, NY 10011 Association of Metropolitan
212-727-4425 Sewerage Agencies
Fax: 212-727-1773 1000 Connecticut Avenue, NW
Suite 410
Washington, DC 20036
202-833-9106
Fax:202-833-4657
l
Workshop Organizers
AtalEralp Kevin Weiss Jim Wheeler
Physical Scientist Permits Division . Environmental Engineer
Municipal Technology Branch Municipal Technology Branch Municipal Technology Branch
Office of Wastewater Management Office of Wastewater Management Office of Wastewater Management
401M Street, SW (4204) ' 401M Street, SW (4203) 401M Street, SW (4204)
Washington DC 20460 Washington, DC 20460 Washington, DC 20460
202-260-7369 202-260-9524 202-260-5827
202-2^0-0116 Fax:202-260-1040 Fax:202-260-0116
'* ,
Robert Lee
Chief
Municipal Technology Branch
Office of Wastewater Management
401M Street, SW (4204)
Washington, DC 20460
202-260-9412 '
Fax: 202-260-0116
-------
D
-------
-------
DRAFT - January 31, 1995
DEFINITIONS FOR SSO ADVISORY COMMITTEE
The following working definitions nave been developed to provide clear points of reference
in the discussions of the SSO policy dialogue. The definitions are not intended to be legally
binding. Where appropriate, definitions and interpretations can be modified in the future to
better support the efforts of the policy dialogue.
COLLECTION SYSTEMS
COMBINED SEWER SYSTEM - A wastewater collection system owned by a State or
municipality which is designed to convey sanitary wastewaters (domestic, commercial
and industrial wastewaters) and storm water through a single-pipe system to a Publicly
Owned Treatment Works (POTW). (see Combined Sewer Overflow Control Policy
April 19, 1994).
..SANITARY SEWER SYSTEM - A wastewater collection system owned by a State or
municipality which is designed to convey municipal and industrial wastewaters, with
allowances for ground water infiltration'and unavoidable storm water that are not
admitted intentionally, (see 40 CFR 35.2005(b)(37)).
COMMON TRENCH SEWERS - A sanitary sewer system where storm sewers are located
in the same trench as the sanitary sewers, but they are not necessarily directly
interconnected.
OVER-AND-UNDER SEWERS - A sanitary sewer system with common trench sewers
which have the storm sewer positioned directly over the sanitary sewer hi the same
trench. Common manholes are used in this design, with a removable plate in the
lower half of the storm sewer providing access to the sanitary sewer below.
STORM SEWER - A conveyance designed to carry only storm waters, surface runoff, street
wash waters and drainage, (see 40 CFR 35.2005(b)(48)), :
CLASSES OF DISCHARGES/FACILITIES
OVERFLOW - The intentional or unintentional diversion of flow from a.sewage collection
system which occurs before the headworks of a sewage treatment plant. Overflows
include discharges to waters of the United States as well as diversions to public or
. private property and the environment that do not reach waters of the United States,
such as basement floodings. For the purpose of Advisory Committee discussions,
overflows are not bypasses (see 4Q CFR 403.7(h)).
DRAFT ... 1 ' : DRAFT
-------
BYPASS - the intentional diversion of waste streams from any portion of a treatment facility.
(see 40 CFR 122.41(m)(l)(i)). The treatment facility begins at the headworks where
equalization of the waste streams takes place or the collection system otherwise
ends1, (see 1989 CSO Control Strategy (September 8, 1989, (54 FR 37371))). For
the purpose of Advisory Committee discussions, overflows are not bypasses.
EXCUSED BYPASS - Bypasses which are not subject to the prohibition of bypasses at
40 CFR 122,41(m)(4)(i). The two types of excused bypasses are: 1) bypasses which
do not cause effluent limitations to be exceeded, but only if it also is for essential
maintenance to assure efficient operation (40 CFR 122.41(m)(2)); and 2) bypasses
which meet the following three conditions: (A) are unavoidable to prevent loss of life,
personal industry, or severe property damage; (B) no feasible alternatives exist to the
bypass and (C) the permittee submits the notices required by 40 CFR 122.41(m)(2)
and (3).
PROHIBITED BYPASS - Bypasses which are prohibited under 40 CFR 122.41(m)(4)(i).
(Bypasses other than excused bypasses are prohibited - see "excused bypass").
ANTICIPATED BYPASS - A bypass where the permittee knows in advance of the need for
a bypass.
UPSET - An exceptional incident in which there is unintentional and temporary
non-compliance with technology-based permit effluent limitations because of factors
beyond the reasonable control of the permittee. An upset does not include
noncompliance to the extent caused by operational error, improperly designed
treatment facilities, inadequate treatment facilities, lack of preventative maintenance,
or careless or improper operation. An upset constitutes an affirmative defense to an
action brought for noncompliance with technology-based limitations if the regulatory
requirements of 40 CFR 122.41(n) are met. (see 40 CFR 122.41(n)).
OVERFLOW POINT - A location in a sewer collection system prior to the headworks
of the treatment plant where untreated wastewater is released to the environment.
Overflow points include discharges to waters of the United States as well as releases
that do not result in a discharge to a waters of the United States.
CONSTRUCTED SSO POINT - A .conveyance at a pump station or other location in a
collection system (prior to the headworks of the treatment facility) that is intentionally
designed by the municipal entity operating the system to discharge during peak flow
events. Constructed SSO points include intentionally placed connections between
sanitary sewers and storm sewers. In general, a constructed SSO point does not
1 Some Regions and States interpret bypass more broadly to include discharges from
sanitary sewer systems before the headworks.
DRAFT 2 ' DRAFT
-------
; include overflowing manholes, unless the manhole has been intentionally modified to
discharge. The term 'constructed SSO point' does not reflect whether a discharge is
authorized under the Clean Water Act.
WET WEATHER FACILITY - A storage or treatment facility designed to
manage or control flows associated with wet weather conditions and which is designed
to discharge partially or fully treated wastewater and storm water under certain
conditions. .- ' ,
PUBLICLY OWNED TREATMENT WORKS - (POTW) means any device or system used
in treatment (including recycling and reclamation) of municipal sewage or industrial
wastes of a liquid nature Which is owned by a State or municipality. This definition
includes sewers, pipes or other conveyances only if they convey wastewater to a
POTW providing treatment, (see 40 CPR 122.2)
HEADWORKS - The transition area between the collection system and the treatment
facility. Headworks buildings often house influent pumps and preliminary treatment
equipment.
STANDARDS/LIMITATIONS
TECHNOLOGY-BASED STANDARD - Requirements in NPDES permits which represent
the minimum level of control that must be imposed in an NPDES permit. Under the
Clean Water Act, different technology-based standards apply to different classes of
discharges. The technology-based standard for publicly owned treatment works
(POTWs) is secondary treatment. For discharges other than POTWs, the technology-
based standards are best conventional pollutant control technology (BCT) for
conventional pollutants and best available technology economically achievable (BAT)
for other pollutants. The nature of receiving waters is not considered when
developing technology-based standards. Instead, technology-based standards are
based on a consideration of factors such as the nature of the discharge, pollutant
removal efficiencies of control options, and control costs (see 40 CFR 125).
SECONDARY TREATMENT - The technology-based standard that must be maintained by
all POTWs except facilities granted modified limitations for discharges into marine
waters under section 301(h) of the CWA. EPA has defined secondary treatment in
terms of concentrations of (biochemical oxygen demand) BOD5 and suspended solids
(SS) and level of pH. In general, secondary treatment requires:
BOD5 and SS - for each independently, the 30 day averages shall not exceed
30 mg/1 and the 7 day average shall not exceed 45 mg/1, and the 30 day
average percent removal shall not.be less than 85 percent.
DRAFT
DRAFT
-------
pH - shall be maintained within 6.0 and 9.0 except under certain conditions.
The secondary treatment regulations allow for adjustments to be made based on
special considerations such as combined sewers; less concentrated influent where the
less concentrated influent is not the result of excessive inflow and infiltration; and the
use of lagoons or trickling filters (see 40 CFR 133).
NO DISCHARGE LIMITATION - An effluent limitation that requires no flows to be
discharged except when rainfall events exceed a wet weather event specified hi the
limitation (e.g. 10 year/24 hour).
WATER QUALITY STANDARDS - Provisions of State or Federal law which consist of a
designated use or uses for the waters of the United. States, an anti-degradation policy,
and criteria or other factors to protect the designated uses. Water quality standards
are to protect the public health or welfare, enhance the quality of water and serve the
purposes of the Clean Water Act (see 40 CFR 131.3(1)).
WATER QUALITY-BASED EFFLUENT LIMITATIONS - Requirements in NPDES
permits which are in addition to or more stringent than technology-based requirements
and which are necessary to achieve water quality standards. Such requirements are
based on considerations of the effect or potential effect of the discharge on receiving
waters and in general are. not based on a direct consideration of cost, (see 40 CFR
122.44(d)).
MISCELLANOUS TERMS
ADVERSE WATER QUALITY IMPACTS - Conditions which do not allow attainment
of the designated use or uses of waters of the United States, which do not meet the
conditions set forth hi a State's water quality standards and/or do not protect the
chemical, physical, and biological integrity of waters of the United States.
ANTI-DEGRADATION POLICY - State-wide policy and implementation methods that,
at a minimum, are consistent with the following: 1) existing water uses and the level
of water quality necessary to protect the existing uses shall be maintained and
protected; 2) where the quality of waters exceed levels necessary to support the goals
listed in Section 101 of the Clean Water Act (protection and propagation of fish and
wildlife and recreation hi and on the water), that quality shall be maintained and
protected unless the State finds that allowing lower water quality is necessary to
accommodate important economic or social development in the area hi which the
waters are located; 3) where high quality waters constitute an outstanding National
resource, that water quality shall be maintained and protected; and 4) in cases where
thermal discharges are involved, is consistent with section 316 of the CWA. (see 40
CFR 131.12).
DRAFT 4 DRAFT
-------
HIGH INTENSITY WET WEATHER EVENT - A storm event where a specified rate of
rainfall is equalled or exceeded (e.g. 5 inches per hour).
HIGH VOLUME WET WEATHER EVENT - A storm event where a specified volume of
rainfall is equalled or exceeded (e.g. 5 inch/24 hours). Such events may also be
defined in terms of return frequency ((e.g. 10-year, 24 hour storm).
TRANSPORT - Conveying wastewater through a sewerage collection system and through
the headworks of the treatment facility.
WATERSHED - A defined area where surface waters drain to a water body or a portion of
a water body (e.g. a river segment). Watershed boundaries are based on hydrologic
considerations.
URBAN WATERSHED - That portion of a watershed that is developed in a manner such as
to support urban populations.
COORDINATED APPROACHES - Efforts to evaluate, address, and/or otherwise control
multiple sources of pollution to the same waterbody. In urban areas, a coordinated
wet weather approach may address storm water, SSOs, wet weather bypasses at
sewage treatment plants, combined sewer overflows (CSOs) industrial sources, and
nonpoint sources. . .
ELIMINATE - To close, seal or otherwise remove a SSO discharge so as to prevent all
overflows. All flows are conveyed to a wastewater treatment plant.
SURCHARGE - The hydraulic conditions that occur when a sewer is flowing full. For
circular pipe, surcharging when the flow depth exceeds the pipe diameter.
. Surcharging can occur with or without overflowing:
URBAN - A population classification defined by the Bureau of Census which includes all
persons living in places recognized by the Bureau of Census of 2,500 or more people
or that are part of an urbanized area of more than 50,000 people. (Based on Bureau
of Census definition).
URBANIZED AREA - An area designated by the Bureau of Census as having a population
of 50,000 or more persons and a population density generally greater than 1,000
persons per square mile (just more than 1.5 persons per acre) hi the urban fringe.
(Based on Bureau of Census definition).
BEST PROFESSIONAL JUDGEMENT (BPJ) - The duty of care used by a regulatory
authority in establishing requirements in a permit or enforcement action on a case-by-
case basis hi the absence of uniform national standards.
DRAFT 5 , DRAFT
-------
INFLOW - Water other than waste water that enters a sewer system (including sewer
service connections) from sources such as, but not limited to, roof leaders, cellar
drains, yard drains, area drains, drains from springs and swampy areas, manhole
covers, cross connections between storm sewers and sanitary sewers, catch basins,
cooling towers, storm waters, surface runoff, street wash waters, or drainage. Inflow
does not include, and is distinguished from, infiltration (see 40 CFR 35.2005(21)).
INFILTRATION - Water other than waste water that enters a sewer system (including sewer
service connections arid foundation drains) from the ground through such means as
defective pipes, pipe joints, connections, or manholes, Infiltration does not include,
and is distinguished from, inflow, (see 40 CFR 35.2005(20)).
M ' *
RAINFALL INDUCED INFILTRATION - The portion of infiltration flows (flows coming
from infiltration sources) that enters the, sewerage system during and immediately
after rainfall events.
EXCESSIVE INFILTRATION/INFLOW - The quantities of infiltration/inflow which can
be economically eliminated from a sewerage system, as determined in a cost-
effectiveness analysis that compares the costs for correcting the infiltration/inflow
conditions to the total costs for transportation and treatment of the infiltration/inflow.
Inflow is npnexcessive if the total flow to the POTW (i.e., wastewater plus inflow
plus infiltration) is less than 275 gallons per capita per day. This standard was used
in the construction grants and NPDES programs2. (See 40 CFR 35.2005 and
133.103(d)).
EXFILTRATION - Wastewater that leaks from or otherwise leaves a sewerage collection
system from locations generally other than sanitary sewer overflows, combined sewer
overflows or treatment facilities, and that generally goes into the soil or bedding
material of the sewer line.
2 The success of efforts to eliminate excessive I/I under the construction grants
program was limited by a number of factors. See "Evaluation of Infiltration/Inflow
Program, Final Report", February 1981,.U.S. EPA, EPA-68-01-4913.
DRAFT 6 DRAFT
-------
BYPASS - the intentional diversion of waste streams from any portion of a treatment facility.
The treatment facility begins at the headworks where equalization of the waste
streams takes place. For the purpose of Advisory Committee discussions, overflows
are not bypasses (see 40 CFR 122.41 (m)).
OVERFLOW T The intentional or unintentional diversion of flow from a sewage collection
system which occurs before the headworks of a sewage treatment works. Overflows
include diversions to public or private property and the environment that do not reach
waters of the United States, such as basement floodings. For the purpose of Advisory
Committee discussions, bypasses are not overflows (see 40 CFR 403.7(h)).
Regulatory Status of Bypass
ALLOWED BYPASS - Bypasses which are not prohibited under 40 CFR 122.41(m) of the
NPDES regulations. Bypasses which are not prohibited under the NPDES regulations
include bypasses which do not cause effluent limitations to be exceeded, but only if it
also is for essential maintenance to assure efficient operation; and bypasses which are
unavoidable to prevent loss of life, personal industry, or severe property damage
where there are no feasible alternatives to the bypass and 'the permittee submits the
notices required by 40 CFR 122.41(m).
PROHIBITED BYPASS - Bypasses which do not meet the regulatory criteria for a bypass
, provided at 40 CFR 122.41(m).
Status of Overflow
OVERFLOW TO WATERS OF THE U.S. - A release of untreated or partially
treated sewage from a sanitary sewer collection system which directly or indirectly
discharges to waters oftfie U.S. This term includes releases which reach waters of
the United States (either directly or indirectly through groundwater hydrologically
connected to surface waters) violate the CWA. Similarly, SSOs into streets or other
areas which drain through storm sewers to waters of the United States that are not /
authorized by an NPDES permit violate the CWA.
OVERFLOW WITHOUT DISCHARGE - A release of sewage from a sanitary sewer
collection system which does not directly or indirectly discharge to waters of the U.S. This
term includes releases which drain back into the sanitary sewer collection system.
AUTHORIZED WET WEATHER FACILITY DISCHARGE - A discharge to waters of
the United States from a storage or treatment facility located before the headworks of a..
publicly owned treatment works that only occurs during wet weather events and that is
authorized by an NPDES permit. .
DRAFT 9 DRAFT
-------
Frequency of Overflow
CHRONIC OVERFLOW - An overflow that occurs two or more times per year at the
same location.
' - f " ;'..?'... , , .
TEMPORARY OVERFLOW LOCATION - An overflow that occurs less than twice a
year, and that is caused by conditions that are corrected (e.g. tree roots, grease block, etc.).
WET WEATHER OVERFLOW - Overflows that only occur during or immediately after a
precipitation or snowmelt event.
ALL WEATHER OVERFLOW - Overflows that occur during dry weather periods as well
as during
-Location of Overflow
BASEMENT OVERFLOW - A release of sewage into a building. A basement overflow
may ultimately drain back into the sewage collection system or may be removed from the
building by some other means =
PUMP STATION OVERFLOW - An overflow of untreated or partially treated sewage at a
pump station. Such overflows may be intentional or unintentional.
MANHOLE OVERFLOW - A release of sewage from or through a manhole cover to the
surface. This term does not include underground discharges to storm sewers.
f ' '' ', ' , , '*
HIDDEN OVERFLOW - An overflow location that is not clearly visible, such as a
discharge to a storm sewer that occurs underground.
1 ' , ' -
OVERFLOW ON PRIVATE PROPERTY - A release of sewage from a clean out point,
manhole or other location that spills onto private property. An overflow on private property
may ultimately drain back into the sewage collection system or may discharge to waters of
the U.S.
i , '' '
CONSTRUCTED SSO POINT - A conveyance at a pump station or other location in a
collection system that is intentionally designed by the municipal entity operating the
system to discharge during peak flow events. Constructed SSO points include
intentionally placed connections between sanitary sewers and storm sewers. In
general, a constructed SSO point does not include overflowing manholes, unless the
manhole has been intentionally modified to discharge. The term 'constructed SSO
point' does not reflect whether a discharge is authorized under the Clean Water Act.
DRAFT 10 DRAFT
------- |