science BRIEF
BUILDING A SCIENTIFIC FOUNDATION FOR SOUND ENVIRONMENTAL DECISIONS
www.epa.gov
National Risk Management
Research Laboratory
www.epa.gov/nrmrl/
Aging Water Infrastructure Research Program
Addressing the Challenge Through Innovation
Rehabilitation of Wastewater Collection Systems
"Our nation's extensive water
infrastructure has the capacity to
treat, store, and transport trillions
of gallons of water and wastewater
per day through millions of miles
of pipelines. However, as our
infrastructure deteriorates, there
are increasing concerns about
the ability of this infrastructure
to keep up with our future needs."
George Gray, Ph.D.
Assistant Administrator for
Research and Development
United States Environmental
Protection Agency
EPA has begun a new research program
intended to generate the science and
engineering that will address our aging
water infrastructure. The program,
entitled "Innovation and Research for
Water Infrastructure for the 21st Century,"
calls for research relating to condition
assessment, advanced concepts, and
system rehabilitation.
System rehabilitation is the application
of infrastructure repair, renewal, and
replacement technologies in order to
reinstate functionality of a wastewater
system or subsystem. The proper balance
of the repair, renewal, and replacement
depends on the condition assessment, the
life-cycle costs of various rehabilitation
options, and the related risk reductions.
Current Issues
Rehabilitation includes a range of
approaches that return the system to near-
original condition and performance. For
example, repair techniques are used when
the existing sewer is structurally sound.
But when the existing sewer is severely
deteriorated or collapsed, or when its
flow capacity should be increased, the
system is usually replaced. Current
rehabilitation methods address unsound
structural conditions. There are many
causes for wastewater collection system
deterioration and failure:
• Poor design and installation
• Inadequate or improper
bedding material
• Chemical attack
• Traffic loadings
• Soil movements
• Root intrusion
• Compromised joint integrity
• Subsequent construction damage
• Ground water fluctuation
• Inadequate maintenance
Deposition of material and sewer
blockages that occur because of flat
grades along with high ambient
temperatures and poor ventilation
can lead to the development of sulfuric
acid and resulting crown corrosion.
This reduces the structural integrity
of concrete and its reinforcing steel.
In addition, inadequate inspections and
quality assurance, and poor workmanship
during sewer installation, can result in
long-term problems. Other issues include:
• Pipe defects can cause blockages that
lead to dry-weather sewer overflow
and backups into buildings.
• Water that flows into sewer pipes
through defects (e.g., holes, cracks,
and failed pipe joints) can weaken
the critical soil-pipe structure.
• Fine soil particles carried into the
sewer can eventually reduce soil
support and cause pipe deformation
or subsidence.
• Exultation of water from the sewer
into the surrounding soil can weaken
support provided by the soil.
• Soil movement due to traffic can
exceed design assumptions and
result in soil support problems.
State of the Technology
Collection system rehabilitation
includes many repair and replacement
options, each of which could return
the system to acceptable levels of
performance. Options include repairing
the pipeline using common methods,
such as chemical and cement grouting,
to address ground water movement,
washouts, soil settlements, collapses,
and soil voids.
U.S. Environmental Protection Agency
Office of Research and Development, National Risk Management Research Laboratory
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Trenchless technologies have moved
to the forefront of sewer system
rehabilitation. These techniques enable
workers to install new pipe in the
location of the old pipe without total
surface digging and its accompanying
traffic and business disruptions.
Selection of rehabilitation materials is
an important factor. New materials are
emerging; the application of plastic pipe
(as opposed to more traditional sewer
pipes made of concrete, clay, or ductile
iron) is becoming standard practice. The
most commonly used for wastewater
applications are glass-reinforced plastic,
polyvinyl chloride, and polyethylene.
Innovations using plastic include
structured wall pipe and composite pipe
that use different materials to address
both structural and corrosion issues.
However, long-term performance testing
is needed to understand the capabilities of
new materials under field conditions and
to determine life-cycle cost. In addition,
raw materials and formulations can vary
widely, resulting in different quality pipe
from the same plastic.
Studies have shown that sewer
rehabilitation at the street alone does
not completely solve the infiltration
problem for various reasons, including
those involving private ownership of
service laterals. It is at these service
laterals (the pipe that conveys wastewater
from the property line or easement to the
public sanitary sewer) where entry can
occur when successive rainfalls elevate
the ground water table. Rehabilitation of
service laterals is generally done by point
repair or replacement; cured-in-place
lining, sliplining, and pipe bursting are
also used. However, these approaches
do not resolve the private ownership
problem or the problems associated with
the location and configuration of the line
(e.g., sharp bends and transitions) or the
line condition (e.g., nearby massive roots
that can cause line damage).
f- A f\ r
FLOODED
New Research
Beginning in fiscal year 2007, EPA's new
research program will initiate projects
that address rehabilitation of wastewater
collection systems in the following areas:
• Assess State of the Technology
- Convene technology forum
- Evaluate rehabilitation of:
0 Service laterals
0 Sewer liners
0 Manholes
0 Force mains
0 Siphons
0 Combined sewer overflow
regulators
0 Pumping stations and wet wells
- Evaluate decision support —
rehabilitation vs. replacement
• Conduct Technology Demonstration
Studies
- Develop protocols and metrics
for field demonstrations
- Determine site selection criteria
for field demonstrations
- Initiate field demonstrations
The Door Is Open for
Collaboration
EPA, whose primary role is that
of advocate for a sustainable water
infrastructure, is only one partner in
this effort. The Aging Water Infrastructure
research program presents opportunities
for utilities, vendors, researchers,
academics, water associations (trade
and professional), and other agencies
and organizations to collaborate. In
fact, the success of the program depends
on stakeholder involvement, sharing
information and tools, and working
together toward the long-term
stewardship of our water infrastructure
CONTACT
Daniel J. Murray, Jr., P.E.,
Senior Environmental Engineer
Office of Research and Development
U.S. Environmental Protection Agency
National Risk Management Research Laboratory
(513)569-7522
murray. dan(g!epa. gov
REFERENCES
Sustainable Infrastructure for Water and Wastewater
http://www.epa.gov/waterinfrastructure/index.html
U.S. EPA. (2007). "Innovation and Research for
Water Infrastructure for the 21st Century, Research
Plan." April 30.
U.S. EPA. (2007). Statement of George Gray,
Ph.D., Assistant Administrator for Research and
Development and EPA Science Advisor, before
the Subcommittee on Energy and the Environment,
Committee on Science and Technology, United States
House of Representatives. March 14.
Recycled/Recyclable
Printed with vegetable-based ink on
paper that contains a minimum of
50% post-consumer fiber content
processed chlorine free
U.S. Environmental Protection Agency
Office of Research and Development, National Risk Management Research Laboratory
EPA/600/F-07/012
September 2007
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