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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