Chapter 1
Introduction
1.0
OVERVIEW
1
2.0
PURPOSE AND SCOPE OF THIS CHAPTER
1
3.0
HISTORY OF CHANGING SEWER ASSET NEEDS
12
4.0
EVOLVING REGULATIONS
13
5.0
THE NEED FOR GUIDELINES
14
6.0
FORMAT OF THIS MANUAL
15
7.0
REFERENCES
15
1.0 OVERVIEW
This manual summarizes the evolution of sewer design, maintenance, and rehabilitation
technologies and provides detailed guidance on how to apply those technologies to meet today’s
exacting performance expectations. This chapter documents a broad background for sewer
evaluation and rehabilitation, followed by a short description of how the subsequent chapters are
organized, to provide a ready reference to detailed guidance.
2.0 PURPOSE AND SCOPE OF THIS CHAPTER
This manual provides guidance to owners, engineers, technicians, and operators responsible for
sewer design, construction, rehabilitation, and maintenance. It is written to provide reference
beyond the initial training garnered in the education of professional engineers.
This manual is intended to provide a bridge between academia and the practice of sewer
engineering. Most recently, it requires updating to address new requirements in federal guidance
for sewerage, particularly guidance requiring capture of wet-weather flows in sanitary sewers.
The Water Environment Federation and U.S. Environmental Protection Agency (U.S. EPA)
recently collaborated to publish a wet-weather guidance document titled Guide to Managing
Peak Wet Weather Flows in Municipal Wastewater Collection and Treatment Systems (WEF,
2006). This current manual provides more detailed practical guidance on implementation of both
that wet-weather guidance and more traditional dry-weather sewer guidance. Section 3.0
provides further information on how the expectations for sewerage designs have changed, and
Section 4.0 explains the evolution in the regulations governing sewer construction.
The field of sewer management incorporates an unusual vocabulary and set of acronyms.
Table 1.1 is provided to help the reader understand the acronyms throughout this manual. Table
1.2 is a glossary of terms that take on specific meanings in the context of sewer evaluation and
regulatory performance expectations.
This manual, Existing Sewer Evaluation and Rehabilitation (WEF Manual of Practice No. 6
and ASCE/EWRI Manuals and Reports on Engineering Practice No. 62, Third Edition) builds on
and augments previous related documents, including the following:
1
• Sewer system capacity planning guides:
n
-Sewer System Evaluation, Rehabilitation and New Construction (Sullivan et al., 1977);
n
-Prevention and Control of Sewer System Overflows (WEF, 1999); and
-Guide to Managing Peak Wet Weather Flows in Municipal Wastewater Collection and
Treatment Systems (WEF, 2006).
n
• Regulatory guidance:
n
-Combined Sewer Overflows Guidance for Long-Term Control Plan (U.S. EPA, 1995); and
n
-Facilities Planning 1981 (U.S. EPA, 1981).
3.0 HISTORY OF CHANGING SEWER ASSET NEEDS
An extensive summary of historical developments in sewers is available at
http://www.sewerhistory.com (Schladweiler, 2008). Sewers have been part of our culture since
the Babylonian empire. Sewer materials have changed. Early sewers were constructed primarily
of clay pipe, a material that continues to be used today. Larger sewers were originally constructed
of brick and some of paving stone and more recently using reinforced concrete. Today, sewers are
built using a variety of concrete, iron, plastics, ceramics, steel, and composites.
Similarly, construction techniques have evolved since the original sewers. The original
construction techniques were primarily based on manual labor—trenches dug with picks and
shovels. In today’s world, trenches are dug with backhoes, trenching tools, or avoided through
the use of tunnel-boring machines and other trenchless technologies. Maintenance equipment has
similarly evolved from manual grubbing to hydraulic jets, mechanical pigs, and alternative
flushing means. The equipment used for rehabilitating sewers has changed substantially in recent
decades. Historically, rehabilitation required digging up and replacing the entire sewer section.
Now, sewers are often replaced with in-place pipe bursting or lining with cured-in-placed
materials. With either method, the service lateral connections should be renewed.
The mixture of materials carried in the sewer flow has also changed substantially. Original
sewers were built to carry a combination of waste material and stormwater—primarily all of the
animal and human waste disposed of on the streets of ancient cities. In the early part of the 20th
century, engineers began designing dual sewer systems—one for human waste and one for street
runoff. The older combined sewers were sized to carry a small amount of dry-weather waste flow
and a large amount of stormwater flow. The newer separate sanitary sewers are sized to carry
only a small amount of waste flow, while the separate storm sewers are sized to carry a larger
amount of stormwater flow. Since the Clean Water Act Construction Grants regulations,
engineers have sized sanitary sewers to carry both the dry-weather waste flow and a moderate
amount of rainwater infiltration and inflow.
Throughout this evolution of sewers and their contents, the public expectations for sewer
performance have changed even more substantively. The original expectations were merely to get
the waste and water out of the streets and out of site. In the middle of the 19th century, medical
science encouraged carrying the waste far enough to protect from reexposure to communicable
diseases (cholera and plague). In the 21st century, sewers are expected to deliver all waste
materials to treatment plants that reduce the wastes to innocuous materials that pose no threat to
human health or the environment.
Today’s sewer systems consist of a network of sanitary or combined sewer pipes eventually
2
leading to pump stations and treatment facilities, with excess flow from combined sewer systems
occasionally being discharged to area streams, rivers, and lakes. These collection systems consist
of interceptor, trunk, and local collector sewers within the street or other public right-of-way.
Connected to the sewers are building and house lateral sewers, which connect building and house
drains to the collection system. The above sewers are generally divided into two categories of
ownership and responsibility—public and private.
4.0 EVOLVING REGULATIONS
Regulations governing sewer design, construction, and operation have morphed to meet the
changing expectations. Early sewers were built with no governing regulations. With the industrial
revolution, sewers were built for the convenience of the community. With the recognition of the
health effects of sewerage exposure, regulations were imposed to govern discharge locations. The
Ports and Harbors Act of 1878 codified a number of these local regulations for national
application. By the mid-20th century, state and regional organizations (i.e., the Ohio River Valley
Water Sanitation Commission [Cincinnati, Ohio]) promulgated more refined regulations. The
Water Pollution Control Act of 1972 (U.S. EPA, 1972) and its subsequent policies and guidance set
very specific criteria and performance expectations for sewers, including guidance to limit the
quantity of rainwater captured as infiltration or inflow to separate sanitary sewers.
In the last decade of the 20th century, U.S. EPA promulgated several strategies that placed
greater emphasis on ensuring that all sanitary wastewater received a categorical level of
treatment before discharge to streams, lakes, oceans, or other receiving waters. The most notable
of these policies include the Combined Sewer Overflow Policy (U.S. EPA, 1994). U.S. EPA
convened a federal advisory committee to address issues related to wet-weather outfalls. That
committee recommended a capacity management, operation, and maintenance approach that has
since been incorporated to several regional and state programs for sewer management. U.S. EPA
also issued a strategy for enforcement related to combined sewer overflow and sanitary sewer
overflow discharges (U.S. EPA, 2000) and proposed a policy for treatment requirements for the
wet-weather discharges from separate sanitary sewer collection systems (U.S. EPA, 2005).
5.0 THE NEED FOR GUIDELINES
The changes in regulations and higher expectations for sewer performance resulted in a need for
guidance to cost-effectively improve the aging sewer systems and meet the current standards to
minimize adverse effects to public health. Because the expectations for sewer performance have
changed so drastically, there is a substantial risk of dissatisfaction with systems built to
traditional standards. Not meeting current expectations or federal, regional, and state regulations
often results in administrative orders or consent decrees. The expected performance is further
challenged by the fact that the infrastructure is aged to the point where failures are not
unexpected. Nevertheless, most municipalities and sewer agencies are challenged to fund asset
management beyond repair of catastrophic failures. In addition, the sewerage management
industry is threatened with analysis paralysis in the face of evolving regulatory expectations that
are often negotiated in court before the design expectation can be articulated. Using the industry
standard guidance provided in this manual will assist municipalities and agencies in minimizing
the risk for regulatory enforcements and lawsuits brought by the public and environmental
groups when their sewer system expectations are not being met.
3
6.0 FORMAT OF THIS MANUAL
In general, this manual includes seven chapters, with the following contents:
(1)
(2)
(3)
(4)
(5)
(6)
(7)
This brief introduction and overview comprised Chapter 1,
The systematic approach to existing sewer system analysis is explained in Chapter 2,
Structural evaluation methodologies are explained in Chapter 3,
Hydraulic evaluations are the subject of Chapter 4,
Infiltration and inflow identification and quantification is presented in Chapter 5,
Methods and materials for sewer rehabilitation are outlined in Chapter 6, and
Metrics and means for effectiveness evaluation are presented in Chapter 7.
7.0 REFERENCES
American Water Works Association (1999) Water Quality and Treatment, 5th ed.; McGrawHill: New York.
Random House (1968) Dictionary of the English Language; Random House: New York.
Schladweiler, J. (2008) Tracking Down the Roots
http://www.sewerhistory.com (accessed June 2008).
of
Our
Sanitary
Sewers,
Sullivan, R. H.; Cohn, M. M.; Clark, T. J.; Thompson, W.; Zaffle, J. (1977) Sewer System
Evaluation, Rehabilitation and New Construction, EPA-600/2-77-017d; U.S. Environmental
Protection Agency: Washington, D.C.
U.S. Environmental Protection Agency (1972) Clean Water Act, Public Law 92-500 (formerly
the Water Pollution Control Act); U.S. Environmental Protection Agency: Washington,
D.C.
U.S. Environmental Protection Agency (1981) Facilities Planning 1981; EPA-430/9-91-002;
U.S. Environmental Protection Agency: Washington, D.C.
U.S. Environmental Protection Agency (1994) Combined Sewer Overflow Control Policy, Fed.
Regist., 59, No. 75.
U.S. Environmental Protection Agency (1995) Combined Sewer Overflows Guidance for LongTerm Control Plan; EPA-832/B-95-002; U.S. Environmental Protection Agency:
Washington, D.C.
U.S. Environmental Protection Agency (1996) U.S. EPA NPDES Permit Writers’ Manual; EPA833/B-96-003, Office of Water; U.S. Environmental Protection Agency: Washington, D.C.;
Dec.
U.S. Environmental Protection Agency (2000) Compliance and Enforcement Strategy
Addressing Combined Sewer Overflows and Sanitary Sewer Overflows; U.S.
Environmental
Protection
Agency:
Washington,
D.C.,
http://www.epa.gov/compliance/resources/policies/civil/cwa/strat312.pdf (accessed
June 2008).
U.S. Environmental Protection Agency (2004) Report to Congress: Impacts and Control of
CSOs and SSOs; EPA-83/R-04-001, Office of Water; U.S. Environmental Protection
Agency: Washington, D.C.; Aug.
U.S. Environmental Protection Agency (2005) National Pollutant Discharge Elimination
System (NPDES) Permit Requirements for Peak Wet Weather Discharges from Publicly
4
Owned Treatment Plants Serving Separate Sanitary Sewer Collection Systems, Fed.
Regist., 70, No. 245.
Water Environment Federation (1999) Prevention and Control of Sewer System Overflows,
2nd ed.; Manual of Practice No. FD-17; Water Environment Federation: Alexandria,
Virginia.
Water Environment Federation (2006) Guide to Managing Peak Wet Weather Flows in
Municipal Wastewater Collection and Treatment Systems. Water Environment Federation:
Alexandria, Virginia.
5