Historically, most wastewater collection and treatment
facilities have reacted to capacity, management, operations and maintenance
(CMOM) problems as they occurred instead of taking a proactive approach by
reviewing their system periodically, predicting where problems might occur and
then taking action to prevent such problems in the first place.
Times are changing. The federal government is in the process
of establishing a CMOM philosophy for wastewater collection and treatment
facilities that hinges on an aggressive, proactive approach, calling for
utilities to act like investigative reporters rather than firefighters.
Eventually, utility providers will have to follow federal CMOM guidelines, and
states may establish similar guidelines. The result will be a holistic approach
to service and protection.
"CMOM is going to help all municipalities take a very
close look at their systems," said Mark Fowler, wastewater resources
director for the City of Concord, N.C. "In the wastewater industry right
now, it's 'out of sight, out of mind.' You don't worry
until you have a problem. CMOM will force us to evaluate our systems and get a
better handle on the assets we have."
Because of its focus on prevention, CMOM ultimately will
change the way municipalities operate and maintain wastewater collection and
treatment facilities. A successful CMOM program promises to produce better
water quality, prevent sewer system overflows (SSOs), eliminate environmental
impacts from infiltration/inflow (I/I) and SSOs and maintain wastewater systems
at a higher level of service.
Nevertheless, many cities and states are waiting cautiously
on the sidelines, making little or no changes until the unfunded federal
mandate for CMOM is officially issued. Other municipalities are indicating they
want to start a CMOM-type program, but they cannot do much more with the staff,
resources or funding they currently have.
This is not the case in North Carolina, which is on the
verge of establishing a statewide program that embraces the CMOM philosophy and
requires municipalities and utility providers to comply with new collection
permit requirements. Some of these requirements include frequent visits to
inspect system condition and operation, internal inspections to ensure no
blockages exist and strict enforcement of I/I regulations.
"We want to get a step ahead," Fowler said.
"We realize there are many environmental impacts, and we don't want
to wait on the EPA mandate. There's just no reason to wait."
Proactive, Systematic Measures
Some municipalities may be waiting because they are not sure
how to tackle such an enormous task. The answer is a systematic approach, with
municipalities not needing to fix all their problems tomorrow. Instead, they
will be expected to have a plan for preventing SSOs and routinely addressing
problems. They will be expected to take initial steps to understand the
condition and operation of their system, to identify and fix the worst problems
first and to follow a course of action outlined in a five-, 10- or 15-year
rehabilitation plan - something many wastewater utilities have never
For most communities, addressing the magnitude of I/I (a
major contributor to high wastewater flows) is an important first step to
beginning a CMOM-type program. "By reducing I/I, we are trying to reduce
our cost obligation to the treatment authority in Cabarras County,"
Fowler said. "I don't want to pay the county to treat stormwater
getting into our system."
The city of Concord maintains more than 2.3 million lineal
feet of sanitary sewer lines and has a collection system that ties into the
countywide wastewater system owned and maintained by the Water and Sewer
Authority of Cabarras County (WSACC). Like Concord, many municipalities have
wastewater systems that are 50 or more years old. Some portions of
Concord's system are more than 100 years old. Thus, parts of the
structural system have reached the end of their useful life. However, if the
structural condition can be rehabilitated, operational performance will still
be adequate for another 40 or 50 years.
According to Fowler, Concord had experienced significant
maintenance problems (e.g., failing pipes, root intrusions and chronic
blockages) since the early 1990s. Customers were calling to complain. In-field
CCTV investigations revealed severe defects. Spot repairs had been performed
routinely, but Fowler knew the problem was getting worse.
"We were tracking it, monitoring where our
blockages were occurring," he said. "During wet weather events, our
peak flows were well over 100 percent of our average daily flows. We knew we
had to do something."
City crews focused on the oldest parts of the system,
visually inspected major trunk sewers and tributary lines and found significant
"We decided to replace these lines to get back the
structural integrity, accessibility and capacity we might have lost through
root intrusion and pipe degradation," Fowler said.
Using its own staff and equipment, the city has replaced an
average of 20,000 linear feet of pipe a year since 1994. But that still was not
enough. Were these repairs providing the greatest benefits?
"We were expecting better results after storm events,
so we knew we had not captured or repaired all the problems," Fowler
said. "By then we had exhausted all our in-house methods of determining
where the problems were - we knew we had to go to the next level."
The city's proactive, aggressive approach involved a
Sanitary Sewer Evaluation Study (SSES), performed by Woolpert LLP, to address
the system's structural condition and operating performance, and answer
questions such as the following.
pipes are cracked?
roots causing blockages in the system? Where?
grease buildup restricting flow? Where?
illicit connections causing I/I during rain events? Where?
The goal of the SSES was to identify the worst problems
first (the greatest contributors to I/I) to ensure the city would get maximum
benefit from its investment. This information would become the basis for a
rehabilitation program that involved ongoing maintenance activities.
Concord's I/I reduction program not only addressed its
own collection system piping but also the WSACC interceptor system. The
three-phase SSES program was designed to review the overall system, focus on
smaller areas contributing most significantly to the I/I problem and then
locate inflow sources so rehabilitation recommendations could be made.
Phase I: Flow monitoring. Woolpert located 49 flowmeters to
capture data during dry weather and wet weather conditions for 45 days. Major
priority areas contributing the most I/I to the system were identified. style="mso-spacerun: yes">
Phase II: Additional flow monitoring. Once major priority
areas were identified, 31 flowmeters were relocated for 30 days to further
define locations of the most significant problems.
Phase III: Smoke and dye testing. Of the subareas monitored,
nine were deemed significant contributors to I/I and selected for smoke testing
to determine the sources of excess inflow. Nine dye tests were performed in
conjunction with CCTV to investigate the precise locations of inflow sources
and pinpoint improvements necessary to reduce I/I.
existed not only in older portions of the system but in newer areas where
Concord did not expect to find defects.
sewer laterals contribute significantly to I/I, more than the city
initially believed. "Typically it's a small problem with a private
system that creates a large I/I problem for us," Fowler said.
In the end, Woolpert recommended $252,875 in rehabilitation
efforts with a five-year return on investment. These recommended improvements
had the potential to reduce I/I up to 46 million gallons per year (savings that
would produce more than $500,000 in savings over the life of a 40-year system. style="mso-spacerun: yes">
Besides implementing the recommended rehabilitation
measures, Woolpert suggested the city perform further investigation to locate
additional defects, maintain its ongoing maintenance program and monitor
results from improvements. All efforts are on track. Almost all the repairs
have been identified, with the exception of major infrastructure replacements.
Before the project began, Woolpert recommended several
collaborative efforts to not only save the city money ($57,000) but also give
Concord staff a deeper level of knowledge and understanding about their system.
"By allowing our staff to participate, we could double our
efforts," Fowler said. "To get the most benefit from this type of
analysis, it's important that the staff be exhaustively involved."
During flow monitoring, city crews assisted with periodic
meter maintenance. Crews checked and cleaned sensors to ensure debris had not
accumulated and that meters were recording data properly. Parameters being
collected such as velocity and depth were verified to ensure accurate data
collection. City staff recalibrated flowmeters as needed.
During meter maintenance, city crews observed problems in
the field such as surcharging of manholes that led to debris accumulation.
"The flow monitoring gave our crews good insight into how to track down
I/I problems on the system," said Aaron Cook, wastewater maintenance
superintendent for the city. "They saw the severity of defects. Now they
know how much stormwater can actually enter the system with these types of
defects and what impact they have on our system."
City crews assisted by maintaining the smoke-blowing
machines, making observations during the tests, completing data log sheets,
identifying the severity of problems observed, estimating inflow sources and
"We had done smoke testing for many years," Cook
said, "but these tests gave us the opportunity to quantify how much flow
can be attributed to a particular defect. Previously when we found a defect, we
just fixed it; we didn't look at how much flow it contributed. But if you
don't start determining an amount, you don't know if you have fixed
the problem or not."
The city collaborated during dye testing by providing city
staff and equipment to determine the precise points (at either direct or
indirect connections) where inflow was occurring. During one dye test, crews
observed that a storm pipe under a road had been installed perpendicular to and
on top of an existing sanitary line. During a rain event, the weight of the
stormwater cracked the sanitary pipe underneath, the joints in the storm pipe
separated, and a flood of stormwater was seen seeping into the sanitary line.
By observing precise inflow sources such as these, Woolpert could identify how
many feet of pipe had to be repaired and the rehabilitation cost for
eliminating this condition.
Fowler said the collaborative effort gave city staff a
deeper, more global understanding of system performance and more knowledge
about how the system will react during a rain event. Now crews can anticipate
which areas might need close observation if rain is imminent. The SSES
experiences also are helping crews establish proactive maintenance and
inspection priorities and take more ownership of the system.
Data Integrity and Leveraged GIS
Collecting and reporting accurate data during field work is
crucial. If flowmeters are not maintained routinely, if smoke test defect data
is not recorded objectively and consistently, and if dye test procedures are
not followed precisely, then not all defects will be apparent, or defects may
be represented. Thus, inaccurate data may be used to make decisions about
rehabilitation, and the extent of recommended improvements could be
overestimated or underestimated.
City crews assisting with the flow monitoring and dye
testing received in-the-field training to ensure the integrity of data
collected. Before the smoke tests, Woolpert and city crews spent a half day
reviewing written procedures and evaluation standards to ensure objective data
recording in the field. For example, defects observed had to be photographed
similarly from defect to defect; a naming convention was adopted so photographs
could be identified and referenced based on their location. City staff received
training on leak codes (i.e., which set of conditions defined a defect as
minor, moderate or severe). Staff also learned procedures for estimating
inflows so flow monitoring results could be verified.
During the SSES project, Woolpert enhanced and used the
city's GIS to manage, analyze and simplify data collected and produce
maps of problem areas. For example, smoke testing data including digital
photographs of defects were organized in a database and linked to the GIS that
displayed the locations of defects based on color-coded severity ratings. GIS
maps showing dye testing results also were used to make rehabilitation
recommendations and estimate costs.
A Systematic Approach
As stated earlier, it is important to adopt a systematic
method for addressing issues related to capacity, management, operations and
maintenance. The following systematic approach will help a municipality begin
addressing all four areas.
Beginning to understand and address capacity issues is
important as it relates to development. Does the system have the capacity to
handle new development in certain areas? Which ones? Are lines large enough?
Are new lines needed? Which areas present limitations? By understanding
capacity in all areas of the wastewater system, a utility immediately will be
able to determine what impact a new development will have on existing
infrastructure and respond appropriately. If impacts will be significant, the
developer could be asked to provide improvements to existing infrastructure as
a condition of approving the development.
Municipalities can address capacity issues by collecting
data and creating a detailed system-wide hydraulic model to determine capacity
limitations. However, this requires a major investment in time and money.
Concord's solution was to perform a second level of
flow monitoring that examined the collection lines immediately upstream to
determine if capacities were sufficient. "An organization can smoke test
an entire collection system, but if it fails to collect capacity data on pipes
using flow monitoring, it's missing the boat on an issue that CMOM is
definitely going to address," Fowler said.
In order to zero in on potential major problems, managers
can begin by listening to and asking questions of maintenance staff to
understand today's problems such as cleaning issues or chronic blockages
and overflows. Managers and maintenance staff can participate in a series of
roundtable discussions to begin learning what needs to be done to reduce I/I.
What chronic problems do maintenance staff deal with daily? Where do these
problems routinely occur? Staff should pinpoint problem areas on a map so
managers can begin determining where to focus efforts. These discussions will
be a good starting point to target all other efforts for investigating the
source of system deficiencies.
One way to begin understanding operations issues is to focus
immediately on I/I reduction through a comprehensive flow monitoring, smoke
testing and dye testing program, the approach that Concord used. This program
can be performed at lesser or greater levels of detail based on an
organization's needs or budget and lets managers and staff get a snapshot
of how the system responds during wet and dry weather conditions.
Another method is to rethink and reallocate maintenance
activities for better operations results. What additional preventive
maintenance activities could staff assume? Is staff conducting periodic
inspections to locate problems? Are line cleaning operations tracked based on
location and date? Is the number of staff efficient? Is the right equipment
available for cleaning and inspection efforts? These questions and others can
help define new proactive measures.
Preventing problems before they occur is the goal of
maintenance. These efforts include processes such as routine cleaning and CCTV
inspections. Like Concord, many wastewater utilities perform an extensive
amount of preventive maintenance work already. Concord has begun a simple
tracking effort to monitor proactive maintenance monthly. "Concord also is
implementing a GIS-based Computerized Maintenance Management System (CMMS) that
will ensure the repair work we do in the field doesn't get lost in
the paper shuffle," Fowler said. Preventive maintenance and CMMS
implementation will allow the city to meet collection permit requirements and
use data to improve decision making and support policies in the future.
Concord is moving ahead with other proactive CMOM-type
measures. These measures include
capacity analysis. By accessing population data, using state criteria to
project future flows, and using the GIS to calculate acreage, Concord can
determine if current pipe capacities are sufficient based on projected future
capacities in defined areas. If additional capacities are required, new
customers will be expected to pay for improvements needed to increase
how to handle costs for fixing I/I problems caused by individual property
owners. The average property owner may not be able to pay $1,000 or more to
repair lateral lines causing I/I problems downstream. Concord is considering
several options for working with property owners to make repairs, including
allowing customers to finance improvements over several years.
input on a potential I/I
policy being developed by the WSACC. Fowler said the Water
and Sewer Authority of Cabarras County is considering an I/I policy that would
cover all jurisdictions governed by the authority and result in better asset
management. "The goal is to have each jurisdiction make sure its system
is performing properly so it does not negatively impact the systems in other
jurisdictions," Fowler said. "If one jurisdiction has excess I/I,
there may have to be surcharges penalizing that jurisdiction. After all, no
jurisdiction wants to pay for treatment plant capacity from someone
CMOM is coming, and municipalities and utilities will have
to start doing something soon. If a wastewater system is more than 30 years
old, it is bound to have some problem with I/I. Materials have changed; joints
have deteriorated over time. Communities unsure about the extent of their I/I
problem can begin by analyzing large areas within the system. For example, dry
weather treatment plant effluent can be compared to wet weather effluent. The
next step is performing flow monitoring to validate I/I assumptions and
collecting enough data to draw valid conclusions.
There is no wrong way to proceed with CMOM; each systematic
approach is unique based on system needs, age and budget. A fairly new system
may not have significant structural issues; instead, capacity may be a bigger
issue, especially in a developing community that needs to satisfy
There's no reason to wait on the federal mandate.
Communities with sufficient staff, resources and funds should proceed. Those
that believe they do not have sufficient staff, resources and funds may need to
consider reallocating existing resources.
"CMOM is a 'pay me now or pay me later'
situation," Fowler said. "Right now, we can't get lines in
fast enough to accommodate all the people involved in development. If
there's a major development coming in, I don't want to go before
Council and say we can't allow the developer to build here because we
don't have enough capacity in the lines. I'm not going to get
myself in that boat."
"If you are the manager of a wastewater system and you
don?t think you have problems, then you've got a problem. If you
don't know your problems, you just haven?t identified them. If you
don't start getting your hands around the problems, they will perpetuate
and be twice as bad later," Fowler said.
Communities that choose to remain in a reactive mode and
take no steps to reduce I/I will likely face premature expansion of their
treatment plants. However, a good CMOM-type program will provide a healthy
return on investment with annual savings because of less inflow, increase the
life of the community's current treatment plant and minimize or eliminate