HomeMy WebLinkAboutStaff Report 1524City of Palo Alto (ID # 1524)
City Council Staff Report
Report Type: Informational Report Meeting Date: 5/2/2011
May 02, 2011 Page 1 of 4
(ID # 1524)
Council Priority: Emergency Preparedness
Summary Title: Gas System Risk Assessment
Title: Informational Report on Gas System Assessment and Risk Reduction
From:City Manager
Lead Department: Utilities
Recommendation
This is an informational report.
Background
The City of Palo Alto Utilities department (CPAU) conducts on-going, proactive maintenance
and upgrade programs to assure the integrity of its gas system. In response to nationwide
concerns over natural gas system safety, Palo Alto’s Gas Utility staff has conducted a more
intensified review of its current system conditions. Staff’s goal is to determine the existence of
new potential hazards that could affect our customers. As a result of the safety review, CPAU
identified a potential risk to the public that requires mitigation. This issue and risk exists in
communities across the country. This report outlines the conditions which led to that risk and
describes CPAU’s proactive program to resolve the problem.
By the time this report goes out in the Council’s packet, staff will have already launched the first
efforts in an extensive public information and outreach campaign (explained in greater detail
later in this report). While the industry practice this report reviews exists around the country,
City staff have chosen to take an aggressive approach of investigation, identification, and
correction.
In the 1980s, gas utilities began installing gas service lines to customers’ properties using
techniques that eliminated the disruption caused by the older method of digging trenches
across property and through yards. These newer techniques included both pneumatic boring
and horizontal directional drilling (HDD). Both of these techniques involve creating a small
underground tunnel through the soil and then pulling the new gas line through that tunnel. By
the early 1990s, CPAU used only HDD.
Since the earliest implementation of these new installation methods, CPAU has undertaken all
standard precautions to place these new pipes in areas distant from the alignments of other
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underground utilities, such as water and sewer lines. However, over the years since then, it has
become apparent that in rare cases some property owners’ wastewater laterals (sewer pipes)
did not follow the expected alignments. In those cases, it is possible that the tunnel boring
equipment operator could unintentionally and undetected bore through a wastewater lateral,
and the gas pipe would then be installed at intersection with the sewer pipe. The industry term
for this situation where different utility pipes intersect is a “crossbore.”
Description of the Potential Problem
The possibility of this inadvertent intersection of gas and sewer pipes during installation means
that some gas service lines in the City may pass through the property owner’s wastewater
lateral lines. This potential crossbore situation is not unique to the City. Today, utilities across
the country are facing the same issue since pneumatic boring and HDD were standard gas
industry pipe installation methods for a period of years.
Crossbores do not pose a dangerous situation under normal circumstances. However, in cases
of a slow sewer drain, blockage or sewer overflow, either a plumber or the property owner may
use what is known as a snake fitted with a cutter to remove the blockage from the lateral. The
cutter can create a serious safety problem if, during the clearing process, it accidentally severs a
gas line that intersects with the sewer line.
Discussion
The City has taken a number of actions over the last ten years to limit the risk associated with
possible crossbores. Staff has proposed a program to inspect sewer laterals for crossbores in
the 2012 Operating Budget. This program is being initiated now because of the growing
concern nationwide that the crossbores could pose a risk to gas customers. To ensure the
safety of our customers, staff has proposed that we investigate and correct any instances that
may exist on the gas distribution system.
Remedial Action Already Taken
Over the last ten years, the Gas Utility has revised its construction practices to eliminate the
possibility of creating a crossbore. Beginning in 1999, the Gas Utility began installing devices
known as excess flow valves (EFV), which limit the flow of gas when a line is severed. The City
was one of the early adopters of this practice. The Department of Transportation began
requiring EFVs on residential services in 2009, which was ten years after the City had already
begun installing these devices.
On Gas Main Replacement Project 10 which was constructed in 2000, CPAU began a practice of
video inspection of every wastewater lateral where a gas service was replaced on a property.
That practice continues today.
Implementation of a Proactive Cross Bore Safety Program
At this time the City does not have an accurate estimate of the number of crossbores that may
still exist in our system. The few utilities who have recently started inspecting wastewater
laterals have found two to four crossbores per mile of main. There are approximately 200 miles
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of mains, and 19,300 services within the City. However, it is important to emphasize that staff
does not know if these rates of crossbore incidents are representative of the City’s situation
because different utilities use different operating and construction procedures.
Improved construction practices have reduced the possibility of a crossbore occurring. All gas
lines installed in the City’s Capital Improvement Projects since 2000 have been inspected for
crossbore. If a crossbore occurs, the installation of EFVs has lowered the risk of a hazard
resulting from a gas line being accidentally cut. However, approximately 2,300 services were
installed in the City prior to implementation of these improved construction practices.
Therefore, in an effort to improve the safety of the gas system, staff is recommending a
program to inspect every sewer system lateral in the community that might have a crossbore.
CPAU can undertake this program now because advances in video technology have made it
possible to efficiently inspect laterals by running a camera from the sewer mains through the
laterals.
CPAU has already started inspecting wastewater laterals that service schools and public
meeting places. These inspections are expected to be complete by July 1, 2011. In the summer
of 2011, the City will begin the inspection of the residential and commercial wastewater
laterals. The City is targeting completion of this inspection by January 2013.
During this inspection process, the City will repair any crossbores by rerouting the gas lines and
either replacing or repairing the customers’ wastewater laterals. After video recording the
wastewater laterals, CPAU will inform customers as to whether their sewer laterals are in need
of other repairs and will make the digital video available to the customers. While CPAU will
take responsibility for the repair of any laterals that have a crossbore problem and will share
information on the conditions of the sewer laterals with customers, any other repairs of other
sewer conditions unrelated to crossbores that are discovered during video review are the
property owners’ responsibilities to repair.
Public Communication Plans
While a crossbore situation should exist in only a relatively small number of sewer laterals, and
because a safety problem only exists when the sewer line is being cleaned, the City has notified
residents and plumbers that they should call the Utilities Department before they attempt to
clear a sewer line. CPAU will make staff available 24/7 to respond to these calls promptly, since
a sewer emergency is a situation requiring immediate repair. Based on the caller’s address if
staff determines a potential crossbore exists, CPAU will send out a qualified employee or
contractor immediately to perform an inspection and determine if additional precautions need
to be taken.
CPAU has developed an outreach program explaining the crossbore situation, the simple safety
precautions that will prevent a hazardous situation, along with the City’s inspection and repair
program. This message is being communicated through press notifications, billing inserts,
website updates, outreach to neighborhood associations, training for local plumbers, and
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provision of brochures at equipment rental agencies for do-it-yourselfers who might be
cleaning out their own sewers. It is a very high priority for CPAU to get this information out as
widely as possible.
Timeline
The following is the proposed timeline for actions being taken by staff.
Action Date
Complete public information pieces and post information on the City Website May 1, 2011
Complete the inspection of sewer laterals for public meeting places and schools July, 1, 2011
Complete RFP and award of a contract to contractor performing video inspection August 30, 2011
Complete inspection of wastewater laterals requiring inspections January 1, 2013
Resource Impact
This project will require a one-time expense in the Gas Utility Operating Budget. The
expenditure will be part of the 2012 operating budget that will be considered by Council. The
expense is roughly estimated to be $3.8 million and will depend upon the number of services
that require inspection.
Policy Implications
If the City Council approves the 2012 budget recommendation from staff this project will
further reduce the risks posed by the operation of the Gas Utility.
Environmental Review
This report is not a project under the California environmental Quality Act. Therefore, an
environmental review is not required.
Prepared By:Tomm Marshall, Assistant Director
Department Head:Valerie Fong, Director
City Manager Approval: James Keene, City Manager