HomeMy WebLinkAboutStaff Report 14704
City of Palo Alto (ID # 14704)
Utilities Advisory Commission Staff Report
Meeting Date: 9/14/2022 Report Type:
City of Palo Alto Page 1
Title: Informational Update on Utilities Cross Bore Verification Projects
From: Director of Utilities
Lead Department: Utilities
Recommendation
This report is for information only. No action is required.
Executive Summary
A “cross-bore” occurs when a pipe is installed by trenchless technology and inadvertently
penetrates pre-existing pipe in its path. Cross-bores create an intersection of infrastructure
that compromises the integrity of one or both pipes involved, with potentially severe
consequences. In rare cases, if cross-bores have occurred between sewer laterals and gas lines,
a potentially hazardous situation can be created during sewer lateral cleaning or plumbing
work. Proactive investigation and prompt repair reduces risk.
In 2011, the City of Palo Alto Utilities (CPAU) Department launched a proactive cross-bore
verification program of all active sanitary sewer laterals in the City. The main purpose of the
cross-bore verification program was to help ensure natural gas pipelines or other utilities were
not unintentionally installed through sewer laterals. The first phase of the program (Phase I
Cross-Bore Verification Program) concluded in 2013. During Phase I, the City’s contractor
successfully inspected and cleared a total of 7,192 City and private sewer laterals and CPAU
Operations identified and repaired 26 natural gas cross-bores.
During August 2019, the City started the second phase of the cross-bore verification program
(Phase II Cross-Bore Verification Program). Initially, 2,500 sewer laterals were scheduled for
inspection, but the parties terminated the contract during the COVID-19 pandemic because the
original bid price did not include the additional expenses to meet Santa Clara County’s COVID-
19 safety requirements and the contractor would not execute a contract change order for the
additional expenses. As a result, the City’s contractor inspected 408 of the highest priority City
and private sewer laterals, and no cross-bores were identified during Phase II of the program.
The Phase III Cross-Bore Verification Program began during April 2021. Phase III of the program
was completed during September 2022 and the City’s contractor inspected a total of 1,480 City
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and private sewer laterals. Only one natural gas cross-bore has been observed thus far during
Phase III and CPAU Operations repaired the cross-bore on the same day it was identified.
The final Phase IV Cross-bore project has not yet been scoped or budgeted. Staff will continue
to assess the number of sewer laterals that meet the criteria for cross-bore inspection for cross-
bore. Staff will prioritize the remaining sewer laterals, and prepare a cost estimate for
subsequent phase(s) of the program. Staff will report the findings and recommendation at a
future UAC meeting.
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