Crossbore Inspection Program

Clogged sewer line? ALWAYS call us first at (650) 329-2579 to have the line cleared of a potential crossbore.

The City of Palo Alto leads with its proactive natural gas safety programs. The Cross-Bore Safety Program inspects crossings between natural gas pipelines and sanitary sewer laterals. These unintended natural gas pipelines and sanitary sewer lateral intersections are Cross Bores. In July 2011, the City began the first phase of the safety program. Over 13,000 sanitary sewer laterals were scheduled for inspection. High congregation areas such as churches, schools, and the downtowns were scheduled first. Commercial and residential neighborhoods throughout the City were last. Of the 13,000 sanitary sewer laterals scheduled for inspection, 7,000 were completed. A total of 26 natural gas pipeline cross bores were identified and repaired. This project concluded in 2013. 

 Crossbore Situation
 Correct Alignment
Correct alignment


Check out this short video recently created by the Mayor's Youth Video Corp.  The video will give you some background on the cross-bore issue and how the City is addressing it. 

In August 2019, the City started the second phase of the safety program. 1,200 sanitary sewer laterals were scheduled for inspection. Due to the impacts of Covid-19 on the construction industry, approximately 400 addresses were completed. The City will issue a new contract to complete the remaining laterals. 


  • Call 811 before excavating in your yard to verify the location of your utility lines. 
  •  Do not use invasive equipment to clear sewer laterals until assessing the obstruction. 
  •  If you smell a strong odor of natural gas immediately leave the premises and leave all exits open. 
  •  From a safe distance, call 911 and City of Palo Alto Utilities at (650) 329-2579. 


 Frequently Asked Questions

  1. What is a cross bore? A cross bore is the unintended intersection between one utility line and another. This happens during construction using “horizontal directional drilling” or underground pneumatic boring equipment. The City safety program focuses on locating natural gas cross bores in sewer lines. 
  2. How can a natural gas pipeline run through a sanitary sewer lateral and the utility not know it?  During the pipeline installation, the installation equipment drills a tunnel. The installation equipment can drill through very hard soils and rock. If a sewer pipe is not located, the installation equipment can pass through a sewer pipe. There would be no sign to the operator this has happened.
  3. What is Horizontal Directional Drilling (HDD)?  HDD is a method of trenchless construction where pipelines are installed underground. In the 1970s, the City used HDD to install natural gas pipelines on customer's property. This eliminated the need to excavate from the gas distribution main in the street to the gas meter. 

What to expect when we're inspecting: 

What is the City’s current inspection program? Since 2001, all Gas Capital Improvement Projects must video inspect sanitary sewer laterals. Since 2010, all gas installed by City Staff must inspect sanitary sewer laterals. In 2011, the City started the cross-bore safety program and inspected 7,000 sewer laterals. The City is contracting out the next phases of the safety inspection program. 

What is the City’s schedule of cross bore inspections?  Cross Bore Verification Program Phase 2 began in August 2019. Due to the impact of Covid-19 on the construction industry, only 400 addresses were cleared before the shutdown.

Will I be notified when my property is inspected? The City contractor provides 7 day and 24-hour notifications before beginning work. If re-inspection or property access is needed, the contractor will provide 24-hour notice before beginning work.

Do the City contractors carry ID? Contractors will wear an identification card at all times during the inspection. Residents or owners can verify workers by calling Utilities Engineering at (650) 329 – 2168. 

What happens if my sewer line can't be easily inspected? The City’s contractor will place door hangers at each house that needs more work. These door hangers give information to the property owner about scheduling an on-site inspection. 

Will the City pay for a private sewer inspection before the City inspects my private sewer line? The City will not reimburse for inspection done by private sewer cleaning professionals. Property owners are responsible for expenses incurred by a hired plumber (i.e., Non-City hired contractor). 

Will the City inspect for cross bores other than sanitary sewer lines and natural gas service pipelines? During the inspection, we are looking for other utility cross bores. Phase 2 of Cross Bore safety program will focus on natural gas pipelines and sanitary sewer lateral intersections. 

 More crossbore background:

  • How many cross bores are in Palo Alto? During the 1st phase of Cross Bore Verification Program, 56 cross bores were identified. Of the 56 cross bores identified, 26 were natural gas. 
  • Are there cross bores involving other utilities? (electric, cable and water)? There are 30 cross bores identified that are not natural gas cross bore in the 1st phase of the program. 
  • How many cross bores have resulted in fires or explosion in Palo Alto? None. 
  • Is the City now inspecting every sewer line in Palo Alto? For all gas services installed since 2010 have had the sewer lateral inspected. The City will continue the cross-bore inspection program until all identified sewer laterals are inspected. 
  • How will the City be changing installation and inspection practices in the future so that cross bores are eliminated? The City requires sewer laterals be inspected before introducing gas in the pipeline. This will ensure a clear sewer line before leaving the work site. For previously installed services, the City will continue inspections until complete.
  •  Is the Building Department responsible for the approval of natural gas projects? No, the utility infrastructure is regulated by the U.S. Department of Transportation. The natural gas utility infrastructure is not subject to local building code requirements. 
  •  Does the City have records of the private sewer laterals? No, the City does not have records of the private sewer line. Local building codes do not require the submission of private plumber record drawings. Property owners make repairs or alterations after a permit has been issued. For these reasons, the exact location of a private sanitary sewer laterals is not known. 
  •  Will I see higher gas or wastewater rates as a result of this program? No, this program is funded through the Utilities Department's existing preventative maintenance program. 
  •  What will it cost to fix this problem? Council approved $1,905,475 for the 2nd Phase of Cross Bore Safety Program over a two-year period. 
  • How do I make sure to get the latest information? Sign up on our email list to get updates on programs, rebates and workshops, or go to our Twitter Feed or Facebook page to get the latest.