NASSCO takes safety very seriously through its mission to set standards for the assessment, maintenance and rehabilitation of underground infrastructure. The assessment of sewer pipes to identify cross bores – the intersection of an existing underground utility or underground structure by a second utility, resulting in direct contact between the utilities that compromises the integrity of either utility or underground structure—is a critical step in the overall safety of sewer pipes.
As a result, the NASSCO Cross Bore Workgroup, part of NASSCO’s Infrastructure Assessment Committee, has recently introduced the NASSCO Cross Bore Specification Guideline. The goal of this document is to support the prevention of further damage to gravity pipeline infrastructure and to locate existing cross bores.
Utility infrastructure is now commonly installed using trenchless technology practices and can sometimes penetrate gravity wastewater mains and service laterals. If these penetrations remain undetected, they can be accidentally cut during maintenance practices and result in damage to life and property. There are typically two types of cross bore programs: prevention and legacy.
A prevention program is a process utilizing robotic inspection cameras equipped with locating transmitters to identify location and approximate depth of all subsurface gravity pipelines at the intended crossing points of the horizontal bore path.
Prevention programs should include both pre-construction and post-construction inspection for both new utility installations and replacement of existing utilities:
- Pre-construction inspects gravity pipeline infrastructure prior to a utility install via robotic trenchless camera equipment, or similar, for the purposes of locating potential crossing points.
- Post-construction inspects gravity pipeline infrastructure after a utility has been installed via trenchless CCTV inspection equipment for the purpose of confirming the existing infrastructure was not compromised during the trenchless pipeline construction.
A cross bore legacy program utilizes a process to inspect gravity pipeline infrastructure that was historically subject to damage due to trenchless technology practices without a formal or adequate preventative program.
To review and download the entire specification, visit nassco.org/resources/guideline-specs.