April 2015, Vol. 70, No.4
Editor's Log
The Unfortunate Legacy Of Crossbores
The April issue of Underground Construction has devoted several pages of information regarding the rather frightening history of pipe installations unwittingly intersecting existing pipe, commonly referred to as “crossbores.”
There is an active association that has been working for several years on how best to deal with the crossbore situation. The Cross Bore Safety Association (CBSA) defines a crossbore as: “An intersection of an existing underground utility or underground structure by a second utility resulting in direct contact between the transactions of the utilities that compromises the integrity of either utility or underground structure.” Generally, the pipe being intersected is some kind of sewer/water main or lateral.
Crossbore issues have actually been around for some time. Piercing tools have been known to break through pipe. Sometimes, even larger auger boring work could crush or intersect other pipes as well. But ironically, it has been one of our industry’s biggest game-changing trenchless breakthroughs that has been the principal instigator of the crossbore problem.
The emerging horizontal directional drilling (HDD) market was booming in the 90s. It was a technology tailor-made for installation of the thousands of miles of fiber, gas distribution pipe and electric conduit. It was a time of excitement and profit for both the contractors and vendors. But it was also a time when a young industry began to suffer growing pains, sometimes at a deadly cost.
Because the demand for HDD was so strong, there was a mad rush to buy an HDD rig today and start work tomorrow. That haste created inexperience workers. While most utilities would mark their lines, cities typically were exempt or chose not to participate. Municipalities justified their lack of participation in One-Call Systems by claiming lack of funds and resources combined with the fact that typically laterals are on private property, out of their control and responsibility.
It was no surprise then when sewer and water pipes were drilled through with regularity, especially through unknown or hard to find neighborhood laterals. Generally drillers never knew that they had created a crossbore.
Predictably, when sewer/water contractors and plumbers attempted maintenance on the pipes, problems often erupted. It’s one thing for cleaning equipment to hit a fiber conduit – that’s more of an inconvenience. But when cleaning equipment collides with gas pipe, disaster often follows. Pipe damaged or cut by sewer cleaning equipment allows natural gas to escape, frequently leaching up a lateral and pooling under homes and businesses until concentrated enough that any spark can ignite a firestorm.
Fortunately, through hard times and good, a more mature HDD industry today is very much aware of the crossbore problem and has made great strides to ensure crossbores are a legacy issue only. The results clearly show that new crossbores are becoming increasingly rare. If a crossbore is inadvertently created, post-boring inspection methods catch the crossbore so steps can be taken immediately to remove the pipe – and subsequent risk.
Unfortunately, the onus for preventing crossbores is shouldered by contractors and gas, telecom and electric utilities who typically are active in One-Call groups and aggressively avoid problems by providing timely locates. These utilities recognize the cost and risk of not working together as an industry to eliminate crossbores.
Also, the CBSA is preparing a report titled Leading Practices for Cross Bore Safety to address underground utility crossbores, a continuing issue that affects utility providers, contractors and the general public. It is a benchmark document that should provide further guidelines and direction for avoiding future crossbores.
But to this day, the legacy issues of crossbores remains. Continued research reveals that the density of crossbores is much greater than previously thought. Without accurate and complete locates that include participation by municipalities, the risk for new crossbores remains.
The Distribution Contractors Association has produced a position paper regarding how crossbores should be addressed and eliminated by contractors and utilities taking appropriate steps in partnership. The DCA makes an interesting point that for those municipalities claiming impunity from laterals, those cities do rely on laterals for revenue and therefore have a significant measure of control and thus, responsibility for maintaining those laterals.
The bottom line is that this is an industry-wide issue, even for municipalities. The argument of “it’s not our problem or responsibility” doesn’t sit well when a citizen is looking at the smoldering ruins of their home or worse, identifying a body at the morgue.
As an industry, our fiduciary responsibility is to ensure potential crossbores are eliminated by active prevention combined with aggressive diffusion of the ticking legacy time bombs.
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