Could Your As-Built Save a Life?

Be aware of cross-bore issues and what you can do to minimize them

Could Your As-Built Save a Life?

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Several decades ago I was called out to a new house experiencing problems with their onsite system. They had effluent coming up out of the manhole covers of their brand-new system.

This was before effluent filters were required so it wasn’t a plugged filter. Typically, our first response back then would have been to put the sewer machine in and cut through and remove the blockage. Boy, am I glad we didn’t. For some reason their pumper already measured out the blockage and said it was 15 feet out from the tank. So we dug down and found that an electric line had been directionally drilled through our sewer pipe and was still there. If we would have used a sewer machine, someone could have been electrocuted. 

Fast-forward 10 years. A municipality called and had an issue with a storm sewer pipe: a gas line had been directionally drilled through it. I don’t even have to describe the catastrophe that could ensue if we used a sewer machine on that one. This problem has become more prevalent as directional drilling becomes more common.

Cross bore, the situation where another utility has directionally drilled through a different utility pipe, is a real problem, sparking the need already for a cross-bore inspections industry.

Here are a few things that must be done now to keep your employees and your customers safe:

  1. Contact your state’s utility locating system. Here in Wisconsin, that is Diggers Hotline. Sometimes the utility locate marks make it really apparent that there is another utility running perpendicular, or across the pipe you are looking to repair. 
  2. If someone has a blockage, consider using a sewer camera first in an effort to determine if you have a cross bore situation. In most blockage situations the pipe might be filled with water but in some cases if the water is getting through but not the solids, you might get a better view of the errant utility inside your pipe. 
  3. Sometimes you can partner with a pumper who has a 2-inch reduced pipe that can go into a 4-inch pipe and pump out any water to give you a better view. 

What are things that we as onsite installers can do to minimize cross bore from occurring to our systems?

Consider using tracer wire when installing systems. While typically not a requirement in most onsite settings, this could possibly help others locate where the onsite systems are. Without this, the directional drillers have no idea where your pipes are. 

One of the things our company is starting to do is draw our as-builts using a Global Navigation Satellite System receiver. Think GPS on steroids. This receiver accurately locates the pipes and even their elevation on a visual report using an aerial image of the lot. By using this information somebody could accurately locate the pipe and even know its depth. 

There has long been some resistance within our industry to use of tracer wire, and regulators have been kind enough to not require it in most onsite systems. However, not only would this help to minimize cross bores, it would have a great side benefit. Using tracer wire or GNSS can also be very helpful in that instance where years after a system is installed, the current homeowner wants to install an outbuilding or a pool. Their question is always where is the pipe leading to the system, or the force main crossing the yard? 

Without tracer wire or other method, locating PVC pipe underground is not an easy task, nor is it always accurate. Of course you could use a sewer camera with a transmitter that works in 4-inch pipes. But smaller force mains with bends are going to be harder to fit cameras into. And the tracer wire or GNSS could save all that effort. 

Obviously a much simpler as-built — drawing multiple setbacks so the pipe location can be triangulated (like municipalities used to do to locate curb stops) — would also be a proactive way of helping to find pipes in the future. But this type of drawing takes time, which seems to be in short supply; especially when reviewing hundreds of as-builts, when most show little to no detail. 

Cross bores are really bad for at least two reasons. First, they typically put a person out of service and cause sewer backups. Second, they are extremely dangerous if you don’t know they are there. A little effort in advance, creating an accurate as-built, or using tracer wire can help minimize the potential for dangerous cross bores. This effort will also help homeowners in the future if they are looking to add a pool, outbuilding, or other change to their lot. A little effort on the as-built now could protect someone, or at minimum help someone, in the future.


About the author: Todd Stair is vice president of Herr Construction, Inc., with 34 years’ experience designing, installing, repairing, replacing and evaluating septic and mound systems in southeast Wisconsin. He is the author of "The Book on Septics and Mounds" and a former president of the Wisconsin Onsite Water Recycling Association. 



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