Joint trenching is the practice of burying different utilities together in one trench. The pipes and cabling for gas, water, electricity and telecommunications can be run through one single trench -- not only main lines, but service lines can also be installed. Also called common trenching, the practice has several advantages, including cost savings and the relief of underground congestion in areas of high development.
In the United States, joint trenching was first used in 1960 by Commonwealth Edison and Illinois Bell, according to the Texas Department of Transportation. The practice is increasing in the United States, but as of 2011 has not been universally adopted. Obstacles to adoption include the inability of utilities to coordinate, determining cost responsibility and conflicts of interest, according to a report by the Telecommunications Management Group. Trenching is more extensively used outside the U.S. The Federal Highway Administration took a look at European practices in its 2002 report "European Right-of-Way and Utilities Best Practices," recommending an expansion of joint trenching as one of the solutions to right-of-way issues in the U.S.
Reduced Construction Costs
Joint trenching saves money in a building construction project. Instead of clearing several paths, one for each company coming to install an underground utility, a construction project need only create one. This translates into time shaved off a project's completion and reduced costs, according to CenterPoint Energy. Joint trenching also means building projects can be offered more quickly to the market.
The process of joint trenching allows all the utility companies to coordinate the installation scheduling among themselves. According to CenterPoint Energy, the electrical lines typically go in first. The construction company creates the trench and provides site information to the utilities.
Besides reduced construction costs and relieving underground congestion of utilities, joint trenching makes it easier to know where not to dig, making landscaping simpler. It's also easier to find the trench for repairs. Planning property improvements is simpler, too, because there is only one trench to work around. One trench for all utilities means less environmental disturbance. Additionally, in places where there isn't a lot of available ground or where digging is difficult, joint trenching provides a solution.
Water and electricity shouldn't mix. Neither should electrical currents and telecommunication lines, since electrical signals can disrupt telecommunications. To prevent problems, codes have been written governing how the pipes and cables are laid in the trench. Measures include adequate spacing between utilities, dirt buffers between lines and requiring qualification programs for those who might later work on certain utilities within the trench.