• A worker prepares to install a shrink sleeve over the pipe joint to keep dirt and rock away from the connection as the trench is backfilled. Welding then occurs underground within the buried pipe.

    Credit: Southern Delivery System

    A worker prepares to install a shrink sleeve over the pipe joint to keep dirt and rock away from the connection as the trench is backfilled. Welding then occurs underground within the buried pipe.

Colorado Springs Utilities (CSU) trimmed costs when installing 50 miles of steel pipeline by implementing a time-saving, joint-sealing method.

Weld-after-backfill (WAB) calls for first fitting the pipe together and installing joint coatings, then backfilling the open trench, and finally welding the joints from inside the pipe. This minimizes trench length and speeds installation, saving money by reducing equipment and labor costs and reducing project impacts in residential communities by minimizing the time that trenches remain open.

The 66-inch pipe was joined via both single- and double-lap welds, where one piece of pipe overlaps another. The project team employed WAB for portions where joints required welding on only one surface of the pipe (single lap).

Contractors were asked to prepare bids for one section of pipe comparing WAB to an alternative in which joints were double-lap welded before backfill. Averaged across bids, WAB and the use of single-lap joints saved $988 per joint. Extrapolated over 2,000 joints, the process saved $2 million.