How do you use heavy equipment to excavate a three-mile corridor filled with crisscrossing utilities, removing some of them without damaging the rest? That was the challenge faced by Sundt and a joint venture partner while we performed complex underground utility work for a major expansion of Phoenix’s light rail system, known as the Northwest Extension. Sundt’s response was to develop a solution that hadn’t yet been used anywhere in the industry: combining civil information models (Building Information Modeling for infrastructure) of the project with automated machine guidance. Neither technology was new, but putting them together to improve accuracy and efficiency was an innovation that advanced the industry.


The approach works like this: equipment such as excavators and scrapers are outfitted with global positioning system (GPS) antennae and sensors on the front end that detect the machine’s exact orientation in space. That information is then relayed to the machine’s “brain box,” which is essentially a small computer in the cab. It figures out where the exact tip of the bucket is and then gives the operator real-time feedback on where to cut or fill based on the location of the blade or bucket.


The major advantage of this approach is the ease with which it can detect a buried utility line before the equipment gets too close and causes damage. The operator can set a limit – two feet, for example – and once he or she reaches that mark in time and space, the system gives an alert indicating that the no-go zone is being approached.


This innovative and creative combination of two existing technologies not only improves accuracy and efficiency during underground utility work; it also greatly reduces the incidence of damage and costly repairs.


Valley Metro Light Rail, Inc.


Metro Light Rail Transit Northwest Extension