In Toronto, a 16-in. PVC water main replacement for an aging 6-in. steel main underwent a Subsurface Utility Engineering (SUE) investigation at 60% design completion.

The study revealed discrepancies, prompting a shift in the water main's route, resulting in significant savings of over $100,000 and a favorable benefit-to-cost ratio of approximately 3.25, while the SUE investigation cost was $31,000.

In Toronto, ON, Canada, a new 16-in. PVC water main was to be constructed to replace an existing 6-in. steel main that was nearing the end of its service life.

A SUE investigation was initiated when the design was about 60% completed. The study included QL-C verification of maps and records and 6,000-ft. of QL-B designation.

A total of 13 test holes were excavated along the proposed alignment at critical locations.

The main findings of the SUE investigation were a 12-in. steel gas main that was found to be nearly 2-ft. off its marked location along the north side of Weston Road, and an unmarked 12-in. steel gas main branch serving properties on the south side of the street that was in a direct conflict with the proposed alignment.

Based on data provided by the SUE investigation, the route of the water main was moved from the south to the north side of the street, resulting in significant savings in terms of shorter service connections and reduced pavement restoration requirements.

In addition, several unmarked electrical ducts and a storm sewer were located, and their location incorporated in the design.

The cost of the SUE investigation was $31,000 while the savings from eliminating construction delays and reduced pavement restoration cost were estimated by a University of Toronto to be just over $100,000, thus yielding a benefit-to-cost ratio of approximately 3.25.