Model-Based Deep Line Utility Survey

By John W. Jaeger, Senior Project Manager, Binkley and Barfield Inc. | April 2014, Vol. 69 No. 4

The Subsurface Utility Engineering (SUE) Group of Binkley & Barfield Inc. (BBI) has established a systematic methodology to manage risk through the Quality Level A through D system (QL-A – test holes, QL-B – designation, QL-C – surface feature survey and QL-D – records information) as prescribed by the American Society of Civil Engineers (ASCE).

This framework has proven very successful in preventing damage to existing utilities throughout the nation. Technological advancements in equipment have led to more accurate horizontal positioning of utilities while the vertical positioning has remained a function of the SUE QL-A Test Hole. What alternatives are there when access or economics renders a SUE QL-A Test Hole unfeasible? BBI faced this dilemma on four projects where subsurface utility lines were excessively deep or access for the vacuum truck was not possible.

BBI is a Houston-based engineering design firm with branch offices in Austin, Dallas and College Station that has been in business more than 43 years. BBI provides multiple discipline design services in transportation, municipal and industrial facilities, wet and dry subsurface utilities, telecommunication, overhead and underground electric and power distribution. They also provide inspection services, SUE and through their subsidiaries Baseline Corporation and Landev Engineers Inc., provide survey and land development services.
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In October 2013, BBI was asked by Landev to provide SUE QL-A Test Hole Services to find the horizontal and vertical position of a water line and a gas line in one of their large land development projects. These two lines crossed perpendicular to gas lines and Landev needed to know the depth and separation of the crossing line. Review of the requested project quickly revealed that the gas line would require building a bridge to gain access for the vacuum truck. From an economical perspective, the project wasn’t feasible. In further discussions it was discovered that the data required didn’t need to be the Test Hole accuracy of 2 to 4 cm. BBI proposed use of 3D designating technology to alleviate the access and economic issues while still rendering an accuracy well within the client’s needs.