The Importance of SUE - Part IV

Subsurface Utility Engineering = More Power

Though usually overhead, electric transmission projects significantly benefit with Subsurface Utility Engineering (SUE) data incorporated in the design. Whether installing a new transmission line, or rerouting an existing line, power transmission companies must make difficult decisions on where to place overhead tower structures.

Drill shafts for electric transmission towers could damage underground utilities if existing utility information is not known or is inaccurate. SUE, performed in accordance with the recommended practices and procedures described in ASCE publication CI/ASCE 38-02 “Standard Guidelines for the Collection and Depiction of Existing Subsurface Utility Data,” is the most accurate method to help determine transmission line routing and structure locations.

It’s also not uncommon to expand existing transmission substations to keep up with increased demand of electric services. Design engineers can determine where future expansion is possible with the use of accurate SUE data. TRG recommends performing Quality Level (QL) “B” for substation expansion projects and design of new transmission tower locations. QL “D” utility record information can be utilized when working on preliminary routing for transmission lines, but should not be relied upon for design decisions.

Vacuum excavation and hydro-excavation are also utilized on many electric transmission design projects to perform test holes (QL “A”) on nearby underground utilities to identify potential conflicts. In some cases, L-shaped or X-shaped trenches are excavated at proposed tower drill shafts to ensure that there are no underground utilities crossing through the excavation area.

Applying SUE on Electric Transmission Projects

TRG has performed SUE services for the Lower Colorado River Authority (LCRA) on numerous electric transmission projects. In Central Texas between Smithville and Winchester, TRG performed utility records research and designating QL “B” SUE services at 18 proposed tower locations along an existing transmission corridor. TRG designated underground utilities within a 30-foot radius at each of the proposed locations. TRG crews also performed 2-man active sweeps with electromagnetic designating equipment to search for unknown utilities within the project limits. This underground utility data helped the LCRA determined where to place the towers. This project required that TRG crews coordinate with LCRA for property access and provide land owner notifications.    

TRG recently performed SUE for a substation project at the LCRA substation near Evant, Texas. QLB SUE services were performed surrounding the existing substation for a proposed expansion. During the field investigation, TRG crews had to perform due diligence to differentiate between the installed grounding grid and the existing underground utilities. Close coordination with LCRA staff was required for access to certain areas within the substation.

Electric transmission is just one sector where SUE information can help keep projects on budget and on schedule. Keep an eye on this blog for updates. This is the fourth installment in an 8-part series on SUE, in which we will touch on the importance of SUE in several different markets, including transportation, water & wastewater, campuses and facilities design, and more.

Our experts are happy to answer your questions or lead your team in a more in-depth “Lunch & Learn” on SUE. Feel free to contact us at / 817-345-7500 or 512-580-5440.