The following is the opinion and analysis of the writer:
Art Kopcsak
Tucson is a jewel in the desert of the SW. Tucson is not a northern factory town with industrial complexes. Nor is Tucson a sprawling city of 10 plus story buildings. The Tucson City Council must revoke the Permit issued to TEP for the installation of 130-foot steel towers for their 138 Volt KVA lines. It is blatantly obvious that the City Zoning Examiner did little to no research about the undergrounding of the lines. A quick discussion with the proper authorities in Wisconsin would have provided the necessary background information to deny the permit permanently.
It is entirely feasible to underground this transmission line. Actually, even 132KV lines have been placed underground since 1927. There are basically three ways to place a high voltage line underground, 1. Mount it to walls of an existing underground or underwater tunnel. 2. Excavate a trench and then basically direct burying the cable or placing it in a pipe/conduit. 3. Using Horizontal Directional Drilling (HDD) which has been used since the 1990s. The size and length of a single bore-can be 3000 feet long and 30 inches in diameter. A single or multiple pipes may be placed into the bored horizontal shaft.
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HDD utility boring can use a standard underground concrete maintenance vault with street level manhole access for maintenance stations. Note also overhead power lines and poles require maintenance/replacement the locations of which may be inconvenient or burdensome to the public and residential areas.
There are three types of cable for underground high voltage lines, 1. High-Pressure, Fluid-Filled Pipe-Type Cable or 2. High-Pressure, Gas-Filled Pipe-Type Cable or 3. Solid Cable, Cross-Linked Polyethylene (XLPE) (a solid dialectic cable). XLPE cable has become the national standard for underground electric transmission lines for less than 200 kV. There is less maintenance for XLPE cables than gas or liquid filled cables. Yes, the diameter of the cables does increase with voltage but the cable diameter will never exceed the 30 inch capability of HDD boring. Yes, it is much more difficult to monitor and detect impending insulation failures but not impossible particularly with the properly spaced vaults for installing, accessing, testing and maintaining the conductors. The vaults also provide some heat dissipation.
Depending upon the design required by TEP the XLPE conductors could be placed into a single large pipe or into multiple properly spaced pipes. Either configuration could easily be placed into a 30” HDD shaft. The placing of conductors into separate pipes which are adequately spaced would help to dissipate the heat load.
Any corporation wishing to do business in Tucson and the surrounding County, especially a foreign owned corporation, does not have the right or privilege to deprive Tucson, the County or the State of Arizona of our natural beauty, intrinsic appeal, scenic beauty and background as well as the amalgamation of culture going back hundreds of years. Just drive along Ina/Sunrise, Campbell, 6th Ave or the Mt. Lemmon Highway. It appears Tucson is faced with a predicament similar to “Project Blue” and the residents of the City and County need rally against the permit issuance.
Follow these steps to easily submit a letter to the editor or guest opinion to the Arizona Daily Star.
Art Kopcsak is a retired engineer from Corps of Engineers and other corporate engineering. He has taught engineering at West Point and holds a master’s degree from the University of Arizona. He has also done engineering work for US Missile Defense and is a combat engineer with 3 combat tours.
