Flatonia – Plum TL Upgrade, Texas

A 19.64-mile 138kV transmission line ampacity upgrade project consisted of installing new Suwannee ACCR conductor, replacing one shield wire with OPGW and replacing existing structures to improve clearance and structural capacity requirements. The existing alignment consisted of 174 structures of which 47 required replacement. The existing structures were lattice towers and wood/light duty h-frames. The proposed structures were engineered steel poles and engineered steel and hybrid steel/concrete h-frames. The existing double-circuit tower was replaced with two single-circuit deadend steel pole structures to separate the T112 and T133 transmission lines.

Phase spacing also was improved on two existing structures to maintain differential ice clearances. The project challenges included a double circuit 345kV line crossing, highway crossings, and the addition of a structure to maintain blowout in the easement. During project site visits additional structures were identified for replacement due to soil erosion and significant wood pole damage.

As a result, consensus was reached to replace existing wood structures with either steel or concrete structures. Foundations will be designed with PLS Caisson based on guidance provided by the client.

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