SWG-2020-00361 - American Electric Power (AEP) - Laguna Madre - Nueces County, Texas

Public Notice          Project Plans

The applicant proposes construction work needed to remove decommissioned transmission line (T-line) structures within the Laguna Madre.  A total of 38 H-frame structures (36 in-water, 1 on a dredge island, and 1 in adjacent estuarine wetlands) would be removed.  Airboats with booms would be used to de-clip the old T-line wires which would then be pulled out under tension, rolling the old wire up on split reels.  Airboats would surround the end of the wire to guide and prevent the public from entering the area during pulling.  Once the wire is completely removed then work would begin to take out the old structures utilizing the following method:

Turbidity curtains would be installed around both of the in-water concrete pilings to keep suspended sediments generated from the removal process from dispersing away from the site.  At each structure the arms, x-braces, and poles would be taken down using the crane and loaded onto an air barge that would take the old structure components to the western exit/entry point for offloading at the project staging area.  All components would be disassembled whole and not cut up in order to avoid wood shavings/debris from entering into the water.  Once the above-water structure components are removed, an excavator mounted on an air barge would be used to dig around the pilings to a minimum of 5.5 feet below the seabed surface within a 10-foot-diameter around the piling.  Excavation would be done around one piling at a time.  When the proper depth below the seabed is reached, the crawler crane would place a shear around the pilings and cut them off at the base of the excavated hole.  The excavated soils would be placed within the turbidity curtain on the adjacent piling.  If sufficient room is not available between pilings and the surrounding turbidity curtain, then excavated soils would be temporarily held on the air barge deck until the piling can be cut.  Once the old pilings have been cut and removed, the hole would be backfilled with the excavated soils and smoothed out to match the original contours.  The excavated soils would be placed in an area of disturbance, thus no additional disturbance beyond the 10-foot-diameter around each concrete structure is anticipated.  The removal process for each structure is expected to take approximately three days to complete.  The process to remove the old structures and pilings would be repeated at each location, moving across the bay.  The turbidity curtains would be left in place for 48-hours after the removal process is complete to allow sediments to settle and not be dispersed.

The structures on either side of the GIWW would be removed in the same process.  The piling protection around the old structure would also be removed.  The soils would be excavated in the same manner as the old H-frame structures, with each piling cut by hand.  Trench boxes would be placed around the pilings after excavation of soils and a diver would be placed within the trench box to cut the pilings.  The cut pilings would be removed and placed on air boats.  After the diver has finished and exited the trench box, the box would be removed, and the hole backfilled with the excavated soils.  Upon completion of the removal of the derelict structures, the crane would transition from the floating barges to the existing matting used in the construction of the new line.  The crane would remove the barges from the water and place them on the mats to be trucked offsite.  The crane would then be disassembled and removed from site.  All the matting on North Padre Island side and the staging area would be removed and the area returned to the existing contours.  The removal process would utilize the same Best Management Practices and special conductions implemented during the construction of the new line.