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AMEC: Typhoon Recovery Project 34.5 KV Dededo – Electrical Distribution Line Burial

The 34.5kV Dededo Electrical Distribution Line was constructed to supply stand-by electrical service from GPA’s Combustion Turbines 1 & 2 at their Dededo power plant to Andersen Air Force Base during major outages created by typhoons or any other factors resulting in power outages for the Air Force. The project is funded in its entirety by the US Air Force with AMEC a major construction management firm out of Philadelphia as the prime contractor. Black Construction was selected as the prime subcontractor on this project due to its experience and reliability in high voltage underground work with specific emphasis on the installation of 34.5 KV underground transmission circuits.

The primary scope of the work involves the installation of approximately 85,000 linear feet of 6 inch diameter and another 42,240 linear feet of 4 inch Schedule 20 PVC conduit buried in the same trench. The alignment of the 34.5 Kv line underground line begins at the Dededo switch yard where the first primary electric manhole is located. From the CT-2 switch yard, we then cross Marine Corps Drive to the shoulder of the outbound lanes to AAFB running parallel to Marine Corp Drive. After turning right at the Marbo electric substation road, the alignment then snakes its way through various easement locations until the line reaches Route 15. At this point, the line then parallels Route 15 until it finally reaches the back gate of Andersen AFB. From this point, the line now will double in quantity of conduits installed due to the installation of not only the 34.5 circuits but also required will be the installation of the 1 each 13.8 secondary circuit – each having their own manholes. Underground lines are now located and parallel to Santa Rosa Blvd from the back gate and eventually to the main switch yard within AAFB.

Some of the more interesting aspects of the project include the installation of approximately 49 each 8’ x 8’ x 8’ reinforced concrete manholes for the 600 Kcmil 34.5 kv conductor and 11 each 6’ x 6’ x 6’ reinforced manholes for the 13.8 kv conductor. All conductor terminations with in the manholes will have 1 continuous loop for added slack and in addition to being racked and secured on the interior. Manhole covers are rubber gasketed to ensure proper seals from rain run off. Primary conductor for the 2 primary 34.5 kv high voltage circuits consist of 600 Kcmil aluminum conductor installed from 2000 and 3000 linear foot cable reels. Black Construction has provided a state of the art cable pulling unit capable of pulling 2000 linear foot runs of the 600 Kcmil cable while ensuring the least amount of stress is conveyed to the cable during the installation process. Upon completion of the splicing, BCC will conduct hi-pot testing to ensure continuity of the conductors has been achieved prior to the initial energization testing of the system.

This process will also be conducted on the 13.8kv system as well. One item worthy of mentioning is the installation of approximately 253,440 linear feet of the 34.5 kv 600 kmcil conductor cable and another 15,000 linear feet of 250 mcm 13.8 kv conductor. This equates to approximately 51 miles of high voltage conductor. Other elements of the project include major switch yard work at the Dededo combustion turbine where concrete foundations supporting structural steel supports were constructed to support the new system. Also included will be the installation, testing and commissioning of 2 new 34.5 kv circuit breakers to support the new system. Similar work will also be conducted at the AAFB switch where the final termination of the 34.5 system will occur at the T-15 20 megawatt transformer.

Black’s experienced staff and personnel have provided the difference on the project ensuring timely completion and sound quality workmanship. This project has also gained acknowledgement for BCC’s on-site Safety program where all members of the construction team have taken ownership in providing a safe and productive work environment.

Notable Features:

  • Installation of approximately 8 miles underground 34.5 KV ductbank
  • Installation and termination of 34.5 KV cable from the Dededo substation to the AAFB substation (2 sets of 3 – 600 kcmil, 1/c aluminum cables.
  • Furnished and installed concrete manholes.
  • Modifications to Dededo Switchyard to include installation of circuit breakers, structures, busswork, insulators and relay control panels.

Certificate of Award
Guam Contractors Association 2005 Excellence in Construction Awards
Electrical-Industrial $2-10M-Category