PITI TO HARMON 115 KV TRANSMISSION LINE
Scope of Work
The project involved construction of a 115-kV circuit from the new Piti 115-kV substation to the Harmon substation. The project is 13 miles long and was built along urban and semi-urban streets and roads. The construction included a new 927.2 AAAC 11 5-kV circuit on porcelain horizontal post insulators with underbuilds or provisions for underbuilds. The underbuilds include 34.5 kV, 13.8-kV, secondary and communications. The power poles for the project are identified consecutively from Piti to Harmon as No.1 to No. 365 respectively.
Phase 1 is the north most 4.8 miles of the project and includes the installation of 111 new, self-supported, tubular steel poles on 300-foot-long maximum spans. The existing underbuild in this area were transferred to the new poles. Upon the completion of the Phase 1, it was used to back-feed the 34.5-kV or 13.8-kV circuits to help maintain service while the construction progressed on specific sections of the Phase 2. The Phase 1 includes the work from Pole No. 201 to 217, inclusive, and Pole No. 257 to 352, inclusive.
Phase 2 is 8.2 miles long and consisted of constructing new 115-kV on the top of the 223 existing concrete poles. The span lengths in this area generally do not exceed 200 feet. The existing 34.5-kV and 13.8-kV circuits and other underbuilds were rearranged and lowered on crossarms and the 115-kV insulators were mounted to the newly fabricated steel pole-top extensions. The 34.5-kV circuit in the majority of this area were changed to 927.2 AAAC. Included in the Phase 2 construction is the supply and the installation of 33 additional steel poles, the foundation modification of the existing 91 non-guyed octagonal concrete poles and the construction of pole foundations for the 18 octagonal concrete poles at the Agana swamp. The installation of a guardrail system on various pole locations is also included.
There were many challenges on this project like the unforeseen underground utilities, different soil characteristics in the various districts, the high level of the underground water table, soft soil condition, existence of two 10 inch diameter underground jet fuel lines in the Navy fuel easement, the hard rock strata, the deep drilling work (5 feet dia. max x 40 feet deep max) on the road shoulder for the steel embedment installation; the installation of tall (90 feet long max) and heavy (11 tons max) mono-tube steel poles, the extreme height (90 feet max) condition for the cable installation, pulling and tensioning work, the “every other day” power outage granted by GPA on any particular location.
Core Tech overcame the challenges through proper planning and hard work. GPA, the client was very proud of the accomplishment. Core Tech was recognized for this project in the 2002 GCA Excellence in Construction Award.
Piti to Harmon, Guam
February 15, 2000
November 22, 2002
Guam Power Authority