PACIFIC GAS & ELECTRIC (PG&E) – RELIEF RESERVOIR
August , 2011
We were hired to install blanking flanges on the upstream end of a high altitude dam in 150 ffw so our client could perform maintenance on the three valves in the outlet works piping of Relief Reservoir.
This remote reservoir is located in the Sierra Nevada Mountains at an elevation of 7,300 ft with no road access to the facility. All equipment and materials for this site is brought in by helicopter or mules. Due to the high elevation and depth of dive operations mixed gas diving was the primary form of diving employed to maximize working bottom time. Due to the greater decompression requirements of mixed gas techniques decompression chambers are utilized to ensure the diver’s safety.
A heavy lift helicopter (Sky Crane) was brought in to transport sectional barge pieces since the the crest of the dam was not wide enough for the dive equipment. Each piece was 15 ft by 7 1/2 ft and weighed over 8,500 pounds. Together they created a 30 ft by 45 ft dive barge. The heavy lift helicopter then lifted two decompression chambers and a dive van from the staging area in Kennedy Meadows to Relief Reservoir,a five minute flight.Helicopter operations included a comprehensive security plan as the staging area is a high traffic tourist site for pack trains and hikers.