From our April 2003 newsletter

Rusty Rhoads, Project Manager of RCI Construction Group headquartered in Sumner, Washington, has had an extended stay on the Island of Oahu. RCI is installing 2 1/2 miles of iron water main pipes along the two-lane Kamehameha Highway. What makes this job particularly challenging is the scenic highway’s proximity to the ocean – much of it runs within 20' of the shore – and excessive ground water hampers the work.

In addition, the City and County of Honolulu’s Board of Water Supply has had to restrict RCI to an 8:00AM-3:00 PM work schedule in order to keep traffic flowing during peak traffic hours. The project began in April 2000 and is expected to finish in February 2003.

The specifications call for 36" iron piping to be laid to a depth of 3', dropping to 15' to 20' under utility crossings and 25' under stream crossings. By the job’s end, RCI will have encountered 15 storm drain crossings, 3 water main crossings, and 3 streams.

Use of Vibro Hammer A Big Improvement Over Initial Approach
RCI is driving 8' to 20' steel plates along the route to protect the adjacent roadbed and to hold back the ever-present groundwater. (Rhoads tells us, “I’ve never seen anything like this before, the groundwater is really excessive.”) An extensive system of pumps aids the effort, and trench boxes are installed to support the metal sheets.

Work proceeds approximately 24' at a time (the length of a trench box), as 20' sections of pipe are laid. Initially, trenches were dug for the steel piles which were then pounded into the ground using a bucket attached to the boom of a Hitachi 450LC. This was not only slow and inefficient, but proved harmful to the excavator.

The solution came from Alan Kunewa of Allied Machinery in Waipahu, HI, who sold Tramac’s 625B Vibro Hammer to RCI. According to Rhoads, the vibro hammer is “working great, driving through sand and hard coral. There’s no need to dig trenches. The vibro hammer’s vibrations push the sheet piles directly into the ground to the exact depth we’re looking for.” After each section is completed, the vibro hammer is used to extract the piles and drive them into the next section.

When not in use, the vibro hammer is quickly and easily replaced by the bucket (it operates from the bucket’s hydraulic circuit), resulting in multi-function versatility for the excavator.

Tramac vibro hammers are designed for installing and extracting piles and beams and can be mounted on excavators weighing from 16.5 to 45 tons.