Direct Pipe Method Proves Comes To U.S.

November 2011, Vol. 66 No. 11

The Direct Pipe method was also used at the Highway 39 site in Plant City where an existing water main obstructed the prescribed bore path. At this location, REM was faced with the challenge of drilling under the 5-1/2‐foot water main, which was located on top of a two‐foot gravel bed. The method was successfully used with only a 6‐foot launch pad and without compromising the stability of the utility gravel bed. On the launch side, REM also had to drill parallel to an existing 30‐inch natural gas line. On the exit side, they ended up crossing under the same 30‐inch line.

If a conventional method had been used in this scenario, REM officials said they would have had to dig a pit up to 21‐feet deep, which would have posed a potential threat of road collapse, given the typically sandy soil conditions that are prevalent in Florida.

Also, clay material was encountered in the soil during this bore and drilling was drastically reduced to two-inches per minute. In an attempt to resolve this issue and speed up the process, REM used a water blaster and was able to increase the penetration rate to nearly double the typical speed. As this bore was being completed, the team used the next three days to demobilize the site and begin set up at the third bore site. This proactive approach allowed REM to streamline their resources effectively to coordinate multiple crews to save the owner time and money.

REM began their third bore in a Lutz, FL project that required drilling under existing power poles located at the center of the actual ditch line. The team was not required to utilize a method of transportation at this site, so adjacent roadways did not need to be shut down. The first challenge REM encountered at this site was setting bore calculations to go around an existing cemetery.

The site was also adjacent to a busy roadway and a local neighborhood. REM’s surveyor designed a proposed direct pipe profile, which included a compound curve of 10 degrees (3,200 feet) horizontal curve and 11 degrees vertical curve (3,200 feet). The deepest point of soil coverage was approximately 29 feet. The degree of this angle was designed to alleviate cutting beneath the cemetery. As a result, REM was able to successfully maneuver around this obstruction in addition to existing fiber optic lines.