NUCA contractor Boyer, Inc., Houston TX, recently completed a difficult casing installation under a heavily used rail line in Highlands, TX. The project called for the installation of approximately 70 feet of 66-inch casing under a section of Union Pacific railroad tracks for the San Jacinto River Authority (SJRA). The casing, once installed would serve as a bypass siphon to move water from an adjacent canal on one side of the tracks to the other. The bypass would also facilitate the repair of the original siphon that was failing.
According to Boyer Project Manager William O’Fiel, signs of the failing siphon were apparent for quite sometime. He said, “For several months prior to the project, Union Pacific Track Maintenance Crews were having to bring in right-of-way ballast rock and equipment to re-grade a reoccurring depression beneath the section of U.P. track above the existing siphon. Upon close investigation, it was concluded that the SJRA siphon must have been collapsing due to its age (installed in the 1940’s) and the heavy rail loads.”
In order to install the 66-inch casing under the tracks, the Boyer crew used a 24-inch diameter Grundoram Taurus pneumatic pipe rammer from Associate NUCA member TT Technologies, Aurora, Ill.
According to O’Fiel, the SJRA managers faced a major dilemma with this project. The rail spur over the deteriorating siphon is used hourly to serve the Exxon Petrochemical Complex in Baytown, TX and stopping rail traffic in order to repair the siphon would not be considered. On the other hand, the siphon is an important part of the SJRA Raw Water Canal System that supplies water to the city of Baytown, as well as several industrial complexes, including the Exxon plant.
Determining a solution was a difficult task. O’Fiel said, “We had previously rehabilitated another siphon for the SJRA, using a bypass pumping system to maintain flow and allow excavation. That project was fairly straightforward. This latest project however, was more complicated. Review of the conditions dictated the need for a second siphon to maintain the flow and repair of the failing siphon without interrupting rail traffic. Shutting down either the rail or canal to make the repair was out of the question.”
It was determined that a casing needed to be installed under the tracks to serve as a bypass while the original siphon was repaired. According to O’Fiel, pipe ramming was the method of choice. He said, “In order to install the secondary siphon beneath the railroad without shutting it down or causing R.O.W. earth settlement we elected to utilize pneumatic pipe ramming. We had used this method on several 60-inch railroad crossings during a recent project for the City of Galveston, Texas. The railroad industry, because of the absence of soil settlement, is universally accepting of this method. The soil is compacted instead of loosened, as in conventional excavation, and then removed from the casing while supporting the soil around it.”
On The Job
According to TT Technologies Pipe Ramming Specialist Mike Schwager two 66-inch diameter casings arrived, one 35-foot section and one 40-foot section. The Boyer crew prepared a pit for ramming and moved the 35-foot section of casing in place for ramming. The connection between the 66-inch casing and the 24-inch diameter Taurus ramming tool was made using a 66-inch segmented ram cone, a 60-inch tapered ram cone and a 31-inch tapered ram cone. Once the equipment was positioned and all connections made ramming was ready to begin.
The first section of pipe was installed without difficulty. Crews then removed the Taurus, positioned the next section of casing in the pit and welded it to the first casing. The ramming tool was then re-positioned to continue ramming. The second section of casing was also installed without incident. According to O’Fiel, from start to finish the entire ramming process took nine hours to complete, including five hours of welding time.
Boyer crews went on to successfully repair the original siphon. The original siphon was put back in operation. The bypass remained in operation as well in an effort to increase flow capacity.
NUCA, November 2003