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New Pipeline Construction Product Allows for Simple Installation of Standard PVC Pipe in Houston HDD Project
Schwanke’s Direction Drilling of Hannibal, MO, was selected as the sub-contractor for the HDD portion of the project. Schwanke used a Vermeer Navigator D50x100 HDD rig, Figure 3, for each of the lines. A 17-inch hole was bored for the eight-inch pipeline and a 22-inch hole was bored for the 12-inch line. Native soil in this area of Houston is predominantly clay. As a result, Schwanke used a drilling fluid consisting of Baroid EZ-Mud polymer emulsion for clay stabilization, Penetrol wetting agent to control the sticking action of the clay and soda ash to moderate the pH level.
The design plans called for the existing eight and 12-inch asbestos cement pipelines to be abandoned in place and, as is typical with rehab projects in populated areas, there were a number of additional utilities underground that were to be avoided including sewer, gas, electric and cable. This resulted in the need for the pipeline to be installed at a depth of eight feet.
The use of full lengths of standard C900 PVC pipe meant no requirement to assemble/fuse and stage lengths of pipe above ground with an extended entry pit. This enabled a standard construction box to be placed for pipe insertion. Bore hole lengths of 150 to 180 feet were utilized because of fitting and interconnection requirements.
With the limited amount of space at the project site, the Mega-Stop bell stops were assembled on the pipe spigots at an offsite location. That installation was quick and simple requiring less than five minutes per pipe joint. The required pipe lengths were then taken to the bore location for insertion/installation as shown in Figure 4.
The spigot end of the first pipe length was fitted with a common bullet tip on the spigot. The pipe was placed in the box with the tip covered spigot placed at the bored hole. Schwanke used a block of wood on the face of the pipe bell so that the excavator bucket could be used to push the pipe through the bore without damaging the bell as can be seen in Figure 5. (On a subsequent 16-inch project, Schwanke fabricated a steel “cap” that fit over the bell for this purpose.) From that point it was a simple matter to lower the next piece of pipe into the box, place the wood block at the bell, and continue pushing the pipe until the tip was visible at the next pit location.