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Connecting East & West Under The Mississippi
Dual River Crossings Connect Separate Water Systems For St. Charles Parish
Soil conditions on both bores were sandy clay. A Tensor magnetic steering probe and Tru Tracker Trugyde software were used to guide the pilot bores. J M Manufacturing provided the 24 inch diameter SDR9 HDPE pipe for both installations.
Every long river crossing has its own unique issues, and Simon said there were several that affected both installations.
"We were working inside U.S. Army Corps of Engineers levee areas, and to bring in equipment required temporary access roads over the levees," he explained. "Roads were constructed in accordance with Corps permits. Timing of the projects was closely monitored due to the required river stage – work could only be performed once the river stage was below 11 feet NGVD (National Geodetic Vertical Datum) in elevation."
The most challenging task on both projects was steering the pilot bore, said Simon.
"Drill entry and exit locations were within only 100 feet of the water's edge of the Mississippi River," he continued. "This limited options available when choosing an azimuth for crossing the river. Adding to this complication was continued boat traffic in the river. As large tugs and barges passed in the waterway, drilling operations would cease due to the magnetic interference to the steering tool. For the second crossing, 11 barges were parked near the exit spot, which disrupted the azimuth as the steering tool crossed this location."
Even so, pilot bores were completed with extreme accuracy.
"The exit location for the first crossing was 11 inches from the exit stake," Simon said. "And for the second crossing the drill head surfaced only four inches from the target stake. The expertise of Survey Engineer Daniel Dodgen of Ranger played a large role in the success of both crossings. Drill operator was Jody Utz."
Because of the length of both crossings and limited space for pipe fusion, road closures were required on both projects. Area newspapers and television stations carried notices in advance of the closings, and the St. Charles Parish police implemented procedures to close roads and divert traffic as necessary.