Mosaic opts for minimally invasive pipeline installation
By MELODY JAMESON
Miles of pipeline measuring two feet in diameter are being buried at 18-foot depths across South County neighborhoods and many of their residents are going to be completely unaware.
This, at least, is the objective of phosphate mining giant Mosaic and its contractor, Riverview-based Moretrench, as they begin work this week applying technology as minimally invasive to the earth’s surface as laser surgery can be to the human anatomy.
For some 60 years, the fresh water critical to phosphate processing at the plant on U.S. 41 has been drawn through about 12 miles of pipeline beginning at Lithia Springs. And when that line, now aged to the point it’s subject to rupture, was constructed six decades ago, it was installed laboriously, using heavy duty open trenching, disturbing every inch of the ground surface, mile after mile, whether adjacent to homes or businesses or vacant land.
Today, however, there’s Horizontal Directional Drilling (HDD), a method of breaking ground at a single point and pulling pipe for hundreds of feet beneath the surface without disturbing anything else above – driveways, roadways, other structures, even ponds.
It’s not brand new technology, but it has been improved to the point
it makes good sense for Mosaic’s Lithia Water Line Replacement project, indicated Gary Roberts, the company’s project engineer. HDD originated in the 1940s in the oil fields and has been gaining popularity in recent years with other industries as the technology has been perfected with use and experience.
It also is not cheap. The water line replacement all told will be a $10 million project - considerably more than if conventional trenching were used, Roberts said. If there’s a downside, he indicated, it’s in the costs of applying the technique.
On the other hand, he added, there are compensating advantages. From the construction perspective, the HDD technique minimizes site preparation, allows greater directional control, permits the depth of cover to be varied, accommodates deeper and/or longer installations, makes installation possible where vertical access is difficult or impossible, shortens completion times and leaves a much smaller construction foot print.
For those in the vicinity of the work, the technology means radically reduced disturbance of landscaping features, generally avoided damage to driveways and roadways, plus less traffic disruption, Roberts noted. What’s more, he added, HDD is a safer construction method and is more environmentally friendly.
For all of these reasons, HDD is the installation method of choice as the new Mosaic water line is being put in place during the project’s Phase II, along Riverview Drive from U.S. 301 west to I-75. Close observers may see workmen and equipment break ground, drill a “pilot hole,” and then bore a distance underground before pulling as much as 1,000 feet of the new high density polyethylene pipe with 2.5-inch walls through the fresh tunnel, steadily working their way westward along the 1.5 miles.
Phase II work, though, will be somewhat more complex than that in completed Phase I – the straightway along Hackney Drive from Providence Road to U.S. 301 – because of the pavement turns, Roberts said. As Riverview Drive approaches the interstate overpass from the east, the roadway turns sharply at four points in close proximity, the project engineer pointed out, and these turns will inhibit the straight line underground boring for the new pipe tunnel. In such instances, some surface disturbance with trenching may become necessary. Any driveway, landscaping or other features impacted, however, will be restored or replaced, Roberts said.
The project engineer said he expects Phase II work to be completed by December, 2010.
Phase III, a two-mile section along Riverview Drive stretching from I-75 into the plant on the west side of U.S. 41, is to be undertaken in July, 2011, with wrap-up anticipated before the end of that year, Robert said. Contracts for that final project segment have not yet been signed.
With conclusion of the last two phases, the entire 12-mile pipeline will be replaced with a water line expected to last many lifetimes into the future. “And, we hope when it’s done,” Roberts summed up, “no one will even realize it was undertaken.”
Copyright 2010 Melody Jameson