Rock of Ages

Horizontal directional drilling ensures northeastern Wisconsin customers receive an uninterrupted water supply.
Rock of Ages
A chain and excavator boom help lift a 20-inch rock reamer as workers break apart the bore assembly in preparation for pulling drill rods to the south side of the Fox River power canal in Menasha, Wis. (Photos courtesy of Waas Boring and Cable

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The Menasha (Wis.) Water Utility wanted to connect the Water Street distribution main on the north side of the Fox River power canal to the River Street main on the south side. The loop would provide another means of distributing water to the narrow dike if officials had to close the main supply valves.

Dorner Inc. in Luxemburg, Wis., won the general contractor bid, and subcontracted the horizontal directional drill under the canal. After workers bored down 17 feet through clay, they hit solid limestone and stalled. Unable to complete the bore, they filled in the pits and left.

Superintendent Todd Dorner called Randy Waas, vice president of Waas Boring and Cable in Lomira, Wis. “Although we had the equipment and expertise, we hadn’t bid the job because of its difficulty,” says Waas. A team of seven worked three weeks to bore 400 feet before pulling in an 18-inch HDPE pipe.

Proper equipment

The project required a D100x120 and a D50X100 Series II Navigator directional drill (Vermeer), a 20-foot-long mud motor (SlimDril International), three custom-built rock reamers (Century Products), three vacuum excavators and a twin tank MCM-4000 reclaimer (American Augers). The latter mixes, cleans and transfers drilling fluid.

After the crew excavated pits in parking lots on both sides of the canal, drill operator Ed Feucht followed the preestablished bore path using the D100 machine set up on the north side. “Our biggest challenge was getting the pilot hole through to the other side,” says Waas. “Ed was boring down at a 30-degree pitch, an angle sufficient enough to deflect the 8-inch bit if he didn’t engage the limestone just right.”

Waas used a mud motor with low speed/high torque gear reduction to provide additional power to the bit. The configuration reduced the output speed of the 1:2 lobe high-speed positive displacement hydraulic pump by a factor of three, and increased the output torque by the same multiple. The system converted hydraulic power to mechanical power and maintained consistent bit speed as Feucht applied pressure to it.

Slow and easy

Eric Feucht used a Digi-Trak Eclipse locator (Digital Control) to track the sonde on the mud motor. Meanwhile, workers at the bore pit added bentonite and water to the reclaimer’s mixer to create a slurry. When the bit was about 6 feet from entering the limestone, Ed Feucht started the mud pump on the drilling rig, sending the slurry through the rods to the drilling motor, which rotated the bit.

As the fluid circulated to clean the motor, he advanced the bit until it touched the rock, then slowly increased the pressure against it. “It’s takes patience and experience to get the mud motor to start cutting into rock,” says Waas. “Ed had to take his time and let the bit do its job.”

The rig’s pressure gauge enabled Feucht to monitor how the drilling motor was performing, and another gauge gave the weight on the bit, as an excessive amount could damage the mud motor’s on-bottom thrust bearings. Feucht tried to drill with a steady pump pressure and flow rate of 3,000 psi/170 gpm. The work was so demanding that the bore advanced only 50 feet per day.

After traveling another 8 feet at the same pitch through solid rock, the bit broke through under the canal. The next challenge was to level off in a short radius at 25 feet deep, then bore 250 horizontal feet before beginning the 30-degree ascent to the exit pit on the south side of the canal. The bore exited at 9 feet deep and precisely on target.

Mud, glorious mud

As slurry flowed into the exit pit, workers used a Vermeer vacuum tank trailer with a 1,200-gallon spoils dump tank to transfer the liquid to the 5-foot-deep reclamation pit on the north side. A pump in the 4,000-gallon reclaimer sucked up the fluid and sent it to the 1,333-gallon screening tank, in which three 50-mesh shaker screens and two 140-mesh shaker screens separated clay and silt from the debris.

Next, the bentonite mixture was pumped through seven desilter Hydro-Cyclones before entering the 2,667-gallon cleaning fluid/mixing tank. A charging pump in the tank transferred the slurry to the mud pump on the drill rig parked alongside. The project used 15,000 pounds of bentonite.

“This was a double-entry or surface-to-surface bore,” says Waas. “Once we removed the mud motor, we attached a 12-inch rock reamer to the drill string and began pulling it north toward the D100 rig.” As it advanced, the D50 operator on the south side attached a drill rod to the trailing end of the string, enabling workers to attach the next size reamer without leaving the borehole open and subject to unrecoverable collapse.

The 12-, 20- and 30-inch rock reamers each had six carbide Tri-Cone bits. Their large cone offsets, chisel-shaped inserts and irregular tooth spacings ground rock into fine gravel, enabling it to flow out of the borehole and into the exit pit. Four fins symmetrically spaced ahead of the reamer centered it in the smaller hole, ensuring that the bits cut evenly.

Crank up the volume

Pumping 170 gpm of drill mud quickly filled the 5- by 6- by 9-foot-deep exit pit. Besides running the company’s two vacuum excavators, Waas hired a hydroexcavator and operators from Valley Hydro-Excavation in Campbellsport, Wis., to help transport the flow to the reclamation pit.

“When a reamer arrived on the south side, we removed it and tied on rods as the D100 pulled back the string,” says Waas. “Bores always run in one direction.” Each of the three upsizes took a day and a half.

A field service technician from supplier Ferguson Waterworks in Appleton, Wis., had fused the 40-foot-long HDPE pipe sections for the initial boring contractor. “We fused our pulling head onto the pipe, then used the Hitachi excavator arm to bring the head around while the John Deere 544H payloader guided the pipe into the pit at the proper angle,” says Waas. “HDPE pipe is very flexible and a good material for directional boring, especially when there are severe entry and exit angles.”

Workers then shackled the pulling head to a 26-inch fluted reamer that would further break up material as it was pulled through and facilitate flushing it out. As the pull began, a backhoe suspended the mechanical joint fused at the end of the pipe to prevent it from dragging against the asphalt. “We didn’t worry about damaging the pipe because the wall is 1.25 inches thick,” says Waas.

After the pull, the crew fused a mechanical joint to the head of the pipe. Utility workers then connected the joints to the PVC mains to establish the desired loop.


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