2in mult-duct installation

LT Directional’s Large 27-Way, 2-in. Multi-Duct Installation

During a rainy week in San Mateo, California, LT Directional was up against some mighty odds. Not only was Mother Nature on their tails with some major rains threatening the productivity of the job, but they also were in a metropolitan area that put them up against a public transportation railway on the surface, as well as the risk and hazards that come with drilling next to that. They were also battling an especially complex maze of existing underground utilities under the surface.

With some major high-tech companies — such as Survey Monkey, Sony Interactive and GoPro — headquartered on neighboring streets, LT Directional had a lot to lose if they inadvertently hit some existing power or communication utility lines. The safety of the crew was paramount from the time they arrived on the scene at 6 a.m., ready for the safety briefing. It was made clear that the weather was not going to be favorable or sunny anytime before sundown, so with several hundred feet to bore, it was going to take full alertness from every member of the crew — from rig operator to mud specialist.
That job was to install 27, 2-in. pipes over a few hundred feet that paralleled the San Mateo rail. This meant that there were a few different factors to take into consideration for the job.

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Bore Hole Size

First, LT Directional would need to widen the hole enough to provide enough clearance for a 24-way puller. This meant that the final hole size would need to be at least 32 in. in diameter. With 27 pipes bundled together, the hole would need to be large enough that there was clearance for the pipes to pull freely without creating suction that often accompanies the deadly combination of too little clearance in a hole with not the right mud recipe. When you create a hole that large in the shale, clay and sand composite mixture often found in Northern California, suddenly the wall pack also becomes a concern — which leads to the next factor.

Hole Stability

With a 32-in. hole, there is a lot of room for gravity to take over, and the hole collapse in on itself or deforms. LT Directional worked with the local Melfred Borzall HDD specialist to get the right mud mix for the rainy conditions, but they also decided to opt for a barrel stabilizer to ensure the wall pack’s integrity stayed true. They opted for a Deluxe Barrel, or pig, from Melfred Borzall with added hardfacing, mudflow ports and cutter teeth options. It proved to be a wise choice as they reamed and pre-reamed prior to pullback.

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2in mult-duct installation

LT Directional’s HDD Tooling

Average tooling was not going to cut it for this big of a job. LT Directional knew they needed tooling custom-fit to this large bore, tooling that was not quite maxi, but larger than typical jobs. The tools they decided to include in their arsenal were a 32-in. Deluxe Barrel and Tornado Reamer combo for mixing and pumping action that simultaneously provided wall-pack stability. The reamer they chose was due to the ground conditions. Northern California is known for its varying conditions as much as for its rocky, hard drilling. If one thing is certain, it is that you will encounter more than one ground type within a bore that is deeper than 18 in. This job was no different. Running a Ditch Witch JT100, this crew encountered rocky conditions but ample amounts of sandy soil that posed the risk of collapsing the hole. The Tornado’s large paddle cutter blades provide the mixing action needed to keep the risk low for balling up. The barrel stabilizer also kept fluid flowing with its built-in fluid ports.

They trailed that with a swivel and custom-manufactured multi-duct puller from the Melfred Borzall engineering team. The multi-duct puller had 27 eyes that connected to 27 DCD Deluxe Duct Pullers that protected the pipe ends with a bell.

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Melfred Borzall engineers had a challenge ahead of them as they had to build this from scratch and tailor it to the specs of LT Directional’s job. After sharing designs, collaborating and finalizing the puller, it was tested and delivered on-site by their Northern California HDD specialist.

Mud & Fluid Management

This was the sticky part (pun intended). With the steady light rain and the necessity for mud flow to be just right, the mud specialist had to be on point that day. With a proper mix of bentonite and Melfred Borzall’s Drill Kleen Plus Additives, they were able to keep the cuttings at the right level of viscosity to keep it moving downhole. It did not come without some effort though — with the rains — LT Directional did make the call to bring in a vac truck to excavate some excess mud and not risk the bore.
Taking all the proper safety precautions with the crew members, a spot-on mud mix and the correct tooling choices that were customized and tailored to this specific job enabled LT Directional to have a successful day. With no more than a few feet of clearance on either side of the bore, the rig operator had a great day as he successfully threaded that needle and the crew was done before sundown.

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This was a great example of careful planning, proper preparation and investment in the right areas to ensure a successful job … even when Mother Nature isn’t cooperating with the job.

Josh Parker is director of marketing at Melfred Borzall.

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