Case Studies, Built Like Whitepapers

Overview

A regional carrier needed to extend a long-haul fiber route across a navigable shipping channel. Every surface option had been ruled out: the banks were environmentally protected, the waterway carried continuous barge traffic, and an open cut or aerial span was off the table. The route had to go under the channel in a single trenchless shot, deep enough to satisfy the Army Corps clearance and accurate enough to surface at a pre-cleared exit pit on the far bank.

The Challenge

The crossing left no margin for error. Barge traffic could not be interrupted, so a stalled bore or an inadvertent drilling-fluid return into the channel was not an option. Environmental setbacks on both shorelines constrained where equipment and entry and exit pits could sit, and the product — a continuous fused fiber conduit string — had to be installed in one pull without a mid-span joint.

Site & Ground Conditions

Subsurface investigation showed interbedded sands and stiff clays beneath the channel with a cover depth that demanded a deep, flat bore profile. The sands raised the risk of frac-out — drilling fluid finding a path to the surface — which drove the fluid program and the depth of cover held under the waterway.

The Engineered Solution

A maxi-rig HDD spread drilled a pilot bore on an engineered profile, steered by a downhole mud-motor and gyro-based guidance to hold line and grade beneath the channel. The bore was progressively reamed to accept the product, and a fused HDPE DR-11 conduit string — welded and pressure-tested on the exit bank — was floated into position and pulled back through the bore in one continuous operation.

• Maxi-rig HDD, mud-motor and gyro steering
• 24-inch reamed bore, 18-inch HDPE DR-11 product string
• Closed-loop bentonite system with fluid recycling
• Real-time annular-pressure monitoring to prevent frac-out

Execution & Safety

Drilling fluid was managed on a closed loop and recycled on site so nothing entered the waterway, with annular pressure monitored in real time to keep the bore within a safe window. Crews worked inside cordoned entry and exit zones clear of the pull path, and marine coordination kept the crew and the barge traffic separated throughout.

Outcome

The bore intersected the exit pit on line and on grade, and the conduit pulled back clean on the first attempt. The channel never closed, both banks were left undisturbed, and the route was handed over splice-ready and ahead of the carrier's schedule.

Overview

A utility converting overhead distribution to underground needed a duct-bank spine run through the center of a downtown business district. The corridor was dense with legacy utilities, active on all sides with traffic and pedestrians, and governed by a municipal permit that restricted work to night windows and required full restoration of every block before the next was opened.

The Challenge

Undocumented and mislocated existing utilities were the core risk — a strike on a live gas or electric line in a crowded downtown is a public-safety event, not just a schedule hit. The work also had to stay inside night-work windows, keep lanes and sidewalks open by morning, and hold a continuous concrete-encased duct profile through constant grade and alignment conflicts.

Site & Ground Conditions

The corridor carried more than a century of overlapping infrastructure — gas, water, sewer, legacy duct, and abandoned lines — much of it poorly recorded. Pavement sections and vault structures further constrained where the duct bank could run and how deep it could sit.

The Engineered Solution

Every conflict was daylighted and verified by hydro-excavation before the excavator arrived, turning unknowns into fixed points on the plan. Work then advanced in short, staged trench-and-shore lifts so no block stayed open longer than a single shift, with the concrete-encased duct bank placed and backfilled behind a rolling maintenance-of-traffic plan coordinated with the city.

• Hydro-excavation potholing of 600+ existing crossings
• Staged trench-and-shore with engineered trench boxes
• Concrete-encased duct bank to utility standard
• Shift-by-shift maintenance-of-traffic with the municipality

Execution & Safety

Non-destructive daylighting removed the strike risk that makes downtown undergrounding dangerous, and trench-safety shielding protected crews in every open reach. Pedestrian and traffic management was rebuilt each shift, and every block was restored to grade before it reopened to the public.

Outcome

The full spine was installed energized-ready with full-depth restoration and no lost-time incidents across the program. The utility received a documented, as-built corridor it could pull cable into on its own schedule.

Overview

A gas utility needed a new distribution mainline extended across a right-of-way that spanned three counties, tying into its live system at both ends. The corridor mixed rural open ground with road and rail crossings, and the operator needed a single accountable partner rather than a patchwork of local subcontractors handing work — and liability — back and forth across county lines.

The Challenge

Three jurisdictions meant three sets of permits, inspectors, and crossing requirements, with a real risk of the standard drifting from one county to the next. Twelve road and rail crossings had to be installed trenchlessly without disrupting traffic, and the final tie-ins had to be cut into a live, pressurized system without taking customers out of service.

Site & Ground Conditions

Soils shifted from workable loam to rock and high-water reaches along the route, and the road and rail crossings each carried their own cover and casing requirements. Coordinating those crossings with the open-cut mainline reaches drove the sequencing of the entire program.

The Engineered Solution

One self-performed crew carried a single quality and safety standard across all three counties, so nothing changed at a jurisdiction line except the paperwork. HDD handled the 12 road and rail crossings while open-cut advanced the mainline through the balance of the route, and subsurface mapping plus as-builts were delivered at each phase gate for the operator's permanent records.

• Self-performed HDD for 12 road and rail crossings
• Open-cut installation for mainline reaches
• Steel and fused-PE mainline to code
• Phase-gate mapping and as-builts for the operator

Execution & Safety

Live-system tie-ins were planned and executed by crews carrying an oil-and-gas safety discipline, with the pressurized network protected throughout. Trenchless crossings kept roadways and rail open, and consistent crewing across jurisdictions kept the safety culture identical from the first county to the last.

Outcome

The mainline was installed and tied in on the committed in-service date, with the live cut-ins completed without an outage. The operator received one continuous, documented record across a corridor that would normally involve several contractors.

Overview

A growing service area needed a new gravity sanitary interceptor to carry flow to treatment. Because it runs on gravity, the pipe had to hold a precise, continuous slope over nearly three miles — with almost no tolerance for settlement — while sitting deep below the water table in soils that wanted to flow into the excavation.

The Challenge

Depth and water were the whole problem. Reaches ran up to 28 feet deep with a high groundwater table, which threatens both crew safety, from cave-in, and grade, from soil instability and flotation. A gravity line that settles even slightly loses its slope and its function, so the interceptor had to be set and held to an exacting tolerance the first time.

Site & Ground Conditions

Saturated, unstable soils with a high water table dominated the corridor, and existing utility crossings intersected the alignment at depth. Both conditions had to be controlled before pipe could be safely and accurately set.

The Engineered Solution

Wellpoint dewatering drew the water table down ahead of each reach so pipe was set in stable, workable ground, and engineered trench shielding protected crews at full depth. Laser-guided grade control held line and slope on every joint, and hydro-excavation exposed each existing crossing before the excavator reached it.

• Wellpoint dewatering ahead of each reach
• Engineered trench shielding to full depth
• Laser-guided grade control on every joint
• Hydro-excavation of all existing crossings

Execution & Safety

Dewatering and shielding together removed the two conditions that make deep wet excavation dangerous, and crews worked every reach inside a protected, dewatered box. Continuous grade verification kept the line true as it advanced, so no section had to be reopened and reset.

Outcome

The full interceptor was installed to a 0.08% grade tolerance with no cave-ins and no dewatering failures. The owner received a gravity system built to hold its slope — and its function — for its full design life.