Case Studies

Project Type
Length / Hole Diameter
Two 780 m (2,560 ft) crossings / 914 mm and 1067 mm (36 in and 42 in) SAWL steel pipe
The HDD Company



Project Summary

Environmental standards have changed dramatically over the years. In 1960, a natural gas line was permitted to be installed along the bed of Cache Creek near the town of Capay (an hour west of Sacramento). In 1991, a larger parallel line was placed at the same location. When the owner applied to replace both lines in 2014, the new 914 mm and 1067 mm (36 in and 42 in) lines were required to be installed at a safe depth safely below the water crossing. The HDD Company was subcontracted to complete the drilling.

The plan called for both lines to be installed parallel to one another at a depth of 24.4 m (80 ft) below the creek bed.

Key Challenges

This project involved tight timelines. The initial plan called for one HDD rig working in 24-hour shifts. After assessing the sites entry and exit points, the HDD company provided an alternative suggestion: to bring two HDD rigs onsite (located 21.3 m/70 ft apart) and complete both crossings simultaneously. It was felt the entry point was more than sufficient for both rigs and all support equipment, while the exit point allowed ample room for materials, the welding crew and pipe stringers.

Both pilot holes were completed in little over two weeks, then reamed to the required size. The larger pipe emerged 0.37 m (1.2 ft) from the designated exit point, while the smaller pipe emerged 13.4 m (44 ft) from the expected exit.

Clear communication, a collaborative planning process and solid execution ensured this important pipeline was back online in little over four months from the start of construction.

Services Provided



Tunnel Boring and Pipe Jacking Systems are used to hydraulically install underground pipelines up to 4.2 m (168 in) in OD range within strict alignment and grade tolerances. The likelihood of settling or sloughing is very low. Wheel machines are equipped with various cutter heads and sand shelves. A closed-face attachment is available for boring in unstable ground conditions. This versatile system can be easily adapted to work with any jacking pipe, in any pipe joint length. It can accommodate a wide range of pipe diameters.

Tunnel Boring Machines are used to excavate tunnels with a circular cross section through a variety of soil and rock strata. They can bore through hard rock, sand, and almost anything in between. Tunnel diameters can range from 1 m and exceed 15 m (3 ft to 49 ft).

The Crossing Group - The Tunneling Company - Tunnel Boring - Pipe Jacking - Trenchless Construction - Tunneling - Augering, Boring & Pipe Ramming


A boring technique commonly used for installing oil & gas pipelines ranging from 51 mm to 1067 mm (2 in to 42 in) in diameter without leaving casing in the ground. Product pipe is welded to steel casings and either pushed or pulled through the ground in sections. The casing is cut off and removed, leaving just the product pipe. Maximum installation length is 150 m (492 ft).

The Crossing Group - The Tunneling Company - Slip Boring - Trenchless Construction - Tunneling - Augering, Boring & Pipe Ramming


A pneumatic hammer is attached to the inside edge of the casing. The front of the DTH breaks cobles, boulders and even solid rock into small pebbles or dust. The spoil makes its way through the hammer and into the casing, where it is removed by airway augers.

The Crossing Group - The Tunneling Company - Down The Hole Hammer - DTH - Trenchless Construction - Tunneling - Augering, Boring & Pipe Ramming


A Guided Boring Machine (GBM) is used to install 305 mm to 3.6 m diameter pipe (12 in to 144 in) with grade and alignment precision. It is commonly used for installations 50 m to 150 m in length (164 ft to 492 ft) or when line and grade accuracy is critical in displaceable soil. Our GBM is extremely versatile and our customers continually approach us with new applications.

The pipe installation involves a two-step process where launch and reception shafts are strategically located to minimize surface disruption. A pilot tube with a theodolite guidance system is then pushed through the ground at the precise grade and alignment specified in the design into the reception shaft. A reaming head is welded to the pilot tube and the casing and the pilot tube is used as a guide to install casing. The GBM can be used in conjunction with auger boring or pipe ramming methodologies.

The Crossing Group - The Tunneling Company - Guided Boring - Trenchless Construction - Tunneling - Augering, Boring & Pipe Ramming


Pipe Ramming is used in a wide variety of soil types including gravel, cobble or sand. A pneumatic hammer is attached to the back of the casing pipe and driven through the material at any angle: from horizontal to vertical. The material is cleaned out of the pipe using an auger boring machine. Pipe Ramming methods are used for pipe diameters of 305 mm to 3.6 m (12 in to 144 in).

The Crossing Group - The Tunneling Company - Pneumatic Pipe Ramming - Tunneling - Augering, Boring & Pipe Ramming