COMPLEX TRENCH EXCAVATION - Machine Guidance TRENCH EXCAVATION GPS machine control helps contractor succeed with challenging Steam Tunnel Relocation project Author: Jack Lucic May

COMPLEX TRENCH

EXCAVATION

GPS machine control helps contractor succeed with

challenging Steam Tunnel Relocation project

Author: Jack Lucic

May 2013

www.machineguidance.com.au

Think of Russian nesting dolls and you’ll have an idea of the

construction challenge that faced Schneider Excavating, Inc.,

Lannon, Wis., when they worked on a steam tunnel relocation

project on the Clement Zablocki VA Medical Center grounds in

Milwaukee, Wis. Unlike shelf-size Russian matryoshka dolls, the

proportions were massive on this project. The steam system is

within a concrete tunnel, which was within a temporary trench-

shield box, which is all located underground.

A steam power plant on the grounds provides heat and hot water to the various

buildings on the 125-acre CZVA Medical Center campus. C3T Construction

Company, Milwaukee, Wis., the general contractor on the steam tunnel project,

completed the project within three months.

“We were working in a tight space — a 50-foot (15.2m) corridor — next to the

construction of a new spinal cord injury treatment facility,” states Ron “Slim”

Lange, project manager with Schneider Excavating. “Our task was to install a 600-

foot (183m) section of new steam tunnel within a relatively tight schedule.”

The 2.4 metre, 23,000 pound, steam-tunnel sections were placed on grade in a 8

metre deep trench. The bottom required precise grading before 150mm of #1

clear ¾-inch chip limestone (dolomite) rock was added. The excavation and

achieving grade was a challenge.

Schneider Excavating partnered with D. F. Tomasini Contractors, Sussex, Wis. to

help with the excavating, D. F. Tomasini is a large water and sewer main

contractor. “Because we were operating in tight confines, we weren’t able to dig

with the excavator facing forward,” Lange says.” We had to dig reaching over to

the side.”

Schneider Excavating used two large machines—a Cat 385C L and a Volvo

EC460B—both crawler hydraulic excavators equipped with Topcon GPS 3Dxi

systems supported by a Topcon HiPer Lite base station.

“The Topcon systems allowed us to excavate precisely to the plan and ensured

that we used the correct amount of the expensive rock,” Lange says. “The GPS

systems on the excavators saved us at least 25 percent of the production time

while allowing us to be in control at all times.” Interestingly, the D. F. Tomasini

excavator operator had his first experience working with the Topcon system on

this job. According to Lange, the operator couldn’t believe how accurately he was

able to dig.


“The GPS systems on the

excavators saved us at

least 25 percent of the

production time while

allowing us to be in

control at all times.”

A triple-stack system of huge trench shields was

positioned in the excavated trench before the

precast concrete steam tunnels were placed. The

trench shields measure 7.3m long and have a

200mm baffled thickness. The triple stack included

two 2.4m tall sections topped with a 1.2m tall

panel. The bell-and-spigot joints on the panels were

coated with rubberized mastic waterproofing.

There were roughly 70 sections that had to be

installed and 70 joints that had to be sealed. In

addition to a coating of waterproofing which was

applied before the shields were delivered to the site, 9.5mm protection board

was installed inside the shield to protect the waterproofing surface. One foot

over the top of the tunnel was filled with #1 stone, ¾-inch chips.

When the trench shields were in position, the Cat excavator lowered each of the

2.4m, 23,000 pounds sections of steam tunnel in place. The rectangular-shaped

precast concrete sections measured approximately 2.1 by 2.6 metres.

“One of our biggest challenges was bringing in the steam tunnel sections onto

the site precisely when we needed them,” says Lange. “The sheer logistics of

receiving shipments and maneuvering each of them into place required planning

and tight execution.”

With all projects, there are surprises.

“One particular challenge we faced was a

steam-tunnel section that needed to run

under an existing Milwaukee

Metropolitan Sewerage District (MMSD)

service line,” states Lange. “The MMSD

couldn’t tolerate more than a quarter-

inch (6.35mm) of movement of the line

when working near it.”

Schneider needed to install two 15m

sections of steel H-beams to support the

MMSD line before carefully maneuvering

a section of the steam tunnel underneath

it. The process took four days to

complete.

“

nightmare without the

The steam tunnel was built with two low

access points to the 1.8m wide by 2.1m high tunnel interior. The steam tunnel

pitch was one

existing steam tunnel sections to provide the seamless fit that C3T Construction

was expecting.

Even during the typical cold, occasionally snowy, Wisconsin winter, Schneider

was able to keep the

sealants were applied at proper temperatures.

“Being able to work from a digital 3D model that

management, me, and my machine operators

In the end, all the pieces of this giant

as designed.

management, and insurance topics. He can be reached at [email protected].

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productivity, communication, precision, and

eliminating rework,” Lange concludes. “This

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Additionally, with the technology we never

needed workers in any unprotected

areas, which is consistent with our corporate

priority on safety. Schneider Excavating’s owner

was adamant that no one would get hurt on this

job, and no one did.”


Jack Lucic is a freelance writer covering construction,


achineGuidance.com.au is an online portal committed to providing up

biased information on machine control products and processes. For


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COMPLEX TRENCH EXCAVATION - Machine Guidance TRENCH EXCAVATION GPS machine control helps contractor succeed with challenging Steam Tunnel Relocation project Author: Jack Lucic May