Oak Creek Pipe Ramming
Pneumatic Tool Rams 42-Inch Casing

The zero degree weather and biting winds of January didn’t make the work any easier. The Amtrak, CPC, and Soo Railroad trains speeding above at 65 mph, didn’t help either. However, Globe Contractors Inc. of Pewaukee, Wisconsin, persisted — successfully installing a 42-inch casing under the double-track rail line in Oak Creek, a southern suburb of Milwaukee, Wisconsin.

Globe Contractors Inc. won the bid from the city of Oak Creek to install a new 24-inch feeder water line for eventual connection to its new water tower on the west side of Interstate 94. Globe’s crews worked throughout the winter to finish the project, which included installing and tying in over 150 feet of new water main.

The toughest part of the project was setting the water line beneath the double-rail tracks. The city of Oak Creek and the railroad had detailed specifications for Globe’s crew had to follow. One of these specifications was that the line was to be tightly secured in a 42-inch steel casing. That specification didn’t worry Globe’s managers since they had been using large-diameter pipe for water installations for years throughout Wisconsin. They felt they could either tunnel the casing in, hire a jack-and-bore subcontractor, or use their own 12-inch HammerHead Mole pneumatic tool to ram the casing in.

Since they had successfully pipe-rammed during the past year and a half — including over 800 feet of casing recently in Wautoma, Wisconsin — Globe had confidence that this was the method to use despite the size of the casing. They acquired a custom-made adapter ring to fit tightly against the 9/16-inch-thick casing wall. This adapter ring would fit into the ramming collets which locked into the ramming tool. The force of the pneumatic tool would be transferred from the collets through the adapter ring to the face of the casing.

Snow in the launch pit of this pipe
ramming machine couldn't slow the
crews of Globe Contractors.

A Globe crewman prepares the
HammerHead pneumatic ramming
tool for another ram.

The crew dug the launch pit on a Wednesday, preparing for what would be a 50-foot push by the time they arrived at on the other side of the tracks. The bottom of the launch pit was 12 feet lower than the train tracks. Shored with trench boxes, it was carefully graded to the municipality’s specifications.

According to Mike Gauger, field superintendent for Globe Contractors Inc., it was a minimum grade. “The pitch for this forced-water main was 5/10 over a 100-foot run. They wanted it to go up just a little bit to help keep the air out of the water main as it went to the hydrant. We graded the launch pit so the casing was 5/10 lower than the flow line of the pipe, placing it in the middle of the casing. If the casing rose a bit during ramming, I had that amount of leeway.”

Prior to bringing the first 34-foot casing to the job site and setting it on a steel I-beam, they brought it to Globe’s shop and welded a fabricated soil shoe onto the leading edge. The outside diameter of the soil shoe was thicker than the outside diameter of the pipe. This lessened the anticipated friction between the casing and the earth.

The crew set the HammerHead Mole into the adapter ring and collets the next morning. They rammed in 28 feet of the casing into the gray sandy clay until the late afternoon darkness of January called a halt to production. “In the beginning, the 12-inch HammerHead Mole pushed the casing quite easily into this softer clay,” described Robert Olson, Treasurer of Globe, on the first day’s productivity. “We were getting three feet every 15 minutes at first. In fact, we pushed in the first 25 feet with no problem at all.”

As the large casing entered the earth, there was increasingly higher drag on the outside of the casing from the 42-inch-wide circumference. The spoil inside the casing drags the pace down. Gauger explained that his crew anticipated the reduction in ramming speed. “In addition to the outside and inside drag factor, we also knew the spoil inside a large casing was going to add weight from the loads of dirt piling up inside the pipe. We knew we would spend time moving the spoil out, long before the end of the push.”

The next day, the crew hand-mined out 12 feet of the casing’s spoil with air spades; the tunnel being ventilated and monitored for proper oxygen. Then, they welded on the second 18-foot section of the casing and resumed ramming at the rate of 2.5 feet every 15 minutes.

“We pushed the pipe past MCI’s fiber-optic line which we had located under four feet of cover.” continued Gauger. “Once we got to that point, we dug our exit pit so that we wouldn’t be pushing the bank away from the railroad track.”

With the remainder of the spoil hand-mined, the crew installed the 24-inch ductile iron water main, and according to the specifications in the job, poured cellular concrete around the entire annular space in the casing around the water main to hold it tight in place and completely fill the void in the 42-inch casing. Gauger explained, “The city of Oak Creek didn’t want any vibration from the railroads to move this water pipe. In addition, to protect the water line, this concrete grouting prevented any loss of support to the rail lines. It served both parties’ interest.”

Robert Olson recapped his crew’s experience ramming such a large casing size,“Someone else might have auger-bored this job, another might have used a larger pneumatic tool. But this tool’s ramming time was 10 hours total, and for this size tool, we thought it did pretty well. Every method has its place. We’re getting our required productivity from this one.”

Written by: Richard A. Yach - Des Moines, Iowa
Provided by: Vermeer Manufacturing Company - Pella, Iowa