Pipe Ramming Under Conrail Track

The Conrail train line runs through Massachusetts eight times a day as it makes its way from the rail yard at Selkirk, New York, thirty miles south of Albany, New York, to Boston and back. For every foot of this passenger and freight line, the road bed must remain solid, unweakened by any casings and conduits carrying various utility lines. If anyone wants to install new water or sewer lines through the bottom of the embankment, it's railroad officials who determine how and when it will be done. After all, it's their vital railbed property that's being cut.

The city of Westfield, Massachusetts, located west of Springfield in southern Massachusetts, is planning to expand the Western Massachusetts Hospital. First, the city needed to install two sewer lines, one a forced main and another a gravity sewer line, through the rail embankment in a single casing. The plan was to have the two lines protectively encased by 140 feet of a single 36-inch, half-inch-thick casing. However, before the primary sewer contractor could get the lines installed, the contractor needed Buddy McCord and his crew from McCord Pipeline, Inc. of Deerfield, Massachusetts, to push the steel casing through the embankment.

McCord and his team are not strangers to ramming casings through railbed embankments. With three offices throughout upper New England, this transplanted Texan has plenty of experience installing pipelines for New England natural gas and oil companies. McCord decided to use percussion hammering to get this large casing in, employing a 23-inch HammerHead Mole. The alternatives to pneumatic pipe ramming weren't very appealing, after railroad officials laid down the law about using auger bore equipment.

According to a Conrail representative, there were plenty of concerns about creating voids under this particular roadbed given the soil conditions and water table. Because of this, McCord was advised early on that if conventional jack and bore methods were attempted he would have to keep the auger head five feet under the lead edge of the pipe. This would prevent any hourglass-shaped voids from forming which would threaten the integrity of the railbed. Since this requirement would have made the jacking all but impossible, McCord turned to pipe ramming with a large pneumatic tool.

As it turned out, railroad officials were, in fact, quite accepting of pneumatic percussion as the installation method. During the pipe ramming, the pipe would always be filled with material, eliminating the possibility that voids would form.

McCord's crew dug a launch pit 55 feet in length to accommodate the 23-inch HammerHead Mole and the 40-foot pipe lengths. They leveled the launch pit to grade for the ram, allowing for the sewer contractor to support the gravity sewer line at grade when they installed it inside the casing. The launch pit was carefully graded with three feet of small-sized rock and a four-inch thick poured concrete pad. An I-beam rail was secured for the pipe to ride on as it penetrated the embankment.

McCord wanted this launch site to be right. "These long casing ram jobs have to be perfect. They require a combination of considerable preplanning, patience and concentration. We've found that it saves time to have a concrete pad to work from. For the small amount of expense and the labor used to put this pad together, we save seven or eight working days over the length of the job. Plus we get better working conditions. We were getting a lot of rain; the concrete pad was almost a necessity."

McCord's crew had to deal with incessant rain while digging the launch pit. Two pumps dewatered their launch area. The pump ran 24 hours a day and drained the pit, fighting off the high water table that resulted from the rains of El Niño that flooded New England during the winter of 1998.

. "We have always lubed our pipe rams," described McCord. "By lubricating with water and ConDet, we knew it would help with the ram and with the spoil clean-out. The soil shoe is also a must. Using a piece of the half-inch wall pipe to create a lead cutting shoe gives us the needed clearance between the earth and the outside wall of the pipe."

Only two things delayed this crew before they were able to pound this pipe in on grade and on the exact planned line - torrential rains, and according to McCord "a big ol' stump."

When the pipe was 80 feet in the ground, just past the midpoint of the ram, the rains were so heavy that the crew was forced to stop. The Conrail official allowed them to stop simply because of the method that was used. "Just when we were about to weld on another casing, the thunder and lighting hit," stated McCord. "If we had been auger boring we would not have been allowed to stop, for fear of creating voids. As it was, with the pipe filled with spoil from the pipe-ramming method, there wasn't any fear of that. We were able to leave what was becoming a hazardous area and get out of the rain for the night and resume the following day."

The other obstacle - the stump - proved to be another temporary stopping point on the way to finishing the successful ram. At 110 feet into the ram, the stump stopped them. Placing their auger machine equipment on the pad, McCord's crews cleaned out the spoil and rooted most of the stump. Then they cut away the rest with electric chain saws.

With the spoil out of the pipe, the remainder of the ram was finished by the end of the next day. "This 23-inch HammerHead Mole worked great for us," explained McCord. "And support from the manufacturer and the dealer helped us make this long ram a success. No matter what anybody says, 140 feet is a long way, especially for 36-inch diameter pipe."

Written By: Richard Yach - Technical Writer Des Moines, Iowa
Provided By: Vermeer Manufacturing Company - Pella, Iowa