West Fargo Stormwater Pipe Ramming

Accu-Pipe Ramming Systems, Inc. of Red Deer, Alberta, recently completed a subcontracting project ramming 48-inch casing with pneumatic tools in West Fargo, North Dakota. Faced with tight deadlines, rainy weather, tough clay soil and unforeseen obstacles, the contractor still managed to get the large diameter stormwater pipe rammed in on time.

The purpose of the project was to enable West Fargo to pump stormwater away from the flat areas and direct it east towards the Red River. Two hundred and fifty horsepower pumps were installed to move water through these large carrier pipes.

The general contractor for the project hired Accu-Pipe Ramming Systems Inc. to install 80 feet of carrier pipe under Highway 10, the old main highway running east and west through Fargo and West Fargo. The new line ran up under the middle of Ninth street in West Fargo. The street had been closed for this project and had all its asphalt road base removed for complete street renovation when this stormwater project was completed. To keep up with the project's schedule, the pressure was on Accu-Pipe Ramming Systems Inc. to install 80feet of carrier pipe in one week.

Ron Balzer, general manager of Accu-Pipe Ramming Systems Inc. had crews working in North Dakota, Alberta and Saskatchewan over the past two years installing a whole range of pipeline projects. Prior to starting his pipe-ramming business, Balzer worked with his family construction business that has installed water-treatment facilities and performed other industrial construction projects for the past 60 years.

Balzer and his wife started the specialty earth boring company two years ago employing nothing but pneumatic tools in their business. "In Alberta, particularly, you can go 50 miles and be confronted with entirely different soil conditions for underground pipe installation," Balzer stated. "Pneumatic tools give us versatility that other conventional forms of boring do not. We anticipate driving pipe from six to 72 inches in diameter under roads, railroads, and creeks. We want to be able to push through sand, gravel, glacial till and heavy pit run which is heavy gravel with six-to-eight inch diameter rocks in it, and hard packed clay. Pneumatic-tool pipe ramming gives us a greater chance of success in these varied soil conditions. To auger bore and hit sand or loose gravel would weaken the support structure and create voids which would end up costing me a lot of money," added Balzer.

One key reason why Balzer chose the pipe-ramming method over traditional auger boring as his core business, was the relatively small amount of equipment his crews would have to mobilize across the border when working in the United States.

Balzer brought 16 and 23-inch HammerHead Moles to the West Fargo pipe ramming project along with an adapter ring and collets to fit the 48-inch pipe.

The concept of using tandem pipe rammers is relatively new, but it fit this job. The plan called for two 40-foot sections of half-inch wall pipe to be welded on the ground above the launch pit. The pipe was installed with a slight grade because although it was meant to be a force main water pipe, the engineers wanted a small grade so that if the pumps ever failed, the water would still drain. With this grade requirement, the initial powerful blows of the larger 23-inch HammerHead might lead to swimming of the long pipe at the onset of ramming. Balzer and his crew decided to use the smaller 16-inch HammerHead until the pipe was secured in the earth and then bring the larger 23-inch tool in to finish the job. This plan would prove successful in more ways than one.

The 100 foot long launch pit was excavated 10 feet below the road surface with care taken to avoid an eight-inch gas main and water main that paralleled Highway 10. Both of these utility lines ran perpendicular to the path of the storm drain but since they were buried four feet deep, they narrowed the window for the 48 wide storm-water carrier pipe Balzer and his crew were to install.

The pit floor was graded carefully to the specifications with a layer of loose rock set down as a bed for the long pipe section. Two by eight cross rails were set in every 30 inches along the stretch of pipe with side rails nailed to them to act as a guide rail for the pipe to ride on. This was done while welders were connecting the two 40-foot sections of pipe and also welding on a cutting shoe for the lead pipe and half-inch lube lines that would lubricate the outside and inside of the leading edge with water and polymer.

With the pit floor prepared, Balzer had two trackhoes with slings set the 80-foot long welded pipe with the adapter ring and ramming collets into the pit and onto the rails. Employing two 750cfm compressors, the 16-inch HammerHead started the ram. Although the ramming was stopped several times to check the grade, progress in the moist clay proceeded according to plan.

A city engineer who was on site halted the ramming process when he realized there was a sanitary sewer line (that had not been on the city's blueprints) directly in the storm drain's bore path. This was approximately five feet into the ram.

After a delay to figure out exactly where the obstacle was, the go-ahead was given and Balzer had his trackhoe lift the front edge of the pipe with a sling at the trench face. This raised the bore path grade three-quarters of an inch while the pneumatic tool rammed the storm drain past the sanitary sewer missing it by less than two inches. There was no concern about vibration damage to the surrounding utilities throughout the ramming process. Once past the obstacle, the sling pressured under the carrier pipe was removed and the ram continued.

During the first 30 feet, the 16-inch HammerHead drove the pipe in at approximately one foot every five minutes. Then the crew hit hard dry-packed clay and the progress slowed. Rain halted the job on Thursday and Friday. On Saturday, they lifted in the 23-inch HammerHead down into the pit and pounded the casing the rest of the way.

The HammerHead ramming system allows one tool to be placed in reverse, backing it out of the ramming collets in seconds. The second tool is then installed in minutes. No strapping, cradles or chains are required to mount the unit into the pipe.

Removing one half of the tandem team of rammers and inserting the second half impressed Balzer and his Accu-Pipe Ramming Systems Inc. team. The flexibility of the HammerHead system was proven superior over traditional auger boring machines, where this type of substitution would have taken hours.

Weather delayed the crew's work and they felt that they had to get the job done despite the July 4th holiday weekend. The 23-inch HammerHead took only two and a half hours to ram in the remaining pipe. The crew removed the spoil on Monday of the following week.

Balzer commented on the project and the success of his tandem ramming team. "Considering that the 16-inch tool had to push 22,000 pounds of pipe, another 5,500 pounds with the adapter ring, the collets, its own weight, plus the spoil inside the pipe, I thought it performed well," Balzer stated. "I wasn't sure what to expect from the 23-inch HammerHead, but to say I was impressed with its hitting power in the tougher soil conditions would be an understatement, especially with this large-diameter pipe.

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