Allstate Boring All-Stars Complete Horizontal, Vertical Pipe Rams

Sometimes trenchless is about choices. What method, what tool and what size? How long, how much or how little? Contractors with creativity, knowledge and vision don’t see those choices as challenges, but more as opportunities. Allstate Boring, Bakersfield, California, is exactly the type of contractor.

On a recent project in Kern County California, the utility boring contractor demonstrated how creativity, skill with multiple trenchless methods, and the ability to react quickly can overcome challenges and result in a successful project.

“This was really a case of, ‘the contractor had all the tools that he needed to do the job, but he wasn’t sure what tool it was going to take,’ Allstate Boring president Brian Sherrell explained. “We were subcontracted to install a 30-in. horizontal casing under a river, about 275 ft in length. We started out auger boring it, and we got 73 ft in and hit an underground river. Once we hit the underground river and the flowing soils, we had to make a quick decision and convert the installation to another method. We choose pipe ramming.”

According to pipe ramming specialist Rick Melvin with trenchless equipment manufacturer TT Technologies, Aurora, Illinois, the transition from one method to the next was perfectly executed. He said, “Making that quick decision to switch to ramming helped save the project, but that wasn’t the only bit of creativity and ramming on this project,” said Melvin.

To complete the installation under the river, Allstate Boring used an 18-in. diameter Grundoram Goliath pneumatic pipe rammer from TT Technologies. The installation of the 30-in. casing was a key component to supplying a reliable water source for the camp/park recreation area in Kern County. A vertical pipe ram of a 72-in. casing, on the other side of the river to facilitate a receiving pit, made the completion of this possible and highlighted Allstate Boring’s ramming skill.

Camp Okihi Needs Water

Camp Okihi in Kern County needed water. While the park was apparently permitted to draw water from the river as needed, that situation was both unpredictable and unreliable. Kern County was interested in enhancing the park and bringing it back to life. According to Sherrell, the park features a variety of wildlife including goats, turkeys, and other wildlife that appeal to school-age children. However, they needed to get on a reliable water source.

“Cal Water owns a water facility across the river, so Kern County needed to get an eight-inch water line from that water tie-in point, under the river, and then to the camp so that the camp has a stable water supply for the animals, plants, and the flowers; everything that the elementary school kids are going to come out and enjoy,” said Sherrell. “So, the plan was to install a casing under the Kern River insert a new 8-in. ductile iron water main and then on the other side of the river, bring that line up vertically, creating the water access the park needed.”

The general contractor for the project was RLH Fire Protection, Bakersfield, California. Allstate Boring was the subcontractor. Allstate Boring is a family owned, licensed contractor located in the heart of California, Bakersfield. The utility contractor specializes in trenchless bores ranging in sizes from 4 to 72 in. in diameter.

RLH Fire Protection established a significant launch pit on the north side of the river to facilitate the installation of a 30-in. casing. The Allstate Boring crew started out with auger boring the casing under the river because the ground was a very dense clay. Crews got the casing aligned properly and started boring. The plan was to steer the casing using a bottom window or “shoe,” but that plan changed.

Switching Gears

“We went in [the casing] at 20 ft to make adjustments to the casing alignment and then we went in at 40 ft, and we were going to go in at 80 and make a correction. But we couldn’t do that,” Sherrell said. “We basically hit an underground river at 73 ft. So, we were never able to go back in the pipe again due to water flow. Luckily, the right and left alignment was perfect, and we just had the joint barely pitched up a little bit more than what we wanted. But we had to be satisfied with that.”

From there, the decision to pipe ram the remaining 200 ft of casing was made. Allstate Boring crews brought in the 18-in. diameter Grundoram Goliath and utilized the auger tracks as a ramming platform.
According to Sherrell, safety was a top concern. “We didn’t want to access the front of the pipe,” he said. “We’re trying to keep our employees out of harm’s way. You don’t want to be crawling in a casing underneath the river. When we went to go clean out after the job was over with, we had to go in and get those bigger rocks, bigger boulders. But it was when the job was safe to do it.”

Crews connected the 18-in. diameter pipe rammer to the 30-in. casing through standard ramming gear, a series of tapered, locking ram cones. During ramming, the casing gradually climbed. Sherrell said, “Every joint went up a little bit more, like .05 percent to .10 percent of grade per joint is all we gained while we were pipe ramming. So, it was a very nice, slow, gradual climb that we got in the remaining 205 ft.”

Casing Compass

Approximate drive times per 20-ft casing ranged between an hour and an hour and a half, depending on how firm the soil or how rocky the soil was. Sherrell was able to track the progress and direction of the casing closely using Casing Compass technology from PLG Technologies, Bakersfield, Ca., which played an important role in the horizontal casing install and determining the location for the 72-in. ram.

The patent-pending Casing Compass system is used to remotely monitor the position of a casing bore. It is welded to the top of the lead casing and features a calibrated sensor inside of the unit that provides real time data on the pipe location and the direction as it is being installed. By taking regular readings, grade can be determined and monitored.

“Dealing with groundwater becomes overwhelming. So, the more groundwater you have, the more you want to do things remotely, the more you want to find out information remotely,” said Sherrell. “That’s what the Casing Compass did for us. We were able to know where grade was. There was a requirement on the job that the engineering firm and the agency gave us that we had 15 ft of clearance from the low part of the river to the top of the casing.

“We were able to build a spreadsheet with the starting elevation and then input the Casing Compass pitch readings on 10-ft centers. The spreadsheet calculates the elevation change from the Casing Compass reading and distance traveled. So, we were able to prove that we had 15 foot of clearance underneath the low part of the river at 170 ft.”

Going Vertical

That information also allowed Allstate Boring to know what the elevation of the top of the casing was at the receiving pit area. Then they were able to determine how much of the 72-in. casing they had to drive in the ground.

For the vertical installation, cost effectiveness was a driving factor. The 72-in. casing would serve as an extremely capable and affordable receiving pit.

“For creation of a receiving pit on the other side of the river, we were looking at somewhere near a quarter million dollars’ worth of engineered shoring, digging, clam shelling, excavation, with engineered square or rectangular shoring,” Sherrell said. “Well, you know, as I do, that a round structure is much stronger. And can take the loads from the earth a lot better than something that’s square or rectangle. So, it requires less metal thickness. At today’s steel prices, we were able to shore it without it having to be an extremely expensive rental item. We got to buy the 72-in. casing, and then we were able to drive it in.”

Allstate Boring used a unique rammer configuration to drive the 72-in. vertical. Crews attached the rammer to a 48-in. casing using standard ram gear. That configuration was welded onto a three-inch thick 8-ft by 8-ft plate. The that was welded to the top of the 72-in. casing.

Over two days of ramming, crews were able to install 19 ft of vertical casing. According to Sherrell, drive time was probably four hours total, after aligning everything.

Completing the Work

Allstate Boring contracted the cleanout of the 72-in. casing. After all the material was removed, crews pushed in the 8-in. ductile iron pipe to where the 30-in. and the 72-in. casings met on the west side of the river. A 90-degree fitting was then bolted on, and a vertical ductile iron pipe connect, reaching to ground level.

The 72-in. casing was then removed. At the same time, a control low-strength material grout was pumped in. The general contractor made all the final connections.

Jim Schill is a technical writer in Mankato, Minnesota.