Randy Pentoney of East Coast Builders, Seaford, DE, faced a great challenge when general contractor J. M. Bryan & Sons, St. Michael’s, MD, approached him.
The challenge was to take a slipform machine down a 3.7-meter (12 ft.) incline and pour a 1.2-meter (4 ft.) wide V-ditch with a mold offset of 46 centimeters (18 in.). Another part of the challenge required working part of the ditch underwater because it runs in the water table.
Other factors in the project included a 4-to-1slope; and working in a ditch that is used for drainage improvements alongside airport runways, so one section of the ditch must be poured at night because of plane traffic.
A slipform machine is the only way to go, Pentoney said, and his machine — for years and years — has been a Power Curber 5700-B.
“I would not have bid this without the machine,” he said.
Still, he wasn’t sure about walking a 10,645- kilogram (23,500 lbs.) machine into a hole. And, then there was the water to consider with the job.
“Fifteen hundred feet of it [the pour] was below the water table and we were working in water,” Pentoney said. “It was a difficult situation for everyone. We didn’t anticipate all that water.
“We had to re-think our approach to these unforeseen site conditions. The general contractor kept 8-inch pumps running to help lower the water table and stabilize the sub-grade with stone. We had to make special provisions for the machine to run in the bottom,” he said.
The tracks were sinking in the mud so Phil Rowe, project superintendent for Bryan & Sons, came up with the idea of using timber mats. “We leapfrogged four 20-foot mats forward with two excavators to provide a stable surface for the machine to run on.”
East Coast Builders accomplished the 2,438-meter (8,000 ft.) pour in four sections. Pentoney brought the machine in, poured a section and then left while the next section was being excavated. The last section was poured at night. Pentoney allowed two nights, but actually poured 701 meters (2,300 ft.) from midnight until 8 a.m. “Things went so well, we made it by the deadline, with five minutes to spare,” he said. “We were under the gun to perform, and the machine performed perfectly. The only reason it took eight hours was that they were only running three trucks and their turnaround time wasn’t fast enough.”
Pentoney, who has been in the business since 1984 and has owned a Power Curber since 1986, calls the 5700-B “a great performer.”
“It adjusts and accommodates a lot of situations,” he said. “We can do a lot in our area that a lot of people can’t do. We pour below grade. On a rehab job, we poured curb 6 inches below existing blacktop. No other machine in the area could do it. We offset a couple of feet to get on stable, consistent grade and also dropped it down.
“There’s no other machine in our area that can adapt to these various situations,” he said. “We look for special application jobs because we have the B.”
Pentoney said that he has a good working relationship with his dealer, Eastern Equipment Service. “I can’t say enough about their response time,” he said. “They get us parts right away.”
The irrigation ditch for the Wicomico County Airport in Salisbury, MD, was East Coast Builders’ first experience with V-ditch. Pentoney worked with engineer Alan Champion at the Power Curbers’ factory on designing the mold.
At its deepest point, 3.7 meters (12 ft.), the ditch was 24.4 meters (80 ft.) wide. The concrete truck was located on the bank above the machine, which was on a 4-to-1 slope for the most difficult part of the pour. Pentoney used 5.5 meters (18 ft.) of chute to get concrete from the truck to the machine. Getting concrete to the machine was an even bigger difficulty to overcome than the water problem, he said.
He used a 4- to 5-centimeter (.5 to 2 in.) slump on the V-ditch, as opposed to the 1.3-centimeter (.5 in.) slump he uses for his curb-and-gutter work.
“To me, the only way to do this job was with the machine,” he said. “It would have been a much bigger job without the machine.”