Sewer Authority Breaks Into Rock Barrier

July 1, 2000

In a recent project involving the laying of more than 11,000 ft. of sewer and water pipe for a new development in the city of Buffalo, NY, the Buffalo Sewer Authority was confronted with a massive presence of rock-a layer as thick as 8 ft. in some places. The project, the William B. Price Memorial Parkway, involved laying water and sewer lines, excavating manholes, and installing a retention pond for a new 31-home development. Work started in mid-August and, according to Bob Logalvo, inspector for the City of Buffalo Sewer Authority, was expected to be a real challenge, given the material into which the pipe had to be laid.

Traditional tools for addressing such an environment-hydraulic hammers, for example-can be slow, cumbersome, and in many cases grossly ineffective. Blasting is becoming ever-increasingly regulated and, in even modestly populated areas, might not be an option. Unlike past projects, however, the authority this time found itself looking at a schedule completed months ahead of schedule, a situation made possible by the use of a new hydraulic attachment. The Cyclone Processor from Genesis Equipment & Manufacturing Inc. in Superior, WI, is a rotary attachment-mounted on a 90,000-lb. excavator-that uses pin-on carbide teeth to grind material with which it comes in contact.

“This area, like most of western New York, is heavily laden with rock,” Logalvo points out. “The rock layer rises and falls, so we can be putting pipe into a 2-foot-thick layer of rock and then quickly see that thickness increase to as much as 8 feet. In the past, that would have meant using a hammer to chip away at the layer to get down to the minimal 6-foot depth we need. We know from experience how slow that process is, and we were prepared to work well into next spring to get the pipe in. We certainly weren’t anticipating getting through this quickly.”

Speed Counts, As Does Size

During an eight-week period, Logalvo says, the Cyclone was the key tool for laying 2,900 ft. of 8-in. pipe for sanitary sewer use; 3,000 ft. of 10-in. water pipe; 1,660 ft. of 12-in. pipe for catch-basin lines that connect to the manholes; 215 ft. of 15-in. storm sewer; 600 ft. of 18-in. storm sewer; 360 ft. of 24-in. storm sewer; and 3,125 ft. of 48-in. high-density polyethylene for use in the onsite retention pond. “It has never balked at anything it has encountered.”

“If this contractor were to use a hammer to get through the rock, it would be a far slower process,” states Bill Sams, sales representative for STI Equipment, which provided the Cyclone. “In fact, there was one day when we were not able to be on-site with the Cyclone, and the contractor had to revert back to using the hammer. They chipped away for five hours and laid one 20-foot section of pipe. We have regularly been laying sections that size in about 30 minutes.”

On the parkway project, sizes of the processed material were generally in the 2- to 3-in. range. The size of the material, however, can be altered by changing the rotation speed of the Cyclone attachment, the number of teeth, the size of the teeth, their configuration, or any combination of these factors. This ability to provide a small after-process product has been invaluable at the Buffalo site, notes Sams.

“Material produced by the hammer will be large in size, be unusable as fill on-site, and need to be hauled away,” says Sams. “That adds time, the cost of trucks and drivers, and a disposal fee to the picture. We are generating material that is simply pushed back into the ditch once a 1-inch base and some 2-inch rock has been added. So there is an added savings in not having to bring in the volumes of fill normally needed.”

Making a Clean Cut

In addition to speed and size of the processed material, Cyclone provides controlled, vibration-free operation. “It is common knowledge that hitting rock with a hydraulic hammer causes fractures-it is simply not a clean cut. As a result, the ditch will often be deeper in some areas and not as deep in others, forcing the operator to go back over areas he had already presumably finished,” explains Logalvo. “The Cyclone creates an even, rounded profile on the ditch floor-perfectly suited to laying pipe. And because the vibration from the attachment is minimal, we are able to get within 1 foot of a gas, water, or electric line, without disturbing it. A hammer just doesn’t afford that kind of control.”

That control, adds Logalvo, also came into play in the excavation of more than 30 manholes needed on-site. “We were grinding manholes measuring 6 foot square and 10 foot square in 6 feet of hard rock in as little as an hour. All that was needed to be done after the Cyclone finished was to remove the residual material with a track hoe. Using a hammer, each manhole is easily a full day’s work.”

Getting Into Hard Rock

The material into which the pipe was being laid at the Buffalo site is predominately Onandaga and Helderberg limestone with a cap rock heavily laden with dolomite. The material is extremely stout and abrasive, Sams observes.

“The carbide teeth have shown excellent wear characteristics despite the abrasive nature of the dolomite. That is due in part to a water misting system located just above the drum, which serves to keep the teeth lubricated and also acts as a dust suppressant.”

In 25 full and partial days on the job, the Cyclone has been used to lay more than 2 mi. of pipe, excavate 31 manholes, and dig a 60- x 100-ft. retention pond-all in rock with an average 5-ft. thickness. “We are actually hindered by the fact that we have to wait while the pipe is being laid before proceeding to the next area,” says Sams. “If we could just grind straight down the line without any pauses, production would be even more impressive.”