Optimization helped Haverstraw Quarry increase its production of saleable material.

by Kerry Clines, Senior Editor

Haverstraw Quarry is located on the Hudson River just north of New York City. The 157-acre quarry was originally owned by the New York Trap Rock Co., which opened the quarry in 1923. The quarry passed through the hands of a number of other owners before Tilcon New York bought it in 1981.

The main pit is located on the backside of a 525-foot mountain that faces the river. Though currently at an elevation of 100 feet below sea level, the pit was originally at an elevation of about 400 feet on the side of the mountain. At that time, haul trucks carried the rock from the pit, down the side of the mountain, to the road below for shipment. A special cable system was set up to allow a fully loaded haul truck traveling down the mountain to pull an empty haul truck up the mountain to the pit. “It was kind of like a trolley system,” says Lenny Tellone, a Tilcon employee and former plant manager at Haverstraw Quarry. “The quarry ran that way until about 1950.”

In 1988, a few years after purchasing the quarry, Tilcon began construction of a tunnel through the mountain, underneath the highway (9W) and the railroad tracks, to the river. Construction was completed in the spring of 1990, at which time the secondary plant was moved to the river side of the tunnel, as were the stockpiles and loadout area, making access to the river for barge transport much easier.

The primary crusher feeds material onto a conveyor belt that carries the aggregate through a 1,000-foot tunnel through the mountain, under the highway and railroad tracks, to the secondary plant near the river. The new Rockwell control system allows operators to make small adjustments to the crushers to maximize production of the plant’s biggest selling products.

“The tunnel is 1,000 feet long through the rock and about 21 feet in diameter with a concrete floor,” Tellone says. “A 56-inch conveyor goes through the tunnel along with power lines in the roof. We tied the conveyor into the primary and into the screen towers in the secondary. It cost a lot to do it, but it was the only way we could get to the river.”

A tunnel with conveyors and chutes runs beneath the stockpiles by the river, allowing specific materials to be sent to the dock for loading. “When things are busy, we load four or five barges a day — about 1,000 tons per barge,” says John Rufer, current plant manager at Haverstraw Quarry. “Right now, we’re a little bit slower. We’re loading two or three barges a day. We’re very conscious of not allowing anything to get into the river. We have to minimize the effect on our neighbors and the environment.”

Haverstraw Quarry has made an effort to minimize the amount of blasting at the quarry, as well, by making larger shots once or twice a week instead of smaller shots four times a week. “We spend a lot of money making sure the right controls are in place so we’re not affecting the neighbors too much,” Rufer says. “We have to in order to stay in business.”

Tilcon has an asphalt plant located on site that uses some of the material processed in the quarry, but a majority of the aggregate is shipped to New York City and Long Island for use in construction projects. About two-thirds of the material is shipped by truck and the rest by barge on the Hudson River. “We really want it the other way around, but that’s the way the sales are going this year,” Rufer says. “Barge transportation is a lot cheaper than trucking. It’s a competitive advantage for us.”

One interesting fact, according to Tellone, is that Haverstraw Quarry is the only quarry that dissects the Palisades formation — the five-sided columns of rock found in the area. “It’s a vertical column of rock that varies in width from 12 to 18 inches,” Tellone says. “If it gets bigger than that, it starts losing the formation. Geologists come to the quarry to study the rock formation.”

Optimizing the plant

During the winter months, the plant closes down and workers are laid off while winter maintenance is performed. The time is used for making changes that would normally cause a shutdown during the production season. This year, Haverstraw Quarry used the winter months to optimize its production system, replacing an outdated 1980’s control system with an updated Rockwell PLC-based process control system.

“Our biggest selling products here are our asphalt fractions — 1/4-, 3/8-, and 1/2-inch,” Rufer says, “and we can never make enough. We were trying to figure out how to maximize production of asphalt fractions with our regular crushing operation. That was one of our main objectives in upgrading control of the crushing process at Haverstraw.”

Alan Bessen, P.E., served as a consultant and project manager during the automation process. “When people in the aggregate business think of automation,” Bessen says, “they often think in terms of merely automating start/stop sequencing. In this case, we replaced an obsolete PLC and associated software with a new Rockwell control system configured to manage standard start/stop and equipment monitoring functions, including a new Rockwell PLC and an updated operator interface.”

Performance monitoring instrumentation was also added, including 15 belt scales that provide product yield data to the plant operator, enabling him to manage the yield of key products by making process adjustments in real-time. The new control interface will be automated in the second phase to use both current and historical data, enabling the computer to track, report, and adjust key process variables in real-time.