Crushing in the USA

STEPHEN RICHARDS, owner/manager of Richards Quarries & Concrete from the Victorian High Country, recently visited the West Coast of the USA. Here he reports on his visit to a quarry operation at Corona, 75km east of Los Angeles, California.

STEPHEN had arranged to visit several quarries in the area with Tim O’Brien a geologist with Vulcan Materials but the long arm of the law interfered. Tim was called up for jury duty that week and was only able to spend part of a morning showing Stephen around the Corona Quarry owned and operated by Vulcan Materials.

Tim O’Brien, as a geologist for Vulcan Materials, covers the California, Arizona and North West coast areas. He had recently completed a program of drilling trials and blasting to determine the ongoing feasibility of another quarry in Southern California.

An internet search shows that Vulcan Materials is one of the leading producers of construction aggregate in the country. They have over 300 aggregate plants and related facilities in about twenty two states. They are a leader in ready-mixed concrete, asphalt and road construction material. About 50% of the company aggregates produced is used to construct highways, bridges, roads and railroads.

There are three quarries (individual companies) working on the same mountain deposit at Corona. Vulcan Materials’ Corona Quarry has excellent quality material and is in a high demand area. It services North San Diego, Orange County and the Western part of Riverside County. The rock is granite with an LA loss of 19.

Corona Rock and Asphalt plant is located about 3km from a residential area and 1km from an industrial zone and had been in operation for more than 40 years when Vulcan Materials purchased it in 1989. The operation covers about 400 acres and is a blue granite quarry which produces asphalt, asphalt aggregate, asphalt coatings, base material, concrete aggregate, railroad ballast and beaching.

Vulcan’s Corona quarry is currently producing about 2 million tons per year although the plant has the ability to produce up to 4 million tons per year. The economic downturn has reduced the demand and thus production output has been scaled down.

Stephen was told that Sandvik cone crushers have replaced Nordberg cones as it was explained that they were easier to maintain and gave better liner life. Polyurethane screening media gives good wear life but appeared to be prone to blinding when water sprays are used to control dust.

When Stephen enquired about their use of foam for dust suppression he was informed they have one foaming unit at the secondary section but the rest of the operation just uses water.

The Corona site utilizes gravity to reduce electricity costs by conveying downhill. California electricity prices increase dramatically after midday, in summer when all the air conditioners are turned on. The quarry starts at 4.00am and shuts off at midday to beat the price increase. The design and construction of the new aggregate plant in Corona uses some downhill conveyors that generate electricity as it carries the rock to the processing plant below. It was suggested it may save up to $30,000 in power costs annually.

An interesting idea Stephen observed was screen discharge chutes sliding on rails to expose the ends of screens for easy cloth replacement. Fitters obtain unhindered access to screening media on the bottom deck for quick change out of polyurethane media.

Vulcan has an onsite hot mix plant; conveyors feed from under surge piles to top up overhead gravity bins as required. Ballast for railroad use has the highest specification requirements of all materials produced. It requires hardness and must be washed to a standard far in excess of road aggregates.

Repair works were underway on the access bridge into the quarry site as the creek running between the asphalt plant and quarry had risen to a flood level not previously experienced.

Readers may recall the storms and heavy rain events that afflicted the West Coast of America from California to Washington State and the extreme cold conditions experienced across the North Central and Eastern states prior to Christmas 2010.

Several quarries that Stephen had arranged to visit in Northern California were closed with staff on extended leave due to the extreme amounts of rain forcing cancellation of jobs requiring quarry products.

A mobile crushing plant operator in Butte, Montana had also lost considerable time during the US summer and autumn due to exceptional rain causing screen blockages when working alluvial deposits. The majority of aggregates used in Montana are gained from alluvial deposits including the 10mm minus grit spread on icy or snowy roads to gain grip.

Thanks to Stephen & Kaye Richards for contributing this article to Sand & Stone. If any Members have interesting stories they wish to have included please contact the Secretariat on 03 5781 0655.

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