All of the remaining overburden is used in some way, with excavated topsoil stock-piled for site rehabilitation projects and clay subsoil used for quarry backfill.

Limestone superintendent Tony Guerrera reports annual primary production of 1.6 million tonnes at Beachville, of which about 900 000 tonnes is utilised as feed stone for Beachville’s two quarry based rotary kilns.

In terms of markets, burnt product from the kilns is used mainly as a flux in the steel making process by Hamilton’s Dofasco and Stelco steel plants 90 km to the northeast.

Other applications including paper production, sugar refining, and acid lake treatment, to name a few. Markets for the 700 000 tonnes of annual raw stone production include blast furnace stone for pig iron production, the Carmeuse Dundas lime plant, Federal White Cement’s Woodstock plant and Flue Gas Desulphurisation (FGD), as well as construction, agricultural and automotive applications.

The overall production process is geared to maximize the product sizes required by these customers, starting at the quarry face with blast design and extending right through the operation’s crushing and screening plants.

54 mm x 25 mm stone is in demand as both kiln feed and blast furnace stone, while 25 mm x 13 mm is also utilised by the steel plants, Dundas lime plant and FGD applications. Smaller still, 13 mm x 6 mm sized stone is also used for FGD and as feedstock for the quarry’s Pulverized Stone Plant (PSP) that produces fine sizes for feed mills, chicken farmers and glass production.

The stripping process in the quarry begins with the removal and stockpiling of a 600 mm thick layer of topsoil, used later for the construction of perimeter berms and rehabilitation areas. Conditions vary underneath the topsoil, with lenses of sand and gravel up to 6 m deep present in a number of locations.

These are processed separately by contractor AAROC Aggregates & Recycling utilising a portable production spread. Elsewhere, stripping involves the removal of heavy clay subsoils and a hardpan clay layer up to 18 m deep. Dirt moving contractor Blue Con Inc.

utilises its Caterpillar fleet for the job, starting with a 375 excavator in mass excavator configuration and fitted with a 4.6 m 3 bucket.

The 375 loads up to four 36.3 tonne capacity D400E 6x6 trucks, with two dump and two ejector units in the fleet. Theses trucks have a typical haul of 800 m to the dump point, where a D6H dozer profiles the material to specific job requirements. Each D400E normally makes 10 round trips per hour, carrying 15 bank m 3 , for a daily production total of about 4600 m 3 . The stripping job operates on a single shift year round, occasionally ramping up to a double shift if required.

Stripping continues until a 1.5 m bench of thinly bedded cap rock overlying the main limestone bench is exposed. The high silica content of the cap rock rules out its use in metallurgical applications, but it is in strong demand for construction applications such as decorative landscaping, retaining walls and erosion control, with annual production exceeding 200 000 tonnes.

Unlike most quarry production blasts, the cap rock blasts are designed to just crack the rock and so maximize the yield of large slabs. Beachville Lime’s production drill, an Ingersoll-Rand DM30 down-the-hole crawler rig, typically drills fifty 171 mm diameter holes 2.44 m deep into the cap rock, on a 2.75 m burden by 3.66 m spacing blast pattern. Each hole is then charged with 3.6 kg of Orica’s Apex Elite, a packaged booster sensitive emulsion, plus a Pentex D 0.45 kg booster. After blasting, pieces are sorted by Blue Con’s Cat 245B excavator, then individually shaped by a Cat 320B excavator fitted with a Breaker Technology 3000 ft-lb hammer. A Cat IT28 integrated toolcarrier finishes the job by stockpiling finished pieces and loading highway trucks.

Nothing goes to waste even here: surplus cap rock material is recovered and either used to stabilize exposed earth side slopes, or further processed by subcontractor Arts Crushing to make 100 x 250 mm gabion stone for erosion control applications.

Removal of all the overburden and cap rock finally reveals the quarry’s 25 m high main limestone bench. The limestone here has a calcium carbonate content of about 98 per cent and, from a drilling and blasting perspective, is almost ideal with uniform horizontal bedding and regularly spaced vertical joints. Here too, drilling and blasting differs from many operations. Guerrera explains that the rock’s natural blocky texture allows it to be drilled on an unusually large 7.02 m x 7.93 m pattern, producing a shot with a maximum 760 mm lump size and only a small percentage of finely sized material.

This size profile in turn optimizes the yield of the clear stone by the downstream plants, particularly the 54 mm x 25 mm stone that is at a premium for kiln feed.

The quarry is worked in a single bench, with the DM30 drilling the full face height plus a further 1.5 m of sub-grade drilling.

Blasts are single row with 8 hole shots of 31 750 tonnes shots in winter and 12 hole, 45 350 tonne blasts during the summer months, giving a year round weekly average production of about 36 250 tonnes. Drilling is completed in-house by one operator on a single shift. After drilling, each hole is loaded with Orica’s Apex Gold 2171 pumpable gassed emulsion (the main explosive charge), normally in three decks and with a 25-milli-second delay between each deck to control ground vibration. A 9.2 m column of the blasting agent is followed by two 4.6 m columns, with each column separated by 25 mm x 13 mm stone stemming.

During the blast, each deck is initiated by a Pentex D 0.45 kg booster that is in turn initiated by non-electric Handidet detonators. Regular blast monitoring at three fixed locations confirms that the resulting vibration is well below the provincial limits of 12.5 mm/s while air blast measurements at receptors also come in well below the stipulated limits of 128 dBA.

Guerrera notes that water management is an ongoing issue for many quarries in the area, and this one is no exception. As a result, waterproof explosives such as the emulsion are being used more frequently, while the DM30 is periodically drilling shallow surface ditches in the quarry floor to facilitate surface drainage.

After blasting, the company’s new Caterpillar 990 face loader, fitted with a 7.7 m 3 capacity spade nose toothless bucket, loads the 760 mm minus shot rock into two new 63-tonne capacity Cat 775D haul trucks.

The 775D’s currently have a haul of about 1000 m to a Fuller Traylor gyratory primary crusher, recently rebuilt and relined at a cost of $500,000.

The primary reduces the shot rock to 305 mm minus at an average throughput of 725 tonnes/h, aided by a Breaker Technology 3000 ft-lb hydraulic breaker on a 7.6 m boom. From here, crusher run is conveyed to a 4000-tonne live capacity surge pile that in turn feeds the semi-automated secondary plant. Here it is initially screened on Tyler F-900 6x14 and F-800 6x14 double-deck screens, with oversize going to a McLanahan 36x40 double roll secondary crusher and smaller sizes going forward to twin F-800 6 x 14 screens.

Product is then further screened by twin F-800 5x14 screens, either going to product bins, a further pair of F-600 5x14 screens, or a tertiary crusher for further reduction. The tertiary is a Pioneer double-roll crusher that has been rebuilt to 26x30 size by Automatic Welding and operates in closed circuit with the screening plant.

Also noteworthy is how this operation has tackled the familiar problem of effectively dry screening sticky fine sized material.

Guerrera reports that the Productionv Engineered Products (PEP) screen, inclined at 40 degrees, is effectively screening raw stones fines to deliver a popular agricultural limestone product. The screen is fed 6.35 mm minus feed at 110 tonnes/h and produces 14 mesh minus (1.4 mm minus) aglime at about 45 tonnes/h.