A Few Quarry Problems Solved

Here are a few examples of seemingly major problems that in some cases had actually stopped the quarrying, but they were solved by identifying the key points without distraction from surrounding stuff. Identify the simple truths.

Coastal gravel quarry in a Scottish raised beach

The solution was to simply reverse the direction of working.

A deep glacial coastal sand and gravel operation with wet peat overburden. Gravels vary from zero to over 20 metres thickness, peat is relatively consistent 4 to 6 metres. Quarry was muckbound and peat was going into the sea. Previous operator was working the maximum thickness of gravel so for a given volume of product was earning very little surface area for overburden disposal.

By moving to the other end of the quarry with very thin gravels a given volume of sand and gravel production earned a substantial surface area for peat overburden disposal and thereafter each strip could be single handled back into the excavation in the conventional manner.

Limestone quarry in Staffordshire

The solution was recognising and acting on a simple truth.

A limestone quarry with a 28 degree dip on west faces into the quarry and unraveling. Projecting that set of faces to their safe limit demonstrated limited accessible reserves and that the only option was to demolish an existing processing plant that was situated on a stable block of limestone in the east of the quarry. The cost of demolishing and moving the plant was set against a substantial increase in permitted reserves.

Gritstone quarry in South Wales.

Recognising a simple truth and taking clear action to unlock a quarry.

A project to purchase a Gritstone quarry that was working uphill - always difficult, but also critically short of space in the valley floor and completely muckbound. An opportunity arose, and was taken, to sell waste at a very modest revenue with purchaser collecting. Even at a financial loss it would have been a good deal since its removal unlocked sufficient space to get the quarry going again. A high value company asset was created.

Limestone quarry in France

Solution was to turn the quarry working through 90 degrees.

Steeply dipping limestones at 55 degrees to the Southeast with some hard black shale beds. Company believed it had only 12 years life at approximately 1 million Tonnes per annum due to moving into a shale deposit to Northwest. Previous drilling had been a series of vertical holes, plus possibly mis-identification of black shale against black limestone. A new drilling programme involved inclined holes drilled perpendicular to the dip therefore properly transecting the geological succession and identifying the true shale thicknesses. Showed that the shales were in fact relatively thin at 4 to 5 metres. Quarry working was turned through 90 degrees such that the production faces worked across the dip and took a representative geological section whilst enabling shale removal. Increased life at same production volume to 37 years.

Mixed rock quarry in Tanzania

Do basic geological mapping, exclude 1 rock type, turn the working progression through 90 degrees and work a blended product.

Quarry in a linear outcropping series of 5 metamorphic rocks, with quality and consistency problems that had been investigated at the mineralogical/petrological level but not at a bigger scale. The quarry visit revealed a very obvious large fold structure with working faces parallel to the structure such that the entire face would be yielding an acceptable rock for a while then move into poor quality rock and back again.

The solution was basic geological mapping across a hillside to identify the rock trends and then turn the working through 90 degrees such that a blended source material could be worked, the plant could process out the 1 poor layer and consistent quality products could be made.

Jurassic limestone quarry in Cambridgeshire

Identify and selectively work a better quality band in Jurassic limestone instead of diluting a whole deposit.

The company owned a quarry in Cambridgeshire in the soft Jurassic limestones that generally serve the low value fill market. This was not a market that particularly interested the company management so the asset sat dormant for years whilst still carrying a value on the asset register. A modest drilling programme and some mapping gave an understanding of the rock deposit in more detail and identified a layer capable of selectively producing concreting aggregates. This enabled the working of a new reserve previously assumed to be poor quality and uneconomic.

Gabbro quarry in Cornwall

New working plans and a planning application to merge two quarries to maximise yield, and create space for waste by tipping over final position faces at their planning and practical limit.

Coastal operation comprising two adjacent quarries each being worked to depth with a spine between them on which tipping had taken place for decades. So the clear problem was a diminishing working area in each separate quarry whilst the spine became wider at each sinking and potentially more expensive to quarry due to waste being tipped on potential reserves. The top bench of each quarry was close to the planning boundary. A new working plan, that required planning permission, enabled the problem to be designed out.

Limestone quarry in the Rhone Valley, France

Recognise the simple truth that waste rock continued to be tipped over reserves, redesign the working scheme to move a million Tonnes of tip elsewhere, at a cost, but in the process unlocking the quarry.

In the course of a Due Diligence to acquire a multi-quarry company it became apparent that a major proportion of the company value was vested in this single quarry. D Wardrop's assessment of recoverable reserves was considerably lower than that of the selling company owing to the presence of an estimated 1 million Tonnes of quarry waste that was tipped in the middle of the quarry and covered a number of faces.

The site ownership enabled a new tip site to be identified and a revised working scheme was designed to move the central quarry tip and pay for it by releasing reserves.

Oxfordshire gravel pit

Key points were identifying the one place where there was sufficient water depth over a regional high pressure gas main and sufficient air draught under a 33Kv electricity line.

The Great Britain rowing squad were looking for a still water practice course, that had to meet international standards, and were in negotiation over a gravel pit lake in Oxfordshire. The project was fronted by a property development team and some technical matters became overlooked whilst a multitude of layout options were drafted creating too many variables and slowing the project development. At a single meeting the key non-negotiable technical features that defined the rowing course possibilities were identified and the 18 expensively drafted options reduced immediately to two. Everything else was elective. The site is now the Redgrave Pinsent Rowing Lake.

Ukraine

A solution based on prosaic site investigation and appropriate pit design.

The company was seeking to develop a very large greenfield gravel resource that had been investigated in the Soviet era. A hugely detailed but not very relevant study had been carried out, and the relatively new national team had little experience of project development. Appropriate drilling and trial pitting was carried out with relevant laboratory testing to establish the viability of the project. A realistic working and restoration scheme was designed and the site was brought into successful operation.

Derbyshire limestone quarry 'chatter'

Utilising logical thinking with skill and experience to critically assess the possibility of water supply options. Clear decision making.

One of the major limestone quarries acquired after a takeover had a long history of seeking to secure a water supply but no progress had been made. The ambition was to wash and process clay contaminated crusher waste known as 'chatter' which was building up in the quarry and totalled several million Tonnes. The previous owners had over 16 years commissioned a number of reports by external consultants on water supply options, but on no occasion had the management team included anyone with appropriate technical expertise to interpret the reports and decide on a course of action.

A single afternoon studying the files made it clear that drilling a deep waterwell was the cheapest and lowest risk option to try, whilst having a reasonable chance of success. If successful it would offer cheap water, if unsuccessful it would be the cheapest way to justify the next most expensive option. The borehole was successful and enabled several million Tonnes of discards to be converted into saleable reserves whilst unlocking quarry floor area and preventing sterilisation of resources.

Granite quarry in the Massif Central, France

A solution derived by geological observation on site, proving the hypothesis by drilling, and re-designing the working scheme to suit.

In the Due Diligence on a multi-site company one of the granite quarries was found to have poor and variable product quality. On site geological mapping made it reasonably apparent that weathered rock, probably from hydrothermal weathering, was distributed in predominantly vertical zones that broadly shared a similar orientation. A core drilling exercise confirmed this hypothesis by means of inclined cored boreholes drilled approximately perpendicular to the orientation of the zones. The quarry working scheme was subsequently redesigned to work a blend of weathered and fresh rock such that the processing plant could discard unsuitable material whilst maintaining a flow of marketable feedstock.

South Wales quarry lime waste

Speak to appropriate people and seek advice rather than rely on received wisdom. Identify the right consultant to design a solution. clover patches.

A one million Tonne per annum limestone quarry included in the landholding a very old hillside tip of lime waste from former kilns. This material was of very high pH and nothing would grow on it causing a notable scar on a hillside otherwise covered in an SSSI beech wood. Poor advice given to the company had been followed comprising futile attempts to alter the soil pH whilst also removing pioneer plants such as Buddleia. The latter action was taken in the received belief that the regulator required this to be done.

At a meeting with the regulator to clarify it was stated that they didn't mind what plants grew initially provided that the hillside went green. A consultant had been noted at a conference detailing their experience in working with some very challenging mine waste tips so they were approached for a proposal. This involved planting fenced trial plots of clover and other ground flora designed to fix Nitrogen and later extending the most successful mix over the hillside. Meanwhile Buddleia was permitted to grow on and eventually some indigenous tree saplings were planted. Within a few years the hillside was covered in 2.4 metre high sycamore and birch trees with a healthy ground cover.

The solution lay in establishing the facts rather than hearsay, recognising poor advice, and identifying the correct specialist.

Irish Coastal quarry

Recognise a flawed consented working scheme and reverse the designed direction of working.

A coastal source of high Polished Stone Value gritstone was being promoted by a quarry developer. The site was a relatively linear landholding extending inland from the coast and working an inclined sequence of interbedded gritstones and softer shales. The proportion of softer shales was higher near the coast and improved inland. The permitted working scheme allowed for excavating rock nearest the coast first with a short conveyor haul to the jetty. Unfortunately this would mean generating the maximum proportion of waste whilst not generating sufficient void into which to place the waste.

D Wardrop's proposed solution, at a higher conveyor capital cost, was to reverse the direction of working such that void was generated at the distant part of the quarry. The proportion of waste was lower, and the void could be completely filled without obstructing other quarry operations. It is not known if this solution was ever adopted.


Other Articles from Wardrop Minerals Management Limited

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For many years, since minerals planning was formalised through a Minerals Local Plan based system in the early 1980s, County Councils as mineral planning authorities have carried a general responsibility to try and avoid mineral resources - mainly bulk materials such as aggregates and clays - from being sterilised, or put beyond use, by permanent surface development.

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Read more about - Minerals Sterilisation considerations for Land Developers...

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Prior to purchasing the operation a core drilling exercise was carried out involving drilling through the full relevant sequence.

Read more about - Frequency Analysis of Clays in a Sedimentary Sandstone Sequence...

Aggregates Landsearch - Then and Now - Changing practices in land search for aggregates and other construction materials

It is a simple truism that minerals can only be worked where they lie, and quarries for sand and gravel or for crushed rock need landsearch activity to identify mineral bearing land for greenfield developments or extensions to existing operations.

Read more about - Aggregates Landsearch - Then and Now - Changing practices in land search for aggregates and other construction materials...

Supply Chain Risks due to Extreme Weather Events

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Read more about - Supply Chain Risks due to Extreme Weather Events...

Responding to DEFRA at the MIRO Review of Aggregates Levy Sustainability Fund Research Projects, Wellington Arch, London - 12th March 2008

Minister, Ladies and Gentlemen:

It is a privilege to be able to respond on behalf of the Mineral Industry Research Organisation to DEFRA's Review of the Sustainability Fund Research Projects. MIRO and English Heritage have selected a most interesting venue for this launch and The Wellington Arch is perhaps slightly more relevant than many people might at first think.

Read more about - Responding to DEFRA at the MIRO Review of Aggregates Levy Sustainability Fund Research Projects, Wellington Arch, London - 12th March 2008...

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