2015 - Page 7
The Life Of A Mine Depends On:-
- Situation of the mine - road/rail access. Ideally situated away from heavily built-up areas, and adjacent to a main road and not accessed down country lanes. Modern electric winding favoured as it dispensed with steam winding and the associated noise, plus the added benefit of no tall smoking chimney. Necessary power supply e.g. 11Kva also water supply from a stream, river, well or borehole.
- Manpower and management to enable the mine to be worked safely and efficiently and housing for the workforce (although colliery village housing was not so important in later years of the 20th Century because men travelled to work by car or other transport, e.g. buses, from outlying villages or towns). Generally a stable and efficient and non-aggressive workforce lead to higher output and higher wages. Sufficient and qualified and / or competent Managers, Undermanagers, and Under-officials and a Surveyor and various Clerical jobs.
- Target seams (from borehole information) thickness etc, and type and strength of roof and floor, and problems such as having to leave a layer of coal in the roof to form safe working conditions and having to cut soft floor with modern face coal cutting machines (also middle bands of dirt in the seam if they exist) leading to the percentage vend of coal to dirt that is economical.
- Depth of shafts and size in diameter relevant to heat of strata (the deeper the shaft the hotter it gets) and cooling of the air as well as a large surface ventilation fan and underground booster fans, underground cooling units were necessary in some pits for keeping the men in comfortable working conditions (again increasing the cost of production). The diameter of the shafts was also relevant regarding size of cages or skips and the various power cables, water pipes, methane pipes etc that was installed in them and extra cost incurred with pumping, tubbing etc. whilst sinking through water bearing strata. Also the type and size of winding gear.
- Infrastructure of the lease area and the planned mine layout regarding cleat, gradients, faulting etc, of the relevant seams of coal. The position of faults and other geological conditions such as swilleys or washouts or deterioration or thinning of the seams or thickening dirt bands within the seam etc, dictated the size of the area that could be worked by the modern panel method. Allowance had to be made for repairing roadways etc, crushed by pressures underground. This was called bye work and again an extra cost to mining of the coal.
- Quality of the coal, because seams with high sulphur, chlorine or other chemicals lead to the production of acid rain harming the ecology and producing carbon dioxide and also damage to the grates at the Power Stations (albeit that a certain amount of dirt and moisture was accepted). In the last Century seams that had certain characteristics such as used for steam raising, and to produce coke, coal gas, for industrial and household use, and production of petrol and other by-products were favoured. With the successful fracking for gas in the USA the price of coal plumetted to around £35 a tonne (2014-2015) a price that was impossible to produce at any deep mine in the UK.
- A stable market for the product was necessary (because in past years strikes unfortunately created lack of confidence in the supply of coal to consumers and many turned to other forms of energy, mainly natural gas). Note 90 millions tons were exported in 1913 but since the 1970s coal imports began.
- Working time for men at the coal face (including travelling time by manriding and walking), the further the faces are from the pit bottom, the less working time. The main types of transporting men and materials were under-rope haulage, battery or diesel-hauled vehicles, belt conveyors and free-steered vehicles (FSV's).
- Following the latest change when the mines were privatised again in 1994 the hours of work underground were extended, e.g. up to 12 hours or more to cater for the increasing distances from the pit bottom, whereas previously 7¼ hours plus 1 winding time was the limit). Note, it took quite sometime to transport men down the shaft in cages and also to wind them back again at the end of the shift. Time was wasted also whilst paddy cars for manriding were filled before moving inbye or outbye and of course the more distant the faces were from the pit bottom the longer it took. The number of conveyors to transport the coal increased to suit also the supply of equipment and supports etc requiring more installations and maintenance and more personnel and bye work outbye of the face.
- After July 1948 Town and Country Planning permission was required for underground working at new mines as well as for surface works, such as agreed site area, size, height and extent of dirt tips and their stability at all mines. With modern mining methods all waste discard from the Coal Preparation / Washery Plant is sent to the dirt tip and thereby more dirt, the quicker the tip grows, and its life diminishes. A further major factor is the positioning and size of tailings lagoons.
- Restoration of tips after layering and compacting waste dirt became compulsory, such as soiling, grassing and tree planting to agreed projected profiles and some areas were returned to the local farmers for crops or animal grazing. Tips at some abandoned mines were sold to local authorities for a peppercorn fee of £1 and Country Parks etc established.
- Subsidence factors limited working under densely populated areas, as well as under Rivers where flooding could occur due to altering the gradient and rate of flow, Sewage works similarly, and damage to Large buildings, Shopping Centres, Churches, Electrical Sub-stations and Pylons and Major Large diameter Gas pipe lines as well as Local Roads, domestic Sewer pipes, Water mains, Cables etc. Also Historic buildings, for example Hardwick Hall, Bolsover Castle and other Stately Homes, such as Welbeck Abbey Motorways, Major Trunk Roads, Large Lakes, Airfields and Railways, particularly the high-speed lines, etc, etc. It is impossible to work all the coal seams available at the relevant colliery due to many of the above factors with the continual lowering of the surface of the land, using the total caving system and dramatically damage to properties numerous times. This unfortunately led to large areas of coal being sterilised and could not be extracted. Even with the older type panel working with packs and wastes the surface still subsided in simple terms by more than 1/4 the thickness of the seam. Working short length faces with equal size pillars between to lessen the chance of subsidence is reliant on development keeping ahead of extraction and in mining coal nothing can be planned and taken for granted.
- Access to a nearby water course, such as a stream, river or sewer for water pumped out of the pit to be discharged. The workings of the coal and would require a number of pumps with a capacity to cope. Strict regulations are imposed by the River Authority to determine the amount to be allowed and the constituents of the water. The acidity and/or the amount of ochre of underground water could affect the input and this could entail a possible high cost of water treatment and/or an overland pipe line to a different water course.
- Profit, loan repayments and high wages bill, maintenance of buildings etc and cost of subsidence repairs.
- The cost of modern materials and repair and/or purchase of updated mining machinery, with technology developing constantly. A sufficient number of suitable qualified experienced engineering personnel and associated staff required to maintain the equipment, and skilled and trained miners to operate it.
- Health and Safety Rules and Regulations in MASHAM (Mines Administration and Safety and Health at Mines) and various other Coal Mines Acts etc.
- Green Tax on carbon fuels imposed by the European Parliament.
- However as soon as the first tonne of coal is extracted, that mine is on a limited life. The average life for a mine that was sunk in the 19th and 20th Centuries was between 70 to 100 years maximum. Most of the collieries in the Midlands region have achieved that figure, in fact some by half as much again.