people have come this way since
1st May 2001
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An extract from an article by Jonathan Wright - "Carbon Dioxide: A danger underground"
Since the extremely high water levels experienced during February and March 1990, concentration of carbon dioxide has occurred at the water levels within the mine. The first occasion, when the matter was brought to our attention at the Caves was at the beginning of April 1990, after a caver had been down to the pit bottom area and was unable to light his 'roll up'; after cursing his lighter he then began to wonder whether there was a more serious implication.
We took a Draeger hand pump and the appropriate tubes down to pit bottom (where the oil is) we used candles to help check the oxygen levels; half-way down the incline, towards the shaft the candle would not remain alight. In order to check the air down by the shaft I walked into the bad air holding my breath and took a reading which showed a CO2 concentration of 5.25%!
The CO2 levels are variable and appear to increase as the water level rises.
The cause of the problem is not clear, some cavers have said there has always been this level of CO2 and no-one has bothered to measure it before (like Radon?)!
The problem came to light after the extremely high water table during the winter of 1990, although I believe that the air has always been suspect. The water may have pushed 'old' air from out of pockets particularly from within the shaft. Sewerage and rotting materials over the years may have taken their toll, using up oxygen and increasing CO2 levels during their breakdown.
Carbon dioxide is abundant in limestone rock, sometimes the rock can reach a purity of up to 98% calcium carbonate, giving a carbon dioxide content of 44%! Carbon dioxide is extremely soluble in water, forming carbonic acid (CO2 + H2O = H2CO3). Calcium carbonate when either heated or treated with an acid gives off carbon dioxide; CaCO3 = CaO + CO2
Some of the old miners we have talked to remember 'bad air' in the mine particularly in the Sling Mine area. Since the shafts have been filled, the problem would not have improved. Recently John Pit on the Sling gale was infilled making matters considerably worse as this shaft was draughting towards New Dun and providing some ventilation to the pit bottom area.
Jonathan Wright
June 91.
Caves & Caving - Update by Forest of Dean Regional Correspondant Paul Taylor
The situation appears to be at an almost stalemate situtation. Although the local council have issued an enforcement order (120 days to comply) the site owners have now changed the name of the company and installed a new set of directors, this being a possible way around picking up the bill for the removal of the infill/pollution.
A company has been employed, we are informed, to carry out tests and prepare a report on what is going to be required to empty the shaft.
With Greenpeace now involved and their own report indicating the inclusion of PCBs and other similar chemical cocktails, the cost is likely to be very high and not one that the site owners are going to want to pay.
The inference is that even with the shaft emptied, access to the lower reaches of the system is likely to be restricted by the installation of grilles, something that the Forest of Dean seems to be getting over its fair share of.
Caves & Caving - Update by Forest of Dean Regional Correspondant Paul Taylor
For a long time now the general caving fraternity have been unable to gain access to the Old Ham - New Dunn - Old Bow complex of mine passages without being accompanied by a mine deputy.
Even with this person present on the trip, the lower levels of the mines have still been well out of bounds.
This situation was brought to about by the spread of contaminated air within these levels caused by the vast levels of pollutants that over the years have been tipped down the mine shaft from the engineering works around the shaft top.
There has over the last few years been much lobbying and complaining done by various bodies, concerned people and companies. A variety of writs have been issued and numerous plans put forward on how to deal with the problem and clear up the site. Until recently these have involved vast sums of money and a total stalemate position had been reached.
It is pleasing to report that an acceptable, workable and realistically priced plan has been put together and work is now underway on removal of the pollution.
Full details have not as yet been released as to the extent of the work or to what depth they intend to go, however I think it is fair to say that any move is a move in the right direction and I'm pretty sure that those who have been responsible for the pollution in the first place are very unlikely to carry out any similar acts.
Hopes are high within the local caving community that the work will lead to a clearing of the bad air and a subsequent return by cavers to the lower mine levels.
Snippet of Info from the GSS
A borehole has been drilled down into the mine to monitor the atmosphere by the Environment Agency but there is no open access as there are still high levels of CO2 in the lower levels.
It is possible to arrange higher-level trips with leaders from Clearwell Caves and RFDCC
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