To all it may concern,
The watercourse that used to flow through this culvert has now been diverted, leaving the tunnel in a somewhat disused state. Upon entering via the outfall, me Yaz and Toothdoctor discovered that the lowered water level has now left the previously-submerged coal deposits on the floor of the drain exposed. As a result, oxygen levels in the tunnel have now dropped.
In the first 50-80m heading upstream in the concrete section from the outfall we had no problems, but the next 40-50m leading to the junction room saw the oxygen levels rapidly drop from 20.9% down to 17.9%, at which point we aborted exploration.
It is worth noting that the drop in oxygen happened very consistently as we moved slowly through the tunnel right up to the point we turned round, suggesting that the air may well reach lethal levels only a small distance further into the culvert. In addition, there now appears to be absolutely no air flow in the tunnel whatsoever so the situation is likely to get even worse over time. I suspect the lack of ventilation may be due to the infall being sealed but we didn't have enough time to go and check.
In addition, as with coal mines, the quality of the air could well depend on many other factors such as the atmospheric pressure from day to day and the time of year.
For identification purposes, the culvert has a very distinctive 7-8ft parabolic concrete shape at it's downstream end
And a decaying 6-7ft brick arch shape at it's upstream end (which may or may not now be sealed)
(Picture by JonDoe)
A sad farewell to one of my all-time favourite drains
The watercourse that used to flow through this culvert has now been diverted, leaving the tunnel in a somewhat disused state. Upon entering via the outfall, me Yaz and Toothdoctor discovered that the lowered water level has now left the previously-submerged coal deposits on the floor of the drain exposed. As a result, oxygen levels in the tunnel have now dropped.
In the first 50-80m heading upstream in the concrete section from the outfall we had no problems, but the next 40-50m leading to the junction room saw the oxygen levels rapidly drop from 20.9% down to 17.9%, at which point we aborted exploration.
It is worth noting that the drop in oxygen happened very consistently as we moved slowly through the tunnel right up to the point we turned round, suggesting that the air may well reach lethal levels only a small distance further into the culvert. In addition, there now appears to be absolutely no air flow in the tunnel whatsoever so the situation is likely to get even worse over time. I suspect the lack of ventilation may be due to the infall being sealed but we didn't have enough time to go and check.
In addition, as with coal mines, the quality of the air could well depend on many other factors such as the atmospheric pressure from day to day and the time of year.
For identification purposes, the culvert has a very distinctive 7-8ft parabolic concrete shape at it's downstream end
And a decaying 6-7ft brick arch shape at it's upstream end (which may or may not now be sealed)
(Picture by JonDoe)
A sad farewell to one of my all-time favourite drains
