yes all of this is correct, the colliery would be idle for numerous reasons. besides the ones stated here, they could be doing maintenance work in the mine, the mine could be shut down for "safety" reasons or violations, miners on strike, hit a fault in the coal and have to expand the mine elsewhere, could have robbed a section and proceeding to a new vein. many factors determined if the colliery was operational or idle. another thing that i can mention here, is that everyone seems to think that the knox mine disaster ended anthracite mining in the northern coal field. the knox mine disaster only flooded 3 collieries all other mines continued working just as they did before. the northern field is seperated in 2 basins, the wyoming and lackawanna. the split being the "moosic saddle" it is an anticline in all veins of coal. so even if the entire wyoming valley flooded not one drop would have reached into the lackawanna basin. what ended deep mining in the northern field was the coal companies greed, if you will. there was supposed to be barrier pillars, 100 foot thick coal pillars left between company mineral rights. well most collieries not only robbed these down to a small percentage, maybe 10 foot thick, some actually bored through them and "stole" coal from another company. we have actually seen this first hand, a coal tunnel driven through an old barrier pillar and workings on the other side from the same mining company! well what happened is one colliery would shut down for one reason or another and the pumps would be shut down. in the 60s, im not sure of the exact date, the state no longer took care of running the mine pumps. so the mine would be allowed to flood. well this water would pour into the neighboring colliery and their pumps would have to work twice as hard as before. making their coal less profitable. they would shut down and the next mine "downstream" would get hit. this continued until the last mine ceased operation in the early 70s. another thing getting back to taking coal from the barrier pillars, alot of people refer to "robbing the pillars" as stealing coal. thats another common misconception in the valley. drawing the pillars, robbing, or retreat mining was and still is common practice in anthracite and bitty mines. what the company does is advance the gangway and chambers 60 feet. of that 60 feet there would be 50 feet of coal then a 10 foot chamber. next another 50 feet of coal then a 10 foot chamber. some mines advanced 70 feet and left a 60 foot pillar. upon reaching the end of their property they would retreat back to the main tunnel, shaft, drift or slope, removing up to 75% of that coal they left on the advancement. sometimes this brought the pillars to less than 8 feet. this was considered normal practice in mining as the coal companies were not responsible for subsidences on the surface before sometime in the 20s i believe. im not sure of the exact date, i have it written down somewhere. for safety of the miners they would heavily timber the chambers to keep it somewhat safe where they were robbing but remember they got paid by the car load not to put props in so every prop they installed was time wasted loading coal, so thats where your collapses, injuries and deaths came from. sorry if this got off topic, but you know how it goes once you start typing
