Gleision deaths: Miners worked 'near known reservoir'
An investigator at a Swansea Valley pit was "chilled" after seeing a mining plan which suggested colliers worked near a known underground reservoir.
Tony Forster told Swansea Crown Court he was "taken aback" by sketches mapping where the men had excavated coal at the Gleision mine.
Four men died when the mine flooded in September 2011.
Former pit manager Malcolm Fyfield and owners MNS Mining Ltd deny manslaughter charges.
David Powell, 50, Charles Breslin, 62, Philip Hill, 44, and Garry Jenkins, 39, all died in the 100-year-old mine when 650,000 gallons of water gushed into the area they were working.
The miners had blasted into a flooded old section of the mine near Pontardawe causing contaminated water to fill the area they were working in within six seconds.
Mr Fyfield, 58, denies the gross negligence manslaughter of the four men while MNS Mining Ltd, represented by directors Maria Seage and Gerald Ward, deny four counts of corporate manslaughter.
Mr Forster, now chief inspector of mines in New Zealand, said he felt the pressure of being responsible for finding out what happened and described his first trip down the pit as "just awful".
He said the first thing he did on arriving at the pit was to check a map of the Gleision workings.
"The plan was in a pretty poor state, it was wet, damp, people had been using it," he said.
"But that wasn't what registered with me, immediately I recognised a concerted drive in (the direction of the water).
"That immediately chilled me."
Mr Forster said he was conscious of investigations into previous mining tragedies.
'Full of fog'
"I was aware that from previous incidents that when something like this happens the inspector investigating comes under close scrutiny," he said.
"It's a horrible feeling."
Mr Forster was asked by Gregg Taylor QC, prosecuting, about the state of the pit in the aftermath of the tragedy.
He replied that timber supports had been washed out, floor stones had been "propelled" backwards, a steel conveyor belt had jack-knifed and the whole area was covered in silt and debris.
"I went to the very bottom of H1 (the area where the miners were working) and when I got there it was just awful," he said.
"The place was full of fog, it was very misty, there were two big air pumps going which were very loud."
Describing how far he went into the mine, Mr Forster said: "I went as far as I dared to go."
The court has previously heard the 200ft (60m) stretch of mine was full almost immediately after an explosion and water gushed in at a speed of 21mph.
The trial continues.