THE manager of the Gleision Colliery at the time four men died had been warned there was water behind a wall he would later break through.
Malcolm Fyfield took over as manager from Ray Thomas in July 2011.
Mr Thomas told the jury he had warned Fyfield about flooding in the mine and the location of underground water.
He had been manager at the mine between 1998 and 2005 and in 2008 before taking over as interim manager in 2011.
On three days before taking over, Mr Thomas said Fyfield visited the mine to “get a feel” for it. During those visits he says the pair went through mine plans and went into the mine together.
Mr Thomas told the jury he explained to Fyfield there had been problems with water flooding the mine and explained measures that were in place to ease the problem.
At the time of the tragedy in September 2011, the men who died were working in an area – or stall – off the H1 roadway.
Mr Thomas said his plan had been to continue driving along H1 until he met up with “Old South East” workings.
That plan would have allowed access to more coal and better ventilation.
Mr Thomas said that during the meeting with Fyfield: “We went through the plans and I explained about the water trouble we were having and that we had to push that H1 through to our old workings. That was a priority."
By the time of the accident, Fyfield had changed the direction the men were working towards a different set of old workings known as the “Old Central” Workings.
Those workings have a buffer around them, marked on maps by a green hatched zone.
The prosecution have called that a cautionary zone and that any work in that area needs special measures in place but Fyfield had not done that before he joined a new stall into old workings on September 15, 2011.
When that happened, 650,000 gallons of water rushed into the area where the men were working.
But Mr Thomas said that in their meeting he had told Fyfield that the cautionary zone around the Old Central working was full of water.
He told the jury: "The cautionary zone was holding the water back".
He said the water which had been affecting his workers during his time as manager was the “overflow” from the full old workings.
During cross-examination, Elwyn Evans QC asked Mr Thomas about examples shown on a mine plan where he had worked in the green hatched area during his time as manager.
She then asked: "You didn't see anything wrong with that, did you?
Mr Thomas replied: "Yes, we did. We mis-measured. There was no danger to going into it".
She asked: "It would be alright if there was no danger?"
"No, it wouldn't,” he replied.
She then asked: "So why did you do it?"
"I told you, it was a mis-measurement,” he replied.
Fyfield, aged 58, from Caerhenllys in Cwmllynfell, took over as manager in July 2011, denies four charges of manslaughter by gross negligence.
MNS Limited took over ownership of the mine in September 2009. They are represented in court by directors Gerald Ward and Maria Seage and deny four charges of corporate manslaughter.
The trial continues.