LW 104 Methane HPI’s. 9 of the 14 logically are from Floor Seam Methane Emissions.

The Grosvenor Mine have identified inbye 20c/t as the zone of greatest risk for floor seam inrushes/emissions of Methane in the LW 104 Second Workings SOP provided to the RSHQ Inspectorate.

Analysis of the data for the LW 104 Methane HPI’s suggest that there are Two distinct sources/types of Methane HPI’s.

I suggest that there are 9 from the floor and 5 from the goaf.

In plain language it means that the undrained floor seams are certainly almost continuously elevating the Methane concentration on the Longwall Face and are directly responsible for two thirds of the Methane HPI’s in LW104.

Or put another way, the decision of Anglo Grosvenor Management not to drain the floor seams and the Mines Inspectors just allowing Mining to commence without draining the methane from the floor ; led to a 300% increase on the number of Methane HPI’s that would have occurred.

LFI IN.00224943 Ignition of Gas LW104 6th May 2020, has the comments and table below.

No pre-drainage of the GM Lower (GML) seam was conducted for LW104. As outlined in the second workings risk assessment and SOP, the GML seam was expected to release gas to the working section in the GL seam between chainage 4000m and chainage 2000m in LW104 (MG104 20-36c/t) due to the reservoir combined with the thickness of the interburden (between the GML and GM seams) as experienced in prior longwall panels and gateroad development

PLEASE NOTE 21/04/2020. 5% Explosive at the 243 Sensor of the Tailgate Chock #149 Canopy

Since commencing production in LW104, 14 events of methane detected > 2.5% have occurred, which have been reported through to the DNRME

THERE ARE TWO DISTINCT TYPES OF EVENTS. My analysis suggests that there are 9 from the floor and 5 from the goaf

THE NINE IN RED COMING FROM FACE or FLOOR.

The S243 Sensor in the Tailgate does read anywhere near as high as the Inbye Sensor.

That means that the source of the additional methane is not from the Goaf as it would have to migrate past the sensor before reaching the Inbye Sensor.

Logically that means that the source of methane is from the face, not the goaf.

One thing we do know is that methane gas from floor seams continues up until the day of the Methane Ignition on the Longwall Face, or as injured Mineworker Wayne Sellars put it 

Q During the life of longwall 104, do you recall instances of methane essentially coming up through the floor of the longwall?

A. Yes.

Q Do you recall whether that was something that happened all the way through from 9 March onwards or did it start to 28 happen towards 6 May?

A It had been there for a while, actually, yes.  I can’t recall if it was right at the very start, but, yes, we had methane coming through the floor, bubbling through the floor, for quite some time, yes.

THOSE IN BLUE COMING AT TAILGATE END OF ROADWAY FROM GAS MIGRATION FROM GOAF. The 400m and Outbye Sensor quantities at no stage go near 2%.