In March 1978, water inundated some abandoned sections in the Moss No. 3 Portal A Mine, soon after work began on the creation of a 265 foot single-entry drainway in the coal seam that connected an abandoned area of the mine to the surface.  The drainway was designed to prevent additional flooding by funneling rising waters from the worked-out area into the nearby Fryingpan Creek.

At about 12:30 p.m. on April 4, four men were working to advance the drainway into an abandoned, mined-out area on the left side of the drainway face.  Although the air in the abandoned area was not first tested or analyzed for carbon dioxide after a test borehole penetrated the area.  The continuous mining machine was used to intentionally breach the area with a hole that measured 14 by 20 inches.  Immediately after creation of the hole, the drainway was inundated by blackdamp (oxygen-deficient air).

Two of the four miners who were advancing the drainway when the inundation occurred successfully retreated to the surface (one dragged the other).  However, the other two miners perished.  The blackdamp also killed three other men who went underground without protective equipment or adequate gas testing equipment to search for the missing men.  Similarly unequipped during rescue attempts, two other men were also overcome by blackdamp, but were successfully assisted to the surface.

MSHA investigators identified the following causes of the disaster:

• Failure to consider the possibility that the abandoned 1 Right area of the mine might contain blackdamp.
• Failure to develop and initiate adequate plans to permit penetration of the abandoned area under controlled conditions that would have protected workers from blackdamp hazards.
• Failure to identify contaminants in the air flowing from the abandoned area before intentionally penetrating the area with a continuous mining machine.l
• Failure to comply with the mine's ventilation plan and to adequately ventilate the drainway area.

MSHA investigators also concluded that the accident was compounded by rescue attempts made without protective equipment.

Source:
	Historical Summary of Mine Disasters in the United States - Volume I

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List of those killed in the disaster:

• William Arden, 25, Roof Bolter
• Richard Carson, 29, Superintendent
• Willis D. Ison, 46, MSHA Subdistrict Manager
• Marion Johnson, 34, Maintenance Foreman
• Lawrence Shelby, 56, Equipment Service Manager