GENERAL52334

• Permit No: C1981041
• IBM Index Class Name: General Documents
• Doc Date: 9/12/1997
• Doc Name: REFUSE DISPOSAL PILE PIEZOMETER #307
• From: DMG
• To: DAN MATHEWS
• Permit Index Doc Type: GENERAL CORRESPONDENCE
• Media Type: D
• Archive: No

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STATE OF CO~UKADO
DIVISION OF MINERALS AND GEOLOGY
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I f l 1 Shuman SL, Room '_ 1 5
Denver, Columdu 8U!0 4
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FAX IP1418L'~81111~
DEPARTMENT OF
NATURAL
RESOURCES
DATE: September 12, 1997 ~~ Roy Romer
' '~~ Governor
lames 5. lrKhhead
TO: Dan Mathews // Ereiunve Direciur
~_ Michael B Lonti
FROM• Jim Pendleton Di,nsinn Director
RE: Roadside ne - Re se Disposal Pile - Piezometer #307
(Permit No: C-81-041)
I have reviewed the information which you sent via facsimile to my attention. I understand your
concern regards the status of piezometer #307, installed on the second bench of the refuse
disposal pile at the Roadside mine. It is my understanding Larry Reschke informed you, during
your recent inspection of the pile, that this piezometer has been unusable (incapable of entry with
the m-scope water table depth probe) for the majority of its life. You have requested my opinion
whether this piezometer needs to be replaced by the operator.
In 1994, a series of thirty piezometers were required to be installed within the refuse pile after
seeps had developed above the second facial bench. The Division wanted the operator to
determine whether this seep was the expression of a perched seep along the surface of the bench,
or rather an indication that the entire pile was saturated to that elevation. The assemblage of
piezometers have satisfactorily demonstrated to the Division that the seep was an expression of
a perched water bearing lens within the pile, probably resulting from the high compaction of a
surface exposed to truck fire traffic for an extended period of time. Further, as the pile's
thickness increased and the upslope diversion of surface drainage was improved, the flow from
these seeps diminished. Finally, there has been no evidence of renewed instability of the refuse
saturated by the seepage.
No other of the thirty piezometers has indicated any potential problematic ground water
elevations. Nor has the refuse pile demonstrated any slope stability problems. I do not believe
it would be warranted at this time to require the operator to replace piezometer #307. I
recommend that we require the operator to continue to attempt to monitor piezometer #307. A
changed condition in the future might warrant a more in depth reconsideration of the situation.
cc: Larry Routten
doe: M:\COALUAP\piez307.wp5
JP/JP