REP12275

• Permit No: C1981028
• IBM Index Class Name: Report
• Doc Date: 7/6/2005
• Doc Name: 2004 AHR Review Memo
• From: Tom Kaldenbach
• To: File
• Annual Report Year: 2004
• Permit Index Doc Type: Hydrology Report
• Media Type: D
• Archive: No

MEMO
Date: July 6, 2005 ~j
From: Tom Kaldenbach I 'C
To: File
Permit: C1981028
Type: Hydrology Report 2004
Name: Review Memo
From: DMG
I have reviewed Keenesburg's 2004 annual hydrology report, and have the following
comments.
The report was timely filed and contained the required information. The operator met all
required sampling frequencies and pazameters in 2004. There were no exceedances of
standazds. Keenesburg's CDPS permit was terminated a few years, ago. There were no
surface water discharges from the mine's two ponds in 2004. These ponds have not
discharged for several years. I have verified compliance with the regulations on
protection of hydrologic balance, as explained below.
Ground Water Imaacts
Saturation of mine spoil and ash. The Keenesburg mine pits aze backfilled with coal
combustion ash and mine spoil. Figure 1 shows hydrogeologic conditions for A pit. The
pit backfill material will become saturated with rain and snowmelt that infiltrates
downward from the land surface. Infiltration from the land surface can be expected to
occur at a rate on the order of at least 1 inch per yeaz, based on infiltration rates reported
in a lysimeter study by the U. S. Geological Survey at the Seneca II Mine in Routt
County, Colorado. Infiltration of 1 inch per yeaz, would result in the Keenesburg pits
reaching maximum saturation over a period of a few decades after backfilling is
complete.
Formation of leachate in pit backfill. Meteoric water infiltrating from the land surface
will become mineralized as it migrates through backfill in the pits. The main processes
of leachate formation can be expected to be oxidation, dissolution, and cation exchange.
The resulting leachate will be high in total dissolved solids (TDS), mainly salts of sulfate
and sodium. The leachate will have a high sodium adsorption ratio (SAR).
Hydrocarbon-based contaminants are not produced during the formation of coal spoil
leachate. Metals which occur in trace amounts in the ash and spoil will not be mobilized
due to the near neutral pH of the leachate. This predicted composition of spoil leachate
has been verified from monitoring data from wells SMW-2 and AMW-2.
Seepage of leachate into downgradient aquifers. When the water level (leachate) in the
spoil backfill in A pit exceeds the piezometric elevation of water in the adjacent unmined