_GENERAL DOCUMENTS - C1981017 ‎(251)‎

• Permit No: C1981017
• IBM Index Class Name: GENERAL DOCUMENTS
• Doc Name: Bid Documents ‎(IMP)‎ 1993 Correspondence
• Permit Index Doc Type: General Correspondence
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
He
1313 Sherman St.,Room 215 r ,
Denver,CO 80203
Phone:[phone]
*187b
FAX-[phone]
Roy Romer
DATE: October 4, 1993 Governor
Michael B Long
TO: Tony Waldron, David Berry, and Steve Renner Division Director
FROM: Kent Gorharni;�>
RE: Coal Basin Hydrology Review
I have completed review of the hydrology data collected from the period 1978-1992 at
the Coal Basin Mine, File No. C-81-017. My conclusions are as follows:
Surface Water
High flows exhibit high TSS values as expected; high iron is usually associated with
the high flows due to the presence of sediment.
pH is -good and within the range typically found in the Colorado Coal provinces
(6.9-8.5) .
Temperatures indicate ground water discharge as the major contributor of flow during
low flow periods and this water source is very near the mine area.
Electrical conductivity averages 600 umhos/cm.
TDS averages 401 mg/l. Unaffected Bear Creek TDS averages 248 mg/l.
TDS/EC ratio averages .66 which is normal. Sulphate is in the 100-200 mg/1 range
generally.
Iron is not usually high but does show some variability.
Overall, surface water quality is very good and mining appears to have a minimal
affect on the surface system with regard to chemical quality. My understanding is
that total suspended solids are an issue downstream. From my review, it does appear
curious that outfall 016 is having so many problems and exceedances of TSS
limitations. However, without a detailed surface water review, I cannot make any
conclusions with regard to TSS.
Downstream site #20 on Coal Creek shows no impact approaching material damage for
those parameters tested.
Groundwater
Groundwater is monitored mainly in conjunction with the many refuse piles at the
site due to the lack of use of bedrock aquifers in the mine plan and adjacent area.
As expected, the quality is generally worse than the surface water quality.
Temperature is a consistent 47°F, +/- 20F on average.
Electrical conductivity averages 1216 umhos/cm.
TDS averages 864 mg/l. TDS/EC ratio is .71.
Iron and manganese showed no consistent trend.
One concern would be the depth of water with regard to the refuse piles. If the
piezometric surface is above the base of any of the waste piles this could cause
instability and the slide potential rises dramatically. My understanding is that a
consultant is looking into this issue at the present time.
No impact to the groundwater system is evident at the present time.