2009-02-27_REVISION - C1991078

• Permit No: C1991078
• IBM Index Class Name: REVISION
• Doc Date: 2/27/2009
• Doc Name: Ground Water Points of Compliance
• From: Tom Kaldenbach
• To: Harry Ranney
• Type & Sequence: RN2
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
1313 Sherman St„ Room 215
Denver, Colorado 80203
Phone: [phone]
FAX: [phone]
Memo
D I V I S I ON OF
MINERALS
GEOLOGY
RECLAMATION
MINING-SAFETY
Date: February 7, 2002 Bill Owens
Governor
To: Harr Ranne
y y Greg tiWatcher
Executve Director

Michael B. Long
From: Tom Kaldenbach Division Director
Re: Hamilton Mine (Permit C-91-078)
Ground Water Points of Compliance
My conclusions below are based on my previous hydrologic analysis of the Hamilton Mine
completed for TR-7. That analysis included a hydrogeologic cross-section and calculation of the
resaturation time of Hamilton's backfill.
Bedrock stratigraphic units
The dry climate (12 inches annual precipitation) and the relatively small land area above
Hamilton's backfilled pit (59 acres), indicates a leachate plume will not form down-gradient
from the pit until several decades after the bond liability period. The improbability of a plume
forming until then indicates a bedrock ground water point of compliance is unwarranted for the
Hamilton Mine. Although a point of compliance is unwarranted, well BW-2 meets the
requirements of a ground water point of compliance at the Hamilton Mine. Designation of BW-2
as a compliance point at this time would be preliminary because DMG has not yet finalized its
guidelines for establishing ground water points of compliance. Well 13W-2 is located
downgradient from Hamilton's backfilled pit, and is close enough to the pit to intercept leachate
should it discharge from the pit during the bond liability period. No other bedrock unit warrants a
ground water point of compliance because no other units are in hydraulic communication with
the pit.
Alluvial stratigraphic units
Naturita Creek alluvium is located a few thousand feet downstream from the Hamilton Mine.
Should a spoil spring form at Hamilton Mine, it would discharge to an ephemeral drainage that
flows to Naturita Creek. The review completed for TR-7 predicted an 11-gpm spoil spring to
form several decades in the future. Disregarding evaporation en route, an 11-gpm spoil spring
would possibly increase the TDS in Naturita Creek surface water by 22 mg/1 at low flow, raising
it from 1700 mg/1 to 1722 mg/1. The small magnitude of this impact, and its projected
occurrence in the distant future, do not warrant establishment of an alluvial ground water point of
compliance for Hamilton.
cc: Dan Hernandez