PERMFILE52747

• Permit No: M2005065
• IBM Index Class Name: Permit File
• Doc Date: 12/22/2005
• Doc Name: Second Adequacy - Upper Animas Sand and Gravel
• From: DMG
• To: Charles Ponchak
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
1313 Sherman $t., Room 215
Denver, Colorado 80203
Phone: [phone]
FAX: [phone]
COLORADO
DIVISION OF
M[N &RALS
GEOLOGY
RECLAMATION•MIN ING
SAFETT~SCIEN CE
Bill Owens
Governor
INTEROFFICE MEMORANDUM
Russell George
Executive Director
December 21, 2005 Ronald W. Cottony
Division Director
To: Wally Erickson Natural Resource Trustee
f=rom: Harry Posey
HE: Potential for release of acid-toxic substances from proposed gravel operation, Ja ck Clark Jr.; Upper
Animas Sand and Gravel Pit; San Juan County; M-2005-065.
The proposed gravel pit area may be a site of tailings deposition from the upstream Eureka mining district. The
following comments presume, for discussion sake, that tailings do indeed exist in the target area, and presumes
that such tailings have the potential to generate acid and release metals, much like the pre-law tailings at
fiowardsville Mill area and elsewhere in the upper Animas basin.
Tailings residing above the water table are most susceptible to acid generation (and metals release) because
oxygen is readily available. Periodic wetting and drying generates acid in sulfidic tails. In turn, the acid dissolves
local minerals and may evaporate to form soluble metals salts, which are released quickly when re-saturated by
rain or snowmelt.
Tailings stored below the low water level can contact only the oxygen that is dissolved in the ground water, an
amount that is miniscule relative to oxygen in air. Hence, the generation and release of sulfuric acid and dissolved
metal from the weathering of sulfide minerals in saturated tailings would be trivial, and environmentally benign.
The amount of soluble salts released from a single locale -from tailings in the proposed gravel pit area, for
instance -can be compared with salts from those same tailings spread regionally (on roads for instance). Metal
salts released from road beds during rain or snowmelt would be diluted broadly whereas those released from a
single site would be more concentrated in metals and acid and therefore more problematic to aquatic life.
I find no compelling reason to conduct studies to determine the abundance or manner of occurrence of tailings in
the proposed gravel pit. There is little evidence supporting the notion that mining a sulfide tailings-bearing gravel,
which admittedly would generate acid and could release dissolved metals, would cause problems worse than those
already potentially caused at the site (if tailings are indeed present). Moreover, assuming tailings are present, it
would be more environmentally beneficial to spread out those tailings regionally, as on roadbeds, and take
advantage of the dilution that would follow from the more regional rather than local distribution.
Considering only the acid-generating and metals release potential of mining the gravel vs leaving it in place, I find
no convincing reason to deny the proposed operation. Other issues, however, must be considered separately.
cc: Bruce Humphries
Office of Office of Colorado
Mined Land Reclamation Ac[ive and Inactive Mines Geoloeical Survev