GENERAL49968

• Permit No: C1981019
• IBM Index Class Name: General Documents
• Doc Date: 8/23/2005
• Doc Name: Lower Wilson Project Investigation
• From: Dan Mathews
• To: Jim Stark
• Permit Index Doc Type: General Correspondence
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
1313 Sherman 5[., Room 215
Denver, Colorado 80203
Phone: [phone]
FAX: [phone]
DATE:
TO:
FROM:
RE:
Backoround
August 23, 2005
Jim Stark
Dan Mathews
Wilson Creek Alluvial Valley Floor Investigation
COLORADO
DIVISION O F
MINSRAL5
GEOLOGY
REC LAN ATION•MININO
SAf ETT•SCIENCE
Bill Owens
Governor
Russell George
Executive DIreQOr
Ronald W. Cattany
Division Director
Natural Resou¢e Trustee
I have reviewed the letter and map prepared by Edward Baltzer of Walsh Environmental (Walsh),
dated August 16, 2005 and titled Alluvial Valley Floor Determination, Lower Wilson Mining Area
Expansion Project. The map provided depicts the segment of Wilson Creek extending from
upstream of the Lower Wilson Mine Project Access Road downstream to the northern boundary
of the proposed expansion area, immediately upstream of the Gossard loadout. On the map, the
stream valley is divided into three areas. Area 1 is the segment upstream (south) of the mine
project access road, Area 2 is downstream of the mine project access road to the vicinity of the
proposed new Gossard Loadout Haul Road, and Area 3 is the stream valley in the vicinity of the
Gossard Loadout Haul road.
The letter notes that Area 1 is upstream of the area of potential impact, being hydrologically up-
gradient of proposed disturbance. Area 2 is the segment described as deeply entrenched by the
highly erosive mass wasting event in 1985. The letter indicates that channel incision effectively
drained the alluvial aquifer within Area 2, to a depth of approximately 50 feet. This
characterization of Area 2 is consistent with the observations made on our recent field trips to the
site. Two alluvial wells were referenced as providing data showing the alluvial water level in this
segment. Area 3 is downstream of the entrenched segment, and will be affected by construction
of the gravel haulroad to connect the county road with the Gossard Loadout. The letter indicates
that impacts associated with road construction and use will be minor and temporary, and will be
fully reclaimed. Potential water quality impacts will be minimized by stormwater ponds and
alluvial groundwater will be monitored.
The letter closed with the following request.
Please let Walsh know if the above presented information is sufficient to drop the AVF
status for Area 2 as shown on the attached figure. Also, please provide comments on the
adequacy of the presented information for use in the permit revision.
Preliminary Assessment
I believe it is likely that Area 2 no longer meets the AVF criteria. I also believe it is likely that we
will be able to approve the proposed disturbance within Area 3, on the basis that farming will not
be interrupted or precluded, and reclamation will restore the essential hydrologic functions.
However, in order for us to confirm these assumptions, and make the necessary findings, the
necessary supporting documentation will need to be provided in conformance with Section 2.06.8
of the regulations. Currently approved permit narrative and maps will need to be updated as
appropriate, in association with the proposed South Wilson Project revision and the associated
Wilson Creek alluvial valley floor investigation.
Office of Office of Colorado
Mined Land Reclamation Active and InaRive Mines Geological Survey