2017-01-13_REPORT - M1977004

• Permit No: M1977004
• IBM Index Class Name: Report
• Doc Date: 1/13/2017
• Doc Name: Geotechnical Report
• From: Homestake Mining Company
• To: DRMS
• Annual Report Year: 2016
• Email Name: DMC
• Media Type: D
• Archive: No

Homi STAKE
RECEI'V'ED
SAN 13 2017
DIVISION OF RECLAMATION
MININGAND SAFETY
Colorado Department of Natural Resources December 31, 2016
Division of Reclamation, Mining and Safety
Attention: Mineral Division
1313 Sherman Street, Room 215
Denver, CO 80203
RE: HOMESTAKE PITCH RECLAMATION PROJECT
2016 ANNUAL GEOTECHNICAL REPORT (M-1977-0OARV--'
Dear Division;
Attached is the 2016 Annual Geotechnical Report (report) for the waste rock management areas at the
Homestake Pitch Reclamation Project The waste rock management areas include the Indian and the Tie
Camp rock dumps as shown on Figure 1. The history of the rock dumps has been provided in previous
annual reports and is not repeated in this report. The rock dumps were inspected monthly in 2016, except
when winter conditions prohibited access, in accordance with the recommended monitoring program.
The inspections and monitoring conducted in 2016 indicate stable conditions for the Indian and Tie Camp
rock dumps.
The rock dump piezometers are presented on Figure 2 Detailed analysis and presentation of the 2016
data from the Indian and Tie Camp rock dump piezometers are provided in the following pages. In 2016,
shallow piezometers were installed near the toe of the Indian Rock Dump, as highlighted on Figure 3, to
facilitate treatment of uranium as water flows from upgradient areas through an emplaced reactive zone.
These piezometers were approved by the Division of Reclamation, Mining and Safety on May 9, 2016
under Technical Revision #7 -
The water level readings in 2016 are plotted on Figure 4, and a graph with piezometer water levels since
1996 is provided as Figure 5. The Y-axis on these plots is labeled as depth to water from the ground
surface, but note the reverse -order of the axis to more intuitively reflect water level increases and
decreases Two of the piezometers in the Indian Rock Dump were replaced in 2011 after several years of
issues associated with corrosion and silt buildup in the well casing made it difficult to obtain an accurate
reading of the phreatic surface in the rock dump The piezometers are now functioning to provide
accurate water level information The 2016 monthly water level measurements are provided in Table 1 of
the attached report- The piezometer readings in 2016 were indicative of a moderate snow pack when
compared with the 2012 and 2013 readings, but below the snow pack and total annual precipitation in
2014 and 2015. During the monitoring period of November 2015 through October 2016, the onsite
precipitation gage recorded 20 inches of precipitation, compared with 23 and 31 inches during the 2015
and 2014 periods, respectively As reflected on Figure 5, the water levels in the rock dump piezometers
show little fluctuation in the winter months with a temporary rise in response to the spring snow melt or
summer rain events. Water levels usually return to normal levels in mid- to late summer
Please feel free to contact me in the Sargents Colorado office [phone] or via cell phone at (719)
530-1656 if you have any questions.
Sincerely,
Dale Davis 1caA-2�
Pitch Site Manager
cc Holton Bums — Homestake Mining Company -Toronto, Canada
Phillip DeDycker — Arcadis, U S , Inc.
HOMC9TAKE MININD COMPANY OF CALIFORNIA %% PQ Box 4d,
9ARo ENT61, COLORADO 912481
TELE: 19701 641-4541 0 MOBILE: [phone]