2006-04-19_REPORT - M1977004

• Permit No: M1977004
• IBM Index Class Name: Report
• Doc Date: 4/19/2006
• Doc Name: Annual Fee/Report/Map
• From: Homestake Mining Company
• To: DMG
• Permit Index Doc Type: Annual Fee / Report
• Media Type: D
• Archive: No

Pitch Reclamation Project April 1a, 20U6
2005 Annual RectamaUon Report Pago 8
• 4.3 Pinnacle Mine Workings Monitoring
A concrete plug was constructed in the Pinnacle Add in September 1995. Authorization for the
placement of the Pinnacle Adil plug was requested by Homestake in April 1995, through Technical
Revision #4 (TR4) -Pinnacle Adif Closure, Pitch Project, Technical Revision for Pemtif #77~4NR
(Golder Associates, Inc, ). Conditional approval of the Technical Revision request was granted by
the Colorado -Division of Minerals and Geology in a teller dated May 26, 1995.
The intention of the plug was to partially seal the Pinnacle Adit and allow the area around the mine
workings to resalurate. The resaturation of the workings was predicted to re-establish a
geochemically reducing environment and lower the solubility of uranium and radium within the
underground workings of the Pinnacle Mine. DMG's approval of TR4 required Homestake to
monitor the effects of resaturation in the Pinnacle workings For five years or until hydrologic
conditions stabilized. Components in the Monitoring Plan outlined In TR4 (Section 4.0). included
continuation of discharge water quality monitoring al the POC (SW•33), monitoring of groundwater
resaturation levels, annual spring and seep surveys in areas down-gradient from Pinnacle workings,
and monitoring For changes in water quality that could be attributable to resaturation. The stated
purpose of the monitoring program was to verify the intended effectiveness of the adit plug.
Homestake has continued to monitor the following facets of resaturation through 2005:
• Survey of springs and seeps,
• Groundwater levels in piezometers installed in the area of the Pinnacle workings.
• Water quality and flow from the Pinnacle Adit at sampling point PP•01, and
• Monitor discharges from the property at the Point-of-Compliance SW-33.
In 2006, HMC wdl continue to monitor the resaturation of the south wall of the North Pit as done in
2005.
4.3.1 Spring and Seep Monitoring
Spring and seep surveys were conducted to monitor changes in shallow groundwater conditions due
to construction of the Pinnacle Adit plug. These surveys have been conducted annually since July
1995 and were repeated in 2005. In general, flow from some springs and seeps increased for a
beef period after the adit plug installation and have declined to a steady state since the spring of
1997. Small variances. noted since 1997, are believed to be attributable to conditions including
precipitation, depth of snow pack, timing of snowmelt, and the potential for infiltration with respect to
frozen ground. All "active" spring and seep locations are presented in Figure 3. Locations of
springs and seeps currently designated as "inactive" (not observed over the past five years) have
been removed from Figure 3. Locations of inactive springs and seeps can be found on maps issued
with past reports. An eleven-year cumulative summary of the all spring and seep surveys including
flow measurement results is provided as Table 2.
4.3.2 Groundwater Levels
Seven piezometers were installed in the area of the Pinnacle Mine to monitor the piezometic
surface within the workings area behind the adit plug. The piezometers are identi5ed as P4 through
f' 10 Piezometer P7 was installed as a replacement for P6, which was lost during plug
yroulinglconstruction. The locations of these piezometers are provided in Figure 3. All seven
i;~r..~ometers fluctuate seasonally with the highest levels in late May or early June. The water levels
are sympathetic with snowmelt and large precipitation events and decrease to stable levels after