UNITED STATES ENVIRONMENTAL PROTECTION AGENCY - REGION IX
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September 2006 Newsletter / Fact Sheet
September 7, 2006 Presentation to Lyon County Commission (Use Your Browser "BACK" Button to Return)
The schedule on Slide 17 is preliminary and will most likely change in regards to prioritizations. This presentation takes a moment to load and requires MS PowerPoint to view.
EPA COMPLETES CAPPING DUST SOURCES - EARLY!
Mason Valley residents have long been concerned about fugitive mine site dust and its potential contents, especially on windy days when dust particulates can be easily spotted as they blow in clouds across the valley floor. Tom Dunkelman, EPA Region IX's Emergency Response Manager Yerington Mine, announced on Monday, May 8, 2006, that the dust mitigation projects which began on April 5th have been completed.
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(Photos courtesy of Tom Dunkelman, EPA's Onsite Emergency Response Coordinator. Posted May 6, 2006)
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(Old transformers containing illegal limits of PCBs were removed from the minesite in April, 2005. Photos provided by Tom Dunkelman, EPA's Onsite Emergency Response Coordinator, May 6, 2006)
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(The results of high winds blowing across the mine site are readily apparent. Dust particles have been pushed beyond the site boundaries and into the Mason Valley in the past. Note snow covering portions of the Singatse Mountains in the background and tailings on the mine site. Photos provided by Tom Dunkelman, EPA's Onsite Emergency Response Coordinator, May 6, 2006)
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disrepair due to years of neglect. This Megapond liner was designed to keep contaminants from leaching into the soils and groundwater below the site. EPA is examining this and other ponds to determine how to best provide temporary and effective repairs until site remediation and cleanup is completed. (Photo provided by Tom Dunkelman, EPA's Onsite Emergency Response Coordinator, May 6, 2006)
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Many of the
minsite components have fallen into
Scanner Van Results, April 2005
EPA Radiation and Indoor Environments National Laboratory Scanner Van Survey of the Yerington Mine Site and Surrounding Areas
Yerington, Nevada
April 18 - 26, 2005
Table of Contents
Page
Introduction..........................................................................................................1
Scan
Methodology................................................................................................1
Results..................................................................................................................1
Summary..............................................................................................................4
References...........................................................................................................5
Figures
Fig. 1A Yerington, Nevada
Fig. 1B Mine Processing Area
Fig. 1C Evaporation Basins
Fig. 1D W3 Waste Rock and Slot Heap Leach Pad Area
Fig. 2 MacArthur Pit Haul Road
Fig. 3 MacArthur Pit
Fig. 4 Wabuska, Nevada
Fig. 5 Yerington Paiute Reservation
Fig. 6 Mesa and the Sunset Hills Drive Area
Fig. 7 Penrose Area
Fig. 8 Luzier Road and Valley View Estates
Fig. 9 Weed Heights and Access Roads
Fig. 10 Mason Valley South of Yerington
Fig. 11 Yerington, Nevada
Fig. 12 Schurz, Nevada
Fig. 13 Southeast of Schurz, Nevada
Introduction
At the request of EPA Region 9 a scan of the Yerington Mine Site and surrounding
areas was performed with the Radiation and Indoor Environments (R&IE) National
Laboratory’s Scanner Van to locate and assess anomalously high gamma-ray
emitting sources. The scan took place in late April of 2005. Compilations of the
map data and a discussion of the findings are presented in this report.
Scan Methodology
Gamma-ray surveys conducted with the R&IE Scanner Van are used for the
identification of areas of elevated gamma-ray radioactivity relative to the
surrounding environment. Information about the Scanner Van principals and
operations can be found in the Yerington Mine Project Quality Assurance Project
Plan and the Sampling and Analysis Plan (Ref. 1 and 2). Scans are performed with
a sodium iodide scintillation detector that is shielded so that the field of
view is limited to the right side of the van. Live time data in the form of
gamma-ray interactions with the detector in units of counts per second (cps) are
superimposed on ariel photographs of the scan area as the van moves. The data is
recorded electronically for later processing. In some instances handheld Ludlum
microR meters are used at site locations to obtain exposure rates.
Results
A baseline activity (also referred to as the “background” in this survey) was
selected after evaluating collecting ambient levels at several locations
believed to be free of anomalous gamma-emitting sources. Based on the range of
levels seen a count rate of 264 cps was chosen. This baseline was compared daily
to data collected during quality control checks in the town of Yerington and
found to be comparable in magnitude. Additionally, preliminary scans showed that
count rates in areas where sediments associated with the Walker River are
predominant were somewhat lower than in the surrounding environments. Because
the selected baseline was representative of these low-background areas it was
decided that it would be used for all scans as an added precautionary measure.
The continuous count rate data are shown in this report as colors which
represent incremental
count rates. Successive count rate
ranges of seven standard deviations (17 cps each) above the baseline are
represented by colors green (baseline and below to 383 cps), yellow (383 to 502
cps), red (502 to 621), and on where applicable, magenta (621 to 740 cps) and
purple (740 cps and above). It should be kept in mind, however, that the data is
stored numerically and the color representations are intended only to show only
relative differences. The data are to be interpreted as screening information
only. Experience in the interpretation of scanner van data has indicated that
activities several times baseline are of concern, however, for this purposes of
this study consistent readings above the threshold of the yellow limit were
noted and investigated throughout the scans as described below.
The Yerington Mine Site
Continuous count rates above 502 cpm were first encountered in the lower
processing unit immediately north of the iron precipitate launder unit (Fig.1A,
1). The activity appeared to be related to soils in the basin and berms of the
area and may have been deposited as residual sediments in impoundments. Further
scans of the processing and facility areas showed the highest readings of the
study north and south of the iron precipitate launder unit (Fig.1A, 2). The
strongest activity was found on the south side of the unit and had been
previously designated as a radioactive area. Scanner van count rates exceeded
7500 cps and the gamma radioactivity appeared to be associated with metal piping
and other debris. A microR reading on one piece of pipe at the location exceeded
5 mR/hr on contact.
The acid solution storage tank area (Fig.1A, 3) south of the launder unit had
highly localized areas that exceeded 2700 cps. The activity appeared to be
associated with debris and single point sources on the ground that may be
indicative of buried materials or pipe scale. MicroR readings at these locations
varied from 1 mR/hr to 3 mR/hr on contact.
The road scan north of the FX Pad along the oxide tailings pile (Fig.1B, 1)
showed multiple locations with readings greater than 502 cps east of the road.
This is due to the effect of the mass of material and close proximity of the
tailings pile to the right side of the van (and the detector) on the return scan
while moving south.
The road northwest through the evaporation basins showed readings as high as
1000 cps even though the road was elevated above the floor of the basins
partially obscuring the line of sight for the scanner van’s detector. The
activity was recorded on both sides of the road (Fig. 1C, 1) and appeared to be
associated with a fine red deposit. A cursory scan of the capped portion of the
sulfide tailings in the northeast portion of the mine site (Fig.1C, 2) showed
readings in the 383 to 502 cps range but no higher. Many of the readings were
associated with small pits that had been dug into the sulfide tailing cover
material to look for clay deposits.
A scan of the W-3 Waste Rock and Slot Heap Leach Pad area of the site was
conducted in a clockwise direction to observe activity from the waste piles.
Readings in the 502 to 740 cps range were observed adjacent to the main mine
access road (Fig.1D, 1) where the right side of
the van passed closely to the road cut
on the side of the hill. Readings above 383 cps were observed at other similar
portions of the road.
MacArthur Pit and Haul Road
The east side of the MacArthur Pit haul road was scanned (Fig.2). Activities in
the 383 to 502 range were detected where the van past closely to material on the
road side. A return scan (west side) was not conducted due to the condition of
the road. The MacArthur Pit itself (Fig. 3) also showed some areas with readings
of 383 to 502 cps where the van passed closely to the pit walls.
The Wabuska Rail Spur
The Wabuska rail spur, which lies approximately 10 miles north of Yerington on
Highway 95A and was used to transport product and other materials to and from
the mine, was scanned as completely as the existing roads would allow (Fig.4).
No notable activities were detected.
The Yerington Paiute Indian Reservation
A scan of the accessible roads of the Yerington Paiute Indian Reservation was
conducted (Fig.5). No activities exceeding 383 cps were detected in the rural or
suburban locations.
Mesa and the Sunset Hills Drive Area
Accessible roads in the Mesa and Sunset Hills Drive area were scanned (Fig.6).
Some areas of activity in the 383 to 502 cps were found on the western portion
and were consistently associated with the rock of the rising hillside. One other
location had readings in that range that were associated with some granitic
decorative rock in front of a residence and adjacent to the roadway.
The Penrose Development Area
All roadways in the Penrose community were scanned as was Scarsdale Drive to its
south (Fig.7). No notable activities were found.
Luzier Road and Valley View Estates to the West
Luzier Road west from Highway 95 and roadways northwest of the mine site (Pine
Street, Locust Drive, Mason Pass Road, and others) were scanned. Several areas
on the far western side showed activities greater than 383 cps that were
associated with the exposed rock of the hillside. Readings taken in the area
northeast of the intersection of Luzier and Mason (Fig.8, 1) registered
approximately 25 R/hr at a one meter height apparently due to fill material
used for the road. The scanner van recorded readings in the 383 to 502 cps range
at the location. At the request of a resident, a cursory walkover of a property
on Juniper Court showed microR readings of between 15 and 20 R/hr at a one
meter height.
Weed Heights and Access Roads
The community of Weed Heights was scanned with no notable readings. The access
roads were also scanned. Boatwright Lane (to the southeast) showed readings in
the 383 to 502 range on both sides of the road, and readings as high as 600 cps
were detected on Burch Drive (to the northeast) due to the proximity of exposed
rock to the side of the van (Fig.9, 1). The later were taken near the same
location where high rates where found during the east processing area scan
(Fig.1D, 1).
Locations in Mason Valley South of Yerington
Several roads south of Yerington were scanned, including Cremetti Lane and
Pursel Lane east
of Route 208, Osborne Lane and Osborne Drive east of Route 208, Snyder Lane east
of
Highway 339, Rebecca Road and Zachary Road west of Highway 339, Hot Plant Road
and Sheltered Hills Drive west of Highway 339, and Fourth Avenue and Bluestone
Avenue in the town of Mason, Nevada. The only notable count rates (383 to 502
cps) were encountered on Cremetti Lane where road cuts were in close proximity
to the side of the van (Fig.10, 1).
Yerington, Nevada and Adjacent Roadways
Sections of the town of Yerington were scanned as time allowed, as were Highway
95A to the junction of Highway 339 and Highway 339 south to West Bridge Street
(Fig.11). A gravel lot in the rest area on the east side of Highway 339 showed
rates of 383 to 502 cps. MicroR readings in the area taken at a one meter height
were approximately 25 R/hr and may have been due to fill material used for the
lot. A gravel lot adjacent to a softball field and Highway 95A in the northeast
corner of town showed count rates of 383 to 502 cps and microR readings of about
20 to 25 R/hr. A decorative granitic rock display showed a slightly elevated
reading in the 383 to 502 cps range when the van was in close proximity. Some
other readings in the same range were detected when the van past closely to
block walls in some alleyways.
Schurz, Nevada and Roadways to the Southeast
The town of Schurz and the rural roads to the southeast of town on the Walker
River Paiute Indian Reservation were scanned (Fig.12 and Fig.13). The parking
lot of the combined school on highway was also scanned. Some elevated readings
in the range of 383 to 502 cps were encountered toward the south of town near
Highway 95A and were associated with rocks from the adjoining mountainside. No
other notable rates were detected.
Summary
This gamma-ray scan of the Yerington area indicates that sources significantly
higher than the ambient background of the surrounding areas lie on the mine site
in the processing areas (with activities exceeding 5mR/hr on contact) and the
old evaporation basin area on the northeast side of the site. The scanner van
detected no anomalously high locations at any of the surrounding areas. In
general, the lowest readings were found in areas associated with Walker River
sediments, such as in the Town of Yerington and the central Mason Valley, and
slightly higher readings were recorded in areas approaching the surrounding
mountainsides probably due to the presence of naturally occurring radioactive
materials in outcrops or roadcuts. This also appeared to be the case in the town
of Schurz on the Walker River Paiute Indian Reservation where slightly higher
readings were encountered on the southern parts of town where granitic rocks
were observed.
It is important to note that this scan does not represent a comprehensive survey
of the areas in question. The Scanner Van is limited by access and the results
indicate only the relative presence or absence of gamma-ray emitting sources.
Other radioactive sources (sources that do not emit gamma-rays) and
non-radioactive pollutants are not addressed in this study.
References
1. Quality Assurance Project Plan, Scanner Van Survey, Yerington Mine Site and
Surrounding Areas, Yerington, Nevada, April, 2005. Submitted to EPA Region 9
April, 2005.
2. Scanner Van Survey of Yerington Mine Site and Surrounding Areas of Yerington,
Nevada Sampling and Analysis Plan. Submitted to EPA Region 9 April, 2005.
On June 6, 2005, USEPA held a tour of the mine site for Kevin Kirkeby from U.S. Senator Ensign's office, Susan Lisagore from U.S. Senator Reid's office, and Jodi Stephens from Congressman Gibbons' office. Other attendees included representatives from the Yerington Paiute Tribe, Community Action Group of Yerington, BLM and ARCo. Documents and other handouts which became part of the tour will be included here within the next few days, (June 11, 2005).