PRELIMINARY ASSESSMENT

Bretz Mine Section 3, T41S, R41E, W.M. Malheur County, ECSI # 2493

March 12, 2001

Prepared by: John Dadoly Oregon Department of Environmental Quality Environmental Cleanup Division Pendleton, Oregon 97801 Bretz Mine PA Report March 12, 2001 ECSI # 2493

GENERAL SITE DATA

Site Name and Address: Bretz Mine, Section 3, T41S, R41E, W.M.

Current Owner(s): U.S. Bureau of Land Management

Current Operator(s): John Ruiz, Della Lossing, Sparks, NV

Site Contact(s): David Rosenkrance Civil Engineer BLM Vale District Office 100 Oregon Street Vale, OR 97918

Latitude: 42 deg. 2’ 45.03” N

Longitude: 117 deg. 54’ 3.46” W

Legal Description: Section 3, T41S, R41E, W.M.

Directions to site: County Road 592 west from McDermitt, approximately 10 miles, then north on road up Little Cottonwood Creek approximately 2 miles to Bretz Mine.

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Table of Contents

1. INTRODUCTION 4

2. BACKGROUND 5 2.1 Site Description 5 2.2 Ownership and Operational History 5 2.3 Regulatory History 7

3. WASTE CHARACTERISTICS 7 3.1 Source Areas 7 3.2 Sampling Results 9

4. GROUNDWATER PATHWAY 10 4.1 Hydrogeologic Setting 10 4.2 Groundwater Targets 10 4.3 Groundwater Conclusions 11

5. SURFACE WATER PATHWAY 11 5.1 Hydrologic Setting 11 5.2 Surface Water Targets 11 5.3 Surface Water Pathway Conclusions 12

6. DIRECT CONTACT AND AIR PATHWAY 12 6.1 Physical Conditions 12 6.2 Direct Contact and Air Pathway Targets 12 6.3 Direct Contact and Air Pathway Conclusions 12

7. SUMMARY AND CONCLUSIONS 13

8. REFERENCES 14

APPENDIX A: LABORATORY DATA

APPENDIX B: WELL LOGS

APPENDIX C: CLIMATE DATA

APPENDIX D: SITEINFO REPORT

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1. INTRODUCTION

This report presents the results of a Preliminary Assessment (PA) for the Bretz Mine site located in Malheur County, OR. The PA was conducted by the Site Assessment Program of the Oregon Department of Environmental Quality (DEQ).

A PA is required by Oregon state law where a significant threat to human health or the environment is suspected from a release of hazardous substances (as defined in Oregon Revised Statutes (ORS) Chapter 465.200). Authority for conducting PAs is provided in ORS 465.245 and DEQ regulations, Oregon Administrative Rule (OAR) 340-122-072. This PA was designed to investigate chemical and waste handling practices, and to evaluate potential exposure pathways (surface water, air, groundwater and direct contact) for hazardous chemicals that may have been released to the environment from operations at the Bretz Mine facility.

PAs are intended generally to identify potential hazards at a site, identify sites that require immediate action, and to establish priorities for sites requiring in depth investigations. The PA is not a full investigation or characterization of the site. The scope of the investigation includes review of available file information, interviews, a comprehensive target survey, and an on-site reconnaissance inspection.

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2. BACKGROUND

2.1 Site Description

The Bretz Mine is an inactive mine located on public land administered by the Bureau of Land Management (BLM). It is located in the extreme southern end of Malheur County Oregon, approximately 10 miles northwest of McDermitt, Nevada (Figure 1). The area is within the Vale District of the BLM.

The climate of the area is arid, and the sparse vegetation consists of grasses, sagebrush and other shrubs. Willows and other woody vegetation is present along many of the local creeks. The elevation of the site is approximately 5,400-5,500 feet above sea-level.

The site is approximately 100 acres in size, and consists of two main mine pits, dozens of small exploratory prospect excavations, and several waste rock piles. The site history, which is detailed in the next section, gives no indications of on-site processing. However, there is an area located south of the two mine pits which contains four small retorts, a water storage tank, and the concrete foundations of other structures. Little Cottonwood Creek flows through the west pit, and an unnamed tributary flows along the west side of the east pit (Figure 2). There are at least four dikes across Little Cottonwood Creek which contain runoff and sediment from both pits.

Adjacent land use mainly consists of livestock grazing, there are no residences or other structures within 4 miles of the site. Access to the site is unrestricted.

2.2 Ownership and Operational History

The deposit was discovered in 1917 by William S. Bretz. Assessment work was done for many years before high grade mercury ore was discovered in 1931. The mine was then sold to the Bradley Mining Company, operators of the Opalite mercury mine, which is located approximately 6 miles west of the Bretz Mine (Schuette, 1938).

The Bretz Mine was actively worked by the Bradley Mining Company from 1931 through 1936. All ore was shipped to the Opalite Mine for processing during this period. At the end of the 1936 mining season the option to purchase the Bretz mine was released, and Bradley Mining apparently stopped work there (Schuette, 1938). Production values reported by Brooks, 1971, indicate that further mining occurred after 1936. The total mercury production given by in Brooks, 1971 was 15,185 flasks, and the last year of production recorded was 1968. A flask of mercury is equivalent to 76 pounds. The presence of processing equipment (observed June 6, 2000), suggests that some processing may have occurred at the site.

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There are currently several active mining claims on and nearby the site. According to the BLM Vale District Office, the claimants are performing exploratory work for potential gold mineralization and no recent mercury mining has occurred at the site.

2.3 Regulatory History

Other than regulation of mining claims by the BLM, there appears to be no regulatory history at the site. The significant mining operations that have occurred pre-date both state and federal mining regulations.

3. WASTE CHARACTERISTICS

3.1 Source Areas

Based on the site visit performed by DEQ in June, 2000 several source areas were identified:

• Mine pits - Mineralized rock is exposed in the mine pits. This material is a potential source of mercury and other heavy metals. Sulfide minerals that may be present are also a potential source of Acid Rock Drainage (ARD). Little Cottonwood Creek flows through the west pit and an unnamed tributary of Little Cottonwood Creek flows through the east pit.

• Waste Rock Dumps - This material is likely to contain mercury and other heavy metals and to also be a source of ARD.

• Impoundments – There are at least four impoundments constructed in Little Cottonwood Creek downstream of the mine (Figure 3). The dikes which were constructed across the stream channel may be composed of waste rock and could be a source of metals and ARD. The sediment accumulated behind the dikes is likely to contain mercury and other heavy metals.

• Ore Processing Areas – Approximately ¼ mile south of the west pit is an area which contains evidence of ore processing. There is a large steel tank (Figure 4) which was apparently used for water storage along with four small retorts (Figure 5). Retorts are ovens which are used to liberate mercury vapor from ore. The mercury condenses in tubing after it leaves the retort. Other contaminants of concern may be present at the processing areas. An empty 55-gallon drum, riddled with bullet holes and labeled “Carbon Tetrachloride” was present in this area.

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Figure 3. Photograph of Bretz Mine from south, looking up Little Cottonwood Creek. Dikes across creek channel are in foreground, mine pits are in background. The ore processing area is in the left center.

Figure 4. Photograph of Ore Processing area showing retorts on left and steel tank in center.

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Figure 5. Photograph of four retorts in ore processing area.

3.2 Sampling Results

Two samples of what appeared to be ore material were collected during the June, 2000 site visit. One sample was collected from what appeared to be a low-grade ore stockpile, and one sample was collected from inside one of the retort furnaces. Both samples were analyzed for total mercury. A mercury concentration of 168 mg/kg was detected in the low-grade ore sample and a mercury concentration of 1370 mg/kg was detected in the retort sample. These levels are in excess of the EPA Region 9 Preliminary Remediation Goal (November, 2000) value for total mercury in a residential setting (23 mg/kg). The retort sample is also above the PRG value for an industrial setting (610 mg/kg). The total mercury concentrations detected are also well in excess of the State of Oregon Level II Ecological Screening Benchmark Values for Terrestrial Receptors (DEQ, 1998). The screening value for plants is 0.3 mg/kg and the screening value for invertebrates is 0.1 mg/kg. The toxicity and bioavailability of mercury is complicated and strongly dependent on the chemical species of the mercury present at the site. Further characterization is necessary before conclusions can be drawn. The analytical report for these samples is included in Appendix A.

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4. GROUNDWATER PATHWAY

4.1 Hydrogeologic Setting

The Bretz Mine is located in the northern extension of the Basin and Range physiographic province of Oregon, Nevada, Utah, Idaho, Arizona, California, New Mexico, and Mexico. The is characterized by north-south trending block mountain ranges alternating with broad basins. Most of the Basin and Range Province is part of the Great Basin, which has no outlet to the ocean. Many of the sub-basins within the Great Basin are isolated from each other.

The Basin and Range Province is a geologically active area with a high heat flow from the earth’s interior. It has a thin outer crust and high regional elevation. It is characterized by stretching or extension of the crust and the movement of large tectonic blocks (Orr, Orr, and Baldwin, 1992). These forces result in the structure of tilted blocks forming the ranges and down-dropped blocks forming the basins. Large amounts of volcanic activity are also part of the geologic setting, and many of the basins are filled with volcanic material up to 10,000 feet thick (Orr et. al, 1992).

The Bretz mercury deposit, and the nearby deposits at the Opalite and Cordero mines, formed within the McDermitt Complex (Orr, et. al, 1992) which is of Miocene Age (7-10 million years ago). Local well logs indicate that the site is underlain by fine-grained clay-rich sediments and opalite. Crystalline igneous rock was encountered at approximately 600 feet below grade. These geologic units are considered to be part of the Volcanic and Sedimentary Aquifer unit of Eastern Oregon. Permeable units within this aquifer are capable of yielding over 250 gallons per minute of ground water to wells (Gonthier, 1985).

Six wells were on record with the Oregon Water Resources Department within a four mile radius of the site (Water Resources Department, 2001). One well yielded 200 gallons per minute, this well has a reported industrial use, and the other five are recorded as yielding less than 5 gallons per minute, with one of those yielding no water, no use was recorded for these wells. Water was first encountered at depths ranging between 200 and 300 feet below ground surface. Static water level generally stayed within a few feet of the depth where water was first encountered. Well logs are included in Appendix B.

4.2 Groundwater Targets

There are six wells on record within 4 miles of the site. One well was abandoned, one well is listed as having an industrial use, the other four have no listed use. There are no dwellings or other significant structures in the site vicinity.

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4.3 Groundwater Conclusions

Due to the depth of ground water, and lack or receptors, the ground water pathway does not appear to be significant at this site.

5. SURFACE WATER PATHWAY

5.1 Hydrologic Setting

The Bretz Mine is located along Little Cottonwood Creek, tributary of Cottonwood Creek, which flows into McDermitt Creek near the Oregon–Nevada state line. McDermitt Creek is a tributary of the Quinn River which flows southwesterly into a closed basin in northern Nevada.

The climate is arid, vegetation is sparse, and many creeks, including Little Cottonwood Creek, flow only seasonally. Precipitation data from the nearest weather station (Burns Junction, located approximately 50 miles northeast of the site) indicates that mean annual precipitation is 8.25 inches (1972-1990 period of record). There was no evapotranspiration data for this station, therefore net precipitation could not be calculated. The extreme 24 hour rainfall event for the same period was 2.00 inches. Climate data for the Burns Junction weather station are included in Appendix C. Flood plain areas have not been mapped in the site vicinity.

5.2 Surface Water Targets

Little Cottonwood Creek and its tributaries flow through or adjacent to the mine pits and waste rock piles at the site. Little Cottonwood Creek enters Cottonwood Creek approximately 2 ½ miles downstream of the site. Cottonwood Creek enters McDermitt Creek approximately 3 miles downstream of the site. McDermitt Creek contains Lahontan Cutthroat Trout, which is federally listed as a Threatened Species. Lahontan Cutthroat Trout are also known to be present in Indian Creek, a tributary which enters Cottonwood Creek approximately ¼ mile upstream of the confluence of Cottonwood and Little Cottonwood Creeks (ODF&W, 1999).

There are no surface water rights on record with the Oregon Water Resources Department for the segments of Little Cottonwood Creek, Cottonwood Creek, and McDermitt Creek which are downstream of the site, and within the State of Oregon. This is a downstream distance of approximately four miles. It is assumed that some livestock watering occurs in these creeks, along with recreational activities such as fishing.

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5.3 Surface Water Pathway Conclusions

The surface water exposure pathway is very significant at this site. Source areas at the Bretz Mine site are directly connected to surface water bodies. The potential for mercury contamination to impact sensitive receptors such as Lahontan Cutthroat Trout is high.

6. DIRECT CONTACT AND AIR PATHWAYS

6.1 Physical Conditions

The site is located in an arid area with sparse vegetation. Disturbance of the soil during mining operations has left large areas totally unvegetated. There is a high potential for exposure to mercury through direct contact with soil or through inhalation of dust during windy conditions or during activities which disturb soil. There is also the potential for exposure to mercury vapors which may be emanating from mercury-bearing materials at the site. The site is accessible via a gravel road and there is no site security.

6.2 Direct Contact and Air Pathway Targets

Census data (Siteinfo Report, see Appendix D) indicates that there are no residents within 5 miles of the site. No residences were observed in the site vicinity during the site visit in June, 2000. The lack of residences or other facilities in the area limits the human exposure targets to occasional visitors and workers performing mineral exploration duties.

The nearest sensitive environments to the site include Little Cottonwood Creek (flows through the site), Cottonwood Creek (one mile from the site), Indian Creek (2 miles from the site) and McDermitt Creek. (3 miles from the site). Significant riparian vegetation was observed in these creeks, and Lahontan Cutthroat Trout (federally listed as a threatened species) are present in Indian Creek and McDermitt Creek. Indian Creek and McDermitt Creek are listed as 303d water quality limited streams for temperature (DEQ, 1998a).

6.3 Direct Contact and Air Pathway Conclusions

There is significant potential for direct contact with contaminated soil and the generation of mercury bearing dust and mercury vapor at the site. However, the limited number of human receptors and the limited amount of time that they would potentially be present, moderates the exposure risk. Blowing dust may be impacting the sensitive environments identified in the site vicinity.

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7. SUMMARY AND CONCLUSIONS

The Bretz Mine is an inactive mercury mine located in the southeastern corner of Oregon. It was active from 1931 to at least 1936. Historical records indicate that most of the ore was sent to the nearby Opalite Mine for processing, however, some processing equipment is present at the site.

The site is located in a remote area with an arid climate. Surrounding land use is mainly livestock grazing. There are no residences within 5 miles of the site. Human receptors include occasional site visitors, and workers performing mineral exploration activities. Limited soil sampling data indicates the presence of mercury at levels which are higher than residential and industrial PRG levels, and much higher than State of Oregon Ecological Screening values. Ecological receptors include Lahontan Cutthroat Trout which are federally listed as a Threatened Species. Lahontan Cutthroat Trout are known to be present approximately 3 miles downstream of the site, and are also present in a tributary stream located upstream of the site.

Due to the presence of mercury contamination at the site and the potential for impacts to human and ecological receptors, a Site Inspection (SI) or Remedial Investigation (RI) is recommended. Sampling should focus on all source areas including: mine pits; processing areas; waste rock and ore piles; and the sediment accumulating behind the dikes in Little Cottonwood Creek. Off-site sampling should be conducted downstream in Cottonwood Creek and McDermitt Creek.

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8. REFERENCES

1. Brooks, Howard, C., 1971, Quicksilver Deposits in Oregon , Oregon Department of Geology and Mineral Industries, Miscellaneous Paper 15.

2. DEQ, 1998, Guidance for Ecological Risk Assessment, Level II Screening.

3. DEQ, 1998a, Water Quality Limited Streams – 303(d) List

4. Gonthier, Joseph, B., 1985, A Description of Aquifer Units in Eastern Oregon, U.S. Geological Survey, Water Resources Investigations Report 84-4095, 1985.

5. Oregon Department of Fish and Wildlife, Fish Distribution Data, rainbow.dfw.state.or.us/data.html .

6. Oregon Climate Service, www.ocs .orst.edu/ .

7. Oregon Water Resources Department, Water Rights Database, www.wrd .state.or.us/.

8. Orr, Elizabeth, L., Orr, William, N., and Baldwin, Ewart, M., 1992, Geology of Oregon , Fourth Edition, Kendall/Hunt Publishing Company, Dubuque, Iowa.

9. Preliminary Remediation Goals, U.S. EPA Region 9, San Francisco, California, www.epa .gov.region9/waste/sfund/prg/index.html .

10. Schuette, C.N., 1938, Quicksilver in Oregon , Bulletin Number 4, Oregon Department of Geology and Mineral Industries, Portland, Oregon.

11. Siteinfo Report, U.S. EPA Region 10, Seattle, Washington, www.epa .gov/docs/region10/www/siteinfo.html .

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Appendix A Laboratory Data

Appendix B Well Logs

Appendix C Climate Data

Appendix D Siteinfo Report