Amendment2_Attachment 1 -PASI.pdf

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4 PATHWAY AND ENVIRONMENTAL HAZARD ASSESSMENT

There are two components to this section; an identification of pathways, and a hazard assessment:

1) The identification of pathways was completed by using professional judgment when reviewing site conditions of waste source areas, possible transport mechanisms and possible receptors (both human and ecological) to exposure. The following subsections describe whether a possible fate and transport pathway between the waste source to receiving media (groundwater, surface water and soil) is possible. It also describes the possible receptors (targets) exposed to the affected media, and the exposure pathways to these receptors. Observations of the area populations and environmental features were noted, in order to determine the possible exposure pathways that could occur.

2) The hazard assessment was completed by comparing the measured concentrations of contaminants (resulting from the sampling and analysis completed at the Site) to background concentrations and toxicity threshold concentrations protective of human health and ecological receptors. If the measured concentrations exceed these protective values, then an impact may be inferred. However, there are uncertainties associated with this method which may either over or under- estimate the impact. These uncertainties are described within each media pathway and target evaluation. Within this part of the Snake River watershed, an unimpacted stream does not exist near the Site. Therefore, comparison to background water chemistry is unattainable. For the purpose of hazard assessment, dissolved metals samples are used as metals are considered to be more bioavailable in the dissolved (aqueous) form. Total metals samples were also collected but due to the acidic (low pH) chemistry of surface and mine adit water concentrations of total metals are similar to dissolved metals (Appendix E).

For the purposes of this evaluation, the hazard assessment relied upon available thresholds from various literature sources in order to determine potential impacts attributable to the Site. A description of each type of threshold, the source, and the limits of their use is as follows;

1) EPA Drinking Water Standards. Criteria protective of potable water supplies are regulated by the EPA and summarized within their health advisories for drinking water sources as either maximum concentration level goals (MCLGs) or maximum concentration levels (MCLs) (EPA, 2009). The MCLs are promulgated criteria, whereas the MCLGs are ‘goals’ for future consideration. Both values are protective of human consumption of water supplies assuming chronic exposure conditions and conservative assumptions (i.e.

compromised individuals).

2) CDPHE Table Value Standards (TVS) for the Protection of Aquatic Life – Cold Water Class 1 advisories and site-specific criteria. These criteria are set forth by the State of Colorado to protect the designated uses of the waters of the state (CDPHE, 2008). The segment of the Snake River is defined as a Cold Water Class 1 designated use - protective of cold water aquatic species. The site-specific table value standards (TVS) set forth for this segment as well as default values when site-specific TVS were not available, ambient water quality control values were used for the hazard assessment for aquatic life.

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3) USFWS Ecological Screening Values (ESVs). The US Fish and Wildlife Service have summarized background concentrations and thresholds indicating the degree of contamination within a hazardous waste site (USFWS, 1999). These values are a compilation of the most conservative threshold screening levels set forth by various agencies for aquatic and terrestrial organisms. Measured contaminant concentrations can be compared to these values to determine if they are within the range of background levels observed across the United States or if they exceed these levels and therefore require further evaluation. These values are screening tools to determine the measure of contamination present. They do not provide an indication of the toxicity potential.

4) Bureau of Land Management, Risk Management Criteria (RMC) for Metals at BLM Mining Sites. The BLM had developed both human health and ecological threshold values for groundwater, surface water, and soils (Ford, 2004). The values vary by receptor and exposure type. Camper values are based on a seven-day exposure, while residential values are based on domestic residences located adjacent to BLM lands. The exceedance of the RMC has been interpreted as follows: < RMC means there is low risk; one to ten times RMC means there is moderate risk; 10-100 times RMC values indicates high risk; and more than 100 time RMC indicates extremely high risk (Ford, 2004). These values were useful for all pathways assessed and are therefore used for the groundwater, surface water, and mine waste hazard assessment. These values do not represent cleanup criteria, but rather they are screening thresholds to determine if certain receptors and exposure settings would be a concern if exceeded.

4.1 Groundwater Migration Pathways and Targets

The geology at the Site is largely the Montezuma quartz monzonite stock, which encompasses most of Sullivan Peak, including the mine site. Much of the Snake River valley is composed of glacial till and alluvium on top of bedrock (Lovering, 1935). Soil cover at the Site is most likely part of the Frisco–Peeler complex that exists on 25-65% slopes. These soils are well-drained and are found on mountainsides and ridges. This soil is typically covered with duff of litter (needles and twigs), which is underlain by a sandy loam. The Frisco-Peeler complex has a moderate permeability, moderate to high water capacity, and high water erosion capacity (Miles R. and Fletcher L., 1980). The hydrology of the Site is typical for high-altitude mountainous watersheds where seasonal snow melt significantly factors into surface water and groundwater distribution and flow. Sources of water that contribute to flow in the unnamed gulches located north (SC North) and south (SC Background) of the Site is likely seasonal where snow melt contribution in the spring to early-summer results in high flow conditions. The presence of flow during fall 2020 in drought-like conditions suggests that groundwater discharge into the gulches is likely throughout the year. The Snake River is a perennial stream that receives flow from numerous tributaries (including the ones described in this PA/SI) and groundwater. Sources of groundwater in and near the Site has not been fully characterized but is likely a combination of aquifers in glacial alluvium and in the fractured parts of bedrock. Recharge of the local aquifer is likely from snow melt originating from the seasonal snowpack resulting seasonal fluctuations of water tables. Due to the lack of wells in and near the Site, the water quality of groundwater is unknown.

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Releases of hazardous material into the groundwater from the Site, would occur from mine waste rock piles as well as underground mine workings (adits, tunnels, and stopes) and contact with mineralized deposits in the country rock. The mine waste piles can release metals to underlying groundwater through the processes of infiltration and leaching. Precipitation from snow and rainfall can infiltrate through the waste, and mobilize metals into solution if the conditions permit.

Additionally, groundwater that moves through underground mine workings oxidizes sulfide minerals that are exposed in the mine workings, producing acidic water mainly due to pyrite oxidation reactions. The production of acidic water allows metals to be mobilized into the groundwater. Both processes produce Acid Mine Drainage (AMD), which can allow for migration of hazardous materials into the groundwater system.

Metals are generally considered to be bioavailable when they are in solution (dissolved form) when released from soils and mobilized into pore-water (EPA, 2000). Metals show variable mechanisms of interaction in soils. Metals can exist in the pore-water as ionic species, as soluble complexes, or associated with colloids. Metals existing as cations (Zn, Cu, Cd, Pb, Al, Fe, Ni, and Ag) have an affinity to bind with soil particulates and organic matter which tends to be anionic reducing their bioavailability. In contrast, certain metals (As, Se, and Sb) typically stay in anionic form as oxyanions (i.e., AsO3-) and generally remain in pore-water solution and retain their bioavailability to organisms (EPA, 2000). A general trend is often observed with the mobilization of metals from soil when acidic water sources percolate the medium. Acidic conditions provide the potential for soil bound metals to be released and leached into groundwater. This is likely the case for the Site as the background soil pH was 5.00. Similarly, mine waste leachate tests display more acidic nature of the mine waste with pH ranges from 2.56, which allows metals to leach out of the mine waste.

In order to determine the potential of mine waste at the Site to impact the groundwater, a mine waste leachate (Table 5) from Pile 200 located at the Climax Mine was produced and analyzed in the TAL. The mine waste leachate results provide essential water chemistry data to model potential leachability of metals from mine waste to a water source. Every source of AMD, which could impact the groundwater at the Site, is presumed to either enter the groundwater system, in which connections are unknown or enter surface water of the Snake River and potentially later become groundwater once again further down gradient in the Snake River valley.

There are likely wildlife receptors within the area. The Site has year-round water sources and vegetation-forage at the immediate Site and adjacent area conducive to several species of biota.

However, due to the extremely poor water quality of all streams sampled in and near the Site, aquatic life is limited in the area, and most likely does not contain fish but may contain macroinvertebrates. Wildlife receptors would be exposed if they ingested the surface water sources from any of the streams and drainage from the Climax Mine adit.

There is a potential for human health targets within the immediate area and downstream of the Site, if groundwater is ever used as a source of water. Human exposure at the Site would occur if surface water and groundwater from the Site were ingested, which may occur by recreators in the area. There is also evidence of camping below the Site along Webster Pass Road and on Pile 200 (fire ring) which may mean recreators are visiting the Site and potentially are exposed to either groundwater or surface water. Since there are no domestic wells in or near the Site, the primary pathway for groundwater by ingestion of discharge from the Climax Mine adit located at Pile 200.

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Comparison of measured concentrations in the only expression of groundwater (SC Adit), and mine waste leachate to applicable groundwater thresholds for human health are provide in Table

4. Results are summarized as follows:

1) The SC Adit site had several metals that were detected in both dissolved and total forms (See Appendix E) for which dissolved Al, As, Fe, Mn, and Zn exceed groundwater threshold values shown in Table 4.

2) Leachate analysis of mine waste Pile 200 had detectable concentrations of Al, As, Cd, Cu, Fe, Mn, and Zn. The background soil leachate sample has detectable concentrations of Al, Cu, Fe, Mn, and Zn. Leachate concentrations of metals in the background soil are considerably lower than the mine waste (Pile 200).

4.1.1 Human Health Hazard Assessment

Due to the presence of residential wells within the watershed boundary downstream of the Site there is a possible pathway of metals transported by groundwater. The nearest wells (Figure 1) are located approximately 1 mile down gradient of the Site near the confluence with Deer Creek. Since there are no other wells between the Site and the nearest documented wells it is assumed groundwater flow likely exists along the valley floor glacial alluvium. However, it is unclear if metals released from the Site are transported to the nearest domestic wells.

If discharge from the mine adit (SC Adit) were used as drinking water a threat to human health exists due to the concentrations of Al, As, Fe, and Mn exceeding primary and secondary drinking water standards (EPA, 2010). However, it is unlikely that the adit at the Site would be used for a drinking water source due presence of iron-hydroxides. But if used for drinking water, concentrations of Fe and Mn exceed secondary drinking water standards, while concentrations of Al and As exceed both the MCLG and MCL.

4.1.2 Ecological Health Hazard Assessment – Aquatic Life

Besides discharge from the mine adit at Pile 200, there was no indication of other sources of surface expressions of groundwater as springs or seeps. The valley floor south of the Site appears to be a bog that suggest a shallow water table fed by groundwater. Due to the lack of wells, it is indeterminate if the water chemistry of the mine adit discharge is representative of local groundwater. As shown in Table 2, Al, As, Cd, Cu, Fe, Mn, and Zn concentrations in the SC Adit samples exceed the USFWS Ecological Screening Values.

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Table 4. Groundwater results in ug/L at the Site, compared to groundwater threshold values. *Secondary standards with known toxicological reference doses available from the EPA‘s Integrated Risk Information System. NM = Not measured; Diss = Dissolved metals.

MCLG (EPA Drinking Water)

Al As Be Cd Cu Fe Mn Pb Sb Se Tl Zn

50* 0 4 5 1300 - 50* 0 6 50 0.5 5000*

MCL (EPA Drinking Water) 200* 10 4 5 1300 300* 50* 15 6 50 2 5000*

BLM Groundwater Resident - 0.1 - 0.2 18 - 2 15 0.2 2 - 142

BLM Groundwater Camper - 1 - 2 137 - 18 15 1 18 - 1106

USFWS Ecological Screening Values 87 2.2 0.53 0.7 6.5 1000 80 1.32 160 5 4 59

Sample ID Date Al As Be Cd Cu Fe Mn Pb Sb Se Tl Zn

SC Adit Diss 8/5/1993 3600 <1 NM 1 12 11000 2700 <5 NM NM NM 1200

SC Adit Diss 8/7/2009 5240 <4 NM 3 8 19280 3630 <4 NM NM NM 1600

SC Adit Diss 7/3/2019 6992 <8 1.3 3 <6 23121 4669 <5 <4 <8 <11 1728

SC Adit Diss 10/7/2020 9316 26 NM 5 17 29377 5300 <5.7 NM <8 <8.3 2260

Table 5. Leachate results in ug/L from mine waste piles at the Site. Dash indicates metals that were not included in Site Characterization report.

Sample ID Date of Analysis Al As Be Cd Cu Fe Mn Pb Sb Se Tl Zn

Pile 200 8/7/2009 18970 10 - 10 630 84250 1370 - - - - 640

SC Background 8/7/2009 1720 <8 - <1 40 1050 500 - - - - 140

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4.2 Surface Water Migration Pathways and Targets

The Site sits within the Snake River watershed and is located below Sullivan Peak. Surface water at the Site exists mainly as discharge from the mine adit near Pile 200 and seasonal surface run-off during snow melt. Two gulches bound the site to the north (SC North Gulch) and south (SC Background Gulch) that appear to have perennial flow evident by flow during the October 7, 2020 sampling event. Precipitation in the 2019/2020 winter and 2020 summer periods in the area were particularly dry with below average snow pack and summer precipitation. Flow in the gulches appears are likely related to groundwater and run-off during snowmelt and both gulches were observed to flow into the Snake River. As suggested in the 2009 Site Characterization report, the North Gulch was sampled in 2019 and 2020.

The release of hazardous material from the Site via surface water can occur in the two ways noted above for groundwater, the production of AMD by interaction with mine waste piles or from underground mine workings. Release into the North Gulch, Background Gulch, and Snake River would occur if snowmelt and storm runoff from mine waste piles directly entered the gulch or if discharge from the adit entered the gulch. However, due to the presence of expansive mineralization in the area, releases from naturally occurring Acid Rock Drainage (ARD) is also a likely contributor to water quality surface waters. It is not clear if any hazardous material is transported and released by groundwater into surface waters particularly during low flow periods.

However, it can be inferred that groundwater does contribute to flow during low flow periods particularly in the two unnamed gulches located near the Site.

In order to determine the amount of potentially hazardous material entering the surface water system, water samples were collected from the unnamed south gulch above (SC Background) and below (SC-05) the Climax Mine adit and waste pile (Pile 200). Samples were collected from the Snake River above (SC-SA) and below (SC-SB) to bracket where any discharge from the Climax Mine is likely to enter the Snake River.

Overall, water quality is generally poor among all the surface water sites. In-situ water quality measurements of pH and conductivity indicate water that is acidic (Appendix E) and contains high amounts of dissolved metals exist throughout the Site and Snake River (Table 6). Samples represented by the SC Adit (collected at the adit opening), SC-02 (below Pile 200) and SC-04 (surface water on Climax Mine Road from Climax Mine adit) likely surface water pathways from the Climax Mine and, in general, all have similar water quality. The SC-01 sample was collected on the Climax Mine Road above the Climax Mine and likely represents snow melt surface run-off due to the lack of flowing water in October 2020. There is a noticeable difference in water quality at SC-01 between the 8/7/2009 and 7/3/2019 samples which may be a factor of dilution from greater snowmelt in 2019. Samples SC Background and SC-05 are located in the south unnamed gulch above and below the Site to account for any water quality changes related to releases from the Site. As shown in Table 5 and in Appendix E, it is evident that dilution from snow-melt factors into concentrations of metals when samples collected on 7/3/2019 and 10/7/2020 are compared. In general, only Mn and Zn concentrations increase at SC-05 compared to SC Background which may be related to groundwater contributions. Water quality in the north unnamed gulch (SC North Gulch) is poor and generally has the greater concentrations of metals compared to other sites. The source of acidity and metals in the north unnamed gulch is not clear and was not explored due to the extremely difficult terrain above tree line. Photos taken during the 2009 Site Characterization

30 | P a g e event show the existence of several mine waste piles not associated with the Lower Sullivan – Climax Mine site located further up the north unnamed gulch. Water quality and metals concentrations in the Snake River above and below the site are relatively similar indicating that contributions from the Site is very small or non-existent. There is some dilution that results in a decrease in metals concentrations due to snow melt.

4.2.1 Human Health Hazard Assessment

Threats to human health from the Site’s surface water would occur if humans ingested water from the adit (SC Adit) and immediately down gradient of the Climax Mine (SC-02 and SC-04). Due to evidence of camping and recreators within and near the Site, there may be potential for humans to come into contact with water from the Site if used as a source of drinking water. Furthermore, water from the north unnamed gulch, south unnamed gulch, and the Snake River also pose a threat to human health.

If water from SC Adit, SC-02 or SC-04 were ingested, there will be exceedances of Al, As, Fe, and Mn as related to primary and secondary drinking water standards (EPA, 2009). Water from the unnamed gulches poses a greater human health hazard due to exceedances of Al, As, Cd, Fe, Mn, and Zn as related to primary and secondary drinking water standards (EPA, 2009) and BLM Camper for As, Cd, and Mn. Water from the Snake River near the Site exceeds EPA primary and secondary drinking water standards for Al, As (one sample), Fe, and Mn.

4.2.2 Ecological Receptor Hazard Assessment

Threat to ecological receptors is present at the Site, for varying elements, for all of the sampled surface water locations. Exceedances of USFWS Ecological Screening Values (ESVs) and CDPHE TVS exist at all sites sampled with the exception of Pb, Sb, Se, and Tl. Ecological receptors at the Site include any terrestrial invertebrates, birds and mammals that could ingest or have dermal exposure to surface water. It unlikely that aquatic receptors exist due to the poor water quality of all surface waters sampled.

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Table 6. Dissolved metals results by ICP-OES in ug/L from the Site in comparison to screening values including EPA drinking water standards (EPA, 2009), BLM camper risk management criteria (Ford, 2004), Ecological Screening Values (USFWS, 1999) and site-specific table values set for the Snake River (CDPHE, 2008). (NM: not measured. *Secondary standards with known toxicological reference doses available from the EPA’s Integrated Risk Information System)

Al As Be Cd Cu Fe Mn Pb Sb Se Tl Zn EPA Drinking Water MCL 200* 10 4 5 1300* 300* 50* 15 6 50 2 5000*

EPA Drinking Water MCLG - 0 4 5 1300* - - 0 6 50 0.5 -

BLM Camper - 93 - 155 11490 - 1548 50 124 1548 - 92909

USFWS ESV 87 2.2 0.53 0.66 6.54 1000 80 1.32 160 5 4 58.9

CDPHE TVS - - - 0.15 – 0.27 2.8 – 5.4 19 - 0.6 – 1.3 - 0.9 - 39 – 75

Sample ID Date Al As Be Cd Cu Fe Mn Pb Sb Se Tl Zn

SC-01 8/7/2009 5800 <4 NM 3 11 19260 3880 <4 NM NM NM 1590

7/3/2019 931 <8 <0.2 <0.6 <6 7 231 <5 <4 <8 <11 50

10/7/2020 N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

SC-02 8/7/2009 5760 <4 NM 3 9 14390 3800 <4 NM NM NM 1640

7/3/2019 6528 8 1.3 3 <6 18044 4619 <5 <4 <8 <11 1687

10/7/2020 9261 28 NM 5 7 25327 5315 <5.7 NM <8 <8.3 2236

SC-04 7/3/2019 937 <8 <0.2 <0.6 <6 71 295 <5 <4 <8 <11 78

10/7/2020 9604 23 NM 5 11 19508 5377 <5.7 NM <8 <8.3 2304

SC-05 7/3/2019 6803 <8 <0.2 <0.6 55 1780 587 <5 <4 <8 <11 276

10/7/2020 11810 29 NM 4 60 2711 4105 <5.7 NM <8 <8.3 1479

SC N. Gulch 7/3/2019 32045 <8 2.1 33 190 11177 10167 <5 <4 <8 <11 4047

10/7/2020 225458 104 NM 314 497 156800 74698 <5.7 NM <8 <8.3 33233

SC Background 8/7/2009 11830 <4 NM 2 11 1210 540 <4 NM NM NM 350

7/3/2019 7213 <8 <0.2 <0.6 59 2543 356 <5 <4 <8 <11 180

10/7/2020 23607 24 NM 5 121 1900 1567 <5.7 NM <8 <8.3 905

SC-SA 7/3/2019 1179 <8 <0.2 <0.6 6 517 203 <5 <4 <8 <11 89

10/7/2020 7964 10 NM 4 47 4650 1221 <5.7 NM <8 <8.3 552

SC-SB 7/3/2019 1539 <8 <0.2 <0.6 9 549 235 <5 <4 <8 <11 102

10/7/2020 9120 20 NM 4 47 4614 1338 <5.7 NM <8 <8.3 637

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4.3 Soil Pathways and Targets

The area surrounding Montezuma is a sparsely populated, although it does attract recreation users who come to the area for four-wheel driving, cross country skiing, hiking, and other recreation.

Visitors to the Site will be limited due to the necessary effort to reach the Site using the Climax Mine Road from Webster Pass Road. Access to the Climax Mine requires a high clearance vehicle and is only accessible once snow has cleared. The Climax Mine Road is not marked and appeared to be lightly used. There are no obvious roads to the other mine waste piles therefore it is assumed that they are inaccessible. Mine waste piles at the Site are sparsely to non-vegetated and contain varying degrees of a kill zone. Due to the lack of vegetation and water there were no obvious kill zones associated with the piles 201 - 204. To access the four mine waste piles (201 – 204) requires hiking on very steep, rocky terrain above timberline. At the top of pile 200 located with the Climax Mine the presence of a fire ring suggests evidence of camping.

In general contamination is limited to the actual mine waste piles, although some contain kill zones or areas of erosion, which increase the area of contamination. The only kill zone is particularly evident at the Climax Mine pile (Pile 200). In order to determine the soil contamination at the Site, samples from mine waste pile 200 was collected and analyzed for metal concentrations in both solid and leachable form (Figure 1). A background soil sample was also collected (Figure 1) in order to determine the background metals concentrations at the Site.

Results of the solid mine waste sample analysis (XRF) yielded detectable concentrations of As, Ag, Cr, Cu, Fe, Hg, Ni, Pb, Se, and Zn whereas the background soil had detectable concentrations of Ag, Cr, Cu, Fe, Ni, Pb, and Zn. A comparison of mine waste to both human and ecological threshold criteria is presented in Table 7. Comparison of soil mine waste results to BLM camper risk management criteria (RMC) values (Ford, 2004) shows that all detectable metals do not exceed the screening values. However, As and Ag exceed the BLM resident RMC values.

Ecological screening values (ESV) are the most conservative soil screening levels put forth by numerous regulatory agencies, including the EPA, Oak Ridge National Laboratory, and Canadian and Dutch governments (USFWS, 1999). They are used here along with BLM elk soil RMC values to compare mine waste results to ecological threshold values. Ecological threshold values from Pile 200 are exceeded for As, Ag, Cr, Cu, Fe, Hg, Ni, Pb, and Se.

In order to determine the ability of the mine waste to leach out metals and acidity into solution a paste and leachate analysis were performed. From pH, conductivity, and acidity results on the mine waste it can be determined that it is highly reactive. Due to the presence of sulfide bearing minerals (i.e. pyrite) in the waste rock pile, water interaction with the piles produces highly acidic water.

The leachate analysis reveals that Al, As, Cd, Cu, Fe, Pb, Mn, and Zn are leached from Pile 200.

These concentrations cannot be compared to human health or ecological threshold values for soil, but have been previously compared to groundwater and surface water criteria.

4.3.1 Human Health Hazard Assessment

At the Site none of the detectable metals exceed human RMC for campers in levels that pose a moderate to high risk (Ford, 2004). Due to the relative remoteness of the Site there is not a significant number of visitors, but the potential for the completion of pathway exists with visitors who recreate in the area.

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<LOD = Less than limit of detection

4.3.2 Ecological Receptor Hazard Assessment

The mine waste at the Site poses a significant threat to ecological receptors. For ecological receptors, Ag, As, Cr, Cu, Fe, Hg, Mn, Ni, Pb, and Se exceed USFWS ecological threshold criteria (USFWS, 1999). In comparison to RMC for elk, Hg and Pb display exceedances that pose high to extremely high risk for the receptor. Table 8 lists potential ecological receptors that are affected by elevated levels of metals. During the Site visits there were no documentations of stressed ecological receptors, other than vegetation that is located in the kill zone of Pile 200.

Table 8. Metals of concern for ecological receptors Detected Metals Soil Receptors for Elevated Concentration Levels

Arsenic Plants, avian and mammalian

Chromium Avian and mammalian

Copper Plants, avian, invertebrates, and mammalian

Lead Plants, avian, invertebrates, and mammalian

Manganese Plants and invertebrates

Mercury Avian and mammalian

Nickel Plants

Silver Avian and mammalian

Table 7. Results from solid mine waste analysis by XRF in mg/kg compared to screening threshold values for ecological and human receptors. Exceedance of USFWS (1999) ecological standards values are in bold. (LOD: limit of detection).

As Ag Cd Cr Cu Fe Hg Ni Pb Se Zn

20 700 70 - 5000 - 40 2700 1000 700 40000

1 35 3 - 250 - 20 135 400 35 2000

328 - 3 - 131 - 11 - 127 - 275

USFWS ESV 10 2 1.6 0.4 40 200 0.1 30 50 0.81 50

Sample ID

Pile 200 16 91 <LOD 243 73 93057 20 122 336 7 20

SC Background <LOD 62 <LOD 167 103 71489 <LOD 75 103 <LOD 99

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4.4 Air Pathways and Targets

Air particulates were not sampled during the sampling event and therefore pathways and targets cannot be confirmed in this particular PA/SI report. Part of the Lower Sullivan – Climax Mine is located within the steep and heavily vegetated area below Sullivan Peak and therefore is protected to some degree from wind erosion. Potential pathways of particulates released from Pile 200 may occur by recreators that visit the Climax Mine. However, Piles 201 – 204 are located above treeline and are thus exposed to wind and are more susceptible to wind erosion. The remote nature of those piles makes their potential to expose air particulates to humans unlikely.

4.4.1 Human Health Hazard Assessment

No determination could be made for air particulate pathways and targets. If exposure pathways did occur it would do so through human inhalation of mine waste material mobilized from the Site through recreational disturbance, adverse weather conditions, or prolonged occupation at the mine waste site.

4.4.2 Ecological Receptor Hazard Assessment

A hazard for wildlife through airborne particulate inhalation would exist in the case that mine waste particulates are mobilized by human activity or adverse weather conditions. It may also occur if wildlife proceeds to disturb the mine waste.

5 SUMMARY AND CONCLUSIONS

An overview of environmental pathways, receptors, and any exceedances are shown in Table 9.

Results of the hazard assessment indicate that current conditions may be suitable for short-term human and ecological receptor exposure conditions. Due to the direct hydrologic connection between mining activity in the watershed to surface water and likely groundwater there is potential threat for humans to be exposed to elevated levels of hazardous substances. Similarly, if recreators utilize Site water as a source of drinking water there may be metal constituents of potential concern ingested from the Site. Recreators may also be exposed to mine waste through incidental ingestion and inhalation. Results of the mine waste solids measured concentrations of several metals of concern above resident and camper protective thresholds. This pathway may also be complete and be of concern, particularly due to the presence of nearby camping sites at the Climax Mine and along Webster Pass Road below the Site.

Due to the lack of surface expressions (springs and seeps) and wells, groundwater generally presents little risk to recreators. The only surface expression of groundwater is drainage from the Climax Mine adit that may be influenced by exposed mineralization in the mine tunnel. Seasonal fluctuations (snow melt run-off and precipitation events) appear to affect water quality of the mine adit drainage. This pathway is only complete if water from the mine adit is ingested.

Results from surface water samples indicate that all surface waters in and near the Site generally have poor water quality and, in some cases, present a significant hazard to human health. Snow melt does tend to decrease the concentrations of certain metals by dilution but likely for a short period of time in the spring/early-summer. Pathways exist by ingestion of surface water as a source of drinking water for recreators and wildlife. Due to the lack of pristine, unimpacted surface water

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Several metals of concern were detected in the mine waste and exceeded BLM risk management criteria and soil screening level concentration levels for wildlife, avian, and other terrestrial receptors. The mine waste at the lower Lancaster Mine is vegetated which poses potential risks for wildlife and terrestrial biota receptors exposed to the Site. Plants have a high potential for the accumulation of contaminates by uptake and there is potential for ingestion by wildlife. Wildlife, however, require large forage ranges for their life cycle stages and the Site provides a portion of a typical wildlife receptor range (especially small mammals). The results of acidic soil pH levels amplify the impacts and mobility of contaminates by increasing the potential risks at the Site for receptors. This pathway may also be complete and be of concern.

In summary, given the nature and extent of source areas, and the possible significant hazards posed therein, it appears that the Site may be a potential issue to both human and ecological receptors.

However, due to the significance of mineralization and widespread mining near the Site contributing to poor water quality ingestion of any water poses a hazard to human health. The source of metals and acidity in the unnamed gulches north and south of the Site is unknown. There are visible signs of mining activity (waste rock piles) along the hill sides and near the top of the ridges. Due to the steep terrain and poor access in these gulches the source of water was not determined. It is recommended that future documentation of the source of water and their relation to any abandoned mine sites in the gulches be considered for any future investigations in the area.