APPENDIX C

RESPONSIVENESS SUMMARY

1.1 Stakeholder Issues and EPA Responses

During the Public Comment Period for the Proposed Plan, comments were received from UPCM, the Marsac Corridor Association and Utah Department of Fish and Wildlife. Their comments and EPA’s response to these comments are in the following sections.

1.1.2 Comments Received From United Park City Mines

Remedy Selection. United Park supports the remedy selected in the Proposed Plan. Like EPA, United Park believes that Alternative 3 provides more than adequate protection of human health and the environment, will prove to be effective (both in the long and short terms), will be cost-effective, and will otherwise address the remaining environmental conditions necessary to achieve final closure of the Site.

Possible Wetlands Operable Unit. The Proposed Plan states that the timing of remediation as to the small wetland area between the impoundment and Silver Creek will be delayed until upstream remediation and reclamation efforts are complete. United Park’s understanding is that the wetland area will be remediated following remediation of several upstream areas, some of which are located on United Park property. In any event, because the timing for the remediation of the wetland area will not be linked to the remediation process for the remainder of the Site, United Park suggests that EPA consider designating the wetland area as a separate operable unit. EPA has the discretion to designate multiple operable units with respect to the Site. Doing so here makes sense in part because it will facilitate negotiation of the anticipated Consent Decree, enabling EPA and United Park to define construction completion as to each operable unit.

EPA Response: While EPA understands this is an option that would allow the Site to be archived by OU more quickly, EPA feels strongly that the timing of cleanup throughout the Watershed will work to everyone’s advantage. By cleaning up the upstream sites along Silver Creek in a time efficient manner, the Site wetlands can then be excavated according to the plan set forth in this ROD. It is critical to EPA that the entire Silver Creek Watershed be addressed and by further dividing sites by OU or through some other approach, EPA believes this will slow the process down rather that expedite it.

Site Impacts on Silver Creek. There are a number of statements in the Proposed Plan suggesting that the Site is presently having a significant impact on water quality in Silver Creek. See page A-2 (first paragraph) (linking Site to other sites that are all impacting Silver Creek); page A-3 and A-4 (remediation of Site will play direct role in watershed remediation). United Park finds these statements confusing. The Remedial Investigation (“RI”) for the Site determined that surface waters leaving the Site present no significant impact on water quality in Silver Creek. While it is true that surface waters in areas upstream of the south diversion ditch exhibit elevated metal concentrations, the water in the south diversion ditch outfall has consistently met surface water quality standards. The remedial action proposed for the Site is more appropriately described at addressing potential future impacts the Site may have on Silver Creek. While United Park recognizes that many of the issues addressing Silver Creek arose generally from historic mining operations, United Park believes it is inappropriate to group the Site with other areas in the Silver Creek Watershed that may have actual present impacts on water quality in Silver Creek.

EPA Response: EPA recognizes that the data from the Remedial Investigation relating to the Site’s impact on Silver Creek support this statement. It was written in the Proposed Plan that historic mining activities throughout the Upper Silver Creek Watershed have adversely affected Silver Creek. In Section 12, The Selected Remedy, and in Section 5, Summary of Site Characteristics, it is made clear that water from the Site that enters Silver Creek is of better quality than Silver Creek itself. It is accurate to state that the selected remedy will be protective of human health and the environment in that it will minimize any future exposures or impacts contamination at the Site may present.

Human and Ecological Risks. United Park believes that the Proposed Plan mischaracterizes the results and findings of the human health and ecological risk assessments relating to the Site. More specifically, the discussion in the Proposed Plan under Human Health Risks (page A-4) states that "if the necessary cleanup action is not taken . . . there is a risk to future recreational users at the Site because of lead and arsenic present in the tailings." In fact, the Baseline Human Health Risk Assessment ("BHHRA") conducted by EPA concluded no significant risk to recreational users of the Site from the existing soils and mine tailings unless the soil cover is somehow disturbed. With respect to the ecological risk assessment discussion, the Proposed Plan states that the Ecological Risk Assessment ("ERA") determined that ecological receptors are potentially exposed to metals in several ways, as summarized in the chart on page A-4 of the Proposed Plan. It would be more accurate to state that the ERA concluded contaminated sediment in the wetland area is the primary ecological risk driver, although surface water in a portion of the south diversion ditch may also present some risk, to a lesser degree. This conclusion is supported by Table 7-8 in the ERA.

EPA Response: Again, it is EPA’s intent to make it clear that if the necessary remedial actions are not taken at the Site, which include both enhancing the soil cover and ensuring that it will remain intact in the future, potential risks to human health and the environment exist. EPA agrees with the comment addressing sediments as the primary risk driver at the Site.

Future Consolidation of Material. United Park understands the practical benefits that could arise from the future use of the Site as a consolidation area for mining materials and impacted soils. However, United Park notes the potential complications related to defining completion of construction for purposes of the remedial action described in the Proposed Plan. United Park suggests that one way to address this concern would be for EPA to provide in the ROD that: (i) any materials so consolidated at the Site during implementation of the remedial action will simply be incorporated into the remedial action and covered with the required amount of clean cover material and revegetated; and (ii) any material to be consolidated after completion of construction will be subject to institutional controls requiring that mine wastes or impacted soils consolidated at the Site after the remedial action is completed would be covered with the required amount of clean material and revegetated. This will allow United Park to achieve a state of completion with the remediation while providing maximum flexibility for the future consolidation of material from the Watershed and any potential reuse of the property.

EPA Response: EPA agrees with this comment; evidence of incoorporation of this comment into the ROD can be found in the Remedy Selection section.

1.1.3 Comments Received from the Marsac Corridor Association

One component of the remedy allows for waste to be transported from Empire Canyon and deposited at Richardson Flat. The Marsac Corridor Association (MCA) is a group of homeowners that live in the neighborhood through which trucks carrying the waste would drive. The members of the MCA had two specific comments: 1) The waste in Empire Canyon should be left in place, and 2) If the waste must be moved, it should be transported up the Mine Road and down Royal Street, rather than using only the Mine Road and Lower Marsac.

EPA Response: EPA understands MCA’s concerns and has considered its comments. It is our perspective that the waste may be left in place or moved to Richardson Flat. Factors such as space to contain the waste, the cost of transportation, and potential migration of waste left in place will be considered by the parties involved in order to make a decision about the fate of the waste in Empire Canyon. EPA understands that this is a local issue and one that will be resolved through discussion and consideration amongst the stakeholders. These stakeholders include Park City, UPCM, MCA and other concerned public. A public hearing will be held by Park City in the upcoming future to resolve this issue.

1.1.4 Comments Received from United States Fish and Wildlife Service (the Service) Utah Field Office

The Service submitted comments concerning the remedy’s protectiveness in relation to ecological receptors at the Site. The Service’s primary concern is that the sediments found in the South Diversion Ditch, the pond at its terminus and in the wetland at the base of the embankment are not being addressed in a manner efficient enough to substantially minimize risk to ecological receptors at the site. The Service proposes excavation of the sediments in all three areas.

EPA Response: The sediments within the wetland area will be excavated and placed within the impoundment through the selected remedy. EPA understands that the wetland is a naturally occuring ecological phenomenon that existed before the impoundment was created. Therefore, the remedy should allow for the restoration of the wetland as a habitat for ecological receptors at the Site. However, the diversion ditch and small pond are engineered features at the site that were constructed to help contain the tailings in the impoundment and minimize groundwater infiltration from Area B into the main impoundment. Therefore, these areas will be sufficiently remediated through the described mechanisms (placement of 18 inches of gravel over contaminated sediments). While this action does not create habitat or restore habitat, it will minimize risk to ecological receptors at the Site. The requirements set forth in the NCP are met. Lastly, this does not preclude continued negotiation concerning the restoration of these features between UPCM and EPA surrounding Natural Resource Damages. These damages are currently being addressed, and they are a complicated issue. It is possible these damages could be mitigated through the restoration of other areas within the Watershed. So, until a settlement concerning these damages has been reached the exposure pathways will be interrupted with gravel and risk to ecological receptors will be minimized in the diversion ditch and the pond at its terminus as it is described in the selected remedy.

APPENDIX A

FIGURES FOR THE RECORD OF DECISION

APPENDIX B

TABLES FOR THE RECORD OF DECISION

Table 7-1 Summary of Chemicals of Concern and Medium-Specific Exposure Point Concentrations
Scenario Timeframe: Current Medium: Sediment Exposure Medium: Sediment
Exposure Point	Chemical of Concern	Concentration Detected		Units	Frequency of Detection	Exposure Point Concentration	Exposure Point Concentration Units	Statistical Measure
		Min	Max
Sediment: Ingestion	Arsenic	101	310	mg/kg	12/12	200	mg/kg	95% UCL
	Lead	1,880	6,520	mg/kg	12/12	3,500	mg/kg	AM
Key:
mg/kg: milligrams per kilogram 95% UCL: 95% Upper Confidence Limit of Arithmetic Mean MAX: Maximum Concentration AM: Arithmetic Mean

Table 7-2 Summary of Chemicals of Concern and Medium-Specific Exposure Point Concentrations
Scenario Time frame: Current Medium: Surface Water Exposure Medium: Surface Water
Exposure Point	Chemical of Concern	Concentration Detected		Units	Frequency of Detection	Exposure Point Concentration	Exposure Point Concentration Units	Statistical Measure
		Min	Max
Surface Water - Ingestion/ dermal exposure	Arsenic	0.025	0.75	mg/L	99/291	0.012	mg/L	95% UCL
	Lead	260	0.0015	mg/L	211/425	0.13	mg/L	AM
Key
mg/L: milligrams per liter 95% UCL: 95% Upper Confidence Limit MAX: Maximum Concentration

Table 7-3 Summary of Chemicals of Concern and Medium-Specific Exposure Point Concentrations
Scenario Time frame: Current Medium: Soil & Tailings Exposure Medium: Soil & Tailings
Exposure Point	Chemical of Concern	Concentration Detected		Units	Frequency of Detection	Exposure Point Concentration	Exposure Point Concentration Units	Statistical Measure
		Min	Max
Soil& Tailings: Ingestion	Arsenic	2.5	2400	mg/kg	59/64	55	mg/kg	95% UCL
	Lead	14	5900	mg/kg	62/62	660	mg/kg	AM
Key
mg/kg: milligrams per kilogram 95% UCL: 95% Upper Confidence Limit AM: Arithmetic Mean

Table 7-4 Cancer Toxicity Data Summary
Pathway: Ingestion
Chemical of Concern	Oral Cancer Slope Factor	Slope Factor Units	Weight of Evidence/Cancer Guideline Description	Source	Date
Arsenic	1.5	(mg/kg)/day	A	Region 3 RBC Table	8/28/2001
Lead	NA	NA	NA	NA	NA
KEY EPA Group: A- Human carcinogen B1 -Probable human carcinogen - Indicates that limited human data are available B2 -Probable human carcinogen - Indicates sufficient evidence in animals and inadequate or no evidence in humans C -Possible human carcinogen D -Not classifiable as a human carcinogen E -Evidence of noncarcinogenicity RBC- Risk Based Concentration NA: Not Applicable

Table 7-5 Non-Cancer Toxicity Data Summary
Pathway: Ingestion
Chemical of Concern	Chronic/ Subchronic	Oral RfD Value	Oral RfD Units	Dermal RfD	Primary Target Organ	Combined Uncertainty/ Modifying Factors	Sources of RfD: Target Organ	Dates of RfD: Target Organ
Arsenic	Chronic	3.0E-04	mg/kg-day	—	skin	—	Region 3 RBC Table	8/28/01
Lead^a	—	—	—	—	—	—	—	—
Key (1) The dermal RfD was assumed to equal the oral RfD. No adjustment factor was applied (2) Toxicity values were pulled from the EPA Region 3 RBC Table a There are no established criteria for lead; evaluation is made using blood lead levels

Table 7-6 Risk Characterization Summary – Carcinogens
Scenario Timeframe: Future Receptor Population: Low Intensity Recreational User Receptor Age: Child-Adult
Medium	Exposure Medium	Exposure Point	Chemical of Concern	Carcinogenic Risk
Medium	Exposure Medium	Exposure Point	Chemical of Concern	Ingestion	Inhalation	Dermal	Exposure Routes Total
Soil/Tailings	Soil/Tailings	Ingestion	Arsenic	2E-05	---	NE	2E-05
Soil/Tailings	Dust	Inhalation	Arsenic	---	3.5E-10	NE	3.5E-10
Soil risk total=							2E-05
Sediment	Sediment	Ingestion	Arsenic	3E-06	---	NE	3E-06
Sediment Risk Total=							3E-06
Surface Water	Surface Water	Ingestion	Arsenic	1.8E-07	NA	---	2.0E-07
Surface Water	Surface Water	Surface Water Direct Contact	Arsenic	---	NA	3E-08	3.0E-08
Surface Water Risk Total							4E-07
Total Risk =							2E-05
Key NA: Route of exposure is not applicable to this medium. NE: Not evaluated

Table 7-7 Risk Characterization Summary – Carcinogens
Scenario Timeframe: Future Receptor Population: High Intensity Recreational User Receptor Age: Adult
Medium	Exposure Medium	Exposure Point	Chemical of Concern	Carcinogenic Risk
				Ingestion	Inhalation	Dermal	Exposure Routes Total
Soil/Tailings	Soil/Tailings	Soil On-site- Direct Contact	Arsenic	1.1E-05	--	NE	1.1E-05
	Dust	Soil on-site inhalation of soil as dust	Arsenic	--	6.1E-07	NE	6.1E-07
Total Risk =							1.1E-05
Key NE: Not Evaluated

Table 7-8 Risk Characterization Summary - Non-Carcinogens
Scenario Timeframe: Future Receptor Population: Low Intensity Recreational User Receptor Age: Child-Adult
Medium	Exposure Medium	Exposure Point	Chemical of Concern	Primary Target Organ	Non-Carcinogenic Hazard Quotient
Medium	Exposure Medium	Exposure Point	Chemical of Concern	Primary Target Organ	Ingestion	Inhalation	Dermal	Exposure Routes Total
Soil/ Tailings	Soil/ tailings	Ingestion	Arsenic	Liver	8.0E-02	N/A	---	8.0E-02
Soil/ Tailings	Dust	Inhalation	Arsenic	Liver	---	1.0E-07	---	1.0E-07
Soil/tailings Hazard Index Total =								8.0E-02
Sediment	Sediment	Ingestion	Arsenic	Liver	—	—	—	1.0E-02
Sediment Hazard Index Total								1.0E-02
Surface Water	Surface Water	Ingestion	Arsenic	Liver	9.0E-04	N/A	----	9.0E-04
Surface Water	Surface Water	Dermal contact	Arsenic	Liver	----	N/A	2.0E-04	2.0E-04
Surface Water Hazard Index Total =								1.1E-03
Total Risk=								9.0E-02
Key — : Toxicity criteria are not available to quantitatively address this route of exposure. N/A: Route of exposure is not applicable to this medium.

Table 7-9 Risk Characterization Summary –Non-carcinogens
Scenario Timeframe: Future Receptor Population: High Intensity Recreational User Receptor Age: Adult
Medium	Exposure Medium	Exposure Point	Chemical of Concern	Carcinogenic Risk
				Ingestion	Inhalation	Dermal	Exposure Routes Total
Soil/Tailings	Soil/Tailings	Ingestion	Arsenic	6.0E-02	--	NE	6.0E-02
	Dust	Inhalation	Arsenic	--	3.0E-04	NE	3.0E-04
Total Risk =							6.0E-02
Key N/A: Route of exposure is not applicable to this medium.

Table 7-10

Occurrence, Distribution, and Selection of Chemicals of Concern (COC)

Exposure Medium: Surface Water, Dissolved (Aquatic Receptors)

Chemical of Potential Concern

Min Conc.¹

(ug/L)

Max Conc.¹

(ug/L)

Mean Conc.

(ug/L)

95 % UCL of the Mean ²

(ug/L)

Bkg Conc.

(ug/L)

Screening Toxicity Value

(ug/L)

Screening Toxicity Value

Source ³

HQ Value ⁴

COC Flag

(Y/N)

Cadmium

1.0

46.3

4.3

5.2

N/A

0.22 ⁵

NAWQC Chronic

210

Zinc

83,000

1,143

1,749

N/A

103 ⁵

NAWQC Chronic

806

Key

Conc. = Concentration

N/A = Not Applicable

Notes

¹ Minimum/ maximum detected concentration above the sample quantitation limit (SQL).

² The 95% Upper Confidence Limit (UCL) represents the RME concentration.

³ NAWQC Chronic = USEPA National Ambient Water Quality Criteria for chronic exposures.

⁴ Hazard Quotient (HQ) is defined as Maximum Concentration/ Screening Toxicity Value.

⁵ Chronic NAWQC value is hardness-dependent; calculated based on the lowest measured hardness in site surface water samples (85 mg/L).

APPENDIX C

RESPONSIVENESS SUMMARY

Table 7-4

Cancer Toxicity Data Summary

Table 7-5

Non-Cancer Toxicity Data Summary

Risk Characterization Summary – Carcinogens

Soil risk total=

Sediment Risk Total=

Total Risk =

Key

Key