Conceptualization and Cost Estimate for Remediation Alternatives Cotter Mill Site Cañon City, Colorado

Transcription

1 Conceptualization and Cost Estimate for Remediation Alternatives Cotter Mill Site Cañon City, Colorado Prepared for: P.O. Box 1750 Cañon City, Colorado Prepared by: December 2009 Project No Specht Point Rd. #209 Fort Collins, CO (970)

2 Cotter Mill Site Cañon City, Colorado Prepared for: Mr. John Hamrick, V.P. Milling P.O. Box 1750 Cañon City, CO Prepared by: Engineering Analytics, Inc Specht Point Road, Suite 209 Fort Collins, Colorado (970) Fax (970) Project No December 18, 2009

3 Conceptualization and Cost Estimate for Corrective Measures TABLE OF CONTENTS 1.0 INTRODUCTION Purpose Scope CONCEPTUAL HYDROGEOLOGY SOURCES Facility Area Area Lincoln Park Area Golf Course Area CORRECTIVE MEASURES Facility Area Alternatives Area Alternatives Lincoln Park Alternative Golf Course Alternatives COST ANALYSIS Facility Area Area Lincoln Park Area Golf Course Area SUMMARY AND CONCLUSIONS LIMITATIONS Engineering Analytics, Inc. i December 18, 2009

4 Conceptualization and Cost Estimate for Corrective Measures LIST OF TABLES Table 5-1 OMB 2009 Discount Rates Table 5-2 Capital Cost and Present Value Costs for Alternative FA-1 Table 5-3 Capital Cost and Present Value Costs for Alternative FA-2 Table 5-4 Capital Cost and Present Value Costs for Alternative Table 5-5 Capital Cost and Present Value Costs for Alternative Table 5-6 Capital Cost and Present Value Costs for Alternative LP-1 Table 5-7 Capital Cost and Present Value Costs for Alternative GC-1 Table 5-8 Capital Cost and Present Value Costs for Alternative CG-2 Table 6-1 Summary of Total Capital + Present Value MNA/O&M Costs LIST OF FIGURES Figure 1-1 Figure 3-1 Figure 3-2 Figure 3-3 Figure 3-4 Figure 3-5 Figure 3-6 Figure 3-7 Figure 3-8 Site Plan, Delineation of Remediation Areas Facility Area, Uranium Groundwater Concentrations Facility Area, Molybdenum Groundwater Concentrations 006 Area, Uranium Groundwater Concentrations 006 Area, Molybdenum Groundwater Concentrations Lincoln Park Area, Uranium Groundwater Concentrations Lincoln Park Area, Molybdenum Groundwater Concentrations Golf Course Area, Uranium Groundwater Concentrations Golf Course Area, Molybdenum Groundwater Concentrations LIST OF APPENDICES Appendix A Appendix B References Detailed Cost Spread Sheets Engineering Analytics, Inc. ii December 18, 2009

5 Conceptualization and Cost Estimate for Remediation Alternatives 1.0 INTRODUCTION 1.1 Purpose Results of conceptual groundwater mitigation strategies and cost estimates for the four Remediation Areas associated with the Cotter Mill are presented in this report. The four Remediation Areas consist of the Facility, 006, Lincoln Park, and Golf Course (Figure 1-1). The Cotter Mill site is located south of Cañon City, Colorado. The development of the Remediation Alternatives was completed in response to the Colorado Department of Public Health and Environment (CDPHE) requirement to provide a surety bond estimate for groundwater remediation. 1.2 Scope EA s scope of work includes: 1. A site visit by Dan Overton on September 30, 2009 with (Cotter) personnel. 2. Development of Remediation Alternatives for the four Remediation Areas (Figure 1-1) using the groundwater data provided by Errol Lawrence of Hydrosolutions. 3. Preparation of surety bond cost estimates for the Remediation Alternatives using the present worth analyses of the proposed remediation period for each alternative. 4. Meet with Cotter at their offices in Greenwood Village, Colorado to review and discuss the Remediation Alternatives and cost estimates. 5. Meet with Edgar Ethington of the Colorado Department of Public Health and Environment to review proposed groundwater remediation alternatives. 6. Preparation of this report presenting the groundwater Remediation Alternatives for each of the four Remediation Areas and associated cost estimates. Engineering Analytics, Inc. 1 December 18, 2009

6 Conceptualization and Cost Estimate for Remediation Alternatives 2.0 CONCEPTUAL HYDROGEOLOGY Groundwater flow at the Cotter site has been analyzed in numerous studies. The site is underlain by Terrace alluvium, the Poison Canyon Formation, Raton Formation, Vermejo Formation, and the Trinidad Sandstone. The two primary groundwater flow regimes are the alluvium primarily along Sand Creek, and the underlying bedrock flow, which is controlled by fracture flow. Groundwater quality has been impacted from site milling processes, ore storage and waste management practices. Two primary constituents of concern (COC) that exceed Colorado Groundwater Quality Standards (CGWQS) are uranium and molybdenum. The CGWQS for uranium and molybdenum are 0.03 mg/l and mg/l, respectively. Contaminant transport in the Golf Course and Facility areas is largely controlled by groundwater flow within the bedrock aquifer, most likely dominated by fracture flow. Groundwater flow in the alluvial material controls the contaminant transport in the Lincoln Park Area. Contaminant transport in the Facility Area along the Sand Creek drainage and the 006 area is controlled by a combination of alluvial and bedrock groundwater flow. Groundwater flow at the Facility Area is predominately in the bedrock. Localized groundwater flow is present in the alluvium associated with the Sand Creek drainage. Much of the alluvium that was historically present in the contaminated portions of the Facility Area has been excavated and hauled away. Groundwater in Areas 006 and Lincoln Park that is contaminated by uranium and molybdenum above CGWQS is primarily in the alluvium along Sand Creek. Groundwater extraction in the alluvium may be relatively productive compared to the Golf Course and Facility Areas. Standard extraction technologies may prove effective in 006 and Lincoln Park. The original source of the alluvial contamination is thought to be historic runoff events that carried contaminated storm water from the mill area down Sand Creek that infiltrated into the water table aquifer. Persistence of elevated molybdenum and uranium in the 006 area may be related to slow release of those constituents from the aquifer matrix (i.e., desorption), low groundwater velocity due to low permeability and low hydraulic gradient, continued leakage under the SCS dam, or a combination of these factors. Residual molybdenum and uranium in the Lincoln Park Area is believed to be the result of either slow desorption or recycling of contaminants via current irrigation practices. Uranium is present above the CGWQS in the groundwater in the Golf Course Area. Molybdenum levels are elevated within one well in the Golf Course Area. The elevated molybdenum appears to be related to the groundwater plume derived from the Facility Area and has migrated down the Sand Creek Drainage. The groundwater contamination beneath the golf course may be from ore stockpiles, the CCD tanks or other unknown sources including natural occurrence of uranium and molybdenum. Groundwater flow in the Golf Course Area is believed to be controlled by fractures in the bedrock, which can be expected to be highly variable. Consequently, any remediation activities that involve groundwater extraction will be focused on intersecting as many fractures as possible to maximize the effectiveness of any extraction techniques. Engineering Analytics, Inc. 2 December 18, 2009

7 Conceptualization and Cost Estimate for Remediation Alternatives 3.0 SOURCES Milling operations consisting of the unlined impoundments, ore piles, CCD tanks, and the milling process are the sources of the groundwater contamination in the four Remediation Areas. Historic overland flow along Sand Creek has also contributed to uranium and molybdenum above the CGWQS. The original sources of the groundwater contamination within the four Remediation Areas of concern are historic in nature and have either been removed or are in the process of being removed. Secondary sources, such as contaminants sorbed onto either the aquifer matrix or geologic materials in the unsaturated zone, may still exist. 3.1 Facility Area Groundwater contaminants in the Facility Area are believed to have originated from the unlined tailings impoundments, ore piles, CCD tanks, and the milling process. The potential sources in the Facility Area have been largely removed or are in the process of being removed. The excavated source materials in the Facility Area have been placed in the lined impoundment. Groundwater uranium concentrations are shown on Figure 3-1. Groundwater molybdenum concentrations are shown on Figure Area The 006 Area is located down-gradient of the Facility Area and the groundwater contamination in the 006 Area is believed to have originated from a combination of overland flow from the Facility Area and groundwater flow that passed beneath the SCS Dam. Uranium concentrations in the 006 Area groundwater are shown on Figure 3-3. Molybdenum concentrations in the 006 Area groundwater are shown on Figure 3-4. Contamination in overland flow from the Facility Area has been mitigated and is not an ongoing source of uranium and molybdenum in groundwater in the 006 Area. Groundwater flow passing beneath the SCS Dam may still be contributing minor amounts of uranium and molybdenum to the 006 Area. No sources are known to exist within the 006 Area. However, historic overland flow may have resulted in infiltration and sorption of uranium and molybdenum in subsurface materials. Slow release (desorption) of uranium and molybdenum may be an ongoing secondary source of groundwater contamination in the 006 area. Leakage from unlined portions of an agricultural ditch (DeWeese Dye Ditch) forms an intermittent hydraulic barrier at the down-gradient end of the 006 Area and limits migration of the groundwater plume. 3.3 Lincoln Park Area The primary source of uranium and molybdenum contamination in the Lincoln Park Area is a result of historic overland flow originating in the Facility Area. The contaminated material and water was believed to have migrated down Sand Creek into the Lincoln Park Area. Material with high concentrations of uranium and molybdenum in the Sand Creek drainage was removed during historic cleanup activities. As previously described, contaminant sources in the Facility Area have either been removed or are being removed. The DeWeese Dye Ditch, located up-gradient from the Lincoln Park Area, is flushing and diluting the contamination in this area. Uranium and molybdenum concentrations in the groundwater are shown in Figures 3-5 and 3-6, respectively. The Lincoln Park Area includes rural land users who irrigate their pastures and Engineering Analytics, Inc. 3 December 18, 2009

8 Conceptualization and Cost Estimate for Remediation Alternatives crops with water from shallow groundwater wells. It is possible that the use of these wells may be recycling uranium and molybdenum into the shallow aquifer, thus slowing the natural attenuation of the groundwater contamination in the Lincoln Park Area. 3.4 Golf Course Area Uranium concentrations above the CGWQS in the Golf Course Area are shown on Figure 3-7. Molybdenum concentrations are above the CGWQS in one well (804) outside the Restricted Area, within the Golf Course Area (Figure 3-8). Low molybdenum concentrations north and west of well 804 have been measured in the Golf Course Area. The elevated molybdenum value at well 804 appears to be part of the contamination plume that originated from historic unlined tailings impoundments (referred to as the Old Pond Area). Extensive groundwater characterization of the Golf Course Area and the other areas of concern indicates that the golf course plume is from a different source than the plume that has moved down Sand Creek toward Lincoln Park. Potential sources include the CCD tanks, the ore stock piles, or even naturally occurring uranium or molybdenum. The known or suspected sources at the Facility Area have been removed or are being removed. Engineering Analytics, Inc. 4 December 18, 2009

9 Conceptualization and Cost Estimate for Remediation Alternatives 4.0 CORRECTIVE MEASURES Engineering Analytics, Inc. met with Errol Lawrence of Hydrosolutions to discuss the four Remediation Areas. These meetings involved review of the historical usage, historic corrective measures taken, site geology, groundwater hydrology, and contamination at the site. Remediation Alternatives were reviewed including Monitored Natural Attenuation (MNA), groundwater pumping, and flushing, among others. Remediation Alternatives were reviewed for practicability, implementability, and likelihood of mitigating the public exposure risk. Remediation alternatives were selected by Hydrosolutions (Hydrosolutions, 2009) for costing from the range of options considered. The pumping rates and duration used in the development of costs are based on the Hydrosolutions report dated December 14, Facility Area Alternatives The Facility Area groundwater has elevated concentrations of molybdenum and uranium that have been measured in groundwater well samples from the underlying Poison Canyon formation. Elevated uranium and molybdenum concentrations have also been measured in the alluvium along the sand creek drainage. Remediation in this area focuses primarily on the remaining groundwater contamination. EA understands that contaminated surface soils and the remaining ore piles have been excavated and placed into the tailings impoundment. Active remediation alternatives discussed for this area assume that any soil and/or groundwater removed in this area can be disposed of in the lined tailings impoundment. Remediation costs have been prepared for the following alternatives Fate and transport modeling and MNA (Alternative FA-1) EA understands that has excavated, or is currently excavating surficial soil contamination and the ore storage piles, and that these materials will be disposed of in the lined tailings impoundment. Four additional monitoring wells will be installed and groundwater in the Facility Area and down-gradient will be monitored. The data from post-source removal samples will be modeled to estimate COC transport and attenuation rates. The results of the modeling will be used to develop a groundwater monitoring plan to monitor natural attenuation (MNA) Drain installation in high concentration area and fate and transport modeling (Alternative FA-2) In Alternative FA-2, a trench 20 feet deep will be installed down-gradient of the area with uranium concentrations above 10 mg/l (Figure 3-1). The material excavated from the trench will be disposed in the lined tailings impoundment. The trench will be backfilled with free-draining gravel and sloped to flow to a series of extraction wells that will be installed in the more permeable gravel. The free-draining materials in the trench combined with the extraction wells will provide a sump where groundwater can be collected and pumped back to the lined tailings impoundment. The pumping rate is assumed to be 10 gpm. At that rate it will take approximately 6.2 years to remove 1 Pore Volume of the uranium plume that exceeds 10 mg/l. For purposes of this assessment, it is assumed that 3 PVs removed will significantly lower the uranium concentration of Engineering Analytics, Inc. 5 December 18, 2009

10 Conceptualization and Cost Estimate for Remediation Alternatives groundwater in this area. Therefore, the duration of this alternative is assumed to be approximately 20 years. Four additional monitoring wells will be installed and groundwater down-gradient of the interceptor trench will be monitored. The data from post-source removal and drain installation will be modeled to estimate COC transport and attenuation rates Area Alternatives Elevated concentrations of uranium and molybdenum in the groundwater downstream of the SCS dam are thought to have originated from the Facility Area. However, the alluvial flow to this area has been substantially cut off by the collection system at the SCS dam. Furthermore, the north boundary of this plume is flushed by the DeWeese Dye ditch, when the ditch is running. The combination of the dam and the ditch appear to be reducing further migration of contaminated groundwater from the 006 Area. The implementation of the Remediation Alternatives in the Facility Area will further reduce contaminate transport to the 006 Area. The remediation alternatives in this area focus on the groundwater contamination down-gradient of the SCS dam and up-gradient of the Lincoln Park Area (Figure 1-1). The highest concentrations of COCs in this area have been detected just down-gradient of the SCS dam. Active remediation alternatives discussed for this area assume that groundwater removed as part of the remediation measures can be disposed of in the lined tailings impoundment. Remediation costs have been prepared for the following alternatives Fate and transport modeling and MNA (Alternative 006-1) EA understands that has excavated, or is currently excavating surficial soil contamination in the Facility Area. Four additional monitoring wells will be installed and groundwater in the 006 Area will be monitored. Data from post-source removal samples will be modeled to estimate COC transport and attenuation rates. The results of the modeling will be used to develop a groundwater monitoring plan to monitor natural attenuation Surface water infiltration and groundwater extraction and fate and transport modeling (Alternative 006-2) The groundwater flux in this area is relatively low and this low flux combined with the presence of a possible hydraulic barrier under the DeWeese Dye ditch makes efficient groundwater extraction in this portion of the plume relatively difficult. Therefore, Alternative includes installation of a 500-foot long subsurface infiltration gallery down-gradient below the SCS dam. This will increase the groundwater flux across this area and result in greater extraction rates resulting in more effective groundwater removal than groundwater extraction alone. This alternative includes limited investigation for aquifer characterization and locating extraction wells, modeling for those areas outside of the 1.0 mg/l uranium contour, purchase of water, drilling extraction and monitoring wells, installation of the infiltration gallery, installing and operating pumps and the associated piping system. Engineering Analytics, Inc. 6 December 18, 2009

11 Conceptualization and Cost Estimate for Remediation Alternatives Based on the hydraulic conductivity of the aquifer down-gradient of the SCS dam, it is anticipated that a maximum of 10 gpm can be infiltrated into the gallery. Alternative includes the installation of 6 extraction wells to a depth of 60 feet just up-gradient of the Cotter property boundary. Each of the wells will pump at a rate of 3 gpm for a total pumping rate of 18 gpm. Based on the increased extraction rate, it will take 5.4 years to remove 1 PV of the molybdenum plume greater than 1.0 mg/l and 16 years to remove 3 PVs. Modeling and MNA analyses will be performed down-gradient of the DeWeese Dye ditch. Subsurface water infiltration will be completed using municipal water. 4.3 Lincoln Park Alternative The highest concentrations of COCs in the Lincoln Park/Cotter Mill Superfund Site (Lincoln Park Area) have been detected in monitoring wells 129 and 189 located near the center of the mapped plume area (Figures 3-5 and 3-6). The contaminant plume in this area is in the Arkansas River alluvium. This alluvium has a relatively high hydraulic conductivity. Individual wells in the alluvium can easily sustain pumping rates of 20 gpm or more. The source of impacted groundwater in the Lincoln Park Area is thought to be from historic mill operations and releases. No sources are known to be currently contributing to the elevated concentrations in the Lincoln Park Area Fate and transport modeling and MNA (Alternative LP-1) Concentrations of COCs in the groundwater in the Lincoln Park Area are relatively low and appear to be slowly declining. The implementation of Remediation Alternatives in the Facility Area and the 006 Area will reduce the probability of transport of additional COCs into the Lincoln Park Area. The MNA alternative will include installation of additional monitoring wells, evaluation of the existing COC concentrations, and groundwater modeling to predict fate and transport times. Results of this modeling will be used to develop a groundwater monitoring plan to monitor natural attenuation. 4.4 Golf Course Alternatives Uranium concentrations above the CGWQS have been measured in the Golf Course Area (Figure 3-7). Elevated molybdenum concentrations above the CGWQS have also been detected within the southeast area of the golf course. As discussed in Section 3.4, the elevated molybdenum concentrations in the Golf Course Area appear to be associated with Facility Area plume. The source of groundwater contamination does not appear to be from the former unlined tailings impoundments. Possible sources include former ore piles at the mill, the CCD tanks or even naturally occurring uranium or molybdenum. Remediation costs have been prepared for the following alternatives Fate and transport modeling and MNA (Alternative GC-1) Groundwater in the Facility Area and down-gradient will be monitored. Data from post-source removal samples will be modeled to estimate COC transport and attenuation Engineering Analytics, Inc. 7 December 18, 2009

12 Conceptualization and Cost Estimate for Remediation Alternatives rates. The MNA alternative will include installation of four additional monitoring wells, evaluation of the existing COC concentrations, and groundwater modeling to predict fate and transport times. Results of this modeling will be used to develop a groundwater monitoring plan to monitor natural attenuation Groundwater extraction and fate and transport modeling (Alternative GC-2) Alternative GC-2 includes the installation of four extraction wells along the north side of the access road within the Cotter property boundary. Wells will be located at 120-foot spacing to a depth of 70 feet. Each well will be pumped at a rate of 1.5 gpm resulting in a total flow of 6 gpm. Because the source has not been adequately determined, it is difficult to estimate the duration of this alternative. For purposes of this assessment it is assumed that the wells will be pumped for 20 years. The discharge water will be pumped back to the tailings impoundment at the Facility Area. Additional monitoring wells will be installed, evaluation of the existing COC concentrations, and groundwater modeling to predict fate and transport times will also be conducted. Engineering Analytics, Inc. 8 December 18, 2009

13 Conceptualization and Cost Estimate for Remediation Alternatives 5.0 COST ANALYSIS Estimated costs for implementation of each of the options discussed in Section 4.0 have been prepared. Cost estimates are based on estimates of the quantities of materials and labor required for implementation and the standard unit costs for those materials and labor. Costing assumptions and quantities are discussed in the following sections. All of the estimated costs presented herein are broken down into the initial capital cost of implementation, the costs associated with future operation and maintenance (O&M), and monitoring. Capital costs include the initial costs of investigation, design, construction and startup. Annual O&M and monitoring costs include routine maintenance, energy costs, monitoring, and replacement. Groundwater monitoring has been assumed to occur on a semi-annual schedule for the Remediation Areas with the exception of the Facility Area, which will be sampled once a year. The groundwater monitoring has been assumed to occur for 30 years. Annual and periodic O&M and monitoring costs have been converted using a present value for the comparison of the different alternatives based on the duration of the alternative. The present value analyses were conducted using discount rates from the Office of Management and Budget (OMB, 2008). The discount rates are shown in Table 5-1. Table OMB 2009 Discount Rates 3-Year 5-Year 7-Year 10-Year 20-Year 30-Year 2.7% 3.3% 3.7% 4.2% 4.7% 4.5% 5.1 Facility Area The cost estimates in this area focus primarily on the remaining groundwater contamination in the Facility Area. It is our understanding that contaminated surface soils and the remaining ore piles have been excavated and placed into the lined tailings impoundment. Active remediation alternatives discussed for this area assume that any soil and groundwater removal conducted in this area can be disposed of in the lined tailings impoundment. Possible remediation alternatives for the Facility Area include: Fate and transport modeling and MNA (Alternative FA-1); and Drain installation in high concentration area and fate and transport modeling (Alternative FA-2) Fate and transport modeling and MNA (Alternative FA-1) Groundwater concentrations within the Facility Area will be discretized to develop a 3-dimensional view of the contamination plume. The resulting groundwater concentrations will then be modeled to provide an estimate of the rate at which the COC s will travel or be attenuated in the subsurface. The results of this modeling will be used to develop a monitoring plan to be used to implement an MNA solution for this site. In preparing this cost estimate EA assumed that the surficial soil contamination and ore Engineering Analytics, Inc. 9 December 18, 2009

14 Conceptualization and Cost Estimate for Remediation Alternatives storage piles have been excavated and disposed of in the tailings impoundment. Capital costs associated with this alternative include installation of four additional monitoring wells, annual sampling, and groundwater modeling. We have provided costs to install four additional monitoring wells and sample them annually for 30 years. The estimated costs of this alternative are shown in Table 5-2 and Appendix B. Table Capital Cost and Present Value Costs for Alternative FA-1 Capital Costs: $126,720 Annual MNA Costs: $2, year Present Value of MNA: $38,279 Total Capital + Present Value MNA Costs: $164, Drain installation in high concentration area and fate and transport modeling (Alternative FA-2) In Alternative FA-2, a 20 feet deep trench will be installed in the area of high COC concentrations. The trench will be 2,400 feet long and 3 feet wide. The trench will be backfilled with free-draining gravel and slope to flow to a series of thirteen extraction wells installed in the permeable gravel. The free-draining materials in the trench combined with the extraction wells provide a sump where groundwater will be collected and pumped back to the lined tailings impoundment. Four monitoring wells will be installed and monitored down-gradient of the interceptor trench. The resulting groundwater concentrations will be modeled to provide an estimate of the rate at which the COC s will travel or be attenuated in the subsurface. Capital costs for Alternative FA-2 include trench excavation, disposal of excavated materials, purchase and installation of the free-draining materials, installation of the wells and associated pumping systems, and installation of monitoring wells. O&M costs include periodic pump replacements, and piping and system repairs. O&M costs for the trench are based on a pumping duration of 20 years (Hydrosolutions, 2009). Costs for semi-annual sampling and reporting of the four monitoring wells were also included. The estimated costs of this alternative are shown in Table 5-3 and Appendix B. Table 5-3- Capital Cost and Present Value Costs for Alternative FA-2 Capital Costs: $434,158 Annual O&M: $52, year Present Value of O&M: $665,078 Annual MNA Costs: $2, year Present Value of MNA: $38,279 Total Capital + Present Value MNA/O&M Costs: $1,137, Area The cost estimates in the 006 Area focus on the groundwater contamination down-gradient of the SCS dam and up-gradient the Lincoln Park Area (Figure 1-1). The highest concentrations of COCs in this area have been detected just down-gradient of the SCS dam. Active remediation alternatives discussed for this area assume that any groundwater removed as part of the Engineering Analytics, Inc. 10 December 18, 2009

15 Conceptualization and Cost Estimate for Remediation Alternatives remediation measures can be disposed of in the lined tailings impoundment. Possible remedial alternatives for the 006 Area include: Fate and transport modeling and MNA (Alternative 006-1); and Surface water infiltration and groundwater extraction and fate and transport modeling (Alternative 006-2) Fate and transport modeling and MNA (Alternative 006-1) Groundwater concentrations within the Facility Area will be discretized to develop a 3-dimensional view of the contamination plume. The resulting groundwater concentrations will then be modeled to provide an estimate of the rate at which the COC s will travel or be attenuated in the subsurface. Groundwater concentrations will then be modeled to estimate the COC transport and attenuation rates. The modeling results will be used to develop a monitoring plan to support implementation of MNA. Four additional monitoring wells will be installed. Six monitoring wells will be sampled semi-annually to confirm results of the modeling. Capital costs associated with Alternative include limited additional investigation and data collection, installation of the monitoring wells, and groundwater modeling. MNA includes ongoing sampling and reporting. The estimated costs of this alternative are shown in Table 5-4 and Appendix B. Table Capital Cost and Present Value Costs for Alternative Capital Costs: $105,620 Annual MNA Costs: $6, year Present Value of MNA: $102,620 Total Capital + Present Value MNA Costs: $208, Surface water infiltration and groundwater extraction and fate and transport modeling (Alternative 006-2) Alternative includes the installation of six extraction wells just up-gradient of the Cotter property boundary. As discussed in Section 2.0 the groundwater flux in this area is relatively low. This occurrence, when coupled with the presence of a seasonal hydraulic barrier under the DeWeese Dye ditch makes efficient extraction in this portion of the plume relatively difficult. Therefore, Alternative includes the installation of a subsurface infiltration gallery just down-gradient of the SCS dam. The extracted groundwater will be pumped over the SCS dam to the existing pump and sump system. The existing pump and sump system will pump the water back to the lined impoundments. Modeling and MNA analyses will be completed for those portions of the COC plumes located down-gradient of the extraction well array. Four additional monitoring wells will be installed. Six monitoring wells and six extraction wells will be sampled semi-annually. Capital costs associated with Alternative include limited investigation and modeling for those areas down-gradient of the extraction wells, installing the infiltration gallery, purchase of water, drilling extraction and monitoring wells, installing pumps and the associated piping system. O&M costs include periodic Engineering Analytics, Inc. 11 December 18, 2009

16 Conceptualization and Cost Estimate for Remediation Alternatives pump replacements, piping repairs, electrical costs, annual water purchases, and system monitoring. MNA costs include groundwater sampling and reporting. The estimated costs of this alternative are shown in Table 5-5 and Appendix B. Table Capital Cost and Present Value Costs for Alternative Capital Costs: $467,518 Annual O&M: $49, year Present Value of O&M: $547,210 Annual MNA Costs: $6, year Present Value of MNA: $102,620 Total Capital + Present Value MNA/O&M Costs: $1,117, Lincoln Park Area The cost estimate in this area focuses on the groundwater contamination in the Lincoln Park/Cotter Mill Superfund Site (Lincoln Park Area). The highest concentrations of COCs in this area have been detected at monitoring wells 129 and 189 located near the center of the mapped plume area (Figures 3-5 and 3-6). The contaminant plume in this area is in the Arkansas River alluvium Fate and transport modeling and MNA (Alternative LP-1) Concentrations of COCs in the groundwater in the Lincoln Park Area are relatively low and appear to be slowly decreasing. The MNA alternative will include evaluation of the existing COC concentrations and groundwater modeling to predict fate and transport of the COCs. Groundwater concentrations within the Lincoln Park Area will be discretized to develop a 3-dimensional view of the contamination plume. The resulting groundwater concentrations will then be modeled to provide an estimate of the rate at which the COC s will travel or be attenuated in the subsurface. Groundwater concentrations will then be modeled to estimate the COC transport and attenuation rates. The modeling results will be used to develop a monitoring plan to support implementation of the MNA alternative. Two additional monitoring wells will be constructed. Four monitoring wells will be sampled semi-annually to confirm the results of the modeling. Capital costs associated with Alternative LP-1 include limited additional investigation, data collection, and groundwater modeling. MNA costs include semi-annual sampling of four monitoring wells based on a 30 year present value cost. The estimated costs of this alternative are shown in Table 5-6 and Appendix B. Table 5-6- Capital Cost and Present Value Costs for Alternative LP-1 Capital Costs: $92,560 Annual MNA Costs: $4, year Present Value of MNA: $76,558 Total Capital + Present Value MNA Costs: $169,118 Engineering Analytics, Inc. 12 December 18, 2009

17 Conceptualization and Cost Estimate for Remediation Alternatives 5.4 Golf Course Area The cost estimates in this area focus on the groundwater contamination that is migrating onto the golf course across the northwest Cotter property boundary. A review of the groundwater monitoring data collected for this area indicates that the groundwater plume associated with this area is limited to uranium. Possible remedial alternatives for the Golf Course Area include: Fate and transport modeling and MNA (Alternative GC-1); and Groundwater Extraction and fate and transport modeling (Alternative GC-2) Fate and transport modeling and MNA (Alternative GC-1) Groundwater concentrations within the Golf Course Area will be discretized to develop a 3-dimensional view of the contamination plume. The resulting groundwater concentrations will then be modeled to provide an estimate of the rate at which the COC s will travel or be attenuated in the subsurface. Groundwater concentrations will then be modeled to estimate the COC transport and attenuation rates. The modeling results will be used to develop a monitoring plan to support implementation of MNA. Capital costs associated with Alternative GC-1 include limited additional investigation and data collection, groundwater modeling, installation of four additional monitoring wells, and modeling of the groundwater plume. MNA costs include semi-annual sampling of eight monitoring wells. The estimated costs of this alternative are shown in Table 5-7 and Appendix B. Table 5-7- Capital Cost and Present Value Costs for Alternative GC-1 Capital Costs: $105,620 Annual MNA Costs: $7, year Present Value of MNA: $128,682 Total Capital + Present Value MNA Costs: $234, Groundwater extraction and fate and transport modeling (Alternative GC-2) Alternative GC-2 includes the installation of four extraction wells (each 70 feet deep) between the mill site and the golf course and pumping the extracted groundwater back to the lined tailing impoundment. Pumping rates are anticipated to be 6 gpm (1.5 gpm per well) for a duration of 20 years. Four additional monitoring wells will be installed down-gradient of the extraction wells and sampled semi-annually. Groundwater concentrations will be modeled to estimate the COC transport and attenuation rates. Capital costs associated with this alternative include drilling extraction wells, installing pumps and the associated piping system, installing monitoring wells, and modeling of the groundwater plume. O&M costs include periodic pump replacements, piping and system repairs. MNA costs include semi-annual groundwater monitoring and reporting. The estimated costs of this alternative are shown in Table 5-8 and Appendix B. Engineering Analytics, Inc. 13 December 18, 2009

18 Conceptualization and Cost Estimate for Remediation Alternatives Table 5-8- Capital Cost and Present Value Costs for Alternative CG-2 Capital Costs: $303,067 Annual O&M: $30, year Present Value of O&M: $389,146 Annual MNA Costs: $7, year Present Value of MNA: $128,682 Total Capital + Present Value MNA/O&M Costs: $820,895 Engineering Analytics, Inc. 14 December 18, 2009

19 Conceptualization and Cost Estimate for Remediation Alternatives 6.0 SUMMARY AND CONCLUSIONS EA has presented the results of the selected Remediation Alternatives and the associated costs for each alternative. The Remediation Alternatives and costs are provided to develop a surety bond estimate for the CDPHE. The total capital cost plus the present value MNA/O&M costs are summarized in Table 6-1. Table 6-1- Summary of Total Capital + Present Value MNA/O&M Costs Alternative Title Total Capital +Present Value Costs FA-1 Fate and transport modeling and MNA $164,999 FA-2 Drain installation in highest concentration area and fate and transport modeling $1,137, Fate and transport modeling and MNA $208, Surface water infiltration and groundwater extraction and fate and transport modeling $1,117,348 LP-1 Fate and transport modeling and MNA $169,118 GC-1 Fate and transport modeling and MNA $234,302 GC-2 Groundwater extraction and fate and transport modeling $820, LIMITATIONS The above Remediation Alternatives and costs are based on a reasonable degree of engineering certainty. This report has been prepared based upon discussions with Hydrosolutions, review of their December 2009 report (Hydrosolutions, 2009), a site visit and meeting with Cotter personnel, and our experience. The conclusions presented represent our best judgment based on the information available. Should additional information become available, we must be allowed to review that information and modify our conclusions accordingly. No warranty is made, express, or implied. Engineering Analytics, Inc. 15 December 18, 2009

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29 APPENDIX A REFERENCES

30 REFERENCES Craftsman Book Co. (2009). Get-a-quote.net. Retrieved from Environmental Alternatives, Inc Personal correspondence with Angela Bellantoni. December 4. Hydrosolutions, Inc Site Conceptual Model and Proposed Corrective Measures for the Canon City Milling Facility, Colorado. December 14. Office of Management and Budget, Executive Office of the President Discount Rates for OMB Circular No. A-94. December 12. RSMeans, Heavy Construction Cost Data, A division of Reed Construction Data, MA.

31 APPENDIX B DETAILED COST SPREAD SHEETS

32 FA 1 Area Option Facility FA-1: Fate and transport modeling and monitored natural attenuation (MNA) Monitoring Period (years) Year Discount Rate 4.5% Category Description Qty Unit $ / Unit Total Capital Construction Costs Monitoring well (2") (2) 4 WELL $ 5,275 $ 21,100 Engineering Design & Oversight % of capital costs 20 % $ 4,220 Client / Agency Interaction 1 LS $ 7,500 $ 7,500 Modeling 480 HR $ 150 $ 72,000 Subtotal $ 104,820 Permitting Well permit 4 EA $ 200 $ 800 Total Capital Cost $ 126,720 Operational Costs MNA Costs Sampling (Annual) 4 WELL $ 200 $ 800 Lab analysis (Annual) 4 WELL $ 200 $ 800 Reporting (Annual) 1 EA $ 750 $ 750 Subtotal $ 2,350 Total Annual MNA Cost $ 2,350 Present Value MNA Cost $ 38,279 Total Present Value Operational Cost $ 38,279 Option Total (Capital Costs + Present Value Operational Costs) $ 164,999 (1) Environmental Alternatives Inc. (2) RS Means 2010 Heavy construction cost data book (3) Get-A-Quote.net (4) (5) Hydrosolutions 1

33 FA 2 Area Option Facility FA-2: Drain installation in highest concentration area and fate and transport modeling and MNA Remediation Period (years) Year Discount Rate 4.7% Monitoring Period (years) Year Discount Rate 4.5% Category Description Qty Unit $ / Unit Total Capital Costs Remediation Construction Trench excavation (2) 5333 CY $ 9 $ 48,000 Dewatering (2) 4 WEEK $ 1,000 $ 4,000 Hauling (1) 5333 CY $ 3 $ 16,000 Fill gravel (3) 5333 CY $ 13 $ 69,333 Water truck (1) 1 MO $ 6,345 $ 6,345 Air monitoring (3) 1 MO $ 785 $ 785 Standpipe (2) 13 EA $ 231 $ 3,003 Well pump & motor (2) 13 EA $ 1,500 $ 19,500 Piping (2) 5000 LF $ 19 $ 95,000 Control system & wiring (2) 13 WELL $ 500 $ 6,500 Power drop (2) 1 EA $ 10,715 $ 10,715 Construction Oversight 4 WEEK $ 5,000 $ 20,000 Well permit 13 EA $ 200 $ 2,600 Health & safety plan 1 LS $ 10,000 $ 10,000 Decon 1 LS $ 12,000 $ 12,000 Remediation Subtotal $ 323,781 MNA Construction Monitoring well (2") (2) 4 WELL $ 5,275 $ 21,100 Client / Agency Interaction 1 LS $ 7,500 $ 7,500 Modeling 80 HR $ 150 $ 12,000 Well permit 4 EA $ 200 $ 800 MNA Subtotal $ 41,400 Engineering Design & Oversight % of capital costs 20 % $ 68,976 Total Capital Cost $ 434,158 1

34 FA 2 Area Option Facility FA-2: Drain installation in highest concentration area and fate and transport modeling and MNA Remediation Period (years) Year Discount Rate 4.7% Monitoring Period (years) Year Discount Rate 4.5% Category Description Qty Unit $ / Unit Total Operational Operation and Maintenance Costs Annual Costs Energy (well pump) 13 WELL $ 3,429 $ 44,577 Inspection and maintenance 13 WELL $ 200 $ 2,600 Sampling (Annual) 1 WELL $ 200 $ 200 Lab analysis (Annual) 1 WELL $ 200 $ 200 Reporting (Annual) 1 EA $ 1,500 $ 1,500 Subtotal $ 49,077 Periodic Costs Well pump & motor repl. (5, 10, & 15-year) (3) 13 EA $ 1,500 $ 19,500 Total Annual O&M Cost $ 52,019 Present Value O&M Cost $ 665,078 MNA Costs Sampling (Annual) 4 WELL $ 200 $ 800 Lab analysis (Annual) 4 WELL $ 200 $ 800 Reporting (Annual) 1 EA $ 750 $ 750 Subtotal $ 2,350 Total Annual MNA Cost $ 2,350 Present Value MNA Cost $ 38,279 Total Present Value Operational Cost $ 703,357 Option Total (Capital Costs + Present Value Operational Costs) $ 1,137,515 (1) Environmental Alternatives Inc. (2) RS Means 2010 Heavy construction cost data book (3) Get-A-Quote.net (4) (5) Hydrosolutions 2

35 006 1 Area Option 006 Area 006-1: Fate and transport modeling and MNA Monitoring Period (years) Year Discount Rate 4.5% Category Description Qty Unit $ / Unit Total Capital Construction Costs Monitoring well (2") (2) 4 WELL $ 5,275 $ 21,100 Engineering Design & Oversight % of capital costs 20 % $ 4,220 Client / Agency Interaction 1 LS $ 7,500 $ 7,500 Modeling 480 HR $ 150 $ 72,000 Subtotal $ 83,720 Permitting Well permit 4 EA $ 200 $ 800 Total Capital Cost $ 105,620 Operational Costs MNA Costs Sampling (Semi-annual) 6 WELL $ 400 $ 2,400 Lab analysis (Semi-annual) 6 WELL $ 400 $ 2,400 Reporting (Semi-annual) 1 EA $ 1,500 $ 1,500 Subtotal $ 6,300 Total Annual MNA Cost $ 6,300 Present Value MNA Cost $ 102,620 Total Present Value Operational Cost $ 102,620 Option Total (Capital Costs + Present Value Operational Costs) $ 208,240 (1) Environmental Alternatives Inc. (2) RS Means 2010 Heavy construction cost data book (3) Get-A-Quote.net (4) (5) Hydro solutions 1

36 006 2 Area Option 006 Area 006-2: Surface water infiltration and groundwater extraction and fate and transport modeling and MNA Remediation Period (years) Year Discount Rate 4.7% Monitoring Period (years) Year Discount Rate 4.5% Category Description Qty Unit $ / Unit Total Capital Remediation Construction Costs Well (6") (5) 6 WELL $ 12,000 $ 72,000 Well pump & motor (2) 6 EA $ 3,925 $ 23,550 Piping, double lined (2) 1600 LF $ 27 $ 43,200 Valves & fittings 1 LS $ 5,000 $ 5,000 Lift pump & motor (3) 1 EA $ 12,044 $ 12,044 Surge tank (2) 1 EA $ 47,700 $ 47,700 Control system & wiring (2) 6 WELL $ 356 $ 2,136 Excavation & loading (2) 926 CY $ 2 $ 1,722 Hauling (1) 926 CY $ 3 $ 2,778 Infiltration field (2) 1500 SF $ 9 $ 13,500 Fill gravel (3) 926 CY $ 13 $ 12,037 Power drop (2) 1 EA $ 10,715 $ 10,715 Fresh water tap fee (1) 1 LS $ 5,000 $ 5,000 Fresh water piping (2) 3000 LF $ 28 $ 84,000 Well permit 6 EA $ 200 $ 1,200 Health & safety plan 1 LS $ 10,000 $ 10,000 Decon 1 LS $ 5,000 $ 5,000 Subtotal $ 351,582 MNA Construction Monitoring well (2") (2) 4 WELL $ 5,275 $ 21,100 Client / Agency Interaction 1 LS $ 7,500 $ 7,500 Modeling 80 HR $ 150 $ 12,000 Well permit 4 EA $ 200 $ 800 Subtotal $ 41,400 Engineering Design & Oversight % of capital costs 20 % $ 74,536 Total Capital Cost $ 467,518 1

37 006 2 Area Option 006 Area 006-2: Surface water infiltration and groundwater extraction and fate and transport modeling and MNA Remediation Period (years) Year Discount Rate 4.7% Monitoring Period (years) Year Discount Rate 4.5% Category Description Qty Unit $ / Unit Total Operational Operation and Maintenance Costs Costs Annual Costs Energy (well pump) 6 WELL $ 3,429 $ 20,574 Energy (lift station) 1 EA $ 3,429 $ 3,429 Water (4) 16.1 AF $ 408 $ 6,575 Inspection and maintenance 7 WELL $ 1,000 $ 7,000 Sampling (Semi-annual) 6 WELL $ 400 $ 2,400 Lab analysis (Semi-annual) 6 WELL $ 400 $ 2,400 Reporting (Semi-annual) 1 EA $ 1,500 $ 1,500 Subtotal $ 43,878 Periodic Costs Well pump & motor repl. (5, 10, & 15-year) (3) 6 EA $ 4,000 $ 24,000 Lift pump motor repl. (7 & 14-year) (3) 1 EA $ 12,044 $ 12,044 Subtotal $ 36,044 Total Annual O&M Cost $ 49,419 Present Value O&M Cost $ 547,210 MNA Costs Sampling (Semi-annual) 6 WELL $ 400 $ 2,400 Lab analysis (Semi-annual) 6 WELL $ 400 $ 2,400 Reporting (Semi-annual) 1 EA $ 1,500 $ 1,500 Subtotal $ 6,300 Total Annual MNA Cost $ 6,300 Present Value MNA Cost $ 102,620 Total Present Value Operational Cost $ 649,830 Option Total (Capital Costs + Present Value Operational Costs) $ 1,117,348 (1) Environmental Alternatives Inc. (2) RS Means 2010 Heavy construction cost data book (3) Get-A-Quote.net (4) (5) Hydrosolutions 2

38 LP 1 Area Option Lincoln Park LP-1: Fate and transport modeling and MNA Monitoring Period (years) Year Discount Rate 4.5% Category Description Qty Unit $ / Unit Total Capital Construction Costs Monitoring well (2") (2) 2 WELL $ 5,275 $ 10,550 Engineering Design & Oversight % of capital costs 20 % $ 2,110 Client / Agency Interaction 1 LS $ 7,500 $ 7,500 Modeling 480 HR $ 150 $ 72,000 Subtotal $ 81,610 Permitting Well permit 2 EA $ 200 $ 400 Total Capital Cost $ 92,560 Operational Costs MNA Costs Sampling (Semi-annual) 4 WELL $ 400 $ 1,600 Lab analysis (Semi-annual) 4 WELL $ 400 $ 1,600 Reporting (Semi-annual) 1 EA $ 1,500 $ 1,500 Subtotal $ 4,700 Total Annual MNA Cost $ 4,700 Present Value MNA Cost $ 76,558 Total Present Value Operational Cost $ 76,558 Option Total (Capital Costs + Present Value Operational Costs) $ 169,118 (1) Environmental Alternatives Inc. (2) RS Means 2010 Heavy construction cost data book (3) Get-A-Quote.net (4) (5) Hydrosolutions 1

39 GC 1 Area Option Golf Course GC-1: Fate and transport modeling and MNA Monitoring Period (years) Year Discount Rate 4.5% Category Description Qty Unit $ / Unit Total Capital Construction Costs Monitoring well (2") (2) 4 WELL $ 5,275 $ 21,100 Engineering Design & Oversight % of capital costs 20 % $ 4,220 Client / Agency Interaction 1 LS $ 7,500 $ 7,500 Modeling 480 HR $ 150 $ 72,000 Subtotal $ 83,720 Permitting Well permit 4 EA $ 200 $ 800 Total Capital Cost $ 105,620 Operational Costs MNA Costs Sampling (Semi-annual) 8 WELL $ 400 $ 3,200 Lab analysis (Semi-annual) 8 WELL $ 400 $ 3,200 Reporting (Semi-annual) 1 EA $ 1,500 $ 1,500 Subtotal $ 7,900 Total Annual MNA Cost $ 7,900 Present Value MNA Cost $ 128,682 Total Present Value Operational Cost $ 128,682 Option Total (Capital Costs + Present Value Operational Costs) $ 234,302 (1) Environmental Alternatives Inc. (2) RS Means 2010 Heavy construction cost data book (3) Get-A-Quote.net (4) (5) Hydrosolutions 1

40 GC 2 Area Option Golf Course GC-2: Groundwater extraction, fate and transport modeling and MNA Monitoring Period (years) Year Discount Rate 4.7% Observation Period (years) Year Discount Rate 4.5% Category Description Qty Unit $ / Unit Total Capital Costs Remediation Construction Well (6") (5) 4 WELL $ 12,000 $ 48,000 Well pump & motor (2) 4 EA $ 3,925 $ 15,700 Piping (2) 3200 LF $ 19 $ 60,800 Valves & fittings 1 LS $ 5,000 $ 5,000 Lift pump & motor (3) 1 EA $ 12,044 $ 12,044 Surge tank (2) 1 EA $ 47,700 $ 47,700 Control system & wiring (2) 5 WELL $ 356 $ 1,780 Power drop (2) 1 EA $ 10,715 $ 10,715 Well permit 4 EA $ 200 $ 800 Health & safety plan 1 LS $ 10,000 $ 10,000 Decon 1 LS $ 2,000 $ 2,000 Subtotal $ 214,539 MNA Construction Monitoring well (2") (2) 4 WELL $ 5,275 $ 21,100 Client / Agency Interaction 1 LS $ 7,500 $ 7,500 Modeling 80 HR $ 150 $ 12,000 Well permit 4 EA $ 200 $ 800 Subtotal $ 41,400 Engineering Design & Oversight % of capital costs 20 % $ 47,128 Total Capital Cost $ 303,067 1

41 GC 2 Area Option Golf Course GC-2: Groundwater extraction, fate and transport modeling and MNA Monitoring Period (years) Year Discount Rate 4.7% Observation Period (years) Year Discount Rate 4.5% Category Description Qty Unit $ / Unit Total Operational Operation and Maintenance Costs Costs Annual Costs Energy (well pump) 4 WELL $ 3,429 $ 13,716 Energy (lift station) 1 EA $ 3,429 $ 3,429 Inspection and maintenance 5 WELL $ 1,000 $ 5,000 Sampling (Semi-annual) 4 WELL $ 400 $ 1,600 Lab analysis (Semi-annual) 4 WELL $ 400 $ 1,600 Reporting (Semi-annual) 1 EA $ 1,500 $ 1,500 Subtotal $ 26,845 Periodic Costs Well pump & motor repl. (5, 10, & 15-year) (3) 4 EA $ 4,000 $ 16,000 Lift pump motor repl. (7 & 14-year) (3) 1 EA $ 12,044 $ 12,044 Subtotal $ 28,044 Total Annual O&M Cost $ 30,437 Present Value O&M Cost $ 389,146 MNA Costs Sampling (Semi-annual) 8 WELL $ 400 $ 3,200 Lab analysis (Semi-annual) 8 WELL $ 400 $ 3,200 Reporting (Semi-annual) 1 EA $ 1,500 $ 1,500 Subtotal $ 7,900 Total Annual MNA Cost $ 7,900 Present Value MNA Cost $ 128,682 Total Present Value Operational Cost $ 517,829 Option Total (Capital Costs + Present Value Operational Costs) $ 820,895 (1) Environmental Alternatives Inc. (2) RS Means 2010 Heavy construction cost data book (3) Get-A-Quote.net (4) (5) Hydrosolutions 2