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EPA/ROD/R07-05/048 2005

EPA Superfund

Record of Decision:

ANNAPOLIS LEAD MINE EPA ID: MO0000958611 OU 01 ANNAPOLIS, MO 09/29/2005

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RECORD OF DECISION

ANNAPOLIS LEAD MINE SUPERFUND SITEOPERABLE UNIT 1

IRON COUNTY, MISSOURI

Prepared by:

U.S. Environmental Protection Agency, Region 7901 North 5th Street

Kansas City, Kansas 66101

September 2005

40216205

TABLE OF CONTENTS

PageDeclaration 1

Site Name and Location 1Statement of Basis and Purpose 1Assessment of the Site 1Description of the Selected Remedy 1Statutory Determination 2ROD Data Certification Checklist 3Authorizing Signatures 3

I. Decision Summary 4

A. Site Name, Location, and Brief Description 4B. Site History and Enforcement Activities 4C. Community Participation 5D. Scope and Role of Operable Unit 6E. Site Characteristics 6F. Current and Potential Future Site and Resource Uses 7G. Summary of Site Risks 8H. Remedial Action Objectives 13I. Description of Alternatives 12J. Comparative Analysis of Alternatives 15

K. Principal Threat Waste 18L. Selected Remedy 18M. Statutory Determinations 20

Appendix A. Figures

Figure 1: Site Location MapFigure 2: Mine Waste Pile before Removal ActionFigure 3: Tailings in Sutton Branch Creek before Removal ActionFigure 4: Remaining Structure at the ALMFigure 5: Annapolis Conceptual Site Model from the BERAFigure 6: Annapolis Conceptual Site Model from the HHRA

Appendix B. Tables

Table 1: Candidate Remedial Alternatives Screening SummaryTable 2: Potential Chemical Specific ARARSTable 3: Potential Location Specific ARARSTable 4: Potential Action Specific ARARS

Table 5: Present Cost Analysis of Alternative 2 (Preferred Alternative)

Appendix C. Responsiveness Summary

a. Stakeholder Comments and Lead Agency Responsesb. Technical and Legal Issues

RECORD OF DECISION

DECLARATION

SITE NAME AND LOCATION

Sutton Branch Creek Flood Plain and Mine Area, Operable Unit 1 (OU 1)Annapolis Lead Mine Superfund Site (Comprehensive Environmental Response,Compensation, and Liability Information System [CERCLIS] ID #: MO0000958611)Iron County, Missouri

STATEMENT OF BASIS AND PURPOSE

This document presents the selected remedial alternative for addressing mine wastes atthe Annapolis Lead Mine Site, OU 1. This decision was chosen in accordance with theComprehensive Environmental Response, Compensation, and Liability Act (CERCLA),as amended by the Superfund Amendments and Reauthorization Act (SARA), and to theextent practicable, the National Contingency Plan (NCP). This decision is based on theAdministrative Record for the Site. The Administrative Record File is located in thefollowing information repositories:

Annapolis City Hall EPA Region 7204 School Street Records CenterAnnapolis, Missouri 901 N. 5th Street

Kansas City, Kansas

The EPA has coordinated selection of this remedial action with the Missouri Departmentof Natural Resources (MDNR). The state of Missouri concurs with the selected remedy.

ASSESSMENT OF THE SITE

Actual or threatened releases of hazardous substances from this Site, if not addressed byimplementing the response action selected in this Record of Decision (ROD), maypresent an imminent and substantial endangerment to the public health, welfare, or theenvironment.

DESCRIPTION OF THE SELECTED REMEDY

This selected remedy deals with the control of mining and milling wastes, soil, andselected sediments contaminated with metals from past mining activities at the Site. Thiscleanup action is one part of the Environmental Protection Agency's (EPA) overallefforts under Superfund to deal with environmental contamination resulting from historiclead mining operations at the Annapolis Lead Mine. Cleanup activities of the originaltailings pile have already occurred and are nearly complete. The EPA believes that theselected remedy is protective of human health and the environment.

The major components of the selected remedy are:

• Addition of phosphate to floodplain soils (away from the outer edge ofriparian zone) during the dry season to improve the density of vegetation andto reduce the bioavailability of lead to terrestrial receptors.

• Mining wastes in heavily forested, thickly vegetated areas, such as the riparianbuffer, will not be subject to excavation, consolidation, or capping.

• Excavation of sediments from Sutton Branch Creek in pockets or depositionalareas. The amount of excavation will be determined during the RemedialDesign (RD) phase.

• Placement of excavated sediments in the existing repository area and cap witha soil cover.

• Stabilization of the Sutton Branch Creek channel with large rock and/or othermaterial to prevent wash-outs and stream channel meandering. The extent ofstabilization will be determined during the RD phase.

• Implementation of Institutional Controls (ICs)

• Performance of annual monitoring to determine remedial effectiveness. Themonitoring frequency will be evaluated to determine whether it should bemore frequent or can be extended to periods beyond annual monitoring.

• Regular water quality monitoring (including phosphorus) will be carried outby MDNR at established monitoring stations, pursuant to the Clean Water Act(CWA).

• The MDNR will manage post-removal maintenance of the protective coverconsistent with all federal and state laws.

STATUTORY DETERMINATIONS

The selected remedy is protective of human health and the environment, is expected tocomply with the chemical-, location-, and action-specific federal and state requirementsthat are legally applicable or relevant and appropriate to the remedial action, and is costeffective. This remedy utilizes permanent solutions to the maximum extent practicable.Treatment of waste will occur over time to reduce the mobility of the metalscontamination in the wastes and to increase the density of existing vegetation.

Because this remedy will result in hazardous substances remaining on the Site abovehealth-based levels, a review will be conducted within five years to ensure that theremedy continues to provide adequate protection of human health and the environment.

ROD DATA CERTIFICATION CHECKLIST

The following information is included in the Decision Summary of this ROD. Additionalinformation can be found in the Administrative Record for this Site.

• Chemicals of concern and their respective concentrations• Baseline risk represented by the chemicals of concern• Cleanup levels established for chemicals of concern and the basis for these

levels• How source materials constituting principal threats are addressed• Current and reasonably anticipated future land use assumptions and current

and potential future beneficial uses of groundwater used in the baseline riskassessment and ROD

• Potential land and groundwater use that will be available at the Site as a resultof the selected remedy

• Estimated capital, annual operation and maintenance (O&M), and totalpresent worth costs, discount rate, and the number of years over which theremedy cost estimates are projected

• Key factor(s) that led to selecting the remedy (i.e., describe how the selectedremedy provides the best balance of tradeoffs with respect to the balancingand modifying criteria key to the decision).

AUTHORIZING SIGNATURES

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RECORD OF DECISION

DECISION SUMMARY

A. SITE NAME, LOCATION. AND BRIEF DESCRIPTION

The Annapolis Lead Mine (ALM) Superfund Site (Comprehensive EnvironmentalResponse, Compensation, and Liability Information System [CERCLIS] ID #MO0000958611) Operable Unit 1 (OU 1) is located in Southern Iron County in the OldLead Belt of Southeast Missouri. The OU 1 Site covers approximately 200 acres. Leadmining occurred at the Site from approximately 1919 to 1940. Over one million tons ofmining waste was generated during this time. Heavy metal contamination aboveacceptable levels has been identified in mining waste, soil, surface water, and sediments.The Site is arranged into two OUs for administrative efficiency in conductingenvironmental cleanups: OU 1, Sutton Branch Creek Flood Plain and Mine Area, and OU2, city of Annapolis and Big Creek. The Site is depicted on Figure 1.

The Environmental Protection Agency (EPA) is the lead agency and the MissouriDepartment of Natural Resources (MDNR) is the support agency for this remedyselection. As there are no viable responsible parties for the Site, the sources of cleanupmonies will include the Superfund Trust Fund and the state of Missouri cost share.

B. SITE HISTORY AND ENFORCEMENT ACTIVITIES

The ALM Site was placed on the National Priorities List (NPL) on J u l y 22, 2004. It waslisted due to elevated levels of heavy metals, particularly lead, which were presentthroughout the Site. Contaminated media at the Site include mining wastes, sediments,soils, and surface water. The contaminants of concern (COCs) are arsenic, cadmium,lead, and zinc. The contamination was caused by lead ore mining and processing. Themining and processing generated chat piles and tailings, collectively known as millingwastes, which are the sources of the COCs. In addition, surface water bodies locateddownstream from the Site contained elevated concentrations of site-related hazardoussubstances that could pose a threat to recreational fisheries and wetlands in the area.

Prior to the NPL listing, several investigations of the Site occurred. The MDNRcollected sediment and surface water samples near OU 1 in September 1992. Theanalyses showed sediments in Sutton Branch Creek contained elevated lead, copper,nickel, and zinc concentrations. Lead levels in the creek water were near thresholdconcentrations for safe drinking water and protection of aquatic life, as established byMissouri water quality standards at that time (Smith 1988). The state did not conductsource area sampling of sediment, soil, surface water, or groundwater.

A Screening Site Inspection was conducted June 1996 collecting data primarily onbackground information, waste and source sampling, groundwater exposure pathways,surface water exposure pathways, soil exposure pathways, and air exposure pathways.

Results of this report were documented in the Expanded Site Investigation/RemovalAssessment and can be found in the Administrative Record.

In September 2003, EPA proposed a time-critical removal action for the ALM Site. Thegoal of the removal action was to identify, consolidate, and stabilize the lead-contaminated waste mine tailings onsite. The time-critical removal action work began atthe Site in May 2004. When the removal action began at the Site, settling basins wereconstructed to manage storm water runoff. Earth moving equipment was used to formthe tailings and contaminated soil into a mound in the middle of the ravine where the pilewas originally located. All areas in the tailings pile vicinity that had a mean lead surfaceconcentration greater than 1,000 parts per million (ppm) were delineated and excavated.Excavations proceeded to the lesser of a depth of 18 inches or until a lead level below400 ppm in the soil was achieved. All excavated areas were backfilled with cleanmaterial (<240 ppm lead) and excavated soil was consolidated into the onsite tailingspile. The tailings pile was graded and compacted, and an engineered protective coverwas installed over the tailings. The protective cover consists of uncontaminated clay andtopsoil, allowing for the establishment of vegetative cover.

The time-critical removal action minimized both the potential for human exposure to leadthrough contact with the soil and the potential for transport of the tailings by surfacerunoff, wind, or human activity. Monitoring and site control measures were conductedduring the removal action work to ensure removal activities did not expose nearbypopulations and site workers to harmful levels of contaminants.

The Remedial Investigation (RI), with expanded report sections on surface water,sediments, and soil was completed in August 2005. The purpose of the RI was todetermine the nature and extent of contamination from the historical tailings pile to theconfluence of Sutton Branch Creek and Big Creek. A Hydrology and Flood Plain Reportwas conducted to evaluate the existing conditions and behavior of the Sutton BranchCreek Flood Plain. These reports can be found in the Administrative Record.

A Feasibility Study (FS) was completed in August 2005. The FS combined theinformation about the nature and extent of contamination in and around the Site describedin the RI and developed alternatives for remedial action for OU 1. Studies utilized indeveloping the alternatives described in the FS have been conducted by the EPA, theMDNR, the United States Fish and Wildlife Service (USFWS), and others. These reportscan be found in the Administrative Record.

C. COMMUNITY PARTICIPATION

The EPA issued the Proposed Plan for OU 1 on August 25, 2005, and provided a 30-dayreview and comment period opening on August 25, 2005, and closing on September 24,2005. A public meeting to present the plan and receive comments was held September 7,2005, at the South Iron County Community Center from 7:00 to 9:00 p.m. Included inthis ROD is a Responsiveness Summary that addresses in writing the significantcomments the EPA received from the public during the comment period.

D. SCOPE AND ROLE OF OPERABLE UNIT

The ALM Site is arranged into the following two OUs for administrative efficiency inconducting environmental cleanups: OU 1, Sutton Branch Creek Flood Plain and MineArea, and OU 2, city of Annapolis and Big Creek. A brief overview of the status of eachOU is provided below:

• OU 1: Sutton Branch Creek Flood Plain & Mine Area - Addressed in thisROD

• OU 2: City of Annapolis and Big Creek - Will be addressed in the future

As mentioned in the previous section, the investigation and study of the Site included themining waste in and around the former ALM located in the 200-acre area, includingSutton Branch Creek. This ROD addresses OU 1, which includes areas where miningand milling occurred, as well as the nature and extent of contamination within the SuttonBranch Creek Flood Plain. The migration of contamination beyond OU 1 will beaddressed in OU 2.

As stated in the previous section, the EPA initiated and completed a time-critical removalaction to address the majority of the human health and ecological risks at OU 1. ThisROD is necessary to mitigate the principal threat for OU 1, which is the residual risk tohuman health and the environment from exposures to hazardous substances in soils,sediments, and surface water. The RI/FS has shown that further action at OU 1 isnecessary. These necessary actions are described under the selected alternative.

E. SITE CHARACTERISTICS

The ALM Site is located approximately one mile east-northeast of Annapolis, Missouri,adjacent to and within the Sutton Branch Creek Flood Plain. The Site includes the mineworks. The mine lies on the east side of the county road. Runoff from the mine areaenters Sutton Branch Creek. The area affected by the mining wastes is rural/residential.The geographic coordinates of the Site are latitude 37°21'40" N and longitude 90°40'30"W. The ALM Site is located on the Des Arc, Missouri Quadrangle 7.5-MinuteTopographic Map in Sections 13 and 14, Township 31 North, Range 3 East (USGS,1980) (Figure 1).

The dominant feature of the Site was a chat/tailings residue pile that coveredapproximately 10 acres in the northern portion of the Site (Figure 2). The pile wascomposed of grey- to tan-colored material that resembled course to fine-grained sand.The material was highly erodible, resulting in steep-sided features and an outwash areathat fanned westward to Sutton Branch Creek. The creek flows north to south on thewest side of ICR 138 (Figure 3). Prior to the response action by EPA, the chat/tailingsresidue dominated the substrate of Sutton Branch Creek for approximately 0.75 mile,where it merges with Big Creek.

Galena ore (lead-bearing ore) was mined from the Site beginning in the 1920s. Miningactivities continued sporadically until 1940. The mine had one shaft extending 450 feetbelow the ground surface with several hundred feet of laterals to work the ore bodies(Kiilsgaard, 1967). In addition to mining the ore, various equipment onsite was used tocrush and mill the ore to concentrate the lead. An appraisal report prepared in 1934stated that Annapolis Lead Company, a now-defunct company, owned/operated the minefrom 1919 to 1931, when the majority of ore was extracted (Neustaedter, 1934).Production figures from 1923 to 1931 indicated that approximately 1,173,000 tons ofmining waste was generated during that time period (Neustaedter, 1934). The OzarkLead Mining Corporation, a defunct company, owned the property from 1931 to 1934,but apparently did not conduct mining activities. Basic Metals Mining Corporation, alsodefunct, owned the mine from 1934 to 1941 and conducted mining activities for a shorttime between 1938 and 1940 (no production figures were located for that time period).Apparently, no mining occurred onsite after that time. American Waste MaterialCorporation owned the property for several months in 1941 and then sold the property toH. Hoffman et al. St. Joseph Lead Company owned the mine from 1952 to 1982 andretained the mineral rights until 1987. Doe Run Company has owned the mineral rightsfrom 1987 until present.

Other Site features included numerous former mining operation buildings, locatedprimarily in the northern portion of OLJ 1. Most of the buildings have deteriorated towhere only foundations are present. An exception is a single story of a once multi-storiedstructure near the center of the Site (Fig. 4), which was being used as a residence.Mining refuse is interspersed among the former buildings (E & E, 1997).

According to the Strategic Plan of Operation between the EPA and MDNR regardingRoles and Responsibilities for the Removal and Post-Removal Activities of the ALM OU1, MDNR will manage post-removal maintenance of the protective cover consistent withall federal and state laws. The Strategic Plan of Operation also provides that EPA andMDNR will collaborate to put future ICs in place, both physical and legal.

F. CURRENT AND POTENTIAL FUTURE SITE AND RESOURCE USES

The Site is located within one mile of the city of Annapolis, which has a population of310. The population living within a four-mile radius of the Site, as of 1996, is estimatedto be 1,325 persons, with 180 people living within a one-mile radius. A school attendedby 489 students is located within two miles of the Site.

There are no known drinking water intakes from Big Creek for residential use. Onemanufacturing facility is known to use water from Big Creek during the manufacturingprocess to produce roofing granules. The MDNR also may use water from Big Creek atSam A. Baker State Park, which is 15 miles downstream of the ALM Site. Both thevillages of Vulcan, population 157, and Des Arc, population 187, are located downstreamalong Big Creek. Fishing is popular south of Annapolis near Des Arc village; localfishermen take crappie, catfish, large and smallmouth bass, and sunfish.

OU 1 is situated on relatively rugged terrain that slopes towards Sutton Branch Creek,with the eastern drainage area being significantly greater than the western portion of theSutton Branch Creek drainage area. The Site is a mixture of forested areas, stream,riparian and flood plain adjacent to Sutton Branch Creek, except for the chat/tailings area,and the road cut for ICR 138. The land surrounding the Site is predominantly forest, withlimited agricultural production and isolated residential properties.

G. SUMMARY OF SITE RISKS

In general, EPA has determined that the principal threat from the ALM Site OU 1 is theecological risk to aquatic biota caused by surface water and sediments containing COCsin concentrations exceeding Federal Ambient Water Quality Criteria (AWQC). Anadditional risk at the Site is the risk of lead to terrestrial receptors in the flood plain soils.There are some limited risks to human health as well. The purpose of this ROD is todocument the EPA's selected remedial alternative to mitigate the unacceptable humanand ecological risks. The objective is to achieve significant reductions in COC loadingsto surface waters. The remedy relies on the ICs component, engineering controls, and theconsolidation and capping work completed during the removal action to achieve thisobjective.

Ecological Risk Assessment

As evaluated in the Baseline Ecological Risk Assessment (BERA), maximum dissolvedCOC concentrations in surface water and sediments of Sutton Branch Creek exceeded theAWQC. The BERA evaluated risk to aquatic and terrestrial systems at the Site. TheBERA addresses risks to aquatic biota and terrestrial biota by comparing the maximummeasured concentrations of COCs to AWQC and standards and conservative toxicitycriteria.

The EPA analytical data document metal contamination (cadmium, lead, zinc) insediments and surface water above background concentrations. There is obvious andsubstantial contamination of Sutton Branch Creek and the adjacent floodplain withvisible and buried tailings. Sutton Branch Creek is a small, intermittent tributary to BigCreek, but contains a diverse number of organisms including the endemic Big CreekCrayfish. Big Creek is a perennial flowing stream and a 'Missouri Outstanding Water'that is ecologically and recreationally important.

In general, EPA has determined that the remaining principal threat for the ALM Site OU1 is the ecological risk to both the aquatic and terrestrial environments. Living organismswithin both ecosystems have elevated exposure to mining-related metals, and the metalscan cause adverse effects on some receptors in each ecosystem. The potential ecologicalreceptors for this Site were determined and are included in the Conceptual Site Model(CSM) in Figure 5. Specific conclusions taken from the BERA regarding the impact ofthese elevated exposures are summarized below.

Aquatic Ecosystem

• Algae, which are common in most Ozark streams, appear to be nonexistent.

• There is a decrease in species richness and in the abundance of some sensitivespecies of benthic macroinvertebrates in Sutton Branch Creek below the ProbablePoint of Entry (PPE), and this could be due to metals.

• The density offish in Sutton Branch Creek and Big Creek is lower than in typicalOzark streams. Metals are judged to be a contributor to this effect. The metals-related exposure pathway contributing to this decrease in population is uncertain,but is more likely related to acutely lethal pulse events (increases in flowfollowing precipitation events) than to ambient levels of metals in surface wateror diet.

Terrestrial Ecosystem

• There is evidence of phytotoxicity to terrestrial plants in mine waste areas.

• There is evidence that soil organisms (worms, microbes) are adversely impactedby soils from mine waste.

• The hazard to some terrestrial vermivores is predicted to be quite high in all areasof the ALM Site.

Ecological Risk Addendum

The northern section of the ALM was reevaluated by the Region 7 Ecological RiskAssessor after the time-critical removal action. The results of the revaluation are asfollows.

• Vermivores are still at risk of accumulating lead into their tissues at 400milligrams per kilogram (mg/kg). However, Region 7's Ecological Risk Assessoracknowledges that capping the ALM pile has greatly reduced the risk to terrestrialwildlife by a factor of 12 for shrews and 7 for woodcock for a No ObservedAdverse Effect Level. Further information can be found in the baselineEcological Risk Assessment in the Administrative Record.

Human Health Risk Assessment

The EPA prepared a baseline Human Health Risk Assessment (HHRA) in August of2005. The purpose of this report was to document the current human health risk for theSite, which included the former mining operations area and the Sutton Branch CreekFlood Plain. The HHRA evaluated current and potential future risks to human healthassociated with the presence of heavy metals, particularly lead, in soils, surface water,

sediment, and groundwater at the Site. The potential human receptors for this Site wereincluded in the CSM in Figure 6. Specific objectives of the HHRA were:

• Evaluate available data for applicability to the risk assessment process andidentify existing data gaps

• Identify chemicals of potential concern (COPCs) to human health

• Identify areas of elevated COPC concentrations (exposure units) within Siteboundaries

• Evaluate potential health risks associated with exposure to COPCs for severalexposure groups, based on anticipated or potential land uses

• Identify uncertainties associated with risk characterization

Based on the results of field investigations and the HHRA, the following conclusionswere reached concerning human health risks and hazards associated with mine wastes inthe ALM Site OU 1.

• Surficial residual contamination in the mine operations area is generally belowlevels of concern for lead; however, hotspots exist under the 18-inch engineeredsoil cover in limited areas that could be associated with unacceptable exposures tolead. Unacceptable exposure could be realized for both future constructionworkers and future residents if soil excavation activities occur.

• Lead is the only COPC that was assessed for the mine operations area. Post-removal data were not specifically available for other constituents, but there islittle to indicate that they will be a problem.

• Lead exposure for the capped mine tailings area would be realized only if residualcontamination beneath the 18-inch soil cover is excavated or brought to thesurface. In the absence of development of the area, no complete exposurepathways for residual soil contamination would exist.

• Lead exposures for recreational visitors to the flood plain could reachunacceptable levels. However, these exposure estimates are based on frequentvisits by recreational users to an area that appears to be unattractive for recreation.The flood plain areas are heavily vegetated, which limit exposures tocontaminated soils.

• Lead exposures for recreational users' exposure to surface water and sediment inSutton Branch Creek do not appear to cause unacceptable risks.

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Cancer risk due to exposure to arsenic in groundwater falls within EPA's acceptable riskrange. Hazards due to exposure to iron and thallium are above the target hazard of oneand may imply some potential for unacceptable non-cancer hazards. Iron and thalliumappear to be naturally occurring and are not a result of the mine workings (See RI).

• Cancer risks and non-cancer hazards for recreational exposures in the flood plainand creek fall within the acceptable risk range for cancer and below one forhazards. These results suggest that recreational exposure to COPCs other thanlead may be in an acceptable range.

H. REMEDIAL ACTION OBJECTIVES

Remedial Action Objectives (RAOs) are cleanup goals that are addressed by reducing oreliminating contaminants or exposures routes. The RAOs are media specific and aredescribed below. There are four total RAOs, two for soils and source materials and twofor surface water and sediments.

The media-specific RAOs are discussed in the following sections:

Soils and Source Material RAQs

The RAOs for soils and source materials are based on the findings of the BERA andHHRA. These RAOs are designed to address the potential ecological risks associatedwith direct exposure to COCs in mine and mill wastes, and in the affected soilssurrounding the wastes. Terrestrial vertebrates, specifically vermivores whose dietconsists of earthworms and other soil-dwelling invertebrates, are identified as thereceptors of concern based on the information from the BERA. Ecological risksassociated with source material erosion (as sediment) and seepage/runoff are addressed inother RAOs. Due to these findings, the following RAO was developed.

Limit the exposure of terrestrial biota to COCs in suriicial materialsthat would potentially result in excessive ecological risks associatedwith intake of Site COCs.

The human health exposure routes have been addressed at much of OU 1. However,surficial contamination in the southern portion of OU 1 could cause unacceptableexposures. Due to this minor risk, the following RAO was developed.

Limit human ingestion of COCs from onsite soils or source materialsthat would potentially result in cancer risks greater than10~6, non-carcinogenic hazard indexes greater than 1, or unacceptableblood lead levels that present human health risks.

1 1

Surface Water and Sediment RAOs

Aquatic and terrestrial biota are exposed to COCs in surface waters or sediments derivedfrom mill wastes. Site-specific, risk-based contaminant levels for aquatic biota have notbeen established for the Site. However, consensus-based sediment quality guidelineshave been used as reference material and may be used when establishing cleanup goals.

Aquatic biota are exposed to COCs in surface waters by three general mechanisms. First,surface runoff may contain dissolved metals due to leaching of the salts of metal oxidescontained in the weathered surficial waste deposits. Second, participate metals aretransported by surface runoff and erosion of mill waste. The third water exposuremechanism involves the deposition of sediments containing mill waste in surface waterbodies.

Typically, the first two mechanisms operate together during rainfall or snowmelt events.The dissolved metals, suspended metals (particulates), and metal-laden sediments allbecome entrained in the runoff transported to surface water bodies. Once deposited,these sediments have the potential to act as secondary sources of dissolved metals insurface waters resulting in risks to fish and other aquatic organisms. Sediments withelevated COC concentrations may pose risks to benthic communities that live and feed insediment deposits and benthic feeders that may ingest sediment. Applicable or relevantand appropriate requirements (ARARs) for sediments are not developed for the ALM SiteOU 1, but consensus-based guidelines can be followed.

Based on the discussion presented above, a surface water and a sediment RAO have beendeveloped. These RAOs address the interactions between source materials and surfacewaters and the potential exposure of aquatic biota to COCs from mill waste. The surfacewater and sediment RAOs are as follows:

Limit the exposure of aquatic biota to waters contaminated withCOCs in Sutton Branch Creek in excess of chronic and acute FederalAmbient Water Quality Criteria (AQWC) for such COCs.

Limit the risks to aquatic biota by controlling erosion and transportof lead-contaminated mill wastes and sediments containing lead-contaminated mill wastes in classified perennial or state-listedephemeral streams or rivers.

Note that actions taken to meet the surface water and sediment RAOs would alsobenefit terrestrial biota (soil and surface material RAOs) that consume fish, drinkSite waters, and incidentally ingest sediments.

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I. DESCRIPTION OF ALTERNATIVES

Various cleanup alternatives were evaluated in order to select the optimum approach toaddress Site risks. A total of six candidate alternatives were initially screened, and fourof these approaches were carried forward for a more detailed assessment of theirviability. The four cleanup alternatives subjected to the detailed analysis are described onTable 1 and were developed in order to address the site-specific RAOs. Each of the fourpotential alternatives is summarized in the following paragraphs. Alternatives 5 and 6 arenot included since they were eliminated during the screening process. More detailedinformation regarding the various alternatives is available in the FS within theAdministrative Record file. Under each alternative, MDNR will manage post-removalmaintenance of the protective cover consistent with all federal and state laws. Undereach action alternative, regular water quality monitoring will be carried out by MDNR atestablished monitoring stations, pursuant to the CWA. Periodic monitoring of sediments,surface water, pore water, and biota would also occur.

Alternative 1: No Further Action - Consideration of a "no further action" alternative is arequirement of the NCP as a baseline for comparing other active remedial alternatives.Under the no further action alternative, no active mitigation measures are prescribed tomeet the RAOs or address identified risks.

Alternative 2: Phosphate Amendment of Flood Plain Soils with In-Stream StabilizationTechniques and Limited Sediment Removal - Alternative 2 would address all of theRAOs. Alternative 2 is designed to reduce lead bioavailability in the terrestrialecosystem and limit the movement of contamination further into the flood plain.Alternative 2 involves the amendment of flood plain soils with phosphate and in-streamstabilization techniques to reduce sediment transport and stream channel meandering.Removal of sediments from Sutton Branch Creek would be performed on a limited basis,primarily to remove sediment pockets from those depositional areas where the risk offuture erosion is greatest. Contaminated bank deposits that are not protected byvegetation and that are at significant risk of erosion will be physically stabilized.However, if the bank stabilization requires the excavation and disposal of contaminatedsoils they will be taken to the onsite repository. This alternative is designed to reducemetal and sediment loading in Sutton Branch Creek, reduce lead bioavailability in openflood plain soils, and increase the density of vegetation in the open flood plain soils. Thisalternative provides protection while limiting damage to the existing habitat.

Alternative 2 includes the implementation of the following site-wide ICs. Thechat pile cap area is currently fenced. In particular, a Declaration of Covenantsand Restrictions that will be patterned on one of the following:

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• Model Restrictive Covenant and Grant of Access found in the MDNR Cleanup Levelsfor Missouri (CALM) Appendix E, Attachment E1: RSMo Section 260.565, et.seq.

• The proposed Model Declaration of Restrictive Covenant and Grant of Access whichis anticipated to be located in the MDNR Long-term Stewardship for Risk-basedCorrective Action Sites, Appendix J, Technical Guidance

• Other appropriate instruments

The objectives of imposing a restrictive covenant or easement on the respectiveproperties within OU 1 are to eliminate or minimize exposures to contaminationremaining at OU 1 and limit the possibility of the spread of contamination. Theseobjectives will be achieved by use of the restrictive covenant or easement as it will : 1)provide notice, 2) l imit use, and 3) provide for all required access.

Specifically, the restrictive covenant and easement will achieve this by:

• Providing notice to prospective purchasers and occupants that there may becontaminants in the subsurface soils and groundwater

• Ensuring that future owners are aware of engineered controls put into place as part ofthis remedial action and under the prior removal action

• Prohibiting residential, commercial, and industrial uses, except those uses whichwould be consistent with the remedial action

• Requiring EPA/MDNR approval for groundwater well installation• Prohibiting or limiting other ground penetrating activities which may result in

subsurface contamination being brought to the surface• Providing access to EPA and the state of Missouri for verifying land use• Prescribing actions that must be taken to install and/or maintain engineered controls

and providing access to EPA and the state of Missouri for sampling and themaintenance of engineered controls

Alternative 3: Excavation of Sediments in Sutton Branch Creek - This alternativeincludes ICs described in Alternative 2 and also addresses the surface water andsediment RAOs. Alternative 3 involves the excavation of sediments in SuttonBranch Creek from the Probable Point of Entry (PPE) to the confluence with BigCreek. Excavated sediments would be piled onto high ground outside of the floodplain. Piles would be capped, contoured, and vegetated to prevent erosion. Thisalternative does not address the residual contamination of flood plain soils.Terrestrial ecological risks posed by areas of mining wastes would not beaddressed by this remedy, and human health risks related to these remainingaccumulations would be reliant upon ICs.

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Alternative 4: Excavation of Sediments in Sutton Branch Creek and Soil Cap -Alternative 4 includes the ICs described in Alternatives 2 and 3 and addresses theRAOs. Alternative 4 is designed to protect the environment by reducing metaland sediment loadings in Sutton Branch Creek and reduce contamination in thesurrounding flood plain soils. Periodic monitoring of sediments, surface water,pore water, and biota would also occur. Alternative 4 focuses on achieving thesurface water and sediment RAOs by dredging the contaminated sediments toreduce metal and sediment loadings in Sutton Branch Creek. Excavated materialswould be consolidated with contaminated soils and capped with 12 inches ofclean soil in the flood plain. This alternative addresses the terrestrial risks byimplementing an engineered soil cover, or cap, over all contaminated areas in theflood plain.

J. COMPARATIVE ANALYSIS OF ALTERNATIVES

The NCP requires the EPA to evaluate selected remedial alternatives consideringnine criteria. Any selected or preferred remedy must satisfy all nine criteriabefore it can be implemented. The nine criteria are divided into the followingcategories: two threshold criteria, five balancing criteria, and two modifyingcriteria. The two threshold criteria are overall protection of human health and theenvironment and compliance with ARARs. Tables 2, 3, and 4 depict the ARARsfor this Site. Generally, alternatives must satisfy the two threshold criteria or theyare rejected without further consideration of the remaining criteria. The fivebalancing criteria consist of the following: long-term effectiveness andpermanence; reduction in toxicity, mobility, and volume achieved throughtreatment; implementability; short-term effectiveness; and cost. The twomodifying criteria consist of state and community acceptance. The modifyingcriteria cannot be fully evaluated until the state and public have been provided anopportunity to comment on the preferred alternative. The state has provided inputas discussed in this document.

Threshold Criteria Evaluation

The threshold criteria of overall protection of human health and the environmentand compliance with ARARs addresses whether a remedy provides adequateprotection by reducing, eliminating, or controlling pathway risks throughtreatment, engineering, and ICs in addition to meeting the ARARs of federal andstate laws. Compliance with chemical-, location-, and action-specific ARARs isrequired unless a site-specific waiver is justified. No ARARs have been waivedfor OU 1.

Alternative 2 (Phosphate Amendment of Floodplain Soils with In-StreamStabilization Techniques and Limited Sediment Removal) The preferredalternative is Alternative 2, Phosphate Amendment of Floodplain Soils with In-Stream Stabilization Techniques and Limited Sediment Removal. This alternativewill meet the threshold criteria of protecting human health and the environment

15

and will comply with ARARs through the implementation of engineeringcontrols. Engineering methods such as selective excavation of impacteddepositional sediments, incremental stream bank and channel erosion preventiontechniques, and amendments of impacted flood plain soils will mitigate humanand ecological risks. Additionally, ICs over soils and groundwater will prohibithuman access. All chemical-, location-, and action-specific ARARs will be metby the preferred alternative.

Alternative 1 (No Further Action) may not meet the threshold criteria ofprotecting human health and the environment and ARAR compliance.

Alternative 3 (Excavation of Sutton Branch Creek Sediments) may not satisfy thethreshold criteria because it does not address any of the residual contamination ofthe flood plain soils and thus may not be fully protective of ecological receptors.This alternative would also be harmful to the existing stream habitat and may notcomply with the ARARs. Alternative 3 may not satisfy the threshold criteria.

Alternative 4 (Excavation of Sediments in Sutton Branch Creek and Soil Cap)meets the threshold criteria by addressing all surficial mining wastes, maximizingthe degree of mine waste excavation and consolidation, and employing the use ofadvanced engineering cap and cover designs for maximum infiltration reduction.However, residual contamination would remain in the flood plain soils.Additionally, this alternative would be the most destructive of the actionalternatives with regard to the existing physical habitat. The remainingassessment of balancing and modifying criteria will focus on the alternatives thatfully satisfy the threshold criteria, Alternatives 2 and 4.

Balancing Criteria Evaluation

Descriptions of the five balancing criteria include the following:

• Long-term effectiveness and permanence - addresses the ability of a remedyto maintain protection of human health and the environment over time,inclusive of residual risks following implementation

• Reduction in toxicity, mobility, or volume through treatment addresses thedegree to which a remedy employs recycling or treatment methodologies tocontrol principal threats

• Implementability describes the technical and administrative feasibility ofimplementing a cleanup approach including the difficulty of undertakingadditional follow-on actions

• Short-term effectiveness addresses the time required for implementation andany adverse impacts during implementation

• Cost describes the direct and indirect capital costs of the alternative

16

The balancing criteria are applied to potential remedies that satisfy the earlierthreshold criteria and are thus moved forward for additional evaluation. PreferredAlternative 2 and Alternative 4 met the threshold criteria.

Alternatives 2 and 4 meet all five of the balancing criteria although distinctionsexist. Alternative 2 may potentially have a lesser degree of long-termeffectiveness and permanence as contrasted to Alternative 4 due to the residualcontamination in the flood plain soils. The residual contamination is expected tobe mitigated to some degree by future deposition of clean sediment in the area.However, residual contamination would also remain under Alternative 4.Alternative 4 would have a greater area to maintain and thus may also have issueswith the long-term maintenance aspects of engineering caps. Alternative 2 has anadvantage of a lesser area subject to long-term maintenance.

Alternative 2 would employ phosphate treatment of flood plain soils to reduce thebioavailability of lead and increase the density of vegetation.

Both remedies are implementable, but Alternative 2 has advantages overAlternative 4 in this regard. Each alternative requires standard constructionequipment. However, Alternative 4 would require much more time to implement,mainly due to the requirement of tree removal in the riparian and the hauling ofsoils for the cap. Alternative 2 is favored with regard to time for implementation.Additionally, Alternative 2 utilizes a smaller area for remediation as contrasted toAlternative 4.

Short-term impacts could occur under Alternative 2 due to the potential impactsof lead on the terrestrial community. However, Alternative 4 may also haveshort-term impacts due to the excavation and transportation of large volumes ofmaterial, as well as the impacts from significant areas of habitat destruction.

With regard to cost, Alternative 2 is more cost effective than Alternative 4.Alternative 2, with estimated capital and operation and maintenance (O&M) costsof less than $320,000, is less costly than Alternative 4 which has an estimated costof $1.7 million.

In summary, Alternative 2 is favored in regard to cost and implementability.Alternative 2 may prove to be as successful in long-term effectiveness andreliability, and the implementation would serve as a valuable remedial-scale testof a fairly new technology. Alternative 2 is also favored in regard to short-termeffectiveness due to the impact of Sutton Branch Creek habitat destruction thatwould take place under Alternative 4.

17

Modifying Criteria Evaluation

The two modifying criteria of community and state acceptance are intended toassess the views of the two groups regarding various cleanup approaches. Thestate of Missouri is represented by the MDNR and the public is represented by thelocal affected community. The EPA has held meetings with MDNR to discuss thepotential effectiveness of the preferred alternative. The EPA held a publicmeeting and comment period to assess the public opinion and preference for aremedy. The MDNR supports the preferred alternative as the selected remedy aspresented in this ROD. Comments received from the public indicate that thecommunity fully supports Alternative 2 as the preferred alternative. Views of thestate and public were evaluated during the public comment period.

K. PRINCIPAL THREAT WASTE

Principal threat wastes are source materials that require remediation based ontoxicity, mobility, and the potential to create unacceptable human health orecological risks. The NCP establishes a preference that treatment will be used toaddress principal threat wastes when practical. Phosphate treatment will beemployed in the open flood plain soils at this Site to reduce lead bioavailabilityand increase the density of existing vegetation to limit exposure to contaminatedsoils.

The principal threat wastes at the Site consist of mining wastes, mining impactedsediments, and mining impacted soils. The wastes and their characteristics arediscussed in detail in the RI/FS.

L. SELECTED REMEDY

The preferred cleanup approach for addressing the mining waste impacts at theALM Site OU 1 is Alternative 2 (Phosphate Amendment of Floodplain Soils withIn-Stream Stabilization Techniques and Limited Sediment Removal). Thisalternative addresses all waste and allows flexibility with regard to excavatingsediments. It does not mandate the excavation of all materials in the stream or theuse of complex cap designs as required by Alternative 4. It is an engineeringsolution as contrasted to Alternative 1, the No Further Action approach. It isexpected that the Federal AWQC will be met by the actions prescribed byAlternative 2, and risks will be reduced in the most cost effective manner.

Areas of impacted sediment may not be removed based on the potential fordestruction of critical habitat and the physical characteristics at that location.Contaminated sediments found in specific depositional areas within SuttonBranch Creek which exhibit the potential for significant down stream movementwill be removed. Bank deposits will be physically stabilized to limit downstreammovement. However, if the bank stabilization requires the excavation and

disposal of contaminated soils, they will be taken to the onsite repository. Naturalrecovery along with physical stabilization will be employed as necessary invarious stream segments.

The specific elements of preferred Alternative 2 include the followingcomponents for OU 1 of the ALM Site.

• Add phosphate to flood plain soils (away from the outer edge of riparian)during the dry season. This will reduce terrestrial bioavailability of lead andincrease the density of vegetation. Application rates, specific locations, andmethods of application will be determined during the RD phase.

• Mining wastes in heavily forested or thickly vegetated areas, such as theriparian buffer, will not be subject to excavation, consolidation, capping, orphosphate treatment. This will protect the existing riparian zone and otherareas considered as important habitat. However, if mine waste on the streambank is not stable, it wil l be physically stabilized.

• Excavation of sediments from Sutton Branch Creek in pockets or depositionalareas where the benefit of excavation/removal outweighs the habitatdestruction that will result. Areas of sediment removal will be determinedduring the RD phase.

• Placement of excavated sediments in the existing repository area and cap witha simple soil cover. The capped tailings deposits would be revegetated byplanting with an appropriate site-specific seed mix selected through a Siterevegetation plan.

• Stabilization of the Sutton Branch Creek channel with large rock, othermaterials, and structures to prevent wash-outs and stream channelmeandering. The quantity of rock used and the location of structures and theirdesign will be determined during the RD. The material would be placed inincrements in Sutton Branch Creek. The placement of the structures mayrequire the excavation of bank material. If it is determined that excavatedmaterial is hazardous, it will be placed with the excavated sediment in theonsite repository.

• Implementation of ICs as described in Section 1, above.

• Perform annual monitoring to determine remedial effectiveness. The natureand extent of the monitoring will be determined during the RD. Initialmonitoring will be annual. At each five-year review the length of themonitoring period (annual or otherwise) will be evaluated to determinewhether monitoring should be less or more frequent.

19

• Regular water quality monitoring (including phosphorus) will be carried outby MDNR at established monitoring stations, pursuant to the CWA.

• The MDNR will manage post-removal maintenance of the protective coverconsistent with all federal and state laws.

Based on the information currently available, EPA as the lead agency, and MDNRas the supporting agency, believe the Preferred Alternative meets the thresholdcriteria and provides the best balance of tradeoffs among the other alternativeswith respect to the balancing and modifying criteria. The EPA expects thePreferred Alternative, Alternative 2, to satisfy the following statutoryrequirements of CERCLA section 121 (b): (1) be protective of human health andthe environment, (2) comply with ARARs, (3) be cost effective, (4) ut i l izepermanent solutions and alternative treatment technologies or resource recoverytechnologies to the maximum extent practicable, and (5) satisfy the preference fortreatment as a principal element.

The support agency, MDNR, has been consulted in the preparation of this RODand has provided concurrence for the selected alternative in this ROD.

M. STATUTORY DETERMINATIONS

The EPA's primary legal authority and responsibility at Superfund sites is toconduct response actions that achieve adequate protection of human health andthe environment. Section 121 of CERCLA also establishes other statutoryrequirements and preferences that include the need for federal and state ARARscompliance for selected remedial actions in addition to cost effectiveness and theuse of permanent solutions and alternative treatment technologies, or resourcerecovery technologies, to the maximum extent practicable. Additionally, thestatute includes a preference for remedies that reduce the mobility, toxicity, andvolume of contaminants and include treatment. The following sections discusshow the selected alternative meets these statutory requirements.

Protection of Human Health and the Environment

Alternative 2 would reduce metal and sediment loadings from Sutton BranchCreek to Big Creek. Actions prescribed under this alternative are expected toprevent exceedances of AWQC in Sutton Branch Creek under most flowconditions. Loading reductions would result primarily from physical stabilizationof the Sutton Branch Creek channel and banks to prevent stream meandering andchannel wash-outs. Contaminated sediments would be removed fromdepositional areas in Sutton Branch Creek under Alternative 2. Extensiveremoval of sediments is not anticipated under this alternative. The proposedcontrol actions would further reduce risks to aquatic life, preserve habitat, andprovide an additional increment of protectiveness over the no action alternative.

20

Alternative 2 would reduce the bioavailability of lead in the terrestrialenvironment by treating the flood plain soil with phosphate. Treatment ofphosphate has been shown to reduce the bioavailability of lead by 40-50 percentin other mining sites of Region 7. Phosphate application would also improve thedensity of the existing vegetation, which in turn would prevent erosion of theflood plain during high water events.

In conclusion, Alternative 2 is expected to be protective of human health and theenvironment under most flow conditions. Alternative 2 would eventually meetthe RAOs for soils and source materials and surface water and sediments.

Compliance with ARARs

Alternative 2 is expected to eventually comply with the chemical-specific ARARsfor surface water in Sutton Branch Creek because the anticipated reductions inmetal and sediment loads would prevent independent exceedances of AWQC.

The action-specific ARARs identified for Alternative 2 include the dredge and fillprovisions of Section 404 of the Federal CWA. Alternative 2 would comply withthese action-specific ARARs through appropriate design and coordination withother agencies during the remedial actions.

With regard to the location-specific ARARs, RD work would need to take intoconsideration compliance with the Missouri Wildlife Code 3 CSR Section 10 -4.111, which requires a determination of the presence or absence of endangered orthreatened species, and provides for regulation of non-game wildlife. This sectionalso places restrictions on actions affecting protected species. The Big CreekCrayfish (Orconectes peruncus), a species of conservation concern, is found inSutton Branch Creek. Additional location-specific ARARs are: the Fish andWildlife Coordination Act, which requires any federal agency or permitted entity toconsult with the U.S. Fish and Wildlife Service and appropriate state agency priorto modification of any stream or other water body. The intent of this requirement isto conserve, improve, or prevent loss of wildlife habitat and resources; the Fish andWildlife Conservation Act, which requires federal agencies to utilize their statutoryand administrative authority to conserve and promote conservation of non-gamefish and wildlife species; and the Federal Migratory Bird Act, which requiresremedial actions to conserve habitat and consultation with the Department ofInterior if any critical habitat is affected.

Cost Effectiveness

The selected remedy is cost effective because it will provide overall effectivenessproportional to its costs. The selected remedy will achieve the RAOs and thuseffectively reduce unacceptable risks to human health and the environment, at anestimated cost of $320,000. An analysis of the cost for the selected remedy is given

21

in Table 5. The selected remedy is the least expensive remedy that is protective ofhuman health and the environment and is selected because it is protective, reliable,and permanent and is the alternative preferred by the state and public.

Utilization of Permanent Solutions and Alternative Treatment Technology

The selected remedy represents the maximum extent to which permanent solutionsand treatment technologies can be utilized in a cost-effective manner for thisremedial action. Treatment of contaminated soils and physical stream stabilization,as opposed to excavation and capping, provides the most cost-effective remedy ofthe identified remedial actions. The other actions which are part of the selectedremedy, ICs and monitoring, are not as permanent as the engineering actions, butwil l provide a high degree of long-term effectiveness.

The selected remedy provides the best balance among the alternatives evaluatedwith respect to the evaluation criteria. The EPA relied strongly on the issue ofhabitat preservation, permanence and reliability, and community acceptance inselection of the remedy. The selected remedy best meets the statutory requirementto utilize permanent solutions to the maximum extent practicable.

Preference for Treatment

The preference for treatment is satisfied by Alternative 2 with regard to actions atthe ALM Site. The mining wastes located in the open flood plain soils will betreated with phosphate to increase the density of existing vegetation and to reducethe bioavailability of lead to terrestrial receptors. Monitoring will occur to evaluatethe effects of phosphate application.

Reduction of Toxicity, Mobility, and Volume

Alternative 2 will reduce the mobility and toxicity of the COCs; however, thevolume of waste materials will not be reduced. The open flood plain soils will betreated with phosphate to increase the density of vegetation and to reduce thebioavailability of lead, thus decreasing the mobility and toxicity of the wastes. Thevolume of the waste materials will be unaffected by the selected remedy.

Five-Year Review Requirements

The selected remedy is subject to periodic five-year reviews in accordance withSection 121 (c) of CERCLA and the NCP. Although mining wastes will beremoved from the stream and placed in the existing repository and contaminatedsoils will be treated in the open flood plain, wastes will remain onsite at elevatedlevels. Ongoing O&M requirements for integrity and monitoring of the cappedarea and stream bed will be assessed during the five-year review process.Additionally, the status and effectiveness of ICs will be evaluated.

22

APPENDIX A: FIGURES

j»jwr^7'/:•<T-'/A:V w>^v ^ :

\ ^-;' Kamp:oTi Branch '-^s'\ . *-. .-' y ' it jr<- ff "' X.-

^yfi

z*. Lead Mln= Rli'FS SiteAnrapo~s. WJ

Figure 1S3e localion Map

Figure 2. Annapolis Lead Mine Waste Pile beforeTime-Critical Removal Action

Figure 3. Tailings in Sutton Branch Creek beforeTime Critical Removal Action.

...J r n

Figure 4. Remaining Structure at the FormerAnnapolis Lead Mine.

Figure 5. Annapolis Conceptual Site Model (CSM) to determine potentialecological receptors that may be exposed to heavy metal chemicals of concern.

HEAVY METAL CONTAMINATION (ARSENIC, CADMIUM, LEAD, NICKEL, ZINC)

Wind Blown Mine Waste Dost can result in:Air Deposition

in the water columnof streams, rivers,ponds, and lakes

in the watercolumn of seeps

and springs

algae & emergent plants

Benthic algae

sunfishminnows crayfishtadpoles

Bearer

dragonflleswater snakes

Bass/Suckers SedgesBjpttleb.rush

waterfowl(ducks,geese)

OspreyKingfishers/Herons

mink family

•:• . ®«wBip^fe;;:.earthworms

grubssoil invertebrates

\^s^Zismmm.

iroofeocksAhtebirisslums/voles

sptteiswood frogs

\

K^b Q/fiw^t (EtiiiviiuuPK

snakesfox

owls/hawks

Terrestrial insectsCanadian Geese

Wood DuckGray/red squirrels

SITE CONCEPTUAL MODELKEY

Pmrcallr Compete Piv.wiy:qualiurtvi inalvsis

Rgc°^ »

Figure 6. Conceptual Site Exposure Model (CSM) for the Annapolis Lead Mine

Dermal Contact I Ax stiu< cnlyj

ticidcntxl Icgestin

hliilrton

t'plalte b>' Hoots

tt'tnJ Erosion Atoocphtftic Depoatioa

Dcroul Contact

Up»J<.byRoob

Fufroi

Surf jet Wain/

Dtmul Coattcf ^^

Incidcaf al l;tgt?tion

E:o*«uBttd*iionBi Koaccctri&tm

Fuh'Cnyfti

ConductionWod»r

R«CT»Jtion J

APPENDIX B: TABLES

Table 1. Candidate Remedial AlternativesScreening Summary

Alternative Screening CriteriaNo. Description Effectiveness Implementability Cost Comment

No Further Action Would eventually achievethe Federal AmbientWater Quality Criteria(AWQC). However,would not address residualterrestrial risk.

Readily implementable. Capital andOperation &Maintenance(O&M) Costs: Lessthan $100,000.

The no furtheraction alternative isrequired by theNCP to be carriedforward forconsideration in thedetailed analysis.

Phosphate Amendment of FloodPlain Soils with In-StreamStabilization Techniques andLimited Sediment Removal.

Implement institutionalcontrols to reduce soils andsource material risks as wellas risks to groundwater.Excavate selected SuttonBranch Creek sediments indepositional areasPlace contaminatedsediments in existingrepository and recontourand revegetate.Amend flood plain soilswith Phosphate to lowerbioavailability and toincrease standingvegetation.Use in-stream stabilizationto control channel and bankmeandering.

Effective in reducingmetal and sedimentloadings to surface waters.Would eventually achievethe AWQC for SuttonBranch Creek. Wouldeffectively addresspotential human healthrisk because institutionalcontrols are beingimplemented. Wouldeffectively addressresidual risk in the floodplain soils. Monitoring offlood plain soils,sediments, and physicalhabitat of the streamwould be an effective toolto evaluate risk after theinitial removal action.

Implementable. However,implementation would bedifficult due to the denseriparian in some areas.

Capital and O&MCosts: Less than$350,000.00

Retained for furtherconsideration.

Table 1 Continued

AlternativeNo.3

DescriptionExcavation of Sedimentsin Sutton Branch Creek

Excavate Sutton BranchCreek sedimentsPlace contaminatedsediments outside of theflood plain and recontourand revegetate, possiblyadding soilImplement institutionalcontrols to reduce soils andsource material risks, aswell as risks to groundwater.Monitoring of SuttonBranch Creek

Screening CriteriaEffectivenessEffective in reducingmetal and sedimentloadings to surface waters.Would eventually achievethe AWQC for SuttonBranch Creek. Wouldeffectively addresspotential human healthrisk because institutionalcontrols are beingimplemented. Would notaddress residual risk in theflood plain soils.Monitoring would be aneffective tool to determinethe increase or decrease inrisk after the initialremoval action.

ImplementabilityImplementable. However,implementation would bedifficult due to the denseriparian in some areas.

CostCapital and O&MCosts: Less than$555,000.00

CommentRetained for furtherconsideration.

Table 1 Continued

Alternative

No.

4

Description

Excavation of Sediments in SuttonBranch Creek and Soil Cap

Excavate Sutton BranchCreek sedimentsConsolidate sediments withcontaminated soilsCap all contaminated soilswith 12 inches of topsoilImplement institutionalcontrols to reduce soils andsource material risks, aswell as risks fromgroundwaterPrevent the effects offlooding from SuttonBranch onto the capped areaMonitoring of SuttonBranch Creek.

Screening Criteria

Effectiveness

Effective in reducingmetal and sedimentloadings to surface waters.Would address the residualcontamination in the floodplain soils. Wouldachieve the AWQC.

Implementability

Implementable. However,technical implementationwould be difficult due to thedense riparian in someareas. This alternativewould require the removalof many trees.

Cost

Capital and O&MCosts: Less than$2,000,000.00

Comment

Retained for furtherconsideration

Table 2. Potential Federal and Chemical-Specific ARARsand Guidance to be Considered

Standard, Requirement, Criteria,or Limitation Citation Description

PotentialARARs

To BeConsidered

AIR

Federal Requirements

Clean Air Act - National Primary andSecondary Ambient Air Quality Standards

State Requirements

Missouri Air Conservation Law

42 USC Sees. 740 1-767140 CFR Part 50

RSMo 64310CSR10

The Clean Air Act and implementing regulations define air qualitycriteria for protecting human health, including standards forpaniculate matter and lead.

Set ambient air quality standards for a variety of constituents,including paniculate matter and lead.

X

X

SOURCE MATERIALS AND SOILS


Risk Management Considerations forTerrestrial Vermivores

Baseline Ecological Risk Assessment for theAnnapolis Lead Mine Superftmd Site, Iron

County, Missouri.

Revised Interim Soil Lead Guidance forCERCLA Sites and RCRA Corrective

Action Facilities.

USEPA Region 7, 2004

USEPA Region 7, 2004

OSWER Directive No. 9355.4-12, July 14, 1994

The BERA provides a screening level evaluation of potential risksto ecological receptors in the Site. Although this report providesno specific guidance for evaluating candidate remedial alternatives,it initially identified the potential exposure pathways addressed inthe Risk Management Considerations document cited above.

Recommends a screening level of 400 ppm for lead in residentialsoils. Describes a methodology for developing site-specificpreliminary remediation goals and media cleanup standards.Describes a plan for soil lead cleanup at sites with multiple sourcesof lead. In general, human exposure in the ALM is expected to beminimal. Nevertheless, this directive provides guidance for

X

X

X

Table 2 Continued

Standard, Requirement, Criteria,or Limitation

Soil Screening Guidance

State Requirements

Missouri Department of Health - Any UseSoil Levels

Citation

OSWER Directive 9355.4-23,July 1996

EPA/540/R-96/108and 128

1 9 CSR 20-9.020 (Proposed)

Description

evaluating the extent to which proposed remedial actions mightenhance protection of human health.

Recommends the development of site-specific soil screeninglevels. Provides general screening levels below which areas aredetermined to be adequate and do not need further assessment.Further evaluation of risks is recommended for areas above thescreening levels.

These proposed regulations recommend baseline levels for leadand cadmium in soil for residential or "any use" land use.However, the proposed clean up levels are extremely conservativecompared to values used in the HHRA and Risk ManagementStrategies documents. These are not ARARs but may be TBCs.

PotentialARARs

To BeConsidered

X

X

SURFACE WATER


Clean Water Act - Water Quality Standards,Chronic Aquatic Life Criteria

State Requirements

Missouri Clean Water Law - Water QualityStandards

40CFRSec. 131

RSMo 644.006 - 564

10 CSR 20-7.031

Federal chronic AWQC are applicable, as they are relevant andappropriate requirements for the stream at this Site. The FederalAWQC for the COCs is based on the site-specific hardness of thesurface water body.

Missouri has adopted AWQC which could be ARARs for the site.

X

X

Table 2 Continued


Missouri Clean Water Law - TMDLRegulations

Citation

Pending

Description

Under this program, the State designates beneficial uses for watersof the state and to takes steps to determine if the uses are attainableand what the total maximum daily loads (TMDLs) should be toprotect the designated uses. The TMDLs would be applicable topoint discharges from abandoned mined lands, as well as activechat quarrying operations. The state TMDLs are currently notARARs. However, Missouri and EPA are currently gatheringsupporting information for future implementation of a state TMDLprogram, and the TMDLs promulgated under this program couldbecome ARARs when this program is formally implemented.

PotentialARARs

To BeConsidered

X

SEDIMENT

Probable Effect Concentrations

Equilibrium-Partitioning SedimentGuidelines (ESGs)

McDonald et al., 2000

EPA Draft November 10, 1999"Draft Metal Mixtures ESGDocument"

Probable effect concentrations (PECs) are screening levelconcentrations of metals in fresh water sediments above whichadverse effects may be expected to occur. PECs identified byMcDonald et al. (2000) include 4.98 mg/kg for Cd; 128 mg/kg forPb; and 459 mg/kg for Zn. However, these PECs are strictlyTBCs, as they are extremely conservative and there are noapplicable or relevant and appropriate criteria for sediments.

Equilibrium-Partitioning Sediment Guidelines (ESGs) are EPA'sbest estimate of the concentration of the mixture of cadmium,copper, lead, nickel, silver and/or zinc that is protective of thepresence of benthic organisms.

X

X

Table 3. Potential Federal, State, and Local Location-Specific ARARsand Guidance to be Considered.


FEDERAL REQUIREMENTS

Archaeological and Historic PreservationAct

Archaeological Resources Protection Act

National Historic Preservation Act

Historic Sites, Buildings, and AntiquitiesAct

Fish and Wildlife Coordination Act

Fish and Wildlife Conservation Act

Endangered Species Act

Citation

16 DSC Sec. 46940 CFR Sec. 6.301 (c)

1 6 USC Sees. 470 aa- mm

16 USC Sec. 47040 CFR Sec. 6.30 l(b)36 CFR Part 800Executive Order 1 1593, May 3,1971

16 USC Sees. 46 1-46740 CFR Sec. 6.301 (a)

16 USC Sees. 661-66640 CFR Sec. 6.302(g)

16 USC Sees. 2901 -2912

16 USC Sees. 1531-154450 CFR Parts 17,40240 CFR Sec. 6.302(h)

Description

Establishes procedures to provide for preservation of historicaland archaeological data which might be destroyed throughalteration of terrain as a result of a Federally licensed activity orprogram.

Requires permits for any excavation or removal of archaeologicalresources from public or Indian lands. Provides guidance forFederal land managers to protect such resources.

Requires Federal agencies to take into account the effect of anyFederally assisted undertaking or licensing on any district, site,building, structure, or object that is included in or eligible forRegister of Historic Places.

Requires Federal agencies to consider the existence and locationof landmarks on the National Registry of Natural Landmarks toavoid undesirable impacts on such landmarks.

Requires any Federal agency or permitted entity to consult withthe U.S. Fish and Wildlife Service and appropriate state agencyprior to modification of any stream or other water body. Theintent of this requirement is to conserve, improve, or prevent lossof wildlife habitat and resources.

Requires Federal agencies to utilize their statutory andadministrative authority to conserve and promote conservation ofnon-game fish and wildlife species.

Requires that Federal agencies insure that any action authorized,funded, or carried out by the agency is not likely to jeopardize thecontinued existence of any threatened or endangered species ordestroy or adversely modify critical habitat.

PotentialARAR

X

X

X

X

X

X

To BeConsidered

X

Table 3. Potential Federal, State, and Local Location-Specific ARARsand Guidance to be Considered.


Federal Migratory Bird Act

Executive Order on FloodplainManagement

Executive Order on Protection ofWetlands

/

Farmland Protection Policy Act

RCRA - Location Standards forHazardous Waste Facilities

Rivers and Harbors Act

STATE REQUIREMENTS

Missouri Wildlife Code

Citation

16 USC Sees. 703-712

Executive Order No. 1 198840 CFR Sec. 6.302(b) andAppendix A

Executive Order No. 1 199040 CFR Sec. 6.302(a) andAppendix A

7 USC Sec. 420 l e f . seq.40 CFR Sec. 6.302 (c)

42 USC Sec. 690140 CFR 264. 18

33 CFR Sees. 320 - 330

3CSRSec. 10-4.111

Description

Requires remedial actions to conserve habitat and consultationwith the Department of Interior if any critical habitat is affected.

Requires Federal agencies to evaluate the potential effects ofactions they may take in a floodplain to avoid, to the maximumextent possible, the adverse impacts associated with direct andindirect development of a floodplain.

Requires Federal agencies to avoid, to the maximum extentpossible, the adverse impacts associated with the destruction orloss of wetlands and to avoid new construction in wetlands, if apracticable alternative exists.

Protects significant or important agricultural lands fromirreversible conversion to uses that result in its loss as anenvironmental or essential food production resource.

Requires that any hazardous waste facility located within the 100-year floodplain be designed, constructed, operated, andmaintained to avoid washout. Also, contains requirements forlocating facilities away from seismically active zones.

Requires pre-approval of the US Army Corps of Engineers priorto placement of any structures in waterways and restricts theplacement of structures in waterways.

Requires a determination of the presence or absence ofendangered or threatened species, and provides for regulation ofnon-game wildlife. Places restrictions on actions affectingprotected species.

PotentialARAR

X

X

X

X

X

To BeConsidered

X

X

-

Table 4. Potential Federal and State Action-Specific ARARsand Guidance to be Considered

Standard, Requirement, Criteria,or Limitation Citation Description Potential

ARARsTo Be

Considered

FEDERAL ARARs

National Ambient Air Quality Standards(NAAQS)

42USCSec.m\elseq.

40 CFR Part 250

These regulations establish ambient air quality standards foremissions of lead and paniculate matter. Remedial actions takenunder any of the alternatives (except no action) are likely to resultin release of airborne lead and dust. These regulations areapplicable to "major sources" as defined under the Clean Air Act.Although remediation sites at the ALM are not expected to bemajor sources, these regulations would be relevant and appropriatefor the remedial activities at the Site.

X

Resource Conservation and Recovery Act(RCRA), Subtitle D, Solid WasteRegulations

42 USC Sec. 6941

40 CFR Part 257, Criteria forClassification of Solid WasteDisposal Facilities and Practices

This section of the RCRA regulations requires the closure ofexisting solid waste facilities, design of new landfills, and disposalof solid wastes to be in accordance with various standards andcriteria. These standards are applicable to solid waste disposalfacilities, including mining and mill waste facilities. Among otherthings, these regulations require that facilities be maintained toprevent wash out of solid wastes and that the public not be alloweduncontrolled access.

RCRA, Subtitle C, Identification andListing of Hazardous Wastes

RCRA Section 3001 (b) (3) (A)(iii), Beville exclusion ofmineral extraction andbeneficiation wastes.

40 CFR Part 264.2, Definitionof solid waste and 40 CFR Part261.4(b)(7)

Mill waste within the Site is specifically excluded from regulationas hazardous wastes under the Beville exclusion because they arewastes resulting from mineral extraction and beneficiation.Therefore, the RCRA Subtitle C regulations are not ARARs.However, these regulations are TBCs because of the guidance theyprovide regarding the mining and milling waste exclusion.


Standard, Requirement, Criteria,or Limitation Citation Description Potential

ARARsTo Be

Considered

RCRA, Subtitle C, Standards for Ownersand Operators of Hazardous WasteTreatment, Storage, and DisposalFacilities

RCRA Section 3001 etseq. 42

USC Sec. 6921, etseq.

40 CFR Part 264.522, DisposalOf Hazardous Wastes InDesignated Corrective ActionManagement Units (CAMUs).

40CFSPart264.554(D)(l)(i)and (ii) Staging Piles

The section defines Corrective Action Management Units(CAMUs) to be used in implementing corrective actions atSuperfund Sites. A CAMU is defined as a disposal site used forconsolidation or placement of remediation wastes within thecontaminated areas of the site. Under these regulations, placementof wastes in a CAMU does not constitute land disposal ofhazardous waste and does not constitute creation of a unit subjectto the RCRA land disposal restrictions and minimum technologyrequirements (40 CFR Part 268). This Section of RCRA is not anARAR because of the Seville exclusion, but is relevant andappropriate.

This subsection describes standards and design criteria forestablishing staging piles within a CAMU. The design criteria tobe developed for each staging pile should be consistent with thefollowing:

• The staging pile must facilitate a reliable, effective andprotective remedy.

• The staging pile must be designed so as to prevent orminimize releases of hazardous wastes and hazardousconstituents into the environment, and minimize oradequately control cross-media transfer, as necessary toprotect human health and the environment (for example,through the use of liners, covers, run-off/run-on controls, asappropriate).

Toxic Substances Control Act-Strategyfor Reducing Lead Exposures

EPA, February 21, 1991 Presents strategies for reducing lead exposures by reducing theamount of lead in the environment, as well as reducing blood leadlevels, especially in children.

X

Surface Mining Control and ReclamationAct (SMCRA)

30 USC Sees. 1201-1328

30 CFR Part 816

SMCRA regulations govern coal exploration and active coalmining. Hence, these regulations are not applicable to remedialactions taken at the ALM Site. Nevertheless, some of the surfacemining standards found in 30 CFR Part 816 are relevant andappropriate requirements because they address circumstances that

X



DOT Hazardous Materials TransportationRegulations

Clean Water Act - Dredge or FillRequirements (Section 404)

Clean Water Act - Effluent DischargeStandards

Clean Water Act - Discharge ofStormwater

EPA Mine Waste

Citation

49 CFR Parts 107, 171-177

33 USC Sees. 1251-1376

40 CFR Parts 230, 231

40 CFR Sec. 125.100

40 CFR Sec. 122.41

40 CFR Sec. 122.21

40 CFR Sec. 122.26

EPA Region 7 Fact Sheet,February 2003.

Description

are similar to those found at the ALM Site. The relevant andappropriate requirements include Part 816.45, Sediment ControlMeasures; Part 816.46, Siltation Structures; Part 816.102, GradingRequirements; and Part 816. I l l , Revegetation.

Regulates transportation of hazardous materials. Would berelevant and appropriate for the transport of excavated materialswithin the site.

Regulates discharge of dredged or fill material into navigablewaters.

Requires that best management practices be maintained by theoperator of a facility that discharges pollutants directly into theenvironment and requires that point source discharges bemonitored to assure compliance with effluent discharge limits.

Regulates point and non-point storm water discharges associatedwith industrial activity and construction activities; includesrequirements for best management practices and for pollutionprevention plans. Industrial activity includes active and inactivemining areas.

Provides public guidance on mine waste usage in the states ofMissouri and Kansas. Provides a list of uses for mine waste whatis not likely to present a threat to human health or the environment.

PotentialARARs

X

X

X

X

To BeConsidered

X



STATE REQUIREMENTS

Missouri Fugitive Particulate MatterRegulations

Missouri Clean Water Law - EffluentRegulations

Missouri Clean Water Law - Constructionand Operating Permits

Missouri Clean Water Law - Storm WaterRegulations

Missouri Clean Water Law-TMDLRegulations

Citation

10CSR 10-6. 170

RSMo 644.006 -564

10CSR 20-7.01 5

10CSR20-6.010

10CSR 20-6.200

MOU between EPA and MDNRregarding the state's

Description

The Missouri fugitive paniculate matter regulations containrestrictions on the release of particulate matter to ambient air. Theseregulations are applicable to any dust emissions that occur as a resultof remedial actions taken at the site.

Regulates the discharge of constituents from any point source,including storm water, into waters of the state. Provides for themaintenance and protection of public health and aquatic life uses ofsurface water and groundwater. Regulates effluent discharges bylimiting the amounts of various pollutants discharged to waters ofthe state. State permits would not be required under CERCLA, butthe substantive provisions would be applicable. The Missouristandards would be considered ARARs only if they are morestringent than the Federal standards.

Requires permits for discharges from point sources of watercontamination. Although permits are not required for remedialactions conducted under CERCLA, these regulations may berelevant and appropriate to corrective actions taken at the site.

Requires permits for metal and non-metal mining facilities andland uses or disturbances that create point source discharges of stormwater. These regulations define Best Management Practices for landdisturbances, including practices or procedures that would reduce theamount of metals in soils and sediments available for transport towaters of the state. Permits would not be required for actions takenunder CERCLA, but the substantive provisions of these regulationswould be applicable. The Missouri standards would be consideredARARs only if they are more stringent than the Federal standards.

Requires the state to designate beneficial uses for waters of thestate and to takes steps to determine if the uses are attainable and

PotentialARARs

X

X

X

X

X

To BeConsidered



Missouri Solid Waste Disposal Law

Missouri Hazardous Waste ManagementLaw

Missouri Metallic Minerals WasteManagement Act

Citation

implementation of Section303(d) of the federal CleanWater Act and 10CSR 20-7

RSMo 260.200 - 345

10CSR80

RSMo 260.350 -434

10CSR25

RSMo 444.350 -380

10CSR45

Description

what the total maximum daily loads (TMDLs) should be to protectthe designated uses. The TMDLs would be applicable to pointdischarges from abandoned mined lands, as well as active chatquarrying operations.

Regulates facilities used for the disposal of non-hazardousindustrial, commercial, agricultural, infections, and domesticwastes. Does not apply to the disposal of overburden, rock,tailings, matte, slag, or other waste material resulting from mining,milling, or smelting. However, the regulations are consideredrelevant and appropriate.

Regulates the generation, identification, treatment and disposal ofhazardous wastes. These regulations are not applicable, relevant orappropriate to mining and beneficiation wastes or to wastesgenerated from the reclamation of mined lands. However, certainsubstantive requirements related to design, operation and closure ofdisposal sites should be considered.

Regulates disposal of waste from active metallic mineral mining,beneficiation, and processing. The regulations also containtechnical guidelines, permitting, and closure requirements.Because these regulations contain closure standards for activemetal mines, they are not ARARs but may be reviewed andconsidered during the design of removal actions. They areconsidered TBCs.

PotentialARARs

X

X

To BeConsidered

X



Citation Description PotentialARARs

To BeConsidered

Missouri Land Reclamation Act-Industrial Mineral Law

RSMo 444.760-790

10CSR40.010

This law and regulations contain permitting and performancerequirements for non-metal mining, surface and underground coalmining, in-stream sand and gravel, industrial mineral open pitmining, limestone, clay, etc. However, the law and implementingregulations are not applicable to chat recycling operations becausechat piles are not natural formations. However, some of thesurface mining standards are relevant and appropriate requirementsbecause they address circumstances that are similar to those at chatrecycling and quarrying operations in the Jasper County Site.

Table 5Alternative 2

Present Worth Cost Analysis

Year

2006200720082009201020112012201320142015201620172018201920202021202220232024202520262027202820292030203120322033203420352036Totals

Direct CapitalCosts

45,78545,78545,785

0000000000000000000000000

' 000

137,355

IndirectCapital Costs

13,73513,73513,735

0000000000000000000000000000

41,205

Operation andMaintenanceCosts

31,25026,25026,2504,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,000

195,750

Total Capitaland O&MCosts

90,77085,77085,7704,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,0004,000

374,310

*Net PresentValue ofAlternative 1

90,77085,77085,7703,4553,2913,1342,9852,8432,7072,5782,4562,3402,2272,1202,0201,9251,8321,7451,6621,5831,5081,4331,3681,3021,2381,1801,1251,0721,020971926

316,356Total Net Present Value of Alternative 2 = $316,356.00

^Includes the annual 5% discount rate

APPENDIX C: RESPONSIVENESS SUMMARY

Annapolis Lead Mine Site

Responsiveness Summary

This Responsiveness Summary addresses all comments pertaining to the Proposed Plan receivedduring the public comment period. The Responsiveness Summary consists of the followingsections: Comments received during the public hearing on September 7, 2005; commentsreceived from the Missouri Department of Natural Resources (MDNR); comments received fromthe general public; comments received from political subdivisions of the state of Missouri; andcomments received from business and industry.

COMMENTS RECEIVED DURING THE PUBLIC HEARING, SEPTEMBER 7, 2005.

The following comments concerning the proposed remedy were raised during the public meetingheld at the Southern Iron Community Center on September 7, 2005. Other questions andcomments raised during that public meeting which did not directly concern the proposed plan arenot included in this responsiveness summary. There were several comments from members ofthe audience at the public meeting concerning the removal action,'but no specific comments onthe Proposed Plan. There appeared to be general acceptance of the Proposed Plan by those inattendance.

COMMENT: From Dave Mosby, Chief Superfund Unit, MDNR: MDNR has reviewed theproposed plan and is in basic agreement with the remedy. MDNR believes that a little moresampling is required to conduct additional risk assessment and that MDNR should be involvedwith the determination of the parameters of the phosphate treatment.

RESPONSE: EPA wil l involve the state directly in the design of the remedy. The AnnapolisLead Mine Site project has been accomplished with predominately in-house EPA resources,rather than contract resources. The design of the remedial action will also be utilizing in-houseresources. The state wil l be a full partner in that design. Any additional sampling that isrequired for the design can be accomplished by EPA or state personnel. EPA will consult withthe state in all phases of the design, including any phosphate treatment and stream bankstabilization.

COMMENT: Continuation of the state's comments: MDNR is concerned that there are soilsareas with high lead levels where we will be unable to reduce the toxicity of the lead to belowacceptable levels by turning it under with phosphate. MDNR believes those soils should beplaced in the on-site repository.

RESPONSE: Phosphate treatment will reduce the toxicity of the lead regardless of theconcentrations. It is understood that there will be areas of the flood plain that will continue tohave lead in soils at levels above health based limits. It is also understood that the exposure tothese soils will be limited by a number of factors, including the fairly dense vegetation in themajority of the flood plain area, the infrequent visitation anticipated to the area andsedimentation during future flood events that will deposit additional non-contaminated materials

over the existing lead contaminated soils. Application of phosphates will take place, whereappropriate, in a manner which disturbs the existing vegetation to the least degree possible. Thestate will be involved with those decisions.

Regarding materials that will be removed and placed in the on-site repository, it is not practicalto remove large amounts of soil from the flood plain. EPA and MDNR agree that contaminatedsoil and sediment on the banks of Sutton Branch Creek which are highly vulnerable to erosionwill be removed and placed in the repository. The common practice when installing bankstabilization structures is to excavate vertical banks and slope them prior to installation of theerosion control structure. Excavated contaminated material will be placed in the repository.

RESPONSE TO COMMENTS FROM MDNR.

MDNR sent a letter, dated September 26, 2005, which serves as their acceptance of the ProposedPlan. The letter includes six 'issues'. These six issues are not considered direct comments to theProposed Plan since the letter specifically states "We expect the following issues to be addressedwith our involvement during the remedial design and remedial action." However EPA doesbelieve that these issues merit formal recognition and response.

1. The Human Health Risk Assessment was unable to conclusively determine if riskremains in the northern portion of the site. This is because no post-removal data wasavailable for metals other than lead. Additional sampling should be conducted (aminimum of three samples taken) to confirm that other metals do not pose a risk.Samples may be analyzed by XRF.

An analysis of (he existing data has determined that the ratios of 'other metals' tolead is such that we can determine the risk from other metals based on theconcentrations of lead that remain and extrapolating the concentrations of othermetals and determining the potential risk. However, additional samples will be takenduring the course of the remedial design.

2. The department's Hazardous Waste Program has expertise in the area of phosphateamendment of soils; this expertise should be utilized in the Remedial Design ProcessforOUl .

As previously discussed, EPA plans to utilize the MDNR's expertise during theRemedial Design Process.

3. Monitoring runoff from the site will be very important due to application of highlevels of phosphorous in the flood plain.

Monitoring runoff will be more fully detailed in the Remedial Design.

4. Institutional controls should include prohibiting domestic well construction in thenorthern portion of the site and prohibiting alluvial wells construction in the southernportion of the site.

Institutional controls, prohibiting domestic well construction in these areas areincluded in this ROD.

5. The stream bank stabilization in the preferred alternative must be designed for a 100-year/24 hour flood event to reduce long-term operation and maintenance (O&M).

Specific design parameters will be determined during the Remedial Design.Standards appropriate to the site and the conditions will be used.

6. Long-term O&M costs appear to be greatly inflated in the Feasibility Study. Thesecosts should be re-visited and presented more accurately as soon as possible;definitely within the public comment period.

No accurate estimate of O&M costs is possible until the type, number and placementof structures are determined in the Remedial Design. EPA has revised the estimatesof O&M in the final ROD.

COMMENTS RECEIVED FROM THE GENERAL PUBLIC

No comments specific to the Proposed Plan have been received from the general public.

COMMENTS RECEIVED FROM POLITICAL SUBDIVISIONS OF THE STATE OFMISSOURI

No specific comments on the Proposed Plan have been received from any political subdivision ofthe state of Missouri.

COMMENTS RECEIVED FROM BUSINESS AND INDUSTRY

No comments were received from Business or Industry.

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