US FPA RECORDS CENTER REGION 5

509968

Explanation of Significant Differences

Eagle Zinc Site

EPA ID: ILD980606941

Hillsboro, Illinois

U.S. Environmental Protection Agency

Region 5

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Executive Summary

The U.S. Environmental Protection Agency (EPA) is issuing an Explanation of Significant Differences (ESD) to document remedy changes to the soils portion of the Eagle Zinc Site, in Operable Unit (OU) 2. These changes are needed because, while conducting the OU 2 Remedial Action (RA), additional soil contamination was identified in the residential area near the Eagle Zinc property.

The significant differences in the remedy include: (1) the inclusion of a human health based remedial action objective (RAO) for residential soil, (2) the excavation of lead-contaminated soils from residential properties based on a site specific cleanup level, and (3) a clarification that the Synthetic Precipitation Leaching Procedure (SPLP) analysis, not Toxicity Characteristic Leaching Procedure (TCLP), should be used to determine if waste should be treated prior to disposing of it in an on-site management cell. The total cost to test and remediate the additional, properties is estimated to be $460,000.

The Eagle Zinc Site encompasses about 132 acres, 30 acres of which previously consisted of buildings and structures. The Site is divided into two OUs. OU 1 was an interim action that addressed the contamination associated with the buildings and structures on the Site. OU 2, the focus of this ESD, addresses the soil, ground water, surface water, sediment, and manufacturing residues on the Site.

Explanation of Significant Differences

Eagle Zine Superfund Site

1. Introduction

A. Site Name and Location

The Eagle Zinc Site (the Site) is located on the northeastern side of Hillsboro, Illinois, approximately 50 miles northeast of St Louis, Missouri. According to the 2010 census, Hillsboro is home to a little over 6,200 citizens. The Site is located in a mixed commercial/industrial/residential area and the nearest residential area is approximately 100 feet southwest of the Site. The Site was historically used for zinc oxide production, zinc smelting and related operations for about 90 years, until 2003. The property encompasses approximately 132 acres, on which there were buildings covering approximately 30 acres. The Site has been divided into two operable units (OUs): OU 1 addressed the interim remedial action regarding the contaminated buildings, while OU 2 addresses the soil, residue, sediment, surface water and groundwater at the Site.

B. Identiflcatioii of Lead and Support Agencies

U.S. Environmental Protection Agency (U.S. EPA) is the lead agency for the Site; and Illinois EPA (lEPA) is the support agency.

C. Statement of Purpose

This decision document sets forth the basis for issuing an ESD to the September 6, 2012 OU 2 Record of Decision (ROD) for the Eagle Zinc. Site in Hillsboro, IL. Section 117(c) of the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) and Section 300.435(c)(2)(i) of the National Oil and Hazardous Substances Pollution Contingency Plan (NCP) establish procedures for explaining, documenting, and informing the public of significant changes to the remedy that occur after the ROD is signed. An ESD is required when the remedial action to be taken differs significantly from the remedy selected in the ROD but does not fundamentally alter the remedy with respect to scope, performance or cost.

This ESD will address additional remedial activities for more recently discovered lead contamination in residential soils present on the Site. Additional sampling will be conducted to determine a site specific cleanup level for the residential properties. Properties with soil concentrations above the cleanup level will be excavated and backfilled. In addition, this ESD clarifies that the leachate analysis, used to determine which material must be treated prior to consolidating them in the on-site management cell, is the SPLP leachate analysis.

D. Statutory Basis for Issuance of the ESD

This decision document sets forth the basis for the determination to issue an ESD to the September 2012 ROD. for Eagle Zinc Superfund Site, Operable Unit (OU) 2. 0U2 included the waste piles, residue, soil, surface water and groundwater for the Site.

Section 117(c) of the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, as amended (CERCL A)' and 40 Code of Federal Regulations (CFR) 300.435(c)(2)(i) and 300.825(a)(2) of the National Contingency Plan states that U.S. EPA shall write and publish an ESD when the remedy to be implemented differs significantly from the remedy selected in the ROD. U.S. EPA policy and regulations^ indicate that an ESD, rather than a ROD Amendment, is appropriate where the changes being made to the RA are significant but do not fundamentally alter the overall remedy with respect to scope, performance, or cost.

E. Summary of Circumstances Necessitating this ESD

The circumstances necessitating this ESD include the discovery of additional site-related ^ contamination and the realization that the ROD requirement for identifying and treating hazardous waste was not clearly defined. During the remedial action confirmatory sampling effort for OU 2, EPA identified four residential yards with elevated levels of lead in the soil. When the ROD was signed, EPA believed that contamination was limited to property boundaries, so the selected remedial action did not extend to nearby residential areas.

E. Agency Determination

EPA, in consultation with lEPA, has reviewed the changes to the Eagle Zinc Site remedial action in accordance with CERCLA and EPA policy and guidance. EPA has determined that the changes to the OU 2 ROD are significant, but do not fundamentally alter the overall action for the Site with respect to scope, performance, or cost. The modified remedy complies with the NOP and the statutory requirements of CERCLA and remains protective of human health and the environment. Thus, it is appropriate to issue an ESD to document the changes resulting in that modification.

G. Administrative Record

In accordance with Sections 300.435(c) and 300.825(a) (2) of the NCP, this ESD and supporting documentation will become part of the administrative record for the Site.

The administrative record is available for public review at the following location:

EPA Region 5 Records Center 77 West Jackson Boulevard - 7th Floor Chicago, IL 60604 8:00 a.m. - 4:00 p.m. M-F

' 42 United States Code (USC) §9617(c). - See 40 CFR §300.435(c) (National Contingency Plan); EPA Office of Solid Waste and Emergency Response Directive 9355.3-02.

An information repository is also located at:

Hillsboro Public Library Hours: 214 School Street Monday and Friday - 9:30 a.m. - 5 p.m. Hillsboro, IL 62049 Tuesday, Wednesday, and Thursday - 9:30 a.m. - 7:30 p.m.

Saturday - 9:30 a.m. - 1:00 p.m.

II. Site History, Contamination, and Selected Remedy

A. Site History

From 1912 to 2003, the Site was used for smelting and the manufacture of sulfuric acid, zinc oxide, and leaded zinc oxide. In 1912, Lanyon Zinc Company opened the first facility, a smelter producing zinc and sulfuric acid, at the Site. In 1919, the Site was purchased by Eagle-Picher Industries (Eagle-Picher), who continued to conduct similar activities until 1935. During the early 1920s, the manufacture of zinc oxide and leaded zinc oxide commenced at the Site. The leaded zinc oxide was manufactured by combining lead sulfate with zinc oxide. These activities ceased around 1958. Eagle-Picher continued to manufacture zinc oxide at the Site until November 1980, at which time the Site was purchased by The Sherwin-Williams Company (Sherwin-Williams). •Sherwin-Williams continued zinc oxide manufacturing operations at the Site until the company sold the plant in 1984 to Eagle Zinc Company, a division of T.L. Diamond & Company (Eagle Zinc). Eagle Zinc continued manufacturing zinc oxide using the process employed by Sherwin-Williams and Eagle-Picher.

Both direct and indirect processes were used at the Site to manufacture zinc oxide. The indirect process involved the processing of zinc metal in a muffle fumace. The direct process, which was used until the plant closed in early 2003, involved the processing of zinc ores and the stockpiling of fumace residues in a rotary kiln fumace. Residual materials, historically generated by the manufacturing operations, included rotary kiln residue, muffle dross, metallic zinc particles, and refractory bricks from the facility's fumaees.

According to historical documents, during industrial operations large amounts of ore and smelter waste were stored on the property. Significant portions of the Site are currently covered with smelter Waste and other materials associated with historical smelting operations. An estimated 43,500 cubic yards of residue waste currently resides onsite in 15 residue piles. Residue is also spread across the Site, and the residue thickness ranges from a few inches thick to 28 feet thick based on soil borings; totaling approximately 210,000 cubic yards of residue. In addition, 43,500 cubic yards of residue are consolidated into 15 piles around the Site.

In 1981, while the Site was still in operation, Sherwin-Williams notified the EPA that slag/residual materials had been disposed of on the Site. Illinois EPA (lEPA) took surface water samples which indicated that some metals (zinc, iron, lead, and copper) exceeded state surface water quality standards, and subsequently gave Sherwin-Williams a notice of violation, which resulted in the removal of 18,000 tons of residue material from 10 acres of the Site. In 1984, lEPA conducted a

preliminary site assessment and concluded that soil samples collected in the early 1980s were not hazardous waste, and not subject to RCRA actions. Subsequent RI work conducted under CERCLA found that characteristic hazardous waste is on the Site.

The remedial investigation (RI) was conducted between 2001 and 2005, following an expanded site inspection and subsequent groundwater monitoring initiated by lEPA; The RI identified residue piles, soil areas, sediment, groundwater and surface water contamination which posed a potential threat to human health and the environment, and the Site was listed on the NPL in 2007. To expedite cleanup, the Site was split into two operable units (OUs) and an interim ROD was signed in 2009 to address contamination in and around on the buildings. The remedial action for GUI was completed in September, 2015, and included demolishing over 30 buildings, removing asbestos containing material, hazardous materials removal, and on site consolidation of the remaining building debris.

Following a supplemental RI, the U.S. EPA issued a ROD for OU2 in September 2012 that addressed the contaminants (antimony, cadrnium, cobalt, lead, nickel and zinc) in residue piles, soil, groundwater, and sediment. This ESD only addresses significant changes to the 0U2 remedy.

B. Contaminants of Concerns

The residue and residue piles from previous manufacturing processes were the main source of contamination. Residue that exceeded the industrial regional screening level (RSL) for soil covered approximately 56 acres of the Site - totaling approximately 255,000 cubic yards (cy) of residual materials. Total arsenic and lead were found above their RSLs in a large portion of the residue samples; 52% of the samples exceeded the RSL for arsenic and 40% exceeded the RSL for lead. Leachability tests were conducted using both SPLP and TCLP analyses, in order to identify the potential for metals to leach from the residue into groundwater and surface water.

Table 1: Cleanup Levels Media Contaminant Cleanup Level

(CL) Basis for CLs

Residue/Soil

Lead 700 ppm Illinois Tiered Approach to Corrective Action Objectives

Residue/Soil Zinc 61,000 ppm Illinois Tiered

Approach to Corrective Action Objectives

Residue/Soil Cobalt 12,000 ppm Illinois Tiered Approach to Corrective Action Objectives

Residue/Soil Nickel 4,100 ppm

Illinois Tiered Approach to Corrective Action Objectives

Residue/Soil

Antimony 82 ppm

Illinois Tiered Approach to Corrective Action Objectives

Surface Water Cadmium 2.61 ppb Illinois EPA General

Use Surface Water Standards

Surface Water Zinc 62.8 ppm Illinois EPA General Use Surface Water Standards

Sediment Cadmium 1 ppb Ecological Screening

Levels Sediment

Zinc 121 ppb Ecological Screening Levels

C. Selected Remedy The selected remedy for OU 2 consists of the following:

• Hazardous Waste Treatment: The residue piles will be consolidated and treated in-situ to meet SPLP and TCLP treatment standards.

• On-site Consolidation and Containment: All residue material above CLs, including the treated material, soils, excavated sediments, and stockpiled demolition materials from GUI will be consolidated and covered with an lEPA (35 I AC) 807 compliant soil cover.

• Stream Re-alignment, Sediment Excavation, and Wetland: The westward flowing ephemeral stream will be realigned to reduce surface water interaction with the existing residue and to return the ephemeral stream to its natural flow pattern. Contaminated sediment above CLs will be excavated, as needed, and consolidated on the Site, under the soil cover.

• Institutional Controls: A Restrictive Covenant was implemented on the property in November 2011, and provides notice to future property owners that the contamination at the Site poses risks to human health and the environment. The Covenant restricts potable use of groundwater and prevents disturbance of the remedy. The Covenant also prohibits residential use of the property, including homes, hospitals, and schools.

• Monitoring and Assessment: Although there is some contamination in the on-site groundwater, the hydraulic conductivity is too low to produce sufficient water for potable use. EPA will monitor the groundwater and surface water quarterly; if conditions change, appropriate steps will be taken to address any unacceptable risk or impairment to beneficial use.

III. Basis for ESD

The changes to the OU 2 ROD are summarized in Table 2. Further descriptions of the changes are provided in the subsequent section. With these changes, the remedy will continue to be protective and meet applicable or relevant and appropriate requirements (ARARs). Because hazardous substances will remain on-site at levels that do not allow for unrestricted use and unlimited exposure, five-year reviews will be required.

Table 2: Changes to Remedy Being Documented in ESD

Remedy Component in 2012 OU2 ROD Change in Remedy Documented in ESD Hazardous Waste Treatment Hazardous waste will be treated to meet

SPLP standards On-site Consolidation and Containment Contaminated residential soils will be

added to the on-site consolidation cell Stream Re-alignment, Sediment Excavation, and Wetland

No change

Institutional Controls No change Monitoring and Assessment No change

- Excavation of contaminated soils from residential properties

Additionally, this ESD amends the remedial action objectives (RAOs) for the Site, described in Table 3, to account for the recently discovered residential exposure to elevated levels of lead in soil.

Table 3: Changes to RAOs being documented in ESD

Media RAO(s) in 2012 OU2 ROD Change in RAO documented in ESD

Residue and Soil Prevent exposure to industrial and construction workers from COC concentrations in residue and soil immediately underlying the residue that exceed the cleanup levels (CLs). Prevent residue erosion of COCs into the surrounding water bodies so that CLs are not exceeded in those water bodies or the sediment. Minimize leaching of COCs into the groundwater or perched water that discharges into surrounding water bodies in order to prevent unacceptable risk to aquatic receptors.

Retain previous RAOs and add: • Reduce or eliminate lead

exposure pathways in residential areas such that the probability of an individual child (aged 0 to 84 months) exceeding a blood lead level of 5 mg/dL is 5% or less^.

Surface Water • Minimize the discharge of COCs exceeding the CL into the surrounding water bodies

No change

Surface Water and Sediment

Prevent unacceptable risk to the aquatic receptors from COCs that exceed the CL in surface water and/or sediment within a reasonable time frame

No change

IV. Significant Differences from the OU 2 ROD Remedial Action

The initial cleanup addressed only on-site contamination exceeding commercial/industrial screening levels and sediment contamination posing a risk to ecological receptions. However, data from confirmatory sampling and a supplemental investigation revealed that contaminated soil is present in residential yards in the flood plain area of the stream that runs through the Site.

^ 5ug/dl is the current CDC reference level used to Identify children with elevated blood lead levels (corresponding to the 97.5"" percentile, nationwide). EPA policy Is to set a cleanup level such that at least 95% of children exposed on site would have a blood lead level below the reference (OSWER 9285.7-50).

A. Clariflcation of Hazardous Waste Treatment Standards The 2012 0U2 ROD stated that EPA would treat all soil to meet SPLP and TCLP standard. This ESD clarifies that contaminated soil will be treated to meet SPLP standards only. The TCLP was designed to simulate material in a more acidic environment, such as a landfill with exposure to acid rain, while SPLP simulates material in-situ. The soil will be consolidated on site, rather than in a landfill, and the on-site conditions are not acidic, so SPLP has been determined to be a more appropriate standard.

B. Addition of Residential Soil RAO OU 2 remedial action confirmatory sampling, and supplemental sampling efforts, indicate that contaminated soil is present on four residential properties and the floodplain to the west of the Eagle Zinc property. In order to address this contamination, this ESD amends the RAOs for 0U2 to include the reduction of lead exposure pathways, at residential properties^ such that the probability of an individual child's blood lead level exceeding 5 pg/dl is no more than 5%.

C. Remediation of Residential Properties In order to achieve the residential lead RAO, EPA will use the Integrated Exposure, Uptake, and Biokinetic (lEUBK) model to derive a site specific cleanup level based on lead bioavailability and site specific exposure parameters.

EPA will collect 5-point composite samples in the residential yards that had soil samples with concentrations of lead greater than 200 ppm, and properties adjacent to those with elevated lead (for a total of 19 properties). These samples will be used to screen properties for remediation. Figure 1 identifies the residential areas, to the west of the Site, that have been identified for further screening. Additionally, a subset of these residential samples will be analyzed for bioavailability, which will be used to calculate the site specific cleanup level.

Properties where sampling shows that the soil lead concentration exceeds the site-specific residential cleanup level established through the lEUBK model will be excavated and backfilled with clean soil. For lawn areas, the top 12 inches of soil will be excavated, and bedding areas, which are more likely to be disturbed at greater depths, will be excavated to 18 inches. A marker material will be placed at the base of the excavation to indicate the extent of the remediated soil.

The total cost, for the remediation of the residential properties and flood plain area, is estimated to be $460,000. This includes remediating 4 residential properties at $40,000 per home, and the flood plain (adjacent to the residential area) for $300,000.

V. State Comments

Illinois EPA has reviewed this ESD and concurs with the significant change in remedy. The Concurrence letter will be added to the administrative record upon receipt.

VI. statutory Determinations

EPA has determined that the addition of residential cleanups and modification of waste treatment standards is necessary for the adequate implementation of the selected remedial action. EPA has determined that this change, as documented in the ESD, is in accordance with CERCLA Section 121 and is protective of human health and the environment. The change complies with federal and state requirements that are applicable and or relevant and appropriate, use permanent solutions to the maximum extent practicable, and is cost-effective. Since hazardous substances will remain on-site at levels that do not allow for unrestricted use and unlimited exposure, five-year reviews of the remedy will be required.

VII. Public Participation Compliance

EPA shall publish a brief description of the ESD in the local newspaper as required by the NCP at 40 C.F.R. Section 300.435 (c)(2)(i)(B). This ESD will also be placed in the administrative record files and information repository which are located at the Hillsboro Public Library and in the EPA Region 5 office as required by the NCP Section 300.435(c)(2)(i)(A). See Section I, paragraph F, of this ESD for further details about the information repositories. An electronic copy of this ESD will be available online at httDs://cumulis.epa.gov/supercpad/cursites/csitinfo.cfm?id=0500648

VIII. Declaration by EPA

EPA has detennined that the modifications to the OU 2 ROD for the Eagle Zinc Site documented in this ESD are significant, but do not fundamentally alter the overall Site remedial action with respect to scope, performance, or cost. I therefore approve the issuance of this ESD for the Eagle Zinc Site and the changes to the remedial action stated herein.

Douglas Ballotti, Acting Director Date

Superfund Division US EPA Region 5

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Figure 1: Site Map and Identification of Residential Areas for Further Investigation and Remediation

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