PROPOSED PLAN

RECORD OF DECISION AMENDMENT

CHEROKEE COUNTY SITE OPERABLE UNIT 04 -

TREECE SUBSITE

CHEROKEE COUNTY, KANSAS

Prepared by:

U. S. Environmental Protection Agency Region 7

11201 Renner Blvd Lenexa, Kansas 66219

July 2016

Table of Contents

I. PURPOSE OF THE PROPOSED PLAN 1 II. SITE BACKGROUND 2

Site Location and Description 2 History of Contamination 3 Site Characterization 3 Health Effects 5 EPA Response Actions 5

III. REASON FOR THE PROPOSED CHANGE 7 IV. SCOPE AND ROLE OF THE PROPOSED RESPONSE ACTION 7 V. SUMMARY OF SITE RISKS 8

Ecological Risk 8 Human Health Risk 10

VI. REMEDIAL ACTION OBJECTIVES 10 Sediment RAOs 10

VII. SUMMARY OF ALTERNATIVES 11 VIII. EVALUATION OF ALTERNATIVES 13

Detailed Analysis of Proposed Remedial Alternative Compared to Current Selected Remedy 13 Overall Protection of Human Health and the Environment 14 Compliance with ARARs 14 Long-term Effectiveness and Permanence 14 Reduction of Toxicity, Mobility or Volume of Contaminants through Treatment 14 Short-term Effectiveness 15 Implementability 15 State/Support Agency Acceptance 16 Community Acceptance 16

IX. PREFERRED ALTERNATIVE 16 Statutory Determination 17

X. COMMUNITY PARTICIPATION 17

Appendices FIGURES

FIGURE 1 - SITE MAP FIGURE 2 - LOCATION OF NW TRIBUTARY OF TAR CREEK

TABLES TABLE TABLE

TABLE TABLE TABLE

ARARS

1 - SELECTED REMEDY COMPARISON 2 - COC CONCENTRATIONS EXPECTED TO PROVIDE ADEQUATE

PROTECTION OF ECOLOGICAL RECEPTORS 3 - CANCER TOXICITY DATA SUMMARY 4 - NON-CANCER TOXICITY DATA SUMMARY 5 - DETAILED COST ESTIMATE FOR MODIFIED ALTERNATIVE 8A

I. PURPOSE OF THE PROPOSED PLAN

The United States Environmental Protection Agency (EPA) is issuing this Proposed Remedial Action Plan (Proposed Plan) to present EPA's Preferred Alternative to address heavy metals contamination in sediment in the non-perennial (intermittent) streams as part of the remedy selected in the August 28, 1997 Record of Decision (ROD) for Operable Unit (OU) 04, as amended by the September 29, 2006 ROD Amendment, for the Cherokee County Superfund site (Site).

The Site is located in Cherokee County, Kansas, the most southeastern county of the state of Kansas and represents the Kansas portion of the former Tri-State Mining District (TSMD). Refer to Figure 1 for a map showing the location of the Site. The National Superfund Database Identification Number for the Site is KSD980741862.

EPA is proposing to address contaminated sediments in the intermittent portion of Tar Creek, known as the NW Tributary concurrently with the mine waste and contaminated soil at the OU 04 Treece subsite. The original remedy and the 2006 ROD Amendment specifically excluded the removal or remediation of sediments in Tar Creek and other streams within the OU 04 Treece subsite. The assumption was to address the sediment at the OU 04 Treece subsite after all mine waste cleanups have been conducted to remove source contamination to the sediment. This proposed remedy modification will allow for the removal, consolidation, and capping of contaminated sediments only in the intermittent portion of Tar Creek, known as the NW Tributary. Refer to Figure 2 for a map showing the location of the NW Tributary of Tar Creek. By addressing the sediments of the stream during the same remedial action as the surrounding mine waste and impacted soils, it allows for a more efficient remediation due to reduced costs associated with remobilization, disturbance of capped areas, and/or construction of new capped areas. The remaining perennial portion of Tar Creek will be addressed under a new OU, OU 09 -Tar Creek Watershed. This proposed modification is explained in detail herein. EPA is not proposing to modify the existing remedy for the remaining components of the final action specified in the 1997 ROD, as amended by the 2006 ROD amendment.

EPA is the lead agency for the Site, and the Kansas Department of Health and Environment (KDHE) is the support agency. This Proposed Plan summarizes information from the 1997 ROD, 2006 ROD Amendment to the 1997 ROD (2006 ROD Amendment), and subsequent remedial actions and investigations. The selected alternative is expected to meet ARARs and be protective of human and ecological receptors. All the documents EPA considered for this proposed remedy modification are contained in the Administrative Record for the Site.

This Proposed Plan is being issued as part of EPA's public participation requirements under Section 117 of the Comprehensive Environmental, Response, Compensation and Liability Act (CERCLA) of 1980, as amended, 42 U.S.C. § 9617, commonly known as Superfund, and Section 300.430(f)(ii) of the National Oil and Hazardous Substances Pollution Contingency'Plan (NCP), 40 CFR § 300.430(f)(ii).

After the close of the public comment, EPA will announce its selection of the remedy modification for the OU 04 Treece subsite in an additional Amendment to the 1997 ROD (ROD

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Amendment). The public's comments will be considered and presented with discussion in the Responsiveness Summary of the ROD Amendment. EPA encourages the public to review the documents that make up the Administrative Record to gain a more comprehensive understanding of the Site and the Superfund activities that have been conducted.

The Administrative Record for the Site can be accessed at https://semspub.epa.gov/src/home/search.isf. or at the following location:

U.S. Environmental Protection Agency Program Representative Region 7 Records Center 11201 RennerBlvd Lenexa, Kansas 66219 Phone:(913) 551-7939 Hours: Monday - Friday, 8:00 am to 5:00 pm (by appointment only)

The Proposed Plan includes the following sections:

• Site Background • Reason for the Proposed Change • Scope and Role of the Proposed Response Action • Summary of Site Risks • Remedial Action Objectives • Summary of Alternatives • Evaluation of Alternatives • EPA's Preferred Alternative • Community Participation

II. SITE BACKGROUND

Site Location and Description

Cherokee County encompasses 591 square miles. The county is bordered by Crawford County on the north, by Newton and Jasper Counties in Missouri on the east, by Labette County on the west and by Ottawa and Craig Counties in Oklahoma on the south. The Site encompasses 115 square miles of southeast Cherokee County. The communities of Baxter Springs, Galena and Riverton are located within the Site boundaries. Land use is predominantly agricultural interspersed with light industrial and residential areas. The Site is arranged into nine OUs for administrative efficiency in conducting environmental cleanups: OU 01, Galena Alternate Water Supply; OU 02, Spring River Basin; OU 03, Baxter Springs subsite; OU 04, Treece subsite; OU 05, Galena Groundwater/Surface Water; OU 06, Badger, Lawton, Waco, and Crestline subsites; OU 07, Galena Residential Soils; OU 08, Railroads; and OU 09 Tar Creek Watershed.

This Proposed Plan is concerned solely with OU 04, consisting of the Treece subsite which is located in the southwestern portion of the Site and is contiguous with the Tar Creek Superfund

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site in Oklahoma. The surface area of the OU 04 Treece subsite is approximately 11 square miles or 7,040 acres.

Contaminated media at the OU 04 Treece subsite include mine waste (source material), soils, groundwater, sediments, and surface water. The contaminants of concern (COCs) are lead, zinc, and cadmium. The contamination was caused by lead and zinc ore mining and processing that began in Kansas in the 1870s and continued until 1970. The mining and processing generated chat piles and tailings that are the sources of the COCs. It is estimated that 795 acres within the OU 04 Treece subsite was covered with surficial mine waste piles, tailings impoundments, and stream outwash tailings deposits.

History of Contamination

Lead and zinc mining began in the middle 1800s and continued for over a century in the TSMD; the final mining activities ceased in 1970. Sphalerite (zinc sulfide) and galena (lead sulfide) were the principle mined ores, and several other metal sulfides were found in association with the economic ores. The mining activities changed the hydrology of the area by creating a labyrinth of underground voids and many open conduits. These features facilitate surface subsidence and collapse as well as enhanced flow of mineralized groundwater in the subsurface. Surficial mining wastes also leach metals into the groundwater system and surface water bodies and sediments. The normal surface and subsurface flow characteristics have been modified by past mining activities; and since much of the surface vegetation is impacted or absent, there is increased infiltration of surface water into the shallow groundwater system and erosion of mining wastes into surface water bodies. During the active mining years, water was continually pumped out of the mines because the ore was predominantly located in the saturated zone of the same bedrock formations that contain the area's shallow aquifer. When mining ceased, the mines refilled with water as a result of natural groundwater recharge and surface water inflow through mine shafts and subsidence areas. The upper aquifer is now contaminated with metals and is acidic in some areas. Acid mine drainage is prevalent throughout many areas of the TSMD. Additionally, past practices in the Site have resulted in mine waste being distributed to residential yards as fill or driveway material.

Site Characterization

The mining-related physical characteristics of the OU 04 Treece subsite include mine shafts, mine subsidence pits, impoundment tailings, chat piles, overburden piles, and bull rock piles. Overburden and bull rock, classified as non-milling wastes are generally considered to be non-hazardous. Chat and tailings, broadly classified as milling wastes are hazardous source materials of concern due to elevated levels of heavy metals, especially zinc, lead, and cadmium. Based on the RI, the average concentrations of cadmium, lead, and zinc in chat mine waste are 45 ppm, 750 ppm, and 8,056 ppm, respectively. The average concentrations in tailings are 124 ppm cadmium, 3,800 ppm lead, and 21,600 zinc. Additionally, the maximum values of cadmium, lead, and zinc in chat mining wastes .are 89 ppm, 1,660 ppm, and 13,000 ppm, respectively, while the maximum values for tailings are 540 ppm cadmium, 13,000 ppm lead, and 52,000 ppm zinc. Thus, overall, the finer particles (tailings) are more highly concentrated in the COCs than the larger particles (chat). Previously some of the berms and dikes around tailings impoundments have eroded or been overtopped and the tailings have washed into nearby streams (outwash

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tailings). There are five major areas of these outwash tailings associated with Tar Creek at the OU4 Treece subsite. These outwash tailings are major sources of contamination to stream sediment and surface water.

Soils in the immediate vicinity of the mine waste have elevated levels of metals, likely the result of several transport processes, including windblown dust from the mine waste, surface water flows, groundwater seeps, and redistribution from chat removal or quarrying operations. Residences and residential features (e.g., baseball playing field) abut or are situated on mine waste within the OU 04 Treece subsite. Overall, the primary source material to the OU 04 Treece subsite is the chat piles, tailings, and outwash tailings. Since the 1997 ROD and 2006 ROD Amendment, subsequent commercial chat sales have reduced the overall mine waste volume at chat piles located at the OU 04 Treece subsite.

The subsite is underlain by two aquifers that are separated by a confining unit. The shallow aquifer is comprised of Mississippian limestones which host the lead-zinc deposits that were mined at the subsites. Water quality in the shallow aquifer is generally poor, with some water samples exceeding Maximum Contaminant Levels (MCLs) for arsenic, cadmium, lead, mercury, and nickel. Ground water from the lower levels of the mine pools tend to be acidic. The shallow aquifer is not used at the subsite for domestic or stock water supplies. The regional ground water flow direction within the shallow aquifer is downgradient to the northwest. Other than movement downgradient, shallow aquifer ground water seeps from limestone outcrops to the downstream portions of Willow Creek and Spring River. The deep aquifer occurs in the Lower Ordovician Roubidoux Formation and provides the principal source of water for public, industrial, domestic and stock supplies at the subsites and surrounding areas.

All surface water flows in the OU 04 Treece subsite are to Tar Creek. Tar Creek, flows south into Oklahoma and drains into the Neosho River approximately ten miles south of the OU 04 Treece subsite. In 2004, the USGS conducted streambed sediment sampling across the Site. This report can be found in the Administrative Record (Assessment of Contaminated Streambed Sediment in the Kansas Part of the Historic Tri-State Lead and Zinc Mining District, Cherokee County, 2004). The report indicated that cadmium, lead, and zinc sediment concentrations ranged from 1.2 ppm to 270 ppm; 58 ppm to 3,400 ppm; and 250 ppm to 41,000 ppm, respectively, at various points in Tar Creek and it's tributary Lytle Creek.

The state of Kansas has established Total Maximum Daily Loads (TMDLs) for metals for the Tar Creek watershed that seek to control and minimize impacts to the streams and watersheds. Specifically, since periodic monitoring began at Tar Creek in 1993, 66% of the surface water samples exceeded Kansas Clean Water Act Water Quality Criteria for chronic aquatic life for lead. For zinc and cadmium, 100% of the surface water samples exceeded the chronic aquatic life criterion for Tar Creek. Thus, the KDHE has determined that Tar Creek is not supporting aquatic life, one of its designated uses. Additionally, the TMDL indicated that two different mechanisms appeared to be responsible for metal exceedances: one for lead exceedances and a different one for cadmium and zinc exceedances. Since they occurred mostly with increased run off, the lead exceedances seemed to be due to mine waste run off. In contrast, the cadmium and zinc exceedances were determined to be the result of base flow, which was water percolating through the mine waste and seeping into Tar Creek. However, both of these mechanisms are the

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result of the presence of mine waste at the surface. Unremediated mine waste serves as a continual loading source of heavy metals to the Tar Creek watershed.

Health Effects

In 1989, the Agency for Toxic Substances and Disease Registry (ATSDR) completed a Preliminary Health Assessment (PHA) for the community of Galena. The study indicated that "lead and cadmium in surface soil, surface water, and groundwater, are found at levels that are of public health concern." Children were identified as the main sensitive subpopulation of concern because of their potential exposure to contaminated soil and surface water. ATSDR concluded that the Site was a public health concern because of the risk to human health caused by the probable human exposure to hazardous substances at concentrations that may result in adverse health effects.

EPA Response Actions

The EPA placed the Site on the National Priorities List (NPL), set forth at 40 C.F.R. Part 300, Appendix B, by publication in the Federal Register on September 8, 1983, 48 Fed. Reg. 40658. Subsequent to the NPL listing, investigation of the OU 04 Treece subsite has consisted of the Remedial Investigation/ /Feasibility Study (RI/FS), the FS Addendum, the 1997 ROD, the 2006 ROD Amendment, various Remedial Action (RA) reports, successive Five-Year Review Reports, and Proposed Plan that form the basis for this proposed ROD Amendment, plus visits by the EPA and the KDHE to the OU 04 Treece subsite.

The EPA, through its enforcement authorities, negotiated an Administrative Order on Consent (AOC) with certain potentially responsible parties (PRPs) to conduct the RI/FS for both the OU 03 Baxter Springs and OU 04 Treece subsites. The PRPs performing these activities under the AOC were Cyprus Amax Minerals Corporation (corporate successor is currently Freeport-McMoRan); ASARCO, Inc.; Gold Fields American Corporation; Blue Tee Corporation; NL Industries Inc.; St. Joe Minerals Corporation (corporate successor is currently The Doe Run Co.); and Sun Company, Inc. Following the submittal of the RI/FS, the EPA requested and received an FS Addendum from the PRPs, detailing an additional, EPA-suggested remedial alternative. The FS Addendum remedial alternative subsequently formed the basis of a Proposed Plan generated by the EPA. After considering public and PRP comments on the Proposed Plan, the EPA published its selected remedy for both the OU 03 Baxter Springs and OU 04 Treece subsites in a ROD in August 1997. The selected remedy for the OU 04 Treece subsite included investigation and potential remediation of residential yards impacted by mine waste; closure and abandonment of poorly constructed, existing deep water wells and borings to prevent contamination migration from the upper aquifer to the lower"aquifer; and institutional controls on future development. The selected remedy; however, did not address any surficial mine waste and employed a TI waiver for select chemical ARARs for surface water (Tar Creek and its tributaries) and groundwater in the shallow aquifer. A Consent Decree for the planned Remedial Design (RD) and RA for both the OU 03 Baxter Springs and OU 04 Treece subsites was formalized in 1999 with the same PRPs who conducted the RI/FS. Additionally, bankruptcy funds were recovered from an additional PRP, Eagle-Picher Industries, Inc., and utilized for response actions at the OU 03 Baxter Springs subsite and OU 04 Treece subsite.

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The 1997 ROD and subsequent RA addressed metals-impacted residential properties at the OU 04 Treece subsite. The former town of Treece was located near several former mining areas and waste from these areas were transported to residential locations for a variety of purposes such as driveway construction, landscaping, fill material, and alley/road construction. Properties with values exceeding 800 parts per million (ppm) lead or 75 ppm cadmium were excavated until lead and cadmium levels were less than 500 ppm and 25 ppm, respectively, or until a maximum excavation depth of one foot was achieved. Properties were backfilled with clean native soils and revegetated. The residential work at the OU 04 Treece subsite was completed by the PRPs in 2000 under the 1999 CD. A total of 148 properties were tested and 41 yards were remediated. Additional components of the OU 04 Treece subsite response action included a well search to determine if any residents in the Treece area were consuming contaminated water from private water wells followed by the abandonment of these wells when identified. Moreover, any deep wells providing a conduit to transmit contaminated water from the upper aquifer to the lower pristine aquifer were to be abandoned under the Treece cleanup. Well search activities did not identify any deep wells transmitting contaminants to the lower clean aquifer or any residents consuming impacted groundwater. The former town of Treece was served by a municipal water system regulated by the state and provided safe drinking water.

The 1997 ROD was amended in 2006 to address the nonresidential surface mine waste and contaminated soils at the OU 04 Treece subsite. The 2006 ROD Amendment also retracted the technical impracticability waiver for surface water chemical specific ARARs. The nonresidential remedy components include excavate, grade, and consolidate mine wastes and contaminated soils followed by capping and revegetation and fill mine shafts and collapse features. Institutional Controls (ICs) include the State of Kansas Environmental Use Controls (EUCs) on most properties that contain capped wastes. EPA completed a mine waste RA for several hundred acres in conjunction with the work for the OU 03 Baxter Springs subsite. The second phase mine waste RA for the OU 04 Treece subsite was completed in 2014 and is awaiting the completion of punch-list items and inspections prior to completion of the operational and functional (O&F) period. EPA is also conducting a RD for the next phase of cleanup that will address the remaining mine waste in the OU 04 Treece subsite. The next phase of cleanup, the third and final, for the OU 04 Treece subsite is titled as Phase III and has been separated into sub-phases to facilitate remedial action contractor support. The Phase 11 LA RD is completed and , it is planned to begin the Phase IIIA RA by September 30, 2016. It is anticipated that the Phase IIIA RA will address mine waste, contaminated soils, and contaminated sediments in the intermittent portion of Tar Creek, known as the NW Tributary.

A second Consent Decree with PRPs was signed in October 2013, and this document will ensure the implementation of a mine waste RA for several hundred acres of wastes at the OU 04 Treece subsite. The PRP design work is completed and one PRP has begun their cleanup action. The other PRP will begin on-site construction work in mid-2016.

EPA implemented a voluntary residential buy-out for the community of Treece, Kansas, that was conducted by the KDHE. This work was specified in a 2010 Explanation of Significant Differences (ESD) for the adjacent Tar Creek Superfund site OU 04 ROD in Oklahoma. Residential buy-outs for Oklahoma communities adjacent to Treece were historically conducted

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by EPA Region 6 and the state of Oklahoma. The influence of Oklahoma-based mining wastes upon the community of Treece lead to the modification of the EPA Region 6 Tar Creek ROD to address the impacts to Treece citizens. All buy-out activities in the community of Treece were concluded with the disbandment of the Treece Relocation Assistance Trust on May 22, 2014. The second phase mine waste RA for the OU 04 Treece subsite also included the remediation of the footprint of the former city of Treece due to the remaining waste left after the voluntary residential buy-out.

III. REASON FOR THE PROPOSED CHANGE

The original remedy and the 2006 ROD Amendment specifically excluded the removal or remediation of sediments in Tar Creek and other streams within the OU 04 Treece subsite. The assumption was to address the sediment at the OU 04 Treece subsite after all mine waste cleanups have been conducted to remove source contamination to the sediment. This proposed remedy modification will allow for the removal, consolidation, and capping of contaminated sediments only in the intermittent portion of Tar Creek, known as the NW Tributary. By addressing the sediments of the stream during the same remedial action as the surrounding mine waste and impacted soils, it allows for a more efficient remediation due to reduced costs associated with remobilization, disturbance of capped areas, and/or construction of new capped areas. This proposal aligns with similar decisions made at the Oronogo-Duenweg Mining Belt and Newton County Mine Tailings Superfund sites in the Missouri portion of the TSMD to address intermittent streams. The remaining perennial portion of Tar Creek will be addressed under a new OU, OU 09 - Tar Creek Watershed.

The cleanup of contaminated sediments within the NW Tributary under this Proposed Plan is needed to mitigate the principal threat of exposure from mine wastes to aquatic and terrestrial ecosystems through sediments. The additional component of the proposed remedy is excavation of contaminated intermittent stream sediments with disposal in selected on-site mine subsidence pits or constructed on-site repositories. Upland mine waste will be addressed prior to addressing the channel sediments. This remedial action is essential to provide long-term protection of ecological health from exposure to the mine wastes. The proposed remedy will significantly enhance the effectiveness of earlier OU removal and remedial actions by removing additional materials causing the contamination within the OU 04 Treece subsite.

IV. SCOPE AND ROLE OF THE PROPOSED RESPONSE ACTION

The scope and role of the Preferred Alternative is to modify the remedy for the OU 04 Treece subsite described in the 1997 ROD, as amended by the 2006 ROD Amendment. For the remedy selection and status of other OUs at the Site, the EPA completed the Fifth Five-Year-Review Report for the Site in September 2015 found in the Administrative Record. EPA is not proposing to modify the remedy selected for any of the other remaining features described in the 1997 ROD and 2006 ROD Amendment, which include the mine waste and contaminated soil in the OU 04 Treece subsite.

The Preferred Alternative will provide for a cost effective and permanent solution for the intermittent stream sediments in the NW Tributary by addressing them concurrently with the

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mine waste and contaminated soil remaining at the OU 04 Treece subsite. EPA will excavate, consolidate, and/cap all surficial mine waste, contaminated soil, and contaminated intermittent stream sediments followed by disposal and capping in on-site repositories. EPA may utilize subaqueous mine waste disposal to the maximum extent practicable. The cap cover system will consist of the following elements: 12 inches of clay/fill material; 6 inches of organic topsoil; and a vegetated surface.

The remedy modification described in this Proposed Plan will modify the following component of the 1997 ROD, as amended by the 2006 ROD Amendment with respect to the OU 04 Treece subsite non-perennial stream sediments. (See Table 1)

1997 ROD & 2006 ROD Amendment Proposed Remedy Modification • Excavate, consolidate, and/or cap all

surficial mine waste and contaminated soil followed by disposal and capping.

• Excavate, consolidate, and/or cap all surficial mine waste, contaminated soil, and contaminated intermittent stream sediments followed by disposal and capping.*

*Remedy modification includes the proposed addition of contaminated intermittent stream sediments.

V. SUMMARY OF SITE RISKS

Human and ecological risks are present due to elevated levels of heavy metals in sediments within the OU 04 Treece subsite. Zinc, lead, and cadmium are the major COCs for human and ecological receptors. For human receptors, the primary exposure scenario is incidental ingestion of sediments. For ecological receptors, the primary exposure scenario consists of heavy metals uptake by ingestion of sediments for receptors such as fish, macro-invertebrates, birds, and other terrestrial species.

It is EPA's current judgement as the lead agency that the Preferred Alternative identified in this Proposed Plan is necessary to protect human health and the environment from actual or threatened releases of hazardous substances into the environment. This view is also held by the KDHE, the support agency.

Ecological Risk

In 1993, an Ecological Risk Assessment (ERA) was conducted by the same group of PRPs who conducted the HHRA for both the OU 03 Baxter Springs and OU 04 Treece subsites. The ERA identified significant risk to both aquatic and terrestrial life. Elevated levels of these three heavy metals in surface water and stream sediment at both the OU 03 Baxter Springs and OU 04 Treece subsites and their comparison to sediment guidelines have been documented and illustrate significant risks to ecological receptors.

In 2006, EPA developed ecological preliminary remediation goals (PRGs) for metals-impacted soil and sediment for the Site based on site-specific data. In the absence of site specific data on

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sediment chemistry and corresponding biological data, the initial PRG range for sediment was based on Sediment Quality Guidelines (MacDonald, Ingersoll, & Berger, 2000). The SQGs include a Threshold Effect Concentration (TEC; below which adverse effects are not expected to occur) and a Probable Effect Concentration (PEC; above which adverse effects are expected to occur more often than not). The TEC is typically used as a screening concentration (similar to a NOAEL), and the PEC is typically used as an upper threshold concentration (similar to a LOAEL). Therefore, ecological PRGs for sediment ranged from 0.99 ppm to 4.98 ppm for cadmium; 35.8 ppm to 149 ppm for lead; and 121 ppm to 459 ppm for zinc.

While the SQGs provide a useful tool for evaluating potential effects on the benthic invertebrate community, they have the potential to over-estimate toxicity due to their conservative nature. For this reason, MacDonald et al. (2009) evaluated the predictive ability of the consensus-based SQGs (i.e., PECs) in the TSMD. The results of this evaluation indicated that the PECs may over-estimate toxicity to amphipods, midges, and/or freshwater mussels exposed to sediment samples from the study area. Therefore, MacDonald et al. (2009) developed Site-Specific Toxicity Thresholds (SSTT) for individual contaminants of potential concern (COPCs) and various COPC mixtures using matching sediment chemistry and sediment toxicity data from the TSMD.

The Advanced Screening Level Ecological Risk Assessment (Macdonald Environmental Sciences, LTD, 2010) used these SSTTs to evaluate the available primary data on the condition of aquatic habitats in the TSMD. This evaluation indicated that the survival, growth, and/or reproduction of benthic invertebrates were likely being adversely affected within the TSMD. First, the concentrations of divalent metals exceeded the SSTT in 50% (268 of 537) of the surface-water samples collected from the study area (compared with 6% for reference surface-water samples). Second, comparison of the concentrations of sediment-associated cadmium, lead, and zinc to the SSTT indicated that toxicity to amphipods is predicted to occur in 49% (566 of 1162) of the sediment samples included in the project database (compared with 0% for reference sediment samples).

The fmal metal specific clean-up numbers were developed based on the concentration-response relationships from MacDonald et al., 2009. Using amphipod survival as a basis for developing toxicity thresholds, Tio (low risk threshold, toxic to 10% of the population) and T20 (high risk threshold, toxic to 20% of the population) values were developed. The T20 values were selected based on the sensitivity of the endpoint used (amphipod survival) and the overall predictive ability of the T20 for amphipod survival.

Based on survival of freshwater amphipods, the T20 cleanup levels for sediment in the intermittent tributaries to protect the perennial streams are:

Lead - 219 ppm • Cadmium - 17 ppm

Zinc - 2,949 ppm

EPA believes, based on the toxicity studies conducted for the OU 04 Treece subsite, that the sediment cleanup levels are protective of the aquatic systems in the NW Tributary of Tar Creek. (See Table 2)

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Human Health Risk

A Streamlined HHRA was conducted in June 2016 in support of the ROD Amendment to include intermittent stream sediments. Incidental ingestion of sediment was evaluated for both recreational visitors and trespassers. Since most metals do not readily cross the skin into the body, quantifying uptake from dermal exposure to lead is not recommended due to the uncertainty in assigning a dermal absorption fraction that would apply to the numerous inorganic forms of lead that are typically found in the environment and would result in de minimis exposure.

Risks from exposure to lead in sediment at the site are below the EPA's health-based goal of no more than 5% chance that a child will have a blood lead value above 10 pg/dL (P10<5%) based on the default intake rates. However, risks based on assuming intake rates as the default values + 45% are slightly above the EPA's health-based goal (P10<5%) and assuming the higher reasonable maximum exposure (RME) intake rate of 200 mg/day are above the EPA's health-based goal (P10<5%). Risk estimates based on the default intake rates likely underestimate actual site risks to children because ingestion of wet sediment is likely to be greater than ingestion of typical yard soil. Conversely, risk estimates based on assuming a sediment intake rate of 200 mg/day for each age group likely overestimates actual site risks to children. This is because the intake rate of 200 mg/day is considered to represent the default, RME value generally used to assess risks from compounds other than lead for an RME receptor. Thus, the best estimate of true site risks associated with exposure to lead in site sediments likely falls between these two estimates. On this basis, the risk estimates based on the sediment intake rates of default soil-dust intake rates + 45% represent the best approximation of true site risks. Using these intake rates, risks to children from exposure to lead in sediments at the site slightly exceed the EPA's health-based goal (PI0<5%). (SRC, 2016)

Cancer and non-cancer toxicity data summaries for COCs are provided in Tables 3 and 4, respectively. In order to prevent human ingestion of lead from intermittent stream sediments that would potentially result in blood lead levels causing unacceptable human health risks. EPA developed a PRG for lead in intermittent stream sediments as 559 ppm. Based on the Streamlined HHRA and the uncertainty in the exposure assessment, the PRG for lead of 559 ppm was rounded down to 500 ppm. The intermittent stream sediments containing less than 500 parts per million (ppm) lead are deemed acceptable for preventing these potential human health risks.

VI. REMEDIAL ACTION OBJECTIVES

Remedial Action Objectives (RAOs) are quantitative, medium-specific goals for protecting human health and the environment. The RAOs specific to sediment is presented in this section.

Sediment RAOs

Contaminated intermittent stream sediments within the NW Tributary of Tar Creek will be addressed as part of this proposed remedy modification, whereas contaminated perennial sediments will be addressed under the OU 09 Tar Creek Watershed.

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Sediments represent a unique category of source materials that have been transported, or may be transported in the future to aquatic environments where they potentially affect water quality and streambed substrate, thereby posing risks to human receptors and aquatic biota. The exposure pathway of concern for the sediment RAOs is the movement and redistribution of source materials that could result in exposure of human receptors and aquatic biota to elevated COC concentrations. The COC for intermittent stream sediments for human receptors is lead and for ecological receptors the COCs are lead, zinc, and cadmium. The sediment RAOs for OU 04 Treece subsite is as follows:

• Prevent human ingestion of lead from contaminated sediments in the intermittent tributary of Tar Creek that would potentially result in blood lead levels causing unacceptable human health risks. Based on the Streamlined HHRA, intermittent stream sediments containing less than 500 parts per million (ppm) lead are deemed acceptable for preventing these potential human health risks.

• Mitigate risks to aquatic biota in perennial streams and their tributaries where COC levels exceed federal aquatic life criteria (ALC) by controlling the transport of mine waste from contaminated sediments in the intermittent tributary of Tar Creek. Based on survival of freshwater amphipods, the T20 cleanup levels for sediment in the intermittent tributaries to protect the perennial streams are: Lead - 219 ppm; Cadmium - 17 ppm; and Zinc -2,949 ppm.

VII. SUMMARY OF ALTERNATIVES

Remedial alternatives for addressing the OU 04 Treece subsite intermittent stream sediments are presented below. Alternatives include the current selected remedy along with EPA's Preferred Remedy. During the upcoming public comment period, EPA welcomes and encourages public comment on the Preferred Alternative, the other evaluated alternatives, or any other ideas or approaches.

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Current Remedy, per the 1997 ROD, as amended by the 2006 ROD Amendment: Complete Source Removal, Consolidation, Capping and On-Site Disposal. (Modified Alternative 8A) Under this alternative, the OU 04 Treece subsite intermittent stream sediments would not be remediated. This remedy addresses all surficial mine waste and soil by conventional excavation and/or consolidation, and multi-layer (borrow clay and topsoil, together approximately 18-inches thick) capping of excavated mine waste in addition to select subaqueous disposal of the mine waste. Wastes to be addressed include all mine wastes and soil that are actively contributing metals to streams or potentially threatening human or ecological receptors. The mine waste will be consolidated and capped above the ground surface, capped in-place, or disposed in collapses, shafts, or pits (subaqueous disposal) and capped. Erosion and drainage controls will be utilized during implementation to limit short-term impacts. Although the remedy predominantly utilizes conventional consolidation and capping methods for source disposal, subaqueous disposal may be utilized if conditions are deemed favorable. However, subsidence pit disposal will not be employed as a remedy near streams or floodplains to ensure unknown groundwater hydrologic impact to surface water does not occur. Before and during the remedy implementation period,

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subsite chat sales conducted under Best Management Practices (BMPs) will be highly encouraged. The overall approach is to concurrently address non-marketable mine waste by remediation while encouraging the sale and use of commercial mine waste. Lastly, a previously proposed institutional controls program, augmented by new approaches, will be implemented, addressing restrictions on the drilling and installation of new domestic water supply wells; encouragement of local citizens to utilize existing water districts for domestic needs; and the implementation of casing integrity standards and oversight for the design and construction of new deep aquifer supply wells. This remedy addresses the large quantity of source material remaining at the OU 04 Treece subsite. (EPA, 2006)

Estimated Capital Cost for OU 03 and 04: $66,404,001.60 Estimated Total O&M Cost for OU 03 and 04: $1,383,416.70 (See attached Table 4 for the detailed cost estimate for Modified Alternative 8A)

Preferred Alternative: Complete Source Removal, Consolidation, Capping and On-Site Disposal. Under this alternative, the OU 04 Treece subsite contaminated intermittent stream sediments would be addressed concurrently with the mine waste and contaminated soils by excavation and capping. EPA is not proposing to modify the remedy selected for any of the other remaining features described in the 1997 ROD, as amended by the 2006 ROD Amendment. The Preferred Alternative would be the remedy described above with the addition of intermittent stream sediments as a media. Potential exposure pathways to human health and the environment would be eliminated via disposal and capping. Because the OU 04 Treece subsite mine waste and contaminated soil remedial design is nearing completion, this alternative could be started within the coming months. The addition of the estimated 3,650 linear feet of creek channel including 38,800 cubic yards of sediment from the intermittent streams would have a limited impact on the scope, performance, and cost of the OU 04 Treece subsite remedy, because:

• The total volume of sediments in the OU 04 Treece subsite intermittent streams is low compared to the total volume of mine waste and contaminated soil already being capped within OU 04 Phase III RA (approximately 3,041,000 cubic yards for the remaining OU 04 Treece subsite work); ^

• Contaminants present in the OU 04 Treece subsite intermittent stream sediments are consistent with the contaminants present in the OU 04 Treece subsite mine and milling waste and contaminated soils; and

• The cost of placing the OU 04 Treece subsite intermittent stream sediments under the OU 04 Treece subsite caps (approximately 1% of total capping costs, $24,968.46) is low due to fewer site mobilizations and fewer on-site repositories.

• Placement of the OU 04 Treece subsite intermittent stream sediments under the OU 04 Treece subsite caps would not have a significant increase O&M labor or material cost because O&M will be conducted regardless of whether the intermittent stream sediments are placed under the OU 04 Treece subsite caps or capped under a future remedial action at a different OU.

Estimated Capital Cost: Estimated Total O&M Cost: Estimated Present Worth Cost:

$71,307,871 $2,139,236.10 $25,845,254

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After implementing the Preferred Alternative, a substantial amount of currently inaccessible land will meet the objective of unlimited use and unrestricted exposure. Instances where unlimited use and unrestricted exposure cannot be achieved will be addressed with ICs and under O&M. Additionally, the Preferred Alternative will eliminate surface water and sediment contamination from surficial runoff from mine waste and allow for the NW Tributary of Tar Creek to return to a native stream and wetland environment. The remaining waste in the OU 04 Treece subsite, present in the perennial portion of Tar Creek, would be addressed under the OU 09 Tar Creek Watershed.

VIII. EVALUATION OF ALTERNATIVES

Nine criteria are used to evaluate the different remediation alternatives individually and against each other in order to select a remedy. This section of the Proposed Plan profiles the relative performance of each alternative against the nine criteria, noting how it compares to the other options under consideration. The nine criteria are discussed below.

• Evaluation Criteria for Superfund Remedial Alternatives ' 1. Overall Protection of Human Health and the Environment determines whether an alternative eliminates, reduces, or controls threats to public health and the environment through institutional controls, engineering controls, or treatment. 2. Compliance with ARARs evaluates whether the alternative meets Federal and State environmental statutes, regulations, and other requirements that pertain to the site, or whether a waiver is justified. ' 3. Long-term Effectiveness and Permanence considers the ability of an alternative to maintain protection of human health and the environment over time. 4. Reduction of Toxicity, Mobility, or Volume of Contaminants through Treatment evaluates an alternative's use of treatment to reduce the harmful effects of principal contaminants, their ability to move in the environment, and the amount of contamination present. 5. Short-term Effectiveness considers the length of time needed to implement an alternative and the risks the alternative poses to workers, residents, and the environment during implementation. • 6. Implementability considers the technical and administrative feasibility of implementing the alternative, including factors such as the relative availability of goods and services. 7. Cost includes estimated capital and annual operations and maintenance costs, as well as present worth cost. Present worth cost is the total of an alternative over time in today's dollar value. Cost estimates are expected to be accurate within a range of +50 to -30 percent. 8. State/Support Agency Acceptance considers whether the State agrees the EPA's analyses and preferred alternative, as described in the RI/FS and Proposed Plan. 9. Community Acceptance considers whether the local community agrees with EPA's analyses and preferred alternative. Comments received.on the Proposed Plan are an important indicator or community acceptance.

Detailed Analysis of Proposed Remedial Alternative Compared to Current Selected Remedy

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Overall Protection of Human Health and the Environment The Preferred Alternative will protect human health and the environment by eliminating exposure or the potential for exposure to Site-related contaminants by excavating, disposal, and capping the OU 04 Treece subsite intermittent stream sediments concurrently with the OU 04 Treece subsite mine waste and contaminated soil. The Preferred Alternative would protect ( human health and the environment by remediating the OU 04 Treece subsite intermittent stream sediments to the cleanup levels listed in Section V that are consistent with performance standards for similar media and COCs at the adjacent Oronogo-Duenweg Mining Belt and Newton County Mining Belt Superfund sites.

Compliance with ARARs The Preferred Alternative is expected to meet ARARs and be protective of human and ecological receptors.

Since the RI was completed in 1993, the Kansas Department of Wildlife, Parks, and Tourism (KDWPT) has updated and changed the number of threatened and endangered species in Cherokee County. In total, there are 18 threatened and endangered species whose designated critical habitats are partially within the subsite. The 18 threatened and endangered species consist of the following: Neosho madtom, cave salamander, eastern narrowmouth toad, Ouachita kidneyshell mussel, western fanshell mussel, longtail salamander, ellipse mussel, Arkansas darter, elktoe mussel, butterfly mussel, flutedshell mussel, redspot chub, green frog, grotto salamander, eastern newt, gray bat, Neosho mucket mussel, and the rabbitsfoot mussel. Recent KDWPT fact sheets on these species have been included in the AR.

Long-term Effectiveness and Permanence The Preferred Alternative uses a well-demonstrated remediation approach to lead-, zinc-, and cadmium-contaminated intermittent stream sediments that will provide a permanent remedy. Removal, disposal, and capping of mine waste and contaminated soils and intermittent stream sediments permanently removes heavy metal contaminants'as a potential source of exposure. To remain effective over the long-term, O&M, including management of vegetation and burrowing animals and repairs of cracks and erosional features, are a long-term component of this Preferred Alternative. Because wastes would be left in place, reassessment of the effectiveness of the Preferred Alternative would be necessary at five-year intervals as required by CERCLA § 121(c).

The Preferred Alternative would result in the substantial removal of contaminants from the OU 04 Treece subsite and allow the area to be restored to beneficial use. The remedy would effectively and permanently remove the contamination in NW Tributary once all of the intermittent stream sediments are remediated.

Reduction of Toxicity, Mobility or Volume of Contaminants through Treatment: The preferred alternative represents the maximum extent to which treatment technologies can be utilized in a cost-effective manner for this remedial action. The only treatment technology identified in the FS was treatment of the wastes with biosolids containing high phosphate concentrations to reduce the bioavailability of metals. Phosphate additives are also often used in sediment treatment. (Olsta and Darlington, 2005) Various biosolids have been used at the Site and the Oronogo-Duenweg Mining/Belt site to treat mine waste and lead-contaminated soil. In

1 4

both cases, the phosphate compounds were shown to be an unfeasible alternative when compared to removal and replacement due to the unavailability of biosolids. No other treatment technologies were identified to adequately remediate the limited volume of contaminated intermittent stream sediments in OU 04 Treece subsite. If such technology is identified at a later date, pilot studies and related analysis may support a remedy decision change.

The residual waste found in the NW Tributary is considered a low-level threat waste, which is defined as source materials containing COCs that generally is relatively immobile in air or groundwater in the specific environmental setting (OSWER, Publication 9380.3-06FS, 1991). However, the residual waste in the NW Tributary have the potential to be a principal threat waste when it is mobilized by mechanical means, making remediation necessary to mitigate the potential risk. If the residual waste in the NW Tributary becomes a principle threat waste, a treatment alternative will be assessed in a remedy change decision document such as an ESD or ROD Amendment. Overall, containment will be employed due to the effectiveness of nontreatment technologies (excavation, consolidation, capping, revegetating, subaqueous disposal) for contaminated intermittent stream sediments. It should be noted that subaqueous disposal may constitute treatment if altered geochemical conditions are established. This aspect of the remedy will be assessed over time.

Short-term Effectiveness Short-term risks to construction workers and the environment are expected to occur from the implementation of the Preferred Alternative. These risks include exposure to dust and suspended sediments during construction activities, as well as the continued risks from the current Site conditions before the alternatives are fully implemented. Short-term risks associated with the Preferred Alternative can be managed by a combination of Personal Protective Equipment (PPE), stream sediment control and monitoring, and dust suppression measures to be employed during construction activities.

Implementabilitv The Preferred Alternative would be straightforward to implement. It has minimal impact on the scope, performance,"and cost of the OU 04 Treece subsite remedial action. The OU 04 Treece subsite intermittent stream sediments would be capped along with the mine waste and contaminated soil in on-site repositories and represents a small percentage of total waste addressed at the OU 04 Treece subsite (approximately 1:0%). Remedial design investigation and sampling led to the following assumptions in the estimated volume: 12 inches of contaminated soils beneath the surficial mine waste; 12 inches of contaminated sediments in the dewatered ponds; 18 inches of contaminated sediment below mine waste or the normal flowline of the creek bottom (within the banks of the creek channel); and 12 inches of contaminated surface soil within 100 feet of the creek bank segments where contaminated sediment is concurrently removed. Mine waste and contaminated sediment within the banks of the creek channel shall be removed to the depths described on the design drawings or until the cleanup goals are met, whichever is encountered first.

Cost The estimated present worth cost of the Preferred Alternative is $25,845,254. These costs include the addition of the contaminated non-perennial stream sediments to the OU 04 Treece subsite

1 5

capped areas. Placement of these sediments with the OU 04 Treece subsite capped areas would not significantly increase the area to be capped, so there are little to no additional costs. Since the Preferred Alternative includes wastes left in place, O&M costs are considered. O&M costs and efforts related to the Preferred Alternative do not significantly change with the inclusion of non-perennial stream sediments since the OU 04 Treece subsite mine and milling wastes and contaminated soils constitute a larger portion of the capped areas. The addition of sediments to the OU 04 Treece subsite capped areas is estimated to cost $21,392.36 in O&M, approximately 1% of the total estimated cost of O&M. O&M was estimated to be 3% of the total direct cost, consistent with the 2006 ROD Amendment cost estimation process. Additional O&M costs may be attributable to any contaminated non-perennial stream sediments left in place.

The total volume of materials to be remediated at the OU 04 Treece subsite is estimated at 3,041,000 cubic yards. The cost estimate for the completion of the OU 04 Treece subsite is $71,307,871. This estimate is compared to the 38,800 cubic yards of estimated contaminated non-perennial stream sediments, which is approximately 1.3% of the estimate of total volume of material. Cost associated with the additional cubic yards of sediments is an estimated $580,010, approximately 0.8% of the total cost of remaining remedial actions at the OU 04 Treece subsite.

State/Support Agency Acceptance The State of Kansas has indicated their support of the Preferred Alternative. Any comments received from the State will be reviewed and addressed in the Responsiveness Summary.

Community Acceptance Community acceptance of the Preferred Alternative will be evaluated after the public comment period ends and EPA will be addressing questions and comments in the Responsiveness Summary of the ROD Amendment.

IX. PREFERRED ALTERNATIVE

EPA's Preferred Alternative to modify the remedy selected in the 1997 ROD, as amended by the 2006 ROD Amendment, is to address contaminated intermittent stream sediments of Tar Creek concurrently with the nonresidential mine waste and contaminated soils by disposal and capping. EPA is not proposing to modify any other component of the remedy selected in the 1997 ROD, as amended by the 2006 ROD Amendment. The Preferred Alternative will modify the currently selected remedy with respect to the sediments as follows:

Current Remedy Proposed Remedy • Excavate, consolidate, and/or cap all

surficial mine waste and contaminated soil followed by disposal and capping.

• Utilize subaqueous mine waste disposal to the maximum extent practicable.

• Encourage source reduction via responsible chat sales before and during remedy implementation.

• Excavate, consolidate, and/or cap all surficial mine waste, contaminated soil, and contaminated intermittent stream sediments followed by disposal and capping.

• Utilize subaqueous mine waste disposal to the maximum extent practicable.

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, • Adopt Institutional Controls for future • Encourage source reduction via development specified in an earlier responsible chat sales before and ROD. during remedy implementation.

• Adopt Institutional Controls for future development specified in an earlier ROD.

The Preferred Alternative consists of the following:

EPA will excavate,.consolidate, and/cap all surficial mine waste, contaminated soil, and contaminated intermittent stream sediments followed by disposal and capping. EPA may utilize subaqueous mine waste disposal to the maximum extent practicable.

The cleanup level for lead for human receptors is 500 ppnt. The cleanup levels for ecological receptors are more stringent and therefore will be protective of human receptors. Based on survival of freshwater amphipods, the T20 cleanup levels for sediment in the intermittent tributaries to protect the perennial streams are:

• Lead - 219 ppm • Cadmium - 17 ppm

Zinc - 2,949 ppm

EPA is prepared to begin construction of the Preferred Alternative within six months of issuance of the ROD Amendment.

Statutory Determination Based on the information currently available, the EPA has determined that the Preferred Alternative would be protective of human health and the environment, would comply with ARARs with the exception of the ARAR being waived, and would be a timely and a cost effective solution for permanently addressing the OU 04 Treece subsite. The Preferred Alternative does not satisfy the statutory preference for treatment as a principal element of the remedy. However, protection of human health and the environment will be achieved through excavation, disposal, and capping as engineering controls. The modified remedy selected by EPA for the OU 04 Treece subsite may differ from the Preferred Alternative described in this Proposed Plan based on public comments or new information.

X. COMMUNITY PARTICIPATION

EPA relies on public input so that the remedy selected for each Superfund site meets the concerns of the local community. The public is encouraged to participate in the Proposed Plan and ROD Amendment process at OU 04. This Proposed Plan highlights key information from the RI and FS Reports, FS Addendum Report, ROD dated August 1997, ROD Amendment dated September 2006, final Remedial Action (RA) reports for the Treece subsite, ecological risk studies, Five-Year Review Reports, and Administrative Record (AR). Additionally, the public historically has been made aware of the environmental issues in the county through the many public meetings, public availability sessions, newspaper articles, television coverage, radio

1 7

broadcasts, and press releases that have occurred at the Site for the many environmental cleanups conducted to date.

Public Comment Period - To allow for community involvement, a public comment period will be open from July 9, 2016 and extend through August 9, 2016. During this time the public is encouraged to submit to EPA any comments on the Proposed Plan.

Public Meeting - A public meeting will be held to discuss the Proposed Plan on July 11, 2016, from 6:30 p.m. to 8:30 p.m. The public meeting will be held at the Baxter Springs Community Center at 1101 East Avenue, Baxter Springs, Kansas.

It is important to note that although EPA has proposed a Preferred Alternative, no changes to the remedy selected in the 1997 ROD and 2006 ROD Amendment will be implemented until the community participation component of this Proposed Plan is completed. All relevant comments received will be considered and addressed by EPA before any changes are made to the remedy selected in the 1997 ROD, as amended by the 2006 ROD Amendment.

Detailed information on the material discussed herein may be found in the Administrative Record for the Site, which includes the OU 03 Baxter Springs subsite and the OU 04 Treece subsite RI, FS, FS Addendum, HHRA, ERA, and other information used by EPA in the decision making process. The Administrative Record also includes relevant information related to the OU 04 Treece subsite, including the 1997 ROD and 2006 ROD Amendment. EPA encourages the public to review the Administrative Record in order to gain a more comprehensive understanding of the subsite and the Superfund activities that have taken place there. Copies of the Administrative Record are available for review at https://semspub.epa.gov/src/home/search.isf. or at the following location:

U.S. Environmental Protection Agency Region 7 Records Center 11201 RennerBlvd Lenexa, Kansas 66219 Hours: Monday through Friday, 8:00 am to 5:00 pm; by appointment with representatives below.

The deadline to submit comments is August 9, 2016. Written comments, questions about the Proposed Plan or public meeting, and requests for information can be sent to either representative below:

Elizabeth Hagenmaier Remedial Project Manager. U.S. Environmental Protection Agency Region 7 - SUPR/SPEB 11201 Renner Boulevard Lenexa, Kansas 66219 (913) 551-7939 Hagenmaier. Elizabeth@epa. gov

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Brendan Corazzin Community Engagement Specialist U.S. Environmental Protection Agency Region 7 - RGAD/ECO 11201 Renner Boulevard Lenexa, Kansas 66219 (913)551-7429 Corazzin.Brendan@epa.gov

Following the conclusion of the public comment period on this Proposed Plan, EPA will prepare a Responsiveness Summary. The Responsiveness Summary will summarize and respond to comments on EPA's Preferred Alternative for the OU 04 Treece subsite. EPA will also prepare a formal decision document, ROD Amendment, which summarizes the decision and the remedy modification for the OU 04 Treece subsite. The ROD Amendment will include the Responsiveness Summary. Copies of the ROD Amendment will be available for public review in the designated repositories, described above.

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Figures

.)

Figure 1. Site Location Map

A Site Location. Cherokee County. KS Superfund Site Subsites:

ZZl Baxter Spnnos H Lmton fAVJ IT i 1 Ks^ss3?i Sle Boundary i-t- 4i Crestline/Badaer •BH| Treece 012 4MHe •• . , ••••*.. '—1—1—•—1—1—1—•—1

• Galena Wbco ^ m WDSF10-07-001 Taskl ZDong

Figure 2. Location of NW Tributary of Tar Creek (OU 04 - Treece Subsite)

Cherokee County, Kansas

0.25 0.5

I Miles

NOTE: The Environmental Protection Agency does not guarantee the accuracy, completeness, or timeliness of the information shown, and shall not be liable for any injury or loss resulting from reliance upon the information show.

EMH 7/6/2016

Legend

NW Tributary of Tar Creek (non-perennial/intermittent)

Tar Creek (perennial)

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Tables

Table 1

Selected Remedy Comparison for OU 04

1997 ROD 2006 ROD Amendment 2016 ROD Amendment Did not address surficial mine wastes/sediments at Treece subsite

Remediate all surficial mine wastes at the Treece subsite: TC-2 through TC-4, TC-7, TC-9, TC-15, TC-16, TC-20, TC-21, TC-23, TC-27, TC-29, TC-37, TC-45, TX-2, TX-4, TX-5, TX-7, TX-10 through TX-12, TX-14, TX-16, TX-18, TX-20 through TX-25, TX-27, TX-29 through TX-33, TX-39, TX-40, TX-42 through TX-46, and TX 59; tailings TT-1, TT-5, TT-6, TT-8, TT-10 through TT-14, TT-14, TT-17 through TT-19, TT-21, TT-22, TT-22N, TT-24 through TT-26, TT-28 through TT-33, TT-35, TT-36, TT-38, TT-41, TT-42, TT-44, and TT-45; and outwash tailings TOW-1 through TOW-5

Remediate all sediments in NW Tributary of Tar Creek with all surficial mine wastes in areas: TC-2, TX-7N, TX-12, TX-33, TX-47, TT-1, and TT-38

Remediate all impacted residential properties at the Treece subsite.

No new action, one follow-up property identified and remediated

No new action

Implement institutional controls

Continue to seek institutional control adoption and add State of Kansas controls to augment existing approach

No new action

Table 2

COC Concentrations Expected to Provide Adequate,Protection of Ecological Receptors

Habitat Type/Name

Exposure Medium

COC Protective Level

Units Basis' Assessment Endpoint

Small Freshwater Intermittent Stream/ NW Tributary of Tar Creek

Sediment Lead 219 mg/kg SSTTs Benthic invertebrate community species diversity and abundance

Small Freshwater Intermittent Stream/ NW Tributary of Tar Creek

Sediment Zinc 2949 mg/kg SSTTs

Benthic invertebrate community species diversity and abundance

Small Freshwater Intermittent Stream/ NW Tributary of Tar Creek

Sediment

Cadmium 17 mg/kg SSTTs

Benthic invertebrate community species diversity and abundance

Notes 1 Provide Basis of Selection: MacDonald el at. (2009) developed Site-Specific Toxicity Thresholds (SSTT) for individual COPCs and various COPC mixtures using matching sediment chemistry and sediment toxicity data from the Tri-State Mining District.

Table 3

Cancer Toxicity Data Summary

Pathway: Ingestion Chemical of Concern

Oral Cancer Slope Factor

Slope Factor Units

Weight of Evidence/Cancer Guideline Description

Source Date (MM/DD/YYYY)

Lead - - B22 IRIS 09/26/1988 Zinc - . - - IRIS 08/03/2005 Cadmium - - Bl1 IRIS 03/31/1987 Notes 1B1 - Probable human carcinogen - Indicates that limited human data are available 2B2- Probable human carcinogen - Indicates sufficient evidence in animals and inadequate or no evidence in humans

IRIS: Integrated Risk Information System, U.S. EPA

Table 4

Non-Cancer Toxicity Data Summary

Pathway: Ingestion

Chronic/ Subchronic

Oral RfD Value

Oral RfD Units

Primary Target Organ

Combined Uncertainty / Modifying Factors

Sources of RfD: Target Organ

Dates of RfD: Target Organ (MM/DD/YYYY)

Lead1 Chronic Neurological, Developmental, Blood, Reproductive

IRIS 07/08/2004

Zinc Chronic 3.0E-01 (mg/kg)/ day

Blood UF=32 IRIS 08/03/2005

Cadmium Chronic . 1.0E-03 (mg/kg)/ day

Kidney, Respiratory

- IRIS 10/01/1989

Notes 'Lead is assessed using toxicokinetic models (EPA's IEUBK and ALM models). :Uncertainty factor (UF) used to account for variability in susceptibility in human populations.

ALM: Adult Lead Methodology IEUBK: Integrated Exposure Uptake Biokinetic IRIS: Integrated Risk Information System, U.S. EPA

Table 5.*

Detailed Cost Estimate for Modified Alternative 8A Cherokee County, Kansas Superfund Site

Item Description Unit Cost Baxter Springs Quantity

Treece Quantity

Baxter Springs Cost ($) Treece Cost ($) Total Cost ($)

1.0 SOURCE MATERIALS ACTIONS

1.1

Excavate and place appoximately 20% of current mine waste either with ex sting wastes or in mine openings (per cubic yard) $5.00 1,250,172 $6,250,860.00

1.2 Regrade and revegetate excavated areas (per acre) $5,000.00 151 $754,600.00

1.3 Regrade, cap and revegetate remaining mine waste areas (per acre) $35,000.00 1,023 $35,805,000.00

1.4

Excavate and place contaminated soil either with existing wastes or in mine openings (per cubic yard) $5.00 495.446 $2,477,230.00

Subtotal Source Materials Actions (1.0) I $45,287.690 00

2.0 SURFACE WATER ACTIONS

2.1 Stream Channel and Erosion Controls (per linear foot) $26.00 6,300 14.400 $163,600.00 $374,400.00 $538,200.00

2.2 Sedimentation Basins $48,000.00 2 4 $96,000.00 $192,000.00 $288,000.00

Subtotal Surface Water Actions (2.0) | $826,200.00

SUBTOTAL DIRECT COSTS FOR SOURCE MATERIALS AND SURFACE WATER ACTIONS | $46,113,890 00

3.0 INDIRECT COSTS 3.1 Engineering Design 6% $2,766,833.40 3.2 Construction Management 10% $4,611,389.00 3.3 Contingency 20% $9,222,778.00 3.4 Operation and Maintenance 3% $1,383,416.70 3.5 Mobilization and Demobilization 5% $2,305,694.50

Subtotal Indirect Costs for Source Materials and Surface Water Actions (3.0) I $20,290,111.60

TOTAL ESTIMATED COST OF MODIFIED ALTERNATIVE 8A IN 2006 $66,404,001.60

Assumptions: 1. The unit costs are based on approximate actual costs for the recently completed remedy at the Baxter Springs subsite. 2. The Baxter Springs Quantity and Treece Quantity are based on the remedial work conducted under the 1997 Record of Decision, select chat piles at Treece sold for commercial purposes (see Note 3), and Tables A-1 and A 2 in Appendix A in the Feasibility Study. These tables are entitled Baxter Springs Mine/Mill Waste Piles and Treece Mine/Mill Waste Piles, respectively. 3. Select current chat piles at Treece are anticipated to be sold in the future during remediation, leaving behind only a footprint. These future footprints may be included in Items 1.1 and 1.2. Pile TC-3 is currently being sold and pile TC-23 is being used for construction projects. Piles TC-9. TC-15 (Section 14), TC-16 (Section 14), and TC-45 have been used historically for commercial purposes and some deposits have existing commercial potential. 4. The engineering design cost for the project was estimated to be 6% of the total direct cost.' 5. The construction management cost for the project was estimated to be 10% of the total direct cost. 6. The contingency cost for the project was estimated to be 25% of the total direct cost. 7. The operation and maintenance cost for the project was estimated to be 3% of the total direct cost. 8. The mobilization and demobilization cost for the project was estimated to be 5% of the total direct cost.

Taken from the 2006 ROD Amendment for OU 03 and OU 04.

ARARs

This Page Intentionally Left Blank

Federal Chemical-Specific ARARs

A. ARARs Citations Description

Safe Drinking Water Act National Primary Drinking Water Standards 40 C.F.R. Part 141 Subpart B and G

Establish maximum contaminant levels (MCLs), which are health based standards for public waters systems.

Safe Drinking Water Act National Secondary Drinking Water Standards 40 C.F.R. Part 143

Establish secondary maximum contaminant levels (SMCLs) which are non-enforceable guidelines for public water systems to protect the aesthetic quality of the water. SMCLs may be relevant and appropriate if groundwater is used as a source of drinking water.

Safe Drinking Water Act Maximum Contaminant Level Goals (MCLGs) 40 C.F.R. Part 141, Subpart F

Establishes non-enforceable drinking water quality goals. The goals are set to levels that produce no known or anticipated adverse health effects. The MCLGs include an adequate margin of safety.

B. To Be Considered EPA Revised Interim Soil-lead Guidance for CERCLA Sites and RCRA Corrective Action Facilities and 1998 Clarification

Office of Solid Waste and Emergency Response (OSWER) Directive 9355.4-12, July 14, 1994,

OSWER Directive 9200.4-27P, August 1988

Establishes screening levels for lead in soil for residential land use, describes development of site-specific preliminary remediation goals, and describes a plan for soil-lead cleanup at CERCLA sites. This guidance recommends using the EPA Integrated Exposure Uptake Biokinetic Model (IEUBK.) on a site-specific basis to assist in developing cleanup goals.

EPA Strategy for Reducing Lead Exposures

EPA, February 21, 1991

Presents a strategy to reduce lead exposure, particularly to young children. The strategy was developed to reduce lead exposure to the greatest extent possible. Goals of the strategy are to 1) significantly reduce the incidence above 10 pg Pb/dL in children; and 2) reduce the amount of lead introduced into the environment.

Technical Impracticability Waiver in Groundwater ARARs, Cherokee County Superfund site

EPA, Region 7 Record of Decision for OU 03 and OU 04 of the Cherokee County site, August 1997.

This document established the technical impracticability (Tl) of restoring the shallow groundwater aquifer in mined areas of the Cherokee County site. The Tl waiver determined that aquifer restoration was impracticable based on the large size and heterogeneous nature of the aquifer, lack of effective pumping and treatment technology, and the inordinate costs associated with groundwater treatment.

Sediment Quality Guidelines Threshold Effect Concentrations

Development and Evaluation of Consensus-Based Sediment Quality Guidelines for Freshwater Ecosystems. 2000. MacDonald, D.D., C.G. Ingersoll, and T.A. Berger. Archives of. Environmental Contamination and Toxicology 39:20-31

Identifies Threshold Effect Concentration (TEC) to be used to assess sediment effects.

Superfund Lead-Contaminated Residential Sites Handbook

EPA OSWER 9285.7-50, August 2003. Handbook developed by EPA to promote a nationally consistent decision making process for assessing and managing risks associated with lead contaminated residential sites across the country.

State Chemical-Specific ARARs

A. ARARs Citation Description

Kansas Surface Water Quality Standards

K.A.R. 28-16-28b through 28-16-28g

Establishes water quality criteria in surface waters of the state to maintain and protect the existing uses of those surface waters.

Will be relevant and appropriate at sites where surface waters of the state are affected.

Kansas Primary Drinking Water Regulations

K.A.R. 28-15a-1 1

Establishes maximum contaminant levels (MCLs) for inorganic chemicals that are health risk based standards for drinking water.

Will be applicable at the distribution point (i.e., at the tap). Will be relevant and appropriate at sites where potential drinking water sources—rivers, lakes, reservoirs, springs, and ground water wells—are affected.

B. To Be Considered

Screening Goals for Contaminants in Soil and Groundwater

Kansas Department of Health and Environment (KDHE), Bureau of Environmental Remediation (BER), Risk Based Standards for Kansas, RSK Manual - 5th Version, October 2010, Revised September 2015, as amended

Identifies risk-based cleanup screening goals for contaminants in soil and groundwater.

Federal Location-Specific ARARs

A. ARARs Citation Description

Site within an area where action may cause irreparable harm, loss, or destruction of artifacts.

Archeological and Historic Preservation Act; 16 U.S.C. 469, 40 C.F.R. 6.301.

Provides for the preservation of historical or archaeological data which might be destroyed or lost as the result of 1) flooding, building of access roads, relocation of railroads and highways, and other alterations of terrain caused by the construction of a dam by government or persons, or 2) alteration of terrain caused by Federal construction projects or federally licensed activity or program.

Will be applicable if construction projects or alteration of terrain at a site have the potential to destroy historical or archaeological materials.

Historic project owned or controlled by a federal agency

National Historic Preservation Act: 16 U.S.C. 470, et.seq; 40 C.F.R. § 6.301; 36 C.F.R. Part 1.

Establishes a national registry of historic sites. Provides for preservation of historic or prehistoric resources.

Will be applicable if a site is listed on historic registry and if activities requiring permitting are initiated at a site.

Site located in area of critical habitat upon which endangered or threatened species depend.

Endangered Species Act of 1973, 16 U.S.C. 1531-1543; 50 C.F.R. Parts 17; 40 C.F.R. 6.302. Federal Migratory Bird Act; 16 U.S.C. 703-712.

Provides a program for conservation of threatened and endangered plants and animals and the habitats in which they are found.

Will be applicable if threatened or endangered species, or their habitats are present at or near a site.

Clean Water Act (CWA) of 1977 Wetlands Protection

40 CFR 22, 40 CFR 230 to 233, and 33CFR 320 to 330

Allows for permitting of discharge of dredged or fill material to the waters of the United States if no practicable alternatives exists that are less damaging to the aquatic environment. Applicants must demonstrate that the impact to wetlands is minimized.

Will be applicable if designated wetlands are affected by a remedy.

Site located within a floodplain soil.

Protection of Floodplains, Executive Order 11988; 40 C.F.R. Part 6.302, Appendix A.

Requires federal agencies to avoid to the extent possible the long and short-term adverse impacts associated with the occupancy and modification of flood plains and to avoid direct and indirect support of floodplain development wherever there is a practicable alternative.

Will be applicable if a site is located on a designated flood plain.

Wetlands located in and around the soil repository.

Protection of Wetlands; Executive Order 11990; 40 C.F.R. Part 6, Appendix A.

Requires federal agencies to avoid to the extent possible the long and short term adverse impacts associated with the destruction or modification of wetlands and to avoid direct or indirect support of new construction in wetlands wherever there is a practicable alternative.

Will be applicable if designated wetlands are affected by a remedy.

Fish and Wildlife Conservation Act

Fish and Wildlife Conservation Act of 1980, 16 U.S.C. Part 2901 et seq.; 50 C.F.R. Part 83.9 and 16 U.S.C. Part 661, et seq. Federal Migratory Bird Act, 16 U.S.C. Part 703.

Action to conserve fish and wildlife, particularly those species that are indigenous to the state.

Will be applicable if significant populations are present at a site or they are affected by site activities.

A. ARARs Citation Description

Fish and Wildlife Coordination Act

16 U.S.C Section 661 et seq.; 33 C.F.R Parts 320-330; 40 C.F.R 6.302

Requires consultation when a Federal department or agency proposes or authorizes any modification of any stream or other water body, and adequate provision for protection of fish and wildlife resources.

Historic Site, Buildings, and Antiquities Act

16 USC Section 470 et seq., 40 CFR Sect. 6.301(a), and 36 CRF, Parti.

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

Clean Air Act National Ambient Air Quality Standards/ NESHAPS 42 U.S.C. 74112; 40 C.F.R. 50.6 and 50.12

Emissions standards for particular matter and lead.

Rivers and Harbors Appropriation Act of 1899

33 U.S.C. 401; 33 U.S.C. 403; and related regulations 33 C.F.R. 320

Prohibits building of structures (Section 9) and the disposal of dredged and fill-material into waters of the U.S. without a permit by a designated federal agency. Will be applicable if structures are constructed or a discharge of dredged or fill material occurs in waters of the U.S.

100-year floodplain Location Standard for Hazardous Waste Facilities- RCRA; 42 U.S.C. 6901; 40 C.F.R. 264.18(b).

RCRA hazardous waste treatment and disposal. Facility located in a 100-year floodplain must be designed, constructed, operated, and maintained to prevent washout during any 100-year/24 hour flood.

B. To Be Considered None - -

State Location-Specific ARARs

A. ARARs Citation Description

Water Structures and Stream Obstructions and The Levee Law

K.S.A. 82a-301 through 82a-328; K.A.R. 5-40 through 5-46; K.S.A. 24-105 and K.S.A. 24-126; K.A.R. 5-45-1 through 5-45-23

Requires the Division of Water Resources to permit certain actions including dam construction or modification, stream obstruction construction, stream channel modification, levee construction, and floodplain fill.

Will be applicable for any action requiring dam construction or modification, stream obstruction, channel modification, levee construction, or floodplain fin:

Kansas Historic Preservation Act K.A.R. 118-3-1 to 118-3-16

Provides for the protection and preservation of sites and buildings listed on state or federal historic registries.

Will be applicable if a site or building is listed on the state or federal historic registry and if activities requiring permitting are initiated at a site.

Nongame and Endangered Species Conservation Act of 1975

K.S.A. 32-957 through 32-963, 32-1009 through 32-1012, 32-1033 and K.S.A. 32-960a and 32-960b, and amendments thereto

Places the responsibility for identifying and undertaking appropriate conservation measures for listed species directly upon the Department of Wildlife, Parks and Tourism. Regulations require the department to issue special action permits for activities that affect species listed as threatened and endangered in Kansas.

Will be applicable if state-listed threatened or endangered species, or their habitats are present at or near a site.

B. To Be Considered None

Federal Action-Specific ARARs

A. ARARs Citation Description

National Pollutant Discharge Elimination System (NPDES)

40 C.F.R. Part 122.26; 33 U.S.C 402 (p)

Regulates discharges of pollutants from any point source into waters of the United States.

Will be applicable if water from the site will be discharged onto land or into streams, rivers or lakes.

Storm Water Discharge Requirements NPDES

40 CFR 122.26

Provide requirements to obtain a permit to discharge to the storm water sewer system under the NPDES program.

Will be applicable if the site has storm water that comes in contact with construction or industrial activity or if the selected remedy involves discharge of treated wafer to surface waters.

Federal Water Quality Standards

40CFR131 Establishes non-enforceable standards to protect aquatic life.

National Ambient Air Quality Standards (NAAQS)

42 U.S.C. 74112; 40 C.F.R. 50.6 and 50.12

Emissions standards for particular matter and lead.

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

42 USC Sec. 6941 40 CFR Part 257, Criteria for Classification of Solid Waste Disposal Facilities and Practices

This section of the RCRA regulations requires the closure of existing solid waste facilities, design of new landfills, and disposal of solid wastes to be in accordance'with various standards and criteria. These standards are applicable to solid waste disposal facilities, including mining and mill waste facilities. Among other things, these regulations require that facilities be maintained to prevent wash out of solid wastes and that the public not be allowed uncontrolled access.

Surface Mining Control and Reclamation Act (SMCRA)

30 USC Sees. 1201-1328 30 CFR Part 816

SMCRA regulations govern coal exploration and active coal mining. Hence, these regulations are not applicable to remedial actions taken at the Cherokee County Site. Nevertheless, some of the surface mining standards found'in 30 CFR Part 816 are relevant and appropriate requirements because they address circumstances that are similar to those found at the Cherokee County Site. The relevant and appropriate requirements include Part 816.45, Sediment Control Measures; Part 816.46, Siltation Structures; Part 816.102, Grading Requirements; and Part 816.111, Revegetation.

DOT Hazardous Materials Transportation Regulations

49 CFR Parts 107, 171-177 Regulates transportation of hazardous materials. Would be relevant and appropriate for the transport of excavated materials within the Site.

Clean Water Act - Dredge or Fill Requirements (Section 404)

33 USC Sees. 1251-1376 40 CFR Parts 230,231

Regulates discharge of dredged or fill material into navigable waters.

B. To Be Considered

RCRA, Subtitle C, Standards for Owners and Operators of Hazardous Waste Treatment, Storage, and Disposal Facilities

RCRA Section 3001 et seq. 42 USC Sec. 6921, et seq.

40 CFR Part 264.522, Disposal Of Hazardous Wastes In Designated Corrective Action Management Units (CAMUs).

40 CFS Part 264.554(D)(1 )(i) and (ii) Staging Piles

The section defines Corrective Action Management Units (CAMUs) to be used in implementing corrective actions at Superfund Sites. A CAMU is defined as a disposal site used for consolidation or placement of remediation wastes within the contaminated areas of the site. Under these regulations, placement of wastes in a CAMU does not constitute land disposal of hazardous waste and does not constitute creation of a unit subject to the RCRA land disposal restrictions and minimum technology requirements (40 CFR Part 268). This Section of RCRA is not an ARAR because of the Beville exclusion, but certain substantive requirements related to design, operation and closure of disposal sites should be considered.

RCRA, Subtitle C, Identification and Listing of Hazardous Wastes

RCRA Section 3001(b)(3)(A)(iii), Beville exclusion of mineral extraction and beneficiation wastes. 40 CFR Part 264.2, Definition of solid waste and 40 CFR Part 261.4 (b) (7)

Mill waste within the Site is specifically excluded from regulation as hazardous wastes under the Beville exclusion because they are wastes resulting from mineral extraction and beneficiation. Therefore, the RCRA Subtitle C regulations are not ARARs.

Toxic Substances Control Act - Strategy for Reducing Lead Exposures

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

EPA Mine Waste EPA Region 7 Fact Sheet, February 2003

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

State Action-Specific ARARs

A. ARARs Citation Description

Mined Land Reclamation K.A.R. 47-16-1 to 47-16-11 Allows for the reclamation of mined land and associated waters.

Will be applicable if mined land or associated waters are to be reclaimed.

Environmental Use Controls K.S.A. 65-1,221 to 65-1,235

An environmental use control "means an institutional control or administrative control, a restriction, prohibition or control of one or more uses of, or activities on, a specific property, as requested by the property owner at the time of issuance, to ensure future protection of public health and the environment when environmental contamination which exceeds department standards for unrestricted use remains on the property following the appropriate assessment and/or remedial activities as directed by the department pursuant to the secretary's authority".

These restrictions are strictly voluntary as the landowner applies for the restriction to their property to mitigate the risk posed to human health and the environment from contamination at their property (in lieu of active remediation).

Hazardous Waste Management Standards and Regulations

K.S.A. 65-3430 et seq., as amended; K.A.R. 28-31-4 et seq., as amended

Identifies the characteristics and listing of hazardous waste. Prohibits underground burial of hazardous waste except as granted by EPA or KDHE. Establishes restrictions on land disposal. Establishes standards for generators or transporters of hazardous waste. Establishes standards for hazardous waste storage, treatment and disposal facilities.

Will be applicable if hazardous wastes are present at a site.

Kansas Board of Technical Professions

K.A.R. 66-6-1 through 66-14-12

Establishes the requirements for licensing of engineers, land surveyors, geologists, and architects.

Will be applicable if the services of a geologist, engineer or land surveyor are required for site investigations or remediation.

Spill Reporting K.A.R. 28-48-1 to 28-48-2

Requires reporting of unpermitted discharges or accidental spills. Requires that containment and immediate environmental response measures be implemented. Also provides for technical assistance for mercury-related spills.

. Will be applicable if unpermitted discharges or accidental spills occur at a site.

B. To Be Considered

Sediment Policy KDHE BER Policy #BER-ARS-045 Provides a consistent definition and assessment approach for contaminated sediment sites in Kansas.