UNITED STATES PROIIX-TICN AGENCY PROPOSED PLAN FOR THE US ECOLOGY, INC. SITE SHEFFIELD, ILLINOIS May 1990 ------- TABLE OF CONTENTS SECTION I Statement of Document's Purpose 1 II Site Background 3 III Feasibility Study Surmery 7 IV Summary of Remedial Alternatives 8 Analyzed Ground-water Remediation 8 Source Control 14 V The Preferred Alternative 20 VI Criteria for Comparison of 24 Alternatives VII Comparison of Alternatives 26 VIII The Comnunity's Role in the 37 Selection Process Attachments (9) Figures Tables List of Documents in Repository (partial) ------- I. STATEMENT OF DOCUMENT'S PURPOSE An Administrative Order By Consent (Consent Order) was entered into on September 30, 1985, by the United States Environmental Protection Agency (U.S. EPA) pursuant to Section 3008(h) of the Resource Conservation and Recovery Act (RCRA), as amended, 42 U.S.C. §6928(h), and by US Ecology, Inc. of 9200 Shelbyville Road, Louisville, Kentucky 40207. The stated mutual objectives of the Consent Order are: (1) to perform a Remedial Investigation (RI) to determine fully the nature and extent of the presence or any release of hazardous wastes and constituents at or from the hazardous waste management facility owned and operated by US Ecology near Sheffield, Illinois (the Facility); (2) to perform a Feasibility Study (FS) to identify and evaluate alternatives for the appropriate extent of corrective action necessary to prevent or mitigate any migration or release of hazardous wastes or constituents at or from the Facility; and (3) to perform any corrective action deemed necessary by the U.S. EPA to protect human health or the environment. US Ecology is required under Section VI of the Consent Order to perform all RI/FS work in conformance with U.S. EPA "Guidance on Remedial Investigations Under CERCLA," dated May 1985, and U.S. EPA "Guidance on Feasibility Studies Under CERCLA," dated April 1985. The RI/FS work is required to be consistent with the guidelines, criteria, and considerations set forth in the National Contingency Plan (NCP), 40 CFR Part 300.68, as amended. ------- -2- On April 28, 1989, U.S. EPA approved the Revised Final RI Report submitted by US Ecology. US Ecology submitted a conplete, two volume report titled "Draft Feasibility Study For Groundwater Remediation For the Sheffield Hazardous Waste Disposal Sites." It was received by U.S. EPA on July 6, 1989. On September 1, 1989, U.S. EPA received another report from US Ecology titled "Draft Feasibility Study For Source Control For the Sheffield Waste Disposal Sites." Section 117(a) (42 U.S.C. §9617(a)) of the Comprehensive Environmental Response, Compensation, and Liability Act (CERGLA), as amended by the Superfund Amendments and Reauthorization Act of 1986, requires publication of a notice and a brief analysis of the Proposed Plan for site remediation. The Proposed Plan must also be made available to the public for conment. In general, the Proposed Plan will: (l) provide background information on the site; (2) describe the alternatives considered for the site; (3) present the rationale for identification of a preferred alternative for the site; and (4) outline the public's role in selection of a site remedy. This Proposed Plan, hereafter referred to as "Plan", is issued to describe proposed corrective action alternatives for the US Ecology, Inc. facility located near Sheffield, Illinois (Attachment 1). This Plan summarizes the alternatives that US Ecology developed and evaluated further in the two draft FS documents. This Plan also presents and evaluates the alternative preferred by the U.S. EPA. The preferred alternative combines control of ground water migration with control of the contamination source. ------- -3- II. SITE BACKGROUND The US Ecology site is located about three (3) miles southwest of the town of Sheffield, Illinois in Bureau County. The facility (see Attachment 2) consists of two presently inactive RCRA hazardous waste disposal areas: a 5.8 acre hazardous waste disposal landfill (the Old Site); and a forty (40) acre landfill (the New Site). The rural area in which the facility is located is zoned primarily for agricultural use. A 160-acre area located 1500 feet south-southwest of the site is zoned for recreational use (hunting and camping). Coal mining activities in the area were discontinued over a decade ago. Adjacent to the Old Site is an inactive 20.45-acre site zoned for special use, specifically, low-level radioactive waste disposal (LLRW site). US Ecology accepted industrial, laboratory, and agricultural wastes between 1967 and 1983. Reportedly 4,432,000 cubic feet of various waste types (93% of it in the New site) are buried in the landfills. Records indicating waste types accepted for disposal in the Old Site are fewer and less detailed, generally, than those for the New Site. Wastes accepted for disposal include, but are not limited to: paint and paint-related wastes, plating waste, herbicides/pesticides/ insecticides, laboratory wastes, miscellaneous sludges, polychlorinated biphenyls (PCBs) and PCB-containing and/or contaminated wastes, printing wastes (inks), miscellaneous solvents and still bottoms, benzene, xylene, and toluene compounds, acid ------- -4- wastes, phenols compounds, hydrocarbons, metal-bearing wastes, and miscellaneous acids. The facility was proposed for the CERCLA National Priorities List (NPL). Because of the Consent Order signed by US Ecology with U.S. EPA to conduct the Rl/FS activities under RCRA, the facility was removed from the proposed list in 1989. RI/FS activities were undertaken to identify the types, quantities, and locations of hazardous wastes and contaminants on site and to develop ways of remediating any threat to human health and/or the environment. The nature and extent of actual or potential site-related contamination were determined by a series of field investigations including: 0 Geophysical survey 0 Surface and subsurface soil sampling 0 Surface water and ground-water seep sampling and analysis 0 Sediment sampling (at seeps and in Trout Lake) 0 Soil borings and rock corings and associated laboratory analyses 0 Ground-water monitoring well installation and sampling. The RI/FS also includes an endangerment assessment performed to define the threat which the actual or potential site-related contaminants pose to human health and/or the environment. The results of the field investigations and laboratory analyses support the following conclusions: ------- -5- 1. The ground water has been contaminated by the migration of hazardous waste and/or hazardous constituents (both organic and inorganic) from burial trenches in both waste disposal sites (see Attachment 3): 0 North, east, and southeast of the Old Site (See discussion in item 3 below); 0 South of the New Site at Trench 18BC (See discussion in item 4 below); 0 Along the north slope of the New Site at the previous location of monitoring well G-120 and a series of north slope ground- water seeps (See items 2 and 4 below); and 0 Along the west side of the New Site (indicated in 1987 RI ground-water sampling results, but not confirmed in 1988 sampling results). 2. Surface water has been affected where contaminated ground water has discharged to Trout Lake and into a valley along the north slope of the New Site as seeps. Analytical results from a surface water sample collected from Trout Lake in April 1989, (see Soils Addendum to the Final RI) indicated the presence of tetrachloroethylene (PCE) at a level of 5 micrograms per liter (ug/1) and detectable amounts of barium and zinc. Surface water sample analyses from the north slope seeps indicate the release of both organic constituents (1,2-dichloroethene, chloroform, trichloroethene (TCE), and PCE) and inorganic constituents (barium, chromium, zinc, and sulfide). 3. Old Site plume: Covers about 23 acres in areas north, east, and southeast of Old Site; ------- -6- 0 Principal hazardous organic constituents include acetone, benzene, carton tetrachloride, chloroform, methyl ethyl ketone (MEK), methylene chloride, and PCE; 0 Inorganic constituents include arsenic, lead, and manga- nese; 0 Mixes with a plume containing radionuclides that is emanating from the LLEW site; 0 May be contributing to contamination in the well G-120 area in the northeast corner of the New Site; 4. New site releases: 0 Trench 18EW3 plume (covers about one acre and contains both organic and inorganic constituents); 0 North slope seeps (discussed above in item 2); 0 G-120 area (shallow bedrock contamination; organic constituents detected include TCE, PCE, chloroform, and dichloroethene); 5. Soil and sediment sampling results (April 1989): 0 Two sediment samples in Trout Lake contained barium at 55 milligrams/kilogram (mg/kg); 0 One sediment sample in Trout Lake detected 2-butanone at 53 ug/kg; 0 North slope: one sediment sample had elevated levels of zinc and sulfates; 0 Hazardous organic constituents detected in soils (TCE, PCE, chloroform, toluene, benzene, xylene, dichloroethenes) may represent compounds that have volatilized from the contaminated ground water; 0 One Old Site soil sample contained the pesticides dichloro- diphenol dichloroethane and dichloro-diphenyl- trichloroethane (ODD and DDT). The contaminants identified in various environmental media during the RJ were evaluated to determine the level of risk they pose to ------- -7- public health and the environment. The results of the public health risk evaluation are presented in Attachments 4, 5, 6, and 7. Exposure assumptions vary for ground water, surface water, and soil ingestion pathways (see pages 7-23 and 7-24 of the RI and 3-2 of the Soils Addendum to the RI). The hazard index (HI) indicates a potential for adverse noncarcinogenic effects when the number is greater than one. The excess lifetime cancer risk of exposure to these water and soil sources is expressed in the tables as additional cancer risks (e.g., 6.0E-03 equals 6.0 x 10~3 which means that the excess risk is 6 in 1,000). Results indicate the following contaminant problems present the greatest threat to human health using the assumptions specified in the Final RI Report: Carcinogenic risks would be associated with long-term ingestion of contaminated shallow ground water from both the New and Old Sites. The risks would be associated primarily with the presence of PCE, 1,2-dichloroethane, TCE, arsenic, benzene, chloroform, l,l-dichloroethylene, and methylene chloride. Contaminated ground water from the bedrock aquifer at the previous location of well G-120 yields a lower combined risk to that identified in the Old Site shallow (glacial) aquifer (i.e., 6.25 x 10~3 versus 1.66 x 10~2). Noncarcinogenic risk associated with long-term ingestion of the contaminated shallow ground water would be caused primarily by TCE, lead, chloroform, methylene chloride, and PCE. Surface water originating from ground-water seeps in the north slope of the New site had levels of 1,2-dichloroethene and TCE which exceed maximum contaminant levels (MCLs). However, evaluation of ingestion of surface water resulting from north slope seepage and water in Trout Lake and other ponds studied did not result in a determination of adverse effects (carcinogenic or noncarcinogenic). III. FEASIBILITY STUDY SUMMARY During the Feasibility Study (FS), US Ecology identified and ------- -8- evaluated a potential list of alternatives that could be used to remediate the threats and/or potential threats identified at the site. The original list of alternatives was presented in the "Preliminary Screening of Remedial Technologies and Development of Alternatives" dated August 19, 1988. US Ecology further evaluated alternatives which passed the initial screening and submitted two separate draft FS documents: one describing alternatives for source control and one describing alternatives for remediation of ground- water contamination resulting from releases from the Old and New Sites. Ultimately, alternatives from both draft FS documents will be selected and will, in combination, be implemented to address the environmental and human health threat. TV. SIFMARY OF REMEDIAL ALTERNATIVES ANALYZED 1. Ground^water Remediation Alternatives "Die final five alternatives proposed by US Ecology for ground-water remediation at its Sheffield, Illinois site are briefly described below: a. Alternative 1 0 No action 0 Ground-water monitoring This alternative is required in order to establish a baseline for comparison with other alternatives. This alternative provides no control or treatment of the ground water and no further action at the site to control the source of contamination. It would ------- -9- include, however, a long-term ground-water monitoring program. Signs would be posted along the fence warning of hazardous waste disposal at the facility. All wastes, routes of contaminant migration, and human environmental exposure pathways would remain unchanged. This alternative would not reduce the threats to human health and/or the environment at the site. Assuming the ground-water quality does not worsen, Attachments 4, 5, 6, and 7 provide tabular and graphical representation of the health risk which would result if Alternative 1 were selected. Estimated Cost 0 Capital Cost: NA 0 Annual O&M Cost: Ground-water monitoring cost 0 Present Worth (30 yrs. 10%) NA Estimated ftnths to Inplemsit: NA b. Alternative 2 0 Capping of Old Site 0 Ground-water monitoring Capping - Under this alternative, US Ecology would place a RCRA- approved cap over the Old Site (Attachment 3). The cap would be constructed of natural and/or synthetic materials. The cover would be designed to be durable and to reduce or eliminate surface infiltration of precipitation through the hazardous waste site. The cap would decrease the potential for erosion and transport of hazardous waste or contaminated soil by air or water thereby reducing adverse affects due to inhalation and/or dermal contact. ------- -10- Ground-watering monitoring - A long-term ground-water monitoring program (the same type as in Alternative 1 above) would be implemented, but no treatment of ground water would be involved. Estimated Cost 0 Capital Cost: $900,000 (capping cost) 0 Annual O&M Cost: $ 3,000 0 Present Worth (30 yrs. 10%) $928,000 Estimated Months to Implement: 18 months c. Alternative 3 0 Capping of Old Site 0 Ground-water extraction 0 Ground-water treatment 0 Discharge of treated effluent to surface water Capping - Same as described in Alternative 2. Ground-water Extraction System - US Ecology proposes the partial extraction of contaminated ground water using sixteen (16) extraction/eductor wells and a subsurface drain system installed in the Old Site glacial aquifer plume near the source of contamination. The proposed location of eductor wells and drains is indicated on Attachment 3. Total flow from the system is expected to be 100 gallons per minute (gpm). This draft FS emphasizes ground-water migration control and ground-water extraction for the Old Site plume, but US Ecology states in Appendix A of Volume II that "the technologies discussed here apply to ground water from both the new and old sites." ------- -11- US Ecology has proposed the following chemical-specific aquifer remediation goals for eleven indicator chemicals: Arsenic: 1.0 micrograms per liter (ug/1) Benzene: 5.0 ug/1 Chloroform: 5.0 ug/1 1,1-Dichloroethane: 5.0 ug/1 1,2-DichIoroethane: 5.0 ug/1 1,1-Dichloroethylene: 1.0 ug/1 1,2-Dichloropropane: 5.0 ug/1 Methylene Chloride: 5.0 ug/1 Tetrachloroethylene: 5.0 ug/1 Trichloroethylene: 5.0 ug/1 Vinyl Chloride: 1.0 ug/1 US Ecology states in the draft FS for ground-water remediation (page 2-9) that "these 11 indicator chemicals account for more than 99 percent of the baseline cancer risk estimate" and "for approximately 75 percent of the combined hazard index for noncarcinogenic effects that was determined during the baseline risk assessment." US Ecology has estimated that a minimum of thirty (30) years would be necessary to reduce the levels of contamination in the ground water to these chemical-specific remediation goals. Attachment 8 presents graphical representation of the risk US Ecology estimates would remain if the ground-water contamination were reduced to the chemical-specific remediation goals proposed ------- -12- by US Ecology. For comparison purposes, Attachment 8 indicates the estimated existing health risk from the Old Site plume which would continue if no corrective action were taken. In addition, Attachment 8 indicates the natural background health risks (i.e., unrelated to past facility operations) associated with drinking the ground water. Tnis risk was calculated using ground water data from the two background wells. Ground-water Treatment - Following its extraction, the ground water would be treated as follows: 0 Chemical addition, flocculation, and precipitation (for removal of metals); 0 Air stripping followed in sequence by activated carbon adsorption of volatile organic compounds (VDCs) from the vapor phase in air discharged from the stripper prior to its release into the atmosphere; 0 Carbon adsorption (as a polishing step, if required) for removal of base/neutral/acid extractable organics with discharge of treated water to surface water after achieving established pretreatment standards; and 0 Disposal of sludge in off-site RCRA landfills. Ground-Water Mcnitoring - A long-term monitoring program would be undertaken to note the effectiveness of both ground-water migration control and the ground-water treatment efforts. Estimated Cost 0 Capital Costs: $ 2,765,000 0 Annual O&M : $ 852,000 0 Present Worth (30 yrs. 10%) $10,797,000 Estimated Months to Implement: 18 months ------- -13- d. Alternative 4 0 Capping of Old Site 0 Ground-water extraction and treatment 0 Discharge of treated effluent to surface water Capping - Same as described in Alternative 2. Ground-water Collection System - Same as described in Alternative 3. Ground-^water Treatment - Under this alternative, the water treatment process is the same as under Alternative 3 except that biological treatment replaces the air stripping step. Neutralized effluent from the metals precipitation step flows to a trickling filter for treatment of biologically degradable organics. The biological sludge would be dewatered and the filter cake hauled off site for incineration. Ground-water Monitoring - Same as described in Alternative 3. Estimated Cost 0 Capital Costs: $ 3,143,000 0 Annual O&M costs: $ 1,397,000 0 Present worth (30 yrs. 10%) $16,312,000 Estimated Months to Implement: 18 months e. Alternative 5 0 Capping the Old Site 0 Ground-water extraction using wells and subsurface drains 0 Treatment of ground water: - metals precipitation - biological treatment ------- -14- - air stripping - discharge of treated effluent to surface water Alternative 5 is the same as Alternative 4 with the exception of the method of treatment of the extracted ground water. In this alternative, the effluent from biological treatment is pumped to an air stripper, rather than to an activated carbon adsorption column train, for removal of VDCs. The air stream from the air stripper column is also treated by activated carbon adsorption prior to release into the atirosphere. As in Alternatives 3 and 4, the treatment plant effluent is to be discharged to a tributary to lawson Creek about 2000 feet east of the proposed plant. Gravity would carry the water to its discharge point. Estimated Cost 0 Capital Cost: $ 3,123,000 0 Annual O&M: $ 612,000 0 Present worth (30 years at 10%) $ 8,892,000 Estimated Months to Inplement: 18 months 2. Source Control Alternatives a. Alternative 1 0 Capping of the Old Site (extending over the slurry walls) 0 Soil bentonite slurry walls placed: - Circumferentially around Old Site trenches (Attachment 3) - Around waste contaminated areas of the New Site near trenches at 18EWC and G-120 (Attachment 3) ------- -15- 0 Extension of existing New Site cap at 18EWZ and G-120 over the slurry walls 0 Extraction wells within Old Site slurry walls (to dewater the Old Site) Slurry Walls - Under this alternative, soil bentonite (SB) slurry walls are installed completely around the Old Site trenches. The SB slurry walls are projected to have a permeability of 1 x 10~^ centimeters/second, be 2.5 feet wide, extend from the ground surface to bedrock, and be keyed three (3) feet into bedrock. Under tnis alternative, SB slurry walls are also to be placed in semi circular fashion around the extent of the contaminated plume at the 18EWT trench and around the boundary of trenches 1,2, and 3 of the G-120 areas of the New Site. Ihese two semicircular slurry walls will tie into existing barrier walls of the New site and extend downward from ground surface and be keyed three (3) feet into bedrock. Capping - This alternative also proposes to place a landfill cap, meeting RGRA guidance criteria, over the whole Old Site area and to tie it into the existing New Site cap. Figure 4-1 of the draft FS for source control indicates that the multilayer cap will both be in contact at the ground surface with the SB slurry walls and extend outside beyond the slurry wall (i.e., away from the buried waste). In addition, the existing New site clay cap would be extended over the top of the 18EW3 and G-120 contaminated areas enclosed by the slurry walls installed there. (Note: This alternative assumes that the existing New Site cap ------- -16- satisfies RCRA requirements for a hazardous waste landfill cap. If it does not, IEPA will require that any appropriate modifications be made.) Extraction Wells - Alternative 1 places extraction wells within the Old Site trench area after it is encircled with the SB slurry wall. Those wells will allow for the removal of existing contaminated ground water from within the slurry wall and permit the isolation of the wastes from ground water. Piezometers would be enployed to monitor the effectiveness of the slurry wall. Ml of the Old Site and New site wastes will remain at the site under this alternative. Estimated Cost o Capital Costs: (See ground $1,153,500 (exclusive of Old water FS for cap costs) Site cap costs) 0 Annual O&M Costs: None listed 0 Present Worth (30 yrs. at 10%) $1,153,500 Time to Implement: Design and contractor procurement = 1 1/2 yrs Construction time = 1/2 yr. Total = 2 yrs. b. Alternative 2 0 Capping of the Old Site (extending over subsurface drains/ trenches) 0 Subsurface extraction trenches: - circumferentially around Old Site trenches - around 18EW3 plume - around plume in G-120 area ------- -17- 0 Extension of existing New Site cap at 18EW3 and G-120 over area enclosed by trenches Capping - Under this alternative, capping for the Old Site and G-120 and 18BC New Site areas is the same as proposed under Alternative 1. The only difference is that the capping extends over extraction trenches rather than SB slurry walls. Subsurface drains (trenches) - US Ecology proposes the placement of bio-polymer (BP) interceptor trenches in the same configuration as the SB slurry walls described in Alternative 1 above. Trenching for installation of the subsurface drains is done in a manner similar to that for the slurry walls. The drains are keyed into bedrock three (3) feet. Then a perforated collector pipe with jump risers is lowered to the trench bottom. The BP trench is backfilled with coarse gravel and thus intercepts leachate and ground water allowing extraction and subsequent treatment. The effectiveness of the trench walls would be monitored throughout their use. Under this alternative, excavated soils containing high concentrations of volatile organic compounds (VOCs) are to be incinerated on site prior to off-site disposal. Estimated Cost 0 Capital costs: $10,612,220 0 Annual O&M Costs: $ 3,000 0 Present Worth (30 yrs. at 10%): $10,640,000 ------- -18- Time to Inplement: Design and contractor procurement =1 yr. Construction time = 1/2 yr. Total = 1 1/2 yrs. c. Alternative 3 0 Capping of Old Site (over slurry walls) 0 Slurry walls around Old Site trenches 0 Subsurface drains/trenches around: - 18EWZ plume - G-120 plume 0 Extension of existing New site cap at 18EWZ and G-120 over the area enclosed by the drains This alternative simply conbines the slurry walls around the Old Site from Alternative 1 with the two New Site semicircular subsurface drain configurations of Alternative 2. All other details are the same as described previously. Estimated Cost 0 Capital Costs: $2,193,146 Annual O&M Costs: $ 1,000 Present worth (30 yrs. at 10%): $2,202,000 o o Time to Implement: Design and contractor procurement = 11/2 Construction time = 1/2 Total = 2 yrs. d. Alternative 4 0 Excavation of hazardous waste and contaminated soil from Old Site trenches ------- -19- Qn-site incineration of Old Site waste and soil and disposal of treatment residue off site Slurry walls encircling plumes at 18EM: and G-120 Extension of existing cap at 18EWZ and G-120 over areas enclosed by proposed slurry walls Slurry Walls and Capping - The placement of slurry walls at 18BC and G-120 and extension of the existing New Site cap in both locations is exactly as proposed in Alternative 1. Excavation of Old Site Trenches - Old Site excavation will entail removal of all waste from the six disposal trenches and all contaminated soil to bedrock. All the excavated waste and soil will be treated by incineration on site. The incinerator, whose owner or operator would have to obtain a RCRA permit for its construction and operation, will be a rotary kiln with a 40 ton/hour capacity and will be operated around the clock. The incinerator will be designed to achieve 99.9999% destruction efficiency of all combustible constituents. Treated offgases will corply with all new source performance standards (NSPS) and prevention of significant deterioration (PSD) requirements. Incinerator ash will be transported off site for solidification and disposal. Estimated Cost 0 Capital Costs: $307,444,986 0 Annual O&M Costs: None listed 0 Present Worth (30 yrs. at 10%): $307,444,986 ------- -20- Time to Inplement: Design and contractor procurement = 1 1/2 yrs. Tijne for excavation and disposal = 2 yrs. Total = 3 1/2 yrs. V. THE PRKKhKPFTl ALTERNATIVE 1. U.S. EPA's preferred ground-water alternative for ground-water remediation is one which will: a. Enploy ground-water pumping to: i. Limit expansion of the existing contaminated ground water by hydraulic controls; and ii. Remove the contaminated ground water from each location of contamination until ground-water quality at the completion of the remediation meets the following ground-water protection standards: Arsenic: 1.0 ug/1 Benzene: 2.0 ug/1 Chloroform: 0.5 ug/1 1,1-Dichloroethane: 1.0 ug/1 1,2-Dichloroethane: 0.5 ug/1 1,1-Dichloroethylene: 1.0 ug/1 1,2-Dichloropropane: 0.5 ug/1 Methylene Chloride: 5.0 ug/1 Tetrachloroethylene: 0.5 ug/1 Trichloroethylene: 1.0 ug/1 Vinyl Chloride: 1.0 ug/1 ------- -21- b. Treat the removed ground water as necessary to comply with applicable State regulatory programs for discharge to air and surface water; and c. Provide a ground-water monitoring program to verify progress toward achieving U.S. EPA's ground-water protection standards. U.S. EPA has selected the above-listed ground-water protection standards for the eleven ground-water constituents based on the practical quantitation limits (PQLs) listed in 40 CFR Part 264, Appendix IX. By definition, the PQLs "are the lowest concentrations of analytes in ground waters that can be reliably determined within specified limits of precision and accuracy by indicated methods under routine laboratory operating conditions." U.S. EPA has selected more stringent remediation objectives for all but two of the eleven constituents (i.e., arsenic and vinyl chloride are the same as those proposed by US Ecology). The calculated residual excess cancer risk resulting from extended ingestion of ground water contaminated with the eleven constituents at the concentrations US Ecology has proposed for remediation is 1.8xlO~4. This risk is in excess of the maximum risk range (i.e., 10~6 to 10~4) which U.S. EPA has established as protective of human health and appropriate for selecting corrective measures. Attachment 8(a) graphically displays the carcinogenic risks associated with long-term ingestion of contaminated ground water from the Old Site plume if: 0 The "No Action" alternative were selected; 0 US Ecology's proposed remediation goals were achieved; ------- -22- 0 U.S. EPA's ground-water protection standards were achieved; and 0 Ground water were remediated to background cancer risk levels. Attachment 8(b) indicates corresponding non-carcinogenic effects. Conceivably, ground water Alternatives 3, 4, and 5 could, with modifications, meet all these criteria. Ground water Alternatives 3, 4, and 5 differ only in the manner in which extracted ground water is proposed to be treated at the surface. Each alternative proposes the same configuration of extraction wells and subsurface drains. US Ecology's proposed extraction well system (see Attachment 3) is insufficient to meet U.S. EPA's preferred alternative. US Ecology must modify its proposed ground-water extraction and treatment alternatives to: 0 Include placement of additional extraction wells at or near plume boundaries which will hydraulically prevent further migration of contaminated ground water; 0 Provide for individual extraction wells screened in the glacial aquifer and in the bedrock aquifer (including the G-120 area), as necessary, to achieve the ground-water protection standards specified herein in both saturated zones; 0 Specify that extraction of contaminated ground water will continue until ground-water protection standards are achieved; and 0 Provide for regular sampling of the extracted ground water for those radionuclide parameters in Table 5-7 of the RJ plus 1-129. A plan and schedule for these sampling activities will be required. 2. One preferred source control alternative is Alternative 1 consisting of the following: ------- -23- a. Slurry walls around the Old Site trenches; b. Slurry walls at trench 18QC and the G-120 area; c. Capping of the Old Site with a RORA-required cap (discussed in draft FS for ground-water remediation under Alternatives 2, 3, 4, and 5, but considered part of source control) ; d. Extension of RGRA-required caps over areas encircled by slurry walls tied into existing barrier walls at 18EW3 and the G-120 area; and e. Placement of recovery/extraction wells screened near bedrock in areas encircled by slurry walls (i.e., the Old Site trenches). The purpose of these wells is to lower the level of the ground water within the slurry walls to a level below that of the buried hazardous waste and a high percentage of the contaminated soils. Alternative 1 for source control needs to be modified to address: 0 Releases of hazardous waste and/or hazardous waste con- stituents from 18EW3 by repairing or modifying the existing trench barrier walls; 0 Potential continuing or future releases from the north and west slopes of the New site. Items can be incorporated into the future post-closure permit by IEPA which will require additional leachate control activities in trenches of concern based on historical ground-water sampling data (i.e. , trenches 1, 2, 3, 23, 24, and 18EW3). Installation of new sumps and/or extraction wells inside the proposed slurry walled and capped areas at 18EWZ and G-120 and additional sumps in trenches 1, 2, and 3 would allow interception and removal of more leachate. 0 Implementation of modifications to the existing New Site clay cap, if required by IEPA. Estimated Cost (total for preferred alternative) ------- -24- 0 Capital Costs: $ 3,918,500 0 Annual O&M Costs: $ 852,000 0 Present Worth (30 yrs. at 10%): $11,950,500 In addition to these costs, the above-listed modifications to the ground water and source control aspects of this preferred alternative will add additional costs. However, the additional expense would not be significant conpared to the overall cost. Modifications of the existing New Site cap, if necessary, could potentially increase the total costs significantly. Tune to Inplement: 2 yrs. VI. CRITERIA FOR COMPARISON OF ALTERNATIW-S Each alternative in the draft FS reports was evaluated against the following list of criteria, as required by the NCP and RI/FS guidelines. 1. Overall Protection of Human Health and the Environment addresses whether or not a remedy provides adequate protection and describes how risks are eliminated, reduced or controlled through treatment, engineering controls or institutional controls. 2. Compliance with ARARs addresses whether or not a remedy will meet all of the applicable or relevant and appropriate requirements (ARARs) of other environmental statutes and/or provide grounds for invoking a waiver. 3. Long-term Effectiveness and Permanence refers to the ability of a ------- -25- remedy to maintain reliable protection of human health and the environment over time once cleanup goals have been met. 4. Reduction of Toxicity. Mobility or Volume is the anticipated performance of the treatment technologies a remedy may employ. 5. Short-term Effectiveness involves the period of time needed to achieve protection and any adverse impact on human health and the environment that may be posed during the construction and implementation period until cleanup goals are achieved. 6. Implementabilitv is the technical and administrative feasibility of a remedy, including the availability of goods and services needed to implement the chosen solution. 7. Cost includes capital and operation and maintenance costs. 8. State Acceptance indicates whether, based on its review of the draft FS reports and Proposed Plan, the State of Illinois concurs, opposes, or has no comment on the preferred alternative. 9. Community Acceptance will be assessed in the responsiveness summary following a review of the public comments received on the draft FS reports and the Proposed Plan. The FS documents will be combined and finalized incorporating the selected corrective action. Each alternative was evaluated against these nine criteria. A discussion of how the preferred alternative compares to the other alternatives is presented under the following section. ------- -26- VII. CCMPARISCN Of ALTERNATIVES After evaluating the remedial alternative developed in the draft FS documents in regard to the nine (9) criteria described above, the U.S. EPA has made a preliminary recommendation that ground water Alternative 3 and source control Alternative 1 be used to address contamination at the US Ecology, Inc. landfill. The rationale for this recommendation is provided below. 1. Overall Protection of Human Health and the Environment: a. Ground water Alternatives 1 (the No Action alternative) and 2 do not provide for the extraction and treatment of contaminated ground water and, therefore, do not provide for overall protection of human health and the environment. Alternatives 3, 4, and 5 (as modified by U.S. EPA) will provide for adequate protection of human health and the environment since they provide for remediation of the plumes of contamination by extraction and treatment of ground water (i.e., from the Old Site, trench 18EW3, the G-120 area, and the north slope seeps). Following ground- water remediation to the concentrations proposed by U.S. EPA, the residual health risks from ingestion of ground water will be reduced to acceptable levels. Therefore, the preferred alternative for ground-water remediation can potentially be any one of Alternatives 3, 4, or 5, as modified. Extraction and ground-water treatment will continue indefinitely toward achieving U.S. EPA's ground-water protection standards. A NPDES permit will restrict the effluent discharge levels of the various ------- -27- parameters of concern. Monitoring wells will be sampled regularly to test for the effectiveness of the extraction and treatment systems by monitoring for changes in plume size and contaminant concentrations levels. Because US Ecology owns all of the land surface under which hazardous constituent plumes are currently delineated, no third party has a well water supply screened in a plume. Containment of the plume and extraction and treatinent of the ground water will reduce or eliminate potential risks from ingestion of contaminated ground water downgradient of the landfill at any off-site location. b. Source control Alternative 1 is preferred because it is expected to provide an appropriate degree of overall protection of human health and the environment by containing (with slurry walls) all Old Site hazardous wastes and most contaminated soil at the Old Site and the 18EWT and G-120 areas. The slurry walls will be designed to be compatible with the chemicals in the buried wastes and will be constructed to isolate the wastes and contaminated soils and reduce further contaminant migration to ground water. RCRA- required caps over the Old and New site and extensions over the G-120 and 18EWT plume areas will reduce the chance of exposure to contaminated soil and significantly reduce surface-water infiltration and leachate generation and help control future releases of contamination. Extraction wells placed inside the encircling slurry walls of the Old Site will be designed to create a reduced hydraulic head ir.side the walls which will ------- -28- reduce the probability of contaminated water exiting outward through the walls; to draw the ground-water surface level down inside the slurry walls to below the buried waste elevation; and to transmit extracted ground water to the proposed treatunent system. Alternative 2, using subsurface extraction trenches, is judged to be less effective in isolating or containing the buried hazardous waste although caps would still be instrumental in reducing leachate generation. Alternative 3 is slightly less protective than Alternative 1. Alternative 4 is intuitively more protective than each of the other alternatives because the Old Site waste (7% of the total waste volume at the Facility) would be excavated, treated, and disposed of off site. However, short-term hazards would be increased for workers and those living nearby from exhumation (e.g., potential explosions, increased air emissions, airborne chemical contaminated particulate matter, etc.), incineration, and off-site transport of the wastes. By engineering the effective long-term isolation and containment of the relatively small volume of the Old Site waste and by reducing the volume of ground water in contact with the buried waste and contaminated soil through implementation of Alternative 1, it is felt that short-term protection is greater and that long-term goals for protection of human health and the environment will be achieved as well. ------- -29- 2. Compliance with ARARs: a. Ground water Alternatives 1 and 2 will not attain chemical-specific ARARs because no extraction and treatment is involved. Alternatives 3, 4, and 5 will meet all the chemical-specific ARARs. Treated ground water will be discharged to surface water only after complying with the lEPA-approved NPDES permit. Because the aquifers are contaminated with multiple chemicals, aquifer remediation which achieves maximum contaminant levels (M3Ls) is still insufficiently protective of human health. The additive health risks necessitate setting cleanup goals, in some cases, below MZLs. Air emissions related to ground-water extraction and treatment will be controlled and regulated, as necessary, under the IEFA air permitting program. b. Source control No matter which alternative is chosen, all closure requirements under PCRA will be included in a closure plan to be approved by IEFA. Landfill caps will meet RCRA standards. Long-term post- closure ground-water monitoring and cap maintenance will be incorporated into a RCRA permit based on standards found at 35 111. Adm. Code Part 724 Subparts F, G, and N. Capping the landfill (proposed to some degree in each alternative) will eliminate the potential for exposure (ingestion, inhalation, or direct dermal contact) to any contaminated surface soils. ------- -30- Air emissions resulting from exhumation and/or trenching activities (for drains or slurry walls) will be addressed in an IEFA air permit. Alternative 1 is expected to result in the fewest emissions and Alternative 4 the most. 3. Long-term Effectiveness and Permanence a. Ground water Alternatives 1 (No Action) and 2 (only capping Old Site) will not provide long-term effectiveness or permanence. Alternatives 3, 4, and 5 appear to provide equal effectiveness and permanence by extracting and treating the contaminated ground water. The extraction well system (the same for Alternatives 3, 4, and 5), as modified, will halt plume expansion and begin and continue aquifer remediation until ground-water protection standards are achieved. The remediation by enhanced aquifer purging is projected to require a minijnum of thirty (30) years whichever alternative is selected. Alternative 3 is tentatively recomnended because it does not utilize biological treatment technology as do Alternatives 4 and 5. Biological systems can be subject to "shock" loads of toxic organics and to failure of mechanical equipment potentially re- sulting in destruction of the microorganisms. In addition, as biological oxygen demand (BCD) levels will be reduced over time in influent water, nutrient supplements would be required to sustain the performance of microorganisms thus increasing costs and the uncertainty of the technology's effectiveness. Therefore, the ------- -31- carbon adsorption technology (liquid and vapor phase) used in Alternative 3 is judged to be more reliable long-term. b. Source control Alternatives 1, 2, and 3 propose installation of vertically positioned containment barriers and FORA-required caps installed over both the Old and New sites and the 18EW3 and G-120 areas. The cap design and containment technologies will incorporate details necessary to achieve the maximum effective lifetimes with the lowest maintenance. Of these alternatives, Alternative 1 is deemed most protective. Alternative 4 will remove all Old Site buried waste and soil to bedrock, destroy the organics by incineration and dispose of the ash off site. That would reduce the magnitude of residual risk somewhat, but estimates indicate that 93% of the buried waste is in the New Site and, under this alternative, that would still remain buried on site, but capped. 4. Reduction of Toxicity, Mobility, and Volume a. Ground water Alternative 1 and 2 rely on "no action" or capping of the landfill sites in conjunction with natural attenuation of contaminated ground water rather than active aquifer purging activities to reduce toxicity, mobility, or volume. Alternatives 3,4, and 5, as modified, will actively extract the water and treat it to required ground-water protection standards. The ------- -32- draft FS estimates a 98% reduction of the total mass of organic contaminants in the ground water within thirty (30) years. b. Source control Alternatives 1,2, and 3 will adequately contain and isolate the buried wastes from ground water and reduce the production and mobility of additional leachate to ground water thereby achieving the remedial action objectives. Alternative 4 will reduce the total buried volume of waste by an estimated 7% (i.e., by exhuming the Old Site), will remove VOCs by soil/waste incineration, and transport the ash off site for disposal. Migration of contaminants from the Old Site will be reduced accordingly. 5. Short-term Effectiveness (including implementation time and adverse impacts) a. Ground water Alternative 1 and 2 provide no effectiveness (i.e., no ground- water remediation is provided by either). Alternatives 3,4, and 5 would all take eighteen (18) months to implement and are judged to provide similar levels of short-term effectiveness with -regard to protection of workers, the community, and the environment during the construction and implementation stages. Fewer organic air emissions are anticipated from the implementation of Alternatives 3 and 5. Alternatives 4 and 5 will produce biological sludge necessitating additional transport and disposal activities potentially negatively impacting nearby communities. ------- -33- Alternative 3 is tentatively preferred because: No biological sludge is produced requiring transport and disposal; Regenerated activated carbon will reduce overall hazardous waste generated from treatment and requiring off-site dis- posal; and The technology is more reliable. b. Source control Alternative 4 is projected to result in adverse noncarcinogenic and carcinogenic effects to off-site receptors during exhumation and incineration (about 3 1/2 years). Alternative 2 will involve incineration of some trenched soil and air emissions of VOCs will occur during construction activities lasting about 1 1/2 years. Alternatives 1 is preferred because it produces the least volume of excavated waste requiring transport and disposal and is comparable in air emissions and risks with Alternative 3. Alternatives 1 and 3 would take about two years to implement. 6. Implementability a. Ground water Alternatives 1 and 2 are easily inplementable but not sufficiently protective to consider. All components of the technologies proposed for Alternatives 3, 4, and 5 (as modified) are readily available and have been utilized at other sites. The technologies are reasonably effective, reliable, and employ standard engineering and construction techniques. None of these alternatives restrict future modification or expansion of the ------- -34- selected grouivi-water remedy if determined to be necessary after implementation. The preferred alternative (Alternative 3) is favored because it incorporates widely used and easily implemented technologies for treating contaminated ground water (i.e., activated carbon adsorption and air stripping). Biological treatment, a technical component of both Alternatives 4 and 5, is more difficult to implement, has been less widely used, and its performance is reportedly difficult to predict. b. Source control All four alternatives incorporate landfill capping. Installation of RCRA-required caps and their maintenance is straightforward. Slurry walls (Alternatives 1 and 3) and subsurface drains (Alternatives 2 and 3) are both commonly used technologies and difficulties in implementation are not anticipated. Both technologies require care in the design and implementation to achieve the desired goals of containment or interception of leachate. Alternative 4 (exhumation of the Old Site) is a technically feasible alternative. However, implementation will be more difficult because of required permits and special equipment for incineration (in Alternative 2 also), uncertainties and dangers to workers during exhumation (accurate information on quantities, ------- -35- locations, and types of wastes is nonexistent for the Old Site), and off-site transport and disposal arrangements for the residuals of treatment (i.e., potential disposal capacity issues and vehicular accidents). 7. Cost a. Ground water Alternative 2 would cost $928,000 over thirty (30) years, but is insufficiently protective. Of those alternatives implementing active extraction and treatment of ground water for a minimum of 30 years, Alternative 5 is projected to be the least expensive at $8,892,000. Alternatives 3 and 4 are $10,797,000 and $16,312,000 respectively. b. Source control The cost estimates for capping the Old Site and for maintaining that cap are projected to be about $928,000 over 30 years for Alternatives 1,2, and 3. Alternative 4 is the most expensive to implement at an estimated $307.5 million. Alternative 2, also incorporating incineration (i.e., soils excavated from trenches), will cost $10,640,000. Alternatives 1 and 3 will cost $1,153,500 and $2,202,000 respectively. Alternative 1 is preferred. 8. State Acceptance The Illinois Department of Nuclear Safety (ITNS) was briefed on ------- -36- U.S. EPA's preferred alternative on December 21, 1989. IDNS concurs with the alternative selected in that: a. Placing a slurry wall around the Old Site, rather than subsur- face drains, is anticipated to have a lesser effect on the local ground-water flow direction associated with the Low-level Radioactive Waste Site; and b. Trie alternative will require testing of extracted ground water for the presence of a specified list of radionuclides and, if any are detected, appropriate treatment of the water and management of associated wastes generated. •Die IEPA, unable to attend the December 1989, meeting, was briefed on the preferred alternative on February 26, 1990. IEPA has expressed concerns about the long-term effectiveness and technical feasibility (because of the depth to bedrock) of implementation of slurry walls as a component of the preferred alternative. U.S. EPA will address these aspects of the remedy after IEFA has had an opportunity to review and cament on other aspects of the proposed plan during the comment period. 9. Community Acceptance Acceptance by the community of the preferred alternative will be evaluated based on comments received at the public hearing on U.S. EPA's proposed plan and during the formal public contnent period. ------- -37- In summary, based on the information available and analysis of the Final Remedial Investigation Report and'the two draft Feasibility Study documents, U.S. EPA proposes that the preferred alternative for the US Ecology site is consistent with the requirements of RCRA. The combination of the draft ground water FS Alternative 3 for ground-water remediation and Alternative 1 from the draft source control FS, along with the specified modifications listed in Section V, is sufficiently protective of human health and the environment. Ground-water monitoring, extended aquifer remediation, containment of buried hazardous waste, added prevention of leachate generation (to the extent possible) by capping and collection of any leachate that is generated are the key components to ensure that the preferred alternative will provide long- term protection. VIII. THE (XWUNITY'S ROLF Th} TOF .qFT.fyTTffl PROCESS To encourage public participation in the selection process, the U.S. EPA has set a public ccmnent period from May 28 , 1990 , through July 11 , 1990. Interested parties are requested to comment on the alternatives presented in this Plan and elaborated upon in the draft FS reports. Tne RI/FS documents, as well as any other pertinent documents in the administrative record (e.g., work plans, analytical data, etc.), may be consulted for the details on the development and evaluation of the alternatives considered. The documents listed in Attachment 9 to this Plan are available for public review at the: Sheffield Public Library 136 East Cook Street Sheffield, Illinois 61361 (815) 454-2628 ------- -38- Tne final corrective action remedy for US Ecology's Sheffield facility will not be selected until the public conrnent period is conpleted and all cements have been evaluated. Based on new information or public Garment, U.S. EPA may modify the preferred alternative or select another response action presented in this Plan and the draft FS documents. Therefore, the public is encouraged to review and coiment on all the alternatives considered for the site. Written Garments on this Plan and the draft FS reports will be accepted throughout the public conment period. A Responsiveness Sunrnary will be prepared by U.S. EPA which will address all significant public Garments received during the Garment period. Inis Responsiveness Summary will be made available to the public. If the Garments are such that significant changes are made in the corrective measure alternative identified by U.S. EPA, the Agency will seek public Garments on the revised corrective measures alternative. Written Garments should be sent to: Mr.Jonathan Cooper IL/TN Technical Enforcement Section, 5HR-12 RCRA Enforcement Branch U.S. Environmental Protection Agency 230 South Dearborn Street Chicago, Illinois 60604 Written Garments must be postmarked no later than July 11, 1990. A public hearing to discuss the Proposed Plan, the Final RI Report, and the draft FS reports has been scheduled for 7:00 p.m. June 28, 1990, at the Bureau County Court House in Princeton, Illinois. Upon consideration of public conment and after the Responsiveness Summary has been publicly noticed, U.S. EPA will approve a final ------- -39- corrective measure alternative for the US Ecology facility in Sheffield, Illinois. If anyone has questions regarding the public comnent period or the process, further information may be obtained from: Ms. Suzanne Kircos Community Relations Coordinator U.S. Environmental Protection Agency Office of Public Affairs, 5PA-14 230 South Dearborn Street Chicago, Illinois 60604 (312) 353-3209 Also a toll free number ((800) 572-2515) is available to Illinois residents between 9 a.m. and 4:30 p.m. on Monday through Friday. Please be advised that a two-week informational period will precede the public comment period. This period will extend from May 14, 1990, to May 28, 1990. There will be an informational meeting held at the Buda-Sheffield Western School cafeteria, Stewart Street, Buda, on June 14, 1990. The meeting is scheduled to begin at 7 p.m. ------- ATTACHMENT 1 BUREAU COUNTY SITE LOCATION MAP ------- ATTACHMENT 2 $ II ./ /I/ 11 / /. II / L? II / TROUT < US ECOLOGY SHEFFIELD HAZARDOUS WASTE DISPOSAL SITES ------- ATTACHMENT 3 GROUND WATER SEEPS m i U.IA—ay 18EWC AREA LEGEND SLURRY WALL CAP/COVER GROUND WATER CONTAMINATION (OLD SITE PLUME) • GROUND WATER EXTRACTION WELLS PROPOSED PLAN FOR U S ECOLOGY SHEFFIELD SITE ------- ATTACHMENT 4 Table 7-12. Risk^Assessment Summery fop Chronic Exposure: US Ecology Shefield Facility s===s=== • --=* ==s========e==s==" = = ======£=sz»»ss=ar*a3s»s*as»*«a»s Site Exposure Pathway Hazard Index Noncarcinogenic Effects: Confined Exposure Excess Lifetime Cancer Risk: Contained Exposure Old Site: Bedrock Old Site: Glacial Mew Site: Bedrock New Site: Glacial Trout Lake North Slope Seeos Pond/Gravel Pit CW Ingest ion GV Ingestion GU Ingestion GW Ingestion SW Ingestion SW Ingestion SW Ingestion 1.50E-01 6.58E-01 5.27E*01 3.21E»01 8.38E-04 6.81E-Q3 6.51E-W 1.09E-05 1.66E-02 6.25E-03 4.93E-03 1.02E-07 2.63E-06 O.OOE»00 7-33 ------- ATTACHMENT 5 OCCUN1CS TABLE 3-1. IISl CM»»ACTEBir»T;o«: IHCESTIOn EXPOSURE TO SU»»»CE SOUS Oewicel INOtCANICS Antimony Arsenic Barium Beryl 1 ium Cacfnium Chromium Cobait Copper lead •ercury Nickel Selenium Tin Vanadium Zinc Man Dean naiimum Background Chronic Dote Naiard Inde* Excess Concentration Concentration. Concentration Ingestion Chronic lifetime in Soil (a) in Soil in Soil (b) Exposure (c) Ciposure Cancer tisk (*B/kg) (mg/kg) (mg/kg) (ng/kg/day) (Dose/lfD) (Dote i Q'*) 0.473 13.963 8S.7SO 0.645 0.173 16.250 6.419 9.519 6.669 0.014 13.419 0.100 0.061 30.063 32.6Sfl 1.400 21.000 190.000 0.960 0.320 23.000 7.900 13.000 9.300 0.085 18.300 1.600 0.570 44.000 58.000 0.41 8.20 43.00 0.55 0.11 13.00 6.50 12.10 3.35 0.00 15.50 0.32 0.80 18.00 31.50 1.59£-07 t.TOt-06 z.sac-tt 2.171-07 5.8CE-08 5.47E-06 2.161-06 3.20E-06 2.24E-06 4.S4E-09 4.51E-06 1. Jit -08 2.04E-08 1.01E-05 1.10E-05 S. 971-04 4.rt>E-03 8.22E-06 J. 771-04 4.Jtf -05 1.16E-04 J.An-06 I.65E-05 1.60E-03 1.6U-OS 2.26C-04 1.121-CS 3.40E-C8 1.UE-03 5.50E-55 Acetone Carbon Tetracniorioi* Chloroform Hethylene Chloride Tetrachloroethylene 1,1, 1-Tricfi(oro«tnane Trichloroethylen* 0.013 0.003 0.280 0.008 0.092 0.002 0.025 0.019 O.OS4 2.600 0.010 1.200 0.019 0.200 0.00 0.00 0.00 0.02 0.00 0.00 0.00 4.291-09 1.14E-09 9.42E-OJ 2.69E-09 3.10E-W 6.39t-10 8.55E-09 4.29E-08 1.63E-06 9.42E-06 4.49E-08 3.10E-06 7.10E-C9 8.55E-07 1.491-10 5.75E-10 2.02E-11 1.3BE-09 9.41E-11 Hazard [ndei: Caoeincd Expoiure Enceti Lifetira* Carcinogenic titk: eti Eipofurt 9.29E-03 8.22E-06 a. Arithmeti: aean of turficia! toil tanvies (0 to 2 fe«t BIS). Not o>tect»d retjlti M«re tr.itro ai 0.0 ana inc:uo»O in calculation of :ne mean. Swclcs for ynich attoeiated fiele blantt ««rt fcura to be carManiriataa, vere not incluoeti in calculation of the mean. Available data ««re aggreagatee far both the r*. and old titet. b. Arithmetic mean of two background tanvles. See Section 2.0 for additional infonwtioo. c. Dose calculated attuning ingestion eioosure to 0.1 g of toil per vork day, 5 days per «e«k, 4C veets ptr year (taking into consideration inc. cover), for 30 years of a 70 year lifetime, acceptors are assomee to oe 70 15 3-3 ------- ATTACHMENT 6 Figure 7-1. Risk Assessment Summary Noncarcinogenic Effects (Potential for Noncar. Effects) 100.000 | 10.000 i Chronic Exposure OSB OSG G-120B NSG Trout Seep Sites Under Investigation Pond OSB-Old Site bedrock aquifer OSO-Otd Site galcial aquifer G-120B-Bedrock aquifer. G-120 area NSG-New Site glacial aquifer Trout-Trout Lake Seep-North Slope seep Pond-Gravel Pit/Stock Pond Noncarcinog. Effects HH Hazard Index (•) Hazard Index >1.0 indicates potential for adverse noncarcinogenic effects. ------- ATTACHMENT 7 Figure 7-2. Risk Assessment Summary Carcinogenic Effects 1.000E-01 i 1.000E-02| 1.000E-03 g 1.000E-04 1.000E-05 1.000E-06 i| 1.000E-07 1.000E-08 (Excess Lifetime Cancer Risk) Chronic Exposure OSB OSG G-120B NSG Trout Seep Sites Under Investigation Pond OSB-Old Site bedrock aquifer OSG-Old Site galcial aquifer Q-120B-Bedrock aquifer. G-120 area NSG-New Site glacial aquifer Trout-Trout Lake Seep-North Slope aeep Pond-Gravel Pit/Stock Pond Excess Lifetime Cancer Risk (•) EPA has established the risk range of 10-7 to 10-4 as protective of human health and appropriate for selecting remedial alternatives. ------- ATTACHMENT 8a RISK ASSESSMENT SUMMARY FOR GROUND WATER (CARCINOGENIC EFFECTS) 10 TARGET RISK RANGE Current US Ecology RCRA Practical Background Ground Water Proposed Quantttation Ground Water Concentrations Cleanup Goal* Limit* (POL) Concentration* 04/20/90 ------- ATTACHMENT 8b RISK ASSESSMENT SUMMARY FOR GROUND WATER (NONCARCINOGENIC EFFECTS) 100 -r 10 -- 0.1 -- 0.01 J- 0.001 -- 0.0001 -- RISKS SIGNIRCANT RISKS NOT SIGNIRCANT Current Ground Water Concentrations US Ecology Proposed Cleanup Goals RCRA Practical Quantitation Umrta (POL) Background Ground Water Concentrations 008-OOS013 NONCAflC.GRF 04/20/80 ------- ATTACHMENT 9 DOCUMENTS CM FILE AT REPOSITORY LOCATED IN SHEFFIELD PUBLIC LIBRARY 136 East Cook St. Sheffield, Illinois 61361 1. Copy of Administrative Order by Consent (dated 9/30/85) 2. Preliminary Screening of Remedial Technologies and Development of Alternatives (August 19, 1988) 3. Revised Final RJ Report (2nd revision: April 17, 1989) 4. Draft Feasibility Study for Ground«ater Remediation (June 27, 1989) - - 2 volumes 5. Draft Feasibility Study for Source Control (3/31/89) — 1 vol'jree 6. Soils ^Jer.dum to the Final RI Report (July 14, 1989) — 3 vclur.es (one is larelec Vol. 1 and the others are Appendix A and B) 7. Appeici:: 0: Toxicity Profiles (July 14, 1989) (Appendix to Fir.al RI Report) 8. Appendix H-4, January 1983, Analysis Data * 9. Revised .^'jppendices for the Revised Final RI Report (Dated February 15, 1989) 10. Work Plan for the Acquisition of Soil and Sediment Chemical Data (February 8, 1989) 11. Work Plan for Conducting Treatability Studies (March 31, 1989) 12. Treatability Study Report (June 23, 1989) ------- |