HRS DOCUMENTATION RECORD COVER SHEET Name of Site: Washington County Lead District-Richwoods EPA ID No.: MON000705032 Contact Persons EPA Contact: Michelle Quick U.S. Environnemental Protection Agency, Region 7 901 North 5th Street Kansas City, Kansas 66101 (913)551-7335 Site Investigation: David Gray Tetra Tech EM Inc. Documentation Record: Stephanie Luebbering Tetra Tech EM Inc. Pathways. Components, or Threats Not Scored The air pathway was not scored for this site. In addition, the ground water to surface component of the surface water migration pathway was not scored because the overland flow component yields a higher score. The air migration pathway was not a priority for investigation in assessments conducted to date in Washington County. Mining activities ended in the mid 1980s and resulting source areas are now substantially vegetated reducing the threat of particulate migration via airborne dispersion. ------- HRS DOCUMENTATION RECORD Name of Site: WASHINGTON COUNTY LEAD DISTRICT-RICHWOODS EPA Region: 7 Date Prepared: September 2007; Page 1 revised March 2008 City, County, State: Richwoods, Washington County, Missouri 63071 General Location in the State: The site is located near the eastern Ozark Mountains in southeastern Missouri. The Richwoods site is in east central Washington County and consists of Study Area 10 delineated by EPA Region 7. Within the study area are numerous potential source areas where mining related wastes have been deposited. Six source areas are included in this documentation record. These sources correspond to tailings piles associated with inactive commercial barite mining operations. Topographic Maps: Richwoods and Fletcher, Missouri Latitude: (North) Longitude: (West) 38°09'58.14" 90°48'51.35 Ref. 3 The latitude and longitude measurements were determined based on the point in the approximate center of Richwoods Area 10 at the intersection of Highway 47 and Highway A/H (Ref. 3). Figure 1 shows the location of Richwoods. Scores Air Pathway Not Scored Ground Water Pathway 100.00 Soil Exposure Pathway 100.00 Surface Water Pathway 60.00 HRS SITE SCORE 76.81 *The street address coordinates, and contaminant locations presented in this HRS documentation record identify the general area of the site's location. They represent one or more locations EPA consider part of the site based on the screening information EPA used to evaluate the site for NPL listing. EPA lists national priorities among the known "releases or threatened releases" of hazardous substances; thus, the focus is on the releases, not precisely delineated boundaries. A site is defined as where a hazardous substance has been "deposited, stored, placed, or otherwise come to be located." Generally, HRS scoring and the subsequent listing of a release merely represent the initial determination that a certain area may need to be addressed under CERCLA. Accordingly, EPA recognizes that the preliminary description of facility boundaries at the time of scoring may be refined as more information is obtained concerning location(s) of contamination. March 2008 1 ------- WORKSHEET FOR COMPUTING HRS SITE SCORE S S2 1. Ground Water Migration Pathway Score (Sgw) (from Table 3-1, line 13) 100.00 10,000.00 2a. Surface Water Overland/Flood Migration Component (from Table 4-1, line 30) 60.00 3,600.00 2b. Ground Water to Surface Water Migration Component (from Table 4-25, line 28) Not Scored -- 2c. Surface Water Migration Pathway Score (Ssw) Enter the larger of lines 2a and 2b as the pathway score. 60.00 3,600.00 3. Soil Exposure Pathway Score (Ss) (from Table 5-1, line 22) 100 10,000.00 4. Air Migration Pathway Score (Sa) (from Table 6-1, line 12) Not Scored -- 5. Total of Sgw2 + Ssw2 + Ss2 + Sa2 23,600.00 6. HRS Site Score Divide the value on line 5 76.81 by 4 and take the square root September 2007 2 ------- TABLE 3-1-GROUND WATER MIGRATION PATHWAY SCORESHEET Factor Categories and Factors Maximum Value Value Assigned Likelihood of Release to an Aquifer: 1. Observed Release: 550 550 2. Potential to Release: 2a. Containment 10 Not Scored 2b. Net Precipitation 10 Not Scored 2c. Depth to Aquifer 5 Not Scored 2d. Travel Time 35 Not Scored 2e. Potential to Release [lines 2a x (2b + 2c + 2d)] 500 Not Scored 3. Likelihood of Release (higher of lines 1 and 2e) 550 550 Waste Characteristics: 4. Toxicity/Mobility a 10,000 5. Hazardous Waste Quantity a 1,000,000 6. Waste Characteristics 100 100 T argets: 7. Nearest Well 50 50 8. Population: 8a. Level I Concentrations b 832.8 8b. Level II Concentrations b 49 8c. Potential Contamination b NS 8d. Population (lines 8a + 8b + 8c) b 881.8 9. Resources 5 Not Scored 10. Wellhead Protection Area 20 Not Scored 11. Targets (lines 7 + 8d + 9 + 10) b 931.8 GROUND WATER MIGRATION SOURCE FOR AN AQUIFER 12. Aquifer Source [(lines 3 x 6 x 1 l)/82,500]c 100 100 GROUND WATER MIGRATION PATHWAY SCORE 13. Pathway Score (Sgw), (highest value from line 12 for all 100 100 aquifers evaluated)0 aMaximum value applies to waste characteristics category. bMaximum value not applicable. cDo not round to nearest integer. September 2007 3 ------- TABLE 4-1-SURFACE WATER OVERAND/FLOOD MIGRATION COMPONENT SPREADSHEET Factor Categories and Factors Maximum Value Value Assigned Drinking Water Threat Likelihood of Exposure: 1. Observed Release. 550 550 2. Potential to Release by Overland Flow: Not Scored 2a. Containment 10 Not Scored 2b. Runoff 25 Not Scored 2c. Distance to Surface Water 25 Not Scored 2d. Potential to Release by Overland Flow (lines 2a[2b+2c]) 500 Not Scored 3. Potential to Release by Flood: Not Scored 3a. Containment (Flood) 10 Not Scored 3b. Flood Frequency 50 Not Scored 3c. Potential to Release by Flood (lines 3a x 3b) 500 Not Scored 4. Potential to Release (lines 2d + 3c, subject to a maximum of 500) 500 Not Scored 5. Likelihood of Release (higher of lines 1 and 4) 550 550 Waste Characteristics: 6. Toxicity/Persistence 00 Not Scored 7. Flazardous Waste Quantity 00 Not Scored 8. Waste Characteristics 100 Not Scored T argets: 9. Nearest Intake 50 Not Scored 10. Targets (lines 5 +6c+ 7 + 8 +9) Not Scored 10a. Level I Concentrations 00 Not Scored 10b.Level II Concentrations 00 Not Scored 10c. Potential Contamination (to Not Scored lOd.Population (lines 10a + 10b + 10c) (to Not Scored 11. Resources 5 Not Scored 12. Targets (lines 9 + lOd + 11) 00 Not Scored Drinking Water Threat Score: 13. Drinking Water Threat Score ([lines 5 x 8 x 12]/82,500, subject to maximum of 100) 100 Not Scored Human Food Chain Threat Likelihood of Release: 14. Likelihood of Release (same value as line 5) 550 550 Waste Characteristics: 15. Toxicity/Persistence/Bioaccumulation 00 Not Scored 16. Hazardous Waste Quantity 00 Not Scored 17. Waste Characteristics 1,000 Not Scored T argets: 18. Food Chain Individual 50 Not Scored 19. Population (to Not Scored 19a. Level I Concentrations (to Not Scored September 2007 4 ------- Factor Categories and Factors Maximum Value Value Assigned 19b.Level II Concentrations (b) Not Scored 19c.Potential Human Food Chain Contamination (b) Not Scored 19d.Population (lines 19a + 19b + 19c) (b) Not Scored 20. Targets (lines 18 + 19) (b) Not Scored Human Food Chain Threat Score: 21. Human Food Chain Threat Score ([lines 14 x 17 x20]/82,500, subject to a maximum of 100) 100 Not Scored Environmental Threat Likelihood of Release: 22. Likelihood of Release (same value as line 5) 550 550 Waste Characteristics: 23. Ecosystem Toxicity/Persistence/Bioaccumulation (a) 50,000,000 24. Hazardous Waste Quantity (a) 10,000 25. Waste Characteristics 1,000 560 T argets 26. Sensitive Environments (b) 26a. Level I Concentrations (b) 0 26b.Level II Concentrations (b) 75 26c. Potential Contamination (b) 0 26d. Sensitive Environments (lines 26a + 26b + 26c) (b) 75 27. Targets (value from line 26d) (b) 75 Environmental Threat Score: 28. Environmental Threat Score ([lines 22 x 25 x 27]/82,500, subject to a maximum of 60) Surface Water Overland/Flood Migration Component Score for a Watershed 60 60 29. Watershed Scorec (lines 13 + 21 + 28, subject to a maximum of 100) Surface Water Overland/Flood Migration Component Score 100 60 30. Component score (S0f)c (highest score from line 29 for all watersheds evaluated, subject to a maximum of 100) 100 60 aMaximum value applies to waste characteristics category. bMaximum value not applicable. cDo not round to nearest integer. September 2007 5 ------- TABLE 5-1.-SOIL EXPOSURE PATHWAY SCORESHEET Factor Categories and Factors Maximum Value Value Assigned Resident Population Threat Likelihood of Exposure 1. Likelihood of Exposure: 550 550 Waste Characteristics: 2. Toxicity a 10,000 3. Hazardous Waste Quantity a 10,000 4. Waste Characteristics 100 100 T argets: 5. Resident Individual 50 50 6. Resident Population: 6a. Level I Concentrations b 46.4 6b. Level II Concentrations b 79.2 6c. Resident Population (lines 6a + 6b) b 125.6 7. Workers 15 Not Scored 8. Resources 5 Not Scored 9. Terrestrial Sensitive Environments C Not Scored 10. Targets (lines 5 +6c+ 7 + 8 +9) b 175.6 Resident Population Threat Score: 11. Resident Population Threat (lines 1x4x10) b 9,658,000 Nearby Population Threat Likelihood of Exposure 12. Attractiveness/Accessibility 100 Not Scored 13. Area of Contamination 100 Not Scored 14. Likelihood of Exposure 500 Not Scored Waste Characteristics: 15. Toxicity a Not Scored 16. Hazardous Waste Quantity a Not Scored 17. Waste Characteristics 100 Not Scored T argets: 18. Nearby Individual l Not Scored 19. Population Within 1 Mile b Not Scored 20. Targets (lines 18 + 19) b Not Scored Nearby Population Threat Score: 21. Nearby Population Threat (lines 14 x 17 x20) b Not Scored SOIL EXPOSURE PATHWAY SCORE 22. Soil Exposure Pathway Score" (Sg), lines [11 + 21] / 82,500, 100 100 subject to maximum of 100) aMaximum value applies to waste characteristics category. bMaximum value not applicable. cNo specific maximum value applies to factor. However, pathway score based solely on terrestrial sensitive environments is limited to maximum of 60. dDo not round to nearest integer. September 2007 6 ------- LIST OF ACRONYMS amsl above mean sea level AOC Area of contamination bgs Below ground surface cfs cubic feet per second DGLS Division of Geology and Land Survey EPA U.S. Environmental Protection Agency ft feet GIS Geographical Information System gpm gallons per minute HRS Hazard Ranking System HWQ Hazard Waste Quantity ICP Inductive coupled plasma ID Identification MCL Maximum Contaminant Level MCLG Maximum Contaminant Level Goal MDNR Missouri Department of Natural Resources Hg/L micrograms per liter MEGA Missouri Environmental Geology Atlas mg/kg milligrams per kilogram mg/L milligrams per liter ND not detected NWI National Wetland Inventory PA/SI Preliminary Assessment/Site Investigation pCi/L picoCurries per liter PPE Probably point of entry QAPP Quality Assurance Project Plan RSE Removal Site Evaluation SCDM Superfund Chemical Data Matrix SQL Sample Quantitation Limit TDL Target distance limit USFWS U.S. Fish and Wildlife Service USGS U.S. Geological Survey XRF x-ray fluorescence September 2007 7 ------- SITE DESCRIPTION The Washington County Mining District sites are composed of the releases of hazardous substances, mainly cadmium, lead, and barium, into the environment due to the over 300 years of mining activities. These activities have resulted in the contamination of ground water, surface water, and surface soil at concentrations often well above public health criteria. The mining district encompasses most of the central and northeastern part of Washington County and extends a short distance into Jefferson and St. Francois Counties in the vicinity of the Big River which flows along the north Eastern Edge of Washington County (Ref. 28, pp. 4-5). This district was one of the most productive barite producing areas in the world and produced over 11 million short tons of crude barite ore over an 86 year period from 1885 through 1970 (Ref. 28, p. 5). The Washington County area can be described as having steep ridges and narrow valleys, being the result of a major uplift event (Refs. 3; 17, p. 3). The event also created an extensive system of faults and fissures not necessarily conforming to the surficial topography locally (Refs. 3; 5, p. 28; 17, p. 3, 4; 18; 30, pp. 2-3). The upper formations in the mining district, the Potosi and Eminence, are dolomites that have become extensively karstic and have outcrops in many areas (Refs. 18; 21; 30, p. 3). Because of this, the surficial aquifers flow mainly through solution channels locally and regionally conform to the topography (Refs. 5, p. 28; 17, pp. 4-5; 30, pp. 2-3). Each valley may constitute individual aquifers in the surficial formations. Deeper formations may have ground water flow that conforms directionally, at least in part, to the fault system (Ref. 40, pp. 21,23). The ore is located mainly along fissures and faults in the dolomite layers. The barite and lead ores in Washington County consist of fragments and lumps of these minerals irregularly scattered within the residual clays at or near the ground surface (Ref. 28 p. 6; 30, pp. 1-2). It is theorized that the barite rich clays are accumulated insoluble materials derived from long periods of surface weathering and solution into particular horizons of the dolomite bedrock (Ref. 28, p. 6). The well developed fault and fracture system in the district acted as channel ways for ascending ore-bearing solutions. The solutions then migrated laterally into porous and permeable horizons in the upper Cambrian Potosi and Eminence Dolomites where barite and associated galena (lead) were deposited as runs. The soluble dolominates were eroded over time and replaced with clays leaving the ores in the clay. The ore enriched clays are often capped at the surface by thin layers of barren soil and loess (Ref. 28, p. 6). The earliest documented mining in Washington County was recorded in the early 18th century and focused on the collection and recovery of near surface lead ores (Ref. 30, p. 1). Early mining operations were conducted by farmers to supplement income and usually consisted of hand dug pits advanced into the residuum over the bedrock (Ref. 30, pp. 1-2). Mining for barite (the ore from which barium is derived) did not occur until after the civil war when barium became economically valuable as a white pigment in paint (Ref. 30, p. 1). In the early 20th century, several thousand people mined barite in Washington County. In 1926, barite mining boomed in Washington County when the mineral was discovered to be useful as a weighting agent in oil drilling mud. Mechanized strip mining did not occur to a great extent until 1924 (Ref. 30, p. 3; 28, p. 7). By the mid 1980s, production started to decline in Washington County due to competition from Nevada and overseas operations (Ref. 30, p. 1). EPA Region 7 and the State of Missouri Department of Natural Resources are investigating this district to identify impacted residential yards and wells (Ref. 22, pp. 8 and 12). Ongoing, time-critical removal actions are being conducted at properties where lead in soil or ground water exceeds defined action levels (Ref. 22, p. 16). To aid in the management of data and available resources, the barite has been split into September 2007 8 ------- three areas named Potosi, Richwoods, and Old Mines. These areas represent the highest density population areas and are also associated with the largest mining complexes. However, the areas between these areas are also associated with mining related contamination. Over 300 private and public supply wells out of 1,466 sampled in the District by 2006 have elevated lead and or barium levels above public health criteria. The number of people exposed to the contamination in their private and municipal drinking water wells is at least 1,438. The mining related ground water contamination from a regional perspective is ubiquitous throughout the area, but wells with high lead and barium levels can be found within a few hundred feet of wells with no significant contamination (Ref. 5, Figure 5). The pattern of ground water contamination, just as is the location of the mined ore deposits, is a function of the geology, topography, and ground water hydrology. Contamination has migrated from the mine processing areas into ground water via infiltration by rain on the waste piles and via discharge of the process waters, into surface water via erosion and direct deposition, and most likely into air via wind blown dust and smelter emissions. The tailing piles associated with the larger mining activities cover over 3,502 acres (Ref. 31, p. 10). The ore processing (washing) procedure utilized a tremendous amount of high-pressure water to separate the ore from the clays. Water requirements for a washer were as high as 5,000 gallons per minute (Ref. 28, p.7). In addition, over 910 residences have been built in former mine facility areas and have contaminated soils on their properties. The actual number, size, and location of all the mines and related waste sources in the Washington County area have not been determined but exceeds 1,400. The State of Missouri maintains a database known as the Inventory of Mines, Occurrences and Prospects (IMOP). As of 2006 in Washington County alone, 1,426 mines or prospects have been identified (Ref. 30, p. 4). The locations of these mines are presented on Reference 52. Figure 2 of Reference 30 shows the location of the mines in the northeast part of Washington County (Ref. 30, p. 8). For much of the ubiquitous ground water contamination in the Mining District, it is not possible to attribute the contamination to any single mining operation. Because of the extensive mining and large number of individual operations, most wells are downgradient of multiple mines (Figure 2 of this document and Ref. 52). Even for those wells that are relatively close to a major mining facility, the karst conditions and faults in the water bearing formations result in a maze of channels that make it impossible to document with certainty that the contamination is a result of releases from the nearby mine (Ref. 40, p. 19 and 21). For this reason, EPA has focused the site investigations and the HRS evaluations on the aquifers associated with the population centers in the mining district and not on individual mines. However, to best inform the public of the breadth of contamination, EPA has also evaluated the surface water and soil exposure pathways for some of these areas as part of the listing process. This package presents information pertaining to the area named Washington County Lead District- Richwoods. Within the Richwoods portion of the Washington County Mining District are hundreds of prospects and areas that have been subject to anthropogenic disturbance of the ore body (Figure 2 of this document and Ref. 52). At this time, it is impractical to characterize each potential source area. Therefore, this documentation record characterized some of the larger source areas within the district with maximized the HRS score. At this stage of the investigation it is generally not possible to attribute contamination documented at specific targets back to any of the source areas named in this documentation record. The many smaller source areas, not characterized below, may be contributing to contamination. The Richwoods area is located in Richwoods, Missouri, and is comprised of Study Area 10, which encompasses approximately 44.86 square miles in the northeastern portion of Washington County, Missouri (see Figure 1 of this document). The area is located approximately 12 miles north of Potosi, Missouri on West State Highway 47 and bisected by Highway H and A vertically (Figure 1 of this September 2007 9 ------- document; Ref. 3). Approximately 23,955 people reside in Washington County and 3,581 people live within a 4-mile radius of Area 10 (Refs. 4, p. 1; 5, p. 6; 24, pp. 1-6). Washington County is bordered on the north by Franklin County, on the east by Jefferson and St. Francois Counties, and on the south by Iron County, and on the west by Crawford County (Refs. 3; 16, p. 2). Analytical results and x-ray fluorescence (XRF) screening has confirmed significantly elevated levels of lead in ground water and soil. Because the area is so large, the extent of contaminated soils and the ground water contamination has not been fully characterized at this time. Figures 1 and 2 depict the general area and topographic layout of the Richwoods area, and the estimated extent of the site evaluated as part of this deliverable. Area 10 is primarily residential with limited commercial and industrial land use including an auto body shop, gas station, motor cross racing tracks, an active landfill, and others (Ref. 22, p. 6). Large tailings piles associated with past mining activities are visible in the aerial photograph (Ref. 49) and are annotated on the U.S. Geological Survey (USGS) 7.5-minute Quadrangle maps reviewed for the Richwoods area (Ref. 3). Tailings impoundment dams were commonly constructed for large commercial operations. No known underlying, engineered clay liners are present below any tailings areas at the site. Water-filled subsidence ponds, impoundments, and remnants of mine waste were visible during the 2005 EPA screening and sampling effort (Refs. 5, pp. 43-227; 22, pp. 27-52). Tailings ponds and residences with significantly elevated levels of barium and lead are also present throughout the site. Drainage in Area 10 is divided. The portion of the Richwoods area west of Highway 47 drains to the Little Indian Creek which eventually leads to the Meramec River. The eastern portion of the site drains to Turkey Creek or a tributary to Calico Creek and both eventually drain to the Big River. Soil and ground water in the area contains contaminants typically associated with historical mining districts, including barium and lead. Analytical results and XRF screening have confirmed significantly elevated levels of lead in ground water and soil. The historical ground water and soil sampling that occurred within the Richwoods Area 10 is shown on Figures 3 and 4. Lead has been detected above the EPA's action level of 15 parts per billion (ppb) in the surficial aquifer. However, the extent of contaminated soil and ground water has not been fully characterized at this time. Source areas of mining- related contaminants within the Richwoods area included contaminated soils, chat piles, tiff (barite) cuts, and mined pits. September 2007 10 ------- Legend ~ Cross-section of Hwy 47 and Hwy A/H |__| Richwoods study area n County boundary 0 0.5 1 N A Source: USGS Cyclone Hollow, MO 7.5 Minute Topo Quad, 1969 USGS Ebo, MO 7.5 Minute Topo Quad, 1972 USGS Old Mines, MO 7.5 Minute Topo Quad, 1970 USGS Richwoods, MO 7.5 Minute Topo Quad, 1970 Miles Washington County Lead District Richwoods Study Area Washington County, Missouri Figure 1 Site Location Map It TETRATECH EM INC. Date: 05/29/07 Drawn By: Bill Spiking Project No: I9004.L.06.0027.000 ------- Source Area 3 Source Area 4 Source Area 2 Source Area 5 Source Area 1 Washington County1 MDNR Washington County Mined Lands Mine not identified Desoto Mining Company Plants A & B | Desoto Mining Company Joe Smith Mine Desoto Mining Company Politte Mine Desoto Mining Company Twin NL Baroid Big 4 Mine Pfizer Kingston School Mine iFanklin Countyf -Jefferson County^ Source Area 6 Legend ~ Cross-section of Hwy 47 and Hwy A/H State highway HHl Tailings pond iocation 0 Richwoods study area " Jj County boundary ISource: Washington County, MO NAIP Aerial Imagery, 2005 Miles Washington County Lead District Richwoods Study Area Washington County, Missouri Figure 2 Source Area Site Location Map "It TETRA TECH EM INC. Drawn By: Bill Spiking Project No: I9004.L.06.0027.000 ------- eg en ~ Cross-section of Hwy 47 and Hwy A/H Q Historical ground water sample location — State highway q o 5 1 Richwoods study area r I County boundary N A Miles Source: Washington County, MO NAIP Aerial Imagery, 2005 Washington County Lead District Richwoods Study Area Washington County, Missouri Figure 3 Historical Ground Water Sample Location Map it TETRA TECH EM INC. Date: 05/29/07 Drawn By: Bill Spiking Project No: I9004.L.06.0027.000 ------- Legen ~ Cross-section of Hwy 47 and Hwy A/H 0 Historical soil sample location — State highway q o 5 1 Richwoods study area r I County boundary Miles Source: Washington County, MO NAIP Aerial Imagery, 2005 Washington County Lead District Richwoods Study Area Washington County, Missouri Figure 4 Historical Soil Sample Location Map it TETRA TECH EM INC. Date: 05/29/07 Drawn By: Bill Spiking Project No: I9004.L.06.0027.000 ------- REFERENCES Reference Number Description of the Reference U. S. Environmental Protection Agency (EPA). 1990. Hazard Ranking System, Final Rule, 40 CFR Part 300, Appendix A. December 14. Excerpt. 1 Page. 2 EPA. 2004. "Superfund Chemical Data Matrix." January. Excerpt. 9 Pages. U. S. Geological Survey (USGS). 1981. 7.5 minute series Topographic Quadrangle Maps of Missouri: 1981. Fletcher and Richwoods. Scale 1:24.000. 2 Sheets. U. S. Census Bureau. 2000. Washington County QuickFacts from the U.S. Census Bureau. On-line Address: http://quickfacts.census.gov/qfd/states/29/29221.html. Accessed on May 19, 2006. 2 Pages. Tetra Tech EM, Inc. (Tetra Tech). Preliminary Assessment/Site Inspection Report. Richwoods Area (Area 10), Washington County Lead District Missouri. April 4. 625 Pages. USGS. 2005. Lead Mining History. On-line address: http://mo.water.usgs.gov/mining/minehistory.htm. Accessed on May 19, 2006. 2 Pages. EPA Region 7. 2006. Transmittal of Sample Analysis Results for ASR #2937 for the Washington County Lead District - Richwoods Area. April 24. 138 Pages. EPA Region 7. 2006. Transmittal of Sample Analysis Results for ASR #2991 for the Washington County Lead District - Richwoods Area. May 4. 73 Pages. EPA Region 7. 2006. Transmittal of Sample Analysis Results for ASR #2959 for the Washington County Lead District - Richwoods Area. May 5. Ill Pages. Missouri Department of Natural Resources (MDNR). 1982. "Field Trip Guidebook to the St. 10 Francois Mountains and the Historic Bonne Teere Mine." Open File Report Series OFR-82-16-MR. Excerpt. 8 Pages. EPA Region 7. 2005. Transmittal of Sample Analysis Results for ASR #2690 for the Washington County Lead District Site. August 24. 148 Pages. EPA Region 7. 2005. Transmittal of Sample Analysis Results for ASR #2691 for the Washington County Lead District Site. September 1. 127 Pages. EPA Region 7. 2005. Transmittal of Sample Analysis Results for ASR #2730 for the Washington County Lead District Site. September 20. 94 Pages. Tetra Tech. 2006. Residential Property Screening Forms for 2006 Sampling Event. March 16-April 1. 322 Pages. Tetra Tech. 2005. Residential Property Screening Forms for 2005 sampling event. July 20-August 9. 290 Pages. United States Department of Agriculture. 2003. Soil Survey of Washington County, Missouri. November. Excerpt. 20 Pages. Stohr, C.J., St. Ivany, G„ and Williams, J.H. 1981. Geologic Aspects of Hazardous-Waste Isolation in Missouri. Excerpt. 8 Pages. 18 MDNR. 2007. Missouri Environmental Geology Atlas (MEGA). Excerpt. 2 Pages. 19 MDNR. 2003. Geologic Map of Missouri. Excerpt. 3 Pages Thompson, Thomas L. 1995. "The Stratigraphic Succession in Missouri" Original Preparation 20 (1961) coordinated by Wallace B. Howe. Edited (1961) by John W. Koenig. MDNR Volume 40 (Second Series) Revised. Excerpt. 12 Pages. MDNR. 2001. Bedrock Geologic Map of the Richwoods 7.5"Quandrangle, Franklin, Jefferson; Washington Counties, Missouri; Bedrock Geologic Map of the Old Mines 7.5' Quadrangle Washington County, Missouri; and Bedrock Geologic Map of the Fletcher 7.5' Quadrangle; Jefferson and Washington Counties, Missouri. July. 3 Sheets. Tetra Tech. 2006. Removal Site Evaluation Report. Washington County Lead District - Richwoods Area Site, Richwoods Missouri. June 15. 773 Pages. Unklesbay, A.G. and J.D. Vineyard. 1992. "Missouri Geology: Three Billion Years in Volcanoes, Seas, Sediments, and Erosion." Excerpt. 10 Pages. U. S. Census Bureau. ESRI, 20050401, U.S. Census Block Centroid Populations: ESRI® Data & Maps 2005. ESRI. Redlands. California, USA. 6 Pages. 1 2 3 4 5 6 7 8 9 1C 11 12 13 14 15 16 17 21 22 23 24 September 2007 15 ------- Reference Number Description of the Reference 26 27 28 29 Wharton, H.M., J.A. Martin, A.W. Rueff, C.E. Robertson, J.S. Wells, and E.B. Kisvarsanyi. 1969. 25 "Missouri Minerals - Resources, Production, and Forecasts." Missouri Geological Survey and Water Resources Special Publications Number 1. December. Excerpt. 7 Pages. Tetra Tech. 2007. Linear Regression of Dissolved and Total Barium and Lead Ground Water Results. 4 Pages. Winslow, Arthur. 1894. "Lead and Zinc Deposits Section 2 assisted by James D. Robertson." Missouri Geological Survey Volume VII. Excerpt. 4 Pages. Wharton, H.M. 1972. "Barite Ore Potential of Four Tailings Ponds in the Washington County Barite District Missouri." Missouri Geological Survey and Water Resources. Excerpt. 20 Pages. Litton, A, M.D. "A Preliminary Report of some of the Principal Mines in Franklin, Jefferson, Washington, St. Francois, and Madison Counties, Missouri. Excerpt. 29 Pages. Seeger, Cheryl, Missouri Department of Natural Resources to Kumud Pyakuryal, Tetra Tech EM 30 Inc. 2006. Memorandum regarding the Richwoods Area Sample Area Mining History and Geology. June 30. 8 Pages. Missouri Department of Natural Resources Division of Geology & Land Survey prepared in 31 cooperation with Division of Environmental Quality. Non-Coal Mined Lands (208 strategy) Data Date 1981. Washington County Mine Sites Table. Dated January 1983. 10 Pages. Missouri Department of Natural Resources Division of Geology & Land Survey prepared in cooperation with Division of Environmental Quality. Non-Coal Mined Lands (208 strategy) Data Date 1981. Presented on U.S. Geological Survey, Richwoods, Missouri Quadrangle, 7.5 Minute Series. Topographic Map. 1982. 1 Sheet. EPA Region 7. 2006. HRS Analysis Results Supplement for ASR #2690 for the Washington County Lead District - Richwoods Area. September 20. 13 Pages. EPA Region 7. 2006. HRS Analysis Results Supplement for ASR #2691 for the Washington County Lead District - Richwoods Area. September 20. 11 Pages. EPA Region 7. 2006. HRS Analysis Results Supplement for ASR #2730 for the Washington County Lead District - Richwoods Area. September 20. 9 Pages. EPA Region 7. 2006. HRS Analysis Results Supplement for ASR #2937 for the Washington County Lead District - Richwoods Area. September 20. 14 Pages. EPA Region 7. 2007. HRS Analysis Results Supplement for ASR #2959 for the Washington County Lead District - Richwoods Area. Janaury 19. 14 Pages. EPA Region 7. 2007. HRS Analysis Results Supplement for ASR #2991 for the Washington County Lead District - Richwoods Area. January 22. 9 Pages. EPA Region 7. 2006. Transmittal of Sample Analysis Results for ASR #3169 for the Washington County Lead District - Richwoods Area. October 4. 63 Pages. Miller, D. and J. Vandike. 1997. Ground water Resources of Missouri. Missouri State Water Plan Series Volume II. Excerpt. 28 Pages. Adamski, J.C., J.C. Peterson, D.A. Freiwald, and J.V. Davis. 1995. Environmental and Hydrologic 41 Setting of the Ozark Plateaus Study Unit, Arkansas, Kansas, Missouri, and Oklahoma. U.S. Geological Survey Water-Resources Investigations Report 94-4022. Excerpt. 52 Pages. MDNR Geological Survey and Resource Assessment Division. 2003. List of Certified Wells in 42 State of Missouri and Geological and Well Completion Information from Richwoods Certified 32 33 34 35 36 37 38 39 40 Wells. January 10th. 8 Pages. ^ EPA Region 7. 2006. HRS Analysis Results Supplement for ASR #3169 for the Washington County Lead District - Richwoods Area. October 16. 6 Pages. MDNR. 2006. Missouri Dam Report. On-line Address: 44 http://www.dnr.mo.gov/env/wrc/damsft/Crvstal Reports/damsafetv/Washington dams.pdf. Accessed October 18, 2006. 6 Pages. 45 Tetra Tech. 2006. Logbook for Richwoods HRS Sampling. August 26th-31st. 6 Pages. USGS. 2006. Surface-Water Annual Statistics for Missouri. Meramec River at Robertsville, MO. 46 On-line Address: http://nwis.waterdat.usgs.gov/mo/nwis/annual. Accessed October 24, 2006. 2 September 2007 16 ------- Reference Number Description of the Reference USGS. 2006. Surface-Water Annual Statistics for Missouri. Big River near Rich woods, MO. On- 47 line Address: http://nwis.waterdat.usgs.gov/mo/nwis/annual. Accessed on October 24, 2006. 3 Pages. U.S. Fish & Wildlife Service. 2006. National Wetlands Inventory. On-line Address: 48 www.fws.gov/nwi/. Accessed on October 30, 2006 and January 12, 2007. Last updated October 12, 2006. 10 Pages. National Agricultural Resources Conservation Service Aerial Photograph. 2005. Produced in 49 collaboration with the U.S. Department of Agriculture and the Natural Resources Conservation Service. 1 Page. Tetra Tech. 2007. Memorandum to the File Concerning the Analytical Data for the Richwoods, Washington County, Missouri FIRS Package. January 21. 1 Page. 51 Tetra Tech. 2006. Addendum to Quality Assurance Project Plan. August 7. 3 Pages. MDNR. 2005. Washington County Lead District Site Former Lead and Zinc Mining Inventory Project. May. 1 Sheet. EPA Region 7. 2007. Teleconference Form between Michelle Quick, NPL Coordinator and Lawrence Marchin, Project Officer Contract Laboratory Program on January 17. 1 Page. Tetra Tech. 2006. Quality Assurance Project Plan. Removal Site Evaluation and Removal Action for Washington County Lead District-Richwoods Site. February 9. 22 Pages. University of Missouri-Columbia. 2007. Center for Agricultural, Resources and Environmental 55 Systems. Map Identifying the 11-Digit Hydrologic Units in the Richwoods Area. On-line Address: http://www.cares.missouri.edu/. Accessed on January 21, 2007. 3 Pages. MDNR. 2001. Surficial Material Geologic Map of the Richwoods 7.5"Quandrangle; Franklin, Jefferson and Washington Counties, Missouri. July. 1 Sheet. Tetra Tech, Jenna Mead and Jim Vandike, MDNR Telephone Conversation Regarding the Missouri Well Construction Requirements. January 28, 2007. 1 Page. 58 EPA. 2003. Superfund Lead-Contaminated Residential Sites Handbook. August. 124 Pages. Tetra Tech. 2007. Oversized Figures for the Richwoods, Missouri HRS Documentation Record. 7 Figures. Orndorff, Randall. 2001. Geologic Framework of the Ozarks of South-Central Missouri- Contributions to a Conceptual Model of Karst. 7 Pages. MDNR Department of Geology and Land Survey. 2007. Scanned Files of Historical Strip Logs for 61 City of Potosi wells # 4 and # 5- Well Logs Numbers 19906 and 24128 received on Computer Disk from MDNR Water Resources Center. January. 10 pages. Elliot, William. 2007. Below Missouri Karst. On-line Address: http://mdc.mo/gov/conmag/2000/03/10.htm. Accessed May 29, 2007. 2 Pages. USGS. 1997. Ground Water Atlas of the United States Kansas, Missouri, and Nebraska. On-line Address: http://capp.water.usgs.gov/gwa/ch_d/index.htm. Accessed May 29, 2007. 11 Pages. Tetra Tech, Stephanie Luebbering, CHMM, Washington County Lead District Sites, Well Elevation Determination, Rich wood. August 21, 2007. 1 Page. Tetra Tech, Stephanie Luebbering, CHMM, Washington County Lead District Sites, Richwoods Site Sample Collection. August 22, 2007. 1 Page. 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 September 2007 17 ------- 2.2 SOURCE CHARACTERIZATION This section presents the known and characterized source areas associated with the site. Documented lead mining in the area dates back over 300 years and has been conducted for most of that period on a small scale by settlers or farmers to supplement income. It was not until the 20th century that mechanized mining in the County gave way to large scale surficial strip mining and processing and the need for constructed tailings ponds as a place to manage the wastes. In Washington County, 67 barite tailings ponds characterized as small, medium, and large were inventoried in 1970 (Ref. 28, pp. 5, 20). In 1981, 3,502 acres of tailings ponds were identified in Washington County (Ref. 31, p. 10). As discussed below, these waste ponds contain elevated concentrations of barium and lead. Lead mining has occurred in Washington County for hundreds of years (Refs. 6, pp. 1-2; 25, p. 4). The first written record of a lead mine in Missouri was made in 1700 by Father James Gravier, S.J., who noted a lead mining region in what is now Washington County. The first period of continuous lead mining in Missouri began in 1721, when Phillipe Francois Renault brought slave labor into the area north of Potosi in order to mine the surface and near-surface lead ores. Numerous small mines rapidly opened throughout northeastern Washington County, and produced as much as 1,500 pounds of ore per day (Ref. 30, p. 1). The first mines were mostly surface diggings advanced by manual labor with pick and shovel. In 1763, Mine a' Breton opened at what is now the City of Potosi. The mines throughout this Old Lead Belt area ranged from surface mines to mines that extended several hundred feet below the ground surface (Refs. 6, pp. 1-2; 10, p. 3). By the 1940s, lead reserves in the Old Lead Belt on the eastern side of the St. Francois Mountains were depleted and the exploration for new lead reserves moved to the western side of the Francois Mountains. Lead ore was discovered near Eminence in Shannon County in the late 1950s, and lead ores were discovered in the Viburnum Trend in the 1960s. The Viburnum Trend extends from the southwest corner of Washington County—about 20 to 25 miles southwest of Area 10—southward for about 25 miles (Refs. 6, pp. 1-2; 10, p. 3). Washington County is considered one extensive lead digging site because lead can be found throughout the entire county disturbed from its natural stage. The past success in lead mining in Washington County justified further and deeper exploration in the area (Ref. 29, p. 15). Economic ore bodies are not near the ground surface in this area, but are present at depths ranging from about 500 feet to 1,500 feet below ground surface (bgs) (Ref. 6, pp. 1-2). Northeastern Washington County is located in the barite mineralization district of Missouri. Barite mining began about 1850 and continued into the 1990s. From 1885 through 1971, Missouri was the leading mine producer of barite in the United States (Refs. 10, pp. 3, 8; 23, pp. 2-3; 25, p. 3; 28, p. 2). The barite deposits in the Washington County area are residual ores contained in red clays derived from weathered bedrock. Lateral distribution of the ore is irregular, occurring in discontinuous streaks that probably represent original concentrations along bedrock fractures or solution features (Ref. 10, pp. 3, 8; 27, p. 2). The well-developed fault and fracture system in Area 10 acted as channelways for the ascending ore-bearing solutions (Refs. 10, pp. 3, 8; 28, p. 6). Early miners tossed the barite aside into waste piles, as it originally had few uses. It became valuable after the Civil War, when it was used as a long-lasting white pigment. Barite mining boomed in 1926, when the mineral was discovered to be a useful weighting agent in oil drilling mud (Refs. 23, pp. 3-4; 30, p. 1). The production of barite in Washington County started to decline in 1985 because of competition in Nevada and overseas (Ref. 30, p. 1). Mineralization in the sample area is the result of a district-wide mineralizing event. Bodies of mined ore were often defined by availability of land, rather than by the extent of potentially economic ore. Cessation of mining also created artificial boundaries on the edges of mineralization. The scattered nature September 2007 18 ------- of the small mines found between large barite mines in the Washington County (Ref. 30, pp. 2, 8) is likely an artifact of the mining method, rather than due to discontinuities of the ore. The older mining required spacing of the pits and shafts to allow stability of the mines. In addition, in older mining operations most small individual pits and/or shafts were given individual names. Under later mining practices, the entire operation would have been given a single name. These practices create the illusion that there were numerous small ore bodies present during the early days of mining in the district (Ref. 30, p. 2). In 1972 a report was published by the Missouri Geological Survey & Water Resources which evaluated the barite ore potential of tailings ponds in Washington County (Ref. 28). The intent of the study was to quantify the amount of barite ore in the tailings ponds to determine if it is economically feasible to recover the ore using modern separation techniques (Ref. 28, pp. 2-3). The report summarized that there are large barite reserves present in the district tailings ponds (Ref. 28, pp. 3, 18). As part of the 1972 study, a total of 865 samples were collected and assayed from 185 boreholes collected from four representative tailings ponds (Ref. 28, pp. 10, 12). The average amount of barite in the tailing that was determined for district estimates was 5 percent (Ref. 285, p. 18). Quantitative analysis of low grade composite samples from the four tailings ponds tested indicated trace amounts of lead (Ref. 28, p. 19). This section presents only the tailings ponds in the Richwoods study area where environmental samples were collected in 2006 and analyzed by the US EPA Region 7 laboratory. Listed sources described below consist only of large tailings piles associated with large mechanized mining operations. These piles are presented by the study area defined by EPA Region 7. September 2007 19 ------- 2.2.1 SOURCE IDENTIFICATION Name of source: Desoto Mining Company Politte Mine South Tailings Pond Number of source: 1 Source Type: Tailings Pile Description and Location of Source (with reference to a map of the area): This tailings pile is associated with a former barite mine has been assigned a site number of 221-017 by the MDNR, DGLS (Refs. 31, p. 4; 32). This source is evaluated as source type "pile" because it was designed and used as a disposal site for tailings processed by washer plants (Ref. 28, pp. 7-9). These disposal ponds allowed the tailings to dewater. There is no evidence that they were constructed to treat water (Refs. 22, p. 3; 31, p. 4). This source is shown on the Richwoods, Missouri Quadrangles (Figures 2 and 5 of this document; Refs. 3; 32) in the eastern half of Section 32 (projected) of Township 40 north, Range 2 east (Ref. 59, Figure 11; 3; 31, p. 4; 32). Figure 5 on page 37 of this document presents an aerial photograph of the tailings pile with overlays showing the locations of samples collected from the pile as well as the boundaries of the pile defined by the Missouri IMOP database. Features associated with the tailings pile were mapped by the Missouri DGLS and Department of Environmental Quality in the early 1980s as part of a project referred to as the 208 project. The 208 project was completed in 1982, and it delineated areas of non-coal mined lands, tailings ponds and plant areas. These maps were derived from topographic maps, orthophoto quadrangles and personal communications. The maps were digitized heads-up in GIS software, using the topographic base as a guide. While improving the coverage over that derived from the topographic maps, these maps also pre- dated cessation of barite mining in Washington County (Ref. 30, p. 5). IMOP identified source 1 as being 62 acres of tailings pond covered by water, swampy intermittent water, and trees (Figure 5 of this document; Refs. 31, p. 4; 32). According to the Missouri Dam Report for Washington County, the tailings pond described above is contained by a dam known as the Little Indian Creek Dam that was completed in 1972. The dam is 58 feet tall and 1,680 feet long. The dam's identification number is MO30718, and its permit number is R-067 (Ref. 44, p. 3). The tailing piles associated with barite mines were designed to receive the overflow from the log washers and jig that separated the barite from the waste gravel. The overflows included waste mud and sand and two-thirds of the barite lost during the mining process was typically discharged into tailing ponds with the slimes (Ref. 28, pp. 7-9). This tailing pile is no longer actively used in the mining process, and no known underlying, engineered clay liner is present below this tailings area (Ref. 22, p. 3; 30, p. 1). 2.2.2 HAZARDOUS SUBSTANCES ASSOCIATED WITH THE SOURCE EPA conducted additional sampling in August 2006 to identify source areas located in the Richwoods area. In situ readings were collected with the XRF for lead concentrations to help delineate the source areas of former tailing piles (Ref. 50, p. 1; 39). The source samples only include samples collected from the former tailings ponds within the mining complexes as shown on Figure 5 of this document. Analytical results and XRF readings have confirmed significantly elevated levels of barium and lead in this source (Ref. 39, pp. 5-12, 19-61). The XRF data collected is not presented because it was not used in the HRS scoring; only the laboratory confirmatory samples are documented below. September 2007 20 ------- Source Samples: Waste samples from the tailings pond were collected in August 2006 under ASR 3169 and were analyzed for arsenic, barium, cadmium and lead (Figure 5; Refs. 39; 59, Figure 11). Analysis of the tailings samples was conducted by the U.S. EPA Region 7 laboratory in accordance to the site specific QAPP (Refs. 39, p. 5; 51; 65). Sample ID Sample Type Date Hazardous Substance Hazardous Substance Concentration (mg/kg) Sample Quantitation Limit* (mg/kg) Reference 3169-18 tailings 8/30/06 Barium 5,990 49.0 Refs. 39, pp. 3, 5-6, 11,38, 63; 43, p. 3 Lead 1,740 1.23 3169-19 tailings 8/30/06 Barium 5,310 29.5 Refs. 39, pp. 3, 5-6, 12, 39, 63; 43, p. 3 Lead 445 1.48 Notes: * The SQLs provided in this table are referred to as reporting limits in Reference 43. They are the laboratory's reporting limit (also known as the method detection limit - see the method for more details) for that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. ID Identification mg/kg milligrams per kilogram 2.2.3 HAZARDOUS SUBSTANCES AVAILABLE TO A PATHWAY Containment Description Containment Factor Value Reference Gas release to air: Not Scored NS NS Particulate release to air: Not Scored NS NS Release to ground water: Source 1 has no liner, nor does it have a maintained engineered cover or run on and/or run off control system. In addition, the source also lacks a leachate collection system. The 208 report indicated the source is partially covered in water, trees, and grasses. 10 Ref. 1, Table 3-2; 22, p. 3; 31, p. 4 Release via overland migration and/or flood: Source 1 has no maintained engineered cover or run on and/or run off control system. The 208 report indicated the source is partially covered in water, trees, and grasses. 10 Refs. 1, Table 4- 2; 31, p. 4 September 2007 21 ------- 2.2.4 HAZARDOUS WASTE QUANTITY 2.4.2.1.1. Hazardous Constituent Quantity (Tier A) The information available is not sufficient to adequately determine Tier A, as required in Section 2.4.2.1.1 of the HRS. As a result, the evaluation of Hazardous Waste Quantity proceeds to evaluate Tier B, hazardous wastestream quantity (Ref. 1, Section 2.4.2.1.1). 2.4.2.1.2. Hazardous Wastestream Quantity (Tier B) The information available is not sufficient to adequately determine Tier B, as required in Section 2.4.2.1.2 of the HRS. As a result, the evaluation of Hazardous Waste Quantity proceeds to evaluate Tier C, volume (Ref. 1, Section 2.4.2.1.2). 2.4.2.1.3. Volume (Tier C) The information available is not sufficient to adequately determine Tier C, as required in Section 2.4.2.1.3 of the HRS. Assign the source a value of 0 for the volume measure and proceed to evaluate Tier D, area (Ref. 1, Section 2.4.2.1.3). 2.4.2.1.4. Area (Tier D) Description According to IMOP the source 1 tailing pond covers 62 acres (Figure 5 of this document). According to the 208 project the tailings pond consists of water, swampy intermittent water, and trees (Refs. 31, p. 4; 32). An acre is equivalent to 43,560 square feet (ft2). The approximate size of the tailing pile is 2,700,720 ft2 (62 times 43,560 ft2). Source Type Area Units References Pile 2,700,720 Square feet Figure 5 of this document; Ref. 32 Sum (ft2): 2,700,720 Equation for Assigning Value (Ref. 1, Table 2-5): A/13 Area Assigned Value: 207,747.7 2.4.2.1.5. Source Hazardous Waste Quantity Value Highest assigned value assigned from Table 2-5: 207,747.7 September 2007 22 ------- 2.2.1 SOURCE IDENTIFICATION Name of source: Desoto Mining Company Politte Mine North Tailings Pond Number of source: 2 Source Type: Tailings Pile Description and Location of Source (with reference to a map of the area): This tailings pile is associated with a former barite mine has been assigned a site number of 221-017 by the MDNR, DGLS (Refs. 31, p. 4; 32). This source is evaluated as source type "pile" because it was designed and used as a disposal site for tailings processed by washer plants (Ref. 28, pp. 7-9). These disposal ponds allowed the tailings to dewater. There is no evidence that they were constructed to treat water (Refs. 22, p. 3; 31, p. 4). This source is shown on the Richwoods, Missouri Quadrangles (Refs. 3; 32) in the western half of Section 33 (projected) of Township 40 north, Range 2 east, and the north half of Section 4 (projected) of Township 39 north, Range 2 East (Ref. 59, Figure 11; 3; 31, p. 4; 32). Figure 6 on page 38 of this document presents an aerial photograph of the tailings pile with overlays showing the locations of samples collected from the pile as well as the boundaries of the pile defined by the Missouri IMOP database. Features associated with the tailings pile were mapped by the Missouri DGLS and Department of Environmental Quality in the early 1980s as part of a project referred to as the 208 project. The 208 project was completed in 1982, and it delineated areas of non-coal mined lands, tailings ponds and plant areas. These maps were derived from topographic maps, orthophoto quadrangles and personal communications. The maps were digitized heads-up in GIS software, using the topographic base as a guide. While improving the coverage over that derived from the topographic maps, these maps also pre- dated cessation of barite mining in Washington County (Ref. 30, p. 5). IMOP identified source 2 as being 28 acres of tailings pond covered by water, swampy intermittent water, and trees (Figure 6 of this document; Refs. 31, p. 4; 32). According to the Missouri Dam Report for Washington County, the tailings pond described above is contained by a dam known as the Heimos Lake Dam that was completed in 1955. The dam is 37 feet tall and 1,350 feet long. The dam's identification number is MO30999 (Ref. 44, p. 3). The tailing piles associated with barite mines were designed to receive the overflow from the log washers and jig that separated the barite from the waste gravel. The overflows included waste mud and sand and two-thirds of the barite lost during the mining process was typically discharged into tailing ponds with the slimes (Ref. 28, pp. 7-9). This tailing pile is no longer actively used in the mining process, and no known underlying, engineered clay liner is present below this tailings area (Ref. 22, p. 3; 30, p. 1). 2.2.2 HAZARDOUS SUBSTANCES ASSOCIATED WITH THE SOURCE EPA conducted additional sampling in August 2006 to identify source areas located in the Richwoods area. In situ readings were collected with the XRF for lead concentrations to help delineate the source areas of former tailing piles (Refs. 39; 50, p. 1). The source samples only include samples collected from the former tailings ponds within the mining complexes as shown on Figure 6 of this document. Analytical results and XRF readings have confirmed significantly elevated levels of barium and lead in the source (Ref. 39, pp. 5-8). The XRF data collected is not presented because it was not used in the HRS scoring; only the laboratory confirmatory samples are documented below. Source Samples: Waste samples from the tailings pond were collected in August 2006 under ASR 3169 and were analyzed for arsenic, barium, cadmium and lead (Figure 6; Refs. 39; 59, Figure 11). Analysis of the tailings samples was conducted by the U.S. EPA Region 7 laboratory in accordance to the site specific QAPP (Refs. 39, p. 5; 51; 65). September 2007 23 ------- Sample ID Sample Type Date Hazardous Substance Hazardous Substance Concentration (mg/kg) Sample Quantitation Limit* (mg/kg) Reference 3169-5 tailings 8/28/06 Barium 6,860 71.3 Refs. 39, pp. 3, 5-6, 8, 23, 63; 43, p. 1 Lead 4,610 1.19 3169-6 tailing 8/28/06 Barium 8,100 87.1 Refs. 39, pp. 3, 5-6, 8, 24, 63; 43, p. 1 Lead 1,160 1.45 Notes: * The SQLs provided in this table are referred to as reporting limits in Reference 43. They are the laboratory's reporting limit (also known as the method detection limit - see the method for more details) for that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. ID Identification mg/kg milligrams per kilogram 2.2.3 HAZARDOUS SUBSTANCES AVAILABLE TO A PATHWAY Containment Description Containment Factor Value Reference Gas release to air: Not Scored NS NS Particulate release to air: Not Scored NS NS Release to ground water: Source 2 has no liner, nor does it have a maintained engineered cover or run on and/or run off control system. In addition, the source also lacks a leachate collection system. The 208 report indicated the source is partially covered in water, trees, and grasses. 10 Ref. 1, Table 3-2; 22, p. 3; 31, p. 4 Release via overland migration and/or flood: Source 2 has no maintained engineered cover or run on and/or run off control system. The 208 report indicated the source is partially covered in water, trees, and grasses. 10 Refs. 1, Table 4- 2; 31, p. 4 September 2007 24 ------- 2.2.4 HAZARDOUS WASTE QUANTITY 2.4.2.1.1. Hazardous Constituent Quantity (Tier A) The information available is not sufficient to adequately determine Tier A, as required in Section 2.4.2.1.1 of the HRS. As a result, the evaluation of Hazardous Waste Quantity proceeds to evaluate Tier B, hazardous wastestream quantity (Ref. 1, Section 2.4.2.1.1). 2.4.2.1.2. Hazardous Wastestream Quantity (Tier B) The information available is not sufficient to adequately determine Tier B, as required in Section 2.4.2.1.2 of the HRS. As a result, the evaluation of Hazardous Waste Quantity proceeds to evaluate Tier C, volume (Ref. 1, Section 2.4.2.1.2). 2.4.2.1.3. Volume (Tier C) The information available is not sufficient to adequately determine Tier C, as required in Section 2.4.2.1.3 of the HRS. Assign the source a value of 0 for the volume measure and proceed to evaluate Tier D, area (Ref. 1, Section 2.4.2.1.3). 2.4.2.1.4. Area (Tier D) Description According to IMOP the source 2 tailing pond covers 28 acres (Figure 6 of this document). According to the 208 project the tailings pond consists of water, swampy intermittent water, and trees (Refs. 31, p. 4; 32). An acre is equivalent to 43,560 square feet (ft2). The approximate size of the tailing pile is 1,219,680 ft2 (28 times 43,560 ft2). Source Type Area Units References Pile 1,219,680 Square feet Figure 6 of this document; Ref. 32 Sum (ft2): 1,219,680 Equation for Assigning Value (Ref. 1, Table 2-5): A/13 Area Assigned Value: 93,821.5 2.4.2.1.5. Source Hazardous Waste Quantity Value Highest assigned value assigned from Table 2-5: 93,821.5 September 2007 25 ------- 2.2.1. SOURCE IDENTIFICATION Name of source: Desoto Mining Company Plants A & B (Agers) Northwest Number of source: 3 Tailings Pond Source Type: Tailings Pile Description and Location of Source (with reference to a map of the area): This tailings pile is associated with a former barite mine has been assigned a site number of 221-021 by the MDNR, DGLS (Refs. 31, p. 5; 32). This source is evaluated as source type "pile" because it was designed and used as a disposal site for tailings processed by washer plants (Ref. 28, pp. 7-9). These disposal ponds allowed the tailings to dewater. There is no evidence that they were constructed to treat water (Refs. 22, p. 3; 31, p. 5). This source is shown on the Richwoods, Missouri Quadrangle (Refs. 3; 32) in Section 28 (projected) of Township 40 north, Range 2 east (Ref. 59, Figure 11; 3; 31, p. 5; 32). Figure 7 on page 39 of this document presents an aerial photograph of the tailings pile with overlays showing the locations of samples collected from the pile as well as the boundaries of the pile defined by the Missouri IMOP database. Features associated with the tailings pile were mapped by the Missouri DGLS and Department of Environmental Quality in the early 1980s as part of a project referred to as the 208 project. The 208 project was completed in 1982, and it delineated areas of non-coal mined lands, tailings ponds and plant areas. These maps were derived from topographic maps, orthophoto quadrangles and personal communications. The maps were digitized heads-up in GIS software, using the topographic base as a guide. While improving the coverage over that derived from the topographic maps, these maps also pre- dated cessation of barite mining in Washington County (Ref. 30, p. 5). IMOP identified source 3 as being 53.8 acres of tailings pond covered by swampy intermittent water and dry and barren land (Figure 7 of this document; Refs. 31, p. 5; 32). According to the Missouri Dam Report for Washington County, the tailings pond described above is contained by a dam known as Desoto Pit and Plant B Dam that was completed in 1980. The dam is 54 feet tall and 1,360 feet long. The dam's identification number is MO30469 (Ref. 44, p. 2). The tailing piles associated with barite mines were designed to receive the overflow from the log washers and jig that separated the barite from the waste gravel. The overflows included waste mud and sand and two-thirds of the barite lost during the mining process was typically discharged into tailing ponds with the slimes (Ref. 28, pp. 7-9). This tailing pile is no longer actively used in the mining process, and no known underlying, engineered clay liner is present below this tailings area (Ref. 22, p. 3; 30, p. 1). 2.2.2 HAZARDOUS SUBSTANCES ASSOCIATED WITH THE SOURCE EPA conducted additional sampling in August 2006 to identify source areas located in the Richwoods area. In situ readings were collected with the XRF for lead concentrations to help delineate the source areas of former tailing piles (Refs. 39; 50, p. 1). The source samples only include samples collected from the former tailings ponds within the mining complexes as shown on Figure 7 of this document. Analytical results and XRF readings have confirmed significantly elevated levels of barium and lead in the source (Ref. 39, pp. 5-12, 19-61). The XRF data collected is not presented because it was not used in the HRS scoring; only the laboratory confirmatory samples are documented below. Source Samples: Waste samples from the tailings pond were collected in August 2006 under ASR 3169 and were analyzed for arsenic, barium, cadmium and lead (Figure 7; Refs. 39; 59, Figure 11). Analysis of the tailings September 2007 26 ------- samples was conducted by the U.S. EPA Region 7 laboratory in accordance to the site specific QAPP (Refs. 39, p. 5; 51; 65). Sample ID Sample Type Date Hazardous Substance Hazardous Substance Concentration (mg/kg) Sample Quantitation Limit* (mg/kg) Reference 3169-22 tailings 8/31/06 Barium 5,430 48 Refs. 39, pp. 3, 5-6, 12, 42, 63; 43, pp. 3-4 Lead 632 1.2 Notes: * The SQL provided in this table is referred to as the reporting limit in Reference 43. It is the laboratory's reporting limit (also known as the method detection limit - see the method for more details) for that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. ID Identification mg/kg milligrams per kilogram 2.2.3 HAZARDOUS SUBSTANCES AVAILABLE TO A PATHWAY Containment Description Containment Factor Value Reference Gas release to air: Not Scored NS NS Particulate release to air: Not Scored NS NS Release to ground water: Source 3 has no liner, nor does it have a maintained engineered cover or run on and/or run off control system. In addition, the source also lacks a leachate collection system. The 208 report indicated the source is partially covered in water, trees, grassy, or swampy. 10 Ref. 1, Table 3-2; 22, p. 3; 31, p. 5 Release via overland migration and/or flood: Source 3 has no maintained engineered cover or run on and/or run off control system. The 208 report indicated the source is partially covered in water, trees, grassy, or swampy. 10 Refs. 1, Table 4- 2; 31, p. 5 September 2007 27 ------- 2.2.4 HAZARDOUS WASTE QUANTITY 2.4.2.1.1. Hazardous Constituent Quantity (Tier A) The information available is not sufficient to adequately determine Tier A, as required in Section 2.4.2.1.1 of the HRS. As a result, the evaluation of Hazardous Waste Quantity proceeds to evaluate Tier B, hazardous wastestream quantity (Ref. 1, Section 2.4.2.1.1). 2.4.2.1.2. Hazardous Wastestream Quantity (Tier B) The information available is not sufficient to adequately determine Tier B, as required in Section 2.4.2.1.2 of the HRS. As a result, the evaluation of Hazardous Waste Quantity proceeds to evaluate Tier C, volume (Ref. 1, Section 2.4.2.1.2). 2.4.2.1.3. Volume (Tier C) The information available is not sufficient to adequately determine Tier C, as required in Section 2.4.2.1.3 of the HRS. Assign the source a value of 0 for the volume measure and proceed to evaluate Tier D, area (Ref. 1, Section 2.4.2.1.3). 2.4.2.1.4. Area (Tier D) Description According to IMOP the source 3 tailing pond covers 53.8 acres (Figure 7 of this document). According to the 208 project the tailings pond consists of swampy intermittent water and dry and barren land (Refs. 31, p. 5; 32). An acre is equivalent to 43,560 square feet (ft2). The approximate size of the tailing pile is 2,343,528 ft2 (53.8 times 43,560 ft2). Source Type Area Units References Pile 2,343,528 Square feet Figure 7 of this document; Ref. 32 Sum (ft2): 2,343,528 Equation for Assigning Value (Ref. 1, Table 2-5): A/13 Area Assigned Value: 180,271.4 2.4.2.1.5. Source Hazardous Waste Quantity Value Highest assigned value assigned from Table 2-5: 180,271.4 September 2007 28 ------- 2.2.1. SOURCE IDENTIFICATION Name of source: Desoto Mining Company Plants A & B (Agers) Central Number of source: 4 Tailings Pond Source Type: Tailings Pile Description and Location of Source (with reference to a map of the area): This tailings pile is associated with a former barite mine has been assigned a site number of 221-021 by the MDNR, DGLS (Refs. 31, p. 5; 32). This source is evaluated as source type "pile" because it was designed and used as a disposal site for tailings processed by washer plants (Ref. 28, pp. 7-9). These disposal ponds allowed the tailings to dewater. There is no evidence that they were constructed to treat water (Refs. 22, p. 3; 31, p. 5). This source is shown on the Richwoods, Missouri Quadrangle (Refs. 3; 32) in Sections 27 and 28 (projected) of Township 40 north, Range 2 east (Ref. 59, Figure 11; 3; 31, p. 5; 32). Figure 8 on page 40 of this document presents an aerial photograph of the tailings pile with overlays showing the locations of samples collected from the pile as well as the boundaries of the pile defined by the Missouri IMOP database. Features associated with the tailings pile were mapped by the Missouri DGLS and Department of Environmental Quality in the early 1980s as part of a project referred to as the 208 project. The 208 project was completed in 1982, and it delineated areas of non-coal mined lands, tailings ponds and plant areas. These maps were derived from topographic maps, orthophoto quadrangles and personal communications. The maps were digitized heads-up in GIS software, using the topographic base as a guide. While improving the coverage over that derived from the topographic maps, these maps also pre- dated cessation of barite mining in Washington County (Ref. 30, p. 5). IMOP identified source 4 as being 70 acres of tailings pond covered by water and trees (Figure 8 of this document; Refs. 31, p. 5; 32). According to the Missouri Dam Report for Washington County, the tailings pond described above is contained by a dam known as Richwoods Mine B Dam that was completed in 1943. The dam is 48 feet tall and 3,700 feet long. The dam's identification number is MO31404 (Ref. 44, p. 5). The tailing piles associated with barite mines were designed to receive the overflow from the log washers and jig that separated the barite from the waste gravel. The overflows included waste mud and sand and two-thirds of the barite lost during the mining process was typically discharged into tailing ponds with the slimes (Ref. 28, pp. 7-9). This tailing pile is no longer actively used in the mining process, and no known underlying, engineered clay liner is present below this tailings area (Ref. 22, p. 3; 30, p. 1). The Missouri Geological Survey and Water Resources evaluated four large tailing ponds including this tailings pond from the De Soto mine that was formerly owned by Baroid Division, N L Industries (Baroid). Baroid operated the mine and washer plant that utilized the tailings pond from February 1945 to April 1957. It is estimated that approximately five million tons of ore were mined and treated in the washer which yielded approximately 310,000 short tons of barite concentrations (Ref. 28, pp. 5, 13-14, 17-18,20). According to the Missouri Geological Survey, Cambrian Potosi Dolomite was exposed in several mine cuts in the vicinity of this tailings pond. It was assumed that the Cambrian Potosi Dolomite was the main source of ore from this area. In addition, quartz druse was identified in the waste gravels. The surface area of this pond was measured to be 35 acres, and impounds a valley that drains eastward into Ditch Creek. At the time of the Missouri Geological Survey investigation the 9-acre depression in the southwest corner of the pond was covered with water most of the year. The 13-acre section directly east was intermittently flooded. The drilling conducted during the investigation was confined to the 13-acre dry section of the pond on the north side near the old washer site. The sampling conducted revealed that the total tonnage of tailings in the pond likely exceeds one million tons (Ref. 28, pp. 13-14). September 2007 29 ------- 2.2.2 HAZARDOUS SUBSTANCES ASSOCIATED WITH THE SOURCE In 1972, a report was published by the Missouri Geological Survey & Water Resources which evaluated the barite ore potential of tailings ponds in Washington County, including those in the Richwoods area. The intent of the study was to quantify the amount of barite ore in the tailings ponds to determine if it is economically feasible to recover the ore using modern separation techniques (Ref. 28, pp 1-3). The report summarized that there are large barite reserves present in the district tailings ponds (Ref. 28, pp. 2, 18). As part of the study, a total of 865 samples were collected and assayed from 185 boreholes collected from four representative tailings ponds (Ref. 28, pp. 10-12). The average amount of barite in the tailing that was determined for district estimates was 5 percent (Ref. 28, p. 18). Quantitative analysis of low grade composite samples from the four tailings ponds tested indicated trace amounts of lead (Ref. 28, p. 19). This 1972 investigation is being discussed because it documents barium and lead contamination associated with the tailings ponds in general throughout Washington County. EPA conducted additional sampling in August 2006 to identify source areas located in the Richwoods area. In situ readings were collected with the XRF for lead concentrations to help delineate the source areas of former tailing piles (Refs. 39; 50, p. 1). The source samples only include samples collected from the former tailings ponds within the mining complexes as shown on Figure 8 of this document. Analytical results and XRF readings have confirmed significantly elevated levels of barium and lead in the source (Ref. 39, pp. 5-9, 19-61). The XRF data collected is not presented because it was not used in the HRS scoring; only the laboratory confirmatory samples are documented below. Source Samples: Waste samples from the tailings pond were collected in August 2006 under ASR 3169 and were analyzed for arsenic, barium, cadmium and lead (Figure 8; Refs. 39; 59, Figure 11). Analysis of the tailings samples was conducted by the U.S. EPA Region 7 laboratory in accordance to the site specific QAPP (Refs. 39, p. 5; 51; 65). Sample ID Sample Type Date Hazardous Substance Hazardous Substance Concentration (mg/kg) Sample Quantitation Limit* (mg/kg) Reference 3169-9 tailings 8/28/06 Barium 5.190 28.6 Refs. 39, pp. 3, 5-6, 9, 27, 63; 43, p. 2 Lead 243 1.43 3169-10 tailings 8/28/06 Barium 10,300 84.5 Refs. 39, pp. 3, 5-6, 9, 28, 63; 43, p. 2 Lead 968 1.41 3169-11 tailings 8/28/06 Barium 5,700 71.2 Refs. 39, pp. 3, 5-6, 9, 29, 63; 43, p. 2 Lead 639 3.56 Notes: * The SQLs provided in this table are referred to as reporting limits in Reference 43. They are the laboratory's reporting limit (also known as the method detection limit - see the method for more details) for that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. ID Identification mg/kg milligrams per kilogram September 2007 30 ------- 2.2.3 HAZARDOUS SUBSTANCES AVAILABLE TO A PATHWAY Containment Description Containment Factor Value Reference Gas release to air: Not Scored NS NS Particulate release to air: Not Scored NS NS Release to ground water: Source 4 has no liner, nor does it have a maintained engineered cover or run on and/or run off control system. In addition, the source also lacks a leachate collection system. The 208 report indicated the source is partially covered in water, trees, grassy, or swampy. 10 Ref. 1, Table 3-2; 22, p. 3; 31, p. 5 Release via overland migration and/or flood: Source 4 has no maintained engineered cover or run on and/or run off control system. The 208 report indicated the source is partially covered in water, trees, grassy, or swampy. 10 Refs. 1, Table 4- 2; 31, p. 5 September 2007 31 ------- 2.2.4 HAZARDOUS WASTE QUANTITY 2.4.2.1.1. Hazardous Constituent Quantity (Tier A) The information available is not sufficient to adequately determine Tier A, as required in Section 2.4.2.1.1 of the HRS. As a result, the evaluation of Hazardous Waste Quantity proceeds to evaluate Tier B, hazardous wastestream quantity (Ref. 1, Section 2.4.2.1.1). 2.4.2.1.2. Hazardous Wastestream Quantity (Tier B) The information available is not sufficient to adequately determine Tier B, as required in Section 2.4.2.1.2 of the HRS. As a result, the evaluation of Hazardous Waste Quantity proceeds to evaluate Tier C, volume (Ref. 1, Section 2.4.2.1.2). 2.4.2.1.3. Volume (Tier C) The information available is not sufficient to adequately determine Tier C, as required in Section 2.4.2.1.3 of the HRS. Assign the source a value of 0 for the volume measure and proceed to evaluate Tier D, area (Ref. 1, Section 2.4.2.1.3). 2.4.2.1.4. Area (Tier D) Description According to IMOP the source 4 tailing pond covers 70 acres (Figure 8 of this document). According to the 208 project the tailings pond consists of water and trees (Refs. 31, p. 5; 32). An acre is equivalent to 43,560 square feet (ft2). The approximate size of the tailing pile is 3,049,200 ft2 (70 times 43,560 ft2). Source Type Area Units References Pile 3,049,200 Square feet Figure 8 of this document; Ref. 32 Sum (ft2): 3,049,200 Equation for Assigning Value (Ref. 1, Table 2-5): A/13 Area Assigned Value: 234,553.8 2.4.2.1.5. Source Hazardous Waste Quantity Value Highest assigned value assigned from Table 2-5: 234,553.8 September 2007 32 ------- 2.2.1. SOURCE IDENTIFICATION Name of source: Desoto Mining Company Plants A & B (Agers) South Number of source: 5 Tailings Pond Source Type: Tailings Pile Description and Location of Source (with reference to a map of the area): This tailings pile is associated with a former barite mine has been assigned a site number of 221-021 by the MDNR, DGLS (Refs. 31, p. 5; 32). This source is evaluated as source type "pile" because it was designed and used as a disposal site for tailings processed by washer plants (Ref. 28, p. 7-9). These disposal ponds allowed the tailings to dewater. There is no evidence that they were constructed to treat water (Refs. 22, p. 3; 31, p. 5). This source is shown on the Richwoods, Missouri Quadrangle (Refs. 3; 32)in the eastern half of Sections 33 and 34(projected) of Township 40 north, Range 2 east (Ref. 59, Figure 11; 3; 31, p. 5; 32). Figure 9 on page 41 of this document presents an aerial photograph of the tailings pile with overlays showing the locations of samples collected from the pile as well as the boundaries of the pile defined by the Missouri IMOP database. Features associated with the tailing pile were mapped by the Missouri DGLS and Department of Environmental Quality in the early 1980s as part of a project referred to as the 208 project. The 208 project was completed in 1982, and it delineated areas of non-coal mined lands, tailings ponds and plant areas. These maps were derived from topographic maps, orthophoto quadrangles and personal communications. The maps were digitized heads-up in GIS software, using the topographic base as a guide. While improving the coverage over that derived from the topographic maps, these maps also pre- dated cessation of barite mining in Washington County (Ref. 30, p. 5). IMOP identified source 5 as being 171.6 acres of tailings pond covered by water and trees (Figure 9 of this document; Refs. 31, p. 5; 32). According to the Missouri Dam Report for Washington County, the tailings pond described above is contained by a dam known as Desoto Mine Pit and Plant A Dam that was completed in 1980. The dam is 78 feet tall and 3,700 feet long. The dam's identification number is MO30468 (Ref. 44, p. 2). The tailing piles associated with barite mines were designed to receive the overflow from the log washers and jig that separated the barite from the waste gravel. The overflows included waste mud and sand and two-thirds of the barite lost during the mining process was typically discharged into tailing ponds with the slimes (Ref. 28, pp. 7-9). This tailing pile is no longer actively used in the mining process, and no known underlying, engineered clay liner is present below this tailings area (Ref. 22, p. 3; 30, p. 1). 2.2.2 HAZARDOUS SUBSTANCES ASSOCIATED WITH THE SOURCE EPA conducted additional sampling in August 2006 to identify source areas located in the Richwoods area. In situ readings were collected with the XRF for lead concentrations to help delineate the source areas of former tailing piles (Refs. 39; 50, p. 1). The source samples only include samples collected from the former tailings ponds within the mining complexes as shown on Figure 9 of this document. Analytical results and XRF readings have confirmed significantly elevated levels of barium and lead in the source (Ref. 39, pp. 5-13, 19-61). The XRF data collected is not presented because it was not used in the HRS scoring; only the laboratory confirmatory samples are documented below. Source Samples: Waste samples from the tailings pond were collected in August 2006 under ASR 3169 and were analyzed for arsenic, barium, cadmium and lead (Figure 9; Ref. 39; 59, Figure 11). Analysis of the tailings samples was conducted by the U.S. EPA Region 7 laboratory in accordance to the site specific QAPP (Refs. 39, p. 5; 51; 65). September 2007 33 ------- Sample ID Sample Type Date Hazardous Substance Hazardous Substance Concentration (mg/kg) Sample Quantitation Limit* (mg/kg) Reference 3169-12 tailings 8/30/06 Barium 7,880 62.4 Refs. 39, pp. 3, 5-6, 9, 30, 63; 43, p. 2 Lead 1,320 1.56 3169-13 tailings 8/30/06 Barium 8,480 74 Refs. 39, pp. 3, 5-6, 10,31,63; 43, p. 2 Lead 1,230 1.23 3169-16 tailings 8/30/06 Barium 7,910 74.3 Refs. 39, pp. 3, 5-6, 11,35, 63; 43, p. 3 Lead 409 1.24 3169-23 tailings 8/31/06 Barium 3,700 78.4 Refs. 39, pp. 3, 5-6, 13, 43, 62; 43, p. 4 Lead 1,070 3.92 Notes: * The SQLs provided in this table are referred to as reporting limits in Reference 43. They are the laboratory's reporting limit (also known as the method detection limit - see the method for more details) for that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. ID Identification mg/kg milligrams per kilogram 2.2.3 HAZARDOUS SUBSTANCES AVAILABLE TO A PATHWAY Containment Description Containment Factor Value Reference Gas release to air: Not Scored NS NS Particulate release to air: Not Scored NS NS Release to ground water: Source 5 has no liner, nor does it have a maintained engineered cover or run on and/or run off control system. In addition, the source also lacks a leachate collection system. The 208 report indicated the source is partially covered in water, trees, grassy, or swampy. 10 Ref. 1, Table 3-2; 22, p. 3; 31, p. 5 Release via overland migration and/or flood: Source 5 has no maintained engineered cover or run on and/or run off control system. The 208 report indicated the source is partially covered in water, trees, grassy, or swampy. 10 Refs. 1, Table 4- 2; 31, p. 5 2.2.4 HAZARDOUS WASTE QUANTITY 2.4.2.1.1. Hazardous Constituent Quantity (Tier A) The information available is not sufficient to adequately determine Tier A, as required in Section 2.4.2.1.1 of the HRS. As a result, the evaluation of Hazardous Waste Quantity proceeds to evaluate Tier B, hazardous wastestream quantity (Ref. 1, Section 2.4.2.1.1). September 2007 34 ------- 2.4.2.1.2. Hazardous Wastestream Quantity (Tier B) The information available is not sufficient to adequately determine Tier B, as required in Section 2.4.2.1.2 of the HRS. As a result, the evaluation of Hazardous Waste Quantity proceeds to evaluate Tier C, volume (Ref. 1, Section 2.4.2.1.2). 2.4.2.1.3. Volume (Tier C) The information available is not sufficient to adequately determine Tier C, as required in Section 2.4.2.1.3 of the HRS. Assign the source a value of 0 for the volume measure and proceed to evaluate Tier D, area (Ref. 1, Section 2.4.2.1.3). 2.4.2.1.4. Area (Tier D) Description According to IMOP the source 5 tailing pond covers 171.6 acres (Figure 9 of this document). According to the 208 project the tailings pond consists of water and trees (Refs. 31, p. 5; 32). An acre is equivalent to 43,560 square feet (ft2). The approximate size of the tailing pile is 7,474,896 ft2 (171.6 times 43,560 ft2). Source Type Area Units References Pile 7,474,896 Square feet Figure 9 of this document; Ref. 32 Sum (ft2): 7,474,896 Equation for Assigning Value (Ref. 1, Table 2-5): A/13 Area Assigned Value: 574,992 2.4.2.1.5. Source Hazardous Waste Quantity Value Highest assigned value assigned from Table 2-5: 574,992 September 2007 35 ------- 2.2.1 SOURCE IDENTIFICATION Name of source: N.L. Baroid Big 4 Mine East Tailing Pond Number of source: 6 Source Type: Tailings Pile Description and Location of Source (with reference to a map of the area): This tailings pile is associated with a former barite mine has been assigned a site number of 221-019 by the MDNR, DGLS (Refs. 31, p. 4; 32). This source is evaluated as source type "pile" because it was designed and used as a disposal site for tailings processed by washer plants (Ref. 28, pp. 7-9). These disposal ponds allowed the tailings to dewater. There is no evidence that they were constructed to treat water (Refs. 22, p. 3; 31, p. 4). This source is shown on the Richwoods, Missouri Quadrangle (Refs. 3; 32) in the eastern half of Section 34 (projected) of Township 40 north, Range 2 east (Ref. 59, Figure 11; 3; 31, p. 4; 32). Figure 10 on page 42 of this document presents an aerial photograph of the tailings pile with overlays showing the locations of samples collected from the pile as well as the boundaries of the pile defined by the Missouri IMOP database. Features associated with the area were mapped by the Missouri DGLS and department of Environmental Quality in the early 1980s as part of a project referred to as the 208 project. The 208 project was completed in 1982, and it delineated areas of non-coal mined lands, tailings ponds and plant areas. These maps were derived from topographic maps, orthophoto quadrangles and personal communications. The maps were digitized heads-up in GIS software, using the topographic base as a guide. While improving the coverage over that derived from the topographic maps, these maps also pre-dated cessation of barite mining in Washington County (Ref. 30, p. 5). IMOP identified source 6 as being 65.8 acres of tailings pond covered by swampy intermittent water (Figure 10 of this document; Refs. 31, p. 4; 32). According to the Missouri Dam Report for Washington County, the tailings pond described above is contained by a dam known as Big Four Mine Dam that was completed in 1978. The dam is 73 feet tall and 1,200 feet long. The dam's identification number is MO30729 (Ref. 44, p. 1). The tailing piles associated with barite mines were designed to receive the overflow from the log washers and jig that separated the barite from the waste gravel. The overflows included waste mud and sand and two-thirds of the barite lost during the mining process was typically discharged into tailing ponds with the slimes (Ref. 28, pp. 7-9). This tailing pile is no longer actively used in the mining process, and no known underlying, engineered clay liner is present below this tailings area (Ref. 22, p. 3; 30, p. 1). 2.2.2 HAZARDOUS SUBSTANCES ASSOCIATED WITH THE SOURCE EPA conducted additional sampling in August 2006 to identify source areas located in the Richwoods area. In situ readings were collected with the XRF for lead concentrations to help delineate the source areas of former tailing piles (Refs. 39; 50, p. 1). The source samples only include samples collected from the former tailings ponds within the mining complexes as shown on Figure 10 of this document. Analytical results and XRF readings have confirmed significantly elevated levels of barium and lead in the source (Ref. 39, pp. 5-13, 19-61). The XRF data collected is not presented because it was not used in the HRS scoring; only the laboratory confirmatory samples are documented below. Source Samples: Waste samples from the tailings pond were collected in August 2006 under ASR 3169 and were analyzed for arsenic, barium, cadmium and lead (Figure 10; Refs. 39; 59, Figure 11). Analysis of the tailings samples was conducted by the U.S. EPA Region 7 laboratory in accordance to the site specific QAPP (Refs. 39, p. 5; 51; 65). September 2007 36 ------- Sample ID Sample Type Date Hazardous Substance Hazardous Substance Concentration (mg/kg) Sample Quantitation Limit* (mg/kg) Reference 3169-26 tailings 8/31/06 Barium 5,830 58.3 Refs. 39, pp. 3, 5-6, 13, 46, 62; 43, p. 4 Lead 544 1.46 Notes: * The SQLs provided in this table are referred to as reporting limits in Reference 43. They are the laboratory's reporting limit (also known as the method detection limit - see the method for more details) for that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. ID Identification mg/kg milligrams per kilogram 2.2.3 HAZARDOUS SUBSTANCES AVAILABLE TO A PATHWAY Containment Description Containment Factor Value Reference Gas release to air: Not Scored NS NS Particulate release to air: Not Scored NS NS Release to ground water: Source 6 has no liner, nor does it have a maintained engineered cover or run on and/or run off control system. In addition, the source also lacks a leachate collection system. The 208 report indicated the source is partially covered in water, grasses, or swampy. 10 Ref. 1, Table 3-2; 22, p. 3; 31, p. 4 Release via overland migration and/or flood: Source 6 has no maintained engineered cover or run on and/or run off control system. The 208 report indicated the source is partially covered in water, grasses, or swampy. 10 Refs. 1, Table 4-2; 31, p. 4 September 2007 37 ------- 2.2.4 HAZARDOUS WASTE QUANTITY 2.4.2.1.1. Hazardous Constituent Quantity (Tier A) The information available is not sufficient to adequately determine Tier A, as required in Section 2.4.2.1.1 of the HRS. As a result, the evaluation of Hazardous Waste Quantity proceeds to evaluate Tier B, hazardous wastestream quantity (Ref. 1, Section 2.4.2.1.1). 2.4.2.1.2. Hazardous Wastestream Quantity (Tier B) The information available is not sufficient to adequately determine Tier B, as required in Section 2.4.2.1.2 of the HRS. As a result, the evaluation of Hazardous Waste Quantity proceeds to evaluate Tier C, volume (Ref. 1, Section 2.4.2.1.2). 2.4.2.1.3. Volume (Tier C) The information available is not sufficient to adequately determine Tier C, as required in Section 2.4.2.1.3 of the HRS. Assign the source a value of 0 for the volume measure and proceed to evaluate Tier D, area (Ref. 1, Section 2.4.2.1.3). 2.4.2.1.4. Area (Tier D) Description According to IMOP the source 6 tailing pond covers 65.8 acres (Figure 10 of this document). According to the 208 project the tailings pond consists of swampy intermittent water (Refs. 31, p. 4; 32). An acre is equivalent to 43,560 square feet (ft2). The approximate size of the tailing pile is 2,866,248 ft2 (65.8 times 43,560 ft2). Source Type Area Units References Pile 2,866,248 Square feet Figure 10 of this document; Ref. 32 Sum (ft2): 2,866,248 Equation for Assigning Value (Ref. 1, Table 2-5): A/13 Area Assigned Value: 220,480.6 2.4.2.1.5. Source Hazardous Waste Quantity Value Highest assigned value assigned from Table 2-5: 220,480.6 September 2007 38 ------- Insert Figure 5 September 2007 39 ------- Insert Figure 6 September 2007 40 ------- Insert Figure 7 September 2007 41 ------- Insert Figure 8 September 2007 42 ------- Insert Figure 9 September 2007 43 ------- Insert Figure 10 September 2007 44 ------- SUMMARY OF SOURCE DESCRIPTIONS Source No. Source Hazardous Waste Quantity Value Source Hazardous Constituent Quantity Complete? (Y/N) Containment Factor Value by Pathway Ground Water (GW) (Ref.l, Table 3-2) Surface Water (SW) Air Overland/flood (Ref. 1, Table 4-2) GW to SW (Ref. 1, Table 3-2) Gas (Ref. 1, Table 6-3) Particulate (Ref. 1, Table 6-9) 1 207,747.7 No 10 10 NS NS NS 2 93,821.5 No 10 10 NS NS NS 3 180,271.4 No 10 10 NS NS NS 4 234,553.8 No 10 10 NS NS NS 5 574,992 No 10 10 NS NS NS 6 220,480.6 No 10 10 NS NS NS Description of Other Possible Sources To date, very few of the tailing ponds in the Washington County barite district have been characterized by EPA Region 7. The focus of the removal site evaluations has been to evaluate whether any threats to human health or the environment exist because of possible impacts of past mining activities on surface soils, ground water, surface water, sediment, or interior dust (Ref 54, p. 13). Thus the focus of sampling activities has been at residential homes and not at the tailings ponds. In Washington County, 67 barite tailings ponds characterized as small, medium, and large were inventoried in 1970 (Ref. 28, pp. 5, 20). In 1981, 3,502 acres of tailings ponds were measured in Washington County (Ref. 31, p. 10). As discussed below, these waste ponds likely contain elevated concentrations of barium and lead. In 1972 a report was published by the Missouri Geological Survey & Water Resources which evaluated the barite ore potential of tailings ponds in Washington County (Ref. 28). The intent of the study was to quantify the amount of barite ore in the tailings ponds to determine if it is economically feasible to recover the ore using modern separation techniques (Ref. 28, pp 2-3). The report summarized that there are large barite reserves present in the district tailings ponds (Ref. 28, pp. 3, 18). As part of the 1972 study, a total of 865 samples were collected and assayed from 185 boreholes collected from four representative tailings ponds (Ref. 28, pp. 10, 12). The average amount of barite in the tailing that was determined for district estimates was 5 percent (Ref. 28, p. 18). Quantitative analysis of low grade composite samples from the four tailings ponds tested indicated trace amounts of lead (Ref. 28, p. 19). In the Richwoods area, a number of tailings piles have been identified but have not yet been sampled to characterize the hazardous constituents associated with them. These large former mining operations in the Richwoods area include the following: Site number 221-018 (Desoto Mining Company Joe Smith Mine) (Refs. 3; 32). This 75 acre complex includes 8 acres of area described as "tailings pond" (Refs. 3; 31, p. 4; 32). This mine is shown on Figure 2. Site number 221-021 (Desoto Mining Company Plants A & B (Agers) (Refs. 3; 32). This mining complex contains six additional tailings ponds that were not included as sources listed above. September 2007 45 ------- Site number 221-044 (Desoto Mining Company Twin Barite Plant) (Refs. 3; 32). This 142 acre complex includes 90 acres of area described as "tailings pond" (Refs. 3; 31, p. 9; 32). This mine is shown on Figure 2. Site number 221-019 (N.L. Baroid Big 4 Mine) (Refs. 3; 32). This mining complex contains one additional tailing pile located west of Source number 6 that was not included as a source above. In addition to the large operations described above, at one time Washington County was host to hundreds and possibly thousands of small mines that were worked by hand (Ref. 30, pp. 1-3, 8; 52). It is not known what impact these smaller diggings may have had on the environment. An additional source not included above but associated with the site is "contaminated soil." A major focus of the work accomplished to date at the site includes screening of soils at residential properties for lead and performing removal actions at homes where lead levels in the soil exceed the action level (Ref. 22, pp. 5, 16). The source of the elevated lead in the contaminated soils is not clear and may be a results of previous small hand-worked mines near the residential properties, imported contaminated soil used as fill, houses built on lands previously strip mined by commercial mining operations, airborne dispersion of contaminants from nearby haul roads, or runoff from mine process areas or tailings ponds. In some cases, homes were built near or are located on tailings ponds (Ref. 59, Figure 22). September 2007 46 ------- 3.0 GROUND WATER MIGRATION PATHWAY The Richwoods area is located in the Salem Plateau ground water province (Ref. 40, p. 6) of the Ozark Plateau Physiographic province (Ref. 17, p. 2). 3.0.1 GENERAL C ONSIDERATIONS Regional Geology Soils in the site area are dominantly tiff gravelly clay, having 1- to 20-percent slopes. Tiff soils are well drained, very rocky clays, formed on hills in clayey residuum that weathered from dolomite. Numerous areas of mine tailings are mapped within the tiff gravelly clays. Silt loams and gravelly silt loams of the Gravois, Glensted, and Goss Associations are generally located in the un-mined areas along the edges of the Richwoods area. Gravois soils formed on fine-silty loess overlying residuum formed from dolomite. Glensted soils formed from clayey loess over residuum weathered from cherty dolomites and shales. Goss soils—generally found along the southern edge of the Richwoods area—are formed from gravelly colluvium over residuum weathered from cherty dolomite. Sonsac gravelly silt loams and Alred-Sonnsac are generally located along the northern and western edges of the Richwoods study area (Ref. 16, pp. 9, 13-15, 17, 20). The soil overburden in the Richwoods area typically ranges from none to about 20 feet (Ref. 18). Bedrock Units The table below presents a summary of the geologic units and rock thicknesses present in the Richwoods Area. Age Geologic Unit Average Thickness (Feet) Occurrence of Unit Ordovician Roubidoux Formation 200 Present on ridge tops in the western portion of the study area. Not present at source areas in Richwoods Florst Block. Gasconade Dolomite 240 Present in the northwestern and southwestern portions of the study area. Not present at source areas in Richwoods Florst Block. Cambrian Eminence Dolomite 150-200 Uppermost bedrock around edges of Richwoods Florst Block. Remnants present within mined area. Potosi Dolomite 250 Major host rock for barite and lead ores mined in area. Uppermost bedrock in source areas of Richwoods Florst Block. Elvins Group (Derby - Doerun and Davis 300 Underlies entire area Bonneterre Formation 350 Underlies entire area Lamotte Sandstone 200 Underlies entire area The Ordovician-aged Roubidoux Formation is the youngest bedrock unit in the Richwoods area. Remnants of the Roubidoux are present on isolated ridgetops in the northwestern portion of the study area. It is also present over much of the southwestern study area (Refs. 18; 21, sheets 1-3). This September 2007 47 ------- formation consists of varying amounts of dolomite, sandstone, and chert. It is deeply weathered and eroded, with sandstone boulders, chert residuum, and colluvium marking its presence. The unit is reported to be about 200 feet thick (Ref. 21, sheets 1-3). The Gasconade Dolomite underlies the Roubidoux and occurs over a larger area in the western portion of the study area. The Gasconade is composed of two units separated by an algal bed—typically silicified and vertically fractured— referred to as "the cryp reef." The Gasconade dolomites form glades, benches, and small bluffs in the northern and western portions of the Richwood geologic map quadrangle. The upper Gasconade consists of 40 to 60 feet of gray to tan to brown, medium to coarsely crystalline, thick to massively bedded dolomites with less than 10 percent chert. The lower Gasconade is about 180 feet of gray to tan, fine to medium crystalline, thin bedded dolomite with up to 30 percent chert (Ref. 21, sheets 1-3). The Gunter Member, a persistent sandstone unit, is present at the base of the Gasconade. In some areas, the lower part of the lower Gasconade, above the Gunter Member, is identified as the "Van Buren." The Van Buren is generally a finely crystalline dolomite containing little chert, and is similar to the upper Gasconade (Ref. 20, pp. 10-11). The total thickness of the Gasconade in the Richwoods area is approximately 240 feet (Ref. 21, sheets 1-3). The Gasconade formation is the most cavernous rock formation in Missouri (Ref. 62, pp. 1-2). Underlying the Gasconade is the Cambrian-aged Eminence dolomite. In the Richwoods area, the Eminence Dolomite consists of gray to tan, medium- to coarsely-crystalline, thick to massively bedded dolomite with minor nodular chert. The Eminence varies from about 150 to 200 feet thick in northeastern Washington County and has a gradational contact with the underlying Potosi dolomite. This gradational contact is marked by approximately 20 feet of druse and chalcedony increasing downward (Ref. 21, sheets 1-3). The Potosi Dolomite consists of dark brown to gray to tan (at bottom) medium- to finely-crystalline dolomite. Exposures are generally massive and frequently have extensive vertical fractures and joints. The Potosi has distinctive weathering products of red clay, quarts druse, and masses of banded chalcedony. Dissolution, mineralization and secondary alteration are prevalent along structural features and associated fractures. The Potosi dolomite is approximately 250 feet thick in the area and is the major host rock for the barite and lead ores in Washington County. This formation is frequently very porous due to interconnected dissolution cavities (karst). The contact with the underlying Derby-Doerun dolomite is gradational and problematic in the Richwoods area (Ref. 21, sheets 1-3). Underlying the Potosi is the Elvins Group, which consists of the Derby-Doerun Dolomite and Davis Formation (Ref. 20, pp. 3-6). The Elvins Group is about 300 feet thick and consists of shales, siltstones and dolomites. The Derby-Doerun is an argillaceous dolomite and the upper part maybe difficult to distinguish from the overlying Potosi. It is approximately 120 feet thick in the area (Ref. 21, sheets 1-3). The underlying Davis formation consists of about 180 feet of shale, siltstone, fine-grained sandstone, dolomite and limestone conglomerate (Ref. 40, p. 8). The Cambrian Bonneterre formation underlies the Davis formation and is a medium to finely crystalline dolomite. Locally the Bonneterre can be a limestone, and some parts of the Bonneterre are glauconitic and shaly. The Bonneterre increases in sand content towards its base (Ref. 40, p. 9). The Bonneterre is the host-rock for the ore deposits of the Old Lead Belt in St. Francois County to the east and the Viburnum Trend—sometimes called the "New Lead Belt"—to the southwest. Together, these lead deposits form a roughly circular pattern around the pre-Cambrian formations of the St. Francois Mountains. Most of the ores occur where lead-bearing solutions have permeated porous zones in the Bonneterre formation (Ref. 23, pp.9-10). The presence of ore is controlled by structures such as clastic carbonate bars or ridges, algal structures, and masses of submarine breccia. Major ore production has been from the lower half of the formation. In the Lead Belt and Viburnum Trend area, the Bonneterre is September 2007 48 ------- approximately 375 to 400 feet thick (Ref. 20, pp. 4-5). On average the thickness of the Boneterre is 350 feet (Ref. 40, pp. 8-9). The Bonneterre conformably overlies the Lamotte Sandstone, which is the oldest sedimentary rock formation in the Salem Plateau (Ref. 40, p. 5). The Lamotte is predominantly a quartzose sand, but grades laterally to an arkosic sandstone or conglomerate. It varies in color from light gray to dark brown or red. The Lamotte unconformably overlies Precambrian basement rocks. The Lamotte ranges in thickness from about 100 feet, along the margins of the St Francois Mountains, to over 300 feet in the western and southern parts of the Salem Plateau. It averages about 200 feet in thickness (Ref. 40, pp. 5, 8). Structural Features The Missouri Environmental Geology Atlas (MEGA) includes geographic information system (GIS) drawing files and database information for bedrock geology, faults, sinkholes, and water wells (Ref. 18). Included in Reference 18 is a geological map of the Richwoods area superimposed on a shaded relief map. This geologic map groups similar formations; however, detailed geologic information available for the area (Ref. 21, sheets 1-3), is referenced for this section. Certified wells (wells drilled since about 1986) and wells identified from old Missouri well logs, and locations and general results for the wells sampled during this investigation are also shown on the Figure 3 and on Figure 12 in Reference 59. Bedrock in the Richwoods area has been deformed by both normal and strike-slip faulting. In general, structural features trend both northeast-southwest and northwest-southeast and are probably related to the Sainte Genevieve Fault System. Regional dip is generally northward and locally controlled by structural deformation along fault zones (Ref. 21, sheets 1-3). In the central and eastern portion of the study area, bedrock has been faulted upward in an area known as the Richwoods Horst Block. In this block, the younger rocks have eroded, leaving the Cambrian-aged Eminence and Potosi dolomites as the uppermost bedrock. The geologic map from Reference 18 combines these rock units; however, the detailed geologic maps in Reference 21 indicate that bedrock in this area is predominantly the Potosi dolomite, with remnants of the overlying Eminence dolomite present mainly near the edges. The older Derby-Doerun Dolomite (mapped as the Elvins Group and Bonne Terre Dolomite in Reference 18) forms the uppermost bedrock along stream beds, particularly near the eastern side of the study area. The Richwoods Horst Block is bounded on the southwest by the Cruise Mill- Fertile Fault Complex, to the northwest by the Providence Fault, and to the northeast by the Fletcher Fault. The greatest displacement is along the Fletcher Fault where several hundred feet of deformed, brecciated, silicified, upturned dolomites and sandstones are present. Mineralization and ore deposits are extensively developed in this horst block area and numerous mines and waste products are present in the area. The Potosi dolomite is the major host rock for the barite and lead ores in the area (Ref. 21, sheets 1- 3). Karst Development A USGS study of karst hydrology in the Viburnum Trend area of southwestern Washington County indicates that karst features including caves have developed in the Roubidoux, Gasconade, and Eminence in the Ozark Plateau. The majority of caves studied in this area occurred within stromatolitic dolomite beds beneath sandstone layers. The cemented sandstones are believed to act as confining units, allowing artesian conditions and mixing of waters having differing chemistries to occur, thereby enhancing dissolution. The study found that the dominant geologic control on cave and conduit development were bedding and stratigraphy. Vugs within the stromatolitic dolomites act as primary porosity and solution along joints provide secondary porosity. However, the study found that ground water flow is mostly occurs along bedding planes rather than joints because they are more continuous (Ref. 60, pp. 1-7). September 2007 49 ------- Washington County is indicated as having more than 10 sinkholes per 100 square miles (Ref. 63, p. 9). The Washington County soil survey indicates that solution weathering along structural features has created numerous springs, fens, caves, and related karst features in Washington County, with over 75 caves and 100 springs documented in the county (Wash co SS page 14). Reference 18 indicates that a sinkhole is located north of the Desoto Mining Company Plants A&B mining complex and indicates several springs are present. Relation of Source Areas to Drainage Basins All of the mines and tailing ponds identified as source areas in the study area are situated in the upfaulted area of the Richwoods Horst block. The Potosi Dolomite, the major host for the lead and barite ore, is the uppermost bedrock (Figure 2 of this document; Refs. 18; 21, sheets 1-3). Reference 18 shows the regional ground water elevations and the topographic highs separating the hydrologic drainage basins. The Reference 18 figure shows the locations of the source areas (tailings ponds) relative to ground water flow and shows the general correlation of the ground water elevations to topography (Ref. 18; Figure 2 of this document). Based on the regional flow directions, two ground water basins are defined. These areas are west and east of a topographic high generally following Highway 47 (Ref. 18; Figure 2 of this document). Elevations in the mined areas of the Richwoods Horst block are generally about 800 to 860 feet above mean sea level (amsl) with elevations along the Highway 47 topographic divide ranging from about 850 to 1,000 feet amsl (Ref. 3). The area east of Highway 47 can be divided into two sub-basins: a generally northeast flowing area and a generally east to southeast flowing area (Ref. 18; Figure 2 of this document). The distance is less than four miles from the sources located in the northeast and southeast sub-basins to the Big River into which the ground water would drain together; therefore, these sub-basins are interconnected and scored as one aquifer (Ref. 18; Figure 2 of this document). Elevations along this topographic high range from 900 feet amsl at Highway 47 to about 820 feet amsl (Ref. 3). Source areas 1 and 2 of the DeSoto Mining Company's Politte mine, Joe Smith mine, and a portion of Plants A and B are located west of the Highway 47 divide and lie within the west drainage basin. The rest of the Plants A and B property, DeSoto's Twin mine and NL Bariod Big 4 mine are east of this topographic divide. The area east of Highway 47 having a northeastern ground water gradient contains the bulk of the DeSota Plants A and B lands (tailings ponds 3 through 11) as well as the northern portion of DeSoto's Twin mine. The southern portion of the DeSoto's Twin mine property and most of NL Bariod Big 4 mine—including source area 6—are south of the ground water divide in the area where the regional ground water gradient is generally east or southeast. Drainage Basin 1 - West of the Highway 47 Topographic Divide Aquifer/Stratum 1: Eminence Dolomite The geologic bedrock map and MDNR well logs indicate remnants of the Eminence dolomite remain in the area. MDNR well log number 10978, for private well located just west of the Highway 47 divide about 0.5 mile northeast of Source 2, indicated 90 feet of Eminence overlying the Potosi. In contrast, well log 7409 for a mineral exploration hole about 0.5 mile east of Source 2 indicates 30 feet of residual clay overlying the Potosi. The well logged as having the Eminence is about 20 feet lower in elevation than the mineral exploration hole. The Eminence Dolomite consists of gray to tan, medium- to coarsely- crystalline, thick to massively bedded dolomite with minor nodular chert. Approximately 20 feet of druse and chalcedony forms the gradational contact of the Eminence with the Potosi (Ref. 21, sheets 1-3). The Eminence is karst dolomite and is assigned a hydraulic conductivity of lxlO"2 centimeters per second (cm/sec) based on Table 3-6 in Section 3.1.2.4 of the HRS. September 2007 50 ------- Aquifer/Stratum 2: Potosi Dolomite The Potosi Dolomite has distinctive weathering products of red clay, quarts druse, and masses of banded chalcedony. It is the major host rock for the lead and barite ores mined in the source areas and is the main bedrock unit outcropping in the Richwoods Horst Block. The dolomite consists of dark brown to gray to tan (at bottom) medium- to finely-crystalline dolomite. Dissolution, mineralization and secondary alteration are prevalent along structural features and associated fractures. The Potosi dolomite averages 250 feet thick in the area; however, the thickness may vary due to erosion and faulting. MDNR well log number 10225, for a Desoto Mining Company industrial well just northeast of Source 2, indicated 10 feet of clay overlying the Potosi. This well was only 65 feet deep; however, MDNR well log 7409, located about 0.5 mile east of Source 2, penetrated 210 feet of Potosi beneath 30 feet of clay. In addition, 90 feet of unidentified dolomite (possibly Potosi) was logged between the Potosi and the underlying Derby - Doerun. This formation is frequently very porous due to interconnected dissolution cavities (karst). The contact with the underlying Derby-Doerun dolomite is gradational and problematic in the Richwoods area (Ref. 21, sheets 1-3). The karstPotosi dolomite is assigned a hydraulic conductivity of lxlO"2 cm/sec based on Table 3-6 in Section 3.1.2.4 of the HRS. The Eminence and Potosi dolomites are the lowermost units of the Ozark Aquifer system. Because the same hydraulic conductivity is assigned to these karst dolomites, it is reasonable to combine the units as a single aquifer. The Richwoods Horst block (mined area) is separated by faults (discontinuities) from the areas to the northwest and southwest, where younger Gasconade and Roubidoux dolomite are present. These two areas are separated from each other by Little Indian Creek (and fault), where the Eminence Dolomite is the uppermost bedrock (Ref. 21, sheet 1). Little Indian Creek has an elevation of about 700 feet amsl, while elevations in the areas of younger bedrock are typically between 800 and 1,000 feet amsl (Ref. 3). Consequently, Little Indian Creek is a discontinuity dividing these two areas. Drainage Basin 2 - East of the Highway 47 Topographic Divide Aquifer/Stratum 1: Eminence Dolomite Although not generally present in the source areas, MDNR well logs indicate remnants of the Eminence dolomite remain in the mined areas of the Richwoods Horst Block. MDNR well log 7672, for an industrial well located between source area 5, indicated 50 feet of Eminence overlying the Potosi at this location. The Eminence Dolomite consists of gray to tan, medium- to coarsely-crystalline, thick to massively bedded dolomite with minor nodular chert. Approximately 20 feet of druse and chalcedony forms the gradational contact of the Eminence with the Potosi (Ref. 21, sheets 1-3). The Eminence is karst dolomite and based on Table 3-6 in Section 3.1.2.4 of the HRS is assigned a hydraulic conductivity of lxlO"2 cm/sec. Aquifer/Stratum 2: Potosi Dolomite The Potosi Dolomite has distinctive weathering products of red clay, quarts druse, and masses of banded chalcedony. It is the major host rock for the lead and barite ores mined in the source areas and is the main bedrock unit outcropping in the Richwoods Horst Block. The dolomite consists of dark brown to gray to tan (at bottom) medium- to finely-crystalline dolomite. Dissolution, mineralization and secondary alteration are prevalent along structural features and associated fractures. The Potosi dolomite averages 250 feet thick in the area; however, MDNR well logs less than 170 feet of Potosi is present southwest of source area 9 (well log 8758), while 255 feet of Potosi Dolomite is present between source area 5 (well log 7672). This formation is frequently very porous due to interconnected dissolution cavities (karst). The contact with the underlying Derby-Doerun dolomite is gradational and problematic in the Richwoods September 2007 51 ------- area (Ref. 21, sheets 1-3). Based on Table 3-6 in Section 3.1.2.4 of the HRS, the karstPotosi dolomite is assigned a hydraulic conductivity of lxlO"2 cm/sec. The Eminence and Potosi dolomites are the lowermost units of the Ozark Aquifer system. Because the same hydraulic conductivity is assigned to these karst dolomites, it is reasonable to combine the units as a single aquifer. Ozark Aquifer - Regional Ground water is the principal source of public and private water supplies in the site area. The Cambrian Eminence and Potosi dolomites along with younger Ordovician rocks, eroded in this area, form the Ozark Aquifer. The Ozark Aquifer is the most important aquifer in the Salem Plateau, providing water for nearly ever, town, city, rural water district, and the vast majority of private wells in the area (Ref. 40, p. 17). Of the Ozark aquifer formations, the Potosi dolomite is the most prolific and reliable aquifer. In its outcrop area or where it is near surface, such as in the site area, the Potosi dolomite generally produces water at about 20 to 30 gallons per minute (Ref. 40, p. 19). The upper part of the Eminence yields 50 to 75 gallons per minute (gpm), principally due to secondary porosity developed along fractures (Ref. 40, p. 20). The Ozark aquifer is regionally considered to be unconfined; however, deeper units can be locally confined or semiconfined in some areas because of local rock characteristics. The Ozark aquifer consists of relatively permeable horizontal zones separated by less permeable zones (Ref. 40, p. 21). Reference 18 shows the correlation between the bedrock geology and topography, with older rocks along drainageways and younger rocks present on topographic highs. Elevations in the up-faulted Richwoods Horst Block are typically between 800 and 900 feet amsl. This area is generally a topographic high; however higher elevations occur to the north and northwest along Highway 47, which follows the topographic high. In that area, elevations are generally between 920 and 1,020 feet amsl. Elevations along streams radiating outward from the topographic high are about 600 to 700 feet amsl. At Big River, east of the study area, elevations are around 540 feet amsl (Ref. 3). The direction of shallow ground water flow is controlled by many factors. In areas lacking karst development, flow in the shallower units is usually controlled by topography, with ground water elevations highest along topographic divides and lowest along streams. Ground water flow in these areas is towards the local drainage. Deeper ground water movement is generally dependant on the region dip of the rocks, away from the St. Francis Mountains. Although primary permeability accounts for some ground water flow, secondary porosity provided by faulting, jointing, fracturing, and dissolution of carbonate rock has a greater influence on current hydro logic conditions in the Salem Plateau (Ref. 40, p. 21). Where the Ozark aquifer is unconfined, such as in Washington County, the potentiometric surface in the shallow aquifer units generally mimics topography (Ref. 41, pp. 49) and ground water divides generally correspond to topographic divides (Refs. 40, p. 21; 41, p. 49). A major topographic ridge extends across southern Missouri, forming a regional ground water divide, with water in the deep part of the Ozark aquifer system flowing away from that ridge and discharging into major rivers. In Washington County, this ground water flow would be northwest towards the Meramec River (Ref. 41, p. 45). The Ozark aquifer is recharged nearly everywhere by meteoric waters, and ground water generally flows laterally from higher elevations to discharge points along springs and seeps (Refs. 17, p. 4; 41, p. 49). Based on the thicknesses of the bedrock units, as much as 890 feet of aquifer thickness may be present where the Roubidoux formation occurs. In contrast, where only the Potosi Dolomite is present, the Ozark aquifer is likely less than 250 feet thick (Ref. 21, sheets 1-3). Information on certified wells presented in September 2007 52 ------- Reference 42 has been grouped by uppermost bedrock to allow comparison of well depth to geologic strata. However, faulting and erosion of the bedrock units allow only rough comparisons. In general, wells drilled in areas where the Roubidoux is present are between 170 and 250 feet deep; those drilled where the Gasconade is uppermost are typically 100 to 375 feet deep; wells in the areas where the Eminence appears to be uppermost, generally range from 110 to 390 feet deep. Based on these depths, most of these wells are likely producing exclusively from the Ozark Aquifer. Two wells had depths greater than 500 feet in these areas; one was along a fault zone. The other had a total depth of 815 feet bgs in the Lamotte Sandstone (Ref. 42, pp. 4-8). Static water levels for the Ozark Aquifer wells ranged from 10 feet below ground surface (bgs) to 270 feet bgs, but are typically between 80 and 130 feet bgs (Refs. 18; 42, pp. 1-8). Well records indicated test yields for these wells ranged from 9 to 40 gpm. The wells identified in the MDNR well records are shown on Figure 12 in Reference 59 (Ref. 42, pp. 1-8). Wells drilled in areas where the Potosi is the uppermost outcrop are more likely to be completed in both the Ozark and the St Francis Aquifers. Six certified wells drilled in this area had depths of 254 feet or less, and may be producing exclusively from the Ozark Aquifer (Ref. 42, pp. 1-3). Reference 18 presents the static water levels available from certified wells in MEGA converted to feet amsl. Surface elevations—seldom provided— were calculated based on the well location information in MEGA. Because of the rugged terrain, a location error can result in a significant surface elevation error, and subsequently produce a ground water elevation error. The static water levels used on this map were taken over many years; however, the figure generated from the certified well water levels presents 100-foot contour intervals, which should make seasonal or annual variances negligible. These contours indicate that ground water flow is generally controlled by topography, with the highest ground water elevations following the topographic high extending from the southwest portion of the study area northward along Elighway 47. Ground water elevations exceeding 900 feet amsl occur in the southwestern area, while elevations along Elighway 47 through the central site are generally between 800 and 900 feet amsl. The ground water flow in the western part of the Richwoods area is generally northwestward, towards and with Indian Creek. East of Highway 47, ground water flow is generally eastward towards Big River. Flow in a small area along the southern edge of the Richwoods study area appears to be southward, towards Mineral Fork (Figure 2 of this document; Ref. 18). The MEGA database files document the presence of karst topography in the Richwoods area, revealing the site is within a cave area and identifying a sinkhole about 1.5 miles northeast of the junction of Highways 47 and A/H (Figure 2 of this document; Ref. 18). This sinkhole, located about 1,000 feet west of sample location 2937-153, is shown on the geologic map included as Reference 21. In addition, springs, fens and seeps, associated with faulting and solution weathering along structural trends, occur along tributaries in the Richwoods area (Ref. 56). Because dissolution and fracturing have created abundant secondary porosity in the Ozark aquifer, hydraulic properties vary with direction. Horizontal hydraulic conductivities typically range from 0.001 to 86 feet per day (ft/day), and yields range from 50 to 100 gpm (Ref. 41, p. 49). Permeable residuum coupled with karst features produce complex ground water conditions, with rapid percolation of waters to the bedrock aquifers. Municipal wells completed at depths of 950 to 1,500 feet below ground surface have shown increased turbidity following rainstorms, illustrating the rapidity of the recharge from the surface (Refs. 17, p. 4; 41, p. 49). In addition, mine shafts or tunnels and deep exploratory borings could also act as conduits for ground water flow both vertically and laterally. Because of these features, ground water flow may not always September 2007 53 ------- follow topography or, for deeper ground water, the generally northwestern regional flow towards the Meramec River (Ref. 41, pp. 45-46). Aquifer/Stratum Name: St. Francois Confining Unit—Derbv-Doe Run Dolomite and Davis Formation Underlying the Ozark aquifer is the St. Francois confining unit, consisting of the lower permeable Elvins Group (Refs. 18; 40, p. 19). The St. Francois confining unit is saturated, but its hydraulic conductivity is generally too low to yield appreciable water (Ref. 40, p. 19). These confining units hydro logically separate the overlying Ozark aquifer from the deeper St. Francois aquifer; however, they only restrict rather than prevent water interchange between the two units (Ref. 40, p. 15). Penetration of the St. Francois confining unit could increase the ability of contaminants to enter the underlying St. Francois aquifer. Where both the Ozark aquifer and the St. Francois aquifer are open to a well, it is possible that water from the shallow Ozark aquifer formations infiltrates the deeper Lamotte. Because the potentiometric surface of the Ozark aquifer is generally above that of the Lamotte, the potential exists for down-hole water movement in the well during non-pumping periods (Ref. 40, p. 16). Aquifer/Stratum Name: St. Francois Aquifer—Bonneterre Dolomite and Lamotte Sandstones The St. Francois aquifer underlies the St. Francois confining unit and consists of Cambrian-age dolomites, and limestones of the Bonneterre Formation and the underlying Lamotte Sandstone (Ref. 40, pp. 7-9, 14). The St. Francois aquifer is used in the unconfined outcrop area around the St. Francois Mountains, where it is the only local source of ground water (Ref. 40, p. 15). This aquifer is rarely used where it is confined, because the thicker overlying Ozark Aquifer is more readily available. Consequently, in the site area, the St. Francis Aquifer is not considered to be a significant source of ground water. Horizontal hydraulic conductivities in the St. Francois aquifer range from 0.1 to 8.6 ft/day and yields range from 100 to 500 gpm (Ref. 41, p. 50). The Lamotte Sandstone is responsible for most of the water produced from the St. Francois aquifer. The overlying Bonneterre typically has low hydraulic conductivity and yields only modest quantities of water (Ref. 40, p. 14). Throughout the Salem Plateau, the St Francois Aquifer is generally not in use; however, some deep municipal wells—including those for the nearby City of Potosi— are producing from the Lamotte sandstone (Ref. 61, pp. 1-10). The MDNR certified well records indicate 13 wells deeper than 500 feet in the Richwoods area (Ref. 18; 42, pp. 1 -3). Based on well records in MEGA, ten of these wells appear to be located in areas where the uppermost bedrock is the Potosi or Derby-Doerun. One was along a fault zone, and one was logged as being completed in the Lamotte Sandstone. Wells drilled in this area are more likely to be completed in both the Ozark and the St Francis Aquifers. Wells having depths greater than about 254 feet are more likely to penetrate strata underlying the Potosi. The St. Francis Confining Unit is about 300 feet thick; therefore, wells over about 550 feet deep are likely to be partially producing from the Bonneterre (Ref. 18;42,pp. 1-3). Because wells are completed as open hole below the casing depth (Ref. 57,p. 1)— generally 80 feet—it is likely that these wells are also producing from the overlying Ozark Aquifer. SUMMARY OF AQUIFER(S) BEING EVALUATED Aquifer No. Aquifer Name Is Aquifer Interconnected with Upper Aquifer within 2 miles? (Y/N/NA) Is Aquifer Continuous Within 4-mile TDL? (Y/N) Is Aquifer Karst? (Y/N) 1 Ozark Aquifer Yes Yes Yes September 2007 54 ------- 3.1 LIKELIHOOD OF RELEASE 3.1.1 OBSERVED RELEASE Aquifer Being Evaluated: Ozark Aquifer composed of the Eminence and Potosi strata As discussed in the previous section, a topographic high is identified along Highway 47, which runs roughly through the center of the Richwoods study area. This topographic high may serve as an aquifer discontinuity. As a conservative approach, the Ozark aquifer will be evaluated both as one aquifer and as two separate sub-aquifers, called herein as the sub-aquifer 1 (western) and sub-aquifer 2 (eastern). Sources 1 and 2 evaluated in Section 2.2 are in sub-aquifer 1; sources 3, 4, 5, and 6 presented in Section 2.2 are in sub-aquifer 2. The scoresheets at the front of this document reflect the single aquifer approach, and the scoresheets in Appendix A reflect the pathway score of each sub-aquifer. Chemical Analysis As part of the Preliminary Assessment / Site Inspection (PA/SI) and Removal Site Evaluation (RSE) conducted by EPA, ground water samples were collected from private drinking water wells (Figure 3; Ref. 5, pp. 27-29, 229-518; 22, pp. 12-15,53-664). Samples were submitted to the EPA Region 7 laboratory for analyses of total barium and lead. In addition, some of those samples were also analyzed for dissolved barium and lead. The purpose of the dissolved metal samples was to determine if the metals found in the private wells occurred in a dissolved state or as a result of entrained particulates (Ref. 5, p. 29; 22, p. 12-13). As shown in the background and contaminated concentrations tables below, the results for dissolved and total metals analysis are very similar suggesting the metals exist in a dissolved state. Reference 26 provided further statistical analysis of dissolved and total metals results for lead and barium in ground water. Reference 26 presents the linear regression and measures the strength of the linear relationship between the total and dissolved results. The linear regression was computed for the ground water samples collected and analyzed for both total and dissolved metals. If the analyte was not detected in both total and dissolved metal analysis, the data was not used. However if the analyte was detected in either the dissolved or total analysis and not in the other, then the data was retained and the detection limit was used for the non-detect sample. One outlier sample (2937-149) was removed when calculating the linear regression for the lead analysis. The linear regression result for the barium results was 0.998 and 0.924 for lead. Since the results are near one that shows a strong linear relationship between the dissolved and total results for both barium and lead. Background Concentrations: Background wells were selected based on the following criteria. Wells were selected that were located away from known areas of mining activities as identified on the 208 study maps (Refs. 31, pp. 4-5; 32; 59, Figures 13 and 14). Samples were collected from the same environmental media (ground water) at a variety of depths, collected and analyzed using the same procedures and laboratory as the release samples. These wells contained no or low concentrations of barium and lead. The background wells are in a similar geologic setting as the release wells (see the background concentration table below and Refs. 18; 21, sheets 1-3; 59, Figures 13 and 14). The background wells are upgradient to the source mine areas on the east side of the ground water divide traversing the study area (generally marked by Highway 47). These background wells are also located in a similar geological setting and across the ground water divide to wells located west of Highway 47, as shown on Figures 13 and 14 in Reference 59. The well depths of the background wells are similar to the release wells located east of the ground water divide. September 2007 55 ------- Sample similarity Missouri well construction regulations currently require that private wells be cased a minimum of 80 feet, with the casing set a minimum of 30 feet into unweathered bedrock. These requirements only went into effect in February 1987 (Refs. 40, pp. 25-26; 57, p. 1). Well logs for older wells indicate casing lengths as short as 12 feet designated in the date completed or date drilled columns (Ref. 42, pp. 1-3, 8). Below the cased depth, the wells are open hole; consequently, water produced from the well is a composite of all water bearing units between the depth of casing and total well depth (Ref. 40, p. 26) and pull from the Ozark Aquifer. Prior to these regulations being enacted in 1987, casing requirements were set by the Department of Health but were not enforced (Ref. 57, p. 1). Because most of the sampled wells were not certified, it is likely that they predate the 1987 casing requirements. The private wells were not likely drilled into a deeper aquifer than the Ozark Aquifer since the purpose is only domestic use; therefore, for screening purposes, it is assumed that all the wells including the background wells are completed as open hole below the depth of casing and obtain ground water from the Ozark Aquifer. MDNR records for 106 certified private wells in the Richwoods study area indicate that wells range in depth from 100 to 850 feet, 13 wells have depths greater than 500 feet. Casing lengths recorded for these wells generally ranged from 70 to 189 feet (Ref. 42, pp. 1-3). In comparison, well log records for 19 older private wells indicate depths between 40 and 350 with casing depths between 12 and 171 feet bgs. Several of these wells indicate no casing; however, this may indicate that no information available rather than no casing (Ref. 42, pp. 4-8). Samples presented below were collected and submitted for laboratory analysis under six separate analytical services requests (ASRs) starting in July 2005 and ending in April 2006 (Refs. 7; 8; 9; 11; 12; 13). Ground water sampling is ongoing with the intent of characterizing drinking water from all wells. The rationale for choosing these private well sampling locations was to document metal contamination in the Ozark aquifer. Figures 13 and 14 in Reference 59 identifies the background and contaminated ground water sample locations, and Figure 13 in Reference 59 shows the samples that meet the Level I criteria. Because most of the overlying units of the Ozark Aquifer have been removed by erosion in the Richwoods study area, some wells have penetrated the St. Francois confining layer and are partially producing from the underlying St. Francois aquifer. This confining unit only restricts rather than prevent water interchange between the two units (Ref. 40, p 15). Where both the Ozark aquifer and the St. Francois aquifer are open to a well, it is possible that water from the shallow Ozark aquifer formations infiltrates the deeper Lamotte. Because the potentiometric surface of the Ozark aquifer is generally above that of the Lamotte, the potential exists for down-hole water movement in the well during non-pumping periods (Ref. 40, p. 16). Reference 18 shows the ground water elevations for the Richwoods area based on data from the 2007 version of MEGA. This figure shows the locations of the source areas relative to ground water flow and shows the general correlation of the ground water elevations to topography. Based on the regional flow directions, two ground water basins are defined. These areas are west and east of a topographic high generally following Highway 47 between the USGS watersheds as shown on Figure 15 of this document. Elevations in the mined areas of the Richwoods Horst block are generally about 800 to 860 feet amsl with elevations along the Highway 47 topographic divide ranging from about 850 to 1,000 feet amsl (Ref. 3). The area east of Highway 47 can be divided into two sub-basins: a generally northeast flowing area and a generally east to southeast flowing area (Refs. 18; Figures 2 and 15 of this document). The distance is less than four miles from the sources located in the northeast and southeast sub-basins to the Big River into which the ground water would drain together; therefore, these sub-basins are interconnected and scored as one aquifer (Ref. 18; Figure 2 of this document). Elevations along this topographic high range from 900 feet amsl at Highway 47 to about 820 feet amsl (Ref. 3). This topographic high may serve as an aquifer discontinuity. As a conservative approach, the Ozark aquifer will be evaluated as two separate September 2007 56 ------- sub-aquifers, called herein as the sub-aquifer 1 and sub-aquifer 2. Sources 1 and 2 evaluated in Section 2.2 are in sub-aquifer 1; sources 3, 4, 5, and 6 presented in Section 2.2 are in sub-aquifer 2. Individual score sheets for each sub-aquifer are presented as Appendix A to the documentation record. Background Levels for Sub-aquifer 1: Sample ID Property Number Hazardous Substance Concentration (Hg/L) Sample Quantitation Limit* (ng/L) Well Depth (feet)** Elevations (feet amsl) References Surface (Ref. 64) Well Depth Refs. 9, pp. 3, 5-6, 14, 29, 60; 2959-105 40013 Lead (total) 1 U 1 Unknown 910 NA 14, pp. 25-26; 18; 37, pp. 5-6; 59, Figure 13 and 14 Refs. 9, pp. 3, 5-6, 14, 29,61; 2959-106 40094 Lead (total) 1 U 1 135 877 742 14, pp. 175- 176; 18; 37, p. 6; 59, Figure 13 and 14 Refs. 9, pp. 3, 5-6, 14, 29, 62; 2959-107 40093 Lead (total) 1 u 1 Unknown 855 NA 14, pp. 173- 174; 18; 37, p. 6; 59, Figure 13 and 14 Refs. 9, pp. 3, 5-6, 15, 29,64; 2959-109 40111 Lead (total) 1 u 1 Unknown 925 NA 14, pp. 207- 208; 18; 37, p. 6; 59, Figure 13 and 14 2959-114 Lead (dissolved) Refs. 9, pp. 3, 40160 1.28 1 300 851 551 5-6, 16, 29, 69; 14, pp. 293- 294; 18; 37, p. Lead (total) 1.8 U 1 7; 59, Figure 13 and 14 2959-115 Lead (dissolved) 1 U 1 Unknown 904 NA Refs. 9, pp. 3, 5-6, 14, 29, 70; 14, pp. 189- 190; 18; 37, p. 7; 59, Figure 13 and 14 40101 Lead (total) 1.62 U 1 Refs. 9, pp. 4, 5-6, 19, 30, 82; 2959-127 40110 Lead (total) 1 U 1 Unknown 816 NA 14, pp. 205- 206; 18; 37, p. 10; 59, Figure 13 and 14 September 2007 57 ------- Sample ID Property Number Hazardous Substance Concentration (Hg/L) Sample Quantitation Limit* (ng/L) Well Depth (feet)** Elevations (feet amsl) References Surface (Ref. 64) Well Depth 2959-131 40043 Lead (total) 1.82 1 Unknown 882 NA Refs. 9, pp. 4, 5-6, 20, 30, 86; 14, pp. 85-86; 18; 37, p. 10; 59, Figure 13 and 14 2959-133 40175 Lead (total) 1.35 1 Unknown 904 NA Refs. 9, pp. 4, 5-6,21, 30, 88; 14, pp. 309- 310; 18; 37, p. 11; 59, Figure 13 and 14 2959-135 40045 Lead (total) 2.4 1 Unknown 731 NA Refs. 9, pp. 4, 5-6,21,30, 90; 14, pp. 87-88; 18; 37, p. 11; 59, Figure 13 and 14 2959-136 40054 Lead (total) 1 U 1 300 902 602 Refs. 9, pp. 4, 5-6,21,30,91; 14, pp. 103- 104; 18; 37, p. 11; 59, Figure 13 and 14 2959-137 40173 Lead (total) 1 U 1 175 784 609 Refs. 9, pp. 4, 5-6, 22, 30, 92; 14, pp. 307- 308; 18; 37, p. 11; 59, Figure 13 and 14 2991-124 40124 Lead (dissolved) 2.82 1 Unknown 776 NA Refs. 8, pp. 3, 5-6, 15,21,61; 14, pp. 231- 232; 18; 38, p. 7; 59, Figure 13 and 14 Lead (total) 1.54 1 2991-134 40026 Lead (total) 2.8 1 Unknown 758 NA Refs. 8, pp. 4- 6, 18,22,71; 14, pp. 51-52; 18; 38, pp. 8-9; 59, Figure 13 and 14 September 2007 58 ------- Notes: * The SQLs provided in this table are referred to as reporting limits in References 37 and 38. They are the laboratory's reporting limit (also known as the method detection limit - see the method for more details) for that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. ** Wells with unknown depths are believed to be drawing in part, if not entirely from the Ozark Aquifer. Drilling to the deeper St. Francois aquifer would be cost prohibitive for most private homeowners when the Ozark aquifer provides ample supply for domestic use. If the well is completed to the lower aquifer, the open casing construction would draw water, in part, from the overlying Ozark aquifer (Refs. 18; 42; 57). amsl Above mean sea level ID Identification NA Not available jig/Lmicrograms per Liter Bolded These concentrations considered to be the background concentration for lead Fourteen background well concentrations from wells sampled in sub-aquifer 1 are presented above. In addition to the measurement of analyte concentrations as "total" in these samples, "dissolved" concentrations were measured in samples from three of the background wells. Lead as "total" was identified in five of the 14 background well samples with concentrations ranging from 1.34 to 2.8 |ig/L, and was not detected above the reporting limit (1.00 |xg/L) in the remaining nine samples. Lead as "dissolved" was identified in two of the background well samples that were analyzed for metals as "dissolved," with concentrations ranging from 1.28 to 2.82 |xg/L, and was not detected above the reporting limit (1.00 |xg/L) in the remaining samples. In accordance with the HRS (Ref. 1, Section 2.3), an observed release is established when the sample measurement equals or exceeds the sample quantitation limit when the contaminant is not found in the background sample. In addition, if the analyte is found in background samples, an observed release is established when the sample measurement is three times or more above the background concentration. Finally, some portion of the release must also be attributable to the site. Using the background data set above, an observed release is established in wells containing lead as "total" and "dissolved" in wells at a concentration of 8.4 |xg/L (three times 2.8 |xg/L) or higher and 8.46 |xg/L (three times 2.82 |xg/L) or higher, respectively. Contaminated Samples in Sub-aquifer 1: Listed below are wells that document a significant increase in contaminants for an observed release of lead. The highest concentration of lead detected in the background samples was 2.82 |ig/L; therefore, an observed release is established when the sample measurement is three times or more above the background concentration (8.46 |ig/L). Estimated results (J-coded data) were not considered if the reported number was biased high (the actual sample result had a chance of being lower than what was reported). Estimated results (J-coded data) were considered if the reported number was biased low (the actual sample result had a chance of being higher than what was reported). The biased low concentrations meet the observed release criteria at the lower estimated concentration; therefore, if the actual sample result is higher than what was reported it would still meet the observed release criteria presented in HRS, Table 2-3 (Ref. 1, Table 2-3). The locations of all release samples are shown of Figures 13 and 14 in Reference 59. September 2007 59 ------- Sample ID Hazardous Concentration Sample Quantitation Limit* ((ig/L) Well Depth Elevations (feet amsl) References Property Number Substance O^g/L) (feet)* * Surface (Ref. 64) Well Depth ASR2690 2690-103 Refs. 11, pp. 3, 6-7, 20028 Lead (total) 15.1 10 Unknown 826 NA 16, 36, 76; 15, pp. 61-62; 18; 33, p. 5; 59, Figure 13 2690-111 Refs. 11, pp. 3, 6-7, 20018 Lead (total) 20.8 10 Unknown 822 NA 18, 36, 84; 15, pp. 41-42; 18; 33, p. 6; 59, Figure 13 2690-134 Refs. 11, pp. 4, 6-7, 20108 Lead (total) 10.1 10 110 890 780 24, 39, 107; 15, pp. 205-206; 18; 33, p. 8; 59, Figure 14 2690-147 Refs. 11, pp. 4, 6-7, 20051 Lead (total) 26.6 10 452 954 502 27, 39, 120; 15, pp. 99-100; 18; 33, p. 10; 59, Figure 13 2690-158 Refs. 11, pp. 5-7, 20016 Lead (total) 22.3 10 Unknown 865 NA 30, 40, 132; 15, pp. 37-38; 18; 33, p. 11; 59, Figure 13 2690-159 Refs. 11, pp. 5-7, 20005 Lead (total) 26.8 10 Unknown 922 NA 30, 40, 133; 15, pp. 11-12; 18; 33, p. 11; 59, Figure 13 2690-163 Refs. 11, pp. 5-7, 20052 Lead (total) 21.7 10 280 918 638 31,40, 137; 15, pp. 101-102; 18; 33, p. 12; 59, Figure 13 2690-166 Refs. 11, pp. 5-7, 20008 Lead (total) 13.7 10 Unknown 879 NA 32, 40, 140; 15, pp. 17-18; 33, p. 12; 59, Figure 14 2690-169 Refs. 11, pp. 5-7, 20024 Lead (total) 20.7 10 Unknown 961 NA 33, 40, 143; 15, pp. 53-54; 18; 33, p. 13; 59, Figure 13 2690-170 Refs. 11, pp. 5-7, 20004 Lead (total) 35.5 10 Unknown 907 NA 33, 40, 144; 15, pp. 9-10; 18; 33, p. 13; 59, Figure 13 2690-172 Refs. 11, pp. 5-7, 20002 Lead (total) 24.2 10 Unknown 934 NA 33, 40, 146; 15, pp. 5-6; 18; 33, p. 13; 59, Figure 13 ASR2937 Lead 28.2 1 Refs. 7, pp. 4, 6-7, 2937-155 (dissolved) Unknown 983 NA 29, 37, 124; 15, pp. 20032R Lead (total) 28.8 1 65-66; 18; 36, p. 13; 59, Figure 13 September 2007 60 ------- Sample ID Property Number Hazardous Substance Concentration O^g/L) Sample Quantitation Limit* ((ig/L) Well Depth (feet)* * Elevations (feet amsl) References Surface (Ref. 64) Well Depth 2937-158 20158R Lead (dissolved) 31.2 1 Unknown 971 NA Refs. 7, pp. 5-7, 30, 37, 127; 14, pp. 283-284; 18; 36, p. 13; 59, Figure 13 Lead (total) 33.3 1 2937-161 40011 Lead (total) 15.4 1 Unknown 944 NA Refs. 7, pp. 5-7, 30, 37, 130; 14, pp. 21- 22; 18; 36, p. 14; 59, Figure 13 2937-163 40154 Lead (total) 50.8 1 Unknown 910 NA Refs. 7, pp. 5-7, 31, 37, 132; 14, pp. 283-284; 18; 36, p. 14; 59, Figure 13 ASR2959 2959-111 40103 Lead (total) 13.7 1 90 859 769 Refs. 9, pp. 3, 5-6, 15, 29, 66; 14, pp. 191-192; 18; 37, p. 6; 59, Figure 14 2959-118 20031R Lead (dissolved) 25 1 Unknown 718 NA Refs. 9, pp. 3, 5-6, 17, 29, 73; 18; 37, p. 8; 59, Figure 13 Lead (total) 26.7 1 2959-119 20007R Lead (dissolved) 40.2 1 Unknown 859 NA Refs. 9, pp. 3, 5-6, 17, 29,74; 18; 37, p. 8; 59, Figure 13 Lead (total) 46.6 1 2959-124 20014R Lead (dissolved) 45.1 1 100 887 787 Refs. 9, pp. 4-6, 18, 29, 79; 15, pp. 31- 32; 18; 37, p. 9; 59, Figure 13 Lead (total) 47.8 1 2959-143 40009 Lead (total) 55.8 J1 1 Unknown 895 NA Refs. 9, pp. 4-6, 23, 30, 98; 14, pp. 19- 20; 18; 37, p. 12; 59, Figure 13 ASR2991 2991-103 40128 Lead (total) 27.8 1 Unknown 963 NA Refs. 8, pp. 3, 5-6, 10, 20, 40; 14, pp. 239-240; 18; 38, p. 4; 59, Figure 13 2991-107 40040 Lead (total) 52.9 1 400 982 582 Refs. 8, pp. 3, 5-6, 11,20,44; 14, pp. 79-80; 18; 38, p. 4; 59, Figure 13 2991-114 40012 Lead (total) 37 1 140 940 800 Refs. 8, pp. 3, 5-6, 13,21, 51; 14, pp. 23-24; 18; 38, p. 5; 59, Figure 13 2991-120 40115 Lead (dissolved) 38.5 1 300 904 604 Refs. 8, pp. 3, 5-6, 14,21, 57; 14, pp. 215-216; 18; 38, p. 6; 59, Figure 13 Lead (total) 42.8 1 September 2007 61 ------- Sample ID Property Number Hazardous Substance Concentration O^g/L) Sample Quantitation Limit* ((ig/L) Well Depth (feet)* * Elevations (feet amsl) References Surface (Ref. 64) Well Depth 2991-121 40025 Lead (total) 13.2 1 Unknown 863 NA Refs. 8, pp. 3, 5-6, 14, 21, 58; 14, pp. 49-50; 18; 38, p. 6; 59, Figure 14 2991-125 40024 Lead (dissolved) 7.71 1 Unknown 754 NA Refs. 8, pp. 3, 5-6, 15,21,62; 14, pp. 47-48; 18; 38, pp. 7-8; 59, Figure 14 Lead (total) 9.04 1 2991-126 40042 Lead (total) 14 1 Unknown 821 NA Refs. 8, pp. 3, 5-6, 16, 21, 63; 14, pp. 83-84; 18; 38, p. 7; 59, Figure 14 2991-127 40126 Lead (total) 20.5 1 60-80 827 747 Refs. 8, pp. 3, 5-6, 16,21,64; 14, pp. 235-236; 18; 38, p. 8; 59, Figure 13 2991-132 40139 Lead (total) 30.8 1 Unknown 864 NA Refs. 8, pp. 4-6, 17, 21, 69; 14, pp. 261- 262; 18; 38, p. 8; 59, Figure 13 2991-133 40140 Lead (total) 25.2 1 208 857 649 Refs. 8, pp. 4-6, 17, 21,70; 14, pp. 263- 264; 18; 38, p. 8; 59, Figure 13 Notes: * The SQLs provided in this table are referred to as reporting limits in References 33, 36, 37, and 38. They are the laboratory's reporting limit (also known as the method detection limit - see the method for more details) for that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. ** Wells with unknown depths are believed to be drawing in part, if not entirely from the Ozark Aquifer. Drilling to the deeper St. Francois aquifer would be cost prohibitive for most private homeowners when the Ozark aquifer provides ample supply for domestic use. If the well is completed to the lower aquifer, the open casing construction would draw water, in part, from the overlying Ozark aquifer (Refs. 18; 42; 57). Amsl Above mean sea level J1 The analyte was positively identified; however, the reported value is an estimate due to serial dilution percent difference being above the control limit. The reported result may be biased low. However, even if the value was actually higher, it would still meet the observed release criteria. NA Not available jig/L micrograms per liter Background Levels for Sub-aquifer 2: Sample ID Property Number Hazardous Substance Concentration (Hg/L) Sample Quantitation Limit* (Hg/L) Well Depth (feet)** Elevations (feet amsl) Reference Surface (Ref. 64) Well Depth 2937-106 40108 Barium (dissolved) 291 10 365 757 392 Refs. 7, pp. 3, 6-7, 17, 35, 75; 14, pp. 201- 202; 18; 36, p. 6; 59, Figure 13 and 14 Barium (total) 299 10 1 Lead (dissolved) 1.05 Lead (total) 1.67 1 September 2007 62 ------- Sample ID Property Number Hazardous Substance Concentration (Hg/L) Sample Quantitation Limit* (ng/L) Well Depth (feet)** Elevations (feet amsl) Reference Surface (Ref. 64) Well Depth 2937-111 40019 Barium (dissolved) 170 10 300 721 421 Refs. 7, pp. 3, 6-7, 18, 35, 80; 14, pp. 39-40; 18; 36, p. 7; 59, Figure 13 and 14 Barium (total) 171 10 Lead (dissolved) 1 U 1 Lead (total) 2.42 1 2937-112 40073 Barium (total) 251 10 725 672 -53 Refs. 7, pp. 3, 6-7, 18, 35, 81; 14, pp. 137- 138; 18; 36, p. 7; 59, Figure 13 and 14 Lead (total) 1 U 1 2937-113 40018 Barium (total) 171 10 300 715 415 Refs. 7, pp. 3, 6-7, 18, 35, 82; 14, pp. 37-38; 18; 36, p. 7; 59, Figure 13 and 14 Lead (total) 1 U 1 2937-115 40143 Barium (total) 649 10 140 864 724 Refs. 7, pp. 4, 6-7, 19, 35, 84; 14, pp. 269- 270; 18; 36, p. 7; 59, Figure 13 and 14 Lead (total) 2.15 1 2937-116 40067 Barium (total) 10U 10 900 837 -63 Refs. 7, pp. 4, 6-7, 19, 35, 85; 14, pp. 129- 130; 18; 36, pp. 7-8; 59, Figure 13 and 14 Lead (total) 1 U 1 2937-118 40123 Barium (total) 627 10 Unknown 801 NA Refs. 7, pp. 4, 6-7, 20, 36, 87; 14, pp. 229- 230; 18; 36, p. 8; 59, Figure 13 and 14 Lead (total) 1 U 1 2937-122 40000 Barium (total) 570 10 Unknown 823 NA Refs. 7, pp. 4, 6-7,21,36,91; 14, pp. 1-2; 18; 36, p. 8; 59, Figure 13 and 14 Lead (total) 2.06 1 2937-123 40017 Barium (total) 207 10 780 782 2 Refs. 7, pp. 4, 6-7,21,36,92; 14, pp. 35-36; 18; 36, p. 8; 59, Figure 13 and 14 Lead (total) 2.13 1 September 2007 63 ------- Sample ID Property Number Hazardous Substance Concentration (Hg/L) Sample Quantitation Limit* (ng/L) Well Depth (feet)** Elevations (feet amsl) Reference Surface (Ref. 64) Well Depth 2937-124 40068 Barium (total) 54.6 10 1000 654 -346 Refs. 7, pp. 4, 6-7,21,36, 93; 14, pp. 131- 132; 18; 36, p. 8; 59, Figure 13 and 14 Lead (total) 1 U 1 2937-131 40058 Barium (total) 138 10 700 668 -32 Refs. 7, pp. 4, 6-7, 23, 36, 100; 14, pp. 111-112; 18; 36, p. 9; 59, Figure 13 and 14 Lead (total) 1 U 1 2937-133 40078 Barium (total) 117 10 Unknown 766 NA Refs. 7, pp. 4, 6-7, 23, 36, 102; 14, pp. 145-146; 18; 36, p. 9-10; 59, Figure 13 and 14 Lead (total) 1 U 1 2991-115 40083 Barium (total) 27 10 500 827 327 Refs. 8, pp. 3, 5-6, 13, 21, 52; 14, pp. 153- 154; 18; 38, p. 5; 59, Figure 13 and 14 Lead (total) 3.71 1 Notes: * The SQLs provided in this table are referred to as reporting limits in References 36 and 38. They are the laboratory's reporting limit (also known as the method detection limit - see the method for more details) for that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. ** Wells with unknown depths are believed to be drawing in part, if not entirely from the Ozark Aquifer. Drilling to the deeper St. Francois aquifer would be cost prohibitive for most private homeowners when the Ozark aquifer provides ample supply for domestic use. If the well is completed to the lower aquifer, the open casing construction would draw water, in part, from the overlying Ozark aquifer (Refs. 18; 42; 57). amsl Above mean sea level ID Identification NA Not available jig/Lmicrograms per Liter Bolded These concentrations considered to be the background concentrations for each of these metals Thirteen background well concentrations from wells sampled in sub-aquifer 2 are presented above. In addition to the measurement of analyte concentrations as "total" in these samples, "dissolved" concentrations were measured in samples from two of the background wells. Barium as "total" was identified in 12 of the 13 background well samples with concentration ranging from 27 to 649 |xg/L, and was not detected above the reporting limit (10.0 |xg/L) in the remaining sample. Barium as "dissolved" was identified in two of the background samples ranging from 170 to 291 |xg/L. Lead as "total" was identified in six of the 13 background well samples with concentrations ranging from 1.67 to 3.71 |xg/L, and was not detected above the reporting limit (1.00 |xg/L) in the remaining seven samples. Lead as "dissolved" was identified in one of the background well sample that were analyzed for September 2007 64 ------- metals as "dissolved," with concentration of 1.05 |ig/L, and was not detected above the reporting limit (1.00 ng/L) in the second background sample. In accordance with the HRS (Ref. 1, Section 2.3), an observed release is established when the sample measurement equals to or exceeds the sample quantitation limit when the contaminant is not found in the background sample. In addition, if the analyte is found in background samples, an observed release is established when the sample measurement is three times or more above the background concentration. Finally, some portion of the release must also be attributable to the site. Using the background data set above, an observed release is established in wells containing lead as "total" and "dissolved" in wells at a concentration of 11.13 |xg/L (three times 3.71 |xg/L) or higher and 3.15 |xg/L (three times 1.05 |xg/L) or higher, respectively; and barium as "total" and "dissolved" in wells at a concentration of 1,947 |xg/L (three times 649 |xg/L) or higher and 873 |xg/L (three times 291 |xg/L) or higher, respectively. Contaminated Samples in Sub-aquifer 2: Listed below are wells that document a significant increase in contaminants for an observed release of barium and lead. The highest concentration of lead detected in the background samples was 3.71 fj.g/L; therefore, an observed release is established when the sample measurement is three times or more above the background concentration (11.13 |ig/L). As shown above, the highest background concentration for barium was 649 fj.g/L; therefore, an observed release is established when the sample measurement is three times or more above the background concentration (1,947 |ig/L). Estimated results (J-coded data) were not considered if the reported number was biased high (the actual sample result had a chance of being lower than what was reported). Estimated results (J-coded data) were considered if the reported number was biased low (the actual sample result had a chance of being higher than what was reported). The biased low concentrations meet the observed release criteria at the lower estimated concentration; therefore, if the actual sample result is higher than what was reported it would still meet the observed release criteria presented in HRS, Table 2-3 (Ref. 1, Table 2-3). The locations of all release samples are shown on Figures 13 and 14 in Reference 59. Sample ID Property Number Hazardous Substance Concentration O^g/L) Sample Quantitation Limit* O^g/L) Well Depth (feet)** Elevations (feet amsl) References Surface (Ref. 64) Well Depth ASR2690 2690-104 20101 Lead (total) 13.7 10 300 982 682 Refs. 11, pp. 3, 6-7, 16, 36, 77; 15, pp. 191-192; 18; 33, p. 5; 59, Figure 14 2690-130 20125 Lead (total) 14.6 10 Unknow n 824 NA Refs. 11, PP-4, 6-7, 23, 39, 103; 15, pp. 235-236; 18; 33, p. 8; 59, Figure 14 2690-133 20124 Lead (total) 11.3 10 156 875 719 Refs. 11, PP-4, 6-7, 24, 39, 106; 15, pp. 233-234; 18; 33, p. 8; 59, Figure 14 ASR2937 2937-143 40007 Lead (dissolved) 10.6 1 Unknow n 839 NA Refs. 7, pp. 4, 6-7, 26, 37, 112; 14, pp. 15-16; 18; 36, p. 11; 59, Figure 14 September 2007 65 ------- Sample ID Property Number Hazardous Substance Concentration O^g/L) Sample Quantitation Limit* O^g/L) Well Depth (feet)** Elevations (feet amsl) References Surface (Ref. 64) Well Depth 2937-145 40005 Barium (dissolved) 3,330 10 280 857 577 Refs. 7, pp. 4, 6-7, 26, 37, 114; 14, pp. 11-12; 18; 36, p. 11; 59, Figure 13 Barium (total) 3,410 10 Notes: * The SQLs provided in this table are referred to as reporting limits in References 33, 36, 37, and 38. They are the laboratory's reporting limit (also known as the method detection limit - see the method for more details) for that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. ** Wells with unknown depths are believed to be drawing in part, if not entirely from the Ozark Aquifer. Drilling to the deeper St. Francois aquifer would be cost prohibitive for most private homeowners when the Ozark aquifer provides ample supply for domestic use. If the well is completed to the lower aquifer, the open casing construction would draw water, in part, from the overlying Ozark aquifer, amsl Above mean sea level NA Not available jig/L micrograms per liter Attribution Lead and barium mining in the Richwoods area of Washington County has a long history dating back hundreds of years (Refs. 6, pp. 1-2; 29, p. 4). Early miners tossed the barite aside into waste piles, as it originally had few uses. It became valuable after the Civil War, when it was used as a long-lasting white pigment. Barite mining boomed in 1926, when the mineral was discovered to be a useful weighting agent in oil drilling mud (Ref. 30, pp. 1-2). The production of barite in Washington County started to decline in 1985 because of competition in Nevada and overseas (Ref. 30, p. 1). Commercial mining operations created large piles of mining wastes, six of which were evaluated as sources in Section 2.2. At least four other large tailings piles are known to exist in the Richwoods study area but were not included as sources due to a lack of analytical data to characterize the nature of contaminants associated with them (Refs. 3; 32). Samples collected from the tailings piles, and analyzed by the laboratory, contained concentrations of lead and barium (see Section 3.1.1 of this document). None of the piles are known to have liners or other containment features to prevent the migration of contaminants to ground water (Ref. 22, p. 3). The release wells presented above are located down- gradient of the evaluated sources and contain elevated concentrations of barium and lead (Figure 2 of this document; Refs. 18; 59, Figures 13 and 14). The occurrence of these metals in the ground water samples is at least partially attributed to the tailings piles. Some of the metals in the ground water may be naturally occurring; however, there are a significant number of wells located up-gradient of the evaluated sources that contain low levels, or no levels of barium or lead, which indicates the naturally occurring levels of barium and lead are significantly less than what is found in the vicinity of the source areas (Ref. 5, Figure 5; Figure 2 of this document). September 2007 66 ------- Level I Samples for Sub-aquifer 1 The samples collected from private residential wells associated with targets listed below meet the Level I contamination criteria because concentration meets the observed release criteria, and it exceeds an HRS health based benchmark (see Section3.1.1 of this document and Ref. 1, Section2.5). Sample ID Hazardous Substance Hazardous Substance Concentration O^g/L) Benchmark Concentration (Hg/L)* Benchmark References ASR2690 2690-103 Lead (total) 15.1 15 MCL/MCLG Refs. 2, p. 9; 11, pp. 3, 6- 7, 16, 36, 76; 15, pp. 61-62 2690-111 Lead (total) 20.8 15 MCL/MCLG Refs. 2, p. 9; 11, pp. 3, 6- 7, 18, 36, 84; 15, pp. 41-42 2690-147 Lead (total) 26.6 15 MCL/MCLG Refs. 2, p. 9; 11, pp. 4, 6- 7, 27, 39, 120; 15, pp. 99- 100 2690-158 Lead (total) 22.3 15 MCL/MCLG Refs. 2, p. 9; 11, pp. 5-7, 30, 40, 132; 15, pp. 37-38 2690-159 Lead (total) 26.8 15 MCL/MCLG Refs. 2, p. 9; 11, pp. 5-7, 30, 40, 133; 15, pp. 11-12 2690-163 Lead (total) 21.7 15 MCL/MCLG Refs. 2, p. 9; 11, pp. 5-7, 31,40, 137; 15, pp. 101- 102 2690-169 Lead (total) 20.7 15 MCL/MCLG Refs. 2, p. 9; 11, pp. 5-7, 33,40, 143; 15, pp. 53-54 2690-170 Lead (total) 35.5 15 MCL/MCLG Refs. 2, p. 9; 11, pp. 5-7, 33,40, 144; 15, pp. 9-10 2690-172 Lead (total) 24.2 15 MCL/MCLG Refs. 2, p. 9; 11, pp. 5-7, 33,40, 146; 15, pp. 5-6 ASR 2937 2937-155 Lead (dissolved) Lead (total) 28.2 28.8 15 MCL/MCLG Refs. 2, p. 9; 7, pp. 4, 6-7, 29, 37, 124; 15, pp. 65-66 2937-158 Lead (dissolved) Lead (total) 31.2 33.3 15 MCL/MCLG Refs. 2, p. 9; 7, pp. 5-7, 30, 37, 127; 15, pp. 283- 284 2937-161 Lead (total) 15.4 15 MCL/MCLG Refs. 2, p. 9; 7, pp. 5-7, 30, 37, 130; 14, pp. 21-22 2937-163 Lead (total) 50.8 15 MCL/MCLG Refs. 2, p. 9; 7, pp. 5-7, 31,37, 132; 14, pp. 283- 284 ASR 2959 2959-118 Lead (dissolved) Lead (total) 25 26.7 15 MCL/MCLG Refs. 2, p. 9; 9, pp. 3, 5-6, 17, 29, 73 2959-119 Lead (dissolved) Lead (total) 40.2 15 MCL/MCLG Refs. 2, p. 9; 9, pp. 3, 5-6, 17, 29, 74 2959-124 Lead (dissolved) Lead (total) 45.1 47.8 15 MCL/MCLG Refs. 2, p. 9; 9, pp. 4-6, 18, 29, 79; 15, pp. 31-32 2959-143 Lead (total) 55.8 J1 15 MCL/MCLG Refs. 2, p. 9; 9, pp. 4-6, 23, 30, 98; 14, pp. 19-20 September 2007 67 ------- Sample ID Hazardous Substance Hazardous Substance Concentration fag/L) Benchmark Concentration (H-g/L)* Benchmark References ASR2991 2991-103 Lead (total) 27.8 15 MCL/MCLG Refs. 2, p. 9; 8, pp. 3, 5-6, 10, 20, 40; 14, pp. 239-240 2991-107 Lead (total) 52.9 15 MCL/MCLG Refs. 2, p. 9; 8, pp. 3, 5-6, 11,20, 44; 14, pp. 79-80 2991-114 Lead (total) 37 15 MCL/MCLG Refs. 2, p. 9; 8, pp. 3, 5-6, 13,21,51; 14, pp. 23-24 2991-120 Lead (dissolved) 38.5 15 MCL/MCLG Refs. 2, p. 9; 8, pp. 3, 5-6, 14,21, 57; 14, pp. 215-216 Lead (total) 42.8 2991-127 Lead (total) 20.5 15 MCL/MCLG Refs. 2, p. 9; 8, pp. 3, 5-6, 16,21,64; 14, pp. 235-236 2991-132 Lead (total) 30.8 15 MCL/MCLG Refs. 2, p. 9; 8, pp. 4-6, 17,21,69; 14, pp. 261-262 2991-133 Lead (total) 25.2 15 MCL/MCLG Refs. 2, p. 9; 8, pp. 4-6, 17,21,70; 14, pp. 263-264 Notes: * Benchmark is the Maximum Contaminant Level listed in the EPA Superfund Chemical Data Matrix (Ref. 2). MCL/MCLG Maximum contaminant level (MCL)/MCL goal J1 The analyte was positively identified; however, the reported value is an estimate due to serial dilution percent difference being above the control limit. The reported result may be biased low. Level I Samples for Sub-aquifer 2 The samples collected from private residential wells listed below meet the Level I contamination criteria because they contained a concentration of lead exceeding the action level of 15 (ig/L (Ref. 2, p. 9). Sample ID Hazardous Substance Hazardous Substance Concentration O^g/L) Benchmark Concentration (H-g/L)* Benchmark References ASR 2937 2937-145 Barium (dissolved) 3,330 2,000 MCL/MCLG Refs. 2, p. 5; 7, pp. 4, 6-7, 26, 37, 114; 14, pp. 11-12 Barium (total) 3,410 2,000 MCL/MCLG Notes: * Benchmark is the Maximum Contaminant Level listed in the EPA Superfund Chemical Data Matrix. MCL/MCLG Maximum contaminant level (MCL)/MCL goal Hazardous Substances Released Barium Lead Ground Water Observed Release Factor Value: 550.00 September 2007 68 ------- Other Possible Release Wells As described in Section 3.0.1 above, the geology and hydrogeology of the area is complex. The area is highly faulted and karstic and ground water flow is not fully understood. This section presents additional residential wells that were sampled and contain elevated concentrations of barium and/or lead that meet or exceed the observed release criteria but were not included above as release wells. These wells were not included in the scoring because they are located up-gradient or cross-gradient of the documented source areas. They are included to demonstrate the magnitude of the ground water contamination problem in Washington County. The lead and barium concentrations may be attributable to mine sites located further south in the Old Mines Study area, uncharacterized other possible sources, or the listed sources. Wells in Sub-aquifer 1: Sample ID Property Number Hazardous Substance Concentration O^g/L) Sample Quantitation Limit* Oig/L) Well Depth (feet)** Elevations (feet amsl) References Surface (Ref. 64) Well Depth ASR2991 2991-102 40129 Lead (dissolved) 44.6 1 410 983 573 Refs. 8, pp. 3, 5-6, 10, 20, 39; 14, pp. 241-242; 18; 38, p. 4 Lead (total) 49.1 1 ASR2959 2959-142 40131 Lead (total) 21.2 J1 1 Unknow n 947 NA Refs. 9, pp. 4-6, 23, 30, 95; 14, pp. 245- 246; 18; 37, p. 12 Notes: * The SQLs provided in this table are referred to as reporting limits in References 37 and 38. They are the laboratory's reporting limit for (also known as the method detection limit - see the method for more details) that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. ** Wells with unknown depths are believed to be drawing in part, if not entirely from the Ozark Aquifer. Drilling to the deeper St. Francois aquifer would be cost prohibitive for most private homeowners when the Ozark aquifer provides ample supply for domestic use. If the well is completed to the lower aquifer, the open casing construction would draw water, in part, from the overlying Ozark aquifer. J1 The analyte was positively identified; however, the reported value is an estimate due to serial dilution percent difference being above the control limit. The reported result may be biased low. However, even if the value was actually higher, it would still meet the observed release criteria, amsl Above mean sea level NA Not available jig/L micrograms per liter Wells in Sub-aquifer 2: Sample ID Property Number Hazardous Substance Concentration O^g/L) Sample Quantitation Limit* O^g/L) Well Depth (feet)* * Elevations (feet amsl) References Surface (Ref. 64) Well Depth ASR2937 2937-148 40034 Lead (dissolved) 10.3 1 200 903 703 Refs. 7, pp. 4, 6-7, 26, 37, 117; 14, pp. 67-68; 18; 36, pp. 11-12 Lead (total) 32.8 1 September 2007 69 ------- Sample ID Property Number Hazardous Substance Concentration O^g/L) Sample Quantitation Limit* O^g/L) Well Depth (feet)* * Elevations (feet amsl) References Surface (Ref. 64) Well Depth 2937-149 40008 Lead (dissolved) 18.3 1 Unknown 801 NA Refs. 7, pp. 4, 6-7, 27, 37, 118; 14, pp. 17-18; 18; 36, p. 12 Lead (total) 150 1 2937-150 40084 Lead (total) 45.2 1 160 821 661 Refs. 7, pp. 4, 6-7, 28, 37, 119; 14, pp. 155-156; 18; 36, p. 12 2937-151 40035 Lead (total) 14.8 1 137 875 738 Refs. 7, pp. 4, 6-7, 28, 37, 120; 14, pp. 69-70; 18; 36, p. 12 2937-152 40085 Lead (total) 30.2 1 336 794 458 Refs. 7, pp. 4, 6-7, 28, 37, 121; 14, pp. 157-158; 18; 36, p. 12 2937-154 40152 Lead (total) 13.6 1 300 869 569 Refs. 7, pp. 4, 6-7, 29, 37, 123; 14, pp. 279-280; 18; 36, p. 12 2937-160 40089 Lead (total) 22.6 1 Unknown 873 NA Refs. 7, pp. 5-7, 30, 37, 129; 14, pp. 165-166; 18; 36, p. 14 2937-162 40087 Lead (total) 50.5 1 185 838 653 Refs. 7, pp. 5-7, 31, 37, 131; 14, pp. 161-162; 18; 36, p. 14 2937-167 40088 Lead (total) 30.8 1 Unknown 871 NA Refs. 7, pp. 5-7, 32, 37, 136; 14, pp. 163-164; 18; 36, p. 14 ASR2959 2959-140 40178 Lead (total) 12.2 1 160 841 681 Refs. 9, pp. 4-6, 22, 30, 95; 14, pp. 313- 314; 18; 37, p. 11 Notes: * The SQLs provided in this table are referred to as reporting limits in References 36 and 37. They are the laboratory's reporting limit for (also known as the method detection limit - see the method for more details) that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. ** Wells with unknown depths are believed to be drawing in part, if not entirely from the Ozark Aquifer. Drilling to the deeper St. Francois aquifer would be cost prohibitive for most private homeowners when the Ozark aquifer provides ample supply for domestic use. If the well is completed to the lower aquifer, the open casing construction would draw water, in part, from the overlying Ozark aquifer, amsl Above mean sea level NA Not available jig/L micrograms per liter September 2007 70 ------- 3.2 WASTE CHARACTERISTICS 3.2.1 TOXICITY/MOBILITY Hazardous Substance Source No. Toxicity Factor Value Mobility F actor Value Does Haz. Substance Meet Observed Release? (Y/N) Toxicity/ Mobility (Table 3-9) References Barium 1, 2, 3, and 4 10,000 1.0 Yes 10,000 Refs. 2, p. 5; 7, pp. 1-32; 8, pp. 1- 18; 9, pp. 1-26; 11, pp. 1-34; 13, pp. 1-23 Lead 1, 2, 3, and 4 10,000 1.0 Yes 10,000 Refs. 2, p. 9; 7, pp. 1-32; 8, pp. 1- 18; 9, pp. 1-26; 11, pp. 1-34; 13, pp. 1-23 Toxicity/Mobility Factor Value: 10,000 (Ref. 1, Table 3-9) 3.2.2 HAZARDOUS WASTE QUANTITY Sub-Aquifer Source No. Source Type Source Hazardous Waste Quantity 1 1 Tailings Pile 207,747.7 1 2 Tailings Pile 93,821.5 2 3 Tailings Pile 180,271.4 2 4 Tailings Pile 234,553.8 2 5 Tailings Pile 574,992 2 6 Tailings Pile 220,480.6 Sum of Values: 1,511,867 The above listed hazardous waste quantity of 1,511,867 is a summation of all sources evaluated in Section 2.2 of this documentation record. The sub-aquifer 1 (western) source hazardous waste quantity sum is 301,569.2, which receives a hazardous waste quantity factor value of 10,000. The sub-aquifer 2 (eastern) source hazardous waste quantity sum is 1,210,297.8, which receives a hazardous waste quantity factor value of 1,000,000. In addition, each source evaluated separately would receive a hazardous waste quantity factor value of 10,000 (Ref. 1, Table 2-6). Combined Hazardous Waste Quantity Factor Value: 1,000,000 (Ref. 1, Table 2-6) 3.2.3 WASTE CHARACTERISTICS FACTOR CATEGORY VALUE Toxicity /Mobility Factor Value: 10,000 Hazardous Waste Quantity Factor Value: 1,000,000 (cumulative or sub-aquifer 2); 10,000 (sub-aquifer 1 or each source evaluated separately) Toxicity/Mobility Factor Value X September 2007 71 ------- Hazardous Waste Quantity Factor Value: 10,000,000,000 or 1 x 1010 (cumulative or sub-aquifer 2); 100,000,000 or 1x10s (sub-aquifer 1 or each source evaluated separately) In accordance with the HRS, the waste characteristics factor value is subject to a maximum product of 1x10s or 100,000,000 (Ref. 1, section 3.2.3). Each sub-aquifer listed above, would individually produce the same waste characteristics factor value of 100 as all the sources considered as a whole. In addition, each source listed above, if individually considered, would produce the same waste characteristics factor value of 100 as all the sources considered as a whole. Waste Characteristics Factor Category Value: 100 (Ref. 1, Table 2-7) 3.3 TARGETS 3.3.1 NEAREST WELL Sub-aquifer 1 2991-132 (four people associated with property 40139) and numerous other properties Level of Contamination (I, II, or potential): Level I (See Section 3.1.1 andRefs 59, Figure 13). Sub-aquifer 2 2937-145 (two people associated with property 40005) and numerous other properties Level of Contamination (I, II, or potential): Level I (See Section 3.1.1 andRefs 59, Figure 13). As documented in Section 3.1.1 above, there are numerous drinking water wells containing lead at concentrations that both meet the observed release criteria and exceed a health-based benchmark (the MCL/MCGL for lead and barium). In accordance with Reference 1, Section 3.3.1, Table 3-11, a nearest well factor of 50 is assigned. Nearest Well Factor Value: 50 (Ref. 1, Table 3-11) 3.3.2 POPULATION Population served by individual wells sampled was determined by interviewing home owners at the time of sampling and recording the responses on field data collection sheets (Refs. 14; 15). 3.3.2.1 Level of Contamination Presented below are the numbers of people drinking from wells that have documented observed releases. Section 3.3.2.2 presents the number of people drinking from wells which contain hazardous constituents that meet the observed release criteria and are above an HRS health-based benchmark (i.e., Level I), and Section 3.3.2.3 presents the number of people drinking from wells which contain hazardous constituents that meet the observed release criteria but are below an HRS health-based benchmark (i.e., Level II) (Ref. 1, Section 2.5). September 2007 72 ------- 3.3.2.2 Level I Targets The concentrations of hazardous substance in the samples below and the HRS health based benchmark used for comparison are documented in Section 3.1.1. The well locations are shown on Figure 13 in Reference 59. Sample ID Aquifer Number of Residents References Sub-aquifer 1 2690-103 Ozark 5 Ref. 15, pp. 61-62 2690-111 Ozark 1 Ref. 15, pp. 41-42 2690-147 Ozark 2 Ref. 15, pp. 99-100 2690-158 Ozark 2 Ref. 15, pp. 37-38 2690-159 Ozark 4 Ref. 15, pp. 11-12 2690-163 Ozark 3 Ref. 15, pp. 101-102 2690-169 Ozark 3 Ref. 15, pp. 53-54 2690-170 Ozark 5 Ref. 15, pp. 9-10 2690-172 Ozark 5 Ref. 15, pp. 5-6 2937-155 Ozark 1 Ref. 15, pp. 65-66 2937-158 Ozark 5 Ref. 15, pp. 283-284 2937-161 Ozark 6 Ref. 14, pp. 21-22 2937-163 Ozark 2 Ref. 14, pp. 283-284 2959-118 Ozark 2.641 Ref. 4, p. 2 2959-119 Ozark 2.641 Ref. 4, p. 2 2959-124 Ozark 5 Ref. 15, pp. 31-32 2959-143 Ozark 12 Ref. 14, pp. 19-20 2991-103 Ozark 2 Ref. 14, pp. 239-240 2991-107 Ozark 2 Ref. 14, pp. 79-80 2991-114 Ozark 1 Ref. 14, pp. 23-24 2991-120 Ozark 2 Ref. 14, pp. 215-216 2991-127 Ozark 3 Ref. 14, pp. 235-236 2991-132 Ozark 4 Ref. 14, pp. 261-262 2991-133 Ozark 1 Ref. 14, pp. 263-264 Sub-aquifer 2 2937-145 Ozark 2 Ref. 14, pp. 11-12 Notes: 1 Exact number of residents is not known. Value assigned is the average number (2.64) of residents per household for Washington County as determined in the 2000 Census (Ref. 4, p. 2). Sum of Population Served by Level I Wells: 83.28 Sub-aquifer 1: 81.28 Sub-aquifer 2: 2 Sum of Population Served by Level I Wells x 10: 832.8 Sub-aquifer 1: 812.8 Sub-aquifer 2: 20 LevellConc entrations Factor V alue: 832.8 Level I Concentrations Factor Value (Sub-Aquifer 1): 812.8 Level I Concentrations Factor Value (Sub-Aquifer 2): 20 September 2007 73 ------- 3.3.2.3 Level II Targets The concentrations of the hazardous substance in the samples below are documented in Section 3.1.1. The well locations are shown on Figure 14 in Reference 59. Sample ID Aquifer Number of Residents References Sub-aquifer 1 2690-134 Ozark 2 Ref. 15, pp. 205-206 2690-166 Ozark 5 Ref. 15, pp. 17-18 2959-111 Ozark 2 Ref. 14, pp. 191-192 2991-121 Ozark 8 Ref. 14, pp. 49-50 2991-125 Ozark 4 Ref. 14, pp. 47-48 2991-126 Ozark 2 Ref. 14, pp. 83-84 Sub-aquifer 2 2690-104 Ozark 2 Ref. 15, pp. 191-192 2690-130 Ozark 20 Ref. 15, pp. 235-236 2690-133 Ozark 2 Ref. 15, pp. 233-234 2937-143 Ozark 2 Ref. 14, pp. 15-16 Sum of Population Served by Level II Wells: 49 Sub-aquifer 1: 23 Sub-aquifer 2: 26 Level II Concentrations Factor Value: 49 Level II Concentrations Factor Value (Sub-Aquifer 1): 23 Level II Concentrations Factor Value (Sub-Aquifer 2): 26 3.3.2.4 Potential Contamination Potential contamination was not scored. 3.3.3 RESOURCES The resources factor was not scored. 3.3.4 WELLHEAD PROTECTION AREA The wellhead protection factor was not scored because Level I and Level II contamination maximized the HRS pathway score. September 2007 74 ------- 4.0 SURFACE WATER MIGRATION PATHWAY 4.1 OVERLAND/FLOOD MIGRATION COMPONENT General Hydrology The Washington County Lead District-Richwoods site falls in two separate U.S. Geological Survey (USGS) defined hydrologic units (sub-watersheds or drainage basins). One of the sub-watershed drains to Meramec River in the northwest part of Washington County and the other sub-watershed drains to the Big River in the northeast part of Washington County (Ref. 3). HRS watersheds will normally be subdivisions of these USGS watersheds depending on the location of the PPEs for the site being evaluated. Multiple probable points of entry (PPEs) exist at the site downgradient of the tailings pond sources and within the tailings ponds themselves. The in-water segments (generally defined as the distance between the PPE for a source and a distance of 15 miles) from the numerous sources and possible sources overlap and ultimately discharge to either the Meremac or Big River. Both drainage basins receive run-off from other mine sites up-gradient of the Washington County Lead District- Richwoods site (Refs. 3; 18; 52). The primary drainage feature of the first USGS hydrologic unit (07140102060) is Little Indian Creek to which overflow from Sources 1 and 2 would drain via overland flow. The overland segment along Little Indian Creek extends from on-site sources to Little Indian Creek for about 1,835 feet. From the PPE in Little Indian Creek, flow is north-northwest for 10 miles where Little Indian Creek joins Indian Creek. From this confluence, Indian Creek flows north for 2.5 miles where it joins the Meramec River. The nearest USGS gauging station to the site is on the Meramec River at Robertsville, Missouri. Average flow from 1940 to 1951 was 2,569 cubic feet per second (cfs) (Ref. 59, Figure 16; 3; 46, p. 1). Overland flow from Sources 3, 4, 5 and 6 in Richwoods located in second USGS hydrologic unit (07140104080) is presented from the most up-gradient source in the south to the most downgradient source in the north. This hydrologic unit within Richwoods drains to either Ditch Creek, Turkey Creek or Calico Creek which discharge in the Big River. Drainage water from Sources 3, 4, 5, and 6 discharge to the Big River watershed (Ref. 3). Surface water from Source 6 flows into an unnamed intermittent tributary. The unnamed tributary runs north-northeast for 1.5 miles where it joins Calico Creek. The 15- mile target distance limit (TDL) from Source 6 extends from Calico Creek for 3 miles where it meets the confluence with Big River. Surface water from Sources 3, 4, and 5 drains to either Turkey Creek an intermittent stream or Ditch Creek a perennial stream. The overland segment along Turkey Creek extends from Sources 3, 4, and 5 to Turkey Creek for about 2.5 miles before merging with Ditch Creek. Ditch Creek flows north for 3.75 miles where it meets the Big River. The nearest USGS gauging station from both Turkey Creek and the tributary to Calico Creek to the site is on Big River near Richwoods, located approximately 7.5 miles upstream of the confluence with Turkey Creek. Average flow from 1950 to 2005 for Big River at Richwoods was 702.9 cfs (Ref. 59, Figure 16; 3; 47, pp. 1-2). September 2007 75 ------- Insert Figure 15 September 2007 76 ------- 4.1.1 Definition of Hazardous Substance Migration Path for Overland/Flood Component While there are two USGS defined watersheds, there are multiple HRS watersheds in the Richwoods area. As described below, each source (tailings pond) evaluated in Section 2.2 of this document meets the HRS definition of a surface water body and is also considered an isolated, stand alone HRS watershed (Ref. 1, Section 4.0.2 ). Because they have no perennial water connection to other perennial waters, each is evaluated as its own HRS isolated watershed. The probable point(s) of entry to the wetlands associated with the ponds is where the wetland and mine tailings meet, and the target distance limit is confined to the individual tailings ponds themselves (Ref. 1, Sections 4.0.2 and 4.1.1.1). Presented below is additional information regarding how contamination from the sources could migrate overland to other perennial waters to illustrate the connection of each source to the area wide surface water risk. Source 1, the Desoto Mining Company Politte Mine South Tailings Pond is located in USGS hydrologic unit 07140102060 (Figure 15, Ref. 3). As shown on Reference 3, this source drains to Little Indian Creek. Source 2, the Desoto Mining Company Politte Mine North Tailings Pond is located in USGS hydrologic unit 07140102060 (Figure 15, Ref. 3). As shown on Reference 3, this source drains to Little Indian Creek. Source 3, the Desoto Mining Company Plants A & B (Agers) Northwest Tailing Pond is located in USGS hydrologic unit 07140104080 (Figure 15, Ref. 3). As shown on Reference 3, this source drains to unnamed intermittent tributary to Turkey Creek. Drainage from the pond would have to follow an overland migration route to Ditch Creek, the nearest downgradient perennial stream. Source 4, the Desoto Mining Company Plants A & B (Agers) Central Tailing Pond is located in USGS hydrologic unit 07140104080 (Figure 15, Ref. 3). As shown on Reference 3, this source drains to unnamed intermittent tributary to Turkey Creek. Drainage from the pond would have to follow an overland migration route to Ditch Creek, the nearest downgradient perennial stream. Source 5, the Desoto Mining Company Plants A & B (Agers) South Tailing Pond is located in USGS hydrologic unit 07140104080 (Figure 15, Ref. 3). As shown on Reference 3, this source drains to Turkey Creek which is intermittent. Drainage from the pond would have to follow an overland migration route to Ditch Creek, the nearest downgradient perennial stream. Source 6, the N.L Baroid Big 4 Mine East Tailing Pond is located in USGS hydrologic unit 07140104080 (Figure 15, Ref. 3). As shown on Reference 3, this source drains to an unnamed tributary to Calico Creek. Drainage from the pond would have to follow an overland migration route to Calico Creek, the nearest downgradient perennial stream. Watershed(s) Being Evaluated Four HRS watersheds are evaluated below. The four watersheds are associated with four of the HRS sources: source areas 3 through 6. Each of these sources are a tailings ponds and are also associated with HRS eligible wetlands classified by the U.S. Fish and Wildlife Service (USFWS) National Wetlands Inventory (NWI) program as either: freshwater emergent wetland or freshwater forested/shrub wetland (Refs. 32; 48, pp. 1-10). As directed in HRS Section 4.1.1.3 (Ref. 1), the individual HRS watershed providing the highest surface water migration pathway score is entered in the score sheets in the front of this document and is used to determine the HRS site score. Individual score sheets for each tailings pond watershed are presented as Appendix B to the documentation record. The rational supporting the scores is presented below. September 2007 77 ------- 4.1.2 LIKELIHOOD OF RELEASE 4.1.2.1 Observed Release Surface water, sediment and source samples were collected by EPA in August 2006 under ASR 3169 in accordance with the approved Quality Assurance Project Plan (QAPP) (Ref. 51, pp. 1-3; 65). Ten co- located surface water and sediment samples were proposed; however, due to site access issues only seven sediment and seven surface water samples were collected and submitted for analysis. An insufficient amount of data exists to draw any conclusions about the site as a whole and releases to the creeks in the Richwoods area. In addition, because the main surface water features (Little Indian Creek, Meramec River, Ditch Creek, Turkey Creek, Calico Creek and Big River) all have significant historic mining activities in their watersheds upgradient of the site, background samples that are representative of surface water and sediment samples without the influence of mining activity were difficult to locate. The sampling conducted in August 2006 identifed source-specific concentrations of barium and lead. An observed release is documented by direct observation to isolated wetlands within the Richwoods area. DIRECT OBSERVATION Basis for Direct Observation: The direct contact of the waters in the tailings ponds with the contaminated tailing materials constitutes for HRS purposes a direct observation of an observed release to the ponds and the targets associated with each of the four tailings ponds (see the hazardous substance table below) (see Appendix C). Hazardous substances at each are in direct contact with HRS eligible surface water bodies and the targets associated with them (Ref. 1, Section 4.1.2.1.1). As shown on Figure 17 in Reference 59, each source area evaluated in Section 2.2 of this document has a portion of the tailings pond that is classified as a wetland by the USFWS, NWI program and meets the definition of an HRS eligible wetland target (Ref. 1, Sec. 4.1.4.3.1). All the wetlands in the Richwoods area are isolated to specific tailings ponds. The following Table presents the source areas and the name and size of the wetland associated with it. Source Size Area Wetland Type Wetland Code (acres) Reference 3 PEMKh Freshwater Emergent Wetland 37.04 Ref. 48, pp. 1,5,7 4 PF05Gx Freshwater Forested/Shrub Wetland 18.40 Ref. 48, pp. 1-2,5, 8 5 PEMKh Freshwater Emergent Wetland 77.12 Ref. 48, pp. 1-3 6 PEMKh Freshwater Emergent Wetland 56.03 Ref. 48, pp. 1,9-10 Hazardous Substances in the Release In 1972, a report was published by the Missouri Geological Survey & Water Resources that evaluated the barite ore potential of tailings ponds in Washington County (Ref. 28). The intent of the study was to quantify the amount of barite ore in the tailings ponds to determine if it is economically feasible to recover the ore using modern separation techniques (Ref. 28, pp 2, 3). The report summarized that there are large barite reserves present in the district tailings ponds (Ref. 28, pp. 3, 18). As part of the 1972 study, a total of 865 samples were collected and assayed from 185 boreholes collected from four representative tailings ponds (Ref. 28, pp. 10-12). The average amount of barite in the tailing that was determined for district estimates was 5 percent (Ref. 28, p. 18). Quantitative analysis of low September 2007 78 ------- grade composite samples from the four tailings ponds tested indicated trace amounts of lead (Ref. 28, p. 19). This document indicates that barium and lead are associated with the tailings ponds. In addition soil and ground water samples collected in the study area contained elevated concentrations of barium and lead as documented in Section 5.0.1. Hazardous substances associated with these tailings ponds are also established by analytical data of samples collected from the wetland designated areas in 2006. Samples collected from the source areas are shown on Figures 18, 19, 20, and 21. Figures 18, 19,20, and 21 are maps created with geographic information system (GIS) applications. Figures 18, 19, 20, and 21 also presents the U.S. Fish and Wildlife Service National Wetlands inventory shape files as well as the Incidents of Mines, Occurrences, and Prospects (IMOP) tailings pond shape files. The analytical data from the wetlands sampled during August 2006 are as follows: Sample ID Sample Location Barium (mg/kg) Barium SQL* (mg/kg) Lead (mg/kg) Lead SQL* (mg/kg) Reference 3169-20 Source 3 3,820 27.6 5,410 1.36 Figure 18; Refs. 39, pp. 3, 5-6, 12, 40, 63; 43, p. 3 3169-22 5,430 48 632 1.2 Figure 18; Refs. 39, pp. 3, 5-6, 12, 42, 63; 43, pp 3-4 3169-10 Source 4 10,300 84.5 968 1.41 Figure 19; Refs 39, pp. 3, 5-6, 9, 28, 63; 43, p. 2 3169-13 Source 5 8,480 74 1,230 1.23 Figure 20; Refs 39, pp. 3, 5-6, 10, 31, 63; 43, p. 2 3169-16 7,910 74.3 409 1.24 Figure 20; Refs 39, pp. 3, 5-6, 11,35, 63; 43, p. 3 3169-26 Source 6 5,830 58.3 544 1.46 Figure 21; Refs 39, pp. 3, 5-6, 13, 46, 62; 43, p. 4 Notes: ID Identification mg/kg milligrams per kilogram * The SQLs provided in this table are referred to as reporting limits in References 43. They are the laboratory's reporting limit (also known as the method detection limit - see the method for more details) for that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. Chemical Analysis No observed releases by chemical analysis to surface water have been identified for the the Richwoods area. Surface water, sediment, and source samples were collected in August 2006 under ASR 3169 in accordance with the approved QAPP (Ref. 51; 65) in the rivers and streams in this area. However, because the area is large and has multiple water bodies, an insufficient amount of data exists to draw conclusions about the contamination in the Richwoods area as a whole and releases to the individual creeks and rivers. In addition, because the main surface water features (Little Indian Creek, Turkey Creek, Calico Creek, a tributary to Calico Creek, and Berry Branch) all have significant historic mining activities in their watersheds up-gradient of the site, background samples that are representative of surface water and sediment without the influence of mining activity were difficult to locate. Hazardous Substance Released An observed release factor value of 550 is assigned for each tailings pond that contains freshwater emergent and forested shrub wetlands based on direct observation. Surface Water Observed Release Factor Value: 550 September 2007 79 ------- Insert Figure 18 September 2007 ------- Insert Figure 19 September 2007 ------- Insert Figure 20 September 2007 ------- Insert Figure 21 September 2007 ------- 4.1.4.2 Environmental Threat Waste Characteristics 4.1.4.2.1 Ecosystem Toxicity/Persistence/Bioaccumulation Ecosystem Toxicity Ecosystem Toxicity/ Hazardous Source Factor Persistence Persistence Factor Value Substance No. Value1 Factor Value2 (Table 4-20)3 References Barium 3-6 1 1 1 2, p. 5 Lead 3-6 1,000 1 1,000 2, p. 9 Notes: 1 Freshwater ecotoxicity values used 2 Lake persistence factor value used 3 Table found in Reference 1 Hazardous Substance Ecosystem Toxicity/ Persistence Factor Value Bioaccumulation Factor Value1 Reference Ecosystem Toxicity/ Persistence/ Bioaccumulation Factor Value (Table 4-21)2 Barium 1 500 2, p. 5 500 Lead 1,000 50,000 2, p. 9 5 x 107 Notes: 1 Freshwater bioaccumulation factor values used 2 Table found in Reference 1 An ecosystem toxicity/persistence/bioaccumulation factor value of 5 x 10 7 (50,000,000) is assigned from the table above based on lead. This value is entered below and on line 23 in Table 4-1. This value is also assigned to each tailings pond watersheds in Appendix B. Ecosystem Toxicity/Persistence/Bioaccumulation Factor Value: 5 x 10 7 4.1.4.2.2 Hazardous Waste Quantity Below are the HWQ for Sources 3 through 6 as discussed in Sections 2.2.1 and 2.2.2. Because each tailings pond is being evaluated as a stand alone watershed, hazardous waste quantity is evaluated separately for each tailings pond. Based on the source hazardous waste quantity values presented below and Table 2-6 of the HRS (Ref. 1, Section 2.4.2.2), each source receives a hazardous waste quantity factor value of 10,000. All tailings ponds in the Richwoods area have a surface water containment value that is greater than 0 (see page 43 of this document). Source Number Source Type Source Hazardous Waste Quantity Is Source Hazardous Constituent Quantity Data Complete? (yes/no) 3 Tailings Pile 180,271.4 No 4 Tailings Pile 234,553.8 No 5 Tailings Pile 574,992 No 6 Tailings Pile 220,480.6 No September 2007 84 ------- Sum of Values: not applicable in this case A hazardous waste quantity factor value of 10,000 is assigned from Reference 1, Table 2-6 for each tailings pond above. This value is entered below and on line 24 of Table 4-1 for each watershed in Appendix B. 4.1.4..2.3 Waste Characteristics Factor Category Value In accordance with Section 4.1.4.2.3 of Reference 1, a waste characteristics factor value is computed by multiplying the ecotoxicity/persistence factor value by the hazardous waste quantity factor value (the product of which is subject to a maximum of 1 x 10s) and then multiplying that number by the bioaccumulation potential factor value. This product (subject to a maximum of 1 x 1012) is then entered into Table 2-7 (Ref. 1, Section 2.4.3.1) to obtain a waste characteristics factor category value. Of the metal compounds above, lead produces the highest value. This value is entered below and on line 25 in table 4-1 at the beginning of this documentation record and also in Appendix B for each watershed. Ecosystem Toxicity/Persistence factor value x Hazardous Waste Quantity factor value: (1 x 10s maximum product) 1,000 x 10,000 = 1 x 107 Ecosystem Toxicity/Persistence x Hazardous Waste Quantity) x Bioaccumulation Potential factor value (1 x 1012 maximum product) I x 107 x 50,000 = 5 x 1011 Waste Characteristics Factor Category Value: 560 (Ref. 1, Table 2-7) Thus this value is assigned to all four watersheds being evaluated. 4.1.4.3. Environmental Threat Targets Level I Targets Zones of actual contamination subject to Level I concentrations have not been established. Level II Targets A zone of Level II contamination has been established for the freshwater emergent wetland in all four source areas. Because an observed release by direct observation has been established for each of the wetland areas located on sources 3 through 6, each of these wetlands areas is subject to Level II contamination, and each wetland area is by definition a surface water feature and an HRS eligible wetland sensitive environment as defined in40 C.F.R. 230.3 (Ref. 1, Sections 4.0.2, 4.1.4.3.1 and4.1.4.3.1.2). Because the wetlands occur on the sources, the zone of actual contamination is defined as the perimeter of the wetland. HRS Section 4.1.4.3.1.2 states that in the area of Level II concentrations where the probable point of entry is located in the wetland, measure the perimeter of that portion of the wetland subject to Level II concentrations as the length as shown in the table under basis for direct observation. Wetlands are the only known sensitive environments that occur within the sources areas that meet Level II concentrations. The tailings ponds are located on or adjacent to areas classified as wetland by the September 2007 85 ------- USFWS (Refs. 48; 59, Figure 11). The observed release criterion was met by direct observation. The wetland perimeters were calculated using a GIS shapefile for the tailings pond defined in IMOP. As shown in the table below, all of the mapped wetlands are at least 0.1 of a mile in size (Ref. 48). Source Area Wetland Type Wetland Code Wetland Perimeter (miles) HRS Target Value (Table 4-24) Reference 3 PEMKh Freshwater Emergent Wetland 1.112 50 Figure 18; Ref. 48, pp. 1, 5,7 4 PF05Gx Freshwater Forested/Shrub Wetland 0.719 25 Figure 19; Ref. 48, pp. 1-2,5,8 5 PEMKh Freshwater Emergent Wetland 2.091 75 Figure 20; Ref. 48, pp. 1-3 6 PEMKh Freshwater Emergent Wetland 1.462 50 Figure 21; Ref. 48, pp. 1,9-10 As shown in Appendix B, individual source areas are assigned values between 25 and 75. Assigned values for each source area by itself are entered into the Tables in Appendix B. Wetland Value (Reference 1, Table 4-24): 25 to 75 (for each of the four watersheds) Wetland Value (Reference 1, Table 4-24): 75 (maximum wetland value for tailings ponds listed above) The maximum scoring watershed is that associated with source area 5, and this value is assigned in the scoresheets for the overall site. The individual values are assigned for each watershed in Appendix B. Sum of Level II Sensitive Environments Value + Wetlands Value: 75 Level II Concentrations Factor Value: 75 4.1.4.3.1.3 Potential Targets Potential concentrations was not evaluated because Level II targets maximized the environmental threat component score for each watershed evaluated. September 2007 86 ------- 5.0 SOIL EXPOSURE PATHWAY 5.01. GENERAL CONSIDERATIONS The soil exposure pathway considers both tailings piles and areas of contaminated soils associated with residential sampling. Defined areas can be assigned to the tailings piles. Contaminated soil associated with residential properties was not inferred to extend beyond the boundary of the grid cell sampled because residences are far apart and no data currently exists between residences to support such an assumption. Letter by which this area is to be identified: A Name of the area: Area of observed contamination (AOC) A includes Source 1 Desoto Mining Company Politte Mine South Tailings Pond. As discussed in the Source Characterization Section (Section 2.2.1 of this document), this source is evaluated as a pile. Location and description of area (with reference to a map of the site): AOC A is located south of Highway A and west of Highway 47. AOC A consists of a tailings pile that covers 62 acres covered by water, swampy intermittent water, and trees (Figure 5 of this document; Refs. 31, p. 4; 32). Figure 22 in Reference 59 shows the location of AOC A. Observed Contamination Evidence: In August 2006, EPA collected samples from tailings piles within the Richwoods area to characterize the source areas. In situ readings were collected with the XRF for lead concentrations and results were record on field sheets. Waste samples from the piles were also submitted for fixed laboratory analysis as described below. Background Samples: To document that the waste in this tailings pond contains elevated concentrations of barium and lead, the soil samples identified below are used to establish background levels for the Richwoods area. The samples were collected from areas that were as far away from mined lands as possible and the analytical results were not qualified as estimated by the laboratory (J-coded). Sample ID Sample Medium Depth Date Reference 2691-12 Soil 0-2 inches 8/08/2005 Refs. 12, p. 47; 54, p. 16 2959-8 Soil 0-2 inches 4/04/2006 Refs. 9, p. 39; 54, p. 16 2959-11 Soil 0-2 inches 4/04/2006 Refs. 9, p. 42; 54, p. 16 2959-13 Soil 0-2 inches 4/04/2006 Refs. 9, p. 44; 54, p. 16 2991-12 Soil 0-2 inches 4/17/2006 Refs. 8, p. 34; 54, p. 16 2991-14 Soil 0-2 inches 4/17/2006 Refs. 8, p. 36; 54, p. 16 Background Concentrations: The following table presents the barium and lead concentrations found at the background sample locations. The shaded values, the highest found at any background location are selected as a conservative background level for comparison to concentrations in source samples. September 2007 87 ------- Sample ID Sample Type Date Hazardous Substance Hazardous Substance Concentration (mg/kg) Sample Quantitation Limit* (mg/kg) Reference 2691-12 Soil 8/08/2005 Barium 362 20.3 Refs. 12, pp. Lead 30.5 1.02 10, 32; 34, p. 2 2959-8 Soil 4/04/2006 Barium 735 1.94 Refs. 9, pp. 8, Lead 36.5 4.85 28; 37, p. 2 2959-11 Soil 4/04/2006 Barium 248 1.89 Refs. 9, pp. 9, Lead 26.1 4.73 28; 37, p. 3 2959-13 Soil 4/04/2006 Barium 411 2.00 Refs. 9, pp. Lead 35.3 5.00 10,28; 37, p. 3 2991-12 Soil 4/17/2006 Barium 199 1.96 Refs. 8, pp. 8, Lead 45.0 4.91 20; 38, p. 3 2991-14 Soil 4/17/2006 Barium 371 2.01 Refs. 8, pp. 9, Lead 37.8 5.03 20; 38, p. 3 Notes: * The SQLs provided in this table are referred to as reporting limits in Reference 34, 37, and 38. They are the laboratory's reporting limit for (also known as the method detection limit - see the method for more details) that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. ID Identification mg/kg milligrams per kilogram Bolded These concentrations considered to be the background levels for each of these metals Contaminated Samples: Waste samples from the tailings pile were collected in August 2006 under ASR 3169 and were analyzed for arsenic, barium, cadmium, and lead (Ref. 39). Analysis of the tailings samples was conducted by the EPA Region 7 laboratory in accordance to the site specific QAPP (Ref. 51; 65). Area Letter: A Sample ID Sample Medium Depth Date Reference 3169-18 tailings 0-2 inches 8/30/2006 Refs. 39, pp. 3, 5-6, 11, 38, 63; 43, p. 3; 51, pp. 2-3; 54, p. 16 3169-19 tailings 0-2 inches 8/30/2006 Refs. 39, pp. 3, 5-6, 12, 39, 63; 43, p. 3; 51, pp. 2-3; 54, p. 16 September 2007 88 ------- Contaminated Sample Concentrations: Area Letter: A Hazardous Substance Contaminated Sample(s) (mg/kg) Sample Quantitation Limit* (mg/kg) Reference Sample IDs Concentration Barium 3169-18 5,990 49.0 Refs. 39, pp. 5-6, 11, 38, 63; 43, p. 3 3169-19 5,130 29.5 Refs. 39, pp. 5-6, 12, 39, 63; 43, p. 3 Lead 3169-18 1,740 1.23 Refs. 39, pp. 5-6, 11, 38, 63; 43, p. 3 3169-19 445 1.48 Refs. 39, pp. 5-6, 12, 39, 63; 43, p. 3 Notes: * The SQLs provided in this table are referred to as reporting limits in Reference 43. They are the laboratory's reporting limit (also known as the method detection limit - see the method for more details) for that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. ID Identification mg/kg milligrams per kilogram Attribution Given that the waste in this source was tailings deposited as a result of the mining operations that compose the Richwood site, the contamination in the waste is considered attributable to the site. Area Hazardous Waste Quantity Area: A Description According to IMOP the tailing pile in Area A covers 62 acres (Figure 5 of this document). According to the 208 project the tailings pond consists of water, swampy intermittent water, and trees (Refs. 31, p. 4; 32). An acre is equivalent to 43,560 square feet (ft2). The approximate size of the tailing pile is 2,700,720 ft2 (62 times 43,560 ft2). Source Type Area Units References Pile 2,700,720 Square feet Figure 5 of this document; Refs. 31, p. 4; 32 Sum (ft2): 2,700,720 Equation for Assigning Value (Ref. 1, Table 5-2): A/34 Area Assigned Value: 79,432.9 Area Assigned Value: = 79,432.9 September 2007 89 ------- Letter by which this area is to be identified: B Name of the area: Area of observed contamination (AOC) B includes Source 2 Desoto Mining Company Politte Mine North Tailings Pond. As discussed in the Source Characterization Section (Section 2.2.1 of this document), this source is evaluated as a pile. Location and description of area (with reference to a map of the site): AOC B is located south of Highway A and west of Highway 47. AOC B consists of a tailings pile that covers 28 acres covered by water, swampy intermittent water, and trees (Figure 6 of this document; Refs. 31, p. 4; 32). Figure 22 in Reference 59 shows the location of AOC B. Observed Contamination Evidence: In August 2006, EPA collected samples from tailings piles within the Richwoods area to characterize the source areas. In situ readings were collected with the XRF for lead concentrations and results were record on field sheets. Waste samples from the piles were also submitted for fixed laboratory analysis as described below. Background Samples: To document that the waste in this tailings pond contains elevated concentrations of barium and lead, the soil samples identified below are used to establish background levels for the Richwoods area. The samples were collected from areas that were as far away from mined lands as possible and the analytical results were not qualified as estimated by the laboratory (J-coded). Sample ID Sample Medium Depth Date Reference 2691-12 Soil 0-2 inches 8/08/2005 Refs. 12, p. 47; 54, p. 16 2959-8 Soil 0-2 inches 4/04/2006 Refs. 9, p. 39; 54, p. 16 2959-11 Soil 0-2 inches 4/04/2006 Refs. 9, p. 42; 54, p. 16 2959-13 Soil 0-2 inches 4/04/2006 Refs. 9, p. 44; 54, p. 16 2991-12 Soil 0-2 inches 4/17/2006 Refs. 8, p. 34; 54, p. 16 2991-14 Soil 0-2 inches 4/17/2006 Refs. 8, p. 36; 54, p. 16 Background Concentrations: The following table presents the barium and lead concentrations found at the background sample locations. The shaded values, the highest found at any background location are selected as a conservative background level for comparison to concentrations in source samples. Sample ID Sample Type Date Hazardous Substance Hazardous Substance Concentration (mg/kg) Sample Quantitation Limit* (mg/kg) Reference 2691-12 Soil 8/08/2005 Barium 362 20.3 Refs. 12, pp. Lead 30.5 1.02 10, 32; 34, p. 2 2959-8 Soil 4/04/2006 Barium 735 1.94 Refs. 9, pp. 8, Lead 36.5 4.85 28; 37, p. 2 2959-11 Soil 4/04/2006 Barium 248 1.89 Refs. 9, pp. 9, Lead 26.1 4.73 28; 37, p. 3 2959-13 Soil 4/04/2006 Barium 411 2.00 Refs. 9, pp. Lead 35.3 5.00 10,28; 37, p. 3 September 2007 90 ------- Sample ID Sample Type Date Hazardous Substance Hazardous Substance Concentration (mg/kg) Sample Quantitation Limit* (mg/kg) Reference 2991-12 Soil 4/17/2006 Barium 199 1.96 Refs. 8, pp. 8, Lead 45.0 4.91 20; 38, p. 3 2991-14 Soil 4/17/2006 Barium 371 2.01 Refs. 8, pp. 9, Lead 37.8 5.03 20; 38, p. 3 Notes: * The SQLs provided in this table are referred to as reporting limits in Reference 34, 37, and 38. They are the laboratory's reporting limit (also known as the method detection limit - see the method for more details) for that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. ID Identification mg/kg milligrams per kilogram Bolded These concentrations considered to be the background levels for each of these metals Contaminated Samples: Waste samples from the tailings pile were collected in August 2006 under ASR 3169 and were analyzed for arsenic, barium, cadmium, and lead (Ref. 39). Analysis of the tailings samples was conducted by the EPA Region 7 laboratory in accordance to the site specific QAPP (Ref. 51; 65). Area Letter: B Sample ID Sample Medium Depth Date Reference 3169-5 tailings 0-2 inches 8/28/2006 Refs. 39, pp. 3, 5-6, 8, 23, 63; 43, p. 1; 51, pp. 2-3; 54, p. 16 3169-6 tailings 0-2 inches 8/28/2006 Refs. 39, pp. 3, 5-6, 8, 24, 63; 43, p. 1; 51, pp. 2-3; 54, p. 16 Contaminated Sample Concentrations: Area Letter: B Hazardous Substance Contaminated Sample(s) (mg/kg) Sample Quantitation Limit* (mg/kg) Reference Sample IDs Concentration Barium 3169-5 6,860 71.3 Refs. 39, pp. 5-6, 8, 23, 63; 43, p. 1 3169-6 8,100 87.1 Refs. 39, pp. 5-6, 8, 24, 63; 43, p. 1 Lead 3169-5 4,610 1.19 Refs. 39, pp. 5-6, 8, 23, 63; 43, p. 1 3169-6 1,160 1.45 Refs. 39, pp. 5-6, 8, 24, 63; 43, p. 1 Notes: * The SQLs provided in this table are referred to as reporting limits in Reference 43. They are the laboratory's reporting limit (also known as the method detection limit - see the method for more details) for that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. ID Identification mg/kg milligrams per kilogram September 2007 91 ------- Attribution Given that the waste in this source was tailings deposited as a result of the mining operations that compose the Richwood site, the contamination in the waste is considered attributable to the site. Area Hazardous Waste Quantity Area: B Description According to IMOP the tailing pile in Area B covers 28 acres (Figure 6 of this document). According to the 208 project the tailings pond consists of water, swampy intermittent water, and trees (Refs. 31, p. 4; 32). An acre is equivalent to 43,560 square feet (ft2). The approximate size of the tailing pile is 1,219,680 ft2 (28 times 43,560 ft2). Source Type Area Units References Pile 1,219,680 Square feet Refs. 31, p. 4; 32 Sum (ft2): 1,219,680 Equation for Assigning Value (Ref. 1, Table 5-2): A/34 Area Assigned Value: 35,872.9 Area Assigned Value: = 35,872.9 September 2007 92 ------- Letter by which this area is to be identified: C Name of the area: Area of observed contamination (AOC) C includes Source 3 Desoto Mining Company Plants A & B (Agers) Northwest Tailings Pond. As discussed in the Source Characterization Section (Section 2.2.1 of this document), this source is evaluated as a pile. Location and description of area (with reference to a map of the site): AOC C is located north of Highway H and east of Highway 47. AOC C consists of a tailings pile that covers 53.8 acres swampy intermittent water and dry and barren land (Figure 7 of this document; Refs. 31, p. 5; 32). Figure 22 in Reference 59 shows the location of AOC C. Observed Contamination Evidence: In August 2006, EPA collected samples from tailings piles within the Richwoods area to characterize the source areas. In situ readings were collected with the XRF for lead concentrations and results were record on field sheets. Waste samples from the piles were also submitted for fixed laboratory analysis as described below. Background Samples: To document that the waste in this tailings pond contains elevated concentrations of barium and lead, the soil samples identified below are used to establish background levels for the Richwoods area. The samples were collected from areas that were as far away from mined lands as possible and the analytical results were not qualified as estimated by the laboratory (J-coded). Sample ID Sample Medium Depth Date Reference 2691-12 Soil 0-2 inches 8/08/2005 Refs. 12, p. 47; 54, p. 16 2959-8 Soil 0-2 inches 4/04/2006 Refs. 9, p. 39; 54, p. 16 2959-11 Soil 0-2 inches 4/04/2006 Refs. 9, p. 42; 54, p. 16 2959-13 Soil 0-2 inches 4/04/2006 Refs. 9, p. 44; 54, p. 16 2991-12 Soil 0-2 inches 4/17/2006 Refs. 8, p. 34; 54, p. 16 2991-14 Soil 0-2 inches 4/17/2006 Refs. 8, p. 36; 54, p. 16 Background Concentrations: The following table presents the barium and lead concentrations found at the background sample locations. The shaded values, the highest found at any background location are selected as a conservative background level for comparison to concentrations in source samples. Sample ID Sample Type Date Hazardous Substance Hazardous Substance Concentration (mg/kg) Sample Quantitation Limit* (mg/kg) Reference 2691-12 Soil 8/08/2005 Barium 362 20.3 Refs. 12, pp. Lead 30.5 1.02 10, 32; 34, p. 2 2959-8 Soil 4/04/2006 Barium 735 1.94 Refs. 9, pp. 8, Lead 36.5 4.85 28; 37, p. 2 2959-11 Soil 4/04/2006 Barium 248 1.89 Refs. 9, pp. 9, Lead 26.1 4.73 28; 37, p. 3 2959-13 Soil 4/04/2006 Barium 411 2.00 Refs. 9, pp. 10,28; 37, p. 3 Lead 35.3 5.00 September 2007 93 ------- Sample ID Sample Type Date Hazardous Substance Hazardous Substance Concentration (mg/kg) Sample Quantitation Limit* (mg/kg) Reference 2991-12 Soil 4/17/2006 Barium 199 1.96 Refs. 8, pp. 8, Lead 45.0 4.91 20; 38, p. 3 2991-14 Soil 4/17/2006 Barium 371 2.01 Refs. 8, pp. 9, Lead 37.8 5.03 20; 38, p. 3 Notes: * The SQLs provided in this table are referred to as reporting limits in Reference 34, 37, and 38. They are the laboratory's reporting limit (also known as the method detection limit - see the method for more details) for that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. ID Identification mg/kg milligrams per kilogram Bolded These concentrations considered to be the background levels for each of these metals Contaminated Samples: Waste samples from the tailings pile were collected in August 2006 under ASR 3169 and were analyzed for arsenic, barium, cadmium, and lead (Ref. 39). Analysis of the tailings samples was conducted by the EPA Region 7 laboratory in accordance to the site specific QAPP (Ref. 51; 65). Area Letter: C Sample ID Sample Medium Depth Date Reference 3169-22 tailings 0-2 inches 8/31/2006 Refs. 39, pp. 3, 5-6, 12, 42, 63; 43, pp. 3-4; 51, pp. 2-3; 54, p. 16 Contaminated Sample Concentrations: Area Letter: C Hazardous Substance Contaminated Sample(s) (mg/kg) Sample Quantitation Limit* (mg/kg) Reference Sample IDs Concentration Barium 3169-22 5,430 48 Refs. 39, pp. 5-6, 12, 42, 63; 43, pp. 3-4 Lead 632 1.2 Notes: * The SQLs provided in this table are referred to as reporting limits in Reference 43. They are the laboratory's reporting limit (also known as the method detection limit - see the method for more details) for that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. ID Identification mg/kg milligrams per kilogram Attribution Given that the waste in this source was tailings deposited as a result of the mining operations that compose the Richwood site, the contamination in the waste is considered attributable to the site. September 2007 94 ------- Area Hazardous Waste Quantity Area: C Description According to IMOP the tailing pile in Area C covers 53.8 acres (Figure 7 of this doucment). According to the 208 project the tailings pond consists of swampy intermittent water and dry and barren land (Refs. 31, p. 5; 32). An acre is equivalent to 43,560 square feet (ft2). The approximate size of the tailing pile is 2,343,528 ft2 (53.8 times 43,560 ft2). Source Type Area Units References Pile 2,343,528 Square feet Refs. 31, p. 5; 32 Sum (ft2): 2,343,528 Equation for Assigning Value (Ref. 1, Table 5-2): A/34 Area Assigned Value: 68,927.3 Area Assigned Value: = 68,927.3 September 2007 95 ------- Letter by which this area is to be identified: D Name of the area: Area of observed contamination (AOC) D includes Source 4 Desoto Mining Company Plants A & B (Agers) Central Tailings Pond. As discussed in the Source Characterization Section (Section 2.2.1 of this document), this source is evaluated as a pile. Location and description of area (with reference to a map of the site): AOC D is located just north of Highway H and east of Highway 47. AOC D consists of a tailings pile that covers 70 acres covered by water and trees (Figure 8 of this document; Refs. 31, p. 5; 32). Figure 22 in Reference 59 shows the location of AOC D. Observed Contamination Evidence: In August 2006, EPA collected samples from tailings piles within the Richwoods area to characterize the source areas. In situ readings were collected with the XRF for lead concentrations and results were record on field sheets. Waste samples from the piles were also submitted for fixed laboratory analysis as described below. Background Samples: To document that the waste in this tailings pond contains elevated concentrations of barium and lead, the soil samples identified below are used to establish background levels for the Richwoods area. The samples were collected from areas that were as far away from mined lands as possible and the analytical results were not qualified as estimated by the laboratory (J-coded). Sample ID Sample Medium Depth Date Reference 2691-12 Soil 0-2 inches 8/08/2005 Refs. 12, p. 47; 54, p. 16 2959-8 Soil 0-2 inches 4/04/2006 Refs. 9, p. 39; 54, p. 16 2959-11 Soil 0-2 inches 4/04/2006 Refs. 9, p. 42; 54, p. 16 2959-13 Soil 0-2 inches 4/04/2006 Refs. 9, p. 44; 54, p. 16 2991-12 Soil 0-2 inches 4/17/2006 Refs. 8, p. 34; 54, p. 16 2991-14 Soil 0-2 inches 4/17/2006 Refs. 8, p. 36; 54, p. 16 Background Concentrations: The following table presents the barium and lead concentrations found at the background sample locations. The shaded values, the highest found at any background location are selected as a conservative background level for comparison to concentrations in source samples. Sample ID Sample Type Date Hazardous Substance Hazardous Substance Concentration (mg/kg) Sample Quantitation Limit* (mg/kg) Reference 2691-12 Soil 8/08/2005 Barium 362 20.3 Refs. 12, pp. 10, 32; 34, p. 2 Lead 30.5 1.02 2959-8 Soil 4/04/2006 Barium 735 1.94 Refs. 9, pp. 8, 28; 37, p. 2 Lead 36.5 4.85 2959-11 Soil 4/04/2006 Barium 248 1.89 Refs. 9, pp. 9, 28; 37, p. 3 Lead 26.1 4.73 2959-13 Soil 4/04/2006 Barium 411 2.00 Refs. 9, pp. 10,28; 37, p. 3 Lead 35.3 5.00 September 2007 96 ------- Sample ID Sample Type Date Hazardous Substance Hazardous Substance Concentration (mg/kg) Sample Quantitation Limit* (mg/kg) Reference 2991-12 Soil 4/17/2006 Barium 199 1.96 Refs. 8, pp. 8, 20; 38, p. 3 Lead 45.0 4.91 2991-14 Soil 4/17/2006 Barium Lead 371 2.01 Refs. 8, pp. 9, 20; 38, p. 3 37.8 5.03 Notes: * The SQLs provided in this table are referred to as reporting limits in Reference 34, 37, and 38. They are the laboratory's reporting limit (also known as the method detection limit - see the method for more details) for that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. ID Identification mg/kg milligrams per kilogram Bolded These concentrations considered to be the background levels for each of these metals Contaminated Samples: Waste samples from the tailings pile were collected in August 2006 under ASR 3169 and were analyzed for arsenic, barium, cadmium, and lead (Ref. 39). Analysis of the tailings samples was conducted by the EPA Region 7 laboratory in accordance to the site specific QAPP (Ref. 51; 65). Area Letter: D Sample ID Sample Medium Depth Date Reference 3169-9 tailings 0-2 inches 8/28/2006 Refs. 39, pp. 3, 5-6, 9, 27, 63; 43, p. 2; 51, pp. 2-3; 54, p. 16 3169.-10 tailings 0-2 inches 8/28/2006 Refs. 39, pp. 3, 5-6, 9, 28, 63; 43, p. 2; 51, pp. 2-3; 54, p. 16 3169-11 tailings 0-2 inches 8/28/2006 Refs. 39, pp. 3, 5-6, 9, 29, 63; 43, p. 2; 51, pp. 2-3; 54, p. 16 Contaminated Sample Concentrations: Area Letter: D Contaminated Sample(s) Sample Hazardous (mg/kg) Quantitation Reference Substance Sample IDs Concentration Limit* (mg/kg) 3169-9 5,190 28.6 Refs. 39, pp. 5-6, 9, 27, 63; 43, p. 2 Barium 3169-10 10,300 84.5 Refs. 39, pp. 5-6, 9, 28, 63; 43, p. 2 3169-11 5,700 71.2 Refs. 39, pp. 5-6, 9, 29, 63; 43, p. 2 3169-9 243 1.43 Refs. 39, pp. 5-6, 9, 27, 63; 43, p. 2 Lead 3169-10 968 Refs. 39, pp. 5-6, 9, 28, 63; 43, p. 2 3169-11 639 3.56 Refs. 39, pp. 5-6, 9, 29, 63; 43, p. 2 Notes: * The SQLs provided in this table are referred to as reporting limits in Reference 43. They are the laboratory's reporting limit (also known as the method detection limit - see the method for more details) for that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. ID Identification September 2007 97 ------- mg/kg milligrams per kilogram Attribution Given that the waste in this source was tailings deposited as a result of the mining operations that compose the Richwood site, the contamination in the waste is considered attributable to the site. Area Hazardous Waste Quantity Area: D Description According to IMOP the tailing pile in Area D covers 70 acres (Figure 8 of this document). According to the 208 project the tailings pond consists of water and trees (Refs. 31, p. 5; 32). An acre is equivalent to 43,560 square feet (ft2). The approximate size of the tailing pile is 3,049,200 ft2 (70 times 43,560 ft2). Source Type Area Units References Pile 3,049,200 Square feet Refs. 31, p. 5; 32 Sum (ft2): 3,049,200 Equation for Assigning Value (Ref. 1, Table 5-2): A/34 Area Assigned Value: 89,682.3 Area Assigned Value: = 89,682.3 September 2007 98 ------- Letter by which this area is to be identified: E Name of the area: Area of observed contamination (AOC) E includes Source 5 Desoto Mining Company Plants A & B (Agers) SouthTailings Pond. As discussed in the Source Characterization Section (Section 2.2.1 of this document), this source is evaluated as a pile. Location and description of area (with reference to a map of the site): AOC E is located south of Highway H and east of Highway 47. AOC E consists of a tailings pile that covers 171.6 acres covered by water and trees (Figure 9 of this document; Refs. 31, p. 5; 32). Figure 22 in Reference 59 shows the location of AOC E. Observed Contamination Evidence: In August 2006, EPA collected samples from tailings piles within the Richwoods area to characterize the source areas. In situ readings were collected with the XRF for lead concentrations and results were record on field sheets. Waste samples from the piles were also submitted for fixed laboratory analysis as described below. Background Samples: To document that the waste in this tailings pond contains elevated concentrations of barium and lead, the soil samples identified below are used to establish background levels for the Richwoods area. The samples were collected from areas that were as far away from mined lands as possible and the analytical results were not qualified as estimated by the laboratory (J-coded). Sample ID Sample Medium Depth Date Reference 2691-12 Soil 0-2 inches 8/08/2005 Refs. 12, p. 47; 54, p. 16 2959-8 Soil 0-2 inches 4/04/2006 Refs. 9, p. 39; 54, p. 16 2959-11 Soil 0-2 inches 4/04/2006 Refs. 9, p. 42; 54, p. 16 2959-13 Soil 0-2 inches 4/04/2006 Refs. 9, p. 44; 54, p. 16 2991-12 Soil 0-2 inches 4/17/2006 Refs. 8, p. 34; 54, p. 16 2991-14 Soil 0-2 inches 4/17/2006 Refs. 8, p. 36; 54, p. 16 Background Concentrations: The following table presents the barium and lead concentrations found at the background sample locations. The shaded values, the highest found at any background location are selected as a conservative background level for comparison to concentrations in source samples. Sample ID Sample Type Date Hazardous Substance Hazardous Substance Concentration (mg/kg) Sample Quantitation Limit* (mg/kg) Reference 2691-12 Soil 8/08/2005 Barium 362 20.3 Refs. 12, pp. 10, 32; 34, p. 2 Lead 30.5 1.02 2959-8 Soil 4/04/2006 Barium 735 1.94 Refs. 9, pp. 8, 28; 37, p. 2 Lead 36.5 4.85 2959-11 Soil 4/04/2006 Barium 248 1.89 Refs. 9, pp. 9, 28; 37, p. 3 Lead 26.1 4.73 2959-13 Soil 4/04/2006 Barium Lead 411 2.00 Refs. 9, pp. 10,28; 37, p. 3 35.3 5.00 September 2007 99 ------- Sample ID Sample Type Date Hazardous Substance Hazardous Substance Concentration (mg/kg) Sample Quantitation Limit* (mg/kg) Reference 2991-12 Soil 4/17/2006 Barium 199 1.96 Refs. 8, pp. 8, 20; 38, p. 3 Lead 45.0 4.91 2991-14 Soil 4/17/2006 Barium Lead 371 2.01 Refs. 8, pp. 9, 20; 38, p. 3 37.8 5.03 Notes: * The SQLs provided in this table are referred to as reporting limits in Reference 34, 37, and 38. They are the laboratory's reporting limit (also known as the method detection limit - see the method for more details) for that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. ID Identification mg/kg milligrams per kilogram Bolded These concentrations considered to be the background levels for each of these metals Contaminated Samples: Waste samples from the tailings pile were collected in August 2006 under ASR 3169 and were analyzed for arsenic, barium, cadmium, and lead (Ref. 39). Analysis of the tailings samples was conducted by the EPA Region 7 laboratory in accordance to the site specific QAPP (Ref. 51; 65). Area Letter: E Sample ID Sample Medium Depth Date Reference 3169-12 tailings 0-2 inches 8/30/2006 Refs. 39, pp. 5-6, 9, 30, 63; 43, p. 2; 51, pp. 2-3; 54, p. 16 3169-13 tailings 0-2 inches 8/30/2006 Refs. 39, pp. 5-6, 10, 31, 63; 43, p. 2; 51, pp. 2-3; 54, p. 16 3169-16 tailings 0-2 inches 8/30/2006 Refs. 39, pp. 5-6, 11, 35, 63; 43, p. 3; 51, pp. 2-3; 54, p. 16 3169-23 tailings 0-2 inches 8/31/2006 Refs. 39, pp. 5-6, 13, 43, 62; 43, p. 4; 51, pp. 2-3; 54, p. 16 Contaminated Sample Concentrations: Area Letter: E Hazardous Substance Contaminated Sample(s) (mg/kg) Sample Quantitation Limit* (mg/kg) Reference Sample IDs Concentration Barium 3169-12 7,880 62.4 Refs. 39, pp. 5-6, 9, 30, 63; 43, p. 2 3169-13 8,480 74 Refs. 39, pp. 5-6, 10, 31, 63; 43, p. 2 3169-16 7,910 74.3 Refs. 39, pp. 5-6, 11, 35, 63; 43, p. 3 3169-23 3,700 78.4 Refs. 39, pp. 5-6, 13, 43, 62; 43, p. 4 Lead 3169-12 1,320 1.56 Refs. 39, pp. 5-6, 9, 30, 63; 43, p. 2 3169-13 1,230 1.23 1.24 Refs. 39, pp. 5-6, 10, 31, 63; 43, p. 2 3169-16 409 Refs. 39, pp. 5-6, 11, 35, 63; 43, p. 3 3169-23 1,070 3.92 Refs. 39, pp. 5-6, 13, 43, 62; 43, p. 4 Notes: September 2007 100 ------- * The SQLs provided in this table are referred to as reporting limits in Reference 43. They are the laboratory's reporting limit (also known as the method detection limit - see the method for more details) for that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. ID Identification mg/kg milligrams per kilogram Attribution Given that the waste in this source was tailings deposited as a result of the mining operations that compose the Richwood site, the contamination in the waste is considered attributable to the site. Area Hazardous Waste Quantity Area: E Description According to IMOP the tailing pile in Area E covers 171.6 acres (Figure 9). According to the 208 project the tailings pond consists of water and trees (Refs. 31,p. 5; 32). An acre is equivalent to 43,560 square feet (ft2). The approximate size of the tailing pile is 7,474,896 ft2 (171.6 times 43,560 ft2). Source Type Area Units References Pile 7,474,896 Square feet Refs. 31, p. 5; 32 Sum (ft2): 7,474,896 Equation for Assigning Value (Ref. 1, Table 5-2): A/34 Area Assigned Value: 219,849.9 Area Assigned Value: = 219,849.9 September 2007 101 ------- Letter by which this area is to be identified: F Name of the area: Area of observed contamination (AOC) F includes Source 6 N.L. Baroid East Tailings Pond. As discussed in the Source Characterization Section (Section 2.2.1 of this document), this source is evaluated as a pile. Location and description of area (with reference to a map of the site): AOC F is located south of Highway H and east of Highway 47. AOC C consists of a tailings pile that covers 65.8 acres covered by swampy intermittent water (Figure 10 of this document; Refs. 31, p. 4; 32). Figure 22 in Reference 59 shows the location of AOC C. Observed Contamination Evidence: In August 2006, EPA collected samples from tailings piles within the Richwoods area to characterize the source areas. In situ readings were collected with the XRF for lead concentrations and results were record on field sheets. Waste samples from the piles were also submitted for fixed laboratory analysis as described below. Background Samples: To document that the waste in this tailings pond contains elevated concentrations of barium and lead, the soil samples identified below are used to establish background levels for the Richwoods area. The samples were collected from areas that were as far away from mined lands as possible and the analytical results were not qualified as estimated by the laboratory (J-coded). Sample ID Sample Medium Depth Date Reference 2691-12 Soil 0-2 inches 8/08/2005 Refs. 12, p. 47; 54, p. 16 2959-8 Soil 0-2 inches 4/04/2006 Refs. 9, p. 39; 54, p. 16 2959-11 Soil 0-2 inches 4/04/2006 Refs. 9, p. 42; 54, p. 16 2959-13 Soil 0-2 inches 4/04/2006 Refs. 9, p. 44; 54, p. 16 2991-12 Soil 0-2 inches 4/17/2006 Refs. 8, p. 34; 54, p. 16 2991-14 Soil 0-2 inches 4/17/2006 Refs. 8, p. 36; 54, p. 16 Background Concentrations: The following table presents the barium and lead concentrations found at the background sample locations. The shaded values, the highest found at any background location are selected as a conservative background level for comparison to concentrations in source samples. Sample ID Sample Type Date Hazardous Substance Hazardous Substance Concentration (mg/kg) Sample Quantitation Limit* (mg/kg) Reference 2691-12 Soil 8/08/2005 Barium 362 20.3 Refs. 12, pp. Lead 30.5 1.02 10, 32; 34, p. 2 2959-8 Soil 4/04/2006 Barium 735 1.94 Refs. 9, pp. 8, Lead 36.5 4.85 28; 37, p. 2 2959-11 Soil 4/04/2006 Barium 248 1.89 Refs. 9, pp. 9, Lead 26.1 4.73 28; 37, p. 3 2959-13 Soil 4/04/2006 Barium 411 2.00 Refs. 9, pp. Lead 35.3 5.00 10,28; 37, p. 3 September 2007 102 ------- Sample ID Sample Type Date Hazardous Substance Hazardous Substance Concentration (mg/kg) Sample Quantitation Limit* (mg/kg) Reference 2991-12 Soil 4/17/2006 Barium 199 1.96 Refs. 8, pp. 8, 20; 38, p. 3 Lead 45.0 4.91 2991-14 Soil 4/17/2006 Barium Lead 371 2.01 Refs. 8, pp. 9, 20; 38, p. 3 37.8 5.03 Notes: * The SQLs provided in this table are referred to as reporting limits in Reference 34, 37, and 38. They are the laboratory's reporting limit (also known as the method detection limit - see the method for more details) for that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. ID Identification mg/kg milligrams per kilogram Bolded These concentrations considered to be the background levels for each of these metals Contaminated Samples: Waste samples from the tailings pile were collected in August 2006 under ASR 3169 and were analyzed for arsenic, barium, cadmium, and lead (Ref. 39). Analysis of the tailings samples was conducted by the EPA Region 7 laboratory in accordance to the site specific QAPP (Ref. 51; 65). Area Letter: F Sample ID Sample Medium Depth Date Reference 3169-26 tailings 0-2 inches 8/31/2006 Refs. 39, pp. 3, 5-6, 13, 46, 61-62; 43, p. 4; 51, pp. 2-3; 54, p. 16 Contaminated Sample Concentrations: Area Letter: F Hazardous Substance Contaminated Sample(s) (mg/kg) Sample Quantitation Limit* (mg/kg) Reference Sample IDs Concentration Barium 3169-26 5,830 58.3 Refs. 39, pp. 5-6, 13, 46, 61-62; 43, p. 4 Lead 544 1.46 Notes: * The SQLs provided in this table are referred to as reporting limits in Reference 43. They are the laboratory's reporting limit (also known as the method detection limit - see the method for more details) for that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. ID Identification mg/kg milligrams per kilogram Attribution Given that the waste in this source was tailings deposited as a result of the mining operations that compose the Richwood site, the contamination in the waste is considered attributable to the site. September 2007 103 ------- Area Hazardous Waste Quantity Area: F Description According to IMOP the tailing pile in Area F covers 65.8 acres (Figure 10 of this document). According to the 208 project the tailings pond consists of swampy intermittent water (Refs. 31, p. 4; 32). An acre is equivalent to 43,560 square feet (ft2). The approximate size of the tailing pile is 2,866,248 ft2 (65.8 times 43,560 ft2). Source Type Area Units References Pile 2,866,248 Square feet Refs. 31, p. 4; 32 Sum (ft2): 2,866,248 Equation for Assigning Value (Ref. 1, Table 5-2): A/34 Area Assigned Value: 84,301.4 Area Assigned Value: = 84,301.4 September 2007 104 ------- Letter by which this area is to be identified: G through AH Name of the area: This area represents multiple isolated areas of contaminated soil found in individual residential yards that were sampled and contained elevated levels of barium and lead. Location and description of area (with reference to a map of the site): These multiple points of contamination are shown on Figure 22 in Reference 59. The areas of contamination include individual residential yards that have been sampled and contain elevated concentrations of lead and/or barium. Due to the rural nature of the Richwoods study area, homes are often widely dispersed and there is a lack of data between homes to document a continuous area of contamination. Each residential yard is being evaluated as a distinct AOC. Observed Contamination Evidence: As part of the removal site evaluation for the Richwoods area, these residential yards were sampled in July and August 2005 and April 2006. Soil screening and sampling activities at residential properties was conducted in accordance with the Superfund Lead-Contaminated Residential Sites Handbook (Ref. 58). Residential properties were divided into cells measuring no more than 100 by 100 feet. Nine point composite samples were collected (each aliquot) collected from 0 to 2 inches below ground surface). Homogenized samples were then dried and screened for lead using a Nitron™ XRF instrument. Approximately 10 percent of the samples were submitted to EPA Region 7 laboratory for analysis of arsenic, barium and lead by EPA method 6010B (inductive coupled plasma [ICP] analyses) (Ref. 54, pp. 5, 10, 16-18). All laboratory reports indicate which laboratory performed the analysis, which was either conducted in house at the EPA Region 7 laboratory or out sourced to a laboratory under the contract laboratory program (CLP) (Refs. 7, p. 6; 8. p. 5; 9, p. 5; 11, p. 6; 12, p.6; 13, p. 5; 50). Background Samples for Residential Soil Samples: Background soil samples were selected based on the following criteria. Samples were collected from the same environmental media (surface soil), collected and analyzed using the same procedures and laboratory as the release samples, collected in August 2005 and in April 2006 while the release samples were collected from July and August 2005 and March and April 2006 under similar physical conditions all within the Richwoods area. In addition background locations were selected from areas that were as far away from mined lands as possible and most importantly, were not qualified as estimated by the laboratory (J-coded). Sample ID Sample Medium Depth Date Reference 2691-12 Soil 0-2 inches 8/08/2005 Refs. 12, p. 47; 54, p. 16 2959-8 Soil 0-2 inches 4/04/2006 Refs. 9, p. 39; 54, p. 16 2959-11 Soil 0-2 inches 4/04/2006 Refs. 9, p. 42; 54, p. 16 2959-13 Soil 0-2 inches 4/04/2006 Refs. 9, p. 44; 54, p. 16 2991-12 Soil 0-2 inches 4/17/2006 Refs. 8, p. 34; 54, p. 16 2991-14 Soil 0-2 inches 4/17/2006 Refs. 8, p. 36; 54, p. 16 Background Concentrations: Sample ID Sample Type Date Hazardous Substance Hazardous Substance Concentration (mg/kg) Sample Quantitation Limit* (mg/kg) Reference 2691-12 Soil 8/08/2005 Barium 362 20.3 Refs. 12, pp. 10, 32; 34, p. 2 Lead 30.5 1.02 September 2007 105 ------- Sample ID Sample Type Date Hazardous Substance Hazardous Substance Concentration (mg/kg) Sample Quantitation Limit* (mg/kg) Reference 2959-8 Soil 4/04/2006 Barium 735 1.94 Refs. 9, pp. 8, Lead 36.5 4.85 28; 37, p. 2 2959-11 Soil 4/04/2006 Barium 248 1.89 Refs. 9, pp. 9, Lead 26.1 4.73 28; 37, p. 3 2959-13 Soil 4/04/2006 Barium 411 2.00 Refs. 9, pp. Lead 35.3 5.00 10,28; 37, p. 3 2991-12 Soil 4/17/2006 Barium 199 1.96 Refs. 8, pp. 8, Lead 45.0 4.91 20; 38, p. 3 2991-14 Soil 4/17/2006 Barium 371 2.01 Refs. 8, pp. 9, Lead 37.8 5.03 20; 38, p. 3 Notes: * The SQLs provided in this table are referred to as reporting limits in Reference 34, 37, and 38. They are the laboratory's reporting limit (also known as the method detection limit - see the method for more details) for that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. ID Identification mg/kg milligrams per kilogram Bolded These concentrations considered to be the background levels for each of these metals Contaminated Samples: All the contaminated residential soil samples were selected within 200 feet of a residence as documented on the field sheets in References 14 and 15. In addition, some of the dwellings sampled are located within 200 feet of the tailings piles or mined land areas as shown on Figure 22 in Reference 59. All these samples are within an area of observed contamination because their concentrations exceed three times the background concentration. All laboratory reports indicate which laboratory performed the analysis, which was either conducted in house at the EPA Region 7 laboratory or out sourced to a laboratory under the (CLP) (Refs. 7, p. 6; 8. p. 5; 11, p. 6; 12,p.6; 13, p. 5; 50). AOC Sample ID Sample Medium Depth Date Reference G 2690-5 Contaminated soil 0-2 inches 7/20/2005 Refs. 11, p. 46; 54, p. 16 H 2690-12 Contaminated soil 0-2 inches 7/22/2005 Refs. 11, p. 53; 54, p. 16 I 2690-13 Contaminated soil 0-2 inches 7/25/2005 Refs. 11, p. 54; 54, pp. 15-18 J 2690-28 Contaminated soil 0-2 inches 7/25/2005 Refs. 11, p. 69; 54, pp. 15-18 K 2690-29 Contaminated soil 0-2 inches 7/25/2005 Refs. 11, p. 70; 54, pp. 15-18 L 2691-1 Contaminated soil 0-2 inches 7/28/2005 Refs. 12, p. 36; 54, pp. 15-18 M 2691-3 Contaminated soil 0-2 inches 8/03/2005 Refs. 12, p. 38; 54, pp. 15-18 N 2691-5 Contaminated soil 0-2 inches 8/08/2005 Refs. 12, p. 40; 54, p. 16 O 2691-8 Contaminated soil 0-2 inches 8/01/2005 Refs. 12, p. 43; 54, pp. 15-18 P 2691-10 Contaminated soil 0-2 inches 8/03/2005 Refs. 12, p. 45; 54, pp. 15-18 Q 2691-14 Contaminated soil 0-2 inches 8/03/2005 Refs. 12, p. 58; 49, pp. 15-18 R 2691-15 Contaminated soil 0-2 inches 8/03/2005 Refs. 12, p. 50; 54, p. 16 S 2691-16 Contaminated soil 0-2 inches 8/04/2005 Refs. 12, p. 51; 54, p. 16 T 2691-17 Contaminated soil 0-2 inches 8/04/2005 Refs. 12, p. 52; 54, p. 16 U 2691-18 Contaminated soil 0-2 inches 8/08/2005 Refs. 12, p. 53; 54, p. 16 V 2691-23 Contaminated soil 0-2 inches 7/28/2005 Refs. 12, p. 49; 58, pp. 15-18 W 2691-24 Contaminated soil 0-2 inches 8/08/2005 Refs. 12, p. 59; 54, p. 16 X 2691-27 Contaminated soil 0-2 inches 8/05/2005 Refs. 12, p. 62; 54, p. 16 Y 2691-28 Contaminated soil 0-2 inches 8/10/2005 Refs. 12, p. 63; 54, p. 16 September 2007 106 ------- AOC Sample ID Sample Medium Depth Date Reference z 2691-32 Contaminated soil 0-2 inches 8/10/2005 Refs. 12, p. 67; 54, p. 16 AA 2730-6 Contaminated soil 0-2 inches 8/10/2005 Refs. 13, p. 33; 54, p. 16 AB 2730-12 Contaminated soil 0-2 inches 8/18/2005 Refs. 13, p. 39; 54, p. 16 AC 2730-29 Contaminated soil 0-2 inches 8/23/2005 Refs. 13, p. 56; 54, p. 16 AD 2937-15 Contaminated soil 0-2 inches 3/17/2006 Refs. 7, p. 53; 54, p. 16 AE 2937-16 Contaminated soil 0-2 inches 3/17/2006 Refs. 7, p. 54; 54, p. 16 AF 2937-31 Contaminated soil 0-2 inches 3/21/2006 Refs. 7, p. 69; 54, p. 16 AG 2991-7 Contaminated soil 0-2 inches 4/17/2006 Refs. 8, p. 29; 54, p. 16 AH 2991-8 Contaminated soil 0-2 inches 4/17/2006 Refs. 8, p. 30; 54, pp. 15-18 Contaminated Sample Concentrations: Area Letter: Individual Residential Soils Hazardous Benchmarks (Screening Concentrations) (ing/kg) Contaminat (in? I'd Sample(s) /kg) Sample Quantitation Limit* (mg/kg) References Substance Reference Dose Cancer Risk Sample IDs Concentration 2690-28 3,380 20.1 Refs. 2, p. 5; 11, pp. 3, 6, 2690-29 6,130 41.5 11, 14-15; 33, pp. 2,4 2691-1 5.430 62.1 2691-10 5.090 60.4 2691-14 2.480 20.5 2691-15 5.030 64 2691-] 4.790 61.9 Refs. 2, p. 5; 12, pp. 3, 6, 8- 2691-17 4.220 61.9 14, 13; 34, pp. 1-4 Barium 5,500 NA 2691-18 2691-23 2691-27 2691-28 5.940 3.940 J1 6.610 J1 3,390 J1 60.7 61.8 60.5 61.7 2730-6 3,430 62.6 Refs. 2, p. 5; 13 pp. 3, 5, 8- 9, 14; 35, pp. 1-2,4 2730-12 2.350 20.8 2730-29 5,140 J1 61.5 2937-15 8,300 J2 171 Refs. 2, p. 5; 7, pp. 3, 6,11- 2937-16 7,130 F 103 12, 15; 36, pp. 2-4 Lead NA NA 2690-5 481 1.02 Refs. 2, p. 9; 11, pp. 3, 6, 9- 11, 14-15; 33, pp. 1-2,4 2690-12 727 1.04 2690-13 481 1.02 2691-1 445 1.04 Refs. 2, p. 9; 12, pp. 3, 6, 9, 2691-3 369 1.02 11-15; 34, pp. 1-4 2691-5 559 1.04 2691-8 312 1.02 2691-10 585 1.01 2691-14 434 1.03 2691-] 635 1.07 2691-16 314 1.03 2691-17 1,160 1.03 2691-18 373 1.01 2691-23 375 1.03 2691-24 385 1.04 2691-27 208 1.01 September 2007 107 ------- Hazardous Substance Benchmarks (Screening Concentrations) (mg/kg) Contaminat (in? I'd Sample(s) /kg) Sample Quantitation Limit* (mg/kg) References Reference Dose Cancer Risk Sample IDs Concentration 2691-28 1,790 1.03 2691-32 441 1.01 2730-6 2730-12 2730-29 359 267 185 1.04 1.04 1.03 Refs. 2, p. 9; 13, pp. 3, 5, 8- 9, 14; 35, pp. 1-2,4 2937-15 2937-16 2937-3T 1.100 1.260 254 1.71 1.03 1.05 Refs. 2, p. 9; 7, pp. 3, 6, 11- 12, 15; 36, pp. 2-4 2991-7 514 4.95 Refs. 2, p. 9; 8, pp. 3, 5, 7; 38, p. 2 The SQLs provided in this table are referred to as reporting limits in References 33, 34, and 38. They are the laboratory's reporting limit (also known as the method detection limit - see the method for more details) for that analyte with any dilution factor, volume adjustment, or percent solids for that sample analysis taken into account and are equivalent to a sample quantitation limit. Identification The analyte has been positively identified in the sample; however, the reported value is an estimate due to low recovery of this analyte in the laboratory control sample (LCS). The reported value may be biased low. The analyte has been positively identified in the sample; however, the reported value is an estimate due to serial dilution percent difference being above the control limit. The reported value may be biased low. milligrams per kilogram Notes: * ID J1 J2 mg/kg September 2007 108 ------- Area Hazardous Waste Quantity Area: Individual Residential Soils Description Each of the samples above collected from residential yards represents an area of approximately 100 by 100 feet. The 100 by 100 foot cells were characterized by a 9 aliquot composite sample (Ref. 54, pp. 16). The area for each AOC of contaminated soil is unknown but greater than zero square feet. Source Type Area Units References Contaminated soil >0 Square feet Ref. 54, p. 16 Sum (ft2): >0 Equation for Assigning Value (Ref. 1, Table 5-2): A/34 Area Assigned Value: >0 Area Assigned Value: = >0 Attribution The source of the elevated lead and barium in the contaminated soils is not clear and may be a results of previous small hand-worked mines near the residential properties, imported contaminated soil used as fill, houses built on lands previously strip mined by mining operations, airborne dispersion of contaminants from nearby haul roads, or runoff from mine process areas or tailings piles. In some cases, homes were built on or are located near tailings piles. Although these areas of contaminated soil were not included as listed source areas in this Section 2.2, they were included as areas of observed contamination in Section 5.0, the soil exposure pathway. Samples were selected that were either on or close to areas identified as mined land from the 208 Study (Refs. 7; 8; 9; 10; 11; 12; 13; 59, Figure 22). In all cases the soil samples presented above contain elevated concentrations of barium and lead which were also found in the sources named in Section 2.2 and as AOCs A through F in this section. All soil samples contained lead and barium at concentrations which were significantly greater than the background soil samples. As shown on Figure 22 in reference 59, background soil samples were selected from locations not known to have ever been subject to the influence of mining. 5.1 RESIDENT POPULATION THREAT 5.1.1 LIKELIHOOD OF EXPOSURE All samples presented in Section 5.0.1 above were collected from residential yards as part of a removal site evaluation performed in the Richwoods area in the spring and summer of 2006 (Ref. 22, pp. 8-9). Area Letter Distance of Population/Resource from Area of Observed Contamination Reference F through AH Within 200 feet Refs. 7, pp. 1-32; 8, pp. 1- 18; 9, pp. 1-26; 11, pp. 1-34; 12, pp. 1 30;13, pp. 1-23; 14, pp. 1-322; 15, pp. 1-290 Resident Population Threat Likelihood of Exposure Factor Category Value: 550.00 September 2007 109 ------- 5.1.2 WASTE CHARACTERISTICS All soil samples submitted to the analytical laboratory were analyzed for arsenic, barium and lead only (Ref. 54, p. 5). Both barium and lead have a toxicity factor of 10,000 (Ref. 2, pp. 1-9). As documented above barium and lead were found at concentrations significantly above background in samples collected from residential yards. 5.1.2.1 Toxicity Hazardous Substance Toxicity Factor Value Reference Barium 10,000 Ref. 2, p. 5 Lead 10,000 Ref. 2, p. 9 Toxicity Factor Value: 10,000.00 5.1.2.2 Hazardous Waste Quantity Hazardous Constituent Quantity: Hazardous constituent quantity has not been determined for any source or area of contamination. Hazardous Constituent Quantity Assigned Value: Not scored Hazardous Wastestream Quantity: Hazardous wastestream quantity has not been determined for any source or area of contamination. Sum (pounds): Wastestream Quantity/5,000 (Table 5-2): Hazardous Wastestream Quantity Assigned Value: Not scored Volume: The volume of the tailings piles and associated contaminated soil can not be adequately determined at this time. Sum (yd3/gal): Equation for Assigning Value (Table 5-2): V/2.5 Volume Assigned Value: Not scored Area: Description In determining the Tier D hazardous waste quantity factor value, only AOCs A through F were considered. The AOCs described in Section 5.0.1 and the sizes of the associated tailings piles in the AOCs are presented below. September 2007 110 ------- Area Letter Source Type Area Hazardous Waste Quantity (ft2) A Tailings Pile (Source 1) 2,700,720 B Tailings Pile (Source 2) 1,219,680 C Tailings Pile (Source 3) 2,343,528 D Tailings Pile (Source 4) 3,049,200 E Tailings Pile (Source 5) 7,474,896 F Tailings Pile (Source 6) 2,866,248 Contaminated Soil Contaminated Soil >0 Sum of Values (ft2): 19,654,272 Equation for Assigning Value (Ref. 1, Table 5-2): A/34 Area Assigned Value: 578,067 Calculation of Hazardous Waste Quantity Factor Value (Ref. 1, Section 2.4.2.2): Area Letter Source Type Hazardous Waste Quantity A-F Pile 578,067 Sum of Values: 578,067 Hazardous Waste Quantity Factor Value: 10,000 (Ref. 1, Table 2-6) 5.1.2.3 Calculation of Waste Characteristics Factor Category Value Toxicity Factor Value: 10,000.00 Hazardous Waste Quantity Factor Value: 10,000.00 Toxicity Factor Value x Hazardous Waste Quantity Factor Value: 1.00E+8 Waste Characteristics Factor Category Value: 100 (Table 2-7) September 2007 111 ------- 5.1.3 TARGETS 5.1.3.1 Resident Individual Area Letters: Individual Residential Soils Level of Contamination (Level I/Level II): Level I References: 7, pp. 1-32; 8, pp. 1-18; 9, pp. 1-26; 11, pp. 1-34; 12, pp. 1-30; 13, pp. 1-23 As documented in Section 5.1.3.2.1 below, residential properties are subject to Level I concentrations. Resident Individual Factor Value: 50 5.1.3.2 Resident Population 5.1.3.2.1 Level I Concentrations As identified in Section 5.0.1, barium and lead have been identified in surficial soils at concentrations significantly above background concentrations. Only barium has a health-based benchmark listed in reference 2. The reference dose screening concentration for barium is 5,550 mg/kg (Ref. 2, p. 5). It should be noted that approximately 10 percent of the samples were actually submitted for fixed laboratory analysis. All other samples were analyzed in the field only for lead using XRF methods. Lead has no health-based benchmark for soil exposure. The PA/SI and RSE residential property sampling identified two properties that contained concentrations of barium exceeding the reference dose screening concentration. There were additional samples including 2690-13, 2691-27, 2937-16, and 2937-17 that also exceeded the same health-based benchmark but those laboratory results were J-coded. Since they were J-coded, the laboratory had to estimate the concentration. The actual contamination could be higher than reported; therefore, these samples were not considered as Level I concentrations and were included in the Level II concentrations table in Section 5.1.3.2.2. Sample ID Total Number of Residents References 2690-29/20149 2.641 Ref. 15, pp. 273-274 2691-18/20009 2 Ref. 15, pp. 21-22 Exact number of residents is not known. Value assigned is average number (2.64) of residents per household for Washington County as determined in the 2000 Census (Ref. 4, p. 2). Sum of individuals subject to Level I concentrations: 4.64 Sum of individuals subject to Level I concentrations x 10: 46.4 Level I Concentrations Factor Value: 46.4 5.1.3.2.2 Level II Concentrations The Level II targets include the remaining samples within 200 feet of an area of observed contamination that have documented barium concentrations that exceed threes times the background concentration but less than the SCDM reference dose screening concentration, and the soil samples containing concentrations of lead that exceed three times the background concentration. September 2007 112 ------- Sample ID Total Number of Residents References 2690-5/20109 2 Ref. 15, pp. 207-208 2690-12/20108 2 Ref. 15, pp. 205-206 2690-13/20130 2.641 Ref. 11, p. 3 2690-28/20149 2.641 Ref. 15 pp. 273-274 2691-1 /20033 1 Ref. 15, pp. 67-68 2691-3/20021 7 Ref. 15, pp. 47-48 2691-5/20009 2 Refs 15, pp. 21-22 2691-8/20019 1 Ref. 15, pp. 43-44 2691-10/20017 5 Ref. 15, pp. 39-40 2691-14/20015 6 Ref. 15, pp. 33-34 2691-15/20058 2.641 Ref. 15, pp. 109-110 2691-16/20011 2.641 Ref. 15, pp. 27-28 2691-17/20008 5 Refs 15, pp. 17-18 2691-23/20028 5 Ref. 15, pp. 61-62 2691-24/20014 5 Ref. 15, pp. 31-32 2691-27/20142 2 Ref. 15, pp. 261-262 2691-28/20007 2.641 Ref. 12, p. 3 2691-32/20007 2730-6/20012 4 Ref. 15, pp. 29-30 2730-12/20010 6 Ref. 15, pp. 23-24 2730-29 / 20006 2 Ref. 15, pp. 13-14 2937-15/40032 3 Ref. 14, pp. 63-64 2937-16/40031 3 Ref. 14, pp. 61-62 2937-31 /40079 1 Ref. 14, pp. 147-148 2991-7/40139 4 Ref. 14, pp. 261-262 Exact number of residents is not known. Value assigned is average number (2.64) of residents per household for Washington County as determined in the 2000 Census (Ref. 4, p. 2). Sum of individuals subject to Level II concentrations: 79.2 Level II Concentrations Factor Value: 79.2 5.1.3.3 Workers No workplaces were identified. 5.1.3.4 Resources No resources were identified. 5.1.3.5 Terrestrial Sensitive Environments No terrestrial sensitive environments were identified. 5.2 NEARBY POPULATION THREAT The nearby population threat of the soil exposure pathway was not scored because resident individual maximized the pathway score. September 2007 113 ------- APPENDIX A SUB-AQUIFER SCORESHEETS ------- TABLE 3-1-GROUND WATER MIGRATION PATHWAY SCORESHEET SUB-AQUIFER 1 Factor Categories and Factors Maximum Value Value Assigned Likelihood of Release to an Aquifer: 1. Observed Release: 550 550 2. Potential to Release: 2a. Containment 10 Not Scored 2b. Net Precipitation 10 Not Scored 2c. Depth to Aquifer 5 Not Scored 2d. Travel Time 35 Not Scored 2e. Potential to Release [lines 2a x (2b + 2c + 2d)] 500 Not Scored 3. Likelihood of Release (higher of lines 1 and 2e) 550 550 Waste Characteristics: 4. Toxicity/Mobility a 10,000 5. Hazardous Waste Quantity a 10,000 6. Waste Characteristics 100 100 T argets: 7. Nearest Well 50 50 8. Population: 8a. Level I Concentrations b 812.8 8b. Level II Concentrations b 23 8c. Potential Contamination b NS 8d. Population (lines 8a + 8b + 8c) b 835.8 9. Resources 5 Not Scored 10. Wellhead Protection Area 20 Not Scored 11. Targets (lines 7 + 8d + 9 + 10) b 885.8 GROUND WATER MIGRATION SOURCE FOR AN AQUIFER 12. Aquifer Source [(lines 3 x 6 x 1 l)/82,500]c 100 100 GROUND WATER MIGRATION PATHWAY SCORE 13. Pathway Score (Sgw), (highest value from line 12 for all 100 100 aquifers evaluated)c aMaximum value applies to waste characteristics category. bMaximum value not applicable. cDo not round to nearest integer. ------- TABLE 3-1-GROUND WATER MIGRATION PATHWAY SCORESHEET SUB-AQUIFER 2 Factor Categories and Factors Maximum Value Value Assigned Likelihood of Release to an Aquifer: 1. Observed Release: 550 550 2. Potential to Release: 2a. Containment 10 Not Scored 2b. Net Precipitation 10 Not Scored 2c. Depth to Aquifer 5 Not Scored 2d. Travel Time 35 Not Scored 2e. Potential to Release [lines 2a x (2b + 2c + 2d)] 500 Not Scored 3. Likelihood of Release (higher of lines 1 and 2e) 550 550 Waste Characteristics: 4. Toxicity/Mobility a 10,000 5. Hazardous Waste Quantity a 1,000,000 6. Waste Characteristics 100 100 T argets: 7. Nearest Well 50 50 8. Population: 8a. Level I Concentrations b 20 8b. Level II Concentrations b 26 8c. Potential Contamination b NS 8d. Population (lines 8a + 8b + 8c) b 46 9. Resources 5 Not Scored 10. Wellhead Protection Area 20 Not Scored 11. Targets (lines 7 + 8d + 9 + 10) b 96 GROUND WATER MIGRATION SOURCE FOR AN AQUIFER 12. Aquifer Source [(lines 3 x 6 x 1 l)/82,500]c 100 64.00 GROUND WATER MIGRATION PATHWAY SCORE 13. Pathway Score (Sgw), (highest value from line 12 for all 100 64.00 aquifers evaluated)0 aMaximum value applies to waste characteristics category. bMaximum value not applicable. cDo not round to nearest integer. ------- APPENDIX B INDIVIDUAL WATERSHED SCORESHEETS ------- TABLE 4-1.-SURFACE WATER OVERAND/FLOOD MIGRATION COMPONENT SPREADSHEET SOURCE 3 WATERSHED Factor Categories and Factors Maximum Value Value Assigned Drinking Water Threat Likelihood of Release: 1. Observed Release. 550 550 2. Potential to Release by Overland Flow: 2a. Containment 10 Not Scored 2b. Runoff 25 Not Scored 2c. Distance to Surface Water 25 Not Scored 2d. Potential to Release by Overland Flow (lines 2a[2b+2c]) 500 Not Scored 3. Potential to Release by Flood: 3a. Containment (Flood) 10 Not Scored 3b. Flood Frequency 50 Not Scored 3c. Potential to Release by Flood (lines 3a x 3b) 500 Not Scored 4. Potential to Release (lines 2d + 3c, subject to a maximum of 500) 500 Not Scored 5. Likelihood of Release (higher of lines 1 and 4) 550 550 Waste Characteristics: 6. Toxicity/Persistence W Not Scored 7. Flazardous Waste Quantity W Not Scored 8. Waste Characteristics 100 Not Scored Targets: 9. Nearest Intake | 50 | Not Scored 10. Population 10a. Level I Concentrations (b) Not Scored 1 Ob. Level II Concentrations (t>) Not Scored 10c. Potential Contamination (b) Not Scored lOd.Population (lines 10a + 10b + 10c) (b) Not Scored 11. Resources 5 Not Scored 12. Targets (lines 9 + lOd + 11) (t>) Not Scored Drinking Water Threat Score: 13. Drinking Water Threat Score ([lines 5 x 8 x 12]/82,500, subject to maximum of 100) 100 Not Scored Human Food Chain Threat Likelihood of Release: 14. Likelihood of Release (same value as line 5) | 550 | 550 Waste Characteristics: 15. Toxicity/Persistence/Bioaccumulation w Not Scored 16. Hazardous Waste Quantity w Not Scored 17. Waste Characteristics 1,000 Not Scored Targets: 18. Food Chain Individual | 50 | Not Scored 19. Population 19a. Level I Concentrations (b) Not Scored 19b. Level II Concentrations (t>) Not Scored ------- Factor Categories and Factors Maximum Value Value Assigned 19c.Potential Human Food Chain Contamination 00 Not Scored 19d.Population (lines 19a + 19b + 19c) (b) Not Scored 20. Targets (lines 18 + 19) (t>) Not Scored Human Food Chain Threat Score: 21. Human Food Chain Threat Score ([lines 14 x 17 x20]/82,500, subject to a maximum of 100) 100 Not Scored Environmental Threat Likelihood of Release: 22. Likelihood of Release (same value as line 5) | 550 | 550 Waste Characteristics: 23. Ecosystem Toxicity/Persistence/Bioaccumulation w 50,000,^)00 24. Hazardous Waste Quantity w 10,|000| 25. Waste Characteristics 1,000 560. T argets 26. Sensitive Environments 26a. Level I Concentrations (t>) 0 26b. Level II Concentrations (b) 50 26c. Potential Contamination (t>) Not scored 26d. Sensitive Environments (lines 26a + 26b + 26c) (b) 50 27. Targets (value from line 26d) (b) 50 Environmental Threat Score: 28. Environmental Threat Score ([lines 22 x 25 x 27]/82,500, subject to a maximum of 60) Surface Water Overland/Flood Migration Component Score for a Watershed 60 60 29. Watershed Scorec (lines 13 + 21 + 28, subject to a maximum of 100) Surface Water Overland/Flood Migration Component Score 100 60 30. Component score (S0f)c (highest score from line 29 for all watersheds evaluated, subject to a maximum of 100) 100 60 Comment [CU3]: 37 acres of emergent wetlands are associated with the source , see page 87. Comment [CU1]: Ecosystem Toxicity/ Persistence/ Bioaccum ulation is based on lead. See page 85 of the documentation record. Comment [CU2]: Source 3 is a 53.8 acre tailings pond (see page 28, 85-86). aMaximum value applies to waste characteristics category. bMaximum value not applicable. cDo not round to nearest integer. ------- TABLE 4-1.-SURFACE WATER OVERAND/FLOOD MIGRATION COMPONENT SPREADSHEET SOURCE 4 WATERSHED Factor Categories and Factors Maximum Value Value Assigned Drinking Water Threat Likelihood of Release: 1. Observed Release. 550 550 2. Potential to Release by Overland Flow: 2a. Containment 10 Not Scored 2b. Runoff 25 Not Scored 2c. Distance to Surface Water 25 Not Scored 2d. Potential to Release by Overland Flow (lines 2a[2b+2c]) 500 Not Scored 3. Potential to Release by Flood: 3a. Containment (Flood) 10 Not Scored 3b. Flood Frequency 50 Not Scored 3c. Potential to Release by Flood (lines 3a x 3b) 500 Not Scored 4. Potential to Release (lines 2d + 3c, subject to a maximum of 500) 500 Not Scored 5. Likelihood of Release (higher of lines 1 and 4) 550 550 Waste Characteristics: 6. Toxicity/Persistence W Not Scored 7. Flazardous Waste Quantity W Not Scored 8. Waste Characteristics 100 Not Scored Targets: 9. Nearest Intake | 50 | Not Scored 10. Population 10a. Level I Concentrations (b) Not Scored 1 Ob. Level II Concentrations (t>) Not Scored 10c. Potential Contamination (b) Not Scored lOd.Population (lines 10a + 10b + 10c) (b) Not Scored 11. Resources 5 Not Scored 12. Targets (lines 9 + lOd + 11) (t>) Not Scored Drinking Water Threat Score: 13. Drinking Water Threat Score ([lines 5 x 8 x 12]/82,500, subject to maximum of 100) 100 Not Scored Human Food Chain Threat Likelihood of Release: 14. Likelihood of Release (same value as line 5) | 550 | 550 Waste Characteristics: 15. Toxicity/Persistence/Bioaccumulation w Not Scored 16. Hazardous Waste Quantity w Not Scored 17. Waste Characteristics 1,000 Not Scored Targets: 18. Food Chain Individual | 50 | Not Scored 19. Population 19a. Level I Concentrations (b) Not Scored 19b. Level II Concentrations (t>) Not Scored ------- Factor Categories and Factors Maximum Value Value Assigned 19c.Potential Human Food Chain Contamination 00 Not Scored 19d.Population (lines 19a + 19b + 19c) (b) Not Scored 20. Targets (lines 18 + 19) (t>) Not Scored Human Food Chain Threat Score: 21. Human Food Chain Threat Score ([lines 14 x 17 x20]/82,500, subject to a maximum of 100) 100 Not Scored Environmental Threat Likelihood of Release: 22. Likelihood of Release (same value as line 5) | 550 | 550 Waste Characteristics: 23. Ecosystem Toxicity/Persistence/Bioaccumulation w 50,000,000 24. Hazardous Waste Quantity w 10,000 25. Waste Characteristics 1,000 560 T argets 26. Sensitive Environments 26a. Level I Concentrations (t>) 0 26b. Level II Concentrations (b) 25 26c. Potential Contamination (t>) Not scored 26d. Sensitive Environments (lines 26a + 26b + 26c) (b) 25 27. Targets (value from line 26d) (b) 25 Environmental Threat Score: 28. Environmental Threat Score ([lines 22 x 25 x 27]/82,500, subject to a maximum of 60) Surface Water Overland/Flood Migration Component Score for a Watershed 60 60 29. Watershed Scorec (lines 13 + 21 + 28, subject to a maximum of 100) Surface Water Overland/Flood Migration Component Score 100 60 30. Component score (S0f)c (highest score from line 29 for all watersheds evaluated, subject to a maximum of 100) 100 60 aMaximum value applies to waste characteristics category. bMaximum value not applicable. cDo not round to nearest integer. ------- TABLE 4-1.-SURFACE WATER OVERAND/FLOOD MIGRATION COMPONENT SPREADSHEET SOURCE 5 WATERSHED Factor Categories and Factors Value Value Assigned Drinking Water Threat Likelihood of Release: 1. Observed Release. 550 550 2. Potential to Release by Overland Flow: 2a. Containment 10 Not Scored 2b. Runoff 25 Not Scored 2c. Distance to Surface Water 25 Not Scored 2d. Potential to Release by Overland Flow (lines 2a[2b+2c]) 500 Not Scored 3. Potential to Release by Flood: 3a. Containment (Flood) 10 Not Scored 3b. Flood Frequency 50 Not Scored 3c. Potential to Release by Flood (lines 3a x 3b) 500 Not Scored 4. Potential to Release (lines 2d + 3c, subject to a maximum of 500) 500 Not Scored 5. Likelihood of Release (higher of lines 1 and 4) 550 550 Waste Characteristics: 6. Toxicity/Persistence W Not Scored 7. Flazardous Waste Quantity W Not Scored 8. Waste Characteristics 100 Not Scored Targets: 9. Nearest Intake 50 Not Scored 10. Population 10a. Level I Concentrations (b) Not Scored 1 Ob. Level II Concentrations (t>) Not Scored 10c. Potential Contamination (b) Not Scored lOd.Population (lines 10a + 10b + 10c) (b) Not Scored 11. Resources 5 Not Scored 12. Targets (lines 9 + lOd + 11) (t>) Not Scored Drinking Water Threat Score: 13. Drinking Water Threat Score ([lines 5 x 8 x 12]/82,500, subject to 100 Not Scored maximum of 100) Human Food Chain Threat Likelihood of Release: 14. Likelihood of Release (same value as line 5) 550 550 Waste Characteristics: 15. Toxicity/Persistence/Bioaccumulation w Not Scored 16. Hazardous Waste Quantity W Not Scored 17. Waste Characteristics 1,000 Not Scored Targets: 18. Food Chain Individual 50 Not Scored 19. Population 19a. Level I Concentrations (b) Not Scored 19b. Level II Concentrations (b) Not Scored ------- Factor Categories and Factors Maximum Value Value Assigned 19c.Potential Human Food Chain Contamination 00 Not Scored 19d.Population (lines 19a + 19b + 19c) (t>) Not Scored 20. Targets (lines 18 + 19) (t>) Not Scored Human Food Chain Threat Score: 21. Human Food Chain Threat Score ([lines 14 x 17 x20]/82,500, subject 100 Not Scored to a maximum of 100) Environmental Threat Likelihood of Release: 22. Likelihood of Release (same value as line 5) 550 550 Waste Characteristics: 23. Ecosystem Toxicity/Persistence/Bioaccumulation W 50,000,000 24. Hazardous Waste Quantity W 10,000 25. Waste Characteristics 1,000 560 T argets 26. Sensitive Environments 26a. Level I Concentrations (b) 0 26b. Level II Concentrations (b) 75 26c. Potential Contamination (b) Not scored 26d. Sensitive Environments (lines 26a + 26b + 26c) (t>) 75 27. Targets (value from line 26d) (b) 75 Environmental Threat Score: 28. Environmental Threat Score ([lines 22 x 25 x 27]/82,500, subject to a 60 60 maximum of 60) Surface Water Overland/Flood Migration Component Score for a Watershed 29. Watershed Scorec (lines 13 + 21 +28, subject to a maximum of 100) 100 60 Surface Water Overland/Flood Migration Component Score 30. Component score (S0f)c (highest score from line 29 for all watersheds 100 60 evaluated, subject to a maximum of 100) aMaximum value applies to waste characteristics category. bMaximum value not applicable. cDo not round to nearest integer. ------- TABLE 4-1.-SURFACE WATER OVERAND/FLOOD MIGRATION COMPONENT SPREADSHEET SOURCE 6 WATERSHED Factor Categories and Factors Value Value Assigned Drinking Water Threat Likelihood of Release: 1. Observed Release. 550 550 2. Potential to Release by Overland Flow: 2a. Containment 10 Not Scored 2b. Runoff 25 Not Scored 2c. Distance to Surface Water 25 Not Scored 2d. Potential to Release by Overland Flow (lines 2a[2b+2c]) 500 Not Scored 3. Potential to Release by Flood: 3a. Containment (Flood) 10 Not Scored 3b. Flood Frequency 50 Not Scored 3c. Potential to Release by Flood (lines 3a x 3b) 500 Not Scored 4. Potential to Release (lines 2d + 3c, subject to a maximum of 500) 500 Not Scored 5. Likelihood of Release (higher of lines 1 and 4) 550 550 Waste Characteristics: 6. Toxicity/Persistence W Not Scored 7. Flazardous Waste Quantity W Not Scored 8. Waste Characteristics 100 Not Scored Targets: 9. Nearest Intake 50 Not Scored 10. Population 10a. Level I Concentrations (b) Not Scored 1 Ob. Level II Concentrations (t>) Not Scored 10c. Potential Contamination (b) Not Scored lOd.Population (lines 10a + 10b + 10c) (b) Not Scored 11. Resources 5 Not Scored 12. Targets (lines 9 + lOd + 11) (t>) Not Scored Drinking Water Threat Score: 13. Drinking Water Threat Score ([lines 5 x 8 x 12]/82,500, subject to 100 Not Scored maximum of 100) Human Food Chain Threat Likelihood of Release: 14. Likelihood of Release (same value as line 5) 550 550 Waste Characteristics: 15. Toxicity/Persistence/Bioaccumulation w Not Scored 16. Hazardous Waste Quantity W Not Scored 17. Waste Characteristics 1,000 Not Scored Targets: 18. Food Chain Individual 50 Not Scored 19. Population 19a. Level I Concentrations (b) Not Scored 19b. Level II Concentrations (b) Not Scored ------- Factor Categories and Factors Maximum Value Value Assigned 19c.Potential Human Food Chain Contamination (b) Not Scored 19d.Population (lines 19a + 19b + 19c) (b) Not Scored 20. Targets (lines 18 + 19) (b) Not Scored Human Food Chain Threat Score: 21. Human Food Chain Threat Score ([lines 14 x 17 x20]/82,500, subject to a maximum of 100) 100 Not Scored Environmental Threat Likelihood of Release: 22. Likelihood of Release (same value as line 5) | 550 | 550 Waste Characteristics: 23. Ecosystem Toxicity/Persistence/Bioaccumulation w 50,000,000 24. Hazardous Waste Quantity w 10,000 25. Waste Characteristics 1,000 560 T argets 26. Sensitive Environments 26a. Level I Concentrations (b) 0 26b. Level II Concentrations (t>) 50 26c. Potential Contamination (b) Not scored 26d. Sensitive Environments (lines 26a + 26b + 26c) (b) 50 27. Targets (value from line 26d) (b) 50 Environmental Threat Score: 28. Environmental Threat Score ([lines 22 x 25 x 27]/82,500, subject to a maximum of 60) Surface Water Overland/Flood Migration Component Score for a Watershed 60 60 29. Watershed Scorec (lines 13 + 21 +28, subject to a maximum of 100) Surface Water Overland/Flood Migration Component Score 100 60 30. Component score (S0f)c (highest score from line 29 for all watersheds evaluated, subject to a maximum of 100) 100 60 aMaximum value applies to waste characteristics category. bMaximum value not applicable. cDo not round to nearest integer. ------- APPENDIX C PHOTOLOG ------- Richwoods Area 10 Richwoods, Missouri TETRA TECH PROJECT NO. I9004L060027000 DESCRIPTION This photograph shows the collection of surface water and sediment from a tailings pond/wetland located in Source area 3. 1 CLIENT IJ.S. Environmental Protection Agency Region 7 Date PHOTOGRAPHER David Gray TETRA TECH PROJECT NO. I9004L060027000 DESCRIPTION '111 is photograph shows the collection of surface water and sediment from a tailings pond/wetland located in Source area 3. 2 CLIENT IXS. Environmental Protection Agency Region 7 Date PHOTOGRAPHER Jason Heflin ------- Richwoods Area 10 Richwoods, Missouri TETRATECH PROJECT NO. I9004L060027000 DESCRIPTION This photograph shows the collection of surface water and sediment from a tailings pond, wetland located in Source area 3. 3 (1 II X I TJ.S. Environmental Protection Agency Region 7 Date PHOTOGRAPHER David Gray Ti : I R A TECH PROJECT NO. I9004L060027000 DESCRIPTION Hiis photograph shows the collection of surface water and sediment from a tailings pond/wetland located in Source area 3. 4 CLIENT tJ.S. Environmental Protection Agency Region 7 Date PHOTOGRAPHER Jason Heflin ------- |