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FORBESENVIRONMENTALCONSULTING FEBRUARY 1997
FINAL
FIRST FIVE YEAR REVIEWINDUSTRIAL WASTE CONTROL SITE
SEBASTIAN COUNTY, ARKANSAS
146344
ENVIRONMENTAL SOLUTION ENGINEERING
006595
EXECUTIVE SUMMARY
The attached Final First Five Year Review-Industrial Waste Control Report is prepared incompliance with the Comprehensive Environmental Response, Compensation, andLiability Act(CERCLA), as amended by section 121(c), and section 300.430(f)(4)(ii) of theNational Oil and Hazardous Substance Pollution Contingency Plan(NCP), and OSWERDirective 9355.7-02, "Structure and Components of Five Year Reviews." The report isequivalent to a Level I Review and summarizes the conditions prior to remediation, the keyremediation tasks as completed, and the first 5 year post closure monitoring period fromMarch 29, 1991 through March 29, 1996.
The Review is a review of the Remedial Action Plan(RAP) as implemented at the IWC Siteand the post closure care activities since completion of the RAP. It is completed inaccordance with the Consent Decree, and is based on existing documents and studiescompleted by the USEPA and the IWC Committee. Submittal of the Draft and FinalReview were coordinated through and approved by the EPA Region VI Remedial ProjectManager. The Draft Five Year Review was submitted June 3,1996. Verbal approval ofthe Draft Report was issued by the EPA on January 29, 1997 with instructions to submitthe Final Report revised to include installation of MW-15. The attached report constitutesthe Final First Five Year Review for the Industrial Waste Control Site.
The following is a summary of the attached First Five Year Review for the IWC Site. Keyfigures from the report are placed at the end of this summary for easy reference.
The Site is a closed and covered industrial landfill located about 8 miles southeast of Ft.Smith, Arkansas. The landfill was originally an abandoned coal surface mine. Extensiveabandoned underground mine workings exist immediately north of the Site. Landusearound the Site is primarily pastureland, except for small residential areas to the northeast,east and south of the Site.
Landfill operations began in the late 1960's with the disposal of municipal waste. From1974 until late 1978, the Site was a permitted industrial landfill. The landfill operationsincluded liquid disposal surface impoundments and isolated areas for disposal of solid andliquid waste in 55 gallon drums. Upon final closure by the operator, the Site was assessedby the EPA and placed on the National Priority List in December of 1982. The potentiallyresponsible parties were notified and formed the IWC Committee in November of 1983.Site remedial investigations were completed by the EPA and the IWC Committee.
The primary milestones and studies completed were:
EPA Remedial Investigation ReportEPA Endangerment AssessmentEPA Feasibility StudySupplemental RI: Hydrological andWaste Quantification StudySupplemental Endangerment AssessmentSupplemental Feasibility StudyEPA Remedial Alternative SelectionRecord of Decision includingRemedial Action PlanConsent DecreeRemediation Construction-StartupRemediation Construction-CompletionPost Closure Care-StartupArea C AssessmentFirst 5 Year Review
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March, 1986March, 1986June, 1986
October, 1987February, 1988February, 1988June, 1988
June, 1989July, 1989October, 1989March, 1991March, 1991January, 1994May, 1996
006596
The major findings of the remedial investigations were:
Demographics and Land Use
• The Site lies at the base of the north slope of Long Ridge, which is the smallmountain ridge to the south of the Site. The Site is in a rural relatively sparselypopulated area with an estimated population of 375 within a mile radius.
• The location of the residences are south, east and northeast of the Site.
• There are no residences on the land directly north of the Site or to the west. Thisland is used as pastureland.
• The north slope of Long Ridge is heavily forested.
• The primary water source is the Sebastian County Water User Association. Someresidences in the area do have water wells, but none are reported to be in use at thepresent time.
Geology
The major geologic formations relevant to the Site in descending order from thesurface are:
Apparent Thickness(ft)0 McAlester 0-60 feet
>-Lower Hartshome Coal 3-8>• Weathered bedrock(Transition Zone) 3-5
0 Hartshome Sandstone 50
0 Atoka Formation 6500+
The "Lower Hartshome Coal" in the lower portion of the McAlester was thepredominant coal seam mined extensively in the general regional vicinity of the Site.The coal bed is near the surface at the Site and dips to the north, increasing to a totaldepth of approximately 140 feet within a couple of hundred yards of the Site.
0 The shallow Lower Hartshome Coal was mined from the surface by stripmining method at the Site. The western portion of the abandoned strip minewas later used as the IWC Landfill.
0 The deeper coal north of the Site was mined underground by the room andpillar method. The network of underground mine workings is quiteextensive consisting of large rooms or " mined voids" of mined out areas,and pillars of coal left in place to support the roof. A large portion of themine voids are now filled with water.
0 There were no primary direct openings between the Site surface mine andunderground mine workings, although there was the possibility thatseepage from the Site could enter the mine.
0 Below the coal bed is a weathered sandy shale transition zone from theMcAlester to the Hartshome Sandstone referred to as weathered bed.The weathered bedrock underlies the entire Site and the underground mineworkings.
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The Hartshome Sandstone lies below the weathered bedrock, as identified by pointof refusal for drill rigs. Cores show that the Hartshome is a series ofunweathered alternating thin beds of sandstone and hard sandy shale with similarcharacteristics to the weathered bedrock.
The Atoka Formation is predominantly shale which is reported to extend to greaterthan 6500 feet below the surface.
The dip of the strata indicate that the depth of the formations increases to the northof the Site.
The north bank of strip mine(Landfill) defines the northern boundary of theremediated Site and the southern extremity of the underground mined out coal beds.
In general the Site is contained above the weathered bedrock.
0 North of the Landfill, the McAlester Shale lies above weatheredbedrock and the underground mine workings;
0 South of the Landfill, natural colluvial soils and spoils removed duringstrip mining operations overlie the weathered bedrock. This horizon iscollectively referred to as "colluvium" because it was difficult to differentiatebetween the two. The surface impoundments and drum disposal areas werelocated in the colluvium.
Hydrogeology
There were five ground water bearing zones relevant to the Site identified by siteinvestigation prior to remediation.
0 The interconnected ground water system in the Hartshome and AtokaFormations upgradient( south) of the Site, referred to as theHartshome/Atoka aquifer.
0 The limited and discontinuous perched zones in the colluvium onsite southof the Landfill.
0 A ground water system in the transition zone between the McAlester and theHartshome including the weathered bedrock. It was difficult to determine ifthere are two distinct systems so together this system was referred to asMcAlester/Hartshome or the confined weathered bedrock system. Thissystem lies below the entire Site.
0 An artesian system in the underground mine workings to the north of theSite.
0 A perched system in the McAlester formation above the mine workingsnorth of the Landfill.
There are water wells completed in the Hartshome/Atoka system south of the Site,in the McAlester perched systems north of the Site above the mine workings andin the mine voids themselves. There are no known water wells completed belowthe mine workings. A water purveyor provides water to the local residences andnone of the households depend on water wells. There were no water wellscompleted in the perched zone onsite or in the weathered bedrock and the recoveryrates are too low to support a water supply well.
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• It was determined that there was not an interconnection between the onsite perchedsystem and the confined system in the weathered bedrock, and the flow in theweathered bedrock was confined to within its bedding planes.
• To the north of the Landfill, the McAlester/Hartshome and the Hartshorne/Atokaground water systems lie below the underground mine system. The depth of thesesystems increases with increasing distance to the north from the Site, and arereported at more than 200 feet below the surface a couple of hundred yards fromthe Site.
Areas of Potential Concern
The initial Site investigations identified five areas which presented potential concern andwarranted some level of physical remediation. These areas were:
Area A- The landfill.
• Area B- An area of potential soil contamination due to landfill operationactivities. The area was extended to include an area(Area PA)discovered during remediation.
• Area C- Location of surface impoundments used for liquid waste disposal,and drummed waste disposal.
• Area D- Isolated area of drummed liquid and solid waste disposal.
• Area09B- An isolated area around MW-09B which reported atypicalconcentrations of VOCs.
Endangerment Assessment
The Endangerment Assessment evaluated the potential sources, pathways and receptors todetermine potential risks as a result of the Site conditions. It generally concluded:
• There was no evidence that significant concentrations of Site contaminants hadmigrated offsite via soil, surface water or ground water.
• The majority of the identified contaminants in the wastes and in soils were non-carcinogens.
• Contamination in the soils did not appear to have migrated and did not present anunacceptable risk to ground water at the time, and would not unless there was amechanism to leach significant concentrations and a mechanism for transport.
• Only the ground water reported in MW-09B presented a significant potential risk.
Applicable or Relevant and Appropriate Requirements
In evaluating the remedial alternatives, all the significant environmental regulations wereconsidered. The following regulations were determined to be applicable and/or relevantand appropriate:
• Safe Drinking Water Act• Solid Waste Disposal Act• Arkansas Water, Air and Pollution Act
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Occupational Safety and Health ActClean Water ActResource Conservation and Recovery ActComprehensive Environmental Response, Compensation, and Liability ActSuper-fund Reauthorization ActNational Oil Hazardous Substance Pollution Contingency Plan
Remedial Action Plan
The EPA selected the final remedial action alternative based on the selection criteriamandated by CERCLA. The Remedial Action Plan was developed and became part of thefinal Record of Decision. The primary focus of the Remedial Action Plan was to minimizethe potential risks to the artesian ground water system in the mine voids by conducting thefollowing tasks:
• Reduce toxicitv and volume
0 Treat impacted soils encountered in Areas B(PA), C, D, 09B, and alongthe slurry wall pathway which exceeded Clean Up Criteria to meettreatment standards. Clean Up Criteria were:
Total VOCLeadNickelCadmium
<1000 ppm<1000 ppm<1000 ppm<1000 ppm
Treatment Standards were:
Allowable leachate concentrations per the EPAToxicity Concentration Leachate Procedure(TCLP)for the Hazardous Substance List Constituents
0 Remove drums of liquid from Area D and C and transport to offsitepermitted commercial facility.
0 Place treated soils back into the excavation of Area C, solidify, and containwithin a slurry wall tied into the weathered bedrock and Site Slurry Wall.
Reduce Mobility
The objective of reducing mobility was to minimize ground water flow into theremediated area above the weathered bedrock in order to limit recharge of the onsiteperched ground water zones thereby limiting the leachate transport mechanism by:
0 Installing French Drain upgradient of Site to intercept shallow ground waterflow above weathered bedrock and divert it around the Site.
0 Installing Site Slurry Wall downgradient and parallel to the French Drain tocutoff backflow from the impacted Site soils into the French Drain, cutoffHow on to the Site during construction, and secondarily provide backup forthe French Drain.
0 Covering the entire remediated area including the Landfill, French Drainand Slurry Wall with a multilayer RCRA Cap and Cover to prevent rainfallinfiltration into the remediated area.
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• Long Term Security
0 Installation of Slurry Wall around Area C.
0 Cap and Cover over remediated area.
0 Post Closure Activity Plan.
0 Site Security Fence.
Remedial Construction Phase
The remedial construction was implemented to meet the RAP objectives. The remediatedarea is the area below the Cap and Cover within the perimeter and above the effective depthof the French Drain and Site Slurry Wall. The remedy design components effectivelyaddress the remediated area above the weathered bedrock in accordance with the RAPobjectives.
Area C excavation was completed in the weathered bedrock below the effective depths ofthe French Drain and Site Slurry Wall and below the remediated area.
Post Closure Activity Care
Post closure activity care began upon completion of remedial construction in accordancewith the approved Post Closure Activity Plan. The following activities were conducted:
• Three year quarterly baseline sampling to establish action limits in Site monitoringwells. Samples were analyzed for volatile and semi-volatile organic compounds,lead, nickel, and cadmium. Sample points were:
0 Upgradient well in Hartshome/Atoka Aquifer MW- 102s
0 Downgradient wells in mine voids: MW-103s, MW-10.MW-11
0 French Drain recharge wells: East and West Recharge Wells.
Upon completion of baseline sampling period semi-quarterly monitoring and samplingevents were conducted. On the basis of baseline sample results, semi-volatile compounds,lead, and cadmium were deleted from the analytical parameters. MW-2,3, 4, and 5 wereadded to the monitor well sampling list due to discovery of volatile organics in the wells.
• Water level measurements were recorded in the following wells during eachmonitoring event.
0 Upgradient, and downgradient monitor wells.
0 Landfill monitor wells: MW-1, MW-6, MW-7, MW-8, MW-9
0 French Drain piezometers: P-l, P-2, P-3, P-4
0 Area C Monitor Wells: MW-2, MW-3, MW-4, MW-5
• Site Inspection and maintenance
• Monitor Event Reports
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• Asa result of the conditions identified during the post closure monitoring events thefollowing major additional tasks were performed:
0 reconstruction of three original monitor wells and two piezometers whichhad been completed to the wrong depths during remediation;
0 establish vegetation growth on surface of cap and cover;
0 install offsite drainage diversion ditch to tie into Site diversion ditch;
0 monitoring and sampling of ground water encountered within Area Ccontainment cell;
0 preliminary Area C assessment which included installation of monitor wellsand piezometers in and around Area C;
0 placement of four additional monitor wells completed in the weatheredbedrock below the mine voids north of the Landfill, and samplingthese wells on a quarterly basis;
0 replacement of approximately 200 feet of French Drain discharge line tofrom the west end manway to the west recharge well;
0 remove observation tower.
Current Site Status
• The Cap and Cover is in good condition and vegetation is well established. The Capand Cover is preventing rainfall from infiltrating into remediated area.
• The French Drain is intercepting and diverting shallow groundwater aboveweathered bedrock around the Site into the recharge wells. Low VOCconcentrations have been reported in the recharge wells.
• Upgradient monitor well sample results have consistently reported negativeindicator parameters.
• Downgradient mine void monitor wells(MW-10, 11, 103 D) have consistentlyreported negative indicator parameters with the exception of three isolated anddifferent occurrences in which a low concentration of a single compound wasreported in MW-10 and MW-11. There have been inconsistent changes in nickelconcentrations from non-detect to above action limits.
To date the mine void ground water system has not been significantly impacted byIWC conditions.
• Water levels in the Landfill monitor wells have been consistently measured as"dry" or just above the bottom of the casing. The water levels indicate that there isminimal water entering into the Landfill.
• In general, the remedy is performing as intended within the remediated area.
• Area C excavation was completed into the weathered bedrock below theremediated area. This overexcavation places the lower portion of Area C in thepathway of ground water flow in the weathered bedrock. Anomalous VOC
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concentrations have been reported both inside Area C and immediatelydovvngradient from Area C. The more prevalent compounds frequently reported inwere: cis 1,2 dichloroethene, trichloroethene, vinyl chloride, methylene chloride,toluene, acetone, xylene, ethyl benzene, trans 1,2 dichloroethene.
According to the EPA and HWQS reports, flow in the weathered bedrock isconfined to the bedding planes of the weathered shale which underlies the Site andthe underground mine workings. This appears to be supported by the difference inwater elevations reported in the monitor wells completed in the mine voids ascompared to the downgradient wells discussed below.
Four monitor wells(MW-12, 13, 14, 15) were placed downgradient of Area C.The wells were installed off the Cap and Cover and completed through mine pillarsin the weathered bedrock below the mine workings. The screened intervals ofMW-12, 13, and 15 were isolated from the overlying coal bed in the pillars. Thescreen interval in MW-14 was completed above the weathered bedrock and in thecoal bed. MW-12,13, and 14 are approximately 150 feet south of the property linenear the toe of the Cap. MW-15 is located near the property line downgradient ofMW-12. Sample analytical reports indicate:
<> No VOC have been reported in MW-14.
0 Only one compound-chloroform- has been reported in MW-13. Thereported concentrations have been below MCLs. Chloroform had not beena prevalent or consistently reported compound during the Site investigationor post closure monitoring. Chloroform has not been reported in this well insubsequent sampling events after the 5 year review period.
0 VOC concentrations have been consistently reported in MW-12 aboveMCLs for cis 1,2 dichloroethene, trichloroethene, and vinyl chloride.
0 MW-15 has been sampled during three subsequent sampling events after theperiod covered in this review. The analytical results for the all eventshave been negative.
The water level measurements indicate:
0 A consistent and relatively flat water surface is measured in the minevoid ground water system. The water level measured in MW-14 isconsistently equivalent to that measured in the mine void monitor wells.
0 Water levels measured in the MW-12, and 13, which are in the generalvicinity of the mine void monitor wells, are approximately 6 feet above thewater levels measured in the mine void wells.
0 The mine void ground water system provides excellent yield. It would bedifficult and costly to place a water well into the ground water horizonsbelow the mine voids, and sufficient well yields would be difficult toensure. The depth increases with distance from the Site.
0 Water level in MW-15 was not measured within period covered by reviewreport. To date a trend has not been established but the water level appearsto correspond to the mine void water elevations.
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Next Five Year Monitoring Period(March 1996-March 2001)
• Install MW-15 in weathered bedrock below mine voids downgradient of MW-12near Site property fence line(MW-15 installed 6/19/96). Monitor and sample onquarterly basis for two years, afterwhich sample on semi-annual basis-dependingon analytical results. (Three sample events have been completed, to date all VOCresults have been negative.)
• Continue monitoring and sampling MW-12, 13, and 14 on quarterly basis untilMarch 1997, and incorporate into semi-annual sampling schedule.
• Continue sampling original monitor wells on semi-annual schedule.
Summary
As the Site currently exists primary sources of contamination have been removed therebyreducing contaminant toxicity and volume. The French Drain, and Site Slurry Wallminimize subsurface seepage into the remediated area above the weathered bedrock, and theCap and Cover prevents infiltration, limiting the mechanism for contaminant transport andconsequently reducing mobility. The remedial design as completed minimizes thepotential impact to the underground mine water system and to date mine void monitor wellsindicate that the mine system has not been impacted. These were the intended objectives ofthe remedial design.
Conditions exist in the weathered bedrock below the remediated area which do not reflecton the effectiveness of the remedial design, since the remediated area above the weatheredbedrock is not compromised. These conditions include overexcavation of Area C and VOCconcentrations in the ground water in the weathered bedrock which exceed MCL. Based onthe information and referenced documents available at this time these conditions do notpresent an imminent threat since it would be difficult and unlikely to complete a water wellin the ground water systems below the mine workings.
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006605
LEGENDNO SCALE
RELATIVE WATER LEVEL NOTE;MONITOR WELL LOCATION PROJECTED FORBES ENVIRONMENTAL
SCREENED INTERVALCONCEPTUAL CROSS SECTION OFREMEDIAT10N AREA BELOW CAPAND COVER THRU AREA "C"
FIGURE 4
006606
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FIGURE 8.0
006607
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NVIRONMENTAL
RAL GEOLOGICON OF SITE AREAJRE 9.0
006608
006609
006610
006611
FIRST FIVE YEAR REVIEW
INDUSTRIAL WASTE CONTROL SITESEBASTIAN COUNTY, ARKANSAS
PREPARED FORIWC SETTLING DEPENDENTS
Prepared by
Stephen ForbesForbes Environmental Consulting
San Antonio, Texas
February 1997
006612
TABLE OF CONTENTS PAGE
LIST OFACRONYMS....................................... v
1.0 INTRODUCTION................................................. 1
2.0 THE SITE AND REMEDIATEDAREA........................ 1
3.0 SITE HISTORY.................................................... 6
4.0 REMEDIATION PROCESS, SCHEDULE ANDDOCUMENTS..................................................... 6
5.0 INITIAL SITE CONDITION..................................... 8
5.1 The Site........................................................ 85.2 AreaA.......................................................... 8
5.2.1 Surface Mine Operations......................... 85.2.2 Landfill Operations................................ 8
5.3 AreaB.......................................................... 105.4 AreaC.......................................................... 105.5 AreaD.......................................................... 105.6 Area 09B....................................................... 11
6.0 GENERAL SITE PHYSICAL FEATURES.................... 11
6.1 Topography and Drainage................................... 116.2 Demographics and Land Use................................ 116.3 Sources of Drinking Water................................... 156.4 Geology........................................................ 15
6.4.1 McAlestar Shale.................................... 156.4.2 Hartshome Sandstone............................. 166.4.3 The Atoka Formation.............................. 166.4.4 StrikeandDip...................................... 166.4.5 TheCoal Mine Workings......................... 18
6.5 Hydrogeology................................................. 216.5.1 Hartshome/Atoka Aquifer........................ 216.5.2 McAlester/Hartshome
Groundwater System............................ 236.5.3 Mine No. 17 Ground Water System............. 246.5.4 McAlester Aquifer................................. 246.5.5 Onsite Perched System........................... 24
7.0 ENDANGERMENT ASSESSMENT........................... 25
8.0 REMEDIALACTION DESIGN................................. 26
8.1 RAP Objectives............................................... 278.2 ARARs........................................................ 288.3 EPA Remedy Alternative Selection......................... 28
9.0 REMEDIALACTION DESIGN AND SPECIFICATION... 29
9.1 Change Orders to Specifications............................ 30
006613
10.0 SITE REMEDIATION PHASE................................. 31
10.1 Mobilization.................................................. 3110.2 Waste Management......................................... 31
10.2.1 Soils............................................... 3110.2.2 Trash and Debris Management................. 3210.2.3 Offsite Disposal of Liquid Wastes............. 3310.2.4 RI and Remediation Derived Wastes.......... 3310.2.5 Water Management.............................. 33
10.3 French Drain................................................. 3410.4 Site Slurry Wall Installation................................ 3410.5 Area 09B..................................................... 3610.6 AreaD........................................................ 3610.7 AreaBandPA............................................... 3610.8 AreaC........................................................ 3710.9 AreaC Slurry Wall.......................................... 3710.10 MultiLayerRCRA Cap and Cover...................... 3910.11 Monitor Wells and Piezometers.......................... 3910.12 Site Security Fence........................................ 4110.13 Demobilization............................................. 4110.14 EPA Close Out Report.................................... 4110.15 Remediation as Completed............................... 42
11.0 POST CLOSURE ACTIVITY................................... 42
11.1 Action Limits................................................ 4411.2 DataSummary............................................... 4411.3 Additional Post Closure Activities........................ 44
11.3.1 Well Construction............................... 4411.3.2 Vegetation........................................ 5011.3.3 Offsite Drainage.................................. 5011.3.4 AreaC............................................. 50
11.4 Downgradient Monitor Wells.............................. 5211.5 Repair of French Drain Discharge Line................... 54
12.0 CURRENT SITESTATUS...................................... 54
12.1 Excavation of Identified Sources of Contamination..... 5412.2 French Drain and Site Slurry Wall........................ 5412.3 AreaC........................................................ 6012.4 Landfill....................................................... 6012.5 Cap and Cover............................................... 6012.6 Downgradient Monitor Wells.............................. 6112.7 Mine Void Monitor Wells.................................. 6112.8 Site Security................................................. 61
13.0 POST CLOSURE ACTIVITY -2nd FIVE YEARS (MARCH 1996 TO MARCH 2001)...... 61
REFERENCES................................................... 62
006614
LIST OF FIGURES
I.0 SITE LOCATION MAP........................................... 2
2.0 CURRENT SITE PLAN.......................................... 3
3.0 REMEDIATED AREA BELOW CAP AND COVER......... 4
4.0 AREAC CROSS SECTION..................................... 5
5.0 GENERAL SITE LAYOUT PRIOR TO REMEDIATION... 9
6.0 ARKANSAS RIVER VALLEY.................................. 12
7.0 CURRENT SITE SURFACE DRAINAGE PATTERN...... 13
8.0 LAND USE IN VICINITY OF SITE &LOCATION OFWATER WELLS............................... 14
9.0 N-S GEOLOGICAL CROSS SECTIONFOR THE SITEAREA............................................ 17
10.0 UNDERGROUND MINE WORKINGSIN RELATIONTO SITE......................................... 19
II.0 MAPOFMINENO. 17 NORTH OF SITE.................... 20
12.0 RELATIVE GROUND WATER ELEVATIONS.............. 22
13.0 FRENCH DRAIN AND SITE SLURRYWALLPLAN VIEW.............................................. 35
14.0 AREAC CROSS SECTION..................................... 38
15.0 INITIAL MONITOR WELL ANDPIEZOMETER LOCATION...................................... 40
16.0 LOCATION OF AREA CASSESSMENT PIEZOMETERS................................ 51
17.0 GENERALIZED AREA C ASSESSMENTCROSS SECTION................................................. 53
18.0 CURRENT SITE PLAN VIEW AND LOCATIONOFMONITOR WELLS........................................... 55
19.1 TYPICAL PIEZOMETERS MONITOR WELLCOMPLETION DIAGRAMS.................................... 57
19.2 TYPICAL MINE VOID WELLCOMPLETION DIAGRAMS.................................... 58
19.3 RECHARGE WELL COMPLETION DIAGRAMS........... 59
iii
006615
LIST OF TABLES
1.0 ACTION LIMITS.................................................. 45
2.0 SUMMARY OF POST CLOSURE MONITOR WELLSPOSITIVEANALYTICALRESULTS......................... 46
3.0 SUMMARY OF AREA C ASSESSMENTPOSITIVEANALYTICALRESULTS......................... 47
4.0 SUMMARY OF DOWNGRADIENT MONITOR WELLPOSITIVEANALYTICAL RESULTS......................... 48
5.0 SUMMARY OFWATERELEVATIONS...................... 49
6.0 SUMMARY OF MONITOR WELL AND PIEZOMETERCOMPLETION INFORMATION............................... 56
LIST OF PHOTOGRAPHS
1.1 IWC SITE AERIAL PHOTO(6/20/96).......................... 64
1.2 IWC SITE LOOKING EAST SHOWINGFOOTHILL OF LONG RIDGE.................................. 64
2.1 IWC FROM SOUTH ABOVE LONG RIDGE................. 65
2.2 SITE LOOKING DUE SOUTH,BACKGROUND IS LONG RIDGE............................ 65
3.1 PANORAMIC VIEW OF CAP ANDCOVER LOOKING NORTH.................................... 66
3.2 CAP AND COVER SURFACE LOOKINGNORTHEAST FROM SOUTHWEST CORNER............. 66
4.0 IWC SITE AERIAL PHOTOGRAPH(June 20, 1996)....... 67
5.0 IWC SITE AERIAL PHOTOGRAPH(March 1995).......... 68
6.0 IWC SITE AERIAL PHOTOGRAPH(March 31, 1994)...... 69
7.0 IWC SITE AERIAL PHOTOGRAPH(February 8,1993).... 70
8.0 IWC SITE AERIAL PHOTOGRAPH(August 11, 1990)..... 71
IV
006616
List of Acronyms
ADPC&E Arkansas Department of Pollution Control and EcologyARARS Applicable or Relevant and Appropriate RequirementsASTM American Society of Testing MaterialsCAA Clean Air ActCERCLA Comprehensive Environmental Response, Compensation and Liability ActCORP U.S. Army Corps of EngineersCWA Clean Water ActEA Endangerment AssessmentEPA Environment Protection Agency, Region VIFS Feasibility StudyHDPE High Density PolyethyleneHWQS Hydrogeologic and Waste Quantification StudyIWC Industrial Waste ControlMCL Maximum Concentration LimitMW Monitor WellNCP National Oil and Hazardous Substances Pollution Contingency PlanNPDES National Pollution Discharge Elimination SystemNPL National Priorities ListOSHA Occupational Safefty and Health ActPCAP Post Closure Activity PlanPID Photoionization DetectorPRP Potentially Responsible PartyPVC Polyvinyl ChlorideQA/QC Qual ity Assurance/Quality ControlRAP Remedial Action PlanRA Remedial ActionRAS Remedial Alternative SelectionRCRA Resource Conservation and Recovery ActRD Remedial DesignRI Remedial InvestigationROD Record of DecisionSARA Superfund Amendments and Reauthorization ActSDWA Safe Drinking Water ActSuperfund CERCLA(see above)TCLP Toxicity Characteristic Leaching ProcedureVOC Volati Ie Organic Compound
v
006617
1.0 INTRODUCTION
This Five Year Review is a summary of the significant documents and events which haveoccurred at the Industrial Waste Control Landfill(referred to hereinafter as the "Site")located south of Ft. Smith, Arkansas. The review is prepared in accordance with theComprehensive Environmental Response, Compensation, and Liability Act(CERCLA), asamended by section 121(c), and section 300.430(f)(4)(ii) of the National Oil andHazardous Substance Pollution Contingency Plan(NCP), and OSWER Directive 9355.7-02, "Structure and Components of Five Year Reviews." The EPA establishes three levelsof review. The report is equivalent to a Level I Review. It summarizes the conditionsprior to remediation, the key remediation tasks as completed, and the first 5 year postclosure monitoring period from March 29,1991 through March 29, 1996. It does notinclude a description of the construction procedural plans(e.g. Contingency Plan, Healthand Safety Plans, etc.) or the interim construction facilities(e.g. temporary drum stagingand soil facilities) all of which are described in detail in the referenced Reports. It includesconstruction information in regard to MW-15 which was completed after the reviewreporting period, in order that the well information is complete.
The report is based on existing documents as referenced. The cited documents providemuch greater detail and description of the Site remediation specifications and objectives andare incorporated into this report by references(see Section 4.0, references listed at the endof the report). The original Draft was submitted June 3,1996 in accordance with the PostClosure Activity Report and agreed upon by the Environmental Protection Agency(EPA).Upon review by the EPA and the Arkansas Department of Pollution Control & Ecology,verbal approval of the Draft was given by the EPA on January 27, 1997 with instructionsto submit the Final report including the MW-15 construction detail. The followingconstitutes the Final Five Year Review Report.
Annual aerial photographs were taken in accordance with the Post Closure Activity Plan.These photographs are included in the back of this review along with additional aerial andSite photographs taken during the June, 1996 monitoring event showing site status at theend of the first 5 year period.
2 . 0 THE S ITE AND REMEDIATED AREA
The IWC Site is a closed industrial landfill on an approximately eight-acre tract locatedabout 8 miles southeast of Ft. Smith and 1 mile west of Jenny Lind, Arkansas in SebastianCounty. The town of Bonanza is approximately 4.5 miles to the west of the site(Figure1.0). Access to the site is via an unpaved county maintained road( Racetrack Road) south ofBonanza Road.
The Site as referred to within this report refers to the property within the property fenceline. The remediated area under the Cap and Cover and all monitor wells lie within the Siteboundary. Figure 2.0 presents the current general Site Plan.
The area referred to as "the remediated area" is that area which currently underlies themulti-layer Cap and Cover. The remediated area beneath the Cap and Cover is bounded bythe French Drain and Slurry Wall to the south, east and west and the north bank of theLandfill to the north. It lies above the strata referred to as the weathered bedrock, asdescribed in Sections 5.1 and 6.4.1. The remediated area includes Areas A(Landfill), B,C(surface impoundments), D, and PA, as well as the French Drain, Slurry Wall and theremaining soils and onsite perched water zones in the soils and spoils lying in between theSite Slurry wall and the south bank of the Landfill and above the weathered bedrock.Figure 3.0 shows the remediated area below the Cap and Cover. Figure 4.0 presents aconceptual cross section of the remediated area.
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006619
006620
006621
006622
3.0 SITE HISTORY
Initially the Site was the location of a surface mining operation which mined coal from ashallow coal seam in the mid-1940's by strip mining methods. An extensive network ofabandoned underground coal mines just north old strip mine were operated from the 1890'sthrough the 1932. The western portion of the strip mine was ultimately converted to theLandfill in the early 1960s.
An application for permit to operate the facility as an industrial Landfill was filed November18,1971, and a temporary permit was issued by the Arkansas Department of PollutionControl and Ecology(ADPC&E) on November 23,1971. A full permit to receive industrialwaste at the Site under the name of GNJ, Inc. was issued by the ADPC&E on May 24,1974. In August of 1974 the Site was sold and came under the name of Industrial WasteControl(IWC).
The IWC operations included the Landfill and surface impoundments. The facility receivedprimarily industrial waste including wood shavings, miscellaneous rubbish and drummedsolvents from industrial plants in and around Ft Smith. The surface impoundmentsreferred to as "evaporation ponds" were constructed sometime in the late summer or earlyfall of 1975. These ponds were reportedly used to store and evaporate drummed liquidwastes received at the Site. In addition, drums were deposited in two isolated drumdisposal areas, one in the south area of the surface impoundments and the other located inthe southwest comer of the property. The operations were inspected regularly by theADPC&E. ADPC&E inspection reports noted that the ponds were constructed in clay andunderlain by shale and that vertical migration of fluids from the pond should be minimal.
In general, quarterly ADPC&E inspection reports indicated satisfactory Site conditions.However, in the mid-1977s concerns and issues were raised by the local residents and theAgency in regard to a surface impoundment release. In response to ADPC&E directives,the operator notified the Agency that liquid solvents were no longer accepted. Closureactivities were initiated shortly thereafter. On August 8,1978 the ADPC&E was notifiedthat the Landfill had been closed and covered with compacted material(believed to be thespoils from the former strip mine) and graded to ensure adequate surface drainage. Thestatus of the surface impoundments at the time is unclear, but in late 1979 the ADPC&Einspection reports indicated that a leachate problem existed, and the ERA was notified.
4.0 REMEDIATION PROCESS, SCHEDULE AND DOCUMENTS
Preliminary site assessments were conducted by the EPA in 1980 and 1981. As a result theIWC site was placed on the National Priorities List(NPL) on December 30,1982. ARemedial Action Master Plan was completed for the Site on September 30,1983. The ERAnotified potentially responsible parties(PRPs) regarding the site. A group of the PRPsorganized into the IWC Steering Committee("the Committee") in November of 1983.
The Committee met with the regulatory agencies in November of 1983 to discuss voluntaryremediation. The EPA started its site Remedial Investigation(RI) in March of 1984. TheRI final draft and Endangerment AssessmentfEA) were completed on March 31,1986.The EPA Feasibility StudvfFS) was completed on June 3. 1986.
At the request of the IWC Committee the EPA authorized the Committee under an agreedAdministrative Order to conduct an independent remedial investigation referred to as theHvdrological and Waste Quantification Studv(HWOS). The HWQS Work Plan wasapproved by the EPA and the ADPC&E(referred to collectively as "the Agencies"). Theinvestigation was conducted from March through early July, 1987. All field investigationactivity conducted by the Committee was overseen by the EPA, and coordinated throughthe ADPC&E. The HWQS report was submitted to the Agencies in October of 1987. An
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independent Supplemental Feasibility Study and Supplemental Endaneerment Assessmentwas prepared by the Committee and submitted to the Agencies in February 1988. The
Feasibility Studies evaluated the various remedy options and proposed a specific remedialaction alternative. The EPA and the ADPC&E determined that the proposed remediationalternative met the mandates of SARA. A press release and a fact sheet summarizing thealternative were distributed to the general local population and interested parties on April19,1988. A public meeting was held with the area residents and local officials on May 9,1988 at the South Sebastian County Courthouse. Representatives of the EPA, the State ofArkansas, the IWC Committee, Arkansas' U.S. Senators, the news media, andapproximately 26 other interested persons attended the meeting. Written comments andquestions were received during the comment period which ended June 2,1988. The EPAconcluded that overall, the residents and local officials did not oppose the proposedremedial action, and the EPA's Record of Decision(ROD) was signed on June 28, 1988. ASummary of Remedial Alternative Selection(6/88)(See RAS-Section 7.2) was prepared bythe EPA and included with the ROD.
A final Remedial Action Plan(see Section 7.1) describing the conceptual tasks to becompleted to meet the objectives of the ROD was prepared and was incorporated into thefinal executed Consent Decree. The Consent Decree was entered into the United StatesDistrict Court on July 21,1989.
Upon execution of the Consent Decree, the Remedial Action Design Plans andSpecifications were prepared and upon review and revisions were approved by the EPA onAugust 11,1989. The Design Specifications provide detailed procedures and specificationsin how the RAP was to be implemented subject to approved Change Orders. The RemedialDesign Phase developed the construction designs, specifications, drawings, schedules,procedures, and performance criteria to be used in implement the RAP. The Design Phasealso included bid documents, contract documents, payment measurements, cost estimate,QA/QC, and Health and Safety Plans. The documents were compiled in two volumesreferred to as "Contract Documents and Specifications"(Volume I) and"Attachments"(Volume II). Volume II included the Consent Decree, ROD withcomments, RAS and correspondence index, and the RAP.
The remediation contractor (Tricil Corporation) was selected in September of 1989. TheRemediation Construction Contract was executed on September 20,1989, and Notice toProceed was issued on October 10,1989. EPA assigned the Army Corps ofEngineers(CORP) to act as their onsite representative during remediation. The IWCCommittee retained IT Corporation as their remediation project engineer and coordinator.
Construction mobilization began on October 17,1989. Construction was completed withcompletion of demobilization and approved final inspection. The Certificate of Completionwas issued by the Engineer on March 29,1991. The Site Remediation Report wascompleted by the Project Engineer and Coordinator in March 1992. The EPA submitted itsClose Out Report June 10,1992 which determined that all appropriate response actions hadbeen implemented, and no further action was necessary.
The Post Closure Activity Planf January 1991)(PCAP) as approved by the EPA specifiedthe actions to be carried out during the Post Closure Period. The Post Closure Periodbegan on the date of the Certificate of Completion(3/29/91) and continues for 30years(3/29/21) unless modified with concurrence from the EPA and ADPC&E. This reportconstitutes the First Five Year Review report of the remediation and post closure activity asrequired by CERCLA.
The above referenced documents are incorporated into this report by reference and listedunder References at the end of the Report.
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5.0 INITIAL SITE CONDITIONS
The Site Conditions prior to remediation is described in detail in the EPA RI/FS and EA;the HWQS; Supplemental FS and EA; as well as the EPA RAS. The following descriptionis a summary of the Site Conditions on the basis of these documents. Figure 5.0 presents ageneral site layout prior to remediation.
5.1 THE SITE
The investigation reports identified five areas which required some level of physicalremediation. The areas were designated as Areas A, B, C, D and 09B. The remainder ofthe Site would be addressed by the containment control measures to be implemented for theSite as a whole.
At the time, the Site as a whole was defined by the north bank of the Area A Landfill, thewest end of the Landfill and Area B and D to the west which bordered the countyroad(Race Track Road); the end of the commercial Landfill operations to the east; and thetoe of the hillside exposing the natural weathered bedrock and the outer limits of the surfaceimpoundments to the south.
The Site lies above the strata referred to as weathered bedrock in the HWQS and RAP. Asdiscussed in Section 6.4.1 the weathered bedrock is the base of the McAlester Shale whichunderlies the entire site and the mined out coal bed to the north. It is a weathered sandyshale which lies above an unweathered shale and sandstone referred to as the HartshomeSandstone. The weathered zone is probably the transition zone between the McAlester andthe Hartshorne.
5.2 AREA A
Area A is that portion of the old surface mine which was operated as a commercialindustrial Landfill under IWC.
5.2.1 Surface Mine Operations
The natural soils over the coal("overburden") were excavated and cast to the side of thestrip mine as "spoils". The exposed coal seam was excavated("stripped") and transportedoffsite. The base of the mine was the barren strata directly below the coal which is referredto as the weathered bedrock which underlies the entire site. The average depth of the stripmine was 30 feet, and was 40 feet at its deepest depth. The width from the crest of thenorth bank to the south bank was approximately 100 feet
5.2.2 Landfill Operations
The IWC Landfill as addressed by the EPA NPL is approximately 1200 feet of the stripmine in which waste material was placed as a commercial facility which ultimately operatedunder the IWC permit It extends from the west end of the property to the east end wherethe industrial waste disposal operations ended. Open remnants of the old strip mine lie tome east Site across Race Track Road. The Landfill depth is equivalent that reported for thestrip mine. The Landfill operations extended portions of the south bank of the strip minean additional 125 feet The overall width at its widest point(north of Area C) wasapproximately 225 feet
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r r
UNDERGROUND COAL MINE & RESERVOIR
®
EXTENDEDBOUNDARY,
WATERUNE
OPEN STRIP MREMNANTS
ORIGINAL FENCIBOUNDARY
FORBES ENVIRONMENTAL
TAKEN FROM SUPPLEMENTALFEASIBILITY STUDY.
GENERALIZED PRIMARYSITE COMPONENTS
FIGURE 5.0006626
The waste material placed in the Landfill was predominantly:
Wood(60-75%).Soils(20-40%),Metals including drums( 1.5%),Paper(l%),Plastics(l%), andInsulation(<l%).
While some biodegradation was observed and isolated discontinuous pockets of water wereencountered, for the most part the material was dry, and well preserved. There was not acontinuous saturated zone of ground water with a uniform water table encountered in theLandfill. The relatively minor quantity of ground water seepage into the Landfill along thesouth bank from the onsite perched zones would flow to the bottom and dissipate, some ofwhich could conceivably enter the underground mine working but reportedly there was nota direct connection. The isolated pockets of water located at higher elevations in theLandfill were probably from infiltration which would collect on impermeable barrier or claysoils disposed in the Landfill.
Upon closure of the Landfill the strip mine spoils stockpiled on site were used to contourthe Site and provide cover over the Landfill.
5.3 AREAB
Area B was a surface area which apparently had been impacted by surface activities as aresult of the Landfill operations. An area of contaminated soils above Clean Up Criteriawas located during installation of the Site Slurry Wall during remediation construction. Theimpacted area which was either an extension of Area B or due to migration from Area D.This area was referred to a Area PA during remediation construction. It is considered aspart of Area B for the purposes of this report.
5.4 AREAC
Area C was a surface impoundment reportedly used as evaporation ponds for liquid wastesreceived at the site. The surface impoundment was placed above the weathered bedrockwhich was considered the confining layer for the ponds which minimized vertical migrationof the stored solutions. Upon closure the free liquid was removed and the impoundmentswere backfilled with clean soils and spoils. A subsurface drum disposal area whichincluded drums filled with liquid and solids as well as crushed drums was discoveredduring the HWQS along the south portion of the impoundments. The base of the surfaceimpoundment was estimated to be approximately 15-18 feet at its deepest point followingthe dip of the weathered bedrock which outcrops just to the south of the impoundment
During the site investigations, monitor wells were placed in a cluster at various depths justoutside and downgradient of the impoundments. Analytical results from water samplescollected from these wells did not report significant concentrations of volatile organiccompounds(VOCs).
5.5 AREA D
Area D was a subsurface drum depository area in the southwest comer of the Sitediscovered during the HWQS. It was estimated that approximately 200 drums containingliquids and solid wastes were placed in this area.
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5.6 AREA 09B
Area 09B was the area around an EPA investigation monitor welI(MW-09B). The monitorwell was completed in a shallow perched aquifer in the colluvium above the bedrock inwhich anomalous concentrations of contamination were reported in ground water. Sincethe positive results did not correlate with the relatively low concentrations reported in othermonitor wells completed in the same material, the area was slated for removal duringremediation.
6.0 GENERAL SITE PHYSICAL FEATURES
The following is a brief description of the important demographic and physical features asthey apply to the Site. The Site located in the southern portion of the Arkansas ValleyRegion as shown in Figure 6.0. The features are described in more detail in the referenceddocuments.
6.1 TOPOGRAPHY AND DRAINAGE
Figure 1.0(Site Location Map) shows the general vicinity topography. The Site area ischaracterized by a series of parallel ridges. The Site lies at the foot of Long Ridge whichruns parallel and north of the Backbone Mountain. The elevation of Long Ridge isapproximately 718 feet above mean sea level(msl). The terrain drops to approximately 465feet at Prairie Creek, which is about one half mile north of the Site. Prior to remediationthe Site elevation was 540 feet to the north at the base of Long Ridge to approximately 510feet along the north property line.
The Cap and Cover is the most significant feature which has altered the overall Siteelevation with an average elevation of approximately 530 feet The Cap surface slopes tothe north and northeast from the south west comer.
Runoff from Long Ridge is diverted around the Cap and Cover by the diversion ditch alongits southern and eastern perimeter. The diverted drainage returns to its normal pattern northof the Site. Now that vegetation is established on the Cap and Cover, and its surfacerunoff is primarily sheet flow off the northern bank. Rgure 7.0 shows the current surfacedrainage pattern.
Infiltration on the Cap and Cover surface is captured by the sand layer and discharges at thetoe of the northern bank and returns to its natural course without entering into the coveredremediated area.
6.2 DEMOGRAPHICS AND LAND USE
The nearest populations centers are the villages of Old Jenny Und approximately 1.5 milesto the east of the Site, and New Jenny Lind approximately 2.5 miles to the northeast Bothvillages are within the Rogers Township which has a total population of an estimated 900.The population estimate within one mile of the Site in 1980 was 375. Ft Smith lies about 8miles to the north.
The EPA RI determined that there are a total of 45 to 50 residences within a half mile of theSite with an estimated population of 167. Most of the residences lie to the east and north ofthe Site above Racetrack Road along Long Ridge. There are no residences to the west ofthe Site for over one mile. While some of the residences do have water wells, none arereported to be in use and the primary water source in the Sebastian County WaterAssociation. Figure 8.0 indicates the general locations of the residences in the nearvicinity of the Site. .
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006628
ARKANSAS VALLEYCOAL FIELD
FORBES ENVIRONMENTAL
^fe-y(SCALE IN M1£S)
TAKEN FROM US/EPA/RI
LOCATION OF THE ARKANSASVALLEY COAL FIELD AND SITE AREA
FIGURE 6.0006629
006630
006631
The water wells downgradient and North of the Site are completed in the upper McAlesterand possibly the old mine workings. No water wells were reported to be completed belowthe old mine workings north of the Site. The known water wells located within a half mileof the Site are indicated in Figure 8.0.
There is an old gas well approximately 0.5 miles to northeast of the Site(see Figure 8.0)which had been used as a salt water injection well. The well was plugged in the spring of1995. It was completed to a depth of approximately 7000 feet below reportedly in theHale and Hunter Formation below the Atoka.
The land directly north of the site is used for pasture between Racetrack Road and BonanzaRoad, as is the land to the northwest of the Site west of Racetrack Road. The north slopeof Long Ridge(south of the Site) is heavily forested.
6.3 SOURCES OF DRINKING WATER
In the immediate area of the Site, drinking water is supplied by the South Sebastian CountyRural Water Users Association. The EPA /RI conducted a residential well survey within ahalf mile radius north of the Site and reported that no residences within the area dependedon private water wells for drinking water.
6.4 GEOLOGY
The Site lies within the Arkansas Coal Field area of the Arkansas Valley Region(see Figure5.0). The area is structurally complex due to intense folding and faulting. The Site liesbetween two faults, the Backbone Fault to the south, which is a distinctive andpredominant feature for the area, and a less defined normal fault between Prairie Creek andBonanza Road approximately 0.5 miles to the north. The displacement of the normal faultto the north has been reported as 20 to 63 feet. The exact location of the Backbone fault isnot known but is reportedly a few hundred feet to the south of the Site. Apparently therehas been relatively minor tectonic activity between these faults in the general vicinity of theSite itself. However, faults were identified in the old mine working maps to the north ofthe Site.
There are three geologic formations of importance in relation to the Site ground waterhydrology. These formations in descending order from near surface(i.e. youngest tooldest) are: The McAlester Shale, the Hartshome Sandstone, and the Atoka Formation.The formations are overlain by a relatively thin layer of alluvium. In the immediate vicinityof the Site the alluvium was difficult to distinguish from the surface mine spoils and wasreferred to generically as colluvium. Figure 9.0 represents a conceptual geologic cross-section for the Site Area.
6.4.1 McAlester Shale
The McAlester Shale is a dark gray micaceous shale. During a recent excavation to repair adrain line on the northside of the Landfill, an excellent cross-section of the formation wasexposed and logged by an Arkansas registered geologist The shale was described as a darkgray to black massively bedded strata with silt to very fine sand size particles. No distinctsand laminations were observed in this shale which were distinctive in the sandy shaleunderlying the Site south of the Landfill and the mine workings to the north, as reported bythe same geologist. In the immediate area north of the Landfill, the upper portion of theMcAlester has been eroded away and is overlain by 9-12 feet of alluvium above whichspoils can be easily identified.
The McAlester Formation includes the Upper and Lower Hartshome coal seams. TheLower Hartshome Coal bed was the coal seam mined in the past, both underground and in
— 1 5 - .
006632
the strip mine. The base of the McAlester is placed at the top of the First sandstone belowthe Lower Hartshome Coal. At least 2 feet of shale underlie the coal and overlie thesandstone at the Site. It is this underlying weathered shale that is referred to as weatheredbedrock in the HWQS and remedial action documents and underlies the entire Site and theCoal mines. It is believed to be the transition zone between the McAlester and theHartshome Formations.
Some. but not all, of the investigation and remedial boring logs reported coal south of theLandfill. The boring log for MW-2 located in Area C reported a 5' coal seam at a depth of8.5 feet. The weathered shale bedrock outcrops near the toe of the Long Ridge hillside inthe vicinity of the southern perimeter of the Site. The remnants of Lower Hartshome coalbed may also have extended to the Long Ridge hillside, assumed to be uneconomical tomine.
To the north of the Landfill, the upper portion of the McAlester lies above the Coal seamand underlies the entire surface all the way to Fort Smith and beyond. It's thickness in theFort Smith area is reported as 500 to 1,800 feet. In the immediate vicinity of the Site justnorth of the Landfill it is approximately 60 feet thick. To the South of the Landfill, the 2- 5foot weathered shale may be the remaining remnants of the McAlester overlain by alluviumand/or colluvium and spoils.
6.4.2 Hartshome Sandstone
The weathered gray McAlester shale below the Lower Hartshome coal seam is apparentlythe transition zone between the McAlester and the Hartshome Formations. The weatheredshale becomes increasing more sandy with depth until it becomes a hard sandy shale asindicated by point of refusal for augers and rotary drag bits. Point of refusal was typicallyencountered in all investigation and remediation borings taken to this depth. This hardcontact was presumed to be the Hartshome Sandstone. Subsequent diamond coresampling retrieved from the "sandstone" on the north and south sides of the Cap andCover(see Section 11.4) showed unweathered alternating layers of sandstone and hardblack sandy shale confirming that the strata was indeed the Hartshome Sandstone.
The Hartshome Sandstone is typically placed below the first laterally continuous sandstonebeneath the Lower Hartshome coal seam separated by the intervening lower McAlestershale(weathered bedrock) or transition zone. On a regional basis the Hartshome is amassive, well cemented white to buff sandstone interbedded with shales. The thickness inthe Fort Smith region is reported to vary from 10 to 300 feet.
The Hartshome Sandstone lies below the weathered transition zone both to the north andsouth of the Landfill and together underlie the entire site and mine workings. In the vicinityof the Site it is reported to be approximately 50 feet thick until the Atoka is encountered.
6.4.3 The Atoka Formation
The Atoka Formation underlies the McAlester and Hartshome sequence. It ispredominantly a hard massive shale with a reported thickness of 6,500 feet in the FortSmith Area which becomes considerably thicker as it reaches the Site.
6.4.4 Strike and Dip
In general, the formations strike is east-west. South of the Site the formations dip to thenorth at 80°, decreasing to 25° below the Site, and flattening to less than 5 degrees northof the Site.
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006633
NOF
800'-i
700'-
600'-
500'-
400'-
300' -
200' -
100'-(
.
I
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i
^TH BACKBONE——SITE————FAULT——
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1 RACETRACK ROAD->
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—-—- / ——:———-'————————r\————— =•————•————-— - ^^^f 1 \ ', .-^ •"———"' \ LOWER HARSHORNE-s. ^•S' A \ '1
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5^——w-,——mESS—^i~ ro^0^ McALESTER HARTSBORNE TRANSITION-\ »' ',,;•~——————— '- -ww- !S^-y^ use0- - - (WEATHERED SANDY SHALE) A \
\ — — — — \ /' \— — — A ATOKA FORMATION FAULT -y
\\ \
•i — l l l l l l 1
3 400' 800' 1200' 1600' 2000' 2400' 2800' 3200' 3600' 4000'
I
?
200-11
100 •Na 1 NOTE:S GEOLOGIC CROSS SECTIONS BASEDH . ON ON-S1TE DRILLING DATA AND
0 '1 i | i i | | EXISTING GEOLOGIC LITERATURE.0 200 400
(SCALE IN FEET)(GENERALIZED)
SOL
r- LONG RIDGE
ATOKA FORMATION
^FAULT
\\
4400'
REVISED FROM USEPA
FORBES E
CONCEPTUCROSS SECTI
FIGl
JTH
r-800'
- 700' •
-600'
-500'
-400'
-300'
-200'
^-lOO'
•• '
\RI & HWQS
:NVIRONMENTAL
JRAL GEOLOGICON OF SITE AREAJRE 9.0
006634
6.4.5 The Coal Mine Workings
Coal mining activity in the Arkansas Valley Coal Field has been confined principally to theLower Hartshome Coal bed of the McAlester Shale. The Site is in what is known as theJenny Lind Mining District. Two mining operations are important with respect to the Site,the underground mine(Mine No. 17) and the surface mine which later became the IWCLandfill. There is a third mine operation (underground Mine No. 18) to the west of MineNo. 17 which is a totally separate mine not directly connected to Mine No. 17. Figure 10.0shows the mine workings in relation to me Site. Figure 11.0 is a reproduction of an oldmine map of a portion of Mine No. 17 north of the Site. The map does not show theworkings in their entirety, but illustrates how extensive the workings are.
The mine workings are underlain by the sameweathered and unweathered shale bedrockwhich underlies the site interpreted by the geologist to be the transition zone between theMcAlester and the Hartshome, and underlain by the Atoka. The underground mines areoverlain by the McAlester Shale and surface alluvium.
The underground mines operated from the late 1800' s through the eady 1940' s. Thenearest slope or passageway into the underground mine workings near the Site wasknown as Mama No. 3 which is reportedly exposed in the strip mine to the east of the Site.The extensive workings extend to the east of the Site by approximately one half mile and atleast a mile to the west, and over one mile to the north. The depth of the mine would beover 200 feet one mile from the Site.
The underground mine workings were mined by the mining method referred to as "roomand pillar". As the coal was excavated large mined out rooms or "voids" were created.The size of the rooms are estimated to be approximately 36 feet long and 8 to 12 feet wide.The room height ranged from approximately 2 feet(mined in prone position) to ten feet. Insome areas the slopes has enough height for mules to be used to pull the coal wagons.Columns of coal or pillars of varying dimensions were left in place to support the roof andminimize caving and subsidence.
The surface mine was operated as a strip mine from the mid 1940's through some time inthe early 1950's. The general strip mine operations are described in Section 5.2.1. Theunderground workings are within 30 feet of the north bank of the surface mine pit.Reportedly the surface mine and underground mine workings had been interconnected bysmall "shafts", possibly air shafts, which were subsequently plugged. It is not knownwith certainty whether or not there is direct communication between the Landfill and theunderground mine workings, but the remediation containment system including the SiteSlurry Wall and Cap and Cover were designed to minimize seepage into the Landfill andconsequently into the mine voids.
The underground mine workings are now flooded due to a collapsed pillar resulting incracks in the bottom of Prairie Creek. The cracks were physically sealed with clay, butmay serve as a pathway for recharge. In addition, recharge may occur directly throughopenings into the exposed strip mine east of the Site. According to the HWQS, rechargealong a fault plane is unlikely since the strata is primarily shale which are not verypermeable and would tend to be sealed by "weathered shale clay" as observed in faultsexposed in road cuts east of the Site.
The mine voids nearest the strip mine do not have water; however, within a short distancethe voids have several feet as observed in monitor wells. Further to the north the workingsace completely submerged.
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6.5. HYDROGBOLOGY
The Site hydrogeology is relatively complex due to the difficult of distinguishing betweenthe major geological components and the presence of underground mine workings. Thecomplexities were increased by low recovery rates and atypical responses in the upperzones which inhibited accurate determination of the relative hydraulic characteristics. Ingeneral, there are five separate ground water units in the general vicinity of the Site. Adistinct definitive system for each unit was not established. The five apparent systems are:
• Hartshome/Atoka Aquifer upgradient of Site• Ground water in weathered/unweathered shale underlying
Site. (McAlester/Hartshome transition zone.)• Limited onsite perched system in the colluvium between the
Landfill above the weathered shale subsequently addressedby remedy containment design.
• Perched system in McAlester north of the Site above mineworkings
• Artesian ground water system in Mine No. 17.
Each of these systems are briefly described below, and described in detail in the referenceddocuments- primarily the HWQS and the EPA RI and RAS. Figure 12.0 shows ageneralized cross section indicating the respective ground water elevations based on recentwater levels measurements from the existing Site monitor wells.
6.5.1 Hartshome/Atoka Aquifer
Due to the difficulty of differentiating between the Hartshome and Atoka Shales in thevicinity of the Site, the upgradient aquifer could not be definitively identified as one or theother, and/or may be an interconnected system. Consequently the aquifer was referred toas the Hartshome/Atoka. Whether or not the system is a confined or unconfined aquifer isnot well established. According to the HWQS the system is an artesian aquifer. Waterelevations reported in this system at approximately 518 feet msl were higher than thosereported in the other systems in the natural strata. The elevations in the onsite perchedzones in the colluvium and fill above the shales were slightly higher-approximately 519 feetmsl. The water level elevation in the weathered bedrock the Site was about 486 feet msl.
The recharge was determined to be from formation outcrops south of the Site whichflowed along bedding planes. Row was reported to be confined to the bedding planes.No interconnection with the other systems was established, but it has not been determinedwith clarity that this system and that in the upper shales of the Hartshome are not one in thesame.
Pump tests results conducted during the HWQS determined a hydraulic conductivity of 7.8to 9.2E-04 cm/sec(transmissivity of 293-330 gpd/ft) for this system. Verticalpermeabilities were reported to be <2E-08 cm/sec.
The system to the south of the Site is not hydii^uUcaUy upgradient of those located belowthe Site, but is apparently structurally uplifted w?hin the Backbone fault zone. Noinvestigation wells were placed in this system north of theSite which is overlain by theflooded mine workings. To place wells in this location would have been difficult
Monitor wells tested in this zone to the south(MW-102s and MW-102I) could only sustaincontinuous flow of 0.5 and 1.0 gpm, respectively. There are a couple of inactive privatewater wells further to the south believed to be completed in this horizon, but no water wellshave been identified north of (he Site below the mine workings. Reportedly, the well yield
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in both the Hartshome and the Atoka is dependent on secondary porosity and locating aproducing well is difficult since the strata itself is essentially impermeable. However, waterwells have been installed in both of these formation on a regional basis.
Since County provided water is available, it was considered unlikely that a water wellwould be placed in this horizon south of the Site, but if so, the Site would have no impactIt would be difficult to construct a water well in this system north of the Site due to thedifficulty of locating an adequate yield and the intervening mine workings. To place awater well north of the Site in the Atoka/Hartshome Aquifer would probably requirelocating a mine pillar(since it would be difficult to set surface casing to isolate the mineground water system) and drilling through to a depth of at least 150 feet, which wouldincrease substantially further to the north.
6.5.2 McAlester/Hartshome Ground Water System
Ground water occurs in the upper McAlester/Hartshome transition zone underlying the Siteand mine workings. This unit is the weathered bedrock between the McAlester coal bed,and the Hartshome unweathered shale/sandstone as discussed in Section 6.4.1. Accordingto the most recent measurements of the Area C Assessment piezometers(see Section11.3.4) which are completed in the weathered bedrock above the Hartshome north of AreaC, and stratigraphically downgradient of Atoka/Hartshome monitor well MW-102D, thewater elevation measured in the weathered shale is almost 6 feet higher than those measuredin the topographically upgradient Atoka/Hartshome monitor wells.
The recovery rate in a respective HWQS monitor well(MW-lOlD) was not sufficient toconduct a pump test and bailer tests were conducted to determine hydraulic conductivities.Slug tests were performed in the weathered shale above the Hartshome during the Area CAssessment in an upgradient piezometer(P-5). The recovery rate was very slow and thehydraulic conductivity was calculated to range from 2.3E-06 to 4.8E-06 cm/sec.
Recharge into the transition zone is from rain infiltration along the exposed bedding planessouth of the Site. According to the EPA and HWQS reports, the flow is confined to thebedding planes due to the reported low vertical permeability, and migrates along the planesdirectly below the Site and the mine workings.
Recent water elevations measured in the downgradient monitor wells(MW-12, MW-13)completed in the McAlester/Hartshome strata directly below the mine workings north of theLandfill are higher than the elevations measured in the monitor wells completed in the minevoids(MW-10, MW-11) by about six feet, indicating that the two horizons are two separatesystems and not interconnected. The water elevation measured in MW-14 is equivalent tothat measured in the mine voids indicating an interconnection, probably due to the sandfilter pack being completed above the mine void bottom. However, water was notencountered in mine void exploration borings, so the well is apparently located near thewater line. Slug tests have not been performed on these wells, but based on recovery rates,the hydraulic conductivity is relatively low in all three wells. The recovery rate in MW-12is faster than that in the MW-13 and MW-14, indicating that it may have been completed inarea of secondary porosity, such as a fracture. Initial MW-15 water levels indicate that itcorresponds to the mine void water elevation. MW-15 exploration borings encountered thetotally saturated and flooded mine voids.
As the VOCs detected in MW-12 migrated down dip, the concentrations would decreasethrough natural attenuation, and if they should migrate offsite the impacted ground waterwould migrate down dip along the bedding planes below the mine voids. Based on theinformation available this strata does not appear to be interconnected with either the minevoids or the Atoka/Hartshome Aquifer.
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No water wells are known to be completed in this strata or the underlying Hartshome orAtoka below the mine workings. Due to the excellent yield obtained in the mine voids, andthe difficulty of constructing a conventional water well through the mine voids, as well asthe difficulty of locating adequate yield, it is unlikely that a water well would be installed inthe weathered bedrock directly below the mine workings, or the deeper Atoka/Hartshomeaquifer.
6.5.3 Mine No. 17 Ground Water System
As discussed in Section 6.4.5 the underground mine workings were flooded due to acollapsed pillar in the vicinity of Prairie Creek and sealed with clay. Whether there wassignificant water in the mines prior to this event is not known, but the sealed cracks arereported to be a source of recharge to the water in the mines. In addition, the adjacent mineMine No. 18 is flooded with a hydrostatic head 30 feet higher than the water table reportedin Mine No. 17. While a direct connection between the mines was not reported, there isthe possibility that a hydrogeological interconnection exists creating at least partial rechargeinto Mine No. 17. The HWQS reports openings(e.g. slope Mama No. 3) in the strip mineeast of the Site as another possibility for recharge as a result of direct surface runoffentering the openings east of the Site.
Based on the difference in the water elevations in the downgradient monitor wellscompleted in the weathered bedrock as compared to those in the mine voids, the water inthe mine workings is apparently not directly interconnected as a result of the reportedvertical permeability of <2E-08 cm/sec in the shales; however, there is the possibly ofsecondary interconnections due to the corresponding water levels reported in MW-14 andMW-15.
There are several water wells completed at depth which may be completed in either the minevoids or the McAlester Aquifer system directly above them.
Prior to Site remediation there was a possibility of limited seepage from the onsite perchedsystem into underground workings along the base of the Landfill. The remedial designspecifically addressed the onsite perched zones to mitigate this potential source of seepage.
6.5.4 McAlester AquiferPerched ground water was identified in me upper elevations of the McAlester shale north ofthe Site above the mine workings. There are several isolated perched zones, including alower zone just above the mine voids. It was not clearly established whether this lowerzone is interconnected with the Mine No. 17 system.
Recharge for the perched zones was reported to be infiltration due to rain. Two wells wereknown to be completed in the zone. It was considered unlikely that the system washydraulically interconnected with the onsite perched system, primarily due to the Landfillwhich acts as an interceptor trench. While small pockets of water were encountered in theLandfill, for the most part it was dry and not considered saturated. Water seepage from theonsite perched zones in the south bank of the Landfill would tend to flow down the bank tothe bottom of the Landfill. Therefore, onsite ground water was effectively cut off from theupper McAlester north of the Site. The onsite ground water, as discussed in the nextsection, was ultimately addressed by the remedial design.
6.5.5 Onsite Perched SystemLimited discontinuous onsite perched ground water systems were identified by the EPAand HWQS in the fill and spoils south of the Landfill above the weathered bedrock. Thesesystems were addressed by the remediation plan(French Drain, Site Slurry Wall and Capand Cover) and currently do not exist in the same state. The following summarizes theonsite perched system as described in the EPA RAS and the HWQS prior to remediation.
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Generally the eastern portion of the Site was saturated with ground water, and the westernportion contained limited perched ground water. The recharge for the system was mainlyinfiltration and some seepage from the south hillside. The perched zones were confined tothe colluvium by the underlying shale due its low vertical permeability of <2E-08cm/sec.As a result surface springs were reported. The HWQS reported that there was apparentlyno direct connection between the shallow perched zones in the colluvium and theunderlying aquifers.
During the EPA/RI and HWQS, monitor wells MW-09B and MW-101S had the highestconcentrations of organic constituents. Both of these wells were completed in the onsiteperched zones. The EA concluded that only the water in MW-09B presented a potentialrisk. The HWQS indicated that off-site ground water contamination had not occurred, norhad it occurred to any significant depth vertically.
The EPA reported that the yield of the perched zones was too low to be considered a usablesource. The main concern was that potentially impacted ground water from the zoneswould flow into the Mine No. 17 system which was considered a usable source.
This limited onsite perched system was the focus of the remedial design. The remedialaction included reduction of the perched ground water mobility(French Drain and SlurryWall), and minimization of recharge to the system by the Cap and Cover.
7.0 ENDANGERMENT ASSESSMENT
An Endangerment Assessment(EA) was conducted to develop the remedial actionobjectives and criteria to alleviate potential threat to public health and the environment Thefollowing procedure was used to identify and evaluate the objectives and criteria:
• The possible remedial objectives were identified for each potentialmigration pathway;
• Remedial objectives were evaluated and selected:• Target compounds for each pathway were selected based on
concentration, prevalence, persistence, mobility and toxidty;• Possible criteria for each objective were identified; and• Remedial criteria were developed for the selected remedial
objectives.
The EA determined that migration and exposure pathways of concern were:
• Ground Water0 On-site0 Off-site
• Surface Soils (0-2 feet)
• Subsurface Soils (>2 feet)
• Wastes0 AreaA0 AreaB0 AreaC^ AreaD
• Surface Water<> Prairie Creek0 Henson'sPond
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Air was ultimately determined not to be a potential pathway of concern.
The remedial objectives for the ground water pathway related to migration control actions,while those for the other exposure pathways relate to source control actions. The EAconclusions based on the data evaluated are summarized as follows:
• There were no "unacceptable" risks under the exposure pathways.
• There was no evidence that significant concentration of wastecontaminants had migrated offsite via soil, surface water or groundwater.
• The majority of PolynuclearAromatics, many of the metals, andsome of the volatiles present onsite are also naturally occurring incoal and coal combustion products. These compounds did notappear to be related to the IWC site industrial activities.
• The majority of the identified IWC contaminants in wastes and insoils were non-carcinogens.
• Concentrations of Site indicator chemicals in surface soil did notpresent a significant public health risk under the residential exposurescenario postulated.
• Contamination in me subsurface soils did not appear to havemigrated and did not present an unacceptable risk to groundwater at the time. A future risk could occur if: a leachingmechanism existed; significant toxioological concentrations ofcontaminants were to leach; a transport vehicle was present; and theaffected water was consumed for a lifetime.
• Offsite residential well samples indicated that the Site had not addedan unacceptable health risk. This finding was based on theconservative scenario which assumed that the water was relied uponfor sole source domestic use.
• It was very unlikely that onsite ground water would be useddomestically in the future. However, if it were, insignificantincremental risks to human health was predicted with the exceptionof one isolated monitoring well(MW-09B).
8.0 REMEDIAL ACTION DESIGN
The Remedial Action Plan was prepared to present the basic conceptual tasks to beperformed, general procedures to be implemented, and tentative schedules to be followedduring the site remediation phase to complete the objectives presented in the ROD. Theconceptual plan presented in the RAP was to be developed into detailed designs, andspecifications during the Remediation Design Phase.
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8.1 RAP OBJECTIVES
The primary ROD and RAP objectives were:
1. Excavation of buried drums in the southwest comer(AreaD) of the site, anddisposal or reuse of any liquids encountered in an offsite RCRA compliantfacility.
2. Excavate the contaminated soils above action levels from surfaceimpoundments(Area C), Area D, and the area 09B (MW- 09B). Theexcavated soils which exceeded treatment requirements were to be stabilizedto pass the RCRA Toxicity Characteristic Leaching Procedure(TCLP) andASTM strength tests and replaced in the Area C excavation. A slurry wallwas to be placed around Area C to provide long-term security.
3. A French Drain system was to be installed around the south, west and eastsides of the site to intercept and divert shallow ground water around the site.A Slurry Wall was to be installed parallel and downgradient to the FrenchDrain to prevent on-site ground water from migrating into the French Drain.
4. Ground water encountered during remediation excavation was to becollected and treated to meet effluent limitations established by the ERA andthe ADPC&E or mixed with the stabilized soils to meet TCLP limits.
5. Solid and liquid waste generated during the EPA RI and HWQS were to becharacterized and disposed of appropriately.
6. A multi-layered RCRA cap was to be constructed to cover the entire site areaas defined by the French Drain, and northern boundary of the Landfill(AreaA).
7. A surface drainage ditch was to be constructed on the upgradient side of theCap and Cover, to divert site run-on around the Cap and Cover.
8. Land use restrictions and a security fence were to be put in place to preventdevelopment of the site.
9. Ground water on site and adjacent to the site were to be monitored.The effectiveness of the remedy was to be verified every five years.
As part of the RAP a Contingency Plan was to be prepared to set forth procedures to beimplemented in the event of an emergency or release of hazardous materials to theenvironment. The RAP also addressed the solid and waste management, Health andSafety and QA/QC Plans.
The Remedial Action Plan outlined the general conceptual procedures to be followed duringActual Site Remediation, which included the following:
Mobilization/Site PreparationSite Slurry Wall InstallationArea 09B investigationArea D drum removalFrench Drain InstallationSoil Treatment and managementWaste managementArea C Slurry Wall installation
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RCRA Cap and Cover InstallationLong Term Monitoring Well InstallationDemobilization/Site ClosureReporting RequirementsQuality Assurance/Quality Control PlanContingency & Health and Safety PlanPost Closure Activity Plan
8.2 ARARs
The Superfund Reauthorization Act (SARA) required that remedy selection attain all legallyapplicable or relevant and appropriate requirements(ARARs). However, a SARAprovision did allow a remedy that was protective, cost effective, and adequately satisfiedstatutory preferences, if it was viewed as the all around best remedial alternative and otheralternatives were not acceptable due to: fund balancing; technical impracticability; interimremedy; greater risk to health and the environment, attained equivalent standard ofperformance, and inconsistent application of state standards. ARARs utilized to considerremedy alternatives were:
• Containment Specific ARARs0 Safe Drinking Water Act (SDWA)0 Arkansas Regulations
>• Arkansas Hazardous Waste Management Code>• Arkansas Air Pollution Control Code>• Regulation No. 2(pertaining to surface water quality)
0 Occupational Safety and Health Act (OSHA)
• Site Specific ARARs0 Clean Air Act (CAA)0 Clean Water Act (CWA)
• Technology Specific ARARs0 Resource Conservation and Recovery Act (RCRA)
• General ARARs0 CERCLA/SARA0 NCP
8.3 EPA REMEDY ALTERNATIVESELBCTION
The RAP was designed to comply with the National Oil and Hazardous SubstancePollution Contingency Plan(NCP), the Comprehensive Environmental Response,Compensation and Liability Act( CERCLA or "Superfund"); the Superfund Amendmentsand Reauthorization Act(SARA), and the EPA guidance documents. SARA mandated thatthe remediation option selected by the Agencies must consider the following criteria:
Overall protection of public health and the environmentCompliance with ARARs;Long term effectiveness or performance;Reduction of toxicity, mobility, or volume of contaminants;Short term effectiveness;Implementatrility;Cost;State acceptance; andCommunity acceptance.
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The EPA included as part of the ROD a Remedial Alternative Selection Report(RAS) whichoutlined the various alternatives considered and the basis for selecting the alternative whichbecame the RAP and was incorporated into the Consent Decree. The RAS listed the fourmain areas where wastes were disposed as Area A(Landfill); Area B(surface area south ofstrip pit). Area C(surface impoundments), and Area D(drum disposal).
The remedy alternative selected by the EPA out of six alternatives considered including noaction was: Alternative No. 3-Additional Containment with groundwater controls and"hot" spot treatment(Stabilization).
The selected alternative consisted of continued monitoring, surface water diversion, sitesecurity fencing, multilayer cap, french drain, excavation and onsite stabilization of AreasC and D soils, offsite disposal or reuse of Area D liquid filled drums, slurry wallconstructed around the stabilized waste area, and land use restrictions. Monitor wellswould be located inside and just downgradient of the slurry wall system to monitor theeffectiveness of containment and to provide early warning of contaminant migration.The alternative was selected by the EPA on the basis of the nine evaluation criteriamandated by SARA , i.e.:
• Could be designed to meet ARARs.• Toxicity reduced for materials in Area C and D; mobility of wastes
reduced by installation of containment system; reduction inwaste volume.
• Short term risks associated with construction were moderate relativeto other alternatives.
• Long term effectiveness monitored and maintained, even thoughtoxicity, mobility, and volume of wastes is reduced.
• Although a complex alternative, relatively easy to construct andimplement.
- • Cost moderately low.• No opposition was expressed by the public and therefore
considered acceptable to community.• State was favorable to proposed remedy.• Provides protection by reducing risks due to treatment and
containment
9.0 REMEDIAL ACTION DESIGN AND SPECIFICATIONS
The Design Specifications provided detailed procedures and specifications in how the RAPwas to be implemented subject to approved Change Orders. The Specifications includedContractor contract documents which outlined the Contractor's and Engineer* sresponsibilities.
Detailed specifications were divided into two sections. Division 1 provided scope of workto be conducted, the sequence in which to be completed and general requirements such asmeasurement and payments, survey requirements, meeting and reporting requirementsetc.. Division 2 provided specifications for the tasks to be completed. The DetailedSpecification included the following Sections(note: missing numbers were not part ofspecifications):
2110 Mobilization/Site Preparation2130 Sampling and Plugging Existing Wells2132 New Ground Water Monitoring Wells and Piezometers2232 Temporary Staging Facilities2224 Slurry Wall
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2225 Waste Handling2226 Area C Soil Solidification/Fixation2227 French Drain2229 Area DDrum Removal2230 Cap and Cover2231 Geomembrane2232 Geogrid2235 Landscape Grading2236 Seeding2260 Off-Site Transportation and Disposal2721 Surface Diversion Ditch2722 Slope Protection and Erosion Control2731 Fence and Gates2800 Demobilization
9.1 CHANGE ORDERS TO SPECIFICATIONS
Eighteen Change Orders were executed to modify the Specification during the remediationconstruction. Eight of the change orders were in regard to procedural changes, such aschanging analytical methods. Those Change Orders which related to changes in Scope ofWorkwere:
No. 3 Increase borings for upgradient investigation task.
No. 5 Change depth of slurry wall from 3* key into weatheredbedrock to include "point of refusal" for Caterpillar 225trackhoe.
No. 6 Excavation of Area PA.
No. 7 Install surface casing for MW-10 to prevent interconnectionbetween upper perched aquifer and mine voids during wellinstallation into the mine voids.
No. 10 Excavation of Landfill to accommodate west slurry wallsection.
No. 13 Adjust french drain profile to reflect alignment boring datathat redefined bedrock depth.
No. 14 Excavate to reclassify soils stored in the soil staging facilityto determine by analysis if solidification/fixation necessary.
No. 15 Payment for exhumation of additional buried drumsdiscovered during installation of the French Drain at Station7+75.
No. 16 Extend the Cap and Cover along the north side of Landfill tocover debris discovered during utility line installation.
No. 17 Provide heavy clay liner in the bottom of Area C excavationprior to replacement of treated soils and backfill.
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10.0 SITE REMEDIATION PHASE
The remedial action as implemented for the IWC Site was based on the Record of Decision,the Consent Decree with the Remedial Action Plan, Design Plans and Specifications, andRemedial Construction Contract and associated approved Change Orders. Thesedocuments collectively comprise the planning and implementation of the Site remedy. TheSite Remediation Report and EPA Close Out Report comprise the remediation completionreports. Remediation construction was started on October 17,1989 and was completed onMarch 29.1991.
The following is a general description of the significant tasks performed to meet theobjectives of the RAP in regard to final remediation as completed(not necessarily in order).It is based on the Site Remediation Report which includes as-built drawings, and the EPASuperfimd Close Out Report. This section focuses on final completion and does notaddress the interim facilities and operational plans such as mobilization/site preparation,temporary soil staging area, emergency response, health and safety, etc. all of which wererequired and implemented accordingly. All construction activities were supervised by theUS Corps of Army Engineers(CORP) site representative for the USEPA. Change Orderswere submitted by the Contractor to the IWC Committee Project Engineer andCoordinatoifIT Corporation) and the CORP and implemented upon approval from bothparties.
10.1 MOBILIZATIONMobilization was initiated upon Notice to Proceed( 10/16/89) and was completed on 11/24/89. Mobilization included site survey, installation of security fences, procurement ofutilities, and construction of support facilities.
During this period, investigation of the Upgradient Investigation Area in the southeastportion of the Site was conducted. This area had not been previously assessed and includedthe pathway for the French Drain and Site Slurry Wall. No contamination was discovered.
10.2 WASTE MANAGEMENTIn general, waste management included the treatment of the soils which exceeded CleanupCriteria, offsite disposal of drums of liquids, and waste water discharge. The primarypurpose was to reduce toxicity, volume and mobility of contaminants by treatment, ordeportation.
Landfill waste debris and drums of solid materials which were not susceptible to leachingwere replaced inside the excavations from which they had been removed. The potential forleaching and mobility was further reduced by the French Drain, Site Slurry Wall and Capand Cover which were intended to minimize ground water flow through the remediatedareas.
10.2.1 SoilsAll areas in which soils were removed as identified in the RAP or Change Orders were tobe excavated to the point at which the soils met the established Cleanup Criteria. Theexcavated soils which exceeded Cleanup Criteria were to be treated by fixation andsolidification to reduce the toxidty and mobility of the contaminants. The actual treatmentprocedures were to be developed during a pilot test during the Site Remediation Phase.
The Soils Clean Up Criteria were:
Total Volatile Organics < 1,000 ppmLead < 1,000 ppmNickel < 1,000 ppmCadmium < 1,000 ppm
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Areas which required excavation were:
• Site Slurry wall trench(including west end of landfill)AreaB/PAAreaCArea09BAreaD
In general, soils which were visibly contaminated or exhibited an organic vapor readingusing a Photoionization DetectoifPID) of greater than 10 ppm were excavated. Theexcavated soils were placed in 50 cubic yard stockpiles in the soil staging area. Excavationwas discontinued once the PID measurements were less than 10 ppm. Confirmationsamples were collected from the bottom and side walls of the excavation on a 50 foot gridand 50 foot spacing respectively. The confirmation samples were collected and analyzed inaccordance with EPA Test Methods for Evaluating Solid Waste per SW 846. If the resultsexceeded Cleanup Criteria the excavation was continued until confirmation samplesreported otherwise.
A representative composite sample was collected from each 50 cubic yard stockpile, andanalyzed for the Cleanup Criteria. Those stockpiles for which the sample results exceededCleanup Criteria were transported to the Soil Staging facility for treatment Those whichpassed did not require treatment and were reused on site as backfill material.
jjoil Treatment
All soils which did not pass Cleanup Criteria were treated to meet or exceed treatmentperformance criteria which were Toxitity Concentration Leachate Rrocedure(TCLP) limitsfor VOC and metals per EPA Hazardous Substance List, and a minimum unconfinedcompressive strength of 50 psi.
The treatment procedures were developed by the Contractor during a pilot treatability studywhich were approved by the Agencies and the Engineer. The soils were placed ontreatment pads and mixed with fly ash and water and allowed to cure for 7 days afterwhichthe treated soils were sampled and analyzed for treatment performance standards for each500 cubic yards. Seven treatment pads were used to treat 1,823 cubic yards ofcontaminated soils.
Upon passing the performance criteria, the treated soils were placed into Area C andsolidified as described in Section 10.8.
10.2.2 Trash and Debris Management
Buried trash and debris encountered in the various excavations were separated from thesoils as best able and returned to the excavation. The trash and debris removed from theLandfill for Slurry Wall and French Drain construction or encountered outside the siteboundaries was placed on top of the Landfill in a thin layer and capped with backfillmaterial and ultimately with the Cap and Cover.
Drums encountered with solid waste were visually inspected for free liquid and the materialhardness was determined with a field penetrometer. Solid drum waste with a reading of2.5 tsf or greater was considered a solid waste and was placed back into the excavation.Empty drums were crushed and reburied in the excavation as well and covered with backfillcompacted in 12 inch lifts.
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Areas from which trash and debris were removed and in which reburied onsite were:
French drain gravel bridgePortions of Site Slurry WallArea09BAreaC(dmms)AreaD(drums)
10.2.3 Offsite Disposal of Liquid Wastes
A total of 250 drums of liquid waste were exhumed from the Area D and Area Cexcavations which contained primarily water contaminated with solvents and paint thinners.Depending upon the condition of the drums they were either overpacked or the contentswere removed and placed in new drums for storage and classification. The contents weretested for compatibility, priority pollutants, and incineration parameters. Those drumswhich were reactive were neutralized and solidified on site. The compatible liquid wastewas vacuumed into a tanker truck and shipped to Thermal Oxidation Corporation uponapproval from the EPA. Four thousand and seven hundred(4,700) gallons were shippedoffsite accompanied by the appropriate hazardous waste manifest
10.2.4 RI and Remediation Derived Wastes
Wastes generated during the remediation and investigation phases (drill cuttings, deconsludge) were stored in drums onsite. During remediation the contents were emptied andmixed with soils to be treated.
Drums with highly contaminated liquids as determined visually were placed and managedwith the drums of liquids removed from the excavations. Drums with water wereemptied in the contaminated water storage tank for waste water treatment.
10.2.5 Water Management
Water from decontamination and storm water collected in the remediation zone duringconstruction was stored in 20,000 gallon portable tank trailers(frac tanks) identified as"contaminated storage" over the length of the project Uncontaminated water was stored infrac tanks identified as "clean" storage.
A composite representative sample was collected from the top, middle and bottom of eachtank. The samples were analyzed for the Hazardous Substance list for volatile organics,extractable organics and heavy metals.
The water in the frac tanks in which no contaminants were detected by chemical analysiswere sparged with air and samples were collected for bioassay per ADPC&E NDPESrequirements. Those which passed the bioassays and NDPES limits were dischargedoffsite as approved by ADPC&E. Water from tanks which failed bioassays were re-sparged until they passed.
Water in frac tanks in which contaminants were detected by chemical analysis were spargedwith air and used in the soil treatment process or used during compaction of backfill priorto multi-layer cap installation. Upon completion of alt construction activity one tankremained which did not pass bioassays. With permission from the ADPC&E andconcurrence from the ERA this water was land applied to the surface of the Cap.
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10.3 FRENCH DRAIN
The purpose of the French Drain was to intercept upgradient, shallow ground water anddivert it around the Site, ultimately to be discharged into the old underground mineworkings(mine voids) through recharge wells located at each end. By preventing orreducing ground water flow through the Site, the primary transport mechanism for Sitecontamination would be minimized and contaminant mobility reduced. The French DrainPlan view is shown in Figure 13.0 which includes the Site Slurry Wall, and shows theflow path of the intercepted subsurface ground water.
An exploratory boring program was conducted prior to installation of the French Drain andduring the Slurry Wall installation(See Section 10.4) to ensure that the French Drain wasplaced in clean soils as determined by screening procedure discussed above.
The French Drain was installed around the outside perimeter parallel to me Site slurry wallto the south banks of the Landfill. An 18" trench was keyed into the weathered bedrock atsufficient depth to intercept the ground water flow in the strata above it The grade wasestablished with a laser control system to ensure gravitational flow to the two rechargewells. A 4" HDPE perforated drain pipe with a filter sock was placed in the bottom of thedrain and the trench was backfilled with highly permeable coarse sand to within T of thesurface and capped with site soils.
The flow from the French Drain perforated pipe was carried from the end point manwaysby a solid 4" flexible drain pipe to the discharge points. Since the solid drain pipe crossedthe Landfill at the east end, the Landfill trash and debris was removed and replaced withcoarse gravel "bridge" to provide support to the pipe and prevent subsidence due to wastebiodegradation. The removed trash and debris was spread in a thin layer over the Landfillcovered surface and covered with clay backfill, and ultimately capped with the Cap andCover.
Forty eight inch manways were installed at the end points of the French drain in which thetransition from perforated pipe to solid pipe took place. Additional 48" manways wereinstalled along the path of the french drain at major turning points. These manways werealso to be used as cleanout ports- if necessary.
The recharge wells were placed in a 48" precast manhole installed at the east and west endsof the site(see Figure 19.3-the well completion diagram). A 4" diameter PVC well casingwas placed in the bottom of the manhole into the mine voids. The PVC well screen wasplaced in the mine voids and a grout seal was placed above the screen in the natural soils.
10.4 SITE SLURRY WALL INSTALLATION
As mentioned above, exploratory borings were drilled to determine if any contaminationwas present along and outside the proposed Site Slurry Wall and French Drain pathways.
Three areas were discovered along the slurry wall which exceeded PID screeningreadings(lOppm). The soils were removed until acceptable levels were measured andCleanup Criteria results obtained in excavation side walls and bottom. In this way all soilsencountered which exceeded the PID reading were placed within the boundary .of the SiteSlurry Wall, and minimal impacted soils-if any- would remain outside the Slurry wall.
The Site Slurry Wall was installed along the south, east, and west perimeters of the Site. Itsprimary function was to minimize the possibility that onsite perched ground water wouldbackflow into the French Drain, and secondarily to prevent upgradient ground water from
-34-
006651
LEGENDSLURRY WALLFRENCH DRAINTOE OF CAP AND COVERFRENCH DRAIN MANWAYDIRECTION OF GROUND WATER FLOW
NOTES: . . . .
LANDFILL BOUNDARY APPROXIMATE.NO KNOWN DRUMS (with liquid) LEFTON SITE.
FORBES ENVIRONMENTAL
GROUND WATER FLOWAS INTERCEPTED BY FRENCH DRAIN
FIGURE 15.0
006652
entering the Site during remediation prior to installation of the French Drain. In addition,the Site Slurry Wall was to augment the French Drain and minimize flow into the Site.
The bentonite slurry containment wall keyed into the north bank of the Landfill by at least 3feet on both ends. Initially the Site slurry wall was to key into the underlying weatheredbedrock to a minimum depth of 3 feet However, the weathered bedrock essentiallyoutcropped along portions of the southern section of its pathway. Therefore, the depth inthose locations was changed per Change Order # 5 to the Point of Refusal for theCaterpillar 225 trackhoe.
A portion of the west end of the Landfill extended to the outside of the Site Slurry WallPath. The area was excavated in accordance with Change Order 10. The removed debriswas placed with the debris removed for the French Drain bridge on the east end.Approximately 2,322 cubic yards of debris were removed. The side walls and bottomswere sampled and the results were less than the clean up criteria. The excavation wasbackfllled and compacted to Site grade. The slurry wall was completed through a portionof the backfllled excavation.
The Site Slurry Wall plan view is shown in Figure 13.0. For the most part the remediatedarea is enclosed by the Site Slurry Wall and the north bank of the Landfill.
10.5 AREA09B
The purpose of Area 09B remediation was to remove the anomalous contaminationdiscovered during the HWQS in the vicinity of MW-09B. The monitor well itself wasremoved, and soils in an 8' by 14' area to an approximate depth of 12 feet were excavated.A portion of the excavation intersected the southern edge of the Landfill and excavation inthis direction was discontinued. The soil samples from the side walls and the bottom of theexcavation were collected and analyzed for cleanup indicator parameters. The analyticalresults were less than Cleanup Criteria, and the excavation was backfllled with compactedsand in the lower portion and general fill in the upper portion. The Landfill debris whichhad been removed was placed back in the excavation between the sand and fill layers.
10.6 AREAD
The purpose of the Area D remediation was to remove the drums of liquid and solid wastediscovered in the southwest comer of the site during the HWQS, and the impacted soilswhich exceeded cleanup criteria.
Drums of liquid and solid material and impacted soils were excavated. 108 drums ofliquids were removed and disposed as described in Section 10.2.3.
Soils were excavated until Cleanup Criteria were attained. Approximately 1155. cubic yardsof impacted soils were removed. Upon confirmation that Cleanup Criteria was attained thedrums of solid waste and empty crushed drums were reburied in the excavation andbackfllled with onsite soils which met Cleanup Criteria and clean soils imported fromoffsite. The backfill was placed in 12 inch lifts and compacted to at least 90 percent of themaximum density as determined by ASTM D698 and the moisture content was maintainedwithin 5% of the optimum moisture content
10.7 AREABANDPA
The purpose of Area B remediation was to assess the area to determine whether the soilsexceeded Cleanup Criteria. As per the RAP, it was anticipated that no soils would have tobe removed and mobility of remaining constituents would be minimized by preventingground water flow with the installation of the Site Slurry Wall and French Drain system.
- -36-
006653
However, an area in the southwest comer of Area B was discovered in which the soilsdemonstrated PID readings above the screening criteria. The area was referred to as AreaPA and extended outside the Site Slurry Wall and the Site perimeter fence. Change OrderNo. 6 was prepared to address this area. The soils were excavated until Cleanup Criteriawere met in the excavation side wall and bottom samples. Approximately 2,148 cubic yardsof impacted soils were removed. No drums were encountered.
10.8 AREAC
Area C involved the removal of the surface impoundments. Its purpose was to remove apotential source for site contamination. By treating the impacted soils to meet the treatmentperformance standard(TCLP limits), the toxicity and volume of impacted soils werereduced, and mobility impeded.
According to the design specifications the soils above the weathered bedrock were to beremoved and stockpiled in 50 cubic yard piles for sampling. However, the excavation wastaken to a depth of approximately 3-5 feet into the weathered bedrock. Approximately12,500 cubic yards were excavated to an maximum depth of 21 feet
During the excavation of the upper elevations of Area C drums of liquids and solids wereencountered in two separate areas along the southern perimeter that extended south to theSite Slurry Wall. The additional excavation was addressed by Change Order 15. A total of142 drums filled with liquid were removed and placed in the drum staging area to bemanaged with the drums from Area D as described in Section 10.2.3.
Confirmation samples from the side walls and bottom of the Area C excavation and theupper extension verified that the Clean Up Criteria was met A 1 foot compacted heavyclay liner was placed over the bottom of both areas prior to replacement of treated soils.The liner was placed in the main excavation as a result of the excavation into the bedrock.The clay liner was addressed in Change Order 17.
Based on the stockpile composite sample results which exceeded Cleanup Criteria, 1,823cubic yard of soils were treated to meet treatment performance standards. The treated soilswere placed into the Area C excavation in 12 inch lifts. Each lift was solidified by mixingin eight percent Portland(Type 1) cement and water and then compacted to attain therequired compressive strength. Eight lifts of treated soils were solidified in this manner.
After all the treated soils were replaced in the excavation, the remainder of the openexcavation was backfllled to the subgrade elevation of the Cap and Cover. The backfillconsisted of general excavated soils which passed Cleanup Criteria and did not requiretreatment The backfill was placed in eight 12 inch lifts and compacted to meet densityspecifications (s90%). The removed drums of solid material and crushed empty drums anddebris from Area C were reburied in the south extension and covered with clean compactedsoil to surface grade.
10.9 AREAC SLURRY WALL
The purpose of the Area C slurry wall was to provide additional containment for the treatedsoils stored within the Cell and reduce long term uncertainties. The Area C slurry wallenclosed Area C and tied into the site slurry wall bordering the southern perimeter of thearea, and keyed into the underlying weathered bedrock. In general, the same proceduresand specifications of the site slurry wall applied to the Area C slurry wall. Figure 14.0 is across section of the Area C as completed.
-37-
006654
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•OLMUMeo*HKf-l
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HQIE; WATER ELEVATION TAKEN ON 11-1-93
FORBES ENVIRONMENTAL
CROSS SECTION A-A*THRU AREA "C''
TAKEN FROM AREA "C" ASSESSMENT FIGURE 14.0006655
10.10 MULTI LAYER RCRA CAP AND COVER
The purpose of the Cap and Cover was to prevent infiltration of direct surface rain into theremediated area. In conjunction with the Site Slurry Wall and French Drain, the Cap andCover further minimized the possibility of ground water in the remediated area therebyreducing the mobility of potential contaminants. Figure 7.0(see Section 6.1) shows the planview of the Cap and Cover with the runon diversion ditch. The Cap and Cover crosssection are included in the Site Remediation Report and generally shown in the Area Ccross-section(Figure 14.0).
Upon completion of the primary Site Remediation activities discussed above, the entireSite surface was backfilled and regraded using compacted general site fill to meet thesubgrade requirements of the Cap and Cover.
Once graded and compacted, the subgrade was capped with 24 inches of heavy clay caphaving a Plasticity Index exceeding 20. The heavy clay was imported from offsite havingmet permeability specification requirements. The clay was placed in four separate 8 inchlifts and compacted to 6 inches.
The clay cap was covered with a 60 mil HDPE synthetic liner. Approximately 34,000square feet of liner was installed. Seams were welded in the field. Samples were tested forpeel adhesion and seam strength.
A 12-inch layer of imported coarse sand was placed over the HDPE liner, and compactedto a minimum of 106 pcf. The sand was retained at the toe of the cover by a gravel barrierenveloped in a HDPE geogrid.
The entire surface area of the sand drainage layer was covered with Polyfelt TS 600geotextile filter fabric.
An 18 inch layer of imported general fill clay was placed over the geotextile and compactedto achieve 95% Standard Proctor Density.
A 6 inch top soil layer was placed over the clay fill and fertilized, seeded and sprayed withhydromulch to establish vegetation growth.
A surface water diversion ditch was placed along the toe of the southern embankment of thecap and cover and the east embankment to divert surface runon around the Cap and Coverback to its natural course.
10.11 MONTTORWELLSANDPlEZOMETERS
The long term monitor wells were installed to monitor the Site during the post closure careperiod. Two sets of piezometers were installed on either side of Site Slurry Wall andFrench Drain system to assess the performance of the system. Figure 15.0 shows thelocation of the initial monitor wells and piezometers. Well completion diagrams are locatedin the referenced documents. The completion information is summarized in Table 6.0 inSection 12.0 which includes the typical well completion diagrams(Figure 19.1 and 19.2).
During mobilization, existing investigation monitor wells were removed except those to beretained for monitoring during post closure care. MW-102S and MW-103D wereinvestigation monitor wells retained for post closure monitoring. MW-102S served as the
-39-
006656
006657
Site upgradient monitor well in the Hartshome/Atoka aquifer. MW-103D and two newmonitor wells(MW-10, MW-11), which were all completed in the mine voids, served asdowngradient monitor wells for artesian ground water in the mine workings(see wellcompletion diagram. Figure 19.2 Section 12). Two additional monitors wells(MW-102Iand MW-01), which made up the 102 cluster, were also retained, but they were notincorporated into the post closure monitoring program.
During the installation of the Cap and Cover nine monitor wells were installed on the cap.Four of the monitor wells were placed within Area C(MW-2,3,4.5). MW-2 and 3 wereplaced in the native soils between the solidified material and the northern segment of theArea C slurry wall. They were completed (as corrected-see Section 113.1) to depthequivalent to the depth of the Area C solidified material. MW-4 and 5 were placed in thesolidified material and completed to the top of underlying clay liner. The remaining fivemonitor wells MW-1,6,7,8, and 9) were placed along the center axis of the Landfill andcompleted to the bottom of the Landfill approximately 6 inches into the weathered bedrock.
Two 2" PVC piezometers(P-2 and 4) were completed on top of the Cap and Coverdowngradient of the Site Slurry Wall to the corresponding depth of the Slurry Wall.
All the wells located on the Cap and Cover surface were screened from the bottom of thecasing to within 1 foot of the clay cap. The screen annulus was filled with sand and cappedwith a bentonite seal to below the synthetic liner. A boot was fabricated from HDPEmaterial and welded to the liner and sealed around the casing with a clamp. The remaininglayers of the Cap and Cover were placed around the wells. Figure 19. l(Section 12.0)presents the typical piezometer and monitor well completions diagrams for on and off theCap and Cover.
Two piezometers were placed off of the cap and cover on the upgradient side of the FrenchDrain and directly opposite of the respective piezometers downgradient of the slurry wall.These wells were completed to the corresponding depth of the French Drain and completedas discussed above without the HDPE boot
10.12 SITE SECURITY FENCE
During remediation a permanent fence was been placed around the Site to provide longterm Site Security. The fence is a six foot chain link fence with a 3 strand barb wireextension. The posts were set on 10 foot intervals and placed in a 3 foot by 12 inchdiameter hole and set in concrete.
10.13 DEMOBILIZATION
Demobilization started January 3,1991 following a prefmal inspection and completedupon the final inspection held on March 29, 1991. The Engineer issued the Certificate ofCompletion on that date.
10.14 EPA CLOSE Our REPORT
The EPA issued a Close Out Report dated 6/10/92 which determined that all appropriateresponse actions had been implemented, and no further action was necessary at that time.
-41-
006658
10.15 REMEDIATION AS COMPLETED
The following is a summary of the various remediation tasks completed as discussedabove.
• All known drums of liquids from Area D and Area C were removed fromthe site.
• All known soils encountered which exceeded Cleanup Criteria were treatedto meetTCLP and compressive strength limits and placed within Area C.
• All drums which contained solid waste or were empty were replaced inthe excavations from which they were removed in Areas C and Dbackfilled with compacted clay in 12 inch lifts and capped with cap andcover.
• Remediation and investigation derived solid waste were placed in the Area Cdrum area, backfilled with compacted soil and capped with Cap and Cover.
• The French Drain was installed from the south bank of the Landfill aroundthe outside perimeter of the Site to intercept shallow ground water and divertit around the outside the remediated area.
• The Site Slurry Wall was installed from the north bank of the eastand west ends of the Landfill around the perimeter of the Site inside andparallel to the French Drain. It was keyed 3* into the weathered bedrock oruntil point of refusal was encountered
• Area C was completed 3-5 feet in the weathered bedrock and was enclosedin a slurry wall keyed into the weathered bedrock
• The entire Site from the outside of the French Drain to the northern bankof the Landfill was covered with a multilayer RCRA Cap and Cover.
• Monitor wells were placed upgradient and downgradient of the remediatedarea, and within Area C and the Landfill.
• Two sets of piezometers were placed on both sides of the Slurry Wall andFrench Drain system.
• A permanent security fence was installed around the Site.
11.0 POST CLOSURE ACTIVITY
The Post Closure Activity Pian(January 1991) as approved by the EPA specified theactions to be carried out during the Post Closure Period. The Post Closure Activity periodcommenced upon completion of remediation construction(3/29/91) and has continued asamended through the date of this Report. Initial Post Closure Activity Plan requirementsincluded:
• Baseline quarterly monitoring of Site Monitor wells, recharge wells andpiezometers including water measurements and sample collection in selectwells;(see Section 10.11, re: Monitor Wells and Piezometers).
• Upon establishing baseline action levels, semi annual monitoring;
-42-
006659
Site inspections to coincide with monitoring events;annual aerial photographs for first five years, and then every 5 yearsthereafter;maintenance of vegetation;Site maintenance;Five Year Reports.
Post Closure Activity Plan amendments approved by the Agencies during the first 5 yearperiod:
• deleting semi-volatile compounds and metals other than nickel from theground water sample analytical requirements since none of the constituentswere reported during the baseline period in significant concentrations;
• limit water sample collection schedule of recharge wells to only whenFrench Drain flowing, otherwise the retained stagnated water below theoverflow would not be representative of diverted water,
• incorporate into the monitoring schedule newly installed downgradientground water monitor well&completed in the weathered bedrock underlyingmine voids.
Additional Post Closure Activity conducted by the Committee as approved by the Agenciesduring the first 5 year period and described in Section 11.3:
• reconstruction of three original monitor wells and two piezometers whichhad been completed to the wrong depths during remediation;
• establish vegetation growth on surface of Cap and Cover;
• install offsite drainage diversion ditch to tie into Site diversion ditch;
• monitoring and sampling of ground water encountered within Area Ccontainmentcell;
• preliminary Area C Assessment to identify the potential sources of theground water and migration outside of the slurry wall which includedinstallation of monitor wells and piezometers in and around Area C;
/'
• placement of three downgradient monitor wells completed in the weatheredbedrock below the underground mine workings, and sampling the wells ona quarterly basis; plus a forth monitor(MW-15) downgradient of these nearthe property line installed after the 5 year review period(see Figure 19.2,Section 12, for typical well completion diagrams);
• Replacement of approximately 200 feet of French Drain discharge line fromthe westend manway to west recharge well;
• Remove observation tower.
The three year quarterly baseline monitoring events were completed in March 1994. Thesite monitoring frequency is currently semi-annual, during which the original PCAPmonitoring wells and piezometers are measured and sampled accordingly. Thedowngradient monitor wells are currently measured and sampled on a quarterly basis.
-43-
006660
Post Closure Monitoring Reports were prepared and submitted to the EPA and ADPC&Efor each monitoring event conducted to date. Post Closure Monitoring Reports describingeach event including well measurements and sample analytical results have been submittedfor the following quarterly and semi annual monitoring events:
1. June 26, 19912. September 19.19913. December 9, 19914. March 19,19925. June 18, 19926. September 21,19927. December 15,19928. March 16,1993(with statistical analysis)9. July 7, 199310. September 13.199311. December 6.199312. March 28,1994(with statistical analysis and final action limits)13. September 13,199414. March 28,199515. June 19. 199516. September 24,199517. January 1, 199618. March 28.1996
11.1 ACTIONLlMITS
Action limits were established based on the first three year baseline monitoring sampleresults in accordance with the methods presented in the PCAP(refer to Post ClosureMonitoring Report, March 1994, Twelfth Quarter, 5/94). The Action Limits are presentedin Table 1.0. The limits are constituent and well specific.
11.2 DATA SUMMARY
Tables 2.0 to 4.0 summarize the positive water sample results over the first five yearperiod(Table 4.0 includes MW-15 monitoring event sample results). Table 5.0 summarizesthe water level measurements collected during the review period. The laboratory reports,Chain of Custodies and field notes are located in the specific Post Closure Activity Reports.
11.3 ADDmONALPoST CLOSURE CARE ACTIVITIES
The following additional activities were conducted during the first five year post closureactivity period.
11.3.1 Well Reconstruction
Based on measurements of the monitor wells and piezometers during the initial quarterlymonitoring events it was determined that piezometers P-l, 2,3, and 4, and monitor wellsMW-2,3, and 9 were completed to incorrect depths, and that there was an obstruction inMW-103S. A Work Plan(0ctober 11,1991) was submitted to the EPA and the ADPC&E,and approved to reconstruct the wells to the correct depths. The Work Plan wasimplemented on October 21 through October 27,1991 as described in the wellreconstruction report(Industrial Waste Control Monitor Well & Piezometer CorrectiveAction Report December 1991). The well completion information is summarized in Table6.0 and typical well completion diagrams are shown in Figures 19.1-.3 all of which arelocated in Section 12.0.
-44-
006661
TABLE 1.0
Statistical Action Limits(lnnig/1)
CONSTITUENTS MW-11 iMW-102S|MW-lQ3D|EastRecharge|WestRechargeTrichloroethyleneCarbon Disulfide1,1,1-TrichloroethaneCis-l,2-DichloroehtyleneTrans-U-DichloroethyleneNickelRef: Statistical Analyses to Establish Constituent Action Limits for Detection Monitoring(Ross, D.L. June 1994)
006662
TABLE 2.0
5 YEAR SUMMARY OF POST CLOSURE MONITORWELLS POSITIVE ANALYTICAL READINGS
(lnmg/1)
MonitoringEvents
MW-102SEvent No.1,3-11,13,14,16.18Event No.2Event No.12,15,17Event No. 18MW-103DEvent No. 1,2Event No.3,4-14,16,18Event No.15,17Event No.18MW-10Event No.lEvent No.3Event No.6Event No. 10Event No.13Event No.14Event No.2,4,5.7-9,11.12.16,18Event No.15,17Event No. 18MW-11Event No. 13-5,7-9,11-13,16Event No.2Event No.6Event No. 10Event No. 14Event No. 15.17Event No. 18i. Recharee WellEvent No.lEvent No.2Event No-3Event No.4Event No.5Event No.6Event No.7Event No.8,12Event No.9Event No.10Event No. 11Event No.13,15-17Event No.14Event No. 18y.RechareeWelIEvent No.lEvent No.2,4.10Event No3Event No.5Event No.6Event No.7Event No.8Event No.9Event Nd.11Event No.12EventNo.13,15-17Event No. 14Event No. 18
Trans-1,2-Dichloro
ethylene
NDNDNSMS
DWNDNSNS
NDNDNDNDNDNDNDNSNS
NDNDNDNDNDNSND
0.010.024NDNDNDNDNDNDNDNDNDNSNDND
NDNDNDNDNDNDNDNDNDNDNSNDND
Trichloro
ethylene
NDNDNSNS
DWNDNSNS
NDND
0.0051NDNDNDNDNSNS
NDNDND
0.0061NDNSND
ND0.0074
ND0.0053,0.00790.00610.0073
NDNDND
0.0061NS
0.0040.003
NDNDND
0.00670.00630.0130.0110.00720.0070.0096
NS0.00140.051
Cis1.2-Dichloro
ethylene
NDNDNSNS
DWNDNSNS
NDNDNDNDNDNDNDNSNS
NDNDNDNDNDNSND
NDND
0.0110.00660.00960.02
0.0073ND
0.0089ND
0.009NSND
0.004
NDND
0.0120.0110.00550.0130.0120.00950.0230.02NSND
0.027
1.1,1-Trichloroethane
NDNDNSNS
DWNDNSNS
ND.NDNDNDNDNDNDNSNS
NDNDNDNDNDNSND
NDNDNDND
0.0052NDNDNDNDNDNDNSNDND
NDNDNDNDNDNDNDNDNDNDNSNDND
Toluene
NDNDNSNS
DWNDNSNS
NDNDNDNDNDNDNDNSNS
NDNDNDNDNDNSND
NDNDNDNDNDNDNDNDND
0.0061NDNSNDND
NDNDNDNDNDNDNDNDNDNDNSNDND
MethyleneChloride
NDNDNSNS
DWNDNSNS
NDNDNDNDND
0.012NDNSNS
NDNDNDNDNDNSND
NDND
" NDNDNDNDNDNDNDNDNDNSNDND
NDNDNDNDNDNDNDNDNDNDNSNDND
CarbonDi
sulTide
NDNDNSNS
DWNDNSNS
NDNDNDNDNDNDNDNSNS
NDND
0.015NDNDNSND
NDNDNDNDNDNDNDNDNDNDNDNSNDND
NDNDNDNDNDNDNDNDNDNDNSNDND
Nickel
NDNDNSNS
DWNDNSNS
6.0230.022ND0.090.0980.019NDNSNS
NDNDNDND
0.013NS
0.011
0.0210.038NDNDNDNDNDNDNDNDNDNS
0.0140.044
0.022NDNDNDNDNDNDND
0.0540.045NS
0.0290.026
Lead
ND0.036NSNS
DWNDNSNS
NDNDNDNDNDNDNDNSNS
ND0.011NDNDNDNSND
ND0.024NDND
0.0071NDNDNDNDNDNDNSNDND
NDNDND
0.00550.0140.014NDNDND .NDNSNDND
DW»DiyWellND« Not DetectedNS» Not Sampled
006663
TABLE 3.0
S YEAR SUMMARY OF AREA C ASSESSMENT POSITIVE ANALYTICAL RESULTS<hl>«
MWjEnuNo.i.i&~lN».6E—lNo.7E—lNnJe—xibJBrNo.lOEmiNo.llE—ltb.12
MW.3E—itNo.l-SBnltbJ&«NB.7EmNo.1b—tbi*E—tMlIOE—llil.11bmlb.llE—MH>.13-ltMW.4EmuNo.1-1&-tNo.9B—tN&lOEnolHo.llB~.Mo.l2&WH.13-11aa^E—llKkl-lB——lh*&.MNB.K)B—iNo.lIE—lHi.12Eon N>. 13-11£5EKMNbil-10E—llbLlIE—tNo.ll.ME—xNo.13.15-11ESEnolHo.l-KEr—No.11EnMtb.12-11^7
b—No.1-10EnMNo.llE~oItel2.13.U-lte^MNo.MElExuNo.1 10B...N0.11-11E*E—tNo.1-10EvlNb.11Ef—lNlLll&». ?,.13-11&WE——No.l-K)E——N&llEolNB.11&~.tfc.U-UEJSBnttb.1-10E——tb.14E~tN.ll-U.B-ltEJOfE—ttb.1-10EnotNi.llE tNo.14E~tN..U.13.B-l«E-llemtffa.l.lOE—lNo.lIE—tth.14E^.lbB.U.lS-UEJ2E——NOLl-IOB—tlb.llBrxNo.14E^Mtb. 0,11,15-11
dl.1.2
NS»10»
NDU»NDNS
NSMD•.11039OJ9onO.Oto.oczusNSND
0.04300230026
MS
NS00520044ND003NS
N1NDND1C
(0NDNS
N1NDNSND
N11C
N130UNS
N1NDNDNS
N1NDNS
N1071NDND
N1NDNDNS
N11.4
MDNS
Tli
NS330130350110110m14NS
NSND
0.0);0.02ND
0.0154ND
0.03;NS
MS0270350.110-23NS
NS0.170.230140.13NS
N10.026NDNS
N1NDNS
M0.1NSND
N1NS
N12»100NS
N1150340NS
N10.006
NS
N1o.<n50.011ND
N1ND
0.112NS
N13.112NS
Crtw
NSNDNDNDNDNDNDND
.P"
NSNDNOND
0.0140.014NDNDNS
NSNDNDNDNDNS
NSNDNDNDNDNS
N1NDNDNS
(0NDNS
N1NDNSND
N1NS
NDNDNS
N1NDNDMS
N1NDNS
N1NDNDND
N1NDNDNS
N1NDNDNS
NS250WO15019012013040NS
NSNDNDNDNDNDND
0025NS
NS0140.0710.015VOW
NS
NS0064ND
0.0340046
NS
N1NDNDNS
N1NDMS
MINDNSND
N1• NS
N19951NS
N1<550NS
N10.0)5
NS
M0.020.117ND
• M45057NS
M•a3.4NS
ACMOO.
NSTO5103006«0ND210301NS
NSND0.15NDNDND
0.025NDNS
NS0.90.630.92055NS
NS\1
0.35OB043NS
NNDNDMS
N1NDNS
N10011
NSND
MNS
M19100NS
N1NDNDNS
N1NDNS
N1NDNDND
NNDNDNS
N1ND
O.OMNS
NSS4014007101100590«10210MS
NSNDNDOilNDNDNDNDNS
NSNDND0.27NDNS
NSNDOil021NDNS
t0NDNDNS
N1NDNS
N1NDNSND
N1NS
N1160190NS
MNDNDNS
N1NDNS
N1NDNDND
N1NDNDNS
NNDNDNS
NSr76IT
NDNDNDNDNS
NSND0.11NDNDNDNDNDNS
NSNDNDNDNDNS
MSNDNDNDNDNS
N1NDNDNS
N1NONS
N1NDNSND
N1NS
N119
NDNS
N1NDNDNS
N1NDNS
N1NDNDND
NNDNDNS
MNDNDNS
NS110130no1501101103SNS
NS
3.10.095NDIJ
00170035
NS
NSOOK0.069
0.057NS
NS0.0110.04510420041
NS
N1000(1
NDNS
MNDNS
N10034NSND
N1NS
N1130rNS
»65(0NS
N1NDNS
N10.11097
NDND
W15
0.319NS
N1ND
0007NS
NSU113JNDNDNDNDNS
NSND0.260.0670.070.130.020011
NS
NSNDND
00140012
NS
NSNDND0.01
0.0091NS
N1NDNDNS
N1NDNS
N1NDNSND
N1NS
N1A3NDNS
N1NDNDNS
MNDNS
N1NDNDND
nND
0-29tNS
m09
0054NS
NSND3J1.1NDNDNDNDNS
NSND0140070.0140.03«00370026
NS
NSNDNDNDNDNS
NSNDNDNDNDNS
N1NDNDNS
N1NDNS
MNDNSND
N1NS
N12
NDNS
MNDNDNS
mNDNS
KNDNOND
N1ND
0.09;NS
N1ND
0.007NS
Vinyl
NSNDNDNDNDNONDNDNS
MSND0(3
2OilOil033031NS
NSNDNDNDNDNS
NSNDNDNDNONS
N1NDNDMS
N1NDNS
roNDNSND
MNS
N1NONDNS
N1NDNDNS
N1NONS
N10120.017ND
N1ND
0101NS
N1NO004NS
«k,te»
NSNDNONDNDNDNDNDNS
NSNO
0.0055000740.017NDNDNONS
NSNDNDNDNDNS
NSNONDNDNDNS
N1NDNDNS
mNONS
N1NONSNO
N1NS
N1NDNONS
N1NDNDNS
N1NDNS
N1NO
0003ND
N1ND
0021NS
WND
0.011NS
NSNDNDNONONONONONS
NSND
00140.01
00051NONONDNS
NSNDNDNONDNS
NSNONDNDNDNS
N1NONDNS
N1NONS
N1NDNSND
MNS
N1NONDNS
N1NDNDNS
N1NDNS
N1NDNDND
N1NDNDNS
N1NONONS
B«n~
NSNDNDNONDNDNDNONS
NSND0.030.02NDND
0.015NDNS
NSNDNDNONONS-
NSNDND(IDNDN5
N1NDNDUS.
N1NONS
N1NONSND
N1»".MNDNONS
MNDNDNS
N1NDNS
N1NONONO
N10013NONS
M0.026NONS
TrieUdio<&im
NSNDNONDNDNDNDNDNS
NSNONONO
0.006NONONONS
NSNONONDNDNS
NSNDNDNDNONS
N1NONDNS
N1NONS
MlNDNSND
MNS
roNONONS
N1NDNDNS
NNDNS
N1ND
00113ND
N1NDNDNS
N1NONDNS
lair
NSNDKDNDNDNONDNDNS
NSNDNONONONO01NDNS
NSNONONDNONS
NSNONONDNDNS
N1NDNONS
NNDNS
•aNONSNO
NINS
MNONON8
N1NDNDNS
N1NDNS
N10.0110013ND
M0-2850.101
MS
M00040006NS
•tax
NSNDNDNONDNDNONONS
NSNDNDNDNONONDNDNS
NSNONDNONONS
NSNONONDNDNS
N1NDNONS
toNONS
N1NDNSND
nNS
NINONDNS
NINONDNS
NINONS
NIND
0004ND
»NDLINS
NIND
0.005NS
lam
MSNONDNONDNONONDNS
NSNDNONDNDNDNONONS
NSNDNDNONDNS
NSNDNDNDNONS
(0NDNDNS
MNONS
NINONSND
NINS
NINDNONS
NINDNDNS
NINDNS
NINDNDND
NINO
0012NS
NO0011
NS
l»°p~.
NSNDNDNDNDNDNDNONS
NSNDNDNDNONDNDNONS
NSNDNONONONS
NSNDNONDNDNS
NINDNDNS
MNDNS
NINDNSND
NINS
NINONDNS
NINONDNS
MNONS
N1NDNOND
NIND
0.019NS
NINDNDNS
•htylcir
NSNDNDNDNDNDNDNONS
NSNONONONONDNONONS
NSNONONDNONS
NSNDNONDNONS
NINONONS
NINONS
NINDNSND
NINS
NINDNDNS
NND .NONS
NINDNS
NINONDNO
NINO
0019NS
MlNO
0.061NS
ubm
NSHDNDNDNDNDNDNONS
NSNDNDNONONONDNONS
NSNONONDNDNS
NSNDNONDNDNS
NINDNONS
NINDNS
NINONSND
N1NS
NINDNONS
NINDNDNS
NINONS
NINONOND
N1ND
o.ooaNS
N1NONO
KeW
NSOJI0.4ND0.42OJI0.410.4NS
NSNONDNDNONONDNANS
NSNA3.41.707NS
NSNA2.*2.41.7NS
NINDNDNS
NINONS
NINONSND
NINS
M02602»MS
MND
0.0*7NS
NINDNS
NI0.04;NONO
NI021NONS
NTavNONS
NOK MV-2J.4J>olr«or<ri<>llB>pli>t phlirPCA?
006664
TABLE 4.0
Summary ofDowngradient Monitor WellsPositive Analyical Readings
On mg/L)
DL=0.015mg/lafter 5yr. report periodafter 5yr. report periodafter 5yr. report period
MW-12Mar-95Jun-95Sep-95Jan-%
Mar-96Jun-96Sep-96Jan-97
Event No.1-13*
1415161718
19*20*21*
NDNDNDNDNDNDNDND
0.4560.4560.5890.5070.530*0.5160,5020.649
0.0720.0540.1310.0960.0820.0910.0780.101
0.0960.0630.2040.1010.1190.1670.1110.207
0.0210.0270.0170.0340.057ND
0.0210.027
NDNDNDNDNDNDNDND
MW-13Mar-95Jun-95Sep-95Jan-96
Mar-96Jun-96Sep-96Jan-97
1-13*141516171819*20*2I*
Not installedND
0.0170.0330.0090.003NDNDND
NDNANDNDNDNDNDND
NDNDNDNDNDNDNDND
NDNDNDNDNDNDNDND
0.0250.0580.0880.0890.2
0.0110.026ND
NDNDNDNDNDNDND
MEK-0.078
after 5 yr. report periodafter 5yr. report periodafter 5yr. report period
MW-14Mar-95Jun-95Sep-95Jan-96
Mar-96Jun-96Sep-96Jan-97
1-13*141516171819*20*2I*
Not installedNDNDNDNDNDNDNDND
NDNDNDNDNDNDNDND
NDNDNDNDNDNDNDND
NDNDNDNDNDNDNDND
0.0130.0160.0560.0260.023ND
0.0130.015
NDND
111TCA-0.016NDNDND
CDi-0.011ND
after 5yr. report periodafter 5yr. report periodafter 5yr. report period
IW-15Jun-96Sep-96Jan-97
1-18*l9«
20*21»
NDNDND
NDNDND
NDNDND
NDNDND
0.012NDND
NDNDND
Not installedafter 5yr. report periodafter 5yr. report periodafter 5yr. report period
Field BlankMar-95Jun-95Sep-95Jan-96
Mar-96Jun-96Sep-96Jan-97
141516171819*20*21*
0.013ND0.020.0170.018NDNC0.02
NDNDND•NDNDNDNCND
NDNDNDNDNDNDNCND
NDNDNDNDNDNDNCND
NANDNDNDNDNDNCND
NDND
BDCM-0.008BDCM-0.004BDCM-0.005
NDNCND
after 5yr. report periodafter 5yr. report periodafter 5yr. report period
MCL = Maximum Concentration Levels;ND = Not detected above detection limits;
chloroform = trichloromethanecis-U DCE = cis-1.2 DichloroetheneTCE=TrichloroetheneCDi=Carbon Disulfide
DL= Detection LimitNA = Not Analyzed; NC= Not collected.
111TCA = 1,1 J trichloroethane = methyl chlorofonn(MCL = 0.20 mg/1)BDCM = Bromodichloromethane (MCL = not est)MEK=2-Butanone
-48-
006665
^ ^ c
TABLE 5.0
5 YEAR SUMMARY OF WATER LEVEL ELEVATIONS(mil)
MonitoringEvents
Post ClosureP-lP-2P-3P-4
MW-1MW-2MW-3MW.4MW-5MW-6MW-7MW-8MW-9
MW-10MW-11
MW-102SMW-1Q3DAreaCAsse
P-5P-6P-7P-8P-9SP-9dP-lOsP-lOdP-llP-12P-13
NewDowntMW-12MW-13MW-14
1Monitor
DiyNM
511.68514.11505.16518.24516.29
DrythyDiy
497.1Diy
485.13452.02451.94518.79D-y
SUWIK X*
N1N1N1N1N1N1N1N1N1N1N1
TiKuCDtK
1MIN1N1
2Wells an
DryDiy
51831514.57505.0651834516.24DiyDqrDiyDiyDiyDiy
450.61450.58516.71
Dryczometen
N1N1N1N1N1N1N1N1N1N1N1
Monitor TN1N1 -N1
3riPiezon
521.53Diy
521.04514.96
Diy517.78514.85DiyDiyDVDryDiyDiy
459.49459.83521.1245935
^includesN1N1N1N1N1N1N1N1N1N1N1
ellsN1N1N1
4stem520.73Diy
51934514.41505.13517.23514.43DiyDiyDiyDiyDiyDqr
45537455.67520.93455.41MW-2,
N1N1N1N1N1N1N1N1N1N1N1
N1N1N1
5
520.75Dqr
519.4751436
Dry516.96513.99DiyDVDiyDiyDOTDqr
456.15456.5452136456.27
,4,5)N1N1N1N1N1N1N1N1N1N1N1
N1N1N1
6
517.75Dry
516.93513.81505.07517.45513.8
515.61D»yDiy
488.99DiyDiy
451.86452.14518.21445.88
N1N1N1N1N1N1N1N1N1N1N1
N1N1N1
7
520.81Diy
523.04514.495043516.9151334515.71513.11495.19
DiyDiy
487.91460.28456.94522.68457.2
N1N1N1N1N1N1N1N1N1N1N1
N1N1N1
8
521.46Diy
520.69514.47505.03512.97512.97516.17513.69
Diy496.99
DiyDqr
457.98458.22522.11457.98
N1N1N1N1N1N1N1N1N1N1N1
N1N1N1
EVE9
519.92D^
51837513.69
NM515,82512.45516.49513.9Diy
497.03DryDiy
453.98454.26521.09454.03
N1N1N1N1N1N1N1N1N1N1N1
N1N1N1
NTNUMF10
51638DV516.6
512.91504.71516.075123451638513.92
Diy496.74
DiyDiy
450.41449.68517.1
449.46
N1N1N1N1N1N1N1N1N1MN1
N1N1N1
1ERS11
5213Diy
5243851434505.075163512.68516.74514.21494.92497.06498.65496.99454.86455.1652238454.93
532.8532.53532.94528.01516.1515.71511.82510.07522.2352432
N1
N1N1N1
12
521.44DiyDiy
514.07505.0751531512.17516.9851431Diy
497.16498.69487.03457.1457.45
DiyD^
529.44DiyDiy
528.12516.18514.91511.79509.18522.06DiyN1
N1N1N1
13
516.78Diy
517.15513.2
505.11515.9512.0651736514.69494.86
Dq-498.73487.03449.8450.151733449.87
524.89Dry
52439528.23516.15515,11
Diy508.85521.22523.89
N1
N1N1N1
14
52133DOT
520.21513.75505.0951538D^
517.91516.07495.11497.11
Dor487,02455.42455.71521.9445534
529.17528.97527.98528.2
515.81514.56511.84508355223852432
N1
460.15461.07454.51
15
NMNMNMNMNMNMNMNMNMNMNMNMNMNMNMNMNM
NMNMNMNMNMNMNMNMNMNM
528.95
461.61464.2445739
16
516.75Diy
517.16513.22505.1514.4Diy
51731516.85
Dqr497.06
D»y487.02449.43449.7516.99449.47
524.15Diy
524.44528.2515.65514.6Dry
507.852131523.91524.19
456.29455.994493
17
520.23Diy
520.75513.2505.1515.81Diy
518.28516.93495.29497.05
Diy487.01450.6450.87516.69450.67
530.62529.62532.09528.17515.63514.63Diy
508.04521.78523.28528.43
4563456.56450.6
18
521.6Diy
531.7513.21505.09515.21
Diy518.44517.06495.78497.2Diy
487.05451.17451.45519.74451.22
53137530.15532.82528.1651532514.08
Diy507352233523.63531.62
45736458.1451.25
NI=Not InstalledNM=No Measurement
006666
11.3.2 Vegetation
Initially vegetation was difficult to establish and frequent erosion problems occurred whichwere continuously backfilled. Additional topsoil was placed over the surface. Severalattempts to reseed were unsuccessful. A sprinkler system was installed on the Cap surface,but there was no improvement, and was later removed since it inhibited mowing andtreatment. With the assistance of the Arkansas Agricultural Extension, soil analysisindicated that the soil nutrients and chemistry were not sufficient to support growth. TheExtension service advised that chicken litter and lime be applied to the surface. This advisewas followed and the results were successful. The Site surface now supports a healthy andmature stand of bermuda grass(see the photograph section at the end of this report).
11.3.3 Offsite Drainage
Drainage along the east portion of Race Track Road maintained by the County was causingproblems for the local residents. The Residents asked the IWC Committee to construct adrainage ditch from the road to tie into the Site diversion ditch. The Committee agreed andconstructed the ditch with rip rap from Race Track Road to the Site diversion ditch on theeast side of the Cap and Cover. The drainage ditch crosses the small parcel of land that ispart of the Site property, but outside the Site remediated area. After constructing thediversion ditch, the parcel was fenced to prevent injury to the residents and children.
11.3.4 AREA C
During the initial monitoring events water was observed in two of the Area C monitorwells(MW-2 and MW-3) in volumes not anticipated. It was suspected that the source ofthe water was due to the initial incorrect monitor depths. However, water was stillobserved in these wells after the wells were reconstructed to the correct depth(although thevolumes were less and recovery rates slower). Water was later observed in the remainingwells(MW-4 and 5) completed in the solidified material. These wells were incorporatedinto the quarterly monitoring and sampling program at the time. The water sample resultsindicated positive values of several volatile organic compounds(see Table 3.0 Section11.2).
On November 18,1992 a Work Plan was submitted to and approved by the Agencies toassess the source of the water. The Work Plan was implemented during me September1993 post closure Quarterly monitoring event as described in the Area C AssessmentReport January 1993). Ten 2" piezometers were placed in and around Area C, both in andabove the underlying weathered bedrock. Figure 16.0 shows the location of thepiezometers and Figure 14.0 shows the generalized cross-section of Area C assessment(seeSection 10.9). The well completion data is located in the Area C Assessment Report. Thecompletion information is summarized in Table 6.0, in Section 12.0.
The Area C assessment determined that presence of the water in Area C was apparently dueto excavation of Area C into the weathered bedrock below the effective depths of theFrench Drain and Site Slurry Wall. It is not likely that significant water levels would havebeen measured in the monitor wells otherwise, since the reported water levels are not abovethe apparent top of the weathered bedrock. This supports the HWQS and EPA observationsthat the flow is confined to the bedding planes of the strata.
Free phased product was removed during the initial discovery of the VOC in monitor wellMW-2. It was not encountered in the other wells and has not been encountered in MW-2
-50-
006667
r~' (~ r " r (— (
10=10
• Cw M4 CMr. T«* •K t>«1
e=M
IVMMOfTTHi
TOUEiHOHffl
FORBES ENVIRONMENTAL
LOCATION OF AREA "C"ASSESSMENT WELLS
TAKEN FROM AREA "C" ASSESSMENT FIGURE 16.0
006668
since. The most likely source of the VOCs is solvents in the undisturbed soils which werenot discovered during the remediation.
VOCs were detected in the wells completed in the weathered bedrock just outside thenorthern segment of the Area C Slurry Wall. The source of the contamination in thesewells has not been established and may be from Area C, or a result of similar conditionsoutside Area C, although site investigation monitor wells completed in this area were notsignificantly contaminated.
11.4 DOWNGRADIENT MONITOR WELLS
Due to the conditions encountered in Area C the ADPC&E requested that three monitorwells be placed downgradient of Area C in the weathered bedrock underlying the minevoids. A Work Plan was approved and the wells MW-12,MW-13, MW-14 wereinstalled during the March, 1995 PCAP monitoring event A report describing theinstallation of the wells was prepared(August, 1995). MW-15 was installed after the 5year review period on June 19,1996. The new wells were incorporated into the PCAPsampling schedule. The well were sampled on a quarterly basis, with every other eventcorresponding with the semi annual events of the original PCAP monitor wells. The wellshave been sampled for five quarters. The location of the wells are highlighted in Figure17.0. Well completion diagrams, and completion data are located in Section 12.0.
The/our monitor wells' screened intervals included the weathered bedrock and the upperportion of the Hartshome. The screened intervals in Monitor wells MW-12.13 and 15were sealed below the coal bed in the pillars. The sand filter pack in Monitor well MW-14rose above the coal bed and was sealed in the pillar. Water was not encountered in themine voids in any of exploration borings used to locate the pillars in which to install theMW-12,13, and 14, but was encountered while locating MW-15 since it was furtherdowngradient than the others and in the flooded mine voids.
The water sample analytical results collected from the new downgradient wells summarizedin Table 4.0(see Section 11.2). MW-12 water sample analytical results are consistentlypositive and above MCL for cis 1,2 dichloroethene, trichloroethene, and vinyl chloride.
The results reported for MW-13 samples have been positive for chloroform, but less thanMCL. No other VOCs have been reported in MW-13. The concentrations for nickel hadbeen less than action levels developed for the original monitor wells, however, during thelast sampling event the concentration increased substantially. The next sample event willdetermine if the reported increase was an error. {The subsequent nickel concentrations afterthe review period have returned to the norm, and chloroform has not been detected.}
The VOC analytical results reported in MW-14 have been negative. No VOC constituentshave been reported above detection levels in the three subsequent ground water samplescollected from MW-15. MW-15 is the furthest most downgradient well and is located bythe northern property line.
The source of the VOC in MW-12 may be from Area C, but there are other possibilities aswell. An additional downgradient monitor well is to be installed near the north propertyline(see Section 13.0).
The water levels are summarized in Table 5.0(see Section 11.2). The water elevationsmeasured in MW-12 and 13 have been consistently about 6 feet higher than those measuredin the Mine Void monitor wells. The water elevation measured in MW-14 has beenconsistently equivalent to those measured in the Mine Void monitor wells.
-52-
006669
(— r~ r
0^
LEGEND
MONITOR WELLPIEZOMETERFRENCH DRAIN MANWAYDOWN GRADIENT MONITOR WELLSBELOW MINE VOIDS
FORBES ENVIRONMENTAL
MONITOR WELL LOCATION MAP
FIGURE 17
006670
Point of refusal was encountered while drilling MW-13 with a drag bit at a depth of 71and the bottom two feet was drilled with a diamond core bit. The core samples were ahard strata of alternating thin layers of white sandstone and dark gray sandy shale. Anadditional core was collected in the same strata on the south side of the Cap and Cover(P-13). The core was essentially identical to that cored in MW-13 with thin alternating layersof sandstone and hard black sandy shale. This strata has been identified as the HartshomeSandstone(see Section 6.4.2).
11.5 REPAlROpFRENCHDRAINDlSCHARGELlNE
The west portion of the French Drain was stopped up due to collapse of the solid drainpipe between the northwest manway and the west recharge well. The drain pipe was aflexible 4" plastic pipe typically used for this purpose. Approximately 200 feet of the pipehad to be replaced before flow was re-established. Since flow was re-established, aportion of the collapsed pipe which extended below the Cap and Cover was left in place toavoid disturbing the Cap integrity.
12.0 CURRENT SITE STATUS
This section is a summary of the completed remedy as it currently exists in relation to theRAP objectives. The primary focus of the RAP was to reduce the volume and toxicity ofthe sources of contamination, and reduce the recharge and mobility of onsite perchedground water zones above the weathered bedrock; thereby minimizing potential impact tothe underground mine water system which was considered the most likely and vulnerablepotential usable water source. Figure 18.0 shows the current site Plan View and locationof all monitor wells and piezometers. Table 6.0 summarizes the monitor well andpiezometer completion information. Figures 19.1 and 19.2 show the typical completiondiagrams for the site monitor wells and piezometers. Figure 19.3 is the completiondiagram for the recharge wells.
12.1 EXCAVATION OF IDENTIFIED SOURCES OF CONTAMINATION
Areas which required excavation to remove impacted soils and/or drums of liquids includedArea C, PA, D, 09B, and the slurry wall trench.
All identified drums of liquids discovered in Areas C and D were removed from the Siteand disposed of in an offsite EPA approved permitted commercial facility.
Soils from all excavated areas which were identified through chemical analysis asexceeding Cleanup Criteria were treated to meet treatment standards(TCLP Limits). Thetreated soils were placed in Area C and solidified with Portland cement and covered withcompacted clay backfill.
Removal of the drums of liquids off site, and treatment of the soils significantly reduced thetoxicity and volume of contaminants, and decreased the potential for mobility.
12.2 FRENCH DRAIN ANDSrrE SLURRY WALL
Shallow upgradient subsurface water seepage is intercepted by the French Drain whichdiverts the ground water around the Site to be discharged into the mine void recharge wells.
The Site Slurry Wall essentially encloses the entire remediated area on three sides.
-54-
006671
006672
TABLE 6.0
WELL COMPLETION DETAILS
WellNumber
P-lP-2P-3P-4P-5P-6P-7P-8P-9sP-9dP-lOsP-lOdP-llP-12P-13
MW-1MW-2MW-3MW-4MW-5MW-6MW-7MW-8MW-9
MW-10MW-11MW-12MW-13MW-14MW-15*MW-102IMW-01
MW-102SMW-103D
Top ofCasing
Elevatioa(msl)534.50538.00531.70533.10541.00538.66536.84541.55534.50534.35533.65533.78537.52540.94533.10535.50535.90534.80537.27535.47529.80527.40532.105273051130523.50522.08520.03519.11517.63537.70537.12537.76515.80
WellDepth(ft.)18.1018.8015.3020.6017.0610.2318.0413.7420.1525.1521.9027.0020.1321.5118.9230.8022.4022.9022.5322.8035.2030.9033.8040.8062.2080.8077.7176.5176.91103.7178.30120.6243.2069.70
Bottom ofCasing Hevatioa
ft.(msl)521.20 .519.20516.40512.50523.94 ,528.43518.80527.81514.35509.20511.75506.7851739519.43514.18504.70513.50511.90514.74512.67494.60496.50498.30486.50449.10442.7044437443.52442.20413.92459.40416.50494.56446.10
CasingDiameter
(in.)2222222222222224444444444422224444
ScreenLength
(ft.)5.005.005.005.005.005.005.005.005.005.005.005.005.005.002.5020.0010.0010.0012.5013.5024.0020.0024.0035.5010.0010.005.005.005.005.0020.0029.5015.0010.00
GroundElevationft.(msl)531.80535.50528.50530.70537.08535.27533.78538.46532.76532.64531.56531.52535.38537.65
NS533.10533.00531.90534.80533.4052730525.20529.50525.20509.10520.20519.32517.43516.45
NS536.02536.02536.02513.20
Top ofScreen Elevation
ft(msl)516.20514.20511.40507.50518.94523.43513.80522.8150935504.20506.75501.7851239514.43511.68484.70503.50501.90502.24499.17470.60476.50474.30451.00439.10432.7043937438.52437.20419.13439.40387.00479.56436.10
NS = Not Sureveyed.Ground Hevadon surveyed approximately 2' norm of well.Well Depth taken from top of casing.MW-1 and MW-102I part of MW-102S duster(not monitored).*MW-15 completed June 19,20,1996 after 5 year review period.
-56-
006673
.———— . Sl—1 ProMCim* Loeklut Covr :
____«< ^—— Vtnl*4 Cop
~~ ^———— Sl—1 Prafciiv Leclina C«v«ry—— w*«a M»r /
^ ___»,————Vnfd Cap• /—— 4' Dio—rr CottCfl* P«d |Moun«) | I /
SURFACE /^ >< _-/ -,^O • ^ ._____________• __ p| ITCWl
T^y/yJ-^^ ^^y/////^ a ^—»»»»pH,n////I 777/1 /^/~T/ / / / / /i ^—— CeBef* PW (Mound)ui<ii4<iB»<infiinnnmii •ii< iiniminiinininiilitfijnu ^^« t 2\
•'\'." .'?•'•'f^.•'^••:-:•:'•.•/ '•' '••".•:.1! r'.^'.l'.y—HOM »o<». f*t*f '^'*\ SURFACE
^yyy^ p///^\ L^ ^———//yyy// /////^ —^. • ' ••————— 2% Btiifnit* C—ilil $••1
..——i— 2" PVC CMl— (Scl>*«uf 40,/^ Tlw4«tf, Fkrh JoiMt
4———— 2% a*Rlonit« C*in*nt S«al . . '
^ •«——~—— Granular Bantonil* S*«l^——— . rvc CO«IBI ^ zzr
LANDFILL TRASH OR SITE FILL : =: <——— (Top et Scr«»i>,
*.———- Granular B»A|OIMI* S««l "" ^=:= == -^——— 2" PVC Scfn ISehCur 40,
:= ==== == = —, 0.01 Inch Slot*. Thrf^«4,— ^____ : (Top e( S«r*«li| . ^ ^—=::: ^ —== — Fluih Joint)
^ . ——— f"" of"" s•"- === ==
^ ^——— ' PVC Scrum ———— '
;. .' pnTTOM OF LANDFILLNote- ——— WEATHERED SANDY SHALE .———————————————————————————————————————————.MW'completed with 4" Sch 40 FVC threaded Hush joint casing. PIEZOMETERS OFF_OF CAP AND COVERP completed with 2" Sch 40 FVC threaded Hush joint casing I________(P-l & P-3, P-5 thru P.7. P-13)________[
| LANDFILL/AREA C MONITOR WELLS & PIEZOMETERS] I FORBES ENVIRONMENTALon ^—^^—^——^_^——————^^—
CAP AND COVER SURFACE rrvn^AT ww» T/MW-1 tlim 0. P.9 P-d. P-R thm P-12t TYPICAL WELLI (MWlthm9. P2.P^P8thniP12) ———| j COMPLETION DIAGRAMS
NOTE; There ire slight differences well to well. NOTTO;SCALB FIGURE 19.1
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__ r—irXf SQUARE STEEL fXffSOIUtteCTfctPROTECTIVE COVFB ' ______^___^__^^^^rAff SQUARE S1CE1.PROTECTIVE COVER ^ • " • P R O l E C T l V E COVER
-..—^flS' ^.^^^^ ,.<'D(A. CONCRETE -pgt • i )5m ^ 4-D1A.COHCBETE
f ''S??!?'! !! % '!S5^5~ ^_^_BENTONnESEAL SHALE/SANDSTONHF • *~'?~ • ~~ • — - ' • - ' 'I
WEATlffiRED "——:———— •"•"'' E'!" 5s -£—i :~$I'- O^J5HALBSANDSTONB T. 1 **»^-A* ' =• 32 J'.-~~-£^ s-T^.
•t'^'—Q-.—C .It: =S rp ,iT-.~~'"*'—'"LHANDYSHALE__>L;?:^^;le7.tt ••L ':i-'.•;«^•" ••-7^. r.rDM.sctt<orvc ;SANDY5HALB————»»A,-^.^I^ ••• S :•;? '•H' .'- }*;.- 0 010-SLOTTED SCREEN ,________——————————————————————————————_____———————————,
<r2r- Sr; •. s J . -'' ——' MONITOR WELLS COMPLETED IN MINE VOIDS
————'^S^^ |___________(MW.10.MW.11. MW-KSD)___________|
| FORBES ENVIRONMENTAL
| MONITOR WELLS COMPLETED BELOW MINE V O I D S |(MW-12, MW-13. MW-14, MW-15) TYPICAL WELL1 —' I COMPLETION DIAGRAMS
NOTE: There are slight differencM well to well NOT Td SCALE FIGURE 19.2
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The difference in the hydrostatic head in comparing the upgradient piezometer outside theFrench Drain to downgradient piezometer inside the Site Slurry Wall indicates that theFrench Drain effectively intercepts the subsurface seepage above its completion depth, anddiverts the water around the Site. Intermittent flow can be observed in French Draincorresponding to the amount of rainfall the general region has received.
Together the French Drain and Slurry Wall minimizes subsurface migration into theremediated area which significantly reduces recharge to the onsite perched ground watersystems and reduces the primary mechanism for transport, and consequentlysignificantly reduces mobility.
Low concentrations of trichloroethene have been consistently reported in one or both ofrecharge wells above MCL when the trench drain is flowing. Cis, 1,2 dichloroethene lessthan MCL has also been reported. The source may be from the soils in which the FrenchDrain was completed which were below Clean Up Criteria.
12.3 AREAC
Area C is enclosed by a Slurry Wall keyed into the Site Slurry Wall all of which iscompleted into the weathered bedrock. The largest part of the excavation is above theSlurry Wall. The Area C Slurry Wall minimizes ground water migration into the onsiteperched zones and reduces mobility above the weathered bedrock outside the Slurry Wall.
The lower part of the Area C excavation was completed in the weathered bedrock below theSlurry Wall. Consequently, the lower portion of Area C is directly in the pathway ofground water migration in the weathered bedrock bedding planes below the Slurry Wall.VOC concentrations above MCLs have been reported in the ground water within Area Cand immediately downgradient of the northern segment of the slurry wall. It has not beendetected upgradient of Area C. Based on the hydrogeology discussed above, the impactedground water is confined within the bedding planes of the weathered bedrock and shouldhave minimal -if any- affect on the limited onsite perched ground water systems or theunderground mine artesian system.
12.4 LANDRLL
The bottom of the Landfill lies just above the weathered bedrock. The French Drain andSite Slurry Wall essentially cuts off ground water flow into the remediated area above theweathered bedrock. The multilayer Cap and Cover covers the Landfill and prevents surfaceinfiltration. Therefore, any remaining onsite perched systems south of the Landfill shouldbe essentially immobilized and the amount of seepage into the Landfill should besignificantly reduced. The water levels measured in the Landfill monitor wells, which arecompleted 6" into the weathered bedrock, indicate that minimal water-if any- isaccumulating in the landfill.
12.5 CAP AND COVER
The multilayer RCRA Cap and Cover covers the entire remediated area. There is presentlya healthy and mature growth of bermuda grass on the surface and erosion has beenmitigated. The Cap and Cover provides a reliable mechanism to capture rainfall infiltrationbefore it can reach the remediated area below it, and therefore effectively removes surfacerecharge to any remaining perched water zones in the remediated area and reduces mobility.
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12.6 DOWNGRADIENT MONITOR WELLS
Three monitor wells were placed downgradient from the remediated area north of the Capand Cover, and completed in the strata directly below the underground mine workings.The water sample results collected from MW-14 have been negative. MW-13 results havereported low levels of chloroform. Chloroform has not been a consistently reportedconstituent. MW-12 results have consistently reported concentrations of cis-1,2dichloroethene, trichloroethene and vinyl chloride above MCLs. The source of the VOC ishas not been established. Based on the referenced documentation, the impacted groundwater should not affect the water in the mine workings. The ground water system in theweathered bedrock is an unlikely source of usable water.
As previously mentioned, MW-15 has been installed near the north property line after thefive year review period.
12.7 MINE VOID MONITOR WELLS
Monitor wells placed in the mine voids have been sampled since the completion of theremediation construction. The sample results over the coarse of the first five year postclosure monitoring period to date have been consistently negative. Only isolated incidencesof low concentrations of VOC have been reported without any consistency or correlation.The reported positive values are believed to be due to sampling or laboratory error orartifacts. For the most part the monitor wells indicate that the water in the undergroundmine works has not been significantly effected by the Site conditions.
12.8 SrrESECURrrY
The Site is totally enclosed by a 6 foot chain link fence topped with three strands of barbwire. Access is limited to two gates secured with a chain and lock to which only a selectfew have keys. Over the course of the first five year period there has been infrequent andminor reports of a breach in security. For the most part the Site is considered secure.
13.0 POST CLOSURE ACTIVITY-2ND FIVE YEARS(MARCH 1996 TO MARCH 2001)
The Post Closure Activity for the second five year monitoring period will include theinstallation'of MW-15 downgradient ofMW-12 near the Site property line. The location ofthe well is indicated in Figures 17.0 and 18.0. The well was installed in June of 1996 inthe weathered bedrock below the mine voids. Initially the well will be sampled on aquarterly basis for a period of two years. Afterwhich it will be incorporated into the semi-annual monitoring schedule, unless analytical results indicate otherwise. The well will beanalyzed for the current indicator parameter constituents(i.e. VOC and nickel).
Downgradient monitor wells(MW-12,13, and 14) will be monitored on a quarterlysampling schedule until two years of sampling have been completed(i.e. through March of1997). At that time and assuming the analytical results are relatively consistent, the wellswill be incorporated into the semi-annual monitoring schedule.
The original PCAP monitor wells (MW 10,11,103D and 102S, and east and westrecharge wells)will continued to be sampled on a semi-annual basis throughout the secondfive year post closure monitoring period.
Water level will be measured in all wells during each sample event
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List of References
Area C Assessment Report,Industrial Waste Control Site(Forbes, January 1994).
Draft Report Corrective Action Study,Industrial Waste Control Site(IT, Austin, Texas, August 1987).
Industrial Waste Control Site, Final Draft, Endangerment Assessment,(U.S.EPA/CH,M ?11, March 31,1986).
Industrial Waste Control Site, Final Draft, Feasibility Study Report,(U.S.EPA/CH^M Hill, June 3, 1986).
Industrial Waste Control Site, Final Draft, Remedial Investigation Report,(U.S.EPA/CH^M Hill, March 31,1986).
Industrial Waste Control Site, Final Draft, Remedial Investigation Report,Volume I & II, (U.S.EPA/CH^M ?11, March 31,1986).
IWC Monitor Well and Piezometer Corrective Action Report,Industrial Waste Control Site(Fbrbes, December 1991).
MW-12, MW-13, MW-14 and P-13 New Well Installation Report.Industrial Waste Control Site(Forbes, August 1995).
Post-Closure Monitoring Report,June 1991 Sampling Event, First Quarter,(IT, Austin, Texas. August 1991).
Post-Closure Monitoring Report,November 1991 Sampling Event, Second Quarter,(IT, Austin, Texas. January 1992).
Post-Closure Monitoring Report,December 1991 Sampling Event, Third Quarter,(IT, Austin, Texas, February 1992).
Post-Closure Monitoring Report,March 1992 Sampling Event, Fourth Quarter,(IT, Austin, Texas, May 19,1992).
Post-Closure Monitoring Report,June 1992 Sampling Event, Fifth Quarter,(IT, Austin, Texas, August 20,1992).
Post-Closure Monitoring ReportSeptember 1992 Sampling Event, Sixth Quarter,(Forbes, November 1992).
Post-Closure Monitoring Report,December 1992 Sampling Event, Seventh Quarter,(Forbes, January 1993).
006679
List of References(continued)
Post-Closure Monitoring Report,March 1993 Sampling Event, Eighth Quarter,(Forces, June 1993).
Post-Closure Monitoring Report,July 1993 Sampling Event, Ninth Quarter,(Forbes, July 1993).
Post-Closure Monitoring Report,September 1993 Sampling Event, Tenth Quarter,(Forces, November 1993).
Post-Closure Monitoring Report,December 1993 Sampling Event, Eleventh Quarter,(Forbes, December 1993).
Post-Closure Monitoring Report,March 1994 Sampling Event, Twelfth Quarter,(Forbes, May 1994).
Post-Closure Semi-Annual Monitoring Report,September 1994 Sampling Event, Thirteenth Quarter,(Forbes, November 1994).
Post-Closure Semi-Annual Monitoring Report,March 1995 Sampling Event, Fourteenth Quarter,(Forces, May 1995).
Post-Closure Supplemental Quarterly Monitoring Report,June 1995 Sampling Event, Fifteenth Quarter,(Forces. July 1995).
Post-Closure Semi-Annual Monitoring Report,September 1995 Sampling Event, Sixteenth Quarter,(Forbes, November 1995).
Post-Closure Supplemental Quarterly Monitoring Report,January 1996 Sampling Event, Seventeenth Quarter,(Forces, January 1996).
Post-Closure Monitoring Report,March 1996 Sampling Event, Eighteenth Quarter,(Forces, Date Pending).
Site Remedial Report, Volume I and II,Industrial Waste Control Site(IT. Austin. Texas, March 1992).
Statistical Analyses to Establish Constituent ActionLimits for Detection Monitoring,(Ross, June 1994), {Refer to Post-Closure Monitoring Report, Thirteenth Quarter}.
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IWC FROM SOUTH ABOVE LONG RIDGE
SITE LOOKING DUE SOUTH, BACKGROUND IS LONG RIDGE
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IWC FROM SOUTH ABOVE LONG RIDGE
SITE LOOKING DUE SOUTH, BACKGROUND IS LONG RIDGE
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February 8, 1993
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