EPA Region 5 Records ctr.

II111111111I11111 IIIII IIIII 1111\I\IllllI304494

THIRD FIVE-YEAR REVIEW REPORT

for

Twin Cities Air Force Reserve Base,Small Arms Range Landfill

Minneapolis, Minnesota

June 2008

PREPARED BY:

934th Airlift Wing, U.S. Air Force ReserveMinneapolis-St. Paul International Airport Air Reserve Station

imothy E. Tarchick, Colonel, USAFRCommander934th Airlift WingMinneapolis-St. Paul International Airport Air Reserve Station

Concurrence:

(2Mc-~Richard C. Karl, DirectorRegion 5 Superfund DivisionUnited States Environmental Protection Agency

Date:

Date:

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Table of Contents

List of Acronyms

Executive Summary

Five-Year Review Summary Form

I. Introduction 5

II. Site Chronology 7

III. Background 7Physical Characteristics 7Land and Resource Use 8History of Contamination 8Initial Response 8Basis for Taking Action 9

IV. Remedial Actions 9Remedy Selection 9Remedy Implementation 9Institutional Controls 10System Operation and Maintenance (O&M) 13

V. Progress Since the Last Five-Year Review 13Issues and Recommendations from Last Five-Year Review 13Data Collection 13Water Quality Results for Groundwater 14Water Quality Results for Surface Water 14Trend Analysis 15Groundwater Elevation, Flow Direction and Gradients 17Effectiveness of Access Restrictions and Site Maintenance 17

VI. Five-Year Review Process 17Administrative Components 17Community Notification and Involvement 18Document and Data Review 18Site Inspection 18

VII. Technical Assessment 18Question A: Is the remedy functioning as intended by the decision documents? 18Question B: Are the exposure assumptions, toxicity data, cleanup levels, and 20remedial action objectives used at the time of the remedy selection still valid?Question C: Has any other information come to light that could call into question 22the protectiveness of the remedy?

VIII. Issues

IX.

X.

XI.

Recommendations and Follow-up Actions

Protectiveness Statement

Next Review

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Appendices

Appendix 1 - List of Documents ReviewedAppendix 2 - Figures

Figure 1 - Site Location MapFigure 2 - Site Map

Appendix 3 - TablesTable 1- Groundwater Chemicals of Concern and Applicable or Relevant and

Appropriate Requirements, Small Arms Range LandfillTable 2 - Surface Water Chemicals of Concern and Applicable or Relevant and

Appropriate Requirements, Small Arms Range LandfillTable 3 - Groundwater Chemicals of Concern - 2007 Monitoring Results, Small

Arms Range LandfillTable 4 - Surface Water Chemicals of Concern - 2007 Monitoring Results, Small

Arms Range LandfillTable 5 - History of Nickel Results at Well MW8A, Small Arms Range Landfill

Appendix 4 - Public and Regulatory Agency Notifications

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ACRONYM

ARARsARSCERCLA/SARA

CLCOCFFAFSHRLICMCLMCLGMSP lAPMPCAMWNCPNGVDNPLO&MRALRODRD/RARIRPMSARLSVOCTBCTCAFRTCLTDSTLUSAFUSEPAUU/UEVOC

List of Acronyms

NAME OR TERM

Applicable or Relevant and Appropriate RequirementsAir Reserve StationComprehensive Environmental Response, Compensation andLiability Act/Superfund Amendments and Reauthorization Act of1986 (Superfund)Compliance LevelContaminant of ConcernFederal Facility AgreementFeasibility StudyHealth Risk LimitInstitutional ControlMaximum Contaminant LevelMaximum Contaminant Level GoalMinneapolis/St. Paul International AirportMinnesota Pollution Control AgencyMonitoring WellNational Contingency PlanNational Geodetic Vertical DatumNational Priorities ListOperation and MaintenanceRecommended Allowable LimitRecord of DecisionRemedial Design/Remedial ActionRemedial InvestigationRemedial Project ManagerSmall Arms Range LandfillSemi-volatile Organic CompoundTo Be ConsideredTwin Cities Air Force ReserveTarget Compound ListTotal Dissolved SolidsTrigger LevelUnited States Air ForceUnited States Environmental Protection AgencyUnlimited Use or Unrestricted ExposureVolatile Organic Compound

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Executive Summary

This report documents the third Five-Year Review for the Small Arms Range Landfill (SARL),located at the Minneapolis-St. Paul International Airport Air Force Reserve Station (Twin Cities AirForce Reserve). In 2007, Braun Intertec Corporation, consultant for the Twin Cities Air ForceReserve, completed confirmatory sampling and analysis of groundwater and surface water at theSARL as pa11 of the third Five Year Review. The results of the confirmatory sampling aredocumented in Braun Intertec Corporation's September 2007 report, titled Third Five-Year Reviewfor Small Arms Range Landfill, 934th Airlift Wing, Minneapolis-St. Paul lAP ARS. Based on theseresults, and an evaluation ofthe access restrictions and site maintenance, the remedial actions at theSARL are protective and the site is protective of human health and the environment.

Five-Year Review Summary Form

SITE IDENTIFICATION

Site name (from WasteLAN): Twin Cities Air Force Reserve Base (Small Arms FiringRange)

EPA ID (from WasteLAN): MN8570024275

NPL status: DFinal ~ Deleted 0 Other (specify)

Remediation status (choose all that apply): 0 Under Construction ~ Operating 0 Complete

MUltiple QUs?* 0 YES ~ NO Construction completion date: 02/05/1993(PCOR 09/24/92)

Has site been put into reuse? 0 YES ~ NO

REVIEW STATUS

Lead agency: 0 EPA 0 State 0 Tribe ~ Other Federal Facility (U.S. Air Force Reserve)

Author name: Douglas Yocum

Author title: Physical Scientist IAuthor affiliation: U.S. Air Force Reserve

Review period: May 2007 to June 2008

Date(s) of site inspection: 05/31 - 06/01/2007 and 11/15/2007

..["au" refers to operable unit.]

Five-Year Review Summary Form (continued)

Type of review:IRI Post-SARA 0 Pre-SARA o NPL-Removal onlyo Non-NPL Remedial Action Site o NPL StatefTribe-leado Reqional Discretion

Review number: 0 1 (first) 0 2 (second) IRI 3 (third) 0 Other (specify)

Triggering action:o Actual RA Onsite Construction at au # o Actual RA Start at OU#__o Construction Completion -- IRI Previous Five-Year Review Reporto Other (specify)

Triggering action date (from WasteLAN): 07/31/2003

Due date (five years after triggering action date): 07/31/2008

Issues:

There are no current contamination issues at the site. The second Five-Year Review Report for theSARL, dated July 31, 2003, concluded that the selected remedial action, consisting of naturalattenuation of groundwater contamination, physical access restrictions, site maintenance andmonitoring, had achieved the remediation goals set forth in the March 31, 1992 Record of Decision(ROD). The SARL was deleted from the Superfund National Priorities List (NPL) on December 16,1996.

Analytical results from samples collected since 1988 indicate that monitoring is no longer necessary atshallow well MW7A, deep wells MW7B, MW8B, and MW9B, and for surface water in the retention pondadjacent to the SARL. Applicable or Relevant and Appropriate Requirements (ARARs) have not beenexceeded in groundwater sampled from MW7A since February 1993. No ARAR has ever beenexceeded in groundwater sampled from MW7B. An ARAR has been exceeded only once ingroundwater sampled from MW8B, in a 1997 result that was qualified as unusable due to major qualitycontrol deviation. ARARs have not been exceeded in groundwater sampled from MW9B since 1995.Additionally, MW7B, MW8B, and MW9B are all deep aquifer wells. Upward vertical gradients andsoutheasterly horizontal gradients, calculated from groundwater measurements taken at the site from1988 through 2007, have consistently been interpreted as solid evidence that groundwater dischargesfrom the shallow aquifer into the Minnesota River, making impact to the deep aquifer from the siteunlikely.

In surface water sampled from the retention pond adjacent to the SARL since 1988, the only instanceof COC values exceeding any surface water ARAR occurred in 2002. Beryllium values in samplesfrom both surface water sampling locations were above the ARAR. However, both concentrationswere qualified as blank contamination due to the detection of beryllium in the field blank for themonitoring event.

In analytical results of 2007 groundwater samples from shallow aquifer wells MW8A and MW9A, thenickel concentration at MW8Aand the arsenic concentration at MW9A exceeded groundwater ARARs.Both parameters were also detected at lower concentrations in groundwater from the background wellMW06.

Condition of each of the seven monitoring wells was evaluated in conjunction with the 2007 monitoringevent. All well casings and surface seals were visually observed to be in good condition, and noexterior repair or rehabilitation of the wells is currently necessary for the wells to remain usable.However, excessive thicknesses of sediment were encountered within four of the monitoring wells(MW06, MW7A, MW7B, and MW9B).

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Five-Year Review Summary Form (continued)

Recommendations and Follow-up Actions:

Two remediation goals were noted in the ROD: 1) reduce COC concentrations in the groundwater tomeet the respective ARARs and ensure that groundwater migrating from the SARL to the MinnesotaRiver does not exceed Water Quality Criteria for freshwater species; and 2) limit the potential for theSARL to be exposed directly to human receptors or local fauna. The 2007 sampling results confirmedthe results of the monitoring program conducted during 1993, 1994, 1995, 1997, and 2002, whichestablished that natural attenuation had proven to be an effective remedial agent at the SARL.Additionally, the U.S. Air Force (USAF) has maintained, and will continue to maintain on a permanentbasis, the established site access restrictions and site maintenance program. As a result, the secondremediation goal of limiting the potential of direct exposure to human receptors or local fauna has alsobeen met.

As discussed in the preceding "Issues" section, monitoring of shallow well MW7A and deep wellsMW7B, MW8B, and MW9B should be discontinued, and these wells should be abandoned and sealedin accordance with state code requirements. Surface water sampling of the retention pond adjacent tothe SARL should also be discontinued.

The next Five-Year Review should include confirmatory water quality monitoring of inorganic COCs atbackground well MW06 and shallow wells MW8A and MW9A, as well as confirmation of site accessrestrictions and site maintenance. Prior to future sampling, sediment built up in MW06 should beremoved, and this well should also be redeveloped.

Protectiveness Statement(s):

Because the remedial actions at the Twin Cities Air Force Reserve Base SARL are protective, the siteis protective of human health and the environment.

Condition of each of the seven monitoring wells was evaluated in conjunction with the 2007 monitoringevent. All well casings and surface seals were visually observed to be in good condition, and noexterior repair or rehabilitation of the wells is currently necessary for the wells to remain usable.However, excessive thicknesses of sediment were encountered within four of the monitoring wells(MW06, MWlA, MWlB, and MW9B).

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Five-Year Review Report

I. Introduction

The SARL is a two acre site located near the Minneapolis-St. Paul International Airport (MSP lAP)(Figure 1). The site is bounded to the south by Interstate 494 and to the east by the Minnesota River.A storm water retention pond is located between the SARL and the Minnesota River, as shown onthe site map (Figure 2). The SARL is within the 100 year flood plain for the Minnesota River and isprone to flooding, according to data produced in 2004 by the U.S. Army Corps ofEngineers and theU.S. Geological Survey. There is no residential property located within a one mile radius of theSARL.

USAF previously conducted reviews in 1997 and 2002, both of which documented monitoringresults and concluded that natural attenuation had proven to be effective at the SARL. USEPAconcurred with the results ofthese previous reports prepared by the USAF, and statutory Five YearReview Reports pursuant to CERCLA were signed by USEPA Region 5 on April 4, 1998, and July31, 2003. Since the completion of the second Five-Year Review, the USAF contracted foradditional confirmatory monitoring during 2007, for use in the third Five-Year Review required bythe National Contingency Plan (NCP).

The SARL ROD established remediation criteria for eighteen contaminants ofconcern (COCs) forgroundwater, including twelve metals, five volatile organic compounds (YOCs), and onesemivolatile organic compound (SYOC). The ROD also established trigger levels (TLs) forgroundwater contaminants to evaluate the need for additional action. The trigger levels were set attwice the value ofspecified compliance levels (CLs) for seven metals (arsenic, beryllium, cadmium,lead, nickel, seleneium, and vanadium) and one YOC (trichloroethene). The groundwater COCs andARARs for the SARL are identified in Table 1.

Finally, the ROD also established seven COCs for surface water, including six metals and one YOC.TLs and CLs were not established for surface water. The surface water COCs and ARARs for theSARL are identified in Table 2.

The Purpose of the Review

The purpose ofthis Five-Year Review is to determine whether the remedy at the SARL continues tobe protective of human health and the environment. In addition, this Five-Year Review reportidentifies issues found during the review, if any, and provides recommendations to address them.

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Authority for Conducting the Five-Year Review

USAF is preparing this Five-Year Review pursuant to the Comprehensive Environmental Response,Compensation, and Liability Act (CERCLA) Section 121 and the National Contingency Plan (NCP).CERCLA Section 121 states:

Ifthe President selects a remedial action that results in any hazardous substances, pollutants, orcontaminants remaining at the site, the President shall review such remedial action no less oftenthan each five years after the initiation ofsuch remedial action to assure that human health andthe environment are being protected by the remedial action being implemented. In addition, ifupon such review it is the judgement of the President that action is appropriate at such site inaccordance with section 104 or 106, the President shall take or require such action. The Presidentshall report to the Congress a list offacilitiesfor which such review is required, the results ofallsuch reviews, and any actions taken as a result ofsuch reviews.

USEPA interpreted this requirement further in the NCP; 40 Code of Federal Regulations (CFR)Section 300.430(f)(4)(ii) states:

Ifa remedial action is selected that results in hazardous substances, pollutants, or contaminantsremaining at the site above levels that allow for the unlimited use and unrestricted exposure, thelead agency shall review such action no less often than every five years after the initiation oftheselected remedial action.

Who Conducted the Five-Year Review

USAF, through its contractor, Braun Intertec Corporation, conducted all of the sampling that wasnecessary for this statutory Five-Year Review. Methods, results and Braun Intertec Corporation'sconclusions are documented in a September 2007 report, titled Third Five-Year Review for SmallArms Range Landfill, 934th Airlift Wing, Minneapolis-St. Paul lAP ARS. The USAF representative,Mr. Douglas Yocum, 934th Airlift Wing Environmental Section, Minneapolis-St. Paul InternationalAirport Air Reserve Station, and Mr. Tom Barounis, Remedial Project Manager (RPM), USEPARegion 5, performed an inspection ofthe SARL site on November 15,2007. In addition, the USAFrepresentative reviewed relevant documents, including the ROD and previous Five-Year Reviewreports for the site, and completed this statutory Five-Year Review based upon the informationobtained from these sources and activities.

Other Review Characteristics

This is the third Five-Year Review for the SARL site. The triggering action for this review is thesignature date ofthe previous Five-Year Review.

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II. Site Chronology

EventNational Priorities List ListingFederal Facility AgreementMinnesota Request for Response ActionRemedial InvestigationlFeasibility Study completeRecord of Decision signatureRemedial Design startRemedial Design completeRemedial Action startRemedial Action complete/Preliminary Close-out ReportFinal Closeout ReportDeIetion from National Priorities ListFirst Five-Year ReviewDeletion from Minnesota Permanent List of PrioritiesSecond Five-Year Review

III. Background

Physical Characteristics

Date7/22/8711/06/8911/28/893/31/923/31/924/01/928/25/928/31/929/24/928/29/9612/16/964/02/986/30/987/31/03

The SARL is located within the Mississippi Valley outwash plain of the Outwash ValleyPhysiographic Region. Two distinct topographic areas dominate the relief, an upland area and abottomland (floodplain) area. The upland area is relatively flat, sloping gently eastward toward theMississippi and Minnesota Rivers, with ground surface elevations ranging from approximately 800to 850 feet NGVD (National Geodetic Vertical Datum). Locally, the topographic reliefbetween theupland area and the floodplain is marked by an 80-foot escarpment in the area west of the SARL.The floodplain area ranges in elevation from approximately 690 to 730 feet NGVD. The SARL lieswithin the floodplain of the Minnesota River which overlies a buried bedrock valley.

The site is underlain by an unconsolidated surficial aquifer comprised ofa shallow and deep aquifer.The shallow aquifer extends from the area beneath the SARL to the Minnesota River, and consists ofa gravelly sand layer underlain by heterogeneous unconsolidated materials comprised ofsilty sand,peat, clay, silty sandy clay, and sandy clay, which generally exhibit low permeability. These lowpermeability materials combine to form a confining stratum that separates the underlying aquifer(deep aquifer) from the shallow aquifer. An apparent discontinuity exists in the lateral extent oftheconfining layer and underlying materials to the west of the site. This discontinuity is due to thepresence of the St. Peter Sandstone bedrock formation in this western portion of the site. The St.Peter Sandstone has been eroded away east ofthe SARL, resulting in a bedrock valley that has beenfilled primarily by fluvial depositional processes.

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Land and Resource Use

The SARL is located in the southeast quarter of the southwest quarter of the southwest quarter ofSection 32, Township 28 North, Range 23 West in Hennepin County, Minnesota. The site is withinthe boundaries ofUSAF property at Minneapolis-St. Paul International Airport Air Reserve Station,and is bounded to the south by Interstate 494 and to the east by the Minnesota River. MSP lAP is tothe north and west of the USAF property on which the SARL is located. There is no residentialproperty located within a one mile radius ofthe SARL.

History of Contamination

The site of the SARL was acquired by the USAF in 1955 and served as the main landfill fromapproximately 1963 to 1972. General refuse and industrial wastes formed the bulk of wastematerials deposited at the SARL. The industrial wastes are believed to have included approximately100-gallons of paint sludge, 800 pounds of paint filters and 100 to 200 gallons of leaded aviationgasoline (AVGAS) sludge. Between 1963 and 1969, all refuse was burned in a pit located at thesouthwestern edge of the landfill (see Figure 2). The SARL was closed in 1972, with native soilused to cover the fill area.

The SARL was first identified as a possible hazardous waste site in 1983 in the Phase I InstallationRestoration Program Records Search report. Preliminary studies ofthe site indicated the presence oflow concentrations of groundwater contaminants which were possibly migrating from the SARL.Based upon these preliminary studies, the site was placed on the NPL in 1987. A remedialinvestigation (RI) was conducted in 1988 and 1989 to further characterized the site and obtain thedata necessary for an evaluation of remedial alternatives. The RI indicated that low levels ofinorganic contaminants had been released from the SARL to the soil and groundwater.

A Federal Facility Agreement (FFA), signed by the USAF in October 1989 and by USEPA inNovember 1989, established the procedural framework for remedial action at the site. A feasibilitystudy (FS) was completed in 1991 and a ROD selecting the FS preferred alternative of naturalattenuation of groundwater contaminants in conjunction with access restrictions, site maintenanceand monitoring, was signed by the USAF in January 1992 and by U.S.EPA in March 1992. TheMinnesota Pollution Control Agency (MPCA) concurred with the ROD.

The ROD stipulated that, at a minimum, monitoring of site groundwater and surface water qual itywould take place every two months for a minimum two-year period. The ROD also stated that themonitoring program could be modified, or an alternative remedial action enacted, to reflect the firstyear sampling results. After completing the second year ofsampling, the analytical data were to bereviewed to determine requirements for future sampling work.

Initial Response

Neither USAF nor USEPA performed any removal actions or other initial remedial measures at thesite.

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Basis for Taking Action

As previously noted, the RI indicated that low levels of inorganic contaminants, metals in particular,had been released from the SARL to the soil and groundwater. Based on the results of the RI,ARARs were established in the ROD for groundwater COCs and surface water COCs. COCs forgroundwater included twelve metals, five volatile organic compounds, and one semi-volatile organiccompound. COCs for surface water included six metals and one volatile organic compound.Theroundwater COCs and surface water COCs identified in the ROD are listed in Tables 1 and 2 inAppendix 3.

The purpose of the remedy selected in the ROD was to prevent risk to human health and theenvironment through direct contact with landfill contaminants and to prevent risk for exposure tocontaminants in the groundwater.

IV. Remedial Actions

Remedy Selection

The Remedial Action selected for the SARL in the ROD was natural attenuation of groundwatercontaminants in conjunction with access restrictions, site maintenance and monitoring. Theremedial action objectives were to prevent risk to humans or the environment through contact withlandfill contaminants and to prevent risk to humans or environmental receptors from contaminants ingroundwater.

The selected remedy established cleanup levels for the COCs in groundwater based upon the SafeDrinking Water Act MCLs. Also established as cleanup goals were the Clean Water Act AmbientWater Quality Criteria and the State of Minnesota Recommended Allowable Limits (RALs) fordrinking water contaminants.

Remedy Implementation

The ROD-required site access restrictions included access control, fencing with locked gates aroundthe entire site, and warning signs. These access restrictions were installed by the USAF in 1992.

The first year of monitoring was completed in 1993 with the results presented in the Final 1993Annual Water Quality Rep0l1, which concluded that natural attenuation was serving as an effectiveremedial action at the SARL. It also concluded that the decreasing concentrations ofVOCs, SVOCsand metals justified a modification of the monitoring program. USEPA and MPCA approved thefollowing modifications in May 1994:

• Monitoring MW3R and MW05 for water level only;

• Designating MW06 as the background welI for the SARL;

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• Reducing the sampling frequency from bi-monthly to quarterly; and

• Reducing the analyte list by eliminating five indicator parameters (calcium,magnesium, potassium, sodium and total dissolved solids (TDS).

The second year ofmonitoring was completed in 1994 with the results presented in the Final 1994Annual Monitoring Report. Conclusions in this report were consistent with the prior year's report.After reviewing groundwater monitoring and historical contaminant trends, the USAF concludedthat the selected remedy had effectively achieved remedial action objectives and requested thatUSEPA initiate procedures to remove the SARL from the NPL.

Three additional rounds ofgroundwater monitoring were conducted in January, April and July 1995.All monitoring results were consistent with the 1993 and 1994 annual monitoring results. Therecommendations ofthe 1995 Annual Monitoring Report were consistent with those presented in the1994 Annual Monitoring Report. The SARL was deleted from the NPL on December 16, 1996.

In May 1997 confirmatory monitoring was completed as part of the first Five-Year Review.Monitoring results presented in the 1997 Five-Year Review Report indicated that concentrations ofCOCs in groundwater continued to decrease and that surface water concentrations continued to fallbelow detection limits. The 1997 Five-Year Review Report concluded that all contaminantconcentrations in groundwater were in compliance with ARARs, except for one side-gradient well inwhich selenium was detected at a concentration of 11.7 ppb. This exceeded the MinnesotaDepartment of Health RAL (10.0 ppb). However, it did not exceed the Minnesota Health RiskLimits (HRLs) value 000 ppb, which was promulgated in 1995 and which superseded the RALs.The first Five-Year Review recommended that groundwater and surface water monitoring bediscontinued until the next periodic Five-Year Review. USEPA subsequently concurred withabandonment and sealing of five of the site monitoring wells (MWOl, MW02, MW3R, MW04,MW05).

In May 2002 confirmatory monitoring was completed as part ofthe second Five-Year Review. Themonitoring results showed that beryllium and nickel were the only inorganic COCs detected atconcentrations above an ARAR during May 2002. The beryllium concentrations did not exceed theCL established in the ROD, and all ofthe detected beryllium concentrations were qualified as blankcontaminated. Nickel concentrations detected in two wells (73 ppb at MW06 and 300 ppb atMW8A) exceeded the 70 ppb CL established in the ROD. All surface water analyte concentrationswere less than the ARARs, with the exception of beryllium in both surface water samples. Theseberyllium results were also qualified as blank contaminated. The second Five-Year Review Reportconcluded that the 2002 sampling results confirmed the results ofthe previous monitoring program,which established that natural attenuation had proven to be an effective remedial agent at the SARL.

Institutional Controls

Institutional Controls (ICs) are required to ensure the protectiveness of the remedy. ICs are non-

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engineered instruments, such as administrative and/or legal controls, that help minimize the potentialfor exposure to contamination and protect the integrity of the remedy. Compliance with ICs isrequired to assure long-term protectiveness for any areas which do not allow for unlimited use orunrestricted exposure (UUfUE). The entire site consists ofa landfill which has been covered withsoil as part ofthe final remedy. Therefore, the entire site does not support DUfUE. The table belowsummarizes institutional controls for the restricted area. The cleanup goals for the landfill werebased on limited commercial or industrial use (containment) and restrictions on groundwater use atthe site.

Institutional Controls SummaMedia, Remedy Components &Areas that'd9I,1ot Support YU/LIEBased on Current COIlditions .Small Arms Range LandfillProperty - approximately two­acre soil cover

Ob'ectives oncProhibit interferencewith landfill cap andother remedialcomponents andprohibit residentialuses.

Iit1~ofirtstituiiogal,Contr?L .. '. 'Instrument 1m leniented:~., ~:,.,~ .. ,:::,- Governmental ownership andcontrol;-General Plan;-ROD and FFA recorded in landrecord's file which requires thatdeed restrictions get recordedu on transfer of land

Groundwater under Small Arms Prohibit groundwaterRange Landfill Property - current usagearea that exceeds groundwatercleanup standards.

-Governmental ownership andcontrol;-General Plan;- ROD and FFA recorded in landrecord's file that deed restrictionsget recorded upon transfer ofland

ROD Requirements: The March 31, 1992 ROD selected Alternative 4 which included the need forsite access restrictions and ICs. The ROD for the site required that the necessary deed restrictionsrequired by CERCLA, Section 120 (h)(3) would be implemented ifand when the property is placedunder the ownership of a person or other entity of federal government because a deed does notcurrently exist for the property. The ROD also stated the following:

"Other restrictions to be imposed will be institutional, such as deed restrictionslimiting future development ofthis site, if the property is relinquished by the USAF,and deed restrictions limitingfuture groundwater usage. These deed restrictions willbe imposed in the eventuality that USAF releases the property once a deed is prepared.Additionally, all requirements ofSection 120 ofCERCLA for notification and deednotation will be met. These requirements are imposed on federal facilitiesrelinquishing property on which hazardous substances were storedfor more than 1year or where they were disposed of or released. Included in the requirements isprovision ofa description ofhazardoliS substances stored, disposed of, or released, the

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general time frame of the activity, and the type and quantity of materials and anyremedial action taken. The Air Force must also warrant in the deed notation thatremedial action necessary to protectpublic health and the environment has been takenand any additional remedial action found to be necessary in the future will beconducted by the federal government."

Site Ownership and ICs:The property on which the SARL is located has been under continuous federal governmentownership since the mid-19th century, and currently remains under federal government ownership,with administration and control by the USAF. No deed exists for the property. Release or transferof the property out of USAF control is neither planned nor forecasted.

Documentation of the requirement for a deed restriction, limiting future development andgroundwater usage if the property is ever excessed by the USAF, is included in the Minneapolis-St.Paul Air Reserve Station General Plan. The General Plan is a document prepared as a guide for thestation's long-range development, which provides USAF decision-makers with a concise assessmentofon-station conditions as of2007; recommendations for improvements and future development ofthe station as a whole; and identification ofconstraints on development and land use. It is not a landuse plan solely for the SARL site, nor is it an operational plan. In addition to documenting therequirement for a deed restriction limiting future development and groundwater usage ifthe propertyis ever transferred to another owner, the General Plan also documents the need for access restrictionand fence at the SARL site as a constraint to future land use and development.Access controls, in the form offencing and warning signs, are in place at the SARL. These controls,along with regular site patrol by USAF security personnel, are effective measures to limit access tothe SARL.

Additionally, to ensure that the ICs prescribed for the SARL remain known to future USAFpersonnel and are considered in any land use planning or real property disposal decisions concerningthe SARL, copies of the ROD and 1989 FFA between the USAF and USEPA have beenincorporated in the installation's Real Property file for the tract of property containing the SARL.

Current Compliance: Based on inspections and interviews, neither USAF nor USEPA are aware ofany wells installed within the groundwater restricted area, or site uses which are inconsistent withthe landfill. The access restrictions and ICs are functioning as intended.

Long Term Stewardship: Long term protectiveness at the site requires compliance with land andgroundwater use restrictions. Compliance with effective ICs will be ensured through long-termstewardship by maintaining and monitoring effective ICs as well as maintaining the site remedycomponents. The requirement for continued periodic inspections and site maintenance wasgenerally stated in the Superfund Final Closeout Report, Twin Cities Air Force Reserve Base SmallArms Landfill, NPL #054L, Section V, USEPA, August 29, 1996. The USAF will consider revisingthe Minneapolis-St. Paul Air Reserve Station General Plan, or developing a separate O&M plan, toidentify specific O&M activities and document the monitoring procedures for the SARL. USAF willnotify USEPA ifany situation or activity is discovered that is inconsistent with the IC objectives or

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use restrictions, or that would interfere with the land use controls. Also, the USAF will notifYUSEPA and MPCA of any anticipated changes in land use.

ICs are In-Place and Effective: IC evaluation activities conducted by the USAF have determinedthat the ICs are in-place and effective. All non-UUIUE areas are addressed effectively byinstitutional controls as determined by IC evaluation activities. The objective(s) of the ICs (e.g.prohibit interference with the landfill soil cap, prohibit residential use, and restrict groundwater useat the site) are being met. A mechanism and party responsible for inspecting and monitoringcompliance with land use restrictions and groundwater restrictions exists at the site.

System Operations/Operation and Maintenance (O&M)

The remedy for the SARL does not include any operating systems, other than data collection forfive-year reviews. Operation and Maintenance (O&M) for the SARL site consists of: a) annual siteinspection to assess the integrity of the landfill native soil cover and fence, and identifY need forrepairs; and b) maintenance of the monitoring wells.

v. Progress Since the Last Review

Issues and Recommendations from Last Five-Year Review

The last Five-Year Review, completed in 2003, did not identifY any issues that prevented theselected remedy from being protective at that time. Recommendations stated in the last Five-YearReview were that the next Five-Year Review should include water quality monitoring andconfirmation of site access restrictions. In addition, interim inspections of the monitoring wellsurface seals were also recommended, with surface seal replacement as appropriate.

Data Collection

Sampling was conducted at seven monitoring wells and two surface water locations during the 2007monitoring event, in accordance with the approved Sampling and Analysis Plan (Field SamplingPlan, Quality Assurance Project Plan, and subsequent modifications). Groundwater samples wereanalyzed for Target Compound List (TCL) VOCs and TCL SVOCs, priority pollutant metals,vanadium and chloride. Surface water samples consisted of grab samples collected from theretention pond.

Field and analytical results were evaluated following the 2007 sampling event to assure thatlaboratory and field quality control objectives established in the Quality Assurance Project Planwere met. For the 2007 monitoring event, the organic data were validated using procedures in"USEPA Contract Laboratory Program National Functional Guidelinesfor Organic Data Review,"(USEPA 1999). The inorganic data were validated using the procedures in "USEPA ContractLaboratory Program National Functional Guidelinesfor Inorganic Data Review," (USEPA 2004).

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Water Quality Results for Groundwater

COCs for groundwater at the SARL include five VOCs (benzene, 2-butanone, 1,2­dichloroethene(cis-), toluene, and trichloroethene), one SY~C (di-n-butylphthalate), and twelvemetals (arsenic, beryllium, cadmium, chromium, copper, lead, mercury, nickel, selenium, silver,vanadium, and zinc). Groundwater monitoring results from the 2007 sampling event aresummarized in Table 3. In general, the concentrations of COCs detected in 2007 were spatiallyconsistent with historical data.

Volatile Organic Compounds

Toluene was the only VOC COC detected in groundwater samples during 2007. Toluene wasdetected at estimated concentrations above the Instrument Detection Limit, but below the ReportingLimit, in samples from monitoring wells MW06, MW7B, and MW9B. ARARs. for groundwaterVOC COCs were not exceeded during the 2007 monitoring event.

Semi-volatile Organic Compounds

The single SVOC COC was not detected in groundwater samples during the 2007 monitoring event,and therefore the ARAR for the groundwater SVOC COCs was not exceeded.

Inorganic Compounds

Arsenic, nickel and selenium were detected in samples collected from most ofthe monitoring wellsduring the 2007 monitoring event, including the background well MW06. The arsenic concentrationat MW9A and the nickel concentration at MW8A exceeded the groundwater ARARs. The seleniumconcentration at MW8A also exceeded the groundwater ARAR, but was a qualified result.Concentrations of these COCs detected at other wells were below groundwater ARARs. All otherinorganic COCs were detected sporadically in groundwater samples collected from the monitoringwells during the 2007 monitoring event, all at concentrations below the groundwater ARARs.

Water Quality Results for Surface Water

COCs for surface water at the SARL include one VOC (toluene) and six metals (beryllium, iron,lead, silver, vanadium and zinc). Surface water monitoring results from the 2007 monitoring eventare summarized in Table 4.

Volatile Organic Compounds

Toluene was detected in both surface water samples collected during the 2007 monitoring event.Both results were estimated concentrations less than 1 /lg/L, significantly below the current ARARof 1000 /lg/L.

14

r-

Inorganic Compounds

Zinc and vanadium were the only inorganic COCs detected in surface water samples collectedduring the 2007 monitoring event. The zinc results were estimated concentrations of 0.83 Ilg/L atSWL1 and 1.5 Ilg/L at SWL2, both significantly below the current ARAR of 379 Ilg/L. Thevanadium result was an estimated concentration of 0.58 Ilg/L at SWL 1, significantly below thecurrent ARAR of 50 Ilg/L.

Trend Analysis

Monitoring Well MW06

MW06 is a side-gradient well that was identified as the background monitoring well in 1994.Results for COCs detected during the 2007 monitoring event do not demonstrate any definitivetrends. Results for copper and nickel were lower in 2007 than during 2002. The 2007 result forvanadium was lower than any ofthe previous intermittent detections. The 2007 detection ofarsenicwas the only time that this COC has been detected at this well. Toluene was the only VOC orSVOC COC detected. Its concentration was comparable to previous intennittent detections.

Monitoring Well MW7A

MW7A is a down-gradient shallow aquifer well. Results for inorganic COCs detected during the2007 monitoring event do not demonstrate any definitive trends. The result for nickel was lower in2007 than during 2002. The result for selenium was higher in 2007 than during 2002, but the 2007concentration was a qualified result. The 2007 result for vanadium was lower than any of theprevious intermittent detections. The 2007 detection ofarsenic was the only time that this COC hasbeen detected at this well. VOC and SVOC COCs were not detected in 2007.

Monitoring Well MW7B

MW7B is a deep aquifer well. Results for COCs detected during the 2007 monitoring event do notdemonstrate any definitive trends. Results for cadmium and nickel were lower in 2007 than during2002. The result for selenium was higher in 2007 than during previous events, but the 2007concentration was a qualified result. The 2007 result for vanadium was lower than any of theprevious intermittent detections. The 2007 detection ofarsenic was the only time that this COC hasbeen detected at this well, and the 2007 detection ofcopper was preceded by a single detection, at ahigher concentration, in 1994. The 2007 detection oftoluene was the only time that this COC hasbeen detected at this well. No other VOC and SVOC COCs were detected in 2007.

Monitoring Well MW8A

MW8A is a down-gradient shallow aquifer well. Results for COCs detected during the 2007monitoring event indicate an increasing concentration trend for one COC, nickel. The concentration

15

of nickel detected in samples from this monitoring well has increased during each Five-YearReview. The history ofnickel results at this well is presented in Table 5. Results for all other COCsdetected during the 2007 monitoring event do not demonstrate any definitive trends. The result forselenium was higher in 2007 than during 2002, but the 2007 concentration was a qualified result.The 2007 results for vanadium and zinc were lower than previous detections at this well, but had notbeen detected since 1995. The 2007 detection of copper was lower than any of the previousintermittent detections at this well. The 2007 detection of arsenic was higher than previousintermittent detections at this welL VOC and SVOC COCs were not detected in 2007.

Monitoring Well MW8B

MW8B is a deep aquifer well. Results for COCs detected during the 2007 monitoring event do notdemonstrate any definitive trends. The 2007 results for chromium, copper, and vanadium werelower than any of their previous intermittent detections. The 2007 result for nickel was within therange of previous intermittent detections at this well. The 2007 detection of arsenic was the onlytime that this COC has been detected at this well. Selenium was also detected for the first time atthis well, but the 2007 concentration was a qualified result. The 2007 detection of silver waspreceded by a single detection, at a higher concentration, in 1988. VOC and SVOC COCs were notdetected in 2007.

Monitoring Well MW9A

MW9A is a down-gradient shallow aquifer well. Results for COCs detected during the 2007monitoring event do not demonstrate any definitive trends. The 2007 detection of arsenic washigher than previous intermittent detections at this well. The 2007 result for nickel was within therange ofprevious intermittent detections at this well. The 2007 result for vanadium was lower thanany of the previous detections. VOC and SVOC COCs were not detected in 2007.Monitoring Well MW9B

MW9B is a deep aquifer well. Results for COCs detected during the 2007 monitoring eventdemonstrate decreasing concentration trends. The 2007 result for arsenic was comparable to thesingle previous detection in 1993. The 2007 results for chromium, copper, nickel, and vanadiumwere lower than any of their previous detections. The 2007 result for selenium was higher than itstwo previous detections, but the 2007 concentration was a qualified result. The 2007 detection oftoluene was the only time that this COC has been detected at this well. No other VOC and SVOCCOCs were detected in 2007.

Surface Water Monitoring Location SWL 1

The location is at the northeastern edge of the retention pond adjacent to the SARL. Results forCOCs detected during the 2007 monitoring event are consistent with previous results for thissampling point. The 2007 result for vanadium was lower than any of the previous intermittentdetections. The 2007 result for zinc was also lower than the concentrations typically detected. Theestimated concentration of toluene was comparable to the previously detected concentrations.

16

~,

Surface Water Monitoring Location SWL2

The location is at the southern end of the retention pond adjacent to the SARL. Results for COCsdetected during the 2007 monitoring event are consistent with previous results for this samplingpoint. The 2007 result for zinc was lower than the concentrations typically detected. The estimatedconcentration of toluene was comparable to the previously detected concentrations.

Groundwater Elevation, Flow Direction and Gradients

Groundwater elevations were measured in the site monitoring wells during the 2007 monitoringevent. The measurements were used to construct shallow aquifer and deep aquifer contour maps.The contours indicate groundwater flow within the shallow and deep aquifers is generally southeast,toward the Minnesota River. The average horizontal hydraulic gradient across the site wasapproximately 0.02 ftlft in the shallow aquifer, and 0.0 I ftlft in the deep aquifer. The groundwaterelevation measurements were also used to establish that vertical gradients between the shallow anddeep aquifers ranged from 0.13 to 0.23 ftlft, in an upward direction. The upward vertical gradientsand southeasterly horizontal gradients are consistent with historical observations for the site, andsustain the suppositions that groundwater is discharging to the Minnesota River, and that impact tothe deep aquifer from the site is unlikely.

Effectiveness of Access Restrictions and Site Maintenance

Access restrictions enacted as part of the remedial action have been maintained. To date, accessrestrictions have met the threshold criterion of overall protection of human health and theenvironment by ensuring that pathways involving contact with waste materials are not complete. Thesite maintenance program was established to ensure that the integrity ofthe existing soil cover, fenceand monitoring system are maintained. Interim inspections of the monitoring well surface sealswere accomplished in 2004,2005 and 2006. Condition of each of the seven monitoring wells wasthen evaluated in conjunction with the 2007 monitoring event. All well casings and surface sealswere visually observed to be in good condition, and no exterior repair or rehabilitation ofthe wells iscurrently necessary for the wells to remain usable. Conditions observed during the 2007 inspectionsof the site verify that the site has been adequately maintained.

VI. Five-Year Review Process

Administrative Components

This Five-Year Review is based upon the sampling and analytical methods and results documentedin the Third Five-Year Review for Small Arms Range Landfill, 934th Airlift Wing, Minneapolis-St.Paul lAP ARS, Braun Intertec Corporation, September 24, 2007, and upon the site inspectionactivities performed by USEPA and USAF staff on November 15, 2007.

17

Community Notification and Involvement

A public notice was placed in the Minneapolis-Star Tribune, the primary local newspaper, onJanuary 2nd

, 2008, announcing the preparation of this Five-Year Review. The public noticeidentified USAF and USEPA contacts for more information about the review process, identified apublic library location for review ofthe Braun Intertec Corporation report, and provided opportunityfor citizen input into the drafting of this Five-Year Review report. A copy of the publ ic notice isprovided in Appendix 4. No telephonic or written comments, inquiries, or responses of any kindwere received from the public.

Via letter dated December 20th, 2007, the Minnesota Pollution Control Agency was notified of the

Five-Year Review and offered the opportunity to provide input to the drafting ofthis report. A copyof the notification letter is also provided in Appendix 4. The Minnesota Pollution Control Agencymade no reply to the notification letter.

Document and Data Review

The list of documents and data reviewed in preparing this Five-Year Review Report is listed inthe appendix titled "List of Documents Reviewed".

Site Inspection

The SARL was inspected by USAF and contractor staff during the 2007 monitoring event on May31 and June 1,2007. Mr. Tom Barounis, USEPA Region 5 Superfund Division, and Mr. DouglasYocum, 934th Airlift Wing Environmental Section, Minneapolis-St. Paul Air Reserve Station, alsoinspected the site on November 15, 2007 in conjunction with the Five-Year Review. Theinspections concluded that the physical condition of the site was acceptable on both occasions.

VII. Technical Assessment

Question A: Is the remedy functioning as intended by the decision documents?

Yes. The remedy is functioning as intended with regard to ICs. The waste areas are capped (soilcover) and access to the site is limited. The site remains under the control of the USAF and theMinneapolis-St. Paul Air ResenJe Station General Plan requires deed restrictions to be implementedif the property is ever transferred to another owner.

Remedial Action Performance

Remedial actions continue to function as designed. Natural attenuation of groundwatercontaminants is generally performing as expected, and previously achieved cleanup levels arepredominantly being maintained. Surface water exhibits no contaminants in excess of theestablished cleanup goals. Site access restrictions are in place and are being maintained. In

18

summary, data gathered during the third five-year review indicates that, overall, the remedycontinues to function as designed and is performing as expected.

System Operation and Maintenance

The remedy for the SARL does not include any operating systems, other than data collection forfive-year reviews. Operation and Maintenance (O&M) for the SARL site consists of: a) annual siteinspection to assess the integrity of the landfill native soil cover and the integrity of the fence, andidentify need for repairs; and b) maintenance of the monitoring wells.

Site inspections conducted during 2007 concluded that integrity has been adequately maintained forboth the native soil covering the site and the fence surrounding the site. Future site inspections willcontinue to be used to ensure the effectiveness ofthe maintenance and access restrictions required bythe remedy.

Condition of each of the seven monitoring wells was evaluated in conjunction with the 2007monitoring event. All well casings and surface seals were visually observed to be in good condition,and no exterior repair or rehabilitation of the wells is currently necessary for the wells to remainusable. However, excessive thicknesses ofsediment were encountered within four ofthe monitoringwells (MW06, MW7A, MW7B, and MW9B). If these wells are to be sampled in the future,sediment should be removed from these wells, and these wells should also be redeveloped prior tosampling.

Opportun ities for Opti J11 ization

Two opportunities exist to reduce the costs of sampling and monitoring activities, with nodetrimental impact to the site remedy. Monitoring wells MW7A, MW7B, MW8B, and MW9Bcould be abandoned and sealed in accordance with state code, and surface water sampling of theretention pond adjacent to the SARL could be discontinued.

The rationale for abandonment and sealing ofmonitoring wells MW7A and MW7B is the consistent,long-term attainment of ARARs for COCs at these two wells. No ARAR has been exceeded ingroundwater sampled from MW7A since February 1993. No ARAR has ever been exceeded ingroundwater sampled from MW7B. A similar rationale exists for abandonment and sealing ofmonitoring wells MW8B and MW9B. Groundwater sampled from MW8B since 1988 has had onlyone COC value in excess of an ARAR, and that single value (from May 1997) was qualified asunusable due to major quality control deviation. For MW9B, only two COC values have exceededan ARAR since October 1993. Both values were for chromium in 1995, and have not been repeatedin monitoring conducted in support of any of the Five-Year Reviews for the SARL. Additionally,MW7B, MW8B, and MW9B are all deep aquifer wells. Upward vertical gradients and southeasterlyhorizontal gradients, calculated from groundwater measurements taken at the site from 1988 through2007, have consistently been interpreted as solid evidence that groundwater discharges from theshallow aquifer into the Minnesota River, making impact to the deep aquifer from the site unlikely.Monitoring wells MW06 (the background well), and MW8A and MW9A (shallow aquifer wells)

19

could be retained for future groundwater monitoring at the SARL.

The rationale for discontinuing surface water sampling ofthe retention pond adjacent to the SARL isthe consistent, long-term attainment ofARARs for the surface water COCs. Since 1988, the onlyinstance ofCOC values exceeding any surface water ARAR occurred in 2002. Beryllium values insamples from both surface water sampling locations were above the ARAR. However, bothconcentrations were qualified as blank contamination due to the detection of beryllium in the fieldblank for the monitoring event.

Early Indicators of Potential Issues

Since there are no operating systems at the site, the only early indicators ofpotential issues would beobvious maintenance issues such as damage to the landfill fence or cover, or upward trends inground water or surface water contaminant data. The landfill cover and fence condition remainacceptable. Surface water contaminant data show no upward trends. The detected concentration ofone inorganic COC (nickel) at down-gradient shallow aquifer monitoring well MW8A has increasedin the last two monitoring events, with both values exceeding the ARAR and TL for nickel. Therehas been no similar increase for any ofthe other COCs at well MW8A, and there has been no similarincrease for nickel at any ofthe other site wells. Although the nickel result for MW8A cannot yet bedefinitively characterized as indicative of a failing or ineffective remedy for the SARL, the nickelconcentration at this well will be ofparticular interest during the next groundwater monitoring event.

Implementation of Institutional Controls and Other Measures

Access controls, in the form of fencing and warning signs, remain in place at the site. Thesecontrols, along with the continued USAF control ofthe property on which the SARL is located andregularly scheduled inspections of the site, are effective measures to limit access to the site and tomaintain the integrity of the remedy.

Question B: Are the exposure assumptions, toxicity data, cleanup levels, and remedialaction objectives used at the time of the remedy still valid?

No. Although the exposure assumptions and remedial action objectives used at the time of theremedy remain valid, cleanup levels have changed.

Changes in Standards and To Be Considered Criteria

Minnesota RALs specified in the ROD have been replaced by promulgated HRLs. In addition,drinking water MCLs have been revised for arsenic (from 50 llg/L to 10 llg/L) and beryllium (from 5llg/L to 4 llg/L) (See Table 1 in Appendix 3). Minnesota Surface Water Standards have been revisedfor lead (from 50 llg/L to 477 llg/L), silver (from 50 llg/L to 22 llg/L), zinc (from 5000 llg/L to 379llg/L) and toluene (from 1000 llg/L to 135211g/L). However, since the most current monitoring dataindicate that COC concentrations fall below the revised standards, there is no increased risk and nonegative impact on the protectiveness of the remedy. These changes in standards have not caused

20

any ofthe ARARs to be revised to lower values in 2008 than the corresponding ARARs establishedin the ROD. No TBCs were identified in the ROD for the SARL.

Changes in Exposure Pathways

There have been no changes in the potential exposure pathways at the site since the implementationofthe remedy for the site. There have been no land use changes at the site nor are any expected inthe near future.

Changes in Toxicity and Other Contaminant Characteristics

Neither the toxicity factors for the contaminants of concern nor other contaminant characteristicshave changed in a way that could affect the protectiveness of the remedy.

Changes in Risk Assessment Methods

Standardized risk assessment methods have not changed in a way that could affect the protectivenessof the remedy.

Expected Progress toward Meeting Remedial Action Objectives

Two remedial action objectives were established in the ROD: Prevent risk to humans or theenvironment through contact with landfill contaminants, and prevent risk to humans orenvironmental receptors from contaminants in groundwater. The selected remedy addressed theseobjectives by limiting contact with landfill contaminants through access restrictions and deedrestrictions, and reducing risks from groundwater contaminants through natural attenuation and deedrestrictions.

Achievement of the first objective was documented in the August 1996 Superfund Final CloseoutReport for the site. Fencing and warning signs installed at the site remain in place. Regularlyscheduled inspections of the site are conducted to confirm the adequacy ofthe fence condition, andto ensure that landfill components do not become exposed from erosive action by wind or surfacerunoff. To date, erosion has not been observed on the SARL site, and landfill components have notbecome exposed.

Achievement ofthe second objective was documented in the August 1996 Superfund Final CloseoutReport for the site. This determination was based on the results of groundwater and surface watermonitoring conducted over a two year monitoring period. Subsequent monitoring conducted in 1997for the first Five-Year review, and again in 2002 for the second Five-Year review, confirmed thatnatural attenuation had been an effective remedial agent. During monitoring conducted in 2007 foruse in this third Five-Year Review, surface water contaminant data continued to be lower than thesurface water ARARs. Non-qualified groundwater contaminant results continued to be lower thanthe groundwater ARARs, with two exceptions: nickel at down-gradient shallow aquifer monitoringwell MW8A, and arsenic at down-gradient shallow aquifer monitoring well MW9A. Sporadic results

21

above ARARs for various COCs have been documented over the fifteen years of site monitoringsince the ROD, including a result exceeding the nickel ARAR at background well MW06 during the2002 monitoring event. There are no potable water wells using shallow groundwater on-site ordown-gradient of the site, and no other complete pathways of human exposure for the SARL.Vertical and horizontal gradients of groundwater measured during 2007 sustain prior suppositionsthat groundwater at the SARL site discharges to the Minnesota River. As noted in the ROD,groundwater seepage to the river is unlikely to contribute detectable contamination due to the lowconcentration ofcompounds detected in groundwater and attenuation ofany concentrations releasedto the river due to mixing, natural degradation, and dispersion processes. Therefore, the two resultsexceeding ARARs at separate wells in 2007 do not represent failure of the selected remedy toprevent risk to humans or environmental receptors from contaminants in groundwater.

The ROD specified that the deed restrictions required by CERCLA Section 120 (h)(3) must beimplemented if the property is placed under the ownership of a person or other entity of federalgovernment, because a deed does not currently exist for the property. The SARL property remainsunder federal government ownership, with administration and control by the USAF. Release ortransfer of the property out of USAF control is neither planned nor forecasted.

In November 2007, USEPA Region 5 requested submittal of an Institutional ControlsInvestigation/Study, evaluating ICs for the SARL site. A response was submitted to USEPA inDecember 2007, documenting institutional control requirements and implementation for the site. Theonly institutional control specified in the ROD is that the deed restrictions required by CERCLA,Section 120 (h) (3) will be implemented at the time the property is placed under the ownership ofaperson or other entity offederal government because a deed does not currently exist for the property.Documentation of the ROD requirement for a deed restriction, limiting future development andgroundwater usage if the property is ever excessed by the USAF, is included in the Minneapolis-St.Paul Air Reserve Station General Plan. The General Plan is a document prepared as a guide for thestation's long-range development, which provides USAF decision-makers with a concise assessmentofon-station conditions as of2007; recommendations for improvements and future development ofthe station as a whole; and identification ofconstraints on development and land use. In addition todocumenting the future deed restriction requirement, the General Plan also documents therequirement for access restriction and fencing at the SARL site.

Considering the access restrictions in place, site maintenance, monitored results ofongoing naturalattenuation, and known documented requirements for future deed restrictions in the event ofproperty transfer, the remedy for the site continues to perform as expected. Recalculation or re­assessment of risks is not currently necessary.

Question C: Has any other information come to light that could call into question theprotectiveness of the remedy?

No. No new information has come to light that could call into question the protectiveness of theremedy. There are no newly identified human health risks or ecological risks associated with theSARL. The SARL has not been inundated by flood waters since the previous five-year review, and

22

,-

L

there have been no impacts from any other natural disasters. No other information has beenidentified that could affect the protectiveness of the remedy for the site.

VIII. Issues

No issues have arisen since the previous five-year review which currently prevent the remedy frombeing protective. There are no current contamination issues at the site. The second Five-YearReview Report for the SARL, dated July 31, 2003, concluded that the selected remedial action,consisting of natural attenuation of groundwater contamination, physical access restrictions, sitemaintenance and monitoring, had achieved the remediation goals set forth in the March 31, 1992Record of Decision (ROD). The SARL was deleted from the Superfund National Priorities List(NPL) on December 16,1996.

Analytical results from samples collected since 1988 indicate that monitoring is no longer necessaryat shallow well MW7A, deep wells MW7B, MW8B, and MW9B, and for surface water in theretention pond adjacent to the SARL. Applicable or Relevant and Appropriate Requirements(ARARs) have not been exceeded in groundwater sampled from MW7A since February 1993. NoARAR has ever been exceeded in groundwater sampled from MW7B. An ARAR has been exceededonly once in groundwater sampled from MW8B, in a 1997 result that was qualified as unusable dueto major quality control deviation. ARARs have not been exceeded in groundwater sampled fromMW9B since 1995. Additionally, MW7B, MW8B, and MW9B are all deep aquifer wells. Upwardvertical gradients and southeasterly horizontal gradients, calculated from groundwater measurementstaken at the site from 1988 through 2007, have consistently been interpreted as solid evidence thatgroundwater discharges from the shallow aquifer into the Minnesota River, making impact to thedeep aquifer from the site unlikely.

In surface water sampled from the retention pond adjacent to the SARL since 1988, the only instanceofCOC values exceeding any surface water ARAR occurred in 2002. Beryllium values in samplesfrom both surface water sampling locations were above the ARAR. However, both concentrationswere qualified as blank contamination due to the detection of beryllium in the field blank for themonitoring event.

In analytical results of2007 groundwater samples from shallow aquifer wells MW8A and MW9A,the nickel concentration at MW8Aand the arsenic concentration at MW9A exceeded groundwaterARARs. Both parameters were also detected at lower concentrations in groundwater from thebackground well MW06.

Condition of each of the seven monitoring wells was evaluated in conjunction with the 2007monitoring event. All well casings and surface seals were visually observed to be in good condition,and no exterior repair or rehabilitation of the wells is currently necessary for the wells to remainusable. However, excessive thicknesses ofsediment were encountered within four ofthe monitoringwells (MW06, MW7A, MW7B, and MW9B).

23

IX.. Recommendations and Follow-up Actions

Two remediation goals were noted in the ROD: 1) reduce COC concentrations in the groundwaterto meet the respective ARARs and ensure that groundwater migrating from the SARL to theMinnesota River does not exceed Water Quality Criteria for freshwater species; and 2) limit thepotential for the SARL to be exposed directly to human receptors or local fauna. The 2007 samplingresults confirmed the results of the monitoring program conducted during 1993, 1994, 1995, 1997,and 2002, which established that natural attenuation had proven to be an effective remedial agent atthe SARL. Additionally, the USAF has maintained, and will continue to maintain on a permanentbasis, the established site access restrictions and site maintenance program. As a result, the secondremediation goal of limiting the potential of direct exposure to human receptors or local fauna hasalso been met.

Based on the analytical results during the first, second and third Five-Year Reviews, monitoring ofshallow well MW7A and deep wells MW7B, MW8B, and MW9B should be discontinued, and thesewells should be abandoned and sealed in accordance with state code requirements. Surface watersampling of the retention pond adjacent to the SARL should also be discontinued.

The next Five-Year Review should include confirmatory water quality monitoring of inorganicCOCs at background well MW06 and shallow wells MW8A and MW9A, as well as confirmation ofsite access restrictions and site maintenance. Prior to future sampling, sediment built up in MW06should be removed, and this well should also be redeveloped.

X. Protectiveness Statement

ICs for the site property and groundwater, which are required to ensure that no inappropriate use ofthe site or groundwater occur, are in-place and effective. The remedy is functioning as intendedbecause no inappropriate site or groundwater uses are occurring. Long term protectiveness requirescompliance with effective ICs. Compliance with effective ICs will be ensured through long-termstewardship by maintaining and monitoring effective ICs as well as maintaining the site remedycomponents. Because the remedial actions at the SARL are protective, the site is protective ofhuman health and the environment.

XI. Next Review

The sampling activities for the next five-year review for the SARL are expected to be performed nolater than 2012, with the fourth Five-Year Review Report due five years from the date of signatureon this third Five-Year Review Report.

24

APPENDIX 1

List of Documents Reviewed

1. 1993 Annual Water Quality Report, Small Arms Range Landfill, Prepared for Minneapolis­St. Paul International Airport Reserve Station, Rust Environment & Infrastructure, March 1994.

2. 1994 Annual Monitoring Report (Finan, Small Arms Range Landfill, Prepared for the 934th

Airlift Wing, Braun Intertec, July 1995.

3. 1995 Annual Monitoring Report (Finan, Small Arms Range Landfill, Prepared for the 934th

Airlift Wing, Braun Intertec, April 1996.

4. 1997 Five Year Review, Small Arms Range Landfill, Prepared for 934th LogisticsGroupILGC, Braun Intertec, September 1997.

5. 2002 Ten-Year Review, Small Arms Range Landfill, Prepared for 9341h LSSILGC, BraunIntertec, July 2002.

6. Comprehensive Five-Year Review Guidance, USEPA, Office of Emergency and RemedialResponse, EPA 540-R-OI-007, OSWER No. 9355.7-03B-P, June 2001.

7. Federal Facilities Agreement Under CERCLA Section 120, Small Arms Range Landfill,Minneapolis-St. Paul International Airport Base, November 6, 1989.

8. Five Year Review Report, Twin Cities Air Force Reserve Base - Small Arms Range LandfillSite, Minneapolis, Minnesota, Minneapolis, Minnesota, Prepared by U.S. EnvironmentalProtection Agency, Region 5, Chicago, Illinois, April 2, 1998.

9. Record of Decision, Small Arms Range Landfill, Minneapolis-St. Paul International Airport,Air Force Reserve, March 31, 1992.

10. Second Five-Year Review Report for Twin Cities Air Force Reserve Base, Small ArmsRange Landfill, Minneapolis, Minnesota, Prepared by U.S. Environmental Protection Agency,Region 5, Chicago, Illinois, July 31, 2003.

11. Superfund Final Close-Out Report, Twin Cities Air Force Reserve Base, Small Arms RangeLandfill. NPL #054L, Minneapolis-St. Paul International Airport, Minnesota, USEPA, August 29,1996.

12. Third Five-Year Review for Small Arms Range Landfill, 934th Airlift Wing, Minneapolis-St.Paul lAP ARS, Prepared for 934 CONFILGC, Braun Intertec Corporation, September 24,2007

APPENDIX 2

Figures

USGS TOPOGRAPHIC MAP

1JMJ

S~ LOCIItiol'l MapSma. JlmfI Ral'llll' LandlilMiM"PO~', 51. f'.~ lAPMiIYI"PO~', Minn..olll

BRAUNINTERTEC

'M'flEVlSEO 19930''''111) I "'_Sl!~I!I VI,.

IIIIIIIIIIIIIIIIIII

100'I

BRAUN­INTERTEC

SCALE 1"= 100'

50' 0

~--

MONITORING 'NELL, COMPRISED OFSHALLOW (A) AND DEEP (B) WELL

I:8J ABANDONED WELL LOCAnON

* SURFACE WATER SAMPLING LOCATION

- - FENCE

f' CONTROLGATE

{J

~ MW9A

/ MW98

..I('

/..I('

/..I('

J!

MW8B ~ MW8A-

SITE MAPSMALL ARMS RANGE LANDFILL

MINNEAPOLIS-ST. PAUL INTERNATIONAL AIRPORTMINNEAPOLIS, MINNESOTA

------ - ------- ------ .........- ..........

(

::!l 'NT DATE

~ DRAWN BY: JAG 7-24-97rT'Iz APP'O B"t': CDM 6-26-07P JOB NO. BL0701607

N DWG. NO. MX20176 SHEET OF

SCALE 1"= 100'

---"

APPENDIX 3

Tables

TABLE 1Groundwater Chemicals of Concern and Applicable or Relevant and AppropriateRequirements, Small Arms Range Landfill

Applicable as of 1992 ROD (/lg/L) Applicable in 2007 (/lglL)

Chemicals of Concern RAL 1 I MCe HRC I MCL4

InorganicsArsenic 0.2 50 - 10Beryllium 0.08 5 0.08 4Cadmium 4 5 4 5Chromium 100 100 100 100Copper 1000 1300 - 1300Lead 20 15 - 15Mercury I 2 - 2Nickel 70 - 100 -

Selenium 10 50 30 50Silver 10 - 30 -

Vanadium 20 - 50 -Zinc 700 - 2000 -

VOCsBenzene 10 5 5 52-butanone (MEK) 300 - 4000 -

1,2-dichloroethene (cis-) 70 70 70 70Toluene 1000 1000 1000 1000Trichloroethene 30 5 5 5

SVOCsDi-n-butylphthalate 700 - 700 -

Footnotes:I Recommended Allowable Limits, as established by Minnesota Department of Health, January 1991;

revised October 1991; replaced by Health Risk Limits in December 1994.2 Maximum Contaminant Levels, as established in 40 CFR 141 as of July 1991.

Health Risk Limits, as established by Minnesota Department of Health, effective July 2007.4 Maximum Contaminant Levels, as established in 40 CFR 141 as of July 2007.

,!

TABLE 2Surface Water Chemicals of Concern and Applicable or Relevant and Appropriate RequirementsSmall Arms Range Landfill

Applicable as of 1992 ROD Cllg/L) Applicable in 2007 Cllg/L)

RAL' I MCL2 I Fresh Water Acute I Minnesota Water HRL5

I MCL6 I Minnesota WaterChemicals of Concern Concentration3 Standard4 Standard7

Inorganics

Beryllium 0.08 - - - 0.08 4 -

Iron - - - 300 - - -

Lead 20 15 82 50 - 15 477Silver 10 - 4.1 50 30 - 22Vanadium 20 - - - 50 - -

Zinc 700 - 120 5000 2000 - 379

VOCsToluene 1000 1000 1000 1000 1000 1000 1352

Footnotes:1 Recommended Allowable Limits, as established by Minnesota Depal1ment of Health, January 1991; revised October 1991; replaced by Health

Risk Limits in December 1994.2 Maximum Contaminant Levels, as established in 40 CFR 141 as ofJuly 1991.3 "ARARs Q's and A's. Compliance with Federal Water Quality Criteria," USEPA, June 1990.4 Minnesota Water Standards, Minnesota Rules 7050.0220, November 1990.5 Health Risk Limits, as established by Minnesota Department of Health, effective July 2007.6 Maximum Contaminant Levels, as established in 40 CFR 141 as of July 2007.7 Maximum Standard, Class 2C Surface Water; Minnesota Rules 7050.0220, February 2007.

~1

L

TABLE 3Groundwater Chemicals of Concern - 2007 Monitoring Results, Small Arms Range Landfill

I Chemicals of Concern ~ I I I2007 Result (Ilg/L)

CL TL ARAR1 MW06 MW7A MW78 MW8A MW88 MW9A MW98

InorganicsArsenic 10 20 - 5.881 8.1 81 4.581 7.081 5.881 17.6 3.381Beryllium 1 2 - NO NO NO NO NO NO NOCadmium 4 8 - NO NO NO NO NO NO NOChromium - - 100 NO NO 1.381 NO 0.7881 NO 1.781Copper - - 1300 1.1 81 NO 0.7181 3.581 1.081 NO 1.7 BlLead 15 30 - NO NO NO NO NO NO NOMercury - - 2 NO NO NO NO NO NO NONickel 70 140 - 33.2 Bl 30.3 81 2.681 428 19.2 Bl NO 25.081Selenium 10 20 - NO 8.9N 8.7N 14.8 N 7.2 N 6.2N 5.9NSilver - - 30 NO NO NO NO 0.5381 NO NOVanadium 20 40 - 0.6881 0.7481 NO 0.4981 0.7481 1.4 8 I 0.3481Zinc - - 2000 NO NO NO 0.77 81 NO NO ND

VOCsBenzene - - 5 NO NO NO NO NO NO NO2-butanone (MEK) - - 4000 NO NO NO NO NO NO ND1,2-dichloroethene (total) - - - NO NO NO NO NO NO NOToluene - - 1000 0.9 J NO 1.0 J ND NO NO 1.0 JTrichloroethene 5 10 - NO NO NO NO NO NO NO

SVOCsOi-n-butylphthalate - - 700 NO NO NO NO NO NO NO

Footnotes:1 2007 ARARs are listed where CL and TL were not established in the ROO.81 = Parameter analyzed for and reported value was obtained from a reading that was less than the CRDL but greater than or equal to the IOLJ = Estimated value due to minor quality control deviationN = Sample spike recovery outside of control limits

NO = Not detected

TABLE 4Surface Water Chemicals of Concern - 2007 Monitoring ResultsSmall Arms Range Landfill

2007 Result (ug/L)

Chemicals of Concern ARAR SWLl 1 SWL2

Inorganics

Beryllium 0.08 NO NOLead 15 NO NOSilver 22 NO NOVanadium 50 0.58 Bl NOZinc 379 0.83 Bl 1.5 B1

VOCsToluene 1000 0.8 J 0.9 J

Footnotes:B1 = Parameter analyzed for and reported value was obtained from a reading that was less than the CRDL

but greater than or equal to the IOLJ = Estimated value due to minor quality control deviation

NO = Not detected

TABLE 5History ofNickel Results at Well MW8A, Small Arms Range Landfill

MW8A NickelMonitoring Event Result (Jlg/L)

September 1988 32.9

October 1989 ND

February 1993 20.1

June 1993 ND

August 1993 15.5

October 1993 10.3

December 1993 17.6

February 1994 50.5

April 1994 30.4

July 1994 ND

October 1994 ND

January 1995 24

April 1995 52

July 1995 49.9

May 1997 59.2R

May 2002 300

June 2007 428

Footnotes:ND = Not detected

R = Unusable value due to major quality control deviation

APPENDIX 4

Public and Regulatory Agency Notifications

1067223768 lines

Class 203

PUBLIC NOTICEFive-Year ReviewTwin Cibes Air Force Reserve

. ,Sm,\lll Arms Range Landfill ,Hennepin County, Minnesota

1The U.S. Air Force (I,JSAF) isconducting a five-year reviewof the Twin Cities Air ForceReserve Base Small ArmsRange Landfill site. The sitewas placed on the NationalPriorities List (NPL) in 1987. In'1992, USAF and the U.S. En­vironmental Protection Agency(EPA) selected natural attenu­

'ation, site maintenance, ac-cess restrictions, and grounp­water and surface watermonitoring as the cleanupremedy for the site. Monitor­ing conducted through 1995determined that natural at-

, tenuation proved to be an ef­fective remedy. The site wasdeleted from the NPL in 1996.

; The remedy allows landfilledmaterials to remain on-siteaf,ter the remedy is complete.

, Five-year reviews are requiredto ensure that the site re­mains protective of human

'. heaith .and the environment.During the review, USAF andEPA study info~mation on thesite, including monitoringdata, and inspect the site tomake sure it continues to besafe. In 2007, USAF con­tracted for confirmatory sitemonitoring as part of thisfi ve -year rev i ew. A re po:rtdocumenting monitoring re­sults is available for public re-view at: '

Minneapolis Public LibraryGovernment Documents300 Nicollet MallMinneapolis, MN 55401

Written comments concerningthis review will be accepted for30 days. Submit to: .934 MSG/CEV 'Attn: D.oug Yocum760 Military HighwayMinneapolis, MN 55450-2100

Contacts for further informa-l tion on the review process:: Doug Yocum (USAF)'(612) 713-1955,douglas.yocum@us.af.mil

Tom Barounis (EPA)(312) 353-6577

;bar"ounis.thomas@epa.gov

Public Notice published in Minneapolis-Star Tribune newspaper, January 2, 2008

DEPARTMENT OF THE AIR FORCEAIR FORCE RESERVE COMMAND

20 December 2007

MEMORANDUM FOR MINNESOTA POLLUTION CONTROL AGENCYRemediation Division/Superfund & Emergency Response SectionlUnit 2Attn: David Douglas520 Lafayette RoadSt. Paul, MN 55155-4194

FROM: 934 MSG/CE760 Military HighwayMinneapolis, MN 55450-2100

SUBJECT: Five-Year Review, Twin Cities Air Force Reserve Base Small Arms Range Landfill Site

1. This letter provides notice that a statutory five-year review is being prepared for a former NationalPriorities List (NPL) and Minnesota Permanent List of Priorities (PLP) site identified as the "Twin CitiesAir Force Reserve Base - Small Arms Range Landfill Site." The site is located on property owned by theU.S. Air Force in Hennepin County, Minnesota. This site, which is now in long-term monitoring status,was deleted from the NPL on December 16, 1996, and was deleted from the Minnesota PLP on June 30,1998. Five-year reviews of this site are required by Section 121 of the Comprehensive EnvironmentalResponse, Compensation, and Liability Act/Superfund Amendments and Reauthorization Act, and by theNational Contingency Plan (Code of Federal Regulations, Title 40, Section 300.430(f)(4)(ii)). This willbe the third five-year review for the site.

2. As part of the five-year review process, the Air Force contracted Braun Intertec Corporation toconduct confirmatory sampling and analysis of groundwater and surface water at the Small Arms RangeLandfill Site, and prepare a report of findings. Braun Intertec Corporation concluded in its report that the2007 sampling results generally confirmed previous monitoring, which established that naturalattenuation had proven to be an effective remedial agent at the site.

3. Alegal notice announcing preparation of the five-year review will be published in the Minneapolis­Star Tribune on January 2, 2008. The legal notice will identify a public library where the Braun IntertecCorporation report may be reviewed, and will provide opportunity for citizen input into the drafting ofthe five-year review report. The Minnesota Pollution Control Agency declined participation in thesecond five-year review for the site, prepared in 2002-2003. If your agency would like to review theBraun Intertec Corporation report, or provide input to the drafting, of the third five-year review report,please notify Douglas Yocum, Physical Scientist, via telephone at (612) 713-1955, or via e-mail atdouglas.yocum@minneapolis.af.mil.

LESLIE W. CANARRBase Civil Engineer