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EPA/ROD/R2006040001164 2006 EPA Superfund Record of Decision: HOMESTEAD AIR FORCE BASE EPA ID: FL7570024037 OU 27 HOMESTEAD AIR FORCE BASE, FL 09/26/2006
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  • EPA/ROD/R2006040001164 2006

    EPA Superfund

    Record of Decision:

    HOMESTEAD AIR FORCE BASE EPA ID: FL7570024037 OU 27HOMESTEAD AIR FORCE BASE, FL 09/26/2006

  • United States Air Force

    Environmental Restoration Program

    FINAL

    RECORD OF DECISION FOR

    OPERABLE UNIT 27 – FORMER JET ENGINE TEST CELL FACILITY

    Homestead Air Reserve Base, Florida

    August 2006

  • HOMESTEAD AIR RESERVE BASE

    RECORD OF DECISION FOR OPERABLE UNIT 27 – FORMER JET ENGINE TEST CELL

    FACILITY

    FINAL

    Prepared by Booz Allen Hamilton

    Atlanta, GA

    August 2006

  • ii

    TABLE OF CONTENTS

    SECTION PAGE

    LIST OF ACRONYMS ......................................................................................................................................iv 1.0 DECLARATION ........................................................................................................................1

    1.1 SITE NAME AND LOCATION.......................................................................................................... 1 1.2 STATEMENT OF BASIS AND PURPOSE ....................................................................................... 1 1.3 ASSESSMENT OF THE SITE ............................................................................................................ 1 1.4 DESCRIPTION OF THE SELECTED REMEDY............................................................................ 1 1.5 STATUTORY DETERMINATIONS ................................................................................................. 3 1.6 ROD DATA CERTIFICATION CHECKLIST ................................................................................. 4 1.7 AUTHORIZING SIGNATURES AND SUPPORT AGENCY ACCEPTANCE OF

    REMEDY .............................................................................................................................................. 5 2.0 DECISION SUMMARY ...........................................................................................................6

    2.1 SITE NAME, LOCATION, AND DESCRIPTION ........................................................................... 6 2.2 SITE HISTORY AND ENFORCEMENT ACTIVITIES.................................................................. 6 2.3 COMMUNITY PARTICIPATION..................................................................................................... 9 2.4 SCOPE AND ROLE OF OPERABLE UNIT OR RESPONSE ACTION..................................... 13 2.5 SITE CHARACTERISTICS.............................................................................................................. 14

    2.5.1 Nature and Extent of Contamination.......................................................................................14 2.5.2 Contaminant Fate and Transport..............................................................................................22

    2.6 CURRENT AND POTENTIAL FUTURE LAND AND RESOURCE USES ............................... 22 2.7 SUMMARY OF SITE RISKS............................................................................................................ 23

    2.7.1 Summary of Human Health Risk Assessment........................................................................24 2.7.2 Summary of Ecological Risk Assessment ................................................................................25

    2.8 REMEDIAL ACTION OBJECTIVES ............................................................................................. 26 2.9 DESCRIPTION OF ALTERNATIVES............................................................................................ 27

    2.9.1 Alternative 1 – No Further Action ............................................................................................27 2.9.2 Alternative 2 – Land Use Controls............................................................................................27 2.9.3 Alternative 3 – Excavation and Off-Site Disposal...................................................................27

    2.10 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES ....................................... 28 2.10.1 Threshold Criteria .......................................................................................................................28 2.10.2 Balancing Criteria........................................................................................................................29 2.10.3 Modifying Criteria ......................................................................................................................31 2.10.4 Comparison of Alternatives.......................................................................................................31

    2.11 PRINCIPAL THREAT WASTES..................................................................................................... 33 2.12 SELECTED REMEDY....................................................................................................................... 33 2.13 STATUTORY DETERMINATIONS ............................................................................................... 36 2.14 DOCUMENTATION OF SIGNIFICANT CHANGES................................................................... 37

    3.0 RESPONSIVENESS SUMMARY .........................................................................................39

  • iii

    LIST OF FIGURES

    Figure Title Page

    2-1 IRP Site Locations ......................................................................................................................7

    2-2 1994 Sample Locations ..............................................................................................................8

    2-3 1996 Sample Locations ............................................................................................................10

    2-4 Excavation and Confirmation Sample Locations (April–May 2001) ................................11

    2-5 Post-Excavation Sample Locations (April 2002)..................................................................12

    LIST OF TABLES

    Table Title Page

    1-1 Soil Cleanup Target Levels for Constituents of Concern at Operable Unit 27..................2

    2-1 Summary of Operable Unit 27 History ...................................................................................6

    2-2 Constituents of Concern in Soil Exceeding Soil Cleanup Target Levels (SCTLs), 1994 Confirmation Sampling..................................................................................................15

    2-3 Constituents of Concern in Soil Exceeding Soil Cleanup Target Levels (SCTLs), 1996 Remedial Investigation ..................................................................................................17

    2-4 Constituents of Concern in Soil Exceeding Soil Cleanup Target Levels (SCTLs), 2001 Voluntary Interim Remedial Action – Confirmation Sampling ...............................20

    2-5 Summary Information for Constituents of Concern in Soil Exceeding FDEP Soil Cleanup Target Levels (SCTLs) .............................................................................................25

    2-6 Soil Cleanup Target Levels for Constituents of Concern at OU-27 ..................................26

    2-7 Comparison of Alternatives ...................................................................................................32

    APPENDICES

    Appendix Title

    A References

    B Regulatory Correspondence

  • iv

    LIST OF ACRONYMS

    AF Air Force AFB Air Force Base AFI Air Force Instruction AFRC Air Force Reserve Command ARAR applicable or relevant and appropriate requirement ARB Air Reserve Base BCE Base Civil Engineer BCT BRAC Cleanup Team BGP Base General Plan BRAC Base Realignment and Closure bgs below ground surface BRA baseline risk assessment CERCLA Comprehensive Environmental Response, Compensation, and Liability Act CFR Code of Federal Regulations cm centimeter COC contaminant of concern CRP Community Relations Plan CSF cancer slope factor DERM Department of Environmental Resources Management DoD Department of Defense EPA U.S. Environmental Protection Agency EPC exposure point concentration ERA ecological risk assessment ERP environmental restoration program FAC Florida Administrative Code FDEP Florida Department of Environmental Protection FFA Federal Facilities Agreement FS feasibility study GCTL ground-water cleanup target level GPS global positioning system IC institutional control IRA interim remedial action IRP installation restoration program kg kilogram LUC land use control MCL maximum contaminant level mg milligrams msl mean sea level NCP National Oil and Hazardous Substances Pollution Contingency Plan NPL National Priorities List OU operable unit PAH polynuclear aromatic hydrocarbon PA/SI preliminary assessment/site investigation PCB polychlorinated biphenyl

  • v

    PRG preliminary remediation goal RAB Restoration Advisory Board RAGS Risk Assessment Guidance for Superfund RAO remedial action objective RCRA Resource Conservation and Recovery Act RfD reference dose RI remedial investigation RME reasonable maximum exposure ROD record of decision SARA Superfund Amendments and Reauthorization Act SCTL soil cleanup target level SI site investigation SSL soil screening level SVOC semi-volatile organic compound SWMU solid waste management unit µg micrograms UCL upper confidence limit VOC volatile organic compound

  • 1

    HOMESTEAD AIR RESERVE BASE HOMESTEAD, FLORIDA

    RECORD OF DECISION FOR OPERABLE UNIT 27 – FORMER JET ENGINE TEST CELL FACILITY

    1.0 DECLARATION

    1.1 Site Name and Location

    Homestead Air Reserve Base (ARB) (U.S. Environmental Protection Agency [EPA] Identification Number [ID No.] FL7570024037) is located within southeastern Miami-Dade County near the southern tip of peninsular Florida. The installation is located near U.S. Highway 1, approximately 25 miles southwest of Miami, immediately east of the City of Homestead boundary, and two miles west of Biscayne Bay. Operable Unit (OU) 27 is located in the extreme southwestern portion of Homestead ARB, between the runway and the western boundary of the installation. The weapons storage area lies immediately north of the site.

    1.2 Statement of Basis and Purpose

    Homestead Air Force Base (AFB) was placed on the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) National Priorities List (NPL) on 30 August 1990. This resulted in the adoption of a Federal Facilities Agreement (FFA) between the EPA, the State of Florida, and the U.S. Air Force, which was finalized in early 1991. This record of decision (ROD) is being issued by the U.S. Air Force Reserve Command (AFRC), which is the lead agency for environmental restoration activities at Homestead ARB under CERCLA and the National Oil and Hazardous Substances Pollution Contingency Plan (NCP). The final remedy for OU-27 was co-selected by AFRC and EPA Region IV, with the concurrence of the Florida Department of Environmental Protection (FDEP).

    This ROD presents the Selected Remedy for OU-27 at Homestead ARB, in Miami-Dade County, Florida, which was chosen in accordance with CERCLA regulations, as amended by the Superfund Amendments and Reauthorization Act (SARA), and, to the extent practicable, NCP. This decision is based on the Administrative Record file for this site.

    1.3 Assessment of the Site

    The response action selected in this ROD is necessary to protect the public health or welfare or the environment from actual or threatened releases of hazardous substances into the environment.

    1.4 Description of the Selected Remedy

    OU-27 is one of 31 sites that are part of the cleanup strategy at the former Homestead AFB. Two OUs were transferred to the Florida petroleum program, final remedies have not been selected at eight other OUs, and no action decisions have been made for six OUs. OU-27 has been investigated and remediated independently from all other OUs at Homestead AFB. The remedy selected in this ROD applies to the portions of the site identified in Figure 2-2 as the OU-27 land use control (LUC) Boundary. However, the extent of soil containing contaminants

  • 2

    with concentrations greater than the FDEP residential soil cleanup target levels (SCTLs) shown in Table 1-1 is limited. As indicated in Figure 2-4, only two sample locations contained concentrations of total PAHs that exceeded the residential SCTLs. The selected remedy for OU-27 is not applicable to any other site or OU at the installation.

    Approximately 11 cubic yards of soil are estimated to remain at OU-27 that contain polynuclear aromatic hydrocarbons (PAHs) and benzo(a)pyrene at concentrations that exceed the unrestricted use and unlimited exposure criteria represented by the FDEP’s residential SCTLs shown in Table 1-1.

    As part of the OU-27 risk evaluation, exposure point concentrations (EPCs) were calculated for constituents of concern (COCs). EPCs represent a conservative estimate of the concentration of COCs in OU-27 soil. As shown in Table 1-1, results of the OU-27 risk evaluation indicate that contaminated soil does not pose an unacceptable risk to current and anticipated users of the site (i.e., commercial/industrial workers) because EPCs for all contaminants were less than the FDEP commercial/industrial SCTLs. As a result, no remedial action is required to protect anticipated users of the site. However, the EPCs for total PAHs and benzo(a)pyrene exceeded residential SCTLs. Therefore, LUCs are required to be protective of residential receptors, which represent the unrestricted use and unlimited exposure scenario. The EPC for arsenic also exceeded the residential SCTL but was eliminated from further consideration during the quantification of site risks because it was less than the base-specific background concentration of 10 mg/kg.

    Table 1-1 Soil Cleanup Target Levels for Constituents of Concern at Operable Unit 27

    FDEP Soil Cleanup Target Levels1 Constituents of Concern Units Residential Commercial/Industrial

    Exposure Point Concentrations2

    Total PAHs3 µg/kg4 100 700 441.415 Benzo(a)pyrene µg/kg 100 700 223.12 Antimony mg/kg6 27 370 20.23 Arsenic mg/kg 2.1 12 3.00

    Notes: 1. Chapter 62-777 of the Florida Administrative Code (FAC), dated 17 April 2005 2. EPCs were calculated as the 95% percent upper confidence limit (95% UCL) on the mean using EPA’s ProUCL

    software. 3. PAHs are evaluated as the sum of the benzo(a)pyrene toxicity equivalents for the individual PAHs. 4. µg/kg = micrograms per kilogram 5. Exposure point concentrations (EPCs) were calculated for PAHs as the sum of the benzo(a)pyrene toxicity equivalents

    for the carcinogenic PAHs. 6. mg/kg = milligrams per kilogram

    The contaminants listed in Table 1-1 are not considered principal threat wastes because they are present at concentrations that are not greatly above the SCTLs; they do not pose an excess cancer risk greater than the acceptable risk range if exposure to the contaminants were to occur; and they are relatively immobile in soil. As a result, aggressive removal and/or treatment of the contamination is not warranted and only limited action is necessary to protect human health.

    Principal Threat Wastes are source materials (e.g., contaminated soil or ground

    water) that contain highly toxic or highly mobile chemicals, which generally cannot be

    contained in a reliable manner or would present a significant risk to human health

    and the environment should exposure occur.

  • 3

    The selected remedy for OU-27 is LUCs, which include:

    Use Restrictions – Residential use restrictions will be implemented to prohibit property users from using the property for residential purposes, hospitals for human care, public or private schools, or day care centers for persons under 18 years of age. Residential use will be prohibited on portions of the OU-27 property containing contaminated soil at concentrations greater than the residential SCTLs shown in Table 1-1. Figure 2-4 identifies the locations where contaminant concentrations exceed residential SCTLs. The area where LUCs will be implemented is identified in Figure 2-4 by the dashed box surrounding the five engine test cells and parts of the concrete pad.

    Contaminated Soil Management Restrictions – LUCs will be implemented to require that any contaminated soil that is excavated at OU-27 will be properly managed on site and that any contaminated soil transported off site will be managed in accordance with applicable Resource Conservation and Recovery Act (RCRA) regulations.

    Use restrictions will be identified in the Base General Plan (BGP) and the Homestead ARB Installation Commander will implement, monitor, maintain, enforce, and report on LUCs at Homestead ARB, through the Base Civil Engineer’s (BCE) Environmental Flight Office through existing land-use management programs. Use restrictions will ensure that the future land use of the property remains commercial/industrial and does not change to residential use. LUCs will remain in place until confirmatory sampling data indicate that PAH concentrations decline below unrestricted use and unlimited exposure criteria represented by the residential SCTLs in Table 1-1.

    These LUCs will be implemented, monitored, maintained, and enforced at OU-27 in conjunction with LUCs at other OUs at Homestead ARB to ensure that LUCs are consistently and efficiently implemented as part of the cleanup strategy at Homestead ARB. Homestead ARB Environmental Flight Office personnel will monitor the contaminated areas of OU-27 to ensure that LUCs are not breached and remain protective. Annual reports summarizing the results of the LUC monitoring will be submitted to FDEP and EPA. Homestead ARB Environmental Flight personnel will promptly notify EPA and FDEP if any activity that is inconsistent with the LUCs or may interfere with their effectiveness is observed at OU-27. Homestead ARB Environmental Flight personnel will notify and seek concurrence from EPA and FDEP prior to termination or modification of the LUCs and will notify EPA and FDEP prior to transfer of the property.

    1.5 Statutory Determinations

    The AFRC expects the selected remedy to satisfy the following statutory requirements of CERCLA §121(b). The selected remedy is protective of human health and the environment, complies with federal and state requirements that are applicable or relevant and appropriate to the remedial action, is cost effective, and utilizes permanent solutions and alternative technologies to the maximum extent practicable.

    The remedy for this OU does not satisfy the statutory preference for treatment as a principal element of the remedy for the following reasons:

  • 4

    No principal threat wastes are present for which aggressive removal or treatment is warranted

    LUCs provide comparable protection of human health and are more easily implemented and cost-effective than other remedial alternatives considered in the Streamlined Feasibility Study (FS) (Booz Allen, 2006).

    Because this remedy will result in hazardous substances, pollutants, or contaminants remaining on site above levels that allow for unlimited use and unrestricted exposure, a statutory review will be conducted within five years after initiation of remedial action to ensure that the remedy is, or will be, protective of human health and the environment. Five-year reviews will continue until contaminant concentrations in soil have decreased to levels that allow for unlimited use and unrestricted exposure. This requirement is pursuant to CERCLA § 121 and the NCP 40 Code of Federal Regulations (CFR) 300.430(f)(4)(ii).

    1.6 ROD Data Certification Checklist

    The following information is included in the Decision Summary section of this ROD:

    COCs and their respective concentrations—Sections 2.5 and 2.7

    Potential risk posed by the COCs—Section 2.7

    Cleanup levels established for COCs and the basis for these levels—Section 2.8

    How source materials constituting principal threats are addressed—Section 2.11

    Current and reasonably anticipated future land use assumptions and current and potential future beneficial uses of ground water used in the risk assessment and the ROD—Section 2.6

    Potential land and ground water use that will be available at the site as a result of the selected remedy—Section 2.12

    Estimated costs and the number of years over which the cost estimates are projected—Section 2.10

    Key factors that led to selecting the remedy—Section 2.10

    Additional information can be found in the Administrative Record file for this site, which can be accessed at https://afrpaar.afrpa.pentagon.af.mil/docsearch/newdocsearchform.asp.

  • 1.7 Authorizing Signatures and Support Agency Acceptance of Remedy

    The following signatures certify that all parties agree to the contents of this ROD and the selected remedy.

    Colonel, USAFR Commander, 482d Fighter Wing Homestead Air Reserve Base, Florida

    Beverly H. Banister Acting Director, Waste Management Division U.S. Environmental Protection Agency, Region IV

    Z f 9 0 6 Date

    5-

    7-26 - 0b Date

  • 6

    2.0 DECISION SUMMARY

    2.1 Site Name, Location, and Description

    Homestead ARB (EPA ID No. FL7570024037) is located within southeastern Miami-Dade County near the southern tip of peninsular Florida. The installation is located near U.S. Highway 1, approximately 25 miles southwest of Miami, immediately east of the city of Homestead boundary, and two miles west of Biscayne Bay.

    OU-27 is the former Jet Engine Test Cell Facility, formerly known as solid waste management unit (SWMU) 68. The site encompasses approximately 2.75 acres and is located within the extreme southwestern portion of Homestead ARB. This area of the installation is undeveloped and lies near the runway in an isolated, restricted access portion of Homestead ARB. The munitions storage area is located immediately north of the site, and OU-1, Fire Protection Training Area No. 2, is located approximately 700 feet (ft) east of the site. Portions of the Boundary Canal system are located immediately west and approximately 900 ft south of the site. Figure 2-1 identifies the location of OU-27 and other OUs at Homestead ARB.

    The facility was constructed in the early 1970s and was used to conduct jet engine testing until the mid-1980s. After several years of inactivity, the area was reportedly used for small-scale painting of aircraft ground equipment and other corrosion control activities until 1992. The area included Building 268 (the main test facility) and Building 257 (an auxiliary building). The subject buildings and associated structures are no longer present on site. Figure 2-2 illustrates the site layout and identifies the OU-27 LUC boundary.

    2.2 Site History and Enforcement Activities

    Homestead AFB was placed on the NPL on 30 August 1990. This resulted in the adoption of an FFA with EPA and FDEP, which was finalized in early 1991.

    A list of important historical events and relevant dates in the site chronology are shown in Table 2-1. The identified events are illustrative, not comprehensive.

    Table 2-1 Summary of Operable Unit 27 History

    Event Date Jet Engine Testing Early 1970s–mid-1980s Painting and Corrosion Control Activities Late 1980s–1992 Confirmation Sampling 1994 Remedial Investigation (RI) 1996 Ground-Water Sampling Event 1997 Voluntary Interim Remedial Action (IRA) 2001 Post-IRA soil sampling 2002

  • 9

    Initial investigation of OU-27 was performed as part of a Confirmation Sampling effort in 1994, which determined that soil and ground water at the site had been contaminated as a result of past engine testing and/or equipment painting activities. In 1996, an RI was conducted to collect additional soil and ground-water samples to identify the extent of contamination. In 1997, a follow-up ground-water sampling event was performed to determine whether contamination detected during previous sampling events remained present. During these investigations, soil and ground water were evaluated for the presence of volatile organic compounds (VOCs), semivolatile organic compounds (SVOCs), pesticides, polychlorinated biphenyls (PCBs), metals, and cyanide. Figures 2-2 and 2-3 identify the 1994 and 1996 sample locations, respectively.

    Based on the results of these investigations, a voluntary interim remedial action (IRA) was conducted to excavate approximately 150 tons of contaminated soil from five separate locations at OU-27 and dispose of the soil at a regulatory-approved, off-base landfill. Figure 2-4 provides a site layout map for OU-27 and identifies the five excavation areas. Soil containing the highest concentrations of PAHs, antimony, chromium, and lead were successfully removed from the site. However, PAHs remain at isolated locations at concentrations slightly greater than the FDEP residential SCTLs (Versar, 2002). In April 2002, additional soil sampling was conducted to collect more representative confirmation soil samples from the former excavation area (IT Corporation, 2002). Figure 2-5 shows the locations of these additional confirmation samples.

    Based on the results of these investigations, potential final remedy alternatives were evaluated as part of a Streamlined FS for OU-27 in 2006 (Booz Allen, 2006). The analysis conducted in the FS provides the basis for the final remedy identified in this ROD. The FS for OU-27 was submitted to EPA and FDEP for review, and letters of approval were received from EPA on 31 March 2006 and from FDEP on 20 February 2006. EPA did not raise any substantial comments or concerns with the Final Streamlined FS for OU-27. FDEP commented that FAC § 62-780 should be listed and considered as an Applicable or Relevant and Appropriate Requirement (ARAR). Based on this comment, FAC § 62-780 was added to the ARAR analysis. No other substantial comments or concerns with the final FS for OU-27 were raised by FDEP. The Miami-Dade County Department of Environmental Resources Management (DERM) also provided minor comments on the Streamlined FS, which were adequately addressed in the Final Streamlined FS, as indicated in DERM’s letter dated 4 August 2006.

    2.3 Community Participation

    The AFRC has a public participation program at Homestead ARB to promote public understanding of the cleanup process and its results, and to ensure that the community’s concerns are solicited, considered, and thoroughly addressed. The backbone of this program is the Community Relations Plan (CRP), which assesses the public’s level of knowledge, interest, and information needs by conducting community interviews and researching local social, demographic, economic, and political information. The CRP recommended compatible public involvement strategies that included a Restoration Advisory Board (RAB), newsletters, fact sheets, an information repository, and public meetings at project milestones.

    RABs are a joint creation of the Department of Defense (DoD) and the EPA and are a vehicle for community input during environmental restoration. A RAB was formed for Homestead AFB in October 1993 and meets routinely. Community members of the RAB exchange information and

  • 13

    discuss restoration issues with the government representatives, including representatives from the Air Force, the EPA, and the FDEP.

    RAB meetings provide opportunities for direct public participation. Presentation topics include current investigations, results, plans for the environmental restoration program (ERP), and current issues. All RAB meetings are open to the public and include a public comment period for the audience members to ask questions and express opinions and/or concerns.

    For the purposes of final remedy selection, the AFRC solicited additional public input about the specific issues surrounding the proposed remedy for OU-27. To accomplish this, the AFRC developed a Proposed Plan for OU-27 and made it available for public review and comment. The Proposed Plan described:

    The COCs at the site and the potential risks they pose to human health and the environment.

    Final remedy alternatives that were considered for the site and a summary of the evaluation of alternatives that was conducted in the FS.

    The preferred final remedy for the site and the means by which it is expected to protect human health and the environment.

    The AFRC’s interest in receiving public input on the proposed remedy, the location where the documents were available for review, and methods by which public input could be provided.

    A formal comment period was conducted between 03 April and 03 May 2006. During this period, the proposed plan and supporting documentation were made available to the public at the County Library in Homestead, Florida. In addition, a public meeting was held on 20 April 2006, from 7:00 to 8:00 PM at the City Council Chamber Room in City Hall, located at 790 Homestead Boulevard, Homestead, Florida, where AFRC representatives were available to discuss the proposed remedy for OU-27 and respond directly to public comments and questions. As summarized in the Responsiveness Summary, which can be found in Section 3.0 of this ROD, no public comments were received during the comment period and no members of the public attended the public meeting.

    2.4 Scope and Role of Operable Unit or Response Action

    The remedial action for OU-27 is one component of the overall cleanup efforts that are being completed at Homestead AFB. This remedial action is the final remedy for OU-27 and will address the residual contamination that remains at OU-27, as described in Section 2.5. No principal threat wastes are present for which aggressive removal or treatment is warranted. OU-27 is one of 31 sites that are part of the cleanup strategy at the former Homestead AFB. Two OUs were transferred to the Florida petroleum program, final remedial actions have not been selected at eight other OUs, and no action decisions have been made for six OUs. The remedial action at OU-27 is not intended to address contamination at any other OU, each of which is being addressed independently. LUCs will be implemented, monitored, maintained,

  • 14

    and enforced at OU-27 in conjunction with LUCs at other OUs at Homestead ARB to ensure consistent and efficient implementation.

    2.5 Site Characteristics

    OU-27 is located in an isolated part of the installation, between the munitions storage area and the southwest end of the runway, separated from the main portion of the installation. Access to this area of the installation is highly restricted due to its proximity to the munitions storage area and the runway. Further to the southwest and west, access is restricted by the Boundary Canal system and the perimeter security fence, which is a chain-link fence posted with “No Trespassing” warning signs. An earthen berm is located between the perimeter fence and the Boundary Canal. As a result, access to the site is effectively limited to authorized AFRC personnel and contractors.

    The site itself consists of a series of concrete pads surrounded by a large grass area that is regularly mowed. The concrete pads were originally constructed and formerly used for testing jet engines. However, they have not been used for this purpose since the mid-1980s. An asphalt access road enters the site from the northeast and connects with a large asphalt pad located east of the concrete test pads. All buildings at this unit, including Buildings 297, 268, 257, and 253 sustained moderate to severe damage during Hurricane Andrew and have been removed from the site. With the exception of its periodic use for equipment painting and corrosion control, the site has not been used for any purpose since its use as an engine test cell was discontinued.

    The surface topography of the site is relatively flat, with elevations ranging from 2 ft above mean sea level (ft-msl) to 10 ft-msl. Surface soil at Homestead ARB is typically less than 6 inches thick and consists of native marl, weathered limestone bedrock, or imported fill. The water table occurs at depths ranging from 0 to 5 ft below ground surface (bgs); however, the depth is heavily influenced by season and recent rainfall. Although the general direction of ground-water flow within the shallow aquifer beneath Homestead ARB is southeasterly toward Biscayne Bay, the hydraulic gradients throughout the base are very flat. As a result, local ground-water flow directions are strongly influenced by rainfall and the presence of the drainage canal system along the base boundary (Boundary Canal).

    2.5.1 Nature and Extent of Contamination

    Soil. During the various investigations performed in 1994, 1996, 2001, and 2002, a total of 28 surface soil samples and 21 subsurface soil samples were collected throughout OU-27, as shown in Figures 2-2 through 2-5. Samples were analyzed for the possible presence of VOCs, SVOCs, pesticides, PCBs, metals, and cyanide. The investigations identified five areas of surface and shallow subsurface (i.e., less than 3 ft bgs) soil with elevated concentrations of several PAHs and several metals (antimony, arsenic, barium, chromium, and lead). Data from these sampling events are presented in Tables 2-2 through 2-4.

    During the IRA in 2001, approximately 150 tons of soil and rock were excavated from five separate grassy areas within OU-27 and disposed of at a regulatory-acceptable off-base landfill. The excavations for Areas 1 through 5 were initially extended to 0.5–1.0 foot bgs. Confirmation samples in Areas 2, 4, and 5 identified concentrations of PAHs and antimony, which exceeded

  • 15

    TABLE 2-2 OPERABLE UNIT 27 – JET ENGINE TEST CELL FACILITY

    CONSTITUENTS OF CONCERN IN SOIL EXCEEDING SOIL CLEANUP TARGET LEVELS (SCTLs) 1994 CONFIRMATION SAMPLING

    (WOODWARD-CLYDE, 1995)

    SCTL1

    Constituent Residential Commercial/

    Industrial

    Base-Specific Soil

    Cleanup Goals2,3

    SS-0002-04 0-0.5 ft bgs5 28-Apr-94

    SS-0003-0 0-0.5 ft bgs 28-Apr-94

    SS-9003-0 0-0.5 ft bgs 28-Apr-94

    SS-0004-0 0-0.5 ft bgs 28-Apr-94

    SS-0005-0 0-0.5 ft bgs 28-Apr-94

    Polynuclear Aromatic Hydrocarbons (µg/kg)6 PAHs7 100 700 − ND8 ND ND ND9 ND

    Benzo(a)anthracene − − − ND ND ND ND ND Benzo(a)pyrene 100 700 1,500 ND ND ND ND ND Benzo(b)fluoranthene − − − ND ND ND ND ND Benzo(k)fluoranthene − − − ND ND ND ND ND Chrysene − − − ND ND ND ND ND Dibenz(a,h)anthracene − − 1,500 ND ND ND ND ND Indeno(1,2,3-cd)pyrene − − − ND ND ND ND ND

    Inorganics (mg/kg) 6 Antimony 27 370 − ND ND 5.5 ND ND Arsenic 2.1 12 10 3.310 3.5 3.7 6.6 4.9 Barium 120 130,000 − 34.4 29.1 37.4 747 19.2 Chromium 210 470 − 22.1 43.3 32.2 247 24.8 Lead 400 1,400 − 48.5 68.9 45.6 673 70.7

    NOTES: 1. SCTLs are based on Chapter 62-777, FAC criteria dated 17 April 2005.

    2. The Base-Specific Soil Cleanup Goals for PAHs were agreed upon at the 19 September 1996 BCT meeting, based on the findings presented in “A Practical Approach for the Development of Typical Basewide PAH Concentrations Not Related to Waste Handling Practices for Use in Risk Management Decisions”(Woodward-Clyde, 1996).

    3. The Base-Specific Soil Cleanup Goal for arsenic is based on the Arsenic Background Study completed in November 1996 (AFBCA, 1996). 4. Sample Type: SS = surface soil sample. 5. bgs = below ground surface. 6. Units: µg/kg = micrograms per kilogram; mg/kg = milligrams per kilogram. 7. PAHs were calculated as the sum of the benzo(a)pyrene equivalents for the carcinogenic PAHs. 8. ND = Not detected above the method detection limit. 9. Diagonal hatching denotes sample locations that were excavated during the voluntary IRA in 2001. 10. Bold text denotes results that exceed the residential SCTL.

  • 16

    TABLE 2-2 (CONTINUED) OPERABLE UNIT 27 – JET ENGINE TEST CELL FACILITY

    CONSTITUENTS OF CONCERN IN SOIL EXCEEDING SOIL CLEANUP TARGET LEVELS (SCTLs) 1994 CONFIRMATION SAMPLING

    (WOODWARD-CLYDE, 1995)

    SCTL1

    Constituent Residential Commercial/

    Industrial

    Base-Specific Soil Cleanup

    Goals2,3

    SS-0006-04 0-0.5ft bgs5 28-Apr-94

    SB-0001-44 2-4 ft bgs 21-Jun-94

    Polynuclear Aromatic Hydrocarbons (µg/kg)6 PAHs7 100 700 − 4408 ND9

    Benzo(a)anthracene − − − 320 ND Benzo(a)pyrene 100 700 1,500 300 ND Benzo(b)fluoranthene − − − 440 ND Benzo(k)fluoranthene − − − 390 ND Chrysene − − − 620 ND Dibenz(a,h)anthracene − − 1,500 ND ND Indeno(1,2,3-cd)pyrene − − − 240 ND

    Inorganics (mg/kg)6 Antimony 27 370 − ND 27.1 Arsenic 2.1 12 10 3.9 0.22 Barium 120 130,000 − 22.7 6.6 Chromium 210 470 − 26.9 4.1 Lead 400 1,400 − 56.6 0.44

    NOTES: 1. SCTLs are based on Chapter 62-777, FAC criteria dated 17 April 2005.

    2. The Base-Specific Soil Cleanup Goals for PAHs were agreed upon at the 19 September 1996 BCT meeting, based on the findings presented in “A Practical Approach for the Development of Typical Basewide PAH Concentrations Not Related to Waste Handling Practices for Use in Risk Management Decisions” (Woodward-Clyde, 1996).

    3. The Base-Specific Soil Cleanup Goal for arsenic is based on the Arsenic Background Study completed in November 1996 (AFBCA, 1996). 4. Sample Type: SS = surface soil sample; SB = soil boring. 5. bgs = below ground surface. 6. Units: µg/kg = micrograms per kilogram; mg/kg = milligrams per kilogram. 7. PAHs were calculated as the sum of the benzo(a)pyrene equivalents for the carcinogenic PAHs. 8. Bold text denotes results that exceed the residential SCTL. 9. ND = Not detected above the method detection limit.

  • 17

    TABLE 2-3 OPERABLE UNIT 27 – JET ENGINE TEST CELL FACILITY

    CONSTITUENTS OF CONCERN IN SOIL EXCEEDING SOIL CLEANUP TARGET LEVELS (SCTLs) 1996 REMEDIAL INVESTIGATION

    (WOODWARD-CLYDE, 1997)

    SCTL1

    Constituent Residential Commercial/

    Industrial

    Base-Specific Soil Cleanup

    Goals2,3

    SS-00114 0-0.5 ft bgs5

    18-Jan-96

    SS-0012 0-0.5 ft bgs 18-Jan-96

    SS-0013 0-0.5 ft bgs 18-Jan-96

    SS-0015 0-0.5 ft bgs 18-Jan-96

    SS-0016 0-0.5 ft bgs 18-Jan-96

    Polynuclear Aromatic Hydrocarbons (µg/kg)6 PAHs7 100 700 − 8208 ND9,10 ND 19,755 3,223

    Benzo(a)anthracene − − − 510 ND ND 12,000 1,800 J11 Benzo(a)pyrene 100 700 1,500 480 ND ND 12,000 2,000 J Benzo(b)fluoranthene − − − 840 ND ND 15,000 2,300 J Benzo(k)fluoranthene − − − 490 ND ND 14,000 2,700 J Chrysene − − − 670 ND ND 15,000 2,700 J Dibenz(a,h)anthracene − − 1,500 120 J ND ND 2,700 J 410 J Indeno(1,2,3-cd)pyrene − − − 350 J ND ND 9,400 J 1,300 J

    Inorganics (mg/kg) 6 Antimony 27 370 − 18.8 15.8 3.7 ND 16 Arsenic 2.1 12 10 1.3 14.5 6.2 3 2.3 Barium 120 130,000 − 19.4 J 27.3 J 33.7 J 56.5 J 31 Chromium 210 470 − 28.7 43.2 48.9 116 48.6 Lead 400 1,400 − 77.2 106 99.3 396 289

    NOTES: 1. SCTLs are based on Chapter 62-777, FAC criteria dated 17 April 2005.

    2. The Base-Specific Soil Cleanup Goals for PAHs were agreed upon at the 19 September 1996 BCT meeting, based on the findings presented in “A Practical Approach for the Development of Typical Basewide PAH Concentrations Not Related to Waste Handling Practices for Use in Risk Management Decisions” (Woodward-Clyde, 1996).

    3. The Base-Specific Soil Cleanup Goal for arsenic is based on the Arsenic Background Study completed in November 1996 (AFBCA, 1996). 4. Sample Type: SS = surface soil sample. 5. bgs = below ground surface. 6. Units: µg/kg = micrograms per kilogram; mg/kg = milligrams per kilogram. 7. PAHs were calculated as the sum of the benzo(a)pyrene equivalents for the carcinogenic PAHs. 8. Bold text denotes results that exceed the residential SCTL. 9. ND = Not detected above the method detection limit. 10. Diagonal hatching denotes sample locations that were excavated during the voluntary IRA in 2001. 11. Qualifiers: J = The value is estimated.

  • 18

    TABLE 2-3 (CONTINUED) OPERABLE UNIT 27 – JET ENGINE TEST CELL FACILITY

    CONSTITUENTS OF CONCERN IN SOIL EXCEEDING SOIL CLEANUP TARGET LEVELS (SCTLs) 1996 REMEDIAL INVESTIGATION

    (WOODWARD-CLYDE, 1997)

    SCTL1

    Constituent Residential Commercial/

    Industrial

    Base-Specific Soil Cleanup

    Goals2,3

    SS-00174 0-0.5 ft bgs5

    18-Jan-96

    SS-0018 0-0.5 ft bgs 18-Jan-96

    SS-0019 0-0.5 ft bgs 18-Jan-96

    SB-0002-0 0-0.5 ft bgs 23-Jan-96

    SB-0002-34 3.0 ft bgs 23-Jan-96

    Polynuclear Aromatic Hydrocarbons (µg/kg)6 PAHs7 100 700 − 8 ND8 9 119 ND

    Benzo(a)anthracene − − − ND ND ND ND ND Benzo(a)pyrene 100 700 1,500 ND ND ND ND ND Benzo(b)fluoranthene − − − 81 J10 ND 91 63 J ND Benzo(k)fluoranthene − − − ND ND ND 48 J ND Chrysene − − − 45 J ND 47 ND ND Dibenz(a,h)anthracene − − 1,500 ND ND ND ND ND Indeno(1,2,3-cd)pyrene − − − ND ND ND ND ND

    Inorganics (mg/kg) 6 Antimony 27 370 − 3 ND 4.4 ND 16.3 Arsenic 2.1 12 10 3.611 4 3.8 2.7 J 2.8 Barium 120 130,000 − 16.5 J 12.8 J 24.1 98.1 23.4 Chromium 210 470 − 25.9 15.6 26.1 356 19 Lead 400 1,400 − 72 23.8 71.9 1,050 J 172 NOTES: 1. SCTLs are based on Chapter 62-777, FAC criteria dated 17 April 2005.

    2. The Base-Specific Soil Cleanup Goals for PAHs were agreed upon at the 19 September 1996 BCT meeting, based on the findings presented in “A Practical Approach for the Development of Typical Basewide PAH Concentrations Not Related to Waste Handling Practices for Use in Risk Management Decisions” (Woodward-Clyde, 1996).

    3. The Base-Specific Soil Cleanup Goal for arsenic is based on the Arsenic Background Study completed in November 1996 (AFBCA, 1996). 4. Sample Type: SS = surface soil sample. SB = soil boring. 5. bgs = below ground surface. 6. Units: µg/kg = micrograms per kilogram; mg/kg = milligrams per kilogram. 7. PAHs were calculated as the sum of the benzo(a)pyrene equivalents for the carcinogenic PAHs. 8. ND = Not detected above the method detection limit. 9. Diagonal hatching denotes sample locations that were excavated during the voluntary IRA in 2001. 10. Qualifiers: J = The value is estimated. 11. Bold text denotes results that exceed the residential SCTL.

  • 19

    TABLE 2-3 (CONTINUED) OPERABLE UNIT 27 – JET ENGINE TEST CELL FACILITY

    CONSTITUENTS OF CONCERN IN SOIL EXCEEDING SOIL CLEANUP TARGET LEVELS (SCTLs) 1996 REMEDIAL INVESTIGATION

    (WOODWARD-CLYDE, 1997)

    SCTL1

    Constituent Residential Commercial/

    Industrial

    Base-Specific Soil Cleanup

    Goals2,3

    SB-0003-04 0-0.5 ft bgs5

    23-Jan-96

    SB-0003-4 2-4 ft bgs 23-Jan-96

    SB-0006-1 0.5-1.0 ft bgs

    8-Feb-96 Polynuclear Aromatic Hydrocarbons (µg/kg)6

    PAHs7 100 700 − 768 ND9 ND Benzo(a)anthracene − − − ND ND ND Benzo(a)pyrene 100 700 1,500 58 J10 ND ND Benzo(b)fluoranthene − − − 94 J ND ND Benzo(k)fluoranthene − − − 86 J ND ND Chrysene − − − 68 J ND ND Dibenz(a,h)anthracene − − 1,500 ND ND ND Indeno(1,2,3-cd)pyrene − − − ND ND ND

    Inorganics (mg/kg)6 Antimony 27 370 − 3.2 18 ND Arsenic 2.1 12 10 3.7 J11 2.8 2.6 Barium 120 130,000 − 82.1 14.4 12.9 Chromium 210 470 − 284 20.4 21.3 Lead 400 1,400 − 710 J 18.1 22.3

    NOTES: 1. SCTLs are based on Chapter 62-777, FAC criteria dated 17 April 2005.

    2. The Base-Specific Soil Cleanup Goals for PAHs were agreed upon at the 19 September 1996 BCT meeting, based on the findings presented in “A Practical Approach for the Development of Typical Basewide PAH Concentrations Not Related to Waste Handling Practices for Use in Risk Management Decisions” (Woodward-Clyde, 1996).

    3. The Base-Specific Soil Cleanup Goal for arsenic is based on the Arsenic Background Study completed in November 1996 (AFBCA, 1996). 4. Sample Type: SB = soil boring. 5. bgs = below ground surface. 6. Units: µg/kg = micrograms per kilogram; mg/kg = milligrams per kilogram. 7. PAHs were calculated as the sum of the benzo(a)pyrene equivalents for the carcinogenic PAHs. 8. Diagonal hatching denotes sample locations that were excavated during the voluntary IRA in 2001. 9. ND = Not detected above the method detection limit. 10. Qualifiers: J = The value is estimated. 11. Bold text denotes results that exceed the residential SCTL.

  • 20

    TABLE 2-4 OPERABLE UNIT 27 – JET ENGINE TEST CELL FACILITY

    CONSTITUENTS OF CONCERN IN SOIL EXCEEDING SOIL CLEANUP TARGET LEVELS (SCTLs) 2001 VOLUNTARY INTERIM REMEDIAL ACTION – CONFIRMATION SAMPLING

    (VERSAR, 2002)

    SCTL1

    Constituent Residential Commercial/

    Industrial

    Base-Specific Soil Cleanup

    Goals2,3

    SS-24 0.5-1.0 ft bgs5

    Apr-01

    SS-4 0.5-1.0 ft bgs

    Apr-01

    SS-5 0.5-1.0 ft bgs

    Apr-01

    SS-5-2 1.5 ft bgs 16-Apr-01

    Polynuclear Aromatic Hydrocarbons (µg/kg)6 PAHs7 100 700 − NA8 2049 10,75210 ND11

    Benzo(a)anthracene − − − NA ND 7,400 ND Benzo(a)pyrene 100 700 1,500 NA 170 6,710 ND Benzo(b)fluoranthene − − − NA 340 9,850 ND Benzo(k)fluoranthene − − − NA ND 3,850 ND Chrysene − − − NA ND 7,250 ND Dibenz(a,h)anthracene − − 1,500 NA ND 1,440 ND Indeno(1,2,3-cd)pyrene − − − NA ND 4,850 ND

    Inorganics (mg/kg)6 Antimony 27 370 − 30.4 NA 46.4 63.5 Arsenic 2.1 12 10 ND NA NA NA Barium 120 130,000 − NA NA NA NA Chromium 210 470 − 92.7 11.9 13.6 NA Lead 400 1,400 − NA NA NA NA

    NOTES: 1. SCTLs are based on Chapter 62-777, FAC criteria dated 17 April 2005.

    2. The Base-Specific Soil Cleanup Goals for PAHs were agreed upon at the 19 September 1996 BCT meeting, based on the findings presented in, “A Practical Approach for the Development of Typical Basewide PAH Concentrations Not Related to Waste Handling Practices for Use in Risk Management Decisions” (Woodward-Clyde, 1996).

    3. The Base-Specific Soil Cleanup Goal for arsenic is based on the Arsenic Background Study completed in November 1996 (AFBCA, 1996). 4. Sample Type: SS = surface soil sample. 5. bgs = below ground surface. 6. Units: µg/kg = micrograms per kilogram; mg/kg = milligrams per kilogram. 7. PAHs were calculated as the sum of the benzo(a)pyrene equivalents for the carcinogenic PAHs. 8. NA = The sample was not analyzed for this constituent. 9. Bold text denotes results that exceed the residential SCTL. 10. Diagonal hatching denotes sample locations that were excavated during the voluntary IRA in 2001. 11. ND = Not detected above the method detection limit.

  • 21

    the residential SCTLs. Further excavation of Areas 2 and 4 was not conducted because remaining contaminant concentrations were relatively low (i.e., below the commercial/ industrial SCTLs). Area 5 was further excavated to a depth of 1.5 ft bgs to the top of the limestone bedrock (Versar, 2002). After all excavation was complete, the confirmation samples indicated that PAHs remained at Area 4 (i.e., SS-4) and antimony remained at Areas 2 and 5 (i.e., SS-2 and SS-5-2, respectively) at concentrations greater than the residential SCTLs but significantly less than the commercial/industrial SCTLs.

    Additional post-IRA soil sampling was conducted in 2002 to further evaluate the nature and extent of antimony detected in the final confirmation samples from Areas 2 and 5. Five sidewall and four floor samples were collected from Area 2, and three sidewall and two floor samples were collected from Area 5, as shown in Figure 2-5. Samples were collected from 1 ft bgs and analyzed for antimony and chromium. Results indicated that neither antimony nor chromium were present in the samples at levels of concern (IT Corporation, 2002). The results of the 2002 post-IRA soil sampling suggest that the original antimony results in confirmation samples SS-2 and SS-5 were either anomalous or the contaminated areas were so small that the results could not be replicated. In either case, the results indicate that there is no significant antimony contamination in soil at OU-27.

    The analytical results for the confirmation samples collected after the IRA excavation and during additional confirmation sampling conducted in 2002 (see Figure 2-5) indicate that the IRA was largely successful. The final confirmation sample results indicate that PAHs remain at sample location SS-4 at a concentration of 204 micrograms (µg)/kilogram (kg) and at sample location SS-0006-0 at a concentration of 440 µg/kg , which exceed the residential SCTL but are significantly less than the commercial/industrial SCTL. The lateral and vertical dimensions of the soil contamination exceeding the residential SCTL were estimated based on the location and depth of historical samples and multiplied to derive volume estimates for the contaminated soil. The areas of residual (i.e., post-IRA) contamination are estimated to be approximately 10 ft wide by 10 ft long by 1.5 ft deep, which amounts to approximately 5.5 cubic yards of soil for each sample location. Based on these estimates, approximately 11 cubic yards of PAH-contaminated soil are assumed to remain at the site, as shown on Figure 2-4.

    Although it was not detected in any of the confirmation samples, arsenic remains present at various locations within OU-27. Arsenic was detected in samples during the 1994 and 1996 sampling events at concentrations ranging between 2.6 and 4.9 mg/kg. These concentrations exceed the residential SCTL of 2.1 milligrams (mg)/kg, but are less than the commercial/industrial SCTL of 12 mg/kg and the base-specific background level of 10 mg/kg. These results indicate that the arsenic present in soil at the site is attributable to base-specific background conditions.

    Although concentrations of antimony and chromium in soil remaining at OU-27 exceed the FDEP’s leachability SCTLs of 5.4 mg/kg and 38 mg/kg, respectively, it is unlikely that these concentrations would result in impacts to underlying ground water. Sample results indicate that the mass of contamination that remains is very small and would be insignificant in terms of the mass required to yield significant contamination of underlying ground water. Furthermore, use of OU-27 for jet engine testing was discontinued in the mid-1980s, and painting and corrosion control activities at the site ceased in 1992. Release of any contaminants would have

  • 22

    occurred prior to that time. Thus, it is believed that if leaching of contaminants from OU-27 was likely to occur, it would have occurred over the past 13 to 25 years. As indicated below, during the last round of ground-water sampling performed in 1997, antimony was not detected above reporting limits and chromium has never been detected at concentrations exceeding GCTLs. It is highly unlikely that the relatively low concentrations of antimony and chromium present in soil at OU-27 will impact underlying ground water in the future.

    Ground Water. During the investigations in 1994 and 1996, ground-water samples were collected from 66 direct-push borings and four monitoring wells, as shown on Figures 2-2 and 2-3. Ground-water samples from the direct-push borings were analyzed only for VOCs, whereas samples from the monitoring wells were analyzed for VOCs, SVOCs, pesticides, PCBs, metals, and cyanide. The results of the direct-push samples indicated the presence of VOCs in ground water in the central portion of the site. However, no VOCs were detected in ground-water samples that were subsequently collected from the four monitoring wells. During ground-water sampling in 1996, antimony was the only constituent detected at an elevated concentration. Antimony was detected at monitoring well MW-0004 at a concentration of 24.6 micrograms per liter (µg/L). In response to a request by the FDEP on 28 May 1997, a one-time ground-water sampling event was performed at MW-0004 for selected metals (i.e., antimony and the RCRA eight metals). Only four target metals were detected (i.e., barium, cadmium, chromium, and lead) and all were below ground-water cleanup target levels (GCTLs). Antimony was not detected (Versar, 1997).

    2.5.2 Contaminant Fate and Transport

    As described in Section 2.5.1, limited residual PAH-contaminated soil remains in two locations at OU-27 at concentrations exceeding unrestricted use and unlimited exposure criteria. PAHs are generally stable in the environment, due to the stability of their aromatic ring structure. They are relatively immobile in soil and should not be expected to pose a risk to underlying ground water. This is supported by ground-water sampling and analysis conducted in 1994, 1996, and 1997, in which PAHs were not detected in ground water above GCTLs during any sampling event.

    Contaminant fate and transport modeling was completed as part of the RI for the purpose of evaluating the potential for the site-related COCs in the shallow ground water to migrate toward the nearby Boundary Canal. The COCs included PAHs, arsenic, and antimony in soil and antimony in ground water. The modeling activity included evaluating contaminant migration mechanisms, the characteristics of the COCs, and the relationship between the shallow ground water and the surface water in the Boundary Canal.

    The modeling of the fate and transport of the COCs in the shallow ground water indicated that the contaminants would not reach the canal surface water at concentrations above the appropriate FDEP surface water criteria specified in FAC 62-302.530.

    2.6 Current and Potential Future Land and Resource Uses

    The OU-27 property has not been actively used since 1992. Aircraft engine testing was discontinued at the site in the mid-1980s, when the hush houses were constructed for this purpose and began operation. Painting and corrosion control activities at the site were

  • 23

    sporadic, and this activity was discontinued in 1992. Neither the site nor the underlying ground water are currently used for any purpose, and access to the site is strictly controlled due to its presence on an active AFRC installation, in close proximity to the runway and the munitions storage area. Currently exposed populations associated with OU-27 include commercial/industrial workers such as grounds maintenance workers who occasionally mow the grass. No other personnel enter the site on a regular basis, and trespassing is highly unlikely, given the security measures in place to prevent access to this portion of the installation. Although highly unlikely, hypothetical future exposed populations could include construction workers and on-site residents.

    Homestead ARB is expected to remain an active AFRC installation for the foreseeable future. As such, access to the installation will continue to be strictly controlled and limited to authorized individuals. As a result, the future land use of the OU-27 area is expected to remain commercial/industrial. Use of the contaminated portions of the OU-27 area is expected to remain limited, with the most likely exposure to grounds maintenance workers that occasionally mow the grass at the site.

    The surficial (i.e., uppermost) aquifer, the Biscayne Aquifer, is the sole source of potable water in Miami-Dade County and has been declared a sole-source aquifer by the EPA, pursuant to Section 1425 of the Federal Safe Drinking Water Act. Ground water is not currently used in the OU-27 area. In addition, no active drinking-water wells are currently located within Homestead ARB, and no new potable or non-potable water wells are planned for this area.

    2.7 Summary of Site Risks

    A baseline risk assessment was completed for OU-27 following the RI in 1997; however, the majority of the contamination on which the risk assessment was based was removed during the IRA in 2001. As a result, a streamlined risk evaluation was performed in the FS to determine the risks posed by exposure to contaminated media at OU-27. In general, the steps in the risk evaluation process were as follows:

    1) Maximum concentrations of each contaminant detected in soil and ground water were compared with FDEP residential SCTLs or GCTLs, which were based on cancer target risk levels of 1 x 10-6 or non-cancer hazard indices of 1.0, and EPA’s maximum contaminant levels (MCLs)

    2) Contaminants in soil and ground water whose maximum concentrations did not exceed the FDEP residential SCTLs or MCLs were dropped from further risk evaluation

    3) Exposure Point Concentrations (EPCs), based on the 95% UCL on the mean, were calculated in accordance with EPA guidance for contaminants whose maximum concentrations exceeded residential SCTLs and/or EPA MCLs

    4) The calculated EPCs were compared with the commercial/industrial SCTLs, which also were based on cancer target risk levels of 1 x 10-6 or non-cancer hazard indices of 1.0, and EPA MCLs to identify COCs requiring further risk evaluation

    5) If all EPCs were less than the commercial/industrial SCTLs, GCTLs, or EPA MCLs, the risk evaluation was not continued

    6) Estimated cancer risks and non-cancer hazards were calculated for contaminants whose

  • 24

    EPCs exceeded the residential SCTLs, GCTLs, and/or EPA MCLs (i.e., the COCs) using standard EPA risk assessment methodology

    7) Estimated cancer risks and non-cancer hazards were compared to EPA’s target cancer risk range of 1 x 10-4 to 1 x 10-6 and non-cancer hazard index of 1.0.

    Based on the initial conservative screening level comparison, PAHs, antimony, and arsenic were detected in OU-27 soil at concentrations greater than the residential SCTL. Six of the seven carcinogenic PAHs (i.e., benzo(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, chrysene, and indeno(1,2,3-cd)pyrene) were detected in soil at OU-27, but the seventh (i.e. dibenz(a,h)anthracene) was not. In accordance with Chapter 62-777, FAC, the carcinogenic PAHs are evaluated as the sum of their benzo(a)pyrene toxicity equivalents. Tables 2-2 through 2-4 summarize soil sample results from OU-27 that exceed unrestricted use and unlimited exposure criteria represented by the residential SCTLs. Samples that exceeded the SCTLs but have since been excavated from the site are shown on the tables for information purposes. However, they have been excluded from the risk evaluation described below because they are no longer present at the site, and no longer pose a potential risk. The streamlined risk evaluation for OU-27 stopped after Step 5 because no COCs were identified that exceeded the FDEP commercial/industrial SCTLs, GCTLs, or EPA MCLs.

    Contaminant concentrations detected in ground water during the most recent rounds of ground-water monitoring did not exceed their respective EPA MCLs. Exposure to ground water at OU-27 is not expected to pose a significant risk in the unlikely event that receptors come into contact with ground water.

    2.7.1 Summary of Human Health Risk Assessment

    Following the initial comparison of contaminant concentrations in OU-27 soil with FDEP residential SCTLs and in OU-27 ground water with GCTLs and EPA MCLs, it was determined that PAHs, antimony, and arsenic in soil required additional consideration in the streamlined risk evaluation. Table 2-5 provides summary detection information and EPCs for COCs. Potential risks posed by total PAHs, benzo(a)pyrene, antimony, and arsenic in soil at OU-27 were evaluated by a comparison of the EPCs shown in Table 2-5 with the FDEP commercial/industrial SCTLs from Chapter 62-777 of the FAC.

    The EPCs for both benzo(a)pyrene and total PAHs exceed the FDEP residential SCTL of 100 µg/kg. These results indicate that contamination remains at the site at concentrations that exceed unrestricted use and unlimited exposure criteria and may pose a potential risk in the unlikely event that the property is used for residential purposes. However, the OU-27 property is not currently used for residential purposes and is not anticipated to be used for residential purposes in the future.

    Although the EPC for arsenic exceeded the residential SCTL of 2.1 mg/kg, it does not exceed the base-specific background level for arsenic of 10 mg/kg. Because arsenic contamination was due to non-site-related activity and was lower than the base-specific background level, arsenic was not considered to pose an unacceptable risk. Although no action was taken as a result of the arsenic concentrations, the LUCs to prevent residential use will also prevent unacceptable exposure to soil containing concentrations of arsenic in exceedance of the residential SCTL.

  • 25

    Table 2-5 Summary Information for Constituents of Concern in Soil Exceeding the FDEP Soil Cleanup Target Levels (SCTLs)

    Constituent

    Frequency of

    Detection

    Detected Concentration

    Range

    FDEP Commercial/

    Industrial SCTL1 EPC2

    Upper Confidence

    Limit Method Polynuclear Aromatic Hydrocarbons (µg/kg)3

    Total PAHs4 - 151–440 700 441.41 95% Student’s-t Benzo(a)pyrene 3 / 21 69–300 700 223.12 95% Student’s-t Benzo(a)anthracene 2 / 21 54–320 – – Benzo(b)fluoranthene 6 / 21 81–440 – – Benzo(k)fluoranthene 3 / 21 81–390 – – Chrysene 5 / 21 45–620 – – Dibenz(a,h)anthracene 0 / 21 BDL5 – – Indeno(1,2,3-cd)pyrene 2 / 21 70–240 – –

    Inorganics (mg/kg)3 Antimony 11 / 31 3–63.5 370 20.23 95% Chebyshev Arsenic 18/19 BDL5–4.9 12 3.00 95% Student’s-t

    1. FDEP SCTLs are based on Chapter 62-777, FAC criteria dated 17 April 2005.. 2. EPCs were calculated for PAHs as the sum of the benzo(a)pyrene toxicity equivalents for the carcinogenic PAHs. 3. Units: µg/kg = micrograms per kilogram; mg/kg = milligrams per kilogram 4. Total PAH detections are based on the sum of the benzo(a)pyrene toxicity equivalents for all carcinogenic PAHs where

    half the detection limit was used for non-detected data. 5. BDL – below detection limit.

    Antimony was detected at three sample locations (SB-0001-4, SS-2, and SS-5-2) at concentrations that exceeded the residential SCTL of 27.0 mg/kg. However, the EPC for antimony in OU-27 soil is 20.23 mg/kg, which is less than the residential SCTL of 27.0 mg/kg. These results indicate that antimony does not pose a potential risk to the current or anticipated future users of the site, which are commercial/industrial in nature, or to potential future residential receptors.

    Overall, the results of the OU-27 risk evaluation indicate that only a few isolated soil samples contained total PAH concentrations that exceeded unrestricted reuse and unlimited exposure criteria represented by the residential SCTLs, as indicated in Figure 2-4. The risk evaluation indicates that there are two small areas of PAH-contaminated soil that may pose a potential risk under a residential use scenario.

    2.7.2 Summary of Ecological Risk Assessment

    An ecological risk assessment (ERA) performed at OU-27 as part of the RI in 1997 concluded that, although potential risks may occur due to the presence of PAHs in soil, actual risks are likely to be significantly overestimated because elevated soil concentrations are localized to a few sampling locations. As a result, an insignificant number of individuals affected by OU-15 is unlikely to result in adverse effects at the population or community level. Therefore, no significant ecological risks are anticipated at OU-27 because:

    • The area of soil contamination is small relative to the home ranges of potential target ecological receptors (e.g., opossum)

  • 26

    The site’s proximity to an active runway and the fact that the grassy areas of the site are regularly mown makes the limited habitat unattractive to many animals (e.g., American robin, short-tailed shrew)

    Even in the event that individual ecological receptors are adversely affected by the contamination, there would be no significant adverse impact to the larger population of that receptor.

    The area of soil contamination at OU-27 consists of two isolated sample locations, with low concentrations of PAHs. Because the contaminated portions of OU-27 (e.g., less than one quarter of an acre) are small in comparison to the size of the home ranges of potential target ecological receptors, the potential for significant exposure of wildlife to contaminants is limited. Furthermore, because OU-27 is located adjacent to an active runway, activities associated with flight operations make the limited habitat at the site unattractive to many animals.

    Based on these two points, it is unlikely that ecological receptors will have significant contact with soil contamination at OU-27. While it is possible that contact with contaminant concentrations at OU-27 may cause adverse effects to individual plants or animals, given that contaminated soil at OU-27 represents a small portion of a much larger ecosystem, it is considered highly unlikely that the population of plants and animals as a whole would be significantly impacted. There are no threatened or endangered species known to inhabit the site that would warrant protection of individual receptors.

    2.8 Remedial Action Objectives

    The remedial action objectives (RAOs) for OU-27 are intended to

    • Prevent residential exposure to contaminants in soil in exceedance of the residential SCTLs shown in Table 2-6.

    Table 2-6 Soil Cleanup Target Levels for Constituents of Concern at OU-27

    COCs Units FDEP Residential SCTLs1 FDEP Commercial/ Industrial SCTLs EPC2

    Total PAHs3 µg/kg4 100 700 441.41 Benzo(a)pyrene µg/kg 100 700 223.12

    1. FDEP SCTLs are based on Chapter 62-777, FAC criteria dated 17 April 2005.. 2. Exposure point concentrations (EPCs) were calculated for PAHs as the sum of the benzo(a)pyrene toxicity equivalents for

    the carcinogenic PAHs. 3. Total PAH detections are based on the sum of the benzo(a)pyrene toxicity equivalents for all carcinogenic PAHs where

    half the detection limit was used for non-detected data. 4. Units: µg/kg = micrograms per kilogram.

    The RAOs will impact the ability of the site to be used for residential use. As described in Section 2.7.1, the EPCs for the COCs at OU-27 are less than the commercial/industrial SCTLs identified in Table 2-6, which are based on cancer target risk levels of 1 x 10-6 or non-cancer hazard indices of 1.0. Therefore, the site does not pose an unacceptable risk to commercial/industrial users of the site. In the event that use of the site changes, then the remedy and these RAOs will trigger additional action to prevent unacceptable exposure. The RAOs were developed in response to exceedances of residential SCTLs, which also are based on

  • 27

    cancer target risk levels of 1 x 10-6 or non-cancer hazard indices of 1.0, during the risk evaluation for OU-27 as discussed in more detail in Section 2.7.1.

    2.9 Description of Alternatives

    The Streamlined FS for OU-27 (Booz Allen, 2006) identified three final remedy alternatives for consideration. Based on the site characteristics described in Section 2.5, the current and anticipated future land uses described in Section 2.6, and the potential risks described in Section 2.7, the most viable remedial alternatives for OU-27 are:

    Alternative 1 – No Further Action Alternative 2 – Land Use Controls Alternative 3 – Excavation and Off-Site Disposal.

    Each of these alternatives is described below and was evaluated during the detailed analysis of alternatives in the FS.

    2.9.1 Alternative 1 – No Further Action

    The no further action alternative would require nothing to be done to change the current contaminated soil conditions at OU-27. No excavation, treatment, or containment of the contaminated soil would be conducted. Unrestricted use of the property and unlimited exposure to contaminated soil would be allowed. While it is likely that contaminant concentrations will reduce over time due to natural degradation processes, the rate of reduction would not be measured.

    The NCP, 40 CFR 300.430(e)(6), requires that a no action alternative (or in cases where a previous interim remedial action has been conducted, a no further action alternative) be developed and included in the analysis of alternatives. The no further action alternative is used as a baseline against which to compare other alternatives.

    2.9.2 Alternative 2 – Land Use Controls

    Alternative 2 would include LUCs being implemented to prohibit current and future users of the site from using the property for residential purposes, hospitals for human care, public or private schools, or day care centers for persons under 18 years of age. Alternative 2 would also include LUCs requiring that any contaminated soil that is excavated at OU-27 will be properly managed on site and that any contaminated soil transported off site will be managed in accordance with applicable RCRA regulations. Use restrictions would be specified in the base general plan (BGP) and implemented, monitored, maintained, and enforced by the Homestead ARB Installation Commander through the BCE Environmental Flight Office personnel.

    2.9.3 Alternative 3 – Excavation and Off-Site Disposal

    Alternative 3 requires contaminated surface soil to be excavated, removed from the site, and disposed of at an appropriately permitted landfill. LUCs would be implemented temporarily to minimize contact with the contaminated soil prior to completion of excavation activities. Soil exceeding the residential SCTLs would be excavated using a backhoe, staged on site in covered

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    piles or roll-off boxes pending waste characterization, and transported to an off-site disposal facility for final disposition. If successfully implemented, all contaminated soil would be removed from the site, so long-term implementation of LUCs would not be required. The estimated volume of soil that will require excavation and off-site disposal is approximately 11 cubic yards.

    2.10 Summary of Comparative Analysis of Alternatives

    During the detailed analysis of alternatives conducted in the FS, each of the three potential remedial alternatives was evaluated against seven of the nine criteria specified in the NCP. The first two criteria are threshold criteria. The following are statutory requirements that the alternative must satisfy to be considered a viable final remedy option:

    1. Overall protection of human health and the environment 2. Compliance with Applicable or Relevant and Appropriate Requirements (ARARs)

    Appendix C in the FS provides a comprehensive evaluation of chemical-, location-, and action-specific ARARs.

    The next five criteria are known as the primary balancing criteria. The following are the technical criteria upon which the detailed analysis is based:

    3. Long-term effectiveness and permanence 4. Reduction of toxicity, mobility, and volume through treatment 5. Short-term effectiveness 6. Implementability 7. Cost

    The following two criteria, known as the modifying criteria, also were evaluated; however, they were not evaluated as part of the FS. These criteria were assessed following regulatory and public review of the FS and Proposed Plan.

    8. State acceptance 9. Community acceptance

    A detailed evaluation of each of the three remedial alternatives described in Section 2.9 was conducted in the FS. The comparative analysis from the FS, which describes the relative benefits and deficiencies of each alternative, is summarized below.

    2.10.1 Threshold Criteria

    All remedial action alternatives must be protective of human health and the environment and comply with ARARs in order to be considered acceptable for selection as the preferred alternative. Both Alternative 2, the preferred alternative, and Alternative 3 satisfy the threshold criteria, as described below. Therefore, either Alternative 2 or 3 would be an acceptable final remedy for OU-27. Alternative 1 is not protective of the unrestricted use and unlimited exposure scenario. As such, it is not a viable option for the final remedy at OU-27.

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    Overall Protection of Human Health and the Environment

    As described in Section 2.7.1, COCs do not remain at OU-27 at concentrations greater than the commercial/industrial SCTLs. Therefore, Alternative 1 – No Further Action would be protective of human health and the environment under the current and anticipated future use scenario, which is commercial/industrial in nature. However, Alternative 1 does not include LUCs, which would be required to ensure that it is protective of the unrestricted use and unlimited exposure scenario. Alternative 2 would protect human health and the environment by preventing unacceptable exposure to contaminated soil at the site through the implementation of LUCs. Alternative 3 would protect human health and the environment through removal of the soil contamination from the site.

    Compliance with ARARs

    Alternatives 2 and 3 would comply with ARARs, including, but not limited to Chapters 62-777 and 62-780 of the FAC.

    In order to evaluate the need for LUCs, the concentrations of residual soil contamination also were compared to the residential SCTLs listed in Table 2-6. Based on this comparison, PAHs and benzo(a)pyrene exceed residential SCTLs, indicating a need for LUCs to be protective of the unrestricted use and unlimited exposure scenario. LUCs would not be included in Alternative 1. Alternative 2 complies with these requirements by instituting LUCs to prevent unacceptable exposure to soil containing contaminant concentrations greater than the residential SCTLs. Alternative 3 complies with these requirements by removing soil that contains contaminant concentrations greater than the residential SCTLs, so that LUCs are no longer required.

    2.10.2 Balancing Criteria

    Each of the three alternatives were further evaluated using the balancing criteria described in the NCP. The results of that evaluation are summarized below for Alternatives 2 and 3. Alternative 1 has been excluded from the summary below because it was eliminated from further consideration due to the lack of LUCs required to be protective of the unrestricted use and unlimited exposure scenario. The preferred alternative, Alternative 2, was selected based on the overall ability of the alternative to satisfy these criteria.

    Long-Term Effectiveness and Permanence

    Both Alternative 2 and Alternative 3 would provide adequate long-term effectiveness. Alternative 2 would remain effective over the long term through ongoing imposition of use restrictions and an established monitoring and enforcement program operated by AFRC. Alternative 3 may provide the greatest long-term effectiveness if all soil contamination can be removed from the site. However, the presence of existing site features, such as buildings and utilities, may result in incomplete removal of soil contamination, in which case LUCs would ultimately be required.

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    Reduction of Toxicity, Mobility, and Volume Through Treatment

    Neither Alternative 2 nor Alternative 3 would satisfy the statutory preference for treatment. Alternative 2 would leave contamination in place and Alternative 3 would move contaminated soil to a disposal facility. Neither alternative would treat the soil to reduce the toxicity, mobility, or volume of contamination.

    Short-Term Effectiveness

    Both Alternative 2 and Alternative 3 would provide adequate short-term effectiveness. Alternative 2 would provide immediate protection of human health by imposition of use restrictions. Alternative 3 would provide immediate protection of human health by temporary implementation of land use restrictions and excavation and removal of contamination from the site within one year. It is intuitively reasonable to assume that excavation of contaminated soil conducted as part of Alternative 3 would increase the potential for exposure to contamination. Soil currently located below-grade and inaccessible to receptors at the site would be exposed where direct contact and/or airborne dispersion would be more likely, although no data have been collected to support this conclusion. Therefore, Alternative 3 would be slightly less effective in the short term because the potential for exposure would be increased during excavation.

    Implementability

    Alternative 2 would be more easily implemented than Alternative 3. LUCs would be implemented, monitored, maintained, and enforced by the Homestead ARB Installation Commander through the BCE’s Environmental Flight Office personnel at the installation, so they would be easily implemented. Alternative 3 would require a significantly higher level of effort and additional complexity to implement. Extensive budget programming, contracting, and planning steps would be required prior to implementation, and completion of the action would require mobilization of staff and heavy equipment to the site; excavation, transportation, and disposal of contaminated soil; and confirmation sampling and sample analysis. In addition, full implementation of Alternative 3 may be hindered by the presence of existing concrete and asphalt pavement that could limit the quantity of contaminated soil that can be effectively excavated.

    Cost

    The estimated cost for Alternative 2 of $49,665 is comparable to the estimated cost for Alternative 3, which is $26,200. However, the cost of implementing Alternative 2 assumes that an outside contractor would be used to monitor the LUCs. In addition, the cost of Alternative 3 does not include costs for implementation and monitoring LUCs by an outside contractor, which may be necessary if excavation of contaminated soil is hindered by the presence of existing concrete and asphalt pavement. It is anticipated that the LUCs would actually be implemented and monitored by Homestead ARB Environmental Flight personnel, in which case no external contracting costs would be incurred. As a result, the anticipated cost of Alternative 2 would be negligible and the cost of Alternative 3 would be $26,200 for excavation activities.

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    2.10.3 Modifying Criteria

    The modifying criteria were evaluated based on comments received on the Proposed Plan (Booz Allen, 2006) and during the public comment period, which was held between 3 April and 3 May 2006.

    State Acceptance. FDEP reviewed and provided comments on the investigation and remedy selection documents for OU-27, including the FS, the Proposed Plan, and this ROD. The AFRC has responded to each of FDEP’s comments on these documents in an acceptable manner.

    Community Acceptance. Notices were published in the South Dade News Leader on Friday, 31 March 2006, and in The Miami Herald on Thursday, 30 March 2006, to notify members of the public of the opportunity to provide comment on the Proposed Plan for OU-27. The public notices also indicated that a meeting would be held on 20 April 2006, at 7:00 PM to discuss the preferred remedial alternatives for OU-27.

    Prior to initiation of the public comment period on 3 April 2006, a copy of the Proposed Plan for OU-27 and other historical documents, such as the FS, were made available for public review at the Homestead Branch of the Miami-Dade County Library located at 700 N. Homestead Boulevard in Homestead, Florida.

    A public meeting was held on 20 April 2006, from 7:00 to 8:00 PM at the City Council Chamber Room in City Hall, located at 790 Homestead Boulevard, Homestead, Florida, to inform members of the public of the preferred remedial alternatives to address contamination at OU-27. A poster presentation was prepared that summarized the information provided in the Proposed Plan and identified the preferred remedial alternative as LUCs. Representatives of AFRC were available at the meeting to discuss the preferred remedial alternatives and to answer questions. No comments were provided on the Proposed Plan or Preferred Alternative during the public meeting.

    As indicated in the notices published in local newspapers, a formal public comment period was conducted from 3 April 2006 to 3 May 2006. No public comments were received for OU-27 during the public comment period.

    2.10.4 Comparison of Alternatives

    Table 2-7 provides a side-by-side comparison of the seven threshold and primary balancing criteria for the three alternatives.

    As the table indicates, Alternative 2 – LUCs, and Alternative 3 – Excavation and Off-Site Disposal both satisfy the threshold criteria of protection of human health and the environment and compliance with ARARs. Therefore, either Alternative 2 or 3 would be an acceptable final remedy for OU-27. However, Alternative 1 does not include LUCs required to be protective of the unrestricted use and unlimited exposure scenario. As such it is not a viable option for the final remedy at OU-27.

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    Table 2-7 Comparison of Alternatives

    Criteria

    Alternative 1 No Further

    Action

    Alternative 2 Land Use Controls

    Alternative 3 Excavation and Off-

    Site Disposal Threshold Criteria 1. Overall Protection of Human

    Health and the Environment 3 4 4

    2. Compliance with ARARs 3 4 4 Primary Balancing Criteria 3. Long-Term Effectiveness and

    Permanence 3 3 3

    4. Reduction of Toxicity, Mobility, or Volume Through Treatment

    0 0 0

    5. Short-Term Effectiveness 4 4 4 6. Implementability 4 3 3 7. Cost 4 4 3

    0 = Poor; 1 = Fair; 2 = Moderate; 3 = Good; 4 = Excellent

    Alternatives 2 and 3 would provide adequate short- and long-term effectiveness and provide immediate protection of human health by imposition of use restrictions. Alternative 2 would remain effective over the long term through ongoing imposition of use restrictions and an established monitoring and enforcement program operated by Homestead ARB Environmental Flight Office personnel. Future use of the OU-27 area for residential use would be restricted. These restrictions would be implemented to prohibit current and potential future users of the site from using the property for residential purposes, hospitals for human care, public or private schools, or day care centers for persons under 18 years of age. Alternative 3 may provide the greatest long-term effectiveness if all soil contamination can be removed from the site. However, soil contamination would be disturbed during remedy implementation, so that there would be a short-term increase in the potential for exposure to contaminants. In addition, the presence of existing site features, such as asphalt parking areas and concrete pads, may result in incomplete removal of soil contamination, in which case LUCs would ultimately be required.

    Alternative 2 and Alternative 3 would not satisfy the statutory preference for treatment. Alternative 2 would leave contamination in place and Alternative 3 would move contamination to a disposal facility. Neither alternative would treat the soil to reduce the toxicity, mobility, or volume of contamination.

    Alternative 2 would be more easily implemented and less costly than Alternative 3. LUCs would be implemented, monitored, maintained, and enforced by the Homestead ARB Installation Commander through the BCE’s Environmental Flight Office personnel, so they would be easily implemented and would not incur costs for external contractor support. Excavation and off-site disposal would cost approximately $26,200, and full implementation of the remedy may be hindered by the presence of existing asphalt pavement and concrete pads.

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    2.11 Principal Threat Wastes

    The NCP states that EPA expects to use treatment to address the principal threats posed by a site, wherever practicable. This preference does not impact the decision at OU-27 because there are no principal threat wastes present at the site.

    Principal threat wastes are defined as those source materials considered to be highly toxic or highly mobile that generally cannot be reliably contained or would present a significant risk to human health or the environment should exposure occur. The contamination present at OU-27 is not considered a principal threat waste because:

    They are not highly toxic – Contaminants are present at concentrations that are not significantly greater than the SCTLs and would present an excess cancer risk near the acceptable risk range were exposure to occur.

    They are not highly mobile – The concentrations and solubility of the soil contaminants are relatively low, so they are not a potentially significant source of ground-water, air, or surface-water contamination. This observation is supported by ground-water monitoring results that demonstrate that, in the absence of any controls, soil contaminants are not present in the shallow groundwater beneath the site.

    As a result, aggressive source removal, treatment, or physical containment is not necessary.

    2.12 Selected Remedy

    To achieve the RAOs defined in Section 2.8, Alternative 2, Land Use Controls, was selected by AFRC and the EPA as the final remedy for OU-27. Alternative 2 requires that LUCs be placed on the portions of the OU-27 site containing residual soil contamination that exceed unrestricted use and unlimited exposure criteria represented by the residential SCTLs, as specified in Table 2-6. Alternative 2 includes:

    • Use Restrictions – Residential use will be prohibited on portions of the OU-27 property containing contaminated soil at concentrations greater than unrestricted use and unlimited exposure criteria represented by the residential SCTLs shown in Table 2-6. The residential use restrictions will be implemented to prohibit property users from using the property for residential purposes, hospitals for human care, public or private schools or day care centers for persons under 18 years of age. Use restrictions will ensure that the future land use of the property remains commercial/industrial and does not change to residential use. Figure 2-2 identifies the site boundary for OU-27 that will require LUCs.

    Contaminated Soil Management Restrictions – LUCs will be implemented to require that any contaminated soil that is excavated at OU-27 will be properly managed on site and that any contaminated soil transported off site will be managed in accordance with applicable RCRA regulations.

    LUCs will remain in place until confirmatory sampling data indicate that contaminant concentrations have declined below unrestricted use and unlimited exposure criteria represented by the residential SCTLs in Table 2-6. The Air Force will utilize its BGP as

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    an administrative LUC to prevent any use inconsistent with this ROD. Within 60 days after ROD signature, the Air Force will make appropriate changes to the BGP to incorporate use restrictions for the site. The appropriate section of the BGP will state:

    Residential use, including hospitals for human care, public or private schools, or day care centers for persons under 18 years of age, of OU-27 is prohibited. Any requests (for example, through excavation permits, such as Air Force [AF] Form 103, or the construction review process, Air Force Instruction [AFI] 32-1001) for residential use will be denied, unless the procedures for proposed land use changes described in OU-27 Record of Decision (ROD), dated August 24, 2006 are followed. These procedures involve no less than 45-day notice to EPA and FDEP in advance of any proposed land use changes that are inconsistent with an industrial/commercial use scenario. See the ROD for additiona


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